Detailed modeling of superconducting magnetic energy storage (SMES) system

This paper presents a detailed model for simulation of a Superconducting Magnetic Energy Storage (SMES) system. SMES technology has the potential to bring real power storage characteristic to the utility transmission and distribution systems. The principle of SMES system operation is reviewed in this paper. To understand transient and dynamic performance of a SMES system, a detailed SMES system benchmark model is given with extensive simulation results. This system is demonstrated using an electromagnetic transient program-PSCAD/EMTDC.     

Power oscillation damping by superconducting magnetic energy (SMES) storage unit

With the increase in the size and capacity of electric power systems and the growth of widespread interconnections, the problem of power oscillations due to the reduced system damping has become increasingly serious. Since a Superconducting Magnetic Energy Storage (SMES) unit with a self-commutated converter is capable of controlling both the active (P) and reactive (Q) power simultaneously and quickly, increasing attention has been focused recently on power system stabilization by SMES control. This paper describes the effects of SMES control on the damping of power oscillations. By examining the case of a single generator connected to an infinite bus through both theoretical analyses and experimental tests (performed with a SMES unit with maximum stored energy of 16 kJ and an artificial model system), the difference in the effects between P and Q control of SMES is clarified as follows:

• 1 In the case of P control, as the SMES unit is placed closer to the terminal of the generator, the power oscillations will decay more rapidly.
• 2 In the case of Q control, it is most effective to install the SMES unit near the midpoint of the system.
• 3 By comparing the P control with Q control, the former is more effective than the latter based on the conditions that the SMES unit location and the control gain are the same.

     

Superconducting magnetic energy storage for power systemapplications

A survey of the technology of superconducting magnetic energy storage (SMES) is discussed. This technology is attractive for its high efficiency and fast response, but the economic benefits are dubious. Research done in the USA and Japan resulted in several conceptual designs for utility-scale SMES systems. Experiments on power system models proved that SMES systems offer other benefits in addition to energy storage. Economic evaluations showed that the SMES is competitive with pumped hydro, especially when the energy prices rise. A power flow program was used to verify the application of a SMES plant to the Taiwan power system     

A fuzzy logic controlled superconducting magnetic energy storage,SMES frequency stabilizer

This paper presents application of fuzzy logic controlled superconducting magnetic energy storage device, SMES to damp the frequency oscillations of interconnected two-area power systems due to load excursions. The system frequency oscillations appear due to load disturbance. To stabilize the system frequency oscillations, the active power can be controlled via superconducting magnetic energy storage device, SMES. The error in the area control and its rate of change is used as controller input signals to the proposed fuzzy logic controller. In order to judge the effect of the proposed fuzzy logic controlled SMES, a comparative study is made between its effect and the effect of the conventional proportional plus integral (PI) controlled SMES. The studied system consists of two-area (thermal–thermal) power system each one equipped with SMES unit. The time simulation results indicate the superiority of the proposed fuzzy logic controlled SMES over the conventional PI SMES in damping the system oscillations and reach quickly to zero frequency deviation. The system is modeled and solved by using MATLAB software.     

Performance of a power conversion system for superconductingmagnetic energy storage (SMES)

This paper presents the results of laboratory tests of a power conversion system (PCS) for superconducting magnetic energy storage (SMES) applications. The PCS uses a two-quadrant chopper and a voltage-source power converter. Operating modes of the chopper are discussed. Operation of SMES to provide independent control of real and reactive power, operation as a static VAr compensator, low frequency modulation of the real power and speed of response are demonstrated. A circuit is presented for testing an SMES PCS that does not require a superconducting coil     

基于哈密顿系统理论的超导储能装置控制器的设计

针对电力系统非线性的特点，将电力系统中的一类仿射非线性系统转换为标准的哈密顿系统，进行了超导储能SMES（Superconducting Magnetic Energy Storage)有功功率的控制设计，对无功功率用传统的比例环节进行设计，基于受控哈密顿系统理论，建立了SMES装置的端口受控哈密顿PCH（Port Controlled Hamiltonian)模型，针对系统的外界干扰和参数不确定性，采用自适应KL2增益控制设计方法设计了含有SMES装置的单机无穷大电力系统的自适用L2增益控制器。仿真结果表明，采用基于哈密顿系统理论的自适应L2增益控制方法对SMES有功功率的设计，利用传统的比例积分PI（Proportion Integration)控制器进行无功功率控制，能够有效地抑制干扰，显著地改善系统的动态性能。     

