DE102006050529A1 - Power supply isolation and contactor monitoring circuit arrangement for electric drive of motor vehicle i.e. passenger car, has points arranged such that contactors are connected, and additional point arranged such that it is separated - Google Patents

Abstract

The invention relates to a circuit arrangement (10) for insulation and contactor monitoring of the power supply of an electric drive, comprising - a battery (12) for powering the electric drive, - one of the battery (12) powered power electronics (14) for driving an electric motor of the electric drive, - At least one contactor (16, 18, 20) for all-pole electrical disconnection of the battery (12) from the power electronics (14), - connected to a reference potential (FZG_GND) voltage source (22) for generating a measuring voltage for insulation and contactor monitoring, two voltage measuring devices (24, 32) for measuring a voltage swing (BATT_MESS +, BATT_MESS-, ISO_MESS +, ISO_MESS-) generated by the measuring voltage with respect to the reference potential (FZG_GND), - wherein the voltage source (22) and a first one of the voltage measuring devices (32 ) with a feed point (26, 44) for feeding the measuring voltage u and a second voltage measuring device (24) are electrically connected to a measuring point (28) for measuring the voltage swing (BATT_MESS +, BATT_MESS-) and the feed point (26) and measuring point (28) are arranged such that the at least one contactor (16, 18, 20) therebetween is switched.

Description

The The invention relates to a circuit arrangement for insulation and contactor monitoring the power supply of an electric drive according to claim 1.

In modern hybrid drives of motor vehicles, in particular of passenger cars In addition to an internal combustion engine, an electric drive is used. The electric drive has this one of the electrical system of the motor vehicle separate power supply. This power supply includes a powerful electric Battery that has a high DC voltage of, for example, up to 600 V generates, as well as a power electronics with a converter of the Electric drive. The drive is equipped with an isolated network, thus the danger e.g. is reduced by service personnel. It also introduces Single failure not to a system failure, so he can reported be without the vehicle already fails. Therefore, the isolation should by measuring the insulation resistance of the power supply to Vehicle mass to be monitored. However, not only is the surveillance the isolation for the safety important, but also the reliable disconnection of the battery from the power supply at rest, for example, for service purposes. This will be shooters used, which are open at rest to the battery from the power supply, in particular from the DC link of the inverter electrically disconnect, leaving the wires and the power electronics and the electric motor are voltage-free.

task The present invention is now a circuit arrangement for insulation and contactor monitoring to provide the power supply of an electric drive, with the particular the safe opening the shooter can be recognized.

These Task is by a circuit arrangement for insulation and Contactor monitoring of the Power supply of an electric drive with the features of claim 1 solved. Preferred embodiments of the invention will become apparent from the dependent claims.

One essential idea of the invention is in a circuit arrangement for insulation monitoring make an adjustment that causes the contactor monitoring with in the insulation monitoring is included. This allows a separate monitoring of the shooter for Disconnecting the battery from the power supply of an electric drive omitted, which would otherwise be required for safety reasons. According to the invention In essence, the adjustment is that in addition to Infeed point of the insulation monitoring voltage and the insulation measuring point, which are both on the vehicle side after the shooter, another measuring point is provided, via which the monitoring the contactor contacts can be done. For this purpose, the further measuring point is arranged in such a way that they through the shooter is disconnected from the feed point for disconnecting the battery. Thereby Is it possible, the verification of the function the shooter, in particular of their condition open or closed in the insulation monitoring to integrate.

According to one embodiment, the invention relates to a circuit arrangement for monitoring the insulation and contactor of the power supply of an electric drive, comprising:
a battery for powering the electric drive,
a powered by the battery power electronics for driving an electric motor of the electric drive
at least one contactor for all-pole electrical disconnection of the battery from the power electronics,
a voltage source connected to a reference potential for generating a measuring voltage for insulation and contactor monitoring,
two voltage measuring devices for measuring a voltage swing generated by the measuring voltage with respect to the reference potential,
wherein the voltage source and a first one of the voltage measurement devices are electrically connected to a feed point for feeding the measurement voltage and a second one of the voltage measurement devices is electrically connected to a measurement point for measuring the voltage swing, and the feed point and measurement point are arranged such that the at least one contactor is interposed therebetween.

According to one another embodiment The invention may further comprise a measuring resistor between the voltage source and the voltage measuring device to be switched. The measuring resistor forms with an insulation resistor a voltage divider, the the determination of the insulation resistance by a voltage measurement allows there, depending from the current insulation resistance a voltage divider between results in the measuring resistor and the unknown insulation resistance. From the measured in the circuit divider ratio of this voltage divider can then the insulation resistance in particular by calculation be determined.

