System for regulating the temperature of a thermal energy carrying fluid in a section of a fluid distribution grid

Abstract

A system for regulating the temperature of a thermal energy carrying fluid in a section of a fluid distribution grid, the fluid distribution grid comprising a supply line and a return line, the system comprising: a bypass line connecting the return line to the supply line, at least one bypass pump arranged at the bypass line, a control unit configured to directly or indirectly control the speed of the at least one bypass pump, at least one temperature sensor configured to determine the temperature of the fluid in the supply line downstream of the bypass line, at least one pressure sensor configured to determine an uncontrolled pressure difference between the supply line and the return line or a pressure difference related thereto, wherein the control unit is configured to control the speed of the at least one bypass pump based on a combination of: a closed loop control providing a flow of fluid in the bypass line based on the determined supply line temperature, a feed forward control compensating for fluctuations in the pressure difference between the supply line and the return line based on the determined pressure difference.

Description

Technical Field

[0001] This disclosure relates to a system for regulating the temperature of a heat-carrying fluid in a section of a fluid distribution network (particularly a district heating network). Background Technology

[0002] Typically, a fluid distribution network distributes heat power, in the form of hot or cold fluid, to multiple heat consumers connected to the network. A fluid distribution network usually comprises multiple sections, each containing multiple heat consumers. In the case of a heating distribution network, the sections can be, for example, blocks, streets, or another aggregation of heat consumers (i.e., residential, commercial, and / or industrial consumers). Utility providers operating heating distribution networks are interested in operating them as efficiently as possible. This means that utility providers want to regulate the temperature of the heat-carrying fluids in the sections of the fluid distribution network to a desired target temperature. If the temperature in a section of the heating distribution network is too low, heat consumers are not receiving sufficient heat and may complain. However, if the temperature is too high, energy losses in the heating distribution network are high.

[0003] The idea behind regulating the temperature in sections of a heating distribution network is to mix a portion of the cooler fluid in the return line back into the supply line that carries the heat-carrying fluid to the section via a bypass or diversion line. Because the pressure in the supply line is higher than the pressure in the return line, a pump is required in the bypass or diversion line. EP 2 874 039 B1 generally describes the principle of mixing the return line fluid back into the supply line using a bypass line.

[0004] The heat transfer system described in EP 2 874 039 B1 includes pumps and / or valves in the supply or return lines to control the pressure and / or flow rate in the supply and return lines. In some fluid distribution systems, the use of valves in the supply or return lines of the heat transfer system is undesirable due to hydraulic losses. In these cases, pumps are then used instead in the bypass lines. However, problems arise in this situation when the pressure or flow rate in the supply and return lines is subject to uncontrollable disturbances or fluctuations. For example, disturbances or fluctuations in the pressure difference between the supply and return lines may originate from unpredictable changes in heat power consumption on the consumer side. Therefore, the pressure difference between the supply and return lines in a section of the heating distribution network may, in principle, be uncontrolled or uncontrollable. However, this creates problems for temperature control, because small changes in the pressure difference between the supply and return lines can lead to large changes in the flow rate through the pumps in the bypass lines. Large changes in the flow rate in the bypass lines have a large and delayed effect on the temperature of the supply lines to be controlled.

[0005] A solution to reduce temperature disturbances or fluctuations in the supply line caused by uncontrolled pressure differentials between the supply and return lines could be to install pressure-reducing valves in the supply and / or return lines of the heating distribution network. However, this would alter the pressure balance and increase hydraulic losses, thus reducing the efficiency of heat transfer. This may not be an acceptable solution for utility providers of the heating distribution network. Summary of the Invention

[0006] Therefore, the problem of this disclosure is to control the flow rate in the bypass line to mix the return fluid into the supply line, regardless of uncontrolled disturbances or fluctuations in the pressure difference between the supply and return lines, so that the temperature in the section of the fluid distribution network is effectively regulated to a stable desired target temperature.

[0007] The solution to this problem is given by the subject matter of the independent claims. Preferred embodiments of this disclosure are the subject matter of the dependent claims, the specification, and the drawings.

[0008] According to a first aspect of this disclosure, a system is provided for regulating the temperature of a heat-carrying fluid in a section of a fluid distribution network, the fluid distribution network including a supply line and a return line, the supply line for transporting fluid from a heat source to at least one heat consumer located within the section, and the return line for transporting fluid from the at least one heat consumer back to the heat source. The system includes: - A bypass line connects the return line to the supply line, used to mix fluid from the return line into the supply line. - At least one bypass pump is arranged at the bypass line for pumping fluid from the return line to the supply line. - The control unit is configured to directly or indirectly control the speed of at least one bypass pump. - At least one temperature sensor is arranged and configured to determine the temperature of the fluid in the supply line downstream of the bypass line, and - At least one pressure sensor is arranged and configured to determine an uncontrolled pressure difference or a pressure difference associated therewith between the supply line and the return line. The control unit is configured to control the speed of at least one bypass pump based on a combination of the following: - Closed-loop control for supplying fluid flow in the bypass line based on a determined supply line temperature to achieve a target supply line temperature, and - Feedforward control is used to compensate for fluctuations in the pressure difference between the supply and return lines based on a determined pressure difference.

