CN113752908B

CN113752908B - Vehicle, energy conversion device, and control method therefor

Info

Publication number: CN113752908B
Application number: CN202010500651.2A
Authority: CN
Inventors: 潘华; 王宁; 谢飞跃; 曹露蓉; 彭星星
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2020-06-04
Filing date: 2020-06-04
Publication date: 2023-12-12
Anticipated expiration: 2040-06-04
Also published as: CN113752908A

Abstract

The technical scheme of the application provides a vehicle, an energy conversion device and a control method thereof, wherein the energy conversion device comprises a bridge arm converter, a motor winding and an energy storage element, and the bridge arm converter, the motor winding and the energy storage element are connected with a battery pack to form a battery heating circuit; the control method comprises the following steps: the method comprises the steps of acquiring vehicle states and/or vehicle performance parameters, selecting a heating control mode according to the vehicle states and/or the vehicle performance parameters, controlling a bridge arm converter according to the heating control mode to enable a discharging process of a charging battery pack to a bus capacitor and a charging process of the bus capacitor to the battery pack to be alternately carried out, heating up the battery pack, improving heating efficiency of the battery pack, and simultaneously, selecting a corresponding heating control mode through detecting the vehicle states and/or the vehicle performance parameters to realize accurate control of the heating process of the battery pack.

Description

Vehicle, energy conversion device, and control method therefor

Technical Field

The application relates to the technical field of vehicles, in particular to a vehicle, an energy conversion device and a control method thereof.

Background

With the widespread use of new energy, battery packs are used as power sources in various fields. The battery pack is used as a power source in different environments, and the performance of the battery pack is also affected. For example, the performance of a battery pack in a low-temperature environment is considerably degraded from that of a normal temperature. For example, the discharge capacity of a battery pack at zero temperature may decrease with a decrease in temperature. At-30 ℃, the discharge capacity of the battery pack is substantially 0, resulting in the battery pack being unusable. In order to be able to use the battery pack in a low temperature environment, it is necessary to preheat the battery pack before using the battery pack.

As shown in fig. 1, in the prior art, the bridge arm converter 101, the motor winding 102 and the battery pack 103 are included, when the battery pack 103 is in a discharging process, the transistor VT1 and the transistor VT6 in the bridge arm converter 101 are triggered to be simultaneously turned on, current flows out from the positive electrode of the battery pack 103, passes through two stator inductances of the transistor VT1, the transistor VT6 and the motor winding 102, returns to the negative electrode of the battery pack 103, the current rises, and the energy is stored in the two stator inductances; when the battery pack 103 is in the charging process, as shown in fig. 2, the transistor VT1 and the transistor VT6 are simultaneously turned off, and the current returns to the battery pack 102 from the two stator inductances of the motor winding 102 and the bridge arm converter 101 through the two bleeder diodes VD4 and VD3, and the current drops. The two processes are repeated, the battery pack is in a rapid charge and discharge alternating state, and the internal resistance of the battery pack causes a large amount of internal heat to be generated, so that the temperature is rapidly increased. However, the prior art has the following problems: due to the existence of the bus capacitor C1, a large amount of current passes through the bus capacitor C1 when the battery pack 103 discharges during the operation of the charge-discharge circuit, so that the current flowing through the battery pack is greatly reduced, the heating speed of the battery pack is also seriously slowed down, and the heating control modes are not distinguished in the prior art, so that the heating effect is poor.

Disclosure of Invention

The application aims to provide a vehicle, an energy conversion device and a control method thereof, which can realize that a heating control mode is selected according to the vehicle state and/or the vehicle performance parameters, and a battery pack is charged according to the heating control mode, so that the heating speed of the battery pack is improved, and meanwhile, the heating process is accurately controlled.

The present application has been achieved in such a way that a first aspect of the present application provides a control method of an energy conversion device including:

the bridge arm converter, the motor winding and the energy storage element are connected with the battery pack to form a battery heating circuit;

the method comprises the following steps:

acquiring a vehicle state and/or a vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter;

and controlling a bridge arm converter in the battery heating circuit according to the heating control mode to charge and discharge the energy storage element and the battery pack so as to heat the battery pack.

A second aspect of the present application provides an energy conversion device comprising:

the energy conversion device further includes a controller for:

A third aspect of the application provides a vehicle comprising the energy conversion device of the second aspect.

According to the technical scheme, the battery pack, the motor winding, the bridge arm converter and the energy storage element form the battery heating circuit, the corresponding heating control mode is selected according to the vehicle state and/or the vehicle performance parameter, when the bridge arm converter is controlled according to the heating control mode to enable the battery heating circuit to work, the discharging process of the battery pack to the bus capacitor and the charging process of the bus capacitor to the battery pack are further alternately performed, so that the temperature of the battery pack is increased, the process that the bus capacitor participates in the charging and discharging process in the battery heating circuit is avoided, the problem that a large amount of current passes through the bus capacitor when the battery pack is discharged, the current flowing through the battery pack is greatly reduced, the heating speed of the battery pack is further greatly reduced is solved, the heating efficiency of the battery pack is improved, and meanwhile, the corresponding heating control mode is selected through the detection of the vehicle state and/or the vehicle performance parameter, so that the accurate control of the battery pack can be realized.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a current flow diagram of a motor control circuit provided in the prior art;

FIG. 2 is another current flow diagram of a motor control circuit provided by the prior art;

fig. 3 is a circuit diagram of an energy conversion device according to a first embodiment of the present application;

FIG. 4 is an equivalent circuit diagram of FIG. 3;

FIG. 5 is another circuit diagram of an energy conversion device according to a first embodiment of the present application;

fig. 6 is a flowchart of a control method of an energy conversion device according to a first embodiment of the present application;

FIG. 7 is another flow chart of a control method of an energy conversion device according to an embodiment of the present application;

fig. 8 is a circuit diagram of an energy conversion device according to a first embodiment of the present application;

FIG. 9 is another circuit diagram of an energy conversion device according to a first embodiment of the present application;

FIG. 10 is another circuit diagram of an energy conversion device according to a first embodiment of the present application;

FIG. 11 is a current flow diagram of an energy conversion device according to an embodiment of the present application;

FIG. 12 is a current flow diagram of an energy conversion device according to an embodiment of the present application;

FIG. 13 is a current flow diagram of an energy conversion device according to an embodiment of the present application;

FIG. 14 is a current flow diagram of an energy conversion device according to an embodiment of the present application;

fig. 15 is a time-current waveform diagram of an energy conversion device according to an embodiment of the present application.

Detailed Description

The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.

In order to illustrate the technical scheme of the application, the following description is made by specific examples.

An embodiment of the present application provides an energy conversion device, including: the bridge arm converter, the motor winding and the energy storage element are connected with the battery pack to form a battery heating circuit.

As a first embodiment of the connection relationship among the bridge arm inverter, the motor winding, and the energy storage element, as shown in fig. 3, the energy conversion device includes:

the first ends of all the bridge arms of the bridge arm converter 101 are commonly connected to form a first bus end, and the second ends of all the bridge arms of the bridge arm converter 101 are commonly connected to form a second bus end;

the first end of the bus capacitor C1 is connected with the first bus end, and the second end of the bus capacitor C1 is connected with the second bus end and the negative electrode of the battery pack 103;

the first switch module 104, the first switch module 104 is connected between the bus capacitor C1 and the positive electrode of the battery pack 103;

the motor winding 102, the first end of the motor winding 102 is connected with the middle point of each phase bridge arm of the bridge arm converter 101 respectively, and the second end of the motor winding 102 forms a neutral point;

and a second switching module 105, the second switching module 105 being connected between the neutral point of the motor winding 102 and the positive or negative electrode of the battery pack 103.

