Control of Energy Storage

Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids

Special issue on “Optimal design and operation of energy systems”

With increasing penetration of renewable source in power system, higher requirements for power quality are put forward. Energy storage system represented by chemical battery and flywheel energy storage system is fast-ramping and responses quickly in frequency regulation market. It shows outstanding performance in frequency regulation comparing with the traditional frequency regulation resource. This paper reports a review of the energy storage system participating in frequency regulation, including frequency regulation market and energy storage technology. Also, it contrasts the frequency regulation characteristics and total costs between battery energy storage system (BESS) and flywheel energy storage system (FESS) both applied widely in the projects. The operation mode and Simulink modelling of energy storage system, along with the control strategy and capacity configuration, are also discussed through relative literature.

Harnessing Interfacial Electron Transfer in Redox Flow Batteries

Power system reliability can be improved with the use of energy storage. Energy storage technologies are examined critically, including storage kinds, categorizations, and comparisons. Electrochemical and battery energy storage, thermal and thermochemical energy storage, flywheel energy storage, compressed air energy storage, pumped energy storage, magnetic energy storage, chemical and hydrogen energy storage are all taken into account. The recent research on novel energy storage kinds and its significant achievements and discoveries in energy storage are analyzed. It is the goal of this study to undertake a complete and systematic evaluation of the influence of battery energy storage systems (BESS) on power systems and microgrids. Peer-reviewed studies published between 2010 and the start of 2021 provides the basis of the SLR (Systematic Literature Review). Due to inadequate wind or sunlight, renewable energy sources (RESs) like wind and solar are regularly subjected to swings. Energy storage technologies (ESTs) help to solve the issue by storing extra energy and making it available when it’s needed. Despite the fact that there are several EST investigations, the literature is fragmented and out of date. The comparison of EST features and applications is very brief. The purpose of this article is to fill that void. It identifies major ESTs and offers an updated overview of the literature on ESTs and their potential use in the renewable energy industry, based on a set of criteria. The critical analysis reveals that Li-ion batteries have a high potential applicability in the utility grid integration sector and are BESS suited to alleviate RES volatility. However, Li-ion batteries’ costs must be decreased in order for them to be completely utilized in RES utility grid integration. It has long been shown to improve system dependability and reduce transmission costs by introducing energy storage into power networks. The development of energy storage devices is aided by regulations that promote the use of renewable energy sources rather than fossil fuels. There are also voids in this field of research. To help academics better grasp the dependability implications of energy storage systems and fill in knowledge gaps in the field, this review is available. Reduced emissions and global warming as a result of the increased usage of renewable energy resources In terms of renewable energy, wind turbines and solar PV systems are two of the most common. In contrast, the advantages and downsides of using renewable energy sources are numerous. Renewable energy’s biggest flaw is its inability to generate consistent amounts of power. It is difficult to maintain a balance between generation and demand due to the irregularity of renewable energy sources’ power output and the sudden spikes or dips in demand. Consequently, there will be deviations in grid voltage and frequency, leading to operational difficulties and perhaps jeopardizing grid stability. Battery energy storage systems (BESS) can be used to regulate the output of renewable energy sources and keep the grid stable.

