Method and control device for operating a heat pump in stabilizing a network frequency of an electric power network

Abstract

The invention relates to a method for operating a heat pump (10) in stabilizing a network frequency of an electric power network (15), wherein the heat pump (10) has a first heat exchanger (11), a compressor (12) which can be driven by an electric machine (14) connected to the electric power network (15), a second heat exchanger (13) and an expansion device (16), wherein the first heat exchanger (11) is designed to transfer thermal energy to a process medium; the compressor (12) is designed to compress the process medium downstream of the first heat exchanger (11); the second heat exchanger (13) is designed to transfer thermal energy of the process medium to a load; the expansion device (16) is designed to expand the process medium downstream of the second heat exchanger (13); and the heat pump (10) has a device by means of which a volume flow of the process medium can be adjusted. When an actual network frequency of the electric power network (15) deviates from a setpoint network frequency, in order to stabilize the network frequency, an electric power consumption of the electric machine (14) is controlled in such a way that, by controlling a rotational speed of the electric machine and / or by changing the volume flow of the process medium, the actual network frequency approaches the setpoint network frequency at an approximately constant pressure ratio of the compressor (12) and thus at an approximately constant temperature of the process medium in the region of the second heat exchanger (13).

Description

Technical Field

[0001] The present invention relates to a method and control device for operating a heat pump while stabilizing the network frequency of an electrical power network. Background Technology

[0002] The construction of a heat pump is thoroughly understood through practice. Therefore, a heat pump includes a first heat exchanger equipped to transfer heat energy specifically from the environment to the process medium of the heat pump. Downstream of the first heat exchanger, the heat pump includes a compressor equipped for compressing the process medium of the heat pump, wherein the compressor is driven by an electric motor. Downstream of the compressor, the heat pump includes a second heat exchanger equipped for transferring the heat energy of the process medium of the heat pump to a consuming device or the process medium of the consuming device. Downstream of the second heat exchanger is an expansion device to expand the process medium of the heat pump. The expansion device may be a turbine and / or an expansion valve, or an ejector, or a pressure exchanger.

[0003] The motor of the heat pump, which drives the compressor, is connected to and supplied with electrical energy through an electrical power network. In principle, when the network frequency of the electrical power network fluctuates, it is possible to change the power consumption of the motor driving the heat pump in order to stabilize the network frequency.

[0004] When the motor speed increases, the power consumption of the heat pump and the temperature of the process medium in the second heat exchanger region increase. When the speed of the motor driving the heat pump decreases, the power consumption of the heat pump and therefore the temperature of the process medium in the second heat exchanger region decrease.

[0005] Therefore, when the network frequency of the electrical power network is stabilized via the heat pump, in practice, this leads to changes in the temperature of the heat pump's process medium in the region of the second heat exchanger, and thus fluctuations in the quality of the heat energy that can be transferred to the consuming device. This is disadvantageous.

[0006] There is a need to operate the heat pump so that, especially when the heat pump is used to stabilize the network frequency of the electric power network, the temperature of the process medium of the heat pump in the area of ​​the second heat exchanger, and therefore the quality of the heat energy that can be transferred in the direction of the consuming device, remains constant or almost constant. Summary of the Invention

[0007] From this point forward, the present invention is based on the objective of creating a novel method and control device for operating a heat pump while stabilizing the network frequency of an electric power network.

[0008] This objective is achieved by the method according to claim 1 and the control device according to claim 9.

[0009] Using the invention presented herein, it is proposed to adjust the power consumption of the motor by means of a heat pump, through speed control of the motor of the compressor driving the heat pump and / or through changes in the volumetric flow rate of the process medium of the heat pump, thereby stabilizing the network frequency of the electrical power network.

