Capacitance Design for Low-Capacitance Cascaded H-Bridge STATCOM Considering Inductive Demand

Power density of film capacitor is lower than that of electrolytic capacitor. It is significant to study how to reduce the capacitance for replacing electrolytic capacitor with film capacitor for cascaded h-bridge STATCOM. Increasing fluctuation amplitude on DC-link voltage is able to effectively reduce the capacitance for cascaded H-bridge STATCOM. However, there are few papers on the capacitance design of DC- link capacitor under increasing voltage fluctuation amplitude. The existing methods only consider the capacitive capacity of STATCOM when designing the capacitance. This paper first analyzes the relationship between capacitance and output current under capacitive and inductive conditions, respectively. In addition to considering rated capacitive capacity, a design method is proposed, where certain inductive capacity is retained according to the actual demand. Finally, the theoretical analysis is verified by some key simulation results.