Method for operating an electrical supply device and electrical supply device

Abstract

An electrical supply device is connected on a network side to an electrical supply network and includes a frequency converter having a network-side power converter and an intermediate circuit, and a network filter, which is connected upstream of the network-side power converter. In a method for operating the electrical supply device, during a pulse-blocking operating state of the frequency converter, a check is carried out for the presence of a dangerous state of the network filter, and only in the presence of the dangerous state, only the network-side power converter is actuated such that a network perturbation causing the dangerous state of the network filter is at least damped to protect the network filter from the dangerous state.

Claims

1. A method for operation of an electrical supply device, which is connected on a network side to an electrical supply network and includes a frequency converter having a network-side power converter and an intermediate circuit, and a network filter, which is connected upstream of the network-side power converter, said method comprising: during a pulse-blocking operating state of the frequency converter, checking for the presence of a dangerous state of the network filter; and only in the presence of the dangerous state, actuating only the network-side power converter such that a network perturbation causing the dangerous state of the network filter is at least damped to protect the network filter from the dangerous state.

2. The method of claim 1, wherein the network-side power converter is automatically actuated when the dangerous state is present.

3. The method of claim 1, wherein the network filter is a passive network filter including a filter capacitor.

4. The method of claim 3, wherein the presence of the dangerous state is identified by a detection unit through detection of a capacitor overvoltage at the filter capacitor.

5. The method of claim 1, wherein the presence of the dangerous state is identified by a detection unit through detection of an intermediate circuit overvoltage inside the intermediate circuit of the frequency converter.

6. The method of claim 1, wherein the presence of the dangerous state is identified by a detection unit through detection of an overcurrent inside the supply network.

7. The method of claim 1, wherein the frequency converter includes a load-side power converter.

8. The method of claim 1, wherein the frequency converter is designed as an Active Front End.

9. The method of claim 1, further comprising arranging the frequency converter and the network filter in a shared housing.

10. The method of claim 1, wherein the network-side power converter is automatically actuated by a control unit when the dangerous state is present.

11. An electrical supply device for connection to an electrical supply network, said electrical supply device comprising: a frequency converter including a network-side power converter and an intermediate circuit; a network filter connected upstream of the network-side power converter; and a detection unit configured to check, during a pulse-blocking-operating state of the frequency converter, the presence of a dangerous state for the network filter, wherein only in the presence of the dangerous state, the frequency converter actuates only the network-side power converter such that a network perturbation causing the dangerous state of the network filter is at least damped to protect the network filter from the dangerous state.

12. The electrical supply device of claim 11, wherein the frequency converter includes a load-side power converter.

13. The electrical supply device of claim 11, wherein the network filter is a passive network filter including a filter capacitor.

14. The electrical supply device of claim 13, wherein the detection unit is configured to detect a capacitor overvoltage at the filter capacitor.

15. The electrical supply device of claim 11, wherein the detection unit is configured to detect an intermediate circuit overvoltage inside the intermediate circuit of the frequency converter.

16. The electrical supply device of claim 11, wherein the detection unit is configured to detect an overcurrent inside the supply network.

17. The electrical supply device of claim 11, wherein the frequency converter is designed as an Active Front End.

18. The electrical supply device of claim 11, further comprising a shared housing for arrangement of the frequency converter and the network filter.

19. The electrical supply device of claim 11, further comprising a control unit configured to automatically actuate the network-side power converter when the dangerous state is present.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) An exemplary embodiment of the invention will be explained in more detail below with reference to the FIGURE. In a partially highly simplified representation:

(2) FIG. 1 shows a schematized circuit diagram of an electrical supply device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(3) FIG. 1 shows a schematized circuit diagram of an electrical supply device 2, which is connected on the network side to an electrical supply network 4 and in the exemplary embodiment to an electrical load 6 on the bad side. A (load-side) connection of the electrical bad 6 is not imperative, however, and is used in the exemplary embodiment merely for better understanding.

(4) The electrical supply network 4 is preferably a three-phase system, which is represented in FIG. 1 merely in a schematized manner by means of a rectangle. In the exemplary embodiment according to FIG. 1, the electrical load 6 is an electrical machine, specifically an electric motor.

(5) Furthermore, the electrical supply device 2 has a frequency converter 8, which has a network-side power converter 10, an intermediate circuit 12 and a load-side power converter 14. Both the network-side power converter 10 and the load-side power converter 14 each have six switching elements 16 designed, for example, as semiconductor switches.

