Wide-Area Damping Control To Restrict Low-Frequency Oscillations For AC/DC Hybrid Interconnected Power System With Time-delay

The grid interconnection makes the grid structure more and more complex,and the dynamic behavior of the power system has also become more and more complex.If the damping is insufficient during the disturbance,it will cause low-frequency oscillation(LFO),which will seriously affect the safe and stable operation of the power system.Based on the wide area measurement system(WAMS),this thesis provides additional damping control for HVDC to suppress inter-area LFOs.The main work is as follows:1.High voltage direct current-based voltage source converter(HVDC-based VSC)use gate-controlled power electronic devices and pulse width modulation(PWM)to control the high level of active power and reactive power controllability.Additional damping control for VSC-HVDC can suppress low-frequency power oscillations,thereby achieving better DC power modulation.The MATLAB simulation results show that using VSC-HVDC additional damping control can improve the transient stability and transmission capacity and suppress low-frequency oscillations(LFO)in the power system.2.Wide-Area Damping Control HVDC(WADC-HVDC)considering time-delay through dynamic output feedback controller(DOFC)is presented to enhance the stability of the interconnected power system.The power system model is linearized and reduced in order,and a wide area damping controller is designed.Based on the Lyapunov stability theory,the LMI sufficient condition for the system to have stability is obtained.The simulation is carried out on an AC/DC hybrid system composed of HVDC and a four-machine two-area system.The influence of time delay on system performance and the relationship between stability and time delay upper bound are analyzed with the proposed method to improve the inter-area low-frequency oscillations.