Supercapacitor Based Energy Storage System Research Articles

Neural Network Energy Management-Based Nonlinear Control of a DC Micro-Grid with Integrating Renewable Energies

The broad acceptance of sustainable and renewable energy sources as a means of integrating them into electrical power networks is essential to promote sustainable development. Microgrids using direct currents (DCs) are becoming more and more popular because of their great energy efficiency and straightforward design. In this work, we discuss the control of a PV-based renewable energy system and a battery- and supercapacitor-based energy storage system in a DC microgrid. We describe a hierarchical control approach based on sliding-mode controllers and the Lyapunov stability theory. To balance the load and generation, a fuzzy logic-based energy management system has been created. Using a neural network, maximum power defects for the PV system were determined. The global asymptotic stability of the framework has been verified using Lyapunov stability analysis. In order to simulate the proposed DC microgrid and controllers, MATLAB/SimulinkR (2019a) was utilized. The outcomes show that the system operates effectively with changing production and consumption.

Grid Resilience Enhancement and Stability Improvement of an Autonomous DC Microgrid Using a Supercapacitor-Based Energy Storage System

Grid Resilience Enhancement and Stability Improvement of an Autonomous DC Microgrid Using a Supercapacitor-Based Energy Storage System

DC Voltage Source Based on a Battery of Supercapacitors with a Regulator in the Form of an Isolated Boost LCC Resonant Converter

Studies have been conducted on Energy storage systems (ESS) that replaced lithium-ion batteries (LIB) by the thermal runaway of the existing LIB. Using only the supercapacitor (SC) as a direct current power source in applications such as supercapacitor-based ESSs and mobile electric vehicle charging stations (MCSs) reduces the output voltage of the SC linearly. To solve this problem, this paper combines a boost converter capable of achieving regulatable constant voltage from an input of an SC bank to an output of a rectifier and an inductor/capacitor/capacitor (LCC) resonance converter. In this paper, an electrical double-layer capacitor (EDLC) known as SC was constructed as 64.8-V 400-FEDLC for experimental analysis. This EDLC is a high-capacity EDLC bank using 120 EDLCs with 30 serial connections and 4 parallel connections. In addition, resonance compensation circuits are analyzed and designed using a first-order harmonic approximation method (FHA). The analysis shows that the LCC resonance compensation converter is more suitable for EDLC standalone systems as an energy storage system, for LCC resonance converter topologies combined with EDLC discharge characteristics, constant voltage discharge is designed under an efficient discharge strategy, i.e., variable load conditions after the first constant voltage discharge. Based on LCC compensation analysis, the system has an optimum frequency, which allows the system to operate at the maximum efficiency point. By combining constant voltage power characteristics, constant voltage power becomes the same as the optimal power point, and thus high efficiency could be maintained in the constant voltage stage. Finally, the above design is verified through experiments.

Performance Evaluation of Hybrid Battery–Supercapacitor-Based Energy Storage Systems for Urban-Driven Electric Vehicles

Boosting the performance of energy management systems (EMSs) of electric vehicles (EVs) helps encourage their mass adoption by addressing range anxiety concerns. Acknowledging the higher power densities of supercapacitors (SCs) compared to those of the Lithium-ion (Li-ion) batteries used in EVs, this work proposes an optimal sizing and energy management strategy of a hierarchical hybrid energy storage system (H-HESS). In this system, the SCs are voltage-controlled to solely provide the current requirements of an EV motor during urban driving cycles with frequent accelerations and decelerations, while the EV battery recharges the depleted SCs. The proposed H-HESS is modeled and simulated on MATLAB/Simulink, and its performance is compared to that of a traditional battery-only energy storage system (BESS). Simulation results reveal that this H-HESS system offers a 55.7% peak current reduction and ≈+2% improvement in battery loss of capacity in comparison with BESS. A pulsed battery discharge current profile is imposed by the proposed H-HESS, while C-rate control is implemented. This improves the battery aging by reducing the formation of the solid electrolytic film (SEI) that otherwise decreases its capacity.

