System

Abstract

System (100), comprising: - a DC voltage network (1) with a first potential path (1a) intended to carry a positive potential (ZK+) and a second potential path (1b) intended to carry a negative potential (ZK-), - a three-phase, current-compensated choke (2) having a first winding (2a), a second winding (2b) and a third winding (2c), wherein the first winding (2a), the second winding (2b) and the third winding (2c) are magnetically coupled to one another, wherein the first winding (2a) is looped into the first potential path (1a) and wherein the second winding (2b) is looped into the second potential path (1b), and - a monitoring device (3) which is designed to: - to evaluate a signal (UI) induced in the third winding (2c) for monitoring the DC voltage network (1), and / or - to impress an interference suppression voltage (UE) into the third winding (2c), characterized in that - the third winding (2c) is part of a DC / DC converter (4) or an AC / DC converter (8) for precharging an intermediate circuit (5).

Description

DE 10 2020 004 825 A1 and DE 10 2017 105 839 A1 each disclose a system according to the preamble of claim 1.JP 2006-136 058 A discloses a three-phase current-compensated inductor which is used in a two-phase DC grid, wherein a third winding having a capacitance is used as filter.DE 202 22 013 U1 discloses a current-compensated choke and a circuit arrangement with the current-compensated choke.The invention is based on the object of making available a DC or AC system which is designed with as low an outlay on components as EMC-optimized as possible.The system comprises a DC power supply. The DC voltage network has a first potential path which is provided to carry a positive potential. The DC voltage network further has a second potential path which is provided for carrying a negative potential.The system has a current-compensated inductor, in particular a conventional three-phase inductor, having a first winding, a second winding and a third winding. The first winding, the second winding and the third winding are magnetically coupled to one another, for example via an annular core. The current-compensated choke can form an EMC filter or can be part of an EMC filter. In this respect, reference is also made to the relevant technical literature.The first winding is looped into the first potential path or is part of the first potential path and the second winding is looped into the second potential path or is part of the second potential path. In this case, "looped-in" means in particular that the respective potential path is separated at a point provided for this purpose and the winding is connected between the separation points.The system further comprises a monitoring device which is designed to evaluate a signal induced in the third winding, in particular in the form of an induced voltage, for monitoring the DC voltage system and / or to apply an interference suppression voltage to the third winding.Open DC grid devices typically require an EMC filter in order for each subscriber to comply with uniform limit values for grid-bound and radiated emissions. As an EMC measure in inverters, a filter unit made of a current-compensated inductor is used in conjunction with capacitors.In order to use the same components and possibly circuit parts or devices as in AC networks, according to the invention conventional 3-phase (EMC) interference suppression is used in particular for EMC interference suppression in the DC voltage network. 2 windings of an annular core of the current-compensated inductor are used for suppressing interference from the positive potential or from the negative potential. The third winding is used according to the invention to monitor the operating behavior (condition monitoring).According to the invention, a multiple value of sensor system in the DC network arises by using a possibly broken-down third winding of the current-compensated inductor. In this case, either standard chokes from the AC range can be used, which are used in large numbers, or the 3rd winding of the choke can be optimized specifically for monitoring in the DC grid.In one embodiment, the monitoring device is designed to evaluate the signal induced in the third winding for detecting a (static) fault current, i.e. to detect a fault as soon as the current differs between the two potential paths. The cause of this error current can be, for example, a (creeping) earth error in the path behind the current-compensated choke.In one embodiment, the monitoring device is designed to evaluate the signal induced in the third winding for detecting a (static) fault voltage, i.e. to detect a fault, as soon as the DC voltage or the voltage between the two potential paths is not symmetrical with respect to ground. The cause of this asymmetry can be, for example, a (creeping) earth fault in the DC network.In one embodiment, the monitoring device is designed to evaluate the signal induced in the third winding for impedance measurement, i.e. for measuring the mains impedance, the impedance on the inside of the device (intermediate circuit) and the load impedance on the output side of the device.Furthermore, the monitoring device can be designed to detect temporary current and / or voltage peaks by evaluating the signal induced in the third winding, which indicate impermissible line-bound faults in the DC grid.In one embodiment, the monitoring device is designed to pulse-shape the suppression voltage into the third winding for active suppression. The third winding of the three-phase inductor can be used during the power flow via only two windings to actively act, for example as an inductance in an actuator for precharging an intermediate circuit and / or for active suppression of interference by means of targeted injection of pulses.The third winding can be embodied identically or differently from the first and the second winding, for example with a different number of windings, a different cross section or also a plurality of windings / taps.The third winding is part of a DC / DC converter or an AC / DC converter for precharging an intermediate circuit.In one embodiment, the system comprises an inverter fed from the DC power supply.According to the invention, the third winding of an AC inductor is used for condition monitoring / fault detection in the DC voltage network. In this case, this 3-phase (EMC) inductor can be arranged at any point in the DC voltage network and / or integrated into a DC voltage network composite subscriber, such as an inverter, for example.The invention will be described in detail below with reference to the drawings. The following shows: FIG. 1 shows a system comprising a DC voltage grid, a three-phase current-compensated inductor, an inverter which is fed from the DC voltage grid, and a monitoring device for monitoring the DC voltage grid.FIG. 1 shows a system 100 comprising a DC voltage grid 1 having a first potential path 1 awhich is provided to carry a positive potential ZK+and a second potential path 1 bwhich is provided to carry a negative potential ZK-.The system further comprises capacitors 9 connected between the first potential path 1 aand the second potential path 1 b.The system further comprises capacitors 10 connected between the second potential path 1 band ground potential.The system further comprises a three phase current compensated inductor 2 having a first winding 2a, a second winding 2b and a third winding 2c. The first winding 2 a, the second winding 2 band the third winding 2 care magnetically coupled to one another via an annular core 7 of the current-compensated inductor 2.The first winding 2 ais looped into the first potential path 1 aand the second winding 2 bis looped into the second potential path 1 b.The system 100 further comprises a monitoring device 3 which is designed to evaluate a signal induced in the third winding 2 cin the form of a voltage UIfor monitoring the DC voltage grid 1 and / or to apply an interference suppression voltage UEto the third winding 2 c.The monitoring device 3 is designed, for example, to evaluate the signal Ul induced in the third winding 2 cto detect a residual current, to evaluate it to detect a residual voltage, and / or to evaluate it to measure impedance.The monitoring device 3 can be designed to pulse-shape the suppression voltage UEin the third winding 2 cto actively suppress suppression.The third winding 2 cmay be part of a DC / DC converter 4 or an AC / DC converter 8 for precharging an intermediate circuit 5.The system 100 further comprises a conventional inverter 6, which is fed from the DC voltage network 1 or the intermediate circuit 5.To the left of a dashed line T, a conventional DC grid can be connected, to which the DC grid 1 is connected. The components shown on the right of the line of separation T shown can form, for example, an electrical device, for example a frequency converter.

