Modular Interleaved Soft-Switching DC-DC Converter for High-Altitude Wind Energy Application

High-altitude wind power (HAWP) generating system uses dc-dc converter to transform the dc link voltage to an optimal medium voltage dc for efficient transmission to ground-based station. This paper presents a comparative study of current-fed and voltage-fed (VF) isolated dc-dc converters for HAWP application. VF converters (VFCs) with inductive and capacitive filters are compared with current-fed converters for a 100-kW rated power. The power electronic converters used maintain zero-voltage switching on the primary side switches to reduce switching losses. The current and voltage ratings of the components used are provided to realize higher power-to-weight (P/W) ratio. Losses and P/W ratio are assessed using the components' datasheets and compared with evaluate the converters that exhibit higher P/W ratio and efficiency. It is observed that VFC with capacitive filter exhibits higher P/W ratio and efficiency. Small signal modeling of VFC with capacitive filter is carried out to obtain the state-space model. Transmission voltage is controlled at optimal value using voltage control loop for efficient power transmission. Simulation studies of VFC with capacitive filters are carried out to verify the steady state analysis and performance using the software PSIM-9 at 100-kW power level that converts 600-8000 V. A 1-kW scaled down laboratory prototype is designed, built, and tested using modular devices and accessed to validate the performance. It yields an efficiency of 94.2% at full load converting a ten-times scaled down voltage of 60-800 V.