Power Density Optimization in High Fidelity Power Drive

This paper analyzes factors determining power density in high current and high MVA power electronic converters & solid-state switches and recommends practical approaches to increase power density. For years increase in power density was the result of improvements in the power semiconductors density, which is the determining factor in medium power applications at voltages below 1 KV. However in most high current & medium voltage applications, the power density is more influenced by withstanding of short circuit currents, over-voltage stresses caused by the short circuit current interruption and uneven current sharing between paralleling semiconductors. In practice, these factors determine the power density of the MVA industrial power electronics converters and switches and significant increases in the power density could be achieved by current limiting control system, voltage suppression assemblies to absorb the switching transient energy and novel devices such as inter-phase and ring transformers to balance transient current sharing between semiconductors. This paper describes results of the testing of such devices in bi-directional high current hybrid circuit breaker. It also demonstrates how power density of the hi-fidelity power drive (HFPD) could be increased by cascade hybrid topology and harmonics elimination