Magnetic Energy Storage System Research Articles

Optimal design of PV-SMES systems for power quality enhancement using pelicon optimized multi-level inverter model

In this article, a superconducting magnetic energy storage (SMES) system is integrated with a photovoltaic (PV) renewable energy source. The integrated system can achieve power balancing with voltage stability, high power quality, and reliability. Here, a Bonobo Optimization Algorithm (BOA)-based MPPT control has been developed to get the most electrical energy out of the solar PV cells under fluctuating weather conditions, including temperature and irradiance. The output voltage is greatly increased with minimal switching complexity by using the Zeta DC-DC converter, which helps to meet the energy requirements of load applications. Then, the Total Harmonics Distortions (THD) has been decreased with lower switching stress, power loss, and voltage ripples at the load using the sophisticated and simple five-level MLI circuit model. In addition, the performance of MLI has been greatly improved by tuning the controlling gain parameters with the use of Pelicon Optimization (PO) technique. Moreover, the Shunt Active Power Filter (SAPF) is used in order to achieve the best power quality results with the reduced overall harmonic distortions. The performance and results of the suggested circuit model are validated in this study through a complete simulation analysis using a variety of assessment indicators.

Load frequency control in power systems with high renewable energy penetration: A strategy employing P[formula omitted](1+PDF) controller, hybrid energy storage, and IPFC-FACTS

The high penetration of Renewable Energy Sources (RESs) in the modern power system poses a challenge to power system stability. This stability is affected by the stochastic, fluctuating output of RESs, which is influenced by weather conditions, and a lack of inertia resulting from reduced rotating mass. To address this issue, a new controller, referred to as Proportional-Fractional Integrator Plus Proportional-Derivative with Filter, PIλ(1+PDF), is designed for Load Frequency Control (LFC) with the support of a Hybrid Energy Storage System (HESS) for power systems with high-RES penetration. The HESS comprises a Superconducting Magnetic Energy Storage System (SMES) and a Vanadium Redox Flow Battery (VRFB) coupled with an Interline Power Flow Controller Flexible AC Transmission Systems (IPFC-FACTs) controller. The HESS, working in conjunction with the proposed LFC, injects virtual inertia and maintains power flow to expedite the frequency stability process. These systems are also integrated with Alternating Current (AC) and High Voltage Direct Current (HVDC) transmission lines to collectively enhance both the system's stability and the capacity of its transmission lines. To optimize the PIλ(1+PDF) controller parameters, Zebra Optimization Algorithm (ZOA) is employed utilizing an Integral Time Absolute Error (ITAE) objective function. The proposed controller is tested on a four-area power system integrated with a wind turbine, photovoltaic (PV) panels, a biodiesel generator, and a hydrogen aqua electrolyzer fuel cell, representing a high penetration of RESs in modern power systems. The results are compared with those obtained using Proportional-Integral-Derivative (PID) and Fractional Order Proportional Integral Derivative (FOPID) controllers. Sensitivity analysis and robustness tests are also performed to verify the stability of the power network by changing system parameters and under randomly chosen loading conditions. The proposed PIλ(1+PDF) controller tuned with ZOA outperforms PID and FOPID controllers by minimizing settling time for frequency changes by 62 %, eliminating overshoot, and reducing undershoots for frequency and tie-line power changes by 73 % and 55 %, respectively. Simulation results demonstrate that the proposed controller outperforms PID and FOPID controllers by effectively damping frequency and tie-line deviations, resulting in reduced frequency overshoots, undershoots, and shorter settling times.

A novel hardware implementation approach to enhanced stable island operation of hybrid distributed generation using superconducting fault current limiters

