Charging current adjusting method and alternating current charging pile thereof

Abstract

The invention discloses a charging current adjusting method which is applied to an alternating current charging pile of a new energy automobile. The method comprises the following steps: when the AC charging pile is connected to the new energy vehicle to form a charging loop, detecting and acquiring a no-load voltage of a vehicle end; when the charging current in the charging loop is stable, the load voltage of a vehicle end and the current charging current are detected and obtained; calculating the line impedance of the charging loop according to the load voltage, the no-load voltage and the current charging current; calculating a charging current upper limit value according to the line impedance and a preset voltage drop threshold value; and adjusting the charging current to be less than or equal to the charging current upper limit value.

Description

Technical Field

[0001] This application relates to the technical field of new energy vehicle charging, and particularly to a charging current regulation method and its AC charging pile. Background Art

[0002] With the rapid development of the new energy vehicle industry, AC charging piles, as important charging infrastructure, have begun to be widely used. During actual use, after the AC charging pile establishes an electrical connection line with the new energy vehicle through a cable, it provides an AC power supply to the on-board charger (OBC) with a set fixed current value and rated voltage, and the on-board charger then converts the AC power into DC power to charge the power battery of the new energy vehicle.

[0003] Generally, the AC charging pile operates in a fixed current output mode during charging, continuously outputting the set charging current. Although this fixed current output mode can ensure a stable charging power under ideal conditions, it has obvious limitations in practical applications.

[0004] For example, since the connection cables used by the AC charging pile may have different lengths due to different sites and actual situation requirements. Therefore, when the length of the connection cable changes significantly, it will cause a significant change in the voltage drop in the charging circuit. Keeping the output current of the AC charging pile unchanged will affect the charging efficiency and pose a safety hazard.

[0005] Moreover, when the voltage drop in the charging circuit is too large, it will cause a significant reduction in the actual voltage provided to the on-board charger. When the provided actual voltage exceeds the working voltage range of the on-board charger (the working voltage ranges of many on-board chargers are relatively narrow, such as ±10% of the nominal value), the charging protection mechanism will be triggered, resulting in an accidental interruption of the charging process and seriously affecting the user charging experience.

[0006] To overcome such problems, some existing AC charging piles provide a function of setting line parameters, supporting technicians to manually preset line parameters to adapt to and compensate for the voltage drop changes caused by different connection cable lengths. However, such a method is cumbersome to operate and requires professional personnel to set one by one, increasing the operation and maintenance costs and the difficulty of use. Summary of the Invention

[0007] The embodiments of this application provide a charging current regulation method and its AC charging pile, aiming to solve the defect that the existing AC charging piles cannot automatically adapt to connection cables of different lengths.

[0008] In a first aspect, an embodiment of the present application provides a method for adjusting a charging current, which is applied to an AC charging pile of a new energy vehicle. The method for adjusting the charging current includes: when the AC charging pile is connected to the new energy vehicle to form a charging circuit, detecting and obtaining the no-load voltage at the vehicle end; when the charging current in the charging circuit is stable, detecting and obtaining the load voltage at the vehicle end and the current charging current; calculating the line impedance of the charging circuit according to the load voltage, the no-load voltage, and the current charging current; calculating an upper limit value of the charging current according to the line impedance and a preset voltage drop threshold; and adjusting the charging current to be less than or equal to the upper limit value of the charging current.

[0009] Optionally, the calculating the line impedance of the charging circuit according to the load voltage, the no-load voltage, and the current charging current specifically includes: calculating the line impedance of the charging circuit through the following formula:

[0010]

[0011] wherein, R line is the line impedance, V1 is the no-load voltage, V2 is the load voltage, and I is the current charging current.

[0012] Optionally, the calculating the upper limit value of the charging current according to the line impedance and the preset voltage drop threshold specifically includes:

[0013]

[0014] wherein, I max is the upper limit value of the charging current, ΔV max is the preset voltage drop threshold, and R line is the line impedance.

[0015] Optionally, the preset voltage drop threshold is 5% to 10% of the rated charging voltage of the AC charging pile.

[0016] Optionally, the adjusting the charging current to be less than or equal to the upper limit value of the charging current specifically includes: reducing the charging current to be less than or equal to the upper limit value of the charging current by adjusting the output power of the AC charging pile.

