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This paper is devoted to the quasi‐Z‐source (qZS) converter family. Recently, the qZS‐converters have attracted high attention because of their specific properties of voltage boost and buck functions with a single switching stage. As main representatives of the qZS‐converter family, this paper aims to discuss the traditional quasi‐Z‐source inverter as well as two novel extended boost quasi‐Z‐source inverters.

Steady state analysis of the investigated topologies operating in the continuous conduction mode is presented. Input voltage boost properties of converters are compared for an ideal case. Mathematical models of converters considering losses in components are derived. Practical boost properties of converters are compared to idealized ones and the impact of losses on the voltage boost properties of each topology is justified. Finally, the impact of losses in the components on the boost conversion efficiency is analyzed.

To demonstrate the impact of component losses on the overall efficiency of the qZS‐converter, a number of experiments were performed. The impact of inductor winding resistance was compared with the forward voltage drop of qZS‐network diodes. It was found that the forward voltage drop of diodes has the highest effect on the efficiency. If the diodes are replaced with high‐power Schottky rectifiers with a low forward voltage drop (UD=0.6 V), the effective efficiency rise by at least 5 percent could be expected for all three qZS‐converter topologies. For the same operating parameters and component values, the traditional qZS‐converter had the highest efficiency of the qZS‐converter family. The boost converter was compared with the traditional qZS converter in terms of efficiency. It was found that the boost converter has an efficiency 2 percent higher in the boost operation mode and approximately the same efficiency in the non‐boost operation.

The paper provides a good theoretical background for further practical studies. qZS‐converters have voltage boost and buck functions with a single switching stage, which could be especially advantageous in renewable energy applications.

The paper presents a detailed study of the qZS‐converter family. Mathematical models of converters considering losses in components are derived. It is the first time the boost converter is compared with the qZS converter.

This paper aims to introduce the quasi impedance source inverter (qZSI)-based static compensator (STATCOM), which is incorporated into the hybrid distributed power generation system for enhancement of power quality. The distributed power generation system includes the photovoltaic (PV), wind energy conversion system (WECS) and battery energy storage system.

The WECS is used by the self-excited induction generator (SEIG) and the flywheel energy storage system (FESS). To regulate its terminal voltage and frequency, the SEIG requires adjustable volt-ampere reactive (VAR). A combination of a STATCOM and a fixed condenser bank usually serves to satisfy the VAR demand. The maximum correntropy criterion-based adaptive filter technique (AFT) is proposed to control the qZSI-STATCOM and to guarantee that the voltage at the SEIG terminal is harmonic-free while providing non-linear three-phase and single-phase loads.

The coordinated operation of the suggested voltage control and flywheel control systems ensures that load voltage and frequency are retained in their respective values at very low harmonic distortions regardless of wind speed and load variation. The simulation and experimental studies are carried out under different load conditions to validate the efficiencies of the PV-assisted STATCOM.

To improve system stability and minimize total costs, extra load current sensors can also be avoided. This paper proposes to control the SEIG terminal voltage and harmonic elimination in the standalone WECS systems using maximum correntropy criterion-based AFT with a fuzzy logic controller.