CN110716082A - Terminal voltage acquisition and compensation method for improving precision of power-stage motor simulator - Google Patents

Abstract

A terminal voltage acquisition and compensation method for improving the accuracy of a power stage motor simulator relates to a collection and compensation method for the output terminal voltage of an inverter of a power stage motor simulator. circuit; the terminal voltage acquisition circuit includes a resistor divider, a first operational amplifier, a second operational amplifier, a third operational amplifier and a DSP; the output signal of the first operational amplifier is captured, and the equivalent duty cycle of the terminal voltage is obtained. Sampling the output signal of the operational amplifier to obtain the amplitude of the terminal voltage; calculate the actual equivalent terminal voltage output by the inverter; calculate the phase voltage output by the inverter; repeat steps (3)‑(4 for each control cycle of the motor simulator ) to obtain the actual output phase voltage; the command terminal voltage is subtracted from the actual equivalent terminal voltage to obtain the compensation voltage; the compensation voltage is transformed into a two-phase coordinate system; the compensation voltage is fed forward to complete the voltage compensation; the invention is simple, reliable and accurate High, which can improve the simulation accuracy of the motor simulator.

Description

Terminal voltage acquisition and compensation method to improve the accuracy of power stage motor simulator

technical field

The invention relates to a method for collecting and compensating the output terminal voltage of a power stage motor simulator inverter used for motor driver testing. The terminal voltage acquisition and compensation method of the accuracy of the device.

Background technique

We know that the power stage motor simulator has the advantages of convenient testing, energy can be fed back to the grid, and it can simulate extreme or faulty working conditions of the motor, so it is widely used in the testing of motor drives in electric vehicles, aerospace, wind power and other fields. middle. It is a low-cost, simple and effective way to test motor drives using a DSP-based power stage motor simulator instead of a traditional motor bench. However, due to the slow operation speed of DSP, there is an error in collecting the terminal voltage output by the inverter in the motor driver, which leads to a decrease in the simulation accuracy of the motor simulator. In addition, both the motor driver and the inverter in the motor simulator have non-ideal characteristics such as dead zone and voltage drop, which cause the voltage and current output by the inverter to be distorted, which will also lead to a decrease in the simulation accuracy of the motor simulator.

In order to improve the sampling accuracy of the inverter terminal voltage, the existing research proposes to use the integrator to collect the equivalent value of the terminal voltage in one PWM cycle as the current voltage. The disadvantage of this method is that the integrator will generate a voltage when reset Acquisition error, and the entire sampling process will also generate errors due to the existence of capacitance. There is also research to achieve accurate sampling of the terminal voltage by using a high-speed ADC chip, but this method is generally used in FPGA-based motor simulators, and the cost of the entire system is relatively high. In view of the influence of the non-ideal characteristics of the inverter on the simulation accuracy of the motor simulator, the method of voltage compensation is usually used to eliminate it. Existing voltage compensation strategies require complex algorithms to determine the current polarity and calculate the compensation voltage, and the calculated compensation voltage usually takes the voltage drop of the IGBT and the diode as a fixed value, and the compensation is not accurate.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a terminal voltage acquisition and compensation method that is simple, reliable, high in precision, and capable of improving the precision of a power stage motor simulator.

The technical scheme adopted in the present invention is:

A terminal voltage acquisition and compensation method for improving the accuracy of a power stage motor simulator is characterized by comprising the following steps:

(1) Build a terminal voltage acquisition circuit on both sides of the motor driver and the motor simulator; the terminal voltage acquisition circuit includes a resistor divider, a first op amp, a second op amp, a third op amp and a DSP, and a resistor divider The output terminal of the first operational amplifier is connected to the same-direction input terminal of the first operational amplifier and the second operational amplifier; the reverse input terminal of the first operational amplifier is connected to the reference voltage 1, and the output terminal is connected to the capture module of the DSP; The input terminal is connected to the output terminal through the resistor R1, the output terminal is connected to the third operational amplifier through the resistor R2; the non-inverting terminal of the third operational amplifier is connected to the reference voltage 3, the inverting terminal is connected to the output terminal through the resistor R3, and the output terminal is connected to the DSP connected to the ADC module;

