DE102019128321A1 - Computer-implemented method for calculating the charging energy of an energy store in an electric vehicle - Google Patents

Abstract

The invention relates to a computer-implemented method for calculating the charging energy of an energy store of an electric motor vehicle, comprising the following steps: calculating a maximum electrical resistance of a charging cable (101) (S1); - calculating a minimum electrical resistance of the charging cable (101) (S1); - Determination of an average resistance value from the maximum resistance and the minimum resistance (S2); - Carrying out a charging process of the energy storage device using the charging cable (101) (S3); - Calculation of a charging energy using the average resistance value (S4).

Description

The present invention relates to a computer-implemented method according to claim 1 for calculating a charging energy of an energy store of an electric motor vehicle. In the context of this description, an energy store is understood to mean, in particular, a rechargeable battery.

The calculation of the charging energy is important if the electric vehicle is to be charged from a publicly accessible energy source. The charging energy with which the energy store is charged should usually be paid for by the user of the electric motor vehicle. For this purpose, the amount of charging energy should be known as precisely as possible. Otherwise, the operator of the energy source is at a disadvantage or the user of the electric motor vehicle is at a disadvantage.

In the context of this description, the energy source is understood to mean, in particular, a device that is designed to provide energy for charging electric motor vehicles. For this purpose, the energy source can be connected, for example, to an electrical supply network and have a connection for a charging cable, with which the energy source can then be connected to the electric motor vehicle. Such an energy source can also be referred to as a charging station, for example.

A method for carrying out a charging process for an energy storage device of an electric motor vehicle is disclosed in US Pat DE 10 2017 209 450 A1 known.

In contrast, the present invention is based on the object of creating a method which enables the charging energy transferred to the energy store to be calculated. In addition, such a system is to be created.

This object is achieved by a method according to claim 1 and by a system according to claim 10. Embodiments of the invention are given in the dependent claims.

In order to be able to calculate the charging energy transferred to the energy store, it is advantageous to know the resistance of the charging cable used during the charging process. If this resistance is known, the electrical current and voltage at the energy source can be measured. The charging energy can then be calculated from the resistance, the electrical current strength and the electrical voltage. Systematic disadvantage for the user of the electric vehicle or the operator of the energy source must be avoided; Random errors within the scope of the measurement accuracy are regulated in calibration law.

First, a maximum and a minimum resistance of the charging cable are calculated. The maximum and the minimum resistance can be calculated, for example, taking into account tolerances and / or different temperatures. An average resistance value is determined from the maximum and minimum resistance. The resistance mean value can be, for example, the arithmetic mean of the maximum and the minimum resistance.

The energy storage device is then charged using the charging cable. The charging cable can, for example, connect a connection of the energy source to a connection of the electric motor vehicle. A charging energy is calculated using the average resistance value. The charging energy can in particular be the energy with which the energy store was charged. The use of the resistance mean value is advantageous because this value is likely to have a relatively small deviation from the real value during the charging process. In addition, the deviations from the real value are statistically random errors, the significance of which decreases when different charging cables are used several times. There is no systematic error, the importance of which would add up even if different charging cables were used several times.

According to one embodiment of the invention, the charging cable can electrically connect a contacting point of the energy source to the energy store during the charging process. The contacting point can be the point at which one end of the charging cable electrically contacts a cable of the energy source. The energy source can comprise measuring means which are designed to measure an electrical charging current strength and an electrical charging voltage. The charging current and the charging voltage can be measured by the measuring device during the charging process at the contacting point. The electrical charging current and the electrical charging voltage are preferably measured during the entire charging process. The charging energy can be calculated using the charging current and voltage.

In this way, the measuring means in the energy source can be used in order to calculate the electrical energy transferred to the energy store relatively precisely. Since the average resistance value is known, no additional cables are required that are routed to the electric vehicle. to measure the charging current and voltage directly on the electric vehicle.

