Adaptive droop control in VSC-based MT-MVDC distribution systems considering ESS participation

This paper proposes a novel adaptive droop (ADC) control for voltage source converter (VSC)-based multiterminal medium-voltage direct current (MT-MVDC) distribution systems with heterogeneous energy storage system (ESS) participation. The proposed ADC scheme can achieve MVDC bus voltage management and power sharing between VSCs with overloading operation, solving the issue that all VSCs on the rectifier/inverter side reach their power limits concurrently after a large system disturbance. This is accomplished by factoring in the real-time power/voltage values at VSC stations along with an extended power component. This component is contingent on the actual operational state of the ESSs and inversely correlated with the power delivered/absorbed by the ESSs. Moreover, the controllers of the battery and ultracapacitor systems incorporate two additional control loops, a novel VSC excess power reduction (VEPR) loop as well as inner expanded excess power reduction (EEPR) loop, to obtain the power reference values. The two loops ensure all VSCs operate within individual power limits after the engagement of the ESS. The effectiveness of proposed ADC strategy is confirmed through real-time simulations in a hybrid AC/MT-MVDC system.