(2) The output signal of the first operational amplifier is captured by the capture module of the DSP to obtain the equivalent duty cycle of the terminal voltage for one cycle, and the output signal of the third operational amplifier is sampled by the ADC module of the DSP to obtain the terminal voltage Amplitude of high level and low level;

(3) Calculate the actual equivalent terminal voltage output by the inverter in one cycle according to the expression (1) using the duty cycle and amplitude obtained in step (2);

(4) using the equivalent terminal voltage obtained in step (3) to calculate the phase voltage output by the inverter according to expression (2);

(5) Steps (3)-(4) are repeated in each control cycle of the motor simulator, and the phase voltage actually output by the inverter of the motor driver is obtained in real time;

(6) subtract the actual equivalent terminal voltage obtained in step (3) from the command terminal voltage of the inverter to obtain the compensation voltage in one cycle;

(7) CLARK transform the compensation voltage obtained in step (6) to obtain the compensation voltage under the two-phase coordinate system;

(8) Feed forward the two-phase compensation voltage obtained in step (7) into the command phase voltage of the inverter to complete the voltage compensation;

(9) Steps (6)-(8) are repeated in each control cycle of the motor driver to complete the voltage compensation of the inverter in the motor driver;

(10) Steps (6)-(8) are repeated in each control cycle of the motor simulator to complete the voltage compensation of the inverter in the motor simulator.

Expression (1) described in step (3) is as follows:

U _term =U _H ·Duty+ _UL ·(1-Duty) (1)

In the formula: U _term is the equivalent terminal voltage; U _H is the amplitude of the high level of the terminal voltage; U _L is the amplitude of the low level of the terminal voltage; Duty is the equivalent duty cycle of the terminal voltage;

Expression (2) described in step (4) is as follows:

In the formula: U _A is the A-phase voltage output by the inverter, U _Aterm , U _Bterm , and U _Cterm are the A-phase equivalent terminal voltage, B-phase equivalent terminal voltage, and C-phase equivalent terminal voltage of the inverter respectively; B, C phase voltage.

In the present invention, according to the voltage sampling range (0-3V) of the ADC module in the DSP and the precision of the voltage dividing resistor (5‰), the chip resistor is selected as the resistor divider in the terminal voltage collecting circuit.

In the present invention, the first operational amplifier is used as a voltage comparator to select a high-speed operational amplifier with a response time lower than 20ns, and the reference voltage 1 is set to 1/2 of the terminal voltage after voltage division.

In the present invention, the second operational amplifier is used as a voltage follower and the third operational amplifier is used as a voltage amplifier, both of which should be high-speed and low-noise operational amplifiers with a bandwidth of not less than 50MHz and a total harmonic distortion of not more than -50dBc, and the required ripple is not high. Powered by a 10mV positive and negative dual power supply. The resistors R1, R2, and R3 are selected according to the recommended values of the operational amplifier manual, and the value of the reference voltage 3 is set according to the voltage sampling range (0-3V) of the ADC module in the DSP.

The invention proposes a sampling method to accurately obtain the duty cycle and amplitude of the inverter terminal voltage, and the voltage and current distortion of the motor simulator are caused by changes in these two aspects; the voltage compensation strategy is based on hardware real-time measurement The terminal voltage does not need to judge the current polarity and calculate the compensation voltage through a complex algorithm, and the compensation process is simpler and more reliable. At the same time, the conduction voltage drop of the IGBT and the diode due to the current and the temperature is taken into consideration. Therefore, the method of the present invention is simpler and the supplementary data is accurate.

