DE102018216950A1 - Circuit arrangement for the safe operation of a high-voltage system - Google Patents

Abstract

Circuit arrangement (20) for the safe operation of a high-voltage system (2), comprising a switching unit (4) and a control unit (1), the high-voltage system (2) having a high potential connection HV +, a low potential connection HV- and a basic potential GND, the switching unit ( 4), depending on a control of the control unit (1), it is optionally possible to electrically couple the high potential connection HV + via a first impedance (8) to the basic potential GND, or alternatively the low potential connection HV- via a second impedance (9) to the basic potential To couple GND electrically, and wherein the switching unit (4) is set up to set a value of the first impedance (8) or a value of the second impedance (9) by means of the control of the control unit (1).

Description

The invention relates to a circuit arrangement for the safe operation of a high-voltage system with an IT network, in which the insulation resistance is determined during operation.

In the technical field of high-voltage electrical systems, operational safety must be guaranteed at all times. For this purpose, such high-voltage systems are set up as IT (Isolé Terre) systems, in which all active parts either against the basic HV potential GND isolated or with sufficiently high impedances with the HV basic potential GND are connected.

For example, an electrical battery or a fuel cell or a combination of fuel cell and battery can be used as the DC voltage source in a high-voltage system. These high-voltage systems are used for electrical machines and electrically operated vehicles such as electric bicycles, electric cars, hybrid vehicles or the like and are also used for their units such as heating and air conditioning systems.
Since an initial insulation fault can be tolerated in such an IT system, this is also associated with a greater failure protection. An insulation monitoring device, which is also called an insulation monitor, is required for such IT systems in VDE applications. In vehicles, an insulation monitor can be used to ensure compliance with the relevant limit values. Devices for measuring and monitoring the insulation resistance of high-voltage systems are available on the market and are used in current vehicles with HV systems.

If an insulation fault occurs, the insulation monitor responds and provides a signal at its output that can be evaluated as an alarm or notification. So that the insulation monitor can fulfill this task, it must be integrated into the high-voltage system in such a way that it can safely detect all insulation faults.

State of the art

The proper functioning of an insulation monitor is conventionally ensured by the insulation monitor providing a self-test functionality so that a defect in this unit itself does not lead to an unsupervised operation of the high-voltage system due to a malfunction of the insulation monitor. In the event of an accident involving such a vehicle with a high-voltage system, the greatest possible system security must be guaranteed, just as when parking.

When building a high-voltage system, the functionality of the insulation monitor in the high-voltage system is checked using external, manual test procedures before the high-voltage system is made available.

The disclosure DE 10 2009 001 962 A1 describes a charging system for use in a vehicle with earth potential, comprising a) a vehicle high-voltage network, containing a high-voltage battery with a battery disconnecting device, and optionally one or more consumers; b) a charger connected to the high-voltage battery, which can be integrated into the vehicle and has a mains disconnection device, which can be connected to a charging current network via a mains plug; c) one or more Fl-circuit breakers for residual current monitoring during a charging process, the Fl-circuit breakers being arranged in such a way that the charging system can be separated from a connected charging current network via the Fl-circuit breaker; d) a protective conductor, which can be connected to the vehicle ground, and means for permanent protective conductor function monitoring during a charging process, the means being designed such that the battery separating device of the high-voltage battery and the mains separating device of the charger can be triggered if the protective conductor function is impaired; e) Means for monitoring the insulation of the vehicle high-voltage network and the charger before the start of a charging process, the means being designed in such a way that when an insulation fault is detected, the battery disconnection device of the high-voltage battery and the mains disconnection device of the charger can be triggered.

The object of the present invention is to provide a circuit arrangement which can ensure that different possible operating states of a high-voltage system can be checked and put into a safe state.

Disclosure of the invention

According to the invention, a circuit arrangement is specified according to the features of the independent claim, which has at least in part the effects mentioned. Advantageous refinements are the subject of the dependent claims and the following description.

