Application of magnetic energy storage unit as load-frequencystabilizer

Fast-acting energy storage devices can effectively damp electromechanical oscillations in a power system because they provide storage capacity in addition to the kinetic energy of the generator rotor, which can share the sudden changes in power requirement. The effectiveness of small-sized magnetic energy storage (MES) units (both superconducting and normal loss types) for this application is shown, and means of best utilizing the small energy storage capacity of such units to improve the load-frequency dynamics of large power areas are suggested. The proposed method of improving the load frequency control of power systems has the advantage that it does not require the governor or any other part of the power system to perform any sophisticated control action. The control logic suggested for this purpose takes the area control error as its input and uses inductor current deviation feedback. In a power system with a SMES (superconducting MES) unit, the optimal setting of the integrator gain is altered to a higher value. With the suggested control measure, SMES units of 4-6 MJ capacity would suffice in reducing the maximum deviations of frequency and tie-line power flow by about 40% in power areas of 1000-2000 MW capacity     

Application of magnetic energy storage unit as continuous VArcontroller

It is shown that magnetic energy storage units can simultaneously operate as continuous VAr (volt-ampere reactive) controllers while performing the role of load-frequency stabilizers in electrical power systems. This is achieved by operating the converter in the buck-boost mode with a switched capacitor bank placed across its terminals. The P versus Q modulation ranges of the 12-pulse converter depend on the source inductance, secondary voltage of the input transformers, and output current. Once the input transformer is chosen, the Q modulation range depends on the active power transfer and the current through the inductor at any instant of time. The actual reactive power consumption of the converter is varied continuously, depending on the requirements of the power system, while keeping within the Q-modulation range. Switching of the capacitor bank keeps the required Q consumption of the converter within the available range. It is shown that this mode of control improves the overall performance of the power system in P-f and Q-V loops and obviates the use of any additional VAr compensator in the power area where the SMES (superconducting magnetic energy storage) unit is located     

Application of superconducting magnetic energy storage in electrical power and energy systems: a review

Superconducting magnetic energy storage (SMES) is known to be an excellent high‐efficient energy storage device. This article is focussed on various potential applications of the SMES technology in electrical power and energy systems. SMES device founds various applications, such as in microgrids, plug‐in hybrid electrical vehicles, renewable energy sources that include wind energy and photovoltaic systems, low‐voltage direct current power system, medium‐voltage direct current and alternating current power systems, fuel cell technologies and battery energy storage systems. An extensive bibliography is presented on these applications of SMES. Also, some conclusive remarks in terms of future perspective are presented. Also, the present ongoing developments and constructions are also discussed. This study provides a basic guideline to investigate further technological development and new applications of SMES, and thus benefits the readers, researchers, engineers and academicians who deal with the research works in the area of SMES. Copyright © 2017 John Wiley & Sons, Ltd.     

Application of superconducting magnetic energy storage unit toimprove the damping of synchronous generator

A systematic approach to the design of a controller for superconducting magnetic energy storage (SMES) units to improve the dynamic stability of a power system is presented. The scheme employs a proportional-integral (PI) controller to enhance the damping of the electromechanical mode oscillation of synchronous generators. The parameters of the PI controller are determined by the pole assignment method based on modal control theory. Eigenvalue analysis and nonlinear computer simulations show that SMES with the PI controller can greatly improve the damping of the system under various operating conditions. Although the PI controller is designed for a special load condition, it can also provide good damping under other load conditions     

Application of superconductive magnetic energy storage in anasynchronous link between power systems

The concept that superconductive magnetic energy storage (SMES) can be incorporated into a back-to-back DC link is introduced. With an SMES-DC link, an SMES system can be shared between several neighboring power systems. This results in better economics for SMES usage for each participating power system. In addition to SMES operation, an SMES-DC link also allows asynchronous connection and interchange of power between the interconnected systems. It is demonstrated that an SMES-DC link can achieve significant economic benefits over pure power interchange or SMES operation alone. The basic principle of an SMES-DC link, which is able to interconnect any number of neighboring power systems with a single SMES unit, and various interconnected system operation modes are presented. A battery-DC link is discussed and compared with the SMES-DC link     

