Background
The heating season is divided into an initial cold period, a severe cold period and a final cold period, and the outdoor temperature is continuously changed from high to low and then from low to high. At present, a secondary side circulating pump of an unattended heat exchange station generally adopts a PLC to control flow according to designed flow constant pressure difference, constant flow or staged manual flow, and heat supply operation is carried out in the whole heating season by a mode of measuring the secondary water supply constant pressure difference or the secondary side circulating constant flow. The designed flow meets the flow of the normal operation of the whole pipe network on the basis of ensuring the worst loop design flow at the heating outdoor design temperature (the lowest outdoor average temperature of 5 days is not ensured in the severe cold period). However, for the initial cold period or the final cold period with low temperature, the designed flow is very large, which causes a great deal of electric energy waste.
Disclosure of Invention
The present invention is directed to solving the problems of the prior art to reduce the power consumption of the heat exchange station.
In order to achieve the purpose, the invention adopts a variable flow control method of a secondary side circulating pump of a heat exchange station, which comprises the following steps:
acquiring an outdoor average temperature, and searching a secondary side target control flow corresponding to the outdoor average temperature in a data comparison table of the outdoor average temperature and the secondary side target control flow;
and comparing the secondary side target control flow with the actual flow of the secondary side circulating pump, and adjusting the operating frequency of the secondary side circulating pump according to the comparison result.
Further, the determining process of the data comparison table of the outdoor average temperature and the secondary side target control flow comprises the following steps:
acquiring water supply temperature and water return temperature of a secondary side circulating pump at a heating outdoor design temperature, and water supply temperature and water return temperature of the secondary side circulating pump at different outdoor temperatures;
calculating relative flow under different outdoor temperatures according to the water supply temperature and the water return temperature of the secondary side circulating pump under the heating outdoor design temperature and the water supply temperature and the water return temperature of the secondary side circulating pump under different outdoor temperatures;
taking the product of the relative flow and the design flow at different outdoor temperatures as the secondary side target control flow at different outdoor temperatures, wherein the design flow is the flow corresponding to the heating outdoor design temperature;
and obtaining a data comparison table of the outdoor average temperature and the secondary side target control flow according to the different outdoor temperatures and the corresponding secondary side target control flows.
Further, the comparing the secondary side target control flow with the actual flow of the secondary side circulating pump, and adjusting the operating frequency of the secondary side circulating pump according to the comparison result includes:
acquiring the operating frequency of the secondary side circulating pump;
when the secondary side target control flow is larger than the secondary side actual flow, judging whether the operating frequency of the secondary side circulating pump is smaller than a set maximum operating frequency;
if so, increasing the operating frequency of the secondary side circulating pump;
if not, the operation frequency of the secondary side circulating pump is kept unchanged;
when the secondary side target control flow is smaller than the secondary side actual flow, judging whether the operating frequency of the secondary side circulating pump is larger than a set minimum operating frequency;
if so, reducing the operating frequency of the secondary side circulating pump;
if not, the operation frequency of the secondary side circulating pump is kept unchanged.
Further, still include:
recording the regulation and control frequency of the secondary side circulating pump in real time;
and comparing the regulation frequency of the secondary side circulating pump with a set regulation frequency value, and controlling the regulation frequency of the secondary side circulating pump according to a regulation frequency comparison result.
Further, still include:
and setting flow weighting for the secondary side target control flow during the outdoor temperature reduction period, and increasing the secondary side target control flow under the current outdoor average temperature.
Further, before the obtaining the outdoor average temperature, the method further includes:
and collecting the outdoor temperature of the heat exchange station at regular time, and calculating the outdoor average temperature in a set time period according to the collected outdoor temperature of the heat exchange station.
