High voltage system

Abstract

A high-voltage system (1) comprising at least one high-voltage power source (2), at least one load (7), wherein the high-voltage power source (2) is connected to the at least one load (7) via high-voltage lines (8), and at least one disconnection element by means of which the electrical connection between the high-voltage power source (2) and the at least one load (7) can be disconnected, wherein a series resonant circuit (9) is arranged in parallel with the load (7), characterized in that an inductor (L) is arranged in parallel with a high-voltage line (8), wherein the connection points (VP) of the parallel circuit are arranged between the at least one disconnection element and the series resonant circuit (9), wherein the inductor (L) forms a primary inductance of a transformer (10), wherein the secondary inductance of the transformer (10) is determined by the inductor (L). SR) of the series resonant circuit (9) is formed, wherein a capacitor (C) is connected in parallel to the high-voltage energy source (2), wherein the connection point is located between the high-voltage energy source (2) and the at least one switching element, wherein a switching element (12) is associated with the capacitor (C), and wherein the high-voltage system (1) is configured to close the switching element (12) when the switching element is triggered.

Description

[0001] The invention relates to a high-voltage system, in particular a traction network in a motor vehicle.

[0002] High-voltage systems have a high-voltage energy source, which is designed, for example, as a high-voltage battery and has a voltage of several hundred volts. Such a high-voltage system also has at least one electrical consumer, for example an inverter, to convert the direct voltage of the high-voltage energy source into an alternating voltage. The high-voltage energy source and the electrical consumer are connected via high-voltage cables. High-voltage systems also typically have a shutdown element to break the electrical connection. Such shutdown elements can be designed as fuses and / or as switching elements such as relays or semiconductor switches. The shutdown elements serve, among other things, to quickly interrupt the flow of current in emergency situations. Due to the parasitic inductances of the high-voltage cables, very high overvoltages can occur that can destroy components.

[0003] From DE 10 2017 123 783 A1 a high-voltage system for a vehicle is known, comprising a module having a resonant circuit coupled via power lines, and a controller programmed to propagate a first signal on the power lines at a fundamental frequency for a first period of time during start-up of the high-voltage system and to close main contactors in response to a first impedance measured on the power lines at the fundamental frequency during the period of time being less than a predetermined value in order to switch on the module.

[0004] From DE 18 00 401 A a circuit arrangement for reducing residual ripples and residual interference from direct current power supplies is known, wherein a re-input element is arranged in series with the direct current source, at the terminals of which a detector circuit, which receives at its input an image of the ripple and interference voltages taken from the terminals of the direct current source or those of the load, inputs a voltage which attenuates the ripple and interference voltages at the terminals of the direct current source and the load.

[0005] From DE 433 673 A, a method for suppressing harmonics in electrical power grids by means of resonant circuits tuned to the harmonic frequency is known, whereby in order to completely cancel out the residual voltage caused by the ohmic loss resistance of the tuning circuit, a voltage equal to but opposite to it is introduced into the resonant circuit.

[0006] From DE 10 2013 016 960 A1 a traction network of a motor vehicle is known, comprising a high-voltage battery to which a backup capacitor is arranged in parallel.

[0007] DE 10 2008 007 886 A1 discloses an industrial truck with an electric drive that can be powered by a rechargeable battery and a controller for the electric drive that can switch the drive to generator mode. A second energy storage device is provided that can be charged during generator mode and can supply the drive during motor mode. The second energy storage device can be designed as a capacitor.

[0008] From US 5 568 042 A, a method is known for monitoring and / or controlling a system component which is connected to a high-voltage electrical network, such as, for example, a tunable filter for filtering harmonics in a converter system for high-voltage direct current, the reactive impedance of which is influenced by a control element.

[0009] From DE 44 10 069 A1 a circuit arrangement is known for generating a variable, adjustable, harmonic-free direct voltage from an alternating voltage by means of a controlled power converter and a filter connected downstream of the latter, wherein an arrangement consisting of a smoothing choke and a series circuit is connected downstream of the filter, wherein the series circuit has a coupling coil and a coupling capacitor, wherein the coupling coil is magnetically coupled to the smoothing choke.

[0010] DE 10 2010 038 511 A1 discloses an overvoltage protection circuit for at least one branch of a half-bridge, which comprises a controllable semiconductor switching element and a freewheeling diode connected in series therewith, which are arranged on a common circuit carrier. A commutation branch is connected in parallel with the half-bridge branch and comprises at least one commutation capacitor, which is also arranged on the circuit carrier. A commutation resistor and a commutation coil can be arranged in series with the commutation capacitor, forming a series resonant circuit to dampen overvoltages when switching the half-bridges. The resonant frequency lies in the range of the switching frequencies of the semiconductor switching elements, which are typically in the upper kilohertz range.