Development of supercapacitor hybrid electric vehicle

Hybrid electric vehicle needs dedicated energy storage system suitable for its special operating conditions. The nickel-metal hydride batteries and lithium-ion batteries dominate this market, but they also have some drawbacks. The electric double layer supercapacitors have been employed in passenger vehicles, but the drawbacks of those supercapacitors prevent them from the application of energy storage system for hybrid electric vehicles. A technical route of hybrid supercapacitor-based energy storage systems for hybrid electric vehicles is proposed, this kind of hybrid supercapacitor battery is composed of a mixture of supercapacitor materials and lithium-ion battery materials. We developed a supercapacitor battery cell dedicated for energy storage system of hybrid electric vehicles. The advantages of those supercapacitor cells are low cost, long life cycle, high safety, wide working temperature range, high power density and high energy density. The supercapacitor battery pack and supercapacitor hybrid electric vehicle with the developed supercapacitor cells showed great performance improvements.

Power system stability improvement considering drive train oscillations of virtual synchronous generator‐regulated type‐4 wind turbines

The type-4 wind turbine generators (WTGs) can provide inertial frequency response by implementing the virtual synchronous generator (VSG) concept. However, unstable torsional oscillations (TOs) would be induced in the multi-mass-spring drive-train which can destabilize the entire power system. In this study, participation factor analyses are performed for a power system inclusive of a thermal unit and aggregated WTG system. The system's eigenvalues are characterized and the possible detrimental impacts of TOs on the inertia provision process and overall power system stability are demonstrated and the related stability limits are identified. A comprehensive active torsional oscillations damper (CA-TOD) and a supercapacitor-based energy storage system (ESS) are presented and discussed to implement the CA-TOD. A state of charge (SoC) regulator is also employed to set the reference speed difference for the turbine-generator. Small-signal studies and electro-magnetic transient (EMT) simulations are performed to evaluate the functionality of the CA-TOD and SoC controller and estimate their impacts on the system's dynamics. The robust performance of the CA-TOD is compared to the band-pass filter-based TOD by sweeping key control parameters of the VSG and emulating drive-train parameter uncertainty. Key results are cross-verified by EMT simulations of a multimachine power system.

Supercapacitor Modeling for Real-Time Simulation Applications

Supercapacitor-based energy storage systems have proved their performance in stabilizing the power system, particularly during disturbances, which require high power capability, but low energy density, such as during frequency support services. Several models have been proposed in literature to model the supercapacitors, aiming to maximize the model accuracy in the whole frequency spectrum. However, their real-time modeling has been not deeply studied, in particular, considering the real-time simulation constraints, that limit either the model details or the simulation size. This work introduces a modeling guideline for supercapacitors for real-time simulations, proposing a tradeoff between the model accuracy and the required computational time to simulate it. Compared to existing models, this work assesses their time- and frequency-domain accuracy, estimates required computational time, and recommends which model is suited for a specific power system analysis or application.

Joint coordination of optimal power management and energy storage system sizing for a full-scale marine current turbine considering microgrid integration constraint

The issues of variability and uncertainty of tidal speed result in severe challenges for standalone microgrid (as island grids for examples) operators. Indeed, to maintain the system power balance, existing classical generators which are associated with tidal power units must be able to frequently change their operating point, either up or down, to respond to the fast fluctuations of tidal power and consumption and sometimes exceed their maximal ramp capability. This in turn accelerates aging process and results in serious damage. The switching to a safer and more reliable system seems to be a promising and long-term solution. This paper proposes to associate a supercapacitor-based Energy Storage System (SC-ESS) to a tidal turbine to smooth the fast power production fluctuations. The association of this SC-ESS with the tidal turbine unit aims to meet requirements on the variation of injected tidal power in an islanded microgrid. An original smart power management strategy is proposed for the use of the ESS. Taking into account this strategy, an optimal design methodology based on simulations on the more severe encountered day cases is proposed. This methodology allows to determine a minimal sizing of the ESS to fulfil the grid requirements. The paper also proposes a complete modeling of the whole system behavior. The Energetic Macroscopic Representation (EMR) tool is used to realize the system model where the inversion-based control principle is then used to deduce the control schemes. This global methodology is applied to a test tidal turbine which is based on a real 1 MW prototype setup to the islanded grid of Ushant in France. Using real measured data, it is shown that a relatively small and low cost SCs pack is sufficient to accommodate the high tidal power fluctuations. A comparison is performed between the existing configuration where a resistor bank is used to shave the excessive power variation and the considered case where SCs pack is used. For one tidal cycle, it is shown that a reduction in energy loss of 18.2% is achieved, which presents a non-negligible gain for Ushant's Island microgrid.

