Harmonic suppression method and system during charging of electric vehicles in grid-connected state

Abstract

The present invention discloses a method and system for suppressing harmonics in the process of charging an electric vehicle in a grid-connected state. The method for suppressing harmonics in the process of charging an electric vehicle in a grid-connected state includes: obtaining the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of variation; detecting the charging current in the process of charging the electric vehicle, and judging whether there is harmonic current in the charging current; when the judgment result is yes, obtaining the comparison result of the difference between the detected charging current and the expected charging current and the controllable range of variation; and when the comparison result shows that the difference exceeds the controllable range of variation, filtering out the harmonic current in the charging current in real time through an active power filter. The present invention has a good harmonic suppression effect, selectively processes harmonics, improves the stability of the power grid, and increases the service life of power grid components.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicle charging, and in particular to a method and system for suppressing harmonics during charging of an electric vehicle in a grid-connected state. Background Art

[0002] With the development of science and technology, electric vehicles, as a new generation of transportation, have incomparable advantages over traditional vehicles in energy conservation and emission reduction. However, when electric vehicles are connected to the grid as nonlinear loads for charging, they will generate harmonics, which will affect the quality of power and cause poor power quality. What's worse, it will cause the microgrid system to fail to work properly. Therefore, it is very necessary to control the harmonics generated by electric vehicle charging.

[0003] At present, the method of harmonic control is to remove it. It is well known that the charging and discharging components have a certain service life. After a certain period of use, the charging and discharging components will be damaged. If the current harmonics are weak, it will have no effect on the charging of electric vehicles. If it is continuously processed, it will cause a waste of resources. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for suppressing harmonics during charging of an electric vehicle in a grid-connected state. The method and system for suppressing harmonics during charging of an electric vehicle in a grid-connected state have good harmonic suppression effect, selectively process harmonics, improve the stability of the power grid, and at the same time increase the service life of power grid components.

[0005] In order to achieve the above object, the present invention provides a method for suppressing harmonics during charging of an electric vehicle in a grid-connected state, and the method for suppressing harmonics during charging of an electric vehicle in a grid-connected state comprises:

[0006] Obtain the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of change;

[0007] Detecting the charging current during the charging process of the electric vehicle, and determining whether there is a harmonic current in the charging current;

[0008] When the judgment result is yes, obtaining a comparison result between a difference between the detected charging current and the expected charging current and the controllable range of the change; and

[0009] When the comparison result shows that the difference exceeds the controllable range of variation, the harmonic current in the charging current is filtered out in real time by an active power filter.

[0010] Preferably, the method of obtaining the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of change includes:

[0011] When a charging head is inserted into a charging port of the electric vehicle, obtaining a current model from the electric vehicle;

[0012] Determining the current expected charging current corresponding to the current model according to a preset correspondence between the model of the electric vehicle and the expected charging current; and

[0013] The product of the current expected charging current and the preset limit ratio is calculated as the controllable range of variation corresponding to the current expected charging current, wherein the preset limit ratio is configured to be related to the historical usage data of the current model and the historical charging data of the current electric vehicle, and the historical charging data includes the historical number of charging times and the historical battery usage time.

[0014] Preferably, the method for detecting the charging current during the charging process of the electric vehicle includes:

[0015] The instantaneous reactive power detection method is used to detect whether there is harmonic current in the charging current during the charging process of the electric vehicle, and the value of the harmonic current is detected.

[0016] In addition, the present invention also provides a harmonic suppression system during the charging process of an electric vehicle in a grid-connected state, and the harmonic suppression system during the charging process of an electric vehicle in a grid-connected state comprises:

[0017] A current acquisition unit, used to acquire the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of change;

[0018] A current determination unit, used to detect the charging current during the charging process of the electric vehicle, and to determine whether there is a harmonic current in the charging current;

[0019] a result acquisition unit, configured to acquire a comparison result between a difference between the detected charging current and the expected charging current and the controllable range of the change when the judgment result is yes; and

[0020] The harmonic filtering unit is used to filter out the harmonic current in the charging current in real time through an active power filter when the comparison result shows that the difference exceeds the controllable range of variation.

