A Nonlinear Control Algorithm for Flywheel Energy Storage Systems in Discharging Mode

针对Buck-Boost变换器的非线性特征给飞轮储能系统的放电运行状态带来的控制问题,提出了电压电流双环非线性控制算法。基于输入/输出线性化理论,推导出电流内环的控制律,并证明了内动态的稳定性。电压外环采用鲁棒性强的滑模变结构控制方法,并增加限流环节,保证放电电路安全、稳定运行。在Matlab/Simulink仿真平台中搭建飞轮放电模型,对所提出非线性控制算法进行了仿真验证。仿真结果表明,相比于双环PI控制,该算法能够明显改善输出电压调节时间、超调量等动态特性,在输入电压存在大范围变化的情况下,输出电压能够保持恒定和较低的纹波系数。

Spacecraft Attitude Tracking and Energy Storage Using Flywheels

The control law of the flywheel in an integrated power and attitude control system （IPACS） for a spacecraft is investigated. The flywheels are used as attitude control actuators as well as energy storage device. A feedback control law for attitude tracking is firstly developed by using Lyapunov approach, and then a torque based control law of the flywheel is studied. The control torque vector of the flywheel is decomposed into three parts which are orthogonal to one another by using the method of singularity value decomposition （SVD）. One part is used to provide the attitude control torque, another part is used to store energy with given power, and the last part is used to accomplish wheel speed equalization to avoid wheel saturation caused by large difference among the wheel spin rates. A management scheme for energy storage power using kinetic energy feedback is proposed to keep energy balance, which can avoid wheel saturation caused by superfluous energy. Numerical simulation results demonstrate the effectiveness of the control scheme.

Analysis of the Comprehensive Physical Field for a New Flywheel Energy Storage Motor/Generator on Ships

A novel flywheel energy storage （FES） motor/generator （M/G） was proposed for marine systems. The purpose was to improve the power quality of a marine power system （MPS） and strengthen the energy recycle. Two structures including the magnetic or non-magnetic inner-rotor were contrasted in the magnetostatic field by using finite element analysis （FEA）. By optimally designing the size parameters, the average speed of FEA results of was 17 200 r/m, and the current was controlled between 62 and 68 A in the transient field. The electrical machine electromagnetism design was further optimized by the FEA in the temperature field, to find the local overheating point under the normal operation condition and provide guidance for the cooling system. Finally, it can be concluded from the comprehensive physical field analysis that the novel redundant structure M/G can improve the efficiency of the M/G and maintain the stability of the MPS.

Flywheel Energy Storage with Mechanical Input-Output for Regenerative Braking

The system presented in this paper allows the direct transfer of kinetic energy of a vehicle’s motion to a flywheel and vice-versa. For braking, a cable winds onto a pulley geared to the vehicle’s propulsion driveshaft as it unwinds from another pulley geared to the flywheel and then operates in reverse for the transfer of energy in the opposite direction. The cable windings are in one plane resulting in an effective pulley radius that increases when the cable is winding onto it and decreases when unwinding from it. Thus, an increasing driven-to-driving pulley velocity ratio is obtained during a period of energy transfer in either direction. A dynamic analysis simulating the process was developed. Its application is illustrated with a numerical solution based on specific assumed values of system parameters.

Dynamical investigation and parameter stability region analysis of a flywheel energy storage system in charging mode

In this paper, the dynamic behavior analysis of the electromechanical coupling characteristics of a flywheel energy storage system （FESS） with a permanent magnet （PM） brushless direct-current （DC） motor （BLDCM） is studied. The Hopf bifurcation theory and nonlinear methods are used to investigate the generation process and mechanism of the coupled dynamic behavior for the average current controlled FESS in the charging mode. First, the universal nonlinear dynamic model of the FESS based on the BLDCM is derived. Then, for a 0.01 kWh/1.6 kW FESS platform in the Key Laboratory of the Smart Grid at Tianjin University, the phase trajectory of the FESS from a stable state towards chaos is presented using numerical and stroboscopic methods, and all dynamic behaviors of the system in this process are captured. The characteristics of the low-frequency oscillation and the mechanism of the Hopf bifurcation are investigated based on the Routh stability criterion and nonlinear dynamic theory. It is shown that the Hopf bifurcation is directly due to the loss of control over the inductor current, which is caused by the system control parameters exceeding certain ranges. This coupling nonlinear process of the FESS affects the stability of the motor running and the efficiency of energy transfer. In this paper, we investigate into the effects of control parameter change on the stability and the stability regions of these parameters based on the averaged-model approach. Furthermore, the effect of the quantization error in the digital control system is considered to modify the stability regions of the control parameters. Finally, these theoretical results are verified through platform experiments.

