Grid-connected Energy Storage System Research Articles

Integrating relational values in social acceptance of photovoltaic energy storage systems: A consumers' perspective assessment using structural equation modeling

Photovoltaic (PV) energy sources are considered potential sources of renewable energy for combating climate change. However, consumer acceptance of PV-based energy storage systems must be studied comprehensively and psychologically beyond mere awareness and affordability. This study explores consumer acceptance of PV energy storage systems, along with an added relational value context that demonstrates the conducive human-nature relationship among energy consumers. An online survey of 370 respondents was used to examine consumers’ willingness to prefer PV energy storage systems over non-renewable grid-connected energy storage systems. Results of the study were analyzed using a comprehensive structural equation model to estimate and test hypotheses. The findings indicate the favorable influence of several elements on PV energy system social acceptability, including PV energy system awareness, PV energy system beliefs, environmental knowledge, self-effective perception, and relational values. Conversely, the cost of PV energy systems has a negative effect. This study suggests that relational values may offset the negative impacts of energy costs. The inherent link between relational values and the prioritization of sustainable energy storage options serves as a source of information for energy policymakers and stakeholders to regulate energy consumption by influencing consumers to express their love for nature.

Novel Current Source Converter for Integrating Multiple Energy Storage Systems

The increasing penetration of renewable energy sources (RESs) in transmission and distribution systems presents several challenges for grid operators. In particular, the unpredictable behavior of RESs can disrupt the balance between energy production and load demand, potentially affecting the stability of the entire system. Grid-connected energy storage systems (ESSs) offer a possible solution to manage the uncertainty associated with RESs. In fact, ESSs exchange power with the grid through the adoption of suitable energy management strategies, which are typically implemented by power electronics-based grid interfaces. Unlike other current source converter (CSC) solutions described in the literature, which only interface with a single energy storage device, this paper introduces a novel topology for a three-phase delta-type current source converter (D-CSC), which is capable of integrating three independent ESSs using the same number of semiconductors as traditional CSC solutions. Thus, it considerably enhances the flexibility of a power conversion system (PCS) without increasing the number of converter components. In addition, an innovative energy management control strategy is also introduced. This strategy enables the D-CSC to compensate for energy imbalances arising between the three ESSs, which might be caused by several factors, such as different aging characteristics, converter component tolerances, operating conditions, and temperature drifts. Hence, the D-CSC-based interface is capable of proper grid operation even if the three ESSs have different characteristics, thus opening the possibility of employing this converter to integrate both first and second-life devices. First, the topology of the proposed D-CSC is introduced, followed by a detailed mathematical description of its control strategy. The proper grid operation of the D-CSC was tested under different scenarios, considering the grid integration of three independent superconducting magnetic energy storage systems in a marine vessel. The proposed D-CSC is compared to traditional CSC solutions, highlighting the superior performances of the novel converter topology in terms of efficiency, total harmonic distortion of the output currents, and overall cost reduction for the PCS.

Frequency and power shaving controller for grid-connected vanadium redox flow batteries for improved energy storage systems

In this research, the performance of vanadium redox flow batteries (VRFBs) in grid-connected energy storage systems centering on frequency and power sharing using voltage source inverters was evaluated. VRFBs are increasingly promising due to their scalability and long lifespan. We explore the impact of voltage source inverters on the frequency of the power supply when there is a change in load and power sharing between the grid and VRFB through MATLAB simulations. The test system demonstrates a storage system at an 11-kV substation and considers a load profile commencing from residential and commercial consumers. The outcome of this study reveals that VRFBs provide the required power to maintain load demand. Due to fast response time, VRFBs also regulate the frequency efficiently during the change in load demand and maintaining current total harmonic distortions (THDs). This research confirms the design and operation of VRFB-based energy storage systems, contributing to resilient grid infrastructure and reliable power distribution systems.

Grid-connected lithium-ion battery energy storage system towards sustainable energy: A patent landscape analysis and technology updates

