Switched reluctance motor braking torque control system and method based on four-phase current and voltage
阅读说明：本技术 基于四相电流和电压的开关磁阻电机制动转矩控制系统及方法 (Switched reluctance motor braking torque control system and method based on four-phase current and voltage ) 是由 朱曰莹 吴浩 甄成聪 樊志强 张美威 于 2020-07-03 设计创作，主要内容包括：本发明提出了一种基于四相电流和电压的开关磁阻电机制动转矩控制系统及方法,属于电机控制技术领域。该系统主要包括转矩估计器、电流检测器、转矩选择器和转矩调节器。首先通过开关磁阻电机输出的四相电流和电压输入到转矩估计器当中,计算获得四相的估计转矩输入到转矩选择器,同时电流检测器检测到电机的四相电流输出四相的转矩控制信号；然后转矩选择器根据转矩控制信号对四相估计转矩进行选择输出总估计转矩；最后根据转矩调节器对参考转矩和总估计转矩进行进一步调节输出开关磁阻电机参考电流,形成制动转矩闭环控制。本发明可以准确及时地对实际转矩进行估计,满足驾驶员对制动转矩准确和响应需求,提高用开关磁阻电机驱动的电动汽车在制动或者滑行工况下的综合制动性能。(The invention provides a four-phase current and voltage-based switched reluctance motor braking torque control system and method, and belongs to the technical field of motor control. The system mainly comprises a torque estimator, a current detector, a torque selector and a torque regulator. Firstly, four-phase current and voltage output by a switched reluctance motor are input into a torque estimator, four-phase estimated torque is obtained through calculation and input into a torque selector, and meanwhile, a current detector detects that the four-phase current of the motor outputs four-phase torque control signals; then the torque selector selects the four-phase estimated torque according to the torque control signal to output the total estimated torque; and finally, further regulating and outputting the reference current of the switched reluctance motor according to the reference torque and the total estimated torque by the torque regulator to form closed-loop control of the braking torque. The invention can accurately and timely estimate the actual torque, meet the requirements of a driver on the accuracy and response of the braking torque and improve the comprehensive braking performance of the electric automobile driven by the switched reluctance motor under the braking or sliding working condition.)
1. A switched reluctance motor braking torque control system and method based on four-phase current and voltage are characterized in that: the total estimated torque obtained through four-phase current and voltage lags behind the actual torque by one quarter of an electrical cycle after the total estimated torque of one electrical cycle, so that the estimated switched reluctance motor torque is more accurate, the response time of a switched reluctance motor driving system for the electric automobile is reduced, and the steady state response precision and the torque response speed of the motor driving system under the braking condition of the electric automobile are improved, wherein the driving system comprises a torque estimator, a current detector, a torque selector and a torque regulator;
the torque estimator estimates four-phase current and voltage of the switched reluctance motor to obtain four-phase average estimated torque;
the current detector detects four-phase current and outputs a judgment signal, if the phase current is greater than zero, the current detector outputs a low level signal, and if the phase current is less than or equal to zero, the current detector outputs a high level signal;
the torque selector is used for carrying out logic judgment on the four-phase estimated torque according to the four-phase high and low level signals and selecting the four-phase estimated torque to obtain the total estimated torque of the switched reluctance motor driving system;
the torque regulator obtains a reference current through the total estimated torque and a reference braking torque of a driving system, and further realizes the torque closed-loop control of the motor.
2. The four-phase current and voltage based switched reluctance motor braking torque control system and method according to claim 1, wherein: the four-phase estimated torque obtained by the torque estimator is not calculated by an accurate mathematical expression, so that the four-phase estimated torque needs to be calculated by a mechanical-electrical energy conversion principle, namely, a magnetic energy sharing calculation, firstly, a flux linkage of each phase is calculated by the current and the voltage of the four phases, then, the flux linkage of each phase is integrated, and finally, the four-phase estimated torque is obtained, wherein the calculation formula is as follows:
ψ＝∫(u-Ri)dt+ψ0
where m is the number of motor phases, NrIs the number of poles of the motor rotor, W' (i, θ) is the magnetic common energy of the motor, u is the phase winding voltage, i is the phase winding current, R is the phase winding resistance, Ψ is the flux linkage, Ψ0Is the initial flux linkage.
