Battery backflow control circuit and method

Abstract

The invention discloses a battery backflow control circuit and a control method. A battery is a parallel battery pack and is formed by connecting a plurality of batteries in series and in parallel; each battery string comprises a plurality of battery monomers which are connected in series, two ends of each battery monomer are provided with a backflow limiting unit in parallel, an output end of the battery management system BMS is connected to the backflow limiting unit, and the battery management system BMS acquires voltage and internal resistance of each battery monomer to judge whether the backflow limiting units at the two ends of each battery monomer are started or not. According to the invention, the phenomenon of large current generated at the moment of parallel connection in the parallel battery pack in the prior art is solved, and the safety and reliability of the battery pack are improved.

Description

Technical Field

[0001] The present invention relates to the field of power battery control, and in particular to a battery reflux control circuit and method. Background Art

[0002] With the vigorous development of the new energy industry, the types of lithium battery structures are increasing, and the multi-stage series-parallel mode has also become the mainstream development direction of the industry. However, affected by the consistency of battery capacity and the level of battery capacity and grading technology, the consistency of lithium battery voltage difference and internal resistance is difficult to meet the requirements of less than 1mv and less than 1mΩ. In this way, after the lithium battery is grouped and during its operation, due to the inconsistency of battery voltage difference and internal resistance, when the battery is connected in parallel at multiple levels, it is easy to form a loop between the parallel circuits. The reflux has little effect when it is small, but when the parallel batteries are connected in series, it may generate high current (sparking) and other safety hazards, which will affect the operation of the lithium battery unreliably. At the same time, it will also cause inconsistent attenuation between batteries, indirectly causing the battery system to reduce its power, while continuing to aggravate the imbalance between batteries, further leading to an increase in reflux.

[0003] There is no related technology in the prior art that can solve the backflow phenomenon between parallel battery strings during charging and discharging in a parallel circuit, which restricts the reliability of the parallel battery pack. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a battery reflux control circuit and method for solving the problem of large current generated at the moment of parallel connection in parallel battery packs in the prior art, thereby improving the safety and reliability of the battery packs.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a battery reflux control circuit, wherein the battery is a parallel battery group, which is formed by connecting multiple battery strings in parallel; each battery string includes multiple battery cells connected in series, and a reflux limiting unit is arranged in parallel at both ends of each battery cell, and the output end of the battery management system BMS is connected to the reflux limiting unit, and the battery management system BMS obtains the voltage and internal resistance of each battery cell to determine whether the reflux limiting unit at both ends of each battery cell is started.

[0006] When multiple battery strings are connected in parallel to form a parallel battery pack, a switch K3 is provided in the parallel circuit between the battery strings; the battery management system BMS collects and obtains the voltage and / or resistance value of each battery string, and the output end of the battery management system is connected to the switch K3, which is used to control the opening and closing of the switch K3 to control whether the battery strings are connected in parallel.

[0007] The backflow limiting unit includes a switch K2, a variable resistor R, and a switch K1 that controls the resistance value of the variable resistor R. The variable resistor R and the switch K2 are connected in series and then arranged in parallel at both ends of the corresponding battery cell; the output end of the battery management system BMS is connected to the switches K1 and K2, which are used to control the operation of the backflow limiting unit and the resistance value of the variable resistor R respectively.

[0008] The battery management system BMS is connected to the human-machine interaction module of the vehicle to realize interactive control of human-machine control signals.

[0009] The switches K3, K2 and / or K1 are implemented by MOS tubes.

[0010] A control method for a battery reflux control circuit comprises the following steps:

[0011] The BMS detects the voltage difference and internal resistance difference between the battery cells in each battery string in the battery pack, as well as the overall voltage of each battery string, and determines whether there is a backflow risk. If not, it controls the power on and off of the battery pack according to the received power on and off signals.

[0012] If so, the state of the vehicle at this time is determined and the operation of the backflow restriction unit is started according to the state of the vehicle.

