EP3123033B1 - Method for determining the hydraulic operating point of a pump assembly - Google Patents

Description

The present invention relates to a method for determining a first hydraulic variable of a pump unit operated at a predeterminable speed from a mechanical and / or electrical variable by evaluating a linkage of the hydraulic variable on the one hand and the mechanical or electrical variable on the other hand. Furthermore, the invention relates to a pump control and equipped with a pump control pump unit for performing the method.

A method of this kind is known from US 4,108,574 A1 known, in which case the volume flow is determined as the desired size of the delivery, the speed and / or the drive power based on a mathematical linkage of at least one of these variables with the flow rate.

An alternative method describes the European patent application EP 2 354 556 A9 where, using the affinity laws, a known characteristic QH curve of the pump is converted to match the detected actual speed, and then the operating point of the pump set is determined as the intersection of this converted QH curve with an estimated process curve.

The European patent application EP 2 696 175 A1 describes a method for detecting a flow rate of a centrifugal pump by means of a mathematical model of the pump, which describes the physical relationships of pump and drive motor.

The hydraulic operating point in a pump unit is usually defined by the volume flow and the delivery height or the differential pressure applied by the pump. It is displayed in the so-called HQ diagram in which the delivery head or the differential pressure is plotted against the volume flow. There are numerous control and regulation methods for pump units that influence these hydraulic variables, in particular regulate along predeterminable characteristics. For example, characteristic curves are customary in which a certain delivery height is kept constant for each volume flow, so-called Δp-c regulations. Another known regulation takes place along characteristic curves which define a linear relationship between delivery height and volume flow, so-called Δp-v regulations.

In that regard, it is necessary for the pump control to know the volume flow and / or the delivery head or the differential pressure. In the simplest case sensors can be used, for example a flow sensor for determination the volume flow or a differential pressure sensor for determining the differential pressure, from which then the head can be calculated. However, such sensors make the production of the pump unit more expensive. It is therefore a concern to renounce them.

In addition to the measurement, a hydraulic variable can also be determined mathematically from one or more variables known to the pump unit or its control or regulation, in particular using physical laws of existing physical relationships with the desired hydraulic variable. These relationships can be stored in mathematical form in the control or regulation of the pump unit. The calculation can be made, for example, from the electrical power consumption (motor power or mains input power) resulting from the product of current and voltage. This is a known size of the pump unit, since the current and the voltage is specified depending on the required speed of the pump set by the speed control or regulation, in particular by a frequency converter. In addition, it is particularly easy to measure the current and voltage by electrical means.

On the part of the manufacturer of the pump unit then the performance map can be measured. This means that the power consumption is determined for selected speeds for a large number of volume flows. These values can for example be assigned to one another in a table and stored in the control or regulation of the pump unit. As an alternative to the table, it is possible to determine from the factory-determined or measured values a mathematical function (for example a polynomial) which describes the relationship between volume flow and power at a specific speed. This function can then be stored alternatively or in addition to the table in the control or regulation.

Such a function may for example be formed separately for each speed and used so that the entire performance map is described by a set of functions. Alternatively, a single function can be used that combines the three sizes of power, speed, and flow connected. Using a function instead of a table has the advantage of requiring little storage space because it does not need to store large measurement data. The disadvantage here, however, that the evaluation of the function requires computing power. The use of a function in addition to the table has the advantage that a plausibility check and, if appropriate, an averaging of the value determined from the table and the function can be undertaken.

If the power consumption and the speed are known, then the volume flow can be determined from the table or the corresponding function. From this, in turn, the delivery head can be calculated via the pump characteristic, so that the operating point of the pump unit is obtained.

FIG. 1 shows the relationship between the absorbed electric power and the flow rate Q at a pump unit. Shown are four performance curves for different speeds, with the lowest curve being assigned to the lowest speed used and the upper one to the highest speed used. The performance curves make it clear that there is an ambiguity in the characteristic curve in the upper volume flow range, because the characteristic increases steadily up to a maximum with increasing volume flow, but decreases again as the volume flow increases. Thus, for example, is at maximum speed in both Q1 = 12 m ³ / h and at Q2 = 16 m ³ / h the same power input of about 250 W before. By evaluating the table or the function can therefore be concluded on the basis of the determined power not readily on the flow rate. Thus, the power allocation method can only be used in a restricted area of the operating range.

The problem of the ambiguity of the power characteristic can be circumvented by taking into account only the left part of the power characteristic, ie the volume flow which is smaller than the volume flow present at the maximum of the power characteristic. This means that the hydraulic system of the pump set in this case is designed so that in the intended Operating range, the power is always rising steadily and the maximum flow is where the power has its maximum.

Conversely, this means that the hydraulic efficiency has its maximum (BEP Best Efficiency Point) at the right edge of the operating range and therefore the partial load efficiency is low at low flow rates. However, for high overall efficiency in typical pump applications, high partial load efficiency is far more important than high full load efficiency because the pump set is typically rarely run at full load. This fact is justified by the calculation of the "Energy Efficiency Index (EEI)", an important parameter for the efficiency of a pump set. For an optimal Energy Efficiency Index (EEI), it would be advantageous to place the BEP in the range of medium volumetric flow, because it is very often the operating point of a pump set. In this area, however, the direct determination of the volume flow from the power is no longer possible.

It is therefore an object of the present invention to provide a comparison with the prior art alternative method for determining a hydraulic size of a pump unit that does not require sensor for this hydraulic variable and does not limit the control or regulation of the pump unit.

This object is achieved by the method according to claim 1 and a pump electronics according to claim 21. Advantageous developments are given in the dependent claims.

According to the invention, a method for determining a first hydraulic variable of a pump unit operated at a predeterminable speed from a mechanical and / or electrical variable by evaluating a linkage of the hydraulic variable on the one hand and the mechanical or electrical variable on the other hand, in which a manipulated variable of the pump unit so with a periodic excitation signal of a certain frequency is applied, that a second hydraulic variable is modulated, wherein from the mechanical or electrical quantity as a system response to the Excitation signal is determined using the linkage of the current value of the first hydraulic variable.

This solution resolves ambiguities in the linking of the quantities. It allows a pump set to use the information available to it, i. at least one electrical and / or mechanical quantity, such as the current, the voltage, the electric power, the torque, the rotational speed, or the mechanical power, and without the use of a pressure or flow sensor to close the hydraulic operating point, the For example, by the first and second hydraulic variable, preferably defined by the volume flow and the delivery height.

The pump unit may be an electric motor driven centrifugal pump, for example a heating pump in a heating system or a coolant pump in a cooling system.

It should be noted that "modulating" in the sense of the invention is to be understood as a change, but the type, height and speed of the excitation signal are in no way limited. Furthermore, as far as the following is a control of the pump unit, this term is also a regulation to understand, since a scheme includes only a controller with a feedback of a certain size.

