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Summary: Hybrid energy storage technology, which consists of lithium‐ion batteries (LiB) and super capacitors (SC), is an effective way to ensure the safety of power supply and realize energy saving in metro by reusing the braking power. Aiming at the optimal configuration and control of the metro hybrid energy storage system (HESS), an energy management strategy (EMS) based on dual DC/DC architecture and voltage droop method is proposed. And then the control parameters are adjusted in segments by combining the DC bus voltage and values of SOC of LiB and SC. What's more, a hardware‐in‐loop (HIL) simulation platform of Metro DC power supply system is built to verify the control strategy. The experimental results show that HESS could stabilize the metro voltage within a safe voltage of 580 V and achieve 100% braking energy recovery by optimal energy distribution between two different types of energy storage systems, which are only 79.9% and 39.2% in other single energy storage system by contrast. At the same time, the HIL simulation platform can be used to verify the control effect of different configuration capacities and different control strategies of the HESS, helping to provide the optimal solution of HESS for actual subway lines. [ABSTRACT FROM AUTHOR]

Summary: The peak and transient components of demand power caused by the complex and variable traffic environment could induce the accelerated degradation of the battery lifespan for electric vehicle (EV). This paper proposes a wavelet transform‐based real‐time energy management strategy (EMS) to fully exploit the advantages of the hybrid energy storage system (HESS). First, to adapt the characteristics of battery and ultracapacitor, wavelet transform is employed to decompose driving cycle into high frequency power and low frequency power. Second, since the wavelet transform is difficult to be directly implemented in real‐time control, a power prediction model including four neural network predictors is established, which are trained by the data obtained from wavelet transform to online predict the power of different frequencies. Third, the high frequency power and the low frequency power are distributed to the battery and ultracapacitor by fuzzy logic control (FLC) algorithm, which can significantly reduce the damage caused by current rapid changes into the battery. Accordingly, the battery lifespan is effectively extended because it significantly avoids the impact of rapidly changing and peak current. Finally, simulation results verify the effectiveness of wavelet transform‐based real‐time EMS, and the proposed EMS robustness against temperature is verified at different temperatures. Compared with the wavelet transform strategy (WTS), the peak currents of wavelet transform‐fuzzy logic control strategy (WTFLCS) are decreased by 26.07%, 25.66%, and 25.85% at 10°C, 25°C, and 40°C, respectively. [ABSTRACT FROM AUTHOR]

Supercapacitors attract attention due to their superior values in the parameters like capacitance, discharge currents and cycle lifespan. Supercapacitors are designed and used in many applications where they partially or completely substitute conventional batteries. On the other side, supercapacitors are used in applications which are not so far suitable for these devices. To avoid wrong design and misuse of the supercapacitors it is necessary to correctly understand their properties, key advantages and disadvantages. Similar situation can be found in the field of lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Integrating hybrid energy storage system (HESS) consisting of battery and supercapacitor provides balance over the power generation and load demand, ensuring the system's stability under transient conditions. Along with battery storage, to control its rate of charging/discharging a rate limiter (RTL) is usually employed. However, the impact of the RTL on battery storage efficiency and system performance has not been explored in the existing literature. This paper investigates the performance of a grid‐tied photovoltaic (PV) system with HESS under dynamic scenarios with different RTL values applied to the battery storage. The paper explores the simulation analysis considering transient, linear, and steady‐state conditions with varying PV generation and load demand. The simulation study shows that a lower RTL value may slow down the battery response, leading to inefficient utilization of battery storage. Alternatively, a very high RTL value will not appropriately regulate the battery current, which may lead to frequent charging and discharging and deterioration of battery life. For the proposed system, RTL with a value of 100 A/s seems appropriate, providing 1.29 Wh of energy through battery storage with an energy efficiency of 91.81% for the simulated time. The DC voltage is efficiently maintained at 400 V with a ripple factor of 0.45%. [ABSTRACT FROM AUTHOR]

This thesis proposes a charging equalizer for hybrid energy storage systems, incorporating the Zeta converter, voltage multiplier, and multi‐winding transformer. The objective is efficient charging and equalization for battery and supercapacitor strings. The Zeta converter serves to charge the battery string, while the transformer with multi‐winding shares the inductor of Zeta converter as the primary side, facilitating battery string balancing through the utilization of current ripple in the inductor. Additionally, the voltage ripple generated by the Zeta converter is utilized to drive the voltage multiplier, enabling the charging and equalization of the supercapacitor string. The system's operation halts upon reaching the predefined threshold voltage for the supercapacitor strings. The proposed circuit transforms into a Zeta converter by employing a single‐pole double‐throw switch, facilitating the charging of the battery strings. Experimental validation uses four series‐connected supercapacitors and four series‐connected batteries, demonstrating successful equalization and charging for both energy storage components. [ABSTRACT FROM AUTHOR]

