Research On D-STATCOM Control Strategy And Optimization Of Improved Linear Active Disturbance Rejection

The rapid development of national economy has brought many environmental problems,which makes people pay attention to the development and utilization of clean and renewable energy.However,an increasing number of distributed power sources connected to the main grid have caused many problems such as uneven distribution of power flow and power quality.Among them,reactive power compensation and harmonics are the most prominent.Such problems cause serious pollution and damage to the power network.In addition,reactive power loss will affect the stability of the power system.Distribution static synchronous compensator(D-STATCOM)is an advanced dynamic compensation equipment.The application of D-STATCOM is the best technical means to solve the problem of reactive power compensation and harmonic compensation.D-STATCOM can improve the overall power flow distribution by adjusting the phase angle between the DC side output voltage of the bridge rectifier circuit and the distribution network side voltage,and can reduce the problem of system voltage stability caused by insufficient or excess reactive power,to achieve the purpose of dynamic reactive power compensation.Especially the control method of the device is also the focus of research in recent years.According to the characteristics of static synchronous compensator(STATCOM)which is multivariable,nonlinear and strong coupling,this paper studies the linear active disturbance rejection control technology of D-STATCOM system,and proposes a new double closed-loop control strategy based on linear active disturbance rejection.In the second chapter,this paper analyzes the structure of D-STATCOM and establishes the mathematical model.The working principle of D-STATCOM was introduced in detail,the mathematical model in the time domain was established,and the mathematical model of the static synchronous compensator in the two-phase rotating coordinate system was obtained through the Park transformation.Finally,the stability of D-STATCOM is analyzed by using the Routh-Horwitz criterion.In the third chapter,the traditional reactive current detection is improved.Accurate reactive current detection is the solid foundation for realizing fast,error-free and smooth compensation of D-STATCOM,The detection technology based on the improved reactive current theory is studied and the effectiveness of the improvement is verified by simulation.In the fourth chapter,the design and pole assignment of the unified order LADRC are studied,and the disturbance rejection characteristics are proved by using the classical control theory.Based on this,a double closed-loop controller based on the first-order LADRC is designed.Then,an improved LADRC design based on total disturbance deviation control is proposed and applied to the inner current loop and outer voltage loop of D-STATCOM system.The stability and disturbance rejection characteristics of the combined system are analyzed by using classical control theory.Finally,the control performance of the improved LADRC and the traditional LADRC is compared and analyzed by MATLAB/Simulink simulation.The simulation results show that compared with the traditional LADRC,the improved LADRC has more advantages and feasibility in controlling the DC side steady-state voltage waveform,reactive current tracking,grid side current harmonic content and power compensation waveform when the system load changes.