CN114484582A - Automatic control system of central heating heat exchange station and design method thereof - Google Patents
Automatic control system of central heating heat exchange station and design method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of heat exchange station control systems, and particularly relates to an automatic control system of a central heating heat exchange station and a design method thereof, wherein the system consists of a primary heating network circulating system, a secondary heating network circulating system, a data acquisition processing module and an automatic control module; the design method comprises the steps of collecting and analyzing analog quantity parameters such as meteorological parameters, fluid pressure, fluid temperature and the like in weather forecast in real time, realizing automatic switching of feedforward-feedback control quantity regulation and feedback control quality regulation of the secondary side heat network through a change-over switch according to weather condition changes, realizing automatic control of constant temperature difference of supply water and return water of the secondary side heat network of the heat exchange station through a PID (proportion integration differentiation) controller, keeping the heat supply quantity matched with the heat supply heat load, ensuring the heat balance of the heat network, and realizing economical and reliable operation of the heat exchange station.
Description
Technical Field
The invention belongs to the technical field of heat exchange station control systems, and particularly relates to an automatic control system of a central heating heat exchange station and a design method thereof.
Background
The heat exchange station is a hub and a core of a central heating system and is a bridge and a link for connecting a heat source and a heat user. The heat exchange station control system has the main task of timely adjusting the running state of the heat exchange station according to the change condition of the heat load, meeting the heat utilization requirement of a user and ensuring that the indoor temperature of the heat user is kept within a certain range.
In order to make up for a series of heating quality problems such as local overheating, local non-heating, vertical heating power imbalance and the like in a heating area caused by hydraulic imbalance, a heat exchange station usually adopts a large-flow small-temperature-difference operation mode, so that a heating system is low in efficiency and high in heating energy consumption. At present, a heat exchange station is basically provided with an automatic control system, but most of the heat exchange stations still rely on experience of operators to manually set various adjusting parameters, and when temperature fluctuation is variable due to abnormal climate change, the phenomenon that the heating load is not matched with the demand of a heat user still exists widely.
Therefore, on the premise of ensuring the comfort of heat users, the operation of the heat exchange station is scientifically and reasonably regulated and controlled, the heat supply efficiency can be effectively improved, the energy consumption of a heat supply system is reduced, the energy waste is reduced, and the heat exchange station has great economic value and social benefit.
Disclosure of Invention
The invention provides an automatic control system of a central heating heat exchange station, which comprises a heat supply network primary side circulating system, a heat supply network secondary side circulating system, a data acquisition and processing module and an automatic control module; the data acquisition processing module consists of an air temperature and flow conversion unit and 2 subtracters; the automatic control module consists of a subtracter, an adder, a change-over switch and 2 PID controllers.
In the heat supply network primary side circulating system, high-temperature hot water provided by a heat source is conveyed to the heat exchange station through a heat supply network primary side water supply pipeline, and an electric regulating valve is arranged on the heat supply network primary side water supply pipeline and can change the flow of the high-temperature hot water in the heat supply network primary side water supply pipeline; in the heat exchange station, high-temperature hot water conveyed by a primary side water supply pipeline of the heat supply network enters the plate type heat exchanger and exchanges heat with circulating water at a secondary side of the heat supply network in the plate type heat exchanger, and cooled primary side return water of the heat supply network returns to a heat source through a primary side circulating water pump arranged on a primary side return water pipeline of the heat supply network.
The heat supply network secondary side circulating system is characterized in that after the heat supply network secondary side circulating water absorbs heat in the plate type heat exchanger, the heat is transmitted to a heat user through a heat supply network secondary side water supply pipeline from an outlet of the plate type heat exchanger, and a temperature sensor and a pressure sensor are arranged on the heat supply network secondary side water supply pipeline and used for measuring the temperature and the pressure of the circulating water in the water supply pipeline; the cooled backwater returns to the plate heat exchanger through a secondary side circulating water pump arranged on a secondary side backwater pipeline of the heat supply network, and a temperature sensor and a pressure sensor are arranged on the secondary side backwater pipeline of the heat supply network and used for measuring the temperature and the pressure of the circulating water in the secondary side backwater pipeline of the heat supply network.
The data acquisition and processing module is used for acquiring temperature and pressure signals of water supply and return water on the secondary side of the heat supply network in real time and acquiring outdoor atmospheric temperature and air speed information from weather forecast through connecting the Internet; temperature sensors on a water supply pipeline and a water return pipeline on the secondary side of the heat supply network are connected to a first subtracter to obtain a temperature difference signal delta t of supply and return water on the secondary side; pressure sensors on a water supply pipeline and a water return pipeline on the secondary side of the heat supply network are connected to a second subtracter to obtain a differential pressure signal delta p of supply and return water on the secondary side; outdoor atmospheric temperature and wind speed information are connected to the air temperature and flow conversion unit, and the flow of a secondary side circulation loop of a heat supply network required by meeting the heat supply load of a heat user is obtained and used as the regulating quantity of a feedforward loop for regulating and controlling the system quantity of the heat exchange station; the outputs OUT1, OUT2, and OUT3 of the data acquisition and processing modules are connected to the automation control modules IN1, IN2, and IN3, respectively.
