An Improved Harmonic Suppression Control Strategy for the Hybrid Microgrid Bidirectional AC/DC Converter

Guishuo Wang,Jiechao Lv,Xiaoli Wang

doi:10.1109/access.2020.3042572

Abstract

The nonlinear load in AC/DC hybrid microgrid seriously affects the power transmission quality of bidirectional AC/DC interlinking converter (BIC). In this article, an improved Fryze-Buchholz-Depenbrock (FBD) harmonic current detection method combined with droop control is designed to suppress harmonic current control strategy. The decoupled double synchronous reference frame phase locked loop (DDSRF-PLL) with self decoupled network is used to eliminate the negative sequence fundamental frequency component, and the accurate phase detection can also be realized when affected by nonlinear load. The least mean square (LMS) algorithm adaptive filter can enhance the dynamic response ability when the load current suddenly changes. To solve the problem that the cut-off frequency of low pass filter (LPF) can not take into account the detection accuracy and response speed of FBD harmonic current detection method. Finally, Matlab/Simulink is used for simulation verification. The simulation results show that the improved control strategy not only realizes the bidirectional flow of power and maintains the DC bus voltage stability, but also reduces the total harmonic distortion (THD) at point of common coupling (PCC) by 0.45% compared with the traditional FBD control strategy. And the effectiveness and feasibility of the design method are proved.

Highlights

In recent years, with the smart grid entering the comprehensive construction stage, an AC/DC hybrid microgrid system combines the advantages of both AC and DC microgrids has been widely studied [1]
Based on the droop control strategy combined with the two methods of FBD harmonic detection, both the rectifier mode and the inverter mode had total harmonic distortion (THD) less than 1%, and the improved control strategy had THD reduced by 0.45%
The traditional FBD harmonic detection method adopts the traditional PLL, which is unable to achieve accurate phase locking under the non-ideal condition of voltage and current distortion, and the cut-off frequency of the low pass filter (LPF) cannot give consideration to the response speed and detection accuracy of the FBD method

Summary

INTRODUCTION

With the smart grid entering the comprehensive construction stage, an AC/DC hybrid microgrid system combines the advantages of both AC and DC microgrids has been widely studied [1]. In literature [19], combined with active filtering method, proposed a controllable inductive power filtering (CIPF) method It can effectively reduce the risk of harmonic resonance and greatly improve. In literature [21], [22], the proposed converter control strategy based on neural network and fuzzy control improves the accuracy of harmonic current suppression, with slow convergence speed and complex structure. When the nonlinear load causes the current distortion and generates the harmonic current, this method can suppress the harmonic current transmitted in the BIC, and achieve bidirectional power flow and maintain the DC bus voltage stability under the non-ideal condition. Mode, and the public grid is responsible for regulating the voltage and frequency stability of the AC sub-microgrid

DROOP CONTROL STRATEGY FOR GRID-CONNECTED MODE

Findings

CONCLUSION