| With a large amount of investment in new energy and High-Voltage-DirectCurrent(HVDC)technology,sub-synchronous oscillation(SSO)accidents caused by it and line series repair are becoming more and more prominent,causing huge economic losses.The SSO seriously threatens the stability and safety of power system operation.As an excellent reactive power compensation device,synchronous condenser(SC)can quickly stabilize the system fluctuation and improve the stability of the system.This paper aims at using impedance method to analyze the principle of the synchronous condenser to suppress the system oscillation.In view of the new energy system SSO problem,this paper focuses on the research of the SC on the system SSO accident suppression.It is mainly studied from three aspects of modeling,analysis and simulation,including: 1)Based on the mechanism,the impedance model of each device is established;2)Frequency domain impedance polymerization and impedance analysis of complex new energy systems;3)Application of stability criteria based on frequency domain impedance model and quantitative fitting of accident parameters;4)Factors influencing the inhibition effect of SC.In the aspect of equipment modeling,according to the external performance of each equipment,the incremental equation method is used for the first time to conduct impedance modeling for SC,double-fed induction generator(DFIG)and HVDC system.In the system modeling process,the transmission function of each impedance is connected according to the circuit topology,and the impedance is aggregated according to the circuit principle.This approach achieves the overall modeling of large complex systems.In the aspect of stability analysis,the quantitative analysis method of polymeric impedance is used to analyze the oscillation characteristics of the system,and the RLC second-order circuit is fitted to realize the accurate evaluation of the SSO problem of the system.The method makes full use of the characteristics of impedance in the frequency domain and further deepens the understanding of the mechanism of SSO generation.In the aspect of time domain simulation,the SC inhibition DFIG and the gridconnected system of SC inhibition DFIG and HVDC were respectively established through PSCAD,and the changes of the parameters in the system were observed.The factors that influence SC inhibition effect are studied by using DFIG system. |