The invention is based on the knowledge that a fault in the high-voltage system itself must be simulated to ensure the function of the insulation monitor. For this purpose, additional impedances must be switched in the high-voltage system, which simulate a defect or can be switched for other purposes of safe operation.

For the safe operation of a high-voltage system with a high-potential connection, a low-potential connection and a basic potential, it is equipped with a switching unit and a control unit. This switching unit is set up in such a way that, depending on a control of the control unit, the high-potential connection can be electrically coupled to the basic potential via a first impedance, or optionally the low-potential connection can be electrically coupled to the basic potential via a second impedance. The switching unit is set up such that a value of the first impedance or a value of the second impedance can be set by means of the control of the control unit.

This connection of additional impedances to the high-voltage system, which can also be set by the control unit in relation to the value of the impedance, make it possible to simulate the defects in the insulation and to detect them using an insulation monitor. In addition, such a connection of impedances can also be used to carry out discharge processes in the high-voltage system.

The accuracy of an insulation detection can be adjusted by a suitable choice of the value of the connected impedances. In addition, with the choice of the impedances, by means of the control unit, the applied impedances can be adapted to the different tasks of the circuit.

According to one embodiment of the invention, it is proposed to set up the control unit such that it is possible to interrupt the operation of the high-voltage system by means of a control line to an interruption switch of the high-voltage system. This configuration enables the high-voltage system to be put into a voltage-free, secured operating state from different operating states. The operation of the HV system can e.g. by controlling shooters in an open position, to ensure a particularly safe mode of operation in which the power supply in the high-voltage system is interrupted.

In a further embodiment of the invention it is proposed that the optional electrical coupling of the high potential connection via the first impedance to the basic potential, by means of a first controllable switching element, and the optional electrical coupling of the low potential connection via the second impedance to the basic potential, by means of a second controllable switching element he follows.

The impedances can be omitted as additional discrete components if, for example, a half-bridge with IGBTs is used and this is controlled so that it is a suitable z. B. represents ohmic resistance. That means the adjustable first or second impedance 8th or 9 also in a switching element 11 , 10th can be integrated.

According to a further embodiment of the invention, it is proposed that the first controllable switching element or the second controllable switching element has at least one electromagnetic relay or at least one semiconductor component, and the first controllable switching element or the second controllable switching element is set up to be controlled by the control unit. Thus, for these controllable switching elements, alternatively, simple to implement electromagnetic relays or more robust semiconductor components in continuous operation can be used.

In one embodiment of the invention, it is proposed that the control unit be set up in such a way that it can control both an insulation monitor and the switching unit. If, controlled by the control unit, the high potential connection is electrically coupled to the basic potential via a first impedance with a first value and / or the low potential connection is electrically coupled to the basic potential via a second impedance which has a second value, the control unit can verify the functionality of the insulation monitor using an output signal from the insulation monitor.

If the insulation monitor correctly detects these additional impedances, which act in parallel with the insulation impedances, in the high-voltage system, both the functionality of the insulation monitor itself and its functional integration into the high-voltage system are verified.

The change in the value of the impedances results in a selectable accuracy or sensitivity of the detection of insulation faults in this test scheme, which therefore does not have to be determined when the high-voltage system is built, but can be adapted to special operating conditions during operation.

Furthermore, the adjustable impedances could act in accordance with additional adjustable Y capacitances and generate asymmetrical voltage distributions in the HV network, which extends the test possibility of the insulation monitor.

The variable impedance values can have capacitive as well as inductive as well as ohmic components of different dimensions by means of correspondingly controllable components be integrated into the switching unit, and / or component groups can be interconnected accordingly by the control unit via further switching elements.

According to a measure improving the invention, the correct detection of the connected impedances can be achieved by comparing the output signal of the insulation monitor with a setpoint value of the output signal of the insulation monitor, by means of the control unit, which is dependent on the optional electrical coupling of the first impedance and / or the optional one electrical coupling of the second impedance takes place. Thus, by a suitable choice of the connected impedances and the setpoint, the verification of the functionality of the insulation monitor can be adapted according to the requirements for the accuracy of the verification.

