Magnetic Integrated Five-phase LLC Resonant Converter for Offshore Wind Power System

In the offshore wind power generation system, the high voltage DC (HVDC) system is an important scheme for the long-distance transmission of electric energy. Modular isolated DCDC converter, such as half bridge LLC converter, are connected in series to improve the voltage and power level of system. With the capacity improvement of offshore wind power generation system, isolated DCDC module with higher power density are needed to reduce the volume cost of the system. In this paper, a modular five-phase LLC converter (FPLLC) is proposed. Combined with the higher operating frequency and the advanced transformer magnetic integration technology, the volume of the transformer can be further reduced and the power density of the module can be improved. Based on the first harmonic approximation (FHA), the working principle of FPLLC is analyzed. A parameter design process of FPLLC with the fixed gain characteristic is described. A 3kW prototype proves the feasibility of the proposed FPLLC scheme. The typical frequency modulation experiment shows that the FPLLC scheme can run stably and be used in practice.