| With the development of China’s economy and the background of flexible power generation,it is significant to implement the national energy conservation plan.In order to better energy saving,efficiency and emission reduction of coal-fired units,a reasonable comprehensive evaluation system of units is of great importance to the development of power enterprises.Through the comprehensive benchmarking evaluation of units,it can better guide the production and operation of power plants and effectively improve the operation level of units.In this study,a reasonable comprehensive benchmarking evaluation method is established to analyze the stability of thermal power unit operation.Firstly,the historical data of important indexes of a 660 MW unit were extracted from the real-time database of the power plant at a sampling frequency of one per minute,and the outliers,missing values and abnormal values in the collected data were pre-processed,and the sliding pane method was used to classify the stable working conditions.Subsequently,based on the process capability index and the coefficient of variation,the stability of the extracted important parameters on the pot side,furnace side and auxiliary side were evaluated to obtain the stability scores of each index at different loads.At high loads,the stability levels of superheated steam temperature and reheated steam temperature were better.with stability scores of 98.74 and 94.62,respectively.The stability level of the first-stage desuperheated water flow is better than that of the second-stage desuperheated water flow,and the stability of the reheater desuperheated water flow is much worse than that of the superheater desuperheated water flow,with the highest stability score of 97.75 points for the first-decrease flow and the highest score of 83 points for the re-decrease flow.Furnace side of the important parameters furnace negative pressure,O2 concentration and the stability of the baffle opening are medium and high load stability level is better,stability scores of 94,96 and 96 points respectively.The mill separator airpowder mixture temperature,mill primary air temperature and mill air-powder ratio on the auxiliary side all have the best stability at high load.Then,based on the stability scores of the important parameters obtained,the Gl-TOPSIS algorithm was applied to comprehensively evaluate the stability of different systems at different loads.Both the superheated steam system and the reheated steam system had the best stability at high loads,with stability scores of 97 or more.The stability score of the combustion system reached 97.73 at high load.In the stability evaluation of the pulverizing system,the overall stability level of#6 mill was in the leading position among the six mills,with a stability score of 96.98.Finally,a comprehensive unit stability benchmarking evaluation was conducted for six coal-fired units under the same group.In the process of stability evaluation of important parameters on pot side and furnace side of different units by using Cpk and Cv,it was found that the steam temperature stability of drum boiler units was better than that of once-through boiler,and the deviation of left and right steam temperature and the difference of desuperheated water opening of units with fourcorner cut circle combustion method were significantly larger than that of units with front and back wall hedge combustion method,and the larger the unit capacity the larger the deviation and the worse the stability of unit parameters.The AHP-TOPSIS unit comprehensive benchmarking method was established to evaluate the six units,and the overall stability level of unit D was the highest level among the evaluated units,while the stability levels of units A and B with millions of units were poor.The overall stability level of unit D was the highest level among the evaluated units,and the stability level of million-unit A and B was poor.The final ranking of the six units’ comprehensive stability level was D>F>E>C>A>B.Based on the large amount of operational data in the database of power plants,the stability evaluation of units of different capacities using the comprehensive benchmarking evaluation method can effectively improve the management level of coal-fired units and reduce the impact of deep peaking of coal-fired units on unit reliability in the context of flexible power generation. |