According to a further embodiment of the invention, it is proposed that the control unit be set up to provide a signal at an output of the control unit, depending on the result of the verification of the functioning of the insulation monitor. Such a signal can then be used by higher-level systems to monitor the safe or faulty state of the high-voltage system.

This can trigger maintenance tasks or alarms. The verification of the functioning of the insulation monitor is unsuccessful if the error signal to be expected due to connected impedances is not provided by the insulation monitor at its output.

For the first value of the first impedance or the second value of the second impedance, according to a further embodiment of the invention, it is proposed to use an ohmic resistor, this ohmic first or second resistor preferably having a value in the range between 0.5 MOhm and 5 MOhm having.

This means that the additional impedances introduced are in the value range of the insulation resistance, which ensures sensitive verification. Impedance monitors are typically set up to also detect capacitors or inductors, so that such components can also be used to check the insulation.

According to a further embodiment of the invention, it is proposed that the control unit be set up to symmetrize the potential connections HV + and HV- to control what the switching unit the high potential connection HV + via the first impedance, with a third value, electrically couples to the basic potential, and the low potential connection HV- electrically couples to the base potential via the second impedance, with a fourth value.

Such a circuit arrangement enables the optional balancing of IT high-voltage systems. The third value of the first impedance and the fourth value of the second impedance can preferably be selected as an ohmic resistance from the value range from 0.5 MOhm to 5 MOhm, the end values being included in the range. By means of the latter control of the switching unit, the two potential connections are actively balanced with respect to the basic HV potential GND .

With the adjustable impedance values described above, a discharge function of HV system capacitors can also be carried out by means of the control unit, by selecting a suitable ohmic resistance value and coupling both impedances between the respective potential connections and the HV basic potential. This is typically carried out when the high-voltage system is switched on and off. This is done when switching on to ensure a safe start-up state.

This supports the discharge of system capacities C x and thus a possible lowering of a possible touch voltage to <60V. When switching off, this is done to remove residual voltages from the high-voltage system for a safe idle state.

In one embodiment of the invention, it is proposed that the control unit be set up to control the switching unit such that the high-potential connection is based on a supplied accident signal HV + , over the first impedance with a fifth value, electrically with the basic potential GND couples. Furthermore, the switching unit is controlled so that the low potential connection HV- , over the second impedance with a sixth value, electrically with the basic potential GND couples to bring about a quick stop of a fuel cell of the high-voltage system by means of a suitable impedance through these couplings. If, instead of an HV battery, a fuel cell provides the HV voltage, it is advantageous in the event of an accident, for example, to prevent the fuel cell from restarting unintentionally due to residual media or to rapidly dissipate the residual energy of the fuel cell.

So that no damage is caused by such a quick stop at the high-voltage source, the value of the first impedance and the value of the second impedance can be dimensioned such that a maximum permissible battery current or fuel cell current of the high-voltage source is not exceeded.

For such a gentle quick stop z. B. a fuel cell, the range of values for the fifth value of the first impedance and the sixth value of the second impedance ohmic resistances in the range from 1 ohm to 1000 ohms should be used, the final values being included in the range.

In a further embodiment of the invention, it is proposed that the switching unit be set up by means of the control unit for the high-potential connection HV + over the first impedance, with a seventh value, electrically with the basic potential GND to couple, and the low potential connection HV- over the second impedance, with an eighth value, electrically with the basic potential GND to couple. The switching unit is set up in such a way that these couplings are maintained even without an energy supply to both the control unit and the switching unit. Such a permanent holding function is used to avoid energy build-up due to residual media during downtimes such. B. for a parked vehicle with high-voltage system. The seventh value of the first impedance and the eighth value of the second impedance can be used as an ohmic resistance in the range from 10 kOhm to 500 kOhm, including the boundary values, in order to ensure adequate discharge of residual currents.

Further measures improving the invention are described below together with the description of a preferred exemplary embodiment of the invention using the 1 shown in more detail.

