Constant-frequency direct power control method for PWM converter under condition of power grid voltage imbalance

Abstract

The invention belongs to the field of wind generator power conversion device control, and relates to a constant-frequency direct power control method for a PWM converter under the condition of power grid voltage imbalance. The method comprises the following steps of: determining a sampling frequency; acquiring a three-phase power grid voltage, a three-phase power grid current and a direct-current side voltage, and calculating resultant vectors E and I of the power grid voltage and the power grid current in a three-phase static coordinate system respectively; calculating positive and negative sequence components of the power grid voltage and the power grid current; calculating an instantaneous power and an instantaneous power error; calculating a converter reference voltage, and performing inverse transformation on the converter reference voltage; performing amplitude limit on the converter reference voltage to obtain the resultant vector of the converter reference voltage after the amplitude limit; and modulating the resultant vector of the converter reference voltage after a space vector modulation algorithm is adopted for amplitude limit, and outputting the converter voltage. The method can inhibit the active power fluctuation of the system more effectively and greatly reduce the harmonic wave of the alternating-current side current; and the output converter voltage switch frequency is constant, so the output filter parameter design is simpler.

Description

Technical field [0001] The invention belongs to the field of control of power conversion devices of wind generators, and relates to related technologies in the field of energy conversion devices of AC-DC systems. Background technique [0002] PWM converter has the advantages of high power factor, low input current harmonic content, constant DC side voltage and bidirectional power flow, etc. It is obtained in the fields of distributed power generation, AC drive, active filtering, reactive power compensation and renewable energy utilization. widely used. [0003] At present, foreign control strategies for PWM converters are mainly divided into two categories: vector control and direct power control. Direct power control has attracted the attention of many scholars at home and abroad for its advantages of simple control algorithm, good dynamic performance, high efficiency, and good robustness. . Traditional direct power control has shortcomings such as unfixed output switching frequ...

AI Technical Summary

Problems solved by technology

Traditional direct power control has shortcomings such as unfixed output switching frequency and high system sampling frequency, so constant frequency direct power control has become a research hotspot in this type of control strategy

[0004] The unbalanced grid voltage will generate a large amount of harmonic current on the AC side of the PWM converter and cause large fluctuations in the active power of the system. In severe cases, the system performance will deteriorate sharply

In order to improve the system performance, many scholars have proposed many improved algorithms based on the vector control strategy, but in the constant frequency direct power control strategy, the improved algorithm to deal with the unbalanced grid voltage is still rare.

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