Control system of three-phase Vienna rectifier and Boost-PFC circuit

Abstract

The invention discloses a control system of a three-phase Vienna rectifier and a Boost-PFC circuit, the control system of the three-phase Vienna rectifier comprises a current control inner ring and a voltage control outer ring, the voltage control outer ring samples a bus voltage Vout output by the rectifier, outputs a voltage Vc after loop control, and outputs the voltage Vc after loop control; vc is multiplied by an input AC voltage sample Vg to serve as a reference current of the current control inner ring, the current control inner ring samples an input AC current ig of the rectifier, and a difference value obtained by subtracting the input AC current ig from the reference current is calculated through a current inner ring compensator; the current control loop further comprises a current feed-forward loop connected between an input AC voltage sampling end and an output end of the current inner loop compensator. By adopting the technical scheme of the invention, the PF and THD indexes of the three-phase Vienna rectifier can be optimized.

Description

Technical Field

[0001] The invention relates to the field of rectifiers, and in particular to a control system and a Boost-PFC circuit of a three-phase Vienna rectifier. Background Art

[0002] The three-phase Vienna rectifier has a series of advantages such as high power density, high power factor, and good performance. It is combined with the DC-DC topology to form an AC-DC module, which is widely used in communication power supply, industrial power supply, charging pile module and other fields.

[0003] When the power frequency voltage is input, the full load PF (power factor) and THD (total harmonic distortion) of the three-phase Vienna rectifier can easily reach 99% and 5% respectively. However, as the input AC voltage frequency increases, the input AC current zero-crossing distortion becomes more obvious, resulting in the deterioration of PF and THD, which seriously affects the overall performance indicators of the three-phase Vienna rectifier. Summary of the invention

[0004] The purpose of the present invention is to provide a control system and a control method for a three-phase Vienna rectifier in view of the defects of the above-mentioned prior art, so as to optimize the PF and THD indicators of the three-phase Vienna rectifier.

[0005] In an embodiment of the present invention, a control system for a three-phase Vienna rectifier is provided, characterized in that it includes: a current control inner loop and a voltage control outer loop, wherein the voltage control outer loop samples the bus voltage Vout output by the rectifier, outputs a voltage Vc after loop control, and multiplies Vc by the input AC voltage sample Vg as the reference current of the current control inner loop, and the current control inner loop samples the input AC current ig of the rectifier, and the difference obtained by subtracting the difference from the reference current is calculated by a current inner loop compensator, and the current control loop further includes a current feedforward loop connected between the input AC voltage sampling end and the output end of the current inner loop compensator, and the difference obtained by subtracting the product of the input AC voltage sample Vg and the feedforward coefficient Kp of the current feedforward loop from the output value of the current inner loop compensator is multiplied by the modulation coefficient Fm, that is, the duty cycle of the drive pulse of the rectifier switch tube is obtained.

[0006] In the embodiment of the present invention, the feedforward coefficient Kp of the current feedforward loop is 1 / (kv1×Fm×Vout), wherein kv1 is the input AC voltage sampling proportional coefficient.

[0007] In an embodiment of the present invention, a Boost-PFC circuit is further provided, which includes a three-phase Vienna rectifier and a control system. The control system adopts the control system of the three-phase Vienna rectifier mentioned above.

[0008] Compared with the prior art, in the control system of the three-phase Vienna rectifier of the present invention, the current control loop further includes a current feedforward loop connected between the input AC voltage sampling terminal and the output terminal of the current inner loop compensator, the feedforward coefficient Kp can be made a function of the associated bus voltage Vout to optimize the PF and THD of the three-phase Vienna rectifier under low-voltage conditions; when the feedforward coefficient Kp of the current feedforward loop is 1 / (kv1×Fm×Vout), the influence of the input AC current ig phase leading the input AC voltage Vg can be eliminated, the ig zero-crossing waveform distortion can be prevented, and the PF and THD of the three-phase Vienna rectifier under low-voltage conditions can be optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of a dual-loop control topology structure of a Boost-PFC circuit of a three-phase Vienna rectifier in the prior art.

[0010] Figure 2 yes Figure 1 Schematic diagram of the control of the inner current loop in .

[0011] Figure 3 4 is a control schematic diagram of the current inner loop according to an embodiment of the present invention.

[0012] Figure 4 PF and THD data of the three-phase Vienna rectifier according to the embodiment of the present invention. DETAILED DESCRIPTION

[0013] like Figure 1 As shown, in the dual-loop control topology of the Boost-PFC circuit, the control system of the three-phase Vienna rectifier includes a current control inner loop and a voltage control inner loop.

