CN107645259B

CN107645259B - Driving motor torque closed-loop control method for electric automobile

Info

Publication number: CN107645259B
Application number: CN201710619736.0A
Authority: CN
Inventors: 文彦东; 刘志强; 赵慧超; 暴杰; 张颖; 郭璐璐; 胡晶; 胡波
Original assignee: FAW Group Corp
Current assignee: FAW Group Corp
Priority date: 2017-07-26
Filing date: 2017-07-26
Publication date: 2021-03-05
Anticipated expiration: 2037-07-26
Also published as: CN107645259A

Abstract

The invention relates to a torque closed-loop control method of a drive motor for an electric vehicle, which consists of a vehicle control unit, a motor controller, an inverter switch circuit, a permanent magnet synchronous motor, a position sensor and a three-phase current sensor. The short-circuit control command (ASC_Enable) and the mechanical speed of the motor determine whether active short-circuit control is performed, and the output torque of the permanent magnet synchronous motor is calculated by the active short-circuit method, which does not depend on motor parameters such as stator resistance and DC axis voltage, and the calculated value is more accurate; motor The controller then performs PI adjustment and control according to the torque command sent by the vehicle control unit and the torque online calculation value, which can improve the accuracy of the absolute value of the torque output and speed up the torque closed-loop response time.

Description

Driving motor torque closed-loop control method for electric automobile

Technical Field

The invention belongs to the technical field of motor drive control, and particularly relates to a drive motor torque closed-loop control method for an electric automobile.

Background

The driving motor is a main driving source of the electric automobile, and for the plug-in hybrid power of the hybrid power automobile, the motor and the engine jointly drive the whole automobile; for a pure electric vehicle, the motor is the only driving source. The permanent magnet synchronous motor is widely applied to electric automobiles, and has the advantages of high efficiency, high power density and torque density, more suppliers and rich rare earth resources in China. The motor adopts a torque control mode in the whole vehicle, and the motorThe control modes are more, such as rotating speed, torque, voltage and power, but the torque control mode is mainly used. The core of the torque control method is MTPA (maximum torque current ratio) and flux weakening control. The current torque control method has some problems, namely that the torque is greatly influenced by temperature, the torque is composed of two parts of electromagnetic torque and reluctance torque, and the electromagnetic torque and the permanent magnet flux linkage form y_mThe size is proportional. The output torque of the motor is reduced at high temperature, and the output torque is increased at low temperature; secondly, the temperature of the rotor is difficult to measure, the permanent magnet flux linkage corresponds to the temperature of the rotor one by one, and the temperature of the rotor cannot be directly measured; the cost is high and the arrangement space is limited due to the built-in temperature sensor; the method is based on motor body parameters and a motor structure, and has the advantages of complex algorithm, large calculation amount and poor consistency; and thirdly, the influence on the whole vehicle is mainly reflected in the influence on the torque distribution accuracy of the whole vehicle. The high and low temperature starting characteristics are different. The braking force distribution and the braking energy recovery effect are influenced. Therefore, the electromagnetic torque of the permanent magnet synchronous motor is greatly influenced by the temperature, the higher the temperature is, the lower the output is, and the higher the output is otherwise; the permanent magnet material has great sensitivity to temperature, and when the temperature is increased by 100 ℃ in the case of the neodymium iron boron material, the magnetic flux of each air gap of the motor is reduced by about 12.6%, and the electromagnetic torque is reduced by 12.6% under the condition of the same armature current. The electromagnetic torque is directly related to the rotor temperature, but the rotor temperature cannot be directly measured, and the rotor temperature model has the advantages of complex algorithm, poor consistency and low precision. The actual output torque of the motor is greatly influenced by the temperature.

Application No. 201611002479.8 discloses a "permanent magnet synchronous motor torque control method", which provides estimation and predictive control based on a driving torque demand, and the motor torque predictive control flow is as follows: firstly, converting a torque reference value into a motor stator vector current reference value according to a motor equation; establishing a relational expression between the switching state of the three-phase inverter and the output vector voltage; estimating the current value of the next time domain; the optimal switch combination state acts on the inverter driving motor; the torque control method is to collect pedal information of a driver and wheel rotating speed information and calculate a driving torque value required by the vehicle according to a mechanical external characteristic curve of the permanent magnet synchronous motor. The method uses the d-axis current as zero control, is only suitable for a surface-mounted permanent magnet synchronous motor and is not suitable for an embedded permanent magnet synchronous motor; in addition, the changes of the motor quadrature-direct axis inductance parameter and the stator resistance are not considered when estimating the next time domain current value, so the accuracy of torque demand estimation and control is deteriorated after the temperature changes.

Application No. 200810127261.4 discloses a method of controlling motor torque in a hybrid electric vehicle, which provides a method of controlling motor torque in a hybrid electric vehicle that can reduce current control map formation time and simplify a control algorithm by providing torque control compensation logic for temperature variation of a hybrid electric vehicle motor. The method needs to take the motor temperature as an input condition, but the motor temperature cannot be directly measured, so that the realization and control effects of the algorithm are influenced.

Application number 201510404364.0 discloses a method and a device for suppressing harmonic current of a permanent magnet synchronous motor, which are characterized in that a d-axis current deviation and/or a q-axis current deviation of harmonic current to be suppressed are obtained, a Fourier analysis method is adopted to extract harmonic current signals to be suppressed, filtering and superposition are performed, meanwhile, angle compensation is performed on the electrical angle of the motor, signal reconstruction is performed together with the harmonic current signals, and output of a repetitive controller is obtained. The method can well inhibit the magnitude of harmonic current, thereby achieving the purpose of inhibiting torque ripple.

