A method for preventing voltage saturation during vehicle dynamic process

Abstract

The present invention discloses a method for preventing voltage saturation during a vehicle's dynamic process. By slowing down the acceleration rate, the present invention can improve the actual speed following effect, reduce the required Q-axis current, reduce the weakening magnetic pressure of the D-axis current loop, and alleviate the problem of limited bandwidth of the weakening magnetic loop and inability to converge in time. When the D-axis weakening magnetic current has reached the weakening magnetic limit point, the method reduces the Q-axis current from another dimension through the intervention of the speed outer loop, thereby achieving the effect of the weakening magnetic zone 2. Because the loop only acts on the acceleration and does not intervene in the steady-state operating point, the problem of reduced efficiency caused by inappropriate selection of open-loop weakening magnetic feedforward will not be encountered. The present invention does not require a large amount of offline calibration, thereby shortening the development cycle.

Description

Technical Field

[0001] The present invention relates to the technical field of motor acceleration, and in particular to a method for preventing voltage saturation during a vehicle dynamic process. Background Art

[0002] When the vehicle is running at high speed, a magnetic field weakening algorithm will be used to prevent voltage saturation. The existing magnetic field weakening strategies include: voltage closed-loop magnetic field weakening, D-axis current feedforward magnetic field weakening, offline calibration magnetic field weakening area current combination, etc. In the field of industrial vehicles, due to the large number of manufacturers and products, the offline calibration method is not economical, and most still use voltage closed loop as a general magnetic field weakening strategy. However, this strategy will also encounter various limitations in the dynamic process, resulting in poor results, and requires a good method to solve the problem, such as Figure 1 As shown, the system forms a weak magnetic loop input through the D / Q axis command voltage output and the actual voltage, and the output is a weak magnetic current superimposed on the original D-axis current command. When the command voltage exceeds the actual voltage, the weak magnetic current is output to prevent voltage saturation. Disadvantages of the existing technology: 1. The noise and delay in the loop will limit the adjustment bandwidth of the weak magnetic loop. Therefore, in the dynamic process, the small loop bandwidth will lead to untimely adjustment, resulting in voltage saturation; 2. During rapid acceleration and deceleration, the D-axis current may quickly reach the characteristic current point / weak magnetic current limit point. In the absence of an effective weak magnetic II zone method, it is also easy to saturate; 3. In order to reduce the pressure on the weak magnetic loop in the existing solution, a D-axis feedforward weak magnetic current is sometimes connected in parallel. However, since the feedforward belongs to open-loop control, there is a possibility of reduced efficiency.

[0003] Therefore, it is a problem worthy of research to provide a method for preventing voltage saturation in the dynamic process of the vehicle by slowing down the acceleration rate, improving the actual speed following effect, reducing the required Q-axis current, reducing the weak magnetic pressure of the D-axis current loop, and alleviating the problem of limited bandwidth of the weak magnetic loop and inability to converge in time. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preventing voltage saturation in the dynamic process of a vehicle by slowing down the acceleration rate, thereby improving the actual speed following effect, reducing the required Q-axis current, reducing the weak magnetic pressure of the D-axis current loop, and alleviating the problem of limited bandwidth of the weak magnetic loop and inability to converge in time.

[0005] The object of the present invention is achieved like this:

[0006] A method for preventing voltage saturation during a vehicle's dynamic process includes the following steps: Step 1: Integrating a dynamic anti-voltage saturation algorithm module into a conventional magnetic weakening measurement vector control algorithm module as a control system to implement a magnetic weakening system that prevents dynamic voltage saturation with a small overshoot, weak oscillation, and fast regulation; Step 2: During rapid acceleration, the dynamic anti-voltage saturation algorithm is as follows: the command phase voltage rises rapidly; at this time, the control system calculates the differential value of the command voltage in real time, i.e., the command voltage change rate Uacc = Δu / Δt. The command voltage change rate is multiplied by the actual maximum voltage through a voltage conversion coefficient k to obtain a predicted magnetic weakening limit voltage Uprelimit. The predicted magnetic weakening limit voltage is used to introduce the anti-voltage saturation algorithm in advance before the voltage actually reaches saturation, thereby intervening in dynamic voltage regulation;

[0007] Step 3: Use the difference between the predicted field-weakening limit voltage and the command voltage in step 2 as the loop input. When the command voltage is less than the predicted limit value, the positive limit value is 0, and the dynamic voltage saturation prevention algorithm module does not output. When the command voltage is greater than the predicted value, the dynamic voltage saturation prevention algorithm module outputs a negative acceleration adjustment value for adjusting the acceleration. At this time, the predicted field-weakening voltage enters a latched state and is no longer calculated in real time to prevent unnecessary loop adjustment interference caused by continuous changes in the predicted field-weakening voltage, which affects the field-weakening adjustment effect.

