Method for identifying undersupply or oversupply in a hydraulic network

Abstract

The invention relates to a method for detecting undersupply or oversupply of consumers (R1, R2) in a heating system, the heating system comprising: at least one circulation pump (2) which conveys a heat transfer medium to the consumers (R1, R2); and a plurality of thermostatic valves (V1, V2) which respectively regulate the flow rate through one of the consumers (R1, R2). Provision is made for the circulation pump (2) to generate a periodically fluctuating head (H), and for the volume flow (Q) generated thereby by the circulation pump (2) to be determined, and for a saturation signal (Q) to be calculated from the volume flow. 1,sat , Q n,sat ) and conduct analysis and evaluation, where when the saturation signal (Q 1,sat , Q n,sat ) is higher than the limit value (G), an inference of insufficient supply or excessive supply is made.

Description

Technical Field

[0001] The invention relates to a method for detecting an undersupply or oversupply of a consumer in a heating system, the heating system comprising at least one circulation pump which conveys a heat transfer medium to the consumer and a plurality of thermostatic valves which respectively regulate the volume flow through one of the consumers. Background Art

[0002] Building heating systems have consumers in the form of heating elements, and the problem of undersupply or oversupply of these consumers is well known. In the case of undersupply, the room to be heated is not warm enough because the pressure differential generated by the circulation pump is too low to achieve a sufficient volume flow through the respective consumer, even with a fully open thermostatic valve. In the case of oversupply, the thermostatic valve must be closed significantly due to excessive pressure in the circulation pump to achieve a sufficient pressure drop and thus reduce the volume flow through the respective consumer. However, this pressure drop also means energy losses, which can be avoided or at least minimized with a circulation pump that generates a smaller pressure differential.

[0003] The goal of optimal heating regulation is to meet the required heat demand using the least amount of energy possible. This is the case when the thermostatic valve in a room is at its lower control limit—just barely fully open. If the heat demand increases further or the differential pressure of the circulation pump decreases further, the valve can no longer open further to meet the demand. In other words, the actuator of the control system (in this case, the thermostatic valve) reaches saturation. For this reason, methods have emerged that attempt to identify the (current) system characteristic curve of the heating system resulting from this valve position and adapt the pump regulation to this characteristic curve. However, this often requires a full day of learning, during which changes in the volume flow are evaluated. At the same time, a minimum network parabola is determined, and it is assumed that the system is not undersupplied if this minimum network parabola is not reached. However, this assumption is only valid if the heating system is hydraulically balanced, or in other words, if all valves are saturated simultaneously. However, this is often not the case in heating systems. Furthermore, both oversupplier and undersupplier are undesirable, as this often results in noise from the thermostatic valves. Summary of the Invention

[0004] The object of the present invention is therefore to provide a method which detects both undersupply and oversupply and which requires only a short time, in particular without requiring a learning phase.

[0005] This object is achieved by a method according to the invention for detecting an undersupply or oversupply of a consumer in a heating system, the heating system comprising: at least one circulation pump, which conveys a heat transfer medium to the consumer; and a plurality of thermostatic valves, each of which regulates a delivery flow through one of the consumers, the circulation pump generating a periodically fluctuating head, and the resulting volume flow of the circulation pump being determined, a saturation signal being calculated from this volume flow and evaluated, the saturation signal containing information as to whether the thermostatic valve was able to compensate for the fluctuating head or whether, during the compensation, it reached its upper or lower control limit, wherein an undersupply or oversupply is inferred when the absolute value of the value of the saturation signal exceeds a limit value.

[0006] According to the invention, it is provided that the circulation pump generates a periodically fluctuating head, the resulting volume flow of the circulation pump is determined, a saturation signal is then calculated from the volume flow and evaluated, wherein an undersupply or oversupply is inferred if the value of the saturation signal exceeds a limit value in absolute terms.

[0007] The central idea of ​​the present invention is to induce periodic pressure fluctuations in a heating system (as system disturbances) and to evaluate the thermostatic valve's response to determine whether it is able to compensate for the fluctuations (eliminating them through control), i.e., whether it exhibits high rigidity / stability relative to the disturbance variable of the saturation signal, or whether it has reached its upper control limit (fully open) or lower control limit (fully closed) during the compensation period. The saturation signal according to the present invention carries this information and can therefore be evaluated in this regard. If the system is viewed from the perspective of the pump, an ideally rigid system would have an infinitely high impedance, or a hydraulic conductance value of zero at the excitation frequency, i.e., the frequency of the periodic pressure fluctuations. In other words, despite the (periodic) changes in head, the volume flow rate does not change.