The bridge arm converter 101 includes M bridge arms, a first end of each of the M bridge arms is commonly connected to form a first bus end of the bridge arm converter 101, a second end of each of the M bridge arms is commonly connected to form a second bus end of the bridge arm converter 101, each bridge arm includes two power switch units connected in series, the power switch units may be of a transistor, an IGBT, a MOS transistor and other device types, a midpoint of each bridge arm is formed between the two power switch units, the motor includes M phase windings, a first end of each phase winding in the M phase windings is connected with a midpoint of each bridge arm in a group of M bridge arms in a one-to-one correspondence manner, a second end of each phase winding in the M phase windings is commonly connected to form a neutral point, and the neutral point is connected with the second switch module 105.

When m=3, the bridge arm converter 101 is a three-phase inverter, the three-phase inverter includes three bridge arms, the first ends of each of the three bridge arms are commonly connected to form a first bus end of the bridge arm converter 101, and the second ends of each of the three bridge arms in a group of three bridge arms are commonly connected to form a second bus end of the bridge arm converter 101; the three-phase inverter comprises a first power switch unit, a second power switch unit, a third power switch unit, a fourth power switch unit, a fifth power switch and a sixth power switch, wherein the first power switch unit and the fourth power switch unit form a first path bridge arm, the second power switch unit and the fifth switch unit form a second path bridge arm, the third power switch unit and the sixth switch unit form a third path bridge arm, one ends of the first power switch unit, the third power switch unit and the fifth power switch unit are commonly connected and form a first converging end of the three-phase inverter, and one ends of the second power switch unit, the fourth power switch unit and the sixth power switch unit are commonly connected and form a second converging end of the three-phase inverter.

The motor winding 102 includes three-phase windings, a first end of each phase winding in the three-phase windings is connected with a midpoint of each path of bridge arm in the three-path bridge arm in a one-to-one correspondence manner, a second end of each phase winding in the three-phase windings is commonly connected to form a neutral point, a first end of a first phase winding of the motor winding 102 is connected with the midpoint of the first path of bridge arm, a first end of a second phase winding of the motor winding 102 is connected with the midpoint of the second path of bridge arm, and a first end of a third phase winding of the motor winding 102 is connected with the midpoint of the third path of bridge arm.

The first power switch unit in the three-phase inverter includes a first upper bridge arm VT1 and a first upper bridge diode VD1, the second power switch unit includes a second lower bridge arm VT2 and a second lower bridge diode VD2, the third power switch unit includes a third upper bridge arm VT3 and a third upper bridge diode VD3, the fourth power switch unit includes a fourth lower bridge arm VT4 and a fourth lower bridge diode VD4, the fifth power switch unit includes a fifth upper bridge arm VT5 and a fifth upper bridge diode VD5, the sixth power switch unit includes a sixth lower bridge arm VT6 and a sixth lower bridge diode VD6, the motor is a three-phase four-wire system, which may be a permanent magnet synchronous motor or an asynchronous motor, and the three-phase winding is connected to a point and is connected to the second switch module 105.

The first switch module 104 is configured to implement on/off between the battery pack 103 and the bus capacitor C1 according to a control signal, so that the battery pack 103 charges or stops charging the bus capacitor C1; the second switch module 105 is configured to switch on or off between the motor winding 102 and the battery pack 103 according to the control signal, so that the battery pack 103 outputs electric energy to the motor winding 102 or stops outputting electric energy.

When the first switch module 104 is turned on and the second switch module 105 is turned off, the battery pack 103, the first switch module 104, the bridge arm converter 101, the bus capacitor C1, and the motor winding 102 form a motor driving circuit, and at this time, the bridge arm converter 101 is controlled to output power of the motor. In this embodiment, the bridge arm converter 101 in the battery heating circuit, the three-phase inverter in the motor driving circuit of the vehicle and the motor can be multiplexed to the motor winding 102, and the energy storage module multiplexes the bus capacitance of the motor driving circuit, and uses the same module to use different functions.

When the first switch module 104 is turned off and the second switch module 105 is turned on, the battery pack 103, the second switch module 105, the motor winding 102, the bridge arm converter 101 and the bus capacitor C1 form a battery heating circuit, the battery heating circuit comprises a discharging loop and a charging loop, the discharging loop is that the battery pack 103 discharges the bus capacitor C1 through the motor winding 102 and the bridge arm converter 101, at this time, current flows out of the battery pack 103, and flows into the bus capacitor C1 through the motor winding 102 and the bridge arm converter 101 to charge the bus capacitor C1; the charging circuit is to charge the battery pack 103 through the motor and the bridge arm converter 101 by the bus capacitor C1, at this time, the current flows out from the bus capacitor C1, flows into the battery pack 103 through the bridge arm converter 101 and the motor winding 102, and the internal resistance of the battery pack 103 is present, so that the internal resistance of the battery pack 103 generates heat when the current flows in and out from the battery pack 103 during the operation of the discharging circuit and the charging circuit, and the temperature of the battery pack 103 is further raised.

When the first switch module 104 and the second switch module 105 are both turned on, fig. 3 may be equivalent to fig. 4, where the first bus end of the bridge arm converter 101 is connected to the first end of the bus capacitor C1, the second bus end of the bridge arm converter 101 is connected to the second end of the energy storage element C1, the first end of the motor winding 102 is connected to the bridge arm converter 101, the second end of the motor winding 102 is connected to the first end of the battery pack 101, and the second end of the battery pack 103 is connected to the second bus end of the bridge arm converter 101, so as to form a battery heating circuit.

When the battery heating circuit works, the battery pack 103, the motor winding 102 and the bridge arm converter 101 form a discharge energy storage loop, and the battery pack 103, the motor winding 102, the bridge arm converter 101 and the bus capacitor C1 form a discharge energy release loop; the bus capacitor C1, the bridge arm converter 101, the motor winding 102 and the battery pack 103 form a charging energy storage loop, and the motor winding 102, the battery pack 103 and the bridge arm converter 101 form a charging energy release loop.

The discharging loop comprises a discharging energy storage loop and a discharging energy release loop, the charging loop comprises a charging energy storage loop and a charging energy release loop, when the discharging energy storage loop is controlled to work through the bridge arm converter 101, the battery pack 103 outputs electric energy to enable the winding of the motor to store energy; when the discharging energy release loop is controlled to work through the bridge arm converter 101, the battery pack 103 discharges and the winding of the motor releases energy to charge the bus capacitor C1; when the bridge arm converter 101 is used for controlling the charging energy storage loop to work, the bus capacitor C1 discharges to charge the battery pack 103, and the windings of the motor winding 102 store energy; when the charging and energy releasing loop is controlled to work through the bridge arm converter 101, the winding of the motor winding 102 releases energy to charge the battery pack 103. The bridge arm converter 101 is controlled to alternately perform the discharging process of the battery pack 103 on the bus capacitor C1 and the charging process of the battery pack 103 by the bus capacitor C1, so that the temperature of the battery pack 103 is increased; in addition, the current value flowing through the battery heating circuit is adjusted by controlling the duty ratio of the PWM control signal of the bridge arm converter 101, which is equivalent to controlling the on time of the upper bridge arm and the lower bridge arm, and the current in the battery heating circuit is increased or decreased by controlling the on time of the upper bridge arm or the lower bridge arm to be longer or shorter, so that the heating power generated by the battery pack 103 can be adjusted.

