Method for operating a charger, charger, energy system and motor vehicle

Abstract

The invention relates to a method for operating a charger (1) for a motor vehicle, in particular an on-board charger of a motor vehicle, wherein the charger (1) has a polyphase input connection (3) for connection to a polyphase supply system connection (4), a voltage converter (5) and at least one sensor (V7, V8, V9) for monitoring an electrical voltage of at least one phase (L1, L2, L3, N, PE) of the input connection (3), wherein a system configuration of the supply system connection (4) is determined depending on at least one detected electrical voltage at one phase (L1, L2, L3, N, PE) of the input connection (3). Provision is made for a voltage profile of the monitored voltage to be detected and for the system configuration of the supply system connection (4) to be determined depending on the voltage profile.

Description

[0001] DESCRIPTION

[0002] Method for operating a charger, charger, energy system and motor vehicle

[0003] The present invention relates to a method for operating a charger for a motor vehicle, in particular an on-board charger of a motor vehicle, wherein the charger has a multi-phase input connection for connection to a multi-phase supply network connection, a voltage converter, and at least one sensor for monitoring an electrical voltage of at least one phase of the input connection, wherein a network configuration of the supply network connection is determined as a function of at least one detected electrical voltage at a phase of the input connection.

[0004] Furthermore, the invention relates to a charging device for a motor vehicle which is designed as described above and has a control unit for carrying out the method described above.

[0005] Furthermore, the invention relates to an energy system for a motor vehicle with the above-mentioned charger and to such a motor vehicle.

[0006] State of the art

[0007] Power grids vary worldwide, and can differ from one another in terms of their line voltage, line frequency, and distribution system. With the increasing electrification of motor vehicles in particular, the need for chargers that can be connected to different supply grids is also growing. These can be used, for example, to charge the vehicle's energy storage system as needed. A charger for electrically charging an electric vehicle's high-voltage battery can, for example, be connected to one or more electrical phases of a supply grid connection using multiple available electrical phases. Such a charger must be capable of operating with many different grid configurations. For example, a charger in the German supply system can be connected as a single-, two-, or three-phase device.Depending on the grid configuration of the supply network, it is known that a charger control unit selects an optimal operating strategy for the charging process in order to charge the energy storage device efficiently and to avoid damage. Such a charger usually has a voltage converter in addition to the input connection, which converts, for example, the alternating voltage provided by the supply network into a direct voltage suitable for the energy storage device. Such a charger can be designed as an on-board charger, as part of the energy system of a motor vehicle, or as a separate charger that can be carried by the user or connected externally. Detecting the correct grid configuration of the supply network connection is of great importance for the operational reliability and service life of an energy storage device to be charged.It is known from the prior art to assign a voltage transformer to each phase of the input connection in order to determine the grid configuration by evaluating the detected voltages. For this purpose, several parameters are typically evaluated for each detected voltage, based on the respective detected voltage. These parameters include, for example, the absolute and effective voltage and / or a determined frequency and phase position of the voltage of the respective phase. The grid configuration is then derived from the comparison of the parameters assigned to each phase.

[0008] Disclosure of the invention

[0009] The method according to the invention with the features of claim 1 has the advantage of preventing false detection of a grid configuration. During operation of the charger, impressed or externally induced voltages can cause a voltage signal to be present on one phase which, although it corresponds to the voltage and frequency of a valid grid voltage, does not actually represent a valid grid voltage of the supply grid. The resulting false detection of the grid configuration can lead to an unsuitable charging strategy being selected, which complicates the charging process or damages the energy storage device or the charger. For example, a charger with only a single-phase connection, which in principle can also be connected to a two- or three-phase connection, can also detect a periodic voltage on a non-connected phase.This can occur, for example, through crosstalk of the signals between the sensors or through the imposition of a voltage by the input circuitry of a power output stage. If an imposed voltage is incorrectly detected as a supply network voltage, an incorrect network configuration is assumed as a result. The method according to the invention ensures that the detected voltage is actually a voltage of the supply network. For this purpose, the invention provides that a voltage curve of the monitored voltage is recorded and, depending on the voltage curve, the network configuration of the supply network connection is determined. Based on the voltage curve, it can be determined whether it is a supply voltage or an invalid or unexpected voltage. By taking this curve into account, it is thus ensured that the correct network configuration is reliably detected.Preferably, the method comprises the step of controlling the charger depending on the determined network configuration.

[0010] Preferably, the monitored voltage waveform is recognized as valid if it is sinusoidal. According to the invention, only if the voltage waveform is recognized as valid is it considered for determining the grid configuration. If a detected voltage waveform is thus deemed invalid, the detected voltage is not considered for determining the grid configuration and is instead ignored. Therefore, the detected voltage waveform is preferably compared with a sinusoidal waveform and checked to determine whether it is sinusoidal.