基于超导磁储能装置的MMC-HVDC系统直流振荡抑制方法

基于模块化多电平换流器的柔性直流输电(MMC-HVDC)系统中的功率控制换流站对外呈现负阻性,降低了系统阻尼,使系统产生直流振荡甚至导致系统失稳。通过直流侧并联超导磁储能装置抑制系统功率振荡,以解决MMC-HVDC系统向恒定功率负载供电所导致的弱阻尼问题。建立了双端MMC-HVDC系统的小信号模型,通过小信号稳定性分析方法研究了影响MMC-HVDC系统稳定性的主要因素,并且验证了所提直流振荡抑制方法的有效性。在MATLAB/Simulink中搭建了双端MMC-HVDC系统模型,并与改变控制器的功率阻尼控制策略进行时域仿真对比,结果证明了所提控制策略能有效抑制系统振荡,提高系统稳定性。     

蓄电池/超导混合储能系统非线性鲁棒分数阶控制

针对电动汽车(Electric Vehicle, EV)供电端的蓄电池/超导混合储能系统(Battery/SMES Hybrid Energy Storage Systems, BSM-HESS)设计了一种新型非线性鲁棒分数阶控制(Nonlinear Robust Fractional-Order Control, NRFOC),从而快速精准地跟踪负荷需求变化。首先,基于规则式策略(Rule-Based Strategy, RBS)实现最优的负荷需求分配。然后,通过高增益扰动观测器(High-Gain Perturbation Observer, HGPO)对BSM-HESS的非线性、参数不确定性和未建模动态聚合而成的扰动进行快速估计,最终该扰动通过NRFOC进行在线完全补偿。此外,NRFOC不依赖于精确的系统模型,仅需测量蓄电池电流和直流侧电压两个状态量。通过三种算例进行研究,即重载条件、轻载条件以及参数不确定性,仿真结果验证了NRFOC的有效性和鲁棒性。     

Superconducting magnetic energy storage controller design and stability analysis for a power system with various load characteristics

A simultaneous active power and reactive power (P–Q) control scheme of superconducting magnetic energy storage (SMES) unit is proposed to enhance the damping of a power system. In order to control the P–Q modulation to the power system, a proportional-integral (PI) controller is used to provide a supplementary damping signal. The parameters of the PI controller are determined by a systematic pole assignment method based on modal control theory. Both static load and dynamic load are included to improve the system model fidelity. Eigenvalue analysis and time-domain nonlinear simulation, using a power system incorporating a composite load, are illustrated to validate the effectiveness of the proposed PI SMES controller for the damping of the studied system over a wide range of operating conditions. The control scheme also shows that the stability margin of the power system is expanded.     

高电流密度超导储能磁体的研制

分析了不同结构超导储能磁体的特点,针对储能量为MJ量级的超导储能磁体计算了漏磁场分布和超导材料的利用率,提出了储能为1 MJ的单螺管型超导储能磁体的设计方案。采用窄液氦通道技术,利用多芯NbTi/Cu复合超导线,研制了储能量为1 MJ的紧凑型超导储能磁体。磁体内径为439 mm,外径为600 mm,高为550 mm。在运行电流为305A时,磁体的最大磁场为4.9 T,中心磁场为4 T。对超导磁体的试验结果表明,磁体的最大运行电流为303 A,放电功率为100 kW。研制的超导储能磁体可作为恒压/恒功率放电的不间断电源的关键部件。     

Assessment of utility side cost savings from battery energy storage

A method of determining the dynamic operating cost benefits of energy storage systems for utility applications is presented. The production costing program DYNASTORE is used to analyze economic benefits for “utility B,” an isolated island utility, using heuristic unit commitment algorithms. The unit commitment is done using chronologic load data and a detailed model of the utility characteristics. Several unit commitment scenarios are run for utility B, and the results are presented. Comparisons between various battery energy storage system (BESS) applications, as well as cases with and without battery storage, are shown. Results show that for utility B, a BESS of 300 MW size used for spinning reserve provides the greatest economic benefit     

Techno-economic analysis of MJ class high temperature Superconducting Magnetic Energy Storage(SMES) systems applied to renewable power grids

High temperature Superconducting Magnetic Energy Storage(SMES) systems can exchange energy with substantial renewable power grids in a small period of time with very high efficiency. Because of this distinctive feature, they store the abundant wind power when the power network is congested and release the energy back to the system when there is no congestion. However, considering the cost and lifespan of SMES systems, there is an urgent demand to conduct a cost-benefit analysis to justify its role in smart grid development. This study explores the application and performs economic analysis of a 5 MJ SMES in a practical renewable power system in China based on the PSCAD/EMTDC software. An optimal location of SMES in Zhangbei wind farm is presented using real power transmission parameters. The stabilities of the renewable power grid with and without SMES are discussed. In addition, a financial feasibility study is conducted by comparing the cost and the savings from wind power curtailment of deploying SMES and battery. The economic analysis tries to find the balance between SMES investment cost and wind farm operation cost by using real data over a calendar year. The technical analysis can help guide the optimal allocation of SMES for compensating power system instability with substantial wind power. Further, the economic analysis provides a useful indication of its practical application feasibility to fight the balance between cost and benefit.     