[0009] This system is particularly suitable for regulating the temperature of heat-carrying fluids in sections of a heating distribution network. However, it is also applicable to other types of fluid distribution networks used to deliver heat to consumers, where the pressure difference between the supply and return lines is uncontrolled or uncontrollable. The control unit can directly control the speed of at least one bypass pump by setting a target speed, or indirectly by setting speed-related bypass pump power, motor current, or other operating parameters. For example, the control unit can set at least one bypass pump to operate at a target percentage of its maximum speed.

[0010] Alternatively, the control unit can be configured to determine the target velocity as a parameterized pump-based model function ω = f -1 (q * (T1),p) is used to combine closed-loop control and feedforward control, where the function ω=f is based on the pump model. -1 (q * (T1),p) is determined by at least two predetermined parameters a h1 a h3 Parameterization. Preferably, the control unit sets the target bypass fluid flow rate q. * (T1) so that the determined supply line temperature T1 is equal to the target supply line temperature. The deviation between e T Minimize. More preferably, the control unit sets the pump differential pressure p to compensate for the determined pressure difference Δp. For example, the control unit can use a pump model where the pump head h is described as a function of the flow rate q through the pump and the pump speed ω. For example, such a model can be given by: ha h3 q 2 +a h1 ω 2 . It can also be a higher-order model, such as ha h3 q 2 +a h2 qω+a h1 ω 2 Or even higher, such as

[0011] These models can be described as functions that map pump flow rate q and pump speed ω to pump head h, i.e., hf(q,ω).

[0012] The conversion between pump head and pump differential pressure can be given by the following formula: Where ρ is the mass density of the heat-carrying fluid, g is the gravitational acceleration, and p is the pump differential pressure. Since the mass density ρ and the gravitational acceleration g can be considered constants with good approximation, the pump model can also be represented by the pump differential pressure p = f(q,ω).

[0013] Then the reciprocal of the function f can be used through ω = f -1 (q * (T1),p) is used to determine the target velocity ω, where the pump differential pressure p is set to compensate for the pressure difference Δp measured by the pressure sensor, i.e., p = Δp.

[0014] If a simple secondary pump model is used as shown above, the target velocity can be determined by the two parameters a given in the following formula. h1 and a h3 Parameterization:

[0015] This formula calculates the pump speed based on the set pump differential pressure and target flow rate. As shown in the formula, replace the squared flow rate with its signed counter part q. * (T1)·|q * (T1) is advantageous. This has the following advantages: depending on the target flow q * (T1), which is set by closed-loop control to provide fluid flow in the bypass line, and the pump can be set to a higher or lower speed than that indirectly provided by the set pump differential pressure.

[0016] Target bypass fluid flow rate q * (T1) can be set such that the determined supply line temperature T1 is related to the target supply line temperature. Deviation between Minimize. This is just an example, and any type of closed-loop control can be used to determine the target bypass fluid flow rate q based on the supply line temperature T1. * (T1), for example, can be used entirely or partially as the following closed-loop control feedback value. Among them, K p and K i It is a gain factor.

[0017] Optionally, at least two predefined parameters a h1 a h3 One of them is a parameter without flow, for example, a h1 It indicates the pressure provided by at least one bypass pump at a specific speed ω and without bypass flow (i.e., q = 0).

[0018] Optionally, the system may also include a check valve at a bypass line downstream of at least one bypass pump, wherein the check valve is configured to prevent fluid from flowing from the supply line through the bypass line to the return line. This helps prevent any backflow, which is very inefficient in terms of energy consumption.

[0019] Optionally, at least one pressure sensor may be arranged and configured to determine the pressure difference Δp by measuring the difference between the following pressures: - Pressure in the bypass line upstream of at least one bypass pump or in the return line, and - The pressure downstream of or upstream of the check valve, or - Pressure in the supply line upstream of at least one bypass line.

[0020] Optionally, the system may further include at least one temperature sensor arranged and configured to determine the temperature T2 of the fluid in the return line. The system may also include at least one temperature sensor arranged and configured to determine the temperature T3 of the fluid in the supply line upstream of the bypass line. The control unit may be configured to further set a target speed based on feedforward control to compensate for uncontrolled fluctuations in the temperature difference T3-T2 between the temperature T3 of the fluid in the supply line upstream of the bypass line and the temperature T2 of the fluid in the return line. This is particularly advantageous in the case of uncontrolled fluctuations in the temperature difference T3-T2, in addition to uncontrolled fluctuations in the pressure difference between the supply and return lines. Therefore, if two additional temperature sensors are available to determine the temperature T3 of the fluid in the supply line upstream of the bypass line and the temperature T2 of the fluid in the return line, this constitutes additional feedforward control. Flow balance and energy saving requirements: q1(T1-T2) = q3(T3-T2) and q2(T1-T2) = q3(T3-T1), where q1 is the flow rate in the supply line downstream of the bypass line, q2 is the flow rate through the bypass pump, and q3 is the flow rate in the supply line upstream of the bypass line. This means that the change in return temperature dT2 needs to be compensated by the pump flow difference dq2 according to the following formula:

[0021] The pump flow rate q2 can be estimated based on the pump model, for example, based on pump-related variables such as velocity and / or power and / or pump head. The following formula applies to the time derivative. Now, the bypass flow q can be directed to the target of closed-loop control. * (T1) Add feedforward control flow section As shown below:

[0022] The problem with the integral term in the above equation is the feedforward part. It may drift over time, and the termination of feedforward control should be prevented. As a solution to this, the control unit can optionally be configured to apply a low-pass filter to the differential flow compensation value before setting the target speed based on feedforward control. The sum is used to compensate for uncontrolled fluctuations in the fluid temperature T3 in the supply line upstream of the bypass line and the fluid temperature T2 in the return line. Such a low-pass filter behaves similarly to an integral over high frequencies and outputs a feedforward flow portion. As the output of the filter.