On the other hand, the heat exchange station secondary side circulating pump variable flow control system comprises a PLC controller, a flow meter arranged on the secondary side of a heat exchange unit, a frequency converter used by the secondary side circulating pump and a temperature sensor arranged outdoors of the heat exchanger, wherein a data comparison table of the outdoor average temperature and the secondary side target control flow is stored in the PLC controller; the output ends of the flowmeter, the frequency converter and the temperature sensor are all connected with the PLC, and the output end of the PLC is connected with the driving end of the frequency converter;
the flowmeter is used for acquiring the actual flow of the secondary side circulating pump;
the temperature sensor is used for collecting the outdoor temperature of the heat exchange station at regular time;
the frequency converter is used for acquiring the operating frequency of the secondary side circulating pump;
the PLC is used for calculating the outdoor average temperature in a set time period according to the outdoor temperature regularly acquired by the temperature sensor, and finding out the secondary side target control flow corresponding to the outdoor average temperature in the data comparison table;
and the PLC compares the secondary side target control flow with the actual flow of the secondary side circulating pump and adjusts the operating frequency of the secondary side circulating pump according to the comparison result.
Further, the determining process of the data comparison table of the outdoor average temperature and the secondary side target control flow comprises the following steps:
acquiring water supply temperature and water return temperature of a secondary side circulating pump at a heating outdoor design temperature, and water supply temperature and water return temperature of the secondary side circulating pump at different outdoor temperatures;
calculating relative flow under different outdoor temperatures according to the water supply temperature and the water return temperature of the secondary side circulating pump under the heating outdoor design temperature and the water supply temperature and the water return temperature of the secondary side circulating pump under different outdoor temperatures;
taking the product of the relative flow and the design flow at different outdoor temperatures as the secondary side target control flow at different outdoor temperatures, wherein the design flow is the flow corresponding to the heating outdoor design temperature;
and obtaining the operation regulation characteristic curve of the circulating pump according to the different outdoor temperatures and the corresponding secondary side target control flow.
Furthermore, flow regulation weighting is arranged in the PLC to regulate the secondary side target control flow corresponding to a certain outdoor average temperature.
Further, the PLC controller comprises a first comparison module, a first judgment module, a second judgment module and a circulating pump operation frequency adjustment module;
the first comparison module is used for comparing the secondary side target control flow with the actual flow of the secondary side circulating pump;
the first judging module is used for judging whether the operating frequency of the secondary side circulating pump is less than the set maximum operating frequency or not when the output result of the first comparing module is that the secondary side target control flow is greater than the secondary side actual flow;
the circulating pump operation frequency adjusting module is used for increasing the operation frequency of the secondary side circulating pump when the output result of the first judging module is yes; and the second judging module is used for judging whether the output result of the second judging module is negative or not;
the second judging module is used for judging whether the operating frequency of the secondary side circulating pump is greater than the set minimum operating frequency or not when the output result of the first comparing module is that the secondary side target control flow is smaller than the secondary side actual flow;
the circulating pump operation frequency adjusting module is used for reducing the operation frequency of the secondary side circulating pump when the output result of the second judging module is yes; and the secondary side circulating pump is used for keeping the running frequency of the secondary side circulating pump unchanged when the output result of the second judging module is negative.
Compared with the prior art, the invention has the following technical effects: according to the outdoor temperature recorded in a certain period of time, the outdoor average temperature in the period of time is calculated, and secondary side circulation flow rates corresponding to different outdoor average temperatures are calculated to serve as secondary side target control flow rates. The calculated outdoor average temperature value in the unit regulation period is a smooth curve, so that the corresponding secondary side target control flow change is very small, the corresponding secondary side target control flow under the current outdoor average temperature is used as a basis for regulating the flow of the secondary side circulating pump, the regulation amplitude of the secondary side circulating pump is very small, and the frequent fluctuation of the flow of the secondary side circulating pump is avoided.
Detailed Description
To further illustrate the features of the present invention, refer to the following detailed description of the invention and the accompanying drawings. The drawings are for reference and illustration purposes only and are not intended to limit the scope of the present disclosure.
As shown in fig. 1, the embodiment discloses a variable flow control method for a secondary side circulation pump of a heat exchange station, which includes the following steps S1-S2:
s1, acquiring the outdoor average temperature, and searching the secondary side target control flow corresponding to the outdoor average temperature in a data comparison table of the outdoor average temperature and the secondary side target control flow;
and S2, comparing the secondary side target control flow with the actual flow of the secondary side circulating pump, and adjusting the operating frequency of the secondary side circulating pump according to the comparison result.
