Optimal power flow and sensitivity analysis for power system with DFIG-wind farms integrated through AC/VSC-HVDC power transmission

Considering wind speed fluctuation and switch of VSC(Voltage-Source Converter) control mode,the DCPFC(Direct-Current Power Flow Controller) is introduced to the power system with DFIG-wind farms integrated through AC/VSC-HVDC(AC/VSC-High Voltage Direct Current). An optimal power flow model that minimizes the power loss of AC/VSC-HVDC grid and the DC voltage deviation index is developed,which includes detailed configuration of DFIG,so as to optimize the control variables of DFIG and VSC-HVDC. The sensitivities of the objective function with respect to the constraints of DFIG and VSCHVDC are derived based on Lagrange multipliers at the optimal solution. As a result,the power flow control capability of both DFIG and VSC-HVDC is evaluated. The effectiveness and potential applications of the proposed model and the sensitiveness analysis are validated by numerical results of IEEE 14-bus system.