[0023] A low-pass filter can be described by its transfer function H(s) in the Laplace domain, where Y(s) is the filter's output and X(s) is the filter's input. s is the Laplace variable. The complex transfer function of the low-pass filter, described as a first-order delay element (e.g., a pt1 element), can be chosen as follows: K can be expressed as the filter gain or transfer constant, and τ is a time constant. For higher frequencies, the filter behaves asymptotically in the same way as an integrator, and K can depend on τ. For example, the filter can be used at frequencies of... It has the same gain as the integrator, and the filter gain can be selected as:

[0024] To compensate for any fluctuations in temperature T3 in the supply line upstream of the bypass line, the following differential equation can be used:

[0025] Two differential flow compensation values ​​used to compensate for uncontrolled fluctuations in T2 and T3. The components can be added together and fed into the aforementioned low-pass filter to obtain the feedforward control flow portion.

[0026] Optionally, the control unit can be configured to, if the pump speed is lower than a predetermined stop speed threshold ω stop If so, then at least one bypass pump will be stopped. For example, ω stop It can be defined as 10% or 15% of the maximum pump speed.

[0027] Optionally, the control unit can be configured to, if the pump speed is equal to or higher than a predetermined start-up speed threshold ω start Then at least one bypass pump will be started. ω start It can be with ω stop The same value or different values. For example, ω start It can be higher than ωstop For example, 20% of the maximum pump speed.

[0028] Optionally, the control unit can be configured to perform rise-forward control to compensate for uncontrolled fluctuations in the pressure difference Δp, based on the ramp-up value multiplied by a determined pressure difference Δp, when at least one bypass pump is started. In other words, a ramp function is applied that slowly ramps up the differential pressure signal before supplying it to the pump model. The ramp function can be derived from... The integral is given by dt, where C is a constant chosen such that the output of the integral is 0 at time t0 when the pump starts and 1 at time t1 after time t1-t0 has elapsed. The output of the integral is multiplied by the differential pressure signal, thus causing it to rise slowly over time t1-t0. This has the advantage that if the pump model function is inaccurate, the setpoint overshoot or undershoot of the target temperature T1 remains low.

[0029] According to a second aspect of this disclosure, a method is provided for regulating the temperature of a thermal energy-carrying fluid in a section of a fluid distribution network, the fluid distribution network including a supply line for conveying fluid from a thermal energy source to at least one thermal energy consumer located within the section, a return line for conveying fluid from the at least one thermal energy consumer back to the thermal energy source, and a bypass line connecting the return line to the supply line for mixing fluid from the return line into the supply line. The method includes the following steps: - The temperature T1 of the fluid in the supply line downstream of the bypass line is determined by at least one temperature sensor. - Determine the pressure difference Δp between the supply line and the return line, or the pressure difference associated therewith, using at least one pressure sensor. - Directly or indirectly control the speed ω of at least one bypass pump, which is arranged at a bypass line that connects a return line to a supply line for mixing fluid from the return line into the supply line. The speed of at least one bypass pump can be controlled directly or indirectly based on the following combination: - Closed-loop control for supplying fluid flow in the bypass line based on a determined supply line temperature T1 to achieve the target supply line temperature. and - Feedforward control is used to compensate for uncontrolled fluctuations in the pressure difference Δp between the supply and return lines based on a determined pressure difference Δp.

[0030] Optionally, the combination of closed-loop control and feedforward control includes: determining the target velocity ω as a parameterized pump-based function ω = f -1(q * (T1),p), where the target bypass fluid flow rate q * (T1) is set such that the determined supply line temperature T1 is equal to the target supply line temperature T1. * The deviation between e T Minimize, where the pump differential pressure p is set to compensate for the determined pressure difference Δp, where the function ω = f is based on the pump model. -1 (q * (T1),p) is determined by at least two predetermined parameters a h1 a h3 Parameterization.

[0031] Optionally, at least two predefined parameters a h1 a h3 One of them is a parameter without flow, for example, a h1 It indicates the pressure provided by at least one bypass pump at a specific speed ω and without bypass flow (i.e., q = 0).

[0032] Optionally, the method may further include preventing fluid from flowing from the supply line through the bypass line to the return line by means of a check valve disposed at a bypass line downstream of at least one bypass pump.

[0033] Alternatively, determining the pressure difference may include measuring the difference between the following pressures: - Pressure in the bypass line upstream of at least one bypass pump or in the return line, and - The pressure downstream of or upstream of the check valve, or - Pressure in the supply line upstream of at least one bypass line. Therefore, there are at least six options for determining the pressure difference Δp, i.e., by the difference between the following pressures: 1. The pressure in the bypass line upstream of at least one bypass pump and the pressure downstream of the check valve; 2. The pressure in the bypass line upstream of at least one bypass pump and the pressure in the bypass line upstream of the check valve; 3. The pressure in the bypass line upstream of at least one bypass pump and the pressure in the supply line upstream of at least one bypass line; 4. The pressure in the return line and the pressure downstream of the check valve; 5. The pressure difference between the return line pressure and the bypass line pressure upstream of the check valve; and 6. Between the pressure in the return line and the pressure in the supply line upstream of at least one bypass line.