Summary: The uncertainties in generation from renewable energy sources and randomness in electric vehicle charging/discharging make the generation and load in the grid more volatile. The large‐scale integration of renewable energy sources and electric vehicles has necessitated the remodeling of conventional control schemes in the microgrid. This article presents an adaptive two‐level hierarchical controller that enriches hybrid AC/DC microgrid performance. The virtual synchronous machine‐based primary controller determines the operating mode of the interlinking converter. In addition, it maintains the system's stability by providing virtual inertia support. The communication‐based secondary controller adaptively chooses the scaling factors based on hybrid AC/DC microgrid operating conditions. The adaptive secondary control loop implemented with the primary controller and hybrid energy storage system reduces the frequency/voltage deviations under extreme load volatility and enhances the transient and steady‐state performance. The novelty of the proposed two‐level hierarchical controller is that the general purpose adaptive scheme improves the power sharing in the microgrid under normal and volatile source and load conditions. The simulations and experimental results confirm the efficacy of the proposed controller. Furthermore, the hierarchical two‐level controller performance is validated using real‐time experiments on a hardware‐in‐the‐loop simulator, OPAL‐RT, and Raspberry Pi microcontroller. The real‐time analysis ascertains that the proposed two‐level hierarchical controller effectively preserves the frequency and voltage profiles and provides accurate power sharing between the subgrids. [ABSTRACT FROM AUTHOR]

In hybrid energy storage systems of fuel cell unmanned aerial vehicles (UAVs), achieving energy management while minimizing hydrogen consumption is the main goal for economic aspects and endurance enhancement. The external energy maximization strategy (EEMS) and the equivalent consumption minimization strategy (ECMS) are commonly used energy management strategies. However, they use a gradient descent approach, which converges slowly and does not guarantee the optimal solution. Thus, this paper proposes an optimization method based on a direction prediction optimal foraging algorithm (OFA/DP), which has the advantages of high optimization capability and simple parameter definition. In this study, the hybrid energy storage system comprises fuel cells and lithium‐ion batteries for powering UAVs. To verify the validity of the proposed strategy, it is compared with rule‐based and optimized methods of state machine control, fuzzy logic control based on frequency separation, ECMS, EEMS, and genetic algorithm. The obtained results confirm the superiority of the proposed OFA/DP‐based EEMS method with an efficiency of 88.65% and a minimum hydrogen consumption of 19.06 g. Furthermore, it achieves optimal power distribution and leads to 38.62% minimization in hydrogen consumption. [ABSTRACT FROM AUTHOR]

This paper deals with the power smoothing of the wind power plants connected to a microgrid using a hybrid energy storage system (HESS). In a HESS, the power should be distributed between the battery and capacitor such that the capacitor supplies the peaks of power and its high‐frequency fluctuations, and the battery compensates for the rest. Besides, due to the relatively low lifetime of the batteries compared to the capacitors, it is preferred to transfer power fluctuations to the capacitor as much as possible. In this paper, methods for calculating the output, battery, and capacitor powers are presented. The output power is determined based on the grid restrictions and the battery SOC. The battery and capacitor powers are decided via an adaptive low‐pass filter. The cut‐off frequency of the low‐pass filter is specified by a fuzzy controller such that not only the power spikes and high‐frequency fluctuations are transferred to the capacitor but also the battery SOC variations are reduced. The simulation results show that for the presented wind speed profile, the output power determination reduces 13.7% of the HESS exchanged energy compared to the ramp limiting method. Besides, the proposed power distribution method reduces 92.6% of the unbeneficial charges and discharges of HESS and 8% of the battery exchanged energy compared to the condition that the constant cut‐off frequency filter is utilised. The experimental results confirm the effectiveness of the proposed output power determination and HESS power distribution methods. Analysing the methods' cost proves that although the utilisation of the capacitor bank increases the system initial investment cost, it will return after a while relying on the units' capacity, power fluctuations, control method etc. [ABSTRACT FROM AUTHOR]

