Dead zone compensation method suitable for single-phase four-quadrant control based on PR regulator

Abstract

The invention relates to a dead-zone compensation method of a four-quadrant rectifier, in particular to a dead-zone compensation method suitable for single-phase four-quadrant control based on a PR regulator. According to the method, a double-closed-loop control strategy is adopted, an outer loop is a voltage control loop, and direct current bus voltage is controlled; and the inner loop is a current control loop and is used for controlling the alternating current side current of the rectifier bridge, and finally dead-zone compensation is carried out through the dead-zone compensation module based on the PR regulator. The dead-zone compensation method based on the PR regulator is adopted for dead-zone compensation, and the problem that in a method for conducting dead-zone compensation by judging the polarity of the corresponding bridge arm current, a digital controller adopted by a frequency converter has certain delay, the calculation result of the current beat is updated until the next beat, and the calculation time is shortened is solved. The dead zone compensation effect near the zero crossing point is poor; and the conduction voltage drop of a switching device IGBT and the on-off delay of a switching tube are not considered, so that the dead zone compensation is inaccurate.

Description

TECHNICAL FIELD

[0001] The application relates to a dead-time compensation method of a four-quadrant rectifier, in particular to a dead-time compensation method based on a PR regulator and suitable for single-phase four-quadrant control. BACKGROUND

[0002] The four-quadrant rectifier of an electric locomotive adopts a single-phase alternating current input mode, and a main circuit topology generally adopts an H-bridge two-level circuit structure. Switching devices of a bridge arm adopt high-voltage grade IGBTs. Since the IGBTs are not ideal devices, there are turn-on and turn-off delays, and therefore a certain dead-time needs to be added to driving pulses of upper and lower IGBTs of the same bridge arm to ensure reliable work of the switching devices. The turn-on and turn-off delays of high-voltage grade IGBTs are more serious, and therefore, to ensure reliable work of the devices, longer dead-time needs to be added to the driving pulses of the upper and lower tubes. The added dead-time will cause a problem that an actual output voltage waveform is inconsistent with a theoretical voltage waveform, thereby causing a dead-time effect. The dead-time effect will produce harmonic voltages and currents of different frequencies. These harmonics will affect the power supply quality of a power supply network, and even cause network voltage oscillation, thereby causing the locomotive to be unable to normally operate, and therefore it is necessary to compensate for the dead-time.

[0003] A current mode is adopted to compensate for the dead-time at present, that is, the polarity of four-quadrant input current of an inverter corresponding bridge arm is judged, and the dead-time is added to the driving pulse to compensate for the dead-time. The main problems of the method are as follows:

[0004] 1. The current zero-crossing detection is inaccurate, and the dead-time setting is 10 mu s, which causes poor dead-time compensation effect under light load working conditions.

[0005] 2. The conduction voltage drop of the switching device IGBT and the turn-on and turn-off delay of the switching tube are not considered, which causes inaccurate dead-time compensation of the method. SUMMARY

[0006] In order to solve the problem that the existing dead-time compensation method of a frequency converter adopts a digital controller and has a certain delay, the result of the present calculation is updated only in the next beat, and the dead-time compensation effect is poor near the zero-crossing point, the application provides a dead-time compensation method based on a PR regulator and suitable for single-phase four-quadrant control.

[0007] The application is implemented by adopting the following technical scheme: a dead-time compensation method based on a PR regulator and suitable for single-phase four-quadrant control adopts a double-closed-loop control strategy, an outer ring is a voltage control loop, and a direct current bus voltage is controlled; an inner ring is a current control loop, and an alternating current side current of a rectifier bridge is controlled, and finally a dead-time compensation module based on a PR regulator is used for dead-time compensation.

[0008] The dead-time compensation method based on the PR regulator suitable for single-phase four-quadrant control, the outer ring adopts a PI regulator, and the inner ring adopts a PR regulator.

[0009] The dead-time compensation method based on the PR regulator suitable for single-phase four-quadrant control, the outer ring adopts a PI regulator, and the given DC bus voltage and the DC bus voltage are zero-difference tracked, the given DC bus voltage and the DC bus voltage are subtracted to obtain an error value input to the PI regulator.

[0010] The dead-time compensation method based on the PR regulator suitable for single-phase four-quadrant control, the inner ring adopts a PR regulator, and the output of the PI regulator is multiplied by the of the phase-locked loop output to obtain a given value of the current inner ring, the PR regulator realizes zero-difference tracking of the given value and the rectifier bridge alternating current , and the given value and the rectifier bridge alternating current are subtracted to obtain an output of the PR regulator, and the output of the PR regulator is subtracted from the transformer secondary voltage e to obtain a modulation voltage command value .