[0034] Optionally, the method may further include determining the temperature T2 of the fluid in the return line by at least one temperature sensor, and may further include determining the temperature T3 of the fluid in the supply line upstream of the bypass line by at least one temperature sensor, wherein directly or indirectly controlling the speed ω of at least one bypass pump may include setting a target speed ω based on feedforward control to compensate for uncontrolled fluctuations in the temperature difference T3-T2 between the temperature T3 of the fluid in the supply line upstream of the bypass line and the temperature T2 of the fluid in the return line.

[0035] Optionally, the method may further include: applying a low-pass filter to the differential flow compensation value before setting the target velocity ω based on feedforward control. The sum of these values ​​is used to compensate for uncontrolled fluctuations in the fluid temperature T3 in the upstream supply line and the fluid temperature T2 in the return line.

[0036] Optionally, the method may further include: if the speed ω is lower than a predetermined stopping speed threshold ω stop If so, at least one bypass pump will be stopped.

[0037] Optionally, the method may further include: if the speed ω is equal to or higher than a predetermined start-up speed threshold ω start If so, at least one bypass pump will be started.

[0038] Optionally, the method may further include: when starting at least one bypass pump, performing rise feedforward control to compensate for uncontrolled fluctuations in the pressure difference Δp based on the rise value multiplied by the determined pressure difference Δp. Attached Figure Description

[0039] Embodiments of this disclosure will be described by way of example with reference to the following figures, wherein: Figure 1 An example of a heating distribution network including a system according to this disclosure is illustrated schematically; Figure 2 A first embodiment of the system according to this disclosure is illustrated schematically; Figure 3 Another embodiment of the system according to this disclosure is illustrated schematically; Figure 4 Another embodiment of the system according to this disclosure is illustrated schematically; Figure 5 An embodiment of the control method according to this disclosure is illustrated schematically; Figure 6 Another embodiment of the control method according to this disclosure is illustrated schematically; Figure 7 Another embodiment of the system according to this disclosure is illustrated schematically; Figure 8 Another embodiment of the system according to this disclosure is illustrated schematically; and Figure 9a , Figure 9b It shows in Figure 9a In the absence of application of the control method according to this disclosure and in Figure 9b In the application of the control method according to this disclosure, the temperature T1 of the supply line downstream of the bypass line and the pressure difference Δp over a day. Detailed Implementation

[0040] Figure 1 A fluid distribution network 1 in the form of a heating distribution network is shown. The fluid distribution network 1 includes a thermal energy source 3 in the form of a heat generation plant. Thermal energy fluid, pumped by a supply pump 5 through supply lines, carries the thermal energy to multiple heat energy consumers 7 in the form of households. The heat energy consumers 7 are located within sections 9 of the fluid distribution network 1. The fluid distribution network 1 may include a single section 9 or... Figure 1 Multiple sections 9 are shown. Sections 9 of the fluid distribution network 1 can be defined by a common supply line 11 that supplies fluid to heat-carrying fluid to heat-consuming units 7 located within sections 9 of the fluid distribution network 1. The heat-carrying fluid transfers heat to the heat-consuming unit 7 via a heat exchanger 12 at each heat-consuming unit 7. The fluid then returns from the heat-consuming unit 7 to the heat source 3 via a return line 13. The fluid distribution network 1 also includes a system 15 for regulating the temperature of the heat-carrying fluid in sections 9.

[0041] Figure 2 An embodiment of system 15 is shown in more detail. The idea is to regulate the temperature of the fluid in section 9 by mixing fluid from return line 13 into supply line 11 via bypass line 17. When the pressure in supply line 11 exceeds the pressure in return line 13, bypass pump 19 is installed in bypass line 17 to overcome the pressure difference Δp between supply line 11 and return line 13. To prevent any backflow from supply line 11 to return line 13 through bypass line 17, check valve 21 is installed in the bypass line downstream of bypass pump 19. This means that bypass pump 19 must also provide sufficient pressure to open check valve in the direction toward supply line 11. Differential pressure sensor 23 is installed to determine the pressure difference Δp between the pressure in bypass line 17 upstream of bypass pump 19 and the pressure in bypass line 17 downstream of check valve 21. A first temperature sensor 25 is installed in the supply line 11 downstream of the bypass line 17 to determine the temperature T1 in the supply line 11 downstream of the bypass line 17. The measurement value of the first temperature sensor 25 is transmitted to a control unit 27, which is configured to directly or indirectly control the speed ω of the bypass pump 19.