[0008] Step 4: The output of the dynamic anti-voltage saturation algorithm module controls system acceleration. During the adjustment process in Step 3, the acceleration is gradually reduced, resulting in a slower rise in the command speed. This slows the rise in the command speed, reducing the dynamic following pressure of the velocity loop, which in turn reduces the Q-axis torque current and the D-axis field-weakening pressure. The ultimate control effect of the system is that the output voltage slowly transitions to near the actual maximum voltage limit, preventing voltage saturation during the dynamic process.

[0009] The specific algorithm process of the conventional field-weakening vector control algorithm module is as follows: Based on the command voltages Ud and Uq output by the current loop, the voltage vector modulus Us = sqrt(Ud*Ud+Uq*Uq) is obtained. The given voltage vector Us and the actual voltage limit value Udc / sqrt(3) are used as the inputs of the conventional field-weakening module. After PI regulation and amplitude limiting, the D-axis field-weakening current output is obtained for field-weakening regulation.

[0010] The dynamic anti-voltage saturation algorithm module includes a pre-judgment weakening limit voltage loop and a voltage-acceleration control loop. The pre-judgment weakening limit voltage loop includes a command voltage Us calculation module, a command voltage differential module, a limit voltage conversion coefficient K, an actual maximum voltage limit module and a voltage limit module. The connection relationship between the command voltage Us calculation module, the command voltage differential module, the limit voltage conversion coefficient K, the actual maximum voltage limit module and the voltage limit module is: first, the differential of the command voltage is obtained to obtain the voltage change rate; then, the pre-judgment weakening limit voltage is obtained through the limit voltage conversion coefficient K and the actual maximum voltage limit module, and through the final limit.

[0011] The voltage-acceleration control loop includes a pre-judgment magnetic weakening limit voltage module, a command voltage Us, a PID regulator and its amplitude limiting and a default acceleration rate superposition module; the connection relationship between the pre-judgment magnetic weakening limit voltage module, the command voltage Us, the PID regulator and its amplitude limiting and the default acceleration rate superposition module is as follows: first, the pre-judgment magnetic weakening limit voltage and the command voltage Us are obtained as inputs; then, the acceleration regulation output is obtained through the PID regulator and its amplitude limiting; finally, the initial default acceleration is superimposed to obtain the final acceleration value.

[0012] In step 4, the Iq value of the dynamic process is reduced by adjusting the command speed acceleration.

[0013] Positive and beneficial effects: The present invention can improve the actual speed following effect by slowing down the acceleration rate, reduce the required Q-axis current, reduce the weak magnetic pressure of the D-axis current loop, and alleviate the problem of limited bandwidth of the weak magnetic loop and inability to converge in time; when the D-axis weak magnetic current has reached the weak magnetic limit point, this method reduces the Q-axis current from another dimension through the intervention of the speed outer loop, thereby achieving the effect of the weak magnetic zone 2; because the loop only acts on the acceleration and does not intervene in the steady-state operating point, it will not encounter the problem of reduced efficiency due to inappropriate selection of open-loop weak magnetic feedforward; the present invention does not require a large amount of offline calibration, shortening the development cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the prior art structure;

[0015] Figure 2 It is a structural schematic diagram of the present invention;

[0016] Figure 3 Schematic diagram comparing the voltage change rate of the present invention and the voltage change rate of the transmission field weakening solution.

[0017] Figure 4 This is a simulation experiment data diagram of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and examples.