Description of drawings

Figure 1 is the designed terminal voltage acquisition circuit, in which the serial number 1 is a resistor divider, the serial number 2 is the first operational amplifier, the serial number 3 is the capture module of the DSP, and the serial number 4 is the DSP (for the calculation of the equivalent terminal voltage), The serial number 5 is the ADC acquisition module of the DSP, the serial number 6 is the third operational amplifier, and the serial number 7 is the second operational amplifier.

Figure 2 shows the principle of obtaining the equivalent duty cycle of the terminal voltage.

Figure 3 is the measured waveform of the inverter terminal voltage and current.

Fig. 4 is the sampling principle of terminal voltage amplitude.

FIG. 5 is the terminal voltage waveform and the output signals of the first operational amplifier and the third operational amplifier.

Fig. 6 is the duty cycle of the terminal voltage command and the actual collected duty cycle and duty cycle error.

Figure 7(a) shows the terminal voltage and current waveforms when the terminal voltage is at a high level; Figure 7(b) shows the terminal voltage and current waveforms when the terminal voltage is at a low level.

Figure 8 shows the comparison between the inverter commanded phase voltage and the collected actual output phase voltage and the voltage error.

Figure 9 is the output voltage of the motor driver and the current simulated by the motor simulator before voltage compensation.

Figure 10 is a comparison of the current waveforms of the motor simulator before voltage compensation and the real motor under the same V/f control.

Figure 11 shows the comparison between the inverter commanded phase voltage and the actual output phase voltage and the voltage error in the motor simulator before voltage compensation.

Figure 12 is the comparison between the inverter commanded phase voltage and the actual output phase voltage in the motor driver after voltage compensation.

Figure 13 shows the comparison between the inverter commanded phase voltage and the actual output phase voltage and the voltage error in the motor simulator after voltage compensation.

Figure 14 shows the influence of voltage compensation on the current waveform simulated by the motor simulator and FFT analysis: Figure (a) in Figure 14 shows that neither the motor simulator nor the inverter output voltage of the motor driver is voltage compensated, and Figure (b) In order to perform voltage compensation only on the inverter output voltage of the motor driver, Figure (c) shows that both the motor simulator and the inverter output voltage of the motor driver perform voltage compensation.

Figure 15 is a comparison of the current waveforms of the motor simulator and the real motor after voltage compensation is also performed.

Detailed ways

Table 1 is the system parameters of the DSP-based power stage motor simulator in the experiment.

Table 2 is the basic parameters of the motor to be simulated by the motor simulator.

A terminal voltage acquisition and compensation method for improving the accuracy of a power stage motor simulator is characterized by comprising the following steps:

(1) Build a terminal voltage acquisition circuit on both sides of the motor driver and the motor simulator. The terminal voltage acquisition circuit is respectively connected with the output terminal of the motor driver and the input and output terminals of the motor simulator, and is used to collect the output terminal of the motor driver and the motor simulation terminal. terminal voltage at the output (or input) of the device. The terminal voltage acquisition circuit includes a resistor divider 1, a first op amp 2, a second op amp 7, a third op amp 3 and DSP4 The output end of the resistor divider 1 and the first op amp 2 and the second op amp 7 The same-direction input end of the first operational amplifier 2 is connected to the reference voltage 1, and the output end is connected to the capture module 3 of the DSP4. The reverse input terminal of the second operational amplifier 7 is connected to the output terminal through the resistor R1, and the output terminal is connected to the third operational amplifier 6 through the resistor R2. The non-inverting terminal of the third operational amplifier 6 is connected to the reference voltage 3, the inverting terminal is connected to the output terminal through the resistor R3, and the output terminal is connected to the ADC module 5 of the DSP.

(2) According to the voltage sampling range (0-3V) of the ADC module 5 in the DSP and the precision of the voltage dividing resistor (5‰), the chip resistor is selected as the resistor divider 1 in the terminal voltage acquisition circuit.

