Charging current control method of power battery in fast charging process

Abstract

The invention discloses a method for controlling charging current of a power battery in a fast charging process. The method comprises the following steps: acquiring the optimal charging current Imap of the battery according to the state of a battery pack before charging; after charging is started, acquiring a current Ir requested from the charging pile and a real-time charging current Ic of the battery according to the current Imap; calculating the current charging difference current Id of the battery pack, wherein Id = Image-Ic; and controlling and adjusting the output current Ir of the charging pile according to the current Id until the charging is finished. The method has the advantages that the charging time is reduced by adjusting and controlling the charging current, the charging speed is increased, the charging safety is improved, and the current is reduced or avoided from being too large.

Description

Technical Field

[0001] The present invention relates to the field of power battery fast charging control, and in particular to a method for controlling the charging current of a power battery during fast charging. Background Art

[0002] The fast charging process of electric vehicle power batteries usually needs to comply with the regulations of local market standards. The basic process of fast charging usually involves the interaction between the battery management system and the fast charging pile. The battery management system will communicate the charging requirements to the fast charging pile through a specific communication method based on the current state of the battery, including the required charging current and voltage. This interactive process is the key to ensure that electric vehicles are charged quickly and efficiently, and it also helps to optimize the battery charging process, extend its life, and ensure safety.

[0003] When fast charging electric vehicle batteries in the current market, the current state of the battery is usually considered first, such as the state of charge (SOC), temperature, and single cell voltage. Then, the system will match these states with the corresponding charging allowable current according to the preset charging map table to obtain an optimal current Imap. The electric vehicle will send a request to the fast charging pile according to its own needs, requesting fast charging with a matching current output.

[0004] When other high-voltage components of the vehicle are working, some power will be consumed, resulting in a decrease in the battery charging current and prolonged charging time. Under extreme conditions, the battery may even be in a discharged state, affecting the user experience. Moreover, many charging piles will not output the current required by the vehicle. The output current will be discounted at a certain ratio and output to the vehicle to ensure that the output current does not over-current, which will also extend the charging time and affect the user experience. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for controlling the charging current of a power battery during fast charging, thereby reducing the charging time, increasing the charging speed and improving the charging safety, and reducing or avoiding excessive current by adjusting and controlling the charging current.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for controlling the charging current of a power battery during fast charging, obtaining the optimal charging current Imap of the battery according to the state of the battery pack before charging starts;

[0007] After charging starts, the current Ir requested from the charging pile and the real-time charging current Ic of the battery are obtained according to the current Imap;

[0008] Calculate the current battery pack charging difference current Id, where Id = Imap-Ic;

[0009] The output current Ir of the charging pile is controlled and adjusted according to the current Id until charging is completed.

[0010] Before charging begins, based on the collected current battery power, temperature and single cell voltage, the corresponding optimal charging current Imap of the battery is obtained by looking up a preset charging map table.

[0011] After charging starts, the corresponding requested current Ir is calculated based on the status of the electrical appliances in the vehicle and the current Imap.

[0012] After receiving the request current Ir, the charging pile outputs a charging current Io, where Io=Ir*k, where k is a discount factor.

[0013] When |Id| is less than the set current threshold, the requested current Ir is kept unchanged for charging control; otherwise, Ir is adjusted according to the size of the current Id.

[0014] When the current Ir is adjusted according to the current Id, when Id is a positive number, the current current Ir superimposed on the current Id is sent to the charging pile as a new charging request current, and the charging pile outputs a charging current I0 according to the new charging request current.

[0015] The current Ir is gradually increased by Id*1 / n in a segmented manner; the charging request current is increased by Id through n adjustments.

[0016] When the current Id is negative, the current request current Ir superimposed on the current Id is sent to the fast charging pile as a new charging request current within the overcurrent fault time T1.

[0017] During the overcurrent fault time T1, a segmented regulation method is used to gradually reduce the current request current until the real-time charging current of the battery pack is equal to the current Imap.

[0018] When the current Imap changes, the charging request current Ir is adjusted immediately, and the charging current Ic of the battery pack is adjusted by the current Ir to be close to or equal to the current Imap.

[0019] The advantages of the present invention are: by adjusting and controlling the charging current, the charging time is reduced, the charging speed is increased, the charging safety is improved, and the current is reduced or avoided. By adjusting and controlling the current, the vehicle can adjust the required current in real time according to the current entering the battery during the charging process to make the current entering the battery reach the optimal value, optimize the charging time, and avoid the situation of charging overcurrent damaging the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following is a brief description of the contents expressed in the drawings of the present invention and the symbols in the drawings:

[0021] Figure 1 This is a flow chart of the charging current control method of the present invention. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention will be further explained in detail below by describing the optimal embodiment with reference to the accompanying drawings.