Application No. 201610511750.4 discloses a "permanent magnet synchronous motor control method and system", which calculates a feedback exciting current and a feedback torque current of a motor according to an output current by detecting the output current of a motor stator; then calculating the given torque current and the given exciting current of the motor; and substituting the feedback exciting current, the feedback torque current, the given torque current and the given exciting current into a current loop, and calculating the exciting voltage and the torque voltage of the current loop. And converting the excitation voltage and the torque voltage into driving signals to be applied to the motor, and sampling the feedback excitation current and the given torque current on the motor at the moment. And repeatedly bringing the sampled feedback exciting current and the given torque current into the process, and sampling new feedback exciting current and the given torque current until the torque current and the exciting current of the motor are dynamically stable. Therefore, the calculation process adopts an iterative mode, only a part of the MTPA formula is selected, the MTPA (optimal torque control) effect can be achieved, the calculation amount of the program is reduced, and the chip utilization efficiency of the motor related system is improved.

The application number 201310260278.8 discloses a direct torque control system and method for a permanent magnet synchronous motor for an electric vehicle, which includes detecting three-phase current and voltage output by an inverter and direct current bus voltage of the inverter, obtaining electromagnetic torque, stator flux linkage and sector theta where the stator flux linkage is located in the current state through a torque, flux linkage and theta calculation unit, performing composite control on a speed ring by adopting wavelet multi-resolution control and an integral structure, comparing the calculated flux linkage and torque with a given flux linkage and a given torque signal output by a composite control regulator, outputting a current flux linkage torque error state, determining a voltage vector to be selected together with the sector where the flux linkage is located, further determining the switching state of the inverter, and controlling the operation of the permanent magnet synchronous motor.

As described above, the above-mentioned patent proposes a torque control method from different points of view and aspects, but the case where the torque output is reduced due to the increase in the temperature of the rotor caused by the long-time operation is not considered sufficiently, and the problems such as insufficient torque output or reduced braking capability may occur in the actual application process.

Disclosure of Invention

The invention aims to provide a driving motor torque closed-loop control method for an electric automobile, aiming at the defects of the prior art, which does not depend on motor parameters such as stator resistance, quadrature axis voltage and the like, and has more accurate calculated value; the motor controller carries out PI regulation control according to a torque command and a torque online calculated value sent by a finished automobile control unit, so that the accuracy of a torque output absolute value can be improved, and the torque closed-loop response time is shortened.

The invention is realized by the following technical scheme:

a closed-loop control method for the torque of a driving motor for an electric automobile is characterized by comprising a whole automobile control unit, a motor controller, an inverter switch circuit, a permanent magnet synchronous motor, a position sensor and a three-phase current sensor;

the whole vehicle control unit sends out three-phase short circuit control T to the motor controller through the CAN bus according to the working mode of the whole vehicle_pscAnd torque command T_cmd；

The motor controller comprises a CAN command decomposition unit, a torque PI regulation module, a quadrature axis current command generation unit, a quadrature axis current PI regulation module, a voltage decoupling control unit, a space vector modulation unit, a position and rotating speed processing unit, a CLARK&The device comprises a PARK conversion unit, a torque on-line calculation module and a torque limit value generation module; the motor controller controls T according to the three-phase short circuit sent by the control unit of the whole vehicle_pscJudging whether to carry out active short circuit control according to the mechanical rotating speed omega of the motor, and simultaneously satisfying T_pscIf the rotating speed of the motor is 1 and the mechanical rotating speed of the motor exceeds the rotating speed of an inflection point, the condition is met, an active short circuit PWM signal is output to an inverter switch circuit, and three IGBTs of an upper bridge arm or a lower bridge arm of a three-phase full bridge are controlled to be closed simultaneously; otherwise, if the condition is not met, calculating the duty ratio of the three-phase PWM signal according to the quadrature axis reference voltage and the position signal, and controlling the IGBT to carry out switching operation; the motor controller sends a torque instruction T to a vehicle control unit_cmdAnd the calculated value T output by the torque online calculation module_onlineAnd the output torque is input to a torque PI adjusting module, so that the output torque of the permanent magnet synchronous motor reaches a target value.

The torque PI adjusting module comprises an addition module, an anti-saturation PI structural unit and an amplitude limiter; wherein the addition module generates delta e by making a difference between the two inputs. When the proportional term and the integral term are input into the anti-saturation PI structural unit, the proportional term and the integral term are both effective under the condition that the anti-saturation PI structural unit is not saturated, namely, the anti-saturation integral loop is effective under the condition that the anti-saturation PI structural unit is saturated, namely, the eo and the out are not equal. The anti-saturation PI structural unit outputs out, and the out and the torque instruction T_cmdAdding again, inputting the sum of the two into a limiter, and outputting a torque reference value T after limiting^*(ii) a Wherein, the analytic formula of the anti-saturation PI structure is as follows:

eo＝out{out(t)＝K_p·e(t)+K_i∫e(t)}

wherein eo is the calculated output value of PI, out is the limited output value, K_pIs a proportionality coefficient, K_iIs an integral coefficient; e _ sat is the maximum amplitude limiting output value when the anti-saturation PI structural unit is saturated; e (t) is the deviation value at the time t, and out (t) is the output value of the anti-saturation PI structure unit at the time t;

the rectangular-axis current instruction generating unit generates a rectangular-axis current instruction according to a torque reference value T^*A rectangular axis current command value is obtained by a table look-up, and a line which can be connected with a point of Maximum torque obtained by minimum current in a current torque characteristic curve is a Maximum torque current ratio curve (MTPA)^*The index is output as a rectangular axis current instruction value;

the quadrature axis current PI adjusting module is used for adjusting a command value i according to a quadrature axis current instruction_{d_cmd}And quadrature axis current command value i_{q_cmd}And CLARK&Direct-axis current feedback value i output by PARK conversion unit_dfeedbackAnd quadrature axis current feedback value i_qfeedbackPerforming PI operation to obtain the reference values i of the direct-axis current and the quadrature-axis current_d ^*And i_q ^*The internal structures of the quadrature axis current PI regulation module and the torque PI regulation module are the same, and only the inputs are different.