The automatic control module is connected with a third subtracter together with a secondary side water supply and return temperature difference signal delta t output by the data acquisition module and a secondary side water supply and return temperature difference set value of the heat supply network to obtain an automatic control feedback deviation signal Error; a secondary side water supply and return pressure difference signal delta p output by the data acquisition module is connected to a change-over switch, when the secondary side water supply and return pressure difference signal delta p is within a normal value range, the output end OUT4 of the change-over switch is connected with the input end of a first PID controller, the output of the first PID controller is connected to a frequency converter, the output of the frequency converter is connected with a secondary side circulating water pump, and the quantity regulation control of a heat exchange station system is realized; when the secondary side water supply and return pressure difference signal delta p reaches the upper limit value or the lower limit value, the output end OUT5 of the change-over switch is connected with the input end of the second PID controller, and the output end of the second PID controller is connected to the heat supply network primary side electric regulating valve, so that the quality regulation control of the heat exchange station system is realized.
The invention provides a design method of an automatic control system of a central heating heat exchange station, which collects analog quantity parameters such as meteorological parameters, fluid pressure, fluid temperature and the like in weather forecast in real time, realizes automatic switching of feedforward-feedback quantity regulation control and feedback quality regulation control of a heat supply network secondary side through a change-over switch after analyzing and processing the analog quantity parameters collected in real time, and realizes automatic control of constant temperature difference of water supply and return of the heat supply network secondary side of the heat exchange station through a PID controller, and comprises the following specific steps:
quantity regulation control of a heat exchange station system
1. Feed forward control
Because the heat supply heat source, the heat supply pipe network and the building have great thermal inertia, the influence of the change of the heat supply parameters such as meteorological parameters, water supply temperature, water supply flow and the like on the room temperature of a heat user has long lag time, and in order to ensure the design requirement of the room temperature of the heat user, the operation of the heat supply pipe network is regulated by considering pre-regulation, namely, the change of a regulation scheme has a reasonable time difference relative to the change of the room temperature, the heat supply load is predicted according to meteorological forecast information, the operation working condition of a heat exchange station is regulated timely and reasonably, the system optimization scheduling is realized, the lag time of the heat supply pipe network is reduced, the heating quality is ensured, and the purposes of energy conservation and environmental protection are achieved.
Weather parameters are the basis for designing and adjusting the whole central heating system, main weather parameters influencing the heat load of a building and the operation adjusting strategy of the heating system comprise outdoor atmospheric temperature, wind speed and the like, the forecasting accuracy is steadily improved along with the continuous development of weather forecasting technology, weather forecasting information service based on the internet technology is gradually improved, and the outdoor atmospheric temperature is corrected by adopting the wind speed information in weather forecasting to obtain outdoor comprehensive temperature
tw＝35.74+0.6215×t-35.75×v0.16+0.4275×t×v0.16 (1)
Wherein, twIs outdoor comprehensive temperature in unit; t is the atmospheric temperature in weather forecast, in units; v is the wind power level in weather forecast, in m/s.
Under stable conditions, the heat supply delivered by the heat exchange station is equal to the heating heat load of the heat user
cG(tg-th)＝qvV(tn-tw) (2)
Wherein c is the specific heat capacity of hot water, and the unit J/(kg DEG C); g is the heat supply network secondary side circulation flow, unit kg/s; t is tgSupplying water temperature to the secondary side of the heat supply network in unit; t is thThe temperature of the return water at the secondary side of the heat supply network is unit ℃; q. q.svIs the heating volume of the building and has the unit of W/m3The temperature is controlled; v is the external volume of the building, unit m3；tnThe temperature was calculated in units of degrees celsius for the heating room in winter.
Under the condition of constant temperature difference of supply and return water at the secondary side of the heat supply network, i.e. (t)g-th) Remains unchanged when the outdoor comprehensive temperature t iswWhen the heat supply load is changed, the heat supply load and the heat load are balanced, and only the secondary side circulation flow G of the heat supply network needs to be adjusted, namely, the flow regulation method of the secondary side circulation water pump is changed through frequency conversion regulation to realize energy conservation.
The change relation between meteorological parameters and the secondary side circulating water pump flow can be obtained through the formulas (1) and (2), outdoor atmospheric temperature and air speed information IN weather forecast is connected to the data acquisition processing module, the outdoor atmospheric temperature and the air speed information are converted by the air temperature and flow conversion unit, the outdoor atmospheric temperature and the air speed information are connected to the automatic control module IN1 through the output end OUT1 of the data acquisition processing module, the outdoor atmospheric temperature and the air speed information are connected to the frequency converter through the output end OUT6 of the automatic control module and serve as feedforward control IN a secondary side circulating water pump control loop to adjust the output frequency of the frequency converter, and further the circulating flow of the secondary side of a heat supply network is changed; the secondary side of the heat supply network is adjusted in advance through meteorological parameters in weather forecast, so that the comfort of the indoor environment of a heat user caused by the lagging performance of a heat supply system can be effectively reduced.
