Research On Auxiliary Resonant Commutated Pole Inverters

Nowadays, with the development of soft-switching invert techniques, the high-power soft-switching inverters has become a research focus, which is used to high-power occasions such as UPS (Uninterrupted Power Supply), SVG (Static Var Generator), APF (Active Power Filiter), the grid-connected of distributed generation and so on. Because ARCPIs (Auxiliary Resonant Commutated Pole Inverters) do not increase the current and voltage stresses of main switches, it is more suitable for high power occasions among many soft-switching inverter topologies. So ARCPIs have aroused wide concern of domestic and foreign researchers.By the research of many typical ARCPI topologies, the problem that the ACC (Auxiliary Commutated Circuit) of ARCPIs has a high loss in commutation processes is found out. It causes an unsatisfactory efficiency of ARCPIs when the output power lower than 50% of rated power. And this is the key problem of applying ARCPIs to reality and must be resolved in the future. Aiming at overcoming the problem, this thesis presents a modified modulation strategy based on a improved ARCPI topology.In comparison with the traditional modulation strategy, the modified modulation strategy can not only realize soft-switching for all switches, but also optimize the energy flowing in the circuit. The superposition of resonant current and output current at commutation moments is avoided. So the circulating current loss in ACCs and the current peak stress of auxiliary switches can be effectively reduced. The soft-switching inverter realizes the high conversion efficiency within the whole load range. According to the equivalent circuit in different operation modes under this modulation strategy, this thesis analyses the operation principle, soft-switching implementation condition, power loss and optimal parameter design procedure of the soft-switching inverter. Finally, a lOkW-16kHz experimental prototype with insulated gate bipolar transistor (IGBT) based switches is built. Experimental and simulation results are given to demonstrate the validity and features of the inverter under the modified modulation strategy.