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The article overviews residential and building-integrated photovoltaic (PV) module types. It demonstrates that existing dc–dc converter technologies do not allow building a universal interface microconverter because of wide dispersion of the parameters. However, the absence of universal microconverters limits the widespread adoption of PV modules despite great benefits for energy-efficient buildings and restrains the deployment of residential PV-based dc microgrids. Based on the design requirements formulated, a new approach utilizing a boost half-bridge front-end inverter and a three-mode reconfigurable rectifier (RR) is proposed. The article describes the operating principle of the derived converter. The RR allows keeping the duty cycle of the input side within a favorable range of acceptable efficiencies. An experimental prototype rated for 360 W was assembled and tested in the entire operating range. The experimental results prove the ultrawide input voltage range of over 1:20 and demonstrate the capability of the proposed concept to interface different PV module types while enabling their shade-tolerant operation.

In this paper, the concept of an Optiverter is proposed as a novel class of photovoltaic (PV) module level power electronics systems. Functionally, the Optiverter is a hybrid technology that combines the ultrawide maximum power point tracking (MPPT) voltage window of the PV power optimizers with the direct ac connectivity and inherent safety of the PV microinverters. Thanks to the advanced multimode control with variable dc-link and the shade-tolerant MPPT algorithm, the proposed Optiverter ensures efficient energy harvest from the PV module in different shading scenarios. To justify the superiority of the concept, the performance of a 300 W prototype of the PV Optiverter is experimentally compared to that of the industrial microinverters in different operation conditions, including an extreme case with opaque shading of two out of three substrings of the PV module.

This study proposes a high step‐up galvanically isolated dc‐dc converter based on the quasi‐Z‐source (qZS) network. The voltage gain of the converter can change in a wide range. This feature makes the converter suitable for applications with a wide input voltage range. The range of the dc gain is increased by the implementation of the combined energy transfer principle. A reconfigurable structure is used to combine the energy transfer by the isolation transformer and the coupled inductor of the impedance‐source network. The adaptive mode change activates the energy transfer via an additional winding in the qZS network at lower voltages, which results in considerable efficiency improvement. Consequently, the input voltage range of the converter is extended to the values useful in photovoltaic applications impacted by partial shading. The proposed approach is verified in a photovoltaic (PV) microconverter, where the energy harvest from a PV module is possible during shading by enabling the global maximum power point tracking (GMPPT). It is demonstrated that the dual‐mode operation of the converter helps to achieve a flat efficiency curve along with outstanding maximum power point tracking (MPPT) performance.

In this paper, the analysis and experimental verification of a planar transformer for a high-frequency link converter is presented. The known problem of such topologies is strict limitations related to the transformer leakage inductance and parasitic capacitance. This problem is more pronounced in the systems with high transformer turns ratio. The current research aims to find the low-cost solution, at the same time to ensuring that the values of the parasitic parameters are in the acceptable range. The verification of different 1:10 transformer design approaches was experimentally verified with a 1 kW converter prototype.

This paper presents research findings regarding the post-fault operation possibility of photovoltaic module-level power electronic systems. As the main contribution, it proposes an approach for the realization of photovoltaic microconverters with tolerance to power switch failures. The hybrid switching cell is proposed as a power electronic building block, which enables post-fault operation in the case of the open- or short-circuit failure of any of its power switches. Paper discusses the operation principle and provides experimental results of the 250 W fault-tolerant photovoltaic microconverter.

This paper discusses voltage gain extension intended for the galvanically isolated impedance-source DC-DC converters under the principle of combined energy transfer when the energy is transferred from the primary to the secondary side using an isolation transformer and a coupled inductor of the impedance-source network. Different realization approaches of the combined energy transfer are evaluated; the main emphasis is on the power conversion efficiency and realization complexity. Also, the application of topology morphing control to the galvanically isolated impedance-source DC-DC converters with combined energy transfer is analyzed. An experimental prototype rated for 100 W was used to validate all the findings.

