DE102021206408A1 - Power compensation method in an electric charging system - Google Patents

Abstract

The present invention relates to a method for operating a charging system (1), which has a distributor (4) and at least two charging connections (3), each connected to the distributor (4) by means of an associated electrical line (5), for charging motor vehicles (2). having. The electrical power fed into the respective line (5) for charging a motor vehicle (2) is determined in the distributor (4), the power loss occurring on the line (5) being taken into account for power compensation. The invention also relates to such a charging system (1).

Description

The present invention relates to a method for power compensation in an electrical charging system for electrically charging motor vehicles. The invention further relates to such a charging system.

In the case of at least partially electrically driven motor vehicles, regular charging of an electrical energy store in the motor vehicle is necessary. For this purpose, the motor vehicle is usually connected to a charging connection that charges the motor vehicle.

It is conceivable here to operate the respective charging connection with a self-sufficient infrastructure.

It is desirable to know the electrical power output at the respective motor vehicle as precisely as possible.

The present invention is concerned with the task of specifying improved or at least different embodiments for a method for power compensation in an electric charging system for charging motor vehicles and for such a charging system, which are characterized in particular by a simplified structure and/or improved accuracy.

According to the invention, this object is achieved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

The present invention is based on the general idea of providing a charging system for charging motor vehicles with at least two charging connections, the respective charging connection being electrically supplied by a distributor, and the respective charging connection being connected to the distributor by means of an associated electrical line. In the distributor, the electrical power fed in at an input of the respective line for charging a motor vehicle connected to the associated charging connection is also determined. Components, such as measuring devices for determining the power, can therefore be omitted at the respective charging connection. This leads to a simplified and cost-effective implementation of the charging system. In order to take into account and compensate for power losses that occur between the distributor and the charging connection, the invention also provides that the length of at least one of the lines is determined and the length of the power loss occurring during charging is determined on the line. The power loss is then taken into account to compensate for the power arriving at the motor vehicle. This means that the charging system is still easy to implement and can be operated in a simplified manner, with the charging system being calibratable at the same time.

In accordance with the idea of the invention, the charging system therefore has the distributor and at least two charging connections. An associated electrical line is also provided for the respective charging connection, which connects the charging connection to the distributor. For this purpose, one end of the line, also referred to below as the input, is connected to the distributor and the other end, also referred to below as the output, is connected to the associated charging connection. Furthermore, in particular in the distributor, the determination, in particular measurement, of the power fed in at the respective input when electrically charging a motor vehicle connected to the associated charging connection takes place. In order to take into account the power loss occurring along the line, an electrical signal that rises abruptly to an initial amplitude, also referred to below as a jump signal, is fed in at the input for at least one of the lines, advantageously for the respective line, and thus applied. As a result, the hopping signal is reflected at the output of the line, with the reflected hopping signal reaching the input. The duration between the start time and the arrival of the reflected jump signal is determined in order to determine the length of the line from the duration. The power loss occurring during operation when charging a motor vehicle at the associated charging connection is then determined from the length of the line and taken into account when determining the power delivered at the output.

With the concept according to the invention, it is possible to arrange the respective charging connection at any desired distance from the distributor. It is conceivable to arrange the charging connections at different distances from the distributor. The lines can therefore have different lengths. The lines can each have lengths of several 10 meters.

The distributor is in particular a charging station which supplies the associated charging connections and thus motor vehicles connected to them with electricity.

The jump signal is advantageously fed to the line via a resistor located at the input. The value of this resistance is preferably the value of the characteristic impedance of the connected conductor. The jump signal is thus generated in a simplified and defined manner.

The nature of the respective line is expediently known or is determined beforehand. In particular, a specific resistance and a cross section of the respective line are known or are determined beforehand.

In principle, the method according to the invention can be used for all conductive metals and/or alloys. Especially with high charging currents when charging with direct current and the resulting cable cross-sections, it is conceivable to use aluminum cables. This leads in particular to reduced costs.

At least one of the lines, preferably the respective line, advantageously has copper, and is in particular a copper line. This enables a simple and cost-effective implementation of the charging system with reduced power losses at the same time.

Particular preference is given to embodiments in which for at least one of the at least one lines, advantageously for the respective line, the duration and thus the associated length are determined when the line is disconnected from the associated charging connection. This leads to an improved and/or defined reflection of the jump signal at the output. Thus, the duration can be determined more precisely and consequently the length can be precisely determined. This therefore results in an improved determination of the power loss.

