Efficiency-Optimization Control Strategy With Real-Time Modulation Scheme for Three-Phase Single-Stage Matrix-Type Isolated AC–DC Converters

This article proposes a control strategy for three-phase single-stage matrix-type isolated ac–dc converters. By introducing the global optimization modes of dual active bridge converters, the target current vector of the ac–dc converter is composed of the two working modes in the two adjacent switching periods, which can simplify the calculation of the modulation scheme. However, the scheme will generate a transient dc bias current during different current vector switching, which may lead to the loss of the zero-voltage switching (ZVS). Therefore, a control algorithm to suppress the transient dc bias current is proposed to achieve ZVS and reduce turn-on switching loss. A simplified iteration algorithm is proposed to calculate the combined current vectors. The optimal working mode is calculated by a real-time modulation scheme without a lookup table. A single-loop control strategy without grid current sampling is presented to achieve the unity power factor. Finally, this control strategy is applied to a 1.5-kW three-phase single-stage matrix-type isolated ac–dc converter with 200-V/50-Hz line-to-line input voltage and 200-V output voltage. Experimental results demonstrate the performance of soft switching, fast dynamic response, and high efficiency.