Cascaded H-Bridge topologies comparison for multi-cell current-source inverters under different DC inductor size reduction methods

This work compares multi-cell topologies based on Current Source Inverters (CSIs) which are connected in a Cascade H-Bridge (CHB), where the large DC inductor size needed to compensate the oscillating power drained by the inverter is the main drawback. In order to reduce the DC inductor size, two compensation methods which compensated the oscillating power are evaluated and compared with the basic topology that use a large DC inductor. The first method consists in reducing the oscillating power through active compensation, which needs to supply the oscillating power from the rectifier, and the second method consists in reducing the oscillating power through magnetic coupling. The comparison considers the operating region, the DC inductor size, the magnetic power requirements, and the cell supply voltage requirements. Because the operating region is based on the converter and load parameters but independent of the DC inductor value, the passive parameters are designed as a function of the imposed rectifier input current quality and the load voltage THD. The comparison is done for a 9.33 MVA topology, simulating in PSEVI® in order to corroborate the components design and both the input current and load voltage quality. The operating region comparison is computed with one and two cells per phase and the achieved DC inductor reduction.