In the process of controlling the operation of the discharging circuit and the charging circuit, the discharging energy storage circuit, the discharging energy release circuit, the charging energy storage circuit and the charging energy release circuit in the discharging circuit can be controlled to operate sequentially, the current value flowing through the battery heating circuit can be adjusted by controlling the duty ratio of the PWM control signal of the bridge arm converter 101, the discharging energy storage circuit and the discharging energy release circuit in the discharging circuit can be controlled to be alternately conducted for discharging, the charging energy storage circuit and the charging energy release circuit in the charging circuit can be controlled to be alternately conducted for discharging, and the current value flowing through the discharging circuit and the charging circuit can be respectively adjusted by controlling the duty ratio of the PWM control signal of the bridge arm converter 101.

The technical effect of the present embodiment is that the bridge arm converter 101 is controlled to operate the battery heating circuit, the battery pack 103 in the discharging circuit is caused to discharge the bus capacitor C1, the bus capacitor C1 in the charging circuit is caused to charge the battery pack 103, the temperature of the battery pack 103 is further increased, and the bridge arm converter 101 is controlled to adjust the current in the self-heating circuit of the battery pack 103, thereby adjusting the heating power generated by the battery pack 103.

As a second embodiment of the connection relationship among the bridge arm converter 101, the motor winding 102, and the energy storage element, as shown in fig. 5, a first bus terminal of the bridge arm converter 101 is connected to the positive electrode of the battery pack 103, and a second bus terminal of the bridge arm converter 101 is connected to the negative electrode of the battery pack 103; a first end of the motor winding 102 is connected with the bridge arm converter 101, a second end of the motor winding 102 is connected with a first end of the energy storage element C2, and a second end of the energy storage element C2 is connected with a second converging end of the bridge arm converter 101 to form a battery heating circuit. In this embodiment, the bridge arm converter 101 and the motor winding 102 of the battery heating circuit may multiplex a three-phase inverter and a motor in a motor driving circuit of the vehicle, which is not shown in a bus capacitance diagram in the motor driving circuit.

The difference between the present embodiment and the above embodiment is that the connection manner between the modules is different, and the specific structure of each module is the same, which can be referred to the above embodiment and will not be described herein again.

For the battery heating circuit, the battery heating circuit comprises a discharging loop and a charging loop, wherein the discharging loop is used for discharging the energy storage module C2 through the bridge arm converter 101 and the motor winding 102 by the battery pack 103, at the moment, current flows out of the battery pack 103, and flows into the energy storage module C2 through the bridge arm converter 101 and the motor winding 102 to charge the energy storage module C2; the charging circuit is to charge the battery pack 103 by the energy storage module C2 through the motor winding 102 and the bridge arm converter 101, at this time, the current flows out from the energy storage module C2, and flows into the battery pack 103 through the motor winding 102 and the bridge arm converter 101, and because of the internal resistance in the battery pack 103, when the discharging circuit and the charging circuit work, the internal resistance of the battery pack 103 can generate heat due to the current flowing in and flowing out of the battery pack 103, so that the temperature of the battery pack 103 is increased.

As shown in fig. 6, the control method includes:

s10, acquiring a vehicle state and/or a vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter.

The vehicle state may refer to a vehicle running state, and the heating control mode is selected according to the vehicle running state; the vehicle performance parameter refers to a certain performance index of the vehicle, the performance index is compared with a preset value, and a heating control mode is selected according to a comparison result.

For example, the vehicle state is a vehicle running state, and the vehicle performance parameter is at least one of a cooling parameter, a withstand voltage parameter, a withstand current parameter, an anti-noise parameter, and an EMC emission resistance parameter.

The heating control mode comprises a high-frequency heating control mode and a low-frequency heating control mode, wherein the low-frequency heating control mode refers to a control mode that the switching frequency of the bridge arm converter is the same as the charging and discharging frequency of the battery pack, and the high-frequency heating control mode refers to a control mode that the switching frequency of the bridge arm converter is N times the charging and discharging frequency of the battery pack.

And S20, controlling a bridge arm converter in a battery heating circuit according to the heating control mode, so that the energy storage element and the battery pack are charged and discharged, and heating of the battery pack is realized.

In order to further control the amount of heat generated by the internal resistance of the battery pack, the bridge arm converter can be controlled according to a heating control mode, and different control signals can be input to the bridge arm converter to adjust the current value flowing through the battery heating circuit as the bridge arm converter is connected in series in the battery heating circuit, so that the heat generated by the internal resistance of the battery pack is adjusted.

The embodiment of the application provides a control method of an energy conversion device, which can enable a battery pack, a motor winding, a bridge arm converter and an energy storage element to form a battery heating circuit, and can control the bridge arm converter to enable the battery heating circuit to work according to a heating control mode by acquiring vehicle state and/or vehicle performance parameters and selecting a corresponding heating control mode according to the vehicle state and/or the vehicle performance parameters, so that the discharging process of the battery pack on a bus capacitor and the charging process of the bus capacitor on the battery pack are alternately performed, thereby realizing the temperature rise of the battery pack.

For step S10, when the vehicle state is the vehicle running state and the vehicle performance parameter is at least one of the cooling parameter, the withstand voltage parameter, the withstand current parameter, the anti-noise parameter, and the EMC radiation resistance parameter, the specific process of selecting the heating control mode according to the vehicle state is as follows:

in a first embodiment, when the vehicle state is a vehicle running state, acquiring the vehicle state, and selecting the heating control mode according to the vehicle state, includes:

when the running state of the vehicle is a driving state, selecting a high-frequency heating control mode;

when the running state of the vehicle is a parking state, a low-frequency heating control mode or a high-frequency heating control mode is selected.

When the vehicle is in a driving state, because various working conditions exist in the driving state process, for example, the vehicle is in a light-load working condition or a heavy-load working condition, the switching frequency of the bridge arm converter cannot be fixed, and the switching frequency of the bridge arm converter needs to be changed according to the actual working condition, namely, a high-frequency heating control mode needs to be selected.

When the vehicle is in a parking state, the vehicle is in a stopping state, the switching frequency of the bridge arm converter can be set to be the same as the fixed frequency of the battery pack charging and discharging frequency, or the switching frequency of the bridge arm converter can be set to be a frequency which is a certain multiple of the battery pack charging and discharging frequency, and then the low-frequency heating control mode or the high-frequency heating control mode can be selected.

The technical effects of the present embodiment are as follows: when the energy conversion device is controlled to perform self-heating of the battery pack, the running state of the vehicle is obtained, a corresponding heating control mode is selected according to the running state of the vehicle, and the switching frequency of the bridge arm converter is controlled according to the heating control mode, so that the accurate control of the self-heating process of the battery pack is realized.

In a second embodiment, when the vehicle performance parameter is a cooling parameter, acquiring a vehicle state and/or a vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter, including:

acquiring cooling parameters and judging whether the cooling parameters meet preset conditions;

when the cooling parameters meet preset conditions, selecting a low-frequency heating control mode or a high-frequency heating control mode;

and when the cooling parameters do not meet the preset conditions, selecting a low-frequency heating control mode.

The cooling parameters are used for determining the strength of the cooling effect of the energy conversion device, and are mainly obtained according to the cooling condition of a self-heating system formed by a motor winding, a motor rotor, a motor stator silicon steel sheet, a bridge arm converter copper plate, an electric control IGBT (insulated gate bipolar transistor) and the like when the self-heating system generates heat, the cooling parameters can be cooling time, cooling speed and the like, when the cooling time is shorter, the cooling speed is faster, for example, when the cooling time and the cooling speed are smaller than preset values, the cooling parameters are considered to meet preset conditions, the cooling effect is determined to be strong, otherwise, the cooling parameters are considered to not meet preset conditions, the cooling effect is determined to be weak, and if the cooling effect is strong, a low-frequency heating control mode or a high-frequency heating control mode can be selected; if the cooling effect is weak, the low-frequency heating control mode is selected.