3. The four-phase current and voltage based switched reluctance motor braking torque control system and method according to claim 1, wherein: the current detector detects whether the phase current is larger than zero or not, and outputs a selection control signal of an estimated torque;
the relationship of the detected phase current output selection control signal is as follows:
(1) if the current detector detects that the phase current is larger than zero, the current detector outputs a signal with a low level of 0;
(2) if the current detector detects that the phase current is equal to zero, the current detector outputs a signal with a high level of 1;
(3) if the current detector detects that the phase current is less than zero, the current detector outputs a signal with a high level of 1.
4. The four-phase current and voltage based switched reluctance motor braking torque control system and method according to claim 1, wherein: the torque selector is used for carrying out logic judgment on the four-phase estimated torque estimated by the torque estimator according to the selection control signal output by the current detector, namely selecting the four-phase estimated torque based on the four-phase selection control signal and finally outputting the total estimated torque;
the logic relationship of the selector is as follows:
suppose the stator of the switched reluctance motor is electrified in the sequence of A → D → B → C
(1) The control signal of the phase A is a signal of high level 1, and the control signal of the phase D is a signal of low level 0, and then the selector judges and selects the estimated torque of the phase A as the total estimated torque;
(2) the control signal of the phase D is a signal of high level 1, and the control signal of the phase B is a signal of low level 0, and then the selector judges and selects the estimated torque of the phase D as the total estimated torque;
(3) the control signal of the B phase is a signal of high level 1, and the control signal of the C phase is a signal of low level 0, and then the selector judges and selects the estimated torque of the B phase as the total estimated torque;
(4) the control signal of the C phase is a signal of high level 1, and the control signal of the A phase is a signal of low level 0, then the selector judges and selects the estimated torque of the C phase as the total estimated torque.
5. The four-phase current and voltage based switched reluctance motor braking torque control system and method according to claim 1, wherein: the torque regulator calculates the total estimated torque and the reference torque, and finally outputs the reference current of the motor driving system to form the torque closed-loop control of the switched reluctance motor driving system; the torque regulator comprises two parts, a torque feedforward part and a compensation part; the feedforward part outputs a feedforward current i according to the reference torquerefThe following formula:
wherein, TeIs an electromagnetic torque, kLIs the inductance slope;
the compensation part inputs the error of the total estimated torque output by the reference torque and the torque selector into the PI regulatorIn, the PI regulator outputs a compensation current icThen, the reference current is obtained by adding the feedforward current and the compensation current; the torque feedforward part can increase the dynamic response speed of the switched reluctance motor driving system, and the torque saturation link improves the steady-state torque precision of the system.
Technical Field
The invention relates to the field of control of a switched reluctance motor driving system, in particular to a system and a method for controlling the braking torque of a switched reluctance motor based on four-phase current and voltage.
Background
The electric automobile driven by the switched reluctance motor requires that a braking system can effectively feed back the required braking force of a driver in time under the sliding or braking working condition, the driver can press a brake pedal according to the actual braking working condition to require the electric automobile to brake and decelerate, the braking force is derived from the mechanical braking force of a mechanical braking system and the motor braking force of a regenerative braking system, the motor does not participate in braking only under the conditions of emergency braking and extremely low speed braking, and the motor participates in braking under the conditions of low-intensity braking, medium-intensity braking or different vehicle speeds, so that the braking torque of the switched reluctance motor needs high control precision and high control response speed to ensure the braking safety performance and the stability performance of the electric automobile.
