Research On The Control Of Three Phase Shunt Active Power Filter

With the rapid development of science and technology,new energy grid technology is put into production more frequently,nonlinear load is of more use in power system,which inevitably brings reactive power and harmonic pollution problems.In order to compensate reactive power and weaken harmonic as far as possible,we begin to choose active power filter(APF)as the main research direction.Relying on its strong real-time,strong compensation ability,anti-interference performance characteristics,it is widely used in the field of power control and engineering practice.The research object of this thesis is the three-phase shunt active power filter,firstly the basic principle is elaborated and the proper topology is chosen when the model is in normal mode.Then the mathematical model is established,harmonic detection and compensation control strategy is determined,the strategy based on voltage modulation is put into use.Then,the design of software program which assists main circuit and hardware control circuit is finished.Finally,simulation results in MATLAB confirm the correctness and feasibility of the scheme.The thesis first describes the concept and the way to improve the power quality,illustrates the background and development of active filter and hot technology,and introduces its advantages and classifications.Through the comparison of several common structure of three-phase four line filter,the type of capacitor midsplit is selected as the key content,and a mathematical model is established to explain its working principle.Afterwards,this thesis studies the ip-iq method and FBD method,and improve them to form the new FBD harmonic detection method which is the combination of the two;through the comparison of no deadbeat control and predictive control,the thesis extracts the advantages of prediction method to apply to the no deadbeat method,to make it better as a new compensation method.Then the space vector modulation strategy is selected.Next,this thesis designs the main circuit of APF,including the selection of the device and the setting of parameter;the hardware circuit with the TMS320F28335 chip as its core is also designed,including sampling and regulation,detection and control,drive and protection unit,and the Altium Designer is used to draw the principle diagram;Based on the hardware design,of the system software process program is devised,which consists of three parts,the main program,theinterrupt program and the calculation program,then the thesis makes the flow chart respectively.Ultimately,according to the theoretical analysis and the designed parameters which noted above,we carry out simulation in MATLAB.Using the spectrum of the grid current,the neutral and load current waveform,the stability of DC-link voltage as the basis,the compensation performace of three-phase shunt APF designed in the thesis is great in the power grid,it is capable of filtering harmonic effectively and withstanding the unexpected situations greatly,such as voltage distortion and load mutation.