Development of the Algorithm for Determining PWM Parameters of Active Rectifiers Based on Experimental Data

Abstract

To date, frequency converters with active rectifiers are widely used in regulated medium voltage drives. In order to solve the electromagnetic compatibility problem of these drives with the network feeder, special PWM algorithms of active rectifiers are applied. These algorithms improve the harmonic composition of currents and voltages at the input of the active rectifier by removing or mitigating some of the most significant harmonics by selecting optimal gate switching angles. Some factors such as the presence of non-linear sections in the frequency response of supply network with high impedance value, arising from resonance phenomena can be not taken into account while calculating the optimum angles. In this case, even small amplitude harmonics of the active rectifier current can significantly distort the voltage shape at the point of common connection of the electrical consumers. In order to analyse how to ensure electromagnetic compatibility of frequency converters with active rectifiers in networks with resonance phenomena, it is necessary to know the parameters of the PWM algorithms used in a particular converter by means of mathematical modelling. Since converter manufacturers usually conceal the parameters of the PWM algorithms used in their products, a way to determine these parameters based on experimental data is needed. This paper discusses an algorithm for determining the PWM parameters of active rectifiers based on current waveforms obtained on the primary side of the matching transformer.