Method for regulating a circulation pump and circulation pump

Abstract

The invention relates to a method for regulating a circulating pump with variable speed in a hydraulic system, in particular in a heating system, wherein a pump control device predetermines a target delivery head and adapts the speed of the pump in order to achieve the target delivery head, and wherein the speed change rate is dynamically determined depending on whether the target delivery head is greater or less than the actual delivery head.

Description

Technical Field

[0001] The invention relates to a method for regulating a circulating pump with variable speed in a hydraulic system, in particular in a heating system, wherein a pump control device sets a target delivery head and adapts the speed of the pump in order to achieve the target delivery head. Background Art

[0002] Older heating circulation pumps, in particular for low-power or medium-power heating systems, are usually unregulated. Here, the pump speed must be manually set to the corresponding power requirement of the heating system, wherein the pump usually has different speed stages available for manual selection. The suitable speed stage should be selected in such a way that a sufficient delivery flow is provided for room heating even when power peaks occur over time. Since such power peaks are mostly irregular and occur only for a short time, such pumps are mainly operated in energetically unfavorable operating situations.

[0003] Modern circulation pumps are equipped with a flow converter and a speed regulator, whereby the pump can reduce its power consumption by speed adaptation. The speed adaptation is carried out with the aid of a special control curve. During operation, the pump obtains the current delivery flow and the actual delivery head via a sensor device or an estimation algorithm and sets the speed in such a way that the operating point moves only along the control curve used. The type of control curve therefore defines the basic control strategy. For example, in the case of constant pressure control, the speed is always adjusted to a constant delivery head regardless of the delivery flow. In contrast, in the case of proportional pressure control, the delivery head is adjusted along a linearly increasing gradient, that is, the target delivery head is proportional to the actual delivery flow. Summary of the invention

[0004] The present application focuses on this proportional pressure regulation and seeks optimization possibilities in order to be able to further reduce the power consumption generated by the pump.

[0005] This object is achieved by the method provided by the present invention. Advantageous embodiments of the method are also the subject of the present invention.

[0006] According to the invention, for such a method for regulating a circulating pump, it is proposed to adapt the dynamics of a speed adapter. The dynamics of a speed adapter or speed control device is used to represent the speed of such a speed adapter in order to bring the pump from an actual delivery head to a target delivery head predetermined by a control curve. According to the invention, the dynamics of the speed control device should be varied depending on the difference between the actual delivery head and the target delivery head, more precisely, depending on whether the target delivery head is greater or less than the current actual delivery head.

[0007] The pump control device can work based on a constant pressure control device or a proportional pressure control device. Alternatively, the pump control device can also use the eco-mode developed by the applicant. However, the method can also be used for temperature-regulated pumps.

[0008] In the pump control device used for setting the target delivery head, the speed of the pump drive is not set in a jumpy manner, but is increased or decreased continuously. The dynamics of the speed control device therefore corresponds to the speed change rate. It is therefore important for the invention that at the actual delivery head H ist Less than H soll The speed change rate under the condition of H ist Greater than H soll The speed change rate in the case of is different. By this dynamization of the speed change rate, the average power consumption of the circulating pump can be reduced for the two control situations.

[0009] Ideally, for the target delivery head H soll Smaller than the actual conveying head H ist When the required delivery head H is selected soll Greater than the current actual conveying head H ist A higher speed change rate is required when the speed is reduced. Therefore, the speed changes faster when it is necessary to reduce it than when it is necessary to increase it. By reducing the speed of the pump relatively quickly, a lower power consumption of the pump can be achieved on average. In contrast, a relatively slow speed adaptation takes place when the actual delivery head is increased and the speed is therefore necessarily increased, so that the desired target delivery head is reached only after a certain delay. Although this delay may temporarily lead to insufficient supply of the space to be heated, this is hardly noticeable to the passengers in the space due to the thermal inertia.

[0010] According to a preferred embodiment of the invention, the speed is increased or decreased according to a definable, time-dependent speed ramp until the desired target delivery head is reached. Thus, such a speed control device corresponds to a first-order lag element in terms of control technology, and the speed ramp therefore behaves like a first-order low-pass filter. Thus, by adapting the time constant, the steepness of the ramp and thus the speed of the speed change, i.e. the speed change rate, can be changed.

