Development of adaptive PWM algorithm for an active rectifier and a method for diagnosing resonant phenomena in in-plant networks

Abstract

Currently, adjustable medium voltage electric drives are mostly based on frequency converters with active rectifiers. In cases where the medium voltage network has extended cable lines, adverse resonance phenomena can occur in the network, due to which, when significant harmonics of the FC with AR are applied to the resonance region, critical voltage distortions occur in the distribution network. The solution to this problem can be the installation of special filters that correct the frequency response of the network. However, this requires experimental determination of the frequency response for all possible modes of power supply, which is a difficult technical task in practice. Therefore, it is relevant to study an adaptive method of reducing voltage distortions caused by the operation of a FC in networks with resonant phenomena.When developing a method for diagnosing resonance phenomena and an improved PWM algorithm, the existing PWM algorithms used by manufacturers of electric drives with AR has been analyzed and the well-known methods of mathematical modeling of frequency converters and power supply systems has been used. The main assumption of the model is representation of the inverter as a current source. Anadaptive method for reducing distortion in networks with resonant phenomena based on improved PWM algorithm that allows excluding from the harmonic series of the voltage curve of the frequency converter the group of harmonics included in the resonance region has been developed.A comparative analysis of the FC with non-adaptive and adaptive PWM has been performed using simulation model of the FC system with AR – medium voltage network. It has been found that the use of the adaptive PWM algorithm significantly reduces the distortion in the network in the presence of resonance phenomena.Method proposed can be applied to detect in-plant networks resonance in different frequency ranges when power supply mode is changing. Adaptive algorithm can be applied in the design of FC with AR.