Torque feedforward control based on reactive power and method for improving performance of load control

Abstract

The present application relates to a torque feedforward control and load carrying control performance improvement method based on reactive power, which provides dynamic feedforward torque during heavy load starting, low speed load carrying and load torque mutation by using the dynamic information of reactive power and its reactive power change rate caused by load starting or load mutation, realizes stable and reliable load torque feedforward control, and effectively improves and solves the problems of poor load carrying control performance such as the inability of motor vector control system, especially motor speed sensorless control system, to start under heavy load, poor low speed load carrying ability and large dynamic speed drop caused by load mutation, and improves load carrying ability and control performance.

Description

Technical Field

[0001] This invention belongs to the field of motor drive control technology, and in particular to a method for improving the performance of torque feedforward control and load control based on reactive power. Background Technology

[0002] High-performance AC speed control systems require closed-loop control of motor speed, which can be achieved using speed sensors to obtain relatively accurate speed information. However, the presence of sensors increases system cost, reduces robustness and reliability, and in complex and harsh operating environments, the speed signals obtained from sensors are subject to significant interference and low signal-to-noise ratio, severely impacting system control performance. Therefore, sensorless control technology has been widely researched and applied. Sensorless control technology for motors uses measured stator current and voltage signals to accurately obtain motor speed. Currently commonly used sensorless control methods include: current-voltage models and their improvements, model reference adaptive methods, adaptive state observer methods, methods based on nonlinear Kalman filters, signal injection methods, and optimization algorithms based on intelligent learning. Various methods have their own advantages and disadvantages in practical applications, but motor model-based control methods generally suffer from problems such as low-speed instability and poor parameter robustness. Especially when the motor operates at low frequencies, many methods fail to accurately estimate the speed at zero and low frequencies, causing a sharp decline in control performance. Particularly, the load-carrying capacity and ability to cope with sudden load torque changes at low speeds become very poor, resulting in the motor failing to start under heavy loads, having poor low-speed load-carrying capacity, or experiencing severe speed drops when suddenly loaded. These problems severely restrict the application of sensorless motor control. In traditional sensorless motor control, either there is no torque feedforward compensation, or the load torque is observed or estimated as a slowly changing state variable. When there is no load torque feedforward, the vector control system mainly relies on separating the torque current component from the motor stator current. However, in practical applications, the signal needs to be filtered with a large time constant, resulting in a slow dynamic response of the torque component. It cannot achieve the direct vector transformation to obtain a signal with very small hysteresis, as is possible with vector control systems containing speed sensors. Therefore, using this signal cannot avoid the dynamic speed drop of the actual speed or improve the load-carrying capacity. When observing or estimating load torque, the load torque is modeled as a slow variable. However, the adaptive state observation or estimation method suffers from instability at low speeds and low speed estimation accuracy, resulting in inaccurate load torque observation and poor load-carrying capacity. Furthermore, the slow variable modeling method cannot accurately estimate and track sudden load torque changes, resulting in inaccurate load torque feedforward and estimation lag, which affects the load control performance. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a method for improving the performance of torque feedforward control and load control based on reactive power. By utilizing the dynamic information of reactive power and its rate of change caused by load start-up or load mutation, dynamic feedforward torque is provided during heavy load start-up, low-speed load-bearing, and load torque mutation, thus achieving stable and reliable load torque feedforward control. This method can effectively improve and solve problems such as poor load control performance in motor vector control systems, especially motor control systems without speed sensors, which cannot start under heavy load, have poor low-speed load-bearing capacity, and large dynamic speed drop caused by load mutation, thereby improving load-bearing capacity and control performance.

[0004] The technical problem solved by this invention is achieved through the following technical solution:

[0005] The method for improving the performance of torque feedforward control and load control based on reactive power includes the following steps:

[0006] Step 1: Calculate the motor stator current magnitude I in real time based on the real-time sampling signals of the three-phase voltage and current of the motor-inverter vector control system. m Excitation current component I sd and reactive power Q;

[0007] Step 2: Calculate the friction torque M_mf and the initial load torque M_me of the motor, and obtain the additional feedforward torque signal ML0;

[0008] Step 3: Based on the motor stator current magnitude I obtained in Step 1 m and excitation current component I sd The torque current component I is obtained. sq And according to the motor flux ψ r Thus, the feedforward torque signal ML1, composed of steady-state torque current components, is obtained;

[0009] Step 4: Based on the given motor speed, obtain the reactive power QA with the same direction polarity as the given motor speed, and calculate the rate of change dQdt of reactive power QA to obtain the switching logic signal S1 and the soft switching signal S2.

