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

Abstract

The invention relates to a method for operating a charger (1) of a motor vehicle, in particular an on-board charger of a motor vehicle, the charger (1) having a multi-phase input (3) for connection to a multi-phase network connection (4), a voltage converter (5) and at least one sensor (V7, V8, V9) for monitoring the voltage of at least one phase (L1, L2, L3, N, PE) of the input (3), wherein the network configuration of the network connection (4) is determined as a function of at least one voltage detected at a phase (L1, L2, L3, N, PE) of the input (3). According to the invention, a voltage curve of the monitored voltage is detected and a network configuration of the network connection (4) is determined on the basis of the voltage curve.

Description

Technical Field

[0001] The present invention relates to a method for charging a motor vehicle, particularly a method for charging an on-board charger for a motor vehicle, wherein the charger has a multiphase input terminal for connection to a multiphase power grid connection terminal, a voltage converter, and at least one sensor for monitoring the voltage of at least one phase of the input terminal, wherein the power grid configuration of the power grid connection terminal is determined based on at least one voltage detected on one phase of the input terminal.

[0002] Furthermore, the present invention relates to a charger for a motor vehicle, the charger being configured as described above and having a control device for performing the above-described method.

[0003] Furthermore, the present invention relates to an energy system for a motor vehicle having the aforementioned charger, and also to such a motor vehicle. Background Technology

[0004] Globally, power grids exhibit diverse forms, differing from one another in their grid voltage, frequency, and distribution system. With the increasing electrification of motor vehicles, in particular, the demand for chargers is growing. These chargers can connect to different power grids to charge, for example, the energy storage devices of motor vehicles when needed. For instance, a charger for charging high-voltage batteries in electric vehicles can connect to one or more phases of the grid connection to utilize multiple available phases. Such chargers must be able to operate with many different grid configurations. For example, in the German power supply system, a charger can connect to one, two, or three phases. Based on the grid configuration, the charger's control unit selects the optimal operating strategy for the charging process to efficiently charge the energy storage device and avoid damage. Such chargers typically include a voltage converter in addition to the input, which, for example, converts the AC voltage supplied by the grid to a DC voltage suitable for the energy storage device. Such chargers can be constructed as on-board chargers as part of the vehicle's energy system or as standalone chargers that can be carried by the user or connected externally. Identifying the correct grid configuration at the existing grid connection point is crucial for the operational safety and lifespan of the energy storage device to be charged. As is known in the prior art, a voltage converter is assigned to each phase of the input to determine the power grid configuration by evaluating the detected voltage. For this purpose, multiple parameters based on each detected voltage are typically evaluated. These parameters are, for example, absolute voltage and effective voltage, and / or the determined frequency and phase position of the voltage of the corresponding phase. The power grid configuration is then derived by comparing the parameters assigned to the corresponding phase. Summary of the Invention

[0005] The method according to the invention, possessing the features of claim 1, has the advantage of preventing misidentification of the grid configuration. During continuous operation of the charger, a voltage signal may exist due to applied or externally induced voltage on a phase. This voltage signal, while corresponding to the voltage and frequency of the effective grid voltage, does not actually represent the effective grid voltage. The resulting misidentification of the grid configuration may lead to the selection of an inappropriate charging strategy, making the charging process difficult or damaging the energy storage device or charger. For example, even for chargers that can only be connected to a single phase but can theoretically be connected to two or three phases, periodic voltages may be detected on unconnected phases. This may occur, for example, due to signal crosstalk between sensors or due to the voltage applied by the input circuit of the power output stage. If the applied voltage is incorrectly identified as the grid voltage, an incorrect grid configuration is therefore assumed. The method according to the invention ensures that the detected voltage is indeed the grid voltage. To this end, the invention specifies detecting the voltage curve of the monitored voltage and determining the grid configuration at the grid connection point based on the voltage curve. Based on the voltage curve, it can be identified whether it is the supply voltage or an invalid or unexpected voltage. Therefore, by considering this curve, the correct grid configuration is reliably identified. Preferably, the method includes the step of: controlling the charger according to the determined power grid configuration.

[0006] Preferably, a monitored voltage curve is identified as valid when it is a sine wave. Only when a voltage curve is identified as valid is it considered for determining the grid configuration according to the invention. Therefore, if a detected voltage curve is considered invalid, the detected voltage will not be considered for determining the grid configuration and will be ignored. Therefore, it is preferable to compare the detected voltage curve with a sine wave and check whether it is a sine wave.

