Dmitri Vinnikov

Quasi-Z-Source-Based Isolated DC/DC Converters for Distributed Power Generation

This paper presents new step-up dc/dc converter topologies intended for distributed power generation systems. The topologies contain a voltage-fed quasi-Z-source inverter with continuous input current on the primary side, a single-phase isolation transformer, and a voltage doubler rectifier (VDR). To increase the power density of the converter, a three-phase auxiliary ac link (a three-phase inverter and a three-phase isolation transformer) and a three-phase VDR are proposed to be implemented. This paper describes the operation principles of the proposed topologies and analyzes the theoretical and experimental results.

Step-Up DC/DC Converters With Cascaded Quasi-Z-Source Network

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.

A Review of Galvanically Isolated Impedance-Source DC–DC Converters

Impedance-source converters, an emerging technology in electric energy conversion, overcome limitations of conventional solutions by the use of specific impedance-source networks. Focus of this paper is on the topologies of galvanically isolated impedance-source dc-dc converters. These converters are particularly appropriate for distributed generation systems with renewable or alternative energy sources, which require input voltage and load regulation in a wide range. We review here the basic topologies for researchers and engineers, and classify all the topologies of the impedance-source galvanically isolated dc-dc converters according to the element that transfers energy from the input to the output: a transformer, a coupled inductor, or their combination. This classification reveals advantages and disadvantages, as well as a wide space for further research. This paper also outlines the most promising research directions in this field.

New Shoot-Through Control Methods for qZSI-Based DC/DC Converters

Shoot-through control methods for qZSI-based dc/dc converters are presented and studied. The major goal was to increase efficiency. A new modulation technique, pulse width modulation (PWM) with shifted shoot-through, is compared with the conventional PWM shoot-through control method. The new method reduces switching frequency of bottom side transistors and inherently features partial soft switching. Previous studies have shown that the biggest drawback of PWM control with shoot-through is unequal switching frequencies of transistors. One solution to that problem could be signal swapping that has been proposed by the authors of this paper. All control methods are first simulated and then experimentally verified on a test prototype.

Experimental study of shoot-through control methods for qZSI-based DC/DC converters

This paper proposes a novel step-up DC/DC converter with galvanic isolation - the quasi-Z-source inverter (qZSI) based DC/DC converter and discusses three different shoot-through PWM control methods suitable for this topology. The proposed converter is meant for applications where the wide range of voltage gain is demanded, e.g. with renewable energy sources (fuel cells, photovoltaic cells), in telecom, aerospace and some other applications. For the verification of theoretical assumptions the converter prototype was assembled and tested. Experimental waveforms of the converter operated with different shoot-through PWM control methods are compared and discussed. Design considerations for converter and different control signal generators are provided.

New bi-directional DC/DC converter for supercapacitor interfacing in high-power applications

This paper presents a new bi-directional DC/DC converter for supercapacitor interfacing in high-power applications. The converter acts as a VSI-based step-down DC/DC converter during the supercapacitor charging mode and as a qZSI-based step-up DC/DC converter during the energy recovery mode. To provide voltage matching and galvanic isolation the medium frequency transformer was implemented. To ensure higher voltage boost of the SC voltage during the discharge the qZSI with a two-stage quasi-Z-source (qZS) network was introduced. The paper analyzes and discusses the operation of the new converter mostly concentrating on the energy recovery (boost) mode. The operation of the two-stage qZS-network is analyzed in detail. Guidelines are presented for the new converter design. Finally, theoretical background was verified by the simulations.

Single phase three-level quasi-z-source inverter with a new boost modulation technique

This paper describes a new modulation technique for a single phase three-level neutral-point-clamped qZS inverter. The proposed converter is intended for applications that require input voltage gain and high quality of the output voltage. The simulation and experimental results are presented and discussed.

Galvanically Isolated Quasi-Z-Source DC–DC Converter With a Novel ZVS and ZCS Technique

This paper focuses on the galvanically isolated quasi-Z-source dc-dc converter with a novel zero voltage and zero current switching technique. The unique feature of the impedance network lies in combining the buck-boost operation capability with the short- and open-circuit immunity of transistors; at the same time, it can perform zero voltage and zero current switching on the primary side. The boundary conduction mode of the current in the second inductor of the quasi-Z-source network was used along with snubber capacitors in the two out of four transistors and a special control algorithm to achieve full zero-switching operation of the inverter. Simulation and experimental results prove the discussed ideas. Possible modifications of the algorithm and future applications are also described.

An improved high-power DC/DC Converter for distributed power generation

This paper presents a new step-up DC/DC converter topology intended for the distributed power generation systems. The topology utilizes the voltage fed quasi Z-source inverter with continuous input current on the primary side, a single-phase isolation transformer and a voltage doubler rectifier. To increase the power density of the converter, implementation of the three-phase auxiliary AC-link (three-phase inverter and three-phase isolation transformer) and the three-phase voltage doubler rectifier are proposed by the authors. The paper describes the operation principles of the proposed topologies and analyzes the theoretical and experimental results.

CCM operation analysis of the single-phase three-level quasi-Z-source inverter

This paper presents a CCM analysis of a new modification of a three-level single phase neutral-point-clamped inverter. The proposed topology combines advantages of the three-level neutral-point-clamped full-bridge inverter with those of the quasi-Z-source inverter. The three-level neutral-point-clamped quasi-Z-source inverter is especially suitable for renewable energy sources. The steady-state analysis of a three-level neutral-point-clamped quasi-Z-source inverter in the case of the continuous conduction mode is presented. The conditions of the continuous conduction mode are obtained and analyzed.