[0010] Step 5: Based on the soft switching signal S2, memorize the positive extreme value QA_M of reactive power QA and the positive extreme value dQdt_M of reactive power change rate dQdt during the load torque change process; and based on the switching logic signal S3, realize the soft switching of QA_M and dQdt_M to obtain the feedforward torque signal ML2 based on reactive power information.

[0011] Step 6: Match ML1 and ML2 with the polarity of the motor speed setting N_set to obtain feedforward torque signals ML1A and ML2A with the same polarity as the motor speed direction;

[0012] Step 7: Based on the soft switching signal S2, implement the soft switching between the feedforward torque signals ML1A and ML2A, and then superimpose the soft-switched feedforward torque with the additional torque ML0 to obtain the synthesized feedforward torque signal M_FF.

[0013] Step 8: Add the synthesized feedforward torque signal M_FF obtained in Step 7 to the torque signal M_PI output by the speed regulator to obtain the torque setpoint signal M_SET, thereby realizing torque feedforward control;

[0014] Step 9: Divide the feedforward torque command signal M_SET obtained in Step 8 by the motor flux linkage ψ. r The torque current command signal I is obtained. sq _SET is fed into the current regulator to achieve closed-loop vector control.

[0015] Furthermore, the stator current magnitude I in step 1 m The calculation method is as follows:

[0016]

[0017] Among them, i α and i β The current values ​​in the αβ two-phase stationary coordinate system are obtained by transforming the three-phase currents by 3 / 2.

[0018] Excitation current component I sd The calculation method is as follows:

[0019] I sd =I sd_PI +I sd_add

[0020] Among them, I sd_PI I is the excitation current output by the flux regulator. sd_add This is for the additional excitation current.

[0021] The method for calculating reactive power Q is as follows:

[0022] Q = u α i β -u β i α

[0023] Among them, u α and u β The voltage values ​​in the αβ two-phase stationary coordinate system are obtained by transforming the three-phase voltages by 3 / 2.

[0024] Furthermore, the specific calculation method for the friction torque M_mf in step 2 is as follows:

[0025] M_mf=M_mf0+k_mf1×N_act+k_mf2×N_act2

[0026] Where M_mf0 is the friction torque constant, k_mf1 and k_mf2 are friction coefficients that are proportional to and squared with the actual speed value N_act, and N_act is the actual speed value.

[0027] The initial load torque M_me is either manually set or obtained from the torque memory circuit. It is mainly used in situations where the initial load torque is known to be set, in order to avoid system oscillations caused by changes in initial speed.

[0028] The calculation method for the additional feedforward torque ML0 is as follows:

[0029] ML0 = M_mf + M_me.

[0030] Furthermore, the torque current component I in step 3 sq The calculation method is as follows:

[0031]

[0032] The steady-state feedforward torque signal ML1 is calculated as follows:

[0033] ML1=ψ r I sq .

[0034] Furthermore, the method for calculating the reactive power QA in step 4, which has the same direction polarity as the given motor speed, is as follows:

[0035]

[0036] The reactive power change rate dQdt is obtained by differentiating the reactive power QA and then applying an inertial filter.

[0037] The output condition for the reactive power change rate dQdt is: the given motor speed N_set is greater than the threshold value N_th1, and the reactive power change rate dQdt is greater than the threshold value dQdt_th1. At this time, the reactive power change rate dQdt is effectively output to ensure that the reactive power change rate dQdt has high sensitivity and accuracy. The output stops when dQdt is less than dQdt_th2. At this time, the value of dQdt is very small, which is equivalent to the end of the dynamic process.

[0038] Furthermore, the switching logic signal S1 is obtained from the following logic: the given motor speed N_set is less than the threshold value N_th1, and the extreme value of reactive power QA QA_M (the maximum value of QA when loaded) is greater than the threshold value ML_th1; or dQdt is in the output state. In this case, the switching logic signal S1 is "1"; otherwise, the switching logic signal S1 is "0".