[0008] The head fluctuation can preferably be designed / determined such that the thermostatic valve can compensate for the fluctuating head and thus keep the volume flow through the or the corresponding consumer constant. This is the case when the head fluctuates sufficiently slowly. For example, the head can fluctuate with a cycle time T of between 5 and 60 minutes.

[0009] According to a preferred embodiment variant, the head fluctuation can be generated by speed modulation of the circulating pump. To this end, an excitation signal f(t) can be superimposed on a manipulated variable of the circulating pump. The manipulated variable can be, for example, a setpoint value for the speed, torque, electrical power, or current of the circulating pump. The excitation signal can be sinusoidal, for example, in the form f(t) = a·sin(ωt), where a is the amplitude and ω = 1 / T is the excitation frequency, or T is the period.

[0010] For example, the volume flow can be determined by measurement using a volume flow sensor or by calculation by evaluating other variables of the circulation pump. For example, German patent application DE 102014004336 A1 discloses a method for calculating the volume flow.

[0011] In a first embodiment variant, the saturation signal can be formed by multiplying the volume flow of the circulation pump by the excitation signal f(t) or by a sinusoidal signal sin(ωt) having the excitation frequency ω of the excitation signal f(t) and by subsequent integration (Fourier transform) of the product thus formed over the period of the excitation signal f(t), preferably according to the following formula:

[0012]

[0013] or

[0014]

[0015] The saturation signal Q formed in this way 1,sat This is also referred to below as volume flow integration. In other words, in this embodiment variant, the ratio of the fundamental frequency of the excitation signal to the generated volume flow is evaluated.

[0016] In a second embodiment variant, the saturation signal can be formed by multiplying the volume flow of the circulation pump by a sinusoidal signal sin(nωt) having a frequency ω that is an integer multiple n of the excitation signal f(t) and by subsequent integration (Fourier transform) of the product thus formed over the period of the excitation signal f(t), preferably according to the following formula:

[0017]

[0018] In this second variant embodiment, the saturation signal Q n,sat It is also formed by a volume flow integral. However, in this saturation signal, the ratio of the nth harmonic of the excitation signal to the generated volume flow is evaluated.

[0019] The volume flow integral represents the temporal variation of the volume flow at the excitation frequency or the nth harmonic.

[0020] Ideally, a thermostatic valve ensures a constant volume flow, regardless of the head, when the heat demand is stable. This means the volume flow does not change, as the thermostatic valve compensates (corrects) for changes in head almost instantly. However, the volume flow does change when the thermostatic valve reaches its control limit, as occurs during undersupply and oversupply.

[0021] In the event of an undersupply, the thermostatic valve can no longer regulate the desired volume flow through the consumer because the pressure provided by the circulation pump or its head is no longer sufficient. In this case, the valve is already fully open and cannot be opened further to increase the volume flow. If the modulated head of the circulation pump decreases, the volume flow also decreases when an undersupply occurs. This initially occurs only during the negative half-wave of the head fluctuation, but then also during the positive half-wave as the head continues to decrease. The head drop (speed drop) and the change in volume flow therefore occur in the same direction.

[0022] Periodic fluctuations in head are increasingly reflected in the volume flow integral. More precisely, a drop in head becomes apparent in the frequency spectrum through an increasing positive value of the volume flow integral. Therefore, an undersupply can be inferred when or as soon as the value of the saturation signal is or becomes positive, that is, greater than zero. In practical implementation, due to deviations from idealized conditions (variations in heat demand during the excitation period, noise in the measurement signal (volume flow, speed, etc.)), a limit value G greater than zero is preferably selected as the decision threshold for identifying an undersupply. The saturation signal is compared with this limit value, with an inference of undersupply being drawn when the saturation signal is positive and, in absolute terms, greater than the limit value.

[0023] The above applies, on the one hand, to the integral of the volume flow at the excitation frequency. However, the same approach can also be used to evaluate the harmonics for oversupply detection, particularly the odd harmonics. Thus, if the value of the saturation signal for the nth harmonic nω exceeds a limit value, an undersupply can be inferred.