[0021] Preferably, the current acquisition unit comprises:

[0022] A model acquisition module, used to acquire the current model of the electric vehicle when a charging head is inserted into the charging port of the electric vehicle;

[0023] an expected current determination module, configured to determine a current expected charging current corresponding to the current model according to a preset correspondence between the model of the electric vehicle and the expected charging current; and

[0024] A variable controllable range calculation module is used to calculate the product of the current expected charging current and a preset limit ratio as the variable controllable range corresponding to the current expected charging current, wherein the preset limit ratio is configured to be related to the historical usage data of the current model and the historical charging data of the current electric vehicle, and the historical charging data includes the historical number of charging times and the historical battery usage time.

[0025] Preferably, the method in which the current judgment unit is used to detect the charging current during the charging process of the electric vehicle includes:

[0026] The current judgment unit is used to detect whether there is a harmonic current in the charging current of the electric vehicle during charging based on the instantaneous reactive power detection method, and detect the value of the harmonic current.

[0027] In addition, the present invention also provides a storage medium on which a program is stored. When the program is executed by a processor, the harmonic suppression method in the charging process of an electric vehicle in a grid-connected state is implemented.

[0028] In addition, the present invention also provides a processor, which is used to run a program, and when the program is run, the harmonic suppression method in the charging process of the electric vehicle in the grid-connected state is executed.

[0029] According to the above technical scheme, the harmonic suppression method and system of the present invention in the charging process of an electric vehicle in a grid-connected state utilizes the designed charging current and its corresponding controllable range of changes to determine whether the charging current at this stage needs to be harmonic processed. If it exceeds the controllable range, filtering suppression is required. If it does not exceed the controllable range, filtering is not required, that is, charging and discharging can be avoided without affecting normal use, and the stable use of the power grid is not affected.

[0030] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 is a flow chart illustrating a method for suppressing harmonics during charging of an electric vehicle in a grid-connected state according to the present invention;

[0033] Figure 2 is a block diagram of a harmonic suppression system for an electric vehicle charging process in a grid-connected state according to the present invention; and

[0034] Figure 3is the instantaneous reactive power i p -i q Flowchart of the assay;

[0035] Figure 4 is a flowchart illustrating a command current formation process of the present invention; and

[0036] Figure 5 It is the structural block diagram of hysteresis comparison control. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0038] Figure 1 is a flow chart of a method for suppressing harmonics during charging of an electric vehicle in a grid-connected state of the present invention. Figure 1 As shown, the harmonic suppression method during the charging process of the electric vehicle in the grid-connected state includes:

[0039] S101, obtaining the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of change; for example, the model of the electric vehicle is a certain model of a certain brand, and different brands of cars have different expected charging currents and different charging current requirements. The controllable range of change is related to the size of the charging current and, of course, to the brand model. Some brands are better and have a larger controllable range of change. Specifically, it is implemented according to the following preferred method.

[0040] S102, detecting the charging current of the electric vehicle during charging, and determining whether there is harmonic current in the charging current. The charging current can be detected by measuring the instantaneous reactive power. p -i q Detection method, specifically, the detection process is as follows Figure 3 shown.

[0041] S103, when the judgment result shows whether there is harmonic current in the charging current, obtain a comparison result of the difference between the detected charging current and the expected charging current and the controllable range of variation. The comparison result can show the difference between the detected charging current and the expected charging current and the controllable range of variation.

[0042] S104, when the comparison result shows that the difference exceeds the controllable range of variation, the harmonic current in the charging current is filtered out in real time by an active power filter. The method of filtering out the harmonic current in the charging current in real time by an active power filter may be to use the instantaneous reactive power i p-i q The detection method detects the harmonic components of the electric vehicle current, and then, Figure 4 As shown, through Figure 4 The high-order harmonics are accurately detected and command current is formed by using Figure 5 The hysteresis loop comparison control shown in the figure is used to track the command current formed. The current response of the hysteresis loop control is very sensitive. First, and the actual compensation current i c The deviation value Δi is obtained by subtracting c , the deviation value Δi c Input hysteresis comparator, PWM signal is generated under the combined action of hysteresis width and hysteresis comparator. PWM signal can determine i c The value of .