In a specific embodiment, when the cooling state of the vehicle is an air cooling mode for the bridge arm converter and the motor winding, a high-frequency heating control mode is selected; when the cooling state of the vehicle is a water cooling mode of the bridge arm converter and the motor winding, selecting a low-frequency heating control mode or a high-frequency heating control mode; the vehicle cooling state refers to the cooling state of the bridge arm converter and the motor winding, and if the cooling state of the bridge arm converter and the motor winding is an air cooling mode, the cooling mode is slower in cooling speed, and the cooling parameters are regarded as not meeting preset conditions, the high-frequency heating control mode is selected; if the cooling state of the bridge arm converter and the motor winding is a water cooling mode, and the cooling speed is high in the cooling mode, the cooling parameters of the bridge arm converter and the motor winding meet the preset conditions, and then a low-frequency heating control mode or a high-frequency heating control mode is selected.

The technical effects of the present embodiment are as follows: when the energy conversion device is controlled to perform self-heating of the battery pack, vehicle cooling parameters are obtained, cooling effects are judged according to the cooling parameters, corresponding heating control modes are selected according to the vehicle cooling effects, and the switching frequency of the bridge arm converter is controlled according to the heating control modes, so that accurate control of the self-heating process of the battery pack is realized.

In a third embodiment, when the vehicle performance parameters are the withstand voltage parameter and the current withstand parameter, the vehicle state and/or the vehicle performance parameter are obtained, and the heating control mode is selected according to the vehicle state and/or the vehicle performance parameter, including:

obtaining a withstand voltage parameter and a current withstand parameter, comparing the withstand voltage parameter with a preset voltage value, and comparing the current withstand parameter with a preset current value;

when the withstand voltage parameter is larger than a preset voltage value and the withstand current parameter is larger than a preset current value, selecting a low-frequency heating control mode or a high-frequency heating control mode;

and selecting a high-frequency heating control mode when the withstand voltage parameter is not more than a preset voltage value or the withstand current parameter is not more than a preset current value.

The voltage-resistant parameter and the current-resistant parameter respectively represent the impact resistance of the energy conversion device to voltage and current, the voltage-resistant value and the current-resistant value of the energy conversion device are obtained through the voltage-resistant test and the current-resistant test of the energy conversion device, when the voltage-resistant value is larger than a preset voltage value and the current-resistant value is larger than a preset current value, the voltage-resistant and the current-resistant impact resistance of the energy conversion device are judged to be stronger, a low-frequency heating control mode or a high-frequency heating control mode is selected, when the voltage-resistant value is not larger than the preset voltage value or the current-resistant value is not larger than the preset current value, the voltage-resistant and the current-resistant impact resistance of the energy conversion device are judged to be weaker, and the high-frequency heating control mode is selected.

The technical effects of the present embodiment are as follows: when the energy conversion device is controlled to perform self-heating of the battery pack, the withstand voltage parameter and the current withstand parameter are obtained, the current impact resistance and the voltage impact resistance are judged according to the withstand voltage parameter and the current withstand parameter, the corresponding heating control mode is selected according to the current impact resistance and the voltage impact resistance, the switching frequency of the bridge arm converter is controlled according to the heating control mode, and the accurate control of the self-heating process of the battery pack is realized.

In a fourth embodiment, when the vehicle performance parameter is an anti-noise parameter, acquiring a vehicle state and/or a vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter, including:

the anti-noise parameter is obtained, and the anti-noise parameter is compared with a preset decibel value;

when the anti-noise parameter is larger than a preset decibel value, selecting a low-frequency heating control mode or a high-frequency heating control mode;

and when the anti-noise parameter is not more than a preset decibel value, selecting a high-frequency heating control mode.

The anti-noise parameters of the vehicle are obtained through anti-noise testing of the vehicle, the anti-noise parameters are compared with preset decibels, when the anti-noise parameters are larger than the preset decibels, the low-frequency heating control mode or the high-frequency heating control mode is selected if the anti-noise interference capability is strong, and when the anti-noise parameters are not larger than the preset decibels, the high-frequency heating control mode is selected if the anti-noise interference capability is weak.

The technical effects of the present embodiment are as follows: when the energy conversion device is controlled to perform self-heating of the battery pack, anti-noise parameters are obtained, the anti-noise interference capacity is judged according to the anti-noise parameters, a corresponding heating control mode is selected according to the anti-noise interference capacity, the switching frequency of the bridge arm converter is controlled according to the heating control mode, and accurate control of the self-heating process of the battery pack is realized.

In a fifth embodiment, when the vehicle performance parameter is an EMC (electromagnetic compatibility ) radiation resistance parameter, acquiring a vehicle state and/or a vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter, includes:

acquiring EMC radiation resistance parameters, and comparing the EMC radiation resistance parameters with preset values;

when the EMC radiation resistance parameter is larger than a preset value, selecting a low-frequency heating control mode or a high-frequency heating control mode;

and when the EMC radiation resistance parameter is not more than a preset value, selecting a high-frequency heating control mode.

The EMC test parameters of the vehicle are obtained through EMC test on the vehicle, the EMC test value is compared with a preset value, when the EMC test value is larger than the preset value, the EMC radiation resistance is high, the low-frequency heating control mode or the high-frequency heating control mode is selected, and when the EMC test value is not larger than the preset value, the EMC radiation resistance is weak, and the high-frequency heating control mode is selected.

The technical effects of the present embodiment are as follows: when the energy conversion device is controlled to perform self-heating of the battery pack, EMC test parameters are obtained, EMC radiation resistance is judged according to the EMC test parameters, a corresponding heating control mode is selected according to the EMC radiation resistance, and the switching frequency of the bridge arm converter is controlled according to the heating control mode, so that accurate control of the self-heating process of the battery pack is realized.

Further, the control method further includes: when receiving an instruction for entering a driving mode, the first switch module is controlled to be turned on and the second switch module is controlled to be turned off, so that the battery pack, the first switch module, the bus capacitor, the bridge arm converter and the motor form a motor driving circuit.

When the vehicle needs to output torque, the first switch module is controlled to be turned on and the second switch module is controlled to be turned off, and the bridge arm converter is controlled to control the motor driving circuit to work, so that the motor output power is realized.

As an embodiment, when the heating control mode is the low frequency control mode, as shown in fig. 7, the bridge arm converter in the battery heating circuit is controlled to charge and discharge the energy storage element and the battery pack, and further includes:

and S201, acquiring a charge-discharge period of the battery pack and a target equivalent current value of a battery heating circuit.

Wherein the charge-discharge cycle of the battery pack and the target equivalent current value of the battery heating circuit are controlled by electricityThe battery pack management system gives out that a preset battery pack charging and discharging period exists in the battery pack management system, the battery pack management system calculates the internal resistance of the battery pack, and can discharge/charge through specific current in one charging and discharging period, so that the current internal resistance r=delta U/delta I of the battery pack is calculated; wherein DeltaU is the voltage difference between the initial stage and the final stage of discharging/charging of the battery pack, and DeltaI is the discharging/charging current; after obtaining the internal resistance of the battery pack, obtaining an equivalent current value according to the heating power of the battery pack, wherein the equivalent current value can be obtained according to the formula p=i ² r calculates a target equivalent current value, wherein P is heating power, r is internal resistance of the battery pack, I is a target equivalent current value, and the target equivalent current value can be a value or a group of values.

S202, acquiring a charge-discharge period of a battery heating circuit according to the charge-discharge period of a battery pack, and acquiring a duty ratio of a PWM control signal according to a target equivalent current value of the battery heating circuit.