[0024] The advantage of analyzing the volume flow response to the excitation signal lies in the fact that the Fourier transform exhibits a good filtering effect, making it possible to distinguish the desired signal from any interference signals. These interference signals arise when the system's heat demand varies slowly, for example, over the course of a day. Since these variations have a different spectral content than the excitation signal according to the present invention, which is generated by periodic head fluctuations, the two can be distinguished.

[0025] In a similar way, inferences can be drawn about oversupply. In the case of oversupply, the thermostatic valve receives an excessively high pressure from the circulation pump and is then completely closed (the valve is saturated) because the thermostatic valve cannot usually open the valve as small as desired. This means that, despite the volume flow demand, the thermostatic valve is completely closed in the case of a high pressure difference. The volume flow is therefore zero. Only when the head or pressure drops does the valve open and the desired volume flow can then be adjusted. The volume flow then either corresponds to the rated value or is zero. Despite the drop in head or the drop in speed, the volume flow rises from zero due to the opening of the valve. The drop in head (drop in speed) and the change in volume flow therefore occur in opposite directions.

[0026] This is evident in the frequency spectrum, for example, by the increasing negative value of the volume flow integral. Therefore, if or as soon as the value of the saturation signal is or becomes negative, that is, less than zero, an inference of oversupply can be drawn. Due to deviations from idealized conditions (variations in the heat demand during the excitation period, noise in the measurement signal (volume flow, speed, etc.)), a limit value G can be used as a decision threshold for identifying oversupply, but this limit value is negative in this case. Alternatively, a positive limit value can be used and the absolute value of the saturation signal compared to this limit value, with an inference of undersupply being drawn when the saturation signal is negative and its absolute value is greater than the limit value.

[0027] The above also applies to the integral of the volume flow at the excitation frequency. However, the harmonics, in particular the odd harmonics, can also be evaluated in the same way for oversupply detection. Thus, an oversupply can be inferred if the value of the saturation signal for the nth harmonic nω is negative and its absolute value is greater than a limit value.

[0028] The limit value for undersupply may differ from the limit value for oversupply, so that in practice two different limit values ​​may be used.

[0029] In the method, it is first possible to check whether the saturation signal value is greater than a minimum value Gmin in absolute value at the excitation frequency ω or the nth harmonic, in order to determine whether there is an oversupply or undersupply, that is, whether the saturation signal is not in the noise around zero. Next, the sign can be checked, that is, whether the value of the saturation signal is greater than or less than zero, to determine whether it is an undersupply (>0) or an oversupply (<0). If the same limit value is used for undersupply and oversupply, the minimum value can immediately correspond to this common limit value. If different limit values ​​are used for undersupply and oversupply, after comparison with the minimum value Gmin, the limit value to be used for identifying oversupply or undersupply can be selected based on the sign. This limit value can be greater than the minimum value Gmin in absolute value. This improves the recognition reliability and eliminates incorrect assumptions.

[0030] Preferably, the integrated value of the volume flow at the nth harmonic (e.g. the 3rd, 5th, 7th, 9th, 11th or 13th harmonic) can be evaluated when, due to the high thermal time constant of the room, complete compensation of the head fluctuations is not ensured by the thermostatic valve at the excitation frequency and the excitation frequency cannot be reduced further (in particular to a cycle time of more than 60 minutes) - otherwise the response of the system to the excitation or to the periodic head fluctuations is insignificant.

[0031] To further improve the recognition accuracy of the method, provision can be made for the assumption of undersupply or oversupply to be made over a plurality of cycles. Thus, in one embodiment variant, an assumption of undersupply or oversupply is made only if the saturation signal exceeds the limit value successively over a plurality of (e.g., 3 to 5) integration cycles.

[0032] The saturation signal can also be improved by drift correction, for example by determining the initial and final values ​​of the volume flow integral during each cycle and assuming a linear curve of the average of the initial and final values. This average curve then forms a drift signal, and the volume flow integral can then be corrected by the amount generated by this drift signal.

[0033] The advantage of this method is that undersupply can be detected even in the case of complete saturation, i.e., when the thermostatic valve is open during the entire cycle, because the volume flow follows the actuation signal. However, in the case of oversupply, this oversupply can only be detected if the valve leaves the saturated (closed) state for at least part of the cycle, because otherwise no volume flow flows and the volume flow integral is therefore equal to zero.