Electrical and Mathematical Modeling of Supercapacitors: Comparison

Supercapacitors are energy storage devices with high electrical power densities and long spanlife. Therefore, supercapacitor-based energy storage systems have been employed for a variety of applications. The modelling and simulation of SCs have been of great interest to this objective. This paper presents an electrical schema and mathematical modelling of three models of supercapacitors. The first is the RC model, the second is the two-branch model and the third is the multi-branch model. The objective of this modelling is to choose the best model that can respect the same behaviour of the experimental model. These models are compared with an experimental model. This comparison prove that the response voltage of the multi-branch model correctly describes the behaviour of the experimental model of Belhachemi. The disadvantage of this model is the slow simulation duration in MATLAB/Simulink. The RC model represented the faster model in terms of simulation. The choice of 15 branches in parallel in multi-branch models gives good results and correctly describes the reel model. The automatic charge and discharge voltage of SCs reduce by reducing the charge current.

High performance and remarkable cyclic stability of a nanostructured RGO-CNT-WO3 supercapacitor electrode.

One of the most pressing concerns in today's power networks is ensuring that consumers (both home and industrial) have access to efficient and long-lasting economic energy. Due to improved power accessibility and high specific capacitance without deterioration over long working times, supercapacitor-based energy storage systems can be a viable solution to this problem. So, here, tungsten trioxide (WO3) nanocomposites containing reduced graphene oxide and carbon nanotubes i.e. (RGO-WO3), (CNT-WO3), and (RGO–CNT-WO3), as well as pure WO3 nanostructures as electrode materials, were synthesized using a simple hydrothermal process. The monoclinic phase of WO3 with high diffraction peaks is visible in X-ray diffraction analysis, indicating good crystallinity of all electrode materials. Nanoflowers of WO3 were well-decorated on the RGO/CNTs conductive network in SEM micrographs. In a three-electrode system, the specific capacitance of the RGO–CNT-WO3 electrode is 691.38 F g−1 at 5 mV s−1 and 633.3 F g−1 at 2 A g−1, which is significantly higher than that of pure WO3 and other binary electrodes. Furthermore, at 2 A g−1, it achieves a coulombic efficiency of 98.4%. After 5000 cycles, RGO–CNT-WO3 retains 89.09% of its capacitance at 1000 mV s−1, indicating a promising rate capability and good cycling stability performance.

Experimental characterization of a PEM fuel cell for marine power generation

This study is focused on the possible application of hydrogen-fed PEM fuel cells on board ships. For this purpose, a test plant including a 100 kW generator suitable for marine application and a power converter including a supercapacitor-based energy storage system has been designed, built and experimentally characterised. The plant design integrates standard industrial components suitable for marine applications that include the technologies with the highest degree of maturity currently available on the market. Fuel Cell generator and power converter have been specifically designed by manufacturers to fit the specific plant needs. The experimental characterisation of the plant has been focused on the evaluation of the efficiency of the single components and of the overall system. Results shows a PEM fuel cell efficiency of 48% (when all auxiliaries are included) and an overall plant efficiency, including power conditioning, of about 45%. From load variation response tests, the fuel cell response time was maximum 2 seconds without supercapacitors and increased up to 20 seconds with supercapacitors connected, reducing the stress on the fuel cell generator. Experimental results confirm that PEM fuel cells, when supported by a suitably sized energy storage system, represent a viable technical solution for zero-emission power generation on board ships.

Two-Stage Synthetic Optimization of Supercapacitor-Based Energy Storage Systems, Traction Power Parameters and Train Operation in Urban Rail Transit

The stationary supercapacitor energy storage system (SCESS) is one of effective approaches for the utilization of train's regenerative braking energy in urban rail systems. In this paper, the capacity configuration of SCESSs, the no-load voltage of substation, the control of onboard braking resistors and train operation diagrams are considered comprehensively. Based on the equivalent circuit model, the effects of traction power system parameters on the energy transmission between powering trains, braking trains and SCESSs are analyzed, and the relationships between the train operating parameters and system energy consumptions are revealed. A multi-variable synthetic optimization method is proposed to optimize the SCESS capacity, train operation diagrams and traction power system parameters collaboratively. In order to reduce the search space and improve the efficiency of the optimization algorithm, a hierarchical multi-objective optimization model is established, based on which the design variables and the control variables are optimized iteratively. And as the traffic density has a great impact on the regenerative braking energy distribution of the system, the optimization objective function fully considers the frequency distribution of headways throughout the day. Combined the Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) with the traction power flow simulator, the flowchart of the two-stage optimization algorithm is designed, and the pareto set of the multi-objective problem is obtained. The advantages of reducing system energy consumptions and configuration cost under the proposed algorithm are verified based on case studies of Beijing Batong Line.