2. Feedback control
When weather forecast information is inconsistent with actual meteorological parameters, through the coarse adjustment of feedforward control, the temperature difference of supply return water of the secondary side of the heat supply network changes, and the temperature difference set value of the supply return water produces deviation Error, the deviation Error is connected to the input end of the first PID controller through the change-over switch, after the operation of proportion P, integral I and differential D, the output of the first PID controller passes through the adder, and is connected to the frequency converter through the output end OUT6 of the automatic control module, the output frequency of the frequency converter is changed, and then the circulating flow of the secondary side of the heat supply network is adjusted, the deviation Error is eliminated, and finally the temperature difference of the supply return water of the secondary side of the heat supply network is equal to the set value.
When the working condition of the primary side of the heat supply network changes or is disturbed, the water supply temperature of the primary side of the heat supply network changes, the water supply temperature of the secondary side of the heat supply network also changes, and then the water supply and return temperature difference of the secondary side of the heat supply network changes, the deviation Error generated by the water supply and return temperature difference and the set value of the secondary side of the heat supply network enters the first PID controller through the change-over switch, the proportion P is passed, the integral I is passed, the differential D is operated, the output of the first PID controller is passed through the adder, the output end OUT6 of the automatic control module is connected to the frequency converter, the output frequency of the frequency converter is changed, the flow of the circulating water pump of the secondary side of the heat supply network is changed, after the adjustment is stable, the deviation Error is eliminated, and the water supply and return temperature difference of the secondary side of the heat supply network keeps consistent with the set value.
Quality control of heat exchange station system
In the initial cold period or the final cold period, when the outdoor temperature is higher, the circulation flow of the secondary side of the heat supply network is smaller, and in order to ensure that the phenomenon of the thermal imbalance of the indoor heating system does not occur, when the pressure difference of the water supply and return pipeline of the secondary side of the heat supply network reaches a lower limit set value, the secondary side circulation water pump keeps a certain rotating speed, the action of the switch is switched, the regulating object of the automatic control system of the heat exchange station is changed into an electric regulating valve on the water supply pipeline of the primary side of the heat supply network by the secondary side circulation water pump, the automatic control of the system of the heat exchange station is converted into quality regulation by quantity regulation, the deviation Error between the temperature difference measured value of the water supply and return pipeline of the secondary side of the heat supply network is connected to a second PID controller by a switching switch output end OUT5, after the calculation of proportion P, integral I and differential D, the output end of the second PID controller is connected to the electric regulating valve of the water supply pipeline of the primary side of the heat supply network, reduce the heat supply network and once a side electric regulating valve aperture, reduce the heat supply network and once a side supply channel flow, and then reduce heat supply network secondary side water supply temperature, guarantee the heat supply load that the heat transfer station carried and the heating heat load's of heat consumer balance.
In severe cold period, when outdoor temperature is lower, a secondary side circulating water pump reaches rated rotating speed, the pressure difference of a secondary side water supply and return pipeline of a heat supply network reaches an upper limit set value, the actual measured value of the temperature difference of the water supply and return is still lower than the set value, the heat supply quantity conveyed by a heat exchange station cannot meet the heating heat load of a heat user, a switch is switched to act, the regulating object of an automatic control system of the heat exchange station is changed into an electric regulating valve on a primary side water supply pipeline of the heat supply network by the secondary side circulating water pump, the automatic control of the system of the heat exchange station is converted into quality regulation by quantity regulation, the deviation Error between the measured value of the temperature difference of the secondary side water supply and return pipeline of the heat supply network and return and the set value of the temperature difference of the secondary side water supply and return pipeline of the heat network is connected to a second PID controller by a switching switch output end OUT5, after the calculation of proportion P, integral I and differential D, the output end of the second PID controller is connected to the electric regulating valve of the primary side water supply pipeline of the heat supply network, increase heat supply network once inclines electric control valve opening, and increase heat supply network once inclines supply pipe flow, and then improves heat supply network secondary side water supply temperature, guarantees the heat supply load that the heat transfer station carried and the balance of hot user's heating heat load.
The automatic control system of the heat exchange station adopts a feedforward-feedback control method to keep the heat supply load matched with the heating heat load, ensures the thermal balance of a heat supply network and realizes the economical and reliable operation of the heat exchange station. Due to the adoption of the technical scheme, the invention has the following advantages: 1. the heat exchange station system runs at a constant temperature difference of supply and return water, and the flow of the heat supply system is adjusted by a variable-frequency circulating water pump to achieve the purpose of energy conservation; 2. the weather forecast information is used as feedforward control to pre-adjust a heat supply system of the heat exchange station, so that the heat supply amount is adjusted in advance, and the influence of large inertia and large lag of the heat supply system on the comfort of a heat user is reduced; 3. the feedback control is adopted to realize the constant temperature difference operation of the supply water and the return water of the secondary side of the heat supply network, thereby improving the heat supply efficiency and reducing the energy waste; 4. under the extreme weather condition, in order to ensure the heating quality of a heat user, the automatic control system of the heat exchange station is switched from the quantity regulation control mode to the quality regulation control mode according to the pressure difference of supply water and return water, and resources are reasonably utilized.
