Low-complexity analytical approximations of switching frequency harmonics of 3-phase N-level voltage-source PWM converters

In this paper, analytical calculations of the switching frequency harmonics of PWM-controlled 3-phase voltage-source DC/AC power converters are presented. Detailed knowledge of the modulation-dependent spectra of such systems is highly valuable for the EMI filter design and the estimation of the high-frequency losses in the filter components and the load. The paper presents a formula for the calculation of the switching frequency harmonics which is simple and highly versatile. It can be applied to converters with arbitrary numbers of voltage levels N and in combination with a broad variety of modulation signals. All calculations are verified by means of simulations and show a high accuracy over a wide range of input parameters. Finally, an EMI filter design example demonstrates the practical application and benefits of the derived formula. The MATLAB code used for the calculations is provided at the end of the paper.