Using SMES for Voltage Stabilization of PMSG Based Wind Energy System

With variable speed wind turbines (VSWT), the maximum power point tracking (MPPT) should be implemented through making the rotor following the optimum rotor speed. But, due to wind variability, there will be fluctuations in the output power of wind turbine generators. If these generators are connected to a DC grid, the power fluctuations will negatively be reflected on the DC voltage. So, Superconducting Magnetic Energy Storage (SMES) is proposed in this study as an effective solution for voltage stabilization of DC grids connected to wind energy systems. The adopted wind turbine generator is Permanent Magnet Synchronous Generator (PMSG). The models of wind turbine, PMSG, and interfacing rectifier are built using PSCAD/EMTDC software. Then, a model for SMES is built including a superconducting coil with large inductance and a DC-DC bidirectional converter. The SMES control is built through PI controller to determine the duty cycle to the DC-DC bidirectional converter to achieve charging, freewheeling and discharging modes for the SMES. Two various operating conditions are considered, operation with variable wind speed and operation with sudden load change. SMES could effectively absorb the excess or deliver the shortage in output power enabling DC voltage stabilization at the desired value.