WO2025131663A1

WO2025131663A1 - Fault monitoring device for a power system and method of calculating voltages of a fault monitoring device

Info

Publication number: WO2025131663A1
Application number: PCT/EP2024/084391
Authority: WO
Inventors: Máté Bérces; Csaba BLEUER
Original assignee: Rolls Royce Deutschland Ltd and Co KG
Current assignee: Rolls Royce Deutschland Ltd and Co KG
Priority date: 2023-12-20
Filing date: 2024-12-03
Publication date: 2025-06-26
Anticipated expiration: 2026-06-20
Also published as: GB202319638D0

Abstract

A fault monitoring device (2) for a power system (1) that comprises a DC power source (7), high side voltage rail (3), a low side voltage rail (4) and a chassis (5), wherein a high side voltage (U_H) is present between the high side voltage rail (3) and the chassis (5) a low side voltage (U_L) is present between the chassis (5) and the low side voltage rail (4) The fault monitoring device (2) comprises first and second voltage dividers (21, 23) arranged between the high side voltage rail (3) and the chassis (5) and between the chassis (5) and the low side voltage rail (4), respectively, and first, second and third voltage measurement devices (81-83). A controller (2) is configured to: if the voltage (U_ADCH) measured by the first voltage measurement device (81) is higher than the voltage (U_ADCL) measured by the second voltage measurement device (82), calculate the high side voltage (U_H) on the basis of the voltage (U_ADCH) measured by the first voltage measurement device (81), and calculate the low side voltage (U_L) on the basis of the voltage (U_ADCB) measured by the third voltage measurement device (83) and the voltage (U_ADCH) measured by the first voltage measurement device (81); if the voltage (U_ADCH) measured by the first voltage measurement device (81) is lower than the voltage (U_ADCL) measured by the second voltage measurement device (82), calculate the high side voltage (U_H) on the basis of the voltage (U_ADCB) measured by the third voltage measurement device (83) and the voltage (U_ADCL) measured by the second voltage measurement device (81), and calculate the low side voltage (U_L) on the basis of the voltage (U_ADCL) measured by the second voltage measurement device (82).

Description

FAULT MONITORING DEVICE FOR A POWER SYSTEM AND METHOD OF CALCULATING VOLTAGES OF A FAULT MONITORING DEVICE

Field of the disclosure

The present disclosure relates to a fault monitoring device for a power system and a method of calculating voltages of a fault monitoring device.

Background

Documents US 2022/0413034 A1 and US 2022/0413035 A1 disclose an insulation monitoring device comprising a primary resistance circuit and a secondary resistance circuit arranged in parallel to a high side insulation resistance and a low side insulation resistance, wherein the secondary resistance circuit comprises additional resistors which are selectively connectable to a high voltage bus via a switching circuit. Different states can be implemented by the switches. Voltage values associated with the different states are used to calculate the resistance values for the high side insulation resistance and the low side insulation resistance.

The relevant voltage values are measured by means of voltage measurement devices such as Analog-to-digital converters (ADCs). The ADCs or any other voltage measurement devices should have the ability to measure voltages with high accuracy. However, generally, the accuracy of a voltage measurement device decreases in the lower part of a measurement range when the voltages to be measured are low, whereas the accuracy increases in the upper part of the measurement range when the voltages to be measured are high.

There is a need to provide an improved fault monitoring device and an improved method of measuring voltages which allow to measure voltages in an accurate manner in a measurement range with little or no dependency on the height of the voltage values within the measurement range, or at least to provide a useful alternative to known fault monitoring devices and/or methods for calculating voltages of fault monitoring devices.

Summary of the disclosure

According to an aspect of the invention, a fault monitoring device for a power system is provided. The power system for which the fault monitoring device is provided for is of the kind that comprises a DC power source, a high side voltage rail, a low side voltage rail, and a chassis. The high side voltage rail and the low side voltage rail form part of a high voltage bus connected to the DC power source. A high side voltage is present between the high side voltage rail and the chassis and a low side voltage is present between the chassis and the low side voltage rail.

