Fault-tolerant control method for two-level PWM rectifier based on switching frequency

A switching frequency, fault-tolerant control technology, applied in the output power conversion device, the conversion of AC power input to DC power output, electrical components and other directions, can solve the problem of undercompensation, fault-tolerant control effect is not optimal, unable to achieve multiple bridge arms Switch tube fault tolerance control and other issues

Active Publication Date: 2018-12-21
NANJING UNIV OF SCI & TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The above method does not accurately compensate for the impact of the faulty switching tube on each sector, and also compensates for the sectors that are not affected by the switching tube failure, which belongs to overcompensation
The paper "PWM Rectifier Fault-Tolerant Control System Based on NCAV and Circuit Equivalent Replacement" proposed a fault-tolerant control method for PWM rectifiers based on equivalent circuits, but this method did not accurately compensate for the impact of faulty switching tubes on each sector. And in the sectors affected by multiple fault vectors, no compensation is performed, which belongs to undercompensation
The paper "A Rectifier Fault-Tolerant Control Method Based on Space Vector Control" proposed a space vector-based rectifier fault-tolerant control method. This method does not establish a unified sector division function, and cannot implement fault tolerance for multiple bridge arm switch tube failures. Although the precise compensation of a single switching tube can be realized, the negative impact of the faulty switching tube on the system is not considered, and the effect of fault-tolerant control is not optimal.

Method used

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  • Fault-tolerant control method for two-level PWM rectifier based on switching frequency
  • Fault-tolerant control method for two-level PWM rectifier based on switching frequency
  • Fault-tolerant control method for two-level PWM rectifier based on switching frequency

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Embodiment 1

[0154]In this embodiment, the three-phase two-level PWM rectifier is divided into eight sectors to illustrate the single-tube fault Q1. When a short-circuit fault occurs in the Q1 tube, it will be converted into an open-circuit fault by the thermal fuse. When an open-circuit fault occurs in Q1 , according to the state analysis of the three-phase two-level PWM rectifier in the eight-sector division mode under the fault of the Q1 switching tube in Table 16, the frequency fault-tolerant control method is described.

[0155] Table 16 Analysis of PWM rectifier eight-sector single-cycle state under Q1 switch tube failure

[0156]

[0157] The schematic diagram of the sector distribution affected by the fault switch tube of the three-phase two-level PWM rectifier Q1 tube fault in the eight-sector division mode is as follows: Figure 5 As shown, in the case of Q1 tube failure, for the sectors not affected by the fault switch tube in Table 16, the normal reference voltage rotation v...

Embodiment 2

[0159] This embodiment is described by taking a three-phase two-level PWM rectifier with multi-transistor faults in an eight-sector division mode.

[0160] When two switching tubes in the three-phase two-level PWM rectifier fail at the same time, such as figure 1 As shown, it will be divided into the following four situations:

[0161] a. The two upper and lower switching tubes of the same bridge arm fail at the same time;

[0162] b. Two upper tubes of different bridge arms fail at the same time;

[0163] c. Two lower tubes of different bridge arms fail at the same time;

[0164] d. One upper tube and one lower tube of different bridge arms are faulty.

[0165] Since the short-circuit fault can be converted into an open-circuit fault through the thermal fuse, after other fault diagnosis, the switching tube fault can also be converted into an open-circuit fault by turning off the controller. Here, the open-circuit fault is used for description.

[0166] For case a, the sim...

Embodiment 3

[0174] In this embodiment, the three-phase two-level PWM rectifier is divided into twelve sectors with a single-tube fault Q1 for illustration. When a short-circuit fault occurs in the Q1 tube, it will be converted into an open-circuit fault by the thermal fuse. When an open-circuit fault occurs in Q1 , the frequency fault-tolerant control method is described according to the state analysis of the three-phase two-level PWM rectifier in the twelve-sector division mode under the failure of the Q1 switch tube in Table 18.

[0175] Table 18 Single-cycle state analysis of twelve sectors of PWM rectifier under the fault of Q1 switching tube

[0176]

[0177] The schematic diagram of the sector distribution affected by the fault switch tube of the three-phase two-level PWM rectifier Q1 tube fault in the twelve-sector division mode is as follows: Figure 7 As shown, in the case of Q1 tube failure, for the sectors not affected by the fault switch tube in Table 18, the normal referen...

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Abstract

The invention discloses a fault-tolerant control method of a two-level PWM rectifier based on a switching frequency. The method comprises dividing sectors by selecting a sector dividing mode; determining the influence of the faulty switch on each sector and the change of the basic voltage vector before and after the fault; determining the basic voltage vectors of each sector and the action time ofthe basic voltage vectors before the fault; adjusting the basic voltage vector action time of the sector affected by the faulty switching transistor; determining the on-time of the three-phase switch; increasing the frequency of triangular carrier to make the total distortion rate of three-phase current reach the requirement of system current input; modulating the switching transistor on-time andtriangular carrier wave to determine the switching transistor PWM pulse, determining the switching transistor on-off, and completing the frequency fault-tolerant control. The invention can reduce thepulsation of the current trajectory circle, increase the control precision of the controller and improve the software fault-tolerant control effect when accurately compensating the sector affected bythe fault switch tube.

Description

technical field [0001] The invention relates to power conversion and control technology, in particular to a switching frequency-based two-level PWM rectifier fault-tolerant control method. Background technique [0002] With the development of power electronics technology, three-phase two-level PWM rectifiers have sinusoidal input current, bidirectional flow of energy, and adjustable DC voltage, and are widely used in medium and high-power occasions such as offshore wind power generation and new energy electric vehicles. application. In most cases, the rectifier needs to work uninterruptedly for a long time in a harsh industrial environment, coupled with factors such as unreliability and improper control of the power switch tube, the failure of the rectifier is inevitable. In order to avoid major accidents and reduce downtime, and restore the performance before the failure as much as possible, it is necessary to implement fault-tolerant control on the system. [0003] The e...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/219H02M1/088
CPCH02M1/088H02M7/219
Inventor 冯延晖秦伟黄凯邱颖宁
Owner NANJING UNIV OF SCI & TECH
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