Screw Expander Generating Unit Modeling And Its Simulation Applications In Wind Power Compensation

With the enlargement of the wind farm scale, the negative effects of wind power should not be ignored, and the negative effects on power system stability, power quality as well as power dispatch brought by large-scale connection of wind farms with power grid attract more and more attention of the society. Right now, equipped with a certain energy storage capacity is usually used to alleviate the wind power fluctuation. However, now the usual technical means such as flywheel energy storage, pumping energy storage, super capacitor energy storage can’t meet power dispatch demands for smooth output of large-scale wind power. Therefore, this thesis explore to establish a new wind power balance mode, and attempts to apply screw expansion power generation technology to wind power compensation.Screw expander is a type of mechanical equipment pushing screw rotation to achieve energy conversion by fluid’s decompressional expansion in screw groove. Compared with steam turbine, screw expander has the advantage of low cost, strong adaptability, easy maintenance and low speed; these make it become an ideal kind of expander to replace steam turbine. Therefore, in order to explore the enlarged application of screw expansion power generation technology in power system, this paper first finishes mechanism research of screw expansion power generation equipment component parts, including screw expander, generator, thermal storage unit, working medium pump, cooling pond, etc. At the same time, the working principle of screw expander is elaborated; Considering leakage loss and flow loss in screw expander actual expansion process, thermodynamic analysis of this period is finished; This paper, taking water vapor as working fluid, based on the industrial formulation IAPWS-IF1997 for the thermodynamic properties of water and steam which formulated by the international association for the properties of water and steam(IAPWS), accomplishes water vapor thermodynamic properties calculation, and ensures accuracy of working fluid thermodynamic properties. This paper completed analysis of the running characteristic of screw expander, and consider different operation requirements and application environment of system, based on cage asynchronous generator and double-fed induction generator model, establish the simulation model of screw expander generator unit, and explore its operation and power control strategy.At last, Matlab/Simulink is used to be the simulation platform and the application of screw expansion power generation technology in wind power gap compensation is analyzed. Analysis of power compensation unit’s compensation ability is completed, and a combination of wind power prediction and power monitoring are used in power compensation control strategy; Considering optimal power allocation in multi-machine systems, and this paper takes example of cage asynchronous generator unit, establishes wind farm model with screw expansion power generation technology used in wind power gap compensation. Simulation verifies that screw expansion generator units under the condition of ensuring optimum allocation efficiency can effectively track the wind power gap, proves the validity of model and control strategy, and establishes the base of expanding the application of screw expansion power generation technology in wind power compensation under the condition of existing energy storage techniques.