[0011] Furthermore, it is preferably provided that, in order to detect a sinusoidal shape of the voltage waveform, at least one total harmonic distortion is determined and compared with a predetermined limit value. This utilizes the fact that an impressed voltage, unlike a voltage of the supply network, is typically periodic but not sinusoidal. Thus, by taking the shape of the voltage waveform into account, it is determined whether the detected voltage should be assessed as valid or invalid. The total harmonic distortion assumes larger values ​​as the voltage waveform deviates from a sinusoidal shape and is therefore a good criterion for assessing the sinusoidal shape of the detected voltage.

[0012] Furthermore, it is preferably provided that the total harmonic distortion is determined as a function of an effective value of the measured voltage and the effective value of a corresponding fundamental oscillation. These two parameters allow the voltage value of the corresponding fundamental oscillation to be determined at any time, which is required to assess the total harmonic distortion.

[0013] The total harmonic distortion is preferably only determined once a phase-locked loop for determining parameters of the voltage waveform has settled, and in particular only once a frequency and / or effective voltage of the voltage waveform has been checked for plausibility. This ensures that no incorrect values ​​are determined. The total harmonic distortion is preferably determined by squaring. Because extracting a square root resulting from the definition of the total harmonic distortion is very computationally intensive, the method is simplified and accelerated by using the squared value of the total harmonic distortion. When deciding whether the recorded voltage waveform is sinusoidal or not, the above-mentioned limit value, which is then also squared, must then be taken into account.

[0014] According to an alternative embodiment of the invention, a mean square deviation is determined instead of squaring if the effective value of the fundamental oscillation equals or nearly equals the effective value of the voltage. If the mean square deviation exceeds a correspondingly predefined limit, the detected voltage on the corresponding phase is marked as invalid.

[0015] The charger with the features of claim 8 is characterized in that the control unit is specifically designed to carry out the method according to the invention when used as intended. This results in the advantages already mentioned above.

[0016] The energy system according to the invention with the features of claim 9 is characterized by the inventive design of the charger. This results in the advantages already mentioned above.

[0017] The motor vehicle with the features of claim 10 is characterized by the energy system according to the invention. This results in the advantages already mentioned above.

[0018] Further advantages and preferred features and combinations of features emerge in particular from the above description and from the claims. The invention will be explained in more detail below with reference to the drawings.

[0019] Figure 1 shows an advantageous charger for a motor vehicle in a simplified representation, and

[0020] Figure 2 shows a flowchart for explaining an advantageous method. Figure 1 shows a simplified representation of an advantageous charger 1 for an energy system 2 of a motor vehicle (not shown in detail here). The charger 1 has an input connection 3 on the input side, which is designed to be connected to a supply network connection 4 of a stationary supply network. For this purpose, the input connection 3 and the supply network connection 4 are designed, for example, as plug connections for establishing a plug connection. The input connection 3 has a connection LI, a connection L2, a connection L3, a neutral conductor connection N, and a protective conductor connection PE.

[0021] The charger 1 further comprises a voltage converter 5, which is designed to provide a direct voltage depending on the connected supply network, preferably at an intermediate connection 6. The voltage converter 5 is preferably designed as a PFC stage or power factor correction stage. The intermediate connection 6 preferably comprises a positive intermediate connection and a negative intermediate connection. An intermediate circuit capacitor or a series connection of a first intermediate circuit capacitor 14 and a second intermediate circuit capacitor 15 is preferably connected between the positive intermediate connection and the negative intermediate connection. A DC-DC converter (not shown) is preferably connected to the intermediate connection 6.The DC voltage at the intermediate terminal 6, which is present on the input side of the DC-DC converter, is preferably converted into a charging voltage for charging an energy storage device, preferably a battery, a traction battery, or a high-voltage battery, that can be connected to the output side of the DC-DC converter. Consequently, an energy storage device of the motor vehicle connected to the charger 1 can be charged using the charging voltage. For this purpose, the voltage converter 5 preferably has three half-bridges 7, 8, 9, each of which has two series-connected semiconductor switches 7H, 7L and 8H, 8L and 9H, 9L, one of which is designed as a high-side switch (H) and one as a low-side switch (L).Preferably, the half-bridges 7, 8, 9 and the intermediate terminal 6 are electrically connected in parallel, with each half-bridge 7, 8, and 9 each having a center tap between the respective semiconductor switches 7H, 7L, 8H, 8L, 9H, 9L, which is connected to one of the terminals L1, L2, or L3 via an electrical inductance or resistor 10, 11, 12. The voltage converter 5 further comprises an intermediate circuit 13, which comprises the intermediate circuit capacitor or the series connection of the first intermediate circuit capacitor 14 and the second intermediate circuit capacitor 15, and is electrically connected in parallel to the half-bridges 7, 8, 9. Two freewheeling diodes 16, 17 are preferably connected in parallel to the intermediate circuit capacitors 14, 15. The freewheeling diodes 16,17 are connected in reverse direction and prevent a current flow from the high side to the low side of the voltage converter 5, whereby a center tap between the diodes 16,17 is connected to the neutral conductor N.Preferably, the voltage converter 5 is connected on the input side to the input terminal 3 and on the output side to the intermediate terminal 6. Preferably, the intermediate terminal 6 is connected in parallel to the half-bridges 7, 8, and 9 or the intermediate circuit capacitor or the series circuit of the first and second intermediate circuit capacitors 14, 15.