The measuring resistor may be divided into two intermediate circuit terminals of the power electronics according to an embodiment of the invention, and the voltage source may be connected to a center of the measuring resistor. This solution offers the advantage that due to the symmetry of the circuit, the interference voltages on the high-voltage side largely extinguish itself.

According to one embodiment According to the invention, the voltage source can also be designed in this way be that polarity the generated measuring voltage can be switched periodically. Thereby For example, a switched DC voltage as a measurement voltage be generated. With such a switched DC voltage it interferes with the insulation measurement not if an insulation fault at any potential between the battery connections occurs. Alternatively, the voltage source but also formed be to produce a measuring voltage with only one polarity, which is a lesser Implementation effort means.

Farther can according to a embodiment the invention, the voltage measuring device be designed such that the measured voltage swing after a predetermined settling time Periodically scanned several times and digitized for further evaluation becomes. By taking several samples per period, can by averaging the samples taken disturbances, especially high-frequency interference be essentially eliminated.

According to one another embodiment of the invention, the first of the voltage measuring means for Measuring a voltage generated by the voltage measurement voltage provided be connected to at least one connection of the inverter is, and be designed such that the measured voltage swing periodically scanned repeatedly and digitized for further evaluation. With the second of the voltage measuring devices, the voltage swing measured at another measuring point and then evaluated become. By comparing the through the two Sapnnungsmesseinrichtungen obtained measured values, the state of the contactor contacts can be detected.

To the further processing of the measured by a voltage measuring device voltage swings can according to a embodiment the invention may be provided with a measured value processing device, which is further formed based on the digitized values of measured voltage swings to calculate an insulation resistance. The measured value processing device may for example be implemented in the form of a controller, in turn, the entire electronics for processing the measured values integrated. To enable the digital processing of the measured values can Furthermore, analog-to-digital converters can be provided which display the measured values. i.e. - the Samples of voltage swings digitize.

Especially can according to a embodiment the measured value processing device can be designed according to the invention, from several consecutive digitized values of the measured voltage swings a moving averaging disorders and fluctuations in the To eliminate substantially.

According to a further embodiment, the invention relates to a method for monitoring the insulation and contactors of the power supply of an electric drive by means of a circuit arrangement according to the invention, with the following steps:
Generating the measuring voltage for insulation and contactor monitoring with the voltage source,
Activating the second one of the voltage measuring devices,
Check the voltage swings generated by the measuring voltage at the measuring point, and
Determining the state of the at least one contactor.

The Voltage swings generated by the measuring voltage at the measuring point can, according to another embodiment to be checked according to the invention by passing it through the measuring voltage at a second measuring point generated voltage swings are compared and when a fraction is exceeded the voltage strokes at the second measuring point by the voltage strokes at the measuring point then the Condition of the at least one contactor be determined as closed.

On the other hand can according to a embodiment the invention at a fall below the fraction of the voltage strokes on the second Measuring point through the voltage swings At the measuring point the condition of all contactors can be determined as open. This is a big Advantage, since only the state "are all shooters open "as safe can be viewed.

The Method can according to a embodiment of the invention as an algorithm implemented by a Microcontroller is running, configured to correspond to the circuitry controls.

Further Advantages and applications The present invention will become apparent from the following description in conjunction with the embodiments illustrated in the drawings.

In the description, in the claims, in the abstract and in the drawings are those in the listed below List of reference numbers and abbreviations used terms and associated reference numerals.

The Drawings show in:

1 a circuit arrangement for insulation monitoring of the power supply of an electric drive according to the invention;

2 a circuit arrangement for insulation and contactor monitoring of the power supply of an electric drive according to the invention; and

3 a flowchart of a method for insulation and contactor monitoring the power supply of an electric drive according to the invention.

in the Following can (functionally) be the same elements with the same reference numerals.

By the insulation monitoring or measurement, the insulation resistance of the power supply an electric drive, in particular determined by a hybrid drive become. The insulation resistance is here against the vehicle mass determined, for example, by the chassis is formed. The Vehicle network is due to the battery a direct voltage network. For insulation measurement, therefore, an AC voltage is used. According to the VDE standard In addition, VDE0413 usually requires the insulation measurement to be independent of the supply voltage of the power supply network to be functional.