To solve the problem of battery capacity degradation caused by high current magnitudes and frequent current variations in electric vehicles (EVs), a hybrid energy storage system (HESS) incorporating high energy density storage (battery) and high power density storage (ultracapacitor) is proposed. The HESS contains a multi‐port DC‐DC converter, which controls the energy flow among the battery pack, the ultracapacitor (UC) pack, and the port of output. Considering the state of charge (SOC) of UC, the speed, and demand power of EV, an energy management strategy (EMS) based on fuzzy logic control (FLC) for the HESS is proposed in this paper. According to the strategy, the battery pack serves as a base power source while the UC pack serves as a transient power source so as to smooth the battery pack current and prolong the battery life. Simulation and experiment results illustrate the effectiveness of the proposed strategy for UC/battery HESS in EVs. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

With the increase in new energy power generation and the continuous augment in the penetration rate of electric vehicles, it is of crucial importance to use electric vehicles as energy storage devices to promote the consumption of new energy. Aiming at the uncertainty of electric vehicles, this paper proposes a method based on multiobjective optimization for electric vehicle‐supercapacitor hybrid energy storage system to track PV project output. The hybrid system consists of electric vehicles and supercapacitor. Electric vehicles and supercapacitors supplement the deviation of PV actual power and predicted power by charging and discharging. The electric vehicle is regarded as a nonspecific way to label a piece of equipment that can store energy. First and foremost, on the basis of traditional method of predicting PV output, a PSO‐BP prediction method based on PCA is proposed to improve the accuracy of PV output prediction. Secondarily, according to the different characteristics of electric vehicles and supercapacitors, the empirical mode decomposition (EMD) method is used to decompose the deviation that the hybrid energy storage system needs to bear with the purpose of initially allocating the energy. Furthermore, a multiobjective optimization model is established for the precise energy distribution of the hybrid energy storage system, and the NSGA‐III algorithm is used to solve it. Ultimately, the data of a domestic PV power station are used for simulation. After optimized control, the result shows that the standard deviation of the system output is reduced from 1967 to 75.77. The research in this article provides a theoretical basis for the application of electric vehicle virtual energy storage technology in the field of auxiliary new energy grid connection. [ABSTRACT FROM AUTHOR]

To realise the distributed control of the hybrid energy storage system (HESS) in an islanded AC microgrid, a dynamic HESS power allocation strategy based on the virtual impedance (VI) for supercapacitor (SC) and the battery is proposed. Dynamic power-sharing of two kinds of energy storage devices can be achieved without real-time measuring of load power. The state of charge (SOC) recovery of SC is achieved with a SOC loop integrated into the VI loop. The principle of dynamic power-sharing of HESS is derived based on the establishment of HESS equivalent circuit model. By analysing the influence of the voltage and current double loop controller parameters on the output impedance and the VI of the DC/AC converter, the method of setting the controller parameters for power distribution is presented. A simulation model is established with the designed equivalent power fluctuation conditions. The simulation results show that under various working conditions, the SC loop can compensate for the high-frequency part of the equivalent power fluctuation and the battery loop absorbs the low-frequency part of the power fluctuation. The dynamic power-sharing of HESS with the SC SOC recovery is realised effectively. [ABSTRACT FROM AUTHOR]

For a hybrid energy storage system consisting of battery and super‐capacitor (SC) in More Electric Aircraft, a decentralised control strategy, which is based on the virtual impedance droop control, can implement the frequency domain allocation of load power avoiding communication delay and a single point of failure. Although the output voltage deviation and state‐of‐charge (SoC) limitation are solved by existing methods, it still suffers from settling time extending. Secondary voltage controls (SVCs) of virtual‐droop‐controlled for battery and SC are proposed to solve the issue. SVC for the output voltage is designed to compensate for the output voltage deviation in the battery converter based on virtual resistance droop control. SC converter, which is controlled by the SVC for input voltage in virtual capacitance droop control, enforces SC SoC back to the initial value and maintains consistent settling time. In this study, a set of detailed design methods for the controller parameters of SVC are developed not only to regulate the output voltage and SoC recovery but also to keep the same settling time. The results of the simulation and experiment validate the effectiveness of the proposed SVC and design method. [ABSTRACT FROM AUTHOR]

