Flywheel Energy Storage Unit Research Articles

Hybrid adaptive controlled flywheel energy storage units for transient stability improvement of wind farms

This article introduces a novel hybrid adaptation algorithm comprising both continuous mixed p-norm (CMPN) strategy and the block-sparse Bayesian (BSB) technology to online adapt all the proportional plus integral (PI) controller gains of the power converters of flywheel energy storage units (FESUs). The FESU is based on the doubly fed induction machine (DFIM). The principal target is to improve the transient stability of grid-connected wind farms. To obtain a realistic study, the two-drive train model is utilized in the wind farm modeling affecting the transient analyses. The cascaded control scheme is implemented on controlling both the generator side converter and the grid side inverter of the FESU using the proposed adaptive CMPN-BSB PI controller. The FESU is tied to the point of common coupling of the wind farm, which is tied to the standard IEEE 39 bus system. The performance of the proposed technology is tested under subject the system to different severe faults. The validity of adaptive CMPN-BSB PI controlled FESU is tested by comparing the numerical results with that achieved by least mean square adaptive controlled FESU. The numerical results are performed by PSCAD software. The proposed controlled FESUs will help in improving the transient stability of wind farms and their power quality concerns will be enhanced.

Laboratory-based examination of the effect of rotational inertia on energy recuperation in the regenerative braking process

Dynamic energy recovery in electric and hybrid electric vehicles can assist in restoring kinetic energy during descending and braking operations. The recouped energy can be stored in various storage units, such as a flywheel energy storage (FES) units, ultra-capacitors (UCs) or batteries, thus conserving energy for later use during acceleration condition. The FES is used in a variety of modern applications; for instance, it tends to be associated with the motor shaft to assist in starting the vehicle from rest. Several different components have been utilized to execute the motoring and braking mechanism in a structured test rig. However, there is an urgent need to represent this application within the limits of the laboratory facilities while being able to simulate the natural system. Consequently, this paper will examine the effect of rotating inertia at a different rotating speed in the drive system on propelled energy. It will also evaluate the stored energy in the UC storage unit and the braking time in the regenerative braking (RB) process. Moreover, it will demonstrate the experimental probing and mathematical modeling of the motor/flywheel (lumped into an equivalent inertial mass), which is used in different drive cycle schemes to simulate real system behavior. The analysis is accomplished with experimental verification, highlights the advantage of the new approach for evaluating storage capacity. Also, it gives the static and dynamic (time dependency) equations to show an accurate system representation as a ready-made (black box) models, which will be used to determine the overall system performance.

Charging–Discharging Control Strategy for a Flywheel Array Energy Storage System Based on the Equal Incremental Principle

The widely used flywheel energy storage (FES) system has such advantages as high power density, no environment pollution, a long service life, a wide operating temperature range, and unlimited charging–discharging times. The flywheel array energy storage system (FAESS), which includes the multiple standardized flywheel energy storage unit (FESU), is an effective solution for obtaining large capacity and high-power energy storage. In this paper, the strategy for coordinating and controlling the charging–discharging of the FAESS is studied in depth. Firstly, a deep analysis is conducted on the loss generated during the charging–discharging process of the FESU. The results indicate that the loss is related to the charging–discharging of power. To solve the problems of over-charging, over-discharging, and overcurrent caused by traditional charging–discharging control strategies, this paper proposes a charging–discharging coordination control strategy based on the equal incremental principle (EIP). This strategy aims to minimize the total loss and establish a mathematical model of optimal coordination control with the constraints of total charging–discharging power, rated power limit, over-charging, over-discharging, and overcurrent. Based on the EIP, the optimal distribution scheme of power charging–discharging is determined. Secondly, this paper gives the specific implementation scheme of the optimal coordinated control strategy. Lastly, the charging–discharging coordinated control strategy is verified by examples. The results show that the coordinated control strategy can effectively reduce the loss during the charging–discharging process and can prevent over-charging, over-discharging, and overcurrent of the system. Overall, it has a better control effect than the existing charging–discharging control strategies.

Design of a coordinated control unit for the charge process of a flywheel energy storage unit based on passivity and backstepping methods

Design of a coordinated control unit for the charge process of a flywheel energy storage unit based on passivity and backstepping methods

Analysis of the Peak Load Leveling Mode of a Hybrid Power System with Flywheel Energy Storage in Oil Drilling Rig

The load frequently oscillates in large amplitude like pulses when the draw-works lift or lower in the oil well drilling rig, and that makes the diesel engine run uneconomically. A new solution for the pulse load problem is to add a motor/generator set and a flywheel energy storage (FES) unit to the diesel engine mechanical drive system to form a hybrid power system with energy storage. The storage capacity of the power and energy, and the charging-discharging operation modes are discussed for the first time. The engine power output in frequent fluctuation was measured in the oil well drilling engineering practice. The configuration and the theoretical model of the hybrid power system with energy storage and peak load leveling were established. Furthermore, 1% to 12% saving of fuel is possible for the case of single engine in the load leveling running mode compared to bi-engines in a traditional running mode for the peak load between 900 to 1200 kW and the valley load between 200 to 600 kW. The experimental verification of the load leveling with FES confirmed that the diesel engine worked more smoothly with less smoke emission. In addition, 5% to 10% more fuel was consumed in the load leveling test compared to the traditional running mode with the drive-by 800 kW diesel engine. However, 21% fuel saving was obtained in the load leveling test with the drive-by 400 kW diesel generator.