According to a first embodiment variant, the current value of the first hydraulic variable can be determined from the amplitude and / or the phase position of the alternating component of the mechanical or electrical variable using the link. This means that initially the alternating component of the mechanical or electrical variable is determined and determines its amplitude or phase position. Subsequently, the combination is used to determine the value of the hydraulic variable from the ascertained amplitude or phase position. Preferably, the absolute values for the amplitude and phase position are not used here but rather relative values which relate to the excitation signal. In the case of phasing this would mean that it is determined to how much the phase of the system response to the excitation signal is shifted. In the case of the amplitude, this means that the ratio of the amplitude of the alternating component of the system response to the amplitude of the excitation signal is determined. The evaluation of the system response based on the linkage can therefore take place both with absolute values and with relative values.

In all embodiments of the invention, the link can be given by a table or at least one mathematical function. In the case of the first embodiment variant, this table or the at least one function at a certain speed or at a plurality of speeds would associate each value or a number of values of the first hydraulic variable with an amplitude value or phase value of the alternating component. This makes it possible in a particularly simple way to determine the current value of the first hydraulic variable. This assignment is to be carried out by the manufacturer of the pump set by operating the pump set at different speeds by applying the excitation signal and measuring the first hydraulic variable as well as measuring the amplitude and phase angle of the alternating component or calculating it from known relationships. These determined values can then be assigned to one another in tabular form and stored in a control of the pump set.

The use of the link can then take place in the case of the table in such a way that the line or column in which a rotational speed corresponding to the current rotational speed is searched for the ascertained amplitude value or phase value. If this or a similar one is found, the value of the first hydraulic variable assigned to the amplitude value or phase value by the corresponding column or row can be determined.

If a function is used instead of the table, it can be used, resolved to the first hydraulic variable, to calculate the value of the first hydraulic variable from the ascertained amplitude value or phase value. If the link is given by several functions, one of which is valid for a certain speed, first that function must be determined, which is valid for the current speed. In this function then only needs the Amplitude value or phase value to be input. If, on the other hand, the link is given by a single function, then the determined amplitude value or phase value and the current speed must be entered for the function to supply the value of the first hydraulic variable.

According to a second embodiment variant, the product can be formed from the system response and a periodic function of the same or a multiple of the frequency of the excitation signal. Subsequently, the integral of this product over a predetermined, in particular finite integration period is calculated and determined from the value of the integral using the link, the value of the first hydraulic variable. From the value of the integral, the value of the hydraulic variable (Q, H) is then determined using the linkage.

As an alternative to the periodic function, it is also possible to use the alternating component of the mechanical or electrical variable, for example the actual torque, the actual rotational speed or the electrical power consumption of the pump unit. In this case, the product would be formed and integrated from the system response and this interchange. Also, the value of the hydraulic quantity (Q, H) is then determined from the value of the integral using the link.

The current torque (actual torque), the current speed (actual speed) or the current electrical power consumption can be measured or calculated from other variables. If necessary, measured values must first be preprocessed, for example filtered, before it is suitable for multiplication by the system response. This can be done, for example, by high- or band-pass filtering. With sufficiently large excitation of the system, the alternating component contains a dominant fundamental oscillation which approximately corresponds in phase and frequency to the excitation signal. The result of the integration then corresponds, with the exception of a scaling factor, to the result that would be obtained with a purely mathematical periodic function, for example a sine or cosine function. In particular, the result of this calculation can be linked in the usual way to the first hydraulic variable to be determined, and these can be determined unambiguously.

The linking of the hydraulic variable with the mechanical or electrical variable can also be given in the second embodiment in the form of a table or a mathematical function.

For example, in such a table at a certain speed of a number of values of the first hydraulic variable may each be assigned a value of the integral. This assignment is to be performed by the manufacturer of the pump set at the factory by operating the pump set at different speeds, measuring the first hydraulic variable and calculating the integral as mentioned above or from other known relationships. These determined values can then be assigned to one another in tabular form and stored in a control of the pump set.

As an alternative to the table, a value of the integral can be assigned or assigned to each value of the hydraulic variable by the mathematical function at a specific speed. This assignment also assumes that the manufacturer initially measures the pump set by operating the pump set at different speeds, thereby measuring the first hydraulic variable and calculating the integral as previously mentioned or from other relationships known to it. However, these determined integral values are then not stored in a table. Rather, a function, e.g. a polynomial I (Q) is sought which describes a curve on which the measured values of the hydraulic quantity lie. In this case either a separate mathematical function (polynomial) can be set up for a number of different specific rotational speeds or a general mathematical function (polynomial) can be determined which describes the entire characteristic diagram of the pump set, i. a function (polynomial) I (Q, n) describing the dependence of the integral value on both the first hydraulic quantity (Q) and the speed (n). This also applies to the first embodiment.

It is advantageous if the periodic function used to multiply the system response is a sine function. It is then possible from the table or the mathematical function directly to determine a value of the first hydraulic quantity, which is assigned to the calculated value of the integral or is assigned by the mathematical function, since the sine function causes the integration leads to a value that plotted against the first hydraulic Size, is unique. This is in FIG. 2 illustrated.

Thus, from the table which assigns an integral value to each value of the first hydraulic variable, the value of the first hydraulic variable associated with the calculated value of the integral can be determined backwards. Thus, with regard to the table, the second embodiment variant differs from the first embodiment variant only in that the integral values are shown in the table instead of the amplitude values or phase values.

If a direct assignment can not be made because the integral value lies between two table values, it is possible by interpolation of the integral values assigned to these two table values to find a value of the first hydraulic variable to be assigned to the calculated integral value. This is also possible in the first embodiment.

Further, in the case of using a mathematical function from this mathematical function, by substituting the calculated integral value, the value of the hydraulic quantity can be calculated. Of course, if several mathematical functions are used which are only valid for a particular speed, it must of course first be determined how high the current speed is, in order then to determine which of the mathematical functions is to be used to calculate the first hydraulic variable. The speed is the pump control, for example, known at least in the form of the desired speed.

According to another embodiment variant, values of the mechanical and / or electrical variable are linked to values of the first hydraulic variable instead of the integral values in the table or the mathematical function, as is known per se in the prior art. This means that here the link is given by a table or at least a mathematical function, which is at a given speed any value of the first hydraulic Size assigns a value of mechanical or electrical size. As already explained in the introduction, in this case there is an ambiguity of the linkage. The value of the mechanical or electrical quantity is preferably an average, or in other words, such a value, which is present in the absence of a periodic excitation.

