Investigations on digital modulation techniques for the suppression of electromagnetic interference in power converters

Abstract

Power Electronic Converters play a vital role in various power newlinesystems and industrial drives applications. The usage of grid-connected newlinerenewable energy sources is now becoming significant in creating a green newlineenvironment. In such applications, the three-phase Voltage Source Converters newline(VSCs) are widely used owing to their prominent features, such as newlinebidirectional power flow capability, near sinusoidal source current waveform, newlineand unity power factor operation. However, the power semiconductor devices newlineused in these converters are considered as a potential source of EMI. To newlinecomply with Electromagnetic Compatibility (EMC) standards, various newlinemodulation techniques are applied to a three-phase VSC and a DC-DC Cuk newlineconverter in this work. The grid side performance parameters, namely the newlinePower Factor (PF), the Total Harmonic Distortion (THD) value of the source newlinecurrent, the FFT spectrum of the source current and the peak value of EMI in newlinethe grid are considered. The operation of a three-phase VSC in rectifier and inverter modes newlineis discussed. The conventional Sinusoidal Pulse Width Modulation (SPWM) newlinetechnique is initially implemented in a three-phase VSC. The performance newlineparameters, obtained using the conventional SPWM, do not comply with the newlineCISPR-11 standard. To improve the performance parameters, Random Pulse newlineWidth Modulation (RPWM) technique is employed in a three-phase VSC. In newlinethe RPWM technique, the switching period is randomised so that the newlineharmonic power is spread over a wider bandwidth, however, the THD value newlineof the source current and the peak value of EMI obtained are above the newlinestandard limit. To improve the performance parameters, the bit-stream newlinemodulation technique is implemented in a three-phase VSC, in which a bitii newlinestream based PWM strategy is used to generate a sinusoidal waveform. newlineThough the THD value of the source current is below the standard limit, the newlinepeak value of EMI does not satisfy the EMC standard. newlineIn order to make the performance parameters to meet the EMC newlinestandards, and to improve the grid power qu