A simplified and unified space vector PWM algorithm for multi-level diode clamped VSI

In this paper, a simplified and unified space vector pulse width modulation (SVPWM) algorithm for multi-level diode clamped (DC) voltage source inverter (VSI) is proposed. The traditional SVPWM method for two-level inverter is not very difficult to implement. However, it becomes more and more complex and difficult to realize as the level number of the inverter increases. Based on the relationship between SVPWM and sinusoidal pulse width modulation (SPWM) for two-level inverter and a simplified SVPWM algorithm for two-level inverter, a simplified and unified SVPWM algorithm for multi-level (N≥3) DC VSI is developed. Modulation implicit functions of SVPWM are derived from modulation implicit functions of SPWM, and the simplified SVPWM algorithm is obtained by decomposition of modulation implicit functions of SVPWM. Compared with the conventional SVPWM algorithm, the simplified and unified SVPWM algorithm can be more easily implemented in a digital device because the algorithm directly uses the instantaneous values of three phase reference voltages to calculate actual gating time for each inverter leg. Unlike the conventional SVPWM algorithm which needs coordinate transformations, trigonometric calculations, sector number identification etc., the state of each power switch can be determined directly and easily without much calculation by using the simplified algorithm. The advantages of new method are that realization of SVPWM is greatly simplified and complexity increases little as the number of inverter level increases. The simulation results show that proposed method is valid and feasible.