Superconducting Magnetic Energy Storage System Research Articles

Implementing dynamic evolution control approach for DC-link voltage regulation of superconducting magnetic energy storage system

A Dynamic Evolution Control (DEC) scheme for the Superconducting Magnetic Energy Storage (SMES) system is presented in this article. The DC-link voltage of Power Converter Unit (PCU) is strictly regulated by the proposed control scheme irrespective of load transients. In SMES system, the PCU interfaces the SMES magnet and the AC system in order to give an efficient power exchange, and high quality power flow in the grid. Especially, this paper focuses on power quality improvement, and homogeneous voltage distribution & AC loss reduction across the magnet by achieving excellent DC-link voltage regulation. The harmonic components of magnet current are analyzed which are responsible for AC losses. It has been observed that the 3rd, 4th, 5th, 6th and 7th order harmonic components of the magnet current are significantly reduced. Particularly, a homogeneous voltage profile and less distorted magnet current are attained using the control scheme. The system supply current is found almost balanced, and its Total Harmonic Distortion (THD) is found well below 5%. Moreover, the control performance of DEC scheme is compared with that of the Proportional-Integral (PI) control technique. The proposed system is validated both in MATLAB/SIMULINK and real-time environment using a digital signal processor (dSPACE1104).

A Study on the Design and Comparison of 1–100-MJ-Class SMES Magnet With Different Coil Configurations

The MJ-class superconducting magnetic energy storage system (SMES) is most likely put into commercial utility applications. In China, several 1-100-MJ-class high-temperature superconducting (HTS) SMES projects are undergoing preresearch and conceptual design stage by the government and the power grid corporations, and these SMESs will be developed later. The configurations of commonly used SMES magnets are single-solenoid, multiple-solenoid, and toroidal magnets. Each configuration has its own electromagnetic and mechanical characteristics. In this paper, an optimal design and comparison were carried out to explore the suitable configuration for the MJ-class SMES magnet. As the critical current of the conductor is strongly influenced by the magnetic field and its applied direction, optimization of the HTS coil's configuration is required to minimize the length of the HTS wire. The optimization was conducted with the genetic algorithm and the finite-element method. In order to find the dependence of energy storage capacity on the wire cost, the magnet schemes of seven energy requirements were investigated. An optimal design is performed for the seven stored energies with the three types of magnet configurations. The comparisons between single-solenoid, four-solenoid, and toroidal coils are presented. The magnetic field and stress distribution of the SMES magnet are also depicted.

Frequency Regulation of Micro-grid Connected Hybrid Power System with SMES

This paper presents the frequency regulation analysis of a micro-grid connected hybrid power system based on solar Photovoltaic (PV), Wind and Diesel-Engine Generator (DEG) with Superconducting Magnetic Energy Storage system (SMES) unit. Abrupt change in load demand and power fluctuations from PV and wind power source causes frequency variability in the system. In order to mitigate this issue, the hybrid power system incorporates along with the energy storage devices. A case study of the impact of SMES operations on the performance of frequency stability of hybrid system has been carried out. Simulation of a Hybrid Power System (HPS) model has been carried out in two different scenarios with the two phases. First is the steady state investigation of HPS using PI controller with step load change response. Second is the dynamic performance study throughout a typical day with arbitrary variation in load demands. Controller parameters are tuned with Genetic Algorithm based optimization approach. The limits on the inductor (coil) current due to the possibilities of discontinuous conduction in the presence of large disturbances and limited storage capacity have also been incorporated. HPS has analyzed in the Matlab Simulink environment. Simulation results indicate that SMES system can contribute towards the frequency stability in both cases for variable power generations from renewable sources and irregular demand loads.

A fuzzy-logic-based control methodology for secure operation of a microgrid in interconnected and isolated modes

Summary Due to the global concerns regarding the climate change, integration of renewable energy sources is considered as a mitigation approach in electric power generation. This requires advanced frequency and voltage control methodologies to overcome the challenges especially in microgrids. This paper presents a 2-step frequency and voltage control methodology for microgrids with high penetration of variable renewable energy sources. An optimized Proportional-Integral controller is designed for a Superconductor Magnetic Energy Storage System to minimize the transient frequency deviations. In cases that the Superconductor Magnetic Energy Storage System cannot stabilize the microgrid frequency in the isolated mode, the microgrid controller activates the next level of the frequency control. In the second level, an intelligent fuzzy-logic frequency controller is designed to adjust controllable loads, controllable generation units as well as perform load shedding. In the interconnected mode, the microgrid controller is able to activate the second level to contribute to the system frequency control. Finally, an intelligent fuzzy-logic voltage controller, realized through distribution static synchronous compensator, is devised to control the voltage magnitude of the main feeders of the microgrid. In this work, a real-time operation algorithm for frequency as well as voltage control is proposed and has been tested by set of simulations on a low voltage benchmark network.