[0011] Used to distinguish H soll <H ist or H soll >H ist The speed ramps used differ in their slope or in their time constant. Therefore, preferably, for the first case (H soll <H ist ) sets a very steep speed ramp, that is, H soll <Hist The ramp of the first speed is characterized by a lower time constant than the second speed ramp, which results in a faster speed change of the pump and a significantly faster target delivery head. The average power consumption of the pump is thereby reduced.

[0012] According to an exemplary embodiment of the present invention, a first speed ramp and a second speed ramp can be stored in the pump control device. The pump controller estimates or acquires the current delivery flow and the current delivery head and compares the latter with the target delivery head defined according to the proportional pressure characteristic curve. If the current actual delivery head is higher than the target delivery head, the necessary speed change according to the first speed ramp is implemented to set the target delivery head. In the opposite case, the speed ramp is stored in the pump control device. soll >H ist In the case of , the second speed ramp will be used for the speed change instead.

[0013] As already explained above, when the actual delivery head is increased and the speed is increased as a result, a relatively slow speed adaptation can take place, so that the desired target delivery head is reached with a certain delay. The delayed speed increase provides the necessary prerequisite for monitoring the heating system with respect to possible oversupply or undersupply, because the delayed speed increase ensures a faster reaction time of the thermostatic valve compared to the pump control.

[0014] This firstly enables advantageous monitoring of the delivery flow during speed regulation. In particular, provision is made here for the pump to be monitored during speed adaptation, especially when the speed is adjusted due to H soll >H ist During the increase, the delivery flow is continuously monitored. Here, according to an advantageous embodiment of the method, provision can be made that, while the delivery flow remains almost constant during the speed control, the speed change rate traveled is further reduced, in particular to a minimum value that is only slightly greater than zero.

[0015] For example, it can be provided that in addition to the second speed ramp used here, a third minimum speed ramp can also be used, as long as the actual delivery flow remains at an almost constant level, and the third minimum speed ramp is switched to during the corresponding speed regulation according to the second speed ramp. If the delivery flow remains constant despite the increase in the speed of the pump, it can be assumed that the thermostat valve constructed in the heating circuit is closed at the same time to avoid excessive supply of the space. In this case, it is meaningful in terms of energy to also reduce the speed increase rate to a minimum value, that is, to increase the speed only with a minimum, very flat speed ramp. At the same time, it is meaningful to further monitor the delivery flow in order to check the sufficient supply of the space to be heated. If, for example, a change in the delivery flow, that is, an increase in the delivery flow, occurs, this is a sign of the opening of the heating valve, so that the speed control device should also be switched from the minimum rate of change or the minimum speed ramp back to the initial rate of change, that is, the second speed ramp.

[0016] In addition to the method according to the invention, the invention also relates to a circulation pump, in particular a heating circulation pump, having a pump control device for carrying out the method according to the invention or an advantageous embodiment of the invention. The circulation pump is therefore characterized by the same advantages and properties as the method according to the invention, so that a repeated description will be omitted here to avoid repetition.

[0017] In addition to the circulating pump, the invention also relates to a heating device having a circulating pump according to the invention, in which case the same advantages and properties are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Below, other advantages and characteristics of the present invention are explained in more detail with the aid of the embodiments shown in the accompanying drawings. The drawings show:

[0019] Figure 1 : Example diagram for illustrating the characteristics of a low-pass filter, and

[0020] Figure 2 : Functional sketch for explaining the principle of the method according to the invention with adaptive ramping. DETAILED DESCRIPTION

[0021] In the following, the invention will be described with the aid of a heat cycle pump which uses a boiler and one or more heating bodies in a heat cycle. The heating bodies are equipped with thermostat valves which control the flow through the heaters depending on the room temperature.

[0022] The heat circulation pump comprises a converter with a speed control device, which operates according to a proportional pressure control curve and sets a target delivery head in proportion to the actual delivery flow. However, if the pump control device follows an alternative control strategy, this method can also be used, but for the sake of simplicity, this method is explained below with reference to the proportional pressure control curve. In order to achieve the target delivery head, the pump control device increases or decreases the speed of the pump drive device while taking into account an adjustable speed ramp until the target delivery head is reached. This speed ramp behaves in the function angle like a first-order low-pass filter with an adjustable time constant.

