Method and control unit for operating a compressor connected to an electrical power grid, compressor, and system having a compressor

Abstract

Proposed is a method for operating a compressor (10) connected to an electrical power grid (11), wherein: the compressor (10) has an electrical machine (12) which is connected to the electrical power grid (11) via power electronics (13) and receives electrical power from the electrical power grid (11) in order to drive the compressor (10) having at least one compressor section (16); a control device (19) actuates the power electronics (13) of the electrical machine (12) in order to operate the compressor (10), or a system (35) having the compressor (10), at a defined operating point; the control device (19) receives from the electrical power grid (11) a target value for target reactive power to be received or output by the power electronics (13) of the electrical machine (12) or determines from the actual voltage of the electrical power grid (11) the target value for the target reactive power to be received or output by the power electronics (13) of the electrical machine (12); and the power electronics (13) of the electrical machine (12) are actuated by the control device (19) such that the greatest possible proportion of the target reactive power is received from the electrical power grid (11) or output to the electrical power grid (11) by the power electronics (13).

Description

[0001] Method and control unit for operating a compressor connected to an electrical power grid, compressor and system with a compressor

[0002] The invention relates to a method and a control unit for operating a compressor connected to an electrical power grid. Furthermore, the invention relates to a compressor and a system comprising a compressor.

[0003] In a three-phase electrical grid, electrical energy is transported via three-phase alternating current. Both reactive and active power can be generated. The dot product of reactive power and active power is called apparent power. Depending on the operating point of the electrical grid, there can be either too much or too little reactive power. Reactive power is used to stabilize the electrical voltage in the three-phase grid. Grid operators create a demand plan for this purpose, which power plant operators then follow.

[0004] Various loads can be connected to a three-phase electrical network. For example, a compressor can be connected to a three-phase electrical network; specifically, the compressor's electrical motor is connected to the electrical network via power electronics. The compressor's power electronics then draw electrical power from the electrical network to drive the compressor, which has at least one compressor section, and to compress a medium, such as a process gas. For this purpose, the compressor operates at a defined operating point. At this operating point, the electrical load draws a total power from the electrical network, which includes both reactive and active power. As mentioned above, the reactive power adjustment in a three-phase network is carried out at the highest network level, i.e., at the power plants.However, due to the increasing decentralization of energy supply, it can be desirable to use electrical loads connected to a three-phase power grid to adjust the reactive power within that grid. Thus, an electrical load connected to a three-phase grid can both absorb reactive power from the grid and feed reactive power into it.

[0005] Starting from this, the present invention is based on the objective of creating a novel method and control unit for operating a compressor connected to an electrical power grid, a compressor with such a control unit and a system with such a compressor.

[0006] This problem is solved by a method for operating a compressor connected to an electrical power grid according to claim 1, a control unit for operating a compressor connected to an electrical power grid according to claim 4, a compressor according to claim 5 and a system according to claim 9.

[0007] The present invention proposes that the control device of the compressor, namely the power electronics of the compressor's electric machine, receives a setpoint value of the target reactive power to be absorbed or supplied by the power electronics of the electric machine from the electrical power grid, or determines the target value for the target reactive power to be absorbed or supplied by the power electronics of the electric machine from the actual voltage of the electrical power grid, wherein the power electronics of the electric machine are controlled by the control device in such a way that the power electronics absorb as large a proportion as possible of the target reactive power from or supply to the electrical power grid.The present invention proposes for the first time that the control unit of a compressor connected to a three-phase power grid, namely the control unit of the compressor's power electronics, receives a setpoint value from the electrical grid for the reactive power to be drawn from or supplied to the electrical grid by the power electronics, or determines the setpoint value for the reactive power to be drawn from or supplied to the electrical grid by the power electronics of the electric machine from the actual voltage of the electrical grid, and that the power electronics are then controlled by the control unit to draw or supply as large a proportion of the set reactive power as possible. This makes it possible to influence the reactive power component of a power grid in a decentralized manner.

[0008] Preferably, the control unit monitors the actual reactive power that the power electronics of the electric machine can absorb or supply, taking into account, and in particular maintaining, a defined operating point of the compressor or a system comprising the compressor. The control unit then controls the power electronics of the electric machine in such a way that, taking into account, and in particular maintaining, the defined operating point, the power electronics absorb or supply the largest possible proportion of the target reactive power. This is particularly preferred in order to operate the compressor or the system comprising the compressor at the desired operating point and, on the other hand, to contribute as much as possible to stabilizing the reactive power in the electrical grid.

