Converter For Energy Storage System Research Articles

English

English

Design and Analysis of Integrated Bidirectional DC-DC Converter for Energy Storage Systems

Design and Analysis of Integrated Bidirectional DC-DC Converter for Energy Storage Systems

A Control Design Technology of Isolated Bidirectional LLC Resonant Converter for Energy Storage System in DC Microgrid Applications

This paper presents a new control method for a bidirectional DC–DC LLC resonant topology converter. The proposed converter can be applied to power the conversion between an energy storage system and a DC bus in a DC microgrid or bidirectional power flow conversion between vehicle-to-grid (V2G) behavior and grid-to-vehicle (G2V) behavior. Furthermore, such a converter can be applied to energy storage systems for decentralized renewable energy generation systems, such as solar and wind power. In addition, this converter can be combined with a bidirectional inverter to allow energy storage in the system to improve the safety, stability, and power quality of the microgrid. In the proposed circuit structure, we use a bidirectional DC–DC LLC, which has the advantages of a higher voltage conversion ratio, lower part count, simpler control than similar converters such as DAB, CLLC, and L–LLC converters, and bidirectional power flow and electrical isolation. Specifically, to extend the battery life, it can be employed as a control strategy for discharging the energy stored in the battery (SOC) and reducing the temperature rise generated by the internal solid electrolyte interphase (SEI) when discharging the battery under the variation in distributed energy resource (DER) generation and load demand. To realize the bidirectional power conversion without using any auxiliary inductor and only changing the control strategy, the forward step-down power conversion was based on pulse frequency modulation (PFM) control, and the reverse step-up power conversion was based on pulse width modulation (PWM) control. In this paper, we introduce the bidirectional converter topology and its control strategy for the DC microgrid battery energy storage system. Finally, a 500 W prototype is built to verify the effectiveness of the proposed converter.

Design and control optimization of a three-level bidirectional DC–DC converter for energy storage system

In this paper, a GaN-based bidirectional three-level dc–dc converter is designed for high power energy storage application, the voltage stress of switches at battery side is reduced to half of the input voltage without additional capacitor, PCS of battery unit is utilized to keep the stabilization of positive bus and negative bus. All the switches could achieve zero-voltage-switching by resonant. The operating mode is analyzed in detail, the resonant parameters and timing parameters is derived. In order to improve performance of proposed converter at light-load condition, the principle of ZVS failure in traditional ON/OFF control is analyzed, the relationship between operating state of converter at the end of ON stage and ZVS state entering the next ON stage is revealed, the voltage state of equal capacitor is derived. The modified ON/OFF control with optimal trigger timing and sequence is proposed to reduce switching loss according to the optimal ZVS principle. Finally, the proposed converter under modified ON/OFF control is modeled and tested in Simulink and LTspice, the experimental simulation result verifies the effectiveness of ZVS condition under bidirectional operating mode, the dynamic performance of converter under proposed control strategy is verified to be without degradation, tested efficiency is improved around 1.47% at light-load condition (10% PN) under proposed optimal control strategy.

Frequency and Phase Modulation in a Bidirectional Class-E$^{2}$ Converter for Energy Storage Systems

This paper presents frequency and phase-shift control in a class-E <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> DC-DC converter to provide a wide range of power levels for energy storage applications. The symmetrical design of a class-E inverter and a class-E rectifier in a class-E <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> DC-DC converter achieves high efficiency at MHz frequencies with GaN FETs. However, zero voltage switching (ZVS) requirements limit an output power range, especially in an infinite choke class-E <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> DC-DC converter. This paper proposes modulating the switching frequency from 800 kHz to 1.5 MHz along with a phase shift from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$57^{\circ }$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$295^{\circ }$</tex-math></inline-formula> to control the power flow. The converter's duty ratio is decreased from 60% to 18% with increasing frequency to maintain ZVS. We designed and implemented the proposed class-E <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> DC-DC converter prototype to control the output power above and below the nominal power level. Also, the direction of the power flow is changed by controlling the frequency and phase shift. At a nominal frequency of 1 MHz, the nominal output power is 224 W with an efficiency of 93.5%. In both directions of power flow, the converter's efficiency remains above 91.5% at a power level of 355 W at 800 kHz to 39 W at 1.5 MHz.

