Roman Kosenko

Full soft-switching bidirectional current-fed DC-DC converter

The focus is on a switching control strategy for the galvanically isolated bidirectional current-fed dc-dc converter. The converter under study employs the current-fed full-bridge stage at the low-voltage side and the voltage-fed half-bridge stage at the high-voltage side. The current-fed side of the converter utilizes four-quadrant switches comprised of two MOSFETs each. The switching sequence proposed enables soft-switching operation of all switches in both directions of energy transfer for a wide range of dc voltage gain and load variations. Moreover, it features natural clamping and thus eliminates voltage overshoot at the turn-off of switches at the current-fed side. Full zero-current switching is achieved in the current-fed side, while full zero-voltage switching is accommodated in the voltage-fed side. Theoretical predictions were verified with simulations in PSIM 9.

Comparison of Performance of Phase-Shift and Asymmetrical Pulsewidth Modulation Techniques for the Novel Galvanically Isolated Buck–Boost DC–DC Converter for Photovoltaic Applications

This paper 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 (PSM) was comprehensively compared with the asymmetrical pulsewidth modulation (PWM). Both control techniques were evaluated for the case of the discontinuous current through the resonant network, which made their realization more challenging. The operating principle of the qZSSRC in the buck mode with two compared control techniques was explained by means of steady-state analysis. To verify the theoretical assumptions, a 250-W prototype of the photovoltaic module integrated converter was assembled and tested. It was experimentally confirmed that in contrast to the PSM, the asymmetrical PWM for the buck mode control of the qZSSRC will lead to higher power conversion efficiency at different power levels and dc voltage gains of the converter, except the operating points close to the boundary with the normal mode of the converter.

High-efficiency solar tracker development and effectiveness estimation

The photovoltaic (PV) systems are of great interest nowadays due to the depletion of fossil sources and its environmental impact (greenhouse gas emissions, air pollutions and effects of accidents at nuclear power plants). The maximum power point tracking (MPPT) systems and solar trackers allow significantly efficiency increase of PV systems. This article presents the efficiency calculations for 2-axial active solar tracker taking into account losses on panel orientation for the three most specific months - December, June and September. An algorithm for tracker control is proposed and tested on the developed experimental prototype. It was established, that the optimal PV panel orientation change time interval is 15 minutes.

Wide Input Voltage Range Photovoltaic Microconverter With Reconfigurable Buck–Boost Switching Stage

This paper presents a novel soft-switching galvanically isolated buck-boost dc–dc converter as a module-integrated converter for photovoltaic (PV) applications. It features three major operating modes: boost, normal, and buck mode. Their proper distribution over the input voltage range enables wide voltage regulation capabilities, i.e., close to those of nonisolated power optimizers. The proposed control algorithm requires only one buck-boost switching stage that performs voltage regulation by means of the switching stage reconfiguration with smooth transition between the modes. The design guidelines and the digital control system for PV applications are provided. The module-integrated converter was verified experimentally with a solar array simulator. The converter showed good maximum power point tracking performance and a peak efficiency of nearly 97%.

Zero-voltage switching galvanically isolated current-fed full-bridge DC-DC converter

This paper presents a new soft-switching technique for the current-fed full-bridge DC-DC converter that enables zero voltage switching of the input side inverter switches. To achieve this, the secondary side voltage doubler rectifier has to be realized with active switches. Two control channels synchronous with the control signals of the inverter switches are added for driving those switches. Zero voltage switching achieved is assisted with the body diodes that conduct current during soft-switching transients as a result of the leakage inductance current shaping from the secondary side. Moreover, the converter does not suffer from voltage overshoots thanks to natural clamping from the secondary side. Theoretical predictions were verified with simulation.

Comparative Analysis of Semiconductor Power Losses of Galvanically Isolated Quasi-Z-Source and Full-Bridge Boost DC-DC Converters

Abstract This paper compares semiconductor losses of the galvanically isolated quasi-Z-source converter and full-bridge boost DC-DC converter with active clamping circuit. Operation principle of both converters is described. Short design guidelines are provided as well. Results of steady state analysis are used to calculate semiconductor power losses for both converters. Analytical expressions are derived for all types of semiconductor power losses present in these converters. The theoretical results were verified by means of numerical simulation performed in the PSIM simulation software. Its add-on module “Thermal module” was used to estimate semiconductor power losses using the datasheet parameters of the selected semiconductor devices. Results of calculations and simulation study were obtained for four operating points with different input voltage and constant input current to compare performance of the converters in renewable applications, like photovoltaic, where input voltage and power can vary significantly. Power loss breakdown is detailed and its dependence on the converter output power is analyzed. Recommendations are given for the use of the converter topologies in applications with low input voltage and relatively high input current.

Low-cost photovoltaic microinverter with ultra-wide MPPT voltage range

This paper presents a novel low-cost photovoltaic (PV) microinverter with an ultra-wide MPPT voltage range. This approach is based on the two-stage energy conversion where the front-end boost half-bridge DC-DC converter is used to step up the fluctuating PV voltage to a stabilized high DC voltage, which is next transformed to a grid compliant AC voltage by the grid-tied inverter. The operation principle of the microinverter is explained by the help of the steady-state analysis. To verify theoretical assumptions and evaluate the performance of the proposed concept, a 250 W experimental prototype of a photovoltaic microinverter was assembled and tested. Finally, its shade-tolerant operation is demonstrated with the partially shaded 60-cell Si PV module.

Full soft-switching bidirectional isolated current-fed dual inductor push-pull DC-DC converter for battery energy storage applications

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 wide range of the input voltage and power without requirement of snubbers or resonant switching to be employed. Operation principle for the energy transfer in the both directions is described. Experimental results as well as basic design guidelines are presented.

Full-soft-switching high step-up bidirectional isolated current-fed push-pull DC-DC converter for battery energy storage applications

This paper presents a novel bidirectional current-fed push-pull DC-DC converter topology with galvanic isolation. The control algorithm proposed enables full-soft-switching of all transistors in a wide range of input voltage and power with no requirement for snubbers or resonant switching. The converter features an active voltage doubler rectifier controlled by the switching sequence synchronous to that of the input-side switches. As a result, full-soft-switching operation at a fixed switching frequency is achieved. Operation principle for the energy transfer in both directions is described, followed by verification with a 300 W experimental prototype. The converter has considerably higher voltage step-up performance than traditional current-fed converters Experimental results obtained are in good agreement with the theoretical steady-state analysis.

Feasibility study of cascading of full soft-switching current-fed naturally clamped DC-DC converters

In this paper, a novel input-series output-parallel (ISOP) power electronics system is studied. It is made up of cells based on full soft-switching current-fed naturally clamped DC-DC converter topology. This system could be advantageous for power supply of high voltage remote systems with DC voltage, since parasitic inductance of the wire can be utilized as an energy storage. Three different approaches for ISOP cascading are proposed and compared in terms of input current ripple, effective operating frequency, voltage and current stress and operation performance under fault conditions in one of the cells. ISOP system proposed can be advantageous in specific applications, like subsea mining or intelligent transformer for remote areas due to inherent reliability obtained with (N+1) redundancy.