The ambiguity can be resolved by using a cosine function as the function with which the system response is multiplied and using the calculated value of the integral to distinguish which part of the table or range of values of the mathematical function to determine the value of the first hydraulic variable valid for the current operating point. This can be determined by FIG. 3 explain by way of example. The integral over the product of system response and cosine function (in FIG. 3 By way of example, the power is used as a system response) has a zero crossing where the mechanical or electrical quantity has its maximum as a function of the hydraulic size. In that regard, the value of the calculated integral can then be used to determine the value of the first hydraulic variable, the integral value being compared to a threshold value. For a threshold zero, the in FIG. 3 illustrated case in which the sign can be used to determine which part of the table or range of values of the mathematical function is valid for determining the value of the first hydraulic variable for the current operating point.

If the sign is negative, only those values of the first hydraulic variable are taken into account which are below that value of the first hydraulic variable at which the mechanical or electrical variable has its maximum. Otherwise, i. if the sign is positive, only those values of the first hydraulic quantity are taken into account which are above the value of the hydraulic variable at which the mechanical or electrical variable has its maximum. Optionally, another nonzero threshold may be used to resolve the ambiguity.

Preferably, the manipulated variable acted upon by the excitation signal is a setpoint speed or a setpoint torque of the pump unit, ie a mechanical size, which is attempted by a regulation of the pump set to keep at a certain value. Speed or torque controls are known per se in pump units. The periodic excitation of the desired speed or the desired torque is a simple measure to achieve a modulation of the second hydraulic variable.

As the first hydraulic variable, for example, the volume flow Q of the pump unit can be used. The second hydraulic variable may then suitably be the delivery head H or the differential pressure Δp . The latter can be easily modulated by modulating the speed or torque of the pump set.

The mechanical variable is preferably the torque output by the pump unit or the actual speed of the pump unit. The electrical variable may be, for example, the electric power P _el absorbed by the pump unit or the current. The change of at least one of these quantities due to the modulation of the second hydraulic quantity is then considered as a system response.

Thus, any pairings between the excited manipulated variable and the system response to be analyzed can be used. For example, the target speed can be modulated and the resulting actual speed can be evaluated. Instead of the actual speed, the output torque or the electrical power consumption can be used for the evaluation. And instead of the excitation of the target speed, the target torque can be excited and the resulting actual speed, the torque output or the electrical power consumption are evaluated.

The excitation signal is ideally a periodic signal, in particular a sinusoidal signal or a signal containing a sinusoidal function. The latter can also be, for example, a triangular or sawtooth signal.

The frequency of the excitation signal is advantageously between 0.01 Hz and 100 Hz. However, the disadvantage of too low a frequency is the duration of a complete one Period, which is at an excitation frequency of, for example, 0.01Hz at 1 minute and 40 seconds. The longer the period, the greater the likelihood that the hydraulic resistance of the system, and as a result, the operating point of the pump set changes, so that the determination of the current operating point is falsified. Therefore, the excitation frequency should not be too small. However, the frequency is limited due to the inertia of the rotor, the impeller and the liquid upwards limits.

The amplitude of the excitation signal is preferably less than 25% of the speed setpoint. In particular, it can be between 0.1% and 25% of the speed setpoint. At a setpoint speed of, for example, 2000 rpm, a speed fluctuation of ± 2 rpm to ± 500 rpm can thus be suitable.

ermittelt werden, wobei a, b und c Kenngrößen der Pumpenkennlinie sind. Setzt man für H_P = H₀ + f_A,H ein, wobei f_A,H die gewünschte Schwankung der Förderhöhe H um die stationäre Förderhöhe H₀ beschreibt, so ergibt sich: $$\begin{array}{l}{H}_0+f_{A,H}={\mathit{an}}^2-\mathit{bQn}-{\mathit{cQ}}^2\\ n^2-\frac{\mathit{bQ}}{a}n-\frac{{\mathit{cQ}}^2}{a}-\frac{H_0}{a}-\frac{f_{A,H}}{a}=0\\ n^2-\frac{\mathit{bQ}}{a}n-\frac{{\mathit{cQ}}^2}{a}-\frac{\left({\mathit{an}}_0^2-{\mathit{bQn}}_0-{\mathit{cQ}}^2\right)}{a}-\frac{f_{A,H}}{a}=0\\ n^2-\frac{\mathit{bQ}}{a}n-\frac{\left({\mathit{an}}_0^2-{\mathit{bQn}}_0\right)}{a}-\frac{f_{A,H}}{a}=0\\ n-\frac{\mathit{bQ}}{a}+\sqrt{{\left(\frac{\mathit{bQ}}{2a}\right)}^2+n_0^2-\frac{{\mathit{bQn}}_0}{a}+\frac{f_{A,H}}{a}}\end{array}$$

The amplitude of the excitation signal can be calculated from a desired delivery height fluctuation by means of a mathematical equation describing the relationship between the rotational speed and the delivery height at the pump unit. For example, this equation can be derived from the formula describing the stationary relationship between delivery head H, rotational speed n and volume flow Q. $$H_p\left(Q,n\right)={\mathit{on}}^2-\mathit{BQN}-{\mathit{<figure-callout\; id="2"\; label="c\; Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">c\; Q</figure-callout>}}^2$$

be determined, where a, b and c are characteristics of the pump characteristic. If one sets for H _P = H ₀ + f _{A, H} , where f _{A, H describes} the desired fluctuation of the delivery height H around the stationary delivery height H ₀ , the following results: $$\begin{array}{l}{\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}_0+f_{A.H}={\mathit{on}}^2-\mathit{BQN}-{\mathit{c\; Q}}^2\\ n^2-\frac{\mathit{bq}}{a}n-\frac{{\mathit{c\; Q}}^2}{a}-\frac{H_0}{a}-\frac{f_{A.H}}{a}=0\\ n^2-\frac{\mathit{bq}}{a}n-\frac{{\mathit{c\; Q}}^2}{a}-\frac{\left({\mathit{on}}_0^2-{\mathit{BQN}}_0-{\mathit{c\; Q}}^2\right)}{a}-\frac{f_{A.H}}{a}=0\\ n^2-\frac{\mathit{bq}}{a}n-\frac{\left({\mathit{on}}_0^2-{\mathit{BQN}}_0\right)}{a}-\frac{f_{A.H}}{a}=0\\ n-\frac{\mathit{bq}}{a}<figure-callout\; id="2"\; label="+\; bq"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">+\; </figure-callout>\sqrt{{\left(\frac{\mathit{bq}}{}\right)}^{}}\sqrt{{\left(\frac{\mathit{}}{2a}\right)}^2+{\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_0^2-\frac{{\mathit{BQN}}_0}{a}+\frac{f_{A.H}}{a}}\end{array}$$

For Q = 0 then: $$n=\sqrt{{\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_0^2+\frac{f_{A.H}}{a}}$$

If a certain change f _{A, H of} the head H is to be achieved, so can with equation Eq. 7 or Eq. 8 the change of the speed excitation signal can be determined.

In the second and further embodiment, the integral of the product is calculated from the system response and the periodic function over a period of time T. This integration period T may be one period or may be a multiple of the period of the excitation signal. It is advantageous if the modulation is continuous, ie during the entire operating time of the pump set. In this way, changes in the operating point can be detected immediately. This would not be possible if the method according to the invention would only be used at intervals over a limited period of time.

