Advanced Control Strategies of VSC Based HVDC Transmission System: Issues and Potential Recommendations

The converters and their control strategies play an important role in converting, transmitting, and improving the performance of high-voltage direct current (HVDC) system. There are different types of converter and their control strategies being employed in the HVDC system, such as line-commutated converter and voltage source converter (VSC). However, the existing converter controllers have still some limitations on certain deficiencies in certain aspects such as in weak AC grid or at high voltage and power level. Thus, an advanced converter control strategy is very much important in order to ensure optimal power transfer with minimal loss and stable voltage. This paper presents a comprehensive review of the advanced control strategies to address the problems and enhance the performance of the VSC-based HVDC (VSC-HVDC) transmission system. A detailed study on the overview of VSC-HVDC and their converter classifications are investigated. The main contribution of this paper is to carry out the different types of VSC-HVDC control strategies in controlling voltage, current, power, and the control parameters of the HVDC transmission system. This paper also highlights several factors, challenges, and problems of the conventional VSC-HVDC controllers. Furthermore, this paper provides some suggestions for the advanced control for the future research and development of the HVDC system.