Article ID Journal Published Year Pages File Type
5001189 Electric Power Systems Research 2017 12 Pages PDF
Abstract

•A drawback of droop control is identified which leads circulating power flow during network contingencies.•A novel over-voltage regulation strategy is proposed in order to prevent an unintentional inverter shutdown.•A small-signal analysis is also performed to evaluate a microgrid's stability.

Equal power-rating inverters operating with different power set-points in either an islanded or grid-connected mode may lead to inter-unit circulating power caused by a large mismatch between power generation and demand during network contingencies (faults on the heavy load side or unintentional islanding). This circulating power may violate the dc-link voltage limit and, as a result, the protection scheme may shut down the inverter and reduce the microgrids reliability. This paper proposes a regulator for controlling the dc-link voltage of the microgrid's inverter during a period of circulating power. It includes a discharging resistor with a series-connected switch across the dc-link capacitor which is turned on through a control algorithm if the dc-link voltage exceeds its pre-defined limit. Case studies of parallel-connected inverters are conducted and their stability assessed through a small-signal analysis. In addition, a realistic microgrid is designed as a low-voltage (LV) network and tested to verify the concept and regulator actions presented. The simulation results validate the effectiveness of the proposed regulator during network contingencies.

Related Topics
Physical Sciences and Engineering Energy Energy Engineering and Power Technology
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