Method for cutting off water side of low-pressure heater to participate in primary frequency modulation loading of unit

Method for cutting off water side of low-pressure heater to participate in primary frequency modulation loading of unit

  • CN 106,368,749 B
  • Filed: 09/14/2016
  • Issued: 04/21/2020
  • Est. Priority Date: 09/14/2016
  • Status: Active Grant
First Claim
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1. A method for cutting off the participation of the water side of a low-pressure heater in the primary frequency modulation loading of a unit is characterized in that the method keeps the economic operation mode of fully opening a high-pressure regulating valve, and when the frequency of a power grid is reduced to a set threshold value, the low-pressure heater is cut off from the water side by closing a water inlet regulating valve of the low-pressure heater, so that the energy storage of steam extraction of the low-pressure heater is released, and the function of primary frequency modulation rapid loading is realized;

  • the method specifically comprises the following steps;

    1) the unit operates according to a high-pressure regulating valve full-open sliding pressure mode, and the low-pressure heater is normally put into operation;

    2) when the frequency of the power grid is reduced to a set threshold value, triggering a command of closing a water inlet throttle of the water side of the low-pressure heater;

    3) simultaneously closing a steam side steam inlet valve and a check valve of the low-pressure heater and opening a water side bypass valve of the low-pressure heater;

    4) correspondingly increasing a main control instruction of the boiler, increasing coal burning, water supply and air quantity of the boiler, and increasing the output of the boiler;

    5) after the water inlet regulating valve of the low-pressure heater is closed, the flow of condensed water of the low-pressure heater is rapidly reduced, so that the steam extraction amount of the low-pressure heater is spontaneously reduced, the working steam amount of a low-pressure cylinder is increased, the load of a unit is rapidly increased, and the function of primary frequency modulation and load addition is realized;

    6) after the frequency of the power grid is recovered, the water inlet regulating valve automatically recovers to the original state to participate in the water level regulation of the hot well and the deaerator;

    in order to ensure the minimum flow of the condensate pump and prevent the condensate pump from tripping at low flow, a condensate pump recirculation regulating valve is opened while a water inlet regulating valve instruction of a low-pressure heater is triggered to be closed;

    for a steam turbine set with sequence valve steam distribution, the method is adopted, when the frequency of a power grid is reduced to a set threshold value, the function of cutting off the water side of a low-pressure heater is triggered to participate in primary frequency modulation, and the function is used as a supplement of the original primary frequency modulation function;

    when the frequency of the power grid is reduced to exceed a set value, the water inlet regulating valve is completely closed, and the low-pressure heater is completely cut off;

    when the frequency of the power grid is reduced to be not more than a set value, the water inlet adjusting door is closed to a set position, and partial cutting of the low-pressure heater is realized;

    the low pressure heater belongs to the backheating system of steam turbine thermodynamic cycle, and the part steam is taken out from the middle and low pressure jar and is heated the condensate water, reduces the cold source loss to improve thermodynamic cycle efficiency, when needs primary modulation loading, utilize low pressure heater backheat system'"'"'s extraction energy storage, close low pressure heater water inlet governing valve, thereby reduce the extraction steam volume that gets into low pressure heater voluntarily, make original extraction steam to low pressure heater get back to the cylinder and continue the acting, thereby increase unit load that can be very fast.

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