Presently, as the world advances rapidly towards achieving net-zero emissions, lithium-ion battery (LIB) energy storage systems (ESS) have emerged as a critical component in the transition away from fossil fuel-based energy generation, offering immense potential in achieving a sustainable environment. This study conducts an in-depth analysis of grid-connected LIB ESS patents published from 1998 to 2022, aiming to comprehend essential developments and trends in the technology landscape while identifying key players and inventors. Employing extensive keyword searches within the Lens database, 95 patent documents were extracted along with the bibliometric data. The research highlights two prominent factors in the field of grid-connected LIB ESS patents. Firstly, a detailed patent bibliometric analysis including patent growth trends, keyword analysis, patent distribution over jurisdiction, and subject categories was presented. Moreover, the research identifies key owners, inventors and hierarchical jurisdiction in patent document publishing and evaluates the possibilities for future research sustainability. Secondly, detailed updates regarding technological advancements that are driving sustainable grid-connected LIB ESS development in various sectors such as; gird connected ESS, power conversion system (PCS), energy management system (EMS) and transportation sector are provided. The study concluded that the patents related to grid-connected ESS, minimizing voltage and frequency regulation to achieve grid stability and EMS of LIB are the key trending topics in the field of grid-connected LIB ESS. The comprehensive analysis not only illuminates crucial trends but also provides valuable guidance to future researchers and industry stakeholders, facilitating the path towards sustainable grid-connected LIB ESS and paving the way for a more environmentally conscious energy landscape.

Navigating the Cost-Efficiency Frontier: Exploring the viability of Grid-Connected energy storage systems in meeting district load demand

In this investigation, we explored the cost-effectiveness and operational efficiency of grid-connected Energy Storage System (ESS) technologies—specifically, Proton Exchange Membrane-Reversible Fuel Cell (PEM-RFC) and Li-ion Battery (LIB)—with the goal of meeting load demand. Our conclusion reveals that integrating ESS isn't the optimal solution due to impractical implementation costs, making reliance solely on grid electricity a more pragmatic choice. Despite this, a secondary optimum value emerged, suggesting economic viability for ESS integration and introducing a dynamic trade-off between cost considerations and energy storage utilization. Furthermore, our study conducted a sensitivity analysis, anchored in the target costs set by the US Department of Energy, to identify conditions under which ESS systems could transition from impractical to feasible. The results outlined the potential to reduce the levelized cost of energy (LCOE) but also emphasized the prospect of increasing the storage factor by optimizing various system characteristics. Crucial factors like capital cost, efficiency, and lifetime were identified as pivotal in shaping the economic landscape of ESS integration. The study showcased tangible outcomes upon sensitivity analysis, including a 12% reduction in PEM-RFC LCOE and 58.5% reduction in LCOE for LIB, indicating improved cost efficiency and feasibility of ESS integration to the grid. To address a critical research gap, this study provides a novel comparison between PEM-RFC and LIB technologies as ESS, considering dynamic grid electricity prices. It sheds light on intricate dynamics that must be considered in ESS deployment decisions, emphasizing the delicate balance between cost-effectiveness and operational efficiency. Focused on the electricity load demand of commercial buildings in the Santa Barbara district, our techno-economic assessment contributes valuable insights for informed decision-making in ESS integration.

Voltage Differential Analysis during Power Discharge Operation in Energy Storage Systems

Constant Power Discharge (CPD) is a lucrative operating mode for grid-tied ESS in many energy markets. The CPD mode corresponds to an increasing current drawn as the ESS discharges. The operation can be modeled with an aged anode and cathode open circuit potentials (OCPn/p+RRC) model that can let us identify electrode-level (eSOH) parameters and resistance growth even though we do not have slow discharge with Constant Current. This identification process from realistic ESS field data, namely constant power discharge, will enable continuous eSOH diagnostics and lead to real-time and operando quantification of loss of active material and loss of lithium inventory (LAM and LLI, respectively).In addition, the timing of when the cell groups' differential voltage peaks occur when the battery system is under constant power operations inform us about the imbalance among cell groups in a module of a battery system, as shown in the figure. Using the time separation among cell differential voltage peaks as a metric of cell imbalance can improve cell balancing algorithms that measure cell imbalance using maximum or minimum voltage, which can be directly affected by the power limits of the battery system.The efficacy of the proposed algorithms is evaluated for multi-cell modules consisting of NMC/graphite cells, operating as part of a large-scale grid-connected energy storage system. Ultimately, by enabling improved diagnostics of the state of health of individual cells in a battery system and improved cell balancing algorithms, this work will enhance the performance and safety of large-scale lithium-ion battery systems. Figure 1

Grid-Connected Energy Storage Systems: State-of-the-Art and Emerging Technologies

High penetration of renewable energy resources in the power system results in various new challenges for power system operators. One of the promising solutions to sustain the quality and reliability of the power system is the integration of energy storage systems (ESSs). This article investigates the current and emerging trends and technologies for grid-connected ESSs. Different technologies of ESSs categorized as mechanical, electrical, electrochemical, chemical, and thermal are briefly explained. Especially, a detailed review of battery ESSs (BESSs) is provided as they are attracting much attention owing, in part, to the ongoing electrification of transportation. Then, the services that grid-connected ESSs provide to the grid are discussed. Grid connection of the BESSs requires power electronic converters. Therefore, a survey of popular power converter topologies, including transformer-based, transformerless with distributed or common dc-link, and hybrid systems, along with some discussions for implementing advanced grid support functionalities in the BESS control, is presented. Furthermore, the requirements of new standards and grid codes for grid-connected BESSs are reviewed for several countries around the globe. Finally, emerging technologies, including flexible power control of photovoltaic systems, hydrogen, and second-life batteries from electric vehicles, are discussed in this article.