[0011] The dead-time compensation method based on the PR regulator suitable for single-phase four-quadrant control, the input signals of the dead-time compensation module are , and , and the output is pulses for driving the A and B bridge arms; is the voltage between the two bridge arms of the rectifier, is the resonant frequency of the PR regulator.

[0012] The dead-time compensation method based on the PR regulator suitable for single-phase four-quadrant control, the dead-time compensation module includes a PR regulator and an SPWM generator, and after the modulation voltage command value is subtracted from the actual voltage value , an error value is generated by the PR regulator , the SPWM generator generates waves according to , and outputs .

[0013] The dead-time compensation method based on the PR regulator suitable for single-phase four-quadrant control, the input of the phase-locked loop is the transformer secondary voltage e, and the output is and .

[0014] The application solves the problem of inaccurate current zero-crossing detection in the method of dead-time compensation by judging the corresponding bridge arm current polarity, and the problem of inaccurate dead-time compensation caused by setting the dead-time to 10us, resulting in poor dead-time compensation effect under light load conditions, and not considering the on-state voltage drop of the IGBT switching device and the turn-on and turn-off delay of the switching tube. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a main circuit topology diagram of single-phase voltage type four-quadrant rectifier.

[0016] Figure 2 It is a V1 drive pulse and output voltage waveform diagram of A bridge arm.

[0017] Figure 3 It is a drive pulse and output voltage waveform diagram of A bridge arm V2.

[0018] Figure 4 It is an error voltage waveform diagram.

[0019] Figure 5 It is a four-quadrant rectifier control block diagram.

[0020] Figure 6 It is a principle diagram of dead-time compensation strategy based on PR regulator.

[0021] Figure 7 It is a flow chart of dead-time compensation strategy based on PR regulator. DETAILED DESCRIPTION

[0022] The main circuit of four-quadrant rectifier is shown in Figure 1 , the input is single-phase alternating current input, the main circuit topology adopts bridge circuit, A and B represent two bridge arms of the rectifier respectively, V1 and V2 correspond to the upper and lower tubes of A bridge arm, and V3 and V4 correspond to the upper and lower tubes of B bridge arm. Figure 1 are the leakage inductance and equivalent resistance of the secondary side of the transformer respectively, represents the current of the alternating current side of the rectifier bridge (i.e. the secondary winding of the transformer), is the DC bus voltage, represent the input current and output current of the DC bus rectifier bridge respectively.

[0023] The theoretical drive pulse of A bridge arm upper tube V1 is shown in Figure 2 (a), and the drive pulse after adding dead-time is shown in Figure 2 (b); The theoretical output voltage waveform of Figure 2 (c) is shown; after adding dead-time,​​​ The actual output waveform changes, and the current flowing from the grid into the four quadrants is... ,when When >0, Output waveform as follows Figure 2 As shown in (d), the error voltage like Figure 2 As shown in (e); when When <0, Output waveform as follows Figure 2 As shown in (f), the error voltage like Figure 2 As shown in (g).

[0024] The theoretical pulse of the lower tube V2 in bridge arm A is complementary to that of V1, and the theoretical driving pulse is as follows: Figure 3 As shown in (a), the drive pulse after increasing the dead zone is as follows: Figure 3 As shown in (b); waveform and error voltage waveform and Figure 2 Consistency.

[0025] Figure 2 and Figure 3 This indicates that the added dead time causes the actual output voltage waveform of bridge arm A to be inconsistent with the theoretical waveform, resulting in dead time effects such as voltage and current waveform distortion; the dead time also causes the actual output voltage waveform of bridge arm B to be inconsistent with the theoretical waveform, and the waveform is similar to that of bridge arm A.

[0026] Assumption It is sinusoidal. Figure 4 The figure shows the error voltage caused by the dead zone in the corresponding bridge arm A. The voltage waveform, through the Analysis revealed that the dead-zone effect reduces the fundamental voltage amplitude and increases the content of 5th, 7th, and 11th harmonics. This invention only compensates for the fundamental amplitude caused by the dead zone and does not currently consider other harmonics.

[0027] The control objectives of four-quadrant pulse rectification are twofold: first, to control the DC bus voltage. Command value Secondly, the control grid-side current waveform is sinusoidal, with a power factor close to 1. Therefore, a dual-loop control strategy is adopted: the outer loop is a voltage control loop, controlling the DC bus voltage; the inner loop is a current control loop, controlling the AC side current of the rectifier bridge.

[0028] The four-quadrant rectifier control block diagram is as follows: Figure 5 As shown, dashed box 1 represents the main circuit topology, with a single-phase AC input that is rectified and controlled by a bridge circuit.