The fault monitoring device comprises a first voltage divider arranged between the high side voltage rail and the chassis, wherein the first voltage divider comprises a first resistor and a second resistor, a first voltage measurement device arranged in parallel to the second resistor and configured to measure the voltage of the second resistor, a second voltage divider arranged between the chassis and the low side voltage rail, wherein the second voltage divider comprises a third resistor and a fourth resistor, a second voltage measurement device arranged in parallel to the third resistor and configured to measure the voltage of the third resistor, and a third voltage measurement device arranged in parallel to the second resistor of the first voltage divider and the third resistor of the second voltage divider and configured to measure the voltage over the second resistor and the third resistor.

The fault monitoring device further comprises a controller which is configured to: if the voltage measured by the first voltage measurement device is higher than the voltage measured by the second voltage measurement device, calculate the high side voltage on the basis of the voltage measured by the first voltage measurement device, and calculate the low side voltage on the basis of the voltage measured by the third voltage measurement device and the voltage measured by the first voltage measurement device; and if the voltage measured by the first voltage measurement device is lower than the voltage measured by the second voltage measurement device, calculate the high side voltage on the basis of the voltage measured by the third voltage measurement device and the voltage measured by the second voltage measurement device, and calculate the low side voltage on the basis of the voltage measured by the second voltage measurement device.

Aspects of the invention are thus based on the idea to increase the accuracy of the voltage measurements in that from three available voltage measurements, namely, the voltage measurements of the first, second and third voltage measurement devices, always the two highest and thus the two most accurate voltage measurements are chosen for determining the high side voltage and the low side voltage. The inventive solution takes advantage of the realization that a voltage measurement device is more accurate in the higher half of its measurement range and avoids values from the lower measurement range. Utilizing a more accurate zone in the measurement range of the voltage measurement devices the final calculation is more accurate. Calculating the high side voltage and the low side voltage always from the respective two highest voltage measurements is possible as the sum of the high side voltage and of the low side voltage is equal to the DC power source voltage that is measured by means of the third voltage measurement device. More particularly, if the voltage measured by the first voltage measurement device is higher than the voltage measured by the second voltage measurement device, the low side voltage value is calculated by means of the voltage values of the first and third voltage measurement devices (thereby avoiding the “low” voltage value measured by the second voltage measurement device). The high side voltage is calculated on the basis of the voltage measured by the first voltage measurement device in such case.

On the other hand, if the voltage measured by the first voltage measurement device is lower than the voltage measured by the second voltage measurement device, the high side voltage is calculated by means of the voltage values of the second and third voltage measurement devices (thereby avoiding the “low” voltage value measured by the first voltage measurement device). The low side voltage is calculated on the basis of the voltage measured by the second voltage measurement device in such case.

It is pointed out that the voltage measured by the third voltage measurement device is always a high voltage and thus measured with high accuracy, as it is equal to the sum of the voltages measured by the first and second voltage measurement devices and thus always higher than the latter.

If the voltage measured by the first voltage measurement device is equal to the voltage measured by the second voltage measurement device, the high side voltage and the low side voltage may be calculated by means of the first and second voltage measurement devices, respectively, without the need to include the third voltage measurement device. In some embodiments, it may be provided that in such case one of the high side voltage and the low side voltage is measured by means of the voltage measured by the third voltage measurement device and one of the other voltage measurement devices.

The term “controller” identifies any processing capacity which is able to perform the method to calculate and recalculate the voltages values. The controller may comprise one or several processors, and memory storing instructions that when executed perform the method. The controller may also include input lines to receive measurement values from the first, second and third voltage measurement devices.

In some embodiments, the controller is configured to calculate the high side voltage on the basis of the voltage measured by the first voltage measurement device by means of the formula:

wherein UH is the high side voltage, R1 is the first resistor, R2 is the second resistor and UADCH is the voltage measured by the first voltage measurement device. This formula follows from Ohm’s law and represents one of the basic formulas in a voltage divider.

In a similar manner, the controller may be configured to calculate the low side voltage on the basis of the voltage measured by the second voltage measurement device by means of the formula:

R3 + R4

UL ⁼ UADCL wherein UL is the low side voltage, R3 is the third resistor, R4 is the fourth resistor and UADCL is the voltage measured by the second voltage measurement device.

