Adaptive drooping control scheme for VSC-MTDC system with multiple renewable energy sites based on variable droop constant

Abstract

The generated power from multiple renewable energy sites can be collected and integrated into the conventional alternating current grid by using a multi-terminal high voltage direct current (MTDC) system based on the voltage source converter (VSC). Following the converter outage or large disturbance, this system with a fixed drooping control scheme suffers overloading of the power converter, resulting in the imbalance of active power-sharing and large deviation of direct current voltages. To improve control performance, this paper proposes a novel adaptive drooping control approach according to the variable droop constant to keep balance active power-sharing and manage the alternation of DC voltage in huge power disturbances. The designed scheme is implemented on the both rectifier side and inverter side converters. The variable droop constant is evaluated according to the converter headroom with DC voltage deviations. The performance of the planned control method is compared with the fixed and variable droop control techniques. A 400 kV four-terminal VSC-MTDC test network is developed to verify the effectiveness of the designed control method. The proposed control technique, based on the PSCAD simulation results, can achieve good performance in the rectifier and inverter converter outage and faults operating scenarios.