The voltage decoupling control unit performs decoupling according to a steady-state voltage equation and outputs a quadrature axis voltage reference value u_d ^*And u_q ^*The concrete formula is as follows:

u_d ^*＝Ri_d ^*-pωL_qi_q ^* (2)

u_q ^*＝Ri_q ^*+pω(L_di_d ^*+ψ_m) (3)

wherein, R is the stator resistance,p is the number of pole pairs of the motor rotor, omega is the mechanical rotating speed of the motor, L_dIs a direct axis inductor, L_qIs a quadrature axis inductor, i_d ^*Is a direct-axis current reference value, i_q ^*Is a quadrature axis current reference value, u_d ^*For the direct-axis voltage decoupling value, u_q ^*For quadrature-axis voltage decoupling value, #_mIs a permanent magnet flux linkage.

The space vector modulation unit controls T according to the three-phase short circuit sent by the whole vehicle control unit_pscJudging whether to carry out active short circuit control according to the mechanical rotating speed omega of the motor, and simultaneously satisfying T_pscIf the number is 1 and the mechanical rotating speed of the motor exceeds the rotating speed of an inflection point, the condition is met, an active short circuit PWM signal is output to an inverter switch circuit, and three IGBTs of an upper bridge arm or a lower bridge arm of the inverter switch circuit are controlled to be closed at the same time; otherwise, if the condition is not met, calculating the duty ratio of the three-phase PWM signal according to the quadrature axis reference voltage and the position signal, and controlling the IGBT to carry out switching operation;

the position and rotation speed processing unit calculates the rotor position theta and the mechanical rotation speed omega of the motor according to the output signal of the position sensor;

the CLARK&The PARK conversion unit receives the three-phase alternating current i detected by the current sensor_a、i_b、i_cAnd the position signal theta output by the position and rotating speed processing unit is converted into a direct-axis current i under a rotating coordinate system according to a formula (4), a formula (5) and a formula (6)_dQuadrature axis current i_q；

The CLARK transformation formula is as follows:

i_α＝i_a (4)

the PARK transformation formula is as follows:

wherein i_α、i_βIs alpha in a stationary coordinate systemBeta axis current; i.e. i_a、i_b、i_cIs a three-phase alternating current; theta rotor position electrical angle; i.e. i_d、i_qThe direct axis current and the quadrature axis current under the rotating coordinate system.

The torque online calculation module comprises an alternating current phase current amplitude calculation unit, a permanent magnet flux linkage table look-up module, a quadrature axis inductance table look-up unit and a torque calculation unit; the alternating-current phase current amplitude calculation unit calculates the alternating-current phase current amplitude according to a formula (7) and outputs the alternating-current phase current amplitude to the permanent magnet flux linkage table look-up module;

wherein i_sIs the stator phase current magnitude.

The permanent magnet flux linkage table look-up module is used for looking up a table according to the alternating current phase current amplitude to obtain a permanent magnet flux linkage value; the rectangular-axis inductance lookup unit obtains the rectangular-axis and rectangular-axis inductances L according to the rectangular-axis current lookup table_dAnd L_q(ii) a The torque calculation unit calculates according to a permanent magnet synchronous motor torque formula (8).

Wherein p is the number of pole pairs of the motor rotor; t is_eIs an electromagnetic torque;

in the torque formula (8), the rectangular-to-rectangular axis current is obtained through calculation of a CLARK & PARK conversion unit, the rectangular-to-rectangular axis inductance and the rectangular-to-rectangular axis inductance are obtained through a rectangular-to-rectangular-axis inductance look-up table unit, p is the number of pole pairs of a motor rotor and is a constant, the permanent magnet flux linkage is measured according to the formulas (2) and (3), and under the condition of three-phase short circuit of the motor, the rectangular-to-rectangular axis voltage is zero if the tube voltage drop of a power module is

When the mechanical rotation speed omega of the motor approaches infinity，i_qApproaches zero, i_dIs approximately equal to i_sThen, there is,

ψ_m≈-L_di_s (10)

therefore, the corresponding relation between the permanent magnet flux linkage and the stator phase current amplitude can be calibrated off line at different temperatures, the calibration is stored as a table after being completed, the table takes the stator phase current amplitude as an index and outputs a permanent magnet flux linkage numerical value, and the permanent magnet flux linkage numerical value is brought into a formula (8), so that the output torque of the permanent magnet synchronous motor can be calculated on line. In the rectangular-axis inductance look-up table unit, the rectangular-axis inductance is a function of the current of the rectangular axis, the corresponding relation between the rectangular-axis inductance and the current of the rectangular axis can be obtained through finite element simulation software, and the quadrature-axis inductance can be obtained in the same way;

the torque limit value generation module consists of a maximum electric data table, a maximum power generation data table and a data selection unit; looking up a maximum electric data table and a maximum power generation data table according to the mechanical rotating speed omega of the motor and the voltage of the direct-current bus, judging whether the motor is in an electric or power generation state, and outputting a maximum torque output limit value T by a data selection unit_limit；

The inverter switching circuit comprises six switching elements, wherein the switching elements are Insulated Gate Bipolar Transistors (IGBT) and are used for executing PWM signals sent by the motor controller and controlling the corresponding switching elements to execute switching actions;

the permanent magnet synchronous motor is a three-phase permanent magnet synchronous motor, is a controlled object and is controlled by an inverter switch circuit;

the position sensor is a rotary transformer or an absolute position photoelectric encoder and is used for detecting the absolute position of a motor rotor;

the three-phase current sensor is a non-contact current sensor based on a Hall effect or a contact current sensor based on a principle of generating voltage by using a resistor connected in a phase line in series, and is used for detecting three-phase current of the permanent magnet synchronous motor and outputting an acquired current signal to a CLARK & PARK conversion unit;

the method comprises the following implementation steps:

the first step is as follows: the motor controller receives the control of the whole vehicleCAN bus signal of the unit and the torque command value T generated by the CAN command decomposition unit_cmdAnd three-phase short circuit control T_psc；

The second step is that: with torque command T_cmdTorque on-line calculated value T_onlineAnd torque limit T_limitFor input, a torque reference value T is generated by a torque PI regulation control module^*；

The third step: according to the torque reference value T^*Obtaining direct-axis and quadrature-axis current instruction i by looking up MTPA table_{d_cmd}And i_{q_cmd}；

