Primary frequency modulation control system and method for thermal power units based on safe and stable operation

Abstract

The invention discloses a primary frequency modulation control system and method applied to a thermal power generating unit and based on safe and stable operation. The system comprises a first subtractor module and a high-low limit alarm module, wherein a unit rate limited afterload instruction value and a load measured value are accessed to an input end of the first substractor module respectively, and a difference between the unit rate limited afterload instruction value and the load measured value is sent to the high-low limit alarm module; a high limit exceeding alarm signal and a low limit exceeding alarm signal of the high-low limit alarm module are accessed to set ends of a first switch selector and a second switch selector respectively; the first switch selector and the second switch selector are connected to a block increase end and a block decrease end of a turbine PID controller respectively. According to the system and the method, the priority of primary frequency modulation actions during grid frequency fluctuation can be effectively guaranteed, coordinated operation of AGC (automatic gain control) and primary frequency modulation of the unit can be improved, the frequency fluctuation of a grid system is reduced, and accordingly, safe and effective operation of electrical equipment and power equipment of users is guaranteed.

Description

technical field [0001] The invention relates to the field of frequency modulation and peak regulation of thermal power units, in particular to a thermal power unit primary frequency modulation optimization control system and method based on safe and stable operation. Background technique [0002] With the construction of smart grids such as UHV grid interconnection and new energy grid-connected power generation, the power grid has put forward high requirements for the peak-shaving and frequency-regulating capabilities of thermal power units. , Large-scale thermal power units often operate in a wide load range, generally ranging from 50% to 100% of rated load, and the unit is required to have a fast, accurate and stable response to load changes. At the same time, the relevant management regulations of the State Grid require that the unit should have the ability to respond to changes in the frequency of the grid after the unit is connected to the grid. Since the frequency adj...

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Problems solved by technology

[0007] The above control method can effectively ensure the action effect of the next frequency modulation and AGC in most of the time, but because the frequency modulation is transient and random, there is a long-term small vibration condition of the power grid frequency within a certain period of time, which will cause a The frequency modulation blocks the main control command of the steam turbine for a long time. At this time, the load command increases in the opposite direction. Due to the blocking, the deviation between the load command value received by the steam turbine PID controller and the actual power value continues to increase, such as figure 2 As shown, the line 1 in the figure is the output of the PID controller of the steam turbine, the line 2 is the load command value after the rate limit, the line 3 is the power compensation amount corresponding to the frequency difference, the line 4 is the AGC load command value, and the line 5 is the measured load value. When the primary frequency modulation locking action signal disappears, the load deviation value is released, and the output command of the PID controller of the steam turbine will change greatly, causing severe fluctuations in the main steam pressure, main steam temperature and load of the unit, affecting the safe and stable operation of the unit

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