[0017] Second aspect, an embodiment of the present application provides an AC charging pile. The AC charging pile includes: a voltage detection module for detecting and obtaining the no-load voltage and the load voltage of the vehicle end; a current detection module for detecting and obtaining the charging current; a control module, the control module is respectively connected to the voltage detection module and the current detection module, and is used to calculate the line impedance according to the load voltage and the no-load voltage obtained by the voltage detection module, and the current charging current obtained by the current detection module, and calculate the upper limit value of the charging current according to the line impedance and a preset voltage drop threshold; a power adjustment module, the power adjustment module is connected to the control module and is used to dynamically adjust the output power so that the charging current is less than or equal to the upper limit value of the charging current.

[0018] Optionally, the power adjustment module is specifically used for: dynamically adjusting the output power by adjusting the duty cycle of the PWM signal.

[0019] At least one beneficial effect of the present application is that by automatically calculating the line impedance by real-time detecting the no-load voltage and the load voltage, the upper limit value of the current charging current can be automatically determined and the charging current can be adjusted accordingly, ensuring that the voltage at the charging port always remains within the working range of the on-vehicle charger, effectively avoiding the problem of charging interruption caused by excessive line voltage drop, and improving the safety and efficiency of the charging process. During the whole adjustment process, there is no need to preset parameters manually, significantly simplifying the debugging and use process of the charging pile and improving the usability of the device. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the charging circuit provided by the embodiment of the present application;

[0021] Figure 2 It is a flowchart of the method for adjusting the charging current provided by the embodiment of the present application;

[0022] Figure 3 It is a functional block diagram of the AC charging pile provided by the embodiment of the present application. Detailed Embodiments

[0023] For the convenience of understanding the present application, the present application will be described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is described as "connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "upper", "lower", "inner", "outer", "bottom", etc. used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present application. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0024] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in this specification in the description of the present application are only for the purpose of describing specific embodiments and are not used to limit the present application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0025] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0026] Figure 1 The figure is a schematic diagram of the charging circuit provided for the embodiment of the present application. As Figure 1 shown, when the AC charging pile establishes a physical connection with the charging socket of the new energy vehicle through the connection cable, a charging circuit is formed between the two.

[0027] In this charging circuit, the AC charging pile is the AC power supply 10, which outputs a set voltage and current. The on-vehicle charger of the new energy vehicle is the power receiving end 20, which receives alternating current through the charging circuit (live wire L and neutral wire N) and converts it into direct current to charge the power battery. For the convenience of description below, the power receiving end 20 is called the "vehicle end", and the AC power supply 10 is called the "power supply end".

[0028] Figure 2 The figure is a flowchart of the method for adjusting the charging current provided for the embodiment of the present application. It can be applied to Figure 1 the charging circuit shown to realize the automatic adjustment of the charging current. As Figure 2 shown, the method for adjusting the charging current includes:

[0029] S100. Detect and obtain the no-load voltage.

[0030] Among them, the no-load voltage refers to the voltage at the vehicle end detected during the pre-charge phase after the AC charging pile is connected to the new energy vehicle to form a charging circuit.

[0031] The pre-charge phase is a preparation phase before formal charging after the AC charging pile establishes a physical connection with the new energy vehicle and completes the charging handshake. During this pre-charge phase, the AC charging pile will perform a series of safety detections and parameter acquisitions, including insulation detection, grounding detection, and measurement of various electrical parameters.

[0032] Since there is basically no current flowing through the charging circuit at this time (no-load or very small current), the no-load voltage detected reflects the actual voltage level at the output end of the charging pile and basically does not include the line voltage drop caused by the charging current.

[0033] S200. Detect and obtain the load voltage and the current charging current.

[0034] Among them, the load voltage is the voltage at the vehicle end detected when the charging current in the charging circuit reaches a stable state during the charging phase.

[0035] The charging phase is the working phase when the AC charging pile starts to output the charging current to the on-board charger after completing various safety detections in the pre-charge phase. During the working phase, the charging current gradually reaches a stable state (that is, the fluctuation range of the charging current is within the allowable range). At this time, the detected load voltage reflects the voltage drop generated by the charging current flowing through the line impedance of the charging current.