[0009] Medium-term deviations from an optimal or desired operating point may be permitted, provided the process in which the compressor is integrated allows it, in order to operate the three-phase electrical network accordingly. If necessary, the control unit can report back to the electrical network an actual value of the reactive power or a value of the currently available reactive power potential, which the power electronics of the electrical machine can absorb or supply, taking into account, and in particular maintaining, the defined operating point of the compressor or the system containing the compressor.This enables a particularly advantageous stabilization of reactive power in the three-phase electrical network, as the three-phase electrical network receives feedback on how much of the requested target reactive power can actually be absorbed or delivered by the power electronics of the compressor's electric machine.

[0010] Preferably, in the compressor according to the invention, the at least one compressor section is a component of a hermetically sealed turbomachine assembly, which has a hermetically sealed, one- or multi-part housing in which the at least one compressor section and preferably also the electric motor of the compressor are mounted via active magnetic bearings. The invention is particularly applicable when the compressor connected to the electrical power grid is a hermetically sealed compressor in which both the electric motor and the at least one compressor section are arranged and mounted in a hermetically sealed housing of the hermetically sealed turbomachine assembly.

[0011] In particular, the compressor can be part of a heat pump system comprising a first heat exchanger, a compressor according to the invention connected to the electrical power grid, a second heat exchanger, and an expansion device, wherein the first heat exchanger of the heat pump system is configured to transfer thermal energy to a process medium of the heat pump system, wherein the compressor of the heat pump system is configured to compress the process medium of the heat pump system downstream of the first heat exchanger and upstream of the second heat exchanger, wherein the second heat exchanger of the heat pump system is configured to release thermal energy from the process medium of the heat pump system, in particular to transfer it to a consumer, and wherein the expansion device of the heat pump system is configuredto expand the process medium of the heat pump system downstream of the second heat exchanger and upstream of the first heat exchanger.

[0012] Preferred embodiments of the invention are set forth in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows:

[0013] Fig. 1 shows a compressor connected to an electrical power grid, which is part of a heat pump system.

[0014] Fig. 2 shows a detail of the power electronics of an electric compressor machine.

[0015] Fig. 3 shows a power diagram of the power electronics of the compressor's electric machine.

[0016] Fig. 1 shows a block diagram of a compressor 10 connected to an electrical power grid 11, namely a three-phase power grid. The compressor 10 has an electric motor 12 which is connected to the three-phase power grid 11 via power electronics 13. As indicated by arrow 14, the compressor 10 draws active power from the three-phase power grid 11. As indicated by double arrow 15, reactive power can be transferred back and forth between the compressor 10 and the three-phase power grid 11. The compressor 10 also has at least one compressor section 16.

[0017] In the illustrated embodiment, the at least one compressor section 16 and the electric motor 12 are arranged in a hermetically sealed housing 17. Both the electric motor 12 and the at least one compressor section 16 are mounted in the hermetically sealed housing 17 via active magnetic bearings 18. The number of compressor sections 16 and bearings 18 shown, as well as their arrangement in the housing 17, are exemplary.

[0018] As described above, the power electronics 13 are coupled between the electric motor 12 of the compressor 10 and the three-phase electrical network 11. The power electronics 13 are controlled and / or regulated by a control unit 19 in order to adjust the active power 14 drawn from the electrical network 11 and thus the desired operating point of the compressor 10 or of a system 35 comprising the compressor.

[0019] An arrow 20 illustrates the provision of a corresponding control signal, via which the control unit 19 controls the power electronics 13.

[0020] According to Fig. 1, the control device 19 can also exchange data with sensors of the compressor sections 16, for example measured values.

[0021] In a preferred embodiment of the present invention, the control unit 19 receives a setpoint value directly from the three-phase electrical network 11 in the direction of arrow 22, specifying a setpoint reactive power. This setpoint is intended to either draw power from the three-phase electrical network 11 or supply it to the power electronics 13, and thus to the compressor 10. Depending on this setpoint reactive power, the control unit 13 controls the power electronics 13 in such a way that the latter draws as large a proportion as possible of the requested setpoint reactive power from the three-phase electrical network 11 or supplies it to the same network.For this purpose, it is specifically provided that the control device 19 checks what actual reactive power the power electronics 13 of the electric machine 12 of the compressor 10 can absorb or supply, taking into account, and in particular maintaining, the desired operating point of the compressor 10 or taking into account, and in particular maintaining, the desired operating point of the system 35 comprising the compressor 10. The power electronics 13 is then controlled by the control device 19 in such a way that the power electronics 13 absorbs or supplies as large a proportion of the target reactive power as possible, taking into account, and in particular maintaining, the defined or desired operating point of the compressor 10 or of the system 35 comprising the compressor 10, as shown in Fig.1 the control device 19 according to arrow 23 reports an actual value back to the power grid 11, which actual reactive power and therefore which proportion of the requested target reactive power is absorbed or delivered by the compressor 10 or can be absorbed or delivered.

