Dynamic Microgrids with Voltage Unbalance Mitigation Using Distributed Secondary Control

Abstract

Dynamic microgrids (MG)have shown great potential in distribution system restoration as they could be frequently and actively reconfigured as per request from system operator. MGs usually have smaller inertia compared to conventional power systems thus require more delicate controller for operation safety. In addition, most distribution systems have unbalanced configurations which requires dedicated regulations on system operation states in both positive and negative sequence. This paper proposes a distributed secondary control strategy for unbalanced dynamic MGs operation. System frequency and voltage regulation are constantly enabled, along with voltage unbalance (VU)mitigation on critical load buses. The proposed control strategy provides automatic management of DGs within the same MG and seamless system transition as reconfiguration is requested. Detailed controller designs for both positive and negative sequence regulations are presented. Small-signal stability analysis of the proposed controller is derived and its dynamic performances are validated using MATLAB/Simulink.