This paper presents a new modulation method for the cycloconverter stage of the high frequency (HF) link AC-DC rectifier. The method takes advantage of the parasitic parameters of the circuit to provide zero current switching (ZCS) for the AC- and zero voltage switching (ZVS) of the DC-side transistors. Regulation with the power factor correction (PFC) is ensured using only one control variable and no external auxiliary or snubber circuits are required. Moreover, ¼ of the AC-side transistors are operating with fundamental frequency. The proposed modulation strategy and its design constraints are analysed mathematically and verified with the simulation model of 1kW, 230VAC/48VDC HF-link converter.

This paper discusses an alternative realization approach of the reconfigurable full-bridge/voltage doubler rectifier for implementation in hybrid DC–DC converters, i.e., the power electronic converters that can adaptively change the power circuit topology for optimization of performance or enabling the post-fault operation. The proposed rectifier is characterized by the reduced number of semiconductor components and the ability of independent use of its capacitors for forming the series resonant tank and output voltage filtering. The paper explains the derivation and operation principle of the semi-active reconfigurable rectifier and discusses the experimental results obtained by the help of a 350 W laboratory prototype. Finally, the fully controlled version of the proposed rectifier is presented, which features superior control and reconfiguration possibilities in both directions of the power flow and, therefore, could be used as a versatile power electronic building block for hybrid DC–DC converters.

Two-stage photovoltaic (PV) microinverters with a buck-boost front-end converter can provide unparalleled performance under shading conditions. However, their efficiency curve is not monotonic across the input voltage range. As a result, it is hard to predict energy production under known weather conditions. The proposed methodology utilizes interpolation of microinverter efficiency based on the experimental efficiency look-up table. Modeling of the maximum power point of a PV module based on the Lambert W function could be combined with the interpolated efficiency to estimate energy produced by a microinverter. The proposed methodology requires only two synchronized datasets, solar irradiance and ambient temperature, as the input variables.

This paper presents a novel soft-switching technique for the galvanically isolated impedance-source full-bridge DC-DC converters. It allows reducing the turn off losses of the inverter switches, which otherwise represent a significant portion of the total power loss in such converters. Zero-current switching is achieved by the introduction of the additional energy return interval provided by the secondary side switches in addition to conventional synchronous rectification. This operation allows to redistribute the transformer current from one pair of switches to another, thus decreasing the current in the switch pair to be turned off. The paper presents the generalized operation principle corroborated with the simulation and experimental verification of the proposed modulation method.

This paper presents an improved modulation method for the cycloconverter stage of high frequency-link DC-AC inverters. By applying the quasi-resonant commutation mode during the entire operating period, the fast and reliable discharge of DC-side capacitances can be provided even if the output current is close to zero. This allows to ensure zero voltage switching (ZVS) conditions for the DC-side transistors, while applying small external snubber capacitors to reduce their turn-off losses. The proposed modulation strategy was significantly simplified and requires no external active auxiliary circuits or multi-mode operation. Moreover, two of the AC-side switches can operate at the fundamental frequency, while the rest operate with zero current switching (ZCS). The proposed modulation method is verified with mathematical analysis, simulation model and experimental prototype of full-bridge HF -link inverter.

This paper addresses various oscillation suppression methods in the AC-AC cycloconverter stage of a high frequency link inverter. Such oscillations occur after the natural commutation of the switches due to parasitic parameters of the converter circuit. A mathematic analysis of the resonance process in the cycloconverter stage is presented, followed by a comparative analysis of different snubber circuits that allow to minimize the effect of oscillations. The theoretical analysis is verified with software models and experimental prototype of 1 kW DC-AC converter.

This paper presents an alternative realization approach of the series resonant DC-DC converter with bidirectional power flow control and a possibility of post-fault operation at the open- or short-circuit failure of any of its semiconductors. The converter is based on the hybrid switching cell that can adaptively change the topology from the full-bridge to a half-bridge to enable the post-fault operation. As compared to the prior art, the proposed converter features twice-reduced switch count and independent use of its capacitors for forming the series resonant tank, blocking of DC bias and output voltage filtering. The derivation and operation principle of the novel converter are explained, and the experimental results obtained by the help of a 350 W laboratory prototype are discussed.

