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CN-121995115-A - Method for determining capacitance value of RC circuit capacitor on vehicle direct-current bus

CN121995115ACN 121995115 ACN121995115 ACN 121995115ACN-121995115-A

Abstract

The invention provides a method for determining the capacitance value of an RC circuit capacitor on a vehicle direct current bus, wherein the RC circuit comprises a charging resistor or a discharging resistor, and the method comprises the following steps of measuring a series of values of the charging voltage or the discharging voltage of the capacitor in an evaluation time interval, determining the value of a first-order time derivative of the series of values of the charging voltage or the discharging voltage or a fixed integral of time in the evaluation time interval, determining the value of a second-order time derivative of the series of values of the charging voltage or the discharging voltage or the fixed integral of time in the evaluation time interval, determining the capacitance value of the capacitor by adopting one of the following steps of determining the negative quotient of the value of the first-order time derivative and the second-order time derivative, dividing the negative quotient by the known resistance value of the charging resistor or the discharging resistor, and dividing the negative quotient by the known resistance value of the charging resistor or the discharging resistor. In addition, the invention also provides a corresponding system and a vehicle comprising the system.

Inventors

  • A. Neugebauer

Assignees

  • 阿尔斯通控股公司

Dates

Publication Date
20260508
Application Date
20251106
Priority Date
20241106

Claims (7)

  1. 1. A method for determining a capacitance value (C) of a Capacitor (CA) of an RC circuit on a direct current bus (DCL) of a vehicle, wherein the RC circuit comprises a charging Resistor (RE) or a discharging Resistor (RD), the method comprising the steps of: a) Measuring a series of values (U0-U20; U0-new-U20-new) of the charge voltage (Ut) or the discharge voltage (Ud) of the Capacitor (CA) during an evaluation time interval (T1); b) Determining a first time derivative of the series of values (U0-U20; U0-new-U20-new) of the charging voltage (Ut) or the discharging voltage (Ud) within the evaluation time interval (T1): -number, or -A fixed integral over time; c) Determining a second time derivative of the series of values (U0-U20; U0-new-U20-new) of the charge voltage (Ut) or discharge voltage (Ud) within the evaluation time interval (T1): -number, or -A fixed integral over time; d) -determining the capacitance value (C) of said Capacitor (CA) using one of the following relations: -a negative quotient of the value of the first time derivative and the value of the second time derivative, wherein the capacitance value (C) is obtained by dividing the negative quotient by a known resistance value (R) of the charging Resistor (RE) or the discharging Resistor (RD), or -A negative quotient of the constant integral of the first time derivative and the constant integral of the second time derivative, wherein the capacitance value (C) is obtained by dividing the negative quotient by a known resistance value (R) of the charging Resistor (RE) or the discharging Resistor (RD).
  2. 2. The method of claim 1, wherein determining the value of the first time derivative employs a numerical differentiation based on: -the whole of said evaluation time interval (T1), or -A first sub-interval of the evaluation time interval (T1), wherein the first sub-interval comprises at least three values (U0-U20; U0-new-U20-new) of the charging voltage (Ut) or discharging voltage (Ud); wherein the value of the second time derivative is determined using a numerical differentiation based on: -the whole of said evaluation time interval (T1), or -A second sub-interval of the evaluation time interval (T1), wherein the second sub-interval comprises at least three values (U0-U20; U0-new-U20-new) of the charging voltage (Ut) or discharging voltage (Ud).
  3. 3. Method according to claim 1 or 2, characterized in that a plurality of capacitance values (C) are determined, wherein: -if the predefined statistical dispersion measure of the plurality of capacitance values (C) is not exceeded, the plurality of capacitance values (C) are deemed to be available, and/or -If a predefined statistical dispersion measure of the plurality of capacitance values (C) is exceeded, the plurality of capacitance values (C) are deemed unusable.
  4. 4. A method according to any of claims 1-3, characterized in that the capacitance value (C) and/or the capacitance values (C) if applicable are deemed unusable if a change in the supply voltage (US) of the RC circuit is detected within the evaluation time interval (T1).
  5. 5. A system (1, 10) for determining a capacitance value (C) of a Capacitor (CA) of an RC circuit on a direct current bus (DCL) of a vehicle, wherein the RC circuit comprises a charging Resistor (RE) or a discharging Resistor (RD), the system (1) being configured to be able to perform the method according to any one of claims 1-4, the system (1) comprising: a) A measuring device configured to be able to measure a series of values (U0-U20; U0-new-U20-new) of the charge voltage (Ut) or the discharge voltage (Ud) of the Capacitor (CA) within an evaluation time interval (T1); b) A computing device configured to be capable of: Determining a first time derivative of the series of values (U0-U20; U0-new-U20-new) of the charging voltage (Ut) or the discharging voltage (Ud) within the evaluation time interval (T1): -number, or -A fixed integral over time; and the computing device is configured to: Determining a second time derivative of the series of values (U0-U20; U0-new-U20-new) of the charge voltage (Ut) or discharge voltage (Ud) within the evaluation time interval (T1): -number, or -A fixed integral over time; and the computing means are configured to be able to determine the capacitance value (C) of the Capacitor (CA) using one of the following relations: -a negative quotient of the value of the first time derivative and the value of the second time derivative, wherein the capacitance value (C) is obtained by dividing the negative quotient by a known resistance value (R) of the charging Resistor (RE) or the discharging Resistor (RD); -a negative quotient of the constant integral of the first time derivative and the constant integral of the second time derivative, wherein the capacitance value (C) is obtained by dividing the negative quotient by a known resistance value (R) of the charging Resistor (RE) or the discharging Resistor (RD).
  6. 6. A vehicle comprising a system (1, 10) according to claim 5.
  7. 7. The vehicle of claim 6, wherein the vehicle is a rail vehicle.

