Research On Control Strategy Of Active Power Filter For Aviation Variable Frequency Power System

Three-phase 115V/360-800 Hz variable frequency AC power system has become the main power system for More-Electric Aircraft.With the increase of EMA,EHA,DC/DC power supply and power electronic devices,harmonic problems are brought about,which seriously affect the power quality of power supply.Active power filter can effectively compensate harmonics.However,the aviation variable frequency AC power system is different from the industrial electrical network.It's frequency is high and the frequency range is wide,which poses a challenge to harmonics suppression.This paper studies the three-level active power filter used in aviation variable frequency power supply system.Firstly,the working principle of diode-clamped three-level active power filter is analyzed,and the model under the condition of capacitor voltage equalization and imbalance is deduced.Therefore,this paper proposes to use voltage control loop to control the capacitor voltage balance.Secondly,this paper describes several frequency detection methods and harmonic current detection methods,and proposes improved Rife method for the frequency detection.It is proposed to use the ipiq method to detect harmonic current.And in the case of voltage distortion and asymmetry,it is derived that the harmonic current can still be accurately detected using the ip-iq method.Then,the characteristics of PI control and PR control are compared and analyzed.The quasi-PR controller is used for current tracking,and the parameter design of the quasi-PR controller is analyzed.A block diagram of the harmonic current control loop based on the quasi-PR controller is given.Because the frequency of variable frequency power supply is high,pre-modified Tustin transformation is used to discrete to solve the problem of resonance frequency shift.Finally,the simulation model is built on MATLAB/Simulink,the above algorithm is verified by simulation.The experimental hardware platform is built,and the frequency detection and harmonic current detection experiments at different frequency points are carried out in the frequency range of 360-800 Hz.On this basis,the double-loop control strategy based on quasi-PR control is verified.The experiment results show that harmonic can be effectively compensated and current THD can be reduced to about 6% at different frequency.Compensated current meets the index of GJB 181B-2012 that THD should be less than 10%,which verifies the feasibility of the control strategy proposed in this paper.