Drawings
FIG. 1 is a schematic diagram of a control system of a heat exchange station;
FIG. 2 is a partial schematic view of a data acquisition processing module;
FIG. 3 is a partial schematic view of an automated control module;
fig. 4 is a block diagram of the automatic control operation of the heat exchange station.
Detailed Description
The invention provides an automatic control system of a central heating heat exchange station, as shown in figure 1, the control system consists of a heat supply network primary side circulating system, a heat supply network secondary side circulating system, a data acquisition processing module and an automatic control module; the data acquisition processing module consists of an air temperature and flow conversion unit and 2 subtracters; the automatic control module consists of a subtracter, an adder, a change-over switch and 2 PID controllers.
In the heat supply network primary side circulating system, high-temperature hot water provided by a heat source is conveyed to the heat exchange station through a heat supply network primary side water supply pipeline, and an electric regulating valve is arranged on the heat supply network primary side water supply pipeline and can change the flow of the high-temperature hot water in the heat supply network primary side water supply pipeline; in the heat exchange station, high-temperature hot water conveyed by a primary side water supply pipeline of the heat supply network enters the plate type heat exchanger and exchanges heat with circulating water at a secondary side of the heat supply network in the plate type heat exchanger, and cooled primary side return water of the heat supply network returns to a heat source through a primary side circulating water pump arranged on a primary side return water pipeline of the heat supply network.
The heat supply network secondary side circulating system is characterized in that after the heat supply network secondary side circulating water absorbs heat in the plate type heat exchanger, the heat is transmitted to a heat user through a heat supply network secondary side water supply pipeline from an outlet of the plate type heat exchanger, and a temperature sensor and a pressure sensor are arranged on the heat supply network secondary side water supply pipeline and used for measuring the temperature and the pressure of the circulating water in the water supply pipeline; the cooled backwater returns to the plate heat exchanger through a secondary side circulating water pump arranged on a secondary side backwater pipeline of the heat supply network, and a temperature sensor and a pressure sensor are arranged on the secondary side backwater pipeline of the heat supply network and used for measuring the temperature and the pressure of the circulating water in the secondary side backwater pipeline of the heat supply network.
The data acquisition and processing module is used for acquiring temperature and pressure signals of secondary side water supply and return water of a heat supply network in real time and acquiring outdoor atmospheric temperature and air speed information from weather forecast through connecting the internet as shown in figure 2; temperature sensors on a water supply pipeline and a water return pipeline on the secondary side of the heat supply network are connected with a first subtracter, and the output end of the first subtracter is connected with the output end OUT1 of the data acquisition processing module; and pressure sensors on a water supply pipeline and a water return pipeline on the secondary side of the heat supply network are connected with a second subtracter, and the output end of the second subtracter is connected with the output end OUT2 of the data acquisition processing module. The outdoor atmospheric temperature and wind speed information is connected with the input end of the air temperature and flow conversion unit, and the output end of the air temperature and flow conversion unit is connected with the output end OUT3 of the data acquisition and processing module.
As shown IN fig. 3, the output end OUT1 of the data acquisition module of the automatic control module is connected with the input end IN1 of the automatic control module, the output end OUT2 of the data acquisition module is connected with the input end IN2 of the automatic control module, and the output end OUT3 of the data acquisition module is connected with the input end IN3 of the automatic control module; the input end IN1 of the automatic control module and a temperature difference set value of supply and return water on the secondary side of the heat supply network are connected to a third subtracter; the output end of the third subtracter and the input end IN2 of the automatic control module are connected together to a change-over switch, the output end OUT4 of the change-over switch is connected with the input end of the first PID controller, the output end of the first PID controller and the input end IN3 of the automatic control module are connected together to an adder, the output end of the adder is connected to the output end OUT6 of the automatic control module, the output end OUT6 of the automatic control module is connected to a frequency converter, and the output of the frequency converter is connected with the secondary side circulating water pump; the output end OUT5 of the change-over switch is connected with the input end of the second PID controller, and the output end of the second PID controller is connected with the output end OUT7 of the automatic control module; the output end OUT7 of the automatic control module is connected with the primary electricity measuring electric regulating valve.
