Dead-time compensation method for permanent magnet motor control based on PR regulator

Abstract

The present invention relates to a dead - zone compensation method for motor control, specifically a dead - zone compensation method for permanent - magnet motor control based on a PR regulator. The present invention aims to solve the problem in the prior art that there is a certain delay in the digital controller adopted by the frequency converter, and the calculation result of this cycle is updated until the next cycle, resulting in poor dead - zone compensation effect near the zero - crossing point. Therefore, a new dead - zone compensation method for permanent - magnet motor control based on a PR regulator is provided. The line voltage u ab 、u bc obtained through the sampling circuit is transformed by formulas (1) and (2) to obtain the phase voltages u a 、u b 、u c . After taking the difference between the phase - voltage command value #imgabs0# and the actual values u a 、u b 、u c , the error values generate u a‑ref 、u b‑ref 、u c‑ref through the PR regulator. The SPWM wave generator generates waves according to u a‑ref 、u b‑ref 、u c‑ref and finally outputs PWM1 - PWM6. The present invention solves the problem of inaccurate dead - zone compensation.

Description

Technical Field

[0001] The invention relates to motor control, and in particular to a dead zone compensation method for permanent magnet motor control, in particular to a dead zone compensation method based on a PR regulator and applicable to permanent magnet motor control. Background Art

[0002] The inverter main circuit of electric locomotives generally adopts a bridge circuit, and the switching device adopts IGBT. Since IGBT itself is not an ideal device, there is a delay in opening and closing. It is necessary to add a certain dead time to the driving pulse of the upper and lower tubes to ensure the reliable operation of the device. Figure 1 As shown in the figure, A, B and C represent the three bridge arms of the inverter respectively. The dead zone effect is analyzed by taking bridge arm A as an example. V1 and V2 are the upper and lower tubes of bridge arm A, and i is the motor current. The theoretical driving pulse of upper tube V1 of bridge arm A is as follows: Figure 2 As shown in (a), the driving pulse after adding the dead zone is as follows Figure 2 (b) as shown; AO The theoretical output voltage waveform is as follows Figure 2 (c) As shown; after adding the dead zone, u AO The actual output waveform changes. When i>0, u AO The output waveform is as follows Figure 2 As shown in (d), the error voltage Δu AO like Figure 2 (e) When i < 0, u AO The output waveform is as follows Figure 2 As shown in (f), the error voltage Δu AO like Figure 2 As shown in (g); the theoretical pulse of the lower tube V2 of the A bridge arm is complementary to the upper tube V1, and the theoretical driving pulse is as follows Figure 3 As shown in (a), the driving pulse after adding the dead zone is as follows Figure 3 (b) as shown; AO The waveform and error voltage Δu AO The waveform and Figure 2 of consistency; Figure 2 and Figure 3 It shows that the added dead time makes the actual output voltage waveform of the A bridge arm inconsistent with the theoretical waveform, causing the dead time effect such as voltage and current waveform distortion. The dead time effect also causes the actual output voltage waveform of the B bridge arm to be inconsistent with the theoretical waveform. The waveform is similar to that of the A bridge arm, so it is necessary to compensate for the dead time. Assuming i is sinusoidal, Figure 4 The error voltage Δu caused by the dead zone in the corresponding bridge arm A is shown. AO The voltage waveform is obtained by AO After analysis, it is found that the dead zone effect reduces the voltage fundamental amplitude, so it is necessary to compensate for the dead zone.

[0003] The prior art compensates for the dead zone by judging the polarity of the motor current of the corresponding bridge arm of the inverter. On the one hand, the current zero-crossing point detection is difficult due to the distortion of the current waveform; on the other hand, due to the digital control method adopted by the inverter, the digital control will produce a delay, and the result of the current beat calculation will not take effect until the next beat, resulting in a delay in the dead zone compensation based on the current sampling current, and the dead zone compensation cannot be accurately performed. Summary of the invention

[0004] In order to solve the problems that the existing method of using the polarity of motor current to compensate for the dead zone is difficult to detect the current zero crossing point due to the distortion of the current waveform, and the digital control method adopted by the inverter will produce a delay, and the result of the current beat calculation will take effect only in the next beat, resulting in a delay in the dead zone compensation based on the current sampling current, and the dead zone compensation cannot be accurately performed. Therefore, a new dead zone compensation method based on a PR regulator and suitable for permanent magnet motor control is provided.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A dead zone compensation method for permanent magnet motor control based on a PR regulator comprises the following steps:

[0007] 1) Obtain two motor line voltages u through a voltage and current sampling circuit (the voltage and current sampling circuit is a circuit that can be obtained by those skilled in the art through conventional means) ab 、u bc And the motor three-phase current i A 、i B and i C ;

