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This paper is devoted to the step-up dc/dc converter family with a cascaded quasi-Z-source network (qZS-network). The cascaded (two-stage) qZS-network could be derived by the adding of one diode, one inductor, and two capacitors to the traditional quasi-Z-source inverter (qZSI). The proposed cascaded qZSI inherits all the advantages of the traditional solution (voltage boost and buck functions in a single stage, continuous input current, and improved reliability). Moreover, as compared to the conventional qZSI, the proposed solution reduces the shoot-through duty cycle by over 30% at the same voltage boost factor. Theoretical analysis of the two-stage qZSI in the shoot-through and non-shoot-through operating modes is described. The proposed and traditional qZS-networks are compared. A prototype of a step-up dc/dc converter with the cascaded qZS-network was built to verify the theoretical assumptions. The experimental results are presented and analyzed. Finally, a further optimization method of the cascaded qZS-network is proposed, and some practical design issues are discussed.

The paper presents closed-loop electric vehicle (EV) drive with 5-phase induction motor operating with switched-autotransformer (LCCAt) inverter. Electrical drives with five-phase induction motors are considered for application in electric vehicles. Space vector modulation (SVM) is the most common option for controlling a five-phase inverter. However, if the battery level cannot ensure the controllability over a wide speed range of EV drive, the supply voltage has to be elevated. Bidirectional impedance source inverters (e.g. Z-source inverter, qZ-source inverter) have been presented suitable for EVs. The concept of Z-source/qZ-source inverters has been recently extended to transformer-based inverters (e.g. Trans-Z-source inverter, T -source inverter) which use coupled inductors with an appropriate turns ratio. Unfortunately, coupled inductors store significant portion of the energy during boost operation which tends their cores to saturate at higher currents. The use of four element LCCAt-source (inductor-capacitor-capacitor- autotransformer) network allows proposed switched- autotransformer inverter for obtaining high voltage gain while ensuring high modulation index and reduced volume of inductive elements. Simulation and preliminary experimental results using the laboratory model of switched-autotransformer inverter with designed 4.3 kW, 30V five-phase induction motor are shown to verify the effectiveness of the proposed system.

This paper presents the steady-state analysis of the voltage-fed quasi-Z-source inverter (qZSI) with cascaded (two-stage) quasi-Z-source network (qZS-network). Cascaded qZS-network is derived by the adding of one diode, one inductor and two capacitors to the traditional qZSI. Main focus of this paper is on mathematical models of the cascaded qZS-converter. Static models were elaborated and analyzed for the continuous (CCM) and discontinuous conduction mode (DCM) of the converter. In order to verify the theoretical assumptions a prototype has been built. The experimental results are presented and analyzed.

Many renewable generation units (e.g. PVs, fuel cells, small wind turbines) require integrated DC-AC converters providing efficient high step-up power conversion. The recently proposed Z-source-type integrated buck-boost inverters characterize one stage energy processing and wide range of output voltage regulation. This paper presents the possibility of further extending Z-source-type inverters application area through the topology reconfiguration. The unique property of the proposed Z-source-type inverter with applied high frequency transformer and built-in DC current blocking capacitors is that no energy is stored in the transformer windings. That prevents core saturation and enables high voltage gain. Simulation and experimental results are shown to verify the proposed topology.

Many renewable generation units (e.g. PVs, fuel cells, small wind turbines) require integrated DC-AC converters providing efficient high step-up power conversion. On the basis of recent developments in impedance source (Z-source) inverters the present paper proposes an integration of quasi-Z-source inverter (qZSI) with a built-in high frequency transformer. Two new type LCCT-Z-Source inverters are presented by author. Proposed inverters characterize continuous input current, improved relationship between boost coefficient and modulation index and improved EMI performance. Application of four element (Inductor — Capacitor — Capacitor — Transformer) LCCT impedance network provides higher voltage gain than obtained in quasi-Z-source inverter. The advantage of proposed topology over other recently developed trans Z-source inverters (TZSI) is that two built-in capacitors block DC currents in transformer windings and prevents core saturation. Simulation and experimental results are shown to verify the proposed topologies.

