System for distributing electrical energy

A system includes a first, particularly mobile, unit which has a number m of function terminals, a first potential equalization terminal, which is intended to be galvanically connected to a reference potential, an energy source, a power converter, which is fed from the energy source and produces a number m of signals, a switching unit, the signals produced by the power converter being fed to the input side of the switching unit, and the output side of the switching unit being connected to the function terminals, or the input side of the switching unit being connected to the energy source and the output side of the switching unit being connected to the power converter, an insulation monitoring unit, which detects an undesired galvanic connection of a component of the system to the reference potential, and a connection monitoring unit, which monitors whether the first potential equalization terminal is properly electrically connected to a corresponding potential equalization terminal of a second unit to be connected to the first unit.

BACKGROUND AND SUMMARY

The invention relates to a system for distributing electrical energy.

The invention is based on the object of making available a system for distributing electrical energy that enables ground fault detection in different units to be as simple as possible.

The system comprises at least a first unit. The first unit may be, for example, a mobile or drivable unit, for example a truck tractor unit.

The first unit comprises a number m of functional terminals to which corresponding functional terminals of further units of the system or electrical consumers are able to be connected as intended. The number m may be between 2 and 32, for example.

The first unit further comprises a first potential equalization terminal that is to be or is electrically connected as intended to a reference potential, in particular ground potential.

The first unit further comprises an energy source, for example in the form of a DC voltage source, in particular in the form of an electrical energy store or a battery.

The first unit further comprises a power converter that is fed from the energy source and that is designed to generate a number m of signals. The power converter may be, for example, a DC-AC converter, a DC-DC converter or a combination thereof, supplied from the energy source in the form of the DC voltage source or battery.

The first unit further comprises a controllable switching unit, the input side of which is supplied with the signals generated by the power converter and the output side of which is connected to the functional terminals. The switching unit can, for example, establish or interrupt an electrical connection between terminals on the input side and terminals on the output side. As an alternative, the input side of the switching unit can be connected to the energy source and the output side can be connected to the power converter.

The first unit further comprises an insulation monitoring unit that is designed to detect an undesired galvanic connection of a component of the system to the reference potential. Reference is made to the relevant specialist literature for the basic design and the basic mode of operation of such insulation monitoring units.

The first unit further comprises a connection monitoring unit that is designed to monitor whether the first potential equalization terminal is electrically connected as intended, for example is electrically connected in a sufficiently low-impedance manner, to a corresponding potential equalization terminal of a second unit to be connected to the first unit.

According to one embodiment, the first unit further comprises a first test signal terminal, wherein the connection monitoring unit is designed to supply a first test signal, for example a first test voltage or a first test current, to the first test signal terminal and, depending on a current or voltage signal present at the first potential equalization terminal, to monitor whether the first potential equalization terminal is electrically connected as intended to the corresponding potential equalization terminal of the second unit to be connected to the first unit.

According to one embodiment, the system comprises the second, in particular mobile, unit, that is coupled to the first unit for electrical energy exchange. The second mobile unit may be part of a trailer, for example. According to the invention, the first and the second unit are galvanically coupled to one another.

The second unit comprises its potential equalization terminal that is connected to the corresponding first potential equalization terminal of the first unit and its test signal terminal that is connected to the corresponding first test signal terminal of the first unit. The potential equalization terminal of the second unit is electrically connected to the test signal terminal of the second unit, for example short-circuited inside the second unit.

According to one embodiment, the second unit further comprises a number m of functional connections that are galvanically connected to the number m of functional terminals of the first unit.

According to one embodiment, the switching unit interrupts a connection between the power converter and the signal terminals when the connection monitoring unit detects that the first potential equalization terminal of the first unit is not electrically connected as intended to the corresponding potential equalization terminal of the second unit. As an alternative, the switching unit interrupts a connection between the energy source and the power converter when the connection monitoring unit detects that the first potential equalization terminal of the first unit is not electrically connected as intended to the corresponding potential equalization terminal of the second unit.

According to one embodiment, the system further comprises a third, in particular stationary, unit, that is coupled to the first unit or the second unit for energy exchange. The third unit comprise at least one potential equalization terminal that is connected to a further potential equalization terminal of the first unit or that is connected to a further potential equalization terminal of the second unit. The third unit can comprise two potential equalization terminals, with a first potential equalization terminal of the two potential equalization terminals being connected to a further potential equalization terminal of the first unit and a second potential equalization terminal of the two potential equalization terminals being connected to a further potential equalization terminal of the second unit. The connection monitoring unit is designed to monitor whether the at least one potential equalization terminal of the third unit is electrically connected as intended to a corresponding potential equalization terminal of the first unit or the second unit. According to the invention, the first and the third unit are galvanically coupled to one another.

