Research On Active Filter Technology For High Peak Factor Load Current

Power electronic devices have been widely used in the power grid.However,they also bring serious harmonic pollution problem to the power grid.For the diode-type rectifier with large capacitor filter,the grid-side current of the rectifier is characterized by high peak factor.If active power filter(APF)is compensated by conventional strategy,it will cause problems such as the low harmonic compensation rate,the poor grid-side current quality and the protection misoperation.In this thesis,the APF for load current with high peak factor is deeply studied and analyzed.In this thesis,the typical harmonic sources are classified according to the magnitude of the peak factor.Firstly,the influence of i? quantitative factor construction delay and low-pass filter delay on compensating harmonic current is analyzed.Based on the formentioned research work,a low-delay harmonic detection method is proposed.Then,this thesis points out that the conventional control method for APF is difficult to compensate high-peak-factor harmonics due to the limitation of regulators and bandwidth.To address this problem,the model predictive control(MPC)method is introduced in this thesis.This thesis optimizes the problems of low precision of single-vector control and variable switching frequency of classical MPC by adding a zero vector in each sampling period,fixing the switching frequency and reducing compensation current ripple.To solve the problem of ambiguous inductance parameter range of MPC,an optimized inductance parameter selection method is proposed to improve the harmonic compensation effect.Finally,a single-phase APF experimental platform of the fixed frequency based MPC is built Under reactive power generator consdition,the ripple of steady-state waveform and dynamic regulation time of classical MPC and fixed-frequency MPC are respectively compared with each other.In the harmonic compensation mode,compared with the same peak factor of load current,with the increase of fundamental current,the quality of current waveform after compensation becomes better,the corresponding THDi becomes smaller,and the total harmonic current compensation rate increases.The experimental results verify the effectiveness of the modified control method.