Abstract
Unstable phenomena of propulsion converters with input LC filter for railway vehicles have been already reported and these solutions were proposed in some applications. However, there are many other systems and circuit topologies for vehicles. In these systems, each peculiar solution is needed. On the other hand, in recent years, series line resistor, which limits short-circuit current and compensates interrupting capacity of line breaker, is not required to have so large resistance with the technical development of breaker apparatus. However the resistor contributed not only to assist interruption but also to suppress unstable phenomena. Therefore unstable phenomena caused by smaller resistance becomes more conceivable, and other solutions and its analysis are more eagerly needed now. In this paper, this unstable phenomena of chopper-inverter system for air conditioner are analyzed by using root locus method. It is shown that cooperative response regulation of controllers or supplement of proper dumping circuit is effective to stabilize the system. The validity of these solutions is confirmed through non-linear circuit simulations.