In 1 is a circuit arrangement 11 for the isolation measurement or monitoring in a high-voltage network of the electric drive of a hybrid drive shown. A high-voltage battery 12 is used for DC power supply of a (not shown) power electronics, via which a (not shown) electric motor of the electric drive is supplied. The power electronics in particular comprises a converter, via which the electric motor can be controlled. The high-voltage battery 12 is over (undesirably finite) insulation resistances 36 with the vehicle mass FZG_GND, which is provided as a reference potential in the vehicle, electrically connected. Furthermore, in the vehicle for suppression parallel to the insulation resistance 36 Y capacitors CY switched.

At the middle of the battery 12 is a measuring resistor 30 connected, which acts together with the Y capacitors CY as a low-pass filter, which limits the measurement limit frequency. A switchable voltage source 22 that is a voltage source 38 and a switcher 40 is over the measuring resistor 30 with the middle of the battery 12 connected. The voltage source 22 is electrically connected to the reference potential FZG_GND of the vehicle ground and generates a measurement voltage for insulation monitoring or measurement with respect to the reference potential FZG_GND. The switchable voltage source 22 For this purpose, a bipolar voltage source is included 38 which generates a positive and negative voltage + V or -V with respect to the reference potential FZG_GND. This voltage source 38 For example, in a switching power supply of the circuit 11 be integrated. Furthermore, the voltage source includes 22 a controllable electronic switch 40 which can be controlled by a microcontroller (not shown) via the signal ISO_SWITCH and switches between the positive and negative voltage + V or -V. About the voltage source 22 is therefore the battery 12 can be acted upon by an alternating voltage in the form of a DC voltage which varies periodically with respect to the polarity.

Finally, a first voltage measuring device 32 and a second voltage measuring device 34 provided between the reference potential FZG_GND and measuring points 26 respectively. 44 are switched. The measuring point 44 also forms an entry point for the measuring voltage. The first voltage measuring device 32 Used to measure the voltage swing ISO_MESS of the measuring voltage at the middle of the battery 12 ; the second voltage measuring device 34 measures the voltage swing ISO_REF from the voltage source 22 generated measuring voltage.

For insulation measurement is a switched DC voltage ISO_REF, generated by the voltage source 22 , used. It does not bother if there is an insulation fault at any potential between the terminals of the battery 12 occurs. In order to compensate for constant offset voltages in the insulation measurement, only voltage differences are evaluated to determine the insulation resistance.

For the measuring voltage ISO_MESS form the measuring resistor 30 and the insulation resistance 36 a voltage divider, from the divider ratio of the insulation resistance can be determined, as will be explained below. In each measuring cycle (period), an algorithm switches to determine the insulation resistance 36 the signal ISO_SWITCH, which switches the voltage ISO_REF between + V and -V; Similarly, the voltage ISO_MESS follows this switching. However, due to time constants, the two voltages ISO_REF and ISO_MESS only slowly approach their final values. While at the voltage ISO_REF time constants of filters for a subsequent analog-to-digital conversion act, the time constant of the voltage ISO_MESS is additionally by the time constants of the Y capacitors CY together with the measuring resistor 30 certainly. Because of this Zeitkonstan In each period, the actual measurements are started only after a certain settling time of the two voltages ISO_REF and ISO_MESS. The measurements include sampling the two voltages and digitizing the samples by analog-to-digital converters (not shown). From the digitized samples generated in one period, an average is formed. As a result, in particular high-frequency interference from converters of the power supply of the electric drive can be substantially eliminated.

2 now shows a circuit arrangement 10 , in addition to the isolation, the shooters 16 . 18 . 20 It is possible to monitor what the battery is 12 electrically from the power electronics 14 separate. The function of the shooter is particularly important for the service case, in which it must be ensured that the power electronics 14 High voltage is free. In addition, for the reason explained below, it is still important to be able to determine with certainty whether the contactor 16 is open. The shooters comprise two main shooters 16 and 18 as well as a pre-charging contactor 20 , For a discharged intermediate circuit capacitor ZK of an inverter with intermediate circuit in the power electronics 14 A current limited charge of the DC link capacitor should be used to reduce the load on the contactors 16 . 18 , and 20 as well as the battery 12 and to reduce the capacitor ZK itself as possible. For the current limited charge is the precharge contactor 20 provided that can charge the capacitor ZK via a resistor RL current limited. When charging the capacitor ZK should therefore the contactor 16 be open to any deterioration of the battery 12 and the shooter 16 . 18 , and 20 to avoid.