The charge-discharge period of the battery heating circuit means a period of controlling the upper bridge arm and the lower bridge arm to complete one-time switching, the duty ratio means a percentage of time of outputting a high-level signal to the upper bridge arm or the lower bridge arm in the bridge arm converter to the whole charge-discharge period, the control duty ratio is equivalent to controlling the conduction time of the upper bridge arm and the lower bridge arm, when the battery heating circuit works, the current in the battery heating circuit can be increased or decreased by controlling the conduction time of the upper bridge arm or the lower bridge arm to be prolonged or shortened, for example, the charging circuit can comprise a charging energy storage circuit and a charging flywheel circuit, when the control duty ratio makes the conduction time of the charging energy storage circuit be prolonged, the current in the circuit can be increased, namely, the duty ratio in each period determines the increase or decrease of the current in the battery heating circuit.

The method for obtaining the charge-discharge period of the battery heating circuit according to the charge-discharge period of the battery pack comprises the following steps:

the charge-discharge cycle of the battery pack is set as the charge-discharge cycle of the battery heating circuit.

The method for obtaining the duty ratio of the PWM control signal according to the target equivalent current value of the battery heating circuit comprises the following steps:

and acquiring the duty ratio of the PWM control signal according to the pre-stored corresponding relation between the target equivalent current value and the duty ratio of the PWM control signal.

The battery pack and the battery heating circuit have a corresponding relationship between a charging and discharging period and a charging and discharging period, and the charging and discharging period of the battery heating circuit is equal to the charging and discharging period of the battery pack in a low-frequency control mode. The pre-stored corresponding relation table of the target equivalent current value and the duty ratio of the PWM control signal can be obtained through multiple test measurements, the number of the target equivalent current values in one charge and discharge period is one in the low-frequency control mode, and the duty ratio of the PWM control signal of the charge and discharge period of the battery heating circuit can be obtained according to the corresponding relation table.

Further, controlling the bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack to heat the battery pack includes:

And controlling the switch of the upper bridge arm and the lower bridge arm of the bridge arm converter according to the charge-discharge period of the battery heating circuit and the duty ratio of the PWM control signal, and adjusting the current value flowing through the battery heating circuit so as to adjust the heat generated by the internal resistance of the battery pack.

The charging and discharging period of the battery heating circuit comprises a charging period and a discharging period, wherein the charging period refers to the working period of a charging circuit in the battery heating circuit, the discharging period refers to the working period of a discharging circuit in the battery heating circuit, and one charging and discharging period of the battery pack is divided into one charging duration and one discharging duration. In the low-frequency control mode, the charging duration is equal to the charging period, the discharging duration is equal to the discharging period, namely the charging duration comprises one charging period of the battery heating circuit, the discharging duration comprises one discharging period of the battery heating circuit, the charging period is equal to the discharging period, the charging period can be unequal to the discharging period, the switching of the upper bridge arm and the lower bridge arm of the bridge arm converter can be controlled according to the charging period, the discharging period and the duty ratio of the PWM control signal, a discharging energy storage loop, a discharging energy release loop, a charging energy storage loop and a charging energy release loop in the battery heating circuit are controlled to work in sequence, and the current value flowing through the battery heating circuit is adjusted to be the target current equivalent value so as to adjust the heat generated by the internal resistance of the battery pack.

In the embodiment, a low-frequency control mode is adopted, the charge-discharge period of the battery pack and the target equivalent current value of the battery heating circuit are obtained, the charge-discharge period of the battery heating circuit is obtained according to the charge-discharge period of the battery pack, the duty ratio of the PWM control signal is obtained according to the target equivalent current value of the battery heating circuit, the switch of the upper bridge arm and the lower bridge arm of the bridge arm converter is controlled according to the duty ratio of the PWM control signal, and the current value flowing through the battery heating circuit is adjusted to be the target equivalent current value.

Further, the system also comprises a soft start mode before entering the low-frequency control mode, wherein the soft start mode is to output a minimum duty ratio of PWM control signals to the bridge arm converter, and control a discharge energy storage loop, a discharge energy release loop, a charge energy storage loop and a charge energy release loop in the battery heating circuit to work in sequence, so that the system slowly establishes charge and discharge current of the battery pack, then slowly increases the duty ratio of the lower bridge arm, and gradually increases the charge and discharge current of the battery pack to finish soft start.

In this embodiment, since the busbar capacitance voltage cannot be suddenly changed, if the duty ratio of the control bridge arm converter is too fast, the three-phase current is rapidly increased, even an overcurrent phenomenon occurs, and the busbar capacitance is over-pressed, or a current oscillation problem occurs between the busbar capacitance and the inductance of the motor winding, and the above-mentioned problem is avoided by setting a soft start process.

The present embodiment will be specifically described by a specific circuit configuration:

as shown in fig. 8, the energy conversion device includes a motor winding 102, a bridge arm converter 101, a bus capacitor C1, a switch K2, a switch K3, a switch K4, and a resistor R, wherein a neutral point of a three-phase winding of the motor winding 102 is connected to a first end of the switch K1, a second end of the switch K1 is connected to a positive end of the battery pack 103, a first end of the switch K2, and a first end of the switch K3, a second end of the switch K3 is connected to a first end of the resistor R, the three-phase winding of the motor winding 102 is respectively connected to a midpoint of a three-phase bridge arm of the bridge arm converter 101, a first bus end of the bridge arm converter 101 is connected to a first end of the bus capacitor C1, a second end of the switch K2, and a second end of the resistor R, a second bus end of the bridge arm converter 101 is connected to a second end of the bus capacitor C1 and a second end of the switch K4, and a first end of the switch K4 is connected to a negative electrode of the battery pack 103.

As shown in fig. 9, as another circuit configuration, a second terminal of the switch K1 is connected to the negative electrode of the battery pack 103.

The bridge arm converter 101 includes a first power switch unit, a second power switch unit, a third power switch unit, a fourth power switch unit, a fifth power switch unit and a sixth power switch unit, where the first power switch unit and the fourth power switch unit form a first bridge arm, the third power switch unit and the sixth power switch unit form a second bridge arm, the fifth power switch unit and the second power switch unit form a third bridge arm, one ends of the first power switch unit, the third power switch unit and the fifth power switch unit are commonly connected and form a first bus end of the bridge arm converter, one ends of the second power switch unit, the fourth power switch unit and the sixth power switch unit are commonly connected and form a second bus end of the bridge arm converter, a first phase winding of the motor winding 102 is connected with a midpoint of the first bridge arm, a second phase winding of the motor winding 102 is connected with a midpoint of the second bridge arm, and a third phase winding of the motor winding 102 is connected with a midpoint of the third bridge arm.

The first power switch unit in the bridge arm converter 101 includes a first upper bridge arm VT1 and a first upper bridge diode VD1, the second power switch unit includes a first lower bridge arm VT2 and a first lower bridge diode VD2, the third power switch unit includes a second upper bridge arm VT3 and a second upper bridge diode VD3, the fourth power switch unit includes a second lower bridge arm VT4 and a second lower bridge diode VD4, the fifth power switch unit includes a third upper bridge arm VT5 and a third upper bridge diode VD5, the sixth power switch unit includes a third lower bridge arm VT6 and a third lower bridge diode VD6, the three-phase ac motor is a three-phase four-wire system, which may be a permanent magnet synchronous motor or an asynchronous motor, and is connected to a neutral point at a three-phase winding and leads out a neutral line.

As shown in fig. 9, when the energy conversion device does not perform the heating function, the switch K1 is kept open, the switch K4 is closed, and after entering the heating mode, the switch K3 is closed for the pre-charging, if the pre-charging is unsuccessful, the switch K1 is immediately closed and the switch K3 is opened for the heating state, and at this time, the circuit structure of fig. 9 is equivalent to that shown in fig. 10.

