Janis Zakis | Riga Technical university (original) (raw)
Papers by Janis Zakis
One of major problems related with PV-applications is common mode currents. The issue can be solv... more One of major problems related with PV-applications
is common mode currents. The issue can be solved in two
ways: galvanic decoupling of AC-grid and chopping the
common mode currents by additional actively controlled
circuitry. Flyback converter is good solution for MPPT
tracking for PV-modules up to 100-150 W with galvanic
decoupling. The problem of designing of this type of converter
is that most of design guides and literature is dedicated to
consumer electronics applications. MPPT converter design
have different starting points of calculations. The paper
contains the suggested approaches to the calculations, design
recommendations, considering the specific nature of PVsources
and NOCT model of PV-module.
The approach calculations, design guidelines, recommendations
and simulation of power electronics part of MPPT
converter and experimental results with implemented circuit
are presented and discussed. In order to increase the efficiency
during tests the circuit was upgraded with active clamp. After
the tests active clamp was upgraded to the forward active
clamp topology. The efficiencies and key waveforms of voltages
are compared and analyzed.
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This paper analyzes two maximum power point tracking (MPPT) converter topologies that are part of... more This paper analyzes two maximum power point
tracking (MPPT) converter topologies that are part of an
interface converter for the integration of photovoltaics (PV) in
the grid. Two different MPPT converter topologies (boost
converter and quasi-Z-Source (qZS) converter) were selected and compared. Theoretical comparison includes an analysis of
regulations for obtaining continuous source current and
comparison of necessary parameters of the reactive elements of the systems.
270 W experimental prototypes of both converters were built
and experimentally compared. Theoretical and experimental
efficiency estimation is proposed and discussed. Also, the losses in diodes and MOSFETS are evaluated taking into account technical data from datasheets
Bookmarks Related papers MentionsView impact
This paper shows the bidirectional operation possibility of the single phase three-level neutral-... more This paper shows the bidirectional operation
possibility of the single phase three-level neutral-point-clamped
quasi-Z-source grid connected inverter. The simple traditional
control system for three-level grid connected rectifier was
implemented. Simulation results confirmed bidirectional
operation capability of the discussed topology.
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This paper presents a new modified carrier based single phase modulation technique with maximum c... more This paper presents a new modified carrier based
single phase modulation technique with maximum constant
boost control for three level Z or qZ-source inverter topology.
The proposed technique is explained, analysed and compared
with the previous one in simulation as well in experimental
way. Obtained results are compared from the point of view of
power losses in the electronic switches. Advantages and
disadvantages of the converters performance based on the
proposed modulation techniques implementation are discussed.
Bookmarks Related papers MentionsView impact
Focus is on three operation strategies for a gridconnected three-level neutral-point-clamped quas... more Focus is on three operation strategies for a gridconnected
three-level neutral-point-clamped quasi impedance
source inverter in a single-phase application. Each control
scheme was implemented in the PSCAD/EMTDC simulation tool
and underwent different tests, which involved some steps in the reference values and in the perturbations applied to the system.
A comparison according to their responses was based on
different criteria, such as rise time, settle time, overshoot and
steady state error, in order to determine which would be more
suitable for such application.
Bookmarks Related papers MentionsView impact
This paper presents a novel quasi-Z-source halfbridge galvanically isolated DC-DC converter inten... more This paper presents a novel quasi-Z-source halfbridge
galvanically isolated DC-DC converter intended for the
photovoltaic applications. The topology could be envisioned as an alternative to the boost half-bridge DC-DC converter but the
benefit of its symmetric structure reduces the threat of
transformer saturation due to the dc flux. The proposed
converter features the continuous input current and could be
used either with one or two input voltage sources.
