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Aimed at the lack of effective stability evaluation methods for the current steam power system, an operation stability assessment method suitable for single parameter is proposed. This method is a composite method, which first applied the midpoint and regression based empirical mode decomposition (MREMD) and singular value decomposition (SVD) to decompose the time series of operation parameters and extract their hidden trend terms. Then, the components are selected for reconstruction according to the optimal algorithm parameter permutation entropy (OAPPE) of each component. Finally, the auto-regressive integrated moving average (ARIMA ) model commonly used in the non-stationary time series analysis is utilized to predict the trend and the disturbance of parameters, and their distribution characteristics are also extracted in this process, based on which, the probability of instability (PI) of operation parameters at each point on the predicted trend are calculated, and their stabilities are quantitatively evaluated. The actual case proves that this method can effectively assess the operation stability of a single parameter of the steam power system, which has a certain theoretical innovation and engineering application value.

In response to the problems of boiler low water level and pump cavitation caused by the leakage of feedwater unloading pipeline in the process of boiler load raising of the conventional steam power system, the relational model of water-lift, mass flow, revs of booster pump, and each impeller of the feedwater pump are identified by using a differential evolution algorithm based on residual correction. The relational model of mass flow and resistance of feedwater pipelines and valves, the calculational model of working fluid parameters in feedwater system, and the performance degradation model of feedwater unloading control valve are established by using be mechanism modeling method. On this basis, the process of boiler load raising is simulated, and the main parameters of feedwater system are obtained at different feedwater unloading flow rates. It is found that the performance degradation of the control valve of the feedwater unloading pipeline is one of the main causes for boiler water low level and pump cavitation in the process of boiler load raising. In order to further clarify the degradation rule of the performance reliability of the feedwater system with the working time, a simulation method integrating the mathematical model and Monte Carlo random sampling is adopted to the performance reliability simulation of a certain type of marine water supply system in the process of boiler load raising. Thus the whole performance reliability changes of this boiler and the performance reliability life of this feedwater unloading control valve are obtained. The research results reveal the mechanism and degeneration rule of a unique fault of the steam power system, which has certain theoretical and engineering application value.