A Matrix-Type Back-to-Back Converter With Single-Arm Current Injection

A matrix-type back-to-back converter (MT-BBC) with single-arm current injection, consisting of a three-phase rectifier with a small film dc-link capacitor and a three-phase inverter, is proposed in this article. A clamped modulation strategy is applied to the rectifier, which is featured by only one high-frequency switching bridge arm, reduced switching losses, and enhanced input reactive power control range. By controlling and injecting the quasi-third harmonic current into the phase with a high-frequency switching bridge arm of the rectifier, sinusoidal input currents and controllable input power factor are achieved. A carrier modulation strategy with a variable carrier is applied to the inverter to compensate for the time-varying six-pulse dc-link voltage. The presented converter inherits the advantages of both the conventional voltage-source back-to-back converter (V-BBC) and the matrix converter (MC) including simple main circuit structure, sinusoidal inputs and outputs, bidirectional power flow capability, potentially high power density, high reliability, high efficiency, and direct ac–ac conversion. In addition, the input reactive power control range is extended significantly. The effectiveness of the proposed methods is verified by a 6-kW experimental prototype.