Increasing the power rating of electric vehicles (EV) fast charging stations to reduce charging times is considered critical to accelerate the adoption of electric vehicles. Besides increasing the ...power, other drivers pushing the development of EV fast chargers include the improvement of efficiency and reliability. Partial power converters (PPC) have emerged as an interesting option for some of the power converter stages in fast charging stations due to their potential to increase efficiency and power rating. However, some PPCs operate as switched autotransformers by using high frequency (HF) isolation transformers but without providing galvanic isolation. This is a drawback due to cost, size and losses introduced by the transformer. This paper presents a transformerless DC–DC Type I step‐up PPC for a DC–DC regulation converter for EV fast charging stations. The proposed converter replaces the transformer commonly used in Type I PPC by an impedance network, resulting in a more efficient, cheaper, and less complex converter option. This concept is verified through simulations and experimentally validated with a laboratory prototype.
This paper presents a transformerless DC–DC Type I partial power converters for a DC–DC regulation converter for EV fast charging stations, using an impedance network instead a transformer.
This work presents a partial power converter allowing us to obtain, with a single DC-DC converter, the same feature as the classical interleaved operation of two converters. More precisely, the ...proposed topology performs similarly as the input-parallel output-series (IPOS) configuration reducing the current ripple at the input of the system and dividing the individual converters power rating, compared to a single converter. The proposed topology consists of a partial DC-DC converter processing only a fraction of the total power, thus allowing high efficiency. Experimental results are provided to validate the proposed converter topology with a Flyback-based 100 W test bench with a transformer turns ratio n1=n2 . Experimental results show high performances reducing the input current ripple around 30% , further increasing the conversion efficiency.
Photovoltaic (PV) microinverters have grown rapidly in the small-scale PV market, where typical two-stage converters are used to connect one PV module to the single-phase AC grid. This configuration ...achieves better performance in terms of energy yield compared with other PV configurations. However, the conversion efficiency of a two-stage system is the main drawback, especially when a high-voltage gain effort is required. In this context, single-stage microinverter topologies have been recently proposed since only one power conversion stage is required to extract the maximum power of the PV module and inject the AC power to the grid. This single-stage configuration allows considerable improvement of the overall efficiency of microinverters by reducing the number of elements in the system. However, the main challenge of these topologies is their control, since all variables of the converter are composed by the AC waveform with DC-bias. In this paper, four control strategies are analyzed for the mainstream single-stage topology, which is the dual-boost inverter (DBI). Classical linear control and three non-linear strategies, namely finite control set–model predictive control, flatness-based control, and sliding mode control, are detailed. The main contribution of this work is a complete comparison of the control strategies, to give insights into the most suitable control strategy for the DBI in PV microinverter application.
In photovoltaic (PV) systems, the reliability of the system components, especially the power converters, is a major concern in obtaining cost effective solutions. In order to guarantee service ...continuity in the case of failure of elements of the PV converter, in particular, semiconductor switching devices, a solution is to design power converter with fault-tolerance capability. This can be realized by aggregating hardware redundancy on an existing converter, providing the possibility of replacement of faulty elements. This paper evaluates the reliability of a fault-tolerant power electronics converter for PV multistring application. The considered fault-tolerant design includes a single redundant switching leg, which is used in order to reconfigure the structure in case of a switch failure either on DC-AC or DC-DC stages. This paper details the reliability estimation of the considered PV multistring fault-tolerant converter. Furthermore, a comparison with a conventional structure without fault-tolerant capability is provided. The results show that the introduction of a single redundant leg allows for improving the converter mean time to failure by a factor of almost two and it reduces, by half, the power loss due to system-failure shutdowns in PV applications, while only increasing the converter cost by 2–3%.
DC–DC power converters are essential for various applications, including photovoltaic systems, green hydrogen production, battery charging, and DC microgrids. Partial Power Converters (PPC) are ...notable for their efficiency, processing only a fraction of total power and reducing conversion losses, but this performance is overshadowed by the high cost of its construction, associated with high-frequency transformers (HFT). This paper introduces a transformerless partial power AC-link step-down converter, eliminating the need for an HFT and reducing costs while improving power density. An experimental validation using a reduced-scale prototype demonstrates the converter’s operation with a peak efficiency of 93.2% and overall efficiency above 92%, demonstrating the experimental viability of the converter. The proposed AC-link seen as a two-port network is shown to be very attractive for DC–DC step-down operations, and as a possible replacement of traditional PPC.