Guest Editorial: Situational awareness of integrated energy systems

Electrochemical Energy Storage with Mediator-Ion Solid Electrolytes

The penetration level of renewable energy (RE) resources used to supply electricity is expected to increase rapidly in the coming years. This growth is strongly encouraged by the government through various policies such as renewable portfolio standards and feed-in tariffs. [1]However, because the performance of a power system is critically constrained by many factors that impact its stability, having a high penetration of RE resources with an unpredictable nature in bulk power systems is very challenging for system operators. [2]To address the stability issues of RE, it has been proposed that large-scale energy storage systems (ESS) be applied to bulk power systems. ESS can be controlled to supply quickly the exact amount of power required in securing the stability of the power system, even with a very high penetration of RE resources that can negatively impact the dynamic performance of the power system. In addition, ESS’s can also be used to provide ancillary services, such as frequency regulation, and bulk energy services, such as peak-shaving and load-leveling, in power systems. Load-leveling and peak-shaving are ESS applications that provide long-term services, wherein the charging and discharging of power takes place within several hours. These services involve charging the ESS during periods when the loads of electric power are low and discharging the stored energy to the power system when the loads are high. [3]In this work, a demonstration of a large-scale, grid-connected 4 MW/8 MWh battery ESS (BESS) using lithium-ion batteries (LiB), has been implemented. The 4 MW/8 MWh BESS is simultaneously connected to a 22.9 kV substation bus and distribution line in the Jocheon substation on Jeju Island. Operation strategies of the BESS have also been developed for peak-shaving (or electric energy time-shift). The peak-shaving operation uses the expected load for the next day. Also, the effects of peak-shaving are also analyzed in this work.In this work, 60Ah(Ampere hour) LiB cell was employed, and 16 cells were assembled to 1.8kWh-class module. A tray consisted of two modules, and one rack was installed using 16 battery trays, a rack BMS(Battery Management System), and a switch gear. One container consisted of 18 racks connected in parallel which summed up to 1MWh capacity. The developed energy storage system was based on a technology of small lithium rechargeable battery. The BESS consisted of three-stage control system as Tray, Rack, and System. The smallest component of BESS is battery cell. The rated capacity of battery cell is 60Ah and 3.7V. BESS is available to change battery capacity by connecting the battery cells in series or parallel. The 1MWh LiB system consisted of eighteen battery racks in parallel. BMS is responsible for monitoring the individual control and protection functions for the entire circuit unit cells. The system BMS is in charge of calculating a state of charge, state of health, power prediction, and internal impedance of the system. This can support the communication protocols of CAN 2.08, RS-485, and MODbus-TCP/IP. The rack BMS is used for monitoring the voltage and the current of the rack and calculating a state of charge, state of health, power prediction, and internal impedance of the rack. In addition, this in charge of the switching control and the cell balancing in the rack. Finally, the tray BMS can measure the voltage and the temperature of each cell, and control the cell balancing in the tray. The ESS of a 4MW PCS and 8MWh batteries installed in Jocheon substation, Jeju Island. There are four 1MW PCS configured to have a total capacity of 4MW. Each 1MW PCS is connected to two containers of 1MWh batteries with a total of 2MWh capacity paired in one PCS. This makes the discharge duration of 2 hours. In addition, the BESS may be charged from the grid and discharge power to the grid thru the PCS as dictated by the PMS. Using a large scale energy storage device can give numerous benefits such as load factor improvement, peak shaving and load leveling, improve quality of distributed renewable energy, support emergency power supply, and offer high-quality power service to customers. The introduction of a large scale energy storage system to the grid can enhance the smart grid to respond efficiently to the demand of electricity from consumers with real-time power output control. Fig. 1 shows the original load and shaved one by ESS operation. From ESS operation for peak shaving, the 5.5 percent and 4.8 percent of peak shaving could be obtained in winter and summer peak time respectively. Figure 1

A resilience enhanced hierarchical strategy of battery energy storage for frequency regulation

Energy storage is a new, flexibly adjusting resource with prospects for broad application in power systems with high proportions of renewable energy integration. However, energy storage systems have spare capacity under stable working conditions and may be idle for some periods. These actions are primarily selected for peak shaving and valley filling, frequency regulation, and voltage regulation as the only control target; thus, energy storage cannot be used effectively, which weakens the effect of energy storage on grid support. To improve the utilization rate and economic benefits of the energy storage system and enhance the support performance of energy storage for the safe operation of the power grid, this article proposes a switching control strategy for an energy storage system based on multi-layer logic judgment to maximize energy storage benefits and ensure safe and stable power grid operation. First, this study analyzed the potential multi-ancillary service operation requirements of the energy storage system, combined with the auxiliary compensation benefits of the energy storage power station. Using this information, the study proposed a comprehensive index that considers the economy of the energy storage system and the stable operation of the power grid to support the evaluation needs of energy storage control. Based on this, the study then pre-set multi-layer judgment logic for the operation control of the energy storage system. A multi-objective judgment and smooth switching strategy for the coordinated operation of the energy storage system was proposed based on the typical operating conditions of the energy storage system participating in the grid peak shaving and valley filling, frequency regulation, and voltage regulation. This switching control method effectively utilized the idle capacity of the energy storage system and improved the energy storage system’s support effect on the power grid. Through the improved energy storage control model based on MATLAB/Simulink, this study also verified the effectiveness of the proposed smooth switching strategy of the energy storage system.