Artificial intelligence-based nonlinear control of renewable energies and storage system in a DC microgrid

To minimize the global warming and the impact of greenhouse effect, renewable energy sources-based microgrids are widely studied. In this paper, the control of PV, wind-based renewable energy system and battery, supercapacitor-based energy storage system in a DC microgrid have been presented. Maximum power points for PV and wind have been obtained using neural network and optimal torque control, respectively. Nonlinear supertwisting sliding mode controller has been presented for the power sources. Global asymptotic stability of the framework has been verified using Lyapunov stability analysis. For load-generation balance, energy management system based on fuzzy logic has been devised and the controllers have been simulated using MATLAB/Simulink® (2019a) along with a comparison of different controllers. For the experimental validation, controller hardware-in-the loop experiment has been carried out which validates the performance of the designed system.

Decentralized Cooperative Control of Multiple Energy Storage Systems in Urban Railway Based on Multiagent Deep Reinforcement Learning

Nowadays, the stationary energy storage systems (ESSs) are widely introduced to recover the regenerative braking energy in urban rail systems. And the multiple ESSs along the line, substations, traction, and braking trains in the traction power system make up a multienergy coupling system, whose energy efficiency is expected to be improved. With the aim of power flow optimization, a cooperative control strategy for multiple ESSs based on multiagent deep reinforcement learning is proposed in this article. Under the distributed control structure, the decision process of multiple ESS agents is formulated as a fully cooperative Markov game, in which each ESS makes independent decision and cooperates to improve the overall energy saving effect. And the value decomposition network, which decomposes the joint state-action value into value functions across agents, is adopted to stabilize the multiagent learning process. Three train operation scenarios are presented in simulation, and the power flow distributions are analyzed quantitatively to better evaluate the performance of the proposed cooperative strategy. A power hardware-in-the-loop (PHIL) experimental platform, which integrates the RT-LAB simulator and physical supercapacitor-based energy storage system (SCESS) is developed in this article to emulate the dc traction power system with multitrain operation. Based on the PHIL platform, the proposed cooperative control strategy is implemented experimentally. Both simulation and experimental results show that in comparison with genetic algorithm (GA), the proposed strategy optimizes the energy distribution between different SCESSs and trains, and improves the overall energy saving effect of the multi-SCESSs.

Photovoltaic Synchronous Generator: Architecture and Control Strategy for a Grid-Forming PV Energy System

Transforming a conventional photovoltaic (PV) energy system from a grid-following to a grid-forming system is necessary when PV power generation is dominating the generation mix and for replacing traditional synchronous generators (SGs). The grid-forming PV energy system can provide frequency support functionality, which is vital for the stability of the power grid. This article presents a novel ac coupled solution that transforms an existing grid-following PV system to a grid-forming one without any hardware and software modification of the PV inverter. The resulting system, the PVSG, is achieved by an ac coupled supercapacitor-based energy storage system (ESS). The novel control of the PVSG is implemented in the ESS side. The novel control scheme includes fast and slow instantaneous power controls. The fast-instantaneous power flow control is fulfilled by the dc-link voltage control and ac voltage control. The cascaded voltage source controls enable fast-instantaneous power balance, while a slow instantaneous power control is used to implement inertia and grid synchronization. Two important fundamental functions are realized in the PVSG. The first one is the frequency inertia to resist the grid frequency variation where df/dt -based power control is achieved; the second one is the inertia against the PV intermittent power. The correctness and the effectiveness of the proposed PVSG are experimentally validated in a 480 V PVSG prototype with a TMS320F28379D DSP controller.

Supercapacitor Integrated Railway Static Power Conditioner for Regenerative Braking Energy Recycling and Power Quality Improvement of High-Speed Railway System

In order to increase the utilization rate of the regenerative braking energy (RBE), reduce the operation cost, and improve the power quality of traction power supply system (TPSS) in high-speed railway, a supercapacitor (SC)-based energy storage system (SCESS) integrated railway static power conditioner (RPC) is presented in this article. In this scheme, the SC is connected onto the dc link of the RPC via a bidirectional dc–dc converter. A hierarchical control strategy, with an energy management layer and a converter control layer, is presented. Four operation modes and transition conditions of SCESS-RPC are elaborated in detail in the energy management layer. To obtain rapid and stable control performance, in the converter control layer, a passivity-based control (PBC)-based nonlinear controller is designed for the RPC, and an optimal control strategy based on the linear quadratic regulator with integral action (LQRI) is adopted for the bidirectional dc–dc converter. By means of simulations and experiments, the feasibility of the proposed topology and control strategy are verified.