The detection of the mechanical or electrical quantity as a system response to the modulation can be done either at discrete times or continuously. The system response is then presented as a series of values so that multiplication by function and integration of the product thus obtained can occur at any time.

According to a further advantageous development of the method according to the invention, during the calculation of the integral, at least one further integral can be calculated from the product of the system response and the function over the same integration period, wherein the beginning of this integration period of the further integral is offset in time from the beginning of the integration period of the first integral lies. The calculated values of the integrals can then be combined into an averaged value. This has the effect of smoothing the determined system response.

By using a finite integration period, the values to be integrated are virtually "cut out" from the series of detected system response values. This is known in signal processing as "windowing", ie the values are cut out by multiplication with a window function F _F (t) which has the form F _F (t) = f (t) for t ₀ <t <t ₁ and F _F (t) = 0 otherwise. In the simplest case, for f (t) = 1 (rectangular window), the "cut-out" values are multiplied unchanged with the function and then integrated, ie there is no weighting of the values. However, it is advantageous if a filtering of the values is applied by applying a weighting of the values to be integrated. Such weighting can be done, for example, by multiplying the system response by a window function that weights the values in the middle of the window more than the values at the edge of the window. For such a weighting, a multiplicity of known and in practice usual window functions are available, eg Hamming windows, Gaussian windows, etc.

$$\mathit{mit}T=\frac{k_{I}2\pi }{\omega }$$

wobei I(t₀ +T) das zu berechnende Integral vom Zeitpunkt t₀ über den Integrationszeitraum T, X(t) die Systemantwort ist, S(t) die periodische Funktion, k_l eine positive ganze Zahl und ω die Frequenz des Anregungssignals f_A,n(t), f_A,H(t) ist.If the operating point of the hydraulic system is not constant, the change in the operating point distorts the value of the calculated integral. However, this distortion can be at least partially corrected by assuming a linear shift of the operating point and using this in the calculation of the Integrals is corrected. In the simplest case, the values of the system response at the beginning and at the end of the integration period are determined, in particular measured, and from these two values a linear change of the system response per time is determined. This linear change is then subtracted from all values of the system response determined in the integration period and only then the integral is formed. In this case, however, the determined values must first be saved. The integral can then be calculated as follows: $$I\left({\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">t</figure-callout>}}_0+T\right)={\displaystyle \underset{t_0}{\overset{{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">t</figure-callout>}}_0+T}{\int }}\left(X\left(t\right)-\left(\frac{\mathrm{<figure-callout\; id="0"\; label="X\; t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">X\; </figure-callout>}\left(t_{}\right)\left({}_0+T\right)-X\left(t_0\right)}{T}\right)\cdot \left(t-{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">t</figure-callout>}}_0\right)\right)\cdot S\left(t\right)\mathrm{d}t}$$

$$\mathit{With}T=\frac{k_{I}2\pi }{\omega }$$

where I (t ₀ + T ) is the integral to be calculated from time t ₀ over the integration period T, X (t) is the system response, S (t) is the periodic function, k _{l is} a positive integer and ω is the frequency of the excitation signal f _{A, n} (t), f _{A, H} (t).

It is also possible to carry out this correction only after the integral has been calculated in order to be able to dispense with the intermediate storage of the measured values. For this, reference is made here to the corresponding specialist literature on integral transformations according to the prior art.

According to the invention also a pump electronics for controlling and / or regulating the target speed of a pump unit is proposed, which is set up to carry out the method described above. Likewise, a pump unit comprising such a pump electronics is proposed. The pump unit may be, for example, a heating pump, coolant pump or a drinking water pump. Here it is regularly necessary to determine the flow rate in order to carry out an energy-efficient pump control. By applying the method according to the invention can be dispensed with volumetric flow sensors. This simplifies structurally the pump housing and reduces the cost of manufacturing the pump set. Preferably If the pump unit is an electric motor driven centrifugal pump, ideally in wet rotor design. Such can be used in a heating, cooling or drinking water system.

Figur 1:

Diagramm mit Leistüngskennlinien eines Pumpenaggregats bei verschiedenen Drehzahlen.

Figur 2:

Diagramm mit vier zu unterschiedlichen Drehzahlen gehörenden Kurven, die jedem Volumenstrom einen Wert des Integrals aus dem Produkt der Leistung und einer Sinusfunktion über einen Integrationszeitraum von einer Periode des Anregungssignals zuordnen.

Figur 3:

Diagramm mit vier zu unterschiedlichen Drehzahlen gehörenden Kurven, die jedem Volumenstrom einen Wert des Integrals aus dem Produkt der Leistung und einer Cosinusfunktion über einen Integrationszeitraum von einer Periode des Anregungssignals zuordnen.

Figur 4:

Ablaufdiagramm des Verfahrens

Figur 5:

Arbeitspunkt eines Pumpenaggregats im HQ-Diagramm

Figur 6:

System zur Anwendung des erfindungsgemäßen Verfahrens

Figur 7:

Blockschaltbild einer analogen Schaltung zur Berechnung der modulierten Solldrehzahl

Figur 8:

Diagramm mit vier zu unterschiedlichen Drehzahlen gehörenden Kurven, die jedem Volumenstrom einen Amplitudenwert der modulierten Istdrehzahl zuordnen.

Figur 9:

Diagramm mit vier zu unterschiedlichen Drehzahlen gehörenden Kurven, die jedem Volumenstrom einen Phasenwert der modulierten Istdrehzahl gegenüber dem Anregungssignal zuordnen.

The invention is explained in more detail below with reference to examples and the attached figures. Show it:

FIG. 1:

Diagram with performance characteristics of a pump set at different speeds.

FIG. 2:

Diagram of four curves belonging to different speeds, which assign to each volume flow a value of the integral of the product of the power and a sine function over an integration period of one period of the excitation signal.

FIG. 3:

Diagram of four curves belonging to different speeds, which assign to each volume flow a value of the integral of the product of the power and a cosine function over an integration period of one period of the excitation signal.

FIG. 4:

Flowchart of the method

FIG. 5:

Operating point of a pump set in the HQ diagram

FIG. 6:

System for applying the method according to the invention

FIG. 7:

Block diagram of an analog circuit for calculating the modulated setpoint speed

FIG. 8:

Diagram with four curves belonging to different speeds, which assign an amplitude value of the modulated actual speed to each volume flow.

FIG. 9:

Diagram with four curves belonging to different speeds, which assign each phase flow a phase value of the modulated actual speed with respect to the excitation signal.

In addition to the static hydraulic characteristic, the method of hydraulic operating point determination described below also uses information about the dynamic behavior of the system, which is analyzed by a targeted excitation.

