Research On Frequency Modulation Technology Of Ultra Supercritical Coal-fired Plant Coupled Flywheel Energy Storage

With the rapid development of power industry in China,ultra-supercritical coal-fired units have become the main suppliers and participants in energy power industry.In the future development of the power business,it will become the main force of frequency modulation and peak shaving task to ensure the security of the power system.This requires the power supply that undertakes power frequency modulation to have high climbing rate,short response time and fast speed of recovery stability.However,the current ultra-supercritical unit has not had this feature due to its own complex steam water response and fuel response.Therefore,the flywheel energy storage technology with the feature of the power supply above can be combined with the ultra-supercritical coal-fired unit,and build an ultra-supercritical units-flywheel combination system in the power grid frequency modulation.It will greatly enhance the frequency modulation capabilities of ultra-supercritical units,and reduce the power fluctuation of the steam turbine and the pressure fluctuation of the main steam.The study of frequency modulation technology for the flywheel energy storage-combination system will provide a new solution and reliable technology routes for ultra-supercritical units to participate in power system frequency modulation.This paper discusses bottleneck problems in the development of thermal power unit frequency modulation represented by ultra-supercritical units,as well as the research status and practical application of flywheel energy storage technology.Based on the power frequency change mechanism of the power supply side and the user side when the thermal power unit participates in the power system frequency modulation,the basic composition of the frequency modulation process and the control system are studied.Similar to the simulation modeling mechanism of the subcritical unit,the main heat exchange surface of the boiler is segmented and the physical parameter is assumed,and the calculation ideas and methods for the relevant parameters of the heating surface of the ultra-supercritical boiler model are proposed,and the modular modeling of the ultra-supercritical coal-fired unit is completed.At the same time,a flywheel energy storage equivalent control model is established,and a power-storage combination load distribution system based on flywheel priority dispatch under the state of charge constraint is proposed.Use MATLAB/Simulink to build a simulation model,and simulation tests and analysis on the secondary frequency modulation process involved in the power-storage system in the interconnected regional power grid.The study found that the intervention of the flywheel energy storage system greatly reduced the output fluctuation of steam turbine in the units and the frequency change peak value of the power system.Taking into account that the energy storage system is in the charging/discharging state for a long time in the flywheel priority dispatch mode,and it is very easy to overcharge and over-discharge,which will cause the energy storage system to fail.For this reason,on the basis of the original control system,a load distribution module that flywheel can be cut out is designed,and a simulation model is established for simulation test verification.Research shows that the load distribution module based on time-sharing control can realize the orderly cut-out function of the flywheel in the process of power frequency modulation while only causing small thermal power output fluctuations.