[0022] Medium-term deviations from the defined or desired operating point may be permitted, if this is allowed by a process in which the compressor 10 is involved, in order to be able to operate the power grid 11 accordingly.

[0023] The direct reception of the setpoint value via the setpoint reactive power, which the power electronics 13 and thus the compressor 10 are to either receive from the electrical power grid 11 or supply to it, means that the power grid 11, in particular a control device (not shown) thereof, provides the control device 19 of the compressor 10 with the setpoint value via the setpoint reactive power directly, e.g. via the Internet, so that the control device 19 of the compressor 10 then directly and automatically controls and / or regulates the power electronics 13 of the compressor 10 depending on the setpoint value of the setpoint reactive power.Alternatively, the control unit 19 of the compressor 10, which controls and / or regulates the power electronics 13, can automatically determine the target value for the reactive power to be received or delivered by the power electronics 13 of the electric machine 12 from the current actual voltage of the electrical grid 11, in order to then automatically control and / or regulate the operation of the power electronics 13 depending on this determined target value. For this purpose, the actual voltage of the electrical grid 11 can be measured, whereby the control unit 19 of the compressor 10 then automatically determines the target value for the reactive power to be received or delivered by the power electronics 13 depending on the measured actual voltage, particularly with the aid of a characteristic curve.

[0024] Furthermore, it can be provided that the control device 19 indirectly receives the setpoint value for the reactive power to be absorbed or supplied by the power electronics 13 of the electric machine 12 from the electrical power grid 11, for example via an intermediate control unit (not shown). In this way, the operator of the electrical power grid 11 can provide the intermediate control unit with a schedule containing setpoint values ​​for the reactive power to be absorbed or supplied by the power electronics 13 of the electric machine 12. The control device 19, which controls and / or regulates the power electronics 13, then automatically reads this schedule via a data interface, or preferably enters it automatically into a data interface of the control device 19, which controls and / or regulates the power electronics 13.

[0025] Depending on the setpoint for the reactive power to be received or delivered by the power electronics 13 of the electric machine 12, the power electronics 13 of the electric machine 12 is controlled by the control unit 19 such that the power electronics 13 receives as large a proportion as possible of the set reactive power from or delivers to the electrical grid 11 and provides corresponding capacitive or inductive reactive power for this purpose. Fig. 2 shows a detail of the power electronics 13, in which the power electronics 13 has a circuit arrangement 24, 25 on both the motor and grid sides, each consisting of several controllable power semiconductors 26, 27 and several diodes 28, 29.The motor-side circuit arrangement 24 of the power electronics 13 comprises controllable power semiconductors 27, in particular transistors or thyristors, with each of the controllable power semiconductors 27 interacting with a diode 29. The mains-side circuit arrangement 25 also comprises controllable power semiconductors 26, in particular transistors or thyristors, and diodes 28. A capacitor 30 is connected in parallel between the circuit arrangements 24 and 25.

[0026] The controllable power semiconductors 26, 27, which are preferably IGBT or IGCT power semiconductors, can be controlled by the control device 19 in such a way that, by providing a desired rotational speed at the electric machine 12 and thus by providing a desired operating point of the compressor 10, a defined actual reactive power, which can be absorbed or released depending on the operating point of the compressor 10 or the system 35 comprising the compressor 10, is absorbed or released from the three-phase electrical network 11 or to the same.

[0027] Fig. 3 illustrates a power diagram for the power electronics 13, where arrow 31 visualizes active power that can be drawn from the three-phase electrical network 11. Arrows 32 and 33 visualize reactive power that can be drawn from (arrow 32) or supplied to (arrow 33) the electrical network 11. Arrow 34 visualizes the apparent power at a defined operating point in which both active power and reactive power are drawn from the electrical network 11. The active power and reactive power components at the operating point are obtained by vector decomposition in the direction of arrows 31 and 32. The compressor 10 is a particularly preferred component of a system, specifically a heat pump system 35. Such a heat pump system 35 comprises, in addition to the compressor 10, heat exchangers 36 and 37 and an expansion device 38.

[0028] In compressor 10, a heat pump process medium from the heat pump system 35 is compressed and supplied to the heat exchanger 36. The heat pump process medium flowing through the heat exchanger 36 then enters the expansion unit 38, which may include, for example, an expansion valve and / or a turbine. From the expansion unit 38, the heat pump process medium flows through another heat exchanger 37 before being returned to compressor 10 for compression. In the area of ​​heat exchanger 36, thermal energy is transferred, in particular to a consumer; in the area of ​​heat exchanger 37, thermal energy is transferred to the heat pump process medium.