[0034] The method assumes that when the valve is operating within the normal adjustment range, there is no correlation between the periodic excitation and the resulting volume flow change. Furthermore, it should be noted that due to active head modulation, particularly speed modulation, the visibility of certain events in the saturation signal always occurs with a delay approximately equal to the integration time, since the integration result is always obtained at the end of the integration time and then has to be evaluated (computation time). This means that, in extreme cases, the determination of undersupply or oversupply may only be made after the integration period T. This is the case at least at the beginning of the method, that is, when the function for executing the method is activated in the circulation pump 2. According to one embodiment variant, a further integration interval may be initiated at the end of each integration interval 0 to T, so that undersupply or oversupply can always be determined after a multiple of the period T. However, according to another embodiment variant, a flexible integration time from 0+x to T+x may also be used, so that after the first complete period T, an undersupply or oversupply conclusion can be drawn at any time.

[0035] Furthermore, the present invention relates to a circulation pump for a heating system, which is provided for carrying out the above-described method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Further features, properties and advantages of the invention are explained below with reference to exemplary embodiments and the accompanying drawings.

[0037] In the attached figure:

[0038] Figure 1 It is a simplified schematic diagram of the heating system;

[0039] Figure 2 is the pressure Δp, volume flow Q and volume flow signal Q in the case of insufficient supply 1.sin Curve change line graph;

[0040] Figure 3 are the pressure Δp, volume flow Q and volume flow signal Q in the case of oversupply 1.sin Curve change line graph;

[0041] Figure 4 Flowchart of the method of the present invention. DETAILED DESCRIPTION

[0042] The following is based on Figure 1The method according to the present invention for detecting undersupply or oversupply in a heating system 1 is illustrated by a simulation of a simplified heating system 1 schematically shown in FIG. The building heating system 1 under consideration comprises, for example, only two consumers R1 and R2 in the form of heating elements, arranged in parallel branches 3 of the system 1. A central circulation pump 2 supplies a heat transfer medium to these consumers. Furthermore, a thermostatic valve V1 and V2 is provided in each branch 3 or assigned to each consumer R1 and R2. These thermostatic valves regulate the volume flow Q1 and Q2 through the respective branch 3 depending on the difference between a predetermined room temperature and a measured room temperature. In terms of control technology, the thermostatic valves V1 and V2 each form a P controller and, hydraulically, a variable impedance, while the consumers R1 and R2 and the branch 3 (i.e., the lines forming the supply and discharge lines to these consumers R1 and R2) each form a constant impedance. The adjustment range of the thermostatic valves V1 and V2 ranges from a value of 0 (opening 100%) when the respective valve is fully open to an infinite value (opening 0%) when the valve is closed. However, it is assumed that the valve is already completely closed below an opening of 10%, that is, an infinite resistance is formed, so that no volume flow flows through the respective branch. Figure 1 Also shown are a differential pressure sensor P1 and two volume flow sensors Q1, Q2 in branch line 3. Figure 1 Other components of a conventional heating system, such as a burner, a heat exchanger, a hydronic separator, an expansion tank, and other sensor systems are not shown.

[0043] For the sake of simplicity, it can be assumed that each thermostatic valve V1, V2 adjusts to the required volume flow Q1, Q2 without delay in order to achieve the desired temperature in the respective room or room region that the respective consumer R1, R2 is to heat. In practice, this is achieved by causing the process described below to proceed so slowly that the control time constant of the thermostatic valves V1, V2 is negligible.

[0044] Figure 2 Three line diagrams are shown stacked one above the other, with the time course of the relevant variables. All variables shown are dimensionless here, since this is only a simulation of a model of a basic heating system 1.

[0045] The upper diagram shows the pressure difference Δp of the circulating pump 2 over time t. This pressure difference—aside from the scale and dimensions—also represents the head H of the circulating pump 2, so only the head will be discussed below. According to the present invention, the circulating pump 2 generates a periodically fluctuating head by superimposing a sinusoidal excitation signal f(t) on a manipulated variable n(t) of the circulating pump 2. In this example, the manipulated variable n(t) is a desired speed value for the circulating pump 2, which is predetermined by a higher-level control system. Mathematically, the new manipulated variable n*(t) for the speed thus generated is then expressed as n*(t) = n(t) + f(t). The excitation signal f(t) is formed by f(t) = a·sin(ωt), where a is the amplitude, ω = 1 / T is the excitation frequency, and T is the period. A low excitation frequency ω is selected, for example with a period of between 20 and 60 minutes, so that the thermostatic valves V1, V2 can adapt the volume flows Q1, Q2 to the changing head without delay or significant phase shift. The amplitude a is selected so that the speed fluctuations are between 0.1 and 10% of the maximum speed of the circulating pump 2, for example between 5 and 200 rpm.