[0013] When it is detected that the voltage difference or internal resistance difference between battery cells in the battery string exceeds 1mv or 1mΩ respectively, it is judged that there is a backflow risk at this time.

[0014] Collecting the current state of the vehicle includes collecting whether the vehicle is in a driving state. If not, the reflux restriction unit is directly started and the corresponding reflux restriction reminder information is issued through the on-board human-computer interaction unit; if so, wait until the vehicle is in a parked state before starting the reflux restriction unit and giving the corresponding reflux restriction reminder information.

[0015] When the reflux limiting unit is working to limit the reflux of the battery pack, the vehicle is prohibited from powering on. At the same time, the BMS obtains the user's operation signal in real time. When the user actively inputs the stop signal, the BMS executes the user's instruction to stop the reflux restriction. At this time, the vehicle is restored to allow power on.

[0016] When the battery cells in the battery string are limiting the backflow, the switch K2 is closed, and the variable resistor R2 is adjusted to the maximum resistance through K1 to quickly consume the voltage, and then the resistance of the variable resistor R2 is lowered through the switch K1 to achieve fine adjustment of the consumption voltage. After the adjustment is completed, the K1 and K2 switches of all the battery cells are disconnected.

[0017] The advantages of the present invention are: solving the problem that when there are many parallel circuits in the battery system & battery module (N>3), the parallel circuits form a backflow due to the consistent battery voltage platform of each circuit and the inconsistent internal resistance of the battery circuit, which is easy to cause safety risks and quality problems of inconsistent battery attenuation, thereby improving the safety and reliability of the battery pack and prolonging the life of the battery pack; adding a power resistor to each parallel circuit, if there is a pressure difference in each parallel circuit, the peak current generated when the parallel circuit is connected can be reduced through the intervention of the resistor, thereby avoiding the battery safety risk caused by large current impact; adding a software calculation strategy to each parallel circuit, through the real-time single cell voltage / current, the internal resistance of the single cell circuit is automatically calculated. If the battery internal resistance deviation is large, the industry difficulty of controlling the inconsistent battery attenuation rate can be solved through the backflow control strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The following is a brief description of the contents expressed in the drawings of the present invention and the symbols in the drawings:

[0019] Figure 1 The parallel battery group loop control circuit of the present invention;

[0020] Figure 2 The invention discloses a method for controlling the return current of a parallel battery pack. DETAILED DESCRIPTION

[0021] 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.

[0022] The generation of the backflow scene is still caused by the inconsistency of the resistance and voltage of each battery cell in the battery pack. Therefore, although the existing technology has a balancing strategy to reduce the consistency difference of the battery cells, it is only a temporary solution and cannot fundamentally eliminate the difference. Therefore, if the difference cannot be fundamentally eliminated, the backflow scene cannot be avoided. If it cannot be avoided, the backflow needs to be controlled to avoid the impact of the backflow on the battery and affect safe use. This solution is to realize a backflow limiting circuit for a parallel battery pack, and its specific solution is as follows:

[0023] like Figure 1 As shown, a battery reflux control circuit, wherein the battery is a parallel battery pack, which is formed by connecting multiple battery strings in parallel; each battery string includes multiple battery cells connected in series, and a reflux limiting unit is arranged in parallel at both ends of each battery cell, and the output end of the battery management system BMS is connected to the reflux limiting unit. The battery management system BMS obtains the voltage and internal resistance of each battery cell to determine whether the reflux limiting unit at both ends of each battery cell is activated.

[0024] When multiple battery strings are connected in parallel to form a parallel battery pack, a switch K3 is provided in the parallel circuit between the battery strings; the battery management system BMS collects and obtains the voltage and / or resistance value of each battery string, and the output end of the battery management system is connected to the switch K3, which is used to control the opening and closing of the switch K3 to control whether the battery strings are connected in parallel.

[0025] The backflow limiting unit includes a switch K2, a variable resistor R, and a switch K1 that controls the resistance value of the variable resistor R. The variable resistor R and the switch K2 are connected in series and then arranged in parallel at both ends of the corresponding battery cell; the output end of the battery management system BMS is connected to the switches K1 and K2, which are used to control the operation of the backflow limiting unit and the resistance value of the variable resistor R respectively.