The invention provides a design method of an automatic control system of a central heating heat exchange station, which is characterized in that analog quantity parameters such as meteorological parameters, fluid pressure, fluid temperature and the like in weather forecast are collected in real time, after the analog quantity parameters collected in real time are analyzed and processed, the automatic switching of the feedforward-feedback control quantity regulation and the feedback control quality regulation of the secondary side of a heat supply network and the secondary side of the heat exchange station is realized through a change-over switch, and the automatic control of the constant temperature difference of the water supply and return of the secondary side of the heat supply network of the heat exchange station is realized through a PID controller, and the design method specifically comprises the following steps:
quantity control of a heat exchange station system
1. Feed forward control
Because the heat supply heat source, the heat supply pipe network and the building have great thermal inertia, the influence of the change of the heat supply parameters such as meteorological parameters, water supply temperature, water supply flow and the like on the room temperature of a heat user has long lag time, and in order to ensure the design requirement of the room temperature of the heat user, the operation of the heat supply pipe network is regulated by considering pre-regulation, namely, the change of a regulation scheme has a reasonable time difference relative to the change of the room temperature, the heat supply load is predicted according to meteorological forecast information, the operation working condition of a heat exchange station is regulated timely and reasonably, the system optimization scheduling is realized, the lag time of the heat supply pipe network is reduced, the heating quality is ensured, and the purposes of energy conservation and environmental protection are achieved.
Weather parameters are the basis for designing and adjusting the whole central heating system, main weather parameters influencing the heat load of a building and the operation adjusting strategy of the heating system comprise outdoor atmospheric temperature, wind speed and the like, the forecasting accuracy is steadily improved along with the continuous development of weather forecasting technology, weather forecasting information service based on the internet technology is gradually improved, and the outdoor atmospheric temperature is corrected by adopting the wind speed information in weather forecasting to obtain outdoor comprehensive temperature
tw＝35.74+0.6215×t-35.75×v0.16+0.4275×t×v0.16 (1)
Wherein, twIs outdoor comprehensive temperature in unit; t is the atmospheric temperature in weather forecast, in units; v is the wind power level in weather forecast, in m/s.
Under stable condition, the heat supply quantity delivered by the heat exchange station is equal to the heating heat load of the heat user
cG(tg-th)＝qvV(tn-tw) (2)
Wherein c is the specific heat capacity of hot water, and the unit J/(kg DEG C); g is the heat supply network secondary side circulation flow, unit kg/s; t is tgSupplying water temperature to the secondary side of the heat supply network in unit; t is thThe temperature of the return water at the secondary side of the heat supply network is unit ℃; q. q.svIs the heating volume of the building and has the unit of W/m3The temperature is controlled; v is the external volume of the building, unit m3；tnThe temperature was calculated in units of degrees celsius for the heating room in winter.
Under the condition of constant temperature difference of supply and return water at the secondary side of the heat supply network, i.e. (t)g-th) Remains unchanged when the outdoor comprehensive temperature t iswWhen the heat supply quantity and the heat load are balanced, and only the secondary side circulation flow G of the heat supply network needs to be adjusted, namely, the flow regulation method of the secondary side circulation water pump is changed through frequency conversion regulation to realize energy conservation.
The change relation between meteorological parameters and the secondary side circulating water pump flow can be obtained through the formulas (1) and (2), outdoor atmospheric temperature and air speed information IN weather forecast is connected to the data acquisition processing module, the outdoor atmospheric temperature and the air speed information are converted by the air temperature and flow conversion unit, the outdoor atmospheric temperature and the air speed information are connected to the automatic control module IN1 through the output end OUT1 of the data acquisition processing module, the outdoor atmospheric temperature and the air speed information are connected to the frequency converter through the output end OUT6 of the automatic control module and serve as feedforward control IN a secondary side circulating water pump control loop to adjust the output frequency of the frequency converter, and further the circulating flow of the secondary side of a heat supply network is changed; the secondary side of the heat supply network is adjusted in advance through meteorological parameters in weather forecast, so that the comfort of the indoor environment of a heat user caused by the lagging performance of a heat supply system can be effectively reduced.
2. Feedback control
When weather forecast information is inconsistent with actual meteorological parameters, coarse adjustment through feedforward control is carried OUT, the temperature difference of supply return water of the secondary side of the heat supply network is changed, deviation Error is generated by the temperature difference set value of the supply return water, the deviation Error is connected to the input end of a change-over switch, the output end OUT4 of the change-over switch is connected to the input end of a first PID controller, after proportional P, integral I and differential D operation, the output of the first PID controller passes through an adder, the output end OUT6 of an automatic control module is connected to a frequency converter, the output frequency of the frequency converter is changed, the circulating flow of the secondary side of the heat supply network is adjusted, the deviation Error is eliminated, and finally the temperature difference of the supply return water of the secondary side of the heat supply network is equal to the set value.
When the working condition of heat supply network primary side changes or when disturbing, heat supply network primary side water supply temperature changes, heat supply network secondary side water supply temperature changes equally, and then lead to the heat supply network secondary side to supply the return water difference in temperature to change, the deviation Error that the heat supply network secondary side supplies the return water difference in temperature and the setting value to produce is connected to the change over switch input, change over switch output OUT4 is connected to the input to first PID controller, through proportion P, integral I, differential D operation back, the output of first PID controller passes through the adder, be connected to the converter by automatic control module output OUT6, change the output frequency of converter, and then change the flow of heat supply network secondary side circulating water pump, after the adjustment is stable, eliminate deviation Error, make heat supply network secondary side supply the return water difference in temperature and the setting value keep equal.
