Power Decoupling Control of VSC-HVDC Systems Connected to a Weak Grid

When the voltage source converter based high voltage direct current (VSC-HVDC) system is connected to an AC weak grid, the power coupling will impose the challenge to the stability and controllability of the power system. This paper derives the linear model of dual loop controlled VSC. Based on developed linear model, coupling characteristics of VSC-HVDC system are revealed in two aspects of phase lock loop (PLL) and power control loop under a weak grid condition. Furthermore, it proposed a power decoupling control strategy. Simulation studies have verified the effectiveness of the proposed control strategy.