Study of a 3kW high-efficient wide-bandgap DC-DC power converter for solar power integration in 400V DC distribution networks

Direct current (DC) distribution network has a higher efficiency in energy delivery over alternative current (AC) network, when there is a high penetration of dc renewable energy resources and energy storage systems. In this paper, the energy conversion efficiency (n) of a 3kW Silicon Carbide (SiC)-based Boost Cascaded Buck-Boost power converter is analyzed for solar power integration in 400Vdc distribution networks, compared to a Silicon (Si)-based BoCBB prototype. We found that: 1) there is about 2% reduction in n when the switching frequency of MOSFETs increases from 20 kHz to 100 kHz in Si-based prototype. Comparatively, the efficiency reduction with SiC-based MOSFETs is limited within 1% in the same case; 2) under the same switching frequency, the n increases 2.4% in average by replacing Si MOSFETs with SiC MOSFETs. The differences in n increase along the switching frequency. In addition, the switching frequency of 50 kHz is optimal in overall system performance for SiC-based prototype, which makes a good tradeoff between high n, good power quality, and compact size. These conclusions are verified by theoretical analysis and experiment tests. The experiment tests demonstrated a high efficiency of 97% in peak in power conversion.