[0046] The superordinate control system gradually reduces the head until time t2 by continuously reducing the non-overlapping manipulated variable n(t) for the speed. This control system could, for example, be the superordinate automatic control system of the circulating pump 2, which implements an energy-saving function and simultaneously attempts to always adjust to the minimum head in order to meet the current needs of the heating system 1 with minimal energy consumption. The control system reduces the speed n(t) until it receives information from the undersupply detection according to the present invention that the valve has reached its limit. If this is the case, it increases the speed again to avoid undersupply.

[0047] The middle diagram shows the resulting curves for the volume flow Q1 through the first consumer R1 and the volume flow Q2 through the second consumer R2. A simulation was performed for the first thermostatic valve V1 such that its values ​​for the setpoint temperature and actual temperature were such that a volume flow Q1 of 0.1 had to be set. ref Furthermore, a simulation is performed for the second thermostatic valve V2 so that first a volume flow Q2 of 0.05 must be adjusted. ref , the volume flow rate increases linearly in the later period. Until the time point t1=9, the first thermostatic valve V1 can be readjusted, that is, despite the head fluctuation, the required volume flow rate Q1 of 0.1 is still maintained. ref Remains stable. This means that the first thermostatic valve V1 operates within its operating range and periodically opens when the head H decreases and closes when the head increases, without reaching the control limits. The same is true for the second valve V2 until time t6.

[0048] The lower diagram shows a saturation signal Q determined according to the invention from the volume flow Q=Q1+Q2 of the circulation pump 2 over time t. 1.sat , which is obtained by integrating the volume flow Q multiplied by the unweighted (ie without amplitude a) excitation signal f(t) over a period T:

[0049]

[0050] The lower diagram shows the signal component that the excitation frequency ω (fundamental frequency) has or causes in the volume flow Q. As can be seen, due to the readjustment of the thermostatic valves V1, V2, the saturation signal Q is not present until the time t1. 1,sat The periodic excitation of the head H cannot be identified (when t∈[0,t1], Q 1,sat =0), because the volume flow Q or volume flow Q1, Q2 can be kept constant by the thermostatic valves V1, V2. It can also be said that the stability or impedance of the heating system 1 is infinite at the excitation frequency ω. Therefore, the saturation signal Q 1,sat It is equal to zero until time point t1.

[0051] However, from time t1 onwards, the volume flow Q1ref can no longer be adjusted by the first thermostatic valve V1 for each head. This means that the head has dropped to such an extent that the first thermostatic valve V1 has reached its lower adjustment limit (100% opening), i.e., it cannot be opened further because it is already fully open. This is the beginning of an undersupply, which initially exists temporarily, i.e., during the peak of the negative half-wave, and later for the entire cycle. The volume flow Q1 in the first branch line 3 then changes with the periodic variation of the head H. This is even in the presence of the saturation signal Q 1,sat This can also be seen in , because the saturation signal is no longer zero after time t1. However, due to the integration time T, a delay of one beat (= period T) produces a saturation signal Q different from zero. 1,sat > 0. The hydraulic impedance encountered by the circulating pump 2 at the excitation frequency ω is now significantly reduced.

[0052] In the period between t2 and t3 (period 10 to 20), the head H does not decrease any further. In addition to the lag caused by the integration time, the saturation signal Q 1,satis constant during this period. During this period, the room area heated by the first consumer R1 is continuously undersupplied. The superimposed control system can now react to this information and increase the head again, as occurs here, for example, in the period t3=20<t<30=t6. As a result, the valve V1 is again out of saturation, temporarily from time t4=23 and permanently from time t5=26. This can also be done in the saturation signal Q 1,sat This is detected by the saturation signal which drops back to zero in the time period t4 to t6. The superimposed control system receives this information and reacts by not increasing the lift H any further from the time t6=30 onwards.