[0010] In particular, when the actual network frequency of the electrical power network deviates from the setpoint network frequency, the electrical power consumption used to stabilize the network frequency is adjusted in such a way as to control the motor speed and / or to change the volumetric flow rate of the process medium in the heat pump, so that with respect to the constant or nearly constant pressure ratio of the compressor, and therefore, the constant or nearly constant temperature of the process medium in the region of the second heat exchanger, the actual network frequency of the electrical power network approaches the setpoint network frequency for network frequency stabilization. Therefore, without changing the temperature of the heat pump medium in the region of the second heat exchanger and thus the quality of heat energy that can be transferred to the consuming device, the actual network frequency of the electrical power network can approach the setpoint network frequency for network frequency stabilization.

[0011] In order to maintain a constant or near-constant pressure ratio with respect to the compressor, and therefore a constant or near-constant temperature of the process medium in the region of the second heat exchanger, and therefore a constant or near-constant mass of heat energy that can be transferred to the consuming device, and to ensure the stable occurrence of the network frequency, the power consumption is preferably adjusted simultaneously by controlling the motor speed and by changing the volumetric flow rate of the process medium in the heat pump.

[0012] In particular, when the actual network frequency of the power network is higher than the setpoint network frequency, the power consumption of the motor is preferably increased by increasing the motor speed and / or by increasing the volumetric flow rate of the heat pump process medium. Specifically, when the actual network frequency of the power network is lower than the setpoint network frequency, the power consumption of the motor is reduced by decreasing the motor speed and / or by decreasing the volumetric flow rate of the heat pump process medium. This allows for particularly advantageous stability of the power network frequency.

[0013] Specifically, when the actual network frequency of the power network is higher than the setpoint network frequency, the power consumption of the motor is preferably increased by increasing the motor speed and simultaneously by increasing the volumetric flow rate of the process medium. Specifically, when the actual network frequency of the power network is lower than the setpoint network frequency, the power consumption of the motor is preferably reduced by decreasing the motor speed and simultaneously by decreasing the volumetric flow rate of the process medium.

[0014] Speed ​​control of the speed-controlled motor preferably occurs via frequency adjustment of a frequency converter connected between the power network and the motor. Preferably, the change in the volumetric flow rate of the heat pump's process medium occurs by controlling a device for changing the volumetric flow rate, preferably by controlling the expansion device and / or compressor and / or individual valves or individual throttle valves. Specifically, for this purpose, changes in flow resistance occur in the areas of the expansion device and / or compressor and / or individual valves or individual throttle valves. Attached Figure Description

[0015] Preferred further developments of the invention are obtained from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the accompanying drawings, but are not limited thereto. The drawings show: Figure 1 A diagram is shown illustrating the heat pump of the present invention.

[0016] Figure 2 Display the compressor characteristic diagram. Detailed Implementation

[0017] Figure 1 An exemplary embodiment of the heat pump 10 is shown in a highly schematic manner.

[0018] The heat pump 10 includes a first heat exchanger 11 equipped for transferring thermal energy to the process medium of the heat pump 10.

[0019] The thermal energy transferred to the process medium of the heat pump via the first heat exchanger 11 can be, for example, the thermal energy of ambient air, lake water or seawater, water from a river, or thermal energy from public or industrial wastewater from a waste heat process. The waste heat of the process gas can also be used as thermal energy to heat the process medium of the heat pump.

[0020] Viewed in the flow direction of the process medium in the heat pump 10, downstream of the first heat exchanger 11, the heat pump includes a compressor 12. The compressor 12 is equipped to compress the process medium of the heat pump downstream of the first heat exchanger 11 and upstream of the second heat exchanger 13.

[0021] The second heat exchanger 13 is equipped to transfer the thermal energy of the process medium of the heat pump 10 to the consuming device or the process medium of the consuming device.

[0022] The compressor 12 can be driven by the motor 14 of the heat pump 10. For this purpose, the motor 14 is connected to the power network 15. The motor 14 can be supplied with electrical energy from the power network 15, i.e., via a frequency converter 22 connected between the motor 14 and the power network 15. The motor 14 is connected to the power network 15 via the frequency converter 22. Depending on the speed and torque of the motor 14, the motor 14 consumes or disconnects electrical load from the power network 15. The motor 14 can also be referred to as an electric motor.

