Modeling And Control Methods Of Rapid Load Change For Heat Supply Units

In China's power supply structure,heating units occupy a large proportion.Especially in heating season,Heilongjiang,Jilin,Liaoning,the Eest Inner Mongolia,the West Inner Mongolia,Ningxia and other provincial power grid almost entirely rely on heating units to provide the ability of peak regulation and frequency adjustment.The operation mode of "ordering power by heat" of heat supply units,not only limits the peak regulation scope of unit,but also to a large extent limits the unit's ability of response to dynamic load instructions.In fact,on the premise of the lack of hydropower,gas and other units with fast frequency adjustment capability in the northern region,it is particularly important for the power grid security and stability to improve the performance of response to load instruction and primary frequency regulation on the heating condition.Previous study shows that urban heating network has a large energy storage.The rational use of this part of energy storage can greatly improve the unit's ability of response to power load,and would not cause a noticeable impact on thermal users.However,the quantitative analysis of the heating capacity of the heating network,the modeling and characteristics analysis of the heating unit object,the optimization of the control system design need to be further in-depth.Around the above issues,the following work was carried out:(1)The energy storage capacity was calculated quantitatively.Reject the method of calculating the energy storage capacity based on the specific heat of the heat transfer medium.Put forward the method of calculating the energy storage capacity based on the thermal inertia of heat transfer medium,pipeline and heat exchanger.(2)The opening-flow nonlinear characteristic of the key actuators of heating unit was fitted,the key actuators included low pressure cylinder inlet flow control butterfly valve of steam turbine(LV)and heating-extracting flow control butterfly valve of steam turbine(EV).At the same time the gain compensation control logic was designed.(3)The simplified nonlinear dynamic model of the heating unit was improved.The double-in-double-out model of condensing power unit,fuel quantity-steam turbine inlet steam control valve opening-generation load,was improved into six-in-four-out model of heating unit,fuel quantity-steam turbine inlet steam control valve opening-LV opening-EV opening-heating network circulating water flow-heating network circulating water return water temperature to steam turbine front vapor pressure-generating load-heating extraction pressure-heating extraction of steam flow.(4)A coordinated control system of heat supply unit was designed,it can make full use of heat network energy storage and realize high speed variable load.The system can switch bumpless under pure condensing condition and heating condition.The above research results was applied to the rapid load change control system optimization project of LPS thermal power plant No.1 and No.2 units,the actual system had been in a heating season for continuous operation.The power generation load response rate under heating condition was increased from 1% of rated power load per minute to 3%~ 4%,at the same time the fluctuation range of vapor pressure,fuel quantity and temperature was obviously reduced.The work of the paper further consummated the basic theory and engineering technology of the rapid load change control of the heating unit.