Theory And Application Of Bypass Damping Filter In Suppressing SSR Of Multi-generator Series-compensated System

With the construction of large-scale thermal power bases and projects,the pattern of bulk power transmitted through series-compensated UHV system will be further strengthened,therefore subsynchronous resonance(SSR)caused by series-compensation may become more prominent.And it shows the characteristics of more affected generators,denser distribution of torsional modes in frequency-domain and more complex system operation conditions.In this context,based on the bypass damping filter(BDF)that has not been fully studied,the thesis studies its theory and application on suppressing SSR of multi-generator series-compensated system.The main content is as follows:1)The theory of BDF in suppressing SSR is studied.The qualitative and quantitive theory of BDF in suppressing SSR is studied,and the analytical relationship of BDF parameters and extremum of electrical damping are deduced.It shows that by using BDF the generator negative electrical damping can be adjusted to avoid shaft inherent torsional modes,so that the torsional interaction and transient torque amplification effect can be suppressed.The parameter tuning method of BDF for single-generator infinite-bus system is proposed,and its effectiveness is verified in IEEE 1st benchmark model.2)The feasibility of BDF in suppressing SSR of multi-generator series-compensated system is studied.The analytical relationship of BDF parameters and extremum frequency of electrical damping of parallel generators are deduced based on equivalent multi-generator system.It shows that generators in parallel condition will have identical extremum frequency of electrical damping,hence the electrical damping of parallel generators can be adjusted as a whole.The feasibility of BDF is verified from two perspectives,namely the existence of BDF parameters and the adaptability of BDF parameters with respect to changes in system operation conditions.The effectiveness of BDF in suppressing SSR of multi-generator is preliminarily verified in IEEE 2nd benchmark.3)A parameter tuning method of BDF in complex multi-generator series-compensated system is proposed.This method aims at improving the overall torsional stability by taking all the torsional modes of the target system into consideration.In engineering practice,this method can be solved by genetic algorithm within controllable computational complexity.The feasibility of the proposed method as well as the effectiveness of BDF in complex system is verified in a twenty-generator series-compensated system derived from the northern part of China.4)A method for judging the stability of induction generator effect of complex multi-generator system is proposed.The induction generator effect of multi-generator system is explained based on the concept of electric network resonance stability.Then a method based on nodal admittance matrix in complex frequency domain is proposed for the overall level stability judgment of induction generator effect.Using the method the dominant resonant region and the key influence components can also be identified.The effectiveness of this method is verified in IEEE SSR 1st benchmark model and a twenty-generator series-compensated system,which shows that the induction generator effect is unlikely to happen if the series-compensation level is appropriate.5)The feasibility of combining BDF and STATCOM to suppress SSR is studied.A control method exclusively for STATCOM to suppress SSR is proposed.The relative advantages and disadvantages of BDF and STATCOM in suppressing SSR is analyzed,and a combined scheme of BDF and STATCOM,which is suitable for engineering practice,is proposed for SSR suppression.The scheme is verified in a twenty-generator system,showing that the combination of BDF and STATCOM is can further accelerate the convergence of shaft torsional oscillation while suppressing transient torque amplification effect.