According to one embodiment, the connection monitoring unit is designed to supply a second test signal to a second test signal terminal of the first unit and, depending on a signal present at a corresponding potential equalization terminal of the first unit and/or a signal present at a corresponding potential equalization terminal of the second unit, to monitor whether the at least one potential equalization terminal of the third unit is electrically connected as intended to a corresponding potential equalization terminal of the first unit or to a corresponding potential equalization terminal of the second unit.

According to one embodiment, the insulation monitoring unit is designed to detect an undesired galvanic connection of a component of the first unit and/or the second unit and/or the third unit to the reference potential.

According to one embodiment, the system has a plurality of first units, wherein a respective first unit generates the first test signal and/or the second test signal with a unique identifier. In other words, the two test signals can contain different identifiers that contain a unique identifier for each first unit placed on the market, which means that when the test signals are evaluated, it can be ensured that malfunctions of the connection monitoring unit caused by external signals from similar systems or by external interference are ruled out.

According to one embodiment, the switching unit interrupts a connection between the power converter and the signal terminals as soon as the insulation monitoring unit detects an undesired galvanic connection of a component of the first unit and/or the second unit and/or the third unit to the reference potential.

According to one embodiment, an electrical connection between the potential equalization terminals of the third unit and corresponding terminals of the first unit and/or the second unit is effected via a flexible, movable or sliding connection and/or via a temporarily fixed connection, in particular a grounding rod, screw connections or plug-in contacts.

According to one embodiment, the first test signal terminal is protected up to the first transfer point of the second unit against an undesired connection to the reference potential by double or reinforced insulation and/or the second test signal terminal is protected up to the second transfer point of the third unit against an undesired connection to the reference potential by double or reinforced insulation.

According to one embodiment, the switching unit interrupts the connection between the power converter and the signal terminals depending on the state of the first unit immediately or after a time delay after the connection monitoring unit detects that the first potential equalization terminal of the first unit is not electrically connected as intended to the corresponding potential equalization terminal of the second unit. As an alternative, the switching unit can interrupt a connection between the energy source and the power converter when the insulation monitoring unit detects an undesired galvanic connection of a component of the first unit and/or the second unit and/or the third unit to the reference potential.

According to one embodiment, the insulation monitoring unit determines the location of an undesired galvanic connection of a component to the reference potential of the first unit, the second unit or the third unit depending on the switching state of the switching unit.

The invention is described in detail below with reference to the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG.1schematically shows a schematic block circuit diagram of a system100for distributing electrical energy.

The system100comprises a first, mobile unit50that can be arranged, for example, in a tractor unit of a truck. The first unit50comprises a number m of functional terminals51_1to51_mat which, for example, DC and/or AC voltages can be output/input.

The system100further comprises a second, mobile unit20that can be arranged, for example, in a trailer towed by the tractor unit.

The system100further comprises a third, stationary unit30.

The first unit50comprises a first potential equalization terminal15that is to be galvanically connected to a reference potential23, for example ground potential, when the system100or the first unit50is in operation. The first unit50comprises a second potential equalization terminal18that is to be galvanically connected to the reference potential23when the system100or the first unit50is in operation.

The first potential equalization terminal15of the first unit50is connected to a corresponding potential equalization terminal25of the second unit20. The second potential equalization terminal18of the first unit50is connected to a corresponding potential equalization terminal33of the third unit30.

The first unit50further comprises a first test signal connection14that is connected to a corresponding test signal terminal26of the second unit20. The first unit50further comprises a second test signal terminal17that is connected to a corresponding test signal terminal34of the third unit30.

The second unit20further comprises a second test signal terminal16that is connected to a corresponding test signal terminal32of the third unit30.

The functional terminals51_1to51_mof the first unit50are galvanically connected to corresponding functional terminals24_1to24_mof the second unit20. Functional terminals27_1to27_mof the second unit20are galvanically connected to corresponding functional terminals31_1to31_mof the third unit30.

The first unit50further comprises an energy source40, for example in the form of a rechargeable battery.