In this research study, we have explored the transformative potential of integrating Superconducting Fault Current Limiters (SFCLs) and Superconducting Magnetic Energy Storage (SMEC) systems in hybrid distributed generation setups. Through a meticulous series of experiments, simulations, and detailed analyses, we have delved into the dynamic responses of these advanced technologies amidst various grid disturbances and fault scenarios. Our investigations encompassed a spectrum of grid disturbance scenarios, including voltage sags, frequency variations, and short circuits, revealing the crucial role that SFCLs and SMEC play in maintaining stable islanded operation. The numerical results showcased in this study demonstrate the pivotal role of SFCLs and SMEC in swiftly responding to grid disturbances, effectively limiting fault impacts and ensuring a continuous and uninterrupted power supply to critical loads. For instance, SFCLs reduced fault currents by up to 60 % within 15 ms during short circuit events at Node A, while voltage sags of 20 % were mitigated within 75 ms, showcasing a fault clearing time of 45 ms. Additionally, the SMES system's energy capacity of 10 kWh played a significant role in voltage and frequency stabilization, reducing fault impacts by over 50 % during various fault scenarios. Furthermore, our detailed analyses provide valuable insights into the SFCL performance, including activation times and fault current reduction capabilities. The transient responses of the system exemplify the remarkable ability of SFCLs to expedite fault recovery and stabilize microgrids. This study presents a novel hardware implementation approach aimed at enhancing the stable island operation of hybrid distributed generation systems through the integration of SFCLs and SMEC. The research addresses the pressing need for innovative solutions to ensure grid stability and reliability amidst the increasing penetration of renewable energy sources. Through hardware simulations, the effectiveness of SFCLs in limiting fault currents and improving system stability is demonstrated. Moreover, a quantitative comparison with existing solutions highlights the superiority of the integrated SFCL-SMES system in enhancing stable island operation, with fault tolerance improvements of up to 56 % compared to traditional methods. Overall, this research contributes to advancing the field of hybrid distributed generation and fault management, offering valuable insights into the practical implementation of SFCLs and SMES for grid resilience and reliable renewable energy integration.

Enhanced Grid Integration through Advanced Predictive Control of a Permanent Magnet Synchronous Generator - Superconducting Magnetic Energy Storage Wind Energy System

In this study, the use of an Unscented Kalman Filter as an indicator in predictive current control (PCC) for a wind energy conversion system (WECS) that employs a permanent magnetic synchronous generator (PMSG) and a superconducting magnetic energy storage (SMES) system connected to the main power grid is presented. The suggested UKF indication in the hybrid WECS-SMES arrangement is in charge of estimating vital metrics such as stator currents, electromagnetic torque, rotor angle, and rotor angular speed. To optimize control strategies, PCCs use these projected properties rather than direct observations. To control the unpredictable wind energy’s nature, SMES must be regulated to minimize fluctuations in the DC-link voltage and power output to the main grid. Fractional order-PI (FOPI) controllers are used in a novel control structure for the SMES system to regulate the output power and DC-link voltage. An artificial bee colony optimization approach is employed to optimize the FOPI controllers. Three commonly utilized indicators, including sliding-mode, EKF, and Luenberger, were evaluated using "MATLAB" to evaluate the performance of the UKF estimate. Assessment criteria such as mean absolute percentage error and root mean squared error were used to gauge the accuracy of the estimates. Simulation findings showed the efficiency of fractional order-PI controllers for SMES and the proposed UKF indication for predictive current control, especially in the presence of measurement noise and over a variety of wind speeds. An improvement in estimation accuracy of up to 99.9% was demonstrated by the UKF indicator. Moreover, the stability of the suggested UKF-based PCC control for the hybrid WECS-SMES combination was confirmed using Lyapunov stability criteria."

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.

Improving Grid Reliability in Jordan: A Proposal for Integrated Demand Side Management and Energy Storage Solutions

<p align="left">Increased use of Renewable energy systems (RES) in Jordan has posed a major challenge in maintaining our grid stability. Jordan a country that relies on imported natural resources to power up its grid is using more and more RES with an aim to cut back on costs and CO<sub>2</sub> emissions. This paper investigates the usage of Demand Side Management (DSM) and Energy Storage Systems (ESS) to improve the grid’s reliability. A survey was conducted to analyze the opinion and acceptance of the Jordanian population on the implementation of DSM in Jordan. (ESS) mentioned in detail in this paper are: Compressed Air Energy Storage Systems (CAES), Superconducting Magnetic Energy Storage Systems(SMES), and Pumped Hydro Energy Storage Systems(PHES). The survey conducted showed a general scope of willingness of participation from people with 71.7% out of the 385 individuals who participated in the survey saying that they will participate in such a program if implemented in Jordan.</p>

Numerical analysis of the influence of radiation defects on the transport characteristics of a superconducting CORC-cable

Aim: development of a simultaneous model, calculation and analysis of heat losses of a superconducting CORC cable based on standard HTSC tapes and irradiated HTSC tapes in cyclic load modes for magnetic energy storage system.
 Methods: the CORC cable based on industrial original HTSC tapes and HTS tape with defects from irradiation is considered; to describe the electromagnetic and thermal characteristics of the system are used following methods: the concepts of the macroelectrodynamics, the fundamentals of the applied superconductivity, the finite element method are used; the calculation is implemented in the COMSOL Multiphysics.
 Results: a model was developed, the optimal cooling mode was determined in 5 load cycles, it was shown that the presence of artificial pinning centers can significantly improve the thermal stabilization of the system and leads to a reduction in heat losses with the considered cooling schemes.
 Conclusion: the results can be used in the development of the magnetic energy storage system based on high-temperature superconducting composites (HTS).