[0043] Preferably, in S104 of the present invention, the harmonic components of the electric vehicle current are first detected in real time by using an FFT algorithm. Figure 3 The command current is then formed based on the detection results. The command current uses the i based on the instantaneous reactive power. p -i q Detection method, i p -i q The detection method can detect high-order harmonics in real time and accurately, and is not easily affected by voltage distortion. The command current formation block diagram is as follows: Figure 4 Finally, the three-phase voltage-type PWM converter hysteresis comparison control method is used to track the command current. The current response of the hysteresis control is very sensitive. First, and the actual compensation current i c The deviation value Δi is obtained by subtracting c , the deviation value Δi c Input hysteresis comparator, PWM signal is generated under the combined action of hysteresis width and hysteresis comparator. PWM signal can determine i c The hysteresis comparison control is as follows Figure 5 shown.

[0044] Preferably, S101 includes: when the charging head is inserted into the charging port of the electric vehicle, obtaining the current model of the electric vehicle; determining the current expected charging current corresponding to the current model according to the preset corresponding relationship between the model of the electric vehicle and the expected charging current; and calculating the product of the current expected charging current and the preset limit ratio as the change controllable range corresponding to the current expected charging current, wherein the preset limit ratio is configured to be related to the historical usage data of the current model and the historical charging data of the current electric vehicle, and the historical charging data includes the historical charging times and the historical battery usage time. Among them, the preset limit ratio initial value is 80-120%, and when the historical usage data shows that more than 60% of the users have a battery life after using the limit ratio, and the grid stability exceeds the average value of the service life, the ratio is determined to be the initial ratio, wherein it is also related to the historical charging data of the current electric vehicle. When the current electric vehicle has been charged for more than 100 times, the limit ratio is reduced on the basis, and the ratio is reduced by a part for every 100 times, and the limit ratio is 90-110%. The brand of the car has a great influence, and the data reflected in actual use is also used as a reference for the seed limit ratio.

[0045] In addition, if Figure 2 As shown, the present invention also provides a harmonic suppression system during the charging process of an electric vehicle in a grid-connected state, and the harmonic suppression system during the charging process of an electric vehicle in a grid-connected state comprises:

[0046] A current acquisition unit, used to acquire the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of change;

[0047] A current determination unit, used to detect the charging current during the charging process of the electric vehicle, and to determine whether there is a harmonic current in the charging current;

[0048] a result acquisition unit, configured to acquire a comparison result between a difference between the detected charging current and the expected charging current and the controllable range of the change when the judgment result is yes; and

[0049] The harmonic filtering unit is used to filter out the harmonic current in the charging current in real time through an active power filter when the comparison result shows that the difference exceeds the controllable range of variation.

[0050] Preferably, the current acquisition unit comprises:

[0051] A model acquisition module, used to acquire the current model of the electric vehicle when a charging head is inserted into the charging port of the electric vehicle;

[0052] an expected current determination module, configured to determine a current expected charging current corresponding to the current model according to a preset correspondence between the model of the electric vehicle and the expected charging current; and

[0053] A variable controllable range calculation module is used to calculate the product of the current expected charging current and a preset limit ratio as the variable controllable range corresponding to the current expected charging current, wherein the preset limit ratio is configured to be related to the historical usage data of the current model and the historical charging data of the current electric vehicle, and the historical charging data includes the historical number of charging times and the historical battery usage time.

[0054] Preferably, the method in which the current judgment unit is used to detect the charging current during the charging process of the electric vehicle includes:

[0055] The current judgment unit is used to detect whether there is a harmonic current in the charging current of the electric vehicle during charging based on the instantaneous reactive power detection method, and detect the value of the harmonic current.

[0056] In addition, the present invention also provides a storage medium on which a program is stored. When the program is executed by a processor, the harmonic suppression method in the charging process of an electric vehicle in a grid-connected state is implemented.