Quality control of heat exchange station system
When weather appears unusually in the season of heating, the upper and lower limit value that heat supply network secondary side supply return water pressure differential reached, the volume control mode through adjusting secondary side circulating water pump flow will not satisfy hot user's heating demand, for guaranteeing not appearing heating system heating power maladjustment's problem, through change over switch, with volume regulation control circuit switching to matter regulation control circuit, through adjusting the aperture of heat supply network once side electric control valve, change heat supply network once side supply return water flow, and then change the fluid temperature of secondary side supply channel, the heat supply that adjustment heat exchange station carried for hot user.
In the initial cold period or the final cold period, when the outdoor temperature is higher, the circulation flow of the secondary side of the heat supply network is smaller, and the pressure difference of the water supply and return pipeline of the secondary side of the heat supply network reaches the lower limit set value, the secondary side circulating water pump keeps a certain rotating speed unchanged, the change-over switch acts, the automatic control of the heat exchange station system is converted from quantity regulation into quality regulation, the deviation Error between the temperature difference measured value of the heat supply and return pipeline on the secondary side of the heat supply network and the temperature difference set value of the heat supply and return pipeline on the secondary side of the heat supply network is connected to the input end of the change-over switch, the output end OUT5 of the change-over switch is connected to the second PID controller, after the operations of proportion P, integral I and differential D, the output of second PID controller is connected to heat supply network once and inclines supply line electric control valve, reduces heat supply network once and inclines electric control valve opening, reduces heat supply network secondary side water supply temperature, guarantees the heat supply load that the heat transfer station carried and the heating heat load's of heat consumer balance.
In severe cold period, when outdoor temperature is lower, the secondary side circulating water pump reaches rated rotating speed, the actual measured value of the temperature difference of water supply and return of the secondary side of the heat supply network is still lower than a set value, the heat supply quantity conveyed by the heat exchange station cannot meet the heating heat load of a heat user, the pressure difference of the water supply and return pipeline of the secondary side of the heat supply network reaches an upper limit set value, the action of the change-over switch is carried OUT, the automatic control system of the heat exchanger is switched to quality regulation control, the deviation Error between the measured value of the temperature difference of the water supply and return pipeline of the secondary side of the heat supply network and the temperature difference set value of the water supply and return pipeline of the secondary side of the heat supply network is connected to the input end of the change-over switch, the output end OUT5 of the change-over switch is connected to the second PID controller, and after proportional P, integral I and differential D operations, the output of second PID controller is connected to heat supply network and once inclines supply line electric control valve, and increase heat supply network once inclines electric control valve opening, improves heat supply network secondary side water supply temperature, guarantees the heat supply load that the heat transfer station carried and the heating heat load's of heat consumer balance.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. An automatic control system of a central heating heat exchange station is characterized in that the control system consists of a heat supply network primary side circulating system, a heat supply network secondary side circulating system, a data acquisition and processing module and an automatic control module; the data acquisition processing module consists of an air temperature and flow conversion unit and 2 subtracters; the automatic control module consists of a subtracter, an adder, a change-over switch and 2 PID controllers.
2. The system of claim 1, wherein the hot water from the heat source is delivered to the heat exchange station via a primary water supply line of the heat supply network, and wherein the primary water supply line of the heat supply network is provided with an electrically adjustable valve for varying the flow of the hot water from the primary water supply line of the heat supply network; in the heat exchange station, high-temperature hot water conveyed by a primary side water supply pipeline of the heat supply network enters the plate type heat exchanger and exchanges heat with circulating water at a secondary side of the heat supply network in the plate type heat exchanger, and cooled primary side return water of the heat supply network returns to a heat source through a primary side circulating water pump arranged on a primary side return water pipeline of the heat supply network.
3. The system as claimed in claim 1, wherein the heat-supply network secondary-side circulating water absorbs heat in the plate heat exchanger and then delivers the heat to the heat consumer through the heat-supply network secondary-side water supply line from the outlet of the plate heat exchanger, a temperature sensor and a pressure sensor are installed on the heat-supply network secondary-side water supply line for measuring the temperature and the pressure of the circulating water in the water supply line, the cooled return water is returned to the plate heat exchanger through the heat-supply network secondary-side water return line by means of a secondary-side circulating water pump installed on the heat-supply network secondary-side water return line, and a temperature sensor and a pressure sensor are installed on the heat-supply network secondary-side water return line for measuring the temperature and the pressure of the circulating water in the water return line.
4. The system of claim 1, wherein the real-time collection of temperature and pressure signals of the secondary side water supply and return water of the heat supply network and outdoor atmospheric temperature and wind speed information is obtained from weather forecast through connection with the internet; temperature sensors on a water supply pipeline and a water return pipeline on the secondary side of the heat supply network are connected with a first subtracter through signal lines, and a water supply and return temperature difference signal delta t is obtained and is connected with an output end OUT1 of the data acquisition and processing module; pressure sensors on a water supply pipeline and a water return pipeline on the secondary side of the heat supply network are connected with a second subtracter through signal lines, and a water supply and return differential pressure signal delta p is obtained and is connected with an output end OUT2 of the data acquisition and processing module; the outdoor atmospheric temperature and wind speed information is connected with the input end of the air temperature and flow conversion unit, and the output end of the air temperature and flow conversion unit is connected with the output end OUT3 of the data acquisition and processing module.
