Charging process monitoring method and device of direct current charging equipment

Abstract

The invention relates to the technical field of charging pile fault analysis, and particularly provides a charging process monitoring method and device for direct current charging equipment, and the method comprises the steps: obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of the charging equipment; fitting based on acquired charging equipment output current / voltage data to obtain a time constant in a curvilinear function corresponding to the current / voltage attenuation curve; and adjusting the sampling frequency of the direct current charging equipment based on the time constant, and carrying out current / voltage sampling monitoring. According to the technical scheme provided by the invention, the time scale when the charging equipment is abnormal is analyzed, and the time scale required for observing the transient fault information is confirmed. The method provides guidance for developing hardware equipment, effectively reduces the number of tests, shortens the development period, and improves the development efficiency and the fault monitoring capability of charging equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of charging pile fault analysis, and in particular to a charging process monitoring method and device for direct current charging equipment. Background Art

[0002] Early-built high-power charging facilities for electric vehicles have been in operation for a long time, and there are aging equipment and internal hardware failures, which lead to abnormal failures during the charging process, affecting the user's charging experience. Abnormal failures are often transient processes. In order to observe transient abnormal operating condition data, it is necessary to confirm the time scale of abnormal failures in advance, and then guide the design of the sampling frequency of the charging equipment hardware.

[0003] During the charging process of electric vehicles, the charging process is led by the electric vehicle BMS, which sends information such as required voltage, required current, and required power to the charging pile, and the charging pile matches the BMS charging requirements based on its own output capacity. Although the charging technology standard system has made relatively comprehensive specifications for the charging process, control guidance, communication protocol, etc., the charging pile industry has many equipment manufacturers and complex models, and the charging demand characteristics, battery characteristics, and in-vehicle protection strategies on the vehicle demand side vary greatly under different models, resulting in complex changes in electric vehicle charging conditions. Based on the existing monitoring capabilities of vehicles and piles for the charging process, it is still impossible to reliably trace accidents for abnormal charging events, resulting in unclear accident mechanisms and difficulty in effectively avoiding similar accidents.

[0004] In recent years, there have been many cases of instantaneous overcurrent during charging. Due to the ineffective connection of the protection sensitivity of the vehicle and the charging pile, accidents such as vehicle fuse blowing have occurred frequently. According to the analysis of the charging process of electric vehicles, DC contactor jitter may be caused by reasons such as contactor failure, abnormal operation of the contactor or intermediate relay control power supply, and EMC interference. Contactor jitter is a transient process of closing → disconnecting → closing. When the contactor is disconnected, the charger is still in the state of energized output. The X capacitor at the back end of the charging module will accumulate electricity. After the contactor is closed again, the X capacitor will release the accumulated electricity, resulting in instantaneous overcurrent. Because the vehicle's ohmic internal resistance is small during charging and the X capacitor is uf level, the instantaneous current is large, the decay is fast, and the energy is low.

[0005] For such instantaneous large currents, charging piles use energy-triggered thermal fuses for protection, and some vehicles use signal-triggered explosive fuses for protection. Because the protection strategies are not coordinated, explosive fuses in the vehicle often explode. At present, the monitoring cycle of charging piles in different charging processes varies from 10ms to 250ms, which cannot support the analysis of such events. If the sampling frequency of the charging equipment hardware is too low, the transient process of the abnormality cannot be observed. If the sampling frequency is too high, the equipment development cost will be too high. Therefore, it is necessary to propose a time scale analysis method for the abnormal process of charging equipment to guide the hardware development of charging equipment. Summary of the invention

[0006] In order to overcome the above-mentioned defects, the present invention proposes a charging process monitoring method and device for a DC charging device.

[0007] In a first aspect, a method for monitoring a charging process of a DC charging device is provided, the method comprising:

[0008] Obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device;

[0009] The time constant in the curve function corresponding to the current / voltage decay curve is obtained by fitting based on the collected output current / voltage data of the charging device;

[0010] The sampling frequency of the DC charging device is adjusted based on the time constant, and current / voltage sampling monitoring is performed.

[0011] Preferably, the step of obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device includes:

[0012] During the charging process of the charging device, a switch is used to simulate a circuit-breaking and then reconnecting fault during the charging process of the charging device, and the output current / voltage curve of the charging device is collected;

[0013] The output current / voltage curve is intercepted from the corresponding curve between the charging recovery connection moment and the charging current stabilization moment.