To the shooters 16 . 18 . 20 With the circuit arrangement for insulation measurement or monitoring mittesten, is in the circuit arrangement shown 10 a tension measuring device 24 with measuring points 28 between the battery 12 and the shooter 16 . 18 . 20 electrically connected. The tension measuring device 24 includes voltage dividers to the voltages BATT_MESS + and BATT_MESS- at the terminals of the battery 12 to eat. To ensure a lasting discharge of the battery 12 over the voltage divider of the voltage measuring device 24 To avoid are electrically controllable switches 25 for electrically disconnecting the voltage measuring device 24 from the measuring points 28 intended. The switches 25 are controlled via a signal UBATT_MESS_EN. The voltage divider of the voltage measuring device 24 correspond to the voltage dividers of the voltage measuring device 32 for measuring the voltage swing generated by the measuring voltage ISO_MESS +, ISO_MESS- at the feed points 26 for the measuring voltage coming from the voltage source 22 is produced. As long as at least one contactor 16 . 20 and 18 is closed, the voltage swing at the measuring points 28 essentially like the voltage swing in front of the shooter, ie at the entry points 26 be measured. Via the battery or the DC link capacitor, all signals are then sufficiently adequately low-impedance AC-connected. Will, however, at the entry points 26 a voltage swing measured at the measuring points 28 However, it can not be concluded that the shooters 16 . 18 and 20 open, the battery 12 that is electrically isolated from the rest of the circuit (assuming the switches 25 are closed).

3 Finally, a flowchart of a method for insulation and contactor monitoring of the power supply of an electric drive with a circuit arrangement, as in 2 shown. The absolute voltage values given in the flow chart are only examples and do not limit the invention. Rather, the invention can also be used with other voltage values.

To start the insulation and contactor monitoring, the signal BATT_MESS_EN is first set to logical 1 in a first step, around the switches 25 close and the voltage measuring device 24 with the connections of the battery 12 connect to. In a subsequent step S12, the voltage measuring device is then used 34 measured, whether the measuring voltage ISO_REF lies in a range between ± 50 V ... 70 V. If the measuring voltage ISO_REF is not in this range, it is wrong and no further statement can be made, ie no insulation and contactor monitoring takes place (step S14).

If the measuring voltage ISO_REF is in the required range, it is written in checked in step S16, whether the difference between the measured voltage strokes ΔU ISO_MESS is greater as ¼ ΔU ISO_REF, i. a quarter of the difference in Meßspannungshübe. Is not this inequality Fulfills, the measuring voltage ISO_REF is too low and there can be no more Statement be made. Isolation monitoring via formula works yet, but the insulation resistance is very low. The contactor monitoring can no longer provide a reliable statement. (Step S18).

On the other hand, if the inequality is satisfied, it is checked in a step S20 whether the difference of the measured voltage strokes ΔU BATT_MESS at the battery terminals is greater than ¼ ΔU ISO_MESS, ie a quarter of the difference of the measured voltage strokes at the measuring point 26 ie before the shooters 16 . 18 and 20 , If this is the case, it is determined in a step S22 that at least one contactor is closed and checked in a step S24 whether the Voltage UZK at the DC link capacitor ZK is less than half the battery voltage ½ UBATT. If this is not the case, no statement is possible and it has to wait until the intermediate circuit capacitor ZK has discharged (step S26). Then a new measurement can be started. If, however, UZK <½ UBATT, it is checked in a step S28 whether the mean value of the measured voltage swings at the battery terminals BATT_MESS is greater than half the reference voltage UREF / 2. If this is not the case, it can be stated that the contactor 16 or 20 is closed (step S30). If, on the other hand, the mean value of UBATT_MESS> UREF / 2, it can be determined that the contactor 18 is closed (step S32).

If it is determined in step S20 that the difference of the measured voltage strokes ΔU BATT_MESS at the battery terminals is not greater than ½ ΔU ISO_MESS, then it is checked in step S34 whether the battery voltage is plausible, ie substantially greater than 0V. If this is not the case, either the switches are 25 not closed, ie the signal UBATT_MESS_EN is not set to logical 1, or there is a circuit defect (step S36). However, if the battery voltage is plausible, it is determined in a step S38 that the shooters 16 . 18 and 20 are open.