The large‐scale penetration of wind generation imposes challenges on the security of power system operation due to the intermittency and stochastic volatility. Hybrid energy storage system (HESS), which combines battery banks and super‐capacitors, is applied in this study to smooth wind fluctuations to facilitate the grid‐friendly integration. To optimally schedule HESS charge/discharge in an online receding horizon, a novel two‐stage model predictive control (MPC) scheme is proposed. The first stage determines the initial charge/discharge profiles for battery banks at a large time scale, while the second stage quantifies the optimal amendment to update them and determines the operation strategies for super‐capacitors at a smaller time scale. According to the rolling update of wind forecasting, the two‐stage model is successively solved in a receding horizon to generate the most appropriate operation strategies. The proposed method also optimises the state of charge of HESS, yielding sufficient margin to cope with wind uncertainties, making HESS operation more reliable and robust. The case study demonstrates that the proposed model can enable an effective smoothing effect on wind generation volatility by fully utilising energy storage systems of various distinct characteristics, providing a powerful tool to facilitate the smooth integration in a large scale in practice. [ABSTRACT FROM AUTHOR]

The propulsion system of a medium‐voltage dc (MVDC) ship is subject to large thrust/torque variations due to interactions of the ship and the propeller with sea waves. These variations induce steep power fluctuations on the MVDC bus, adversely impacting the stability, efficiency and power quality. Hybrid energy storage system (HESS) is a promising solution for mitigating these power fluctuations. Dictating the energy that the HESS components must deliver/absorb, the energy management strategy (EMS) impacts the size/capacity of the energy storage system (ESS). Based on this consideration, sizing and EMS of a battery/supercapacitor (SC) HESS are jointly optimised by using a deep reinforcement learning‐based method. The proposed method splits the power between the HESS components such that while the operational constraints are satisfied, energy storage size and losses are minimised. Its features are adaptability to varying sea states, real‐time implementation feasibility, while obviating the requirement for knowledge of the ship propulsion power profile. The efficacy of the joint sizing/EMS on reducing the ESS size is validated by comparing the sizes when battery‐only, SC‐only and HESS are employed in the MVDC shipboard power system. Real‐time implementation feasibility and adaptability to various ship propulsion power profiles is confirmed through real‐time simulations. [ABSTRACT FROM AUTHOR]

With the increasing penetration of renewable energy sources in the power system, the power electronic inverters are widely used to interface with the grid, which will reduce the inertia of the power system. This study proposes ancillary inertial service from single‐phase rooftop solar photovoltaic (PV) based inverter to the grid. The inertia emulation control technique transforms the behaviour of inverter like a synchronous generator under power imbalances. A hybrid energy storage system consisting of battery and supercapacitor (SC) has been connected at the DC bus to take care of the variability in PV output power and load fluctuations. The SC absorbs/injects the fast‐varying power and provides the inertial response to arrest the frequency deviation and battery charges/discharges to bring back the frequency to the nominal value. Real‐time simulation is carried out to test the system behaviour for different operating conditions using OPAL‐RT 5700. [ABSTRACT FROM AUTHOR]

In this study, a proportionate power sharing among the parallel inverters operating in an islanded microgrid is achieved using droop and virtual inductance control. The same droop coefficients are used to achieve the frequency regulation as well. The frequency changes which are inevitable in droop control are measured and used to emulate the behaviour of damping and inertia to the DC link voltage using hybrid energy storage system consisting of battery and supercapacitor units. The proposed DC link voltage regulator restores the DC link voltage quickly by providing power corresponding to the rate of change of frequency and frequency deviation. This reduces the impact of voltage variations on the DC‐load and keeps modulation index within the linear range for voltage source inverter. The design aspects of DC link voltage regulator, damping and inertia constants, selection of battery and supercapacitor units based on rating of the DC link voltage are discussed. The proposed decentralised droop control and DC link voltage restoration methods are validated through detailed simulation and experimental studies. [ABSTRACT FROM AUTHOR]

This study proposes a novel control strategy for a hybrid energy storage system (HESS), as a part of the grid‐independent hybrid renewable energy system (HRES) which comprises diverse renewable energy resources and HESS – combination of battery energy storage system (BESS) and supercapacitor energy storage system (SCESS). The proposed control strategy is implemented into two parts: in the first part, HESS controller is designed and implemented to maintain the active power balance among different constituents of HRES and regulate DC‐link voltage (VDC) under surplus power mode and deficit power mode. The low‐frequency components of imbalance power are diverted to BESS while the high‐frequency components are diverted to SCESS while maintaining the state of charge (SoC) constraints of HESS thereby reducing stress on BESS. In the second part, inverter controller is designed and implemented to maintain AC voltage and frequency within limits in the events of perturbation. The proposed HESS along with its novel control strategy, as implemented in the HRES, is a new proposition in this study. The detailed model of HRES is simulated in MATLAB/Simulink and the results prove the efficacy of the control strategy. Further, hardware‐in‐loop real‐time simulation studies using OPAL‐RT real‐time simulator demonstrate the feasibility of hardware implementation of HRES with the proposed control strategy. [ABSTRACT FROM AUTHOR]

