A Simplified and Effective DPWM Algorithm of NPC Inverter for High Power Factor Load

Currently, 3-phase NPC inverters with high power capacity, are increasingly widely used in industry and especially in the field of renewable energy such as solar energy, where the load has a higher power factor. Switching losses in high-power inverters are large, so reducing this loss will increase the efficiency of high-power inverters. The approach to reducing switching losses in the inverter is the basic method based on space vector and carrier methods. The space vector method often requires angle and sector information to calculate the actual modulation time according to the inverter's patterns, so this approach increases the complexity of the PWM algorithm. To address this issue, this paper presents a simplified and effective carrier-based pulse width modulation (PWM) algorithm for high power loads with a power factor close to the unity value. The proposed PWM method does not require much computation and the zero-sequence function is proposed and added to the modulation signals. The zero sequence will be designed to avoid commutation in phase with high current values. The switching states of the power switches are determined by comparing the control signal and the high-frequency carrier signal. As a result, switching loss is reduced and higher efficiency can be achieved. The effectiveness of the proposed algorithm is studied through simulation by developing the MATLAB/SIMULINK model.