High temperature superconducting CORC cable with variable winding angles for low AC loss and high current carrying SMES system

Owing to the rising demand for enhanced high-current capacity within superconducting magnetic energy storage (SMES) system used in power grids, there is a growing focus on enhancing the current-carrying capability of SMES setups wound with conductor on round core (CORC) cables. However, it is crucial to note that the dissipation of AC losses in CORC cables during rapid charge and discharge cycles can substantially impact the safe operation of SMES. The CORC cable is crafted by spirally winding numerous ReBCO tapes around copper tubes. Even slight alterations in the winding angles of these tapes can result in shifts at current distribution across the ReBCO tapes, thus leading to differences in AC losses. Hence, the primary objective of this paper is to study the effect of varying winding angles of each ReBCO layer on AC loss. The adoption of variable angles results in the reduction of current flowing through the outermost tapes. And the AC losses in the outermost tapes happen to account for the majority of the total AC losses. Through simulations and experiments, it was observed that the AC loss in the CORC cable with variable angles (4 × 12, 25°–40°) was 25% lower than that in the case of fixed angles (3 × 11, 45°). These findings demonstrate a noteworthy downward trajectory in AC losses when variable angles are applied to the CORC cable. These insights hold significant value for the practical application of CORC cables within SMES systems.

Modeling and exergy analysis of an integrated cryogenic refrigeration system and superconducting magnetic energy storage

Superconducting magnetic energy storage (SMES) systems widely used in various fields of power grids over the last two decades. In this study, a thyristor-based power conditioning system (PCS) that utilizes a six-pulse converter is modeled for an SMES system. The main subject of this research is the generation of required helium for an SMES because for the coil to be at superconducting temperature, it needs to always be immersed in liquid helium. In the conducted simulation, the helium production system provided, in which primarily the gaseous helium temperature was reduced by heat transfer in LNG heat exchangers, and then after the sudden pressure drop, it turned into a liquid. The effect of the various firing angles is investigated, and it is found that at angles lower than 90°, at a specific angle, the output current enhances with time. In the 90°, this current remains constant, and at degrees greater than 90°, the output current reduces with time. The percentage of input flows to the expanders is investigated to find the rate of the maximum liquid helium production amount to the inlet gaseous helium. The diverted ratio of mass flow via expander 1 and expander 2 was 0.46 and 0.35, respectively. The system's work utilization of network, and liquid helium production is 67.18 MW and 12.7 kg/h. Also, the exergy analysis is done and the results show 35.7 % exergy efficiency. The efficiency of helium production has a direct relation to liquid nitrogen mass flow. However, due to the required high power for producing liquid nitrogen, with mass flow rate increment, the total system's efficiency is reduced. The results are evaluated with Aspen HYSYS, Aspen Energy Analyzer, and MATLAB. Specific work obtained from the analysis is 290,097 kW.s/kg which indicates that uses lower power in comparison with the other helium production methods which saves power and electrical costs.

Numerical Simulations of Space Charge Waves Amplification Using Negative Differential Conductance in Strained Si/SiGe at 4.2 K

This paper introduces a two-dimensional (2D) numerical simulation of the amplification of space charge waves using negative differential conductance in a typical MOS silicon–germanium (SiGe)-based field-effect transistors (FET) and complementary metal oxide semiconductor (CMOS) technology at 4.2 K. The hydrodynamic model of electron transport was applied to describe the amplification of space charge waves in this nonlinear medium (i.e., the negative differential conductance). This phenomenon shows up in GaAs thin films at room temperature. However, this can be also observed in a strained Si/SiGe heterostructure at very low temperatures (T < 77 K) and at high electric fields (E > 10 KV/cm). The results show the amplification and non-linear interaction of space charge waves in a strained Si/SiGe heterostructure occurs for frequencies up to approximately 60 GHz at T = 1.3 K, 47 GHz at T = 4.2 K, and 40 GHz at T = 77 K. The variation of concentration and electric field in the Z and Y directions are calculated at 4.2 K. The electric field in the Z direction is greater than in the Y direction. This is due to the fact that this is the direction of electron motion. In addition to deep space applications, these types of devices have potential uses in terrestrial applications which include magnetic levitation transportation systems, medical diagnostics, cryogenic instrumentation, and superconducting magnetic energy storage systems.

