Research On Main Circuit Parameters Design Of Shunt Active Power Filter Based On Load Characteristics

With the rapid development of modern power system and the popularization of smart grid,the power electronic characteristics of power system become more and more obvious.The ever-growing non-linear electrical loads make the power quality problem get worse,which threatens the normal operation of power system.Shunt Active Power Filter(APF),which is able to eliminate current harmonics,compensate reactive power and unbalance of distorting and fluctuating loads,is getting more attention.The selection and optimization of APF main circuit parameters,AC side inductance and DC side capacitance and DC voltage,directly affects the compensation precision,dynamic and static compensation performance and system stability.Based on the nonlinear load harmonic current characteristics,this thesis studies the design method of the Active Power Filter main circuit parameters,a design scheme of APF main circuit parameters is proposed based on load characteristics and the parameter coupling effects.The selection of APF AC side inductance plays a decisive role in the equipment compensation effect.In this thesis,the APF main circuit differential equation is used to analyze the existing calculation method of AC inductance,and then taking into account the APF current tracking capability and switching ripple current limit,the algebraic equation is derived from APF voltage constraint equation.Based on the AC inductance selection principle,the analytical formula of APF rated AC inductance was derived,the analytical formula of APF rated DC voltage was also given.Finally,the determining method of the AC inductance is proposed based on the three-phase full-controled rectifier bridge load.DC side capacitance is one of the key parameters for Active Power Filter,appropriate capacitance directly affects APF DC voltage control effect and the cost of APF.This thesis firstly revealed the energy flow equation of the comprehensive compensation system,and then analyzed the existing calculation principle of APF DC side capacitance based on the instantaneous power theory.Then for the typical nonlinear load,three-phase fully controlled rectifier bridge,the DC side active power is analyzed in this thesis,and then the active power AC component and APF DC side capacitor charging and discharging energy are calculated.The analytical formula of the rated DC capacitance is derived.In the choice of APF main circuit parameters,there is a mutual influence and mutual restriction between these parameters.In this thesis,the applicability of APF main circuit parameters calculation formula for load type and harmonic characteristic are studied,the mutual influence of DC capacitance and AC inductance,the influence of DC capacitance and line impedance on APF compensation effect are analysed.Through the APF compensation system simulation model and comparison with the results by other relative article,the validity of the main circuit parameters calculation formula and the correctness of parameter coupling analysis were verified.Based on the above research results,this thesis presents a design method of APF main circuit parameters.An APF main circuit parameter design program is developed by using the graphical development language of LabVIEW,and the independent executable program is generated.In this thesis,APF parameters design method considering the load harmonic characteristics is simple and accurate,which can provide a reference for the accurate selection of compensation equipment in actual engineering.