[0019] A method for preventing voltage saturation during a vehicle dynamic process includes the following steps: Step 1: inserting a dynamic anti-voltage saturation algorithm module into a vector control algorithm module for conventional magnetic field weakening measurement, such as Figure 2 As shown, as a control system, a weak magnetic field system with a small overshoot, weak oscillation and fast adjustment is realized; the dynamic anti-voltage saturation algorithm module includes a pre-judgment weak magnetic field limit voltage loop and a voltage-acceleration control loop, and the pre-judgment weak magnetic field limit voltage loop includes: Figure 2 As shown, 1) command voltage Us calculation module; 2) command voltage differential module; 3) limit voltage conversion coefficient K; 4) actual maximum voltage limit module; 5) voltage limit module; the connection relationship between the above modules is: first, the differential of the command voltage is obtained to obtain the voltage change rate; then, the predicted weak magnetic limit voltage is obtained by limiting the voltage conversion coefficient K and the actual maximum voltage limit, and through the final limit.

[0020] The voltage-acceleration control loop includes: Figure 2 As shown in the figure, 1) the predicted weakening limit voltage module; 2) the command voltage Us; 3) the PID regulator and its limiter; 4) the default acceleration rate superposition module; the connection relationship between the above modules is: first, the predicted weakening limit voltage and the command voltage Us are obtained as inputs; then the acceleration adjustment output is obtained through the PID regulator and its limiter; finally, the initial default acceleration is superimposed to obtain the final acceleration value.

[0021] Step 2: During rapid acceleration, the dynamic anti-voltage saturation algorithm is as follows: the command phase voltage will rise rapidly; at this time, the control system will calculate the differential value of the command voltage in real time, that is, the command voltage change rate Uacc = Δu / Δt, as shown in Figure 3 As shown, the command voltage change rate is multiplied by the actual maximum voltage through the voltage conversion coefficient k to obtain the predicted field-weakening limit voltage Uprelimit. This predicted field-weakening limit voltage is used to introduce an anti-voltage saturation algorithm in advance before the voltage actually reaches saturation, intervening in dynamic voltage regulation. The principle is: if the command voltage rises too quickly, and adjustment is not made until it exceeds the maximum voltage limit, the voltage will already be saturated. The longer the adjustment time, the longer the saturation time. However, the optimal time to add the acceleration loop can be determined based on the slope of the loop voltage rise and the current field-weakening loop bandwidth. That is, when the command voltage reaches Uperlimit but has not yet reached the actual maximum voltage and saturated, voltage-acceleration loop regulation begins.

[0022] Step 3: Use the difference between the predicted field-weakening limit voltage and the command voltage in step 2 as the loop input. When the command voltage is less than the predicted limit value, the positive limit value is 0, and the dynamic voltage saturation prevention algorithm module does not output. When the command voltage is greater than the predicted value, the dynamic voltage saturation prevention algorithm module outputs a negative acceleration adjustment value for adjusting the acceleration. At this time, the predicted field-weakening voltage enters a latched state and is no longer calculated in real time to prevent unnecessary loop adjustment interference caused by continuous changes in the predicted field-weakening voltage, which affects the field-weakening adjustment effect.

[0023] Step 4: After the acceleration decreases, the command speed rises more slowly, the Q-axis torque current decreases, the D-axis weak magnetic pressure decreases, and the output voltage slowly transitions to the actual maximum voltage limit value, and the voltage saturation condition of the dynamic process is alleviated. By adjusting the command speed acceleration, the Iq value of the dynamic process is reduced.

[0024] The specific algorithm process of the conventional field weakening vector control algorithm module is as follows: The voltage vector Us = sqrt(Ud*Ud+Uq*Uq) is obtained from the command voltage Ud and Uq output by the current loop. The given voltage vector Us and the actual voltage limit value Udc / sqrt(3) are used as the input of the conventional field weakening module. After PI adjustment and limiting, the D-axis field weakening current output is obtained for field weakening adjustment. This process is a conventional field weakening control algorithm, such as Figure 1 The present invention is based on the conventional method, adding an anti-dynamic voltage saturation module to obtain Figure 2 Algorithm block diagram.

[0025] Simulation experiment: Figure 4 As shown, it can be seen from the simulation experimental data that the present invention can improve the actual speed following effect by slowing down the acceleration rate, reduce the required Q-axis current, reduce the weakening pressure of the D-axis current loop, and alleviate the problem of limited bandwidth of the weakening loop and inability to converge in time; when the D-axis weakening current has reached the weakening limit point, the method reduces the Q-axis current from another dimension through the intervention of the speed outer loop, thereby achieving the effect of the weakening zone 2; because the loop only acts on the acceleration and does not intervene in the steady-state operating point, it will not encounter the problem of reduced efficiency due to inappropriate selection of open-loop weakening feedforward; the present invention does not require a large amount of offline calibration, shortening the development cycle.

