INVERTER WITH DIRECT VOLTAGE SOURCE AND CONTROLLER

Abstract

A device for feeding electrical energy into a three-phase electrical supply network having a line voltage, a line frequency, a nominal line voltage and a nominal line frequency, comprising: an inverter having at least one property from: a power response to a frequency disturbance in the electrical supply network; a current response to a voltage disturbance in the electrical supply network; a current response to a network disturbance a phase jump capability which permits a phase jump of the line voltage to be passed through by at least 20°; a feed-in of electrical voltages and/or currents to minimize found harmonic oscillations of the voltage or the currents in the electrical supply network; a feed-in of electrical currents to minimize voltage asymmetries in the electrical supply network; and a feed-in of electrical power, which is intended to carry out an attenuation of network oscillations in the electrical supply network.

Claims

1. A device for feeding electrical energy into a three-phase electrical supply network having a line voltage, a line frequency, a nominal line voltage and a nominal line frequency, comprising: an inverter having a nominal power and including: an output configured to output a predetermined maximum current and configured to be coupled to the three-phase electrical supply network; and an inverter input; an electrical direct voltage source that is an electrical storage device that stores an energy content and being associated with a maximum electrical power for charging and a maximum electrical power for discharging, the electrical direct voltage source being coupled to the input of the inverter input and configured to exchange electrical energy with the inverter; and a controller configured to control the inverter such that the inverter has at least one property from a list of properties including: a power response to a frequency disturbance in the electrical supply network; a first current response to a voltage disturbance in the electrical supply network; a second current response to a network disturbance, wherein the second current response does not exceed the predetermined maximum current; a phase change capability permitting passage of a phase jump of at least 20° of the line voltage; a feed-in of electrical voltage and/or current to mitigate harmonic oscillations of a voltage or current in the electrical supply network; a feed-in of electrical current to mitigate voltage asymmetry in the electrical supply network; and a feed-in of electrical power to attenuate network oscillations in the electrical supply network.

2. The device as claimed in claim 1, wherein the inverter is associated with a nominal current and the inverter has a physical load limit that is greater than or equal to 1.5 times the nominal current.

3. The device as claimed in claim 1, wherein the inverter, the direct voltage source or the controller are configured such that the device is voltage-impressing.

4. The device as claimed in claim 1, wherein the direct voltage source is configured such that the inverter provides the nominal power for at least 0.5 seconds exclusively using the direct voltage source.

5. The device as claimed in claim 1, wherein the direct voltage source has at least one partition associated with the at least one property of the list of properties.

6. The device as claimed in claim 1, wherein the direct voltage source has at least one property from a list of properties including: at least 10% of the energy content as a partition for the power response; at least 10% of the energy content as a partition for the first current response; at least 10% of the energy content as a partition for the second current response; at least 10% of the energy content as a partition for the phase change capability; at least 10% of the energy content as a partition for the feed-in of electrical voltage and/or current to mitigate harmonic oscillations of the voltage or current in the electrical supply network; at least 10% of the energy content as a partition for the feed-in of electrical current to mitigate voltage asymmetry in the electrical supply network; and at least 10% of the energy content as a partition for the feed-in of electrical power to attenuate network oscillations in the electrical supply network.

7. The device as claimed in claim 1, wherein the direct voltage source has at least one property from a list of properties including: at least 50% of the energy content as a partition for the power response to the frequency disturbance; at least 20% of the energy content as a partition for the first current response to the voltage disturbance; at least 10% of the energy content as a partition for the feed-in of electrical power to attenuate network oscillations in the electrical supply network; and at least 10% of the energy content as a partition for the feed-in of electrical voltage and/or current to mitigate harmonic oscillations of the voltage or current in the electrical supply network.

8. The device as claimed in claim 1, wherein the inverter is operated with a voltage impressing pulse width modulation (PWM) method.

9. The device as claimed in claim 1, wherein the controller uses a control function, to control the inverter after the at least one property is triggered, wherein the control function has at least one of, comprising: an exponential course with an adjustable time constant; a linear course with an adjustable gradient; and a set point with an adjustable period.

10. The device as claimed in claim 1, wherein: the inverter has at least the power response to the frequency disturbance in the electrical supply network and the first current response to the voltage disturbance in the electrical supply network, the direct voltage source has at least 50% of the energy content as a partition for the power response and at least 20% of the energy content as a partition for the first current response, the controller uses respective control functions for the power response and the first current response, and the respective control functions have function has an exponential course with an adjustable time constant, a linear course with an adjustable gradient or a set point with an adjustable period.

11. A wind power installation, comprising: the device as claimed in claim 1.

12. A charging station for electric vehicles, comprising: the device as claimed in claim 1.

13. A photovoltaic installation, head-end station of a high-voltage direct current transmission or an assembly of a plurality of power electronic circuits for connecting batteries or other storage devices for the electrical supply network, comprising: the device as claimed in claim 1.

14. The device as claimed in claim 1, wherein the feed-in of electrical current to mitigate the voltage asymmetry in the electrical supply network is a feed-in of asymmetric current.

15. The device as claimed in claim 1, wherein the network oscillations are power oscillations.

16. The device as claimed in claim 15, wherein the power oscillations are low frequency or sub-synchronous power oscillations.

17. The device as claimed in claim 4, wherein the direct voltage source is configured such that the inverter provides the nominal power for at least 10 seconds exclusively using the direct voltage source.

