Direct current capacitor voltage control method for power units of SVG (static VAR generator)

Abstract

The invention relates to a direct current capacitor voltage control method for power units of a chained SVG (static VAR generator). The method includes the steps: each phase of converter chain comprises a plurality of series link power units; reactive compensation current is calculated in upper-layer control; 3, a regulating voltage vector for total active and reactive control in a system is calculated; 4, an instantaneous value of regulating control output voltage of each link power unit in lower-layer control; 5, fine adjustment of balance control output voltage is calculated; 6, an actual control output quantity is obtained by stacking the instantaneous values of regulating control output voltages and the fine adjustments of balance control output voltages. The method has the advantages that a hierarchical control method is adopted, an algebraic sum of the fine adjustments of the balance control output voltages of the link power units of the same phase in lower-layer control is approximate to zero, and upper-layer control is unaffected; the lower-layer control and the upper-layer control are decoupled, control characteristics are good, and parameter design is simple; direct current capacitors are well uniform in voltage, and output waveform quality is high.

Description

technical field [0001] The invention relates to the field of reactive power compensation, in particular to a method for controlling the DC capacitor voltage of an SVG power unit. Background technique [0002] The chain structure SVG device is a dynamic reactive power compensation device based on the series connection of H-bridge high-power inverters. Each phase of it is composed of H-bridge power units with the same structure connected in series. The three-phase connection adopts a star connection, and then It is connected to the grid through the connection reactor. It has the following advantages: the number of required power devices is small, and no additional clamping diodes or balancing capacitors are needed; it is easy to realize modularization, easy to expand, and applicable to different voltage levels. The chained SVG can perform dynamic reactive power compensation and harmonic control for nonlinear loads in the medium and high voltage distribution network, and impro...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to provide a method for controlling the DC capacitor voltage of an SVG power unit, which adopts the self-balancing control algorithm of layered control to realize the DC capacitor voltage balance control of the power unit, ensures the safe operation of the device, and has low cost and high system reliability. In order to solve the problems that the existing technology mostly adopts centralized control, which leads to easy interference between control target quantities, poor consistency of DC capacitor voltage, and low output waveform quality

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