As a form of energy storage with high power and efficiency, a flywheel energy storage system performs well in the primary frequency modulation of a power grid. In this study, a three-phase permanent magnet synchronous motor was used as the drive motor of the system, and a simulation study on the control strategy of a flywheel energy storage system was conducted based on the primary frequency modulation of wind power. The speed and current double closed-loop control strategy was used in the system start-up phase, and the power and current double-closed-loop control strategy were used in the power compensation phase. The model reference adaptive control was used to accurately estimate the speed and position of the rotor. The system compensates for the wind power output by using a wind turbine in real-time and conducting simulation experiments to verify the feasibility of the charge and discharge control strategy. At the same time, it can be verified that the flywheel energy storage system has a beneficial effect on wind power frequency modulation.
Converter in EV (electric vehicle) charging-discharging-storage integration station must satisfy the correlation objects. These include: lower harmonic and higher energy conversion efficiency, benefits to battery life, adaption to different batteries, and adjustable charging current. In this paper, we propose a three-stage circuit topology, based on precise charging control, which is able to accomplish these goals on a lithium ion polymer battery pack. It is expected that the converter will also work well on other battery chemistries. In order to use three-stage converter to charge precisely, we need to first design each stage circuit and control strategy. The final strategy can accurately capture the voltage of each DC bus and the charging current of a cell. We also give the analysis of factors affecting battery life and energy conversion efficiency, whereby the three-stage converter is in practice. Comparing with charging simulations of batteries in conventional converter, those in three-stage converter are conducted. Results are presented that that it is possible to achieve more precise charging in integrality of battery charging and extension of battery life than the conventional converter expected in an implementation.
Flywheel energy storage technology has attracted more and more attention in the energy storage industry due to its high energy density, fast charge and discharge speed, long service life, clean and pollution-free characteristics. It is wwidely used in uninterruptible power system, grid frequency modulation, energy recovery and reuse and other fields. With the development of flywheel rotor materials, motors, bearings and control technology, flywheel energy storage technology has been greatly developed. Introducing the basic structure of the flywheel energy storage system in the above three applications. Typical charge-discharge control strategies are given for the three sensor-less algorithms of model reference adaptive control, sliding mode observer andextended Kalman filter, which are suitable for flywheel energy storage devices.
One critical task in wind turbine shaft torsional vibration study involves the modelling of wind turbine and power grid. Focus on the mechanical rotational system of wind turbine, this paper provides three-mass shaft model upon which one wind turbine to infinite bus model can be developed. The model based on small signal stability analysis is used to study the wind turbine shaft torsional vibration. For this reason, this paper concentrates on the union model of stall wind turbine and power grid. The small-signal stability model includes the mechanical system and electrical system. Each of the component-blocks of the wind turbine and power grid is modelled separately so that one can easily expand and modify the model to suit their needs. Then, this is followed by one case study to explain how the small-signal stability model can be used to study wind turbine shaft torsional vibration issues.
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