Research On Coordinated Control Strategy Of STATCOM/BESS Accessing New Energy Grid-Connected System

With the rapid development of new energy,the proportion of new energy in the power grid is increasing.Compared with conventional units,new energy sources such as wind power have obvious volatility and intermittence.Large-scale grid connection will inevitably have a great impact on the safety and stability of power systems,mainly due to the phenomenon of sub-synchronous oscillation(SSO),equivalent moment of inertia,limited voltage regulation and so on,causing a risk of off-network in the case of large fluctuations in frequency and voltage.The new energy consumption capacity of the local power grid is limited,resulting in a serious phenomenon of “abandoning wind and abandoning light”.The combination of FACTS and energy storage expands the operating range,improves performance,makes transmission more flexible,and provides more flexible and diverse power regulation.The static synchronous compensator(STATCOM)is combined with the battery energy storage system(BESS)and uses the current decoupling contr ol method in the rotating coordinate system to achieve independent adjustment of reactive power and active power,thereby expanding the operating range,improving performance,and making the transmission more flexible.(1)To suppress the multi-modal sub-synchronous oscillation problem generated by the wind-thermal power bundled system,a suppression method based on the STATCOM/BESS is proposed.This paper firstly used the eigenvalue analysis to obtain the participation matrix,and according to the particip ation factors exploring the proportion of each STATCOM/BESS control parameters in each oscillation mode.Secondly,using the current decoupling capability of STATCOM/BESS,an improved ADRC damping controller is added to the current inner loop control loop to suppress multi-modal oscillation,and the improved QPSO is used to coordinate and optimize the parameters of the additional damping controller.It can be seen from the time domain simulation that the proposed control strategy can effectively suppress th e SSO problem of the wind-thermal power bundled system,and has the advantages of fast speed and strong adaptability.(2)In order to solve the problem that the wind power grid-connected system lacks sufficient frequency support during frequency fluctuatio n,the virtual synchronous generator(VSG)algorithm is introduced in the wind turbine main control,and STATCOM/BESS is used for the rotation of the wind turbine to enhance the virtual inertia of the system.According to the frequency deviation and freque ncy change rate,the STATCOM/BESS working mode is adjusted to obtain adaptive virtual inertia considering the BESS.Through the analysis of the small signal model of the Wind Turbine-VSG,the setting principle of the virtual inertia is determined,and the reasonable range of BESS capacity allocation is further given and optimized the BESS capacity configuration combined with economic description.The simulation example shows that the proposed method has better effect on frequency support than the droop control and the traditional VSG control,and provides reliable compensation for the fan grid point voltage,which further improves the stability of the system.(3)To solve the frequency fluctuation and voltage rising or dropping caused by the sudden change of load of wind power system,an Intelligent joint optimization control method based on STATCOM/BESS is proposed.The strategy is divided into 3layers in the process.Firstly,in the real-time monitoring layer,the wind speed division and fuzzy control are used to judge the frequency modulation capability,active and reactive power demand.Secondly,in the dynamic decision-making layer,the inertia constant and PCC voltage are comprehensively considered,and combined the fan reactive power adjustable range,dynamically optimize active and reactive power allocation strategies;Finally,in the execution control layer,the wind turbine and STATCOM/BESS execute the power commands.When STATCOM/BESS strengthens the virtual inertia,consider the state of charge of the battery(BESS),and dynamically adjust its working mode based on SOC feedback,and the relevant parameters are fed back in time.By analyzing the simulation results,the method can provide effective support for the frequency,and can provide reliable r eactive power compensation for the fan grid point voltage,effectively improving the system’s frequency and voltage support capability.