(6) Parallel to each switching element 16 is a diode 18 with its flow direction arranged counter to the forward direction of the respective switching element 16.

(7) The general functional principle of the frequency converter 8 will not be discussed here.

(8) The electrical supply device 2 also has a network filter 20, which is connected upstream of the network-side power converter 10.

(9) The network filter 20 also preferably has a filter capacitor 22, in the exemplary embodiment three filter capacitors 22. Here one filter capacitor 22 respectively is provided for one phase of the three-phase electrical supply network 4. The network filter 20 can also have further passive elements such as chokes, resistors or diodes. Mechanical switch components such as, for example, contactors can alternatively also be arranged in the network filter 20.

(10) Furthermore, the electrical supply device 2 in the exemplary embodiment has a control unit 24, which is adapted in such a way as to actuate the two power converters 10, 14, and specifically their switching elements 16, with switching pulses via control lines 26.

(11) Both the control unit 24 and the frequency converter 8 are arranged in a shared housing 28.

(12) The electrical supply device 2 and, in particular, the frequency converter 8 is adapted in such a way as to switch the electrical load 6 present in the exemplary embodiment, in a pulse-blocking operating state, via the load-side power converter 14 in a power-free manner. Furthermore, the frequency converter 8 is adapted in such a way as to actuate only the network-side power converter 10 by means of the control unit 24, only in the case where a dangerous state is present for the network filter 20, in such a way that the network filter 20 is protected from the dangerous state.

(13) For detection and, in particular, identification of the dangerous state the electrical supply device 2 in the exemplary embodiment has a detection unit 30. The presence of the dangerous state is identified by means of the detection unit 30, for example by detection of a network overcurrent I.sub.N. For this, a current measuring element 32 is provided in the exemplary embodiment, which measures the network current and transmits this value to the detection unit 30. The dangerous state is present in this case when the network current of the electrical supply network 4 exceeds a specified threshold value, therefore.

(14) Furthermore, it is provided in the exemplary embodiment that the dangerous state for the network filter 20 is identified in such a way that a capacitor overvoltage U.sub.C is detected at one of the filter capacitors 22 and is transmitted to the detection unit 30. If the voltage at one of the filter capacitors 22 exceeds a specified value, the dangerous state for the network filter 20 is present. A first voltage measuring element 34 is arranged inside the network filter 20 for detection of the capacitor overvoltage U.sub.C, which drops at one of the filter capacitors 22.

(15) As a third and particularly preferred variant for identification of the dangerous state for the network filter 20 it is provided in the exemplary embodiment that an intermediate circuit overvoltage U.sub.ZK of the intermediate circuit 12 is detected. Here a second voltage measuring element 36 is arranged inside the intermediate circuit 12, and this is connected to the detection unit 30.

(16) As a particularly preferred variant, the detection of the intermediate circuit overvoltage U.sub.ZK Is based on the idea that a voltage of this kind is detected anyway for a regulation during normal operation of the frequency converter 8, and additional components can be omitted, therefore. In other words, the second voltage measuring element 36 is not arranged in the frequency converter 8 in addition to the identification of the dangerous state on the basis of the intermediate circuit overvoltage U.sub.ZK, therefore. Instead, a voltage measuring element arranged as standard in the intermediate circuit 12 is used as the second voltage measuring element 36.

(17) When the dangerous state is present, the detection unit 30 transmits a signal to the control unit 24, so this preferably automatically, in other words independently, transmits an actuation signal to the switching elements 16 of the network-side power converter 10, so this is actuated hereby in such a way that the network perturbation causing the dangerous state is preferably damped from the electrical supply network 4 and in particular completely compensated, so the network filter 20 is protected from the dangerous state and against destruction, therefore.

(18) The Invention is not limited to the exemplary embodiment described above. Instead, a person skilled in the art can derive other variants of the invention herefrom without departing from the subject matter of the invention. In particular, all individual features described in connection with the exemplary embodiment can also be combined with each other in different ways, moreover, without departing from the subject matter of the invention.

(19) In particular, the invention can also be applied to frequency converters, which only have a passive network filter, a (active) network-side power converter and an intermediate circuit. In this case, the frequency converter forms either an active network filter or an electrical supply device for a direct current (DC) network.