抄録
In order to get compact and light-weight driving systems for rolling stock, the DC side's filter of the controlling inverter has a very high quality factor Q. This fact often causes an instability in the system.
A damping control, which modifies the inverter frequency according to the filter voltage, have been generally adopted to supress the instability phenomenon. This paper describes an analyzed and synthesized results on damping control, as follows.
(1) An approximated linear model of the system, which is composed of the filter, the voltage type inverter, induction motors and a digital controller, is obtained.
(2) According to the model, the existence of the following closed loop, which causes the unstable phenomenon, is proved.
(3) The damping control improves the characteristics of the closed loop. Then, the system can be stabilized. These results are verified by experiments.
