Application of energy function control strategy to VSC based UPFC Model

전압원 컨버터 기반의 UPFC 모델에 대한 에너지 함수 제어전략의 적용

UPFC(Unified Power Flow Controller) consists of two voltage sourced converter(VSC)s inserted into AC system through series and parallel coupling transformer, where two VSCs are linked by capacitor at DC-side. Since VSC acts as an AC voltage source behind a reactance, where both magnitude and phase angle of the source are controllable, UPFC can be represented by the equation related to input-output relation of two VSCs. Voltage control of DC-link capacitor provides the path of real power flow between two VSCs. While UPFC is controlled for maintaining the given reference value in steady state, it should be controlled for damping power oscillation in dynamics. For such a control objective, the control strategy based on the energy function was proposed and has been shown to be effect and robust for damping power oscillation of power system. In this paper, UPFC model based on the VSC was analysed and applied to power-flow control and stability analysis. The control strategy based on the energy function is adopted for damping power oscillation of power system. The effectiveness of proposed control strategy was verified by simulation study