The Frequency Regulation Characteristics Of Supercritical Units And Its Application In Wind Power Generation Absorption

The volatility and intermittency of wind power bring great pressure to the frequency modulation of power system,resulting in a more severe wind resource abandonment.In view of the supercritical unit,the mainstream type of thermal power units,this paper analyzes the feasibility of its participation in wind power absorption.In this paper,the mechanism model of the supercritical unit has been established.Based on the model,this paper analyzes in depth the frequency modulation capability of supercritical unit for different time scale wind power fluctuations.Taking into account the frequency modulation cost of supercritical unit,this paper proposes a new control strategy to help the supercritical unit to actively participate in the wind power absorption,and achieves a win-win situation in both the power grid side and the power supply side.Firstly,a supercritical unit model for frequency modulation analysis was established.Based on the idea of coordinated control of the once-through boiler and the condensing steam turbine,and the control method of water-feed following the coal-feed,the model of coordinated controller for supercritical units was established.The influence of matching parameters on the operation characteristics of supercritical units was discussed.Then,the mechanism model of the supercritical unit was established.Through dynamic characteristics simulation,the coupling relationship between the inputs and outputs was discussed.Using step and ramp simulation tests,the reliability of the established model was proved.Furthermore,a two-region frequency modulation power system model including supercritical units and wind power units was established.Secondly,the impact of large-scale wind power integration on the power grid side and the power supply side was evaluated.Based on the established frequency modulation model of the two-region system,the wind power penetration rate when the fluctuation of frequency difference in the region just reaches the maximum allowable value of the power grid was calculated and defined as the maximum penetration rate of wind power.The simulation results showed that when the area was operating at the maximum penetration rate of wind power,the main steam pressure operating parameters of the supercritical unit in the system fluctuated violently and seriously exceeded the allowable operating value,threatening the safe operation of the unit and even the entire system.It is proved that the improvement of wind power permeability will have an adverse effect on the life of the supercritical unit through the calculation of the life of the soda separator and the high temperature superheated joint box.The Mallat wavelet algorithm is used to decompose and reconstruct the measured wind power curve.It wasfound that the minute-level fluctuation component of wind power has greater influence on the grid frequency and the main steam parameters of the supercritical unit than the second-level fluctuation component.Through the analysis of the frequency modulation mode of the supercritical unit,the main means of it to deal with the minute-level fluctuation of wind power was proved to be the secondary frequency modulation.Finally,the control strategy of supercritical units participating in wind power absorption was discussed.On the one hand,the boiler load command was modified by adjusting the steam pressure-boiler ratio coefficient in real time and adding the BIR feed forward signal related to the minute fluctuation signal of the wind power.On the other hand,the steam turbine load command was revised by adjusting the power-turbine ratio coefficient in real time.Through simulation analysis,this strategy not only enhances the unit's stability under high wind power penetration rate,but also enhances the unit's frequency modulation capability,achieving the goal of a win-win in both the power grid side and the.power supply side.