Slot corona protection systems for medium voltage rotor windings subjected to PWM voltage in doubly fed induction generators

Doubly fed induction generators using static frequency converters provide the possibility to have adjustable speed pump storage units where the active power can be controlled quickly for both generation (energy discharge) and pumping (energy storage) operation. However, high magnitude voltage spikes with high repetition rate and fast rise times (associated with PWM voltage of the converter) applied to the rotor winding, have adverse effects on the rotor insulation system. In this study using IEC 60034-18-42 test requirements, four different slot corona protection systems were evaluated. The results show that the design and manufacturing of the insulation system have great impacts on the performance of the slot corona protection system subjected to PWM voltages.