[0057] In addition, the present invention also provides a processor, which is used to run a program, and is characterized in that when the program is running, the above-mentioned harmonic suppression method during the charging process of the electric vehicle in the grid-connected state is executed.

[0058] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0059] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes 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 generate 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 1A device that provides the functions specified in a block or multiple blocks.

[0060] 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.

[0061] 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 in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0062] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0063] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0064] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0065] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0066] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt 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.) that contain computer-usable program code.

[0067] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for suppressing harmonics during charging of an electric vehicle in a grid-connected state, characterized in that: The harmonic suppression method during the charging process of the electric vehicle in the grid-connected state includes: Obtain the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of change; Detecting the charging current during the charging process of the electric vehicle, and determining whether there is a harmonic current in the charging current; When the judgment result is yes, obtaining a comparison result between a difference between the detected charging current and the expected charging current and the controllable range of the change; and When the comparison result shows that the difference exceeds the controllable range of variation, filtering out harmonic current in the charging current in real time through an active power filter; The method of obtaining the expected charging current corresponding to the model of the electric vehicle and the corresponding controllable range of the change includes: When a charging head is inserted into a charging port of the electric vehicle, obtaining a current model from the electric vehicle; Determining the current expected charging current corresponding to the current model according to a preset correspondence between the model of the electric vehicle and the expected charging current; and The product of the current expected charging current and the preset limit ratio is calculated as the controllable range of variation corresponding to the current expected charging current, wherein the preset limit ratio is configured to be related to the historical usage data of the current model and the historical charging data of the current electric vehicle, and the historical charging data includes the historical number of charging times and the historical battery usage time.

2. The method for suppressing harmonics during charging of an electric vehicle in a grid-connected state according to claim 1, characterized in that: The method for detecting the charging current during the charging process of the electric vehicle comprises: The instantaneous reactive power detection method is used to detect whether there is harmonic current in the charging current during the charging process of the electric vehicle, and the value of the harmonic current is detected.

3. A harmonic suppression system for electric vehicle charging in a grid-connected state, characterized in that: The harmonic suppression system during the charging process of the electric vehicle in the grid-connected state includes: A current acquisition unit, used to acquire the expected charging current corresponding to the model of the electric vehicle and its corresponding controllable range of change; A current determination unit, used to detect the charging current during the charging process of the electric vehicle, and determine whether there is a harmonic current in the charging current; a result acquisition unit, configured to acquire a comparison result between a difference between the detected charging current and the expected charging current and the controllable range of the change when the judgment result is yes; and A harmonic filtering unit, configured to filter out harmonic current in the charging current in real time through an active power filter when the comparison result shows that the difference exceeds the controllable range of variation; The current acquisition unit comprises: A model acquisition module, used to acquire the current model of the electric vehicle when a charging head is inserted into the charging port of the electric vehicle; an expected current determination module, configured to determine a current expected charging current corresponding to the current model according to a preset correspondence between the model of the electric vehicle and the expected charging current; and A variable controllable range calculation module is used to calculate the product of the current expected charging current and a preset limit ratio as the variable controllable range corresponding to the current expected charging current, wherein the preset limit ratio is configured to be related to the historical usage data of the current model and the historical charging data of the current electric vehicle, and the historical charging data includes the historical number of charging times and the historical battery usage time.

4. The method for suppressing harmonics during charging of an electric vehicle in a grid-connected state according to claim 3, characterized in that: The method in which the current judgment unit is used to detect the charging current during the charging process of the electric vehicle includes: The current judgment unit is used to detect whether there is a harmonic current in the charging current of the electric vehicle during charging based on the instantaneous reactive power detection method, and detect the value of the harmonic current.

5. A storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, the harmonic suppression method in the charging process of an electric vehicle in a grid-connected state as described in any one of claims 1-2 is implemented.

6. A processor for running a program, characterized in that: When the program is running, the harmonic suppression method in the charging process of an electric vehicle in a grid-connected state as described in any one of claims 1-2 is executed.

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