Study On Improving Primary Frequency Modulation Accuracy Of Thermal Power Unit

China's rapid economic growth in twentieth Century, the national and industrial demand for electricity is increasing, the use of various precision instruments and machines, so that the quality of power quality is increasingly high. Grid frequency is an important standard to measure the quality of power. The stability of the power grid frequency has become a concern and attention. Primary frequency modulation of thermal power unit plays an important role in ensuring the stability of the grid frequency, so how to improve the control quality of primary frequency modulation is becoming a focus of attention. The change of the grid frequency corresponds to the side of the grid connected power plant means the change of the generator output and the speed of the turbine. Then, the primary frequency modulation control scheme includes two parts: part is through the generator output feedback to control, generator output is through valve to control; the other part is through the speed feedback to control. In the distributed control system(DCS) and digital electro hydraulic control system(DEH), there are power control loops and the speed control loops.After the introduction of the relevant theoretical knowledge of primary frequency modulation and valve management, this paper introduces the primary frequency modulation control scheme of the DCS side and DEH side, and analyzes the advantages and disadvantages of various schemes. Through the analysis of the problems in the primary frequency modulation of the thermal power units in Northwest China, the optimization scheme is summarized. In the actual operation of the power plant, the main problems are found in the DEH side. In view of the problem of the DEH side and primary frequency modulation control scheme, this paper presents the optimization scheme of the speed control loop of the steam turbine from the valve flow characteristics. The optimization of valve flow characteristics is achieved by using the method of field test in power plant. Through the field test, collect the test data and then optimize the flow characteristic curve, get the accurate flow characteristic curve of the valve to write the electric power control system, improve the control level of the steam turbine, and then achieve the purpose of improving the quality of primary frequency modulation. Turbine speed control loop of the optimization is the author proposed a new method, the domestic thermal power units are generally used turbine speed as primary frequency modulation power command status analysis:it is considered that the turbine speed although can accurately represent actual power frequency, but can not be fully representative of grid frequency, on primary frequency modulation function have adverse effects. In this paper, abandon the traditional method of the use of steam turbine speed as the set point, the use of the actual frequency of grid as a set point for a primary frequency modulation. Through the acquisition of the power plant turbine speed and the actual frequency of the grid, using MATLAB simulation software simulation, to verify the feasibility and applicability of the new method and the existing problems and shortcomings of the traditional method, through these two aspects to achieve the purpose of improving the accuracy of primary frequency modulation.