When the bridge arm converter 101 is controlled to be in a low-frequency control mode, the bridge arm converter 101 enters a heating state, namely, the pre-charging of the bus capacitor C1 is completed, the switch K1 is closed, the switch K3 is opened, the voltage on the bus capacitor C1 is close to the voltage of the battery pack 103, the power tubes of the bridge arm converter 101 are all in a closed state, almost no current exists in the windings of the motor winding 102, and the system is in a ready state.

Firstly, entering a soft start mode, and outputting a minimum duty ratio of a PWM control signal to a bridge arm converter 101 to enable a battery heating circuit to work, wherein when the battery heating circuit works, a battery pack 103, a switch K1, a motor winding 102 and the bridge arm converter 101 form a discharge energy storage loop, and the battery pack 103, the switch K1, the motor winding 102, the bridge arm converter 101 and a bus capacitor C1 form a discharge energy release loop; the bus capacitor C1, the bridge arm converter 101, the motor winding 102, the switch K1 and the battery pack 103 form a charging energy storage loop, the motor winding 102, the switch K1, the battery pack 103 and the bridge arm converter 101 form a charging energy release loop, and the discharging energy storage loop, the discharging energy release loop, the charging energy storage loop and the charging energy release loop in the battery heating circuit are controlled to work in sequence through outputting the minimum duty ratio of PWM control signals to the bridge arm converter 101, so that soft start is completed.

After the soft start process is completed, a formal heating process is entered, a charge-discharge period of the battery pack 103 and a target equivalent current value of the battery heating circuit are obtained, a charge duration and a discharge duration are obtained according to the charge-discharge period of the battery pack 103, wherein the charge duration is equal to the discharge duration, the charge period of the battery heating circuit is obtained according to the charge duration, the discharge period of the battery heating circuit is obtained according to the discharge duration, a duty ratio of a PWM control signal is obtained according to the target equivalent current value of the battery heating circuit, and the on-off of upper and lower bridge arms of the bridge arm converter 101 is controlled according to the duty ratio of the PWM control signal, so that the charge-discharge current of the battery pack 103 is controlled, and the heating power inside the battery pack reaches an expected value, and the method specifically comprises:

The first stage is to work for a discharge energy storage loop: as shown in fig. 11, when the lower arm of the arm converter 101 is turned on, current flows out from the positive electrode of the battery pack 103, passes through the switch K1, the motor winding 102, and the lower arms (the second lower arm VT2, the fourth lower arm VT4, and the sixth lower arm VT 6) of the arm converter 101, and flows back to the negative electrode of the battery pack 103, and the current increases continuously.

The second stage is the work of a discharge freewheel loop: as shown in fig. 12, when the lower bridge arm of the bridge arm converter 101 is turned off and the upper bridge arm is turned on, the current starts from the positive electrode of the battery pack 103, charges the positive electrode of the bus capacitor C1 after passing through the switch K1, the motor winding 102, and the upper bridge arm (the first upper bridge diode VD1, the third upper bridge diode VD3, and the fifth upper bridge diode VD 5) of the bridge arm converter 101, the current is continuously reduced to zero, the inductance energy storage is reduced to zero, the inductance of the battery pack 103 and the motor winding 102 are jointly discharged to charge the bus capacitor C1, and the voltage of the bus capacitor C1 is increased to a certain maximum value.

The third stage is to charge the energy storage loop work: as shown in fig. 13, when the lower arm of the arm converter 101 is controlled to be opened and the upper arm of the arm converter 101 is controlled to be closed and the upper arm of the arm converter 101 is opened, the current starts from the positive electrode of the bus capacitor C1, and charges the positive electrode of the battery pack 103 after passing through the upper arm (the first upper arm VT1, the third upper arm VT3, the fifth upper arm VT 5), the motor winding 102, and the switch K1 of the arm converter 101, the current increases and decreases continuously, and the voltage of the bus capacitor C1 decreases continuously.

The fourth stage is to work for the charging freewheel loop: as shown in fig. 14, when the lower bridge arm of the bridge arm converter 101 is turned on, current flows out from the negative electrode of the battery pack 103, flows back to the positive electrode of the battery pack through the lower bridge arm (the second lower bridge diode VD2, the fourth lower bridge diode VD4, and the sixth lower bridge diode VD 6), the motor winding 102, and the switch K1 of the bridge arm converter 101, and the current is continuously reduced, and the voltage of the bus capacitor C1 is continuously reduced.

The battery pack 103 in the first stage and the second stage is discharged to the outside, and when the first stage is finished, the discharge current reaches the maximum, the battery pack 103 in the third stage and the fourth stage is charged, and at a certain moment in the third stage, the charging current reaches the maximum; the second stage is to charge the bus capacitor C1, the voltage of the bus capacitor C1 rises to the highest, the third stage is to discharge the bus capacitor C1, and the voltage of the bus capacitor C1 drops to the lowest.

The upper bridge arm and the lower bridge arm of the bridge arm converter 101 are controlled by complementary pulses, on the premise that the control period is unchanged, the longer the opening time of the lower bridge arm is, the larger the maximum value of the charge and discharge current of the battery pack 103 is, meanwhile, the higher the highest voltage of the bus capacitor C1 is, the larger the maximum value of the charge and discharge current of the battery pack 103 is, and the larger the heating power of the internal resistance of the battery pack 103 is. Conversely, the shorter the opening time of the lower bridge arm, the smaller the maximum value of the charge-discharge current of the battery pack 103, and the smaller the highest voltage of the bus capacitor C1, the smaller the maximum value of the charge-discharge current of the battery pack 103, and the smaller the heating power of the internal resistance of the battery pack 103.

From the above, on the premise of a certain control period, the charge and discharge current of the battery pack is adjusted mainly by controlling the duty ratio, and the internal heat generating power of the battery pack is positively correlated with the conduction time of the lower bridge arm. The control period is mainly determined by the ac internal resistance of the battery pack, and is selected with the aim of maximum heating power, but the control period affects the variation range of the capacitor voltage, and the variation range of the capacitor voltage and the period are in a negative correlation. The duty ratio of the lower bridge arm is increased, so that the charge and discharge current of the battery pack can be increased, namely the heating power in the battery pack is increased, and conversely, the duty ratio of the lower bridge arm is reduced, so that the charge and discharge current of the battery pack can be reduced, namely the heating power in the battery pack is reduced. In the whole heating process, the states of relevant parts such as an electric control part, a motor and the like are monitored in real time, and if abnormal conditions of current, voltage and temperature occur, the heating is immediately stopped, so that the heating safety is ensured.

As another embodiment, when the heating control mode is the high-frequency heating control mode, the method further comprises controlling the bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack, and further comprising:

Step S301, acquiring a charge-discharge period of a battery pack and a target current waveform of a battery heating circuit in the charge-discharge period of the battery pack, wherein the charge-discharge period of the battery pack comprises a charge duration and a discharge duration, the charge duration comprises a plurality of charge periods of the battery heating circuit, and the discharge duration comprises a plurality of discharge periods of the battery heating circuit.

In this step, the charge-discharge period of the battery pack and the target current waveform of the battery heating circuit are given by the battery pack management system, the preset charge-discharge period of the battery pack exists in the battery pack management system, the target current waveform refers to a current waveform achieved by controlling the bridge arm converter to adjust a current value flowing through the battery heating circuit, the target current waveform can meet a waveform function, for example, the target current waveform can be a waveform of triangular wave, sine wave or the like, one charge-discharge period of the battery pack is divided into one charge duration and one discharge duration, the charge duration refers to a time consumed by a charge process of the battery pack in one charge-discharge period, and the discharge duration refers to a time consumed by a discharge process of the battery pack in one charge-discharge period. In the high-frequency control mode, a plurality of charging periods and discharging periods are included in one charging and discharging period of the battery pack, and the corresponding relationship is that the charging duration corresponds to the plurality of charging periods and the discharging duration corresponds to the plurality of discharging periods.