[0039] Furthermore, in step 4, the soft switching signal S2 is as follows: when the switching logic signal S1 is in state "1", the RS flip-flop is set, and when the feedforward torque ML1 is greater than ML2, the soft switching signal S2 decreases from "1" to "0" at a set slope. When the rate of change of ML1 is less than the threshold value dM_th, it indicates that the system has entered an approximately steady state, and the RS flip-flop is used to remember this state. When ML2 is less than ML_th2, after a delay of 100ms, and when the rate of change of ML1 is less than the threshold value dM_th, it indicates that the system has entered an approximately no-load state. After another 10ms delay, the RS flip-flop is reset, causing the soft switching signal S2 to rise from "0" to "1" at a set slope.

[0040] When the soft switching signal S2 < 0.01, the extreme values ​​QA_M and dQdt_M follow the positive values ​​of their respective signals QA and dQdt, respectively. When QA and dQdt are negative, the extreme values ​​QA_M and dQdt_M are output as 0. When the soft switching signal S2 > 0.01, the extreme values ​​QA_M and dQdt_M retain their previous positive maximum values, thus realizing the positive extreme value memory function for reactive power information.

[0041] Furthermore, the switching logic signal S3 in step 5 includes:

[0042] (1) The rate of change of the reactive power extreme value QA_M is less than the threshold value Q_th;

[0043] (2) The rate of change of reactive power dQdt_M is less than the threshold value dQ_th;

[0044] (3) The steady-state feedforward torque ML1 is greater than the threshold value ML_th3;

[0045] (4) The given rotational speed N_set is greater than the threshold value N_th1;

[0046] (5) The absolute difference between QA_M and dQdt_M is less than the threshold value ML_th4;

[0047] The above five conditions are logically ANDed and ORed with the given speed N_set being greater than the threshold value N_th2 to obtain the switching logic signal S3. When S3 is "1", the feedforward torque ML2 is softly switched from QA_M to dQdt_M; otherwise, the feedforward torque ML2 is softly switched from dQdt_M to QA_M.

[0048] Furthermore, the calculation methods for ML1A and ML2A in step 6 are as follows:

[0049]

[0050]

[0051] Furthermore, the soft-switching calculation method for the synthesized feedforward torque signal M_FF in step 7 is as follows:

[0052] M_FF=S2×(ML2A+ML0)+(1-S2)×ML1A.

[0053] The advantages and positive effects of this invention are:

[0054] This invention utilizes the dynamic information of reactive power and its rate of change caused by load start-up or load mutation to provide dynamic feedforward torque during heavy load start-up, low-speed load-bearing, and load torque mutation, thereby achieving stable and reliable load torque feedforward control. It can effectively improve and solve problems such as poor load-bearing control performance in motor vector control systems, especially motor sensorless control systems, which cannot start under heavy load, have poor low-speed load-bearing capacity, and large dynamic speed drop caused by load mutation, thus improving load-bearing capacity and control performance. Attached Figure Description

[0055] Figure 1 The waveforms of speed, flux linkage, feedforward torque, and torque current during the starting process with 50% rated load are obtained by the method of this invention.

[0056] Figure 2 The waveforms of speed, feedforward torque, and torque current obtained by the method of this invention are as follows: when a 50% rated load is suddenly applied at 50% of the rated speed.

[0057] Figure 3 The waveforms of speed, flux linkage, current, and load torque during the starting process with 100% rated load are obtained by the method of this invention.

[0058] Figure 4 The waveforms of torque feedforward, speed regulator output, and torque setpoint during the starting process with 100% rated load are obtained by the method of this invention.

[0059] Figure 5 The waveforms of speed, flux linkage, current, and load torque during the starting process with 150% rated load are obtained by the method of this invention.

[0060] Figure 6 The waveforms of speed, flux linkage, current, and load torque obtained by the method of this invention are obtained when a 150% rated step load torque is suddenly applied during low-speed operation.

[0061] Figure 7 It is a traditional speed waveform diagram of the starting process with 140% rated load torque based on the load torque observation method;

[0062] Figure 8 The speed waveform diagram of the starting process of the torque feedforward control method based on reactive power information with 140% rated load torque is obtained by the method of the present invention. Detailed Implementation

[0063] The present invention will be further described in detail below with reference to the accompanying drawings.