Photovoltaic (PV) systems are one of the main actors in distributed power generation. In particular, in urban contexts, the PV generators can be subjected to mismatching phenomena due to the ...different orientation of the modules with respect to the sun rays or due to shadowing. In these cases, the maximum power point tracking (MPPT) function must be designed carefully. In this paper, architecture, including one dc/dc converter for each PV generator, is considered. The converters' output terminals are series connected to a high-voltage dc bus, where also a bidirectional dc/dc converter managing the power from/to a storage device is plugged. The functional constraints deriving from the dc/dc converters' connection, the mismatching phenomena, the MPPT capabilities of the inverter, connected with its input terminals at the dc bus, are taken into account in order to determine the best operating point of the system as a whole. The real-time constrained optimization problem is solved by using the particle swarm optimization method, which needs the knowledge of the actual current versus voltage curve of each PV generator. The practical impact of this need is also discussed in the paper. The feasibility and the performances of the proposed approach are experimentally validated by using a laboratory prototype.
Photovoltaic (PV) to electrolyzer power systems are an attractive research topic since the PV produced power can be optimized by skipping power conversion into AC and producing a direct DC-DC ...interface. Existing DC-DC power conversion systems to directly interface the PV generation and Hydrogen (H2) electrolyzer are mainly based in interleaved structures or multi-resonant converters. Soft-switching characteristics are also suitable for these conversion topologies and DCX converters are then serious candidates to be used. DCX provides an isolated high efficiency solution but the DCX-based two-stage converter topology must be optimized in order to obtain better efficiency and energy yield. In this work a detailed comparison of DCX topologies is given for a PV to H2 application. The proposed optimized system is validated through simulation in a multi-string electrolysis system, showing the relevance of the solution for this application. The proposed approach reaches a global maximum efficiency of 98.2%.
For large-scale photovoltaic (PV) systems, the multistring configuration is becoming more and more attractive compared with the classical central inverter, since it results in better energy yield by ...realizing distributed maximum power point tracking. Among the existing solutions, an attractive topology consists in a single dc bus bar collector cascaded H-bridge (CHB) inverter. Through the use of a single dc bus bar collector, the CHB inverter presents inherent balanced operation while the multistring PV-system is fully decoupled from the grid-tie inverter. This paper proposes the experimental validation of this structure on a reduced-size single-phase laboratory prototype. Results confirm the interest of the proposed PV multistring architecture.
Two-stage photovoltaic (PV) configurations have become increasingly popular due to the decoupling between the inverter dc-link voltage and the PV voltage, adding flexibility to extend the maximum ...power point tracking range. However, the additional dc-dc converter increases the power converter losses. The concept of partial power converters (PPCs), which reduce the amount of power handled by the dc stage, can mitigate this effect. However, the type of topology, its power and voltage rating, efficiency, and an operating range can vary significantly depending on the function (boosting or reducing voltage) and type of PV application and scale (micro-, string-, or multi-sting inverter). This paper analyzes the possible configuration of connections of PPC depending on the application and scale of the PV system and introduces a new buck-type PPC. Three solutions for practical PV systems are further elaborated, including experimental validation. Results show that the PPC concept greatly improves the overall PV system efficiency with the added benefit that the dc-dc stage power ratings achieved are only a fraction of the PV system, reducing size and cost of the power converter without affecting the system performance.
In this paper, a control-oriented model of a solid oxide fuel cell system is formulated and analyzed in detail. First, a lumped model based on first principle laws is formulated and tuned using ...experimental data coming from a real solid oxide fuel cell system test bench. The model calibration is carried out based on an optimization approach to minimize the error between the experimental data and the model one. To systematically analyze the system behavior, an equilibrium point analysis is formulated and developed. The analysis results show the maximum steady-state electrical power under each constant stack temperature. This will allow to appropriately select operation points during the system operation. Secondly, Lyapunov's theory is used to characterize the local stability of the equilibrium points. The results show that the equilibrium points are locally stable. Besides, comparison between the initial nonlinear model with the linearized model is performed to show the efficacy of the linearised model analysis. Finally, the frequency response of the linearized model is performed. This analysis provides key information about control system design in order to efficiently operate the solid oxide fuel cell system.
•Formulation, calibration and validation of a lumped SOFC model.•Steady-state characterization of the SOFC system model.•Local stability and step response analysis of the SOFC system based on the model.•Frequency response analysis of the SOFC model. Suggestions to design controllers.
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