S302, obtaining a plurality of target equivalent current values corresponding to the target current waveform according to the target current waveform.

In this step, in order to acquire a target current waveform, a plurality of target equivalent current values conforming to the target current waveform are selected, for example, the target current waveform satisfies a sinusoidal function i=asinωt, and a time and a current value conforming to the function are selected.

S303, acquiring the duty ratio of a PWM control signal according to a target equivalent current value, and acquiring the number of charging periods and the number of discharging periods contained in the charging duration according to the charging and discharging periods of the battery pack and the number of target equivalent current values, wherein one target equivalent current value corresponds to one charging period or one discharging period.

In this step, the duty ratio of the PWM control signal is obtained according to the target equivalent current value of the battery heating circuit, including:

and acquiring the duty ratio of the PWM control signal according to the corresponding relation between the prestored target equivalent current value and the duty ratio of the PWM control signal.

The corresponding relation table of the target equivalent current value and the duty ratio of the PWM control signal, which is stored in advance, can be obtained through multiple test measurement.

In this step, according to the charge-discharge cycle of the battery pack and the number of the target equivalent current values, the obtaining the number of charge cycles included in the charge duration and the number of discharge cycles included in the discharge duration includes:

the charge-discharge period of the battery pack, the number of the target equivalent current values, the charge duration, the discharge duration, the charge period, the discharge period, the number of charge periods, and the number of discharge periods satisfy the following formulas:

T＝T1+T2；

T1＝N1×t1；

T2＝N2×t2；

N＝N1+N2；

wherein T is the charge-discharge period of the battery pack, T1 is the charge period, T2 is the discharge period, T1 is the charge period of the battery heating circuit, N1 is the number of charge periods, T2 is the discharge period of the battery heating circuit, N2 is the number of discharge periods, and N is the number of target equivalent current values.

Acquiring N1 target equivalent current values under the charging duration, wherein the N1 target equivalent current values correspond to N1 charging periods, and the N1 charging periods correspond to the duty ratios of N1 PWM control signals; n2 target equivalent current values are obtained under the discharging time length, N2 charging periods are correspondingly obtained, and N2 charging periods correspond to the duty ratios of N2 PWM control signals.

and controlling the switch of the upper bridge arm and the lower bridge arm of the bridge arm converter according to the charging period and the number of the battery heating circuits, the discharging period and the number of the battery heating circuits and the duty ratio of the PWM control signals, and adjusting the current value flowing through the battery heating circuits so as to adjust the heat generated by the internal resistance of the battery pack.

Controlling the switching of the upper bridge arm and the lower bridge arm of the bridge arm converter according to the number of charging periods, the number of discharging periods and the duty ratio of the PWM control signal, and adjusting the current value flowing through the battery heating circuit, wherein the method comprises the following steps:

obtaining a target equivalent current value corresponding to each charging period and each discharging period and a duty ratio of a PWM control signal;

and controlling the switching of the upper bridge arm and the lower bridge arm of the bridge arm converter in each charging period and each discharging period according to the duty ratio of the PWM control signal, and adjusting the current value flowing through the battery heating circuit to be the target equivalent current value.

The current value in the battery heating circuit is made to be a target equivalent current value by adjusting the duty ratio of the PWM control signal of each charging period and each discharging period, and finally a target current waveform is formed.

In this embodiment, the whole charge-discharge cycle of the battery pack includes N control cycles of the bridge arm converter, where the control cycle refers to a charge cycle or a discharge cycle, and adjusting the duty ratio of the power tube each time changes the direction of current change at the same time, and increasing the duty ratio of the lower bridge arm increases the discharge current of the battery pack or decreases the charge current; and the lower bridge arm duty ratio is reduced, so that the discharging current of the battery pack is reduced, or the charging current is increased, and the whole charging and discharging current can be increased or reduced by controlling the average duty ratio of N times of switch control in each battery pack charging and discharging period. The local current can be changed for each switching control, for example, the current value at a certain point can be increased or decreased, so that the charge and discharge current of the battery pack can be similar to the waveforms of triangular waves, sine waves, square waves and the like through cooperative control of the duty ratio of the N switching tubes. According to the actual control requirement, the battery pack heating power requirement, the battery pack service life and other factors are used for selecting proper current waveforms, so that the control is convenient to realize, the stability of the battery pack is not affected, and the battery pack heating power is high.

Further, according to the duty ratio of the PWM control signal, the switching of the upper and lower bridge arms of the bridge arm converter in each charging period and each discharging period is controlled, and the current value flowing through the battery heating circuit is adjusted to be the target equivalent current value, and then the method further includes:

and acquiring an actual current value in the battery heating circuit, acquiring a duty cycle correction value of a current charging period or a current discharging period according to the relation between the actual current value and a target equivalent current value, and correcting the duty cycle of the next charging period or the next discharging period according to the duty cycle correction value.

When the actual current value does not accord with the target current value, a current difference value between the actual current value and the target equivalent current value is obtained, a duty ratio correction value corresponding to the current difference value is obtained according to the corresponding relation between the current value and the duty ratio of the PWM control signal, the duty ratio correction value is overlapped with the duty ratio corresponding to the next control period, and then the bridge arm converter is controlled.

According to the embodiment, the duty ratio correction value of the current charging period or the current discharging period is obtained through the relation between the actual current value and the target equivalent current value, and the duty ratio of the next control period is adjusted according to the duty ratio correction value, so that the actual current value of the battery heating circuit accords with the target equivalent current value, and the current waveform is more accurate.

According to the embodiment, the high-frequency control mode is set, one target current value corresponds to the discharging period or the charging period of one click controller, the effective value of the current flowing through the battery pack can reach any target current value by continuously adjusting the duty ratio of each control period, and the current waveform can be adjusted, so that the adaptability is higher.

The following describes the operation of the high frequency control mode by a specific circuit structure:

as shown in fig. 9, when the bridge arm converter 101 is controlled to be in the high-frequency control mode, a heating command is received, and the bridge arm converter is in a heating state, namely, the pre-charging of the bus capacitor C1 is completed, the switch K1 is closed, and the switch K3 is opened, at this time, the voltage on the bus capacitor C1 is close to the voltage of the battery pack 103, the power tubes of the bridge arm converter 101 are all in a closed state, almost no current is in the winding inductance of the motor winding 102, and the system is in a ready state.

After the soft start process is completed, the main heating process is started, all the six power tubes of the front bridge arm converter 101 are disconnected, the charge and discharge period of the battery pack 103 is determined, mainly given by a battery pack management system, then the current waveform I=akt+b required to be achieved is obtained, T is time, I is a target equivalent current value, a and b are constants, k is a coefficient, as shown in fig. 15, the charge and discharge period of the battery pack is set to be T, the discharge duration is T0, the charge duration is T-T0, 7 target equivalent current values are selected in the discharge duration T0, the time interval between the two equivalent current values is deltat, the current variation is obtained according to I (t+deltat) -I (T), the duty ratio of a PWM control signal is obtained according to the current variation, the discharge duration corresponds to 7 discharge periods, each discharge period corresponds to the duty ratio of one PWM control signal, 4 target equivalent current values are selected in the charge duration, each charge period corresponds to the duty ratio of one control signal, the battery bridge arm converter is adjusted according to the duty ratio of the PWM control signal so that the battery converter achieves the expected current value in the specific heating stage, and the battery equivalent current value reaches the expected heating stage:

And controlling the discharge energy storage loop and the discharge follow current loop to work for 7 times according to 7 duty ratios corresponding to 7 discharge periods, wherein each time the duty ratio of the lower bridge arm is increased, the discharge current of the battery pack is increased, and the current value of the discharge loop reaches the target current waveform.