A model of the system in which a variant of the method according to the invention can be applied is shown FIG. 6 as a block diagram. There, a variable-speed centrifugal pump unit 1 is shown, which is connected to a piping system 5 respectively incorporated in this. The system may for example be a heating system, the pump unit 1 corresponding to a heating pump. The piping system 5 is then formed by the leading to the radiators or heating circuits and leading from these to a central heating source lines. For example, as liquid, water can circulate in the pipelines 5 which is driven by the pump unit 1. The pump unit 1 consists of a pump unit 2, which forms the hydraulic part of the unit 1, an electromotive drive unit 3, which forms the electro-mechanical part of the unit 1, and a control or regulation 4. The drive unit 3 consists of an electromagnetic part 3a and a mechanical part 3b. The control 4 consists on the one hand of software 4a, on the other hand of hardware 4b, which includes the control and / or regulating electronics and power electronics such as a frequency converter.

The control electronics 4 is a target speed n ₀ specified. From the current current consumption I and the current rotational speed n _, the drive unit 3 calculates, for this purpose, a voltage U which is specified for the power electronics 4b, so that the drive unit 3 provides a corresponding electrical power P _el . The electromagnetic part 3a of the drive unit 3, which describes the stator, rotor and their electromagnetic coupling, generates from the current a mechanical torque M _is . This accelerates the rotor and leads to a corresponding speed n of the drive unit 3, which is included in the mechanical part 3b of the model of the drive unit 3. With the speed n _is the seated on the rotor shaft pump impeller of the hydraulic part 2 of the pump unit 1 is driven. The pump unit 1 thereby generates a delivery height H , which generates a more or less large volume flow Q in the piping system 5 depending on the pipe resistance. From the hydraulic power and thus forming composite losses a hydraulic torque M _hyd can be defined, which _is counteracted as a braking torque to the motor torque M.

• Anregung des Systems, Schritt S3;
• Ermittlung der Systemantwort, Schritt S4;
• Bestimmung der gesuchten hydraulischen Größe respektive des Arbeitspunktes aus der Anregung und der Systemantwort, Schritt S5.

The basic sequence of the method according to the invention is in FIG. 4 shown. The method is carried out in the normal operation of the pump unit, that is, when the pump unit 1 is connected to a pipe power system 5 and operated at the desired speed n ₀ . Based on the specification of the setpoint speed n ₀ in step S1, which may be predetermined manually or resulting from an adjustable characteristic control (eg Δp-c, Δp-v) or a dynamic adjustment of the operating point, the inventive method comprises the three steps to be performed sequentially that can be repeated continuously:

• Excitation of the system, step S3;
• Determination of the system response, step S4;
• Determination of the sought hydraulic variable respectively of the operating point from the excitation and the system response, step S5.

und die Rohrnetzparabel H_R(Q) $$H_R\left(Q\right)={\mathit{dQ}}^2$$

definiert, wobei der stationäre Arbeitspunkt im Schnittpunkt der Pumpenkennlinie und der Rohrnetzparabel liegt, siehe Figur 5. Dort gilt $$H_R\left(Q\right)=H_p\left(Q,n\right)$$

The hydraulic variable to be determined is exemplified by the volume flow Q of the pump unit. From the well-known physical-mathematical relationship between volume flow Q and head H at the pump unit 1, the delivery height H can be determined so that the hydraulic operating point [Q, H] of the pump set is fixed. The physical-mathematical relationship is determined by the pump characteristic H _P (Q, n) $$H_p\left(Q,n\right)={\mathit{on}}^2-\mathit{BQN}-{\mathit{<figure-callout\; id="2"\; label="c\; Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">c\; Q</figure-callout>}}^2$$

and the piping parabola H _R (Q) $$H_R\left(Q\right)={\mathit{<figure-callout\; id="2"\; label="dQ"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">dQ</figure-callout>}}^2$$

defined, with the stationary operating point at the intersection of the pump curve and the piping parabola, see FIG. 5 , There applies $$H_R\left(Q\right)=H_p\left(Q,n\right)$$

The pump characteristic H _P ( Q ) is known by the manufacturer from the measurement of the pump set. The parameters a, b, c are constant characteristics of the pump characteristic. The piping parabola depends on the condition of the piping system connected to the pump unit, whose hydraulic resistance is expressed in the slope d of the piping parabola. The hydraulic resistance is largely determined by the degree of opening of the valves located in the pipeline system, so that the slope d results from the valve position.

The excitation of the system takes place in that the stationary nominal speed n _{0 is} modulated with an excitation signal f _{A, n} (t), so that the new target speed n _{soll to be} set by the pump electronics 4 is calculated from the sum of the previously specified target speed n ₀ and the Excitation signal f _{A, n} (t) gives: $$n_{\mathit{should}}={\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_0+f_{A.n}\left(t\right)$$

mit der Amplitude n₁ und der Frequenz ω = 2πf. It may, for example, a sinusoidal variation of the speed result, but other modulations are conceivable. The excitation signal f _{A, n} (t) is then, for example, a sinusoidal signal of the form $$f_{A.n}\left(t\right)={\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_1\sin \mathit{.omega.t}$$

with the amplitude n ₁ and the frequency ω = 2πf.

The amplitude is between 0.1% and 25% of the setpoint speed n ₀ and can be factory-set and fixed.

mit der Amplitude H₁ und der Frequenz ω = 2πf.However, it is advantageous if not the rotational speed n, but the delivery height H is excited sinusoidally, so that applies $$H\left(t\right)={\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}_0+f_{A.H}\left(t\right)={\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}_0+{\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}_1\cdot \sin \left(\mathit{.omega.t}\right)$$

with the amplitude H ₁ and the frequency ω = 2 πf .

So unless a specific speed variation f _{A, n} (t) but rather a certain head height fluctuation f _{A, H} (t) to be achieved, for example ± 15cm, but which is dependent on the current operating point of the pump unit 2, ie from the current speed n = n _is and the currently funded volume flow Q, so before the excitation of the system, step S3 to achieve the desired delivery height variation f _{A, H} (t) required speed fluctuation f _{A, n} (t) can be calculated, step S2: $$n={\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_0+f_{A.n}=\frac{\mathit{<figure-callout\; id="2"\; label="bq"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">bq</figure-callout>}}{2a}<figure-callout\; id="2"\; label="+\; bq"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">+\; </figure-callout>\sqrt{{\left(\frac{\mathit{bq}}{}\right)}^{}}\sqrt{{\left(\frac{\mathit{}}{2a}\right)}^2+{\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_0^2-\frac{{\mathit{BQN}}_0}{a}+\frac{f_{A.H}}{a}}$$

Since the volume flow Q is generally to be determined here only by the method according to the invention and is thus unknown, Eq. 8 by the approximation Q = 0 to Eq. 9 simplified. $$n={\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_0+f_{A.n}=\sqrt{{\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">n</figure-callout>}}_0^2+\frac{f_{A.H}}{a}}$$

The calculation according to equation Eq. 8 or 9 can be numerically executed in a microprocessor of the pump electronics 4 or by an analog circuit, as exemplified in FIG. 7 is shown as a block diagram.