In order to achieve the determination of the length when the line exits separated from the associated charging port, it is conceivable to carry out the determination of the length during the installation of the associated charging port and/or before the charging port is put into operation. It is also conceivable to trigger the determination of the length manually.

Alternatively or additionally, it is conceivable to provide an interface on the charging connection and/or on the distributor, via which a measuring device can be connected in order to carry out the measuring process for at least one line.

It is conceivable, particularly when the measuring device is connected to the distributor, to determine the lengths of two or more lines at the same time.

Embodiments are preferred in which the electrical resistance, ie the ohmic resistance or the impedance, of the line is determined from the length of at least one of the lines determined by means of the duration. For this purpose, in particular the specific resistance of the line, which has already been determined or is known, and a cross-section of the line are used. The power loss is then determined during charging and thus the flow of an electrical current through the line for charging a motor vehicle using the resistance of the electrical line. In particular, the quadratic relationship between the power loss and the electric current across the resistor can be assumed for this purpose. In particular, the following can essentially be assumed for the power loss P: P=I ² R, where I is the electric current and R is the resistance.

The arrival of the reflected jump signal at the input is preferably detected in that the amplitude of the signal present at the input increases abruptly, starting from the initial amplitude, in particular substantially to twice the initial amplitude. This means that the jump signal is monitored at the input and, if there is a sudden increase, the arrival of the reflected jump signal is concluded. A simple, inexpensive and reliable determination of the duration and thus of the length and the power loss is thus achieved.

In principle, the jump signal can be an electrical signal of any type. The jump signal is preferably a jump voltage which rises abruptly to the initial amplitude and which is applied to the input to determine the duration. This leads to a simple, energy-efficient and reliable determination of the duration and thus the length and consequently the power loss.

In order to determine the length of the line from the duration, the speed of propagation of electrical waves in the line is advantageously included. The propagation speed can be previously determined or stored. Since the propagation speed is typically several cm per ns (nanosecond), a very precise determination of the length of the line is thus made.

The power compensation is advantageously implemented in such a way that the electrical power arriving at the motor vehicle is assumed to be the power fed in at the input of the line minus the power loss.

Advantageously, the power compensation is used for billing purposes, in order to, despite the measurement of the electrical power fed in at the input, which has taken place in the distributor, the respective To determine the power output of the motor vehicle as precisely as possible.

It goes without saying that, in addition to the method, a charging system operated in this way also belongs to the scope of this invention. In this case, the charging system comprises the distributor and the at least two charging connections, which are each connected to the charging connection by means of an associated line.

A power measuring device is preferably provided in the distributor, which during operation determines the electrical power fed in at the respective input. The charging system, in particular the distributor, also has a control device which is designed in such a way that it carries out a corresponding power compensation for at least one of the lines.

The control device advantageously has a timer, which it starts when the step signal is applied and stops when the reflected step signal arrives at the input.

Alternatively or additionally, the control device can have another electrical time measuring device, which can determine the time between two applied edges. An example of this is a digital time module or a so-called "time-to-digital converter".

The respective charging connection is advantageously part of a charging point of the charging system. The charging system therefore advantageously has at least one charging point with at least one charging connection. The charging system preferably has two or more charging points, each with at least one charging connection, with the respective charging connection being connected to the distributor via an associated line.

Further important features and advantages of the invention result from the dependent claims, from the drawings and from the associated description of the figures with reference to the drawings.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, with the same reference numbers referring to identical or similar or functionally identical components.

• 1 eine stark vereinfachte, schaltplanartige Darstellung eines Ladesystems zum Laden von Kraftfahrzeugen,
• 2 ein Diagramm zur Ermittlung einer Länge einer Leitung des Ladesystems.

Show it, each schematically

• 1 a highly simplified, circuit diagram-like representation of a charging system for charging motor vehicles,
• 2 a diagram for determining a length of a line of the charging system.