Enhancing smart grid transient performance using storage device‐based MPC controller

Renewable energy sources (wind turbine and photovoltaic system) are connected to the smart grid to promote the grid power, but the output of these sources is changed due to the sunlight and wind speed variations. Power storage system has the ability to reduce variations in a power system. Battery energy storage system (BESS) and superconducting magnetic energy storage system (SMES) are good solutions for this problem. The storage unit is connected to a power system at the point of common coupling and is able to absorb/store both active and reactive powers from this system and inject them into the power system in the peak demand periods. A control strategy based on proportional–integrative–derivative (PID) and model predictive controller (MPC) are used to control (SMES/BESS) to enhance the transient performance of a smart grid. The proposed algorithm has been tested on standard IEEE 5-bus system connected to wind turbine distributed generator, non-linear loads, and storage device (BESS/SMES) to verify the superiority of the presented method. The simulation results show that the performance of SMES with PID is more efficient than BESS with PID, but they have nearly the same output when MPC control strategy is used.

Robustness Improvement of Superconducting Magnetic Energy Storage System in Microgrids Using an Energy Shaping Passivity-Based Control Strategy

Superconducting magnetic energy storage (SMES) systems, in which the proportional-integral (PI) method is usually used to control the SMESs, have been used in microgrids for improving the control performance. However, the robustness of PI-based SMES controllers may be unsatisfactory due to the high nonlinearity and coupling of the SMES system. In this study, the energy shaping passivity (ESP)-based control strategy, which is a novel nonlinear control based on the methodology of interconnection and damping assignment (IDA), is proposed for robustness improvement of SMES systems. A step-by-step design of the ESP-based method considering the robustness of SMES systems is presented. A comparative analysis of the performance between ESP-based and PI control strategies is shown. Simulation and experimental results prove that the ESP-based strategy achieves the stronger robustness toward the system parameter uncertainties than the conventional PI control. Besides, the use of ESP-based control method can reduce the eddy current losses of a SMES system due to the significant reduction of 2nd and 3rd harmonics of superconducting coil DC current.

A New Design of Fuzzy Logic Control for SMES and Battery Hybrid Storage System

In this paper, the superconducting magnetic energy storage (SMES) and battery hybrid energy storage system has been designed to deal with high fluctuating power demand due to their complementary advantage. A lot of researchers are focusing on using battery technology to deal with low frequency demand and using SMES to deal with the remaining power demand. In this paper, a new energy management control method using 3 input parameters to a fuzzy logic controller is firstly proposed to deal with high fluctuating power demands. An example data processing result is shown in this paper. The results show that the hybrid storage system which applied fuzzy logic control has more flat battery charging/discharging current than an equivalent filtration control method. The low fluctuating battery demand is ideal for extending battery lifetime. Furthermore, the fuzzy logic controller can automatically adapt to the size of the SMES system by applying the state of the charge (SOC) of SMES as an input parameter to the fuzzy logic control.

Multi Solenoid Type Magnet for 1 MJ HTS SMES System

Recently the superconducting technology was more and more mature. The development of the technology allows us to apply superconducting magnetic energy storage (SMES) system to our life. An increasing number of scientists and engineers participate in study of SMES system. The application prospect of SMES system is very extensive, however, the leakage magnetic field limits application of SMES system. In this paper, multi solenoid type magnet, an improved structural for the 1 MJ single-solenoid structure magnet, is designed by using the actively shielding theory. The multi solenoid type magnet has potential to reduce the leakage magnetic field.

A Superconducting Magnetic Energy Storage-Emulator/Battery Supported Dynamic Voltage Restorer

This study examines the use of superconducting magnetic and battery hybrid energy storage to compensate grid voltage fluctuations. The superconducting magnetic energy storage system (SMES) has been emulated by a high-current inductor to investigate a system employing both SMES and battery energy storage experimentally. The design of the laboratory prototype is described in detail, which consists of a series-connected three phase voltage source inverter used to regulate ac voltage, and two bidirectional dc/dc converters used to control energy storage system charge and discharge. “DC bus level signaling” and “voltage droop control” have been used to automatically control power from the magnetic energy storage system during short-duration, high-power voltage sags, while the battery is used to provide power during longer term, low-power undervoltages. Energy storage system hybridization is shown to be advantageous by reducing battery peak power demand compared with a battery-only system, and by improving long-term voltage support capability compared with an SMES-only system. Consequently, the SMES/battery hybrid dynamic voltage restorer can support both short-term high-power voltage sags and long-term undervoltages with significantly reduced superconducting material cost compared with an SMES-based system.

