Cascade H-bridge STATCOM system without electrolytic capacitor and control method

Abstract

The invention discloses a cascade H-bridge STATCOM system without an electrolytic capacitor and a control method, and belongs to the field of power electronic control. The system comprises a three-phase power grid, a three-phase reactive load, a filter inductor and N three-phase cascade Buck multiplexing type H bridges, and N is greater than or equal to 2; the Buck multiplexing type H bridge comprises an H bridge formed by switching tubes S1-S4, a decoupling inductor Lr, and two thin-film capacitors Cd and Cr, the Cr is connected to the midpoint of a second bridge arm of the H bridge through the Lr to form a bidirectional Buck circuit, and the bidirectional Buck circuit and the second bridge arm of the H bridge realize switching tube multiplexing; the midpoint of the first bridge arm of the H bridge is connected with the midpoint of the second bridge arm of the previous H bridge, and the three phases are in star connection. On one hand, the bidirectional Buck circuit carries out active power decoupling, H-bridge direct current side fluctuation power is transferred to an auxiliary capacitor Cr through Lr, so that H-bridge direct current side voltage double frequency fluctuation is eliminated, a thin-film capacitor replaces an electrolytic capacitor, meanwhile, an H-bridge first bridge arm is assisted to complete alternating current and direct current side power conversion, and the power density and reliability of the device are improved.

Description

technical field [0001] The invention relates to the field of power electronic control, in particular to a non-electrolytic capacitor cascaded H-bridge STATCOM system and a control method. Background technique [0002] my country is a large country with a vast territory and uneven energy distribution. The abundant electric energy in the northwest needs to be transported to the eastern region through long distances. On the other hand, with the development of science and technology and industry, many high-power reactive loads such as steel rolling mills, mine hoists, and large-capacity transformers have appeared in the power grid. If the reactive power compensation in the power grid is insufficient, this long-distance power transmission will exist. Huge line loss leads to low efficiency of the power grid; in addition, with the depletion of traditional fossil energy, countries around the world are increasingly calling for strengthening the development and utilization of new ener...

AI Technical Summary

Problems solved by technology

However, this requires the addition of additional power devices, which will increase the cost and volume of the overall system

Based on the single-phase grid-connected inverter, a small number of scholars have studied the multiplexed active power decoupling technology without adding power switch tubes. The second bridge arm switch tube of the H bridge and the active power decoupling circuit The multiplexing of switching tubes has problems such as complex control and difficult design of control parameters. At the same time, most of the research backgrounds are aimed at a single H-bridge. At present, there is almost no research on the multiplexed active power decoupling control of three-phase cascaded H-bridges. Although the phase-cascaded H-bridge multiplexed active power decoupling control is similar to a single H-bridge, there are many differences. There are still many problems to be solved in the three-phase cascaded H-bridge multiplexed active power decoupling control, so The research of cascaded H-bridge multiplexing active power decoupling control is very necessary

Images