Study On Current Detecting And Compensation Of Reactive Power And Harmonics In Three-phase Four-wire System

In recent years, with the development of power electronics technology, many kinds of power electronics devices are widely used. On one hand, they made power energy transformation and application conveniently; on the other hand, they lead to serious reactive power and harmonic current pollution in the power system. Active power filter is a new power electronic device which can effectively compensate harmonic and reactive current of power network, It has many favorite work characteristic such as real-time and accuracy. So active power filter has been studied widely and is stepping into industrialization.This article firstly narrated the development present situation of harmonic suppression and the reactive power compensation technology, introduced many kinds of the existing current detected methods of reactive and harmonic based on the frequency domain and time domain, the principle of the methods and their advantages and disadvantages, the principle of active power filter and the situation of it according to different standard classified, and so on.The performance of active power filter is affected by the reactive and harmonic current detection link and the instruction current tracking control link. The reactive and harmonic current detection methods based on theory of instantaneous reactive power and instruction current tracking control in the three-phase four-wire system is researched as emphases. In order to solve the question of reactive and harmonic current real-time examination, the system instantaneous reactive power theory and reactive and harmonic current detection methods is firstly researched in the three-phase three-wire. In this foundation, how to extended the three-phase circuit instantaneous reactive power theory to the three-phase four-wire system carried on the detailed research, the definition and respective meaning of instantaneous active power, the instantaneous reactive power and the instantaneous zero-sequence power were given, and the simulation and comparison of p - q-0 and i_p - i_q - i₀ detecting methods were researched. Through the simulation research in the different application situation, the advantages and disadvantages of the two methods were presented. Based on the foundation, the balance control of DC side capacitance voltage was increased to methods, and the simulation result was given. Through the simulation and comparison of tracking PWM control method, the triangular wave comparison way finally was chosen to control compensation instruction current.When control signal was discretized by the digital controller of active power filter, causes the digital controller control to have the serious time-delay. In order to solve the time-delay question, the paper chooses forecasting algorithm based on adaptive filter as research object. The theory and simulation of forecasting algorithm based on adaptive filter in the reactive and harmonic current detection application.Because of the difference of compensating way of zero-sequence current, the active power filter main circuit structural style and control modes were different. Compared with two common forms of the parallel active power filter main circuit, the three-phase voltage converter was chosen, the control method of different main circuit structure of the APF and the corresponding control method of DC voltage were given, The active electric power filter capacity and has carried on the choice with the switch component, the active power filter capacity and switch component have been designed, the parameter of connection inductance and the DC side electric capacity was calculated. In this foundation, design the double CPU control system based on TMS320F2812 and AT89S51 of parallel active power filter, and its hardware circuit and the system software is given.Through experimental study and simulation of the algorithm and parameter design of parallel three-phase four-wire active power filter, and the result presents proposed methods were feasibility. Finally, the full work of the paper was summarized, some insufficiencies were pointed out, and the next research work content was made predicted.