Interconnected power systems with superconducting magnetic energy storage

The objective of this work is to discuss the concept of back‐to‐back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back‐to‐back DC link. In this case, each converter of the back‐to‐back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two‐way switch is connected to the AC side of each converter. This two‐way switch can select the interconnected power systems. By using the two‐way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower‐cost power of each power network can be stored through two converters during the off‐peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back‐to‐back interconnection with SMES and discuses the optimal SMES configuration for a 300‐MW‐class back‐to‐back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20482     

超导磁储能装置的功率控制

以电流源型和电压源型变流器作为研究对象,探讨了可对电流源型变流器和电压源型变流器交流侧电流的幅值和相位进行有效控制的SPWM开关策略。在此基础上,研究了能够按照系统要求对2种超导磁储能装置进行有功和无功功率调节的功率控制方法。仿真结果表明所研究的功率调节方法能够在四象限内进行超导磁储能装置输入输出有功和无功功率的快速解耦控制,仿真同时验证了所研究的功率控制策略的正确性和可行性。     

大储能容量超导磁储能系统的拓扑结构及控制策略

随着可再生能源规模化发展,电网对大功率等级储能系统的需求日益增长,因此研究应用于大功率等级场合的超导磁储能(SMES)系统拓扑结构及运行控制策略具有重要的理论意义.提出了一种基于模块化多电平换流器(MMC)的SMES系统拓扑结构,设计了允许多个超导磁体同时接入以成倍数提升系统整体储能容量的新型斩波器.该新型斩波器采用模块化设计,由多个子模块串联构成,可随MMC扩展至多种电压等级和功率等级,且能够均衡各子模块的电容电压和磁体电流.针对新型斩波器的旁路子模块数量难以确定的问题,提出了新型斩波器旁路子模块数量的计算方法.基于线性自抗扰控制设计了MMC双闭环控制器和新型斩波器的直流电压控制器,利用复频域分析法整定了线性自抗扰控制器参数.通过仿真验证了所提拓扑结构和控制策略的正确性和有效性.     

考虑磁体动态特性的高温超导磁储能磁体设计

超导磁体是超导磁储能系统（SMES）的核心部件,其优化设计可以提高SMES的经济性和运行性能。提出了一种考虑磁体动态特性的高温超导磁储能磁体设计方法,该方法以有限元方法为基础,选取遗传算法作为优化工具,对高温超导磁体的内径、单饼匝数和双饼个数进行了优化。该方法将超导磁体的优化分为了两个部分,一次优化以磁体的用线量为优化目标,二次优化将交流损耗低为优化目标。最后用此方法对储能容量为150 kJ的高温超导磁储能磁体进行了优化设计,经过两次优化后的150 kJ磁体方案兼具低用线量和低交流损耗的优点。     

Neural-network-controlled superconducting magnetic energy storage for power system stabilization

It has been clarified that a superconducting magnetic energy storage (SMES) is very effective for power system stabilization. The control methods proposed for power system stabilization by SMES are the pole assignment, the optimal control, and so on, each of which, however, has its drawbacks. This paper is concerned with the power system stabilization by neural network control of the active power of SMES. First, the optimal stabilizing control of the SMES power for the model power system is calculated for various power system operating conditions and fault conditions. Then these optimal controls are used as training data for the neural network. The neural network used is a multilayer type with a feedback from the output layer to the input layer. The trained neural network is examined by untrained operating conditions and faults.     

New combined power-conditioning system for superconducting magnetic energy storage

This paper proposes a new combined power-conditioning system for large-scale superconducting magnetic energy storage; it consists of a DC chopper and a PWM (pulse-width modulation) voltage-source converter. The proposed system can independently control the active and reactive power of the utility network by regulating the chopper duty cycle and the converter firing angle. The operational concept was verified through mathematical analyses using an equivalent circuit. The dynamic interaction was analyzed using a simulation model with EMTP (Electromagnetic Transients Program). The analysis results show that the new system is feasible for development with commercially available components and technologies.