基于储能的无功补偿技术综述

基于无功补偿的无功功率实时平衡是电力系统安全稳定运行的重要保障.储能变流器具有四象限运行功能,可同时输出或吸收无功及有功功率,具有调频调压功能.基于储能的无功补偿技术具有响应速度快,连续可调、规模可控等优点,适用于高比例新能源和高电力电子化的新型电力系统.本文基于储能无功补偿原理,介绍了多种拓扑结构储能变流器的无功控制策略、串并联模块化放大以及中高压级联技术等研究进展.按照储能类型和应用场景,综述了储能以及储能混合无功补偿技术的发展进程及趋势,早期储能无功补偿主要采用超导储能、超级电容器及飞轮储能等短时间尺度的储能技术,电池储能技术的发展使其在电网调压、黑启动等无功补偿领域具有应用前景.基于经济性考虑,储能与STATCOM、新能源机组协同运行实现有功无功联合调压,保障系统电压水平,改善电能质量.新能源为主的新型电力系统给予储能无功补偿技术更重要的角色.储能、新能源机组及无功补偿装置的暂态稳态协同控制是未来新能源场站无功补偿主要形态.储能与其他无功源之间的协调控制策略以及联合规划问题的求解与优化都将是储能无功补偿技术的研究重点.     

飞轮储能在华中区域火电调频中的应用分析

由于运行寿命长、安全系数高、功率倍率高、功率响应速度快、控制精度高等特点,飞轮储能在火储联合调频领域的应用越来越受关注.本文解析了华中区域关于火电厂调频的补偿政策,获得了飞轮储能参与火储联合调频中影响经济收益的几个关键性能指标,并在一套500 kW/100 kW·h飞轮储能系统上进行了性能测试,依据测试结果,结合一台3...     

Direct active and reactive power control of DFIG for wind energy generation

This paper presents a new direct power control (DPC) strategy for a doubly fed induction generator (DFIG)-based wind energy generation system. The strategy is based on the direct control of stator active and reactive power by selecting appropriate voltage vectors on the rotor side. It is found that the initial rotor flux has no impact on the changes of the stator active and reactive power. The proposed method only utilizes the estimated stator flux so as to remove the difficulties associated with rotor flux estimation. The principles of this method are described in detail in this paper. The only machine parameter required by the proposed DPC method is the stator resistance whose impact on the system performance is found to be negligible. Simulation results on a 2 MW DFIG system are provided to demonstrate the effectiveness and robustness of the proposed control strategy during variations of active and reactive power, rotor speed, machine parameters, and converter dc link voltage.     

Dynamics and stability of wind and diesel turbine generators withsuperconducting magnetic energy storage unit on an isolated power system

Dynamic system analysis is carried out on an isolated electric power system consisting of a diesel generator and a wind-turbine generator. The 150 kW wind turbine is operated in parallel with a diesel generator to serve an average load of 350 kW. A comprehensive digital computer model of the interconnected power system including the diesel and wind-power dynamics with a superconducting magnetic energy storage (SMES) unit is developed. Time-domain solutions are used to study the performance of the power system and control logic. Based on a linear model of the system, it is shown that changes in control-system settings could be made to improve damping and optimization of gain parameters and stability studies are done using the Lyapunov technique and eigenvalue analysis. The effect of introducing the SMES unit for improvement of stability and system dynamic response is studied     

规模化电池储能系统的无功功率控制策略研究

无功功率补偿是电池储能系统并网运行时的重要应用。电池储能系统主要包括电池组、变流器以及设备监控系统等。电池储能用变流器可向电网提供无功功率。文章提出了规模化电池储能电站中各储能机组间的无功功率分配方法。采用仿真软件对电池储能系统的无功功率分配策略进行仿真分析,并基于张北储能试验基地的电池储能机组实例验证了控制策略的有效性。     