The first unit50further comprises a power converter10, for example in the form of a DC-AC converter, that is fed from the energy source40via a number of n lines, for example is fed via n=2 lines, and that is designed to generate a number m of signals S1to Sm.

The first unit50further comprises a switching unit11, the input side of which is supplied with the signals S1to Sm generated by the power converter10and the output side of which is connected to the functional terminals51_1to51_m.

The first unit50further comprises an insulation monitoring unit12that is designed to detect an undesired galvanic connection of a component of the units20,30and50of the system100to the reference potential23. Reference is also made to the relevant specialist literature for the basic mode of operation of such insulation monitoring units.

The first unit50further comprises a connection monitoring unit13that is designed to monitor whether the first potential equalization terminal15is electrically connected as intended to the corresponding potential equalization terminal25of the second unit20and to monitor whether the second potential equalization terminal18is electrically connected as intended to a corresponding potential equalization terminal33of the third unit30.

The functions of the first unit50are controlled or coordinated by means of a central control unit41.

The connection monitoring unit13is designed to supply a first test signal (PS1) to the first test signal terminal14and, depending on a signal resulting at the first potential equalization terminal15, to monitor whether the first potential equalization terminal15is electrically connected as intended to the corresponding potential equalization terminal25of the second unit20to be connected to the first unit50.

The connection monitoring unit13is further designed to supply a second test signal PS2to the second test signal terminal17of the first unit50and, depending on a signal present at the corresponding potential equalization terminal18of the first unit50and/or a signal present at the corresponding potential equalization terminal16of the second unit20, to monitor whether the potential equalization terminals32,33of the third unit30are electrically connected as intended to the corresponding potential equalization terminal16of the second unit20or to the corresponding potential equalization terminal18of the first unit50.

The switching unit11interrupts a connection between the power converter10and the signal terminals51_1to51_mwhen the connection monitoring unit13detects that the potential equalization terminals15,16and/or18are not electrically connected as intended.

Furthermore, the switching unit11interrupts a connection between the power converter10and the signal terminals51_1to51_mwhen the insulation monitoring unit12detects an undesired galvanic connection of a component of the first unit50and/or the second unit20and/or the third unit30to the reference potential23.

An electrical connection between the potential equalization terminals32,33of the third unit30and corresponding terminals of the first unit50and/or the second unit20can be effected via a flexible, movable or sliding connection and/or via a temporarily fixed connection, in particular a grounding rod, screw connections or plug-in contacts.

The system100can have a plurality of first units50, second units20and third units30, wherein a respective first unit50generates its first test signal PS1and/or its second test signal PS2with a unique identifier.

FIG.2shows a schematic circuit diagram of an internal design of the connection monitoring unit13.

The connection monitoring unit13comprises two sub-units13aand13bwith the same internal design. The connection monitoring unit13is galvanically isolated from the remaining components of the first unit50.

A respective sub-unit13aor13bcomprises optocouplers60and61, with signals being fed into the sub-units13aor13bvia the respective optocoupler60and being read out via the respective optocoupler61.

Respective resistors64,65and66are connected as illustrated.

A respective current sensor67controls a respective Schmitt trigger63that is used for signal conditioning and control of the respective optocoupler61.

A connection of the test signal terminals14and26and17and34can be protected from an undesired connection to the reference potential23by means of a double insulation19.

The potential output terminals16and32can be connected and the test signal terminals17and34can be connected via a sliding connection35.

According to the invention, instead of the conventional galvanic insulation of the units20,30and50from one another, the insulation monitoring unit12of the first unit50is expanded, which, for example, can also detect a first fault in the second unit20or a towed vehicle through expanded functionality.

FIG.3shows a schematic block diagram of a system for distributing electrical energy according to another embodiment. In contrast to the embodiment shown inFIG.1, the input side of the switching unit11is connected here to the energy storage device40and the output side is connected to the power converter10. In the event of a fault, the power converter10can thus be isolated from the energy store40. In particular, during the precharging of a link circuit of the power converter10, the power converter10can be isolated from the energy store in the event of an insulation fault.

Typical applications of the invention are briefly described below.

1. Monitoring of a Chassis Connection (potential Equalization Via the Potential Equalization Terminals)

By applying a test signal that is galvanically isolated from the overall system, for example a test voltage (low voltage, PWM signal), to the second unit or a towed vehicle (consumer), a current flow can be measured via one or two measuring inputs, which creates an intended electrical connection of the potential equalization terminals, that is to say the existence of a vehicle chassis connection (reference potential or equalization potential), can be reliably determined.