This paper presents a performance enhancement method for the high-gain isolated dc-dc converters intended for module level photovoltaic applications. DC voltage gain of a microconverter should change in a wide range, which requires use of undesirably high or low values of the switch duty cycle that result in high losses in the front-end stage. A reconfigurable rectifier at the output stage of the photovoltaic microconverter enables dc gain control and, consequently, limits variation of the duty cycle to more favourable range. This work proposes use of a reconfigurable rectifier capable of reconfiguring its topology from a voltage doubler to a voltage quadrupler. The paper explains the derivation, operation and the control principle of a reconfigurable rectifier. A single-switch quasi-Z-source front-end stage was used as an application example of the wide input voltage range photovoltaic microconverter in the experimental study. It is demonstrated that by the application of the proposed approach the lower boundary of the input voltage could be shifted from 20 V down to 8 V, which has enabled for the microconverter a unique possibility of shade-tolerant operation with the implementation of a global MPPT.

This paper presents an experimental evaluation of 1200V Reverse-Blocking (RB) IGBTs with different manufacturing techniques aiming to reduce the losses associated with reverse recovery. Obtained results were used to estimate the power dissipation of 230 VAC/3.3 kVA high-frequency link cycloconverter stage featuring soft-switching conditions and natural commutation of semiconductors. The performance of RB-IGBT samples with various techniques were compared with the traditional IGBTs connected in common-emitter configuration to form a bidirectional switch. The estimations show, that the samples with local lifetime control have advantage in terms of overall power dissipation and can provide better performance up to switching frequencies of 15 kHz, when compared to standard IGBTs.

Focus in this paper is on the galvanically isolated impedance-source dc-dc converter topology. It utilizes both a transformer and a coupled inductor to achieve high step-up of the input voltage without additional components. This approach allows for high step-up of the input voltage while avoiding negative effects from the use of multilayer windings. A steady-state operation principle is described and a mathematical model was derived. An experimental prototype was assembled and tested in the wide input voltage range of 1:5 to verify the performance of the converter under study.

This paper presents a comparative analysis of soft switching methods with modulation on the current-fed (grid) side of a high frequency link converter. The focus is on methods that provide clamping and soft switching without auxiliary circuits. Firstly, the case study converter topology used for the generation of the AC line voltage from the low DC voltage, such as a battery, is presented in brief. Secondly, the time Interval requirements for soft switching conditions are described, and the peculiarities of the studied algorithms are summarized. Finally, the algorithms are verified with a simulation model of a 1 kW converter incorporating thermal models of semiconductor switches. The converter performance in terms of regulation capability, current stresses and semiconductor losses with different modulation methods are analyzed and compared.

This paper discusses the essence and application specifics of the multimode rectifiers in high step-up DC-DC converters. It presents an overview of existing multimode rectifiers. Their use enables operation in the wide input voltage range needed in highly demanding applications. Owing to the rectifier mode changes, the converter duty cycle can be restricted to a range with a favorable efficiency. It is shown that the performance of such converters depends on the front-end inverter type. The study considers current- and impedance-source front-end topologies, as they are the most relevant in high step-up applications. It is explained why the full- and half-bridge implementations provide essentially different performances. Unlike the half-bridge, the full-bridge implementation shows step changes in efficiency during the rectifier mode changes, which could compromise the long-term reliability of the converter. The theoretical predictions are corroborated by experimental examples to compare performance with different boost front-end inverters.

This paper presents an overview and analysis of operation of RB IGBT transistors. The series of experiments is devoted characterisation of 600 V, 85 A RB IGBT devices under hard and soft switching conditions using a double-pulse test circuit. The switching behaviour, particularly turn-on and turn-off characteristics, of these devices under various conditions are evaluated. Obtained results allow to assess the impact of reverse recovery process on the turn-on losses and compare the characteristic of RB IGBTs with various types of discrete diodes.

this paper carries applied character, the links onto application notes, that confirmed by a practice, was collected and systematized, in simple terms the substantiation of the need for the three functional units of the gearless precision position stabilizers: power factor corrector (PFC), brake chopper (ballast) and isolated gate driver power supply was given. This allow to design and develop properly operating device, which is a part of rotation platform for angle divergence measurement between real mechanical angle and that is measured by MEMS-based IMU and AHRS modules with a view to adjust the additive and multiplicative error coefficients of mentioned above modules.