Transient modeling of Z-source chopper used for adjustable speed control of DC motor drive

The newly proposed Z-source chopper using LC impedance network with switching converter circuit coupled between power source and load can be used in modern energy conversion system because of both voltage buck and boost capabilities. This paper presents transient modeling of Z-source chopper and complete speed feed back control of separately excited dc motor. In the process of designing the control scheme for controlling the speed of separately excited dc motor, knowledge of transfer function representing the unique dc impedance network is essential. The presence of right-half-plane zero in developed average control-to-output model reveal that the output decreases initially before rising toward its new steady-state value, when a step increase in control input is applied. The nonminimum-phase transient response can be reduced by proper feedback control technique. The speed is controlled using direct measurement of speed and inductor current. Compensator for both speed loop and current loop are designed using classical control technique through small-signal analysis. Hysteresis band modulator is used for finding out the switching function of switches. Performance of control method of the compensated Z-source chopper is verified by simulation.