(3) The first operational amplifier is used as a voltage comparator to select a high-speed operational amplifier with a response time lower than 20ns, and the reference voltage 1 is set to 1/2 of the terminal voltage after the voltage division.

(4) The second operational amplifier is used as a voltage follower and the third operational amplifier is used as a voltage amplifier. Both of them should use high-speed and low-noise operational amplifiers with a bandwidth of not less than 50MHz and a total harmonic distortion of not more than -50dBc, and the need for low ripple Powered by a 10mV positive and negative dual power supply. The resistors R1, R2, and R3 are selected according to the recommended values of the operational amplifier manual, and the value of the reference voltage 3 is set according to the voltage sampling range (0-3V) of the ADC module in the DSP.

(5) The output signal of the first operational amplifier 2 is captured by the capture module of the DSP to obtain the equivalent duty cycle of the terminal voltage for one cycle, and the output signal of the third operational amplifier 6 is sampled by the ADC module of the DSP to obtain Amplitude of terminal voltage high level and low level.

(6) Calculate the actual equivalent terminal voltage output by the inverter in one cycle according to the expression (1) using the duty cycle and amplitude obtained in step (5).

(7) Calculate the phase voltage output by the inverter according to the expression (2) using the equivalent terminal voltage obtained in step (6).

(8) Steps (6)-(7) are repeated in each control cycle of the motor simulator to obtain the phase voltage actually output by the inverter of the motor driver in real time.

(9) Subtract the actual equivalent terminal voltage obtained in step (6) from the command terminal voltage of the inverter to obtain the compensation voltage in one cycle.

(10) CLARK transform the compensation voltage calculated in step (9) to obtain the compensation voltage in the two-phase coordinate system.

(11) Feed forward the two-phase compensation voltage obtained in step (10) into the commanded phase voltage of the inverter to complete voltage compensation.

(12) Steps (9)-(11) are repeated in each control cycle of the motor driver to complete the voltage compensation of the inverter in the motor driver.

(13) Steps (9)-(11) are repeated in each control cycle of the motor simulator to complete the voltage compensation of the inverter in the motor simulator.

The expression described in step 6 is as follows:

U _term =U _H ·Duty+ _UL ·(1-Duty) (1)

In the formula: U _term is the equivalent terminal voltage, U _H is the amplitude of the high level of the terminal voltage, U _L is the amplitude of the low level of the terminal voltage, and Duty is the equivalent duty cycle of the terminal voltage.

The expression described in step 7 is as follows:

In the formula: U _A is the A-phase voltage output by the inverter, and the B and C-phase voltages can be obtained in the same way. U _Aterm , U _Bterm , and U _Cterm are the equivalent terminal voltage of phase A, the equivalent terminal voltage of phase B, and the equivalent terminal voltage of phase C of the inverter, respectively.

The theoretical basis of the present invention is as follows:

(1) The duty cycle and amplitude acquisition principle of the inverter terminal voltage:

The principle of duty cycle acquisition:

After the terminal voltage is divided, the reference voltage 1 is used as the input of the first operational amplifier. After the first operational amplifier is compared, it outputs a square wave signal with the same duty cycle as the terminal voltage. After the signal is collected by the DSP capture module, the terminal voltage can be obtained. duty cycle. It should be noted that when the current is relatively small, due to the influence of the parasitic capacitance of the IGBT, the edge of the inverter output voltage is not a step rise or a step fall, but a slow rise or fall process. According to the principle of volt-second balance, the reference voltage 1 can be set to be 1/2 of the terminal voltage after voltage division to obtain the equivalent duty cycle of the terminal voltage. The principle is shown in Figure 2.