[0022] The charger 1 preferably further comprises a first switching element S1, by means of which the half-bridge 7 can be selectively connected to the terminal LI. Furthermore, the charger 1 preferably comprises a second switching element S2, by means of which the third half-bridge 9 is connected in a first switching position to the terminal LI or the first phase of the voltage converter 5 and in a second switching position to the terminal L3 or the third phase of the input terminal 3. In addition, the charger 1 preferably comprises a third switching element S3, by means of which the second half-bridge 8 can be selectively connected to the terminal L2. Preferably, by means of a fourth switching element S4, the center tap between the diodes 16, 17 can be selectively connected to the center tap between the first intermediate circuit capacitor 14 and the second intermediate circuit capacitor 14, 15.

[0023] Furthermore, the charger 1 preferably has a voltage sensor V7, V8, V9 assigned to the respective half-bridge 7, 8, 9, which is connected between the respective phase of the voltage converter 5 and the neutral conductor terminal N in order to detect the electrical voltage of the respective terminal L1, L2, L3 relative to the neutral conductor terminal N. The inductors or resistors 10, 11, 12 are preferably each assigned a current sensor A10, A11, A12.

[0024] The charger 1 further comprises a control unit 18 which is designed to control the semiconductor switches of the voltage converter 5 and to monitor the values ​​detected by the voltage sensors V7-V9 and / or the current sensors A10-A12.

[0025] The control unit 18 is particularly designed to carry out the method described below. Figure 2 shows an example of a flowchart that will explain the advantageous method. The method begins with the commissioning of the charger 1 in a step S_1, when the input terminal 3 is connected to the supply network terminal 4.

[0026] In a subsequent step S_2, the voltage curve of the respective monitored phase LI, L2, L3 is recorded using the voltage sensors V7-V9.

[0027] In a subsequent step S3, a check is carried out to determine whether the recorded voltage waveform is sinusoidal. For this purpose, the total harmonic distortion (THD) of the respective voltage waveform is determined and compared with a specified limit. If the recorded total harmonic distortion (THD) exceeds the limit, the recorded voltage is marked as invalid and not considered in the further process.

[0028] In the following step S_4, the detected voltages or only those considered valid are evaluated to determine the network configuration of the supply voltage network.

[0029] Thus, the configuration of the supply network is determined solely on the basis of the voltages deemed valid in order to optimally control the charger or voltage converter 5, and preferably the DC-DC converter connected to the intermediate connection, depending on the network configuration in order to charge the energy storage device, in particular the high-voltage battery or traction battery, of the motor vehicle. Consequently, the charger 1 is controlled depending on the determined network configuration. In particular, a phase-locked loop algorithm (PLL) is used to recognize the network configuration of the supply network based on parameters derived from the valid voltages. In particular, a phase angle and a frequency of the respectively detected voltage are continuously derived as parameters based on the currently measured (valid) voltages, with an effective value of the respective voltage also being calculated optionally.For example, for a defined market and thus known possible parameters of the supply grid, the respective lower and upper limits can be defined. If all derived parameters are within the defined limits, the voltage is recognized as valid. For example, for a German power grid with a nominal effective voltage of 230V and 50Hz, all voltages between 200V and 260V are recognized as valid if the determined frequency is also between 48Hz and 52Hz.

[0030] The advantageous step S3 ensures that voltages or voltage signals that are not imposed by the supply network, but rather, for example, by crosstalk between adjacent conductors of input terminal 3, are detected as invalid and are not taken into account in the subsequent evaluation in step S4. This advantageously prevents the false detection of a supply network configuration.

[0031] If the AC voltage is recognized as valid, it has the properties of a periodic signal, depending on the PLL algorithm used. This usually includes the effective value (IT) and the current phase angle (α). With these two parameters, the value of a corresponding fundamental wave U can be determined at any time. g be calculated:

[0032] U g = U * 2 * sin(a)

[0033] At the time the signal is sampled from the respective voltage sensor V7, V8, and V9, the current value Um is determined. The total harmonic distortion (THD) is defined as follows according to IEEE Standard 1459-2010: with U m = Effective value of the measured voltage and U g = Effective value of the voltage of the corresponding fundamental wave.