Further, it is to be noted that the DC power source voltage can be calculated using the third voltage measurement device by means of the formula:

R1 + R2 + R3 + R4

U_B — UADCB

R2 + R3 wherein UB is the DC power source voltage present between the high side voltage rail and the low side voltage rail, R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, R4 is the fourth resistor and UADCB is the voltage measured by third second voltage measurement device.

Based on the above three basic formulas, and further based on the knowledge that the sum of the high side voltage UH and of the low side voltage UL is equal to the DC power source voltage UB (UH + UL = UB), the controller is configured to calculate the low side voltage from the voltage measured by the third voltage measurement device and the voltage measured by the first voltage measurement device by means of the formula:

wherein UL is the low side voltage, UH is the high side voltage, UB is the DC power source voltage, R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, R4 is the fourth resistor, UADCB is the voltage measured by third second voltage measurement device, and UADCH is the voltage measured by the first voltage measurement device.

Similarly, the controller is configured to calculate the high side voltage from the voltage measured by the third voltage measurement device and the voltage measured by the second voltage measurement device by means of the formula:

wherein UH is the high side voltage, UL is the low side voltage, UB is the DC power source voltage, R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, R4 is the fourth resistor, UADCB is the voltage measured by third second voltage measurement device and UADCL is the voltage measured by the second voltage measurement device.

The fault monitoring device may generally be configured to define two different states of the fault monitoring device by selectively switching on an off resistors arranged in parallel to the first and second voltage dividers, wherein the controller determines from the voltage changes associated with the two different states the resistance values for a high side insulation resistance and a low side insulation resistance, wherein the chassis is insulated by the high side insulation resistance from the high side voltage rail and insulated by the low side insulation resistance from the low side voltage rail. For the respective calculations, the high side voltage and the low side voltage need to be measured in an accurate manner.

The first, second and third voltage measurement devices may, in principle, be any voltage measurement devices. In some embodiments, the first, second and third voltage measurement devices are Analog-to-Digital Converters (ADCs). The use of ADCs as measurement devices is associated with the advantage that the voltage measurement provides as output a digital signal which can be used in software calculations without further transformation.

In a further aspect of the invention, a power system is provided. The power system comprises a DC power source having a positive terminal, a negative terminal and a voltage, a high side voltage rail connected to the positive terminal, a low side voltage rail connected to the negative terminal, a chassis, and a fault monitoring device in accordance with the invention.

In a still further aspect of the invention, a method of calculating voltages of a fault monitoring device in an accurate manner is provided for as defined in claim 8. Embodiments of the inventive method correspond to the embodiments of the fault monitoring device discussed above.

In a still further aspect of the invention, a method of calculating voltages of a device is provided for, wherein the device comprises: a first voltage divider connected between a first voltage (such as the voltage present on a high side voltage rail or any other first rail) and a second voltage (such as the voltage present on a chassis or any other intermediate voltage), the first voltage divider comprising a first resistor and a second resistor; a first voltage measurement device arranged in parallel to the second resistor and configured to measure the voltage of the second resistor; a second voltage divider connected between the second voltage and a third voltage (such as the voltage is present on a low side voltage rail or any other second rail), the second voltage divider comprising a third resistor and a fourth resistor; a second voltage measurement device arranged in parallel to the third resistor and configured to measure the voltage of the third resistor; and a third voltage measurement device arranged in parallel to the second resistor of the first voltage divider and the third resistor of the second voltage divider and configured to measure the voltage over the second resistor and the third resistor.

The method comprises the steps: if the voltage measured by the first voltage measurement device is higher than the voltage measured by the second voltage measurement device, calculate the high side voltage on the basis of the voltage measured by the first voltage measurement device, and calculate the low side voltage on the basis of the voltage measured by the third voltage measurement device and the voltage measured by the first voltage measurement device; and if the voltage measured by the first voltage measurement device is lower than the voltage measured by the second voltage measurement device, calculate the high side voltage on the basis of the voltage measured by the third voltage measurement device and the voltage measured by the second voltage measurement device, and calculate the low side voltage on the basis of the voltage measured by the second measurement device.