Research on Ratio Consensus of Flywheel Energy Storage System Based on Hamiltonian Theory

A control strategy based on Hamiltonian energy theory is proposed for the wind farm with flywheel energy storage system (FESS). The control of the ratio consensus of the flywheel energy storage system is realized by adjusting the speed of the flywheel energy storage unit. First, the port-controlled Hamilton (PCH) model of the flywheel energy storage unit is established, and the port-controlled Hamiltonian with dissipation (PCH-D) model is obtained by using the feedback stabilization principle of the PCH system. Then, the problem of the ratio consensus control of the flywheel energy storage system is investigated. In order to realize that all flywheel energy storage units can store and release energy at the same rate, the control strategy of Hamilton energy shaping is applied to adjust the speed of flywheel energy storage units. Finally, the effectiveness of the proposed control strategy is verified by simulations.

Моделирование характеристик спасательного устройства с маховичным накопителем энергии

Моделирование характеристик спасательного устройства с маховичным накопителем энергии

Flywheel Energy Storage Model, Control and Location for Improving Stability: The Chilean Case

A flywheel energy storage (FES) plant model based on permanent magnet machines is proposed for electro-mechanical analysis. The model considers parallel arrays of FES units and describes the dynamics of flywheel motion, dc-link capacitor, and controllers. Both unit and plant-level controllers are considered. A 50-MW FES plant model is tested in the Northern Chile Interconnected System (NCIS) when connected to the Argentinian Interconnected System (AIS). The FES plant provides transient support for primary frequency regulation and its impact on stability is studied using small-signal analysis and time domain simulations. To identify the best location to install the FES plant, eigenvalue sensitivity for the interarea mode is analyzed. The results are validated for different operation scenarios of wind and solar power. By installing the FES plant in the NCIS best location, the damping ratio of the interarea mode is increased from 0.53% to 13.1%. Moreover, the power transfer from the NCIS to the AIS can be augmented from 90 to 180 MW while still keeping the damping ratio above 9%. These findings are promising and may lead to useful planning criteria for energy storage deployment.

Frequency regulation control strategy for PMSG wind‐power generation system with flywheel energy storage unit

To enhance the frequency regulation capability of direct-drive permanent magnet synchronous generator (PMSG)-based wind-power generation system, the frequency regulation control strategy for wind-power system with flywheel energy storage unit (FESU) based on fuzzy proportional plus differential (PD) controller is proposed in this study. According to the mathematical model of PMSG-based wind-power generation system with FESU, the small-signal model of the whole system is deduced in detail. In addition, the eigenvalue loci of the system are investigated to obtain the appropriate ranges of FESU's PD controller parameters for ensuring the system stable operation. Meanwhile, the impact of system equivalent inertia and damping on system frequency stability is analysed. Furthermore, a fuzzy PD controller of FESU is designed to dynamically regulate the system equivalent inertia and damping, leading to improved grid frequency characteristics. Finally, simulation studies on a 2 MW PMSG-based wind-power generation system with 400 kW FESU verify the validity of the proposed control strategy, contributing to enhance the frequency stability of power grid.

Enhanced Control for a Direct-driven Permanent Synchronous Generator Wind-power Generation System with Flywheel Energy Storage Unit Under Unbalanced Grid Fault

—This article presents an enhanced control strategy for a direct-driven permanent synchronous generator based wind-power generation system with a flywheel energy storage unit. The behaviors of the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit under unbalanced grid fault conditions are investigated. Three control targets for the grid-side converter during network unbalance conditions are identified, including eliminating the oscillations in the total active power or reactive power or no negative-sequence current injecting into the grid. Meanwhile, the DC-link voltage oscillations can be effectively suppressed during the unbalanced grid fault by controlling the flywheel energy storage unit. Furthermore, a proportional–integral-resonant controller is designed for the flywheel motor to eliminate the oscillations in the DC-link voltage. Finally, the proposed coordinated control strategy for the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit has been validated by the simulation results of a 1-MW direct-driven permanent magnet synchronous generator wind power generation system with a flywheel energy storage unit under unbalanced grid fault.

Methods for starting an asynchronized flywheel compensator

Known methods for starting a flywheel energy storage unit based on an asynchronized compensator are analyzed, and a new method is proposed. Advantages and disadvantages of the considered methods are discussed.

