Series Z-source converter modeling and controller design method

This paper models the small signal frequency responses of the Series Z-source Inverter network, required for the design of controllers for the DC (Z-source side) of the inverter. The state space model has been derived and from this, series Z-source network small signal transfer functions have been formed to design controllers. The small signal transfer functions have been verified by comparison with the linearized large signal statespace model and with a switch averaged model of the network derived in SPICE. Both an indirect controller (with inner current loop and outer voltage loop) and a voltage mode controller are designed based on the derived transfer functions. For the indirect controller, the control-to-inductor transfer function exhibits a right-half-plane zero, therefore both the use of pure proportional gain and a loop shaping respectively is proposed for the inner current loop. The outer voltage loop of the indirect controller is based on capacitor voltage and PI controller. The voltage mode controller designed is a PID controller based on capacitor voltage.