5. The system of claim 1, wherein the data acquisition module output OUT1 is coupled to the automation module input IN1, the data acquisition module OUT2 is coupled to the automation module input IN2, and the data acquisition module OUT3 is coupled to the automation module input IN 3; the input end IN1 of the automatic control module and a temperature difference set value of supply and return water on the secondary side of the heat supply network are connected to a third subtracter; the output end of the third subtracter and the input end IN2 of the automatic control module are connected together to a change-over switch, the output end OUT4 of the change-over switch is connected with the input end of the first PID controller, the output end of the first PID controller and the input end IN3 of the automatic control module are connected together to an adder, the output end of the adder is connected to the output end OUT6 of the automatic control module, the output end OUT6 of the automatic control module is connected to a frequency converter, and the output of the frequency converter is connected with the secondary side circulating water pump; the output end OUT5 of the change-over switch is connected with the input end of the second PID controller, and the output end of the second PID controller is connected with the output end OUT7 of the automatic control module; the output end OUT7 of the automatic control module is connected with the electric regulating valve on the primary side of the heat supply network.
6. A design method of an automatic control system of a central heating heat exchange station comprises the steps of collecting analog quantity parameters such as meteorological parameters, fluid pressure, fluid temperature and the like in weather forecast, analyzing and processing the analog quantity parameters collected in real time, realizing automatic switching of feedforward-feedback control quantity regulation and feedback control quality regulation of a heat supply network secondary side through a change-over switch, and realizing automatic control of water supply and return constant temperature difference of the heat supply network secondary side of the heat exchange station through a PID (proportion integration differentiation) controller. The method comprises the following specific steps:
quantity control of a heat exchange station system
1. Feed forward control
Because the heat supply heat source, the heat supply pipe network and the building have great thermal inertia, the influence of the change of the heat supply parameters such as meteorological parameters, water supply temperature, water supply flow and the like on the room temperature of a heat user has long lag time, and in order to ensure the design requirement of the room temperature of the heat user, the operation of the heat supply pipe network is regulated by considering pre-regulation, namely, the change of a regulation scheme has a reasonable time difference relative to the change of the room temperature, the heat supply load is predicted according to meteorological forecast information, the operation working condition of a heat exchange station is regulated timely and reasonably, the system optimization scheduling is realized, the lag time of the heat supply pipe network is reduced, the heating quality is ensured, and the purposes of energy conservation and environmental protection are achieved.
Weather parameters are the basis for designing and adjusting the whole central heating system, main weather parameters influencing the heat load of a building and the operation adjusting strategy of the heating system comprise outdoor atmospheric temperature, wind speed and the like, the forecasting accuracy is steadily improved along with the continuous development of weather forecasting technology, weather forecasting information service based on the internet technology is gradually improved, and the outdoor atmospheric temperature is corrected by adopting the wind speed information in weather forecasting to obtain outdoor comprehensive temperature
tw＝35.74+0.6215×t-35.75×v0.16+0.4275×t×v0.16 (1)
Wherein, twIs outdoor comprehensive temperature in unit; t is the atmospheric temperature in the weather forecast, in units; v is the wind power level in weather forecast, in m/s.
Under stable conditions, the heat supply delivered by the heat exchange station is equal to the heating heat load of the heat user
cG(tg-th)＝qvV(tn-tw) (2)
Wherein c is the specific heat capacity of hot water, and the unit J/(kg DEG C); g is the heat supply network secondary side circulation flow, unit kg/s; t is tgSupplying water temperature to the secondary side of the heat supply network in unit; t is thThe temperature of the return water at the secondary side of the heat supply network is unit ℃; q. q.svIs the heating volume of the building and has the unit of W/m3The temperature is controlled; v is the external volume of the building, unit m3；tnThe temperature was calculated in units of degrees celsius for the heating room in winter.
Under the condition of constant temperature difference of supply and return water at the secondary side of the heat supply network, i.e. (t)g-th) Remains unchanged when the outdoor comprehensive temperature t iswWhen the heat supply quantity and the heat load are balanced, and only the secondary side circulation flow G of the heat supply network needs to be adjusted, namely, the flow regulation method of the secondary side circulation water pump is changed through frequency conversion regulation to realize energy conservation.
The change relation between meteorological parameters and the flow of the secondary side circulating water pump can be obtained through the formulas (1) and (2), outdoor atmospheric temperature and air speed information in weather forecast is connected to the data acquisition processing module, the outdoor atmospheric temperature and the air speed information are converted by the temperature and flow conversion unit and then are connected to the automatic control module by the data acquisition processing module, the outdoor atmospheric temperature and the air speed information are connected to the frequency converter by the automatic control module through the adder and are used as feedforward control in a control loop of the secondary side circulating water pump to adjust the output frequency of the frequency converter, and further the circulating flow of the secondary side of a heat supply network is changed; the secondary side of the heat supply network is adjusted in advance through meteorological parameters in weather forecast, so that the comfort of the indoor environment of a heat user caused by the lagging performance of a heat supply system can be effectively reduced.