The method can be implemented in any system which comprises two voltage dividers arranged in series between two voltages. Always the two highest and thus the two most accurate voltage measurements are chosen for determining the voltage over the first voltage divider and the voltage over the second voltage divider to provide for a most accurate measurement. Embodiments of the invention include those of claims 9 to 13.

The skilled person will appreciate that except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and/or combined with any other feature or parameter described herein.

Brief description of the drawings

The invention will be explained in more detail on the basis of exemplary embodiments with reference to the accompanying drawings in which: FIG. 1 is an embodiment of a fault monitoring device for a power system in accordance with the present invention, the fault monitoring device comprising first and second voltage dividers and first, second and third voltage measurement devices;

FIG. 2 is a flow chart of a method for calculating voltages of a fault monitoring device in an accurate manner; and

FIG. 3 is a background fault monitoring device indicating the background of the present invention.

Detailed description

FIG. 3 shows an example fault monitoring device which serves to explain the background before which the present invention takes place. The fault monitoring device is configured to measure a high side insulation resistance RISOH and a low side insulation resistance RISOL of a power system 1.

The power system 1 is shown on the left-hand side of FIG. 3. It comprises a DC power source 7 such as a battery that has a positive terminal 71 and a negative terminal 72. Between the positive terminal 71 and the negative terminal 72 a DC voltage UB is present. A high side voltage rail 3 (which is the positive voltage rail) is connected to the positive terminal 71 and a low side voltage rail 4 (which is the negative voltage rail) is connected to the negative terminal 72. The high side voltage rail 3 and the low side voltage rail 4 form a high-voltage bus.

The power system 1 further comprises a chassis 5. The chassis 5 is insulated from the high side voltage rail 3 by the high side insulation resistance RISOH. The chassis 5 is further insulated from the low side voltage rail 4 by the low side insulation resistance RISOL.

The voltage between the high side voltage rail 3 and the chassis 5 is the high side voltage UH. The voltage between the chassis 5 and the low side voltage rail 4 is the low side voltage UL. The sum of the high side voltage and the low side voltage is equal to the DC power source/battery voltage: UB=UH+UL. For example, if the DC power source positive terminal is +500 V and the DC power source negative terminal is -500 V, UH is 500V, UL is 500V, and UB is 1000V. A common mode voltage UCM is present at the chassis 5, the common mode voltage being defined as the arithmetic mean of the high voltage and the low voltage: UCM = 3 (UH - UL). If the high side voltage UH and the low side voltage UL are equal, the common mode voltage is zero.

In parallel to the high side insulation resistance RISOH a capacitance CISOH is arranged between the chassis 5 and the high side voltage rail 3. Similarly, in parallel to the low side insulation resistance RISOL a capacitance CISOL is arranged between the chassis 5 and the low side voltage rail 4. The capacitances CISOH and CISOL represent capacitive loads of the system.

In a power system such as the power system 1 of FIG. 3, it is required that the insulation of the high side voltage rail 3 and of the low side voltage rail 4 from the chassis 5 is monitored. This can be done by monitoring the values of the resistances RISOH and RISOL. The fault monitoring device of FIG. 3 serves to provide for such monitoring.

The fault monitoring device comprises a first parallel circuit of resistors, the first parallel circuit comprising a first branch 21 and a second branch 22 which are both connected at one end thereof to the high side voltage rail 3 of the power system 1. The first branch 21 comprises a first resistor R1 and a second resistor R2 which are arranged in series and form a first voltage divider.

A voltage UADCH is measured by a first voltage measurement device 81 between a point between the first and second resistors R1, R2 and the chassis 5. The voltage measurement device 81 may be implemented as an analog-to-digital converter (ADC) which provides the measured voltage as a digital signal which is convenient for further processing of the signal.

By measuring the voltage UADCH, the high side voltage UH can be calculated using the formula:

The second branch 22 of the first parallel circuit comprises three electrical resistors R7, R8, R9 arranged in series, wherein two of the electrical resistors R8, R9 can be short- circuited by a first switch S1 and a second switch S2.