[0014] Preferably, the curve function corresponding to the current decay curve is as follows:

[0015]

[0016] In the above formula, I is the real-time charging current, I L To stabilize the charging current, V out is the output voltage of the charging device, V ocv is the open circuit voltage value of the vehicle battery system, R sis the internal resistance of the battery, e is a natural constant, t is a time constant, t is the current moment, and t1 is the moment when charging is restored and connected.

[0017] Furthermore, the curve function corresponding to the voltage attenuation curve is as follows:

[0018]

[0019] In the above formula, V c is the real-time charging voltage.

[0020] Preferably, the time constant in the curve function corresponding to the current / voltage decay curve obtained by fitting the collected output current / voltage data of the charging device includes:

[0021] Based on the collected output current / voltage data of the charging device, a least squares algorithm is used to fit the time constant in the curve function corresponding to the current / voltage decay curve.

[0022] Preferably, the sampling frequency of the DC charging device is adjusted as follows:

[0023]

[0024] In the above formula, k is the sampling frequency of the DC charging device, and T is the sampling period of the DC charging device.

[0025] Furthermore, the sampling period of the DC charging device satisfies:

[0026] T≤-tln(1-rate)

[0027] In the above formula, t is the time constant and rate is the signal attenuation rate.

[0028] In a second aspect, a charging process monitoring device for a DC charging device is provided, wherein the charging process monitoring device for a DC charging device comprises:

[0029] An acquisition module, used to acquire a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device;

[0030] A fitting module, used for fitting the collected output current / voltage data of the charging device to obtain a time constant in a curve function corresponding to the current / voltage decay curve;

[0031] The sampling module is used to adjust the sampling frequency of the DC charging device based on the time constant and perform current / voltage sampling monitoring.

[0032] In a third aspect, a computer device is provided, comprising: one or more processors;

[0033] The processor is configured to execute one or more programs;

[0034] When the one or more programs are executed by the one or more processors, the charging process monitoring method of the DC charging device is implemented.

[0035] In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed, the charging process monitoring method of the DC charging device is implemented.

[0036] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0037] The present invention provides a method and device for monitoring the charging process of a DC charging device, including: obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device; fitting a time constant in a curve function corresponding to the current / voltage attenuation curve based on the collected output current / voltage data of the charging device; adjusting the sampling frequency of the DC charging device based on the time constant, and performing current / voltage sampling monitoring. The technical solution provided by the present invention analyzes the time scale of abnormalities in the charging device and confirms the time scale required for observing transient fault information. It provides guidance for the development of hardware equipment, effectively reduces the number of tests, shortens the development cycle, and improves development efficiency and charging equipment fault monitoring capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic flow chart of the main steps of the method for monitoring the charging process of a DC charging device according to an embodiment of the present invention;

[0039] Figure 2 is an equivalent model diagram of a battery system and a charging device according to an embodiment of the present invention;

[0040] Figure 3 is an abnormal output current curve of a charging device according to an embodiment of the present invention;

[0041] Figure 4 1 is the fault current and fitting curve of the charging device according to the embodiment of the present invention. DETAILED DESCRIPTION

[0042] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] See attached Figure 1 , Figure 1 FIG. 1 is a flow chart showing the main steps of a method for monitoring the charging process of a DC charging device according to an embodiment of the present invention. Figure 1 As shown, the charging process monitoring method of the DC charging device in the embodiment of the present invention mainly includes the following steps:

[0046] Step S101: obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device;

[0047] Step S102: fitting the collected output current / voltage data of the charging device to obtain a time constant in a curve function corresponding to the current / voltage decay curve;

[0048] Step S103: adjusting the sampling frequency of the DC charging device based on the time constant, and performing current / voltage sampling monitoring.

[0049] In this embodiment, first (1) an equivalent model of the battery system and the charging device is established. Figure 2 On the left is the Rint equivalent circuit model of the battery system. According to Kirchhoff's law, the time domain equation mathematical model shown in the equation is established.