[0042] It can be considered that simply controlling the speed ω of the bypass pump 19 in a closed-loop manner based on the temperature T1 measured by the first temperature sensor 25 as feedback is currently sufficient. However, it has been shown that this does not work very well because the temperature T1 can be difficult to stabilize and can fluctuate too much, such as Figure 9a As shown in the diagram above. The reason is that the first temperature sensor 25 is placed downstream of the supply line 11 at a certain distance from the bypass line 17 to measure the temperature of the fluid that is well mixed downstream of the bypass line 17. Therefore, there is a relatively large time delay between the change in the speed ω of the bypass pump 19 and the result showing the change in temperature T1 at the first temperature sensor 25. Furthermore, the pressure difference Δp between the supply line 11 and the return line 13 is outside the control of the system 15; that is, the pressure difference Δp is subject to uncontrolled or uncontrollable disturbances or fluctuations. Such disturbances or fluctuations in the pressure difference Δp may originate from varying consumption behavior at the heat consumption side 7 and / or varying environments at the heat generation plant. However, any fluctuation in the pressure difference Δp between the supply line 11 and the return line 13 strongly affects the performance of the bypass pump 19. Therefore, the measurement of the pressure difference Δp by the differential pressure sensor 23 is also transmitted to the control unit 27 to perform feedforward control to compensate for fluctuations in the pressure difference Δp. The present invention now utilizes a control unit 27 to control the speed of the bypass pump 19 based on a combination of closed-loop control and feedforward control. The closed-loop control is based on a determined first supply line temperature T1, while the feedforward control compensates for fluctuations in the pressure difference Δp between the supply line 11 and the return line 13 based on the pressure difference Δp determined by the differential pressure sensor 23. For example, the control unit 27 can be configured to set a target speed. It is a parameterization based on the pump model, q * The target bypass fluid flow rate is provided by bypass pump 19, and p is the pump differential pressure used to compensate for the determined pressure difference Δp. h1 and a h3 These are model parameters describing the pump's characteristics. Model parameter a h1 and a h3 These can be predetermined pump-specific parameters provided by the manufacturer of the bypass pump 19. For example, parameter a h1 and a h3 One of them is the no-flow parameter, which indicates the pressure provided by the bypass pump 19 at a specific speed ω and without bypass flow (i.e., q = 0). Target bypass fluid flow rate q * (T1) is set in a closed-loop manner so that the determined supply line temperature T1 is close to the desired target supply line temperature. Deviation between Minimize. The result of this combination of closed-loop control based on temperature feedback and feedforward control based on pressure difference is... Figure 9bThe diagram shows a very stable supply line temperature T1 throughout the day, although the pressure difference Δp between supply line 11 and return line 13 fluctuates uncontrollably.

[0043] Figure 3 Another embodiment of system 15 is shown. Figure 3 Implementation examples and Figure 2 The difference in the illustrated embodiment lies in what the differential pressure sensor 23 measures. Figure 3 In this configuration, differential pressure sensor 23 measures the pressure difference between the outlet of the bypass pump (i.e., upstream of check valve 21) and the inlet of the bypass pump 19. This has the advantage that pressure sensor 23 can be pre-installed at and / or integrated into the bypass pump 19. However, this embodiment is less advantageous in terms of control because check valve 21 may have difficulty stabilizing to the correct opening degree quickly in certain situations. Fluctuations in the opening degree of check valve 21 can cause undesirable interference with the differential pressure measurement. This means that the compensating pump differential pressure p should rise more slowly during bypass pump startup to avoid large overshoot or undershoot in closed-loop control based on the supply line temperature T1.

[0044] Figure 4 Another embodiment of system 15 is shown. (Compared to...) Figure 2 Compared to the embodiments shown, Figure 4 The embodiment shown includes two additional temperature sensors, wherein a second temperature sensor 29 is mounted at the return line 13 to determine a second temperature T2. Figure 4 In this system, the second temperature sensor 29 is located at the return line 13 downstream of the bypass line 17. Alternatively, the second temperature sensor 29 can be located anywhere on the return line 13 upstream of the bypass line or on the bypass line 17. The third temperature sensor 31 is located at the supply line 11 upstream of the bypass line 17 to determine a third temperature T3. Using these additional temperature measurements T2 and T3, the system 15 is able to compensate not only for uncontrolled fluctuations in the pressure difference between the supply line 11 and the return line 13, but also for uncontrolled fluctuations in the supply line temperature T3 and / or the return line temperature T2. In particular, the return line temperature T2 can depend on the heat consumption at the heat consumption point 7. Energy saving and flow balance require the following equations to apply: q1(T1-T2) = q3(T3-T2) and q2(T1-T2) = q3(T3-T1), where q1 is the supply line flow downstream of the bypass line 17 at the first temperature sensor 25, q2 is the bypass flow through the bypass pump 19, and q3 is the supply line flow upstream of the bypass line 17 at the third temperature sensor 31. To compensate for the fluctuation dT2 of the return line temperature T2, the bypass flow q2 must be changed by dq2 as follows:

[0045] Over time, the uncontrolled fluctuations in the return line temperature T2 can be controlled by the feedforward-controlled flow portion. Integrate the corresponding time derivative over time. To compensate. Integrating over time may have the following drawbacks: feedforward flow component It may drift over time, and control unit 27 may face termination issues.

[0046] exist Figure 5 The solution to this problem is shown, illustrating an embodiment of the control method described herein. Target supply line temperature. The supply line temperature T1, measured by the first temperature sensor 25, is fed into the flow section for closed-loop control. In the feedback controller, the return pipeline temperature T2, the upstream supply pipeline temperature T3, and the bypass fluid flow rate q2 are fed into the T2 disturbance compensator, which outputs the time derivative of the bypass flow rate q2, i.e., Similarly, the downstream supply line temperature T1, the return line temperature T2, the upstream supply line temperature T3, and the bypass fluid flow rate q2 are fed into the T3 disturbance compensator, which uses the formula... Output the time derivative of the bypass flow q2, i.e. These time derivatives The summation is fed into a low-pass filter, which behaves similarly to an integral over high frequencies, and outputs the feedforward control flow portion. The feedforward control flow section is added to the closed-loop control flow section. Then the sum q * Used as the anti-pumping model function f -1 (q * The target bypass flow rate in (p) (where p is the pump differential pressure used to compensate for the determined pressure difference Δp measured by differential pressure sensor 23), and the target speed ω of the bypass pump 19 is output.