The fault monitoring device further comprises a second parallel circuit of resistors, the second parallel circuit comprising a third branch 23 and a fourth branch 24 which are both connected at one end thereof to the low side voltage rail 4 of the power system 1. The third branch 21 comprises a third resistor R3 and a fourth resistor R4 which are arranged in series and form a second voltage divider. The resistance of the fourth resistor R4 is typically substantially larger than the resistance of the third resistor R3. For example, the fourth resistor R4 may have a resistance in the range between 10 MQ and 50 MQ, while the third resistor R3 may have a resistance in the range between 10 and 100 kQ.

A voltage UADCL is measured by a second voltage measurement device 82 between a point between the third and fourth resistors R3, R4 and the chassis 5. the second voltage measurement device 82 may also be implemented by an ADC. By measuring the voltage UADCL, the low voltage UL can be calculated using the formula:

The voltage dividers of branches 21, 23 thus serve to measure the high voltage UH and the low voltage UL.

The fourth branch 24 of the second parallel circuit comprises three electrical resistors R10, R11 , R12 arranged in series, wherein two of the electrical resistors R10, R11 can be short-circuited by a second switch S3 and a fourth switch S4.

The first branch 21, the second branch 22, the third branch 23 and the fourth branch 24 are each connected at the other end thereof to the chassis 5 of the power system 1.

When applying the fault monitoring device to the power system 1, the first parallel circuit

21, 22 with branches 21, 22 is connected in parallel to the high side insulation resistance RISOH and the second parallel circuit 23, 24 with branches 23, 24 is connected in parallel to the low side insulation resistance RISOL. By switching the switches S1 to S4 a common mode voltage VCM different from zero can be injected, wherein the high side voltage UH and the low side voltage Ui_are not equal, and accordingly the voltages measured by voltage measurements devices 81 and 82 are not equal.

The fault monitoring device further comprises a controller 6 schematically depicted in FIG. 3. The controller 6 may be implemented in software and/or hardware. For example, the controller 6 may comprise software stored in a memory and executed by a processor. The controller 6 is operatively coupled to the switches S1 , S2, S3, S4 and configured to selectively switch the switches S1, S2, S3, S4 of the second branch 22 and of the fourth branch 24, thereby providing for different states of the first and second parallel circuits 21,

22, 23, 24. The controller 6 is further configured to determine from voltage changes associated with the different states the resistance values for the high side insulation resistance RISOH and for the low side insulation resistance RISOL of the power system 1. In this respect, the controller 6 may control and/or read values of other elements of the fault monitoring device 2 as well such as of voltage measurement devices 81, 82.

Further examples to determine the high side insulation resistance RISOH and the low side insulation resistance RISOL are discussed in documents US 2022/0413034 A 1 and US 2022/0413035 A1.

As a common thread, it is essential to measure exact values of the high side voltage UH and of the low side voltage UL to determine if there is an insulation problem. According to formulas (2) and (3), to this end, it desirable that the voltage measurement devices 81, 82 measure voltage values in a highly accurate manner. The isolation resistance calculation is very sensitive to the measured voltage accuracy. One problem associated therewith lies in the fact that voltage measurement devices have some specified errors that cannot be eliminated by calibration. In particular, measurements made in the lower half of a measurement range are typically less accurate than the measurements made in the upper half of a measurement range.

In the following, a method and system is described that allow to measure the high side voltage UH and the low side voltage UL in an accurate manner.

FIG. 1 shows a fault monitoring device in accordance with the present invention. The fault monitoring device is similar to the fault monitoring device discussed with respect to FIG. 3 regarding the features of a DC power source (not shown in FIG. 1), a high side voltage rail 3, a low side voltage rail 4, a chassis 5, a high side voltage UH, a low side voltage UL, a first voltage divider 21 and a second voltage divider 23, wherein a voltage measurement device 81 measures the voltage over resistor R2 of first voltage divider 21 and a voltage measurement device 82 measures the resistance over resistor R3 of the second voltage divider 23. In this respect, reference is made to the description of FIG. 3.

The first voltage measurement device 81 may be implemented as an ADC and is in the following also referred to as ADC 81. The voltage it measures is indicated as voltage UADCH. The second voltage measurement device 82 may also be implemented as an ADC and is in the following also referred to as ADC 82. The voltage it measures is indicated as voltage UADCL. In the fault monitoring device of FIG. 1, there is further provided a third voltage measurement device 83 which may also be implemented as an ADC and is in the following also referred to as ADC 83. ADC 83 measures the voltage between a point between the first and second resistors R1, R2 and a point between the third and fourth resistors R3, R4. It is thus arranged in parallel to the second resistor R2 and the third resistor R3. The voltage measured by ADC 83 is indicated as voltage UADCB.

