Master self-tuning VDCOL function for hybrid multi-terminal HVDC connecting renewable resources to a large power system

To take advantage of line commutated converter (LCC) and voltage source converter high-voltage, direct current (HVDC) technologies a hybrid multi-terminal HVDC (MTDC) is designed to exploit the power from renewable resources. A previous study showed that the voltage dependent current order limiter (VDCOL), an emergency function to reduce the current order of an HVDC converter station when voltage is depressed, should be installed in all of the LCC stations of the hybrid MTDC. This study presents a design for a master self-tuning VDCOL function implemented in a hybrid multi-terminal HVDC system. This controller aims to generate an adaptive current reference for each LCC station of the VDCOL in a low-voltage condition. The parameter of this adaptive VDCOL can be chosen according to the summary table of practical experiences; therefore, no tuning technique is required. The developed HVDC control algorithm is implemented on the simplified South East (SE) Australian 14 generator system using DIgSILENT PowerFactory. The simulation results demonstrate the effectiveness of the proposed control function in reducing the complexity of the control system and operation along with improving system transient stability.