Voltage and Current-Programmed Modes in Control of the Z-Source Converter

The Z-source converter (ZSC) is an alternative power conversion topology that can both buck and boost the input voltage using passive components with improved reliability. Dynamic modeling of the ZSC from different perspectives has been studied. So far, based on these models, the dc-link voltage is controlled using direct measurement, or through measurement of the capacitor voltage. In this paper, two methods of dc-link voltage control of ZSC are analyzed and compared. Both methods are based on measuring the input voltage and state variables of the ZSC and designing a compensator based on the converter state space averaged model. Voltage mode (VM) and current-programmed mode (CPM) controls are derived based on the ideal small-signal model of the Z-source network with inductive loading. Nonminimum phase characteristics caused by the right half-plane zero in the control-to-capacitor-voltage transfer function are minimized by designing proper compensators in both VM and CPM controls. In CPM, since the order of the system reduces by one, it is possible to achieve similar dynamic performance with a simpler compensator. Performance of both control methods of the compensated ZSC are verified by simulation and experimental results for input and load disturbances.