Claims

A system (100) comprising: - a DC power supply system (1) having a first potential path (1a) provided to carry a positive potential (ZK+) and a second potential path (1b) provided to carry a negative potential (ZK-), - a three-phase current-compensated inductor (2) having a first winding (2a), a second winding (2b) and a third winding (2c), wherein the first winding (2a), the second winding (2b) and the third winding (2c) are magnetically coupled to one another, wherein the first winding (2a) is looped into the first potential path (1a) and wherein the second winding (2b) is looped into the second potential path (1b), and - a monitoring device (3), A signal (UI) induced in the third winding (2c) for monitoring the DC voltage network (1) and / or - for injection of an interference suppression voltage (UE) into the third winding (2c), characterized in that - the third winding (2c) is a component of a DC / DC converter (4) or of an AC / DC converter (8) for pre-charging an intermediate circuit (5).System (100) according to Claim 1, characterized in that - the monitoring device (3) is designed to evaluate the signal (UI) induced in the third winding (2c) for detecting a fault current.System (100) according to one of the preceding claims, characterized in that - the monitoring device (3) is designed to evaluate the signal (UI) induced in the third winding (2c) for detecting a fault voltage.System (100) according to one of the preceding claims, characterized in that - the monitoring device (3) is designed to evaluate the signal (UI) induced in the third winding (2c) for impedance measurement.System (100) according to one of the preceding claims, characterized in that - the monitoring device (3) is designed to apply the suppression voltage (UE) pulse-shaped to the third winding (2c) for active suppression of suppression.System (100) according to one of the preceding claims, characterized in that - the system (100) has an inverter (6) which is fed from the DC voltage network (1).

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