[0007] Furthermore, it is preferably specified that, in order to detect the sinusoidal nature of the voltage curve, at least one total harmonic distortion (THD) rate is determined and compared with a predetermined limit value. This utilizes the fact that, unlike the voltage of the power grid, the applied voltage, while typically periodic, is not sinusoidal. Therefore, by considering the shape of the voltage curve, it is possible to identify whether the detected voltage should be evaluated as valid or invalid. The THD rate increases with the degree to which the voltage curve deviates from a sinusoidal shape, and is therefore a good standard for evaluating the sinusoidal nature of the detected voltage.

[0008] Furthermore, it is preferably specified that the total harmonic distortion (THD) is determined based on the effective value of the measured voltage and the effective value of the associated fundamental frequency. Using these two parameters, the associated fundamental voltage value can be determined at any time, which is necessary for evaluating the THD.

[0009] Preferably, the determination of the total harmonic distortion (THD) rate is performed only when the phase-locked loop used to determine the voltage curve parameters has reached a steady state, and in particular only when the frequency and / or effective voltage of the voltage curve has been verified as reliable. This ensures that erroneous values ​​are not determined.

[0010] Preferably, the total harmonic distortion (THD) is determined by squaring it. Because the square root operation derived from the definition of THD is computationally very expensive, this method is simplified and accelerated by using the square of the THD. When determining whether the detected voltage curve is a sine wave, the aforementioned squared limit value must also be considered.

[0011] According to an alternative embodiment of the present invention, when the effective value of the fundamental frequency is equal to or approximately equal to the effective value of the voltage, the mean square error is determined instead of the square. If the mean square error exceeds a corresponding predetermined limit value, the voltage detected by the relevant circuit is marked as invalid.

[0012] The charger having the features of claim 8 is characterized in that the controller is specifically configured to execute the method according to the invention when used as intended. This results in the advantages already mentioned above.

[0013] The energy system according to the invention, having the features of claim 9, is characterized by the charger's construction according to the invention. This results in the advantages already mentioned above.

[0014] The motor vehicle having the features of claim 10 is characterized by the energy system according to the invention. This results in the advantages already mentioned above. Attached Figure Description

[0015] Other advantages, preferred features, and combinations of features are particularly apparent from the preceding description and claims. The invention will now be explained in more detail with reference to the accompanying drawings. For this purpose, it is shown that: Figure 1 A simplified illustration shows an advantageous charger for motor vehicles, and Figure 2 A flowchart is shown to explain an advantageous method. Detailed Implementation

[0016] Figure 1 A simplified illustration shows an advantageous charger 1 for an energy system 2 of a motor vehicle (not shown in detail here). The charger 1 has an input terminal 3 on the input side, which is configured as a grid connection terminal 4 for connection to a fixed power grid. For this purpose, the input terminal 3 and the grid connection terminal 4 are configured as plug-in connectors to establish a plug-in connection. The input terminal 3 has connection terminals L1, L2, and L3, a neutral conductor connection terminal N, and a protective earth connection terminal PE.

[0017] Charger 1 also includes a voltage converter 5 configured to provide a DC voltage according to the connected power grid, preferably at an intermediate connection terminal 6. Preferably, the voltage converter 5 is configured as a PFC (Power-Factor-Correction-Stufe) stage. Preferably, the intermediate connection terminal 6 includes a positive intermediate connection terminal and a negative intermediate connection terminal. An intermediate circuit capacitor or a series circuit of a first intermediate circuit capacitor 14 and a second intermediate circuit capacitor 15 is preferably connected between the positive and negative intermediate connection terminals. A DC voltage converter (not shown) is preferably connected at the intermediate connection terminal 6. The DC voltage at the intermediate connection terminal 6, which is attached to the DC voltage converter on the input side, is preferably converted into a charging voltage for charging an energy storage device (preferably a battery, traction battery, or high-voltage battery) that can be connected to the output side of the DC voltage converter. Therefore, the energy storage device of the motor vehicle connected to charger 1 can be charged using this charging voltage. Therefore, the voltage converter 5 preferably has three half-bridges 7, 8, and 9, each half-bridge comprising two series-connected semiconductor switches 7H, 7L and 8H, 8L and 9H, 9L, one configured as a high-side switch (H) and the other as a low-side switch (L). Preferably, the half-bridges 7, 8, and 9 and the intermediate connection terminal 6 are electrically connected in parallel, wherein each half-bridge 7, 8, and 9 has a midpoint tap between its respective semiconductor switches 7H, 7L, 8H, 8L, 9H, and 9L, which is connected to one of the connection terminals L1, L2, or L3 via inductors or resistors 10, 11, and 12. The voltage converter 5 also has an intermediate circuit 13, which has an intermediate circuit capacitor or a series circuit of a first intermediate circuit capacitor 14 and a second intermediate circuit capacitor 15, and is electrically connected in parallel with the half-bridges 7, 8, and 9. Preferably, two freewheeling diodes 16 and 17 are connected in parallel with the intermediate circuit capacitors 14 and 15. Freewheeling diodes 16 and 17 are connected in a blocking direction to prevent current from flowing from the high side to the low side of voltage converter 5, wherein the midpoint tap between diodes 16 and 17 is connected to the neutral conductor N. Preferably, voltage converter 5 is connected to input terminal 3 on the input side and to intermediate connection terminal 6 on the output side. Preferably, intermediate connection terminal 6 is connected in parallel with half-bridges 7, 8, and 9, or with intermediate loop capacitors, or with a series circuit consisting of first and second intermediate loop capacitors 14 and 15.