A charging system 1 as described in 1 is shown in a greatly simplified manner and in the form of a circuit diagram, is used for the electrical charging of motor vehicles 2. The charging system 1 has at least two charging connections 8 for this purpose. A motor vehicle 2 can be connected to the respective charging connection 8 and thus charged. The charging system 1 also includes a distributor 4 which centrally supplies the charging connections 8 with electricity. The distributor 4 is therefore in particular a charging station 4. In the 1 shown embodiment, the respective charging connection 8 is provided in a charging point 3 of the charging system 1, which is arranged at a distance from the distributor 4. The charging system 1 therefore has at least one charging point 3 . in the in 1 In the exemplary embodiment shown, the respective charging point 3 has a single charging connection 8 purely by way of example.

For the electrical supply of the respective charging connection 8 and thus for charging the respective motor vehicle 2 , the respective charging connection 8 is electrically connected to the distributor 4 by means of an associated electrical line 5 . The distributor 4 is expediently electrically connected to a mains connection (not shown). The respective line 5 is connected at one end 6, hereinafter also referred to as input 6, to the distributor 4 and at the other end 7, hereinafter also referred to as output 7, to the associated charging port 8 and thus connects the associated charging port 8 to the distributor 4. The respective line 5 typically has lengths of several 10 m. in the in 1 The exemplary embodiment shown shows two charging connections 8 purely by way of example. The charging system 1 usually has three or more charging connections 8 which are each connected to the distributor 4 via an associated line 5 . in the in 1 The exemplary embodiment shown here runs the respective line 5 from the distributor 4 to the associated charging connection 8, to which a motor vehicle 2 is connected for charging. In particular, for this purpose an in 1 charging cable 9 indicated by dashed lines is connected to the charging connection 8 and to the motor vehicle 2 . In the exemplary embodiment shown, the distributor 4 also includes a device 10 which determines the electrical power fed in at the respective input 6 for charging a motor vehicle 2 connected to the associated charging connection 8 . The device 10 is hereafter also referred to as power measuring device 10 .

In order to know the electrical power arriving at the motor vehicle 2 during charging as precisely as possible, the electrical power loss occurring along the associated line 5 is taken into account and compensated for. In this case, the electrical power fed in, determined by means of the power measuring device 10 , minus the power loss of the associated line 5 , can be assumed to be the electrical power arriving at the motor vehicle 2 .

In the exemplary embodiment shown, it is assumed purely by way of example that the respective line 5 is made of copper, that is to say that the respective line 5 is a copper line 5a. Lines 5 made of aluminum alloys, for example, are also conceivable.

To determine the power loss on at least one of the lines 5, in particular the respective line 5, the length of the line 5 is determined as described below.

According to the 2 In this case, at an initial point in time t1, a signal which suddenly rises to an initial amplitude A1 is applied to the input 6, which is also referred to below as a jump signal. Here is in 2 the time t is shown along the abscissa axis 11 and the amplitude A of the jump signal determined at the input 6 is shown along the ordinate axis 12, with the jump signal 13 in 2 is shown with a solid line. In the exemplary embodiment shown, the step signal 13 is an electrical voltage and thus a step voltage 14. The step signal 13 applied to the input 6 with the initial amplitude A1 propagates through the line 5 and is reflected at the output 7 of the line 5. The reflected jump signal 13 then reaches the input 5 again, so that the amplitude A determined at the input 5 increases suddenly when the reflected jump signal 13 arrives at the input 6 . This increase takes place at an arrival time t2 of the reflected jump signal 13 at the input 6. A duration 17 between the start time t1 and the arrival time t2 can thus, for example, by means of a timer 15 (see 1 ), to be determined. With the determined duration 17, the length of the line 5 can now be determined with the aid of the propagation speed of electric waves through the line 5. With the copper line 5a assumed here, the processing speed is usually between 20 cm per ns (nanoseconds) and 25 cm per ns, so that the length of the line 5 can be determined very precisely.

The described determination of the length of the line 5 is advantageously based on the duration 17 when the input 6 is connected to the distributor 4 and when the output 7 is disconnected from the charging connection 8, in particular the interface 8. This results in a defined and precise reflection of the Jump signal 13 at the output 7 and consequently an increased precision in determining the length of the line 5.

how 2 can be seen, the sudden increase in the amplitude A present at the input 6 is assumed for the arrival time t2 to an amplitude A2 which essentially corresponds to twice the initial amplitude A1.

