Janis Zakis

Riga Technical University | RTU · Institute of Industrial Electronics and Electrical Engineering

This paper deals with the position detection of automated guided vehicles (AGVs) in dynamic resonant-inductive wireless power transfer (WPT) systems. A position detection is necessary to activate the correct transmitting coil. One of the simplest and most effective approaches for a position detection method is to use optical or magnetic position se...

Chapter 1 of this book presents standards, classification and history of wireless power transfer as well as a description of the parameters of wireless power transfer systems. Chapter 2 is devoted to an overview of wireless power transfer techniques. Major attention is focused on the resonant-inductive wireless power transfer. In Chapter 3, resonan...

Citation: Ibrahim, M.; Rassõlkin, A.; Vaimann, T.; Kallaste, A.; Zakis, J.; Hyunh, V.K.; Pomarnacki, R. Digital Twin as a Virtual Sensor for Wind Turbine Applications. Energies 2023, 16, 6246. https://doi.org/10.3390/ en16176246 Academic Editors: Dan-Cristian Popa and Emil Cazacu Abstract: Digital twins (DTs) have been implemented in various applic...

The aim of the presented investigation is to explore the time gap between an anomaly appearance in continuously measured parameters of the device and a failure, related to the end of the remaining resource of the device-critical component. In this investigation, we propose a recurrent neural network to model the time series of the parameters of the...

Single-loop current sensorless control allows for abolishing of the instantaneous current measurement in the control system using only a single control loop with voltage feedback to stabilise the DC-bus voltage. This approach eliminates current sensors in the control circuit, benefiting from saving space on the printed circuit board and minimising...

The invention relates to the field of electrical engineering and power electronics, in particular to wireless power transmission (for recharging batteries of electric devices or electric drive). The purpose of the invention is to create a wireless power transmission system for moving objects with activation of the transmitting part without position...

The operation of wireless battery chargers at multiple switching frequencies may lead to a noticeable suppression of conducted and radiated electromagnetic interference (EMI) at the cost of decreased efficiency (mainly at lower load resistances) and increased peak and root mean square values of currents of power components of the wireless battery c...

The multi-switching-frequency technique is one of the spread-spectrum techniques for suppression of conducted emissions generated by wireless battery chargers. Its advantage is a relatively easy implementation with a microcontroller. In this paper, an original thorough experimental study of the effect of the multi-switching-frequency-based spread s...

Race to Zero challenge is a world-wide activity for the universities and colleges to foster the climate goals. This paper analyses the potential of Riga Technical University (RTU) for this action. Different renewable energy sources (PV, wind generators) have been discussed to be installed around the RTU campus. The profiles of electric power consum...

The application of conventional spread spectrum techniques for conducted electromagnetic emission (EME) reduction in inductive-resonant wireless power transfer (WPT) systems may not reduce conducted EME enough due to specific frequency characteristics of the resonant systems and it can lead to some "adverse effects", mainly in terms of decreased ef...

Inductive-resonant wireless power transfer systems are often used for wireless transfer of electric power. However, they are significant sources of radiated electromagnetic emissions. The effect of spread-spectrum approach based on classical switching frequency modulation of inductive-resonant wireless power transfer system inverter operating frequ...

In this paper study of the effect of hybrid modulation on inductive-resonant wireless battery charger (in both constant current (CC) and constant voltage (CV) modes) performance characteristics (efficiency, conducted electromagnetic interference levels, etc.) is presented. The study is based on simulation of the wireless charger model in PSIM softw...

This paper presents an inductive power transfer system on the basis of a double single phase three-level T-type inverter and two split transmitting coils for constant current and constant voltage wireless charging of low-voltage light electric vehicle batteries with closed-loop control , considering time-delay communication constraints. An optimal...

Approaches to get higher efficiency of switching-frequency-modulated inductive-resonant wireless power transfer systems (WPT) are proposed in the paper. The approaches are verified by using simulations. The approaches are based on utilization of modified resonant tanks with electronically-switched capacitors or electronically tunable capacitors. Th...

Climatic conditions, such as hail, strongly affect the efficiency of photovoltaic (PV) modules. The aim of this paper is to present comprehensive analytical and experimental research results and to evaluate the impact of hail on PV modules. The experimental study was conducted using a new approach in hail simulation testing the impact on PV modules...

Any energy conversion devices, such as industrial motor-drives, propulsion drives of electric vehicles, pump systems, wind turbines, and others, are prone to failures. Usually, failures result in increased economic costs that come through additional energy losses, loss of production, or in a worst-case even environmental hazard. To prevent failures...

