A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator（DFIG）equipped with a superconducting magnetic energy storage（SMES） device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter（GSC） is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter（RSC） has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive（priority） and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method.

Superconducting Magnetic Energy Storage Integrated Current-source DC/DC Converter for Voltage Stabilization and Power Regulation in DFIG-based DC Power Systems

Unpredictable power fluctuation and fault ridethrough capability attract increased attention as two uncertain major factors in doubly-fed induction generators(DFIGs)integrated DC power system.Present solutions usually require complicated cooperation comprising multiple modules of energy storage,current control,and voltage stabilizer.To overcome the drawbacks of existing solutions,this paper proposes a superconducting magnetic energy storage(SMES)integrated currentsource DC/DC converter(CSDC).It is mainly composed of a current-source back-to-back converter,and the SMES is tactfully embedded in series with the intermediate DC link.The proposed SMES-CSDC is installed in front of the DC-DFIG to carry out its dual abilities of load voltage stabilization under multifarious transient disturbances and power regulation under wind speed variations.Compared with the existing DC protection devices,the SMES-CSDC is designed on the basis of unique current-type energy storage.It has the advantages of fast response,extensive compensation range,concise hardware structure,and straightforward control strategy.The feasibility of the SMESCSDC is implemented via a scaled-down experiment,and its effectiveness for DC-DFIG protection is verified by a large-scale DC power system simulation.

Intelligent Fractional-Order Controller for SMES Systems in Renewable Energy-Based Microgrid

An autonomous microgrid that runs on renewable energy sources is presented in this article.It has a supercon-ducting magnetic energy storage(SMES)device,wind energy-producing devices,and an energy storage battery.However,because such microgrids are nonlinear and the energy they create varies with time,controlling and managing the energy inside them is a difficult issue.Fractional-order proportional integral(FOPI)controller is recommended for the current research to enhance a standalone microgrid’s energy management and performance.The suggested dedicated control for the SMES comprises two loops:the outer loop,which uses the FOPI to regulate the DC-link voltage,and the inner loop,responsible for regulating the SMES current,is constructed using the intelligent FOPI(iFOPI).The FOPI+iFOPI parameters are best developed using the dandelion optimizer(DO)approach to achieve the optimum performance.The suggested FOPI+iFOPI controller’s performance is contrasted with a conventional PI controller for variations in wind speed and microgrid load.The optimal FOPI+iFOPI controller manages the voltage and frequency of the load.The behavior of the microgrid as a reaction to step changes in load and wind speed was measured using the proposed controller.MATLAB simulations were used to evaluate the recommended system’s performance.The results of the simulations showed that throughout all interruptions,the recommended microgrid provided the load with AC power with a constant amplitude and frequency.In addition,the required load demand was accurately reduced.Furthermore,the microgrid functioned incredibly well despite SMES and varying wind speeds.Results obtained under identical conditions were compared with and without the best FOPI+iFOPI controller.When utilizing the optimal FOPI+iFOPI controller with SMES,it was found that the microgrid performed better than the microgrid without SMES.

Superconducting magnetic energy storage for stabilizing grid integrated with wind power generation systems

Due to the interconnection of various renewable energies and adaptive technologies, voltage quality and frequency stability of modern power systems are becoming erratic. Superconducting magnetic energy storage(SMES),for its dynamic characteristic, is very efficient for rapid exchange of electrical power with grid during small and large disturbances to address those instabilities.In addition,SMES plays an important role in integrating renewable sources such as wind generators to power grid by controlling output power of wind plant and improving the stability of power system.Efficient application of SMES in various power system operations depends on the proper location in the power system, exact energy and power ratings and appropriate controllers. In this paper, an effort is given to explain SMES device and its controllability to mitigate the stability of power grid integrated with wind power generation systems.

