Battery Storage Assisted Plug-and-Play of Wind Generator in Standalone Microgrid for Off-Grid Residential Consumers

This paper investigates control for seamless plug-and-play operation of wind generator (WG) in a standalone microgrid consisting a battery energy storage (BES). The BES is connected via a bidirectional voltage source converter (VSC), and the variable speed WG, when available, is connected directly without any conversion stage. The VSC primary control usually operates it in grid-following $(GF_{o})$ mode. It follows the phase and frequency of the WG, which are continuously fed back via a phase-locked loop (PLL). But this control requires switching between $GF_{o}$ and grid-forming (GF) modes during each plug-in and plug-out operation of the WG. Providing an uninterrupted supply to consumers calls for complex control measures in such case. This article presents a method to maintain the primary control of the VSC in the GF mode at all the times irrespective of the presence or absence of the WG. The VSC operates on its own reference independent of the WG output, thus supporting both planned and unplanned plug-out of the WG without any change in the control. For seamless plug-in of the WG, a novel pre-synchronization based secondary control is presented. It attains transient free and swift synchronization even under varying frequency of the incoming WG. The performance of the control scheme, developed in synchronous dq reference frame, is simulated using MATLAB/Simulink. The results are validated on laboratory test bench by implementing the control algorithm on a DSP platform.