[0023] Furthermore, the heat pump 10 has an expansion device 16, which in the illustrated exemplary embodiment includes both a turbine 17 and an expansion valve 18. The turbine 17 and the expansion valve 18 are configured to expand the process medium of the heat pump 10 downstream of the second heat exchanger 13 and upstream of the first heat exchanger 11. The energy generated in the turbine 17 can be used to drive the motor 14.

[0024] Alternatively, in relation to the exemplary embodiments shown, the expansion device 16 may also exclusively include a turbine 17, or exclusively include an expansion valve 18. The expansion device 16 may also alternatively or additionally include an injector or a pressure exchanger.

[0025] also, Figure 1 The optional bypass valve 19 for turbine 17 is shown. The rate of the process medium of heat pump 10, which is directly conducted across turbine 17 in the direction of expansion valve 18, can be adjusted via bypass valve 19.

[0026] In particular, when the network frequency of the power network 15 is changed in such a way that the actual network frequency of the power network 15 deviates from its setpoint network frequency, the power consumption adjustment of the motor 14 is used to stabilize the network frequency, that is, to bring the actual network frequency closer to the setpoint network frequency of the power network 15 (i.e., by controlling the speed of the motor 14 and / or by changing the volumetric flow rate of the process medium of the heat pump 10).

[0027] The adjustment of the electrical power consumption of motor 14 occurs in such a way that the constant or near-constant pressure ratio of compressor 12, and therefore the constant or near-constant temperature of the process medium downstream of compressor 12 in the region of the second heat exchanger 13, makes the actual network frequency of the electrical power network 15 close to its setpoint network frequency.

[0028] Specifically, when the actual network frequency of the power network 15 is higher than its setpoint network frequency, the rotational speed of the motor 14 increases, and preferably, the volumetric flow rate of the process medium in the heat pump 10 also increases simultaneously. Conversely, when the actual network frequency of the power network 15 is particularly lower than its setpoint network frequency, the rotational speed of the motor 14 decreases, and preferably, the volumetric flow rate of the process medium in the heat pump 10 also decreases simultaneously.

[0029] This is particularly advantageous in each case, namely, the constant or near-constant temperature of the process medium downstream of the compressor 12 in the region of the second heat exchanger 13 causes the actual network frequency to approach the setpoint network frequency, and thus the network frequency of the electrical power network 15 to be stable.

[0030] Figure 2 The characteristic diagram of compressor 12 is shown, in which... Figure 2In the diagram, the pressure ratio PI of compressor 12 is expressed as a function of the volumetric flow rate V of the process medium in heat pump 10 (i.e., the ratio between the outlet pressure and the inlet pressure of compressor 12). Figure 2 Point 20 visualizes the operating point of compressor 12 with a defined volumetric flow rate V and a defined pressure ratio PI. For network stability in the context of this invention, operating point 20 can be moved in the direction of the double arrow 21, i.e., when the pressure ratio PI between the compressor 12's outlet and inlet pressures is constant or approximately constant. During the process, the volumetric flow rate V is adjusted, and similarly, the rotational speed of motor 14 is adjusted to maintain a constant pressure ratio PI.

[0031] Based on the fact that the pressure ratio PI of compressor 12 remains constant, the temperature of the process medium downstream of compressor 12 also remains constant in the region of the second heat exchanger 13, so that the quality of heat energy that can be transferred to the consuming device remains unchanged. Therefore, heat pump 10 can be used to stabilize the network frequency of electrical power network 15 without any impact on the consuming device.

[0032] The speed control of the speed-controlled motor 14 occurs by changing the load on the motor 14 and thus changing the frequency (i.e., changing the output frequency of the inverter 22 connected between the power network 15 and the motor 14).