Energy-saving Superconducting Magnetic Energy Storage(SMES)Based Interline DC Dynamic Voltage Restorer

The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional battery energy storage device.In order to improve the energy utilization rate and reduce the energy storage cost under multiple-line power distribution conditions,this paper investigates a new interline DC dynamic voltage restorer(IDC-DVR)scheme with one SMES coil shared among multiple compensating circuits.In this new concept,an improved current-voltage(I/V)chopper assembly,which has a series of input/output power ports,is introduced to connect the single SMES coil with multiple power lines,and thereby satisfy the independent energy exchange requirements of any line to be compensated.Specifically,if two or more power lines have simultaneous compensating demands,the SMES coil can be selectively controlled to compensate the preferable line according to the priority order of the line.The feasibility of the proposed scheme is technically verified to maintain the transient voltage stability in multiple-line voltage swell and sag cases caused by either output voltage fluctuations from external power sources or power demand fluctuations from local sensitive loads.The simulation results provide a technical basis to develop a cost-effective SMES-based IDC-DVR for use in various DC distribution networks.

Extended Cases of Laboratory Generated Gravitomagnetic Field Measurement Devices

A method is described for creating a measurable unbalanced gravitational acceleration using a gravitomagnetic field surrounding a superconducting toroid. A gravitomagnetic toroid for unbalanced force production has been experimentally realized as quite impractical. However recent advances in nanorod superconducting wire technology has enabled a new class of SMES devices operating at current densities and magnetic field strengths sufficient to develop measurable gravitomagnetic fields, while still maintaining mechanical integrity. It is proposed that an experimental SMES toroid configuration uses an absolute quantum gravimeter to measure acceleration fields along the axis of symmetry of a toroidal coil, thus providing experimental confirmation of the additive nature of the gravitomagnetic fields, as well as the production of a linear component of the overall acceleration field. In the present paper relativistic enhancement of this effect is also explored, as well as alternating current (AC) operations of the superconducting toroid to create gravitational waves. Lorentz force concerns are also addressed in Appendix.

High Index SMES Device for Gravitomagnetic Field Generation

A method is described for creating a measurable unbalanced gravitational acceleration using a gravitomagnetic field surrounding a superconducting toroid as described by Forward (1962). An experimental Superconducting Magnetic Energy Storage (SMES) toroid configuration of wound superconducting nanowire is proposed to create a measurable acceleration field along the axis of symmetry, providing experimental confirmation of the additive nature of a Lense-Thirring derived gravitomagnetic field. In the present paper, gravitational coupling enhancement of this effect is explored using a high index or high permittivity material, as predicted by Sarfatti (2020) using his modification to Einstein’s General Relativity Field Equations for gravitational coupling in matter.

超导磁储能装置提高柔性直流配电系统稳定性的研究

柔性直流配电系统中定功率控制的换流器具有恒功率负载特性,会降低系统阻尼,对系统的稳定性产生不利影响。针对该问题,在直流配电系统中加入超导磁储能SMES(superconducting magnetic energy storage)装置来提高系统的稳定性。推导了柔性直流配电系统的反馈控制模型,采用频域分析法研究了换流器恒功率负载特性对系统稳定性的影响,并结合数学模型和频域分析,指出SMES装置能够为电网提供正阻尼,增大了系统开环传递函数在剪切频率处的相位裕度,从而改善了系统稳定性。为防止超导磁体两端电压过高,SMES装置与直流配电网连接的DC/DC换流器需具备一定的电压调节性能,因此研究了采用模块化多电平DC/DC换流器DC-MMC(modular multilevel DC/DC converter)的SMES装置,通过调节子模块个数灵活设置换流器电压变比,在实现换流器能量双向流动的同时控制超导磁体两端电压,以保护储能装置。最后通过时域仿真波形验证了采用DC-MMC的SMES装置在提高柔性直流配电系统稳定性方面的可行性和有效性。