Because the switched reluctance motor is a nonlinear dynamic model and the output torque of the motor is not obtained by calculation through an accurate mathematical expression, the switched reluctance motor is applied to the braking or sliding working condition of the electric automobile and needs to indirectly control the braking torque of the motor. At present, the research on the closed-loop control of the braking torque of the switched reluctance motor through four-phase current and voltage is not carried out, and even if the research on the torque exists, the torque of the motor is controlled through one-phase current and voltage. The total estimated torque obtained by the four-phase current and the four-phase voltage is more accurate than the total estimated torque estimated by the one-phase current and the four-phase voltage, and the total estimated torque only lags behind the actual torque by one quarter of an electrical cycle after one electrical cycle, so that the braking torque control system of the switched reluctance motor is quick in response, the estimated torque can effectively track the reference braking torque required by a driver in time, an electric vehicle driven by the switched reluctance motor is quickly braked and decelerated under the action of the braking torque of the motor, and the braking torque response speed and the dynamic stability of the switched reluctance motor are improved on the premise of ensuring the braking safety.
Disclosure of Invention
The invention aims to improve the braking torque response speed and the braking torque stability of an electric automobile driven by a switched reluctance motor under a braking working condition or a sliding working condition, and therefore provides a system and a method for controlling the braking torque of the switched reluctance motor based on four-phase current and voltage under the working condition that the electric automobile has the motor torque effect.
The purpose of the invention can be realized by the following technical scheme:
the switched reluctance motor brake torque control system based on four-phase current and voltage comprises a torque estimator, a current detector, a torque selector and a torque regulator.
The four-phase current and voltage enter a torque estimator to estimate four-phase estimated torque, the four-phase estimated torque of the torque estimator is not obtained by calculation through an accurate mathematical expression, and therefore the four-phase estimated torque needs to be obtained through an electromechanical energy conversion principle, namely, the four-phase estimated torque is obtained through magnetic common energy calculation. The calculation formula is as follows:
ψ＝∫(u-Ri)dt+ψ0
where m is the number of motor phases, NrIs the number of poles of the motor rotor, W' (i, θ) is the magnetic common energy of the motor, u is the phase winding voltage, i is the phase winding current, R is the phase winding resistance, Ψ is the flux linkage, Ψ0Is the initial flux linkage.
The four-phase current enters a current detector to detect whether the phase current is larger than zero or not, and a selection control signal of the estimated torque is output.
The relationship of the detected phase current output selection control signal is as follows:
(1) if the current detector detects that the phase current is larger than zero, the current detector outputs a signal with a low level of 0;
(2) if the current detector detects that the phase current is equal to zero, the current detector outputs a signal with a high level of 1;
(3) if the current detector detects that the phase current is less than zero, the current detector outputs a signal with a high level of 1.
The torque selector is used for logically judging the four-phase estimated torque estimated by the torque estimator according to the selection control signal output by the current detector, namely selecting the four-phase estimated torque based on the four-phase selection control signal and finally outputting the total estimated torque.
The logic relationship of the torque selector is (assuming that the stator of the switched reluctance motor is electrified in sequence A → D → B → C):
(1) the control signal of the phase A is a signal of
(2) the control signal of the phase D is a signal of
(3) the control signal of the B phase is a signal of
(4) the control signal of the C phase is a signal of
The torque regulator calculates the total estimated torque output by the torque selector and the reference torque required by the switched reluctance motor driving system, and finally outputs the reference current of the motor driving system to form the closed-loop control of the braking torque of the switched reluctance motor driving system. The torque regulator comprises two links, a torque feedforward link and a compensation link. The feedforward link outputs a feedforward current i according to the reference torquerefThe following formula:
wherein, TeIs an electromagnetic torque, kLIs the inductance slope.
Compensation current i of compensation linkcThe method is obtained by inputting errors of a reference torque and a total estimated torque into a PI regulator for calculation, and finally, a reference current is obtained by adding a feedforward current and a compensation current. The torque feedforward link can increase the dynamic response speed of the braking torque of the switched reluctance motor driving system, and the torque saturation link improves the steady-state torque precision of the system.