And controlling the charging energy storage loop and the charging follow current loop to work for 4 times according to 4 duty ratios corresponding to 4 charging periods, so that the current value of the charging loop reaches the target current waveform.

An embodiment of the present invention provides an energy conversion device, including:

the energy conversion device further includes a controller for:

according to the heating control mode, a bridge arm converter in the battery heating circuit is controlled to charge and discharge the energy storage element and the battery pack so as to heat the battery pack.

The specific control manner of the controller may refer to the above control method, and will not be described herein.

An embodiment of the present application provides a vehicle, including the energy conversion device described in the two embodiments.

The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.

Claims

1. A control method of an energy conversion device, characterized in that the energy conversion device comprises:

the method comprises the following steps:

according to the heating control mode, controlling a bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack so as to heat the battery pack;

when the heating control mode is a high-frequency heating control mode, the controlling the bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack further comprises:

acquiring a charge-discharge period of the battery pack and a target current waveform of the battery heating circuit in the charge-discharge period of the battery pack, wherein the charge-discharge period of the battery pack comprises a charge duration and a discharge duration, the charge duration comprises a plurality of charge periods of the battery heating circuit, and the discharge duration comprises a plurality of discharge periods of the battery heating circuit;

Obtaining a plurality of target equivalent current values corresponding to the target current waveform according to the target current waveform;

and acquiring the duty ratio of the PWM control signal according to the target equivalent current value, and acquiring the number of charging periods contained in the charging duration and the number of discharging periods contained in the discharging duration according to the charging and discharging periods of the battery pack and the number of the target equivalent current value, wherein one target equivalent current value corresponds to one charging period or one discharging period.

2. The control method of claim 1, wherein a first bus end of the bridge arm converter is connected to a positive pole of the battery pack, and a second bus end of the bridge arm converter is connected to a negative pole of the battery pack; the first end of the motor winding is connected with the bridge arm converter, the second end of the motor winding is connected with the first end of the energy storage element, and the second end of the energy storage element is connected with the second converging end of the bridge arm converter to form a battery heating circuit.

3. The control method of claim 1, wherein a first bus end of the bridge arm converter is connected to a first end of the energy storage element, a second bus end of the bridge arm converter is connected to a second end of the energy storage element, a first end of the motor winding is connected to the bridge arm converter, a second end of the motor winding is connected to a first end of the battery pack, and a second end of the battery pack is connected to a second bus end of the bridge arm converter to form a battery heating circuit.

4. A control method according to claim 2 or 3, wherein the heating control mode includes a high-frequency heating control mode and a low-frequency heating control mode;

the vehicle state is a vehicle running state;

the vehicle performance parameter is at least one of a cooling parameter, a withstand voltage flow parameter, an anti-noise parameter and an EMC radiation resistance parameter, wherein the withstand voltage flow parameter is a withstand voltage parameter and a withstand current parameter.

5. The control method according to claim 4, wherein, when the vehicle state is a vehicle running state, acquiring a vehicle state and/or a vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter, comprises:

and when the running state of the vehicle is a parking state, selecting a low-frequency heating control mode or a high-frequency heating control mode.

6. The control method according to claim 4, wherein when the vehicle performance parameter is a cooling parameter, the acquiring the vehicle performance parameter and selecting a heating control mode according to the vehicle performance parameter includes:

Acquiring the cooling parameters and judging whether the cooling parameters meet preset conditions or not;

and when the cooling parameters do not meet preset conditions, selecting a low-frequency heating control mode.

7. The control method according to claim 4, wherein when the vehicle performance parameters are a withstand voltage parameter and a withstand current parameter, the acquiring the vehicle state and/or the vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter, comprises:

the withstand voltage parameter and the current withstand parameter are obtained, the withstand voltage parameter is compared with a preset voltage value, and the current withstand parameter is compared with a preset current value;

and when the withstand voltage parameter is not more than a preset voltage value or the withstand current parameter is not more than a preset current value, selecting a high-frequency heating control mode.

8. The control method according to claim 4, wherein when the vehicle performance parameter is an anti-noise parameter, the acquiring the vehicle state and/or the vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter, includes:

Acquiring the anti-noise parameter, and comparing the anti-noise parameter with a preset decibel value;

and when the anti-noise parameter is not larger than a preset decibel value, selecting a high-frequency heating control mode.

9. The control method according to claim 4, wherein when the vehicle performance parameter is an EMC emission resistance parameter, the acquiring the vehicle state and/or the vehicle performance parameter, and selecting a heating control mode according to the vehicle state and/or the vehicle performance parameter, comprises:

10. The control method of claim 4, wherein when the heating control mode is a low frequency heating control mode, the controlling the bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack further comprises:

Acquiring a charge-discharge period of the battery pack and a target equivalent current value of the battery heating circuit;

acquiring a charge-discharge period of the battery heating circuit according to the charge-discharge period of the battery pack, and acquiring a duty ratio of a PWM control signal according to a target equivalent current value of the battery heating circuit;

the controlling the bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack so as to heat the battery pack includes:

and controlling the switch of the upper bridge arm and the lower bridge arm of the bridge arm converter according to the switch period of the battery heating circuit and the duty ratio of the PWM control signal, and regulating the current value flowing through the battery heating circuit so as to regulate the heat generated by the internal resistance of the battery pack.

11. The control method according to claim 10, wherein the obtaining the switching period of the battery heating circuit according to the charge-discharge period of the battery pack includes:

setting a charge-discharge period of the battery pack as a charge-discharge period of the battery heating circuit;

the obtaining the duty ratio of the PWM control signal according to the target equivalent current value of the battery heating circuit includes:

12. The control method according to claim 1, wherein obtaining the number of charge cycles included in the charge duration and the number of discharge cycles included in the discharge duration from the number of charge cycles of the battery pack and the target equivalent current value includes:

T＝T1+T2；

T1＝N1×t1；

T2＝N2×t2；

N＝N1+N2；

13. The control method according to claim 1, wherein the obtaining the duty ratio of the PWM control signal according to the target equivalent current value of the battery heating circuit includes:

14. The control method of claim 13, wherein the controlling the bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack to achieve heating of the battery pack comprises:

15. The control method of claim 14, wherein the controlling the switching of the upper and lower legs of the leg converter according to the number of charging cycles, the number of discharging cycles, and the duty cycle of the PWM control signal, adjusts the current value flowing through the battery heating circuit, comprises:

And controlling the switching of the upper bridge arm and the lower bridge arm of the bridge arm converter in each charging period and each discharging period according to the duty ratio of the PWM control signal, and regulating the current value flowing through the battery heating circuit to be a target equivalent current value.

16. The control method as set forth in claim 15, further comprising: according to the duty ratio of the PWM control signal, the switching of the upper and lower bridge arms of the bridge arm converter in each charging period and each discharging period is controlled, and the current value flowing through the battery heating circuit is adjusted to be the target equivalent current value, and then the method further comprises:

17. An energy conversion device, characterized in that the energy conversion device comprises:

The energy conversion device further includes a controller for:

according to the heating control mode, controlling a bridge arm converter in the battery heating circuit to charge and discharge the energy storage element and the battery pack so as to heat the battery pack

When the heating control mode is a high-frequency heating control mode, the controller is further configured to:

18. A vehicle, characterized in that it comprises the energy conversion device according to claim 17.