Over the past years, wind energy has been considered as a promising solution for clean and sustainable energy development, but wind curtailment remains a challenge to wind power development. On this basis, utilization of non‐grid‐connected wind power becomes crucial and necessary as it can mitigate wind curtailment and improve energy efficiency. This paper proposes the collaboration strategy and optimization model of wind farm‐hybrid energy storage system (WF‐HESS) for non‐grid‐connected wind power based on battery and superconducting magnetic energy storage (SMES) whose combination can effectively cope with fluctuation and intermittence of wind input. The optimization problem is simultaneously investigated by the minimization of total cost, wind curtailment magnitude, and loss of power supply probability (LPSP). The multi‐objective particle swarm optimization (MOPSO) is introduced to find available solutions, and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is applied to determine the optimal one. Results are obtained for a case study, and the effectiveness and the feasibility of proposed model are verified by a comparative analysis and a sensitivity analysis. Results analysis and discussion show that the WF‐HESS model and the application of HESS have important influence on promoting utilization of non‐grid‐connected wind power and mitigating wind curtailment. [ABSTRACT FROM AUTHOR]

In this study, an advanced control strategy is proposed for hybrid energy storage systems (HESS) to smooth wind power generation fluctuations. Compared with the limited performance of solo energy storage system, the HESS, composing of lithium‐ion battery (LiB) and a flywheel energy storage system (FESS), can comparatively show improved flexibility and adaptivity. A novel sequence control scheme for the HESS is proposed in this study to improve the overall economic and smoothing performances. Specifically, based on variable‐interval reference outputs, the control horizon of the HESS is statistically determined. Afterwards, a sequence control scheme for the HESS is presented to improve the internal collaboration of HESS media. Especially when the LiB and FESS are synchronously charging/discharging to smooth wind power, the charge/discharge power are optimally distributed between the LiB and FESS via an optimiser to minimise the equivalent cost during each control cycle. Case studies are conducted to demonstrate the performance of the proposed method. [ABSTRACT FROM AUTHOR]

This study presents a bi‐level optimal sizing approach for hybrid energy storage system (HESS) in distribution network with high share of renewable energy. Differently from the traditional planning methods, the proposed two‐level approach can evaluate the investment risks caused by wind power uncertainty. In particular, the upper level describes the financial composition associated with HESS devices investment cost. The lower level searches optimal operation strategies for the minimal cost of each scenario set. The upper‐level and lower level models are bridged by CVaR, which measures the conditional tail expectation of lower level costs for the entire scenarios and are involved as the additional item of the upper objective. Moreover, to improve solution efficiency, some of the mathematics transformations including second‐order cone programming are adapted to transform the holistic non‐linear model into the more effective pattern that can be computed by the commercially available solver. The proposed method can compute the corresponding energy storage capacity based on the assessment of the risk tolerance of investors. Finally, a test system is used to validate the effectiveness of the proposed approaches. [ABSTRACT FROM AUTHOR]

In a DC microgrid, because the output of renewable energy such as photovoltaic is intermittent, hybrid energy storage system (HESS) combining ultracapacitors and batteries is usually used to solve this issue. According to the characteristics of ultracapacitors and batteries, the low-frequency power fluctuations are assigned to batteries, while the high-frequency power fluctuations are assigned to ultracapacitors. When considering an ultracapacitor group, state-of-charge (SoC) of the ultracapacitors will be unbalanced between each other, on account of the differences of initial states or attributes. A novel distributed control method is proposed in this study. In general, ultracapacitors control the DC bus voltage and batteries control SoC of the ultracapacitors. Additionally, the distributed control adds the difference between one ultracapacitor's SoC and the average SoC of the ultracapacitor group to its current control loop. As a result, the dynamic stability of SoC among the ultracapacitors can be achieved, and the issues of overcharging and/or over discharging of the ultracapacitors can be avoided. At last, the effectiveness of the proposed control strategy is validated by the simulation model built in MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