This paper presents an optimization possibility of the voltage-fed continuous input current quasi-impedance source inverter (qZSI) by the introduction of the two-stage quasi-Z-source network (qZS-network). The two-stage qZS-network could be derived by the adding of one diode, one inductor and two capacitors to the traditional qZSI. The proposed two-stage qZSI inherits all the advantages of the traditional solution (voltage boost and buck functions in a single stage, continuous input current and improved reliability). Moreover, the proposed solution features over 30% shoot-through duty cycle reduction for the same voltage boost factor as compared to the conventional qZSI. Theoretical analysis of the two-stage qZSI in shoot-through and non-shoot-through operating modes is presented. The proposed and traditional qZS-networks are compared. A prototype has been built to verify the theoretical assumptions. The experimental results are presented and analyzed. Finally, a further optimization method of the proposed two-stage qZS-network is discussed.

This paper proposes the performance improvement method for the voltage-fed continuous input current quasi-impedance source inverter (qZSI) by the introduction of the two-stage quasi-Z-source network (qZS-network). The two-stage qZS is derived by the adding of one diode, one inductor and two capacitors to the traditional qZSI. The proposed two-stage qZSI inherits all the advantages of traditional solution (voltage boost and buck functions in a single stage, continuous input current and improved reliability). Moreover, the proposed solution features over the 30% shoot-through duty cycle reduction for the same voltage boost factor and component stresses as compared to conventional qZSI. Theoretical analysis of the two-stage qZSI in shoot-through and non-shoot-through operating modes is presented. The design guidelines for the two-stage qZS-network based step-up DC/DC converter are provided. A prototype has been built to verify the theoretical assumptions. The simulation and experimental results are presented and discussed.

This paper presents different topologies of voltage inverters with alternative input LC networks. The basic topology is known in the literature as a Z-source inverter (ZSI). Alternative passive networks were named by the authors as T-sources. T-source inverter has fewer reactive components in comparison to conventional Z-source inverter. The most significant advantage of the T-source inverter (TSI) is its use of a common voltage source of the passive arrangement. Experimental results for the TSI are in agreement with theoretical and simulated prediction.

This paper presents different topologies of buck-boost converters with passive input networks that have alternative topologies; this is known in the literature as a Z-source inverter. Alternative passive networks were named by the authors as T-inverters; these improve output voltage regulation of the PWM inverters. T-inverter has fewer reactive components in comparison to conventional Z-source inverter. The most significant advantage of the T-inverter is its use of a common voltage source of the passive arrangement. This solves many problems involving electromagnetic compatibility which are present in the Z-source inverter. Experimental results for the T-inverter are in agreement with theoretical and simulated predictions.

Alternating voltage inverters (converters) supplied by low-voltage sources DC (ex. fuel cell, photovoltaic cell) are most frequently realized on the basis of the three fundamental topologies: a) PWM voltage inverter with non-transformer converter DC/DC in the "boost-converter" system, b) PWM voltage inverter with transformed converter DC/DC in the "boost-converter" system, c) PWM current converter. However none of these solutions is claimed to be the best and dominant over the others. Search for new and better solutions continues and among them one finds inverters with input symmetrical passive four-terminal networks, which features are very interesting. The paper describes work principles, attributes and potential of the buck-boost inverters system with symmetrical passive four-terminal networks. The paper focuses on the basic Z-source system and suggested new system of a inverter, which was elaborated by authors. Simplified theoretical analysis of both systems has been verified by simulation research. In the last section of the article, the possibility to build multilevel inverters based on diode clamped typology with new four-terminal networks is presented.

A two-stage speed control algorithm for sensor- less induction motor drives is proposed to obtain high per- formance, as well as high efficiency under nonlinear control. Dependencies for limiting the inverter output voltage and currents based on a multiscalar model of the induction motor are presented. Full decoupling of speed and flux control is the main benefit of the multiscalar model based control system. A passive filter for minimizing additional losses is used.