If the method according to the invention is repeated over and over, step S2 follows step S5. The volume flow Q determined as part of the operating point determination in step S5 can then be used directly in equation 8.

However, it is also possible to determine the excitation signal without consideration of the volume flow Q , in this case Eq. 9;

The excitation frequency f is to be dimensioned such that the delivery height H follows the excitation function f _{A, H} as well as possible despite the inertia of the rotor. In the embodiment, a frequency f of 1 Hz is used.

The system response following the excitation manifests itself in various physical quantities of the pump set as well as purely mathematically in the models, ie the electric model 4b, electromagnetic model 3a, mechanical model 3b and hydraulic model 2 present quantities. However, it is sufficient to evaluate a single mechanical or electrical size of the pump set. In the embodiment, as the system response X (t) to the modulation, the received electric power P _el ( _FIG. FIGS. 1, 2, 3 ) and, alternatively, the mechanical torque M _{mot is} used. The recorded electrical power P _el is measured or determined from measured current and measured or calculated voltage. The torque M _is can be measured or calculated from the torque-forming current available in the mathematical electromagnetic and mechanical model in the control electronics 4 for performing the control or for monitoring the system.

The determination of the power P _el and / or the torque M _ist can be done by sampling at discrete times or continuously, so that the system response X (t) is present as a discrete or continuous series of measured values or calculated values. This is from step 4 of FIG. 4 includes. For the sake of simplicity, only the case of the continuous series will be dealt with here.

oder $$S_{\cos }\left(t\right)=g_2\cdot \cos \left(k\cdot \mathit{\omega t}\right)$$

wobei g₁, g₂ Skalierungsfaktoren sind und k eine positive ganze Zahl. Die Parameter g₁, g₂ und k können unabhängig voneinander gewählt werden. In dem Beispiel sind g₁ = g₂ = k = 1 gesetzt. Dies verdeutlicht, dass die Funktionen S_sin(t), S_cos(t) im einfachsten Fall dieselbe periodische Grundstruktur wie das Anregungssignal f_A,n(t), f_A,H(t) insbesondere dieselbe Frequenz ω bzw. f haben kann, um das erfindungsgemäße Ergebnis zu erreichen.For the calculation of the operating point in step S5, the volume flow Q is first determined. This is done by first multiplying the system response X (t) by a periodic function S (t), ie by constructing the product of the system response X (t) and this periodic function S (t). The periodic function S (t) in the present example is a sine function S ₁ (t) = S _sin (t) or cosine function S ₂ (t) = S _cos (t) of the form $$S_{\sin }\left(t\right)={\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">G</figure-callout>}}_1\cdot \sin \left(k\cdot \mathit{.omega.t}\right)$$

or $$S_{\cos }\left(t\right)={\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">G</figure-callout>}}_2\cdot \cos \left(k\cdot \mathit{.omega.t}\right)$$

where g ₁ , g _{2 are} scaling factors and k is a positive integer. The parameters g ₁ , g ₂ and k can be selected independently of each other. In the example g ₁ = g ₂ = k = 1 are set. This clarifies that the functions S _sin (t), S _cos (t) can in the simplest case have the same periodic basic structure as the excitation signal f _{A, n} (t), f _{A, H} (t), in particular the same frequency ω or f to achieve the result according to the invention.

$$I_{\cos }\left(t_0+T\right)={\displaystyle \underset{t_0}{\overset{t_0+T}{\int }}X\left(t\right)\cos \left(\mathit{\omega t}\right)}\mathrm{d}t\mathit{mit}T=\frac{k_{I}2\pi }{\omega }$$

wobei t₀ den Integrationsbeginn angibt. Durch die Bildung der Integrale I(t₀+T) erfolgt eine Auswertung der Systemantwort X(t) bei der Anregungsfrequenz ω oder einem Vielfachen k_l der Anregungsfrequenz ω über eine oder mehrere Perioden 2π/ω.The product of system response X (t) and the function S _sin (t), S _cos (t) is then integrated over a period T corresponding to the period or a multiple k _{l of} the period of the excitation signal. This can be done both for the electrical quantity X (t) = P _el (t) and for the mechanical quantity X (t) = M _mot (t). The integrals I (t ₀ ) over the product then result in: $$I_{\sin }\left({\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">t</figure-callout>}}_0+T\right)={\displaystyle \underset{t_0}{\overset{{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">t</figure-callout>}}_0+T}{\int }}X\left(t\right)\sin \left(\mathit{.omega.t}\right)}\mathrm{d}t\mathit{With}T=\frac{k_{I}2\pi }{\omega }$$

$${\mathrm{<figure-callout\; id="0"\; label="I\; cos\; t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">I\; </figure-callout>}}_{\cos }\left(t_{}\right)\left({}_0+T\right)={\displaystyle \underset{t_0}{\overset{{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">t</figure-callout>}}_0+T}{\int }}X\left(t\right)\cos \left(\mathit{.omega.t}\right)}\mathrm{d}t\mathit{With}T=\frac{k_{I}2\pi }{\omega }$$

where t ₀ indicates the start of integration. The formation of the integrals I (t ₀ + T) results in an evaluation of the system response X (t) at the excitation frequency ω or a multiple k _{1 of} the excitation frequency ω over one or more periods 2π / ω.

At the same time the evaluation is carried out at a time at which the pump unit 1, a certain volume flow Q is promoted at a certain speed n ₀ , which is due to the current state of the piping system, ie the currently valid piping parabola. This means everyone calculated integral value I ( t ₀ + T) is assigned to a specific volume flow value at a certain speed.

For this reason, the pump unit, as has also been carried out according to the prior art, the manufacturer must be measured on a hydraulic test rig, unless the relationship is known. According to the invention, however, not or not only the relationship between the sought hydraulic variable Q , the rotational speed n and the electrical or mechanical variable P _el , M _is measured and as a characteristic field as a linkage of the hydraulic variable Q on the one hand with the mechanical or electrical variable M. _, P _el other hand, stored in the form of a table or formula in the pump electronics. 4 Rather, the relationship between actual speed n _is , volume flow Q and one of the above-mentioned integrals I (t ₀ + T) determined. For this purpose, in each case the integral I (t ₀ + T) is calculated by the manufacturer on a hydraulic test stand at a number, in particular a plurality of preset nominal speeds n ₀ to a number, in particular a plurality of measured volume flows Q, which is due to the excitation of the system with the excitation signal f _{A, n} (t), f _{A, H} (t) from the product of system response X (t) and the sine or cosine function S _sin (t), S _cos (t). One can then represent the integral I (t ₀ + T) as a function of the rotational speed n _ist above the volume flow Q, ie as I (Q, n).