This article presents a non-conventional approach to a multi-coil wireless power transfer system based on a Z-source network. The novelty of the approach lies in the use of a Z-source as a voltage source for energy transmission through the wireless power transfer coils. The main advantage is in a reduced number of semiconductors. This paper provide...

The current feedback is considered as unavoidable part of most control system driving power electronic converters. However, it is possible to eliminate the use of current sensor, if properly calculated volt-second balance is applied to input inductor. This paper describes the implementation of current sensorless control technique applied to neutral...

Being switch-mode in nature, wireless power transfer systems (WPT) emit significant conducted electromagnetic emissions (EME). In this paper for the first time multi switching frequency scheme is applied to closed-loop WPT systems for reduction of conducted EME. In this method inductive resonant WPT system operates at different discrete switching f...

In this paper spread spectrum technique based on switching frequency modulation for the first time is applied to closed-loop wireless power transfer (WPT) systems with multi level inverters at the primary side. The effect of switching frequency modulation on the main performance characteristics of WPT system with multi level inverter operating in c...

This paper deals with inductive-resonant wireless power transfer (WPT) systems based on multilevel T-type inverters with simultaneous modulation of switching frequency and duty cycle. The effect of the hybrid modulation on the performance characteristics of closed-loop WPT systems with T-type multilevel inverters for wireless battery charging is st...

Proposed coupling coefficient estimation in multicoil systems is a complex task. In most cases it involves special high cost measurement equipment. The aim of this work is to propose simple way to measure coupling coefficient without any complex equipment. For this task RLC meter and special switched relay system is used.

In this paper short-range low-power inductive resonant wireless power transfer system based on modified E class inverter is developed and studied in details. Simulation model of the inductive wireless power transfer system is created, simulation of the model is then performed in PSIM and the simulation results are then analyzed. Additionally, exper...

Conducted electromagnetic emissions (EME) and efficiency of strongly coupled magnetic resonance wireless power transfer (WPT) systems with double-slope modulation signals are studied in details using simulations. It is shown that WPT systems with double-slope ramp modulation waveforms compared to WPT systems with conventional ramp modulation wavefo...

This paper presents comparative analysis of different spread-spectrum techniques for reduction of conducted emissions generated by strongly coupled magnetic resonant wireless power transfer (WPT) systems. The spread spectrum techniques analyzed in the paper are periodic frequency modulation, periodic duty ratio modulation and a combination of them....

Bidirectional DC-DC converters are an essential part of modern power systems, such as electric vehicles and renewable energy. The paper presents a comparative analysis of bidirectional DC-DC converters suitable for high power density application without galvanic isolation. It is based on the comprehensive comparative analysis of conduction losses,...

This paper describes Z-source based inductive power transfer topologies control approaches. The goal of this work is a multi-variable control approach which involves a constant voltage / constant current control along with an optimal frequency control to obtain maximum efficiency. This control is applied to the wireless power transfer system based...

Battery energy storage systems are becoming more and more popular solution in the household applications, especially, in combination with renewable energy sources. The bidirectional AC-DC power electronic converter have great impact to the overall efficiency, size, mass and reliability of the storage system. This paper reviews the literature that d...

p>Battery energy storage systems are becoming more and more popular solution in the household applications, especially, in combination with renewable energy sources. The bidirectional AC-DC power electronic converter have great impact to the overall efficiency, size, mass and reliability of the storage system. This paper reviews the literature that...

Focus is on the case study of a synchronveter model use in the qZS inverter working in an islanding operation mode. Main tasks and control principles of a sychronverter in the microgrid are explained. Theoretical assumptions are tested and verified with Psim simulation model with different types and powers of microinverter loads. General waveforms...

A full bridge converter with electrolytic capacitor on the dc bus is a widely used approach for a single phase interface for renewable energy source generation or energy storage integration in the utility grid. New wide bandgap devices enable higher switching frequency, higher efficiency and higher power density. In the paper, the authors introduce...

The energy stored Quasi-Z-source Inverter (qZSI) allows integrate energy storage in addition to the other energy source mainly for output power smoothening. Single phase inverter suffers from double-frequency power ripple in the input side and also in the energy storage that is transferred there from the ac-side. In qZSI must be used large electrol...

This paper presents a comparative analysis of the bidirectional qZS-based dc-dc converter for storage application with a traditional solution based on the boost dc-dc converter. The analysis estimates the energy stored in the capacitors and inductors, blocking voltage across semiconductors, and conduction losses. The comparison is based on the math...

Solutions for a family of the novel three-level neutral-point-clamped (NPC) inductor-capacitor-capacitor-transformer (LCCT)-derived three-phase inverters are described and compared. Component design guidelines and steady state analysis, current and voltage waveforms are given. The authors' simulation results confirm the theoretical predictions. It...

