A new switching method for PWM inverter with uniform distribution of output current´s spectrum

In this paper, in order to reduce the dominant harmonic clusters in the output current´s spectrum, a new switching method for PWM inverters is proposed. When an inverter with a constant switching frequency is used, it would result in narrow-band harmonics. These harmonic clusters can make acoustic noises and Electromagnetic Interference (EMI). In order to reduce the noises and EMI effect of these harmonic clusters, random-switching PWM techniques have been introduced. The concept of random-switching PWM technique is to spread the original narrow-band harmonic throughout a wide range of frequencies. With the method which is proposed in this paper acoustic noises and EMI are reduced uniformly in output current´s spectrum. Proposed switching pattern is discussed and compared by other switching pattern that proposed earlier. Simulation results of proposed method are shown for a Permanent Magnet Synchronous Motor (PMSM) that is fed by PWM inverter and controlled by Field Oriented Control (FOC) algorithm.