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This paper presents a new converter topology for a permanent magnet synchronous generator based v... more This paper presents a new converter topology for a permanent magnet synchronous generator based variable speed wind turbine. Main emphasis is on the combination of a controlled rectifier and a novel step-up isolated DC/DC converter topology proposed by the authors. The topology (controlled rectifier coupled with a quasi-Z-source based galvanically isolated step-up DC/DC converter) is essential to generate regulated DC voltage (400 V DC typical for 230 V AC output) despite wide variations in the output voltage of a wind generator. The operation principle of the proposed topology is described in detail. Experimental results are presented and analyzed.
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This paper presents an analysis of the continuous current and the discontinuous current mode oper... more This paper presents an analysis of the continuous current and the discontinuous current mode operation of the transformer of a step-up DC/DC converter topology intended for applications with widely changing input voltages. The proposed topology consists of a LC network coupled with a single-phase inverter on the primary side and a full-bridge rectifier on the secondary side of an isolation transformer. When the input voltage is above the nominal value, the converter operates in the buck mode, but when the input voltage level is below the nominal value, the converter operates in the boost mode.
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This paper presents simulation and experimental results of a quasi-Z-source inverter (qZSI) based... more This paper presents simulation and experimental results of a quasi-Z-source inverter (qZSI) based bi-directional DC/DC converter for supercapacitor (SC) interfacing. The bidirectional capability provides both the charging and discharging of the SC. During the charging mode the converter operates as a conventional VSI performing the voltage buck function, but during the discharging mode the converter operates as a qZSI based step-up DC/DC converter performing the voltage boost function. The proposed converter discussed was tested in both operating modes - SC charging and discharging. Theoretical assumptions are proved by the PSIM simulation results and verified experimentally on a 500 W laboratory prototype. The most important results obtained are outlined.
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This paper proposes a novel step-up DC/DC converter with galvanic isolation - the quasi-Z-source ... more 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.
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Scientific Journal of Riga …, 2010
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One of major problems related with PV-applications is common mode currents. The issue can be solv... more One of major problems related with PV-applications
is common mode currents. The issue can be solved in two
ways: galvanic decoupling of AC-grid and chopping the
common mode currents by additional actively controlled
circuitry. Flyback converter is good solution for MPPT
tracking for PV-modules up to 100-150 W with galvanic
decoupling. The problem of designing of this type of converter
is that most of design guides and literature is dedicated to
consumer electronics applications. MPPT converter design
have different starting points of calculations. The paper
contains the suggested approaches to the calculations, design
recommendations, considering the specific nature of PVsources
and NOCT model of PV-module.
The approach calculations, design guidelines, recommendations
and simulation of power electronics part of MPPT
converter and experimental results with implemented circuit
are presented and discussed. In order to increase the efficiency
during tests the circuit was upgraded with active clamp. After
the tests active clamp was upgraded to the forward active
clamp topology. The efficiencies and key waveforms of voltages
are compared and analyzed.
Bookmarks Related papers MentionsView impact
This paper analyzes two maximum power point tracking (MPPT) converter topologies that are part of... more This paper analyzes two maximum power point
tracking (MPPT) converter topologies that are part of an
interface converter for the integration of photovoltaics (PV) in
the grid. Two different MPPT converter topologies (boost
converter and quasi-Z-Source (qZS) converter) were selected and compared. Theoretical comparison includes an analysis of
regulations for obtaining continuous source current and
comparison of necessary parameters of the reactive elements of the systems.
270 W experimental prototypes of both converters were built
and experimentally compared. Theoretical and experimental
efficiency estimation is proposed and discussed. Also, the losses in diodes and MOSFETS are evaluated taking into account technical data from datasheets
Bookmarks Related papers MentionsView impact
This paper shows the bidirectional operation possibility of the single phase three-level neutral-... more This paper shows the bidirectional operation
possibility of the single phase three-level neutral-point-clamped
quasi-Z-source grid connected inverter. The simple traditional
control system for three-level grid connected rectifier was
implemented. Simulation results confirmed bidirectional
operation capability of the discussed topology.