[0047] Figure 6 As shown Figure 5 The embodiment of the control method shown differs in that the pump differential pressure p is not directly fed into the reverse pump model function when the bypass pump 19 starts, but rises slowly. This is for applications based on... Figure 3 The system of the illustrated embodiment is particularly advantageous, wherein a differential pressure sensor 23 integrated into the bypass pump 19 is used for feedforward control. (The last part, "in the form of...", appears to be a fragment and doesn't translate directly. It's left as is.) The differential pressure rise function of dt is multiplied by the pump differential pressure p to achieve a slow rise. A constant C is chosen such that when time t1-t2 has elapsed, the differential pressure rise function is 0 at t0 and 1 at t1.

[0048] Figure 7 Another embodiment of the system 15 according to this disclosure is shown. Unlike the previously described embodiments, the pressure difference Δp is not determined by a single differential pressure sensor 23, but rather based on pressure measurements from two or more pressure sensors 33, 35, 37. A first pressure sensor 33 is installed at the supply line 11 downstream of the bypass line 17. A second pressure sensor 35 is installed at the return line 13. A third pressure sensor 37 is installed at the supply line 11 upstream of the bypass line 17. The pressure difference Δp is then given by Δp = p3 - p2, where p2 is the pressure measured by the second pressure sensor 35, and p3 is the pressure measured by the third pressure sensor 37. Figure 7 In the illustrated embodiment, a second pump 39 is installed at the supply line 11 between the bypass line 17 and the first temperature sensor 25. Such a second pump 39 may already be available or installed to increase the pressure in the supply line 11. The second pump 39 can be controlled by a separate second control unit 41 that receives pressure measurements p1, p2, and p3 from pressure sensors 35, 37, and 39. The second control unit 41 is signal-connected to a control unit 27 for controlling the speed of the bypass pump 19 and transmits information about the pressure difference Δp = p3 - p2 to the control unit 27 for feedforward control to adjust the bypass flow rate accordingly. Control units 27 and 41 are preferably integrated into the bypass pump 19 and the second pump 39, respectively. Alternatively, one or more of the control units 27 and 41 can be implemented in a controller separate from the pumps 19 and 39.

[0049] like Figure 8 As shown, in addition to the control units 27 and 41 integrated in the bypass pump 19 and the second pump 39 respectively, a third control unit 43 is provided, preferably an external programmable logic controller (PLC). The third external control unit 41 can be connected to the other control units 27 and 41 via a bus connection 45. The temperature measurement values ​​T1, T2, and T3 of the temperature sensors 25, 31, and 33 are transmitted to the first control unit 27, and the pressure measurement values ​​p1, p2, and p3 of the pressure sensors 35, 37, and 39 are transmitted to the second control unit 41. The external third control unit 43 can be used to execute control methods and command the control units 27 and 41 to operate the pumps 19 and 39 at a certain speed.

[0050] Figure 9a The bottom plot shows an example of how an uncontrolled pressure difference Δp behaves over a day. The top plot... Figure 9aThe diagram illustrates the fluctuations in supply line temperature T1 that occur without the control methods described herein. It can be seen that the supply line temperature T1 fluctuates significantly due to uncontrolled fluctuations in the pressure difference Δp between supply line 11 and return line 13. This situation is unacceptable for the utility provider operating the fluid distribution network 1. The goal is to achieve a stable, desired supply line temperature T1 regardless of uncontrolled pressure fluctuations Δp. The results of applying the control methods described herein are shown in... Figure 9b As shown in the diagram, pressure fluctuations remain uncontrolled and persist throughout the day, but the supply line temperature T1 is within the target supply line temperature range. The temperature is very stable within a small local area. This indicates that the system and method described in this paper provide an effective solution for regulating the temperature of the heat-carrying fluid in a section of a fluid distribution network. List of reference numerals 1. Fluid distribution network 3. Thermal energy 5. Supply pump 7. Heat energy consumption 9. Sections of the fluid distribution network 11 Supply pipelines 12 Heat Exchangers 13 Return Pipeline 15 Systems 17 Bypass pipeline 19. Bypass pump 21 Check valve 23 Differential pressure sensor 25 First Temperature Sensor 27 First Control Unit 29 Second Temperature Sensor 31 Third Temperature Sensor 33 First pressure sensor 35 Second pressure sensor 37 Third pressure sensor 39 Second Pump 41 Second Control Unit 43 Third Control Unit 45 Bus connection

Claims

1. A system (15) for regulating the temperature of a thermal energy-carrying fluid in a section (9) of a fluid distribution network (1), the fluid distribution network (1) comprising a supply line (11) and a return line (13), the supply line (11) for transporting fluid from a thermal energy source (3) to at least one thermal energy consumer (7) located within the section (9), and the return line (13) for transporting fluid from the at least one thermal energy consumer (7) back to the thermal energy source (3), wherein, The system (15) includes: - A bypass line (17) connects the return line (13) to the supply line (11) for mixing fluid from the return line (13) into the supply line (11). - At least one bypass pump (19) is arranged at the bypass line (17) for pumping fluid from the return line (13) to the supply line (11). - Control units (27, 41, 43) are configured to directly or indirectly control the speed (ω) of the at least one bypass pump (19). - At least one temperature sensor is arranged and configured to determine the temperature of the fluid in the supply line (11) downstream of the bypass line (17). ),as well as - At least one pressure sensor is arranged and configured to determine the uncontrolled pressure difference between the supply line (11) and the return line (13). or the pressure difference associated with it. The control units (27, 41, 43) are configured to control the speed (ω) of the at least one bypass pump (19) based on a combination of the following: - Closed-loop control, used based on the determined supply line temperature ( ) provides fluid flow in the bypass line (17) to achieve the target supply line temperature, and - Feedforward control, used based on the determined pressure difference ( To compensate for the pressure difference between the supply line (11) and the return line (13). fluctuations, Furthermore, the control units (27, 41, 43) are also configured to set the target bypass fluid flow rate. To achieve the determined supply line temperature With the target supply pipeline temperature Deviation between minimize.

