CN109291914B

CN109291914B - Voltage protection method of hybrid electric vehicle

Info

Publication number: CN109291914B
Application number: CN201710613690.1A
Authority: CN
Inventors: 靳超; 张洪建; 纪秉男; 韩光辉; 张广利; 张春敏; 李雪莲
Original assignee: Zhengzhou Yutong Bus Co Ltd
Current assignee: Yutong Bus Co Ltd
Priority date: 2017-07-25
Filing date: 2017-07-25
Publication date: 2020-06-30
Anticipated expiration: 2037-07-25
Also published as: CN109291914A

Abstract

The invention relates to a voltage protection method of a hybrid electric vehicle.A vehicle control unit (hereinafter referred to as a vehicle ECU) monitors bus voltage u in real time and judges a vehicle driving mode at the same time; under different driving modes, different control strategies and measures are adopted for the overvoltage or undervoltage of the bus, and the bus voltage u is ensured to be within a controllable range. The method can automatically solve the problem of bus over/under running on the premise of normal running.

Description

Voltage protection method of hybrid electric vehicle

Technical Field

The invention relates to a voltage protection method of a hybrid electric vehicle, and belongs to the field of new energy vehicles.

Background

As shown in fig. 1, the hybrid electric vehicle is based on two power platforms, namely an engine (6) and a driving motor (10), and is purely driven by the driving motor (10) at low speed, so that the engine (6) is prevented from working in a low-efficiency area, and is driven by the engine (6) at high speed or driven in parallel, so that the hybrid electric vehicle is more energy-saving than a traditional vehicle and is more easily accepted by the public; the driving system adopts permanent magnet synchronous motors in the market at present, the actual road condition faced by the whole vehicle in the driving process is complex, and the permanent magnet synchronous motors have the back electromotive force generated during rotation due to the fact that the rotors are permanent magnets and need to be subjected to weak magnetic control, so that the fluctuation of bus voltage is large. Therefore, a sophisticated voltage protection strategy is indispensable for this type of vehicle.

Fig. 1 shows a deep hybrid vehicle type (hereinafter referred to as deep hybrid) widely used in the current market, which employs a hybrid system, an engine (6) is connected to an ISG motor (8) through a normally closed clutch, the engine and the ISG motor keep the same rotating speed, the ISG motor (8) and a driving motor (10) are connected through a separable clutch, an energy system employs a power battery or a super capacitor for power supply, a basic driving strategy is that when the vehicle is started, the clutch is separated, the engine (6) and the ISG motor (8) are stopped, only the driving motor (10) works, and pure electric driving is performed, when the vehicle speed is higher than a certain speed, the ISG motor (8) starts the engine (6) to control the rotating speed to be close to the driving motor (10), and then the clutch is closed to perform the hybrid mode work.

The current adopted voltage protection strategy is basically to set an over-voltage point and an under-voltage point, the power is cut off and an alarm is given out when the voltage is over-voltage, the power is stopped and electricity is generated by early warning when the voltage is under-voltage, or a power reduction point and a buffer process are additionally set, and the impact on each part of a power system caused by abnormal voltage fluctuation is reduced as much as possible.

Disclosure of Invention

The invention aims to provide a voltage protection method of a hybrid electric vehicle, which is used for solving the problem that the prior art cannot adopt effective measures to solve the problem of bus overvoltage/undervoltage on the premise of ensuring normal driving.

In order to achieve the above object, the scheme of the invention comprises:

the invention relates to a voltage protection method of a hybrid electric vehicle, which comprises the following steps:

1) detecting bus voltage u and vehicle speed v, and judging a vehicle driving mode, wherein the vehicle driving mode comprises a pure electric mode and a hybrid mode;

2) when the whole vehicle works in a pure electric mode and the bus voltage u is less than the undervoltage early warning point umin, at least controlling the ISG motor to generate electricity;

3) when the whole vehicle works in a pure electric mode and the bus voltage u is greater than the overvoltage early warning point umax, at least controlling the engine to stop working;

4) when the whole vehicle works in a hybrid mode and the bus voltage u is less than the undervoltage early warning point umin, at least controlling the engine to increase the load and controlling the driving motor to reduce the load;

5) when the whole vehicle works in a hybrid mode and the bus voltage u is greater than the overvoltage early warning point umax, at least controlling the engine to reduce the load and controlling the driving motor to increase the load.