Application of COOT algorithm optimized PID plus D2 controller for combined control of frequency and voltage considering renewable energy sources

This article presents the combined frequency and voltage regulation of two area interconnected power systems. In addition to conventional generations, renewable energy sources such as wind plants, solar PV plants, and geothermal power plants are considered. The COOT algorithm optimized PID + D2 controller is presented for the first time and its performance found superior to commonly employed PI and PID controllers. The individual and combined effects of the boiler dynamics (BD) non-linearity and superconducting magnetic energy storage (SMES) systems are presented. Studies confirmed that the BD non-linearity jeopardizes, and the presence of SMES suppresses the system dynamics oscillations. The COOT based PID + D2 controller performs well even for the higher magnitudes of perturbations over the PID controller. Sensitivity analysis confirms the toughness of PID + D2 controller parameter values for widely varied time constants of the geothermal plant. The COOT algorithm optimized PID + D2 controller outperforms the PID controller in arbitrary load pattern perturbation. The COOT algorithm shows better convergence and figure of demerit characteristics compared with particle swarm optimization and firefly algorithms. The obtained simulation results are also tested successfully through OPAL-RT OP4500 RT-LAB-RCP/HIL system for their real-time validation.

An effective SMES system control for enhancing the reliability of hybrid power generation systems

Recently, with the rising electrical energy demand, renewable energy resources (RERs) are considered an optimal solution for satisfying consumption needs. The power generated from RERs has an intermittent and unpredictable nature, given that it depends directly on weather conditions. Thus, the amount generated power from RERs will be taken in fluctuated curve form. This paper focuses on addressing the issue of fluctuation in the power output of a Solar-Wind hybrid power generation systems (HPGSs) resulting from variable weather conditions. Superconducting magnetic energy storage (SMES) system provide a viable solving to the issue of power output fluctuations in HPGSs due to their unique characteristics. To this aim, this paper proposes two robust controllers for SMES systems to smooth out the power provided by a HPGS. In order to evaluate the proposed SMES system efficiency's during significant and fast fluctuations (at level of up to ∼1 MW in the range and seconds in the duration), computer simulations were implemented using the MATLAB/Simulink software package. The results obtained from the simulations have confirmed that the controllers of the proposed SMES system could efficiently reduce power output fluctuations from HPGSs, minimize power losses on the transmission lines, and regulate the voltage at the point of common coupling (PCC) at an acceptable standard level.

A Measuring System for HTS Wires and Coils Properties at Low Temperatures

The use of high temperature superconducting materials (HTS) in various applications, requires knowledge of their critical parameters like critical current, critical magnetic field and critical temperature, in DC applications like high magnetic field generators, superconducting magnetic energy storage system (SMES), magnetic resonance imaging (MRI), magnets for particle accelerators, SC Maglev trains and other applications. Also, these parameters are important for specific properties in alternating current applications like fault current limiters, transformers, generators, motors, and power transmission lines. An important characteristic that needs to be tucked into consideration for AC applications is the power losses that occur in the HTS superconducting materials, which limits the maximum performance that the superconducting materials can attain for these applications. In order to measure these characteristics, which depend on the type of material used, but also on the temperature and other parameters, it is necessary to use an appropriate setup device that allows both obtaining the working temperature range (4.2 K to 300 K and other necessary parameters like high vacuum 10-6 mbar, high current supply (500 A), high magnetic field measurement system (1-10 T), etc. For the cryogenic cooling of the entire system, a closed cycle Gifford-McMahon type cryocooler is used, with two cooling stages, stage I at 50 K and second stage at 4.2 K (liquid Helium temperature). The set-up system used for measurement of the parameters of HTS superconducting materials (YBCO, BSCCO or MgB2) and the various coils made with them, is described in this article together with its functional parameters and some experimental results obtained by testing an YBCO coils system. The maximum generated magnetic flux density was 5 T in the centre of the coils system.