Single-phase inverter suffers from double-frequency power ripples in the input side transferred there from the ac-side. To mitigate this ripple, two types of power decoupling approaches can be applied: passive power decoupling and active power decoupling. We present a technique of passive power decoupling realized by modifying the control strategy....

Continuous development of intelligent network applications drives the demand for deployment-ready hardware and software solutions. Such solutions are highly valued not only by distributed producers of energy but by energy consumers as well. The use of intelligent network applications enables the development and improvement of the quality of service...

This study discusses realization possibilities of the buck mode in the novel magnetically integrated quasi-Z-Source Series Resonant Converter (qZSSRC) with secondary resonance. Our aim was to achieve higher power conversion efficiency at different power levels and DC voltage gains of the converter. The phase-shift modulation was comprehensively com...

The main advantages of the interleaved multiphase DC-DC converters over single-phase converters are reduced current stress and reduced output current ripple. However, inductor current ripple can not be reduced only by interleaving method. The integrated magnetic structure can be used to solve this problem and this also allows to achieve higher powe...

This paper presents a novel bidirectional current-fed dual inductor push-pull DC-DC converter with galvanic isolation. The converter features active voltage doubler rectifier, which is controlled by the switching sequence synchronous to that of the input-side switches. The control algorithm proposed enables full-soft-switching of all switches in a...

In this paper the asymmetrical pulse width modulation (APWM) is proposed for the control of galvanically isolated impedance-source series resonant DC/DC converters in the buck mode. Contrary to the variable frequency control, which is most widespread control technique of the series resonant converters, the APWM features fixed frequency operation an...

Instantaneous current measurement increases the cost and size of the control system in switched-mode power supplies. This paper presents the first attempt to apply current sensorless control in conjunction with a half-bridge converter. The proposed single-loop current sensorless control algorithm allows shaping sine-form current in the rectifier mo...

This study compares a three-phase three-level voltage source inverter with an intermediate dc–dc boost converter and a quasi-Z-source inverter in terms of passive elements values and dimensions, semiconductor stresses, and overall efficiency. A comparative analysis was conducted with relative parameters to evaluate converter parameters for any appl...

Chemical-free trough-hole plating process LPKF ProConduct® allows significantly decrease the time of rapid PCB prototyping; this technology is well tested by prototyping a wide spectrum of weak signal and digital electronics boards. Current work presents tests of LPKF ProConduct® technology on applicability for prototyping of power converter boards...

This paper is a first attempt to analyze single-loop current sensorless control (CSC) method applied to three phase converter. The most suitable converter topology is selected among popular bidirectional AC-DC converters. The theory of CSC operation is described and evaluated by means of simulation. Results have confirmed the ability of controlling...

The quasi-switched-boost inverter is an alternative to the quasi-Z-Source inverter. Its passive component number is two times smaller but it contains two additional semiconductor components. Earlier the switched-inductor cell was applied in this topology to enhance dc voltage gain at the cost of high input current ripple. This paper proposes a nove...

The current control is becoming a challenging task for switched mode power supplies, while current sensorless control solutions can avoid the instantaneous current measurements that has been applied for mostly used power factor correction topologies. However, multilevel type of converters haven't been considered to use with current sensorless contr...

Focus is on three operation strategies for a grid-connected three-level neutral-poi n t-clamped quasi impedance source inverter in a single-ph as e application. Each control scheme wa s implemented in the PS CAD/EMTDC simulation tool a n d underwent different tests, which involved some steps in the reference values and in the perturbations applied...

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 c...

This paper provides an analytical overview of different impedance sources networks. General classification and main properties of different impedance source networks and their modifications are summarized and presented.

In this paper authors present a novel voltage measuring system that allows to measure the voltage of each cell for series connected supercapacitors (SCs). Proposed system is based on isolated DC/DC converter with multiple outputs that have equal voltages, which serve as reference voltage for each series connected supercapacitor. Two operation modes...

This paper describes a multiport topology based charging station for light electric vehicles, like electric-motor assisted bicycles (pedelec). The multiport topology allows energy flow control between the charging ports, alternative energy ports and the grid port. Every port can act bidirectionally, enabling easy integration of additional energy st...

This paper presents the full zero voltage switching three-level boost dc-dc converter. The boundary conduction mode and snubber capacitors provide zero voltage switching operation in the whole range of operation. Analytical estimation and simulation results have proved the proposed idea. In advance, it was demonstrated that the multi-cell structure...

In this paper authors present a method for optimal sizing of supercapacitor (SC) energy storage system (ESS) for braking energy recovery in tram network. The method is applicable for segmented tram networks with radial feeding topology and a stationary storage system installed in traction substation. The method is demonstrated for one traction subs...

