| Three-phase unbalanced,reactive power and harmonics current have become common power quality problems in power systems.Based on the three-phase four-wire diode clamped three-level topology,a modular smart power quality correction device has been designed in this paper,which can achieve harmonic suppression,reactive power compensation and three-phase unbalanced management.This paper has thoroughly studied working principle of the three-phase four-wire diode clamped topology,the instruction current extraction algorithm,current tracking control algorithm and phase locked loop technology.In view of the unbalanced three-phase voltage,frequency offset and the harmonic voltage of industrial applications,fundamental positive reactive sequence,negative sequence and zero sequence current extraction algorithm based on SOGI,selective harmonic extraction algorithm based on the novel discrete Fourier transform and the software phase locked loop based on SOGI are proposed in this paper.Moreover,PI + odd harmonics repetitive control is proposed based on the traditional PI + repetitive control.In this paper,a small signal model of single SPC and multi module SPC parallel system is established.On this basis,the resonant characteristics of parallel SPC have been analyzed,and an adaptive active damping algorithm based on hybrid module parallel system is proposed.A three-phase four-wire three-level SPC simulation model is built by Matlab/Simulink,and the validity of the software phase locked loop,current tracking strategy and parallel system resonance analysis is verified.At the same time,two 100 A and a 50 A three level modular SPC prototype were designed,where integrated Wi-Fi communication module and Android App were used to monitor modular SPC.The experimental results show that the three-level modular SPC designed in this paper can not only dynamically compensate reactive,unbalanced and harmonic currents,but also achieve dynamic setting of different kinds of compensation capacity. |
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