The Flywheel Energy Storage System: A Conceptual Study, Design, and Applications in Modern Power Systems

While energy storage technologies cannot be considered sources of energy; they provide valuable contributions to enhance the stability, power quality and reliability of the supply. Many storage technologies have been developed in an attempt to store the extra AC power for later use. Among these technologies, the Flywheel Energy Storage (FES) system has emerged as one of the best options. This paper presents a conceptual study and illustrations of FES units. After brief introduction to the FES system and its theory of operation, the paper focuses on the important role of the FES system in enhancing the operation of the distribution network. Supported by illustrated circuits, the paper describes the major role of each part of the FES system in the improvement of the power quality of the network. Then it discusses a newly proposed design of the FES system that emerged recently, which includes the use of Superconducting Magnetic Bearings (SMB) and Permanent Magnetic Bearings (PMB). In conclusion, the paper analyzes the FES systems great potentials that could be exploited in improving the reliability of the electrical system. 

An electromechanical energy-storage unit based on an asynchronized compensator

A methodology for calculating the basic parameters of a flywheel energy-storage unit based on an asynchronized compensator is reported. Basic properties and potential fields of application are considered.

Flywheel array energy storage system

Flywheel energy storage systems (FESS) store energy in a rotating mass. The advantages of such systems includes high power density, environmental friendliness, long lifespan, wide operating temperature range, and very long charge-discharge cycle life. FESS has therefore been widely used in numerous applications. Integrating multiple flywheel energy storage units to form a flywheel array energy storage system (FAESS) provides a mean for large scale energy storage. In this paper, an overview of the current development status and key technologies of FAESS is given. Design method, parallel topology and control strategy of FAESS are then presented. With enhanced control technologies for parallel operation of flywheel energy storage units, FAESS could be used for grid frequency regulation particularly for dealing with intermittent renewable energy generation.

Flywheel Energy Storage Systems for Ride-through Applications in a Facility Microgrid

Flywheel energy storage (FES) has attracted new interest for uninterruptible power supply (UPS) applications in a facility microgrid. Due to technological advancements, the FES has become a promising alternative to traditional battery storage technologies. This paper aims at developing a tool to demonstrate the use of FES units for securing critical loads during a utility outage in a microgrid environment. The FES is modeled, simulated and evaluated in the MATLAB/SIMULINK® environment. A data center is used to represent a facility microgrid case study. It illustrates how an FES can help improve the load serving capability and provide a highly reliable ride-through capability for critical loads during a utility disturbance. In comparison with batteries, the application of FES for power security is new on the horizon. This limits the availability of experimental data. The simulation model presented in this paper will enable the analysis of short-term ride-through applications of FES during an islanded operation of a facility microgrid. As a result, it can provide a guideline for facility engineers in a data center or other types of facility microgrids to better design their backup power systems based on FES technology, which can be used in combination with traditional fuel-based generators.

Losses of flywheel energy storages and joint operation with solar cells

It is possible to achieve stable levitation over a permanent magnet (PM) by using high temperature superconductor (HTS). This way, very low frictional coefficients can be achieved in the order of 10 −6 or even smaller. This very small frictional coefficient makes flywheels with superconducting bearings adaptable as kinetic energy storages with very low losses. A system consisting of an HTS-based levitated flywheel as the energy storage unit and solar cells as the power supply was installed and investigated as a model of a viable variant of the mini power plant concept. A model was also developed to identify the frictional coefficient of such a superconducting bearing from spin-down measurements. As the different loss components have different speed dependence it is possible to separate them, and hence to give an approximation about the heat generated in the superconductor, which is a very important parameter for the design of the cooling system. The model was successfully applied to the flywheel energy storage (FES) unit of the above system.

Magnetic actuators

The subject of magnetic actuators is very broad, and encompasses various technologies, as well as a wide range of magnetic circuit topologies and performance characteristics, for an ever-increasing spectrum of applications in all market sectors. Magnetic actuators can be rotary or linear, and can have continuous or limited motion, the basic classes being moving-coil, moving-iron and moving-magnet. Within these, the airgap length may either remain constant or vary with displacement, and while the majority of such actuators have only one degree-of-freedom, systems are emerging which are capable of providing multiple degrees-of-freedom of controlled motion. In view of the breadth of the subject, the paper focuses on research which is being undertaken in the Electrical Machines and Drives Group at the University of Sheffield on some specific magnetic actuation systems. These include: • Aerospace—electromechanical and electro-hydraulic actuators for flight control surfaces, • Automotive—short-stroke actuators, for applications such as high-speed diesel fuel injector control valves; active and passive magnetic bearing actuation systems for electric vehicle flywheel energy storage units, • Industrial—long stroke linear motors for high-speed packaging and manufacturing applications, • Healthcare—reciprocating linear actuators for resonant electro-mechanical systems, such as positive-displacement diaphragm air-compressors, • Computer—multi-degree-of-freedom spherical actuators for force-feedback joysticks, manipulators etc. As will be highlighted, much of the research involves the application of high-energy rare-earth permanent magnets, which have facilitated the development of new and improved performance magnetic actuators.