Analysis of a Novel Mechanically Adjusted Variable Flux Permanent Magnet Homopolar Inductor Machine with Rotating Magnetic Poles for Flywheel Energy Storage System

Permanent magnet homopolar inductor machine(PMHIM) has attracted much attention in the field of flywheel energy storage system(FESS) due to its merits of simple structure,brushless excitation, and rotor flywheel integration. However, the air-gap flux generated by the PM cannot be adjusted, which would cause large electromagnetic losses in the standby operation state of FESS. To solve this problem, a novel mechanically adjusted variable flux permanent magnet homopolar inductor machine with rotating magnetic poles(RMP-PMHIM) is proposed in this paper. The permanent magnet poles are rotated by an auxiliary rotating device and the purpose of changing the air-gap flux is achieved. First, the structure and operation principle of the proposed RMP-PMHIM are explained. Second,the flux weakening principle of the RMP-PMHIM is analyzed and the equivalent magnetic circuit models under different flux weakening states are built. Third, the parameters of the PM and its fixed structure are optimized to obtain the good electromagnetic performance. Fourth, the electromagnetic performance, including the air-gap flux density, back-EMF, flux weakening ability, loss, etc. of the proposed RMP-PMHIM are investigated and compared. Compared with the non-rotating state of the PM of RPM-PMHIM, the air-gap flux density amplitude can be weakened by 99.95% when the PM rotation angle is 90 degrees, and the no-load core loss can be suppressed by 99.98%,which shows that the proposed RPM-PMHIM is a good candidate for the application of FESS.

Flywheel Energy Storage System Based on Boost DC-AC Converter

To extend the operating speed range of a conventional configuration of FESS （flywheel energy storage system）, an additional DC-DC boost converter is required between the machine and grid side converters to regulate the output voltage. This paper presents a new FESS based on three-phase boost inverter topology. The proposed system facilitates voltage boost capability directly in a single-stage. The main advantage of the three-phase boost inverter is the deployment of only six switches and undersized passive elements to obtain a boosted AC output voltage weighed against the input DC supply. In this paper, FESS based on boost inverter topology is modeled and simulated using MATLAB/S1MULINK. An experimental setup has been built for the three-phase boost inverter to present its boosting capability. The simulation and experimental results sustain the proposed configuration.

Improving Kinetic Energy Storage for Vehicles through the Combination of Rolling Element and Active Magnetic Bearing

The demand for short term energy storage providing high power for electric and hybrid-electric vehicles is increasing drastically. Stationary FESS （flywheel energy storage systems） is established as UPS （uninterruptible power supply） and represent an emerging market. In contrast, mobile FESSs are currently only used in a few application, e.g., in motor sports. To enable a wider use in personal and public transportation the life-span of the flywheel＇s bearings needs to be increased significantly. This paper presents an alternative approach to extend the lifespan of the flywheel＇s bearings significantly by using a CREAMB （combination of rolling element and active magnetic bearings）.

FESS抑制电力系统低频振荡的机理分析

对应用飞轮储能系统(FESS)抑制电力系统低频振荡的机理进行了研究。在推导了FESS简化动态模型的基础上,采用定子磁场定向控制策略,实现FESS有功、无功的解耦控制,并分别从物理意义、基于阻尼转矩分析(DTA)的理论分析和基于等面积的图解法分析三方面详细地分析了FESS阻尼电力系统低频振荡的机理。最后,以含FESS的单机无穷大系统为例,特征值分析和非线性仿真结果表明在FESS有功和无功控制回路上附加阻尼都能有效抑制电力系统低频振荡,并且阻尼信号附加到有功控制回路上比附加到无功控制回路上抑制效果更好。同时也表明了各种机理分析方法的一致性和正确性。

Study on electromechanical coupling nonlinear vibration of flywheel energy storage system

The electromechanical coupling dynamics of the flywheel energy storage system (FESS) with a hybrid permanent magnetic-dynamic spiral groove bearing has been studied. The functions of the kinetic energy, the potential energys, the magnetic field energy in air gap of the flywheel motor and the energy dissipation of the whole system were obtained, and the differential equations set with electromagnetic parameters of FESS was established by applying the extended Lagrange-Maxwell equation. The four-order implicit Runge-Kutta formula to the equations was derived, and the nonlinear algebraic equations were solved by using the Gauss-Newton method. The analytical solution of an example shows that the upper damping coefficient, the lower damping coefficient and the residual magnetic induction of the rare earth permanent magnet play an important role in electromechanical resonance of the flywheel rotor system. There is a small change for the electromechanical coupling resonance frequency with the upper damping coefficient in-creasing, but the resonance amplitude decreases with the upper damping coefficient in-creasing. With the lower damping coefficient increasing, the resonance frequency in-creases, and the resonance amplitude decreases. With the residual magnetic induction of the permanent magnet increasing, the resonance frequency decreases, and the reso-nance amplitude increases.