The invention has the beneficial effects that:
at present, few researches are available for improving the comprehensive braking performance of the electric automobile by controlling the braking torque of the electric automobile driven by the switched reluctance motor under the braking or coasting working condition. In order to better improve the brake or sliding working condition of the switched reluctance motor for the electric automobile, meet the brake torque requirement of a driver, improve the brake response speed and the brake torque precision of a switched reluctance motor driving system and increase the dynamic stability of the brake torque. The invention aims to solve the problem and provides a system and a method for controlling the braking torque of a switched reluctance motor based on four-phase current and voltage. The flux linkage can be well estimated by the flux linkage integrator through simulation and verification of the established model of the driving system of the switched reluctance motor, and the total estimated torque calculated by the torque estimator can effectively track the actual torque of the motor, so that the aim of outputting the actual braking torque of the motor at any time can be fulfilled according to the requirement of a driver on the reference torque. And finally, the reference current is output through the torque regulator to form the closed-loop control of the braking torque of the switched reluctance motor, so that the accuracy and the stability of the control of the braking torque of the switched reluctance motor based on four-phase current and voltage are met, and the dynamic response speed of the switched reluctance motor is improved.
Drawings
Fig. 1 is a diagram of a four-phase current and voltage based brake torque control system for a switched reluctance motor according to the present invention. Wherein, UphAnd IphFor four-phase voltage and current, TABCD-estIs the four-phase estimated torque, SABCDIs a four-phase torque control signal, TestIs the total estimated torque, TrefIs the reference torque.
Fig. 2 is a phase a torque estimator. Wherein iA(t)，UA(T) is A phase current and A phase voltage, Reset is Reset signal, Trigger is Trigger signal TA_estTorque is estimated for phase a.
Fig. 3 is a graph comparing an estimated flux linkage obtained by a flux linkage integrator with an actual flux linkage.
Fig. 4 is a schematic diagram of a torque selector. T isA_est，TB_est，TC_est，TD_estEstimated torques of phases A, B, C, D, SA，SB，SC，SDThe torque control signals are respectively phase A, phase B, phase C and phase D.
Fig. 5 is a total estimated torque output by the torque selector, an actual torque output by the motor, and a required reference torque.
FIG. 6 is a block diagram of a torque regulator outputting a reference current to form a motor braking torque closed loop control.
Detailed Description
The invention is described in detail below with reference to the figures and the specific examples.
The invention relates to a four-phase current and voltage-based switched reluctance motor braking torque control system and a four-phase current and voltage-based switched reluctance motor braking torque control method, and a control structure block diagram is shown in figure 1. The brake torque control system mainly comprises a torque estimator, a current detector, a torque selector and a torque regulator.
Four-phase current and voltage output by the switch reluctance motor body enter a torque estimator, and four-phase estimated torque T is output by the torque estimator through calculationABCD-estTo the torque selector, the current detector detects four-phase current and outputs four-phase estimated torque control signal SABCDThe torque selector estimates torque in four phases and four phasesOutputting total estimated torque T under the action of torque control signalestAnd (4) a torque regulator, wherein the torque regulator is converted into a reference current of the switched reluctance motor according to the total estimated torque and the reference torque required by the driver, so that the braking torque closed-loop control is formed.
The torque estimator consists of a multiplier, a flux linkage integrator, a current detector, a magnetic common energy integrator and a sample holder, as shown in fig. 2. The torque estimator for obtaining the A-phase current and the voltage outputs a magnetic linkage to the magnetic common energy integrator under the action of the multiplier and the magnetic linkage integrator, the magnetic common energy integrator also obtains a reset signal output by the A-phase current detector to act on output magnetic common energy, the sampling holder outputs a magnetic common energy variable quantity of an electronic period under the action of the magnetic common energy and a trigger signal output by the current detector, and finally, the A-phase estimated torque is output under the action of the multiplier. The calculation formula is as follows:
ψ＝∫(u-Ri)dt+ψ0
where m is the number of motor phases, NrIs the number of poles of the motor rotor, W' (i, θ) is the magnetic common energy of the motor, u is the phase winding voltage, i is the phase winding current, R is the phase winding resistance, Ψ is the flux linkage, Ψ0Is the initial flux linkage
To evaluate the accuracy of the torque estimator, the estimated flux linkage obtained by the multiplier in the estimator is analyzed in comparison with the actual flux linkage, as shown in fig. 3. It can be obviously seen that the estimated flux linkage obtained by the flux linkage integrator is basically coincident with the actual flux linkage, even if the peak position at the time of 0.0075s is amplified, the peak position is also basically coincident, the difference is small, the accuracy of the flux linkage integrator is shown, and the effectiveness of the torque estimator is also reflected.
