Showing papers by "Indrek Roasto published in 2012"
TL;DR: 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) and reduces the shoot-through duty cycle by over 30% at the same voltage boost factor.
Abstract: 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.
184 citations
24 Dec 2012
TL;DR: A general overview of the power electronic transformer technology in terms of smart grids is presented and development trends are shown.
Abstract: The idea of power electronic transformer is known already over 20 years. There are numerous papers written about power electronic transformers. In the literature one can find tens on different topologies, control methods, standards, requirements etc. It is easy to loose insight what topology to use and where. In this paper a general overview of the power electronic transformer technology in terms of smart grids is presented. The information collected from the literature is classified and organized. In conclusion some generalizations are made and development trends are shown.
18 citations
Patent•
28 Feb 2012
TL;DR: In this paper, the authors present three methods for shoot-through generation in the case of modified sine wave control: by overlapping active states, during the freewheeling state and during the zero state.
Abstract: This invention belongs into the field of power electronics and semiconductor converter control and pertains to the method of shoot-through generation for modified sine wave Z-source, quasi-Z-source and trans-Z-source inverters. The inverter can be controlled using either the modified sine wave pulse-width modulation or phase-shift modulation method. There are three methods for shoot-through generation in the case of modified sine wave control: by overlapping active states, during the freewheeling state and during the zero state.
15 citations
09 Nov 2012-Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering
TL;DR: In this article, the impact of losses in the components on the boost conversion efficiency of the converters is analyzed and a steady state analysis of the investigated topologies operating in the continuous conduction mode is presented.
Abstract: Purpose – 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.Design/methodology/approach – 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.Findings – To demonstrate the impact of compo...
15 citations
Journal Article•
TL;DR: In this paper, the authors discuss four novel cascaded quasi-Z-source inverters operating in continuous conduction mode and present a steady state analysis of these topologies, as well as some problematic issues of proposed topologies.
Abstract: The quasi-Z-source inverter is a very attractive topology because of its unique capability of voltage boost and buck functions in a single stage. But its voltage boost property could be a limiting feature in some applications where very high input voltage gain is required. The input voltage gain could be extended by the implementation of the cascaded quasi-impedance network. This paper discusses four novel cascaded quasi-Z-source inverters. Steady state analysis of topologies operating in continuous conduction mode is presented. Performances of topologies were compared and experimentally validated. Moreover, some problematic issues of proposed topologies were pointed out and discussed. Streszczenie. Quasi-Z falownik z prostym obwodem impedancyjnym jest bardzo interesującym rozwiązaniem topologicznym ze wzgledu na unikalną mozliwośc jednostopniowego przeksztalcanie DC/AC w polączeniu z funkcjami obnizania i podwyzszania napiecia. W niektorych aplikacjach jego wlaściwości podwyzszające są jednak niewystarczające. Wyzsze napiecie wejściowe mozna uzyskac w wyniku zastosowania w quasi-Z-falownikach kaskadowych obwodow impedancyjnych. W artykule omowiono cztery nowe topologie kaskadowych quasi-Z-falownikow. Przedstawiono wyniki analizy stanow statycznych tych ukladow przy przewodzeniu ciąglym. Porownano wlaściwości badanych topologii, zweryfikowane eksperymentalnie. Omowiono takze inne problemy związane z proponowanymi ukladami. (Porownanie analityczne ukladow kaskadowych quasi-Z-falownikow z kondensatorem wspomagającym i z diodą wspomagającą).
14 citations
25 Jun 2012
TL;DR: A novel power conditioning system for residential fuel cell power plants, consisting of a step-up DC/DC converter and a single or a multiphase inverter, and an interleaved converter design with shifted switching and active ripple cancellation is described.
Abstract: This paper describes a novel power conditioning system for residential fuel cell power plants, consisting of a step-up DC/DC converter and a single or a multiphase inverter. To increase the efficiency of the whole system a quasi Z-source inverter along with a step-up isolation transformer and a voltage doubler rectifier can be used. Due the continuous input current and low current ripple, the service life of a fuel cell is significantly increased. Further reduction in the output current ripple of a fuel cell is achieved by implementing an interleaved converter design with shifted switching and active ripple cancellation. Interleaved converter design also enables variations in the operating cell count to increase the overall efficiency of a power conditioning system.
9 citations
11 Dec 2012
TL;DR: In this article, a quasi-Z source is used as a filter/boost circuit to stabilize the battery voltage while draining energy from it in fast chargers of electric vehicles, and a class 3 unidirectional charging converters with a current doubler rectifier topology and a controllable full-bridge rectifier/inverter are proposed.