Primary frequency [formula omitted] control in stand-alone microgrids with storage units: A robustness analysis confirmed by real-time experiments

This paper proposes a robust H∞ control design approach for primary frequency regulation in a diesel-photovoltaic (PV)-storage hybrid power generation system operating in stand-alone mode. Based on real-time digital simulators, namely RT-LAB® and dSPACE®, a rapid-prototyping test bench composed of a real supercapacitor-based energy storage system (ESS) and an emulated diesel-PV-load grid is developed in order to experimentally validate this frequency control strategy under realistic operating conditions. Starting from given desired dynamic specifications, a multi-variable H∞ controller is designed via the linear matrix inequalities (LMI) method. In the second step, uncertainty in the steady-state value of the supercapacitor state of charge (SoC) is considered and a robustness analysis using μ–analysis is performed in order to determine its maximum variation range for which the imposed closed-loop performances are respected for the considered operating point. MATLAB®/Simulink® time-domain simulations and real-time experiments show the effectiveness of the proposed robust control approach. Then, a series of real-time experiments are performed to validate the controller’s robustness and performance in the presence of various load disturbances and SoC uncertainty.

Seamless Integration of an Autonomous Induction Generator System into an Inverter-Based Microgrid

A control strategy for an autonomous induction generator (IG) system synchronization and seamless transfer to an inverter-based microgrid (MG) is presented in the current paper. The IG system control in autonomous mode is performed by a combination between a Voltage Source Inverter (VSI) and a Dump Load (DL). The MG consists of an MG leading inverter having on its DC side a supercapacitor-based energy storage system, two MG supporting inverters, and local loads. The paper presents the IG control part for the VSI-DL system, as well as the synchronisation algorithm that enables the smooth interconnection with the MG. An analysis of the IG impact on an islanded MG is also provided. Experimental validations accomplished on a complex laboratory test-bench have focused on the dynamic events associated with the IG system connection/disconnection to/from the MG and also on the MG response to a load being turned on and off when the IG operates connected to the MG. The obtained results have shown that the proposed synchronization algorithm ensures a seamless transfer for the IG system from autonomous to MG connected mode and vice-versa. Moreover, when a significant load transient occurs within the MG operation, the IG presence does not alter the MG stability.

Brake Voltage Following Control of Supercapacitor-Based Energy Storage Systems in Metro Considering Train Operation State

The utilization of a supercapacitor energy storage system (ESS) to store regenerative braking energy in urban rail transit can achieve an energy-saving effect. This paper proposes a brake voltage following energy management strategy of ESS to adjust the charging and discharging threshold voltage based on the analysis of train operation states. The energy storage device state of charge is considered to realize the maximum usage of the ESS. First of all, the mathematical model of the dc traction power system, which encompasses the train, ESS, and traction substation, is established. Then, the energy allocation influence factors are analyzed, in particular for the double train structure. Second, under the different conditions, with the real-time monitoring of the traction network voltage and the train status, an energy management state machine is determined. Meanwhile, a set of effective state switching schemes is given to achieve the transformation of the energy management states. In the end, both the simulations using actual line data and main track field experiments prove the rationality and validity of the proposed management strategy.

Validation of Faster Joint Control Strategy for Battery- and Supercapacitor-Based Energy Storage System

Energy storage system (ESS) is generally used to manage the intermittency of the renewable energy sources (RESs). The proper control strategy is needed to effectively maintain the power balance between the RESs, load demand, and ESS. The conventional control strategy for the hybrid energy storage system (HESS) uses the high-/low-pass filter method for system net power decomposition and the ESS power dispatch. In this paper, a new joint control strategy is proposed for photovoltaic-based dc grid system, with battery and supercapacitor (SC) as a HESS. The new joint control strategy utilizes the uncompensated power from the battery system to increase the performance of the overall HESS. The advantages of the proposed control strategy over the conventional control strategy are faster dc-link voltage restoration and effective power sharing between the battery and the SC. The detailed stability analysis of the proposed control strategy is also presented. The effectiveness of the proposed control strategy over the conventional control strategy is validated with the short-term and long-term experimental studies.