Stability Analysis and Research of Compensation method for DC Microgrids

Abstract

Microgrid technology is the key technology to give full play to the advantages of distributed generation and DC microgrid technology has become a new development direction with its economic and efficient advantages. This paper focuses on the stability of DC microgrid. In this paper, the structure of DC microgrid is introduced in detail. Based on the model of each unit of DC microgrid, the operation principle and control strategy are analyzed. Then, the simplified model of DC microgrid is established, and the impedance ratio type criteria is used to determine the stability of DC microgrid and analyze the influence of some factors, such as the constant power load(CPL), the line inductance and the capacitor of converter, on the stability of the system. A DC microgrid simulation model is established based on Matlab / Simulink. On the basis of ensuring its stable operation, it is proved that reducing the line inductance and increasing the capacitor can improve the stability of the system; The constant power load with negative impedance characteristics has a greater effect on the stability of the system is verified by comparing the stability of the system in the same increments of CPL and resistive load. Moreover, it shows that the poorly damped LC filter in DC microgrid will have interaction with the constant power load and bring in unstable high-frequency oscillations. To solve the problem, a compensation method based on high-pass filter is proposed. The simulation results show that this method can effectively suppress the oscillation and improve the stability of the system.