Enhancing the utilization of photovoltaic power generation bysuperconductive magnetic energy storage

The authors demonstrate that a superconductive magnetic energy storage (SMES) system can enhance large-scale utilization of photovoltaic (PV) generation. Results show that power output from a SMES system can be used to smooth out PV power fluctuations so that the combined PV/SMES output is dispatchable and free from fluctuations. Power generated from PV arrays is shown to be fully utilized under different weather conditions, and PV penetration is increased to significant levels without adversely affecting the power system. Coupled with PV generation, a SMES system is even more effective in performing diurnal load leveling. A coordinated PV/SMES operation scheme is proposed, and its demonstration under different weather conditions is discussed     

无功定价理论在新能源消纳中的应用

文章基于电网无功定价理论和电网稳定约束,结合IEEE14节点的典型接线进行新能源并网的模拟;采用牛顿算法得出新能源并网后导致的有功、无功增量的变化,由此求得各节点的有功、无功成本变化趋势;分析了各电能供应商对改善全网的电压稳定性所付出的无功支撑成本;论证了采用无功定价方法对新能源并网后的无功服务的合理补偿,可起到平衡各方利益的作用,对新能源的就地消纳产生积极的影响。文章可为新能源融入地方电网实现一体化的稳定运营提供市场交易的理论支撑;为制定无功服务定价提供参考;为实现新能源并网后的电力系统安全运行奠定基础。     

Renewable energy integration through optimal unit commitment and electricity storage in weak power networks

In this work, the impact of intermittent renewable energy sources on total production cost is evaluated, using annual data regarding the isolated power system of the island of Cyprus. Once electrical energy storage (EES) is identified as an approach enhancing flexibility and reliability, the selected EES facilities are modelled and evaluated via a life-cycle cost analysis, based on the most realistic characteristics and cost metrics found in the literature. The results derived from the uncertainty analysis performed, show that vanadium-redox flow battery provides the highest net present value (NPV). However, sodium-sulfur battery system offers the most secure investment in terms of uncertainty range and mean value, followed by lead-acid battery system. Lithium-ion battery system exhibits expensive capital cost which still governs its overall cost performance achieving a negative mean NPV far below zero.     

Application analysis and prospect of electrochemical energy storage in power grid

为促进能源产业的优化升级,可再生能源的开发利用力度不断加大,电网的规划运行和调度管理将面临重大变革,亟需先进的大规模储能技术来改善可再生能源发电特性。本文从电化学储能技术在电网系统应用进行探讨,从各种电化学储能安全性、成本、技术特点等进行深入解析,归纳各种类型电化学储能的优势与不足,并对未来电化学储能在电网系统的应用前景做出展望。     

Flywheel energy and power storage systems

For ages flywheels have been used to achieve smooth operation of machines. The early models where purely mechanical consisting of only a stone wheel attached to an axle. Nowadays flywheels are complex constructions where energy is stored mechanically and transferred to and from the flywheel by an integrated motor/generator. The stone wheel has been replaced by a steel or composite rotor and magnetic bearings have been introduced. Today flywheels are used as supplementary UPS storage at several industries world over. Future applications span a wide range including electric vehicles, intermediate storage for renewable energy generation and direct grid applications from power quality issues to offering an alternative to strengthening transmission.One of the key issues for viable flywheel construction is a high overall efficiency, hence a reduction of the total losses. By increasing the voltage, current losses are decreased and otherwise necessary transformer steps become redundant. So far flywheels over 10 kV have not been constructed, mainly due to isolation problems associated with high voltage, but also because of limitations in the power electronics. Recent progress in semi-conductor technology enables faster switching and lower costs. The predominant part of prior studies have been directed towards optimising mechanical issues whereas the electro technical part now seem to show great potential for improvement. An overview of flywheel technology and previous projects are presented and moreover a 200 kW flywheel using high voltage technology is simulated.     