[0053] In the example, it is assumed that, starting from the time t6, the heat demand in the second branch 3 then increases, which results in a necessary volume flow Q2 there. ref The heat demand rises to a value that cannot be satisfied by the pressure difference of the circulation pump 2, so that saturation occurs in the second branch 3 initially temporarily from t7 = 43 and permanently from time t8 = 46.5 (valve V2 reaches its control limit, 100% open). This is indicated by the saturation signal Q 1,sat , which is also visible in the flow rate, since it rises again from zero to a positive value. The higher-level control system can therefore react again by further increasing the head.

[0054] The saturation signal Q used 1,sat It is therefore a carrier of information about the supply shortage. As long as the saturation signal Q 1,sat With a clear positive value, there is a supply shortage. For this purpose, a limit value G1 can be specified, which serves as a decision threshold. 1,sat When this limit value G1 is reached or exceeded, a conclusion of insufficient supply can be drawn.

[0055] It should be noted that in the volume flow Q, the saturation signal Q 1,sin The visibility of certain events in the τ always occurs only at the end of the integration time, that is, with a delay of one period T or one cycle T. In addition, a saturation signal Q is generated if the mean value of periodic fluctuations, more precisely the unsuperimposed speed setpoint n(t) or the volume flow demand, changes during the excitation period. 1,sat For this reason, it makes sense to set the decision threshold G1 to a value greater than zero.

[0056] To increase the reliability of detection, the decision to detect a supply shortage can be made based on multiple consecutive cycles. In addition, the signal can be improved through drift correction.

[0057] The method of the present invention makes it possible to detect undersupply in individual branches without having to wait and analyze the entire daily heating cycle. Undersupply can be detected even in advance, in practice after a time that is a few times the time constant of the thermostatic valve, ideally after 5 to 60 minutes. A particular advantage of this method is that it works even when the heating system is hydraulically unbalanced or incorrectly balanced.

[0058] As follows Figure 3 As illustrated by the example in , oversupply can be determined in a manner similar to the described identification of undersupply.

[0059] and Figure 2 similar, Figure 3 Three superimposed graphs are shown for a periodically fluctuating pressure difference Δp or head H (upper graph), the resulting volume flow Q1 in the branch line 3 of the first consumer 1 together with the setpoint value Q1 to be set there. ref (middle line graph) and saturation signal Q 1,sat (lower line chart).

[0060] In this example, it is first assumed that the heating branch 3 initially has a high heat demand and that the circulating pump 2 generates a correspondingly high head H. The first thermostatic valve V1 can initially be adjusted to the necessary volume flow Q and kept constant by compensating or smoothing out periodic fluctuations in the head H.

[0061] If the heat demand of the first branch line 3 now decreases, as is the case until time t8=30, the first thermostatic valve V1 closes more and more. Assume that the thermostatic valve V1 can be adjusted to an opening between 10% and 100%, but is completely closed below 10%. In this case, the upper control limit is reached. Figure 3 This is the case at time t1. The setpoint value to be adjusted is Q1 ref It then drops to a value at which the first thermostatic valve V1 hits its upper regulating limit due to the fixed high pressure difference and closes completely. The volume flow Q therefore drops to zero. However, this state only exists for the duration of the positive half-wave peak in the pressure curve, that is, until time t2. Outside the peak, the head is small, so that the valve is again adjusted to an opening greater than 10%, and a volume flow Q>0 flows through. This is the case at least until the next positive half-wave peak, that is, until time t3. Here, the valve V1 hits its upper regulating limit again and the volume flow Q drops back to zero. At time t4, the valve V1 opens again. Figure 3In the period between t5 and t6, another positive half-wave is generated in the pressure difference fluctuation. At the maximum value of this half-wave, the valve V1 is closed and the volume flow drops to zero. ref The repeated, almost abrupt changes between t1 and t6 are the saturation signal Q in this region. 1,sat Produces negative values.

[0062] The saturation signal Q used 1,sat It is therefore also a carrier of information about the oversupply. 1,sat With a significant negative value, there is an oversupply. For this purpose, a limit value G2 can also be specified, which serves as a decision threshold. 1,sat If this limit value G2 is reached or exceeded in absolute terms and is simultaneously negative, an oversupply can be inferred.

