A simple method for conducting angle calculation in cascaded inverters using step pulse waves

In recent years, the multilevel inverter synthesizing the output voltage with step pulse has been widely used as a solution for high power and high voltage applications. To get conducting angles of switches, the conventional method needs simultaneous equations corresponding to the fundamental and harmonic components by the use of Fourier series. Since they are calculated by an iterative method, the process is accompanied with a large amount of calculation and much time. Moreover, they are calculated by means of off-line operation. To overcome these drawbacks, this paper proposes a simple method to obtain the conducting angles. They are calculated by using voltage-second areas of the divided reference voltage according to the output voltage levels. The method reduces an amount of calculation for the conducting angles and determines them through on-line operation.