With the increasing trend in the energy demand, power networks are transitioning from conventional generation systems to renewable energy sources (RESs). The energy is harvested from these RESs and fed to grid-connected inverters (GCIs), as the output power of major sources (e.g., solar and fuel cell) is mainly DC. However, owing to the lower output voltage of renewable RESs, power converters play a vital role in two-stage power systems for enhancing its lower value to a higher value. The basic requirement for the GCI is to maintain the constant output voltage for which it is essential to have a constant input voltage. Therefore, high gain and efficient power boost converters are required for a robust and reliable two-stage power system. This paper investigates the performance of an efficient model of a high step-up switched Z-source DC-DC converter (HS-SZSC) for grid-connected 3-phase H-bridge inverter applications. The proposed design achieves high voltage gain and eliminates the problems of circuit complexity by utilizing a smaller number of components, which makes it cost effective and highly efficient. The working principle is discussed in detail. To validate the proposed model, the performance of the conventional Z-source converter (ZSC) and proposed HS-SZSC employed with GCI is analyzed and compared for both normal and transient states through MATLAB simulations. The HS-SZSC with an open- and closed-loop system is tested at different loads (AC), representing varying power factor conditions, and results verify the suitability of the proposed design for grid-connected inverters. Lastly, another model is presented to resolve the issue of grid islanding in GCIs.

Some applications such as fuel cells or photovoltaic panels offer low output voltage, and it is essential to boost this voltage before connecting to the grid through an inverter. The Z-network converter can be used for the DC-DC conversion to enhance the output voltage of renewable energy sources. However, boosting capabilities of traditional Z-network boost converters are limited, and the utilization of higher parts count makes it bulky and expensive. In this paper, an efficient, high step-up, switched Z-source DC-DC boost converter (HS-SZC) is presented, which offers a higher boost factor at a smaller duty ratio and avoids the instability due to the saturation of inductors. In the proposed converter, the higher voltage gain is achieved by using one inductor and switch at the back end of the conventional Z-source DC-DC converter (ZSC). The idea is to utilize the output capacitor for filtering and charging and discharging loops. Moreover, the proposed converter offers a wider range of load capacity, thus minimizing the power losses and enhancing efficiency. This study simplifies the structure of conventional Z-source converters through the deployment of fewer components, and hence making it more cost-effective and highly efficient, compared to other DC-DC boost converters. Furthermore, a comparison based on the boosting capability and number of components is provided, and the performance of the proposed design is analyzed with non-ideal elements. Finally, simulation and experimental studies are carried out to evaluate and validate the performance of the proposed converter.