Stability Study Of Pumped Storage Power Station With Different Excitation

With the rapid development of solar power,wind power,nuclear power and other renewable energy in the national grid,pumped storage power station(PSPS)as a kind of very effective regulation of the power supply plays a more and more important role in the whole power system.The pump turbine governing system(PTGS)is the core of the PSPS,and its safety and stability have an important influence on maintaining the safety and stability operation of the PSPS.Previous studies of the PSPS not focused on the all governing system and paid special attentions of PTGS from the angle of nonlinear dynamics.In this paper,the effect of periodic excitation of grid disturbance is analyzed in different area of hydro-turbine governing system which is simpler compared to PTGS.Then,considering the power grid frequency disturbance and the change of load increase or decrease of complex nonlinear characteristics existing in the operation process of PSPS,corresponding model of PTGS were designed.The numerical simulation and the theoretical analysis were presented by using bifurcation diagrams,time waveforms and so on.The main contents and conclusions in this paper are as follows:(1)A fast-slow coupled model of the hydro-turbine governing system(HTGS)was established by introducing frequency disturbance in this paper.Based on the proposed model,bursting oscillations in the HTGS were carried out on two time scales performance,and the effect of periodic excitation of grid disturbance was analyzed by using the bifurcation diagrams,time waveforms and phase portraits.Furthermore,the comparative analysis for the effect of the bursting oscillations on the system with different amplitude of the periodic excitation had been carried out.We found that stability and operational characteristics of the HTGS had changed a lot at two time scales with bursting oscillations.Meanwhile,we got that the effect of the bursting oscillations on the system is becoming stronger with the increase of the periodic excitation and had the bad influence for stability of the HTGS.(2)A model of the PTGS was established by using the method of modular modeling.Considering different operation point corresponding to the operation of the pump turbine in the relatively high,medium and low head,the theoretical calculation and numerical simulation were carried out on the different operation point.Results showed that under different excitation of load increase or decrease,various properties of the pump turbine in the relatively high,medium and low head operation point had has a certain similar change rule,and the stability of the PTGS in a relatively high head operation point was more adverse compared with the relatively low head operation point.The change of load increase or decrease has a great influence on the dynamic behaviors of the system,and the comparative analysis on stability of the PTGS at different excitation of load was made.(3)A stochastic mathematical model of PTGS was established by introducing frequency disturbance with the characteristics of randomness in this paper.The orthogonality of the Laguerre polynomial is used to simplify the stochastic mathematical model of the PTGS to its equivalent deterministic model,and the numerical simulation were carried out to verify the effectiveness of the equivalent deterministic model.Besides the dynamic behaviors of the PTGS of different stochastic intensity with different head and guide vane opening is studied in detail.Results showed that the intensity of random excitation had the bad influence on the stability of PTGS and the head and guide vane opening conditions have an effect of a certain rule on the stability of PTGS.(4)Models of the PTGS with the three different closing laws were established by considering the transient process of outage of pump mode.Furthermore,the dynamic behaviors at the three different closing laws were studied in detail by using bifurcation diagrams,time waveforms.Results showed that the closing laws had a great influence on the stability of PTGS at the transient process of outage of pump mode and the head and guide vane opening conditions have an effect of a certain rule on the stability of PTGS and the optimal guide vane closing law was that guide vane closure rate should be moderate in the first paragraph as guide vane closing law adopts the two-phase closure rule.