Ten different modulation methods of the isolated quasi Z-source inverter based DC-DC converter were tested to find out radiated emission levels. EMC measurements were performed on a low power 250 W prototype. A radiated emission test was carried out in a GTEM cell (gigahertz transverse electromagnetic cell) according to the EMC standard IEC 61000-4...

A series resonant tank in the quasi-Z-source (qZS) DC-DC converter with a voltage doubler rectifier could significantly increase the input voltage regulation range by adding the buck mode realization possibility. This paper discusses two different control approaches of the qZS series resonant DC-DC converter in the buck mode: variable frequency con...

This paper discusses the performance improvement method of the recently popular galvanically isolated quasi-Z-source DC-DC converter. In order to decrease the conduction losses in the quasi-Z-source network and voltage doubler rectifier the replacement of diodes by the N-channel MOSFETs was analyzed. The proposed approach was validated by the compu...

Current measurement becomes challenging task in power converters operating at high switching frequencies, moreover traditional control system requires two control loops – first (slow) regulates DC-link voltage, second (fast) controls the shape of current, that all together results in complicated transfer function and long transition periods. The cu...

The series resonant DC/DC converter with isolation transformer is investigated. When switching frequency of input inverter bridge is above the resonant one a shortening of the naturally half-waves of current through a L-C resonant circuit takes place resulting in a circulating current through the DC supply source reducing a mean value of supply cur...

Focus of this study is on a new switched-capacitor current-fed (CF) quasi-Z-source inverter (qZSI) topology, which is derived from the conventional CF qZSI. Each capacitor of the quasi-Z-source network is replaced by a switching-capacitor cell built with two capacitors and three diodes. As our steady state analysis of an idealized converter shows,...

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.

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 p...

This paper presents a comparative feasibility study of coupled inductor implementation in a three-level neutral-point-clamped quasi-Z-source (3L-NPC qZS) DC/AC converter. Our theoretical verification shows that coupling of the qZS inductors enables reductions in the size and weight of the magnetic components or in the input current ripple. Our math...

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 o...

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 regula...

The growing energy demand all over the world and the approaching deficit of traditional energy resources makes the development of renewable energy sources including wind energy necessary. A significant part of any wind turbine is the grid interface converter, operation of which depends a lot on the control system. Although this consideration is val...

This paper presents an isolated quasi-Z-source inverter-based (qZSI) resonant DC/DC converter. The explanation of selection of the proposed topology is justified. Both the normal and the boost modes are discussed. Theoretical operation waveforms as well as basic expressions for the calculation of currents and voltages are proposed. A 1500 W laborat...

This paper presents a new active clamp circuit (ACC) for a galvanically isolated current-fed DC/DC converter. New ACC enables reduction of power losses in transistors and diodes. In order to demonstrate the benefits of the proposed ACC the power losses of converters with traditional and new ACC were estimated and compared. In order to validate the...

This paper presents a complete steady-state analysis of the novel commutating LC-filter based dual active bridge (DAB). Such converter is aimed to be used in the isolation stage of the power electronics transformer. The topology consists of the LC filter coupled with a DAB. The LC filter allows to boost the input voltage by means of shoot-through s...

This paper presents a steady state analysis of the commutating LC-filter based dual active bridge (DAB) considering the conduction losses in the components. The aim is to use this converter in power electronic transformer (PET). The LC-filter offers the boost properties with a small component count and DAB allows effective power flow control and so...

The paper analyzes the impact of the component losses on the efficiency of the novel DC/DC converter. The converter is a combination of the quazi-Z-source (qZS) network and dual active bridge (DAB). In the analysis the mathematical loss models of the proposed DC/DC converter are derived and efficiency is estimated. Eventually the efficiency is veri...

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, 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 featu...

The paper analyzes the impact of the component losses on the efficiency of the novel DC/DC converter. The converter is a combination of the quazi-Z-source (qZS) network and dual active bridge (DAB). In the analysis the mathematical loss models of the proposed DC/DC converter are derived and efficiency is estimated. Eventually the efficiency is veri...

Focus is on implementation possibilities of surfacemount device (SMD) to be used in high power applications. SMD capacitors reduce the size and dimensions of a power circuit and increase the flexibility of placement of other components. Ceramic and electrolytic capacitors are compared by means of voltage ripple, volume, labour-intensity and impedan...

This paper presents a bi-directional quasi-Z-source inverter (qZSI) based DC/DC converter for supercapacitor (SC) interfacing in high power applications. In the SC charging mode the proposed converter acts as a conventional VSI based step-down converter, but in the energy recovery mode it acts as a qZSI-based step-up DC/DC converter. The paper anal...