10

circuitry for insulation and contactor monitoring the power supply of an electric drive

11

circuitry for insulation monitoring

12

(High voltage) battery

14

power electronics (comprising a converter with DC link)

16

Contactor on the + page

18

Contactor on the side

20

Precharge contactor

22

voltage source for generating a measuring voltage

24

Voltage measuring device

26 28

measuring point

30

measuring resistor

32 34

Voltage measuring device

36

insulation resistance

38

bipolar voltage source

40

controllable electronic switch

44

entry point

Claims (13)

Circuit arrangement ( 10 ) for the insulation and contactor monitoring of the power supply of an electric drive comprising - a battery ( 12 ) for the power supply of the electric drive, - one of the battery ( 12 ) powered power electronics ( 14 ) for driving an electric motor of the electric drive - at least one contactor ( 16 . 18 . 20 ) for all-pole electrical disconnection of the battery ( 12 ) of the power electronics ( 14 ), - a voltage source connected to a reference potential (FZG_GND) ( 22 ) for generating a measuring voltage for insulation and contactor monitoring, - two voltage measuring devices ( 24 . 32 ) for measuring a voltage swing (BATT_MESS +, BATT_MESS-, ISO_MESS +, ISO_MESS-) generated by the measuring voltage with respect to the reference potential (FZG_GND), - the voltage source ( 22 ) and a first one of the voltage measuring devices ( 32 ) with a feed-in point ( 26 . 44 ) for feeding the measuring voltage (ISO_MESS +, ISO_MESS-) and a second one of the voltage measuring devices ( 24 ) with a measuring point ( 28 ) for measuring the voltage swing (BATT_MESS +, BATT_MESS-) are electrically connected, and feed point ( 26 ) and measuring point ( 28 ) are arranged such that the at least one contactor ( 16 . 18 . 20 ) is interposed. Circuit arrangement according to Claim 1, characterized in that, furthermore, a measuring resistor ( 30 ) between the voltage source ( 22 ) and the voltage measuring device ( 24 ) is switched. Circuit arrangement according to Claim 2, characterized in that the measuring resistor ( 30 ) is divided into two DC link connections of the power electronics, and the voltage source ( 22 ) with a center point of the measuring resistor ( 30 ) connected is. Circuit arrangement according to Claim 1, 2 or 3, characterized in that the voltage source ( 22 ) is designed such that the polarity of the generated measurement voltage can be switched periodically. Circuit arrangement according to claim 1, 2 or 3, characterized characterized in that the voltage source is formed, a measuring voltage with only one polarity to create. Circuit arrangement according to one of the preceding claims, characterized in that the second of the voltage measuring devices ( 24 ) is designed such that the measured voltage swing is scanned periodically multiple times after a predetermined settling time and digitized for further evaluation. Circuit arrangement according to one of the preceding claims, characterized in that the first of the voltage measuring means ( 32 ) is provided for measuring a voltage swing generated by the measuring voltage (ISO_MESS +, ISO_MESS-), which is connected to at least one connection of the power electronics ( 14 ) and is designed in such a way that the measured voltage swing (ISO_MESS +, ISO_MESS-) is periodically scanned repeatedly and digitized for further evaluation. Circuit arrangement according to one of the preceding claims, characterized in that a measured value processing device for further processing of a voltage measuring device ( 24 . 32 ) measured voltage strokes (BATT_MESS +, BATT_MESS-, ISO_MESS +, ISO_MESS-) is provided, which is further formed, based on the digitized values of the measured voltage strokes an insulation resistance ( 36 ; R_ISO). Circuit arrangement according to Claim 8, characterized that the measured value processing device is formed from a plurality successive digitized values of the measured voltage swings a moving averaging disorders and fluctuations in the To eliminate substantially. Method for insulation and contactor monitoring of the power supply of an electric drive by means of a circuit arrangement ( 10 ) according to one of the preceding claims, comprising the following steps: generating the measuring voltage for insulation and contactor monitoring with the voltage source ( 22 ), Activating the second one of the voltage measuring devices ( 24 ; S10), checking the voltage swings generated by the measuring voltage at the measuring point ( 28 ; S20), and determining the state of the at least one contactor ( 16 . 18 . 20 ; S22, S30, S32, S38). A method according to claim 9, characterized in that the voltage pulses generated by the measuring voltage at the measuring point ( 28 ; S20) can be checked by using the measuring voltage at a second measuring point ( 26 ; S20) and that when a fraction of the voltage surges is exceeded at the second measuring point ( 26 ) through the voltage swings at the measuring point ( 28 ) the condition of the at least one contactor ( 16 . 18 . 20 ) is determined to be closed (S22, S30, S32). A method according to claim 11, characterized in that when falling below the fraction of the voltage strokes at the second measuring point ( 26 ) through the voltage swings at the measuring point ( 28 ) the condition of the at least one contactor ( 16 . 18 . 20 ) is determined to be open (S38). Method according to one of Claims 10 to 12, characterized in that it is implemented as an algorithm carried out by a microcontroller which is configured to implement the circuit arrangement ( 10 ) controls accordingly.