Scheduled Power Control and Autonomous Energy Control of Grid-Connected Energy Storage System (ESS) With Virtual Synchronous Generator and Primary Frequency Regulation Capabilities

This paper presents a combined control scheme for the grid-connected energy storage system (ESS). There are two control modes: the power control mode for the charging or discharging condition and the energy control mode for the stand-by condition. In the power control, a derivative element is added in the inertial power-frequency droop as a simple power system stabilizer to enhance the system damping. The energy control is developed from the power control by considering the energy storage dynamics. During system disturbances, both control modes are able to provide autonomous grid support. The small-signal model and the large-signal transient model of the ESS with the proposed control scheme are derived. As a result, the output power and/or the stored energy of ESS is in proportional to the frequency deviation and will be restored to the pre-disturbance condition. By selecting appropriate control parameters, the stored energy is controlled within a safe range constrained by the frequency limits without manual interventions. The primary frequency regulation with both power-frequency and energy-frequency proportional relationships is realized by the energy control, which coordinates with the grid secondary frequency regulation. The control performance and the derived energy model are validated by detailed time-domain simulation studies.

Power output control method of small power photovoltaic grid connected power generation under complex illumination

Due to the irregular change of lighting conditions, there is a large error in the control of photovoltaic grid connected power output. Therefore, this paper proposes proposes a power output control method for low-power photovoltaic grid-connected power generation considering complex illumination. Based on the analysis of the basic characteristics of photovoltaic grid connected power generation, the output characteristics of photovoltaic array under complex lighting conditions are studied. Combined with its variation characteristics, based on fuzzy control strategy, the output of photovoltaic grid connected energy storage system is adjusted by filter control with variable time constant, and economic operation and stable operation are taken as constraints. The test results show that the design method has a high degree of fit between the control of photovoltaic grid connected power output and the actual results, and the error is within a reasonable range, which is obviously due to the two groups of comparison methods.

TPTPC and BHC integrated grid connected energy storage system for power loss reduction

PurposeThis paper aims to propose a bidirectional hidden converter (BHC)-based three-phase DC–AC conversion for energy storage application. BHC is the new concept to vary an energy storage device voltage into wide range. Hidden converter power loss and power rating are reduced by using zero-sequence injection-based carrier-based pulse-width modulation (CBPWM) strategy.Design/methodology/approachBy using this control strategy, a BHC processes only little amount of power during double-stage conversion, mostly during direct or single-stage conversion of the three-phase three-port converter (TPTPC) only processing the maximum power.FindingsTPTPC consists of two sets of positive group switches for inversion process, one set of switches is regular inverter switches called vertical positive group switches, and the second set is anti-series switches, which are horizontally connected for direct or single-stage conversion.Originality/valueCharacteristics, principles and implementations of proposed DC–AC 3Ø conversion system and its PWM strategy are analyzed. Through experimental outputs, the effectiveness and viability of the proposed solutions are validated.

A Single-Phase Synchronization Technique for Grid-Connected Energy Storage System Under Faulty Grid Conditions

The control of a single-phase grid-connected energy storage system (ESS) requires a very fast and accurate estimation of grid voltage frequency and phase angle. A phase-locked loop (PLL) based synchronization algorithm usually extracts this information. The operation and control of the entire system are directly affected by the performance of PLL. In this article, a novel advanced single-phase PLL (ASϕPLL) technique with reduced complexity is proposed for the fast and accurate extraction of grid information in an ESS under distorted and abnormal grid conditions, including harmonics, interharmonics, dc offset, and grid faults. The proposed method provides a faster dynamic response, lower frequency overshoot, and accurate estimation under off-nominal grid frequencies with reduced computational complexity in comparison with the existing method. The advanced performance of the proposed ASϕPLL is verified through the simulation and experimental results.