[0063] If the valve V1 is saturated during the entire activation period, the oversupply cannot be detected because the saturation signal or the hydraulic conductance value is equal to zero. Therefore, a quick response should be made to the oversupply and the head H of the pump 2 should be reduced. Figure 3 In the example shown, the head H decreases starting at time t5. This is initiated by the higher-level control system and continues until time t7. This head reduction allows the valve to be released from saturation and can be adjusted again to the volume flow Q1 required to meet the heat demand. ref , that is, the periodic fluctuations of the head H are balanced or eliminated by control. From the time point t8 = 30 onwards, the heat demand of the first branch 3 is constant.

[0064] One possibility for accelerating the recognition is to increase the excitation frequency ω of the excitation signal f(t), for example, to select the excitation frequency ω of the excitation signal f(t) so that it has a period T of less than 20 minutes, for example between 5 and 20 minutes. Although the thermostatic valve can no longer keep the volume flow Q constant in the case of this excessively rapid modulation of the head H, and thus shows an oscillation in the volume flow Q that is out of phase with the excitation or fluctuating head H, undersupply or oversupply can be detected in this case based on the harmonics in the volume flow curve Q. For this purpose, a corresponding saturation signal Q is determined. n,sat , the saturation signal describes the signal portion of the volume flow Q caused by integer multiples n (nth harmonic) of the excitation frequency ω. This saturation signal Q n,sat It can be formed by multiplying the volume flow of the circulating pump 2 by a sinusoidal signal sin(nωt) having an integer multiple n of the frequency ω of the excitation signal f(t) and subsequently integrating the product thus formed over one period of the excitation signal f(t):

[0065]

[0066] Thus, for example, it is possible to check whether or to what extent harmonic oscillations of the excitation frequency, for example harmonics of the odd sequence n=3, 5, 7, 9, 11 or 13, are present, since these harmonic oscillations are formed in the case of excessively fast modulation. Similarly, the saturation signal Q can be determined by comparison with a limit value and / or by measuring the saturation signal Q at the nth harmonic. n,sat The sign of the value of is analyzed and evaluated. Depending on the situation, several harmonics can also be considered together.

[0067] Figure 4 A flow chart of the method according to the present invention is shown. In step S1, the method or the oversupply / undersupply detection according to the present invention is activated in the control and regulation electronics of the circulating pump 2. Activation can be performed manually. At the same time, the oversupply / undersupply detection can be either an add-on function or a component of a higher-level speed control system, in particular an automatic control system. In this case, the oversupply / undersupply detection is automatically activated when the automatic control system is activated. Provision can also be made for the automatic control system to be activated at the factory together with the oversupply / undersupply detection in the control and regulation electronics of the circulating pump 2.

[0068] The higher-level control system issues a speed setpoint value n(t), which is modulated in step S2 to generate periodic head fluctuations. The modulation is performed by superimposing the speed setpoint value n(t) with a sinusoidal excitation signal having a period T between 5 and 60 minutes as described above. Subsequently, in step S3, the saturation signal Q is calculated. 1,sat And compare the absolute value of its value with a minimum value Gmin, step 4. The minimum value Gmin is greater than the saturation signal Q 1,sat If the minimum value is not exceeded, there is no anomaly and the saturation signal Q is calculated for the next period T. 1,sat As an alternative, a flexible integration time from 0+x to T+x can also be used, so that after the first integration over a complete cycle, a saturation signal Q is present at each time point t. 1,sat value.

[0069] If the minimum value Gmin is exceeded, there is a clear alternating portion in the volume flow which indicates undersupply or oversupply. In order to first distinguish and then verify this, the saturation signal Q is checked. 1,satIs it positive or negative? Step S5. If it is positive, there may be a shortage. This situation belongs to the yes branch of step S5. If it is negative, there may be an oversupply. This situation belongs to the no branch of step S5. Based on this assumption, a specific limit value G1 or G2 can then be used to verify the assumption.

[0070] If the saturation signal Q is checked in step S6, 1,sat If it is greater than the limit value G1, there is insufficient supply, step S8. If after checking in step S7, the saturation signal Q 1,sat On the contrary, if the absolute value is greater than the limit value G2 (and is negative), there is an oversupply, step S9. However, if the saturation signal Q 1,sat If the corresponding limit value G1 or G2 is not exceeded (No branch of S6, S7), no clear conclusion of oversupply or undersupply can be made and the program is continued in step 3. min In this case, this is merely a result of a disturbance, but not of the actual situation that one of the valves V1 , V2 of the heating system 1 has reached a control limit or is in a saturated state.