[0036] S300. Calculate the line impedance of the charging circuit according to the load voltage, no-load voltage, and the current charging current.

[0037] Among them, the line impedance refers to the electrical impedance characteristics presented by the power supply line from the power supply end to the vehicle end, which includes the comprehensive impedance of components such as the charging cable, connector, and contact point.

[0038] During AC charging, when current flows through a line with impedance characteristics, a voltage drop will be generated on the line. As mentioned above, the difference between the aforementioned no-load voltage and the load voltage can be considered as the voltage drop generated by the line impedance of the charging circuit. Dividing this voltage drop by the charging current when the voltage drop is generated can calculate the actual impedance value of the charging circuit.

[0039] Specifically, the line impedance of the charging circuit can be calculated by the following formula (1):

[0040]

[0041] Among them, R line is the line impedance, V1 is the no-load voltage, V2 is the load voltage, and I is the current charging current

[0042] S400. Calculate the upper limit value of the charging current according to the line impedance and the preset voltage drop threshold value.

[0043] Among them, the preset voltage drop threshold value is preset by technicians according to actual needs, and is the maximum voltage drop that can ensure the safe and stable progress of the charging process. For example, the preset voltage drop threshold value is 5% to 10% of the rated charging voltage of the AC charging pile to ensure that it does not exceed the voltage tolerance range of the on-vehicle charger.

[0044] Specifically, the upper limit value of the charging current can be obtained by calculating with the following formula (2):

[0045]

[0046] Among them, I max is the upper limit value of the charging current, ΔV max is the preset voltage drop threshold value, and R line is the line impedance.

[0047] S500. Adjust the charging current to be less than or equal to the upper limit value of the charging current.

[0048] Specifically, when the rated charging voltage of the AC charging pile remains unchanged, the output charging current can be changed by adjusting the output power of the AC charging pile, so that the charging current is reduced to the upper limit value of the charging current.

[0049] Figure 3 This is the functional block diagram of the AC charging pile provided by the embodiment of the present application. As Figure 3 shown, the AC charging pile 10 includes: a voltage detection module 11, a current detection module 12, a control module 13, and a power adjustment module 14.

[0050] Among them, the voltage detection module 11 is used to detect and obtain the no-load voltage at the vehicle end during the pre-charging stage, and detect and obtain the load voltage at the vehicle end during the charging stage. The current detection module 12 is used to detect and obtain the charging current during the charging stage.

[0051] The control module 13 is respectively connected to the voltage detection module 11 and the current detection module 12, and can receive the no-load voltage, the load voltage, and the charging current. The control module 13 is used to calculate the line impedance according to the load voltage, the no-load voltage, and the current charging current, and calculate the upper limit value of the charging current according to the line impedance and the preset voltage drop threshold value.

[0052] The power regulation module 14 is connected to the control module 13 and receives control instructions from the control module 13. When the power regulation module 14 receives the control instruction corresponding to the upper limit value of the charging current, it is used to dynamically adjust the output power so that the charging current is less than or equal to the upper limit value of the charging current.

[0053] Specifically, the power regulation module 14 can dynamically adjust the output power by adjusting the duty cycle of the PWM signal, so that the output charging current is equal to the upper limit value of the charging current.

[0054] The charging current adjustment method and its AC charging pile provided in the embodiments of the present application implement a closed-loop feedback mechanism for line impedance measurement and charging current control. There is no need to manually input line parameters in advance, and the line impedance can be automatically obtained and the charging current can be adjusted accordingly, ensuring the safety, reliability and efficiency of new energy vehicle charging, and effectively improving the usage experience during the charging process.

[0055] In order to fully describe the inventive concept and technical effects of the present application, the efficiency difference between the AC charging pile of the present application and the traditional AC charging pile will be described in detail below by taking the cable tray wiring scenario in a common residential community as an example.

