| With the adjustment of China’s energy structure,the proportion of intermittent renewable energy sources such as wind and solar power in the power system has gradually increased.To ensure the well integration of intermittent renewable energy sources with existing power systems,the power grid must have enough energy storage capacity and frequency regulation capability.Then hydropower is more required to play the role of energy regulation in the current multi-energy complementary power system,so the hydro-power generating unit will face an increase in the cumulative operating time under unstable start-stop transition process and partial load,which will lead to accelerated fatigue of unit components,accelerated degradation of overall stability,and affected the remaining life of the unit.Therefore,to ensure the safe and stable operation of hydro-power generating units,it is particularly important and urgent to carry out research on the effect mechanism of hydro-power generating unit stability and its state variation trend tracking assessment model.At present,stability condition monitoring of hydropower generating units has made in-depth progress,but further research is still needed on the effect mechanism of stability and the theory and method of stability state evaluation.This article will start from the three aspects of physical nature,mathematical methods and engineering measures.Based on the analysis and mining of the stability monitoring data of the full operating condition,systematic research is carried out on the construction methods of the stability state samples,the analysis of the stability influence mechanism,and the construction of state evaluation models.The specific research content is as follows:To excavate deeply the hydro-power generating unit condition monitoring data and excavate the useful stability state information contained in it,the typical operating conditions of conventional hydro-power generating units were analyzed,and the concept of ‘full operating condition’ stability samples for hydro-power generating units was proposed.The full operating condition is composed of six typical working conditions that a hydropower unit undergoes in one start-up operation,including the startup speed-up transition process,startup excitation-up transition process,load-up transition process,given load stable operation conditions,load-down transition process and the transition process of reducing the speed,the stability state monitoring samples obtained by the above-mentioned operating condition monitoring constitute a full operating condition stability sample for one startup operation which at a certain water head.Aiming at the differences in the stability under different operating conditions and due to different sources of vibration,the research on the feature extraction and state sample construction of hydro-power generating units under full operating conditions was carried out.The method of mechanical vibration feature extraction and sample construction based on the process of speed-up in starting up,the method of electromagnetic vibration feature extraction and sample construction based on the process of voltage building-up in starting up,and the method of extracting the hydraulic stability characteristics of hydro-power generating units considering the characteristics of operating conditions are proposed,which lay the foundation for the analysis of the effect mechanism and the state evaluation model of stability in the study of this paper.To realize the monitoring and evaluation of the variation trend of the hydro-power generating unit’s mechanical vibration state during previous startups,based on the samples of the mechanical vibration state obtained from the process of speed-up,the distance theory in the data mining and multivariate statistical analysis theory were introduced.Furthermore,an evaluation model for the mechanical vibration state variation trend of the hydro-power generating unit based on the data mining of the change trend of the peak-to-peak value and multivariate frequency order amplitude during the process of speed up is constructed.In the early stage of the hydro power unit start-up,its mechanical vibration state was evaluated from two aspects: the overall energy of vibration at different speeds together with their details in frequency-domain distribution.In engineering practice,based on many stability state monitoring data samples obtained during the actual speed-up process of a hydro power unit after major repair,the analysis and evaluation of the variation trend of its mechanical vibration state were realized,and the validity and applicability of the model were verified.Taking the real-time monitoring and diagnosis of the electromagnetic vibration state of the hydro-power generating unit and engineering practicality as the starting point,based on the electromagnetic vibration state samples obtained during the voltage building-up process in starting-up,the principal component analysis method and cluster analysis method in the data mining were used to construct the monitoring and diagnosis model of the electromagnetic vibration state.The electromagnetic vibration state is evaluated by the combination of whether the principal component statistics of the electromagnetic vibration state samples exceed the control threshold obtained from the analysis of the electromagnetic vibration state healthy samples,and the principal component clustering analysis results of electromagnetic vibration state samples.Moreover,the analysis of the contribution of the characteristic variables to the principal component space is used to diagnose the cause of the abnormal electromagnetic vibration.Based on the model,the abnormal state of electromagnetic vibration after long-term operation of a hydro-power generating unit is identified and diagnosed,which verifies the validity and practicability of the model.In order to systematically study the performance characteristics,propagation behavior,influence mechanism and evaluation method of the draft tube pressure pulsation of the Francis hydro-power generating unit,the research is conducted by taking a 200 MW prototype Francis hydro-power generating unit with a outstanding hydraulic stability problem as the main research object,and two other prototype Francis hydro-power generating units with rated capacities of 55 MW and 600 MW as comparison objects.Based on the experimental results obtained from these three units,the characteristics of time-frequency and occurrence conditions of the draft tube pressure pulsation under part load conditions were analyzed and compared.The propagation behavior of components in draft tube pressure pulsation were identified.The analysis reveals the effect of different components in the draft tube pressure pulsation on the component vibration,shaft oscillation and output swing.Moreover,a method for identifying the synchronous pressure pulsation in the Francis turbine is proposed,and an evaluation index of the effect of the synchronous pressure pulsation on the shaft oscillation is established.Finally,the validity of this indicator is verified based on the actual measured data of the on-site test.Aiming at the current situation that the condition monitoring data of the hydro-power generating unit has not been thoroughly excavated and utilized,and needs of the tracking analysis and real-time evaluation of the stability state of hydro-power generating units in hydropower industry,a system for tracking and analyzing the stability state of hydro-power generating units under full operating conditions has been designed and developed.A sample database for the full operating stability state of the hydropower generating unit was constructed and implemented,which provided data support for the data mining research on the condition monitoring data in this paper.Then,the software for tracking and analysis of the full operating stability state of the hydroelectric generating unit was designed and developed.Therefore,the model and method proposed in this paper were applied in engineering practice,realizing the analysis and mining of the full-operation stability condition monitoring data generated by the long-term operation of hydro-power generating units,and tracking and evaluation of the unit’s stability state,which provides auxiliary decision-making guidance for operation and maintenance of hydropower stations.At the end of the paper,the main research contents of the paper are summarized,and the problems to be researched in this paper are pointed out,together with the further development direcrion of the research work is prospected. |
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