基于超导磁储能的光伏场站送出线路距离保护

受光伏逆变器控制策略影响,光伏场站呈弱馈性和电流相位受控特性,导致送出线路光伏侧距离保护的测量阻抗无法正确反映故障所在位置,抗过渡电阻能力大大下降。根据送出线路系统的故障分量序网图推导出线路短路阻抗的求解方程组,同时基于光伏场站直流母线接入的超导磁储能(superconducting magnetic energy storage,SMES)改变传统的低电压穿越控制策略,通过控保协同消除方程组中的未知量,进而对线路短路阻抗进行求解,提出了基于超导磁储能的光伏场站送出线路距离保护方案。与现有推导线路短路阻抗的方法相比,该方法不存在近似计算,计算准确度得到很大提升;且相比于其他控保协同方案,该方案在保证距离保护可靠动作的同时也兼顾了故障期间光伏场站对于电网的无功支撑,其低电压穿越能力不仅没有被削弱,反而得到一定的提升。

Superconducting energy storage technology-based synthetic inertia system control to enhance frequency dynamic performance in microgrids with high renewable penetration

With high penetration of renewable energy sources(RESs)in modern power systems,system frequency becomes more prone to fluctuation as RESs do not naturally have inertial properties.A conventional energy storage system(ESS)based on a battery has been used to tackle the shortage in system inertia but has low and short-term power support during the disturbance.To address the issues,this paper proposes a new synthetic inertia control(SIC)design with a superconducting magnetic energy storage(SMES)system to mimic the necessary inertia power and damping properties in a short time and thereby regulate the microgrid(µG)frequency during disturbances.In addition,system frequency deviation is reduced by employing the proportional-integral(PI)controller with the proposed SIC system.The efficacy of the proposed SIC system is validated by comparison with the conventional ESS and SMES systems without using the PI controller,under various load/renewable perturbations,nonlinearities,and uncertainties.The simulation results highlight that the proposed system with SMES can efficiently manage several disturbances and high system uncertainty compared to the conventional ESS and SMES systems,without using the PI controller.

计及储能响应特性的风氢混合并网控制

针对电解槽和燃料电池消纳风电中存在的响应延迟问题,构建风力机、电解槽、燃料电池、蓄电池、超导磁储能耦合于直流母线的结构,基于储能响应的时间尺度特性,利用超导磁储能的快速响应补充吸收电解槽或燃料电池及蓄电池响应延迟造成的功率缺额,制订一套并网控制策略,将系统分为20种工作模式,确保上网功率与负荷调度曲线实时一致;考虑电池模型的动态响应特性,提取动态变化过程的关键因素;基于电池应用场景,简化得到电池的多时间尺度模型,在PSCAD/EMTDC中搭建模型,4种仿真验证了并网控制的有效性。结果表明:配备超导磁储能可充分缓解响应延迟,提高能源利用率。

基于SMES风电不对称故障穿越控制策略研究

并网电网不对称故障会在网侧电压电流中产生2倍工频的正序和负序分量,2倍工频分量会导致并网电流畸变,甚至损坏并网变流器,影响直流母线电压稳定运行。针对风电不对称故障引起的电压波动,提出一种基于超导磁储能(SMES)的不对称故障穿越改进控制策略,分析不对称故障时并网变流器的功率模型特点,在传统不对称故障电流闭环控制中引入零序电流控制环,消除并网负序电流和有功功率波动;考虑电网故障会在直流侧堆积有功功率,造成直流母线电压波动,改进传统斩波器电压电流环,引入功率校正环节,及时消纳故障期间直流侧有功功率堆积,降低直流母线电压波动,最后构建仿真和实验平台验证所提方法的有效性。

超导磁储能系统自抗扰控制策略研究

针对电压源型换流器VSC(voltage source converter)的超导磁储能SMES(superconducting magnetic energy storage)系统,提出了一种自抗扰控制ADRC(active disturbance rejection control)策略。首先,分别建立了SMES的交流侧VSC、直流侧斩波器数学模型;其次,基于非线性扩张状态观测器和线性误差反馈律设计了SMES的交、直流侧ADRC;然后,通过描述函数法分析了ADRC的稳定性;最后,在Matlab/Simulink平台中搭建了仿真模型。仿真结果表明,与传统PI控制相比,ADRC具有更好的动态响应性能和抗扰动特性,并针对不确定的系统参数具有更好的鲁棒性,有效地提高了SMES的运行可靠性。