Abstract: This article focuses on fast chargers of electric vehicles. One of the crucial parts of a fast charger is the secondary charging converter that must be able to regulate efficiently battery charge voltage and current. To be able to use the electric vehicle battery as a temporary energy storage in the electric grid, the topology of a charging converter must enable a bidirectional energy flow. Bidirectional converters need an additional boost circuit to stabilize the battery voltage while draining energy from it. Class 3 unidirectional charging converters could be realized with a current doubler rectifier topology and bidirectional ones with a controllable full-bridge rectifier/inverter, resulting from its advantage over the current doubler in this operational mode. A quasi Z source could be used as a filter/boost circuit.
8 citations
19 Mar 2012
TL;DR: A new voltage mode control method is proposed for the quasi-Z-source isolated DC/DC converter that measures the output voltage directly and therefore better response to load changes can be expected.
Abstract: A new voltage mode control method for the quasi-Z-source isolated DC/DC converter is proposed and analyzed. Conventional control methods for Z-source or quasi-Z-source converters are based on the DC-link voltage regulation, which indirectly also influences the output. The proposed control method measures the output voltage directly and therefore better response to load changes can be expected. Small-signal AC models of the converter are derived and appropriate transfer functions found. Benefits and drawbacks of the proposed control method are analyzed on the basis of mathematical and simulation models. Simulation results are verified with experimental results. Tests were carried out on a 2 kW experimental prototype.
4 citations
01 Jan 2012
TL;DR: In this article, loss analysis of dual active bridge and current doubler rectifier topologies in forward and reverse operating modes are estimated. And the calculated losses and overall efficiency of both converters are verified with simulations and with experimental results on 1 kW experimental prototype.
Abstract: This paper compares two DC/DC converter topologies which are suitable for isolation stage of power electronic transformer. Paper provides loss analysis of dual active bridge and current doubler rectifier topologies in forward and reverse operating modes. In particular, the conduction and switching losses, as well as overall efficiency are estimated. In addition, the calculated losses and overall efficiency of both converters are verified with simulations and with experimental results on 1 kW experimental prototype.
4 citations
11 Dec 2012
TL;DR: In this article, a classification and a comparative overview of quasi-impedance source inverter topologies is given and the working principle, advantages and disadvantages of each topology as well as their possible fields of use are discussed.
Abstract: In this paper a classification and a comparative overview of quasi-impedance source inverter topologies is given. The working principle, advantages and disadvantages of each topology as well as their possible fields of use are discussed and a comparison of the boost properties as well as dynamic behavior of different quasi impedance source network topologies is carried out.
4 citations
20 Jun 2012
TL;DR: In this article, loss analysis of dual active bridge and current doubler rectifier topologies in forward and reverse operating modes are estimated. And the calculated losses and overall efficiency of both converters are verified with simulations and with experimental results on 1 kW experimental prototype.
Abstract: This paper compares two DC/DC converter topologies which are suitable for isolation stage of power electronic transformer. Paper provides loss analysis of dual active bridge and current doubler rectifier topologies in forward and reverse operating modes. In particular, the conduction and switching losses, as well as overall efficiency are estimated. In addition, the calculated losses and overall efficiency of both converters are verified with simulations and with experimental results on 1 kW experimental prototype.
20 Jun 2012
TL;DR: In this paper, the stability analysis of the quasi-Z-Source (qZS) DC/DC converter based on a small signal model was carried out, and the results of the analytical analysis, simulation and experimental investigation showed that a DC and DC converter with qZS-network has limited but predictable stability margin.
Abstract: Focus is on the stability analysis of the quasi-Z-Source (qZS) DC/DC converter based on a small signal model. Control system of the converter is described and its transfer function for the small signal model is presented. The stability estimation was carried out. The results of the analytical analysis, simulation and experimental investigation showed that a DC/DC converter based on the qZS-network has limited but predictable stability margin.
01 Sep 2012
TL;DR: In this paper, a quasi-Z source network is proposed to provide voltage buck and boost operation in one conversion stage. But the proposed topology causes uncontrollable DC-link voltage rise during zero states when the converter is operating in the voltage buck mode.
Abstract: This paper explains the non-shoot-through operation of DC/DC converters with a quasi Z source inverter. Proposed DC/DC converters use the quasi Z source network to provide voltage buck and boost operation in one conversion stage. Used topology causes uncontrollable DC-link voltage rise during zero states when the converter is operating in the voltage buck mode. To explain the processes a steady state analysis was performed. Analytical information was verified by computer simulations and experiments. For experimental purposes a 1.5 kW prototype DC/DC converter with a high frequency galvanic isolation transformer was constructed.
24 Dec 2012
TL;DR: The steady state analysis of the CDR in the bi-directional operation is provided and the impact of the component losses on the efficiency is analyzed.
Abstract: This paper presents a detailed analysis of the bi-directional current doubler rectifier (CDR) that is a good candidate for use in a power electronic transformer (PET). Among various advantages the current doubler rectifier offers a bi-directional power flow capability that is the major requirement for the PET. This paper provides the steady state analysis of the CDR in the bi-directional operation. In addition, the impact of the component losses on the efficiency is analyzed. Finally a suitable snubber circuit is proposed to damp the voltage peaks.