Research of nonlinear control strategy for VSC-HVDC system based on Lyapunov stability theory

A nonlinear control strategy based on Lyapunov stability theory is proposed to satisfy stability requirements under the external interference of the uncertainty condition. Due to the nonlinear of the DC voltage differential equation for VSC-HVDC, the control of DC voltage is transformed to the control of the q-axis component of AC current fundamental component. Suitable Lyapunov functions are adopted according to the difference between reference value and actual value. Two nonlinear control inputs to the converter are obtained based on Lyapunov stability criterion. Due to linear of active power differential equation, active power is controlled based on traditional proportional integral (PI). The simulation results performed on PSCAD/EMTDC verify the feasibility of the control strategies effectively under a short time (0.05s) single phase to ground fault in two terminal AC systems of VSC- HVDC.