Positive and Negative Sequence Voltage Feedforward Method for Three-phase PWM Converter

Abstract

The invention discloses a positive-negative sequence voltage feedforward method of three-phase PWM (pulse width modulation) converter which relates to a positive-negative sequence voltage feedforward method and is capable of lowering the influence of lagging and negative sequence voltage of three-phase PWM control on running of a converter caused by. The method comprises the steps of: carrying out phase-sequence separation on an acquired power grid voltage after carrying out Clarke conversion on the acquired power grid voltage so as to obtain a positive sequence voltage component and a negative sequence voltage component; carrying out phase-sequence separation on an acquired current after carrying out Park conversion on the acquired current so as to obtain a positive sequence current component and a negative sequence current component; calculating a positive sequence current loop set value and a negative sequence current loop set value by adopting a PWM control algorithm; carrying outforward-feeding decoupling control on the positive sequence current component and the negative sequence current component to obtain control set voltage of a PWM converter; calculating and respectively carrying out phase angle compensation on a positive sequence synchronous coordinate system and a negative sequence synchronous coordinate system according to angles needed to be compensated in feedforward of positive sequence power grid voltage and negative sequence power grid voltage; synthesizing the control set voltage of the PWM converter and the compensated phase angles after respectively carrying out Park inverse conversion on the control set voltage of the PWM converter and the compensated phase angles to obtain the final control set voltage of the PWM converter. The positive-negativesequence voltage feedforward method of the three-phase PWM converter is suitable for the control process of the three-phase PWM converter.

Description

technical field [0001] The invention relates to a positive and negative sequence voltage feedforward method of a three-phase PWM converter. Background technique [0002] In the conventional three-phase PWM converter control strategy, it is generally carried out under the assumption that the voltage of the three-phase grid is balanced. , Transmission line asymmetry and other reasons, often cause unbalanced grid voltage. When the power grid is unbalanced, there are not only positive sequence components but also negative sequence components in the grid voltage. If only the control of positive sequence components is considered, the positive sequence components are converted into DC components, and the negative sequence components are converted into components twice the grid frequency. Negative sequence currents are generated on the AC side, and characteristic and non-characteristic harmonic voltages and currents are generated on the DC side, which will affect the operating perf...

AI Technical Summary

Problems solved by technology

However, the grid voltage feed-forward in the traditional feed-forward decoupling control does not consider the angle that the negative sequence component of the grid voltage in the synchronous coordinate system turns from when the voltage and current are sampled to when the PWM signal is sent out.

Moreover, since there is a certain initial angle error between the negative sequence component and the positive sequence component when the positive and negative phase sequences are separated, the feedforward methods of the negative sequence component and positive sequence component of the grid voltage are also different.

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