PCC Voltage Compensation Scheme of MMC-MTDC System for Transient Stability Enhancement Under Communication Delay

Abstract

Multi-terminal High Voltage Direct Current (MTDC) with modular multilevel converter (MMC) is a promising technology, because it integrates diverse energy resources. However, there is still a risk for transient stability of a system with MMC in the case of communication delay. In order to improve the transient stability of hybrid AC/DC networks, the point of common coupling (PCC) voltage compensation scheme is proposed for MMC-MTDC to maintain stable operation when communication delay occurs. Based on the established closed-loop network control system (NCS) which the MMC-MTDC participates in, the proposed control strategy utilizes the multi-layer control according to the dynamic characteristic of MMC-MTDC, and compensates the PCC voltage in the controller input signal to reduce inaccuracy case by time delay, thus offset the negative effect of communication delay on power system transient stability. The proposed control method is fully investigated in a MMC-MTDC model based on 4-generator 10-node system model and the simulation results clearly indicate the proposed strategy can effectively enhance transient stability of system.

Keywords

• Modular multilevel converter (MMC)
• multi-terminal direct current (MTDC)
• transient stability
• communication delay
• multi-layer control
• point of common coupling (PCC) voltage