2. The system (15) according to claim 1, wherein, The control units (27, 41, 43) are configured to determine the target velocity (ω) as a parameterized pump-based model function. To combine the closed-loop control and the feedforward control, wherein the pump-based function It consists of at least two predetermined parameters , Parameterization.

3. The system (15) according to claim 1, wherein, The control units (27, 41, 43) are configured to set the pump differential pressure. To compensate for the determined pressure difference .

4. The system (15) according to claim 2, wherein, The control units (27, 41, 43) are configured to set the pump differential pressure. To compensate for the determined pressure difference .

5. The system (15) according to any one of the preceding claims further includes a check valve (21) at the bypass line (17) downstream of the at least one bypass pump (19), wherein, The check valve (21) is configured to prevent fluid from flowing from the supply line (11) through the bypass line (17) to the return line (13).

6. The system (15) according to claim 5, wherein, The at least one pressure sensor is arranged and configured to determine the pressure difference by measuring the difference between the following pressures ( ): - The pressure in the bypass line (17) upstream of the at least one bypass pump (19) or in the return line (13), and - The pressure downstream of or upstream of the check valve (21), or the pressure in the supply line (11) upstream of the at least one bypass line (17).

7. The system (15) according to any one of claims 1-4 further includes at least one temperature sensor, said at least one temperature sensor being arranged and configured to determine the temperature of the fluid in the return line (13). ), and the at least one temperature sensor is arranged and configured to determine the temperature of the fluid in the supply line (11) upstream of the bypass line (17). ),in, The control units (27, 41, 43) are configured to set the target speed based on feedforward control. ), to compensate for the temperature of the fluid in the supply line (11) upstream of the bypass line (17) The temperature of the fluid in the return line (13) The temperature difference between () (uncontrolled fluctuations) 8. The system (15) according to claim 5 further includes at least one temperature sensor arranged and configured to determine the temperature of the fluid in the return line (13). ), and the at least one temperature sensor is arranged and configured to determine the temperature of the fluid in the supply line (11) upstream of the bypass line (17). ),in, The control units (27, 41, 43) are configured to set the target speed based on feedforward control. ), to compensate for the temperature of the fluid in the supply line (11) upstream of the bypass line (17) The temperature of the fluid in the return line (13) The temperature difference between () (uncontrolled fluctuations) 9. The system (15) according to claim 6 further includes at least one temperature sensor arranged and configured to determine the temperature of the fluid in the return line (13). ), and the at least one temperature sensor is arranged and configured to determine the temperature of the fluid in the supply line (11) upstream of the bypass line (17). ),in, The control units (27, 41, 43) are configured to set the target speed based on feedforward control. ), to compensate for the temperature of the fluid in the supply line (11) upstream of the bypass line (17) The temperature of the fluid in the return line (13) The temperature difference between () (uncontrolled fluctuations) 10. The system (15) according to any one of claims 1-4, wherein, The control unit (27, 41, 43) is configured such that if the speed ( ) lower than the predetermined stopping speed threshold ( ), then stop the at least one bypass pump (19), and if the speed ( ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

11. The system (15) according to claim 5, wherein, The control unit (27, 41, 43) is configured such that if the speed ( ) lower than the predetermined stopping speed threshold ( ), then stop the at least one bypass pump (19), and if the speed ( ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

12. The system (15) according to claim 6, wherein, The control unit (27, 41, 43) is configured such that if the speed ( ) lower than the predetermined stopping speed threshold ( ), then stop the at least one bypass pump (19), and if the speed ( ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

13. The system (15) according to claim 7, wherein, The control unit (27, 41, 43) is configured such that if the speed ( ) lower than the predetermined stopping speed threshold ( ), then stop the at least one bypass pump (19), and if the speed ( ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

14. The system (15) according to claim 8, wherein, The control unit (27, 41, 43) is configured such that if the speed ( ) lower than the predetermined stopping speed threshold ( ), then stop the at least one bypass pump (19), and if the speed ( ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

15. The system (15) according to claim 9, wherein, The control unit (27, 41, 43) is configured such that if the speed ( ) lower than the predetermined stopping speed threshold ( ), then stop the at least one bypass pump (19), and if the speed ( ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

16. The system (15) according to any one of claims 1-4, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 17. The system (15) according to claim 5, wherein, The control unit (27, 41, 43) is configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), raising the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 18. The system (15) according to claim 6, wherein, The control unit (27, 41, 43) is configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), raising the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 19. The system (15) according to claim 7, wherein, The control unit (27, 41, 43) is configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), raising the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 20. The system (15) according to claim 8, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 21. The system (15) according to claim 9, wherein, The control unit (27, 41, 43) is configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), raising the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 22. The system (15) according to claim 10, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 23. The system (15) according to claim 11, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 24. The system (15) according to claim 12, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 25. The system (15) according to claim 13, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), raising the feedforward control to compensate for the pressure difference ( The uncontrolled fluctuations.