Modelling of modular battery systems under cell capacity variation and degradation

We propose a simple statistical model of electrochemical cell degradation based on the general characteristics observed in previous large-scale experimental studies of cell degradation. This model is used to statistically explore the behaviour and lifetime performance of battery systems where the cells are organised into modules that are controlled semi-independently. Intuitively, such systems should offer improved reliability and energy availability compared to monolithic systems as the system ages and cells degrade and fail. To validate this intuition, this paper explores the capacity evolution of populations of systems composed of random populations of cells. This approach allows the probability that a given system design meets a given lifetime specification to be calculated. A cost model that includes the effect of uncertainty in degradation behaviour is introduced and used to explore the cost-benefit trade-offs arising from the interaction of degradation and module size. Case studies of an electric vehicle battery pack and a grid-connected energy storage system are used to demonstrate the use of the model to find lifetime cost-optimum designs. It is observed that breaking a battery energy storage system up into smaller modules can lead to large increases in accessible system capacity and may lead to a decision to use lower-quality, lower-cost cells in a cost-optimum system.

Grid-connected advanced energy storage scheme for frequency regulation

Secure and economic operation of the modern power system is facing major challenges these days. Grid-connected Energy Storage System (ESS) can provide various ancillary services to electrical networks for its smooth functioning and helps in the evolution of the smart grid. The main limitation of the wide implementation of ESS in the power system is the high cost, low life, low energy density, etc. However, improved battery technology is changing the scenario rapidly. Also, any mismatch in power demand and supply causes fluctuation in frequency. Therefore, this paper presents a way for reducing the frequency fluctuation using an Advanced Energy Storage System with utility inductors. To compensate for the mismatch of supply and demand, a new system is proposed so that the nominal frequency of the power system is maintained. Due to the very high penetration of energy systems, there is a need for frequency regulation, hence different control strategies are employed to overcome this problem. In case of extreme power supply, the ESS acts as a load and gets itself charged whereas during the power deficit the ESS supplies power to maintain balance in demand and supply, and hence it mitigates the frequency fluctuation. The simulation model contains an ESS connected to a grid with a varying commercial or residential load profile. Simulation results illustrate the effectiveness of grid-connected ESS in minimizing frequency variation.

Convex Relaxation of Grid-Connected Energy Storage System Models With Complementarity Constraints in DC OPF

Including complementarity constraints in energy storage system (ESS) models in optimization problems ensure an optimal solution will not produce a physically unrealizable control strategy where there is simultaneous charging and discharging. However, the current approaches to impose complementarity constraints require the use of non-convex optimization methods. In this paper, we propose a convex relaxation for a common ESS model that has terms for both charging and discharging based on a penalty reformulation for use in a model predictive control (MPC) based optimal power flow (DC OPF) problem. In this approach, the complementarity constraints are omitted and a penalty term is added to the optimization objective function. For the DC OPF problem, we provide analysis for the conditions under which the convex relaxation of the complementarity constraint ensures that a solution with simultaneous ESS charging and discharging operation is suboptimal. Simulation results demonstrating ESS behavior with and without the penalty reformulation are provided for an MPC-based DC OPF problem on multiple IEEE test systems.

Single-Phase Grid-Connected Inverters With Simplified SPWM Control

The conventional grid-connected inverters require a sophisticated digital signal processor to generate the demanded reference signal as a feedforward signal for the sinusoidal pulse width modulation (SPWM) control. However, the reference signal needs to be re-calculated to maintain the demanded power control as the ac mains varies. It increases the computation burden of the controller and has become a major obstacle of the grid connected energy storage system with demanded power flow control. Therefore, a simplified approach to reduce the computation burden of the controller is proposed in this paper. With the proposed simplified equation for the power flow control, the usage of a low cost microcontroller unit becomes possible. In additional, no additional sensors or circuitries are needed. Meanwhile, the performance of desired power flow control by using the simplified control is almost unaffected. The proposed simplified algorithm is validated via mathematical calculations, computer simulation and experimental results. By using the proposed simplified control, 52.3% of the computational clock cycles can be reduced. Different operation scenarios were tested to validate the performance of the proposed simplified control via the MATLAB/Simulink simulations and the 1kVA prototype experiments.

Optimal Scheduling of Merchant-Owned Energy Storage Systems With Multiple Ancillary Services

Electrical energy storage (EES) can improve the flexibility and reliability of electric power systems. At the same time, they can supply different ancillary services. The profit of the energy storage operation can be maximized by deciding the best level of each service. Merchant-owned facilities require a profit-maximizing formulation for grid-connected energy storage systems with multiple ancillary services. This paper proposes a new linear profit-maximizing formulation for grid-connected merchant-owned energy storage systems operating with multiple ancillary services. All technical characteristics of EES have been modelled, including cycle life loss due to fast charge/discharge and low depth of discharge operations. A piece-wise linear model of an EES converter’s capability curve has also been included for reactive power modeling. The model was assessed considering a battery EES, a flywheel EES, and a compressed air EES, with the results demonstrating the benefits of the formulation. From case studies, it is clear that the merchant-owned battery EES and the flywheel EES can generate profits, especially from voltage regulation and frequency regulation services. The case studies prove that the proposed model can be used as an optimal planning and operation tool for any type or size of EES.