Design and Implementation Bidirectional DC–AC Converter for Energy Storage System

This article proposes a bidirectional single-phase dc–ac converter with triple port converter (T-PC) for application of energy storage. This proposed converter provides three ports such as ac port, dc port, and dc bus port to achieve three power interfacing ports. For the direct conversion process, dc port is directly connected to T-PC, and direct power will be exchanged between energy storage device (ESD) and grid when the ESD voltage peak amplitude is lower than the ac voltage. Thus, a dc–dc converter downstream power process gets reduced, and power loss is decreased considerably. Due to multilevel characteristics, switching losses in the T-PC can be reduced. The efficiency of the overall bidirectional dc–ac conversion process can be increased significantly. The circuit model, working principle, and modulation control of T-PC-based bidirectional dc–ac conversion concepts are analyzed. A 1.5-kW test-bench model is developed and its effectiveness is verified to find the merits of suggested conversion.

High Efficiency and High Voltage Conversion Ratio Bidirectional Isolated DC–DC Converter for Energy Storage Systems

In this paper, a novel high-efficiency bidirectional isolated DC–DC converter that can be applied to an energy storage system for battery charging and discharging is proposed. By integrating a coupled inductor and switched-capacitor voltage doubler, the proposed converter can achieve isolation and bidirectional power flow. The proposed topology comprises five switches and a common core coupled inductor that uses only a set of complementary pulse-width-modulated signals to control and achieve high voltage gain without requiring high turn ratios or excessive duty cycles. Moreover, the proposed topology can recover the leakage inductance energy to improve the conversion efficiency. The main switches exhibit zero-voltage switching, which reduces the switching losses. A 500-W bidirectional converter is used to verify the feasibility of the proposed bidirectional converter through theoretical analysis and experiments. The experimental results indicate that the highest efficiency of the proposed converter in the step-up and step-down modes is 97.59% and 96.5%, respectively.

Proposed hysteresis energy management strategy based on storage system efficiency for hybrid electric vehicle

Varieties of energy management strategies have been developed to control the flow of energy between the traction system and different sources. Many of these control techniques consider as inputs variables the state of charge of the energy storage system (ESS), and the required power by the vehicle to provide the optimal fuel cell power reference. This paper proposes an energy management strategy that gathers the state of charge and the required power using the expression of the ESS converter efficiency as a sole input variable of the energy management. The latter is based on hysteresis control that allows generating the reference power of the fuel cell for each level of the converter efficiency. The topology of the electric vehicle is composed with the proton exchange membrane fuel cell as the main source and ultra-capacitor devices as the auxiliary source. Simulation results show that the proposed strategy allows energy distribution between the sources and the traction system while respecting the constraints on the different systems. Therefore, the energy consumption is reduced by using the fuel cell system and the storage converter on their high efficiencies.

Design and Development of Bidirectional DC-DC Dual Active Bridge Converter for Energy Storage Systems

The ever-increasing demand for renewable energy resources as compared to conventional means of energy generation has resulted in a growing demand for more efficient power storage systems and applications. However, this necessitates the use of different converters that must be employed to achieve efficient voltage conversions right from the generation stage to the point power is stored in the battery banks. To achieve efficient conversions of the voltage levels, Bidirectional DC-DC Dual-Active-Bridge (DAB) converters can be employed. Accordingly, this research work involves use of a closed-loop PI controller for controlling the outputs of a DC-DC converter and compensating for the load disturbances. The Simulink-derived results indicate the input &amp; output characteristics of the converter to achieve the design of a controller that is capable of providing significant tracking reference command without undergoing steady-state error, thereby offering a fast transient response. Hence, by maximizing the performance of the converter, the controller resolves the issues identified in the output current. The system was also implemented on a 400W laboratory experimental model with a view to additionally validate its performance effectiveness. As a whole, a DAB system was successfully designed, simulated, implemented and analyzed for employing in various energy storage applications

A Hybrid Switching Modulation of Isolated Bidirectional DC-DC Converter for Energy Storage System in DC Microgrid

Isolated bi-direction DC-DC converters are widely used for energy storage systems (ESS) of DC microgrids. Particularly, a current-fed isolated bi-directional DC-DC converter (CF-IBDC) receives much attention due to its merits such as the naturally attenuated current ripple on the battery side. However, high efficiency cannot be obtained at the light and heavy load conditions under the conventional control methods. In this paper, a hybrid switching modulation is proposed to improve the power conversion efficiency of the CF-IBDC under light and heavy load conditions. The duty cycle of the secondary sides and the phase shift angle are independently controlled according to the amount of the transferred power. The control strategy is based on the optimization of zero-voltage switching (ZVS) conditions and the minimization of the circulating current in the power converter. Using the proposed control algorithm, the ZVS capability can be obtained under the entire load condition, and the circulating current can be minimized under the single phase-shift modulation (SPSM). Experimental results with a 1-kW laboratory prototype CF-IBDC validate the effectiveness of the proposed modulation algorithm.

