Capacitance reduction in a single phase Quasi Z-Source Inverter using a hysteresis current controlled active power filter

One of the major issues in a single phase inverter topology is the 120Hz ripple which needs large decoupling capacitors. Big bulky electrolytic capacitors can be an issue in applications where compact size and high power density are requirements such as solar converter chargers. In z source inverter systems, the design of the impedance network is critical. In single phase z source inverter systems, the z-source network can get quite bulky if the second harmonic power fluctuations are not compensated. In this paper an active power filter (APF) has been analyzed for the DC side of the Quasi Z-Source Inverter(qZSI) Topology and hysteresis current control technique has been adopted to eliminate the voltage fluctuations in the DC side of the inverter. As a result the impedance network has been designed with the values as low as three phase z-source inverter systems and the capacitor values are low enough to replace the bulky capacitors by film capacitors, which in turn increases the life and power density of such inverter systems. The other advantage of this DC side APF being the control is simpler than an AC side APF.