[0064] The method for improving the performance of torque feedforward control and load control based on reactive power includes the following steps:

[0065] Step 1: Calculate the motor stator current magnitude I in real time based on the real-time sampling signals of the three-phase voltage and current of the motor-inverter vector control system. m Excitation current component I sd And reactive power Q.

[0066] Among them, the stator current magnitude I m The calculation method is as follows:

[0067]

[0068] i α and i β The current values ​​in the αβ two-phase stationary coordinate system are obtained by transforming the three-phase currents by 3 / 2.

[0069] Among them, the excitation current component I sd The calculation method is as follows:

[0070] I sd =I sd_PI +I sd_add

[0071] I sd_PI I is the excitation current output by the flux regulator. sd_add This is for the additional excitation current.

[0072] The reactive power Q is calculated as follows:

[0073] Q = u α i β -u β i α

[0074] u α and u β The voltage values ​​in the αβ two-phase stationary coordinate system are obtained by transforming the three-phase voltages by 3 / 2.

[0075] Step 2: Calculate the friction torque M_mf and initial load torque M_me of the motor, and obtain the additional feedforward torque signal ML0.

[0076] The specific calculation method for the friction torque M_mf is as follows:

[0077] M_mf=M_mf0+k_mf1×N_act+k_mf2×N_act 2

[0078] M_mf0 is the friction torque constant, and k_mf1 and k_mf2 are friction coefficients that are proportional to and squared with the actual speed value N_act, where N_act is the actual speed value.

[0079] The initial load torque M_me is either manually set or obtained from the torque memory circuit. It is mainly used to set a known initial load torque to avoid system oscillations caused by changes in initial speed.

[0080] The calculation method for the additional feedforward torque ML0 is as follows:

[0081] ML0 = M_mf + M_me.

[0082] Step 3: Based on the motor stator current magnitude I obtained in Step 1 m and excitation current component I sd The torque current component I is obtained. sq And according to the motor flux ψ r The feedforward torque signal ML1, composed of steady-state torque current components, is obtained.

[0083] Wherein, torque current component I sq The calculation method is as follows:

[0084]

[0085] The steady-state feedforward torque signal ML1 is calculated as follows:

[0086] ML1=ψ r I sq

[0087] Step 4: Based on the given motor speed, obtain the reactive power QA with the same direction polarity as the given motor speed, and calculate the rate of change dQdt of the reactive power QA to obtain the switching logic signal S1 and the soft switching signal S2.

[0088] The calculation method for reactive power QA, which has the same direction polarity as the given speed of the motor, is as follows:

[0089]

[0090] The reactive power change rate dQdt is obtained by differentiating the reactive power QA and then applying an inertial filter.

[0091] The output condition for the reactive power change rate dQdt is as follows: the given motor speed N_set is greater than the threshold value N_th1, and the reactive power change rate dQdt is greater than the threshold value dQdt_th1. At this time, the reactive power change rate dQdt is effectively output to ensure that the reactive power change rate dQdt has high sensitivity and accuracy. The output stops when dQdt is less than dQdt_th2. At this time, the value of dQdt is very small, which is equivalent to the end of the dynamic process.

[0092] The switching logic signal S1 is obtained from the following logic: the given motor speed N_set is less than the threshold value N_th1, and the extreme value of reactive power QA QA_M (the maximum value of QA when loaded) is greater than the threshold value ML_th1; or dQdt is in the output state. In this case, the switching logic signal S1 is "1"; otherwise, the switching logic signal S1 is "0".

[0093] The soft handover signal S2 is obtained using the following method: When the switching logic signal S1 is in state "1", it is set by the RS flip-flop. When the feedforward torque ML1 is greater than ML2, the soft handover signal S2 decreases from "1" to "0" at a set slope. When the rate of change of ML1 is less than the threshold value dM_th, it indicates that the system has entered an approximately steady state, and the RS flip-flop is used to remember this state. When ML2 is less than ML_th2, after a delay of 100ms, and when the rate of change of ML1 is less than the threshold value dM_th, it indicates that the system has entered an approximately no-load state. After another 10ms delay, the RS flip-flop is reset, causing the soft handover signal S2 to rise from "0" to "1" at a set slope.