[0071] The result of the oversupply or undersupply determination (steps S8, S9) is reported to the higher-level control system (step S10), which can then react accordingly, for example by increasing the speed setpoint value without superposition in the case of undersupply or by reducing the speed setpoint value without superposition in the case of oversupply. Furthermore, the determination result can be displayed on the circulation pump 2 as a warning.

[0072] It should be pointed out that the above description is only used for illustrative purposes and does not limit the scope of protection of the present invention. Features of the present invention listed as "can", "exemplary", "preferred", "optional", "ideal", "advantageous", "depending on the specific circumstances" or "suitable" should be regarded as purely optional and do not limit the scope of protection specified solely by the claims. With respect to the elements, parts, process steps, values ​​or information listed in the above description, they all have known, similar or foreseeable equivalent features, and these equivalent features are included in the present invention. The present invention also includes any changes, modifications or improvements of the embodiments, which involve the exchange, addition, change or omission of elements, parts, process steps, values ​​or information, as long as the basic concept of the invention remains unchanged, regardless of whether the change, modification or improvement leads to an improvement or deterioration of the embodiment.

[0073] Although the above description of the invention lists many tangible, intangible, or process-specific features with respect to one or more specific embodiments, these features can also be used independently of the specific embodiments, at least to the extent that they do not require the mandatory presence of other features. Conversely, these features listed with respect to one or more specific embodiments can be combined in any manner with each other and with other disclosed or undisclosed features of the illustrated or unillustrated embodiments, as long as these features do not exclude each other or do not lead to technical incompatibilities.

Claims

1. A method for identifying an undersupply or oversupply of a consumer (R1, R2) in a heating system, the heating system comprising: at least one circulating pump (2) which delivers the heat transfer medium to the consumers (R1, R2); and a plurality of thermostatic valves (V1, V2) each regulating a delivery flow through one of the consumers (R1, R2), characterized in that a circulation pump (2) generates a periodically fluctuating head (H), and the resulting volume flow (Q) of the circulation pump (2) is determined, and a saturation signal (Q) is calculated from this volume flow 1,sat , Q n,sat ) and is evaluated, the saturation signal contains the following information, namely whether the thermostatic valve (V1, V2) can compensate for the fluctuating head (H) or whether it has reached its upper or lower adjustment limit during the compensation, wherein when the saturation signal (Q 1,sat , Q n,sat ) is higher than the limit value (G), an inference of insufficient supply or excessive supply is made.

2. The method according to claim 1, wherein: The head fluctuations are dimensioned such that the thermostatic valves (V1, V2) can compensate for the fluctuating head (H) and thus keep the volume flow (Q1, Q2) through the respective consumer (R1, R2) constant.

3. The method according to claim 1 or 2, wherein: The head (H) fluctuates with a cycle time between 5 and 60 minutes.

4. The method according to claim 1 or 2, wherein: The head (H) is predetermined by the higher-level control system and is gradually reduced for energy optimization until the saturation signal (Q 1,sat , Q n,sat ) until the absolute value of the value exceeds the limit value (G).

5. The method according to claim 1, wherein: The head fluctuation is generated by speed modulation of the circulating pump (2) in such a way that the control variable of the circulating pump (2) is superimposed with an excitation signal (f(t)).

6. The method according to claim 5, wherein: The excitation signal (f(t)) is sinusoidal.

7. The method according to claim 5 or 6, wherein: Saturation signal (Q 1,sat , Q n,sat ) is formed by multiplying the volume flow (Q) of the circulating pump (2) by the excitation signal (f(t)) or by a sinusoidal signal having the frequency of the excitation signal (f(t)) or by a sinusoidal signal having a multiple frequency of the excitation signal (f(t)) and by subsequently integrating the product thus formed over the period of the excitation signal (f(t)).

8. The method according to claim 1 or 2, wherein: When the saturation signal (Q 1,sat , Q n,sat ) becomes positive, an inference of undersupply is made.

9. The method according to claim 1 or 2, wherein: When the saturation signal (Q 1,sat , Q n,sat ) becomes negative, an inference of oversupply is made.

10. A circulating pump (2) for a heating system, characterized in that: The circulating pump is provided for carrying out the method according to any one of claims 1 to 9 .

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