High Efficiency and Voltage Conversion Ratio Bidirectional Isolated DC-DC Converter for Energy Storage System

This paper proposes a high efficiency and conversion ratio bidirectional isolated DC-DC converter with three-winding coupled inductor, which can fulfil storage system charging and discharging. The proposed topology is improved from traditional Buck-Boost converter. By integrating coupled inductor and switched-capacitor into power stage, the proposed converter can achieve the merits of isolation and bidirectional power flow. The proposed topology has only four switches and a common core coupled inductor, which greatly reduces design costs and achieves high step-up/step-down voltage gain without excessive duty cycles or high turns ratios. In addition, the proposed also has the function of leakage inductance energy recovery, which can recover all the energy stored in the leakage inductance to improve efficiency, and the main switches has a zero voltage switching (ZVS) feature. This paper implements a 500 W converter to verify the feasibility of the proposed topology through software simulation and experiment results, and conducts theoretical analysis, formula derivation, operation principle analysis, and non-ideal analysis. Finally, the experimental results show that the highest efficiency of the step-up and step-down modes are 96.8% and 96.4%, respectively.

Modeling and Performance Assessment of the Split-Pi Used as a Storage Converter in All the Possible DC Microgrid Scenarios. Part II: Simulation and Experimental Results

Bidirectional DC/DC converters such as the Split-pi can be used to integrate an energy storage system (ESS) into a DC microgrid providing manifold benefits. However, this integration deserves careful design because the ESS converter must behave like a stiff voltage generator, a non-stiff voltage generator, or a current generator depending on the microgrid configuration. Part I of this work presented a comprehensive theoretical analysis of the Split-pi used as an ESS converter in all the possible DC microgrid scenarios. Five typical microgrid scenarios were identified. Each of them required a specific state-space model of the Split-pi and a suitable control scheme. The present paper completes the study validating the theoretical analysis based on simulations and experimental tests. The chosen case study encompassed a 48 V, 750 W storage system interfaced with a 180 V DC microgrid using a Split-pi converter. It can represent a reduced-power prototype of terrestrial and marine microgrids. A prototypal Split-pi converter was realized in the lab, and several experimental tests were performed to assess the performance in each scenario. The results obtained from the experimental tests were coherent with the simulations and validated the study.

Six-Switch Bridge CLLC Bidirectional Converter for Energy Storage Systems

Six-Switch Bridge CLLC Bidirectional Converter for Energy Storage Systems

Research on Bi-directional DC / DC Converter for Energy Storage System

When the grid connected photovoltaic power is scarce, the energy storage device can play an important role in power supplement to stabilize the grid. A bi-directional three-level Buck / Boost converter topology has been studied, and its working principle has been introduced in detail in this Paper. Based on the working characteristics of energy storage battery, combined with the battery “Three-stage” charging method, the voltage and current closed-loop control strategy of three-level DC/DC converter has been studied. It can work in constant power charging and discharging as well as constant current charging and discharging. The simulation platform of 50KW energy storage power device has been set up, which can freely switch from charging state to discharging state. The results show that the research on bidirectional three-level DC / DC converter is feasible and effective.

Single Magnetic Element-Based High Step-Up Converter for Energy Storage and Photovoltaic System with Reduced Device Count

The multiport DC-DC power converter is a prominent area of research in power electronics due to its highly dense design, reduced device count, and high energy efficiency. In this paper, a nonisolated single magnetic element-based high step-up three-port converter for an energy storage system is presented. The proposed converter has two input ports and one output port. The coupled inductor with switched capacitor is used to achieve high voltage gain. The key features of the proposed converter are high conversion gain, low voltage stress, zero voltage switching (ZVS), and zero current switching (ZCS). The detailed theoretical analysis and operation of the converter are elaborated. The energy efficiency of the proposed converter is calculated and compared with the other counterparts. Ansys Maxwell is used for the coupled inductor finite element modeling. To verify the applicability and functionality of proposed converter, a 100 W converter with two inputs ( 48 V and 96 V ) and one output 360 V at 100 kHz is tested in the laboratory.