Bookmarks Related papers MentionsView impact
This paper presents a new modified carrier based single phase modulation technique with maximum c... more This paper presents a new modified carrier based
single phase modulation technique with maximum constant
boost control for three level Z or qZ-source inverter topology.
The proposed technique is explained, analysed and compared
with the previous one in simulation as well in experimental
way. Obtained results are compared from the point of view of
power losses in the electronic switches. Advantages and
disadvantages of the converters performance based on the
proposed modulation techniques implementation are discussed.
Bookmarks Related papers MentionsView impact
Focus is on three operation strategies for a gridconnected three-level neutral-point-clamped quas... more Focus is on three operation strategies for a gridconnected
three-level neutral-point-clamped quasi impedance
source inverter in a single-phase application. Each control
scheme was implemented in the PSCAD/EMTDC simulation tool
and underwent different tests, which involved some steps in the reference values and in the perturbations applied to the system.
A comparison according to their responses was based on
different criteria, such as rise time, settle time, overshoot and
steady state error, in order to determine which would be more
suitable for such application.
Bookmarks Related papers MentionsView impact
This paper presents a novel quasi-Z-source halfbridge galvanically isolated DC-DC converter inten... more This paper presents a novel quasi-Z-source halfbridge
galvanically isolated DC-DC converter intended for the
photovoltaic applications. The topology could be envisioned as an alternative to the boost half-bridge DC-DC converter but the
benefit of its symmetric structure reduces the threat of
transformer saturation due to the dc flux. The proposed
converter features the continuous input current and could be
used either with one or two input voltage sources.
Bookmarks Related papers MentionsView impact
This paper presents a new converter topology for a permanent magnet synchronous generator based v... more This paper presents a new converter topology for a permanent magnet synchronous generator based variable speed wind turbine. Main emphasis is on the combination of a controlled rectifier and a novel step-up isolated DC/DC converter topology proposed by the authors. The topology (controlled rectifier coupled with a quasi-Z-source based galvanically isolated step-up DC/DC converter) is essential to generate regulated DC voltage (400 V DC typical for 230 V AC output) despite wide variations in the output voltage of a wind generator. The operation principle of the proposed topology is described in detail. Experimental results are presented and analyzed.
Bookmarks Related papers MentionsView impact
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Technological Innovation for …, 2012
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conference.rtu.lv
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Engineering for Rural …, 2011
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… Drives, Automation and …, 2012
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Industrial Technology (ICIT), …, 2012
This paper presents an analysis of the continuous current and the discontinuous current mode oper... more This paper presents an analysis of the continuous current and the discontinuous current mode operation of the transformer of a step-up DC/DC converter topology intended for applications with widely changing input voltages. The proposed topology consists of a LC network coupled with a single-phase inverter on the primary side and a full-bridge rectifier on the secondary side of an isolation transformer. When the input voltage is above the nominal value, the converter operates in the buck mode, but when the input voltage level is below the nominal value, the converter operates in the boost mode.
Bookmarks Related papers MentionsView impact
… Energies and Power …, 2011
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Compatibility and Power …, 2011
This paper presents simulation and experimental results of a quasi-Z-source inverter (qZSI) based... more This paper presents simulation and experimental results of a quasi-Z-source inverter (qZSI) based bi-directional DC/DC converter for supercapacitor (SC) interfacing. The bidirectional capability provides both the charging and discharging of the SC. During the charging mode the converter operates as a conventional VSI performing the voltage buck function, but during the discharging mode the converter operates as a qZSI based step-up DC/DC converter performing the voltage boost function. The proposed converter discussed was tested in both operating modes - SC charging and discharging. Theoretical assumptions are proved by the PSIM simulation results and verified experimentally on a 500 W laboratory prototype. The most important results obtained are outlined.
Bookmarks Related papers MentionsView impact
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… and Exposition (APEC), …, 2012
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… Drives Automation and …, 2010
This paper proposes a novel step-up DC/DC converter with galvanic isolation - the quasi-Z-source ... more 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.
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Scientific Journal of Riga …, 2010
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