[0033] In order to change the volumetric flow rate of the process medium in the heat pump 10, the device for changing the volumetric flow rate of the process medium is controlled, that is, in order to change the flow resistance of the corresponding device to the process medium.

[0034] exist Figure 1 In exemplary embodiments, for example, the volumetric flow rate of the process medium in the heat pump 10 can occur by changing the opening position of the expansion valve 18 (thereby changing the flow resistance of the expansion valve 18 to the process medium). The volumetric flow rate of the process medium can also occur by changing the opening position of the bypass valve 19 (thereby changing the flow resistance of the bypass valve 19 to the process medium). Particularly when the turbine 17 and / or compressor 12 include adjustable guide vanes or adjustable rotor blades, the flow resistance of the process medium, and therefore the volumetric flow rate of the process medium in the heat pump 10, can also occur through appropriate adjustment of the guide vanes or rotor blades on the turbine 17 and / or compressor 12.

[0035] In the exemplary embodiment shown, it is therefore possible that the device for changing the volumetric flow rate of the process medium of the heat pump is a part of the compressor 12, a part of the turbine 17, or a part of the expander 16.

[0036] A separate device for changing the volumetric flow rate of the process medium in the heat pump 10 can also be used. This separate device is embodied as a separate component, such as a separate valve or a separate throttle valve, compared to the compressor 12 and the expansion device 16.

[0037] Furthermore, the present invention relates to a control device equipped for automatically executing the method according to the invention in terms of control.

[0038] For this purpose, such control devices have data interfaces to exchange data with components involved in performing the method according to the invention, such as the power network 15, the motor 14, the frequency converter 22, and devices for changing the volumetric flow rate of the process medium in the heat pump 10. The control device is equipped to compare the actual network frequency of the power network 15 with its setpoint network frequency, and to stabilize the network frequency of the power network 15, i.e., to bring the actual network frequency close to the setpoint network frequency, i.e., by changing the power consumption of the motor 14 (i.e., by controlling the speed of the motor 14 and / or changing the volumetric flow rate of the process medium) such that the pressure ratio PI of the compressor 12 is maintained, and thus the temperature of the process medium downstream of the compressor 12 in the region of the second heat exchanger 13 remains constant or approximately constant. Preferably, the speed control of the motor 14 and the change in the volumetric flow rate of the process medium occur simultaneously.

[0039] In order to make the actual network frequency close to the setpoint network frequency for network frequency stabilization, in Figure 2 In the exemplary embodiment of the display, the operation point 20 is at Figure 2 The compressor characteristic curve is shifted along double arrow 21, representing the constant pressure ratio PI of compressor 12 between its outlet and inlet pressures. During the process, the electrical power consumption of motor 14 is adjusted by both the speed control of motor 14 and the change in the volumetric flow rate of the process medium via heat pump 10. This can be either open-loop or closed-loop control depending on the characteristic curve.

[0040] Depending on the deviation between the actual network frequency and the setpoint network frequency, it is also possible to determine the load change of motor 14, which is necessary to bring the actual network frequency closer to the setpoint network frequency. Based on this load change, the required speed and required torque of motor 14 can be determined from the motor characteristic diagram. Based on the required torque, the control variables for changing the volumetric flow rate can then be determined.

[0041] List of reference numerals 10 Heat Pumps 11 First heat exchanger 12 Compressors 13 Second heat exchanger 14 Motors 15 Electric Power Networks 16. Expansion device 17 Turbo 18 Expansion valve 19. Bypass valve 20 operation points 21 Double arrows 22. Frequency converter.