The four-phase current of the switched reluctance motor enters a current detector and detects whether the four-phase current is greater than zero, and a selection control signal of the four-phase estimated torque is output to a torque selector.
The relationship of the detected phase current output selection control signal is as follows:
(1) if the current detector detects that the phase current is larger than zero, the current detector outputs a signal with a low level of 0;
(2) if the current detector detects that the phase current is equal to zero, the current detector outputs a signal with a high level of 1;
(3) if the current detector detects that the phase current is less than zero, the current detector outputs a signal with a high level of 1.
The torque selector is used for logically judging the four-phase estimated torque estimated by the torque estimator according to the selection control signal output by the current detector, namely selecting the four-phase estimated torque based on the four-phase selection control signal and finally outputting the total estimated torque. As shown in fig. 4, assume that the stator energization sequence of the 8/6-pole switched reluctance motor is a → D → B → C.
The logic relationship of the torque selector is as follows:
(1) the control signal of the phase A is a signal of
(2) the control signal of the phase D is a signal of
(3) the control signal of the B phase is a signal of
(4) the control signal of the C phase is a signal of
The total estimated torque is output according to the four-phase estimated torque and the four-phase torque control signal after a period, the output total estimated torque has accuracy and timeliness, and the total estimated torque of the four-phase current and the total estimated torque of the voltage, which are compared with the one-phase current and the voltage, only lags behind the actual torque by a quarter of a period.
In order to effectively evaluate the accuracy and effectiveness of the four-phase current and voltage based switched reluctance motor brake torque control system and method, the actual torque output by the motor, the total estimated torque output by the torque estimator and torque selector and the current detector, and the reference torque required by the driver are compared and analyzed, as shown in fig. 5. The braking torque closed-loop control strategy can well estimate the actual torque according to the requirement of the reference torque, the reference torque required by a driver is output by the motor, and meanwhile, the estimated torque can accurately and efficiently track the actual torque. The actual torque of the motor is rapidly reduced at 0.0025s, the estimated torque is also rapidly reduced at about 0.005s, and the estimated torque can be effectively estimated in time according to the change of the actual torque after 0.01s, which shows that the estimated torque can be effectively tracked to the actual torque, and theoretically, the estimated torque only lags behind the actual torque by a quarter of an electronic period.
The torque regulator calculates the total estimated torque output by the torque selector and the reference torque required by the switched reluctance motor driving system, and finally outputs the reference current of the motor driving system to form the closed-loop control of the torque of the switched reluctance motor driving system, as shown in fig. 6. The torque regulator comprises two links, a torque feedforward link and a compensation link. The feedforward link outputs a feedforward current i according to the reference torquerefThe following formula:
wherein, TeIs an electromagnetic torque, kLIs the inductance slope.
Compensation current i of compensation linkcThe method is obtained by inputting errors of a reference torque and a total estimated torque into a PI regulator for calculation, and finally, a reference current is obtained by adding a feedforward current and a compensation current. The torque feedforward link can increase the dynamic response speed of the braking torque of the switched reluctance motor driving system, and the torque saturation link improves the steady-state torque precision of the system.
The reference current and the four-phase current output after the torque control passes through the torque regulator form current closed-loop control, and a braking torque closed-loop control system formed by a switched reluctance motor braking torque control system and a method based on the four-phase current and the four-phase voltage forms a braking torque closed-loop control system to form a double closed-loop braking torque control system.
The invention is not the best known technology.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
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