Quasi Z-Source based Full Bridge Isolated DC/DC Topology as A Basic Module for DC-Series PV Converter Connected to HVDC Grid

DC series-parallel photovoltaic (PV) plants have many advantages. As the most important equipment in the system, DC-Series DC/DC converter has some special technical requirements compared to other applications, especially, the wide input and output voltage regulation range requirement presents a unique challenge to the DC/DC converter design. The paper proposes a Quasi Z-Source based Full Bridge Isolated DC/DC Converter (QZS-FBIC) as a basic module, which cascaded through input parallel and output series (IPOS) to improve power capacity and output voltage adjustment range, so as to meet with the needs of the DC series-parallel PV generation system. The proposed converter can operate both in boost and buck mode. Besides some normal operating modules, several redundant modules are added, and all of these modules putting in and cutting out control to enlarge the range of the output voltage of the converter. A 20kV/500kW DC/DC converter model and 60kV/l.5MW system model are built in Matlab / Simulink to test the proposed topology and control strategies.