Research On Frequency Stability Control Strategy Of High-Penetration New Energy Participating In Peak-Shaving Operation Of Power Grid

With the continuous expansion of renewable energy’s integration to power grid,traditional thermal power units are gradually replaced by renewable energy,resulting in poor frequency characteristics of power system against load disturbance under the condition of high penetration of new energy.At present,energy transformation is actively promoted in China,and new energy is transitioning to the main energy.In order to improve the grid connected consumption capacity of new energy,it is necessary for thermal power units to enter the peak shaving operation state.After the flexibility transformation of conventional thermal power units,the frequency regulation performance of units gradually decreases with the reduction of load operating point,which affects the frequency regulation ability of the system.Therefore,in order to maintain the stable operation of the power grid,it is necessary to study the frequency stability in the peak shaving operation of the power system with high permeability of new energy,analyze the frequency response performance of the system under the mode of start-stop peak shaving and deep peak shaving,and formulate the corresponding control strategy.Firstly,this paper analyzes the basic principle and control strategy of AGC system,considers the governor deadband limit and unit climbing rate constraint in the AGC system model,and uses the state space equation to theoretically analyze the influence and difference of thermal power unit on the system model and frequency regulation characteristics under the mode of start-stop peak shaving and deep peak shaving.Then,the simulation results show that with the increase of wind power permeability,the frequency regulation performance of the system become worse gradually under the mode of start-stop peak shaving and deep peak shaving.In addition,under the same wind power permeability,the ability of the power grid to resist load disturbance during deep peak shaving is stronger than that in start-stop peak shaving,which is conducive to the maintenance of frequency stability of the power system.In order to give full play to the frequency modulation potential of new energy during peak shaving operation of power grid,research can be carried out on wind turbines in new energy units.First,at the level of wind turbine,the mathematical model of D-PMSG is established in this paper,and the operation characteristics and basic control principle of D-PMSG are analyzed.Then,the common inertial control strategies of D-PMSG participating in power grid frequency regulation are described.Aiming at the interaction between traditional integrated inertial control and fan MPPT control,an improved integrated inertial control strategy is introduced,and the speed compensation module is added on the basis of traditional inertial control,which helps to reduce the frequency fluctuation during peak shaving operation of the system.By analyzing the response ability of single thermal power unit to frequency difference signal after flexibility transformation,it is concluded that the ability of thermal power unit to resist load disturbance decreases with the decrease of unit operating condition point,which is not conducive to the frequency stability of power system.In addition,in the aspect of parameter optimization of frequency modulation controller,an improved GWO algorithm is proposed to ensure the optimal control effect under different load conditions.In the meantime,combined with the improved fan integrated inertia control strategy,it can effectively improve the frequency regulation effect of power grid peak shaving and solve the problem of frequency stability of power grid during peak shaving operation.