Partial Power Converter Research Articles

Photovoltaic to electrolysis off-grid green hydrogen production with DC–DC conversion

Green hydrogen (H2), being the product of water electrolysis powered by renewable energy sources, is expected to be an energetic vector of major importance toward a more sustainable energy mix. In this context, photovoltaic (PV) -based H2 production is a key element, where power electronics technologies are critical to enable its development. In off-grid applications, designing DC–DC power electronics converters with high efficiency and high power density is really important since it can impact significantly the global performance of the H2 production system. In this work, a two-stage DC–DC power conversion system composed by an unregulated DCX converter and a regulated partial power converter is considered to increase the H2 production system efficiency. The DCX converter works in open-loop at resonant frequency with a high DC–DC conversion ratio. A partial power converter (PPC), which regulates only a fraction of the total power between its input and output terminals, represents a improvement in PV-to-H2 direct conversion, particularly since the PV panels do not require regulation from zero to nominal voltage, and in this work, is introduced for regulation of the DCX-based system, by optimizing the PV produced power through a maximum power point tracking (MPPT) algorithm along with the current control of the electrolyzer. A comparison with state-of-the-art converters show an important improvement of the proposed DCX with PPC regulated system. Compared to the solution with classical interleaved-buck pre-regulator, significant improvements in terms of efficiency for the whole range of operation are obtained, up to 2.5% higher with the proposed system. Experimental evaluation of the proposed PPC and DCX two stage converter for PV-powered electrolysis system is provided, validating its feasibility and interest for off-grid green hydrogen production application.

A ZCS/ZVS DC–DC Partial Power Converter With Reconfigurable H-Bridge and Variable Turns Ratio for an Integrated On-Board Charger

A ZCS/ZVS DC–DC Partial Power Converter With Reconfigurable H-Bridge and Variable Turns Ratio for an Integrated On-Board Charger

Series partial power converter with half bridge LLC series resonant converter for PV application

Abstract This study proposes a series partial power converter with a half-bridge LLC series resonant converter for photovoltaic (PV) applications. The main advantage of the implementation of a partial power converter with LLC series resonant converter is zero voltage switching (ZVS) operation of primary side enables the converter to work at a higher switching frequency. The partial power topology used in the proposed converter enables low power rating switches in the primary, which in other terms reduces the primary current. The proposed converter achieves excellent efficiency due to its ZVS and partial power operating capabilities. The valuation of the proposed converter is done in MATLAB Simulink with a 300 W PV module, which is made to operate in varying irradiance and module temperature of 25 °C. The operational waveforms and the power outputs obtained when the proposed converter is implemented by using perturbation and observation (P&O) maximum power point tracking (MPPT) control algorithm are discussed in this paper.

Transformerless Partial Power AC-Link Step-Down Converter

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.

Partial-Power Conversion for Increased Energy Storage Capability of Li-Ion Battery Energy Storage System

Full-power converters are used in battery energy storage systems (BESS) because of their simple structure, high efficiency and relatively low cost. However, cell-to-cell variation, including capacity, state of charge (SOC), and internal resistance, will decrease the available capacity of serially connected battery packs, thereby negatively affecting the energy utilization rate (EUTR) of BESS. This article proposes a novel BESS scheme that combines a modular converter with partial power conversion architecture to make a modular partial power converter (MPPC) that addresses the issue. The MPPC consists of input-serial and output-paralleled (ISOP) isolated phase-shift full-bridge (PSFB) sub-modules. It processes only the serial compensation power, about 1/3 of the full power. Consequently, the MPPC shrinks the converter capacity, which can reduce the cost and power loss. Furthermore, this article develops a BESS model considering cell-to-cell variations to analyze the energy storage capability of the MPPC-BESS compared with the existing full-power BESS. To test the model, we run a simulation using parameter values from 100 real retired batteries. Our simulation results show that the MPPC can significantly alleviate the reduction of EUTR as the voltage level increase. Finally, we construct a 36V/720W MPPC-BESS prototype with two battery packs and PSFB sub-modules to verify the bidirectional operating stability and energy storage capability.

Review of DC-DC Partial Power Converter Configurations and Topologies

The Partial Power Processing (PPP) concept has garnered attention as it enables the down-sizing of converter and component ratings. Unlike conventional power processing, PPP addresses a portion of the transferred power, leading to a reduction in conversion losses. Throughout this paper, the state of the art of isolated and non-isolated DC-DC converter topologies will be revised. Partial Power Converter (PPC) systems represent one of the main streams of PPP, which, based on isolation requirements and converter connections, can further be divided into isolated converters, such as: Input-Parallel-Output-Series (IPOS), Input-Series-Output-Parallel (ISOP), and, Input-Series-Output-Series (ISOS), or non-isolated converters. This work intends to evaluate and differentiate the characteristics of each type of topology while developing analytically possible connections that may require further research and reviewing metrics that help in fair comparisons of different PPC arrangements, operating under different conditions. A thorough revision is provided for DC-DC converter topologies due to their increased importance in present-day applications, such as energy storage, Electric Vehicles (EVs), and Photo-Voltaics (PVs).