The fourth step: direct axis and quadrature axis current command i_{d_cmd}、i_{q_cmd}Feedback value i of current of direct axis and quadrature axis_dfeedback、i_qfeedbackInput to the quadrature axis current PI regulation module to generate a quadrature axis current command reference i_d ^*And i_q ^*；

The fifth step: calculating a direct axis and quadrature axis decoupling voltage reference value u according to a permanent magnet synchronous motor steady state voltage equation_d ^*And u_q ^*；

And a sixth step: judging whether the active short-circuit signal is 1 by a space vector modulation unit; if yes, entering a seventh step; if not, entering the tenth step;

the seventh step: judging whether the mechanical rotating speed of the motor exceeds the rotating speed of an inflection point by a space vector modulation unit; if yes, entering the eighth step; if not, entering the tenth step;

eighth step: outputting a three-phase short circuit control signal to an inverter switch circuit;

the ninth step: calculating phase current amplitude i according to a formula_sLooking up a table to obtain a flux linkage numerical value of the permanent magnet;

the tenth step: on-line calculating motor output torque T according to torque formula_onlineExiting the control;

the eleventh step: calculating the duty ratio of a PWM signal according to the rectangular axis voltage reference value and the position signal, outputting the duty ratio to an inverter switching circuit, and exiting the control; the control process is a necessary step of a control period, and the steps are circularly operated in the actual working process.

Compared with the prior art, the invention has the following positive effects:

1. the invention introduces the PI regulation module of the torque command and the torque online calculation value, which is beneficial to the accuracy of the torque output absolute value and quickens the torque response time. The online calculation link of the output torque of the permanent magnet synchronous motor does not depend on motor parameters such as stator resistance, quadrature axis voltage and the like, the calculated value is more accurate, and the quick closed loop of torque control is facilitated. Because the external characteristics of the motor are influenced by the voltage and the rotating speed of the direct-current bus, the higher the voltage of the direct-current bus is, the higher the rotating speed of an inflection point of the maximum torque output of the motor is, and on the contrary, the lower the voltage of the direct-current bus is, a torque limit value module is added in the PI regulation control module, and the torque limit value obtained by the module according to the direct-current bus voltage and the rotating speed lookup table accords with the working characteristics of the motor;

2. the active short circuit instruction is sent by the whole vehicle control unit, and the motor controller does not actively short circuit, so that the control mode is favorable for whole vehicle torque monitoring and function safety, otherwise, the motor automatically performs active short circuit control to generate a large instruction torque, and unexpected deceleration of the vehicle can be caused;

3. the whole vehicle control unit can send an active short circuit instruction according to the current working mode of the motor, such as no-load of the motor, no assistance of the motor or power generation working conditions. In the active short-circuit process, the motor control unit feeds back the short-circuit torque in real time to avoid generating unexpected acceleration and deceleration or other parts from being damaged; the short-circuit torque curve can also be stored in a whole vehicle control unit, and the whole vehicle control unit can directly look up a table or perform feedforward control.

4. In order to avoid discontinuity of permanent magnet flux linkage measurement, the whole vehicle control can adopt a method of sending an active short circuit instruction to a motor at regular time; the permanent magnet flux linkage can also be estimated by storing measurement data for multiple times in the motor control unit and performing interpolation operation.

5. The method does not need an additional hardware circuit and a PWM signal reconstruction software algorithm, only needs to implement active short-circuit control, and is compatible with permanent magnet synchronous motor control.

Drawings

Fig. 1 is a schematic block diagram of an output torque control method of a permanent magnet synchronous motor according to the present invention.

Fig. 2 is a flow chart of the output torque control of the permanent magnet synchronous motor according to the present invention.

Fig. 3 is a maximum torque to current ratio (MTPA) graph of the present invention.

FIG. 4 is a functional block diagram of the torque PI regulation module of the present invention.

FIG. 5 is a schematic block diagram of the torque online calculation of the present invention.

FIG. 6 is a functional block diagram of a torque limit generation module of the present invention.

FIG. 7 is a diagram of the relationship between the direct-axis inductance and the quadrature-axis current parameter according to the present invention.

FIG. 8 is a graph showing the relationship between quadrature axis inductance and quadrature axis current parameters according to the present invention.

Fig. 9 is a relationship curve of three-phase short-circuit current, short-circuit torque and rotating speed.

In the figure, 1, a vehicle control unit 2, a motor controller 3, an inverter switch circuit 4, a permanent magnet synchronous motor 5, a position sensor 6, a three-phase current sensor 21, a CAN command decomposition unit 22, a torque PI regulation module 23, a quadrature axis current command generation unit 24, a quadrature axis current PI regulation module 25, a voltage decoupling control unit 26, a space vector modulation unit 27, a position and rotating speed processing unit 28, a CLARK & PARK conversion unit 29, a torque online calculation module 30, a torque limit value generation module 221, an addition module 222, an anti-saturation PI structure unit 223, an amplitude limiter 291, an alternating current phase current amplitude calculation unit 292, a permanent magnet flux look-up table module 293, a quadrature axis inductance look-up table 294, a torque calculation unit 301, a maximum electric data table 302, a maximum electric data table 303 and a data selection unit are arranged.

Detailed Description

Embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited thereto.

As shown in fig. 1, the vehicle control unit 1 sends a torque command T to the motor controller 2 through the CAN bus_cmdAnd three-phase short circuit control T_psc；

The motor controller 2 consists of a CAN command decomposition unit 21, a torque PI regulation module 22 and a direct-alternating current (AC-AC) power supplyAn axis current instruction generating unit 23, a quadrature axis current PI regulating module 24, a voltage decoupling control unit 25, a space vector modulation unit 26, a position and rotating speed processing unit 27, a CLARK&The device comprises a PARK conversion unit 28, a torque online calculation module 29 and a torque limit value generation module 30; the motor controller 2 controls T according to the three-phase short circuit sent by the whole vehicle control unit 1_pscJudging whether to carry out active short circuit control according to the mechanical rotating speed omega of the motor, and simultaneously satisfying T_pscIf the number is 1 and the mechanical rotating speed of the motor exceeds the rotating speed of an inflection point, the condition is met, an active short circuit PWM signal is output to an inverter switch circuit 3, and three IGBTs of an upper bridge arm or a lower bridge arm are controlled to be closed simultaneously; otherwise, if the condition is not met, calculating the duty ratio of the three-phase PWM signal according to the quadrature axis reference voltage and the position signal, and controlling the IGBT to carry out switching operation; the motor controller 2 sends a torque instruction T according to the whole vehicle control unit 1_cmdAnd the calculated value T output by the torque online calculation module 29_onlineThe PI control is performed so that the output torque of the permanent magnet synchronous motor 4 reaches a target value.

