Research On Inverter Frequency Regulation Control And Parameter Optimization Of Direct Drive Wind Power Generation System With Energy Storage

Frequency is one of the three major standards of power quality.With the increasing penetration of wind power year by year,wind power generation systems actively participate in power system frequency modulation is an inevitable choice for wind power development.At present,the frequency regulation of wind turbines is mainly concentrated on the frequency regulation of the fan side,but at this time,the wind turbine has been operating under "underpower",and the fan has failed to operate at the maximum power point.In order to achieve the maximum utilization of wind energy resources,based on the direct-drive wind power generation system,this paper combines the energy storage system and the load-side inverter to carry out research on the load-side frequency modulation control of the wind power system.In order to solve the problem of low inertia of the system in the primary frequency modulation response,the virtual synchronous generator(VSG)control simulates the frequency modulation performance of the synchronous motor by introducing the rotor motion equation of the synchronous motor into the inverter.Because VSG control parameters affect system stability,this paper provides a more widely used parameter design method in combination with current parameter design methods.First,establish a small signal mathematical model,observe the influence of control parameters on power frequency characteristics and power loop characteristics,and analyze the causes of power oscillations.Then,the power loop shear frequency is introduced to constrain the control parameters,a parameter design scheme is proposed,and the design effect is analyzed theoretically.Finally,the validity of the parameter design scheme is verified by simulation.Aiming at the problem of frequency overrun in the dynamic process of VSG secondary frequency modulation,an improved control scheme was proposed.This control adds a proportional feedforward channel on the basis of the traditional VSG secondary frequency modulation,which suppresses the frequency overrun in the dynamic process of the secondary frequency modulation.Aiming at the control structure,the influence of control parameters on the dynamic and steady-state performance of the system is analyzed,and a parameter design method is given.The validity of the parameter design scheme is verified by simulation.In view of the different frequency fluctuations in the actual microgrid operation,it is necessary to implement primary frequency control and secondary frequency control for different degrees of fluctuation.In this paper,by designing the stop/start of the frequency double-fed self-recovery control,the smooth switching between the primary frequency modulation mode and the secondary frequency modulation mode is realized.Based on the theoretical analysis and simulation verification,this paper designs an experimental platform for load-side inverters in wind power systems,and introduces the experimental platform from two aspects of hardware and software.Finally,based on the experimental platform,one frequency modulation,two frequency modulation and frequency modulation switching control strategy experiments were carried out respectively.The experimental results were compared with theoretical analysis and simulation results to verify the rationality and effectiveness of the control strategy used in this paper.