[0018] The charger 1 preferably also includes a first switching element S1, which selectively connects the half-bridge 7 to the connection terminal L1. Furthermore, the charger 1 preferably includes a second switching element S2, which connects the third half-bridge 9 to the connection terminal L1 or the first phase of the voltage converter 5 in a first switching position, and connects the third half-bridge 9 to the connection terminal L3 or the third phase of the input terminal 3 in a second switching position. Additionally, the charger 1 preferably includes a third switching element S3, which selectively connects the second half-bridge 8 to the connection terminal L2. Preferably, a fourth switching element S4 can be used to selectively connect the midpoint tap between diodes 16 and 17 to the midpoint tap between the first intermediate circuit capacitor 14 and the second intermediate circuit capacitors 14 and 15.

[0019] Furthermore, the charger 1 preferably has a voltage sensor V7, V8, V9 assigned to each of the respective half-bridges 7, 8, 9. This voltage sensor is connected between the corresponding phase and neutral conductor connection terminal N of the voltage converter 5 to detect the voltage of each connection terminal L1, L2, L3 relative to the neutral conductor connection terminal N. Preferably, current sensors A10, A11, A12 are assigned to the inductors or resistors 10, 11, 12, respectively.

[0020] The charger 1 also has a controller 18 configured to operate the semiconductor switches of the voltage converter 5 and monitor the values ​​detected by voltage sensors V7-V9 and / or current sensors A10-A12.

[0021] The controller 18 is specifically configured to perform the following method. Therefore, Figure 2 An exemplary flowchart is shown, which can be used to explain this advantageous method.

[0022] The method begins with the startup of charger 1 in step S_1, at which point input terminal 3 is connected to the power grid connection terminal 4.

[0023] In the subsequent step S_2, voltage sensors V7-V9 are used to detect the voltage curves of the monitored phases L1, L2, and L3.

[0024] In the subsequent step S_3, it is checked whether the corresponding detected voltage curve is a sinusoidal waveform. To do this, the total harmonic distortion (THD) of each voltage curve is determined and compared with a predetermined limit value. If the detected THD exceeds the limit value, the detected voltage is marked as invalid and is not considered in subsequent methods.

[0025] In the subsequent step S_4, the voltages that are considered to be validly detected (or only these voltages are evaluated) are assessed to determine the grid configuration of the power grid.

[0026] Therefore, the grid configuration is determined solely based on the voltage considered valid, so that the charger, or voltage converter 5, can be optimally controlled according to this grid configuration, and preferably the DC-DC voltage converter connected to the intermediate connection terminal, to charge the vehicle's energy storage device (especially the high-voltage battery or traction battery). Thus, the charger 1 is controlled according to the determined grid configuration. Specifically, a phase-locked loop (PLL) algorithm is used to identify the grid configuration based on parameters derived from the valid voltage. Therefore, specifically based on the currently measured (valid) voltage, the phase angle and frequency of the corresponding detected voltage are continuously derived as parameters, where optionally the valid value of the corresponding voltage is also calculated. For example, lower and upper limits can be defined for known possible parameters of the defined market, and thus the grid. If all derived parameters are within the defined limits, the voltage is identified as valid. For example, for a German grid with a nominal valid voltage of 230V and a frequency of 50Hz, if the additionally determined frequency is between 48Hz and 52Hz, then all voltages between 200V and 260V are identified as valid.

[0027] This is achieved through the advantageous step S_3, whereby voltages or voltage signals not applied by the power grid, but caused, for example, by crosstalk between adjacent conductors at input 3, are detected as invalid and disregarded in the subsequent evaluation in step S_4. This advantageously prevents misidentification of the power grid configuration.

[0028] When an AC voltage is identified as valid, it exhibits the characteristics of a periodic signal, depending on the PLL algorithm used. This typically includes, in particular, the effective value (...). The fundamental frequency U can be calculated at any time using these two parameters: the fundamental frequency U and the current phase angle (α). g Value: At the time points when the signals from the corresponding voltage sensors V7, V8, and V9 are sampled, the current value U is determined. m Total Harmonic Distortion (THD) is defined according to IEEE standard 1459-2010 as follows: in = The effective value of the measured voltage. = The effective value of the associated fundamental voltage.