[0011] The invention is based on the technical problem of creating a high-voltage system in which overvoltages are effectively reduced in the event of an emergency disconnection of the current flow.

[0012] The solution to the technical problem is achieved by a high-voltage system having the features of claim 1. Further advantageous embodiments of the invention emerge from the subclaims.

[0013] For this purpose, the high-voltage system has at least one high-voltage energy source and at least one consumer, wherein the high-voltage energy source is connected to the at least one consumer via high-voltage lines. The high-voltage system also has at least one shutdown element, by means of which the electrical connection between the high-voltage energy source and the at least one consumer can be severed, wherein a series resonant circuit is arranged parallel to the consumer. Furthermore, an inductance is arranged parallel to a high-voltage line, wherein the connection points of the parallel circuit are arranged between the at least one shutdown element and the series resonant circuit, wherein the inductance forms a primary inductance of a transformer, wherein the secondary inductance of the transformer is formed by the inductance of the series resonant circuit.If the high-voltage system is now abruptly shut down, a large overvoltage builds up due to the sharp change in current caused by the parasitic inductances. Due to the parallel connection, this current change also occurs in the parallel circuit, so that a large voltage is induced at the inductance, which is then transformed to the secondary inductance. However, the resulting current in the series resonant circuit is 180° out of phase and thus counteracts the cause in the high-voltage lines, so that the induced overvoltage can be effectively reduced. The high-voltage energy source is preferably a high-voltage battery. The at least one shutdown element is preferably a fuse, a pyrotechnic fuse, and / or a relay.

[0014] Furthermore, a capacitor is connected in parallel with the high-voltage power source, with the connection point located between the high-voltage power source and the at least one shutdown element. This effectively dampens overvoltages caused by the parasitic inductances of the high-voltage power source.

[0015] A switching element is assigned to the capacitor, and the high-voltage system is designed to close the switching element when the shutdown element is triggered. This means the capacitor does not interfere with normal operation.

[0016] In one embodiment, the resonance frequency of the series resonant circuit is less than 1 kHz and more preferably less than 300 Hz.

[0017] In a further embodiment, the series resonant circuit is arranged in the consumer so that it is arranged in the immediate vicinity of the components to be protected.

[0018] In a further embodiment, the inductance is also arranged in the electrical consumer, so that primary and secondary inductances can be arranged spatially very close to each other, so that a transmission factor close to 1 can be achieved.

[0019] In a further embodiment, the inductance is several orders of magnitude larger than a parasitic inductance of the high-voltage line.

[0020] The preferred area of ​​application is a traction network in an electric or hybrid vehicle.

[0021] The invention is explained in more detail below using a preferred embodiment. The single figure shows a schematic circuit arrangement of a high-voltage system.

[0022] In the Fig.1 schematically shows a high-voltage system 1, which is, for example, a traction network of a motor vehicle. The high-voltage system 1 has a high-voltage energy source 2, which is designed as a high-voltage battery 3 and has, for example, a nominal voltage of 400 V to 800 V. The high-voltage battery 3 has an internal battery resistance R i and an internal inductance L i Furthermore, the high-voltage system 1 has a fuse 4 and two main contactors 5, 6, by means of which the high-voltage battery 3 can be electrically isolated at all poles. Furthermore, the high-voltage system 1 has at least one electrical consumer 7, which is designed, for example, as an inverter with a downstream electric machine. The consumer 7 has a load capacity C L , which is formed, for example, by an intermediate circuit capacitor. Furthermore, the electrical load 7 has a load resistance R L and a load inductance L Lwhich are caused, for example, by the electric motor. The high-voltage energy source 2 is connected to the consumer 7 via high-voltage lines 8, whereby the high-voltage lines have a parasitic inductance L par On the input side, the load 7 has a series resonant circuit 9 which has a resistance R SR , an inductance L SR and a capacity C SRThe series resonant circuit 9 does not necessarily have to be arranged in the load 7, but can also be arranged outside. The series resonant circuit 9 is located between the two high-voltage lines 8 and thus parallel to the load 7. Furthermore, an inductance L is arranged parallel to the high-voltage line 8, with the connection points VP of the parallel circuit being located between the main contactor 5 and the series resonant circuit 9. The inductance L forms a primary inductance of a transformer 10, with the secondary inductance of the transformer 10 being formed by the inductance L SRof the series resonant circuit 9. Furthermore, a control unit 11 is shown, which, among other things, controls the main contactors 5, 6. The control unit 11 is designed, for example, as a battery management control unit. Furthermore, a capacitor C is arranged in parallel with the high-voltage energy source 2, which can be switched on or off by means of a switching element 12, wherein the switching element 12 is preferably also switched by the control unit 11.