26. The system (15) according to claim 14, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 27. The system (15) according to claim 15, wherein, The control units (27, 41, 43) are configured to, upon activating the at least one bypass pump (19), multiply the rise value by the determined pressure difference ( ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 28. A method for regulating the temperature of a thermal energy-carrying fluid in a section (9) of a fluid distribution network (1), the fluid distribution network (1) comprising a supply line (11) for conveying fluid from a thermal energy source (3) to at least one thermal energy consumer (7) located within the section (9), a return line (13) for conveying fluid from the at least one thermal energy consumer (7) back to the thermal energy source (3), and a bypass line (17) connecting the return line (13) to the supply line (11), the bypass line (17) for mixing fluid from the return line (13) into the supply line (11), wherein, The method includes: - The temperature of the fluid in the supply line (11) downstream of the bypass line (17) is determined by at least one temperature sensor. ), - The pressure difference between the supply line (11) and the return line (13) is determined by at least one pressure sensor. or the pressure difference associated with it. - The speed (ω) of the at least one bypass pump (19) is controlled directly or indirectly, the at least one bypass pump (19) being arranged at a bypass line (17) that connects the return line (13) to the supply line (11) for mixing fluid from the return line (13) into the supply line (11). The speed (ω) of the at least one bypass pump (19) is controlled directly or indirectly based on the following combination: - Closed-loop control, used based on the determined supply line temperature ( ) provides fluid flow in the bypass line (17) to achieve the target supply line temperature, and - Feedforward control, used based on the determined pressure difference ( ) to compensate for the uncontrolled pressure difference between the supply line (11) and the return line (13). fluctuations, Furthermore, the target bypass fluid flow rate is included. Set to the determined supply line temperature With the target supply pipeline temperature Deviation between minimize.

29. The method according to claim 28, wherein, The combination of the closed-loop control and the feedforward control includes: determining the target velocity (ω) as a parameterized pump-based function. Among them, setting the pump differential pressure To compensate for the determined pressure difference The function based on the pump model It consists of at least two predetermined parameters , Parameterization.

30. The method of claim 28 further includes preventing fluid from flowing from the supply line (11) through the bypass line (17) to the return line (13) by means of a check valve (21) disposed downstream of the at least one bypass pump (19) at the bypass line (17).

31. The method of claim 29 further includes preventing fluid from flowing from the supply line (11) through the bypass line (17) to the return line (13) by means of a check valve (21) disposed downstream of the at least one bypass pump (19) at the bypass line (17).

32. The method according to claim 30, wherein, Determine the pressure difference ( This includes measuring the difference between the following pressures: - The pressure in the bypass line (17) upstream of the at least one bypass pump (19) or in the return line (13), and - The pressure downstream of or upstream of the check valve (21), or the pressure in the supply line (11) upstream of the at least one bypass line (17).

33. The method according to claim 31, wherein, Determine the pressure difference ( This includes measuring the difference between the following pressures: - The pressure in the bypass line (17) upstream of the at least one bypass pump (19) or in the return line (13), and - The pressure downstream of or upstream of the check valve (21), or the pressure in the supply line (11) upstream of the at least one bypass line (17).

34. The method according to any one of claims 28 to 33, further comprising determining the temperature of the fluid in the return line (13) by means of at least one temperature sensor. ), and also includes determining the temperature of the fluid in the supply line (11) upstream of the bypass line (17) by means of at least one temperature sensor. ),in, Directly or indirectly controlling the speed (ω) of the at least one bypass pump (19) includes setting a target speed based on feedforward control. ), to compensate for the temperature of the fluid in the supply line (11) upstream of the bypass line (17) The temperature of the fluid in the return line (13) The temperature difference between () The uncontrolled fluctuations.

35. The method according to any one of claims 28 to 33, further comprising if the speed ( ) lower than the predetermined stopping speed threshold ( If the speed (19) is stopped, then the at least one bypass pump (19) is stopped, and the method further includes stopping the at least one bypass pump (19) if the speed (19) is stopped. ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

36. The method of claim 34, further comprising if the speed ( ) lower than the predetermined stopping speed threshold ( If the speed (19) is stopped, then the at least one bypass pump (19) is stopped, and the method further includes stopping the at least one bypass pump (19) if the speed (19) is stopped. ) equal to or higher than the predetermined start-up speed threshold ( If ), then the at least one bypass pump (19) will be started.

37. The method according to any one of claims 28 to 33, further comprising: When starting the at least one bypass pump (19), the pressure difference is calculated based on the increase multiplied by the determined pressure difference. ), raising the feedforward control to compensate for the pressure difference ( The uncontrolled fluctuations.

38. The method of claim 34, further comprising: When starting the at least one bypass pump (19), the pressure difference is calculated based on the increase multiplied by the determined pressure difference. ), and raise the feedforward control to compensate for the pressure difference ( (uncontrolled fluctuations) 39. The method of claim 35, further comprising: When starting the at least one bypass pump (19), the pressure difference is calculated based on the increase multiplied by the determined pressure difference. ), raising the feedforward control to compensate for the pressure difference ( The uncontrolled fluctuations.

40. The method of claim 36, further comprising: When starting the at least one bypass pump (19), the pressure difference is calculated based on the increase multiplied by the determined pressure difference. ), raising the feedforward control to compensate for the pressure difference ( The uncontrolled fluctuations.

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