An Adaptive DC Voltage Control for SiC based Medium Voltage Photovoltaic Inverter

In Medium Voltage (MV) Medium Power (MP) Photovoltaic (PV) application use of high voltage Wide Band Gap (WBG) devices can improve efficiency and power density. However the conventional fixed dc voltage control used in systems having a high frequency transformer have lower efficiencies when compared with systems having a low frequency transformer. To overcome this problem, an adaptive dc-link voltage control scheme which changes the dc link voltage according to the variation in grid voltage is proposed in this paper. To validate the efficacy of the proposed control two systems having identical topologies and filters but different devices (3.3 kV and 6.5 kV SiC MOSFETs) are considered. A simulation study is conducted incorporating the analytical loss models of the SiC MOSFETs. Moreover, the loss distribution in the converter is studied for both the control schemes. Finally, the energy loss in the converter system for a considered mission profile is studied. Based on the obtained results, conclusions are drawn on the selection of the devices and control scheme.