Further, the whole vehicle driving mode also comprises an extreme mode;

in the extreme mode of the operation,

a) when the vehicle enters a high-speed driving road condition and the bus voltage u is greater than the overvoltage early warning point umax, at least controlling the engine to stop working;

b) when the vehicle enters a high-speed driving road condition and the bus voltage u is less than the undervoltage early warning point umin, at least controlling the ISG motor to generate electricity;

c) when the whole vehicle enters a long-time downhill road condition and the bus voltage u is greater than the overvoltage early warning point umax, at least turning off the engine and the driving motor, and sending an overspeed alarm to a driver;

d) when the whole vehicle enters a long-time downhill road condition and when the bus voltage u is smaller than the undervoltage early warning point umin, the driving motor is at least enabled to work in a sliding feed state.

Further, in step 1), the driving mode of the whole vehicle is judged according to the vehicle speed v:

the triggering vehicle speed for converting the pure electric mode into the hybrid mode is v 1;

when the vehicle speed v is less than the hybrid motion triggering vehicle speed v1, judging that the whole vehicle is in a pure electric driving mode;

and when the vehicle speed v is greater than the hybrid triggering vehicle speed v1, judging that the whole vehicle is in a hybrid mode.

Further, in the above-mentioned case,

the triggering speed for converting the hybrid moving mode into the extreme mode is vmax;

when the vehicle speed v1 is greater than the hybrid triggering vehicle speed v1 and less than vmax, the whole vehicle is judged to be in the hybrid mode;

and when the vehicle speed v is greater than the trigger vehicle speed vmax of the extreme mode, judging that the whole vehicle is in the extreme mode.

Further, the triggering vehicle speed vmax of the extreme mode is the vehicle speed of the driving motor working at the peak rotating speed.

Further, the high-speed driving road condition or the long-term downhill road condition of the vehicle is judged according to the vehicle speed and the accelerator signal feedback of the driver:

if the vehicle speed v is maintained at the trigger vehicle speed vmax and the driving motor works under the driving instruction, judging that the road condition of the vehicle is a high-speed driving road condition at the moment;

and if the vehicle speed v is greater than the trigger vehicle speed vmax and the driving motor works under a power generation instruction, judging that the vehicle road condition is a long-time downhill road condition at the moment.

Further, the ISG motor is controlled to generate power, and the output torque value of the ISG motor is calculated according to the fact that the instantaneous power utilization of the whole vehicle is multiplied by a coefficient and then divided by the current rotating speed.

Further, the undervoltage warning point umin is greater than the undervoltage fault point, and the overvoltage warning point umax is less than the overvoltage fault point.

Further, setting voltage return difference values a and b; after the voltage protection step is implemented, when the bus voltage u is greater than umin + a or u is less than umax-b, the corresponding voltage protection step exits.

The invention has the beneficial effects that:

according to the running characteristics of the vehicle in different driving modes, effective measures are respectively adopted to carry out power generation boosting or power consumption voltage reduction, the problem of bus over/under voltage is effectively solved on the premise of ensuring normal running, the system is protected to run automatically, and a driver does not need to take specific measures generally.

Furthermore, the extreme mode is added aiming at the high-speed extreme state, and different voltage stabilization measures are taken based on different road conditions in the extreme mode, so that the voltage stabilization in the extreme mode is more rapid and effective.

Meanwhile, the method intervenes to take processing measures before the over/under voltage point arrives by setting the under voltage early warning point slightly larger than the under voltage point and the over voltage early warning point slightly smaller than the over voltage point, and cannot influence the vehicle and normal driving.

Drawings

FIG. 1 is a hybrid vehicle powertrain configuration diagram;

FIG. 2 is a voltage protection strategy flow diagram;

fig. 3 is a voltage protection strategy flow diagram with extreme modes.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The configuration diagram of a hybrid electric vehicle power system shown in fig. 1 comprises a whole vehicle ECU (1), an engine ECU (2), a motor controller (3), an energy storage device management system (4), an energy storage device (5), an engine (6), a normally closed clutch (7), an ISG motor (8), a clutch (9), a driving motor (10), a transmission system (11) and a transmission shaft (12).

Voltage protection method of hybrid vehicle embodiment 1

The voltage protection method of the hybrid electric vehicle shown in fig. 2 comprises the following steps:

1) after the ECU (1) of the whole vehicle is electrified, the over/under voltage early warning parameter values umax and umin are initialized; the umax value is set to be lower than the maximum voltage allowed by the bus, and the umin value is set to be higher than the minimum voltage allowed by the bus (since the super capacitor can be put to 0V theoretically, when the energy storage device is a super capacitor, the voltage can be set to be the minimum voltage of the motor controller). The initialization state triggers a vehicle speed parameter value v 1; where v1 is the switching speed at which the electric-only mode is switched to the hybrid mode. Initializing voltage return difference values a and b; wherein, the symbols a and b are both positive.

2) Detecting a bus voltage u value and a real-time vehicle speed v value; and judging the vehicle running mode according to the vehicle speed v, wherein the vehicle is in pure electric drive when v is more than or equal to 0 and less than or equal to v1, the vehicle is in parallel hybrid drive of an engine and a driving motor when v is more than v1, and the bus voltage u value is judged after the vehicle running mode is judged.