Claims

1. A method for operating a heat pump (10) while stabilizing the network frequency of an electrical power network (15), The heat pump (10) includes a first heat exchanger (11), a compressor (12) driveable by a motor (14) connected to the electric power network (15), a second heat exchanger (13), and an expansion device (16). The first heat exchanger (11) of the heat pump (10) is equipped to transfer heat energy to the process medium of the heat pump. The compressor (12) of the heat pump (10) is equipped to compress the process medium of the heat pump downstream of the first heat exchanger (11) and upstream of the second heat exchanger (13). The process medium, wherein the second heat exchanger (13) of the heat pump (10) is equipped for transferring the thermal energy of the process medium of the heat pump to a consumption device, and wherein the expansion device (16) of the heat pump (10) is equipped for expanding the process medium of the heat pump downstream of the second heat exchanger (13) and upstream of the first heat exchanger (11), wherein the heat pump (10) includes a device by means of which the volumetric flow rate of the process medium of the heat pump (10) is adjustable, characterized in that, In particular, when the actual network frequency of the power network (15) deviates from the setpoint network frequency, in order to stabilize the network frequency of the power network (15), and therefore, to make the actual network frequency close to the setpoint network frequency, the power consumption of the motor (14) is adjusted in such a way as to control the speed of the motor (14) and / or by changing the volumetric flow rate of the process medium of the heat pump (10), such that with respect to the constant or approximately constant pressure ratio of the compressor (12), and therefore, with respect to the constant or approximately constant temperature of the process medium in the region of the second heat exchanger (13), the actual network frequency of the power network is close to the setpoint network frequency.

2. The method according to claim 1, characterized in that, In order to stabilize the network frequency of the electric power network (15), the power consumption of the motor (14) is adjusted by the speed control of the motor (14) and by the change in the volumetric flow rate of the process medium.

3. The method according to claim 1 or claim 2, characterized in that, In particular, when the actual network frequency of the power network (15) is higher than the setpoint network frequency, the power consumption of the motor (14) increases by the increase in the speed of the motor (14) and / or by the increase in the volumetric flow rate of the process medium of the heat pump (10).

4. The method according to claim 1, claim 2, or claim 3, characterized in that, In particular, when the actual network frequency of the power network (15) is lower than the setpoint network frequency, the power consumption of the motor (14) is reduced by a decrease in the speed of the motor (14) and / or by a decrease in the volumetric flow rate of the process medium of the heat pump (10).

5. The method according to any one of claims 1 to 4, characterized in that, Speed ​​control of the speed-controlled motor (14) occurs via a change in the load of the motor (14) or a change in the frequency of the inverter (22) connected between the power network (15) and the motor (14).

6. The method according to any one of claims 1 to 5, characterized in that, In order to change the volumetric flow rate of the process medium of the heat pump (10), the expansion device (16) is controlled as a means for changing the volumetric flow rate of the process medium, wherein the expansion device (16) includes a turbine (17) whose guide vanes or rotor blades are adjustable to change the flow resistance of the expansion device (16), and thus to change the volumetric flow rate of the process medium. And / or expansion valve (18), the opening position of which is adjustable in order to change the flow resistance of the expansion device (16) and therefore, to change the volumetric flow rate of the process medium.

7. The method according to any one of claims 1 to 6, characterized in that, In order to change the volumetric flow rate of the process medium of the heat pump (10), the compressor (12), which is a device for changing the volumetric flow rate of the process medium, is controlled. The guide vanes or rotor blades of the compressor (12) are adjustable to change the flow resistance of the compressor (12), and thus to change the volumetric flow rate of the process medium.

8. The method according to any one of claims 1 to 7, characterized in that, In order to change the volumetric flow rate of the process medium of the heat pump (10), a separate valve or a separate throttle valve is controlled as a device for changing the volumetric flow rate. The opening position of the separate valve or the separate throttle valve is variable to change its flow resistance, and therefore to change the volumetric flow rate of the process medium.

9. A control device for operating a heat pump (10) while stabilizing the network frequency of an electrical power network, characterized in that, The control device is equipped to automatically execute the method of any one of claims 1 to 8 on the control side.

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