Once the length of the line 5 has been determined, the electrical resistance of the line 5, in particular the ohmic resistance of the line 5, is determined on the basis of the specific resistance of the line and the cross section of the line 5. Here, the cross section of the line 5 is known or previously determined. Since the material of the respective line 5 is also known, in this case copper lines 5a, the specific resistance is also known, so that the ohmic resistance of the line 5 can be determined.

If the ohmic resistance of the line 5 is known, the power loss on the line 5 can be determined during operation when charging a motor vehicle 2 by taking into account the electric current flowing through the line.

In order to determine the length of the respective line 5 and for power compensation, the charging system 1 can have a control device 16 which is designed accordingly. at in 1 In the exemplary embodiment shown, the control device 16 is provided in the distributor 4 and also includes the timer 15.

The determination of the duration 17 and thus the length of the lines 5 is advantageously carried out when the line 5 is connected to the input 6 on the distributor 4 for the first time. The length thus determined or the resistance thus determined can then be stored in the distributor 4 and/or in the control device 16 and taken into account in the power compensation.

The charging system 1 according to the invention allows a simple implementation of the charging system 1 for charging a plurality of motor vehicles 2 with a cost-effective implementation and increased precision of the electrical power arriving at the respective motor vehicle 2 .

Claims (10)

Method for power compensation in an electrical charging system (1) for electrically charging motor vehicles (2), - wherein the charging system (1) has a distributor (4), - wherein the charging system (1) has at least two charging connections (8) for charging one motor vehicle (2) each, - An associated electrical line (5) being provided for the respective charging connection (8), which has an input (6) connected to the distributor (4) and an output (7) connected to the associated charging connection (8) and the associated charging connection (8) thus electrically connects to the distributor (4), - whereby the electrical power fed in at the respective input (6) is determined, - wherein for at least one of the lines (5): • at the input (6) at an initial time (t1) an electrical jump signal (13) suddenly rising to an initial amplitude (A1) is applied, • the arrival of the jump signal (13) reflected at the output (7) is detected at the input (6), • the duration (17) between the start time (t1) and the arrival of the reflected jump signal (13) at the input (5) is determined, • from the duration (17) a length of the line (5) and from the length of the line (5) the power loss occurring via the line (5) is determined, • the power loss is taken into account when determining the power output at the output (7). procedure after claim 1 , characterized in that the length of at least one of the lines (5) is determined when the line (5) is disconnected from the associated charging connection (8) and connected to the distributor (4). procedure after claim 1 or 2 , characterized in that the electrical resistance of the line (5) is determined from the length of at least one of the lines (5) and the power loss is determined from the electrical resistance and the electrical current flowing through the line (5) during charging. Procedure according to one of Claims 1 until 3 , characterized in that the arrival of the reflected jump signal (13) at the input (7) is detected in that the amplitude (A) of the jump signal (13) at the input (6) increases suddenly. procedure after claim 4 , characterized in that the arrival of the reflected jump signal (13) at the input (6) is detected in that the amplitude (A) of the jump signal (13) at the input (6) corresponds essentially to twice the initial amplitude (A1). Procedure according to one of Claims 1 until 5 , characterized in that the length of at least one of the lines (5) is determined from the duration (17) and the propagation speed of electric waves in the line (5). Procedure according to one of Claims 1 until 6 , characterized in that the length of at least one of the lines (5) is determined when the line (5) is connected to the inlet (6) on the distributor (4) for the first time. Procedure according to one of Claims 1 until 7 , characterized in that, in the power compensation, the electrical power arriving at the motor vehicle (2) is taken into account as the power fed in at the input (6) of the line (5) minus the power loss. Charging system (1) for electrically charging motor vehicles (2), - with a distributor (4), - with at least two charging connections (8) for electrically charging one motor vehicle (2) each, - with an associated one for the respective charging connection (8). electrical line (5) is provided, which has an input (6) connected to the distributor (4) and an output (7) to the associated charging connection (8) and thus the associated charging connection (8) is electrically connected to the distributor ( 4) connects - the distributor (4) having a power measuring device (10) which, during operation, determines the electrical power fed in at the respective input (6), - with a control device (17) which is designed in such a way that it is used for at least one of the lines (5) a power compensation according to the method of one of Claims 1 until 8th performs. charging system after claim 9 , characterized in that the control device (17) has a timer (15) and is designed in such a way that it starts the timer (15) when the jump signal (13) is applied and when the reflected jump signal (13) arrives at the input (6 ) stops.

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