Coordinated Optimization Of Multi-controller To Improve Low-frequency Oscillation Characteristics Of Wind-pv-thermal-bundled Power Transmission System

The large-scale application of new energy power generation can optimize the energy structure,improve the natural environment,and is of great significance to the realization of "30·60" carbon emission and peak neutrality goal of China.Thanks to the wind-PV-thermalbundled power transmission system,the development of large-scale new energy bases and energy delivery in northeast,north,and northwest China have become more efficient.At the same time,the application of the system has greatly expanded the scope of new energy consumption and can well meet the electricity demand of users in the eastern and central regions.At present,it has become an important way for large-scale new energy bases in China to realize efficient power transportation.However,with the integration of large-scale wind turbines and photovoltaic arrays into the conventional power system,the uncertainty of the new energy turbines will affect the power flow of the system,which in turn will adversely affect the lowfrequency oscillation characteristics of the interconnected system.Therefore,it is necessary to systematically and thoroughly study the low-frequency oscillation characteristics and stability improvement measures of the wind-PV-thermal-bundled power transmission system,and the specific research of this paper is as follows:(1)Aiming at the low-frequency oscillation of the wind-PV-thermal-bundled power transmission system,the mathematical model of the wind-PV-thermal-bundled power transmission system is constructed and a coordinated optimization strategy of the Static Synchronous Compensator(STATCOM)additional Power Oscillation Damping(POD)controller is proposed.The STATCOM-POD controller is firstly constructed by using the transmission power signal of the tie-line as the POD input signal.And by connecting the POD to the AC voltage control part of STATCOM,the STATCOM-POD controller is constructed.The designed STATCOM-POD parameters are globally coordinated and optimized using the Genetic Algorithm(GA)with the minimum damping ratios of all low-frequency oscillation modes of the system as the objective function.Finally,the effectiveness is verified in the IEEE4 machine 2 area system using eigenvalue analysis and dynamic time-domain simulation,and the results show that the proposed parameter coordination optimization strategy can effectively improve the damping characteristics and dynamic stability of the system.(2)To realize the coordinated design of Power System Stabilizer(PSS)and STATCOMPOD in the wind-PV-thermal-bundled power transmission system,an optimization method is proposed based on the hybrid algorithm of Particle Swarm Optimization(PSO)and GA for coordinating the rectification of multi-controller parameters.Firstly,the control principle of PSS is introduced,and a parameter optimization model based on the PSO-GA algorithm is designed according to the parameters to be optimized.The objective function integrates the damping control and voltage control effects of STATCOM-POD and PSS,which is used to maximize the suppression of low-frequency oscillations and ensure the transient voltage stability of the system in the wind-PV-thermal-bundled power transmission system.Finally,the effectiveness of the proposed method is verified by time-domain simulation and eigenvalue analysis of the IEEE 4-machine 2-area system and IEEE 16-machine 5-area system under different operating conditions.(3)To further improve the low-frequency oscillation characteristics of the wind-PVthermal-bundled power transmission system,the influence of the series compensation degree of the Static Synchronous Series Compensator(SSSC)on the damping ratios of the lowfrequency oscillation modes of the system are analyzed.Based on the tie-line transmission power signal,the SSSC-POD controller is designed to enhance the effect of SSSC on system stability.The objective function is constructed by considering the transient voltage stability,the real part of the eigenvalues,and damping level of the low-frequency oscillation modes of the wind-PV-thermal-bundled power transmission system.The coordinated and optimized design of PSS,SSSC-POD,and STATCOM-POD are carried out to improve the low-frequency oscillation characteristics of the system by PSO-GA algorithm and mode analysis theory.Finally,through simulation,the effectiveness of the designed parameter optimization method is verified under various working conditions,including the change in the output of the new energy unit and the change in the transmission power of the tie-line.