Research On Optimal Control Of Thermal Power Unit Based On Source-Grid-Load State

With the increasing proportion of new energy sources,the security and stability of the power grid will inevitably be affected.On the power supply side,nuclear power units basically do not participate in peak and frequency regulation,and hydropower units have limited peak and frequency regulation capabilities.Wind power and photovoltaic units are unstable power sources and basically cannot participate in peak and frequency regulation.Thermal power units are the most flexible source to participate in peak and frequency regulation.In addition,water resources and hydropower units in northern China are scarce,which undoubtedly highlights the role of peak and frequency regulation of thermal power units.In the case of sufficient peak and frequency regulation capabilities of thermal power units,the output of thermal power units can be changed to smooth out grid fluctuations and reduce the impact of new energy grid-connected.In the case of insufficient thermal power regulation capacity,the conventional approach is to abandon wind and light,which will undoubtedly cause energy loss and economic loss.In addition,as the grid load becomes more and more abundant,such as the use of electric vehicle charging piles,the grid load will inevitably have more irregular fluctuations,which also exacerbates the instability of the grid.Therefore,for the safe,economic and stable operation of the power grid,thermal power units are required to have sufficient regulation capabilities to provide space for the power grid to accept more new energy sources and grid load fluctuations.In the actual operation process of the unit,because the new energy output and the change of the grid load cannot be known in advance,the unit is often in a state of catching up with the variable load command.This caused the unit to be exhausted to follow the instructions quickly and in time,and the thermal power unit’s frequency regulation ability was insufficient.Based on this,this article firstly analyzes the power system structure,builds a source-grid-load system model,and conducts a study on energy storage participating in the frequency modulation of thermal power units.Then,the new energy output and grid load changes are predicted,and this prediction result is introduced into the thermal power unit control system as feedforward information,and the feedforward predictive control strategy is applied to optimize the control of the thermal power unit to improve the peak and frequency modulation ability of the unit.The research work and conclusion of this paper mainly include:(1)The structure of power system is analyzed.The frequency modulation model of thermal power unit,the output model of wind power unit,the output model of photovoltaic power station,the tie line model and the load frequency model of power grid are constructed.These models are combined to form the source-grid-load systemmodel.The simulation results show that the system can simulate the process of peak and frequency regulation of thermal power units.(2)Using the neural network algorithm to build the wind speed correction model,the output forecasting model of photovoltaic power station and the load forecasting model of power system.Using prediction model to predict the power output of the new energy power station and the load value of the power grid.The simulation results show that the accuracy of the predicted wind speed is relatively high,while the power system load forecast trend is relatively correct but not accurate enough,and the output trend of photovoltaic power plants is correct.(3)Researching on electric energy storage to participate in the frequency modulation of thermal power units.Studying the principle of energy storage participating in primary and secondary frequency modulation control.Researching and calculating the choice of energy storage capacity.The simulation results show that the energy storage system can effectively improve the primary and secondary frequency modulation capabilities of the unit,and the established energy storage cost-benefit model can optimize the selection of energy storage capacity.(4)The predicted power plant AGC command is distributed,and the variable load trend obtained from the distribution is introduced into the thermal power unit control system as feedforward information to modify the AGC command curve of the thermal power unit,and assisted by predictive control to optimize the control of the unit.The simulation results show that the feedforward predictive control strategy of thermal power units can improve the variable load capacity of thermal power units.