It should be noted that the designed flow is a flow that satisfies the normal operation of the whole pipe network at the designed temperature outside the heating room, but for the initial cold period or the final cold period when the air temperature is not too low, the designed flow is very large. The heat supply formula is adopted for calculation, the set flow is constant, the indoor temperature is kept at 20 ℃, when the outdoor temperature is-15 ℃, the temperature difference of the secondary side water supply and return is 10 ℃, when the outdoor temperature is 5 ℃, the temperature difference of the secondary side water supply and return is 4.3 ℃, and when the outdoor temperature is 10 ℃, the temperature difference of the secondary side water supply and return is only 2.9 ℃. This shows that when the design flow and the indoor temperature are kept constant, the higher the outdoor temperature is, the smaller the temperature difference between the supplied and returned water is. That is to say, when outdoor temperature rose, the flow that satisfies normal needs can diminish, under the prerequisite that satisfies the heating effect, can adjust secondary side circulating pump water according to outdoor temperature and do the variable flow operation, reaches the purpose that reduces heat exchange station operation power consumption.
In the embodiment, the flow of the secondary side circulating pump is adjusted in real time without adopting the real-time temperature of outdoor weather, and the average temperature of the outdoor weather is used as the basis for adjusting the flow. Specifically, the outdoor temperature may be collected in a unit period of one day and calculated by multiplying 24 hours, and the outdoor average temperature may be calculated according to the outdoor temperature recorded in the period of time per hour. Because the outdoor average temperature value of the unit regulation period is a smooth curve, the change amplitude of the secondary side target control flow is small, the regulation amplitude of the secondary side circulating pump is also small, and the phenomenon that the secondary side flow fluctuates frequently is avoided.
Further, the determining process of the data comparison table of the outdoor average temperature and the secondary side target control flow comprises the following steps:
(1) acquiring water supply temperature and water return temperature of a secondary side circulating pump at a heating outdoor design temperature, and water supply temperature and water return temperature of the secondary side circulating pump at different outdoor temperatures;
(2) calculating relative flow under different outdoor temperatures according to the water supply temperature and the water return temperature of the secondary side circulating pump under the heating outdoor design temperature and the water supply temperature and the water return temperature of the secondary side circulating pump under different outdoor temperatures;
(3) taking the product of the relative flow and the design flow at different outdoor temperatures as the secondary side target control flow at different outdoor temperatures, wherein the design flow is the flow corresponding to the heating outdoor design temperature;
(4) and obtaining a data comparison table of the outdoor average temperature and the secondary side target control flow according to the different outdoor temperatures and the corresponding secondary side target control flows.
Specifically, the secondary side target control flow corresponding to the outdoor average temperature may be calculated by derivation according to the following formula:
first from the thermal equilibrium relationship:
it can be deduced that:
when in use
When the flow rate is equal to 1, the constant flow rate is generally said to output heat
The change of the temperature difference (t) between the supply water and the return water at certain outdoor temperature
g-t
h) The amount of variation in quality control. If we wait for the quality and quantity adjustments of the variables, that is, the amount of change of the quality adjustment is the same as the amount of change of the quantity adjustment, we derive the following formula:
wherein,
indicating the relative heating heat load, i.e. a certain outdoor temperature t
wThe ratio of the lower heating heat load to the design heat load;
represents the relative flow; t is t
g、t
hRespectively representing a certain outdoor temperature t
wThe lower water supply temperature and the return water temperature; t, t,
g、t
hRespectively showing the design temperature t,
wThe lower water supply temperature and the return water temperature; t is t
nIndicating the indoor temperature.
It should be noted that the above-listed formula defines that the variation of the quality adjustment is the same as that of the quantity adjustment, and the magnitude of the variation of the quality adjustment and the quantity adjustment can also be changed by exponentiation in the formula of the quality adjustment and the quantity adjustment according to the actual heating condition. The target flow rate at a certain temperature is calculated according to the product of the design flow rate on the coldest day (in the severe cold period) and the relative flow rate G at a certain outdoor temperature calculated by the formula, and the calculated outdoor temperature and the target flow rate are input into the PLC by a comparison table worker. The operating frequency of the pump is operated according to the target flow rate corresponding to the actual outdoor average temperature. In the embodiment, the target control flow is compared with the actual secondary side circulating flow, and the frequency of the secondary side circulating water pump is adjusted according to the comparison result, so that the purposes of variable-flow economical operation and electric energy saving are achieved.