Amplitude sampling principle:

Figure 3 shows the measured waveforms of the inverter terminal voltage and current. It can be found that the amplitude is not fixed when the terminal voltage is at a low level. When the current is not less than 0, the terminal voltage is negative, when the current is less than 0, the terminal voltage is positive, and the amplitude changes with the current. This phenomenon is caused by the on-voltage drop of the IGBT and diode in the inverter, and the on-voltage drop varies with the current and temperature. It is precisely because the terminal voltage has a negative value that the ADC cannot be directly used to sample the terminal voltage after voltage division. The role of the second operational amplifier as a voltage follower is to achieve impedance matching, which can achieve minimal interference to the original signal during ADC sampling and high quality of the sampled signal. The function of the third operational amplifier is to translate and scale the terminal voltage after the voltage division so that it is within the sampling range of the ADC module. R3/R2 is the voltage scaling factor. Since the terminal voltage has been divided by voltage, in the present invention, R3/ R2=1. It should be noted that the best acquisition time of the ADC in one cycle of the terminal voltage is the midpoint of the high level and the low level, respectively. Sampling here can avoid the influence of the turn-on and turn-off of the IGBTs of other phases. The ADC channel can be triggered at the period value and 0 value by PWM modulating the voltage of this phase to achieve midpoint sampling. The sampling principle of the terminal voltage amplitude is shown in Figure 4.

Fig. 5 is the terminal voltage waveform intercepted from the oscilloscope, the output signal of the first operational amplifier and the output signal of the third operational amplifier. The burrs in the dotted rectangular box in the figure are the interference caused by the turn-on and turn-off of the IGBTs of the other two phases of the inverter to the terminal voltage of this phase, which is a normal phenomenon. This interference is distributed on both sides of the ADC sampling point and is divided by resistors, so it has no effect on the acquisition of the terminal voltage. Accurate equivalent duty cycle and amplitude of terminal voltage can be obtained through the capture module and ADC module of DSP.

(2) Principle of inverter voltage compensation:

The non-ideal characteristics of the inverter, such as dead time and the conduction voltage drop of the IGBT and the diode, make the duty cycle and amplitude of the terminal voltage output by the inverter change compared with the command voltage, resulting in the voltage of the motor simulator. And the current is distorted, which reduces the simulation accuracy.

The invention proposes a sampling method to accurately obtain the duty cycle and amplitude of the inverter terminal voltage, and the voltage and current distortion of the motor simulator are caused by changes in these two aspects. Therefore, the present invention proposes a simpler and more accurate voltage compensation strategy by using the obtained duty cycle and amplitude of the terminal voltage.

The difference between the command terminal voltage and the equivalent value of the measured terminal voltage can be written as:

ΔU=Duty ^* ·U _dc -U _term (3)

where ΔU is the output voltage error, Duty* is the command duty cycle, and U _dc is the inverter bus voltage.

Convert the three-phase voltage error to the two-phase coordinate system through CLARK transformation, and feed forward to the command two-phase voltage to complete the voltage compensation. The conversion formula is:

The voltage compensation strategy proposed by the present invention is based on the real-time measurement of terminal voltage by hardware, and there is no need to judge the current polarity and calculate the compensation voltage through a complex algorithm, and the compensation process is simpler and more reliable. At the same time, the current and temperature of the IGBT and diode conduction voltage drop are taken into account, and the compensation is more accurate.

The experiments that can prove the effect of the method of the present invention are as follows, and the parameters of the experimental platform are shown in Table 1 and Table 2.

1. Analysis of inverter terminal voltage acquisition results

According to the terminal voltage acquisition circuit proposed by the present invention, the duty cycle and amplitude of the terminal voltage are acquired through DSP, and the phase voltage is calculated.

Figure 6 shows the command duty cycle of the A-phase terminal voltage read from the DSP and the equivalent duty cycle waveform actually collected, as well as the difference between the two. It can be seen that the main source of the duty cycle error is the inserted dead time, the on-off delay of the IGBT, the transmission delay of the PWM command signal, and the influence of the parasitic capacitance on the equivalent duty cycle when the current is small. It will cause fluctuations in the duty cycle error.