Description

Method for determining capacitance value of RC circuit capacitor on vehicle direct-current bus Technical Field The invention relates to a method of determining a capacitance value of an RC circuit capacitor on a DC bus of a vehicle, a system configured to perform the method, and a vehicle comprising the system. Background Capacitors are commonly used on dc buses of traction converters for vehicles, in particular rail vehicles, in particular in RC circuits with charging and/or discharging resistances. In this respect, the capacitor can be used in particular as a filter capacitance. During operation, the capacitance may decrease over time due to aging. To prevent subsequent damage, in particular damage to the traction converter components due to reduced filtering capability, accurate monitoring of the capacitance value is required. If a deeper level of aging is detected, the capacitor may need to be replaced. In the prior art, it is known to determine the capacitance value from the charge current measurement and the charge voltage measurement of a capacitor based on the differential equation c×du (t)/dt (c=i/(dU (t)/dt)) where I is the charge current, C is the capacitance value, U (t) is the charge voltage, and dU (t)/dt is the first time derivative of the charge voltage with respect to time t. However, in practical applications, the reliability of this approach may be low. The charging resistor may reduce the charging current to very low levels, which may be below the accuracy limit of the measuring device (e.g., current transformer). In addition, the resolution (e.g., the resolution may be 1A) of the a/D converter used is insufficient in a low value range (e.g., a range of 10A or less) to meet the use requirements. The resolution characterizes the minimum difference between the two current values that the a/D converter can distinguish. Disclosure of Invention The invention aims to provide a method for determining the capacitance value of an RC circuit capacitor on a direct current bus of a vehicle, which has higher precision and simple and economical implementation and use processes. According to the invention, the above object is achieved by a method as claimed in claim 1, a system as claimed in claim 5 and a vehicle as claimed in claim 6. Specifically, the invention proposes a method for determining the capacitance value of an RC circuit capacitor on a vehicle dc bus, wherein the RC circuit comprises a charging resistor or a discharging resistor, the method comprising the steps of: a) Measuring a series of values of a charge voltage or a discharge voltage of the capacitor during the evaluation time interval; b) Determining a first time derivative of the series of values of the charge voltage or the discharge voltage over an evaluation time interval: -number, or -A fixed integral over time; c) Determining a second time derivative of the series of values of the charge voltage or the discharge voltage over an evaluation time interval: -number, or -A fixed integral over time; d) The capacitance of the capacitor is determined using one of the following relationships: -the negative quotient of the value of the first time derivative and the value of the second time derivative, dividing the negative quotient by the known resistance value of the charge resistor or the discharge resistor, obtaining a capacitance value, or -The negative quotient of the constant integral of the first time derivative and the constant integral of the second time derivative is divided by the known resistance value of the charge resistor or the discharge resistor to obtain the capacitance value. "At least one" has the same meaning as "one or more," and "partially" or "at least partially" has the same meaning as "partially or completely. In the following description, features are sometimes described in the singular. Such descriptions may alternatively or additionally contain corresponding disclosures of a plurality of such features, if applicable, and vice versa. The constant integral of the first-order time derivative is the constant integral of the first-order time derivative and the constant integral of the second-order time derivative is the constant integral of the second-order time derivative and the time. An "evaluation interval" may generally refer to the use of all, part or multiple values within the interval for evaluation and/or further calculation. The vehicle may in particular be a rail vehicle, such as a locomotive or a traction wagon (e.g. a tram, subway train, light rail system train, regional train, cross-regional train, long-distance train or high-speed train). The vehicle comprises a direct current bus and a traction system in which traction electrical energy is transmitted to at least one traction motor via the direct current bus. Alternatively, the vehicle may be an electric bus, an electric car, or any electric road or rail vehicle that includes a dc bus. Alternatively, the vehicle may be a hybrid vehicle including a