Dynamic Discontinuous PWM for Grid-tied Inverter Applications

This paper proposes a Dynamic Discontinuous PWM (DDPWM) strategy for Grid Tied Inverter applications utilizing 2 level Voltage Source Inverters (VSIs). DDPWM is a version of Generalized DPWM (GDPWM) optimized for usage with full range of operating power factor values and without need for current feedback signals, such that it provides minimal switching loss. Switching and Conduction Loss expressions are derived, simulated and analyzed for individual transistors and diodes inside inverter module. Simplified thermal model based on available datasheet parameters is presented and used for evaluation of thermal performance of semiconductor devices under DDPWM across full range of power factor and modulation index values. It is demonstrated that high modulation index and low power factor values produce highest overall module losses, but that the individual device temperatures are dependent on module forward and switching characteristics, as well as thermal resistances. Experimental setup is implemented to evaluate thermal performance of DDPWM.