[0034] The effective value of a voltage is defined as follows: with T: period or inverse of the frequency of the fundamental voltage oscillation determined by PLL.

[0035] For a discrete periodic sampling at times ti, as typically implemented in a control unit, For an ideal periodic sampling, Atj = const = At ​​and T = At = n * At Thus:

[0036] The derivation also applies to U g . Since extracting a root on an ECU controller is computationally intensive and THD is used as a binary decision parameter in the present advantageous method, the squared value of THD (THD 2 ) This means that the later

[0037] When applying the decision threshold, the THD threshold, which is also squared, must be used.

[0038] In a software implementation, for example, the sum of the squares of the measured

[0039] voltage and the voltage of the fundamental wave and when a full period is reached after n steps, a current THD 2 Value updated. Because signal U m from signal U g with harmonics, ^F =1 U m 2 > =1 U g 2 . Thus, the THD value 2 with higher proportion of harmonics larger.

[0040] However, this consideration only applies when the respective PLL algorithm has completed its transient response. Thus, the THD 2 Calculation preferably only after valid plausibility checks of other signal parameters, such as the detected frequency or effective voltage, of the PLL algorithm. If the calculated value of THD 2is greater than an applied threshold or the specified limit value, the voltage on the affected phase LI, L2, L3, N, PE is marked as invalid.

[0041] If the PLL algorithm works in such a way that the effective value of the detected fundamental oscillation is very close to the effective value of the measured signal, so that for one period

[0042] U m « U g applies, the calculation rule is preferably switched to the mean squared error (MSE) instead. The MSE value is then calculated for each calculation period:

[0043] Just as with the previously described squaring or THD2 method, the calculated MSE value is compared with an applied threshold or a specified limit. If the limit is exceeded, the voltage at the respective phase is preferably marked as invalid and not considered in step S_4.

[0044] It can thus be seen that the advantageous method prevents false detection of a supply network configuration and thus ensures that the energy storage device is always optimally charged.

Claims

CLAIMS 1. Method for operating a charger (1) for a motor vehicle, in particular an on-board charger of a motor vehicle, wherein the charger (1) has a multi-phase input connection (3) for connection to a multi-phase supply network connection (4), a voltage converter (5), and at least one sensor (V7, V8, V9) for monitoring an electrical voltage of at least one phase (LI, L2, L3, N, PE) of the input connection (3), wherein a network configuration of the supply network connection (4) is determined as a function of at least one detected electrical voltage at a phase (LI, L2, L3, N, PE) of the input connection (3), characterized in that a voltage curve of the monitored voltage is detected and the network configuration of the supply network connection (4) is determined as a function of the voltage curve.

2. Method according to claim 1, characterized in that the respectively monitored voltage curve is recognized as valid if it is sinusoidal, and that only a voltage curve recognized as valid is taken into account for determining the network configuration.

3. Method according to one of the preceding claims, characterized in that in order to detect a sinusoidal shape of the voltage curve, at least one total harmonic distortion (THD) is determined and compared with a predetermined limit value.

4. Method according to one of the preceding claims, characterized in that the total harmonic distortion (THD) is determined as a function of an effective value (Z7) of the measured voltage and the effective value (U g ) of an associated fundamental oscillation (U g ) is determined.

5. Method according to one of the preceding claims, characterized in that the determination of the total harmonic distortion (THD) only takes place when a Phase control loop for determining parameters of the voltage curve has settled, in particular only when a frequency or effective voltage (U, U g ) of the voltage curve were verified.

6. Method according to one of the preceding claims, characterized in that the total harmonic distortion (THD) is determined by squaring (THD 2 ) is determined 7. Method according to one of the preceding claims, characterized in that to determine the total harmonic distortion (THD) a mean square deviation (MSE) is determined when the effective value (U g )) of the fundamental vibration (U g ) corresponds to or nearly corresponds to the effective value (U) of the voltage (U).

8. Charger (1) for a motor vehicle, with a multi-phase input connection (3) for connection to a multi-phase supply network connection (4), with a voltage converter (5) and with at least one sensor (V7, V8, V9) for monitoring an electrical voltage (U) of at least one phase (LI, L2, L3, N, PE) of the input connection (3), characterized by a control device (18) which is specially designed to carry out a method according to one of claims 1 to 7 when used as intended.

9. Energy system (2) for a motor vehicle with at least one electrical energy storage device, characterized in that a charging device (1) according to claim 8 is assigned to the energy storage device.

10. Motor vehicle with an energy system (2) according to claim 9.

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