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 (DAB) 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 1.5kW three-phase single-stage matrix-type isolated AC-DC converter with 200V/50Hz line-to-line input voltage and 200V output voltage. Experimental results demonstrate the performance of soft switching, fast dynamic response, and high efficiency.