MEASUREMENT SYSTEM AND METHOD FOR DETERMINING A STATUS OF A POWER SYSTEM IN A VEHICLE USING THE MEASUREMENT SYSTEM

Abstract

A measurement system for determining a status of a high-voltage power system in a vehicle, the measurement system comprising: a first voltage measurement unit and a second voltage measurement unit, each of the first and second voltage measurement units being connected between a positive pole and a negative pole of the power system; a measurement system control unit connected to the first and second voltage measurement unit and configured to: control the first and second voltage measurement unit to simultaneously measure a voltage to determine a respective first and second pole-to-pole voltage; compare the first pole-to-pole voltage with the second pole-to-pole voltage, and if a voltage difference is higher than a voltage threshold value, provide an indication that the voltage measurement is not reliable.

Claims

1. A measurement system for determining a status of a high-voltage power system in a vehicle, the measurement system comprising: a first voltage measurement unit and a second voltage measurement unit, each of the first and second voltage measurement units being connected between a positive pole and a negative pole of the power system; a measurement system control unit connected to the first and second voltage measurement unit and configured to: control the first and second voltage measurement unit to simultaneously measure a voltage to determine a respective first and second pole-to-pole voltage; compare the first pole-to-pole voltage with the second pole-to-pole voltage to determine a voltage difference, and if the voltage difference is higher than a voltage threshold value, provide an indication that the voltage measurement is not reliable.

2. The system according to claim 1, wherein the control unit is further configured to control the first and second voltage measurement units to repeatedly measure the respective first and second voltage.

3. The system according to claim 2, wherein the control unit is further configured to control the first and second voltage measurement units to repeatedly measure the respective first and second voltages with a fixed interval, wherein the fixed interval is in the range of 10 ms to 500 ms.

4. The system according to claim 2, wherein the control unit is further configured to provide an indication that the voltage measurement is unreliable only if a predetermined number of consecutive voltage differences between the first and second pole-to-pole voltages are above the voltage threshold value.

5. The system according to claim 1, wherein the control unit is further configured to detect a change between an active status and a passive status of the power system, and to suppress providing an indication if the voltage difference exceeds the threshold during the change between active status and passive status.

6. The system according to claim 1, wherein the control unit is further configured to use a first voltage threshold value if the power system is in a stable state and a second voltage threshold value if the system is in a transitional state, wherein the second voltage threshold value is higher than the first voltage threshold value.

7. The system according to claim 1 further comprising a display arranged to be visible to an operator, wherein the display is configured to show the first and second pole-to-pole voltages.

8. The system according to claim 1 further comprising a notification unit configured to provide a visual and/or audible indication if the voltage is not reliable.

9. A power system for a vehicle comprising: a high-voltage energy source; a high-voltage system; and a measurement system according to claim 1.

10. A vehicle comprising a power system according to claim 9.

11. Method for determining a status of a high-voltage power system in a vehicle, the power system comprising: a first voltage measurement unit and a second voltage measurement unit, each of the first and second voltage measurement units being connected between a positive pole and a negative pole of the power system; and a measurement system control unit connected to the first and second voltage measurement unit; wherein the method comprises: controlling the first and second voltage measurement unit to simultaneously measure a voltage to determine a respective first and second pole-to-pole voltage; comparing the first and second pole-to-pole voltages to determine a voltage difference; and if the voltage difference is higher than a voltage threshold value, providing an indication that the voltage measurement is not reliable.

12. The method according to claim 11, further comprising measuring the respective first and second voltages repeatedly and with a fixed interval.

13. The method according to claim 11, further comprising providing an indication that the voltage measurement is unreliable only if a predetermined number of consecutive voltage differences between the first and second pole-to-pole voltages are above the voltage threshold value.

14. The method according to claim 11, further comprising: detecting a change between an active status and a passive status of the power system; and suppressing providing an indication if the voltage difference exceeds the threshold during the change between active status and passive status.