[0094] When the soft switching signal S2 < 0.01, the extreme values ​​QA_M and dQdt_M follow the positive values ​​of their respective signals QA and dQdt, respectively. When QA and dQdt are negative, the extreme values ​​QA_M and dQdt_M are output as 0. When the soft switching signal S2 > 0.01, the extreme values ​​QA_M and dQdt_M retain their previous positive maximum values, thus realizing the positive extreme value memory function for reactive power information.

[0095] Step 5: Based on the soft switching signal S2, memorize the positive extreme value QA_M of reactive power QA and the positive extreme value dQdt_M of reactive power change rate dQdt during the load torque change process; and based on the switching logic signal S3, realize the soft switching of QA_M and dQdt_M to obtain the feedforward torque signal ML2 based on reactive power information.

[0096] The switching logic signal S3 is formed by the following logic:

[0097] (1) The rate of change of the reactive power extreme value QA_M is less than the threshold value Q_th;

[0098] (2) The rate of change of reactive power dQdt_M is less than the threshold value dQ_th;

[0099] (3) The steady-state feedforward torque ML1 is greater than the threshold value ML_th3;

[0100] (4) The given rotational speed N_set is greater than the threshold value N_th1;

[0101] (5) The absolute difference between QA_M and dQdt_M is less than the threshold value ML_th4;

[0102] The above five conditions are logically ANDed and ORed with the given speed N_set being greater than the threshold value N_th2 to obtain the switching logic signal S3. When S3 is "1", the feedforward torque ML2 is softly switched from QA_M to dQdt_M; otherwise, the feedforward torque ML2 is softly switched from dQdt_M to QA_M.

[0103] During the initial loading phase at high speed, the maximum value of reactive power QA changes approximately linearly with the load torque. As the speed increases, the nonlinear relationship between QA and the load torque widens, but its rate of change dQdt responds quickly, exhibiting characteristics of a step load. Therefore, reactive power information can be used to construct a feedforward torque, where QA_M is mainly used for low-speed load starting, and dQdt_M is mainly used for impulsive step load situations.

[0104] Step 6: Match ML1 and ML2 with the polarity of the motor speed given N_set to obtain feedforward torque signals ML1A and ML2A with the same polarity as the motor speed direction.

[0105] The calculation methods for the feedforward torque signals ML1A and ML2A, which are related to the direction of motor speed, are as follows:

[0106]

[0107]

[0108] Step 7: Based on the soft switching signal S2, implement the soft switching between the feedforward torque signals ML1A and ML2A. Then, superimpose the soft-switched feedforward torque with the additional torque ML0 and output the result to obtain the synthesized feedforward torque signal M_FF.

[0109] The soft-switching calculation method for the synthesized feedforward torque M_FF is as follows:

[0110] M_FF=S2×(ML2A+ML0)+(1-S2)×ML1A.

[0111] Step 8: Add the synthesized feedforward torque signal M_FF obtained in step 7 to the torque signal M_PI output by the speed regulator to obtain the torque setpoint signal M_SET, thereby realizing torque feedforward control.

[0112] Step 9: Divide the feedforward torque command signal M_SET obtained in Step 8 by the motor flux linkage ψ. r The torque current command signal I is obtained. sq _SET is fed into the current regulator to achieve closed-loop vector control.

[0113] Simulation and experimental verification were conducted under the condition of sensorless vector control of the motor.

[0114] Figure 1 The present invention provides the motor speed, rotor flux linkage, feedforward torque, and torque current waveforms obtained under sensorless vector control conditions with 50% rated load torque, starting from zero speed to 50% rated speed. Figure 2 The figure shows the motor speed, feedforward torque, and torque current waveforms under sensorless vector control obtained by the method of this invention, with stable operation at 50% of rated speed and a sudden 50% step load applied. As can be seen from the figure, during load start-up and under impact loads, reactive power information can be effectively used to construct feedforward torque, providing a larger starting torque at low speeds and quickly offsetting the speed drop caused by impact loads, thus improving load start-up capability and immunity to step impact loads.