3) When the vehicle speed v is in the interval [0, v1], the clutch (9) is disconnected at the moment, the vehicle runs in a pure electric driving mode, if the value u is judged to be umin < u < umax, the step 2) is returned, and the whole vehicle runs normally; if the u value is judged to be not more than umin, the whole vehicle ECU (1) sends an ISG motor constant torque power generation instruction to the motor controller (3) to enable the ISG motor (8) to generate power in constant torque, the torque value is determined according to the calculated required power of the whole vehicle, and when u is more than umin + a, the processing is finished and the step 2 is returned; and if the u value is judged to be more than or equal to umax, the whole vehicle ECU (1) sends a fuel cut-off instruction to the engine ECU (2) to stop the engine from injecting fuel, and simultaneously sends an ISG motor constant torque driving instruction to the motor controller (3) to drive the engine (6) as a load by the ISG motor (8) to forcibly consume power, and when u is less than umax-b, the processing is finished and the step 2 is returned.

4) When the vehicle speed v is in a range (v1, +/-infinity), the ISG motor (8) starts the engine (6) and controls the rotating speed to be close to the rotating speed of the driving motor (10), then the clutch (9) is closed, the hybrid mode is started, and at the moment, the loads of the engine and the driving motor are distributed according to the external characteristic curves of the engine and the driving motor according to the optimal efficiency through a whole vehicle control strategy. If the u value is judged to be umin less than u and less than umax, returning to the step 2) and normally operating the whole vehicle; if the u value is judged to be more than or equal to umax, the whole vehicle ECU (1) recalculates the load proportion of the distributed engine and the driving motor, increases the load of the driving motor (10), reduces the load of the engine (6), and ends the processing and returns to the step 2 when u is less than umax-b; and if the u value is judged to be less than or equal to umin, reducing the load of the driving motor (10), increasing the load of the engine (6), simultaneously sending an ISG motor small-torque power generation command to the motor controller (3) to enable the ISG motor (8) to generate power with small torque, calculating the torque value according to the instantaneous power consumption of the whole vehicle multiplied by the coefficient divided by the current rotating speed, and ending the processing and returning to the step 2 when u is more than umin + a.

Voltage protection method embodiment 2 of hybrid vehicle

The voltage protection method of the hybrid electric vehicle shown in fig. 3 includes the following steps:

1) after the ECU (1) of the whole vehicle is electrified, the over/under voltage early warning parameter values umax and umin are initialized; the umax value is set to be lower than the maximum allowable voltage of the bus, and the umin value is set to be higher than the minimum allowable voltage of the bus (since the super capacitor can be put to 0V theoretically, when the energy storage device is a super capacitor, the voltage can be set to be the minimum working voltage of the motor controller). The initialization state triggers the values of the vehicle speed parameter values v1, vmax; wherein v1 is the switching speed of the pure electric mode to the hybrid mode, and vmax is the maximum speed per hour (corresponding to the peak rotating speed of the motor) of the whole vehicle. Initializing voltage return difference values a and b; wherein, the symbols a and b are both positive.

2) Detecting a bus voltage u value and a real-time vehicle speed v value; and judging the running mode of the vehicle according to the vehicle speed v, wherein the vehicle is in pure electric drive when v is more than or equal to 0 and less than or equal to v1, the vehicle is in parallel hybrid drive of an engine and a driving motor when v1 and v are more than or equal to vmax, the vehicle enters an extreme mode when v is more than or equal to vmax, and the bus voltage u value is judged after the running mode of the vehicle is judged.

4) When the vehicle speed v is in an interval (v1, vmax), the ISG motor (8) starts the engine (6) and controls the rotating speed to be close to the rotating speed of the driving motor (10), then the clutch (9) is closed, the hybrid mode is entered, and at the moment, the loads of the engine and the driving motor are distributed according to the external characteristic curves of the engine and the driving motor according to the optimal efficiency through a whole vehicle control strategy. If the u value is judged to be umin less than u and less than umax, returning to the step 2) and normally operating the whole vehicle; if the u value is judged to be more than or equal to umax, the whole vehicle ECU (1) recalculates the load proportion of the distributed engine and the driving motor, increases the load of the driving motor (10), reduces the load of the engine (6), and ends the processing and returns to the step 2 when u is less than umax-b; and if the u value is judged to be less than or equal to umin, reducing the load of the driving motor (10), increasing the load of the engine (6), simultaneously sending an ISG motor small-torque power generation command to the motor controller (3) to enable the ISG motor (8) to generate power with small torque, calculating the torque value according to the instantaneous power consumption of the whole vehicle multiplied by the coefficient divided by the current rotating speed, and ending the processing and returning to the step 2 when u is more than umin + a.