[0023] In certain situations, for example a vehicle crash, the control unit 11 opens the main contactors 5, 6 in the load case, ie in an operating situation where a large current of, for example, 160 A flows. The abrupt shutdown results in a large current change (di / dt), so that due to the parasitic inductance L para voltage is induced. This voltage can, for example, be several kV at its peak. Due to the load capacitor C L an alternating current through the parasitic inductance L par This alternating current is now damped by the series resonant circuit 9. A current flows through the parallel inductance L that is in phase with the current through the parasitic inductance L par . The current generates a voltage that acts on the secondary inductance L SR is transmitted, but the voltage on the secondary side is 180° out of phase. A current flows from the series resonant circuit 9 that is 180° out of phase with the current on the high-voltage line 8, so that the resulting current is lower. This leads to a dampening of the overshoot.

[0024] The resonant frequency of the series resonant circuit 9 is tuned to the resonant frequency of the high-voltage system 1. Typical values ​​for the parasitic inductance L par are 2 µH, where C L = 300 - 400 µF. The load inductance L L is, for example, 500 mH and the load resistance R L due to the stator resistance is approximately 2.5 Ω. In this case, for example, R SR = 15 Ω, L SR = 1.5 H and C SR = 750 µF, resulting in a resonance frequency of approximately 4.75 Hz. L is preferably equal to L SR chosen, i.e. L = 1.5 H.

[0025] Attenuations in the amplitude of the overvoltages can be achieved that more than halve the amplitude, while the decay time is reduced by a factor of 3.

[0026] In addition to the overvoltages on the right side of the main contactors 5, 6, overvoltages also occur on the left side, which are primarily caused by the internal inductance L i which is, for example, 10 µH. Capacitor C serves to dampen these overvoltages. This capacitor has a capacitance of 300 µF, for example. If the main contactors 5, 6 are opened, the switching element 12 is closed, thus forming an oscillating circuit that dampens the overvoltages. Preferably, the switching element 12 is also controlled by the control unit 11.

[0027] The described damping effects of the overvoltages are just as effective when the current flow is interrupted by triggering fuse 4. List of reference symbols 1 high-voltage system 2 High-voltage energy source 3 high-voltage battery 4 Security 5, 6 Sagittarius 7 consumers 8 high-voltage line 9 Series resonant circuit 10 Transformer 11 Control unit 12 switching element

Claims

[1] High-voltage system (1), comprising at least one high-voltage energy source (2), at least one consumer (7), wherein the high-voltage energy source (2) is connected to the at least one consumer (7) via high-voltage power supplies (8), and at least one shutdown element, by means of which the electrical connection between the high-voltage energy source (2) and the at least one consumer (7) can be severed, wherein a series resonant circuit (9) is arranged parallel to the consumer (7), characterized by that an inductance (L) is arranged parallel to a high-voltage line (8), wherein the connection points (VP) of the parallel circuit are arranged between the at least one switch-off element and the series resonant circuit (9), wherein the inductance (L) forms a primary inductance of a transformer (10), wherein the secondary inductance of the transformer (10) is formed by the inductance (L SR) of the series resonant circuit (9), wherein a capacitor (C) is connected in parallel to the high-voltage energy source (2), wherein the connection point lies between the high-voltage energy source (2) and the at least one switch-off element, wherein a switching element (12) is assigned to the capacitor (C), wherein the high-voltage system (1) is designed such that the switching element (12) closes when the switch-off element is triggered. [2] High-voltage system according to claim 1, characterized by that the resonance frequency of the series resonance circuit (9) is less than 1 kHz. [3] High-voltage system according to claim 2, characterized by that the resonance frequency is less than 300 Hz. [4] High-voltage system according to one of the preceding claims, characterized by that the series resonant circuit (9) is arranged in the electrical consumer (7). [5] High-voltage system according to claim 4, characterized bythat the inductance (L) is arranged in the electrical consumer (7). [6] High-voltage system according to one of the preceding claims, characterized by that the inductance (L) is several orders of magnitude larger than a parasitic inductance (L par ) of the high-voltage line (8).

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