From UADCB, the voltage UB of the DC power source 7 (which is the sum of UH and UL) can be measured as follows:

The fault monitoring device further comprises a controller 2 which is depicted schematically. The controller 2 may be implemented in software and/or hardware. For example, the controller 2 may comprise software stored in a memory and executed by a processor. The controller 2 is operatively coupled with the other elements of the circuit which may receive a control signal from the controller to and/or provide an input signal to the controller 2. FIG. 1 depicts schematically control lines 21 for controlling elements of the fault monitoring device and input signal lines 22 for receiving input signals from elements of the fault monitoring device and/or from other sensors and/or from other controllers. In particular, controller 2 is configured to read the voltage values of ADCs 81-83.

The controller 2 contains software to implement a method for accurately measuring the high side voltage UH and the low side voltage UL. However, the method may alternatively be carried out by another entity or several other entities.

The method is illustrated in FIG. 2. In step 21 the voltage values for ADCs 81-83 are measured, which are a voltages UADCH, UADCL, UADCB. It is then analyzed whether the voltage UADCH measured by the first voltage measurement device ADC 81 is higher, equal to or lower than the voltage UADCL measured by the second voltage measurement device ADC 82. In this respect, it is to be noted that the voltage values measured by ADCs 81, 82 may change depending on adding other resistors in parallel to the respective voltage divider 21 , 23 such as by switches S1 to S4 in FIG. 3. In the course of such switching, the voltage values measured by ADC 81 and ADC 82 may differ substantially.

According to step 22, if the voltage UADCH measured by ADC 81 is higher than the voltage UADCL measured by ADC 82, the high side voltage UH is calculated on the basis of the voltage UADCH measured by ADC 81. The calculation can be implemented using formula (1) above. On the other hand, the low side voltage UL is not calculated on the basis of formula (2) above, but instead calculated on the basis of the voltage UADCB measured by ADC 83 and the voltage UADCH measured by ADC 81. Such calculation takes into consideration that

U_B = U_H + U_L (4) and is performed on the basis of the following formula:

According to step 23, if the voltage UADCH measured by ADC 81 is lower than the voltage UADCL measured by ADC 82, the high side voltage UH is not calculated on the basis of formula (1), but instead calculated on the basis of the voltage UADCB measured by ADC 83 and the voltage UADCL measured by ADC 82. Such is performed on the basis of the following formula:

On the other hand, the low side voltage UL is calculated on the basis of the voltage UADCL measured by ADC 82. The calculation can be implemented using formula (2) above.

Accordingly, both the high side voltage and the low side voltage are calculated based on the two highest and thus the two most accurate voltage measurements of the three voltage measurement devices 81, 82, 83, wherein the voltage measurement which is the lowest is not taken into consideration for the calculation of the high side voltage and the low side voltage. In other words, the two more accurate measurements are used to calculate the less accurate measurement. By avoiding making measurements in the lower measurement range, the accuracy of the measurements is increased.

If the voltage UADCH measured by ADC 81 is equal to the voltage UADCL measured by ADC 82, several possibilities exist. One option is to calculate the high side voltage UH in accordance with the formula (1) and to calculate the low side voltage UL in accordance with the formula (2). Alternatively, one of the high side voltage and the low side voltage is calculated in accordance with the formula (1) or (2), and the other of the high side voltage and the low side voltage is calculated in accordance with formula (5) or (6). For example, it may be provided for that if the voltage UADCH measured by ADC 81 is equal to the voltage UADCL measured by ADC 82, then the high side voltage UH is calculated in accordance with the formula (6) and the low side voltage UL is calculated in accordance with formula (2).

It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. For example, the method may be implemented in any system and infrastructure in which two voltage dividers (such as voltage dividers 21, 23) are arranged in series between two voltages (such as the high side voltage on high side voltage rail 3 and the low side voltage on low side voltage rail 4) and is not restricted to the particular application in a fault monitoring device as shown in FIG. 3.

