Impedance Detection Based on Ripple Analysis and Current Sharing Control in DC Microgrid

Zhu Xiangchen,Zeng Guohui,Zhao Jinbin

doi:10.1109/access.2020.2976757

Abstract

In the operation of DC micro grid, the uniform load distribution is beneficial to the stable operation of the system and prolongs the service life of the system. In order to solve the influence of line impedance on traditional droop control in DC micro-grid, an impedance detection method based on ripple analysis and the structural characteristics of the DC micro-grid system is proposed. The high-frequency harmonic component of microgrid output current and voltage is mainly from the transistor switching frequency. By using the Fourier transform to analyze the high-frequency harmonic component of the voltage and current detected by the converter, the impedance information is obtained, and then the droop control is compensated base on it. In this paper, the compensation method is extended to the application of multiple devices in parallel. This method does not directly operate the system, so it has done no harm to the power quality. Finally, the feasibility of the proposed method in normal working conditions and its effectiveness in the case of communication interruption and load change is verified by RT-LAB hardware in loop experiment.

Highlights

As a small power generation system, microgrid has selfmanagement function, which can absorb the power generated locally and reduce the pressure on the main grid [1], [2]
Compared with traditional droop coefficient compensation method, droop control based on line impedance value can achieve better current sharing effect
In the first three seconds of the experiment, three converters are working in the current sharing state, and the bus voltage is stable controlled at 400V

Summary

INTRODUCTION

As a small power generation system, microgrid has selfmanagement function, which can absorb the power generated locally and reduce the pressure on the main grid [1], [2]. Xiangchen et al.: Impedance Detection Based on Ripple Analysis and Current Sharing Control the advantages from these two methods as mentioned This control method is able to reduce the dependence on communication between converters, while a global optimization control is achieved. Compared with traditional droop coefficient compensation method, droop control based on line impedance value can achieve better current sharing effect. The accurate droop control and voltage compensation are realized by using the topological characteristics of microgrid This method can accurately measure the resistance value of the corresponding line impedance of each converter. The change of the environment will be detected and compensate in the droop control It can reduce the uncertain factors influence of the environment and maintain current sharing effect of the converter. A hardware in the loop simulation platform based on RT-LAB is established to verify the effectiveness of the proposed method

DC MICRO GRID STRUCTURE AND CHARACTER

EXPERIMENT

Findings

CONCLUSION