Multi Trajectory Based Droop Control of DC Microgrids for Improved Voltage Regulation

Droop control is a conventional method for seamless integration of multiple power sources to feed a power grid. It is a decentralised power flow control mechanism which doesn't involve any communication links between the controllers which feed energy. Droop control mechanism has poor voltage regulation despite its advantage of decentralised control. This is because the droop characteristics of connected systems that feed energy to the grid are different. This paper proposes an advanced multi droop characteristics mechanism which involves selection of droop characteristics based on the tolerance band of the voltage. If the DC bus voltage of the microgrid falls below a particular tolerance band level, the intelligent controller shifts the droop characteristics to a new droop characteristics that makes the system to work within the standard voltage levels. To avoid jerks and transients in the bus voltage due to the shift in droop characteristics in real time, a voltage level-based hysteresis is used. The proposed control strategy is simulated and verified using MATLAB Simulink. Results are discussed towards the end of the paper.