Claims

1. A method for preventing voltage saturation during a vehicle dynamic process, characterized in that: The method includes the following steps: Step 1: A dynamic voltage saturation prevention algorithm module is serially connected to a vector control algorithm module for conventional magnetic field weakening measurement as a control system to realize a magnetic field weakening system with a small overshoot, weak oscillation, and fast adjustment and anti-dynamic voltage saturation; Step 2: During rapid acceleration, the dynamic voltage saturation prevention algorithm is as follows: The command phase voltage rises rapidly. At this time, the control system calculates the differential value of the command voltage in real time, namely the command voltage change rate Uacc = Δu / Δt. This command voltage change rate is multiplied by the actual maximum voltage using the voltage conversion coefficient k to obtain the predicted field weakening limit voltage Uprelimit. This predicted field weakening limit voltage is used to introduce the voltage saturation prevention algorithm in advance before the voltage actually reaches saturation, intervening in dynamic voltage regulation. Step 3: Use the difference between the predicted field-weakening limit voltage and the command voltage in step 2 as the loop input. When the command voltage is less than the predicted limit value, the positive limit value is 0, and the dynamic voltage saturation prevention algorithm module does not output. When the command voltage is greater than the predicted value, the dynamic voltage saturation prevention algorithm module outputs a negative acceleration adjustment value for adjusting the acceleration. At this time, the predicted field-weakening voltage enters a latched state and is no longer calculated in real time to prevent unnecessary loop adjustment interference caused by continuous changes in the predicted field-weakening voltage, which affects the field-weakening adjustment effect. Step 4: The output of the dynamic anti-voltage saturation algorithm module controls the system acceleration. During the adjustment process in step 3, the acceleration will gradually decrease, causing the command speed to rise more slowly. The slowdown in the command speed will reduce the dynamic following pressure of the speed loop, which in turn will reduce the Q-axis torque current and the D-axis weak magnetic pressure. The final control effect of the system is that the output voltage slowly transitions to near the actual maximum voltage limit value, and the voltage saturation condition of the dynamic process is avoided. The specific algorithm process of the conventional magnetic field weakening vector control algorithm module is as follows: the command voltage Ud and Uq output by the current loop are used to obtain the voltage vector modulus Us=sqrt(Ud*Ud+Uq*Uq); the given voltage vector Us and the actual voltage limit value Udc / sqrt(3) are used as the input of the conventional magnetic field weakening module, and after PI adjustment and limiting, the D-axis magnetic field weakening current output is obtained for magnetic field weakening adjustment.

2. The method for preventing voltage saturation during a vehicle dynamic process according to claim 1, wherein: The dynamic anti-voltage saturation algorithm module includes a pre-judgment weakening limit voltage loop and a voltage-acceleration control loop. The pre-judgment weakening limit voltage loop includes a command voltage Us calculation module, a command voltage differential module, a limit voltage conversion coefficient K, an actual maximum voltage limit module and a voltage limit module. The connection relationship between the command voltage Us calculation module, the command voltage differential module, the limit voltage conversion coefficient K, the actual maximum voltage limit module and the voltage limit module is: first, the differential of the command voltage is obtained to obtain the voltage change rate; then, the pre-judgment weakening limit voltage is obtained through the limit voltage conversion coefficient K and the actual maximum voltage limit module, and through the final limit.

3. The method for preventing voltage saturation during a vehicle dynamic process according to claim 2, wherein: The voltage-acceleration control loop includes a predicted magnetic weakening limit voltage, a command voltage Us, a PID regulator and its limiting and a default acceleration rate superposition module; the connection relationship between the predicted magnetic weakening limit voltage, the command voltage Us, the PID regulator and its limiting and the default acceleration rate superposition module is as follows: first, the predicted magnetic weakening limit voltage and the command voltage Us are obtained as inputs; then, the acceleration regulation output is obtained through the PID regulator and its limiting; finally, the initial default acceleration is superimposed to obtain the final acceleration value.

4. The method for preventing voltage saturation during a vehicle dynamic process according to claim 1, wherein: In step 4, the Iq value of the dynamic process is reduced by adjusting the command speed acceleration.

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