Research On Power Grid Dispatching Method Considering Fast Ramping Characteristics Of Thermal Power Unit

In recent years,large-scale extraordinary random renewable energy,such as wind power,photovoltaic integration in grid brings challenges to the power grid and make a new request to the operating flexibility of coal fired units.However,in the energy structure of China,thermal power generation still occupy a leading position,so improving the fast ramping capabilities of thermal power units is an effective way to solve the problem of large-scale new energy integration.So,how to make use of the fast ramping capabilities of thermal power units scientifically and rationally in the dispatching of power grid,so as to reduce the wind power curtailment condition and improving the utilization of new energy,is of great significance to study.Related research shows,utilizing the internal heat storage of the thermal power unit can effectively improve the fast ramping capacity of the units.But the fast ramping capacity maintenance time is short,usually only about 30 seconds.This paper focuses on the AGC control section of the power dispatching link.The decision time of the AGC control making instruction is about 10 seconds?which can make full use of the fast ramping characteristics caused by heat storage generators.Focusing on the above background issues,this paper uses a mathematical model of AGC control strategy based on optimization theory.The model takes the economic efficiency under electricity market as the goal.Considering the economic and security of power system,the CPS evaluation mechanism of power grid and the regulation characteristics of units,a large mixed integer linear programming model with multiple constraints and variables is constructed.Then,a small test system with actual wind power data is simulated,which validates the validity of the model,and can give instructions to AGC units reasonably and efficiently,which lays the foundation for further research.Based on the above model,this paper presents a multi-objective AGC control model which take into account the fast ramping characteristics of thermal power units.And connecting to the different proportion of wind power in the test system,to simulate the influence to power grid of units on the different ramping rate.The simulation results show that with the increase of-the ramping rate of the units,the output times of the generators is reduced and the power deviation of the tie line are obviously improved.Especially when the proportion of wind power access becomes larger,the effect is more significant.This shows that considering the ramping characteristics of the power units in the AGC control model,is conducive to the safe and stable operation of power systems and wind power consumption.Then the characteristics of the heat storage units are considered further,and a AGC control model of the power system with heat storage units is established.First,the real data is used to model the fast ramping characteristics of the regenerator unit,and the model is a piecewise linear function about the unit output.Then the model is added to the ramp rate constraint of the AGC control strategy model,and a nonlinear constraint is formed.In order to facilitate the solution,a large enough positive number is introduced to linearize the constraint,and the final AGC control model with heat storage units is obtained.Finally,the model is simulated on the test system.The simulation results show that increasing the number of heat storage units in the system can not only improve the regulation performance index of the units themselves,but also stabilize the wind power fluctuation and enhance the safety and stability of the power system.