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15 kW Step-up Mode SiC Matrix Converter Design with 3D Commutation-loop Layout and PCB Aluminum Nitride Cooling Inlay

Fig. 1. SiC matrix converter power stage design.
  Matrix converter (MxC) is a direct frequency changer where bidirectional switches are used to directly interface two AC systems. It features low switching loss, small electromagnetic interference (EMI) filter, and potentials for achieving high power density. By employing a current control mode (CCM) operation, MxC can work in step- up mode, thus extending the operation of MxC for power generation and distribution applications. This article aims to demonstrate a 15 kW 380:460 V step-up mode SiC MxC prototype.
  First, as a key component of MxC, bidirectional device configuration is selected based on the trade-off between digital controller and powerline electromagnetic emissions. It is found that the common-source configuration for the bidirectional switch exhibits reduced noise emission at the controller side while the common-drain configuration benefits the power-line noise reduction. Second, as surface- mount device features low manufacturing cost, compact package, and low stray inductance, surface-mount instead of through-hole SiC MOSFETs are adopted. To solve the concern on the heat dissipation, a thorough evaluation on surface-mount device cooling approaches is provided. Thermal via, metal-core PCB and aluminum nitride inlay cooling approaches are considered. The PCB aluminum nitride cooling inlay stands out to be an effective cooling approach which can handle high per-device loss (24 W) with very limited impact on PCB layout flexibility. 3D vertical commutation-loop methodology is then employed to achieve small and symmetrical loop inductance for the 3 coupled commutation loops in a MxC phase-leg. Clean and symmetrical switching transient test results are provided to verify the 3D loop design. A highly integrated 15 kW MxC prototype is eventually demonstrated with a power density of 15 kW/L and 20 kW/kg, as shown in Fig. 1. The prototype exhibits a full-load efficiency of 99.0% and is compliant with DO-160G standard. The CCM operation is experimentally verified on the prototype where the 380 V generator voltage is boosted by the MxC to establish a 480 V three-phase ac bus, as shown in Fig. 2.
Step-up operation
Fig. 2. Matrix converter step-up mode operation. The 380 V generator voltage is boosted to 460 V to establish a three-phase AC system.

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