On robustness of an AMB suspended energy storage flywheel platform under characteristic model based all-coefficient adaptive control laws

A characteristic model based all-coefficient adaptive control law was recently implemented on an experimental test rig for high-speed energy storage flywheels suspended on magnetic bearings. Such a control law is an intelligent control law, as its design does not rely on a pre-established mathematical model of a plant but identifies its characteristic model while the plant is being controlled. Extensive numerical simulations and experimental results indicated that this intelligent control law outperforms a μ-synthesis control law, originally designed when the experimental platform was built in terms of their ability to suppress vibration on the high-speed test rig. We further establish, through an extensive simulation, that this intelligent control law possesses considerable robustness with respect to plant uncertainties, external disturbances, and time delay.

Superconducting Energy Storage Flywheel——An Attractive Technology for Energy Storage

Flywheel energy storage(FES) can have energy fed in the rotational mass of a flywheel,store it as kinetic energy,and release out upon demand.The superconducting energy storage flywheel comprising of magnetic and superconducting bearings is fit for energy storage on account of its high efficiency,long cycle life,wide operating temperature range and so on.According to the high temperature superconducting(HTS) cooling mode,there are zero field cooling(ZFC) bearings and field cooling(FC) bearings.In practice,the superconducting bearings are formed by field-cooled superconductors and permanent magnets(PMs) generally.With respect to the forces between a permanent magnet and a superconductor,there are axial(thrust) bearings and radial(journal) bearings.Accordingly,there are two main types of high-temperature superconducting energy storage flywheels,and if a system comprising both the thrust bearing and the radial bearing will have the characteristics of both types of bearings.Magnetic force,magnetic stiffness and damping are these three main parameters to describe the levitation characteristics.Arrangement and shape of superconductors,thickness of superconductor,superconducting flux creep and critical current density of the superconductor affect the magnetic levitation force of these superconducting bearings.The key factors of FES technology,such as flywheel material,geometry,length and its support system were described,which directly influence the amount of energy storage and flywheel specific energy.All these results presented in this paper indicate that the superconducting energy storage flywheel is an ideal form of energy storage and an attractive technology for energy storage.

Reducing Fuel Consumption Using Flywheel Battery Technology for Rubber Tyred Gantry Cranes in Container Terminals

Flywheel Energy Storage System (FESS) is used as an energy regeneration system to help with reducing peak power requirements on RTG cranes that are used to load or unload container ships. Nevertheless, with the use of FESS, Port Operator can deploy undersized generator for new RTG as this will further reduce fuel consumption. This paper presents the investigation of the amount of energy and fuel consumption that can be reduced in Rubber Tyred Gantry (RTG) cranes in container terminals by the use of simulation. In addition, Variable Speed Generator is integrated to the simulation-hybridized RTG. Simulation results reveal that the total energy saving exceeded 30% relatively to conventional RTG. A hardware-in-loop system is introduced for the purpose of validating the simulation results. The hardware components procured include a FESS, a Variable Frequency Drive (VFD) and brake resistors.

基于FESS的电动汽车快速充电站能量缓冲系统

提出一种基于飞轮储能系统(FESS)的快速充电站能量缓冲系统,一方面利用FESS代替传统电池储能系统(BESS),实现快速充电站可靠功率缓冲;另一方面,利用直流母线电压作为交互介质,提出一种分布式总线信号(DBS)控制方法,摒弃传统集中控制中的通信总线,实现了能量网和信息网的双网融合。首先建立了基于FESS的快速充电站数学模型。其次,分析了DBS控制目标、工作原理及飞轮惯量选取原则。再次,对FESS能量缓冲系统进行小信号稳定性分析。最后,搭建测试样机论证了所提方法的可行性和有效性。

Performance Analysis of the Flywheel Assembly Design Using SolidWorks Modeling and Simulation Capabilities

The flywheel energy storage system (FESS) has been rediscovered a few years ago, it is a rotary system allowing the storage and restoration of kinetic energy which has an inertia wheel. The current paper investigates an assembly design of the flywheel for durable, maintainable and optimal performance. The designed model is based on a geometrical configuration which was already studied in a previous research. Using SolidWorks modelling and simulation capabilities, the model was designed and investigated with different combination of materials. A total of 16 combinations has been tested at high speed and then analyzed in order to optimize the effect of materials on the efficiency of the flywheel and particularly on the specific energy and stress Von-Mises stress. This research shows that a good geometric design of the flywheel and selection of combination of two materials can improve its energy storage capacity. Maximum specific energy of 55,764.538 J/Kg, is observed in the flywheel of combined material which is about 13% higher than flywheel of a single material.