The presence of a sufficient chassis connection can be checked by comparing the measured current with a suitable limit value. If the chassis connection between the towing vehicle and the towed vehicle is interrupted, a current flow can no longer be measured.

2. Insulation Monitoring Unit in the First Unit or in the Towing Vehicle

In a galvanically connected supply system between the first unit or towing vehicle and the second unit or trailer, the insulation monitoring unit detects an initial insulation fault both in the towing vehicle itself and in the trailer, as long as there is a sufficiently low-impedance chassis connection between the towing vehicle and trailer.

3. Switching Off the Energy Supply of the Second Unit or the Towed Vehicle

By immediately switching off the energy supply using the switching unit, a possible insulation fault in the second unit or in the trailer is isolated from the supply system in the first unit or in the towing vehicle, that is to say the detected insulation fault is separated from the towing vehicle. This is an important prerequisite for ensuring that the driving characteristics of the entire vehicle are not impaired.

It is up to the vehicle manufacturer to decide whether the energy supply for the second unit or the towed vehicle is isolated immediately or only after a certain period of time or when another event occurs. It may be that the connection is only disconnected when the vehicle is stopped or parked if it can be assumed that no people can be on the towed vehicle while driving.

4. Reliable Detection of an Initial Error

The above measures can be used to ensure that an initial fault is detected before there is a hazard from electric current in the event of a second fault (touching live parts that are not covered).

5. Switching on Again after an Insulation Fault has been Detected

Since the initial fault can usually be assumed to be harmless, it is possible to switch on again at full voltage. If desired by the vehicle manufacturer, it is possible to switch on again at a lower voltage, for example at a safe 50 V, and this voltage can be used to check whether the insulation fault is still present.

6. Expansion to Electrical Safety in the Vehicle Environment

As an expansion, a second test signal terminal or measurement input on the expanded insulation monitoring unit can be used to monitor a potential connection between the second unit or trailer and the road (ground). The current impressed into the trailer chassis can be routed back to the insulation monitoring unit via a movable ground connection, where it can be measured and checked for a suitable limit value.

The first unit, the second unit and/or the third unit may have a movable ground connection (wiper).

7. Monitoring of a Sufficient Potential Connection to the Ground (Road)

If the second control current is interrupted, it must be assumed that the insulation monitoring unit cannot identify a possible initial fault in the area surrounding the vehicle because the potential shift generated as a result cannot be measured.

In the case of a construction site vehicle, this information can be used, for example, to ensure that the power supply for the second unit or the trailer is either not switched on or is switched off when the measuring current is disconnected. In this case, too, the measured loop current is compared with a suitable limit value.

It is up to the vehicle manufacturer to interrupt the energy supply immediately if the second test signal terminal or measurement input detects a control current that is too low or to make the shutdown dependent on other conditions. It may be that the energy supply (electrical connection) is only disconnected when the vehicle is stopped or parked if it can be assumed that work around the vehicle is only possible when it is stationary.

8. Additional Advantages

As described above, the combination of insulation monitoring unit, power converter or DC-AC conversion and shutdown by means of a switching unit makes it possible to immediately and reliably detect an initial insulation fault and to switch off the energy supply or supply voltage of the corresponding network. However, there are other advantages, especially cost and application advantages:

9. Current-Free Switching of the Switching Elements

The integration of the insulation monitoring unit and the power converter in the first unit makes it possible, in the event of a detected insulation fault, to first switch off the power converter and shortly thereafter the switch of the switching unit as soon as the current has dropped to zero. This is absolutely necessary, especially with a DC voltage supply, in order to avoid arcs. By ensuring the correct sequence, it can be guaranteed that the switches are always switched with no (direct) current, both in the event of an insulation fault and in the event of a short circuit, that is to say overcurrent. As a result, significantly more cost-effective switching elements can be used in the switching unit, thereby saving costs and installation volume.

10. AC Switching of the Switching Elements

With AC power supplies, due to the periodic zero crossings of the currents, shutdown is also possible during operation (current not equal to zero).

According to the invention, a significant cost saving can be achieved by preventing galvanic isolation between the first unit, the second unit and the third unit, which causes significant additional costs for power semiconductors and transformers.