[0014] The loop control process of the voltage control outer loop is as follows: the bus voltage Vout output by the rectifier is sampled, and the difference obtained by subtracting it from the reference voltage Vref is calculated by the voltage outer loop compensator Hv(s) to output the voltage Vc, and Vc is multiplied by the input AC voltage sample Vg as the reference current of the current control inner loop. The loop control process of the current control inner loop is as follows: the input AC current ig of the rectifier is sampled, and the difference obtained by subtracting it from the reference current is calculated by the current inner loop compensator Hi(s), and then multiplied by the modulation coefficient Fm, that is, the duty cycle of the driving pulse of the rectifier switch tube is obtained. Among them, Ki is the input AC current sampling ratio coefficient, Kv1 is the input AC voltage sampling ratio coefficient, and Kv2 is the output voltage sampling ratio.

[0015] The equivalent control block diagram of the current inner loop is as follows: Figure 2As shown, Giv(s) is the transfer function from the input AC voltage Vg to the input AC current ig, Gid(s) is the transfer function from the duty cycle to the input AC current ig, and Vc is the output of the voltage outer loop. Figure 2 The transfer function from input AC voltage Vg to input AC current ig can be solved as follows:

[0016]

[0017] Here,

[0018]

[0019] Since the transfer function Y(s) has a phase lead, the input AC current ig leads the input AC voltage Vg in phase, resulting in ig zero-crossing waveform distortion, which deteriorates PF and THD.

[0020] In order to eliminate the ig zero-crossing waveform distortion, such as Figure 3 As shown, in the embodiment of the present invention, a current feedforward loop connected between the input AC voltage sampling terminal and the output terminal of the current inner loop compensator is added to the current loop. The difference obtained by subtracting the product of the input AC voltage sampling Vg and the feedforward coefficient Kp of the current feedforward loop from the output value of the current inner loop compensator is multiplied by the modulation coefficient Fm to obtain the duty cycle of the driving pulse of the rectifier switch tube. At this time, the expressions of the input AC current ig and the input AC voltage Vg are as follows:

[0021]

[0022] Since the approximate relationship between the main power transfer functions Gid(s) and Giv(s) of the Boost-PFC circuit is:

[0023] Gid(s)=Giv(s)×Vout,

[0024] When the feedforward coefficient Kp is set to 1 / (kv1×Fm×Vout), the influence of the Y1(s) transfer function on ig leading Vg can be eliminated. Therefore, the feedforward coefficient Kp can be used as a function of the associated bus voltage Vout to eliminate the waveform distortion of ig zero crossing and optimize the PF and THD of low voltage conditions. After optimizing the feedforward coefficient, the PF and THD data are as follows: Figure 4 shown.

[0025] In summary, since in the control system of the three-phase Vienna rectifier of the present invention, the current control loop further includes a current feedforward loop connected between the input AC voltage sampling terminal and the output terminal of the current inner loop compensator, the feedforward coefficient Kp can be made a function of the associated bus voltage Vout to optimize the PF and THD of the three-phase Vienna rectifier under low-voltage conditions; when the feedforward coefficient Kp of the current feedforward loop is 1 / (kv1×Fm×Vout), the influence of the input AC current ig phase leading the input AC voltage Vg can be eliminated, the ig zero-crossing waveform distortion can be prevented, and the PF and THD of the three-phase Vienna rectifier under low-voltage conditions can be optimized.

[0026] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control system for a three-phase Vienna rectifier, characterized in that: include: A current control inner loop and a voltage control outer loop, wherein the voltage control outer loop samples the bus voltage Vout output by the rectifier, outputs a voltage Vc after loop control, and multiplies Vc by the input AC voltage sample Vg as the reference current of the current control inner loop. After the current control inner loop samples the input AC current ig of the rectifier, the difference obtained by subtracting it from the reference current is calculated by the current inner loop compensator. The current control loop further includes a current feedforward loop connected between the input AC voltage sampling end and the output end of the current inner loop compensator. The difference obtained by subtracting the product of the input AC voltage sample Vg and the feedforward coefficient Kp of the current feedforward loop from the output value of the current inner loop compensator is multiplied by the modulation coefficient Fm, thereby obtaining the duty cycle of the drive pulse of the rectifier switch tube.

2. The control system of the three-phase Vienna rectifier according to claim 1, characterized in that: The feedforward coefficient Kp of the current feedforward loop is 1 / (kv1×Fm×Vout), wherein kv1 is the input AC voltage sampling proportional coefficient.

3. A Boost-PFC circuit, characterized in that: It comprises a three-phase Vienna rectifier and a control system, wherein the control system adopts the control system of the three-phase Vienna rectifier as claimed in any one of claims 1-2.

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