Figure 7 is the A-phase terminal voltage and current waveforms collected by the ADC module. U _AHD , U _AHF , U _ALD , and U _ALF are the conduction voltage drops of the IGBTs and diodes of the upper and lower bridge arms of the inverter, respectively. Figure 7(b) is consistent with the measured waveform in Figure 3, which proves the correctness of the terminal voltage acquisition principle. It can be seen that the conduction voltage drop of IGBT and diode is not a fixed value.

FIG. 8 shows the A-phase command voltage, the actual phase voltage calculated according to equations (1) and (2), and the difference between the two. Figure 8 shows that the non-ideal characteristics of the inverter can cause errors between the actual output voltage and the commanded voltage, which in turn cause current distortion.

2. Analysis of the experimental results of the motor simulator before voltage compensation

In the motor simulator experiment, the motor model runs without load, the motor driver adopts the V/f open-loop control strategy, and the output is a constant 8V/10Hz sine wave command voltage.

In Figure 9, the upper picture is the A-phase voltage waveform obtained from the DSP, and the lower picture is the comparison between the reference current calculated by the motor model and the actual output current waveform of the motor simulator. Figure 9 shows that the motor simulator can run stably and the actual current can accurately track the command current, but it does not prove that the motor simulator can accurately simulate the characteristics of the actual motor. Figure 10 is a comparison of the current waveform of the motor simulator and the real motor under the same V/f control. It can be found that the phases of the two are very consistent, but the shapes are different. Length and amplitude change.

Through analysis, the current distortion is the root cause of the current error of the motor simulator, and the current distortion is caused by the voltage distortion caused by the non-ideal characteristics of the inverter in the motor driver and the motor simulator. Figure 11 shows the commanded phase voltage and actual output phase voltage of the inverter in the motor simulator and the difference between the two. It can be seen that the output voltage has obvious distortion. The same distortion also occurs in the inverter output voltage of the motor drive in Figure 9. The solution to this problem is to compensate the inverter output voltage.

3. Analysis of the experimental results of the motor simulator after voltage compensation

Figure 12 shows the waveform comparison between the command voltage and the actual voltage after the inverter of the motor driver is compensated, and the output voltage distortion of the inverter almost disappears. Figure 13 shows the voltage comparison after voltage compensation is performed on the inverter of the motor simulator, and the voltage error is already very small. Since the distortion of the output voltage of the motor driver disappears, the inverter command voltage of the motor simulator has a better sine than that shown in Figure 11, and the fluctuation of the output voltage after compensation is caused by the closed-loop regulation of the system.

The current waveform and FFT analysis of the motor simulator without voltage compensation are shown in Figure 14(a). The current distortion is severe and the THD value is large. After only compensating the inverter output voltage of the motor driver, as shown in Figure 14(b), the distortion of the current waveform is reduced, and the THD value drops significantly. Figure 14(c) shows the current waveforms after the inverter output voltages of both the motor driver and the motor simulator are compensated. The current distortion almost disappears, and the THD value is only 2.27%. It can be seen that the compensation strategy proposed by the present invention can realize precise voltage compensation.

Figure 15 is a comparison of the current waveforms of the motor simulator and the real motor after voltage compensation. The phases and shapes of the two are almost the same, which proves that the terminal voltage acquisition method proposed in the present invention and the voltage compensation strategy based on this can improve the power level motor. The simulation accuracy of the simulator.

