A Power Quality Conditioning System Based on Back-to-Back Modular Multilevel Converter

Abstract

The invention discloses a power quality regulation system based on back-to-back modular multilevel converters, which includes two three-phase half-bridge modular multilevel converters, an energy storage capacitor, two bidirectional thyristor groups, two A sensitive nonlinear load; two three-phase half-bridge modular multilevel converters are connected back to back, and the DC side is connected to the energy storage capacitor; the AC side of each three-phase half-bridge modular multilevel converter is connected through the corresponding The bidirectional thyristor group is connected to the busbar of the substation, and the AC side is also connected to the corresponding sensitive nonlinear load. This kind of system can dynamically compensate the voltage sag on the sensitive load when the power system is disturbed, and can suppress the harmonic injection of the load when there is no voltage sag in the power system, and at the same time can control the energy flow in the distribution network. Adjust and optimize to ensure power quality. The present invention also discloses a control method based on the aforementioned power quality regulation system to realize control purposes such as harmonic suppression, voltage sag control and power regulation.

Description

technical field [0001] The invention belongs to the technical field of multi-level power electronic converters, and in particular relates to a power quality regulation system based on back-to-back modules and multi-level converters, as well as harmonic suppression and voltage sag control based on the power quality regulation system. and method of power regulation function. Background technique [0002] With the continuous development of economy and technology and the continuous popularization of complex and sophisticated equipment, users' requirements for power quality of distribution network are also increasing. Voltage sag refers to the phenomenon that the power supply voltage rapidly drops and then rises in a short period of time, mainly caused by instantaneous high-power changes such as system electrical short-circuit, heavy load switching, and large motor startup. Voltage sags have low frequency and short duration, but often cause voltage-sensitive equipment to shut do...

AI Technical Summary

Problems solved by technology

Uninterruptible power supply mainly uses chemical energy such as batteries for energy storage. When the power grid is cut off, it can provide power supply for several minutes to several hours, and can also suppress voltage sags. However, there are excessive energy consumption, high maintenance costs, and occupation Disadvantages such as large area

The solid-state switch is used in a backup power supply system. When there is a problem with one voltage, it can be quickly switched to another power supply. However, the cost of construction and transformation is too high, and the voltage control effect is greatly affected by the switching time of the switch.

The dynamic voltage restorer can quickly compensate the appropriate drop voltage on the load side and eliminate the impact of voltage sag, but it cannot effectively compensate when the grid voltage drops below 50% or is completely interrupted

[0004] In addition, other traditional equipment to improve power quality include static var generators and static var compensators, etc., mainly by connecting capacitors or reactive power sources in parallel on the user side to compensate for the instantaneous reactive power deficit, thereby alleviating voltage drops and harmonics Pollution problems, but there are also problems such as limited reactive power compensation capacity, local compensation, and inflexible adjustment.

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