FIG. 2 shows four curves for the integral I (Q) for the rotational speeds n ₀ = 1350 rpm, 2415 rpm, 2880 rpm and 3540 rpm (from bottom to top), where the electric power P _{el is} examined as a system response X (t) and a sine function S _sin (t) was multiplied. It becomes clear that the simulation curves in FIG. 2 unlike the performance curves in FIG. 1 describe a clear relationship between the volumetric flow and the integral, since the curves increase monotonically over the entire volumetric flow range. This makes it possible, in the intended operation of the pump unit 1 to determine a calculated integral value I (t ₀ + T) from the relationship I (Q) determined on the test stand, to determine the currently conveyed volume flow Q. From this, the delivery height H can then be calculated, for example by means of Equation Eq. 1.

From the value of the integral, the value of the first hydraulic variable, the volume flow Q, is consequently determined using the relationship.

To determine the volume flow Q from the values I (t ₀ + T), n ₀ , Q determined on the test bench, these values are linked to one another and stored in the pump control 4. The linkage takes place in the form of a table which assigns a value of the desired hydraulic variable Q to a plurality of integral values I (t ₀ + T) at the rotational speeds n ₀ used. During operation of the pump unit 1, it is then necessary to extract from the table, for a calculated integral value I (t ₀ + T), only the volume flow value Q assigned to this value. If a calculated integral value I (t ₀ + T) is present, the integral values I between two existing in the table (t ₀ + T), Q can be interpolated in a known manner between these two tabular integral values I (Q) associated with volume flow values.

As an alternative or in addition to the tabular link, the manufacturer can determine from the values determined on the test stand for each rotational speed n ₀ a single mathematical function or a global mathematical function (eg a polynomial) for all rotational speeds, a characteristic curve or, in the case of the global function, a characteristic field describes where all measured values lie. In the case of using several functions, which are valid for each speed, then only the currently valid function must be determined and the calculated integral value used to obtain the corresponding value of the hydraulic variable, ie the volume flow value. If a global function is used to describe the entire characteristic field, the speed and the calculated integral value can be directly used in this equation to obtain the corresponding value of the hydraulic variable.

FIG. 3 shows four simulation curves for the integral I (Q) for the same speeds as in FIG. 2 , where also the electric power P _el was examined as a system response X (t) , but multiplied by a cosine function S _cos (t). It turns out that the simulation curves in FIG. 3 like the performance curves in FIG. 1 describe no clear relationship between the volume flow Q and the integral I (t ₀ + T), since the curves initially fall with increasing volume flow Q, but then rise again. The simulation curves in FIG. 3 however, reveal a peculiarity, which is that the calculated integral I (t ₀ + T). there has the value zero, where the associated power characteristic (see FIG. 1 ) has its maximum. In the simulation, the cosine signal changes the sign exactly at the vertex of the power characteristic, so that the sign of this signal can also serve to identify the operating point, ie right or left of the vertex of the power characteristic.

This realization makes it possible, in the normal operation of the pump set 1, to be able to decide on the basis of a threshold value, ie a threshold value 0 based on the sign of the calculated integral I (t ₀ + T), which of the two in the non-unique range of the power characteristic (see FIG. 1 ) volume flow values Q1, Q2 assigned to a specific power consumption is the correct one. Thus, with a negative sign of the integral I (t ₀ + T), the smaller volume flow value Q1 and with a positive sign the larger volume flow value Q2 can be used.

If this variant of the method according to the invention is to be used, it is not necessary to determine the volumetric flow and the integral value associated therewith at the manufacturer on the hydraulic test rig at different rotational speeds. Rather, it is sufficient, as in the prior art, to measure the performance map and to determine the threshold value and to deposit it as a table or at least one power characteristic equation in the pump electronics 4. The table or at least one function then assigns a value of the mechanical or electrical variable to the values of the hydraulic variable at a specific speed.

During normal operation of the pump set, it can then be decided from the sign of the integral I (t ₀ + T) from the system response X (t) and the cosine function S _cos (t) which part of the table or which value range of the equation is to be evaluated. Thus, for I (t ₀ + T), <0, the left-hand part of the power characteristic is taken into account in relation to the maximum value of the power P _el . Accordingly, for I (t ₀ + T),> 0, the right-hand part of the power characteristic is taken into account in relation to the maximum value of the power P _el .

To further improve the method, during the computation of the integral I (t ₀ + T), at least one further integral I (t ₁ + T) may be obtained from the product of the system response X (t) and the function S ( t ) over the same integration period T, wherein the start of integration t _{1 of} the further integral is offset in time by the offset t ₁ -t _{0 from} the start of integration t _{0 of} the first integral I ( t ₀ + T). The calculated values of the integrals I (t ₀ + T) ,, I (t ₁ + T), are then averaged to a value.

The calculation of the integrals over a finite integration period means that a set of values is cut out of the system response X ( t ), which then represent a "window" of the system response. In the case of the temporal offset of the start of integration of the further integral to the first integral, the correspondingly cut-out windows overlap.

FIGS. 8 and 9 show analogous to the FIGS. 2 and 3 a graphic visualization of the linkage of the volume flow Q as a first hydraulic variable with the actual speed as a mechanical variable for four different speeds, wherein in FIG. 8 the amplitude | n ₁ | the actual speed in revolutions per minute and in FIG. 9 the phase φ (n ₁ ) is given in degrees. The links are each given by four curves, which, seen from top to bottom, the unexcited rotational speeds n ₀ = 1500 rpm, n ₀ = 2000rpm, n ₀ = 2500 rpm and n ₀ = 3000rpm are assigned. The uppermost curve belongs to the speed 1500rpm, the lowest to the speed 3000rpm.

Was inspired in the cases of FIGS. 8 and 9 the setpoint speed n _{is intended} by modulating a periodic signal to a static setpoint speed. The actual speed n _is then given neglecting disturbances from the sum of the average speed n ₀ and the periodic proportion n ₁ (t). The phase φ (n ₁ ) in FIG. 9 is related to the excitation signal and thus represents a kind of phase shift FIGS. 8 and 9 The values shown are measured at the factory and stored as a table or mathematical function in the control of the pump set.

It becomes clear here that the amplitude | n ₁ | and the phase φ (n ₁ ) is unique for each speed over the flow rate. Thus, for a certain operating speed known to the pump controller, after determining the amplitude | n ₁ | or the phase φ (n ₁ ) of the excited actual rotational speed, the volumetric flow Q which, at the present mean operating rotational speed n _{0, of} the determined amplitude | n ₁ | or the phase φ (n ₁ ) is assigned. For example, at an operating speed of 2500 rpm and an amplitude of 120 rpm, a volume flow of 6 m ³ / h would be present.

The method presented here makes it possible in a simple way during operation of the pump set and without the use of a corresponding sensor, a hydraulic variable, e.g. to determine the volume flow.

