An Si+SiC based Hybrid Voltage Source Inverter Topology for Transformerless Grid Tied Inverters

A hybrid H9-VSI topology for transformerless grid-connected inverters is proposed in this paper. The proposed configuration uses six Si-IGBTs and three SiC-MOSFETs as the switching devices, and can realise the zero vector in a non-conventional fashion by isolating and shorting the input DC terminals. Using this feature, a new space vector PWM sequence is also proposed for the H9-VSI which eliminates the IGBT switching losses and transfers the burden of switching losses to the SiC-MOSFETs, thus considerably improving the efficiency of the converter. The common-mode voltage and the common-mode leakage currents are also significantly r educed u sing the proposed methods. Simulations are performed using the PLECS thermal platform incorporating the device loss models supplied by the manufacturers, for a 4 kW grid-connected system. The performance of the system using the H9-VSI is compared to that when using the conventional IGBT-based two-level VSI, and the results are presented to validate the performance of the proposed technique.