18. The device as claimed in claim 1, wherein the controller is configured to reserve storage content of the direct voltage source for the at least one property of the list of properties.

19. The device as claimed in claim 8, wherein the inverter is operated independently of a measurement of the line voltage.

20. The device as claimed in claim 8, wherein the inverter is operated within 1000 ms after the network fault.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0085] The present invention is explained in greater detail hereinafter by way of example using exemplary embodiments with reference to the accompanying figures.

[0086] FIG. 1 shows a schematic view of a wind power installation according to an embodiment.

[0087] FIG. 2 shows a schematic design of a device, in particular as a component of a wind power installation.

DETAILED DESCRIPTION

[0088] FIG. 1 shows a schematic view of a wind power installation 100.

[0089] The wind power installation 100 has a tower 102 and a nacelle 104 for this purpose. An aerodynamic rotor 106 with three rotor blades 108 and a spinner 110 is arranged on the nacelle 104. The rotor 106 is transferred into a rotational movement by the wind during operation and thus drives a generator in the nacelle.

[0090] In this case, the generator itself is connected to a rectifier which, in turn, is connected to a device described previously or hereinafter, in order to feed electrical energy into a three-phase electrical supply network.

[0091] FIG. 2 shows a schematic design of a device, in particular to be used in a wind power installation, as preferably shown in FIG. 1.

[0092] The wind power installation 100 has a generator 120 which is connected to a rectifier 130 in three phases, in particular on the stator side.

[0093] The rectifier 130 generates a direct voltage Vdc from the three-phase alternating voltage of the generator 120.

[0094] This direct voltage Vdc is applied to a direct voltage intermediate circuit, to which the device 200 is also connected.

[0095] The device 200 for feeding electrical energy into the three-phase, electrical supply network 300 comprises at least one inverter 210, a direct voltage source 220 and a control unit (controller) 230 for this purpose.

[0096] The inverter 210 is characterized by a nominal power and further comprises an inverter input 212 and an inverter output 214.

[0097] The inverter input 212 is set up to be connected to the direct voltage source 220, in particular via the direct voltage intermediate circuit 140. The inverter input 212 is therefore also connected to the rectifier 130 via the direct voltage intermediate circuit 140. The inverter output 214 is set up to carry a predetermined maximum current and to be connected to the three-phase, electrical supply network 300, for example via a transformer (not shown).

[0098] For this purpose, the electrical direct voltage source 220 is designed as an electrical storage device and is characterized by a capacitance, an electrical power and an energy content. The direct voltage source 220 preferably has a plurality of battery modules (batteries) or partitions for this purpose.

[0099] In addition, the direct voltage source 220 is connected to the inverter input 212 in such a way that electrical energy can be exchanged between the direct voltage source 220 and the inverter 210.

[0100] In order to control the power flows between the direct voltage source 220 and the inverter, a control unit 230 is provided which is set up to control at least the inverter 210 in such a way that said inverter has at least one of the properties a) to g) described previously or hereinafter. In particular, the inverter has the properties: a) a fast power response to a frequency disturbance in the electrical supply network and b) a fast current response to a voltage disturbance in the electrical supply network.

[0101] The direct voltage source 220 comprises at least two partitions 212, 214 for this purpose which are each associated with one of functions a) and b).

[0102] Additionally or alternatively, the control unit 230 is set up to reserve a storage content of the direct voltage source at least for properties a) and b). In a preferred embodiment, the partitions 212, 214 are therefore implemented via software and are managed by the control unit 230.

[0103] According to the embodiment shown, 50% of the energy content is provided as a partition 212 for property a) and 20% of the energy content as a further partition 214 for property b). The remaining 30% can be used as a buffer for supporting the direct voltage Vdc of the direct voltage intermediate circuit 140, for example.

[0104] In order to release the energy content of the direct voltage source 130 for the properties of the inverter 210 if, for example, a frequency disturbance occurs in the electrical supply network 300, the control unit in each case has at least one control function 232 for the corresponding properties.

[0105] Which control function is used can be saved in a look-up table 234, for example, this is an exponential course with an adjustable time constant in the case of a frequency disturbance or a linear course with an adjustable gradient in the case of a voltage disturbance, for example.

[0106] In order to implement the corresponding control functions 232, the inverter 210 is preferably controlled by means of a PWM method (modulator) 236, which particularly preferably has voltage set points. However, it is also conceivable to control by means of a tolerance band method.

[0107] According to the embodiment shown, the device 200 thus has a voltage impressing design, i.e., it can be operated in the transient and sub-transient time domain in particular measurement independent of the line voltage and nevertheless has the functions described previously or hereinafter. In particular, the device 200 is therefore set up to specify a voltage at the network connection point of the wind power installation and also to keep it within the scope of capabilities of the energy storage device and the possible maximum currents, despite external disturbances which act on the line voltage. The device therefore makes it possible to design a wind power installation as a so called network former.

[0108] In this case, it is particularly advantageous that the wind power installation, on account of the device, is set up to pass through a plurality of network faults without it disconnecting from the electrical supply network in the event of a fault and to stabilize the network by way of suitable current feed-in. In particular, this makes it possible for wind power installations to be able to adopt network-supporting properties which are otherwise usually only provided by rotating synchronous generators.

[0109] Moreover, the wind power installation is also set up to carry out a network-supporting function even if there is no wind, by way of the device. In such cases, the partition is provided in the direct voltage source. The wind power installation can therefore guarantee the functions described previously or hereinafter, which in particular are network supporting, irrespective of the prevailing wind.