Operating-point insensitive voltage control of the Z-source inverter based on an indirect capacitor current control

This study presents a novel design strategy for the capacitor voltage control of a Z-source inverter (ZSI) to overcome the complexity and control performance degradation involved with the conventional small-signal model-based controls. In the proposed approach, the Z-network capacitor voltage of the ZSI is controlled through the average capacitor current over a switching period, and thus, the dynamics of the Z-network capacitor voltage can be easily controlled. To make this happen, the average capacitor current model is derived based on an important finding that the average capacitor current can be indirectly controlled through the average Z-network inductor current. For the inner Z-network inductor current control, the average voltage model of the inductor is developed to control the average inductor voltage directly via the shoot-through duty ratio of the ZSI. In this way, the current control dynamics can be linearised over an entire operating range and the desired bandwidth of each controller can be simply obtained using only Z-network parameters without a gain tuning process unlike the small-signal model-based controls. Thus, the proposed method can simplify the design process while producing an excellent control performance. The simulation and experimental results verify that the transient responses exactly coincide with the desired design goal.