Over the last few decades several innovative ideas have been explored in the energy storage areas, ranging in size, capacity, design complexity, and targeted applications. Some of them are designed for large scale power system applications, others for smallor medium-scale renewable energy or hybrid power systems, while the others are designed to perform short-term energy storage ride through for critical infrastructure (communication systems, hospitals, military facilities, etc.). Energy storage has become an enabling technology for renewable energy applications, grid integration and enhancing power quality and stability in the power transmission and distribution, having a great potential to improve power grid quality and stability and to provide an alternative to fossil fuel-based energy generation. The major constraints for renewable energy penetration are the availability, intermittency, and variability, which can be addressed through energy storage. The energy storage choice depends on specific usage requirements, often incorporating several energy storage systems in order to increase system reliability, capacity, and supply security. In the electric power system, the renewable energy promise lies in its potential to increase grid efficiency, reliability, or in optimizing power flows and supporting variable power supplies. The parameters used in comparisons of various energy storage technologies include efficiency, energy capacity and density, run time, costs, system's response time, lifetime in years and cycles, self-discharge, and maturity of each energy storage technology. The most common energy storage technologies include compressed air, pumped hydro, batteries, fuel cells, flywheels, and super-capacitors. The last four are suitable for the medium scale applications. The chapter discussed energy storage technologies and gives an up to date comparative summary of their performances. After completing this chapter, the readers are able to understand the role, importance, configurations and topologies of energy storage systems, operation principles, characteristics, performances, and operation of major energy storage systems used in power systems, buildings, and industrial facilities. Another benefit is that readers are able to understand the critical role and necessity of energy storage systems in power and renewable energy systems, the differences between large-, mediumand small-scale energy storage systems, and how a system is selected on specific applications based on system characteristics and performances. Major energy storage technologies discussed in this chapter are compressed air energy storage, pumped hydropower storage systems, batteries, flywheels, hydrogen energy storage, fuel cells, supercapacitors, and superconducting energy storage systems. Thermal energy storage systems are covered in detail in the next chapter. This chapter provides comprehensive reviews of the energy storage technologies and gives an up to date comparative summary of their performances, characteristics, and applications.

The role of electricity market design for energy storage in cost-efficient decarbonization

Over the last few decades several innovative ideas have been explored in the energy storage areas, ranging in size, capacity, design complexity, and targeted applications. Some of them are designed for large scale power system applications, others for smallor medium-scale renewable energy or hybrid power systems, while the others are designed to perform short-term energy storage ride through for critical infrastructure (communication systems, hospitals, military facilities, etc.). Energy storage has become an enabling technology for renewable energy applications, grid integration and enhancing power quality and stability in the power transmission and distribution, having a great potential to improve power grid quality and stability and to provide an alternative to fossil fuel-based energy generation. The major constraints for renewable energy penetration are the availability, intermittency, and variability, which can be addressed through energy storage. The energy storage choice depends on specific usage requirements, often incorporating several energy storage systems in order to increase system reliability, capacity, and supply security. In the electric power system, the renewable energy promise lies in its potential to increase grid efficiency, reliability, or in optimizing power flows and supporting variable power supplies. The parameters used in comparisons of various energy storage technologies include efficiency, energy capacity and density, run time, costs, system's response time, lifetime in years and cycles, self-discharge, and maturity of each energy storage technology. The most common energy storage technologies include compressed air, pumped hydro, batteries, fuel cells, flywheels, and super-capacitors. The last four are suitable for the medium scale applications. The chapter discussed energy storage technologies and gives an up to date comparative summary of their performances. After completing this chapter, the readers are able to understand the role, importance, configurations and topologies of energy storage systems, operation principles, characteristics, performances, and operation of major energy storage systems used in power systems, buildings, and industrial facilities. Another benefit is that readers are able to understand the critical role and necessity of energy storage systems in power and renewable energy systems, the differences between large-, mediumand small-scale energy storage systems, and how a system is selected on specific applications based on system characteristics and performances. Major energy storage technologies discussed in this chapter are compressed air energy storage, pumped hydropower storage systems, batteries, flywheels, hydrogen energy storage, fuel cells, supercapacitors, and superconducting energy storage systems. Thermal energy storage systems are covered in detail in the next chapter. This chapter provides comprehensive reviews of the energy storage technologies and gives an up to date comparative summary of their performances, characteristics, and applications.