As shown in fig. 4, the torque PI adjustment module 22 includes an addition module 221, an anti-saturation PI structure unit 222, and a limiter 223; the adder module 221 generates Δ e by subtracting the torque command and the torque online calculated value, and inputs Δ e to the anti-saturation PI structure unit 222, where both the proportional term and the integral term of the PI structure function when saturation does not occur, and the anti-saturation integral loop is effective when the PI output is saturated, that is, when eo and out are not equal. The anti-saturation PI structural unit 222 outputs out, adds the out and the torque command again, inputs the sum of the out and the torque command into the amplitude limiter 223, and outputs the torque reference value T after amplitude limiting^*(ii) a The analytical formula of the anti-saturation PI structure is shown in formula (1).

As shown in fig. 3, the abscissa of the curve is the current phase angle, the ordinate is the output torque of the motor, the current amplitude is firstly fixed, the current phase angle traverses from 40 ° to 320 °, a curve of the current phase angle and the output torque of the motor is formed, then the test is repeated until the Maximum current is reached while increasing the current amplitude, so that a family of curves is obtained, and the vertex of each curve is connected into a line, namely, the Maximum torque-to-current ratio curve (MTPA, Maximum torque per).Ampere), the torque and the rectangular axis current corresponding to each point are made into a table, namely a maximum torque current ratio table, and the table uses a torque reference value T^*For indexing, the value obtained by looking up the table is the command value i of the rectangular-axis current command_d ^*And i_q ^*(ii) a The rectangular axis current command generating unit 23 generates a torque reference value T according to the torque reference value T^*Looking up a table to obtain a rectangular axis current instruction command value; the figure is only a schematic diagram and needs to be recalibrated for different powers, torques and different types of motors.

The quadrature axis current PI regulation module 24 regulates a command value i according to the quadrature axis current instruction_{d_cmd}And i_{q_cmd}And CLARK&Direct-axis current feedback value i output by PARK conversion unit 28_dfeedbackAnd quadrature axis current feedback value i_qfeedbackPerforming PI operation to obtain a rectangular-to-rectangular axis current reference value i_d ^*And i_q ^*The PI structure is the same as that of the torque PI regulation module;

the voltage decoupling control unit 25 performs decoupling according to the steady-state voltage equations (2) and (3), and outputs a quadrature axis voltage reference value u_d ^*And u_q ^*。

The space vector modulation unit 26 controls T according to the three-phase short circuit sent by the whole vehicle control unit 1_pscJudging whether to carry out active short circuit control according to the mechanical rotating speed omega of the motor, and simultaneously satisfying T_pscIf the number is 1 and the mechanical rotating speed of the motor exceeds the rotating speed of an inflection point, the condition is met, an active short circuit PWM signal is output to an inverter switch circuit 3, and three IGBTs of an upper bridge arm or a lower bridge arm are controlled to be closed simultaneously; otherwise, if the condition is not met, calculating the duty ratio of the three-phase PWM signal according to the quadrature axis reference voltage and the position signal, and controlling the IGBT to carry out switching operation;

the position and rotation speed processing unit 27 calculates the rotor position theta and the motor mechanical rotation speed omega according to the output signal of the position sensor 5; the CLARK&The PARK conversion unit 28 receives the three-phase current i detected by the current sensor 6_a、i_b、i_cAnd the position signal theta output by the position and rotation speed processing unit 27 is converted into a direct-axis current i under a rotating coordinate system according to the formula (4), the formula (5) and the formula (6)_dAnd quadrature axis current i_q；

As shown in fig. 5, the torque online calculation module 29 includes an ac phase current amplitude calculation unit 291, a permanent magnet flux linkage look-up table 292, a quadrature axis inductance look-up table 293, and a torque calculation unit 294; the alternating-current phase current amplitude calculation unit 291 calculates the alternating-current phase current amplitude according to the formula (7), and outputs the alternating-current phase current amplitude to the permanent magnet flux linkage look-up table 292;

the permanent magnet flux linkage look-up table module 292 is used for looking up a table according to the alternating current phase current amplitude to obtain a permanent magnet flux linkage value; the quadrature axis inductance lookup unit 293 looks up the table according to the quadrature axis and the quadrature axis currents to obtain the quadrature axis and the quadrature axis inductances L_dAnd L_q(ii) a The torque calculation unit 294 calculates the torque according to the permanent magnet synchronous motor torque formula (8).

In the torque formula (8), the direct-axis and quadrature-axis currents can be obtained by calculation through the CLARK & PARK conversion unit 28, the direct-axis and quadrature-axis inductances are obtained through the direct-axis and quadrature-axis inductance look-up unit 293, p is the number of pole pairs of the motor rotor and is a constant, the permanent magnet flux linkage is measured according to the permanent magnet synchronous motor steady-state equations (2) and (3), the alternating-current phase current amplitude of the permanent magnet synchronous motor is measured under the condition of three-phase short circuit, and the permanent magnet flux linkage value can be obtained through look-up;

the one-to-one corresponding relation between the permanent magnet flux linkage and the stator phase current amplitude at different temperatures is calibrated through tests, the permanent magnet flux linkage numerical value is obtained by table lookup in practical application, and the permanent magnet flux linkage numerical value is brought into the formula (8) to calculate the output torque of the permanent magnet synchronous motor on line. In the rectangular axis inductance look-up unit 293, the rectangular axis and rectangular axis inductances are functions of the currents of the rectangular axis and the rectangular axis, and the corresponding relations of the rectangular axis inductances and the currents of the rectangular axis and the rectangular axis can be obtained through finite element simulation software, and the rectangular axis inductances can be obtained in the same way;