According to one embodiment of the invention, a first resistance value of the charging cable can be determined at a first temperature. The first resistance value can be measured or calculated, for example. The maximum electrical resistance can be calculated by adding the first resistance value and a first tolerance value. The first tolerance value can in particular serve to take into account measurement or calculation inaccuracies.

According to one embodiment of the invention, a second resistance value of the charging cable can be determined at a second temperature. The second resistance value can be measured or calculated, for example. The minimum electrical resistance can be calculated by subtracting a second tolerance value from the second resistance value. The second tolerance value can in particular serve to take into account measurement or calculation inaccuracies. The second tolerance value can be identical to the first tolerance value, for example. Alternatively, it is possible for the second tolerance value to take contact resistances of the measuring means into account.

According to one embodiment of the invention, the second temperature can be lower than the first. This is particularly advantageous since the real resistance of the charging cable is often greater at higher temperatures than at lower temperatures.

According to one embodiment of the invention, the charging current and / or the charging voltage can be time-dependent during the charging process. Due to different charging voltages and charging currents during the charging process, systematic deviations of the real resistance of the charging cable from the average resistance value can be less relevant for certain charging voltages or charging currents. The accuracy of the method is thus increased.

According to one embodiment of the invention, the charging energy can be calculated by first calculating a time-dependent charging power, which is then integrated over time. The time-dependent charging power can be calculated from the average resistance value, the charging voltage and the charging current.

• wobei P(t) die Ladeleistung, I(t) die Ladestromstärke, U(t) die Ladespannung und
• R der Widerstandsmittelwert ist.

According to one embodiment of the invention, the charging power can be calculated using the following formula: $$\text{P.}\left(\text{t}\right)=\text{I.}\left(\text{t}\right)*\left(\text{U}\left(\text{t}\right)-\text{R.}*\text{I.}\left(\text{t}\right)\right),$$

• where P (t) is the charging power, I (t) is the charging current, U (t) is the charging voltage and
• R is the resistance mean.

According to one embodiment of the invention, the charging cable can be designed as a fast charging cable. In the context of this description, this is understood in particular to mean that the charging cable is suitable for carrying out the charging process with a power of more than 20 kW. The charging process is preferably carried out with such a power.

The system of claim 10 comprises a power source and a charging cable. The system is designed to charge an energy store of a motor vehicle when the energy store is electrically connected to the energy source via the charging cable. The energy source is designed to calculate a charging energy using an average resistance value of the charging cable. The energy source can also be designed to carry out various method steps described above in connection with the method.

• 1 ein schematisches Flussdiagramm eines Verfahrens nach einer Ausführungsform der Erfindung; und
• 2 eine schematische Ansicht eines Systems nach einer Ausführungsform der Erfindung.

Further features and advantages of the present invention will become clear on the basis of the following description of preferred exemplary embodiments with reference to the accompanying figures. The same reference symbols are used for the same or similar steps and for steps with the same or similar functions. To distinguish such steps, one or more apostrophes can be appended. It shows

• 1 a schematic flow diagram of a method according to an embodiment of the invention; and
• 2 a schematic view of a system according to an embodiment of the invention.

In the first step S1 a maximum and a minimum resistance of a charging cable are calculated. This calculation can be done after one or more measurements of resistance. In this case, the maximum resistance can be calculated by adding a tolerance to a resistance measured at a first temperature. The minimum resistance can be calculated by subtracting a tolerance and any contact resistances to be taken into account from a resistance measured at a second temperature. The first temperature can be higher than the second temperature.

Then in step S2 an average resistance value is calculated from the maximum and minimum resistance. The resistance mean value can be, for example, the arithmetic mean of the maximum and the minimum resistance.

In step S3 the charging process of the energy storage device is carried out using the charging cable. The charging energy with which the energy store was charged is calculated using the average resistance value in step S4 calculated. This can be done, for example, by first calculating a time-dependent charging power P (t) according to the following formula: $$\text{P.}\left(\text{t}\right)=\text{I.}\left(\text{t}\right)*\left(\text{U}\left(\text{t}\right)-\text{R.}*\text{I.}\left(\text{t}\right)\right).$$

Here I (t) is the time-dependent charging current, U (t) is the time-dependent charging voltage and R is the mean resistance value.