5) When the vehicle speed v is in the range [ vmax, infinity ]), the spindle rotating speed of the driving motor (10) is equal to or exceeds the peak rotating speed of the driving motor (10), the vehicle runs in an extreme mode, and the whole vehicle ECU (1) feeds back and judges the road condition of the whole vehicle according to the vehicle speed v and the accelerator signal of a driver. If the vehicle speed v is maintained at about vmax (namely the vehicle speed fluctuates within a certain range above and below vmax), and the driving motor (10) works in a weak magnetic driving state, the whole vehicle is judged to enter a high-speed driving road condition, and if the value u is judged to be umin < u < umax, the step 2) is returned, and the whole vehicle normally runs; if the u value is judged to be more than or equal to umax, the whole vehicle ECU (1) sends a driving motor electrical angle correction instruction to the motor controller (3) to enable the driving motor (10) to carry out electrical angle correction, the clutch (9) is separated, meanwhile, a fuel cut-off instruction is sent to the engine ECU (2) to enable the engine (6) to stop fuel injection, the ISG motor (8) is made to drag the engine (6) to enter a power consumption mode through the motor controller (3), and when u is less than umax-b, the processing is finished and the step 2 is returned; and if the u value is judged to be not more than umin, the whole vehicle ECU (1) sends an ISG motor small-torque power generation instruction to the motor controller (3) to enable the ISG motor (8) to generate power with small torque, the torque value is calculated according to the fact that the instantaneous power consumption of the whole vehicle is multiplied by the coefficient and divided by the current rotating speed, and when u is more than umin + a, the processing is finished and the step 2 is returned. If the vehicle speed v is greater than vmax and the driving motor (10) works in a weak magnetic power generation state, judging that the whole vehicle enters a long-time downhill road condition, judging that the u value is umin < u < umax at the moment, returning to the step 2) and normally operating the whole vehicle; if the value u is judged to be not more than umin, the whole vehicle ECU (1) sends a command of increasing the feed torque of the driving motor to the motor controller (3) to accelerate energy storage, and when u is more than umin + a, the processing is finished and the step 2 is returned; and if the value u is judged to be more than or equal to umax, the whole vehicle ECU (1) sends a standby instruction to the motor controller (3), the motor controller (3) turns off the IGBT with zero torque, meanwhile, the whole vehicle ECU (1) sends an oil cut-off instruction to the engine ECU (2) to stop the engine from spraying oil, in addition, an instrument panel displays overspeed alarm to prompt a driver to carry out deceleration operation, power consumption processing is carried out after the vehicle speed is reduced back to vmax, and when u is less than umax-b, the processing is finished and the step 2 is returned.

The specific embodiments are given above, but the present invention is not limited to the described embodiments. The basic idea of the present invention lies in the above basic scheme, and it is obvious to those skilled in the art that various methods, models, formulas and parameters can be designed without any creative effort according to the teaching of the present invention. Variations, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the invention, and still fall within the scope of the invention.

Claims

1. A voltage protection method of a hybrid electric vehicle is characterized by comprising the following steps:

2. The voltage protection method of a hybrid electric vehicle according to claim 1, wherein the entire vehicle drive mode further includes an extreme mode;

in the extreme mode of the operation,

3. The voltage protection method of the hybrid electric vehicle according to claim 1, wherein in step 1), the vehicle driving mode is judged according to vehicle speed v:

4. The voltage protection method of a hybrid vehicle according to claim 2,

5. The voltage protection method for a hybrid vehicle according to claim 4, wherein the trigger vehicle speed vmax of the extreme mode is a vehicle speed at which the drive motor operates at a peak rotational speed.

6. The voltage protection method of the hybrid electric vehicle as claimed in claim 2, wherein the high-speed driving road condition or the long-term downhill road condition of the vehicle is judged according to the vehicle speed and the driver's throttle signal feedback:

7. The voltage protection method of a hybrid electric vehicle according to claim 1 or 2, wherein the ISG motor is controlled to generate power, and an output torque value of the ISG motor is calculated according to the instantaneous power consumption of the entire vehicle multiplied by a coefficient divided by the current rotation speed.

8. The voltage protection method of a hybrid vehicle according to claim 1 or 2, characterized in that the undervoltage warning point umin is greater than the undervoltage fault point, and the overvoltage warning point umax is less than the overvoltage fault point.

9. The voltage protection method of a hybrid vehicle according to claim 1 or 2, characterized in that voltage return difference values a and b are set; after the voltage protection step is implemented, when the bus voltage u is greater than umin + a or u is less than umax-b, the corresponding voltage protection step exits.