Vol. 64 | nr. 1 | Ianuarie - Martie 2016 Articolul 1

Analiza armonicilor în curent ale unui convertizor de frecvență cu PWM pentru un motor asincron de medie tensiune
(Current Harmonics Analysis of a PWM Variable Frequency Drive designed for a Medium Voltage Asynchronous Motor)
(Full text in English)

Laurențiu CIUFU, Mihai Octavian POPESCU
The present paper deals with an analysis regarding the generated harmonics spectrum of a Pulse Width Modulation (PWM) Variable Frequency Drive (VFD) designed to supply an industrial asynchronous medium voltage motor with a variable frequency. The main purpose of this ensemble is to drive Nuclear Power Plants cooling systems, to improve the operability and overall safety and to obtain in the same time an energy efficiency percent at the plant level. The objective in this paper is to obtain a technical solution as an ideal schematic diagram topology of a medium voltage VFD by designing the equipment components with the optimal operating parameters. This can be very challenging taking into consideration that any VFD is designed with an ACDCAC conversion parts and harmonics in voltage and current waveforms are considered to exist at the motor terminals. To evaluate these harmonics, the authors propose a series of a schematic diagram hypothesis with specific circuit filters. In order to analyse and compare the frequency response characteristics at the motor terminals, various computational simulations were by carried out using PowerSIM (PSIM) software. Simulation results of the proposed topology prove and validate at the same time the effectiveness of the new developed schematic diagram.
Keywords: Current harmonics, Pulse Width Modulation (PWM), Variable Frequency Drive, Medium Voltage motor, Asynchronous motor, Nuclear Power Plant cooling system