[0115] Figure 3 The waveforms of motor speed, rotor flux linkage, torque current, and load torque when starting at 100% rated load are obtained by the method of this invention. Figure 4 The waveforms of torque feedforward (M_FF), speed regulator output (M_PI), and torque setpoint (M_SET) obtained by the method of this invention for starting with 100% rated load are shown in the figure. As can be seen from the figure, under sensorless control and heavy-load starting, the torque feedforward control based on reactive power information proposed in this invention can provide a large starting torque during load starting. The flux linkage is stable during load starting, the torque current changes smoothly, the difference between the estimated speed and the given speed is very small, and the dynamic fluctuation of the speed PI regulator output is small, with a steady-state value essentially zero. This effectively improves load-carrying capacity and control accuracy.

[0116] Figure 5 The waveforms of motor speed, rotor flux linkage, torque current, and load torque when starting at 150% rated load are obtained by the method of this invention. Figure 6The figures show the motor speed, rotor flux linkage, torque current, and load torque waveforms obtained by the method of this invention when a 150% rated step load torque is suddenly applied during low-speed operation. As can be seen from the figures, the method proposed in this invention can still ensure system stability and control accuracy when starting with a limit load (150% rated torque); at 3.6% of rated speed, a sudden application of 150% rated step load torque results in a very small speed drop, stable torque current and flux linkage, and strong resistance to impact loads.

[0117] Figure 7 Traditional speed waveforms during startup with 140% rated load torque based on load torque observation methods. Figure 8 The figure shows the speed waveform during the start-up process with 140% rated load torque obtained by the torque feedforward control method based on reactive power information, obtained by the method of this invention. As can be seen from the figure, during heavy load start-up, the initial speed drop of the method proposed in this invention is reduced from 15% to 5%, and the speed drop recovery is significantly faster, with a much smaller speed drop area.

[0118] In summary, compared with other methods, the method proposed in this invention can provide reliable dynamic feedforward torque under heavy load starting, low speed load, and load change, and achieve reliable torque feedforward control. It can effectively improve and solve the problems of poor load control performance in motor vector control systems, especially motor sensorless control systems, such as the inability to start under heavy load, poor low speed load capacity, and large dynamic speed drop caused by load change, thereby improving load capacity and control performance.

[0119] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. A method for improving the performance of torque feedforward control and load control based on reactive power, characterized in that: Includes the following steps: Step 1: Calculate the motor stator current magnitude I in real time based on the real-time sampling signals of the three-phase voltage and current of the motor-inverter vector control system. m Excitation current component I sd and reactive power Q; Step 2: Calculate the friction torque M_mf and the initial load torque M_me of the motor, and obtain the additional feedforward torque signal ML0; Step 3: Based on the motor stator current magnitude I obtained in Step 1 m and excitation current component I sd The torque current component I is obtained. sq And according to the motor flux ψ r Thus, the feedforward torque signal ML1, composed of steady-state torque current components, is obtained; Step 4: Based on the given motor speed, obtain the reactive power QA with the same direction polarity as the given motor speed, and calculate the rate of change dQdt of reactive power QA to obtain the switching logic signal S1 and the soft switching signal S2. Step 5: Based on the soft switching signal S2, memorize the positive extreme value QA_M of reactive power QA and the positive extreme value dQdt_M of reactive power change rate dQdt during the load torque change process; and based on the switching logic signal S3, softly switch QA_M and dQdt_M to obtain the feedforward torque signal ML2 based on reactive power information. Step 6: Match ML1 and ML2 with the polarity of the motor speed setting N_set to obtain feedforward torque signals ML1A and ML2A with the same polarity as the motor speed direction; Step 7: Based on the soft switching signal S2, the soft switching feedforward torque signals ML1A and ML2A are soft-switched, and then the feedforward torque after soft switching is superimposed with the additional torque ML0 and output to obtain the synthesized feedforward torque signal M_FF. Step 8: Add the synthesized feedforward torque signal M_FF obtained in Step 7 to the torque signal M_PI output by the speed regulator to obtain the torque setpoint signal M_SET, and perform torque feedforward control. Step 9: Divide the feedforward torque command signal M_SET obtained in Step 8 by the motor flux linkage ψ. r The torque current command signal I is obtained. sq _SET is fed into the current regulator for closed-loop vector control.

2. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: In step 1, the stator current magnitude I m The calculation method is as follows: Among them, i α and i β The current values ​​in the αβ two-phase stationary coordinate system are obtained by transforming the three-phase currents by 3 / 2. Excitation current component I sd The calculation method is as follows: I sd =I sd_PI +I sd_add Among them, I sd_PI I is the excitation current output by the flux regulator. sd_add To provide additional excitation current; The method for calculating reactive power Q is as follows: Q=u α i β -u β i α Among them, u α and u β The voltage values ​​in the αβ two-phase stationary coordinate system are obtained by transforming the three-phase voltages by 3 / 2.

3. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: The specific calculation method for the friction torque M_mf in step 2 is as follows: M_mf=M_mf0+k_mf1×N_act+k_mf2×N_act 2 Where M_mf0 is the friction torque constant, k_mf1 and k_mf2 are friction coefficients that are proportional to and squared with the actual speed value N_act, and N_act is the actual speed value; The calculation method for the additional feedforward torque ML0 is as follows: ML0 = M_mf + M_me.

4. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: In step 3, the torque current component I sq The calculation method is as follows: The steady-state feedforward torque signal ML1 is calculated as follows: ML1=ψ r I sq 。 5. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: The method for calculating the reactive power QA in step 4, which has the same direction polarity as the given motor speed, is as follows: The reactive power change rate dQdt is obtained by differentiating the reactive power QA and then filtering it using inertial filtering. The output condition for the reactive power change rate dQdt is: the given motor speed N_set is greater than the threshold value N_th1, and the reactive power change rate dQdt is greater than the threshold value dQdt_th1. At this time, the reactive power change rate dQdt is effectively output. The output stops when dQdt is less than dQdt_th2. At this time, the value of dQdt is small, and the dynamic process ends.

6. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: In step 4, the switching logic signal S1 is obtained by the following logic: the given speed N_set of the motor is less than the threshold value N_th1, and the extreme value QA_M of the reactive power QA is greater than the threshold value ML_th1; or dQdt is in the output state, at which time the switching logic signal S1 is 1; otherwise, the switching logic signal S1 is 0.

7. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: In step 4, the soft switching signal S2 is as follows: When the switching logic signal S1 is in state 1, the RS flip-flop is set, and when the feedforward torque ML1 is greater than ML2, the soft switching signal S2 decreases from 1 to 0 at a set slope. When the rate of change of ML1 is less than the threshold value dM_th, it enters an approximately steady state, and the RS flip-flop stores this state. When ML2 is less than ML_th2, after a delay of 100ms, and when the rate of change of ML1 is less than the threshold value dM_th, it enters an approximately no-load state. After another 10ms delay, the RS flip-flop is reset, causing the soft switching signal S2 to rise from 0 to 1 at a set slope. When the soft handover signal S2 < 0.01, the extreme values ​​QA_M and dQdt_M follow the positive values ​​of their respective signals QA and dQdt. When QA and dQdt are negative, the extreme values ​​QA_M and dQdt_M are output as 0. When the soft handover signal S2 > 0.01, the extreme values ​​QA_M and dQdt_M remain unchanged at their previous positive maximum values.

8. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: The switching logic signal S3 in step 5 includes: (1) The rate of change of the reactive power extreme value QA_M is less than the threshold value Q_th; (2) The rate of change of reactive power dQdt_M is less than the threshold value dQ_th; (3) The steady-state feedforward torque ML1 is greater than the threshold value ML_th3; (4) The given rotational speed N_set is greater than the threshold value N_th1; (5) The absolute difference between QA_M and dQdt_M is less than the threshold value ML_th4; The above 5 conditions are logically ANDed and logically ORed with the given speed N_set being greater than the threshold value N_th2 to obtain the switching logic signal S3. When S3 is 1, the feedforward torque ML2 is softly switched from QA_M to dQdt_M; otherwise, the feedforward torque ML2 is softly switched from dQdt_M to QA_M.

9. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: The calculation methods for ML1A and ML2A in step 6 are as follows:

10. The method for improving the performance of torque feedforward control and load control based on reactive power according to claim 1, characterized in that: The soft-switching calculation method for the synthesized feedforward torque signal M_FF in step 7 is as follows: M_FF=S2×(ML2A+ML0)+(1-S2)×ML1A.

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