[0029] Control strategy byFigure 5 The lower half is shown. The outer loop uses a PI regulator to achieve the given DC bus voltage. and actual DC bus voltage Zero-difference tracking; the inner current loop uses a PR regulator, and the voltage loop output... Multiply by the output of the phase-locked loop (PLL) Once the setpoint for the inner current loop is obtained, the PR regulator adjusts this setpoint to match the actual current. Zero-difference tracking.

[0030] Dead-zone compensation strategies based on PR regulators, such as Figure 5 As shown in dashed box 2, the input signal of the dead zone compensation module is , and The output drives bridge arms A and B. pulse.

[0031] Dead-zone compensation strategies based on PR regulators, such as Figure 6 As shown, the modulation voltage command value Compared with actual voltage value After the difference is calculated, the error value is generated by the PR regulator. , The resonant frequency of the PR regulator is provided by the PLL module, and the SPWM transmitter is based on... Transmit a wave and output .

[0032] The PR regulator can achieve zero steady-state error tracking of AC quantities, and its transfer function... The expression is as follows:

[0033] (1)

[0034] In the formula, It is the proportional coefficient of the PR regulator; It is the integral gain coefficient of the PR regulator; It is the grid synchronization angular frequency, and also the resonant frequency of the PR regulator.

[0035] This invention has the following technical features:

[0036] 1) This invention employs a PR regulator-based method to compensate for the dead zone of single-phase four-quadrant control. The compensation strategy is as follows: Figure 6 As shown, the modulation voltage command value Compared with actual voltage value After the difference is calculated, the error value is generated by the PR regulator. , The resonant frequency of the PR regulator is provided by the PLL module, and the SPWM transmitter is based on... Performing wave emission, final output .

[0037] 2) The application can more accurately track and compensate for current distortion caused by dead zone effect by using multiple PR regulators. This method considers the pulse change of current and can more flexibly adjust the output voltage during dead zone compensation.

[0038] 3) The method used in the application can maintain the stability of the compensation effect under different load conditions. Compensation is performed in the direct stationary coordinate, without the need for coordinate transformation, reducing the complexity of the algorithm.

[0039] 4) In the compensation process, to prevent system instability caused by overcompensation, the amplitude of the compensation voltage is monitored in real time to avoid exceeding the preset threshold.

[0040] 5) When the load changes dramatically, the dead zone compensation system can quickly respond, reducing the impact of load changes on the compensation system.

Claims

1. A dead-time compensation method based on PR regulator suitable for single-phase four-quadrant control, characterized in that: The double closed loop control strategy is adopted, the outer loop is a voltage control loop, the DC bus voltage is controlled, the inner loop is a current control loop, the AC side current of the rectifier bridge is controlled, and finally the dead zone compensation module based on the PR regulator is used for dead zone compensation.

2. A dead-time compensation method for single-phase four-quadrant control based on PR regulator according to claim 1, characterized in that: The outer loop adopts a PI regulator, and the inner loop adopts a PR regulator.

3. A dead-time compensation method for single-phase four-quadrant control based on PR regulator according to claim 2, characterized in that: The outer ring adopts PI regulator to realize zero difference tracking of given DC bus voltage and DC bus voltage The given DC bus voltage and DC bus voltage After the difference, the error value is input to the PI regulator.

4. A dead-time compensation method for single-phase four-quadrant control based on PR regulator according to claim 3, characterized in that: The inner loop adopts a PR regulator, and the output of the PI regulator is multiplied by the output of the phase-locked loop The output of the phase-locked loop is multiplied by the output of the PI regulator The given value of the current inner loop is obtained, and the PR regulator realizes the given value and the AC side current of the rectifier bridge The given value is obtained by homodyne tracking, and the given value and the AC side current of the rectifier bridge After the difference is input to the PR regulator, the output of the PR regulator is subtracted from the transformer secondary voltage e to obtain the modulation voltage command value .

5. A dead-time compensation method for single-phase four-quadrant control based on PR regulator according to claim 4, characterized in that: The dead-time compensation module inputs signals , and , and outputs pulses to drive the A and B bridge arms; is the voltage between the two bridge arms of the rectifier, is the resonant frequency of the PR regulator.

6. A dead-time compensation method for single-phase four-quadrant control based on PR regulator according to claim 5, characterized in that: The dead-time compensation module comprises a PR regulator and a SPWM generator, and the modulated voltage instruction value is subtracted from the actual voltage value , and the error value is generated by the PR regulator , the SPWM generator generates a wave according to the error value , and outputs .

7. A dead-time compensation method for single-phase four-quadrant control based on PR regulator according to claim 5, characterized in that: The input of the phase-locked loop is transformer secondary voltage e, and the output is and .

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