15. The method according to claim 11, further comprising: if the power system is in a stable state, comparing the voltage difference with a first voltage threshold value; and if the power system is in a transitional state, comparing the voltage difference with a second voltage threshold value, wherein the second voltage threshold value is higher than the first voltage threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

[0024] In the drawings:

[0025] FIG. 1 is a schematic illustration of safety circuit in a power system according to an embodiment of the invention;

[0026] FIG. 2 is a schematic illustration of safety circuit in a power system according to an embodiment of the invention;

[0027] FIG. 3 is a flow chart outlining a method of controlling a safety circuit in a power system according to an embodiment of the invention, and

[0028] FIG. 4 is a vehicle comprising a power system according to an embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0029] In the present detailed description, various embodiments of a safety circuit for a power system according to the present invention are mainly discussed with reference to a power system in a truck. It should however be noted that this by no means limits the scope of the present invention since the described invention is equally applicable in other types of vehicles such as cars, buses and construction vehicles. The described safety circuit may also be used in marine applications such as boats and ships, and in other applications comprising a high-voltage power source and a high-voltage system.

[0030] FIG. 1 is a circuit schematic illustrating measurement system 100 for determining a status of a high-voltage power system in a vehicle. The measurement system comprises a first voltage measurement unit 102 and a second voltage measurement unit 104, each of the first and second voltage measurement units being connected between a positive pole 106 and a negative pole 108 of the power system. The system further comprises a measurement system control unit 110 connected to the first and second voltage measurement units 102, 104.

[0031] The measurement system control unit 110 is configured to control the first and second voltage measurement units 102, 104 to simultaneously measure a voltage to determine a respective first and second pole-to-pole voltage, U.sub.p-p1, U.sub.p-p2, and to compare the first pole-to-pole voltage U.sub.p-p1 with the second pole-to-pole voltage U.sub.p-p2. The resulting voltage difference can be described as U.sub.diff=|U.sub.p-p1−U.sub.p-p2|. If the voltage difference U.sub.diff is higher than a voltage threshold value U.sub.T, an indication is provided that the voltage measurement is not reliable.

[0032] The measurement system control unit 110 may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the control unit includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device. The functionality of the measurement system control unit 110 may also be integrated in one or more general purpose or dedicated ECUs (electronic control units) of the vehicle.

[0033] FIG. 2 further illustrates a display device 112 where the results of the two voltage measurements U.sub.p-p1 and U.sub.p-p2 are displayed. As illustrated in FIG. 1, there are no other components located between the two voltage measurement units. Accordingly, there should be no difference between the two measured voltages assuming that the measurements are performed at the same time. In an example embodiment, the voltage threshold value may be in the range of 30V to 50V, such as 40V. In practice, the threshold value and sampling rate of the voltage measurement units may be determined based on a reliability of the specific units and on the system properties as a while. A typical value would be to measure or sample the voltage every 10 ms and consider that a fault is detected if three consecutive samples indicate a fail, i.e. a voltage difference value higher than the voltage threshold value.

[0034] To further ensure the independence of the voltage measurements, the two voltage measurement units 102, 104 may be arranged in different housings, and the two may also be of different type and/or come from different manufacturers.

[0035] FIG. 2 schematically illustrates an example power system 200 comprising the measurement system 100 described above with reference to FIG. 1. The power system 200 comprises a high-voltage energy source 202 a high-voltage system 204. In the illustrated example, the high-voltage energy source 202 comprises a plurality of battery packs connected to the high-voltage system 204 via a junction box 206. The high-voltage system 204 is here illustrated as two electrical machines 208a-b for providing vehicle propulsion, each electrical machine being controlled by a corresponding electric motor drive unit 210a-b. The voltage measurement units may for example be integrated in the electric motor drive unit 210a-b, and since the two voltage measurement units are then only separated by a junction box, they are expected to give the same result. A voltage measurement unit may also be integrated in a DC-DC converter 212 of the high voltage system.

[0036] FIG. 3 is a flow chart outlining the general steps of a method which may be performed by the above described measurement system control unit 110. The method comprises controlling 300 the first and second voltage measurement unit to simultaneously measure a voltage to determine a respective first and second pole-to-pole voltage, Up-p1, Up-p2.

[0037] Next, the first and second pole-to-pole voltage, U.sub.p-p1, U.sub.p-p2 are compared 302 to determine a voltage difference, U.sub.diff. Finally, if the voltage difference U.sub.diff is higher than a voltage threshold value U.sub.T, the method comprises providing 304 an indication that the voltage measurement is not reliable.

[0038] FIG. 4 is a vehicle 400 comprising a measurement system 100 for determining a status of a high-voltage power system according to any of the aforementioned embodiments and examples.

[0039] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.