Three-Port Converter for Integrating Energy Storage and Wireless Power Transfer Systems in Future Residential Applications

This paper presents a highly efficient three-port converter to integrate energy storage (ES) and wireless power transfer (WPT) systems. The proposed converter consists of a bidirectional DC-DC converter and an AC-DC converter with a resonant capacitor. By sharing an inductor and four switches in the bidirectional DC-DC converter, the bidirectional DC-DC converter operates as a DC-DC converter for ES systems and simultaneously as a DC-AC converter for WPT systems. Here, four switches are turned on under the zero voltage switching conditions. The AC-DC converter for WPT system achieves high voltage gain by using a resonance between the resonant capacitor and the leakage inductance of a receiving coil. A 100-W prototype was built and tested to verify the effectiveness of the converter; it had a maximum power-conversion efficiency of 95.9% for the battery load and of 93.8% for the wireless charging load.

Wide Gain Bidirectional Converters for Energy Storage System of Fuel Cell Vehicles

Fuel-Cell Vehicles have gained reasonable popularity for its low emission, long driving range, and eco-friendly features. A converter of bi–directionalpower flow stands between the energy management system and the dc bus connected to the load through the inverter. Many converter topologies have been proposed for FCVs can be observed in the Electric vehicle market. Hence, there is a need of assessment of the popular topologies of the bidirectional DC-DC converters required to judge. This paper presents analysis and simulation studies between two converter topologies which employ inherent soft switching technique and set forth the suitable performance observed in PSIM 9.0 simulations.

Bidirectional Power Flow Control of a Multi Input Converter for Energy Storage System

The objective of this paper is to propose a multi-input DC-DC converter with bidirectional power flow control capability. Compared to the traditional power converter, the multi-input converter (MIC) can save on the number of components and the circuit cost. Under normal conditions, the MIC is able to transfer energy from different input sources to the load. However, if the battery module is adopted, both the charging or discharging features should be considered. Therefore, the bidirectional power flow control of the MIC is necessary. On the other hand, because of the inconsistency characteristics of batteries, unbalanced circuit operation might occur whereby the circuit and the battery might be damaged. Therefore, dynamic current regulation strategies are developed for the MIC. Consequently, the proposed MIC circuit is able to achieve the bidirectional power flow control capability as well as control the input currents independently. Detailed circuit analysis and comprehensive mathematical derivation and of the proposed MIC will be presented in this paper. Finally, both simulation and experimental results obtained from a 500 W prototype circuit verify the performance and feasibility of the proposed bidirectional multi-input converter.

High‐efficiency three‐phase bidirectional dc–ac converter for energy storage systems

This study presents a high-efficiency three-phase bidirectional dc–ac converter for use in energy storage systems (ESSs). The proposed converter comprises a modified three-level T-type converter (M3LT2C) and a three-level bidirectional dc–dc converter. The M3LT2C comprises two T-type cells to interface with a three-phase grid. By directly connecting the S-phase of the grid to a neutral point on the dc link, the active and passive components are required for only two grid phases, which reduces power losses, system volume, and production cost. A direct nominal voltage compensation control algorithm enables the converter to obtain high grid power quality. Also, the three-level bidirectional dc–dc converter enables low switching and conduction losses with reduced voltage stress across the switches. In addition, a simple dc-link voltage-balancing algorithm enables the balancing of two split dc-link capacitor voltages. To confirm the theoretical analysis of the proposed converter and assess its validity, a 10-kW prototype was implemented and tested.

Bidirectional Series Resonant DC/AC Converter for Energy Storage Systems

This paper presents a novel bidirectional series resonant converter for energy storage systems (ESS). Conversion between a dc energy storage device and an ac grid has grown in importance because of the renewable energy generators and ESS used in microgrids, which usually use batteries or supercapacitors as storage devices in order to provide different services and improve the quality and reliability of the grid. This novel converter avoids the need to have two converting stages: one for converting the energy from the storage device to a regulated dc value, and the other for converting the regulated dc to the ac output. Conversion occurs via a modified dc/dc dual-bridge series resonant converter. The output bridge of the converter is attached to the input bridge through a resonant branch and a high frequency (HF) transformer, and it is also attached to the ac link through an output filter. Therefore, two ac power signals are mixed in the output bridge: a HF signal, which maintains the dc link capacitor voltage, and a low frequency power signal, which transfers energy to the grid. This paper details the different working modes of the converter and presents a 3000 W prototype that validates the design.