Study On Control Technology Of Single-phase Cascade H-bridge Active Power Filter

With the development of power electronic technology,power electronic devices are widely used in modern society.Power electronic equipment is the main source of harmonics in the power grid.The generated harmonics seriously "pollute" the grid environment,reduce the efficiency of power transmission and utilization,affect the stable operation of the system,and seriously hinder the development of power electronic technology.Therefore,controlling the harmonic problem of the power grid and maintaining the "green" environment of the power grid have become urgent problems in the power electronics field.At present,passive power filters(Passsive Power Filter,PPF)and active power filters(Active Power Filter,APF)are mainly used to control harmonics.Passive power filter(PPF)uses a combination of passive components to form a filter,which is a passive control device.Active power filter(APF)is a device that dynamically suppresses harmonics and compensates reactive power.It has many advantages such as good harmonic compensation,fast response,small capacity of energy storage components,and ability to track changes in grid frequency.The use of cascaded H-bridge as the main circuit topology of APF has the characteristics of low voltage stress,high output power quality,and modular expansion.It has been widely used in various fields at home and abroad.This article first analyzes the working principle of the cascaded H-bridge active power filter,and then studies the traditional PWM modulation strategies commonly used in single-phase cascaded H-bridge converters such as carrier phase-shift modulation,discontinuous modulation,and one-dimensional space vector modulation.Analyzed the characteristics and principles of traditional PWM modulation,and proposed a freewheeling modulation strategy using anti-parallel diodes for its shortcomings,and then combined the discontinuous modulation idea with anti-parallel diode freewheeling modulation,and proposed a method that can greatly reduce switching The anti-parallel diode freewheeling discontinuous modulation strategy is designed to reduce the switching loss of the APF system and improve its work efficiency.The modulation strategy mentioned in the paper is simulated and the output waveform quality is compared and analyzed.Then introduced the traditional total capacitor voltage control scheme,capacitor voltage balance control scheme,harmonic current detection and control scheme of single-phase cascaded H-type active power filter.Based on the traditional control scheme,this paper conducts a quantitative analysis of the DC side capacitor voltage fluctuation components,and proposes a definite-integral filter-based capacitor voltage minimum value control scheme,and compares and analyzes the simulation with the traditional scheme to verify the proposed optimization The control scheme has better harmonic compensation effect and faster dynamic response time.Finally,the experimental platform of single-phase cascade H-bridge active power filter is designed and built,and the main circuit,driving circuit and control circuit are designed.Based on TMS320F28335 DSP and Xilinx XC6SLX9-2 type tqg144 c FPGA platform control circuit,the traditional carrier phase-shifting modulation strategy,the parallel fly-wheel diode modulation strategy,the parallel diode stream discrete modulation strategy and reduce the experimental research was conducted on the dc side capacitor control method,and compared with the traditional scheme,verify the correctness and effectiveness of the proposed method.