Optimum reduction of switching losses based on the two-phase PWM modulation method

This paper proposes an optimum PWM method which reduces switching losses of a three-level NPC inverter most effectively by the two-phase modulation method. It selects the optimum one which minimizes a new switching (SW) loss estimation based on reduction effects in switching times considering phase currents among multiple reduction patterns. The proposed method was experimentally verified to select the optimal switching pattern which reduces its SW loss most effectively according to the on-line loss estimation by a DSP-based digital control system. The proposed method made it possible to reduce number of switching times of the largest or secondly largest current phase to 2/3 times. And it can automatically adapt to load conditions with various power factors. Measured switch losses are experimentally reduced about to 60-70% by the proposed method.