[0023] This embodiment provides a method for controlling the charging current during fast charging, which can adjust and control the charging current, achieve the best efficiency of battery charging, reduce the impact of vehicle electrical appliances on fast charging, increase the charging rate, and enhance the user experience during charging. Specific solutions include:

[0024] A method for controlling the charging current of a power battery during fast charging, wherein the optimal charging current Imap of the battery is obtained according to the state of the battery pack before charging starts; the BMS calibrates a preset charging MAP, which is a comparison table of the relationship between battery state information and the optimal charging current; before charging starts, based on the collected current battery power, temperature and single cell voltage, the corresponding optimal charging current Imap of the battery is obtained by looking up a preset charging map table.

[0025] After charging starts, the BMS or VCU or on-board charger obtains the current Ir from the charging pile according to the current Imap; after the charging pile sends the requested current Ir to the charging pile, the charging pile outputs the corresponding current I0 to the charging gun to charge the vehicle according to its own output logic; then the charging current Ic flowing into the battery at this time is monitored in real time;

[0026] Calculate the current battery pack charging difference current Id, where Id = Imap-Ic;

[0027] Then, the output current Ir of the charging pile is controlled and adjusted according to the calculated current Id until charging is completed.

[0028] Since the output charging current I0 of the charging gun will be distributed through the on-board charger, it does not fully charge the battery, but part of it is consumed by the on-board electrical appliances. Therefore, it is necessary to monitor the battery charging current Ic in real time and adjust the charging pile request current Ir according to the difference between Ic and the optimal current Imap, so as to dynamically adjust Ic so that Ic is close to or equal to Imap.

[0029] Specifically: After charging starts, the corresponding requested current Ir is calculated based on the status of the electrical appliances in the vehicle and the current Imap. After receiving the requested current Ir, the charging pile outputs the charging current Io, where Io=Ir*k, where k is the discount factor, which is generally a positive number less than 1; generally less than 1 but close to 1, and the value is generally between 0.9-1. The main purpose is that if the output is completely in accordance with the requested current Ir, there will be no fluctuation margin, resulting in a greater impact on the battery after the fluctuation, while charging after the discount will leave a margin to improve the safety and reliability of charging.

[0030] When Ir is adjusted, when |Id| is less than the set current threshold, the requested current Ir is kept unchanged for charging control; otherwise, Ir is adjusted according to the magnitude of the current Id.

[0031] When the current Ir is adjusted according to the current Id, when Id is a positive number, the current current Ir superimposed on the current Id is sent to the charging pile as a new charging request current, and the charging pile outputs a charging current I0 according to the new charging request current.

[0032] The current Ir is gradually increased by Id*1 / n in a segmented manner; the charging request current is increased by Id through n adjustments.

[0033] When the current Id is negative, the current request current Ir superimposed on the current Id is sent to the fast charging pile as a new charging request current within the overcurrent fault time T1.

[0034] During the overcurrent fault time T1, a segmented regulation method is used to gradually reduce the current request current until the real-time charging current of the battery pack is equal to the current Imap.

[0035] When the current Imap changes, the charging request current Ir is adjusted immediately, and the charging current Ic of the battery pack is adjusted by the current Ir to be close to or equal to the current Imap.

[0036] By adjusting the charging pile request current Ir, the output current Io of the charging pile is controlled to control the charging current Ic of the battery pack, so that Ic approaches Imap and the charging rate is maximized.

[0037] The present invention provides a method for controlling the current of a fast-charged battery, aiming to avoid excessive charging current and optimize the charging rate. The technical solution is as follows: a method for controlling the charging current of a power battery during fast charging, and the components involved include: a battery pack, a fast-charging pile, a shunt, a battery management system (BMS), a fast-charging relay, a battery main positive & main negative relay, a charging overcurrent fault time T1, a battery optimal charging current Imap, a charging request current Ir, a fast-charging pile output current Io, a battery pack charging current Ic, an adjustment current Ie, a battery pack charging difference current Id, an adjustment frequency f, and an adjustment time T2.

[0038] After charging starts, the battery pack requests current Ir from the fast charging pile according to the charging Imap, and the charging pile outputs current Io according to Ir. At this time, Id = Imap-Ic;

[0039] When Id is positive, the actual charging current of the battery is too small and less than Imap. When Id is less than the current regulation threshold, Ir is not adjusted and charging continues in the current state. When Id>current regulation threshold (the current regulation threshold is adjustable, unit A), the charging request current Ir is adjusted.