光储联合系统中储能电站的能量管理

为提高储能设备利用率,实现储能电站能量的合理管理,以浙江地区某光伏电站配置的MW级储能电站示范工程为背景,针对现有单应用模式下储能装置容量和功率存在富余的特点,文章提出了一种平抑波动和分时电价相结合的储能装置控制方案。根据光伏出力特点,在光伏波动较强时进行光伏波动平抑,在光伏出力较弱时,根据储能装置剩余容量(state of charge,SOC)的实际情况,结合当地负荷变化曲线,实施分时电价策略。仿真实验表明,该控制方案维持储能设备SOC在合理范围的前提下,能及时平抑白天光伏的波动。同时在一定程度上实现了对负荷的削峰填谷,提高了储能设备利用率,实现了储能电站能量的合理管理,为项目后续示范应用提供了理论依据与技术支撑。     

储冰蓄能技术削峰填谷大有可为

介绍冰蓄冷空调系统及电锅炉蓄热系统的特点，采用一具体工程实例，对冰蓄冷中央空调与常规中央空调的设备总投资及在某一运行方案的运行费用进行分析比较，说明推广应用冰蓄冷技术有比较好的社会效益和经济效益。     

Enhancement of transient stability of an industrial cogeneration system with superconducting magnetic energy storage unit

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an external fault of utility power system occurs. An actual external fault case and a simulated internal fault case have been selected to verify the accuracy of the load shedding scheme by executing the transient stability analysis. To improve the frequency and voltage responses, an SMES unit with various control modes has been installed in the cogeneration system. The sensitivity analysis of the SMES unit with different parameters is applied to achieve better system responses. Besides, an SMES unit with active power deviation as feedback signal is also considered to improve the electric power fluctuation of the study plant with rolling mills. It is found that the SMES system will enhance the electric power quality and minimize the economic losses of the cogeneration facility due to unnecessary load shedding.     

Grid-tie three-phase inverter with active power injection and reactive power compensation

This paper proposes a methodology for the active and reactive power flow control, applied to a grid-tie three-phase power inverter, considering local and/or regionalized power flow control necessity in the forthcoming distributed generation scenario. The controllers are designed by means of robust pole placement technique, which is determined using the Linear Matrix Inequalities with D-stability criteria. The linearized models used in the control design are obtained by means of feedback linearization, aiming to reduce system nonlinearities, improve the controller's performance and mitigate potential disturbances. Through multi-loop control, the power loop uses active and reactive power transfer adapted expressions to obtain the magnitude of the voltage and power transfer angle to control the power flow between the distributed generation and the utility grid. The methodology main idea is to obtain the best controllers with the lowest gains as possible placing the poles in the left-half s-plane region, resulting in fast responses with reduced oscillations. In order to demonstrate the feasibility of the proposal a 3 kVA three-phase prototype was implemented and a comparison with conventional controller is performed to demonstrate the proposed methodology performance. In addition, anti-islanding detection and protection against over/under voltage and frequency deviations are demonstrated through experimental results.     

Saft lithium-ion energy and power storage technology

Since they were first introduced in the early 1990s, lithium-ion batteries have enjoyed unprecedented growth and success in the consumer marketplace. Combining excellent performance with affordability, they have become the product of choice for portable computers and cellular phones. Building on the same energy and life cycle attributes which marked their consumer market success, but adding new high power storage capability, lithium-ion technology is now poised to play a similar role in the transportation sector. With major programmes in both high capacity and high power lithium-ion technology, Saft has developed a family of products which can address the power and energy storage needs for vehicles, utilities, aviation, satellites, and other applications where light weight, long life, and excellent energy or power storage capabilities are needed. Although further development and refinements are underway, Saft has made a major commitment to bring this technology to the market with the establishment of a major pilot and research facility in Bordeaux France. This paper discusses the performance of this family of products and their potential applications.