Analysis and Suppression of Conducted Common-Mode EMI in WBG-Based Current-Source Converter Systems

The adoption of wide bandgap (WBG) devices in power converters creates challenging conducted common-mode (CM) electromagnetic interference (EMI) issues due to their fast-switching transients and high switching frequencies. This article focused on the analysis and suppression of CM EMI for WBG-enabled three-phase current-source converters (CSCs) consisting of back-to-back rectifier and inverter stages, which have received little attention in the literature. The baseline time-domain waveforms and CM EMI of CSC have been experimentally characterized, showing that even though CSCs have high-quality sinusoidal input–output voltage and current waveforms, their CM EMI still exceeds existing EMI standards. To suppress the CM EMI, the effects of adding different EMI filters at different locations in the CSC topology are evaluated. Based on CSC’s circuit operation and analytical derivation, a CM EMI equivalent circuit (EQC) is proposed for the back-to-back CSC configuration. The proposed EQC achieves fast and accurate CM EMI estimation for CSC using different filtering techniques. Based on the proposed EQC and evaluations of different filter methods, an effective filtering scheme is proposed for the CSC that achieves significant CM EMI attenuation throughout the frequency range from 150 kHz to 30 MHz.

I. Introduction

In renewable energy generation and motor drive applications, three-phase power converters are widely used. For conventional motor drive systems, the three-phase power converter consists of a passive diode front-end that interfaces with the power grid, a dc-link capacitor, and a voltage-source inverter (VSI) that drives the motor [1]. To improve the power quality on the grid side, active front-ends have obtained increased popularity, which normally consists of a voltage-source rectifier (VSR) [1]–[4] to form the back-to-back VSR–VSI scheme in Fig. 1(a). The VSR–VSI combination is also commonly found in renewable power generation systems that require improved current waveforms on both the generator and grid sides [5]. Fig. 1.

Schematics of (a) VSC (consisting of VSR and VSI) and (b) CSC (consisting of CSR and CSI).