Overload mitigation control of droop-controlled grid-forming sources in a microgrid

The droop-controlled grid-forming sources are well known for robust voltage and frequency control and the ability to balance power between multiple sources in a microgrid. However, these sources may become overloaded with the possibility of collapsing the microgrid. This paper presents an overload mitigation control strategy which can autonomously transfer the extra load of the overloaded source to other sources without communications. The main advantages of this control strategy are that it maintains voltage control of the overloaded sources and does not need to switch between grid-forming control and grid-following control. A small signal model is established to study the system stability. Simulation and on-site test results verify the effectiveness of this control strategy.