Electric energy quality adjusting system based on back-to-back modular multilevel converters

Abstract

The invention discloses an electric energy quality adjusting system based on back-to-back modular multilevel converters. The electric energy quality adjusting system comprises two three-phase half-bridge modular multilevel converters, an energy storage capacitor, two bidirectional thyristor groups and two sensitive nonlinear loads, wherein the two three-phase half-bridge modular multilevel converters are connected in a back-to-back manner, and the direct current sides are connected with the energy storage capacitor; the alternating current side of each three-phase half-bridge modular multilevel converter is connected with a transformer substation bus through the corresponding bidirectional thyristor group, and the alternating current side of each three-phase half-bridge modular multilevelconverter is further connected with the corresponding sensitive nonlinear load. The system can dynamically compensate the voltage sag on the sensitive load when the power system generates interference, can inhibit the harmonic injection of the load when the power system does not generate the voltage sag, can adjust and optimize the energy flow in the power distribution network at the same time, and guarantees the quality of electric energy. The invention further discloses a control method for achieving the control purposes of harmonic suppression, voltage sag treatment, power regulation and the like based on the electric energy quality adjusting system.

Description

technical field [0001] The invention belongs to the technical field of multilevel power electronic converters, in particular to a power quality regulation system based on back-to-back modules and multilevel converters, and the realization of harmonic suppression and voltage sag control based on the power quality regulation system and a 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. Among them, the power quality problem mainly caused by voltage sag is the focus of people's attention. Voltage sag refers to the phenomenon that the power supply voltage drops and rises rapidly in a short period of time, which is mainly caused by instantaneous high power changes such as electrical short circuit of the system, large load switching, and large motor sta...

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.

Images