Further, as shown in fig. 2, the step S2: comparing the secondary side target control flow with the actual flow of the secondary side circulating pump, and adjusting the operating frequency of the secondary side circulating pump according to the comparison result, wherein the method comprises the following steps of S21 to S27:
s21, acquiring the operating frequency of the secondary side circulating pump;
s22, when the secondary side target control flow is larger than the secondary side actual flow, judging whether the operation frequency of the secondary side circulating pump is smaller than the set maximum operation frequency, if so, executing a step S23, otherwise, executing a step S24;
s23, increasing the operating frequency of the secondary side circulating pump;
s24, keeping the operation frequency of the secondary side circulating pump unchanged;
s25, when the secondary side target control flow is smaller than the secondary side actual flow, judging whether the operation frequency of the secondary side circulating pump is larger than a set minimum operation frequency, if so, executing a step S26, otherwise, executing a step S27;
s26, reducing the operating frequency of the secondary side circulating pump;
and S27, keeping the operation frequency of the secondary side circulating pump unchanged.
It should be noted that, if the secondary-side target control flow rate is the same as the secondary-side actual flow rate, the operating frequency of the circulation pump is kept unchanged.
It should be noted that the minimum operating frequency is set according to the minimum frequency specified by the manufacturer of the circulating pump, and the minimum frequency of the water pumps of different models is specified differently by different manufacturers. The minimum frequency of a common circulating pump commonly used by people is generally 25HZ, the minimum frequency of the circulating pump with the variable frequency motor is generally 20HZ, and the maximum frequency is 50 HZ.
Preferably, in practical applications, since the historical outdoor average temperature is recorded and has hysteresis, when the temperature gradually decreases from the initial cold period to the severe cold period, in order to avoid a time delay caused by calculating the outdoor average temperature in a past certain period of time, the heating quality is ensured, and the outdoor temperature is corrected by setting a flow rate weight. In the present embodiment, a flow rate weight is set for all or part of the secondary-side target control temperature, for example, during the period from the initial cold period to the severe cold period when the temperature is decreased, and the secondary-side target control flow rate is increased by setting the flow rate weight, so as to cancel out the time delay caused by the calculated average temperature of the past time period.
Preferably, in practical application, the number of times of regulating and controlling the operating frequency of the secondary side circulating pump is not frequent, so as to prevent the circulating pump from being damaged. In the embodiment, the regulation and control frequency of the secondary side circulating pump is recorded in real time, the regulation and control frequency of the secondary side circulating pump is compared with the set regulation and control frequency value, and the regulation and control frequency of the secondary side circulating pump is controlled according to the comparison result of the regulation and control frequency.
The adjustment frequency of the secondary-side circulation pump is generally set to 24 hours/time or more. The adjusting frequency of the circulating pump is recorded, so that the functions of calculating and adjusting the operation instruction and inquiring the historical operating condition parameters can be achieved. Meanwhile, the calculation of the PID or the upper computer platform for adjusting the operating frequency of the pump is calculated on the basis of the last feedback operating parameter.
As shown in fig. 3, the present embodiment discloses a variable flow control system for a secondary side circulation pump of a heat exchange station, which includes a PLC controller 10, a flow meter 20 disposed on the secondary side of a heat exchange unit, a frequency converter 30 for the secondary side circulation pump, and a temperature sensor 40 disposed outdoors of the heat exchange unit, wherein a data comparison table of an outdoor average temperature and a secondary side target control flow is stored in the PLC controller 10; the output ends of the flowmeter 20, the frequency converter 30 and the temperature sensor 40 are all connected with the PLC 10, and the output end of the PLC 10 is connected with the driving end of the frequency converter 30;
the flowmeter 20 is used for acquiring the actual flow of the secondary side circulating pump;
the temperature sensor 40 is used for collecting the outdoor temperature of the heat exchange station at regular time;
the frequency converter 30 is used for acquiring the operating frequency of the secondary side circulating pump;
the PLC controller 10 is configured to calculate an outdoor average temperature within a set time period according to the outdoor temperature periodically collected by the temperature sensor 40, and find a secondary side target control flow corresponding to the outdoor average temperature in the data comparison table;
the PLC controller 10 compares the secondary side target control flow with an actual flow of the secondary side circulation pump, and adjusts the operating frequency of the secondary side circulation pump according to the comparison result.
