Thermal Boundary Portrait of Wind Power Converter under Low Voltage Ride-Through with Maximum Reactive Power Capability

Wind power converters need to comply with the Low Voltage Ride-Through (LVRT) demands from grid code during faults, and a temporary high reactive current output is now needed to support the grid voltage. However, the maximum reactive output capability is mainly restricted by junction temperatures of IGBT, and the thermal boundary under LVRT conditions remains unclear. Multiple approaches including varying switching frequency and modulation schemes can enhance the maximum short-term reactive power capability of wind power converters, yet their contribution to the boundary expansion is difficult to quantify. In this paper, the thermal boundary of a 1MW wind power converter under LVRT is portrayed by novel electrical-thermal simulation based on frequency-domain thermal impedance, then verified on an actual 1MW full-scale direct-drive converter LVRT test-bench. The expanded thermal boundaries by adopting varying switching frequencies and modulation schemes are also depicted and validated.