直流微网蓄电池-SMES混合储能系统容量配置方法

配置混合储能系统(HESS)可以有效减轻光伏发电输出功率波动性对直流微网的安全可靠运行带来的不利影响。为了更好地利用超导磁储能(SMES)响应速度快、功率密度高、效率高、可以无损储存电能等优点,基于与蓄电池组合而成的HESS的互补特性提出了以提高HESS经济性为目标的能量管理策略。对蓄电池-SMES HESS建立系统全生命周期成本(LCC)模型及其约束条件。对HESS进行容量优化配置可以有效降低系统成本,在满足系统功率要求的前提下,将最小LCC作为目标函数,通过引入加速因子的粒子群算法对系统容量进行配置,并结合算例建立微网模型,验证所提容量配置策略的有效性。

新型超导能量转换/存储装置原理及应用展望

基于新发现的永磁体与超导线圈之间的相互作用规律,提出了利用永磁体与闭合超导线圈构成新型短时能量转换/存储装置.通过在不同永磁体运动路径和运行速度时进行的多组实验,测量和分析了永磁体与闭合超导线圈相互作用过程中永磁体处在不同位置时的相互作用力和超导线圈内电流,验证所提装置原理的可行性并掌握其功能规律;进一步测量在静止状态时超导线圈中电流随时间的衰减情况,得到该装置的损耗特征.研究结果显示:该装置可在无需附加发电机/电动机条件下实现机械能→电磁能→机械能转换,能量效率达到9成以上.该新型超导能量转换/存储装置在城市轨道车辆制动能量回收再利用和航母舰载机辅助电磁弹射等领域具有广泛的应用前景.

智能电网中的储能技术应用

阐述坚强智能电网中运用的储能技术的原理和应用,包括抽水储能技术、压缩空气储能技术、飞轮储能技术、蓄电池储能技术、超导磁储备技术,以及智能电网中储能技术的作用。

微网中的多元复合储能技术

储能技术被认为是微网的核心技术之一,它在稳定电网运行及利用可再生能源方面有重要作用。阐述了微网中储能的作用和意义,并结合适用于微网的几种储能方式,如飞轮储能、超导磁储能、超级电容器和蓄电池,分析了其技术特点。提出了未来微网中的多元复合储能应用模式,并简要分析了应用多元复合储能的技术课题。

微电网储能技术研究综述

对储能技术在微电网中的应用研究进行了综述。简要回顾了储能技术的发展历程,阐述了微电网中储能技术研究的意义和价值。分析了储能技术在微电网中的作用,比较全面地介绍了蓄电池储能、飞轮储能、超导储能、超级电容器储能、混合储能和其他储能在微电网中的应用研究现状,分别说明了各种储能方式的优点和不足之处,并对各种储能方式的性能指标进行了比较。根据微电网的特点和要求,指出了微电网储能技术研究目前存在的问题和未来发展趋势。

超导电力磁储能系统研究进展(一)——超导储能装置

介绍了超导磁储能装置 (SMES)的基本原理、系统组成和发展状况 ,阐述了具有高效、快速响应、能与系统独立进行四象限交换有功和无功功率等特性的 SMES在电力系统中应用的重要意义 ,概述了 SMES的应用前景和需要进一步解决的若干问题 ,并针对我国

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1MJ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1MJ的紧凑型超导储能磁体。磁体内径为439mm,外径为600mm,高为550mm。在运行电流为305A时,磁体的最大磁场为4.9T,中心磁场为4T。对超导磁体的试验结果表明,磁体的最大运行电流为303A,放电功率为100kW。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。