30 kW, 200 V/900 V, Thyristor LCL DC/DC Converter Laboratory Prototype Design and Testing

This paper details design, development, and testing of a prototype 30 kW, 200 V/900 V resonant dc/dc converter. The converter achieves stepping ratio of 4.5 without internal ac transformer, and is capable of bidirectional dc power flow as well as fast dc power reversal. Very importantly, it has capability of dc fault isolation on either side, which is of extreme importance for high-power dc applications. The design and selection of the individual passive and active components are presented. A 30-kW test setup including one 900 V voltage source converter (VSC), one 200 V VSC, and one 200 V current source converter (CSC) are designed and built to provide a test rig for dc/dc converter. The analytical studies of efficiency are compared with the converter measured efficiency. The prototype shows overall efficiency of around 92% at full power and weight of around 32 kg, which is promising for scaling to high-power applications. The converter operation at full power in step up mode as well as step down mode, and fast power reversal when connected to CSC on its low voltage side, are demonstrated by experimental results. Severe pole-to-pole dc faults are applied on 900 V and 200 V dc terminals and the inherent dc fault isolation capability is confirmed.