Protection System Architecture for All-Electric Aircraft

To reduce emissions from the aviation industry and meet the targets set by different countries, research has been focused on investigating all-electric aircraft. To make this vision practical, superconducting machines are expected to power the propellers, as they are half the size and a third the weight of conventional machines. The main purpose of this paper is to do a higher-level study of a reliable holistic protection system for all-electric aircraft; that can reduce heat leakage and be able to detect faults reliably. Thus, three main protection systems were investigated; 1) cryogenic voltage source converter superconducting magnetic energy storage system (VSC-SMES), 2) cryogenic dc breaker integrated with superconducting fault current limiter (SFCL), and 3) machine learning algorithm for fault detection. By immersing the protection system at cryogenic temperature, the paper has shown that passive leakage can be eliminated, and thus more energy can be saved for the fuel cell. The paper has also demonstrated that using machine learning for the SFCL-dc-breaker system can consistently eliminate faults and protect the system.

Collaborative decision-making model for capacity allocation of photovoltaics energy storage system under Energy Internet in China

Solving the problem of photovoltaics abandonment and power limitation and improving resource utilization is particularly important to promote the sustainable development of the PV industry. With the innovative development and continuous application of energy storage technology, energy storage has become an indispensable part of photovoltaic power generation, realizing the consuming goal of abandoned photovoltaics. This paper studies the synergistic management of PV power generation based on the perspective of value chain, and constructs a complex value chain system with PV power generation subsystem and energy storage subsystem as the key subsystem—photovoltaics energy storage system (PVESS). Firstly, a value co-creation analysis framework for promoting capacity allocation of PVESS under the Energy Internet is analyzed. Secondly, the basic model of hybrid energy storage system (HESS) combining battery energy storage system (BESS) and superconducting magnetic energy storage system (SMES) is constructed. Thirdly, a multi-objective collaborative decision model is established with the objective functions of minimum economic cost, minimum abandoned photovoltaics and minimum load outage rate for the hybrid energy storage system (HESS). And the hybrid particle swarm algorithm (HPSO) algorithm and Vlsekriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method are used to determine the optimal system configuration. Finally, the validity and feasibility of the model are proved by the results of collaborative decision making and sensitivity analysis. The proposed collaborative decision suggestions for capacity allocation is adopted to facilitate the collaborative and effective operation of the system. This study can also provide insightful enlightenment for PVESS project investors, collaborative decision-making professionals and decision makers.

Stochastic optimisation and economic analysis of combined high temperature superconducting magnet and hydrogen energy storage system for smart grid applications

High Temperature Superconducting (HTS) Magnetic Energy Storage (SMES) devices are promising high-power storage devices, although their widespread use is limited by their high capital and operating costs. This work investigates their inclusion in smart grids when used in tandem with hydrogen fuel cells and other energy storage devices using a novel two-stage model. The first stage presents a stochastic allocation algorithm to optimally size the smart grid assets with the maximum expected profit. The next stage models the time system evolution with these optimal capacities using a dynamic Monte Carlo model to investigate the system reliability, capacity credit and loss of load expectation. A novel energy management algorithm is also presented that maximises the time with which a fleet of energy storage devices can fulfil a stochastically unknown power request. The analysis shows that from a purely economic standpoint, HTS SMES and hydrogen energy do not achieve high penetration levels (up to 10 %) due to their high costs, although the penetration levels can be improved with higher power imbalance penalties in day ahead markets. The novel capacity credit and reliability investigation shows that they can improve the reliability and capacity credit of wind turbines by approximately 30 %, thereby improving potential wind penetration levels. The optimal energy management algorithm improves the fleet lifespan and reliability by up to 9 % depending on the connected capacity.

Control strategy for the magnetic energy storage and transfer system (MEST)

The Magnetic Energy Storage and Transfer system (MEST) aims at improving the power handling in supplying the SuperConducting (SC) coils of fusion experiments. It is based on smart use of Superconducting Magnetic Energy Storage technology and allows the introduction of a certain degree of decoupling between the grid and the load. The MEST operation is based on the storage and transfer of the needed energy between the Load Coil (LC) and an additional storage inductor named Sink Coil (KC); the energy transfer is realized via capacitors switched by fully controllable semiconductors.This paper focuses on the control system of the MEST and proposes a control strategy, based on two decoupled control loops, with the aim both to guarantee the desired current on the load coil and the compensation of the system losses. A model of the MEST with the proposed control system has been developed to analyze the performance through numerical simulations. The control strategy and the simulation results will be presented and discussed in the paper.