Specifically, the outdoor temperature acquisition is realized by an outdoor temperature sensor, the acquisition time and frequency can be set in a PLC, the outdoor average temperature is calculated by dividing the accumulation of the latest acquisition temperature by the acquisition number, and the calculation process is realized by PLC programming.
The determining process of the data comparison table of the outdoor average temperature and the secondary side target control flow comprises the following steps:
acquiring water supply temperature and water return temperature of a secondary side circulating pump at a heating outdoor design temperature, and water supply temperature and water return temperature of the secondary side circulating pump at different outdoor temperatures;
calculating relative flow under different outdoor temperatures according to the water supply temperature and the water return temperature of the secondary side circulating pump under the heating outdoor design temperature and the water supply temperature and the water return temperature of the secondary side circulating pump under different outdoor temperatures;
taking the product of the relative flow and the design flow at different outdoor temperatures as the secondary side target control flow at different outdoor temperatures, wherein the design flow is the flow corresponding to the heating outdoor design temperature;
and obtaining the operation regulation characteristic curve of the circulating pump according to the different outdoor temperatures and the corresponding secondary side target control flow.
Further, the determining process of the data comparison table of the outdoor average temperature and the secondary side target control flow comprises the following steps:
acquiring water supply temperature and water return temperature of a secondary side circulating pump at a heating outdoor design temperature, and water supply temperature and water return temperature of the secondary side circulating pump at different outdoor temperatures;
calculating relative flow under different outdoor temperatures according to the water supply temperature and the water return temperature of the secondary side circulating pump under the heating outdoor design temperature and the water supply temperature and the water return temperature of the secondary side circulating pump under different outdoor temperatures;
taking the product of the relative flow and the design flow at different outdoor temperatures as the secondary side target control flow at different outdoor temperatures, wherein the design flow is the flow corresponding to the heating outdoor design temperature;
and obtaining the operation regulation characteristic curve of the circulating pump according to the different outdoor temperatures and the corresponding secondary side target control flow.
Preferably, a flow regulation weighting is set in the PLC controller 10 to regulate the secondary side target control flow corresponding to a certain outdoor average temperature. In the present embodiment, a flow rate weight is set for all or part of the secondary-side target control temperature, for example, during the period from the initial cold period to the severe cold period when the temperature is decreased, and the secondary-side target control flow rate is increased by setting the flow rate weight, so as to cancel out the time delay caused by the calculated average temperature of the past time period.
Adopt outdoor real-time temperature to adjust secondary side circulating pump flow among the prior art, because outdoor temperature changes in real time, can take place the operating frequency of secondary side circulating pump and change always, the secondary side flow changes always, causes the damage of equipment, two net operating condition unstability, also does not benefit to two net balance adjustment yet. Considering that the building has the functions of heat storage and heat preservation and generates heat inertia to the actual heat supply effect, the secondary side circulation flow does not need to be adjusted in real time according to the real-time temperature of outdoor weather. When the heat exchange unit regulates the secondary side flow at regular time, the average outdoor temperature in a past period of time is used as a regulation basis before the regulation, the period of time can be calculated by taking one day as a minimum unit period and taking 24 hours as a multiple, the average outdoor temperature is calculated according to the outdoor temperature recorded in the period of time every hour, and the calculated average outdoor temperature value in the unit regulation period is a smooth curve, so that the change of the secondary side target control flow is small, the regulation amplitude of a secondary side circulating pump is small, and the phenomenon that the secondary side flow fluctuates frequently is avoided. The scheme can ensure stable operation condition of the heat exchange unit without influencing heat supply effect of residents while saving electricity.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.