[0050] V t (t) = V ocv (t)+I(t)R s

[0051]

[0052] Where t is the current time, I(t) is the load current at time t, V t (t) is the terminal voltage at time t, η is the coulombic efficiency of the battery, Q is the rated capacity of the battery system, z(t) is the SOC of the battery system at time t, V ocv (t) represents the open circuit voltage value of the vehicle battery system at time t, R s Represents the internal resistance of the battery system, I L Indicates the stable charging current output by the charging device, C X Indicates the capacitance of the X capacitor, V x is the voltage across the X capacitor, I C Indicates the partial abnormal current value caused by the fault of the charging device X capacitor, V out is the output voltage of the charging device.

[0053] In this embodiment, the step of obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device includes:

[0054] During the charging process of the charging device, a switch is used to simulate a circuit-breaking and then reconnecting fault during the charging process of the charging device, and the output current / voltage curve of the charging device is collected;

[0055] The output current / voltage curve is intercepted from the corresponding curve between the charging recovery connection moment and the charging current stabilization moment.

[0056] In one embodiment, the output current curve of the charging device is as follows: Figure 3 As shown, a circuit breaker fault occurs at time t0, and the charging current changes from I L becomes 0; the connection is restored at time t1. Due to the additional output current of the X capacitor, a current decay curve is formed from time t1 to t2. From this, it is derived that the curve function corresponding to the current decay curve is as follows:

[0057]

[0058] In the above formula, I is the real-time charging current, I L To stabilize the charging current, V out is the output voltage of the charging device, V ocv is the open circuit voltage value of the vehicle battery system, R s is the internal resistance of the battery, e is a natural constant, t is a time constant, t is the current moment, and t1 is the moment when charging is restored and connected.

[0059] The curve function corresponding to the voltage decay curve is as follows:

[0060]

[0061] In the above formula, V c is the real-time charging voltage.

[0062] In this embodiment, the time constant in the curve function corresponding to the current / voltage decay curve obtained by fitting the collected output current / voltage data of the charging device includes:

[0063] Based on the collected output current / voltage data of the charging device, a least squares algorithm is used to fit the time constant in the curve function corresponding to the current / voltage decay curve.

[0064] In this embodiment, the sampling frequency of the DC charging device is adjusted according to the following formula:

[0065]

[0066] In the above formula, k is the sampling frequency of the DC charging device, and T is the sampling period of the DC charging device.

[0067] In one embodiment, the sampling period of the DC charging device satisfies:

[0068] T≤-tln(1-rate)

[0069] In the above formula, t is the time constant and rate is the signal attenuation rate. In order to effectively observe the transient abnormal process, it is considered that the abnormal signal should be collected at least before the signal attenuates by 50%, and it can also be adjusted according to the actual situation.

[0070] Based on the equipment parameters of a certain operator, a circuit model was built using Simulink to simulate the abnormal charging process of the DC charging pile, and this method was used to analyze the time scale of the charging equipment failure.

[0071] The electric vehicle battery system is set to charge at a constant current of 250A. After a circuit breaker fault occurs during the charging process, the circuit is restored and connected again. After an abnormal charging process occurs, the attenuation curve in the figure is fitted based on this method to obtain the time constant t value of the fault. The fitting diagram is shown in Figure 4, and the fitting result of the time constant t is 7.46ms.

[0072] In this embodiment, the time constant is about 7.46ms. Based on the method proposed in the present invention, the signal attenuation rate is set to 20%. Therefore, to observe the abnormal current information of the transient process, the sampling period shall not be greater than 1.665ms, and the charging device output current sampling frequency k shall satisfy:

[0073]

[0074] Therefore, in order to observe the transient abnormal charging current of the DC charging pile, the charging equipment output current sampling frequency k is at least 600.73 Hz.

[0075] Example 2

[0076] Based on the same inventive concept, the present invention further provides a charging process monitoring device for a DC charging device, the charging process monitoring device for a DC charging device comprising:

[0077] An acquisition module, used to acquire a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device;

[0078] A fitting module, used for fitting the collected output current / voltage data of the charging device to obtain a time constant in a curve function corresponding to the current / voltage decay curve;

[0079] The sampling module is used to adjust the sampling frequency of the DC charging device based on the time constant and perform current / voltage sampling monitoring.

[0080] Preferably, the step of obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device includes:

[0081] During the charging process of the charging device, a switch is used to simulate a circuit-breaking and then reconnecting fault during the charging process of the charging device, and the output current / voltage curve of the charging device is collected;

[0082] The output current / voltage curve is intercepted from the corresponding curve between the charging recovery connection moment and the charging current stabilization moment.