A ZVS Branch-Sharing Partial Power Converter With Bipolar Voltage Regulation Capability

The isolated input-parallel-output-series (IPOS) partial power converter (PPC), which is composed of a dc transformer (DCX) cell and a voltage regulation (VR) cell, is regarded as a promising solution for dc distribution power systems for only a partial power is delivered by the VR cell under different voltage conditions. In this paper, a branch-sharing IPOS-PPC with bipolar voltage regulation capability is proposed, which is composed of two cells: 1) A half-bridge LLC resonant cell works at fixed switching frequency as a DCX with desired performance to realize isolation and main power conversion. 2) An auxiliary full-bridge/push-pull (FB/PP) cell is applied to realize the bipolar voltage regulation and the rest partial power conversion. Two cells share the lagging-leg of FB/PP cell to guarantee zero voltage switching (ZVS) in the whole load range from zero to full load. Compared with the traditional unipolar voltage regulation VR cell, the FB/PP cell can not only reduce the power processed by itself within the same voltage regulation range, but also reduce the component count and achieve a compact structure. Finally, a 180-300 V/ 48 V/ 1 kW experimental prototype is built to verify the feasibility and advantages of the proposed converter.

Analysis and Evaluation of 99% Efficient Step-up/down Converter based on Partial Power Processing

A step-up/and down converter based on partial power processing is proposed in this paper. With the same state equations, the step-up and step-down modes have the same small signal modelling. Therefore, a unified control strategy can be designed for both operating modes, achieving the auto-switching between two operating modes without requiring any additional control. The effect of the transformer's turn ratio on the current and voltage stresses is then analysed. The component stresses are reduced due to the decoupling of transformer. Moreover, the component stress factor method is implemented to evaluate the proposed step-up/down partial power converter. Compared with conventional step-up or step-down partial power converters, the proposed converter has the least component stress factor for a high voltage electrolysis system. In order to validate the proposed topology and modulation strategy, a 400 V prototype is implemented and experimentally evaluated. Measurement results confirm the high efficiency in the overall voltage range, and the maximum efficiency exceeds 99.5%.

An Efficient Three-Port Partial Power Converter based EV On-board Fast Charger

An Efficient Three-Port Partial Power Converter based EV On-board Fast Charger

High-Efficiency Partial Power Converter for Integration of Second-Life Battery Energy Storage Systems in DC Microgrids

High-Efficiency Partial Power Converter for Integration of Second-Life Battery Energy Storage Systems in DC Microgrids

Analysis of Design Requirements and Optimization Possibilities of Partial Power Converter for Photovoltaic String Applications in DC Microgrids

Analysis of Design Requirements and Optimization Possibilities of Partial Power Converter for Photovoltaic String Applications in DC Microgrids

Partial Power Converter for Electric Vehicle Hybrid Energy Storage System Using a Controlled Current Source Cascade Architecture

Partial Power Converter for Electric Vehicle Hybrid Energy Storage System Using a Controlled Current Source Cascade Architecture

Transformerless partial power converter topology for electric vehicle fast charge

AbstractIncreasing 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.

Soft-Switching Bidirectional Step-Up/Down Partial Power Converter With Reduced Components Stress

This paper introduces a step-up/down series partial power converter (S-PPC) based on isolated current-source dc-dc converter topology. The proposed S-PPC exploits the most important feature of the used current-source topology, such as the capability to operate with both voltage polarities in the series port to decrease its rated power. Other advantages include soft-switching in the entire operating range and low current stress of semiconductor components even at very low series voltage. In addition, the proposed S-PPC provides protection and soft-start capabilities due to the integration of a solid-state circuit breaker. The paper explains the operation principle of the proposed S-PPC and compares it to the closest known competing S-PPC based on the dual active bridge topology. An experimental prototype rated for 3.5 kW with maximum processed power of 600 W was built to confirm the converter operation principle and its features. Its experimental efficiency reaches 99.3 %. The proposed S-PPC also shows a good regulation capability at challenging operating points, like nearly zero series voltage.

High Efficiency Converters Based on Modular Partial Power Processing for Fully Electric Maritime Applications

This paper proposes an approach for analyzing the benefits that partial-power-processing-based converters can bring to fully electric maritime applications. With the aim of making the system modular and scalable to different powers/energies, series-connected partial power converters are proposed. Serializing these converters entails significant overvoltage issues, and this paper tackles them for one series-connected module failure case. A reliability analysis has been carried out considering that the components of the battery system follow an independent and identical distribution in terms of failure probability. Furthermore, a redundancy factor has been added to allow a certain failure rate in what is known as a fault-tolerant system. Finally, to demonstrate the high efficiency of partial power converters, a 3 kW prototype is tested at different working points that model the charging process of a battery. The experimental results show a peak efficiency of 99.36%.