基于NSGA-Ⅱ的飞轮-火电联合二次调频最优负荷分配策略

为了在提升飞轮-火电联合二次调频性能的同时控制调频成本、减少飞轮损耗,面向飞轮-火电联合系统,提出一种考虑自动发电控制(AGC)指令及电网频率偏差的基于多目标遗传算法的负荷分配策略。该策略以电网调频偏差、飞轮-火电出力能量和、飞轮损耗为三层最小化目标,考虑火电机组爬坡率及其负荷备用、飞轮荷电状态及其功率等约束条件,基于改进的非支配排序遗传算法(NSGA-Ⅱ),通过AGC功率指令变化速度及频率偏差动态调整飞轮与火电出力权重系数,以频率偏差及其变化方向调整飞轮虚拟下垂、惯性系数,求解飞轮-火电出力比例、飞轮下垂系数和飞轮惯性系数。结合中国宁夏某电厂飞轮储能系统辅助火电机组调频现场AGC指令等历史数据,在双区域两机系统模型上进行仿真实验,结果表明该负荷分配策略有效地减小了火电二次调频偏差和调节时间,提升了调频性能,同时也有效地控制了系统出力能量及飞轮损耗。

功率型储能技术与应用综述

大规模可再生能源发电并网给电力系统安全稳定运行带来了新的挑战,储能技术是解决这一问题的重要手段。为了满足新型电力系统应用场景的多样化需求,储能技术呈现百花齐放、多元化发展新态势。其中,功率型储能技术具有功率密度高、响应速度快、循环寿命长等优势,在新型电力系统的电力调频、平滑新能源波动、负荷跟踪等领域应用具有重要的应用价值。剖析了电化学电容器、飞轮储能、超导磁储能等功率型储能的技术原理和性能特征,梳理了各类功率型储能技术未来发展规划,总结了功率型储能在新型电力系统的应用技术研究工作,同时列举了目前国内外功率型储能的工程示范应用典型案例。最后针对各类功率型储能未来在电力系统应用面临的挑战进行了分析,提出未来功率型储能技术未来发展方向,旨在为功率型储能技术研究和产业发展提供参考。

飞轮储能系统的计算机处理技术研究

目前能源消费与能源发展下的环保问题是我国能源研究的核心,飞轮储能功率较高且操作技术相对直接不会造成环境污染,是一种较为先进的储能技术。本文综述了飞轮储能系统的核心结构,包括飞轮转子结构以及飞轮轴承结构;同时历数了当前较为先进的针对飞轮储能电机控制的计算机处理控制技术,以期为后续研究提供一定思路。

新型储能技术进展与挑战Ⅱ:物理储能与储热技术

新型储能技术日益成为中国建设新型能源体系和新型电力系统的关键技术,已成为中国经济发展的新动能,将在促进可再生能源消纳、实现能源体系转型、提高能源利用效率、减少环境污染等方面发挥重要作用,相关技术研究也在快速发展。开展了该领域的系列评价性综述工作,分为电化学储能技术、物理储能与储热技术、储能集成与规划3个部分,对各类新型储能技术的应用领域、最新研究进展及局限性等问题进行了全面系统的对比分析,并进一步探讨了储能集成、安全、规划调度等储能系统相关领域面临的挑战及发展趋势。第2部分为物理储能与储热技术,重点对物理储能与储热技术中的压缩空气储能、飞轮储能、重力储能、相变储热、热化学储热和卡诺电池技术与工程的相关成果进行了综合分析与讨论。总体而言,物理储能和储热技术大多具有使用寿命长、安全性高的特点,且在能量转化过程中自身多具有转动惯量,属于电网支撑型的储能技术,可满足从大规模长时储能到高功率快速响应的不同需求。在新兴的物理储能和储热技术中,重力储能和卡诺电池的相关技术显示出良好的发展前景。

飞轮储能辅助火电机组一次调频及其性能评价

为促进太阳能、风能等新能源消纳,进一步拓宽火电储能技术升级和灵活性改造渠道,助力双碳目标和新型电力系统建设,提出增设储能系统辅助火电机组调频以解决火电机组爬坡慢、机组振荡不稳定等问题。基于国内外研究现状,提出机组以及储能系统荷电状态出力控制策略模型,通过Matlab/Simulink搭建两区域电网进行模拟仿真。结果表明,在阶跃扰动下区域1机组耦合1 MW飞轮储能系统后,峰值降至1.93×10^(-3)pu,降低4×10^(-4) pu,占原频率波动率的9.39%,机组实际出力从2.45×10^(-2)pu降至1.61×10^(-2)pu,降低34%。结果表明,在外界相同扰动条件下,采用飞轮储能辅助火电机组调频可有效减小系统频率波动量,减少汽轮机输出功率波动,提升调频性能。