[0008] 2) The line voltage u of two motors ab 、u bc Get another motor line voltage u ca , the formula is as follows:

[0009] u ca =-u ab -u bc (1)

[0010] 3) From the motor line voltage u ab 、u bc 、u ca The actual value u of the motor three-phase voltage is obtained by transformation a 、u b 、u c , the transformation formula is as follows:

[0011] 4) The three-phase current i of the motor A 、iB and i C The α and β axis currents i are obtained by the 3 / 2 transformation formula. α 、i β , the transformation formula is as follows:

[0012] 5) The current i of α and β axes α 、i β The d and q axis currents i are obtained by the 2s / 2r transformation formula. d 、i q , the transformation formula is as follows:

[0013] where θ 0 is the synchronous rotation angle of this beat, obtained by sampling the position sensor;

[0014] 6) The d and q axis current command values ​​i sent by the host computer d *、i q *(known value) and the calculated actual value of d and q axis current i d 、i q Calculate the current error, and then use the PI regulator to get the d and q axis voltage values ​​u d 、u q ;

[0015] 7) d, q axis voltage value u d 、u q The voltage values ​​u of the α and β axes are obtained by the 2r / 2s transformation formula. α 、u β , the transformation formula is as follows:

[0016] θ=θ 0 +1.5*w e *T s (6)

[0017] Where θ is the 2r / 2s transformation angle; T s is the interruption time; w e is the synchronization angular frequency;

[0018] 8) From the α and β axis voltage values ​​u α 、u β The three-phase voltage command value of the PR regulator is obtained by the 2 / 3 conversion formula and The transformation formula is as follows:

[0019] 9) Set the PR regulator three-phase voltage command value The actual value of the motor three-phase voltage u a 、ub 、u c The difference is then used to generate the three-phase voltage command value u of the SPWM generator through the PR regulator. a-ref 、u b-ref 、u c-ref , the SPWM generator is based on the SPWM generator three-phase voltage command value u a-ref 、u b-ref 、u c-ref The six driving pulse signals PWM1 to PWM6 for driving the IGBTs of the three bridge arms A, B, and C are output. The PR regulator is used to achieve zero-static-error tracking of the fundamental wave, the fifth harmonic, and the seventh harmonic. The transfer function G PR The expression of (s) is as follows:

[0020]

[0021] Where K P is the proportionality coefficient; K R is the fundamental frequency integral coefficient; K R-5 is the fifth harmonic integral coefficient; K R-7 is the seventh harmonic integral coefficient; w e is the synchronization angular frequency.

[0022] The beneficial effects of the present invention are as follows: The present invention uses a dead zone compensation method based on a PR regulator to perform real-time dead zone compensation for the voltage error caused by the dead zone, solving the problem that in the method of performing dead zone compensation by judging the polarity of the corresponding bridge arm current, on the one hand, the current zero-crossing point detection is difficult due to the distortion of the current waveform; on the other hand, due to the digital control method adopted by the inverter, the digital control will produce a delay, and the result of the current calculation will not take effect until the next beat, resulting in a delay in the dead zone compensation based on the current sampling of the current, and the dead zone compensation cannot be accurately performed. (The present invention uses a regulator to perform real-time dead zone compensation for the voltage error caused by the dead zone, and does not need to judge the current polarity, thereby avoiding the problem of poor compensation effect caused by the delay in the dead zone compensation by judging the current polarity) BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the main circuit of the inverter;

[0024] Figure 2 It is the V1 driving pulse and output voltage waveform of the A bridge arm;

[0025] Figure 3 is the driving pulse and output voltage waveform of A bridge arm V2;

[0026] Figure 4 The waveform of the current i and the error voltage Δu AO The voltage waveform;

[0027] Figure 5 is a schematic diagram of a dead zone compensation method of the present invention;

[0028] Figure 6 It is the control block diagram of PR regulator;

[0029] Figure 7 This is the dead zone compensation flow chart based on PR regulator. DETAILED DESCRIPTION

[0030] A dead zone compensation method for permanent magnet motor control based on a PR regulator comprises the following steps:

[0031] 1) Obtain two motor line voltages u through a voltage and current sampling circuit (the voltage and current sampling circuit is a circuit that can be obtained by those skilled in the art through conventional means) ab 、u bc And the motor three-phase current i A 、i B and i C ;

[0032] 2) The line voltage u of two motors ab 、u bc Get another motor line voltage u ca , the formula is as follows:

[0033] u ca =-u ab -u bc (1)

[0034] 3) From the motor line voltage u ab 、u bc 、u ca The actual value u of the motor three-phase voltage is obtained by transformation a 、u b 、u c , the transformation formula is as follows:

[0035] 4) The three-phase current i of the motor A 、i B and i C The α and β axis currents i are obtained by the 3 / 2 transformation formula. α 、i β , the transformation formula is as follows:

[0036] 5) The current i of α and β axes α 、i β The d and q axis currents i are obtained by the 2s / 2r transformation formula. d 、i q, the transformation formula is as follows: where θ 0 is the synchronous rotation angle of this racket;

[0037] 6) The d and q axis current command values ​​i sent by the host computer d *、i q *(known value) and the calculated actual value of d and q axis current i d 、i q Calculate the current error, and then use the PI regulator to get the d and q axis voltage values ​​u d 、u q ;

[0038] 7) d, q axis voltage value u d 、u q The voltage values ​​u of the α and β axes are obtained by the 2r / 2s transformation formula. α 、u β , the transformation formula is as follows:

[0039]

[0040] θ=θ 0 +1.5*w e *T s (6)

[0041] Where θ is the 2r / 2s transformation angle; T s is the interruption time; w e is the synchronization angular frequency;

[0042] 8) From the α and β axis voltage values ​​u α 、u β The three-phase voltage command value of the PR regulator is obtained by the 2 / 3 conversion formula and The transformation formula is as follows:

[0043]

[0044] 9) Set the PR regulator three-phase voltage command value The actual value of the motor three-phase voltage u a 、u b 、u c The difference is then used to generate the three-phase voltage command value u of the SPWM generator through the PR regulator. a-ref 、u b-ref 、u c-ref , the SPWM generator is based on the SPWM generator three-phase voltage command value u a-ref 、u b-ref 、u c-refThe six driving pulse signals PWM1 to PWM6 for driving the IGBTs of the three bridge arms A, B, and C are output. The PR regulator is used to achieve zero-static-error tracking of the fundamental wave, the fifth harmonic, and the seventh harmonic. The transfer function G PR The expression of (s) is as follows:

[0045]

[0046] Where K P is the proportionality coefficient; K R is the fundamental frequency integral coefficient; K R-5 is the fifth harmonic integral coefficient; K R-7 is the seventh harmonic integral coefficient; w e is the synchronization angular frequency.

Claims

1. Dead zone compensation method for permanent magnet motor control based on PR regulator, It is characterized in that The steps include: 1) Obtain the motor line voltage u through the voltage and current sampling circuit ab 、u bc And the motor three-phase current i A 、i B and i C ; 2) The line voltage u of two motors ab 、u bc Get another motor line voltage u ca , the formula is as follows: in ca =-in ab -in bc (1) 3) From the motor line voltage u ab 、u bc 、u ca The actual value u of the motor three-phase voltage is obtained by transformation a 、u b 、u c , the transformation formula is as follows: 4) The three-phase current i of the motor A 、i B and i C The α and β axis currents i are obtained by the 3 / 2 transformation formula. α 、i β , the transformation formula is as follows: 5) The current i of α and β axes α 、i β The d and q axis currents i are obtained by the 2s / 2r transformation formula. d 、i q , the transformation formula is as follows: where θ 0 is the synchronous rotation angle of this shot; 6) The d and q axis current command values ​​i sent by the host computer d *、i q *Compared with the calculated actual value of d and q axis current i d 、i q Calculate the current error, and then use the PI regulator to get the d and q axis voltage values ​​u d 、u q ; 7) d, q axis voltage value u d 、u q The voltage values ​​u of the α and β axes are obtained by the 2r / 2s transformation formula. α 、u β , the transformation formula is as follows: θ=θ 0 +1.5*w e *T s (6) Where θ is the 2r / 2s transformation angle; T s is the interruption time; w e is the synchronization angular frequency; 8) From the α and β axis voltage values ​​u α 、u β The three-phase voltage command value of the PR regulator is obtained by the 2 / 3 conversion formula and The transformation formula is as follows: 9) Set the PR regulator three-phase voltage command value The actual value of the motor three-phase voltage u a 、u b 、u c The difference is then used to generate the three-phase voltage command value u of the SPWM generator through the PR regulator. a-ref 、u b-ref 、u c-ref , the SPWM generator is based on the SPWM generator three-phase voltage command value u a-ref 、u b-ref 、u c-ref The six driving pulse signals PWM1 to PWM6 for driving the IGBTs of the three bridge arms A, B, and C are output. The PR regulator is used to achieve zero-static-error tracking of the fundamental wave, the fifth harmonic, and the seventh harmonic. The transfer function G PR The expression of (s) is as follows: Where K P is the proportionality coefficient; K R is the fundamental frequency integral coefficient; K R-5 is the fifth harmonic integral coefficient; K R-7 is the seventh harmonic integral coefficient; w e is the synchronization angular frequency.

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