Second-Order Linear Active Disturbance Rejection Control and Stability Analysis of Energy Storage Grid-Connected Inverter

At present, which has gradually become a technical development trend that the energy storage grid-connected inverter system is connected to the grid to ensure the stable operation of the whole system. However, the stability of the energy storage system itself is also very important for the safe operation of the power grid. Therefore, improving the stability of grid-connected energy storage system is still the key technology of current research. Aiming at the strong coupling and low-voltage ride-through fault of grid-connected system, a second-order mathematical model of grid-connected control system is established. Based on its state space model, a linear extended state observer (LESO) for state observation and a linear state error feedback (LSEF) control law for disturbance estimation are designed. The second-order linear active disturbance rejection control (LADRC) is introduced into the voltage loop, the stability of the second-order LADRC controller is proved by the Lyapunov stability theory, and the stability conditions are given. Finally, the simulation model of the grid-connected energy storage system is built on the MATLAB/Simulink digital platform, and the low-voltage ride-through fault is designed on the grid-side. The simulation results show that the effect of the second-order LADRC control is better than that of the traditional PI control obviously, which reflects the superiority of the second-order LADRC in controlling the grid-side low-voltage ride-through fault.

New Double Closed Loop Linear Active Disturbance Rejection Control of Energy Storage Grid-Connected Inverter Based on Lead-Lag Correction Link

The energy storage grid-connected inverter system is a complex system with strong nonlinearity and strong coupling, which quality and efficiency of grid-connection are affected by factors such as grid voltage fluctuations and model uncertainty. Based on the analysis of the working principle of the grid-connected energy storage system, this paper aims to improve the performance of the traditional linear active disturbance rejection control (LADRC) technology, in order to overcome the problems of serious phase lag of linear extended state observer (LESO) and poor ability to suppress high-frequency noise on the basis of introducing the proportional differential link in the traditional LESO, the differential term of output voltage error is introduced in LESO. In addition, the output of the channel for total disturbance is corrected to improve the disturbance observation ability of LESO against high-frequency noise. The theoretical proof of LADRC and the comparative analysis of Bode plots show that the improved LADRC has better anti-interference performance. Finally, to verify the effectiveness of the control strategy designed in this paper, different types of low-voltage ride-through faults are designed on the grid-side. The simulation results show that the new controller can improve the control performance effectively of the energy storage grid-connected system.

An Isolated Bidirectional Single-Stage Inverter Without Electrolytic Capacitor for Energy Storage Systems

This paper presents a new isolated bidirectional single-stage inverter (IBSSI) suitable for grid-connected energy storage systems. The IBSSI contains no electrolytic capacitor. Therefore, its reliability and lifetime are improved in comparison with the well-known two-stage voltage source inverters without increasing the converter cost. In the IBSSI, a high-frequency transformer (HFT) is used to isolate the energy storage device from the grid. In addition, an active snubber is used to suppress the voltage spikes caused by the leakage inductance of the HFT and improve the converter efficiency. Boosting capability with a high-voltage ratio is also provided by the IBSSI. In this paper, a novel switching algorithm based on the space vector modulation is developed to maintain the volt–second balance on the HFT and generate three-phase balanced currents. The switching algorithm also provides soft switching conditions for the main switches, which are explained in this paper. Moreover, a single-loop control system is employed to regulate the input and output currents. The test results of the 3-kW prototype with the SiC power devices show that the IBSSI can inject/draw three-phase currents to/from the grid with a unity power factor and without using any ac current sensors in the discharging/charging mode.

On the integration of the energy storage in smart grids: Technologies and applications

AbstractSmart grids are one of the major challenges of the energy sector for both the energy demand and energy supply in smart communities and cities. Grid connected energy storage systems are regarded as promising solutions for providing ancillary services to electricity networks and to play an important role in the development of smart grids. The aim of the present article is to analyze the role of storage systems in the development of smart grids. The article includes an analysis and a list of energy storage systems that are applied in smart grids. Various energy storage systems are examined raging from electrical, electrochemical, thermal, and mechanical systems. Two case studies are presented that show the role of energy storage in effective management of energy demand and supply.