Battery/supercapacitor (SC) hybrid energy storage system (HESS) is an effective way to suppress the power fluctuation of photovoltaic (PV) power generation system during radiation change. This study focuses on the power sharing between different energy storage components with two optimisation objectives: energy loss and state of charge of SC. First, the topology of HESS and its connection with PV system are analysed. Second, the control targets of the HESS have been organised as optimisation objectives. A linear weighted summation algorithm based on variable weights is proposed to solve the multi‐objective optimisation problem to obtain current reference of SC and battery. Third, the energy management system of the HESS is designed based on proposed algorithms. Simulation and experiment results verified the proposed algorithms and control strategy. [ABSTRACT FROM AUTHOR]

A hybrid energy storage system for electric vehicle using supercapacitors and a battery is studied. Using energetic macroscopic representation formalism, an inversion‐based control (IBC) can be deduced. A comparison between IBC and two other control schemes is performed within a practical aspect. Simulation and experimental tests with a reduced‐scale test bed are provided using a real driving cycle of an electric car. The results point out a more effective behaviour for the IBC than the other control schemes in terms of dynamical response. [ABSTRACT FROM AUTHOR]

Energy storage (ES) has become increasingly important in modern power system, whereas no single type of ES element can satisfy all diverse demands simultaneously. This study proposes a hybrid energy storage system (HESS) based on superconducting magnetic energy storage (SMES) and battery because of their complementary characteristics for the grid integration of wind power generations (WPG). This study investigates the mathematical model and the topology of the proposed HESS, which is equipped with a grid‐side DC/AC converter, a battery buck/boost converter and a SMES DC chopper. The advanced control strategies comprised of device level and system level are designed. The control strategy for the converters which can be considered as device level is briefly discussed. The significant contribution of this study is proposing a novel system‐level control strategy for reasonable and effective power allocation between SMES and battery. According to the control objectives, a fuzzy logic controller optimised with genetic algorithm is adopted. The detailed controller designs are described, meanwhile system stability and HESS operation performance are evaluated. MATLAB simulations are presented to demonstrate the effectiveness of the proposed strategies. [ABSTRACT FROM AUTHOR]

A hybrid power system based on a fuel cell (FC) and an energy storage system appears to be very promising for satisfying the high energy and high power requirements of automotive applications in which the power demand is impulsive rather than constant. This paper deals with the use of a hybrid energy storage system with the battery (BAT)/ultracapacitor (UC) as ancillary power source in FC electric vehicles. The energy management strategy (EMS) is one of the most important issues for the efficiency and performance of such systems. The designed EMS uses a splitting method, allowing a natural frequency decomposition of the power demands. It takes into account the slow dynamics of FC and the state of charge of the UC and BAT. A simulation is conducted using MATLAB/SIMULINK software in order to verify the effectiveness of the proposed control strategy. It confirms the performance of the control method and also demonstrates the robustness and stability of the control strategy with good tracking response (transient performance), low overshoot, zero steady-state error, and control flexibility during a power demand cycle. [ABSTRACT FROM AUTHOR]

A hybrid energy storage system (HESS) composed of electrochemical batteries and supercapacitors is considered. The supercapacitors aim to manage the peak power and thus increase the lifetime of the battery. A control scheme of this HESS is obtained by inversion of its energetic macroscopic representation. This control scheme enables different energy management strategies using a distribution input to share the energy between both devices. A switching strategy and a frequency strategy have been tested using this same control scheme. This flexible control scheme has been validated in real time by using a real HESS and a hardware‐in‐the‐loop simulation of the traction system of an electric vehicle. [ABSTRACT FROM AUTHOR]

This paper suggests the integration of fast acting energy storage systems in existing pumped‐storage power plants as a practical solution to enhance the system's frequency control. The term "fast acting energy storage" is used in the paper to refer to, in the authors' opinion, the most suitable energy storage technologies for the purpose of frequency control, that is, flywheels and supercapacitors. The paper describes the few research works that have so far dealt with the coordination of flywheels or supercapacitors and pumped‐storage or hydropower, and compare the proposed solution with the upgrade of existing pumped‐storage power plants to allow variable speed operation. To finish, the paper describes other side benefits of the proposed solution, discusses the most important barrier for its realization and summarizes a few regulatory changes that have been recently implemented in a few electric power systems which provide some hope for the proposed solution to become a reality. This article is categorized under:Energy Infrastructure > Systems and Infrastructure [ABSTRACT FROM AUTHOR]