Embodiment

The 1 shows a block diagram with a circuit arrangement ( 20th ) for the safe operation of a high-voltage system ( 2nd ) with five functional blocks, the functionality of which is illustrated by schematic components.

According to 1 the exemplary block diagram shows a circuit arrangement ( 20th ) with several circuit units, the actual energy source of the high-voltage system 2nd in this exemplary embodiment is designed as a rechargeable battery, for example an electric vehicle. Alternatively, a fuel cell can be coupled to the rechargeable DC voltage source via a DC / DC converter, or a fuel cell can be provided instead of the HV battery.

The high-voltage system 2nd has a high potential connection HV + and a low potential connection HV- to the load via a contactor 5 is electrically coupled.

The high-voltage system 2nd is designed as an IT system so that the active elements are isolated from the basic potential GND the earth or just over the first cy impedance 16 or the second cy impedance 17th with the basic potential GND are connected. The first symmetry resistor outlined 12th and the second balancing resistor 13 connected in series between the two potential connections HV + and HV- are switched, cause an electrical connection of their node with the basic potential to symmetrize the potentials against the basic potential. Typical values for the balancing resistors 12th and 13 are in the range of 0.5 MOhm to 5 MOhm.

The insulation guard 3rd measures the insulation impedance 14 between the high potential connection HV + and basic potential GND by means of a first measuring arrangement 6 and the insulation impedance 15 between the low potential connection HV- and the basic potential by means of a second measuring arrangement 7 .

The switching unit 4th exhibits a first variable impedance 8th on the first connection via a first switching unit 11 with the basic potential GND is electrically connected. The second connection of the variable impedance 8th is electrical with the high potential connection HV + connected. In addition, the switching unit points 4th a second variable impedance 9 on with its first connection via a second switching unit 10th with the basic potential GND is electrically connected. And the second connection of the second variable impedance 9 is with the low potential connection HV- connected.

The control unit 1 is both with the energy source of the high-voltage system 2nd as well as the insulation monitor and the switching unit. The control unit 1 can at first contactor 21 and the second contactor 22 the energy source of the high-voltage system 2nd act and the electrical connection between the energy source of the high-voltage system 2nd and the burden 5 close and open. This allows the control unit 1 be set up so that if the function of the insulation monitor is not successfully verified 3rd the power supply to the load 5 interrupts to ensure safe operation of the high-voltage system 2nd to ensure. Even in the event of an accident, detected with the help of a sensor, the control unit ( 1 ) the switching unit due to an accident signal 4th control so that both a quick stop, i.e. A rapid discharge of a fuel cell is also carried out by the control unit 1 an interruption in the power supply.

Furthermore, the control unit 1 set up measurements of the insulation monitor 3rd to start and stop, as well as that of the insulation guard 3rd receive and evaluate the determined data in analog or digital form. In addition, the control unit 1 set up the value of the impedances 8th and 9 the switching unit 4th to change and the switching elements 10th and 11 the switching unit 4th to control conductive and non-conductive.

The control unit 1 an evaluation result is still set up at its output 18th to provide. That exit 18th can be an electrical signal, such as a voltage signal at an electrical connection, or a digital signal, which is conducted via a data bus.

Verification of the functionality of the insulation monitor 3rd through the control unit 1 can before the high-voltage system starts operating 2nd take place, or after switching off the high-voltage system 2nd respectively. With a suitable choice of impedances 8th and 9 , ie if the parasitic current caused is small enough and the safe operation and functionality of the high-voltage system 2nd is not impaired, the measurement can also be made while the high-voltage system is in operation 2nd respectively.

For verification of the functionality of the insulation monitor 3rd switches the control unit 1 the first impedance 8th or the second impedance 9 by closing the first switching element 11 or the second switching element 10th between the potential connections HV + respectively. HV- and basic potential GND . This parallel connection of these impedances 8th respectively. 9 for insulation impedance 14 respectively. 15 reduces the measured value of the insulation resistance. This value is used by the insulation monitor 3rd to the control unit 1 passed and from the control unit 1 compared to an expected value. If this value exceeds a predetermined value, the control unit 1 the result at the exit 18th provided.