[0029] The invention provides a particularly advantageous way to absorb or supply reactive power from or to a three-phase electrical network 11 by actively controlling the power electronics 13 of a compressor 10. For this purpose, the three-phase electrical network 11 requests a target reactive power from the compressor 10, and the control unit 19 of the compressor 10's power electronics 13 checks whether and to what extent reactive power can be absorbed or supplied, taking into account, and in particular maintaining, a defined desired operating point of the compressor 10 or the system 35 comprising the compressor 10. The power electronics 13 is then controlled or regulated accordingly. (Reference numeral list)

[0030] Compressor, power grid, electric machine, power electronics, active power, reactive power

[0031] Grain pressor section housing

[0032] Storage

[0033] Control device, control signal, data exchange

[0034] Target reactive power Actual image power

[0035] Circuit arrangement Circuit arrangement Power semiconductor Power semiconductor Diode

[0036] diode

[0037] Capacitor active power

[0038] Reactive power, apparent power, heat pump system, heat exchanger, heat exchanger, expansion device

Claims

Patent claims 1. Method for operating a compressor (10) connected to an electrical power grid (11), wherein the compressor (10) comprises an electric machine (12) which is connected to the electrical power grid (11) via power electronics (13) and which draws electrical power from the electrical power grid (11) to drive the compressor (10) having at least one compressor section (16), wherein a control device (19) controls the power electronics (13) of the electric machine (12) in order to operate the compressor (10) or a system (35) comprising the compressor (10) at a defined operating point, characterized in thatthat the control device (19) receives a setpoint value from the electrical power grid (11) for the setpoint reactive power to be absorbed or supplied by the power electronics (13) of the electrical machine (12) or determines the setpoint value for the setpoint reactive power to be absorbed or supplied by the power electronics (13) of the electrical machine (12) from the actual voltage of the electrical power grid (11), and that the power electronics (13) of the electrical machine (12) is controlled by the control device (19) in such a way that the power electronics (13) absorbs as large a proportion as possible of the setpoint reactive power from the electrical power grid (11) or supplies it to the electrical power grid (11).

2. Method according to claim 1, characterized in that the control device (19) checks which actual reactive power the power electronics (13) of the electric machine (12) can absorb or supply, taking into account the defined operating point, and that the power electronics (13) of the electric machine (12) is controlled by the control device (19) in such a way that the power electronics (13) can supply the greatest possible amount of reactive power, taking into account the defined operating point. absorbs part of the target reactive power from the electrical grid (11) or supplies it to the electrical grid (11).

3. Method according to claim 2, characterized in that an actual value of the actual reactive power or a value of a currently available reactive power potential, which the power electronics (13) of the electrical machine (12) can absorb or supply taking into account the defined operating point, is reported back to the electrical power grid (11) by the control device (19).

4. Control device (19) for a power electronics (13) of an electric machine (12) of a compressor (10), which is configured to carry out the method according to one of claims 1 to 3.

5. Compressor (10), comprising at least one compressor section (16), comprising an electric machine (12) for driving the at least one compressor section (16), comprising power electronics (13) via which the electric machine (12) is connected to an electrical power grid (11), and comprising a control device (19) according to claim 4.

6. Compressor (10) according to claim 5, characterized in that the at least one compressor section (16) is part of a hermetically sealed turbomachine arrangement which has a hermetically sealed, one- or multi-part housing (17) in which the at least one compressor section (16) is mounted via active magnetic bearings (18).

7. Compressor (10) according to claim 6, characterized in that the electric machine (12) together with the at least one compressor section (16) is arranged in the hermetically sealed housing (17) and is mounted via active magnetic bearings (18).

8. Compressor (10) according to one of claims 5 to 7, characterized in that the power electronics (19) has a circuit arrangement (24, 25) on the motor side and on the mains side, each consisting of several controllable power semiconductors (26, 27) and diodes (28, 29), wherein a capacitor (30) is connected in parallel between the two circuit arrangements (24, 25).

9. System (35), namely a heat pump system comprising a first heat exchanger (37), a compressor (10) connected to the electrical power grid (11) according to one of claims 5 to 8, a second heat exchanger (36) and an expansion device (38), wherein the first heat exchanger (37) of the heat pump system is configured to transfer thermal energy to a process medium of the heat pump system, wherein the compressor (10) of the heat pump system is configured to compress the process medium of the heat pump system downstream of the first heat exchanger (37) and upstream of the second heat exchanger (36), wherein the second heat exchanger (36) of the heat pump system is configured to release thermal energy from the process medium of the heat pump system, and wherein the expansion device (38) of the heat pump system (10) is configuredto expand the process medium of the heat pump system downstream of the second heat exchanger (36) and upstream of the first heat exchanger (37).

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