Also, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Various features of the various embodiments disclosed herein can be combined in different combinations to create new embodiments within the scope of the present disclosure. In particular, the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein. Any ranges given herein include any and all specific values within the range and any and all sub-ranges within the given range.

Claims

1. A fault monitoring device (2) for a power system (1) that comprises a DC power source (7), a high side voltage rail (3), a low side voltage rail (4) and a chassis (5), wherein a high side voltage (UH) is present between the high side voltage rail (3) and the chassis (5) a low side voltage (UL) is present between the chassis (5) and the low side voltage rail (4), wherein the fault monitoring device (2) comprises: a first voltage divider (21) arranged between the high side voltage rail (3) and the chassis (5), the first voltage divider (21) comprising a first resistor (R1) and a second resistor (R2); a first voltage measurement device (81) arranged in parallel to the second resistor (R2) and configured to measure the voltage (UADCH) of the second resistor (R2); a second voltage divider (23) arranged between the chassis (5) and the low side voltage rail, the second voltage divider (23) comprising a third resistor (R3) and a fourth resistor (R4); a second voltage measurement device (82) arranged in parallel to the third resistor (R3) and configured to measure the voltage (UADCL) of the third resistor (R3); a third voltage measurement device (83) arranged in parallel to the second resistor (R2) of the first voltage divider (21) and the third resistor (R3) of the second voltage divider (23) and configured to measure the voltage (UADCB) over the second resistor (R2) and the third resistor (R3); and a controller (2) configured to: if the voltage (UADCH) measured by the first voltage measurement device (81) is higher than the voltage (UADCL) measured by the second voltage measurement device (82): o calculate the high side voltage (UH) on the basis of the voltage (UADCH) measured by the first voltage measurement device (81); and o calculate the low side voltage (UL) on the basis of the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCH) measured by the first voltage measurement device (81); if the voltage (UADCH) measured by the first voltage measurement device (81) is lower than the voltage (UADCL) measured by the second voltage measurement device (82): o calculate the high side voltage (UH) on the basis of the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCL) measured by the second voltage measurement device (81); and o calculate the low side voltage (UL) on the basis of the voltage (UADCL) measured by the second voltage measurement device (82).

2. The fault monitoring device of claim 1, wherein the controller (2) is configured to calculate the high side voltage (UH) on the basis of the voltage (UADCH) measured by the first voltage measurement device (81) by means of the formula:

wherein UH is the high side voltage, R1 is the first resistor, R2 is the second resistor and UADCH is the voltage measured by the first voltage measurement device (81).

3. The fault monitoring device of claim 1 or 2, wherein the controller (2) is configured to calculate the low side voltage (UL) on the basis of the voltage (UADCL) measured by the second measurement device (82) by means of the formula:

wherein UL is the low side voltage, R3 is the third resistor, R4 is the fourth resistor and UADCL is the voltage measured by the second voltage measurement device (82).

4. The fault monitoring device of any preceding claim, wherein the controller (2) is configured to calculate the low side voltage (UL) from the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCH) measured by the first voltage measurement device (81) by means of the formula:

wherein UL is the low side voltage, UH is the high side voltage, UB is the DC power source voltage, R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, R4 is the fourth resistor, UADCB is the voltage measured by third second voltage measurement device (83), and UADCH is the voltage measured by the first voltage measurement device (81).

5. The fault monitoring device of any preceding claim, wherein the controller (2) is configured to calculate the high side voltage (UH) from the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCL) measured by the second voltage measurement device (81) by means of the formula: R1 + R2 + R3 + R4 R3 + R4

U_H — U_B U_L — U_ADCB UADCL

R2 + R3 R3 wherein UH is the high side voltage, UL is the low side voltage, UB is the DC power source voltage, R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, R4 is the fourth resistor, UADCB is the voltage measured by third second voltage measurement device (83) and UADCL is the voltage measured by the second voltage measurement device (82).

6. The fault monitoring device of any preceding claim, wherein the voltage measurement devices (81-83) are Analog-to-Digital Converters.