Evaluating and improving technologies for energy storage and backup power

The usage of renewable energy to supply electricity demands is expected to increase drastically in the coming years. This is attribute to the encouragement of the government through policies such as RPS(renewable energy portfolio standards) and FIT(feed-in-tariffs). However, the performance of power system is sometimes critically constrained by stability characteristics. It is very challenging for system operators to manage a high penetration of renewable energy resources in a bulk power system, as they are known to deteriorate the dynamic performance of power systems.Therefore, it has been proposed that the large-scale Energy Storage System (ESS) of which power output can be controlled accurately and quickly can be applied to a bulk power system for securing the stability of the system despite a high penetration of the renewable energy resources. By increasing deployment of renewable energy, importance of power grid stability has been increased. For example, Wind Power has characteristics of difficult prediction and rapid variation depending on the regional climate characteristics. Energy Storage System aims to transform an uncontrollably variable and partially unpredictable renewable energy into a controlled and predictable one. For these purpose, a quickly responsive and highly efficient control-algorithm is essential. It is for using such a high performance of ESS when a disturbance occurs on a electrical grid system.KEPCO implemented a demonstration project on large-scale grid connected 4 MW / 8 MWh Battery ESS (BESS) using Lithium-Ion Battery (LIB). Fig. 1 shows the interconnection of ESS at the demonstration site. The 4 MW / 8 MWh BESS is connected to both the 22.9kV substation bus and the distribution line in Jocheon, Jeju Island for offshore wind turbines. In this study, Operation strategies for the BESS were developed for frequency regulation of the grid-system. Fig. 1 Interconnection of ESS at Jocheon Substation For power system frequency regulation, There are two kinds of control strategies through ESS here. One is for the normal status that the ratio of frequency change is not bigger than reference ratio of frequency change(ξ). The reference ratio is frequency changes per second when the smallest power supply was failed from the power system. The other is for the dynamic status that the ratio of frequency change is bigger than the reference ratio. In case of South Korea, it is about -0.306 Hz/sec. It could be variable every year because the total amount of power supply in the grid-system would be different. In this paper, we researched briefly about the normal status.At normal control mode, the power output(P) of the ESS is proportional to the change in frequency(f). kd is a proportional coefficient set by the droop characteristics of a battery generation.P=kd(60-f) In order to distribute output power of each battery, this study established a SOC(State Of Charge) weighted control strategy that can consider the SOC of each battery. The following factors were considered to provide frequency regulation service while considering the SOC :1) Set proportional coefficient (kd) for calculating total output demand2) Set priority at output distribution according to SOC3) Consider rating output of each battery when distributing outputAt normal status, the proportional coefficient(kd) was set by applying the droop of a general generator. This is to control the ESS output with a performance similar to the droop of the general generator. When allocating output demand determined by each battery SOC through this strategy, the battery with a higher SOC have priority in distribution. This is more efficient way to fulfill the total output demand cost-effectively. The SOC weighted control result is shown in Figure 2.Fig. 2 Result of battery output during SOC weighted control (simulation)It can be found that the distributed quantity of output was provided depending on the SOC level of each battery. It's likely to be seen that a battery with a higher SOC has priority in the distribution of output.SOC management effect of the control algorithm was analyzed through a 5-hour too. The result obtained from a simulation frequency of five hours before and after a credible accident. We can find that, in the range within dead band, the control of battery was conducted in order to reach a SOC sustainment section. When the frequency is in the dead band, ESS is not working for frequency regulation. In the outside range of the frequency dead band, it was observed that control capacity was distributed according to SOC in order to provide frequency regulation.