as shown in fig. 6, the torque limit value generation module 30 is composed of a maximum motoring data table 301, a maximum generating data table 302 and a data selection unit 303; the maximum electric data table 301 and the maximum power generation data table 302 are searched according to the mechanical rotating speed omega of the motor and the direct-current bus voltage, then the state of electric driving or power generation is judged, and the data selection unit 303 outputs the maximum torque output limit value T_limit(ii) a The inverter switching circuit 3 includes six switching elements, each of the switching elements Q1 to Q6 is an Insulated Gate Bipolar Transistor (IGBT), in the inverter circuit, a first switching element Q1, a third switching element Q3, and a fifth switching element Q5 are connected in series to a second switching element Q2, a fourth switching element Q4, and a sixth switching element Q6, respectively, and a node between the switching elements Q1 and Q2 is connected to a U-phase terminal of the motor; a node between the switching elements Q3 and Q4 is connected to a V-phase terminal of the motor; a node between the switching elements Q5 and Q6 is connected to the W-phase terminal of the motor; the inverter switch circuit 3 drives an internal power electronic device to perform the closing or opening actions of a three-phase lower bridge arm Q2, Q4 and Q6 or the closing or opening actions of a three-phase upper bridge arm Q1, Q3 and Q5 according to a PWM signal instruction of the motor controller 2 so as to realize the short circuit or opening operation of three phase lines of the motor;

the permanent magnet synchronous motor 4 is a three-phase permanent magnet synchronous motor, is a controlled object and is controlled by the inverter switch circuit 3;

the position sensor 5 is a rotary transformer or an absolute position photoelectric encoder and is used for detecting the absolute position of a motor rotor; the three-phase current sensor 6 is a non-contact current sensor based on a hall effect or a contact current sensor based on a principle of generating voltage by using a resistor connected in series to a phase line, and is used for detecting three-phase current of the permanent magnet synchronous motor 4 and outputting an acquired current signal to the CLARK & PARK conversion unit 28;

as shown in fig. 2, the method is implemented as follows:

the first step is as follows: the motor controller 2 receives CAN bus signals of the whole vehicle control unit 1 and generates a torque command value T through a CAN command decomposition unit 21_cmdAnd three-phase short circuit control T_psc；

The second step is that: with torque command T_cmdTorque on-line calculated value T_onlineAnd torque limit T_limitFor input, a torque reference value T is generated by the torque PI regulation control module 22^*；

The third step: according to the torque reference value T^*Obtaining direct axis and quadrature axis current instruction i by looking up MTPA table_{d_cmd}And i_{q_cmd}；

The fourth step: direct axis and quadrature axis current command i_{d_cmd}And i_{q_cmd}Feedback value i of current of direct axis and quadrature axis_dfeedbackAnd i_qfeedbackInput to the quadrature axis current PI regulation module 24 to generate a quadrature axis current command reference i_d ^*And i_q ^*；

And a sixth step: the space vector modulation unit 26 judges whether the active short-circuit signal is 1; if yes, entering a seventh step; if not, entering the tenth step;

the seventh step: the space vector modulation unit 26 judges whether the mechanical rotating speed of the motor exceeds the rotating speed of the inflection point; if yes, entering the eighth step; if not, entering the tenth step;

eighth step: outputting a three-phase short circuit control signal to the inverter switch circuit 3;

the eleventh step: and calculating the duty ratio of the PWM signal according to the rectangular axis voltage reference value and the position signal, outputting the duty ratio to the inverter switch circuit 3, and exiting the control.

The control process is a necessary step of a control period, and the steps are circularly operated in the actual working process.

And in the ninth step, the permanent magnet flux linkage table is obtained by a test method, each rotor temperature corresponds to a permanent magnet flux linkage numerical value, and the permanent magnet synchronous motor is subjected to steady-state short-circuit tests at different rotating speeds at different rotor temperatures to obtain the relation between the short-circuit current amplitude and the permanent magnet flux linkage.

In the ninth step, the permanent magnet flux linkage table can also be obtained by a simulation method, and is a relation table of short-circuit current amplitude and permanent magnet flux linkage under different rotor temperatures and rotating speeds obtained according to a finite element simulation model of the permanent magnet synchronous motor.

As shown in fig. 7, it is a graph of the direct-axis inductance and the quadrature-axis current of the present embodiment, where the x-axis is the direct-axis current, the y-axis is the quadrature-axis current, and the z-axis is the direct-axis inductance. The direct-axis inductance L can be seen from the figure_dIs a function of direct-axis current and quadrature-axis current, and the direct-axis inductance L can be obtained by using the direct-axis current and the quadrature-axis current as index table look-up operation_dNumerical values.

As shown in fig. 8, it is a graph of quadrature axis inductance and quadrature axis current of the present embodiment, where the x-axis is the quadrature axis current, the y-axis is the quadrature axis current, and the z-axis is the quadrature axis inductance. The quadrature inductance L can be seen from the figure_qIs a function of direct-axis current and quadrature-axis current, and the quadrature-axis inductance L can be obtained by using the direct-axis current and the quadrature-axis current as index table look-up operation_qNumerical values.