Weight 5 is with a first connection with the high potential connection HV + of the high-voltage system 2nd connected and with the second connection with the low potential connection HV- . The symmetry resistors 12th and 13 are connected in series between the high potential connection HV + and the low potential connection HV- . The contact point of the symmetry resistors 12th and 13 is electrically conductive with the basic potential GND connected.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102009001962 A1 [0007]

Claims (10)

Circuit arrangement (20) for the safe operation of a high-voltage system (2), comprising a switching unit (4) and a control unit (1), the high-voltage system (2) having a high potential connection HV +, a low potential connection HV- and a basic potential GND, characterized in that the switching unit (4) is set up, depending on a control of the control unit (1), to electrically couple the high potential connection HV + via a first impedance (8) to the basic potential GND, or alternatively the low potential connection HV- via a second impedance (9) to couple electrically with the basic potential GND, and wherein the switching unit (4) is set up to set a value of the first impedance (8) or a value of the second impedance (9) by means of the control of the control unit (1). Circuit arrangement (20) after Claim 1 , characterized in that the control unit (1) is set up to interrupt the operation of the high-voltage system (2) by means of a control line to an interruption switch of the high-voltage system. Circuit arrangement (20) after Claim 1 or 2nd , characterized in that the optional electrical coupling of the high potential connection HV + via the first impedance (8) to the basic potential GND, by means of a first controllable switching element (11), and the optional electrical coupling of the low potential connection HV- via the second impedance (9) the basic potential GND, by means of a second controllable switching element (10). Circuit arrangement (20) according to one of the preceding claims, characterized in that the first controllable switching element (11) or the second controllable switching element (10) has at least one electromagnetic relay or at least one semiconductor component, and the first controllable switching element (11) or the second controllable switching element (10) is set up to be controlled by the control unit (1). Circuit arrangement (20) according to one of the preceding claims, characterized in that the control unit (1) is set up to control both an insulation monitor (3) and the switching unit (4) and depending on the electrical coupling of the high potential connection HV + to the basic potential GND, by means of the first impedance (8), having a first value, or the electrical coupling of the low potential connection HV- to the ground potential GND, by means of the second impedance (9), having a second value, the functionality of the insulation monitor (3) by means of a Verify output signal of the insulation monitor (3). Circuit arrangement (20) after Claim 5 , characterized in that the control unit (1) is set up to provide a signal at an output of the control unit (1) depending on the result of the verification of the functioning of the insulation monitor (3). Circuit arrangement (20) according to one of the preceding claims, characterized in that the first value of the first impedance (8) or the second value of the second impedance (9) is an ohmic resistor, this ohmic resistor preferably having a value in the range between 0, 5 MOhm and 5 MOhm. Circuit arrangement (20) according to one of the preceding claims, characterized in that the control unit (1) for symmetrizing the potential connections HV + and HV- is set up to control the switching unit (4) in such a way that the high potential connection HV + via the first impedance (8) electrically couples to the base potential GND with a third value, and the low potential terminal HV- electrically couples to the base potential GND with a fourth value via the second impedance (9). Circuit arrangement (20) according to one of the preceding claims, characterized in that the control unit (1) is set up to control the switching unit (4) on the basis of a supplied accident signal in such a way that the high potential connection HV + has a fifth via the first impedance (8) Value electrically couples to the basic potential GND, and the low potential connection HV- couples via the second impedance (9) with a sixth value electrically to the basic potential GND in order to bring about a rapid stop of a fuel cell of the high-voltage system (2). Circuit arrangement (20) according to one of the preceding claims, characterized in that the switching unit (4) is set up to use the control unit (1) to electrically couple the high potential connection HV + to the basic potential GND via the first impedance (8) with a seventh value, and to electrically couple the low-potential terminal HV- to the basic potential GND via the second impedance (9) with an eighth value, and the couplings being maintained even without an energy supply to both the control unit (1) and the switching unit (4).

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