[0083] Preferably, the curve function corresponding to the current decay curve is as follows:

[0084]

[0085] In the above formula, I is the real-time charging current, I L To stabilize the charging current, V out is the output voltage of the charging device, V ocv is the open circuit voltage value of the vehicle battery system, R s is the internal resistance of the battery, e is a natural constant, t is a time constant, t is the current moment, and t1 is the moment when charging is restored and connected.

[0086] Furthermore, the curve function corresponding to the voltage attenuation curve is as follows:

[0087]

[0088] In the above formula, V c is the real-time charging voltage.

[0089] Preferably, the time constant in the curve function corresponding to the current / voltage decay curve obtained by fitting the collected output current / voltage data of the charging device includes:

[0090] Based on the collected output current / voltage data of the charging device, a least squares algorithm is used to fit the time constant in the curve function corresponding to the current / voltage decay curve.

[0091] Preferably, the sampling frequency of the DC charging device is adjusted as follows:

[0092]

[0093] In the above formula, k is the sampling frequency of the DC charging device, and T is the sampling period of the DC charging device.

[0094] Furthermore, the sampling period of the DC charging device satisfies:

[0095] T≤-tln(1-rate)

[0096] In the above formula, t is the time constant and rate is the signal attenuation rate.

[0097] Example 3

[0098] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the charging process monitoring method of a DC charging device in the above embodiment.

[0099] Example 4

[0100] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in a computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space that stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of a charging process monitoring method for a DC charging device in the above embodiment.

[0101] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0102] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0103] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0104] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for monitoring the charging process of a DC charging device, characterized in that: The method comprises: Obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device; The time constant in the curve function corresponding to the current / voltage decay curve is obtained by fitting based on the collected output current / voltage data of the charging device; The sampling frequency of the DC charging device is adjusted based on the time constant, and current / voltage sampling monitoring is performed.

2. The method according to claim 1, characterized in that The step of obtaining a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device includes: During the charging process of the charging device, a switch is used to simulate a circuit-breaking and then reconnecting fault during the charging process of the charging device, and the output current / voltage curve of the charging device is collected; The output current / voltage curve is intercepted from the corresponding curve between the charging recovery connection moment and the charging current stabilization moment.

3. The method according to claim 1, characterized in that The curve function corresponding to the current decay curve is as follows: In the above formula, I is the real-time charging current, I L To stabilize the charging current, V out is the output voltage of the charging device, V ocv is the open circuit voltage value of the vehicle battery system, R s is the internal resistance of the battery, e is a natural constant, t is a time constant, t is the current moment, and t1 is the moment when charging is restored and connected.

4. The method according to claim 3, characterized in that The curve function corresponding to the voltage decay curve is as follows: In the above formula, V c is the real-time charging voltage.

5. The method according to claim 1, characterized in that The time constant in the curve function corresponding to the current / voltage decay curve obtained by fitting the collected output current / voltage data of the charging device includes: Based on the collected output current / voltage data of the charging device, a least squares algorithm is used to fit the time constant in the curve function corresponding to the current / voltage decay curve.

6. The method according to claim 1, characterized in that Adjust the sampling frequency of the DC charging device as follows: In the above formula, k is the sampling frequency of the DC charging device, and T is the sampling period of the DC charging device.

7. The method according to claim 6, characterized in that The sampling period of the DC charging device satisfies: T≤-tln(1-rate) In the above formula, t is the time constant and rate is the signal attenuation rate.

8. A device for monitoring the charging process of a DC charging device according to any one of claims 1 to 7, characterized in that: The device comprises: An acquisition module, used to acquire a current / voltage attenuation curve in an abnormal output current / voltage curve of a charging device; A fitting module, used for fitting the collected output current / voltage data of the charging device to obtain a time constant in a curve function corresponding to the current / voltage decay curve; The sampling module is used to adjust the sampling frequency of the DC charging device based on the time constant and perform current / voltage sampling monitoring.

9. A computer device, characterized in that: include: one or more processors; The processor is configured to execute one or more programs; When the one or more programs are executed by the one or more processors, the charging process monitoring method of a DC charging device according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the charging process monitoring method of a DC charging device as claimed in any one of claims 1 to 7 is implemented.

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