As shown in fig. 9, the three-phase short-circuit current, the short-circuit torque and the rotation speed are plotted in the present embodiment, where the horizontal axis represents the mechanical rotation speed of the motor and the vertical axis represents the three-phase short-circuit current and the short-circuit torque. The three-phase short-circuit current of the permanent magnet synchronous motor rapidly rises in a low rotating speed section along with the increase of the rotating speed, and when the rotating speed exceeds an inflection point, the rotating speed omega_gThen, the effective value of the current is basically unchanged, and the factors influencing the amplitude of the short-circuit current are mainly the size of the flux linkage of the permanent magnet, which is in direct proportion to the flux linkage value of the permanent magnet and in inverse proportion to the temperature of the permanent magnet. The corresponding relation between three-phase short-circuit current and the mechanical rotating speed of the motor is marked in the figure under the temperature of three rotor permanent magnets of-35 ℃, 60 ℃ and 150 ℃, three different temperatures correspond to three permanent magnet flux linkage numerical values, and the difference of the effective value of the short-circuit current reaches 65A under the conditions of the lowest temperature of-35 ℃ and the highest temperature of 150 ℃ can be noticed, so that the permanent magnet flux linkage numerical value can be effectively detected by utilizing the characteristic; after the rotating speed of the motor exceeds the inflection point rotating speed, the intersection point of the rotating speed of the same motor and curves at minus 35 ℃, 60 ℃ and 150 ℃ corresponds to 3 phase current amplitudes, each phase current corresponds to one permanent magnet flux linkage data, and similarly, a permanent magnet flux linkage table with the phase current amplitudes as indexes can be formed; in practical use, the number of the curves is not limited to 3, and the number of the curves is set according to the temperature range. Three-phase short-circuit torque of permanent magnet synchronous motor and motorResistance torque opposite to the mechanical rotating speed, so that the short-circuit torque of the motor is a negative value under the condition of positive rotation; along with the increase of the rotating speed, the absolute value of the short-circuit torque of the engine is increased and then reduced, and the rotating speed omega exceeds the inflection point_gThen, gradually approaching zero, and similarly, forming a permanent magnet flux linkage table with phase current amplitude as an index; in practical use, the number of the curves is not limited to 3, and the number of the curves is set according to the temperature range.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments.

Claims

1. a drive motor torque closed-loop control method for an electric vehicle, characterized in that it is made up of a vehicle control unit, a motor controller, an inverter switch circuit, a permanent magnet synchronous motor, a position sensor and a three-phase current sensor;

The vehicle control unit sends the three-phase short-circuit control T _psc and the torque command T _cmd to the motor controller through the CAN bus according to the vehicle working mode;

The motor controller consists of a CAN command decomposition unit, a torque PI adjustment module, a quadrature axis current command generation unit, a quadrature axis current PI adjustment module, a voltage decoupling control unit, a space vector modulation unit, a position and rotational speed processing unit, and CLARK&PARK transformation. unit, torque online calculation module and torque limit generation module; the motor controller judges whether to perform active short-circuit control according to the three-phase short-circuit control T _psc and the mechanical speed ω of the motor sent by the vehicle control unit, and at the same time satisfies that T _psc is 1 And the mechanical speed of the motor exceeds the inflection point speed, the condition is established, and the active short-circuit PWM signal is output to the inverter switch circuit to control the three IGBTs of the upper arm or the lower arm of the three-phase full bridge to be closed at the same time; otherwise, the condition is not satisfied, according to The orthogonal axis refers to the voltage and position signal, calculates the duty ratio of the three-phase PWM signal, and controls the IGBT to switch on and off; the motor controller uses the torque command T _cmd sent by the vehicle control unit and the calculated value T _online output by the torque online calculation module Input to the torque PI adjustment module to make the output torque of the permanent magnet synchronous motor reach the target value;

The torque PI adjustment module includes an addition module, an anti-saturation PI structural unit and a limiter; wherein the addition module is to make a difference between two inputs to generate Δe; input to the anti-saturation PI structural unit, in the case of no saturation, Both the proportional term and the integral term work. When the anti-saturation PI structural unit is saturated, that is, when eo and out are not equal, the anti-saturation integral loop is effective; the output of the anti-saturation PI structural unit is out, and the out and turn The torque command T _cmd is added again, the sum of the two is input to the limiter, and the torque reference value T ^* is output after the limit; wherein, the analytical formula of the anti-saturation PI structure is as follows:

eo=out{out(t)=K _p ·e(t)+K _i ∫e(t)}

Among them, eo is the output value of PI calculation, out is the output value after limiting, K _p is the proportional coefficient, K _i is the integral coefficient; e_sat is the maximum limiting output value when the anti-saturation PI structural unit is saturated; e(t) is the deviation value at time t, and out(t) is the output value of the anti-saturation PI structural unit at time t;

The quadrature axis current command generation unit obtains the quadrature axis current command command value according to the torque reference value T ^* by looking up the table, and in the current-torque characteristic curve, the points where the minimum current obtains the maximum torque can be connected into a line, this line It is the maximum torque current ratio curve (MTPA, Maximum torque per.Ampere), which is composed of points on the MTPA curve, with T ^* as the index, and the output is the current command value of the orthogonal axis;

The orthogonal axis current PI adjustment module performs PI according to the direct axis current command command value _{id_cmd} and the quadrature axis current command command value i _{q_cmd} and the direct axis current feedback value _idfeedback and the quadrature axis current feedback value i _qfeedback output by the CLARK&PARK conversion unit. Calculation is performed to obtain the reference values _id ^* and i _q ^* of the orthogonal axis current. The internal structure of the orthogonal axis current PI adjustment module is the same as that of the torque PI adjustment module, but the input is different;

The voltage decoupling control unit performs decoupling according to the steady-state voltage equation, and outputs the reference values _ud ^* and u _q ^* of the orthogonal axis voltage. The specific formulas are as follows:

u _d ^* = Ri _d ^* -pωL _q i _q ^* (2)

u _q ^* =Ri _q ^* +pω(L _d i _d ^* +ψ _m ) (3)

Among them, R is the stator resistance, p is the number of pole pairs of the motor rotor, ω is the mechanical speed of the motor, L _d is the direct-axis inductance, L _q is the quadrature-axis inductance, _id ^* is the reference value of the direct-axis current, and i _q ^* is the alternating-axis inductance. Shaft current reference value, u _d ^* is the direct-axis voltage decoupling value, u _q ^* is the quadrature-axis voltage decoupling value, ψ _m is the permanent magnet flux linkage;

The space vector modulation unit judges whether to perform active short-circuit control according to the three-phase short-circuit control T _psc and the mechanical speed ω of the motor sent by the vehicle control unit. At the same time, if T _psc is 1 and the mechanical speed of the motor exceeds the inflection point speed, the condition is established and the output is actively short-circuited. The PWM signal is sent to the inverter switch circuit to control the three IGBTs on the upper arm or the lower arm to be closed at the same time; otherwise, if the conditions are not satisfied, the duty cycle of the three-phase PWM signal is calculated according to the reference voltage and position signal of the orthogonal axis, and the IGBT is controlled. switch operation;