Analysis and control of partial power processing nonisolated bidirectional DC‐DC converter

SummaryA partial power processing non‐isolated bidirectional DC‐DC converter is proposed, which is composed of non‐isolated bidirectional DC‐DC converter and direct power flow path. Part of the power of the system is transmitted from the power stage to the load through the non‐isolated bidirectional DC‐DC converter, while the other part is transferred via the direct path without processing by the non‐isolated bidirectional DC‐DC converter. This topology not only enhances the energy conversion efficiency but also has the remarkable advantages of high energy density, simple design, small volume, light weight, and low electromagnetic interference. It can be applied in various two‐way energy management scenarios such as photovoltaic, fuel cell, and super capacitor energy storage. The analysis of the operating principle reveals that the converter can realize the increase and decrease of input voltage and the bidirectional flow of current. When the bidirectional DC‐DC converter steps the voltage down, the partial power converter is in the step‐up mode of reverse transmission. As the bidirectional DC‐DC converter is steps input voltage up, the partial power converter is in step‐down mode of forward transmission. The differential equations and mathematical models of each operating mode are established, and the appropriate voltage feedback control strategy is proposed. Finally, a prototype is constructed and experiments verify the analysis.

Design and Implementation of a Low-Voltage Photovoltaic System Integrated with Battery Energy Storage

In this paper, the simulation and design of a power converter suitable for a low-voltage photovoltaic (PV) battery energy storage converter was investigated. The converter was suitable for sources and loads with near voltage levels and were aimed at efficiency improvement. The converter was called a series partial power converter (SPPC). A continuous current and a boost SPPC topology based on an isolated Cûk converter was constructed. The operation modes of the converter were analyzed. The efficiency verification test of the SPPC in a laboratory environment was completed using an outdoor start-up test, a photovoltaic full cover test and a steady-state operation test under different power levels. The results show that the SPPC can achieve 95–98% converter efficiency within the 87 W–242 W power range. The incremental conductance method based on the SPPC can realize the dynamic MPPT under constant illumination and changing meteorological conditions.

Partial-Power Converter Topology of Type II for Efficient Electric Vehicle Fast Charging

The increasing power levels handled by electric vehicle (EV) dc fast chargers will impose additional challenges to the switching devices in order to cope with the efficiency requirements. A cost-effective alternative to achieve highly efficient power conversion is through the partial-power conversion concept. This article validates the advantages of a step-down Type II partial-power converter (PPC), based on the phase-shifted full-bridge converter, for EV fast chargers. By exploiting the reduced voltage range of an EV battery pack along with the reduced power ratio for a Type II PPC, an extremely efficient charging process can be achieved. The concept is validated with the development of a 7-kW demonstrator, and hence, realistic efficiency measurements are obtained. Results indicate the effectiveness of charging a battery by merely handling 13.32% of the power provided to it, with a peak efficiency of 99.11%.

Design and Implementation of an 18-kW 500-kHz 98.8% Efficiency High-Density Battery Charger With Partial Power Processing

The demand for high-density, high-efficiency bidirectional battery chargers is driven by the fast development of energy storage system in renewable energy system, microgrid, and transportation electrification. Isolated dc–dc converter that interfaces a battery with a variable voltage range is one of the critical components. Input-parallel output-series (IPOS) partial power (PP) converter is considered a promising high-efficiency, high-density solution because only a fraction of power is processed via multistage converters to regulate the output voltage. However, due to the tight coupling between two dc transformers (DCXs), the design of PP converter is complicated. To solve this issue, an overall design procedure for a bidirectional soft-switching resonant-type PP converter is proposed. In the parameters design part, a decoupled design method is proposed to simplify the DCXs design. With this method, two DCXs can be designed separately, and a typical optimization method can be easily applied. As for the hardware design part, to minimize the ac loop inductance and resistance, a two-direction (2-D) flux cancellation method and an “intraleaving” winding structure are proposed for circuit layout and high-frequency (HF) transformer to obtain high operation efficiency and power density. Finally, the whole design procedure is verified by an 18-kW-rated, 25-kW peak, prototype operating at 500 kHz. The realized PP converter features a peak efficiency of 98. 8% and a power density of 142 W/in3. This article is accompanied by two videos demonstrating the dynamic voltage regulation test and the efficiency measurement.

A Secondary-Resonance MHz Active-Clamp Flyback Converter With Partial Power Processing

A 1 MHz active-clamp flyback converter for solar street-lighting applications, featuring a partial power processing, is proposed in this article. The secondary-side resonance between the output capacitor and transformer leakage inductor is utilized to reduce rms current and conduction losses. In comparison with the traditional light-emitting diode drivers based on full power converters (FPCs), the proposed approach that uses partial power converters (PPCs) can significantly improve the overall system efficiency by eliminating the redundant power handling process. The universal schemes are discussed and the optimal solution is eventually determined by the partial power ratio. The advantages of PPC compared with FPC in device stress, losses, and regulation capability are demonstrated by simulation. With GaN devices, a 100 W/1 MHz prototype was built to verify the analysis. The experimental results show that the proposed topology can reduce the power rating of the converter by up to about 80% while increasing the system efficiency by up to 95.8%.