[0040] The final result of Ir is Ir+Id. To ensure charging stability, the current needs to be adjusted steadily for multiple times. Then the current Ie is adjusted. Ie=Id / n, n is the number of adjustments (the number and the adjustment frequency f are adjusted according to the actual difference). Therefore, the target Ir=current Ir+Ie, for n consecutive times until Ic=Imap, and the adjustment time T2=n*f;

[0041] When Id is negative, the actual battery charging current is too large, |Id|>current regulation threshold (adjustable), then it needs to be adjusted to Imap within the overcurrent fault time T1, T2<T1. The final result of Ir is Ir+Id. To ensure charging stability, the current needs to be adjusted steadily for multiple times, so it is adjusted by adjusting the current Ie, Ie=Id / n, n is the number of adjustments (the adjustment frequency is adjusted according to the actual difference), so the target Ir=current Ir+Ie, for n consecutive times, until Ic=Imap, T2=n*f<T1;

[0042] When Imap changes significantly, Ir adjusts the Imap change value in real time, and then makes fine adjustments based on the current until Ic = Imap.

[0043] The current regulation control method added by the present invention enables the vehicle to adjust the demand current in real time according to the current entering the battery during the charging process to make the current entering the battery reach the optimal value, optimize the charging time, and avoid charging overcurrent damaging the battery.

[0044] The beneficial effects of adopting the above technical solution are:

[0045] 1. When the vehicle is charging, if other high-voltage components of the vehicle consume power, the battery management system will adjust the requested current according to the actual charging situation until the current reaches the optimal value.

[0046] 2. During the charging process, if the output current of the charging pile is less than Ir, the battery management system will also synchronously adjust the demand current until the current reaches the optimal value.

[0047] 3. During the charging process, if the output current of the charging pile is greater than Ir, the battery management system will also adjust the demand current synchronously within the threshold time according to the fault diagnosis threshold until the current reaches the optimal value.

[0048] Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for controlling charging current of a power battery during fast charging, characterized in that: Before charging starts, the optimal charging current Imap of the battery is obtained according to the status of the battery pack; After charging starts, the current Ir requested from the charging pile and the real-time charging current Ic of the battery are obtained according to the current Imap; Calculate the current battery pack charging difference current Id, where Id = Imap-Ic; The output current Ir of the charging pile is controlled and adjusted according to the current Id until charging is completed.

2. A method for controlling charging current of a power battery during fast charging according to claim 1, characterized in that: Before charging begins, based on the collected current battery power, temperature and single cell voltage, the corresponding optimal charging current Imap of the battery is obtained by looking up a preset charging map table.

3. A method for controlling charging current of a power battery during fast charging according to claim 1 or 2, characterized in that: After charging starts, the corresponding requested current Ir is calculated based on the status of the electrical appliances in the vehicle and the current Imap.

4. A method for controlling charging current of a power battery during fast charging according to claim 1 or 2, characterized in that: After receiving the request current Ir, the charging pile outputs a charging current Io, where Io=Ir*k, where k is a discount factor.

5. A method for controlling charging current of a power battery during fast charging according to any one of claims 1 to 4, characterized in that: When |Id| is less than the set current threshold, the requested current Ir is kept unchanged for charging control; otherwise, Ir is adjusted according to the size of the current Id.

6. A method for controlling charging current of a power battery during fast charging as claimed in claim 5, characterized in that: When the current Ir is adjusted according to the current Id, when Id is a positive number, the current current Ir superimposed on the current Id is sent to the charging pile as a new charging request current, and the charging pile outputs a charging current I0 according to the new charging request current.

7. A method for controlling charging current of a power battery during fast charging as claimed in claim 5, characterized in that: The current Ir is gradually increased by Id*1 / n in a segmented manner; the charging request current is increased by Id through n adjustments.

8. A method for controlling charging current of a power battery during fast charging as claimed in claim 5, characterized in that: When the current Id is negative, the current request current Ir superimposed on the current Id is sent to the fast charging pile as a new charging request current within the overcurrent fault time T1.

9. A method for controlling charging current of a power battery during fast charging as claimed in claim 8, characterized in that: During the overcurrent fault time T1, a segmented regulation method is used to gradually reduce the current request current until the real-time charging current of the battery pack is equal to the current Imap.

10. A method for controlling charging current of a power battery during fast charging according to any one of claims 1 to 9, characterized in that: When the current Imap changes, the charging request current Ir is adjusted immediately, and the charging current Ic of the battery pack is adjusted by the current Ir to be close to or equal to the current Imap.

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