The position and rotational speed processing unit calculates the rotor position θ and the mechanical rotational speed ω of the motor according to the output signal of the position sensor;

The CLARK&PARK conversion unit receives the three-phase currents i _a , _ib , _ic detected by the current sensor and the position signal θ output by the position and rotational speed processing unit, and converts according to formula (4), formula (5) and formula (6) are the direct and quadrature axis currents _{id and i q} _in the rotating coordinate system;

The CLARK transformation formula is as follows:

i _α = i _a (4)

The PARK transformation formula is as follows:

Among them, i _α and i _β are the α and β-axis currents in the static coordinate system; i _a , _ib , and _ic are the three-phase AC currents in the static coordinate system; θ rotor position electrical angle; _id , i _q are Direct and quadrature axis currents in the rotating coordinate system;

The torque online calculation module includes an AC phase current amplitude calculation unit, a permanent magnet flux linkage look-up table module, a quadrature axis inductance look-up table unit and a torque calculation unit; wherein, the AC phase current amplitude calculation unit is based on the formula ( 7) Calculate the AC phase current amplitude and output it to the permanent magnet flux linkage look-up table module;

Among them, i _s is the stator phase current amplitude;

The permanent magnet flux linkage look-up table module is used to look up the permanent magnet flux linkage value according to the AC phase current amplitude value; the orthogonal-axis inductance look-up table unit obtains the orthogonal-axis inductances L _d and L _q according to the orthogonal-axis current look-up table; The torque calculation unit calculates according to the permanent magnet synchronous motor torque formula (8);

Among them, p is the number of pole pairs of the motor rotor; T _e is the electromagnetic torque;

In the torque formula (8), the quadrature axis current is calculated by the CLARK&PARK conversion unit, the quadrature axis inductance is obtained by the quadrature axis inductance look-up unit, p is the number of pole pairs of the motor rotor, which is a constant, and the permanent magnet flux linkage is based on formula (2) and (3) Measurement, in the case of three-phase short circuit of the motor, ignoring the tube voltage drop of the power module, the orthogonal axis voltage is zero, then

When the mechanical speed ω of the motor approaches infinity, i _q approaches zero, and _id is approximately equal to is _s , then there are,

ψ _m ≈ -L _d i _s (10)

Therefore, the corresponding relationship between the permanent magnet flux linkage and the stator phase current amplitude at different temperatures can be calibrated offline. After the calibration is completed, it is stored as a table. The table uses the stator phase current amplitude as an index, and the output is the permanent magnet flux linkage value. The chain value is brought into formula (8), and the output torque of the permanent magnet synchronous motor can be calculated online;

In the quadrature axis inductance look-up table unit, the quadrature axis inductance is a function of the current of the quadrature axis, and the corresponding relationship between the quadrature axis inductance and the current of the quadrature axis can be obtained through the finite element simulation software, and the quadrature axis inductance can be obtained in the same way;

The torque limit generation module is composed of a maximum motor data table, a maximum power generation data table and a data selection unit; according to the mechanical speed of the motor ω and the DC bus voltage, check the maximum motor data table and the maximum power generation data table, and then determine whether it is in motor or power generation. state, the data selection unit outputs the maximum torque output limit T _limit ;

The inverter switching circuit includes six switching elements, and the switching elements are insulated gate bipolar transistors (IGBTs), which are used to execute the PWM signal sent by the motor controller and control the corresponding switching elements to perform switching actions;

The permanent magnet synchronous motor is a three-phase permanent magnet synchronous motor, which is the controlled object and is controlled by the inverter switch circuit;

The position sensor is a resolver or an absolute position photoelectric encoder, which is used to detect the absolute position of the motor rotor;

The three-phase current sensor is a non-contact current sensor based on the Hall effect or a contact current sensor based on the principle of generating a voltage by using a resistance in series in the phase line, which is used to detect the three-phase current of the permanent magnet synchronous motor, and connect The collected current signal is output to the CLARK&PARK transformation unit;

The implementation steps of this method are as follows:

The first step: the motor controller receives the CAN bus signal of the vehicle control unit and generates the torque command value T _cmd and the three-phase short-circuit control T _psc through the CAN command decomposition unit;

The second step: using the torque command T _cmd , the torque online calculation value T _online and the torque limit value T _limit as input, the torque reference value T ^* is generated by the torque PI adjustment control module;

The third step: check the MTPA table according to the torque reference value T ^* to obtain the orthogonal axis current commands _{id_cmd} and i _{q_cmd} ;

Step 4: Input the direct axis and quadrature axis current commands i _{d_cmd} and i _{q_cmd} and the direct axis and quadrature axis current feedback values i _dfeedback and i _qfeedback into the quadrature axis current PI adjustment module to generate the quadrature axis current command reference _id ^* and i _q ^* ;

Step 5: Calculate the reference values _ud ^* and u _q ^* of the decoupling voltage of the orthogonal axis according to the steady-state voltage equation of the permanent magnet synchronous motor;

Step 6: Determine whether the active short-circuit signal is 1 by the space vector modulation unit; if so, enter the seventh step; if not, enter the eleventh step;

Step 7: Determine whether the mechanical speed of the motor exceeds the inflection point speed by the space vector modulation unit; if so, enter the eighth step; if not, enter the eleventh step;

The eighth step: output the three-phase short-circuit control signal to the inverter switch circuit;

The ninth step: calculate the phase current amplitude is according to the _formula , and look up the table to obtain the permanent magnet flux linkage value;

Step 10: Calculate the motor output torque T _{online online} according to the torque formula, and exit this control;

Step 11: Calculate the duty cycle of the PWM signal according to the reference value of the orthogonal axis voltage and the position signal, output it to the inverter switch circuit, and exit this control; the above control process is a necessary step in a control cycle. In the actual working process, the above Steps run in a loop.