Coordinated Control Strategies for SMES-Battery Hybrid Energy Storage Systems

Power swings may cause power system instability; therefore, hybrid energy storage systems (HESSs) are necessary to smooth the output of wind farms. Superconducting magnetic energy storage (SMES) systems have a high power density, whereas battery energy storage systems (BESSs) provide a high energy density. The significant contribution of this paper is the proposal of hierarchical control strategies for an HESS composed of an SMES system and a BESS. Mathematical models and port-controlled Hamiltonian (PCH) models of the HESS are established. At the device level, a novel HESS control strategy based on the PCH models is proposed to improve its output performance. At the system level, a multilevel power allocation method based on empirical mode decomposition, Fuzzy control and advanced control is proposed to achieve an efficient grid connection for a wind farm; the grid connection considers the real-time and future state of charge of the SMES system and BESS. The effectiveness of the proposed strategies are verified through simulation studies.

Study on Unit Commitment Problem Considering Large-Scale Superconducting Magnetic Energy Storage Systems

Large-scale superconducting magnetic energy storage (SMES) systems with the advantages of high storage efficiency and no site limitation have significant impacts on the optimal operation and daily load leveling in modern power systems. In this paper, a combinatorial unit commitment (UC) optimization model incorporating large-scale SMES systems is investigated to minimize operation cost of the currently existing power system. A hybrid particle swarm optimization algorithm is employed to intelligently schedule the thermal units and the SMES system simultaneously. The results obtained from an IEEE ten-unit test system case show that the UC-SMES model is favored for UC optimization with significant operation cost reduction achieved in the daily load leveling applications.

New Structure Design of Magnet for 1 MJ HTS SMES

In recent years, the superconducting technology is popular in our production and life. An increasing number of researchers and institutions participate in study of the super-conducting magnetic energy storage (SMES) system. SMES is widely used in power sup-ply system, new energy system and pulsed power supply system. However, the leakage magnetic field of traditional SMES is more serious, which limited the application in engi-neering. This paper proposes an improved scheme for the 1 MJ single-solenoid structure magnet by using the actively shielding theory. Moreover, by using particle swarm optimi-zation, the structural parameters of the superconducting magnets are optimized respec-tively. Finally, the ANSYS modeling simulation is built by these structural parameters, all simulation data are analyzed and compared.

Numerical Simulation and Experimental Validation of a Cooling Process in a 150-kJ SMES Magnet

The Superconducting Magnetic Energy Storage (SMES) system is expected to keep the power balance and increase the stability in an electric power system. During operation, heat may be dynamically generated in the superconducting magnet when the SMES system exchanges energy with the electric grid due to ac losses in superconductors and eddy losses in metal parts. To design a suitable cooling system for an SMES system, it is necessary to find out the heat transfer process from a superconducting magnet to a cryorefrigerator. This paper presents a model to analyze the heat transfer in a 150-kJ/100-kW conduction-cooled high-temperature superconducting (HTS) SMES system. The simulation results were identical with the experimental data. Thus, it is verified that the analysis method proposed here is useful for designing a cooling system for a conduction-cooled HTS SMES system.

Development of cooling technologies for SMES

A Superconducting Magnetic Energy Storage (SMES) system has good characteristics as energy storage equipment in electric power systems such as high efficiency, quick response and no deterioration in repetition operation. Since 1991, the Agency for National Resources and Energy Japan has carried out a national project to develop an SMES for power control in power systems. Moreover, SMES has been developed to bridge for instantaneous voltage dips since 2003. A field test of 5MVA SMES for bridging instantaneous voltage dips was carried out on an advanced large liquid crystal TV plant in Kameyama from July 2003. Before that, a 10MVA SMES system was working there. After the field test, the commercial SMES for instantaneous voltage dips is working there. In 2015, three commercial SMES units for bridging instantaneous voltage dips are operating in Japan. These SMESs are all equipped with metal superconducting coils. When considering cost-reduction, size-reduction, and maintenance of the SMES in the future, it is necessary to develop a SMES with a high-temperature superconductor and improve the efficiency of its cooling system. We have also developed and conducted operation tests of SMES with a Bi2212 oxide superconductor and high performance cryocooler which enable energy conservation operation by inverter control. In this paper, developed results on cooling systems and cryocooler for SMES are presented.

Design, Construction, and Testing of a Large-Aperture High-Field HTS SMES Coil

This paper presents the design, construction, and test results of a high-energy-density coil for a superconducting magnetic energy storage system (SMES). The coil was designed to reach 25 T at 4 K in a 100-mm bore under a program funded by ARPA-E. The coil used over 6 km of 12-mm-wide second-generation high-temperature superconductors (HTS) provided by SuperPower. Such high fields and large aperture in a coil built with a new and still-developing conductor and magnet technology created several challenges, which included large stresses and quench protection. This paper summarizes an ambitious research program that resulted in an SMES coil reaching 12.5 T at 27 K. This is the first time that such high fields and such high energy densities have been generated at a temperature over 10 K, and it opens the door for the possible use of HTS magnets in energy storage and other applications.