Thereby, a second hydraulic variable, e.g. the delivery height, modulated, in particular to the vibration is excited, which can be done for example by modulation of the target speed or the motor torque as a manipulated variable of the pump unit.

The determination of the system response, e.g. the actual speed, the output from the pump unit torque or the electric power, and their evaluation by determining the amplitude or phase of the alternating component of the system response or by multiplication with a function of the same frequency as the excitation and integration of the product obtained, obtained are values that mathematically have a clear relationship with the sought hydraulic size. Through the evaluation of this, to be deposited in the pump electronics of the pump unit, the relationship can then determine the value of the sought hydraulic variable.

Claims (22)

1. Method for determining a first hydraulic variable (Q) of a pump unit (1) operated at a predeterminable rotational speed (n₀) from a mechanical or electrical variable (M_ist, P_el, n_ist) by evaluating a relationship of the hydraulic variable (Q) with the mechanical or electrical variable (M_ist, P_el, n_ist), characterized in that a control variable (n_soll) of the pump unit (1) is superimposed with a periodic excitation signal (f_A,n(t), f_A,H(t)) of a specific frequency (f) such that a second hydraulic variable (H, Δp) is modulated, and in that the current value of the first hydraulic variable (Q) is determined from the mechanical or electrical variable (M_ist, P_el, n_ist) as system response (X(t)) to the excitation signal (f_A,n(t), f_A,H(t)) using the relationship.
2. Method according to claim 1, characterized in that using the relationship the current value of the first hydraulic variable (Q) is determined from the amplitude and/or the phase position of the alternating component of the mechanical or electrical variable (M_ist, P_el, n_ist), in particular with respect to the excitation signal (f_A,n(t), f_A,H(t)).
3. Method according to claim 2, characterized in that the relationship is given by a table or at least one mathematical function which, for a specific rotational speed (n_ist) or a multiplicity of rotational speeds (n_ist), assigns to each value or number of values of the first hydraulic variable (Q) an amplitude value (|n₁|) or phase value (φ(n1)) of the alternating component.
4. Method according to claim 1, characterized in that the product from the system response (X(t)) and a periodic function (S(t)) of the same or a multiple of the frequency (f) of the excitation signal is formed, or the product from the system response (X(t)) and the alternating component of the mechanical or electrical variable of the pump unit (1) is formed, and the integral (I(t_0+T)) of this product is calculated over a predetermined integration time (T), and in that the value of the first hydraulic variable (Q) is determined from the value of the integral (I(t_0+T)) using the relationship.
5. Method according to claim 4, characterized in that the relationship is given by a table or at least one mathematical function which, for a specific rotational speed (n_ist) or a multiplicity of rotational speeds (n_ist), assigns a value of the integral (I(t_0+T)) to each value or a number of values of the first hydraulic variable (Q).
6. Method according to claim 5, characterized in that the periodic function (S(t)) is a sine function (S₁(t)) and a value of the first hydraulic variable (Q) is determined from the table or the mathematical function, which value is assigned to the calculated value of the integral (I(t_0+T)) in the table or is assigned by the mathematical function.
7. A method according to claim 4, characterized in that the relationship is given by a table or at least one mathematical function which, for a specific rotational speed (n_ist) or a multiplicity of rotational speeds (n_ist), assigns to each value of the first hydraulic variable (Q) a value of the mechanical or electrical variable (M_ist, P_el) and the periodic function (S(t)) is a cosine function (S₂(t)) and the value or sign of the calculated value of the integral (I(t_0+T)) is used to distinguish which part of the table or which value range of the mathematical function is valid for the current operating point, in order to determine the value of the first hydraulic variable (Q).
8. Method according to one of the previous claims, characterized in that the control variable is a set speed (n_soll) or a set torque of the pump unit (1).
9. Method according to one of the previous claims, characterized in that the first hydraulic variable (Q) is the volume flow (Q) of the pump unit (1).
10. Method according to one of the previous claims, characterized in that the second hydraulic variable (H) is the delivery head (H) or the differential pressure (Δp) of the pump unit (1).
11. Method according to one of the preceding claims, characterized in that the mechanical variable is the torque (M_ist) delivered by the pump unit or the actual speed (n_ist) of the pump unit (1).
12. Method according to one of the previous claims, characterized in that the electrical variable is the electrical power (P_el) consumed by the pump unit (1) or the current.
13. Method according to one of the previous claims, characterized in that the excitation signal (f_A,n(t) f_A,H(t)) is a sinusoidal signal or a signal containing a sinusoidal function.
14. Method according to one of the previous claims, characterized in that the frequency (ω) of the excitation signal (f_A,n(t), f_A,H(t)) is between 0.01Hz and 100 Hz.
15. Method according to one of the preceding claims, characterized in that the amplitude (ni) of the excitation signal (f_A,n(t), f_A,H(t)) is smaller than 25% of the speed set point (no) of a speed control of the pump unit (1), in particular is between 0.1% and 25% of the speed set point (no).
16. Method according to one of the preceding claims, characterized in that the amplitude (n₁) of the excitation signal (f_A(t)) is calculated from a desired delivery head variation (f_A,H)) with the aid of a mathematical equation describing the relationship between the actual rotational speed (n_ist) and the delivery head (H) at the pump unit (1).
17. Method according to claim 4 or one of the claims 5 to 16 which are referred back to claim 4, characterized in that the integration time (T) is a period or a multiple (k_l) of the period (2π/ω) of the excitation signal (f_A,n(t), f_A,H(t)).
18. Method according to claim 4 or one of the claims 5 to 17 which are referred back to claim 4, characterized in that the integration is carried out during the modulation of the second hydraulic variable (H), in particular the set speed (n_soll).
19. Method according to claim 4 or one of the claims 5 to 18 which are referred back to claim 4, characterized in that, during the calculation of the integral (I(t_0+T)), at least one further integral is calculated from the product of the system response (X(T)) and the periodic function (S(t)) or the alternating component of the actual torque (M_mot) or the actual speed (n) of the pump unit (1) over the same integration time (T), wherein the start of integration of the further integral is offset in time from the start of integration (t₀) of the first integral (I(t_0+T)), and in that the calculated values of the integrals are averaged to form one value.
20. Method according to claim 4 or one of the claims 5 to 19 which are referred back to claim 4, characterized in that the values of the system response (X(t)) are determined at the beginning (t₀) and at the end of the integration time (T) and a change in the system response (X(t)) per time is determined therefrom, the change being preferably linear, wherein this change then being subtracted from all the values of the system response (X(t)) determined in the integration time (T), and only after that the integral (I(t_0+T)) is formed.
21. Pump electronics for controlling and/or regulating the set speed of a pump unit (1), characterized in that it is configured to carry out the method according to one of claims 1 to 20.
22. Pump unit comprising a pump electronics according to claim 21.

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