Thermal and Electromagnetic Design of a Superconducting Coil

This article presents the methodology followed for the thermal and electromagnetic design of a superconducting coil at the University of Western Macedonia, Kozani, Greece, aimed to be used in a unique superconducting magnetic energy storage system for laboratory education and research purposes. First, we discuss the design constraints of the coil and select its dimensions using both the electromagnetic finite element method (FEM) and analytical equations based on the available length of a YBCO high-temperature superconductor. Then, we select the position of the coil inside a vacuum chamber. Then, an initial experiment without thermal load is performed to measure the cooling characteristics of the cryocooler. Using the results of the experiment and employing thermal FEM, we obtain an approximation of the cryocooler's cooling power versus time. After placing the coil and the thermal shield in the selected position inside the chamber, we carried out an experiment to measure the cooling curve with the load attached. The cryocooler's cooling power is approximated using the same FEM procedure. Thus, for this specific thermal load, the behavior of the apparatus is known. The methodology followed for the design of this unique system can be easily replicated by other researchers.

Load Frequency Control Using Golden Eagle Optimization for Multi-Area Power System Connected Through AC/HVDC Transmission and Supported With Hybrid Energy Storage Devices

The reliability of a power system depends on its ability to handle fluctuations and varying load demands, as uncontrolled frequency deviations can lead to load-shedding and blackouts. Optimally tuned controllers are essential for Load Frequency Control (LFC) applications to efficiently stabilize the power system by minimizing frequency undershoots, overshoots, and settling time. This paper proposed the application of novel Golden Eagle Optimization (GEO) algorithm for the optimal tuning of the LFC controller, which has not been previously employed in any LFC applications. Moreover, this paper presents the first-ever implementation of a hybrid energy storage system consisting of Vanadium Redox Flow Battery (VRFB) and Super Magnetic Energy Storage System (SMES) coupled with AC/HVDC transmission lines in a multi-area power system. A GEO optimized Proportional-Integrative-Derivative (GEO-PID) robust controller is designed with the Integral Time Absolute Error (ITAE) objective function to enhance the power system’s stability. The proposed controller is tested on two and four areas power systems considering the sensitivity and nonlinearity of the power systems. A robustness test is also performed to verify the stability of the system under randomly chosen loading conditions. In comparison with particle swarm optimization, dragonfly algorithm, sine cosine algorithm, ant lion optimization, and whale optimization algorithm, the GEO-PID controller significantly reduced the settling time up to 80% for different area’s frequencies. Simulation results indicate that the proposed controller outperforms other recent optimization algorithms by effectively dampening the frequency and tie-line deviations with less settling times, as well as reduced frequency undershoots and overshoots.

Hierarchical cooperative control strategy of distributed hybrid energy storage system in an island direct current microgrid

This paper presents a distributed hybrid energy storage system (HESS) for an island DC microgrid (MG) with a central superconducting magnetic energy storage (SMES) system and multiple distributed battery energy storage systems (BESS). A hierarchical cooperative control scheme is proposed to realize coordinate power sharing among distributed HESS and uninterrupted operation of SMES. The control scheme adopts filtration control to decouple imbalance power into high frequency component and low frequency component, which will be compensated by SMES and distributed BESSs. The proposed mode switch control (MSC) enables SMES to have higher transient large power regulation capability than filtration control. When the DC microgrid suffers from 400 kW power drops and power surges, the maximum DC bus voltage overshoot is 5.6 % and 5.3 % under MSC control, while the overshoot increases to 26.9 % and 8.2 % under the filtration control. Meanwhile, an autonomous state-of-charge (SOC) recovery control is designed for SMES to regulate its SOC within a set range (0.64, 0.725), which enables uninterrupted operation of SMES without performance trade off. A design scheme is proposed to make sure the desired transient power sharing dynamics and SOC recovery with negligible interactions. Additionally, the proposed distributed HESS structure and cooperative control method allows acceptable communication failure and physical faults. Cases verification conducted in PSCAD/EMTDC demonstrates the feasibility and superiority of the proposed system and control scheme against various kinds of power fluctuations.