The charging energy can be calculated from the charging power by integrating it over time. This has the advantage that a statistical error that occurs when calculating the charging power is further reduced.

Tests have shown that with a maximum resistance of 11.0mΩ and a minimum resistance of 5.5mΩ, the average resistance value of 8.25mΩ, a random error between 0.03% and 0.46% occurs when calculating the charging energy. The error is still dependent on the charging current and charging voltage. The higher the current, the higher the error. The higher the voltage, the lower the error. The above error of 0.46% was determined at a voltage of 300V and a current of 500A. The error of 0.03% has been determined at a voltage of 1000V and a current of 100A.

In 2 is a source of energy 100 shown in the form of a charging station. The energy source 100 can use a charging cable 101 with a connector 102 of an electric vehicle are connected to charge an energy storage device of the electric vehicle. For a reliable billing, the energy with which the energy storage is charged should be determined. Due to the not negligible resistance of the charging cable 101 can not this energy within the energy source 100 be determined.

The resistance of the charging cable 101 must not be neglected, especially in some countries due to legal regulations, since this would be a systematic error that would always disadvantage the user of the electric vehicle financially.

For these reasons, the resistance for the charging cable becomes the mean 101 as above with reference to FIG 1 described, determined and the charging energy calculated using this resistance mean value. The charging current strength and the charging current voltage within the energy source are thereby determined 100 measured.

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• DE 102017209450 A1 [0004]

Claims (10)

Computer-implemented method for calculating a charging energy of an energy store of an electric motor vehicle, comprising the following steps: - Calculation of a maximum electrical resistance of a charging cable (101) (S1); - Calculation of a minimum electrical resistance of the charging cable (101) (S1); - Determination of a resistance mean value from the maximum resistance and the minimum resistance (S2); - Carrying out a charging process of the energy store using the charging cable (101) (S3); - Calculation of a charging energy using the average resistance value (S4). Procedure according to Claim 1 , characterized in that the charging cable (101) electrically connects a contacting point of an energy source (100) to the energy store during the charging process, the energy source (100) comprising measuring means, the measuring means being designed to supply an electrical charging current and an electrical charging voltage measure, the charging current strength and the charging voltage being measured during the charging process at the contacting point, and the charging energy being calculated using the charging current strength and the charging voltage. Method according to one of the preceding claims, characterized in that a first resistance value of the charging cable (101) is determined at a first temperature, the maximum electrical resistance being calculated by adding the first resistance value and a first tolerance value. Method according to one of the preceding claims, characterized in that a second resistance value of the charging cable (101) is determined at a second temperature, the minimum electrical resistance being calculated by subtracting a second tolerance value from the second resistance value. Method according to the previous claim as a function of Claim 3 , characterized in that the second temperature is lower than the first temperature. Method according to one of the preceding claims, characterized in that the charging current strength and / or the charging voltage are / is time-dependent. Method according to one of the preceding claims, characterized in that the charging energy is calculated by first calculating a time-dependent charging power, which is then integrated over time. Method according to the preceding claim, characterized in that the charging power is calculated according to the following formula: $$\text{P.}\left(\text{t}\right)=\text{I.}\left(\text{t}\right)*\left(\text{U}\left(\text{t}\right)-\text{R.}*\text{I.}\left(\text{t}\right)\right),$$

where P (t) is the charging power, I (t) is the charging current, U (t) is the charging voltage and R is the mean resistance value. Method according to one of the preceding claims, characterized in that the charging cable (101) is designed as a fast charging cable. A system comprising an energy source (100) and a charging cable (101), the system being designed to charge an energy storage device of an electric motor vehicle when the energy storage device is electrically connected to the energy source (100) via the charging cable (101), and wherein the Energy source (100) is designed to calculate a charging energy using an average resistance value of the charging cable (101).

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