[0056] 1) AC charging pile and connection cable parameters:

[0057] The AC charging pile is a 7kW AC charging pile for a 220V system;

[0058] The connection cable uses a 150-meter 6-square millimeter copper core cable;

[0059] Therefore, the one-way line resistance is:

[0060]

[0061] The total resistance (neutral and live wires) of the charging circuit is:

[0062] R total = 2 × 0.43Ω = 0.86Ω

[0063] 2) Comparison of the actual charging process:

[0064] 2.1) When using the fixed current output mode:

[0065] The theoretical full-load current is:

[0066]

[0067] The heating power of the charging circuit is:

[0068] P loss = I 2 ·R = 32 2×0.86 = 880.6W

[0069] The charging time is:

[0070]

[0071] 2.2) When using the charging current adjustment method of the present application:

[0072] The preset voltage drop threshold is:

[0073] ΔV max = 220V × 10% = 22V

[0074] The upper limit value of the charging current is:

[0075]

[0076] Adjust the charging current (32A) to the upper limit value of the charging current (25.6A), and the heating power of the charging circuit is:

[0077] P' loss = 25.6 2 ×0.86 = 562.0W

[0078] Adjust the charging current (32A) to the upper limit value of the charging current (25.6A), and the charging time is:

[0079]

[0080] 2.3) Energy consumption comparison result:

[0081] The reduction in heat generation when using the charging current adjustment method of the present application is:

[0082]

[0083] The reduction rate of loss when using the charging current adjustment method of the present application is:

[0084]

[0085] 3) Actual application effect:

[0086] In the scenario of using a 150-meter connection cable, when using the charging current adjustment method of the present application, the surface temperature of the connection cable can be reduced by more than 20°C.

[0087] Using the charging current adjustment method of the present application can effectively avoid the voltage at the vehicle end being lower than 198V (220V - 10%) due to excessive voltage drop, and ensure the normal operation of the on-vehicle charger.

[0088] Calculated based on the daily charging usage time of the AC charging pile being 4 hours, the electrical energy that can be saved by each AC charging pile every year is as follows:

[0089] (880.6W - 562.0W) × 4h × 365 = 185.2kWh

[0090] The above description is only the implementation manner of this application, and does not limit the patent scope of this application accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of this application.

Claims

1. A charging current adjustment method, applied to an AC charging pile of a new energy vehicle, characterized in that, The method includes: When the AC charging pile is connected to the new energy vehicle to form a charging circuit, detecting and obtaining the no-load voltage at the vehicle end; When the charging current in the charging circuit is stable, detecting and obtaining the load voltage at the vehicle end and the current charging current; Calculating the line impedance of the charging circuit according to the load voltage, no-load voltage, and current charging current; Calculating the upper limit value of the charging current according to the line impedance and a preset voltage drop threshold; Adjusting the charging current to be less than or equal to the upper limit value of the charging current.

2. The charging current adjustment method according to claim 1, wherein The calculating the line impedance of the charging circuit according to the load voltage, no-load voltage, and current charging current specifically includes: Calculating the line impedance of the charging circuit through the following formula: Among them, R line is the line impedance, V1 is the no-load voltage, V2 is the load voltage, and I is the current charging current.

3. The charging current adjustment method according to claim 1, characterized in that The calculating the upper limit value of the charging current according to the line impedance and a preset voltage drop threshold specifically includes: Wherein, I max is the upper limit value of the charging current, and ΔV max is the preset voltage drop threshold, and R line is the line impedance.

4. The charging current adjustment method according to claim 1, wherein, The preset voltage drop threshold is 5% to 10% of the rated charging voltage of the AC charging pile.

5. The charging current regulation method according to claim 1, wherein The adjusting the charging current to be less than or equal to the upper limit value of the charging current specifically includes: Reducing the charging current to be less than or equal to the upper limit value of the charging current by adjusting the output power of the AC charging pile.

6. An AC charging pile, characterized in that, It includes: A voltage detection module for detecting and obtaining the no-load voltage and load voltage at the vehicle end; A current detection module for detecting and obtaining the charging current; A control module, which is respectively connected to the voltage detection module and the current detection module, and is used for calculating the line impedance according to the load voltage and no-load voltage obtained by the voltage detection module, and the current charging current obtained by the current detection module, and calculating the upper limit value of the charging current according to the line impedance and a preset voltage drop threshold; A power regulation module, which is connected to the control module and is used for dynamically adjusting the output power so that the charging current is less than or equal to the upper limit value of the charging current.

7. The AC charging pile according to claim 6, characterized in that, The power regulation module is specifically used for: dynamically adjusting the output power by adjusting the duty cycle of the PWM signal.

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