Resonance Analysis of Medium Voltage Multi-Microgrids Considering the Interaction of Controllable Series Compensator and Grid-Connected Inverters

The interaction of a controlled series compensator (CSC) with other power electronics and basic power components in a multi-microgrid (MMG) maybe lead to complex resonance problems. In this paper, the frequency domain analysis method and the mode analysis method are combined to analyze the resonance characteristics of the medium-voltage microgrid cluster system under the action of two controllable series compensators, transformer-coupled series compensator (TCSC) and capacitive-coupled series compensator (CCSC). Firstly, based on the equivalent output impedance models of TCSC and CCSC, the equivalent output impedance characteristics of TCSC and CCSC are explored by frequency domain analysis. Secondly, combined with the impedance network model of cluster system, the resonance characteristics of the MMG after separate and together access to these two controllable series compensators at different locations are explored by modal analysis method. The results show that the equivalent output impedance of the two couple-type compensators in a certain frequency band is capacitive, and CCSC has a wider capacitive frequency band. Changes in controller parameter selection can affect band range and capacitance degree. The CSC control parameters affect the system resonance frequency and resonance center, and when the grid-connected inverter circuit parameters are different, the mode of system resonance will also change. The combination of frequency domain analysis and modal analysis is an effective means to study the resonance stability of microgrid cluster systems.