2. Feedback control
When weather forecast information is inconsistent with actual meteorological parameters, through the coarse adjustment of feedforward control, the supply and return water temperature difference of the heat supply network secondary side changes, deviation Error is generated with the supply and return water temperature difference set value, the deviation Error is connected to the input end of the first PID controller through the change-over switch, after the proportion P, the integral I and the differential D are operated, the output of the first PID controller passes through the adder, the automatic control module is connected to the frequency converter, the output frequency of the frequency converter is changed, the circulation flow of the heat supply network secondary side is adjusted, the deviation Error is eliminated, and finally the supply and return water temperature difference of the heat supply network secondary side is equal to the set value.
When the working condition of the primary side of the heat supply network changes or disturbance occurs, the temperature of the primary side water supply of the heat supply network changes, the temperature of the secondary side water supply of the heat supply network also changes, and then the temperature difference of the secondary side water supply of the heat supply network changes, the deviation Error generated by the temperature difference of the secondary side water supply of the heat supply network and a set value is connected to the first PID controller through the switch-on switch, the proportion P is passed, the integral I is passed, and after the differential D operation, the output of the first PID controller passes through the adder, the automatic control module is connected to the frequency converter, the output frequency of the frequency converter is changed, and then the flow of the secondary side circulating water pump of the heat supply network is changed, after the adjustment is stable, the deviation Error is eliminated, and the temperature difference of the secondary side water supply and return of the heat supply network keeps consistent with the set value.
Quality control of heat exchange station system
When weather appears unusually in the season of heating, the upper and lower limit value that heat supply network secondary side supply return water pressure differential reached will not satisfy heat consumer's heating demand through the volume control mode of adjusting secondary side circulating water pump flow, through change over switch, switch volume regulation control circuit to matter regulation control circuit, through adjusting the aperture of heat supply network once side electric control valve, change heat supply network once side supply return water flow, and then change the fluid temperature of secondary side supply channel, adjust the heat supply amount that heat transfer station carried for heat consumer.
In the initial cold period or the final cold period, when the outdoor temperature is higher, the circulation flow of the secondary side of the heat supply network is smaller, and in order to ensure that the phenomenon of thermal imbalance of an indoor heating system does not occur, when the pressure difference of the water supply and return pipeline of the secondary side of the heat supply network reaches a lower limit set value, the secondary side circulation water pump keeps a certain rotating speed, the action of a switch is switched, an adjusting object of an automatic control system of the heat exchange station is changed into an electric adjusting valve on a water supply pipeline of the primary side of the heat supply network from the secondary side circulation water pump, the automatic control of the system of the heat exchange station is converted into quality adjustment from quantity adjustment, the deviation Error between the temperature difference measured value of the water supply and return pipeline of the secondary side of the heat supply network is connected to a second PID controller through the switch, after the operations of proportion P, integral I and differential D, the output end of the second PID controller is connected to the electric adjusting valve of the water supply pipeline of the primary side of the heat supply network, the opening of the electric adjusting valve of the primary side of the heat supply network is reduced, the flow of a primary side water supply pipeline of the heat supply network is reduced, so that the secondary side water supply temperature of the heat supply network is reduced, and the balance of the heat supply load conveyed by the heat exchange station and the heating heat load of a heat user is ensured.
In severe cold period, when outdoor temperature is lower, a secondary side circulating water pump reaches rated rotating speed, the pressure difference of a secondary side water supply and return pipeline of a heat supply network reaches an upper limit set value, the actual measured value of the temperature difference of the water supply and return is still lower than the set value, the heat supply quantity conveyed by a heat exchange station cannot meet the heating heat load of a heat user, a switch is switched to act, the regulated object of an automatic control system of the heat exchange station is changed into an electric regulating valve on a primary side water supply pipeline of the heat supply network by the secondary side circulating water pump, the automatic control of the system of the heat exchange station is converted into quality regulation by quantity regulation, the deviation Error between the measured value of the temperature difference of the secondary side water supply and return pipeline of the heat supply network and the set value of the temperature difference of the secondary side water supply and return pipeline of the heat supply network is connected to a second PID controller through the switch, after the operations of proportion P, integral I and differential D, the output end of the second PID controller is connected to the electric regulating valve of the primary side water supply pipeline of the heat supply network, the opening of the electric regulating valve of the primary side heat supply network is increased, the flow of a primary side water supply pipeline of the heat supply network is increased, so that the secondary side water supply temperature of the heat supply network is increased, and the balance between the heat supply amount delivered by the heat exchange station and the heating heat load of a heat user is ensured.
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| CN114963297A (en) * | 2022-05-23 | 2022-08-30 | 西安西热锅炉环保工程有限公司 | Heat storage intelligent heat supply control system and method |
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| CN115264555A (en) * | 2022-07-15 | 2022-11-01 | 珠海格力电器股份有限公司 | Heating control method and device and heating system |
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