Coordinated Voltage Control of Offshore Wind Farms Combined with AC Grid based on OPF-MPC Method

This paper proposes a coordinated voltage control (CVC) scheme for the offshore wind farms (OWFs) with AC grid based on the optimal power flow (OPF) and model predictive control (MPC). In the proposed scheme, the AC grid and wind turbine generators (WTGs) are coordinated to keep voltages within the feasible range, reduce the active power losses and optimize reactive power distribution among the OWFs with AC grid. In the upper layer, an OPF-based voltage control method is designed for AC grid, which can achieve the optimal power flow considering the active power outputs of OWFs, to minimize the voltage deviations of all buses. In the lower layer, a MPC-based voltage control method is designed for each OWF, which can optimize reactive power distribution among WTGs inside each OWF with the reactive power output references of each OWF from the upper layer. The analytic sensitivity coefficient calculation method is applied to improve the computation efficiency. Two offshore wind farms with a modified IEEE 5 bus system were used to verify the proposed CVC scheme.