New Method of Industrial Power Supply Systems' Resonances Diagnosis by Using Test Influences of Frequency Converters with Active Rectifier

Abstract

To date, adjustable medium voltage electric drives are most often based on alternating current motors and frequency converters with active rectifiers (FC with AR). Due to the use of multi-pulse circuits as well as the multi-level topology of the active rectifier, such electric drives have better electromagnetic compatibility compared to frequency converters with diode and thyristor rectifiers. However, in some cases, problems with electromagnetic compatibility in the medium voltage network of 6–35 kV may arise when the FC with AR operates. For instance, if the medium voltage network has long cable lines, which, when interacting with the inductance of the network transformer, creates in the distribution network 6 −35 kV adverse resonance phenomena. In this case, the significant current harmonics of the FC with AR when applied to the resonant region can create critical voltage distortions in the distribution network. One of the ways to reduce the negative impact of resonant phenomena on the electromagnetic phenomena quality, on the electricity quality in the system of internal power supply in the presence of high-power FC with AR is the use of adaptive algorithms PWM(pulse-width modulation) AR, ensuring the elimination of the generation of higher harmonics of voltage and current in the region of the resonance. In order to ensure the correct functioning of these PWM algorithms in the conditions of varying power supply modes that affect the shape of the frequency response of the supply network, this article presents a new method for determining resonances in the frequency response due to test the AR effects on the supply network.