System Design And Experimental Study Of Power Quality Disturbance Generator

In recent years,the research on power quality problems at home and abroad is mainly divided into three aspects: first,the establishment of power quality disturbance signal model;second,the improvement of power quality real-time monitoring system;third,the research on voltage disturbance signal generator.The main work of this paper is as follows:(1)This paper focuses on the simulation and detection of power quality disturbance.According to the single disturbance of a phase in three-phase voltage signal,this paper studies the application of instantaneous symmetrical component method in power quality detection and analysis,builds simulation in PLECS,constructs five common voltage disturbance waveforms,and decomposes the sequence component of voltage disturbance signal.In order to solve the problem of voltage disturbance in three-phase signal,the detection and classification based on dq0 component method is adopted,and the disturbance is classified according to dq0 axis component waveform.In view of the problem that seven kinds of voltage sags can not be distinguished between the two methods,the following chapters adopt the classification method based on the types of voltage sags,characteristic voltage and zero sequence component of voltage,and verify it by phase neutral point(X)voltage index and phase phase(Y)voltage index.(2)The voltage sag generator based on power electronics is studied.Firstly,the simulation model of voltage sag generator based on single-phase inverter and voltage sag generator based on three-phase inverter are built in the simulation environment of PLECS.The quality problems of seven different kinds of voltage sag waveform are discussed.The control strategy and the generation method of voltage disturbance are introduced.The influence of different voltage sag characteristics on the output voltage sag waveform is analyzed,and analyze the applicable working conditions of different topologies.At last,the paper focuses on the three-phase four wire circuit,and selects the two-stage three-phase four leg circuit as the simulation and experimental topology.(3)The topology stability and voltage disturbance signal generation of two-stage three-phase four leg inverter system are studied.The main problem of the second-stage system is the stability problem,so this chapter will model the small signal of the second-stage system,and analyze the stability of the system through the impedance criterion to prove the stability of the topology.The input impedance of the front boost circuit and the output impedance of the rear three-phase four leg circuit are calculated.According to the stability criterion of the impedance ratio,the stability of the system is proved,and the stability of the system can be maintained within a certain range of parameter changes.In the simulation environment of PLECS,the voltage sag generator simulation model of two-stage three-phase four leg inverter is built,and the generation of voltage sag waveform based on sequence component control is adopted.The quality of different types of voltage sag waveform and the influence of different voltage sag depth and duration characteristics are analyzed.(4)Finally,based on the simulation topology,the hardware experiment platform of the two stage three-phase four leg circuit is built.Through the experiment topology,interruption and harmonic disturbance signals can be generated,and seven different voltage sag waveforms can be generated,and the duration and depth of voltage sag can be controlled.The correctness of the topology and the proposed control strategy is verified,and the power quality disturbance can be generated by the experiment topology dynamic waveform.