[0023] For example, in Figure 1 The time characteristic of a known first-order low-pass filter is shown in FIG. Figure 1 A setpoint value step 1 of the system and an associated step response 3 are shown. The point of intersection between the tangent 2 of the step response 3 and the final value is the time constant T. According to a rule of thumb, the step response reaches its final value after six times the time constant T.

[0024] In order to save energy, two speed ramps are used. If the target conveying head H soll Less than the actual conveying head H ist , the speed drops. In this case, a steep speed ramp (low time constant) is set to quickly reduce the speed and reduce the power consumption of the pump. soll Exceeds the actual conveying head H ist , a very slow speed ramp (high time constant) is used instead, so that the speed increases only slowly and reaches the actual delivery head H only with a delay. ist In this case, the room to be heated may be under-supplied for a short time due to the delay, but this will not be noticeable to the room occupants due to the normal thermal inertia of the room. However, the pump reduces its average power consumption.

[0025] In addition to reducing the power consumption, the method according to the invention can also be used to determine whether the room is actually undersupplied or whether a delivery head that is less than the target delivery head is sufficient for the heat supply of the room. To this end, it is necessary that the pump is regulated more slowly than the thermostatic valve of the heating element reacts. Experience has shown that the thermostatic valve of the heating element reacts very quickly to speed changes. If the speed of the pump increases very slowly, the valve (in the case of sufficient heating of the room) in contrast closes the supply of the room more quickly and equally. In this case, the delivery flow remains constant despite the increase in the speed of the circulation pump.

[0026] The pump continuously monitors its delivery flow during the speed ramp stop. If the pump detects that a constant delivery flow is being maintained in this case, the pump can stop the speed increase without the space experiencing a drop in temperature. In order to continue to check whether the space is still being adequately supplied, the pump can continue to check the speed at the height of the minimum speed ramp (only slightly above zero) and the change in the delivery flow. This continuously monitors whether a supply shortage is occurring. This principle is used in Figure 2 In the description.

Claims

1. A method for regulating a circulating pump at a variable speed in a hydraulic system, wherein: a pump control device predetermines a target delivery head and adapts the rotational speed of the pump in order to achieve the target delivery head, It is characterized in that The rotational speed change rate is dynamically determined according to whether the target conveying head is greater than or less than the actual conveying head, wherein a higher rotational speed change rate or a smaller time constant is selected when the target conveying head is less than the actual conveying head than when the target conveying head is greater than the actual conveying head.

2. The method according to claim 1, characterized in that The hydraulic device is a heating device.

3. The method according to claim 1, characterized in that The speed is increased or decreased according to a speed ramp over time until the target delivery head is reached, wherein the slope of the ramp is determined dynamically depending on whether the target delivery head is greater than or less than the actual delivery head.

4. The method according to claim 3, characterized in that The speed ramp behaves in terms of control technology like a first-order low-pass filter, and the slope of the speed ramp is described by the time constant of the low-pass filter.

5. The method according to any one of claims 3 to 4, characterized in that A first speed ramp and a second speed ramp are stored in the pump control device, wherein the first speed ramp is used for speed change when the target delivery head is smaller than the actual delivery head, and the second speed ramp is used for speed change when the target delivery head is larger than the actual delivery head, and wherein the first speed ramp is steeper than the second speed ramp, that is, has a lower time constant.

6. The method according to claim 1, characterized in that During the speed change, the delivery flow is monitored.

7. The method according to claim 6, characterized in that The delivery flow is monitored during the increase in speed.

8. The method according to claim 6 or 7, characterized in that In the case of a constant delivery flow, the rate of change of the rotational speed is reduced.

9. The method according to claim 8, characterized in that In the case of a constant delivery flow, the rotational speed change rate is set to a minimum value greater than zero.

10. The method according to claim 8, characterized in that If a change in the delivery flow is detected, the rate of change in rotation speed is increased again.

11. The method according to claim 8, characterized in that If a change in the delivery flow is detected, the rotational speed change rate is reset to the original rotational speed change rate.

12. A circulating pump having a pump control device for carrying out the method according to one of the preceding claims.

13. The circulation pump according to claim 12, which is a heating circulation pump.

14. A heating device comprising a circulation pump according to claim 12 or 13.

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