7. A power system comprising: a DC power source (7) having a positive terminal (71), a negative terminal (72) and a voltage (UB); a high side voltage rail (3) connected to the positive terminal (71); a low side voltage rail (4) connected to the negative terminal (72); a chassis (5); and a fault monitoring device of any preceding claim.

8. A method of calculating voltages of a fault monitoring device (2) for a power system (1) that comprises that comprises a DC power source (7), a high side voltage rail (3), a low side voltage rail (4) and a chassis (5), wherein a high side voltage (UH) is present between the high side voltage rail (3) and the chassis (5) a low side voltage (UL) is present between the chassis (5) and the low side voltage rail (4), wherein the fault monitoring device (2) comprises: a first voltage divider (21) arranged between the high side voltage rail (3) and the chassis (5), the first voltage divider (21) comprising a first resistor (R1) and a second resistor (R2); a first voltage measurement device (81) arranged in parallel to the second resistor (R2) and configured to measure the voltage (UADCH) of the second resistor (R2); a second voltage divider (23) arranged between the chassis (5) and the low side voltage rail, the second voltage divider (23) comprising a third resistor (R3) and a fourth resistor (R4); a second voltage measurement device (82) arranged in parallel to the third resistor (R3) and configured to measure the voltage (UADCL) of the third resistor (R3); and a third voltage measurement device (83) arranged in parallel to the second resistor (R2) of the first voltage divider (21) and the third resistor (R3) of the second voltage divider (23) and configured to measure the voltage (UADCB) over the second resistor (R2) and the third resistor (R3);

- wherein the method comprises: if the voltage (UADCH) measured by the first voltage measurement device (81) is higher than the voltage (UADCL) measured by the second voltage measurement device (82): o calculate the high side voltage (UH) on the basis of the voltage (UADCH) measured by the first voltage measurement device (81); and o calculate the low side voltage (UL) on the basis of the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCH) measured by the first voltage measurement device (81); if the voltage (UADCH) measured by the first voltage measurement device (81) is lower than the voltage (UADCL) measured by the second voltage measurement device (82): o calculate the high side voltage (UH) on the basis of the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCL) measured by the second voltage measurement device (81); and o calculate the low side voltage (UL) on the basis of the voltage (UADCL) measured by the second measurement device (82).

9. The method of claim 8, wherein the high side voltage (UH) is calculated on the basis of the voltage (UADCH) measured by the first voltage measurement device (81) by means of the formula:

R1 + R2

UH ⁼ UADCH wherein UH is the high side voltage, R1 is the first resistor, R2 is the second resistor and UADCH is the voltage measured by the first voltage measurement device (81).

10. The method of claim 8 or 9, wherein the low side voltage (UL) is calculated on the basis of the voltage (UADCL) measured by the second measurement device (82) by means of the formula:

11. The method of any one of claims 8 to 10, wherein the low side voltage (UL) is calculated from the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCH) measured by the first voltage measurement device (81) by means of the formula:

12. The method of any one of claims 8 to 11 , wherein the high side voltage (UH) is calculated from the voltage (UADCB) measured by the third voltage measurement device (83) and the voltage (UADCL) measured by the second voltage measurement device (81) by means of the formula:

R1 + R2 + R3 + R4 7?3 + 7?4

U_H — U_B U_L — U_ADCB UADCL

13. The method of any one of claims 8 to 12, wherein the voltage measurement devices (81-83) are implemented as Analog-to-Digital Converters.

14. A method of calculating voltages of a device which comprises: a first voltage divider (21) connected between a first voltage and a second voltage, the first voltage divider (21) comprising a first resistor (R1) and a second resistor (R2); a first voltage measurement device (81) arranged in parallel to the second resistor (R2) and configured to measure the voltage (UADCH) of the second resistor (R2); a second voltage divider (23) connected between the second voltage and a third voltage, the second voltage divider (23) comprising a third resistor (R3) and a fourth resistor (R4); a second voltage measurement device (82) arranged in parallel to the third resistor (R3) and configured to measure the voltage (UADCL) of the third resistor (R3); a third voltage measurement device (83) arranged in parallel to the second resistor (R2) of the first voltage divider (21) and the third resistor (R3) of the second voltage divider (23) and configured to measure the voltage (UADCB) over the second resistor (R2) and the third resistor (R3);