Table 1 Motor Simulator System Parameters

Table 2 Simulated motor parameters

Claims (5)

1. a terminal voltage collection and compensation method improving the precision of a power stage motor simulator, is characterized in that comprising the steps: (1) Build a terminal voltage acquisition circuit on both sides of the motor driver and the motor simulator; the terminal voltage acquisition circuit includes a resistor divider, a first op amp, a second op amp, a third op amp and a DSP, and a resistor divider The output terminal of the first operational amplifier is connected to the same-direction input terminal of the first operational amplifier and the second operational amplifier; the reverse input terminal of the first operational amplifier is connected to the reference voltage 1, and the output terminal is connected to the capture module of the DSP; The input terminal is connected to the output terminal through the resistor R1, the output terminal is connected to the third operational amplifier through the resistor R2; the non-inverting terminal of the third operational amplifier is connected to the reference voltage 3, the inverting terminal is connected to the output terminal through the resistor R3, and the output terminal is connected to the DSP connected to the ADC module; (2) The output signal of the first operational amplifier is captured by the capture module of the DSP to obtain the equivalent duty cycle of the terminal voltage for one cycle, and the output signal of the third operational amplifier is sampled by the ADC module of the DSP to obtain the terminal voltage Amplitude of high level and low level; (3) Calculate the actual equivalent terminal voltage output by the inverter in one cycle according to the expression (1) using the duty cycle and amplitude obtained in step (2); (4) using the equivalent terminal voltage obtained in step (3) to calculate the phase voltage output by the inverter according to expression (2); (5) Steps (3)-(4) are repeated in each control cycle of the motor simulator, and the phase voltage actually output by the inverter of the motor driver is obtained in real time; (6) subtract the actual equivalent terminal voltage obtained in step (3) from the command terminal voltage of the inverter to obtain the compensation voltage in one cycle; (7) CLARK transform the compensation voltage obtained in step (6) to obtain the compensation voltage under the two-phase coordinate system; (8) Feed forward the two-phase compensation voltage obtained in step (7) into the command phase voltage of the inverter to complete the voltage compensation; (9) Steps (6)-(8) are repeated in each control cycle of the motor driver to complete the voltage compensation of the inverter in the motor driver; (10) Repeat steps (6)-(8) for each control cycle of the motor simulator to complete the voltage compensation of the inverter in the motor simulator; Expression (1) described in step (3) is as follows: U _term =U _H ·Duty+ _UL ·(1-Duty) (1) In the formula: U _term is the equivalent terminal voltage; U _H is the amplitude of the high level of the terminal voltage; U _L is the amplitude of the low level of the terminal voltage; Duty is the equivalent duty cycle of the terminal voltage; Expression (2) described in step (4) is as follows:

In the formula: U _A is the A-phase voltage output by the inverter, U _Aterm , U _Bterm , and U _Cterm are the inverter A-phase equivalent terminal voltage, B-phase equivalent terminal voltage, and C-phase equivalent terminal voltage respectively; B, C phase voltage. 2. the terminal voltage acquisition and compensation method improving the precision of power stage motor simulator according to claim 1, it is characterized in that according to the voltage sampling range of ADC module in DSP and the precision of voltage divider resistor, select patch resistor as terminal voltage Resistor divider in acquisition circuit. 3. the terminal voltage acquisition and compensation method improving the accuracy of power stage motor simulator according to claim 1, it is characterized in that described first operational amplifier selects the high-speed operational amplifier whose response time is lower than 20ns as voltage comparator, refer to Voltage 1 is set to 1/2 of the terminal voltage after voltage division. 4. the terminal voltage acquisition and compensation method improving the accuracy of power stage motor simulator according to claim 1, it is characterized in that described second operational amplifier is used as voltage follower and the third operational amplifier is used as voltage amplifier, all select bandwidth It is a high-speed and low-noise op amp with not less than 50MHz and total harmonic distortion not greater than -50dBc, and requires a positive and negative dual power supply with a ripple not higher than 10mV. 5. The terminal voltage acquisition and compensation method for improving the accuracy of a power stage motor simulator according to claim 1 is characterized in that the resistances R1, R2 and R3 are selected according to the recommended values of the operational amplifier manual, and the value of the reference voltage 3 is based on Voltage sampling range setting of ADC module in DSP.

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