[0029] The effective value of voltage is defined as follows: Where T: the period duration or the reciprocal of the voltage's inherent oscillation frequency determined by the PLL.

[0030] When performing discrete periodic sampling at time point ti (which is typically performed in the controller), the applicable approach is: Here, the ideal periodic sampling is applicable. as well as .

[0031] Therefore, the following occurred: This derivation also applies to U. g Since the square root operation at the controller is computationally intensive, and THD is used as a binary decision parameter in the currently advantageous methods, the squared value of THD is preferred to be used subsequently. 2 This requires further processing. This means that when applying the decision threshold subsequently, the same squared THD threshold must be used. Therefore, it applies to: In software implementation, for example, the sum of squares of the measured voltage and the fundamental voltage can be obtained, and the current THD can be updated when a complete cycle is reached after n steps. 2 Value. Due to signal U m From signal U g Including harmonic components, therefore .

[0032] Therefore, the higher the harmonic component, the higher the THD. 2 The larger the value, the better.

[0033] However, this consideration only applies to the case where the transient process of the corresponding PLL algorithm ends. Therefore, THD 2 The calculation is preferably performed only after other signal parameters of the PLL algorithm (such as the identified frequency or effective voltage) have been effectively verified. If the calculated THD... 2 If the value is greater than the applied threshold or predetermined limit, the voltage on the corresponding affected phases L1, L2, L3, N, and PE will be marked as invalid.

[0034] If the PLL algorithm operates in a way that makes the effective value of the identified inherent oscillation very close to the effective value of the measured signal, then it is suitable for the period: , The preferred calculation rule is to use mean squared error (MSE). Then, the MSE value for each calculation period is calculated as follows: Compared to the previously described square or THD 2Similarly, the calculated MSE value should be compared with the applied threshold or predetermined limit value. If the limit value is exceeded, the voltage on the corresponding phase should preferably be marked as invalid and not considered in step S_4.

[0035] This demonstrates that this advantageous method prevents misidentification of the grid configuration, thereby ensuring optimal charging of the energy storage device at all times.

Claims

1. A method for a charger (1) for operating a motor vehicle, particularly an on-board charger for a motor vehicle, wherein the charger (1) comprises: a multiphase input terminal (3) for connection to a multiphase power grid connection terminal (4), a voltage converter (5), and at least one sensor (V7, V8, V9) for monitoring the voltage of at least one phase (L1, L2, L3, N, PE) of the input terminal (3), wherein the power grid configuration of the power grid connection terminal (4) is determined based on at least one voltage detected on one phase (L1, L2, L3, N, PE) of the input terminal (3). Its features are, The voltage curve of the monitored voltage is detected, and the grid configuration of the grid connection terminal (4) is determined based on the voltage curve.

2. The method according to claim 1, characterized in that, A voltage curve is considered valid only when the corresponding monitored voltage curve is a sine wave; and only voltage curves that are considered valid are considered for determining the power grid configuration.

3. The method according to any one of the preceding claims, characterized in that, To detect the sine wave of the voltage curve, at least one total harmonic distortion (THD) is determined and the THD is compared with a predetermined limit value.

4. The method according to any one of the preceding claims, characterized in that, The total harmonic distortion (THD) is based on the effective value of the measured voltage ( ) and related inherent oscillations (U g ) effective value ( To determine.

5. The method according to any one of the preceding claims, characterized in that, When the phase-locked loop used to determine the parameters of the voltage curve has entered a steady state, especially when the frequency or effective voltage of the voltage curve ( , The determination of the total harmonic distortion (THD) is only performed when it has been verified as reliable.

6. The method according to any one of the preceding claims, characterized in that, By squaring (THD) 2 The total harmonic distortion (THD) is determined by this method.

7. The method according to any one of the preceding claims, characterized in that, To determine the total harmonic distortion (THD), when the inherent oscillation (U) g ) effective value ( ) is equal to or approximately equal to the effective value of the voltage (U) When ), determine the mean square error (MSE).

8. A charger (1) for a motor vehicle, the charger having a multiphase input terminal (3) for connection to a multiphase power grid connection terminal (4), a voltage converter (5), and at least one sensor (V7, V8, V9) for monitoring the voltage (U) of at least one phase (L1, L2, L3, N, PE) of the input terminal (3), characterized in that A controller (18) specifically configured to perform the method according to any one of claims 1 to 7 when used as prescribed.

9. An energy system (2) for a motor vehicle, said energy system having at least one electrical energy storage device, characterized in that, The energy storage device is equipped with a charger (1) according to claim 8.

10. A motor vehicle having an energy system (2) according to claim 9.

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