Voltage Distribution Characteristic of HTS SMES Magnet

HTS superconducting magnetic energy storage (SMES) system can be utilized to ensure stable operation and high-quality power supply in power systems. In SMES system, the power conditioning system (PCS) interfaces the superconducting magnet and the ac system, controlling the active and reactive power flow. Due to high-frequency switching of the PCS, the voltage distribution on the HTS magnet will affect the magnet insulation and quench detection. Considering the interaction between the PCS and the magnet, the output characteristics of the voltage-source-type and current-source-type PCSs are analyzed. Subsequently, the transient model of magnet is deduced to analyze the voltage distribution on the HTS magnet. The voltage distribution on an HTS magnet model is analyzed with the proposed method, which is later utilized to evaluate its insulation design.

A developed control strategy for mitigating wind power generation transients using superconducting magnetic energy storage with reactive power support

The fast variations of wind speed during extreme wind gusts result in fluctuations in both generated power and the voltage of power systems connected to wind energy conversion system (WECS). This paper presents a control strategy which has been tested out using two scenarios of wind gusts. The strategy is based on active and reactive powers controls of superconducting magnetic energy storage (SMES). The WECS includes squirrel cage induction generator (SCIG) with shunt connected capacitor bank to improve the power factor. The SMES system consists of step down transformer, power conditioning unit, DC–DC chopper, and large inductance superconducting coil. The WECS and SMES are connected at the point of common coupling (PCC). Fuzzy logic controller (FLC) is used with the DC–DC chopper to control the power transfer between the grid and SMES coil. The FLC is designed so that the SMES can absorb/deliver active power from/to the power system. Moreover, reactive power is controlled to regulate the voltage profile of PCC. Two inputs are applied to the FLC; the wind speed and SMES current to control the amount active and reactive power generated by SMES. The proposed strategy is simulated in MATLAB/Simulink®. The proposed control strategy of SMES is robust, as it successfully controlled the PCC voltage, active and reactive powers during normal wind speeds and for different scenarios of wind gusts. The PCC voltage was regulated at 1.0pu for the two studied scenarios of wind gusts. The fluctuation ranges of real power delivered to the grid were decreased by 53.1% for Scenario #1 and 56.53% for Scenario #2. The average reactive power supplied by the grid to the wind farm were decreased by 27.45% for Scenario #1 and 31.13% for Scenario #2.

Design and performance of a 1 MW-5 s high temperature superconductor magnetic energy storage system

The feasibility of a 1 MW-5 s superconducting magnetic energy storage (SMES) system based on state-of-the-art high-temperature superconductor (HTS) materials is investigated in detail. Both YBCO coated conductors and MgB2 are considered. A procedure for the electromagnetic design of the coil is introduced and the final layout is arrived at and compared for the two materials. The choice of the inductance of the coil is carried out as part of the design procedure. Both low-field (3 T) and high-field (8 T) designs are considered for the YBCO. AC losses during a complete charge/discharge cycle at full power are estimated and the cooling power needed for continuous operation is derived. The power conditioning system and control algorithms needed to carry out various operations are discussed in detail. Performances of the SMES system during voltage sag compensation, load leveling and power factor correction are investigated by means of numerical simulation.

Performance of a 10-kJ SMES model cooled by liquid hydrogen thermo-siphon flow for ASPCS study

We propose a new electrical power storage and stabilization system, called an Advanced Superconducting Power Conditioning System (ASPCS), which consists of superconducting magnetic energy storage (SMES) and hydrogen energy storage, converged on a liquid hydrogen station for fuel cell vehicles. A small 10- kJ SMES system, in which a BSCCO coil cooled by liquid hydrogen was installed, was developed to create an experimental model of an ASPCS. The SMES coil is conductively cooled by liquid hydrogen flow through a thermo-siphon line under a liquid hydrogen buffer tank. After fabrication of the system, cooldown tests were carried out using liquid hydrogen. The SMES coil was successfully charged up to a nominal current of 200 A. An eddy current loss, which was mainly induced in pure aluminum plates pasted onto each pancake coils for conduction cooling, was also measured.

Cooperative Operation of Superconducting Fault-Current-Limiting Cable and SMES System for Grounding Fault Protection in a LVDC Network

This paper investigates grounding fault protection characteristics in a novel low-voltage direct-current power transmission, distribution, and utilization network integrated with multiple fault-current-limiting (FCL) superconducting cables (SCs) and multiple superconducting magnetic energy storage (SMES) devices. The effectively integrated system is highlighted with a self-acting fault current limitation feature of the FCL SC and a fast-response grid voltage protection feature of the SMES. The simulation results show that the cooperative operations of the FCL SC and the SMES are favorable for achieving advanced fault current limitation, fault-ride-through capability enhancement and critical load protection during a grounding fault.