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This paper gives an overview of a collector-emitter voltage sign-based commutation method. This method is implemented based on the output current sign and commutation voltage polarity signals of matrix converter. All these signals are acquired by a simple unit in the drive and protection boards designed for reverse blocking insulated gate bipolar transistors (RB-IGBTs) of the matrix converter in test. Therefore, no current and/or voltage sensor is required to obtain any other commutation signals. The RBIIGBT samples used are newly developed, and one important feature is that its reverse leakage current is mostly affected by [v.sub.ge]. Under the same temperature condition, when [v.sub.ce] is negative, a positively biased [v.sub.ge] results in a distinct decrease of the reverse leakage current. The proposed commutation method can supply the reverse-blocked RB-IGBTs with positively biased [v.sub.ge]. Hence, the power losses caused by the reverse leakage current can be reduced using the proposed method. Experimental results have proved the feasibility and effectivity of this method. Index Terms--Commutation, matrix converter, reverse blocking insulated gate bipolar transistor (RB-IGBT), reverse leakage current.

A new thyristor current-source rectifier that achieves unity power factor, low-current total harmonic distortion (THD), and dc-bus current and voltage control is presented. The rectifier is suitable for high-power applications such as induction heating and dc arc furnaces. It combines a traditional six-pulse thyristor bridge and a dc chopper that together solve power quality problems such as poor power factor and flicker generation. This topology achieves low input current THD and dc power control without additional power-factor-correction equipment, harmonic trap filters, use of multiple pulse rectifiers, or high-K-factor transformers. Index Terms--Commutated circuits, pulsewidth-modulated power converters, rectifiers, thyristor converters.