[0026] The battery management system BMS is connected to the vehicle's human-machine interaction module to realize interactive control of human-machine control signals. The human-machine interaction module is a vehicle-mounted human-machine interaction module including a vehicle-mounted multimedia central control screen, vehicle-mounted keys, buttons, etc., and is mainly used to send reminder signals to users and obtain control signals entered by users.

[0027] like Figure 1 As shown, a battery pack is formed by connecting multiple battery strings in parallel, and each battery string includes batteries V1, V2...Vn. A loop current limiting unit is arranged in parallel at both ends of each battery cell Vn. The loop current limiting unit is used to realize the start of its operation according to the control of the BMS, and is used to control the backflow limit of the battery cell. The circuit of the loop current limiting unit includes a switch K2 and an adjustable resistor R, wherein the adjustable resistor is adjusted by the switch K1, such as K1 is a plurality of switch contacts, and the resistor R is formed by a plurality of small resistors corresponding to the switch contacts of K1 in series. The contacts of K1 are arranged in parallel at both ends of each small resistor, and the contact switch of K1 is used to control whether the small resistor in the adjustable resistor R is short-circuited or intervenes in the work, thereby realizing the adjustment of the resistance value of the adjustable resistor R. The adjustable resistor R is connected in series with the switch K2 to form a loop current limiting unit, which is connected in parallel at both ends of each battery cell. The switches K3, K2 and / or K1 are implemented by MOS tubes.

[0028] With respect to the above-mentioned battery backflow control circuit, this embodiment provides a control method for the battery backflow control circuit, comprising the following steps: the BMS detects the voltage difference and internal resistance difference between the battery cells in each battery string in the battery pack and detects the overall voltage of each battery string and determines whether there is a backflow risk; if not, the battery pack is powered on and off according to the received power-on and power-off signals;

[0029] If so, the state of the vehicle at this time is determined and the operation of the backflow restriction unit is started according to the state of the vehicle.

[0030] When it is detected that the voltage difference or internal resistance difference between battery cells in the battery string exceeds 1mv or 1mΩ respectively, it is determined that there is a backflow risk at this time. At this time, it is further determined whether the backflow restriction unit can be started to perform backflow restriction control on each cell.

[0031] Collecting the current state of the vehicle includes collecting whether the vehicle is in a driving state. If not, the backflow restriction unit is directly started and the corresponding backflow restriction reminder information is issued through the vehicle's human-computer interaction unit; if so, the backflow restriction unit is started after the vehicle is in a parking state and the corresponding backflow restriction reminder information is issued. Because the backflow is generated at the moment of power on or off or at the moment of charging and discharging, it is necessary to check the state of the vehicle. If the vehicle is in a driving state, it cannot be started at this time, because the battery power supply will be disconnected after starting, affecting the normal use of the vehicle. If the vehicle is not driving, it can be started. At this time, the main positive and negative relays of the power battery pack are disconnected, and then the control loop current limiting unit starts to work to limit the backflow, and a reminder is given at the same time, and a reminder of the start of the backflow restriction is issued through the instrument, the vehicle-mounted multimedia display, etc. Further, if the vehicle is in a driving state at this time, the start is prohibited, and the loop current limiting unit is started again after the vehicle stops driving, and then the power is turned off, and a reminder is displayed through the instrument or the vehicle-mounted multimedia display.

[0032] When the circuit is limiting, the user can control the circuit limiting unit through the vehicle touch screen, buttons, etc. If the user actively cancels the circuit limiting unit, the user's control instructions will be executed to give priority to meeting the user's needs. When the reflux limiting unit is working to limit the reflux of the battery pack, the vehicle is prohibited from powering on or off to avoid the reflux caused by powering on and off. At the same time, the BMS obtains the user's operation signal in real time. When the user actively inputs the stop signal, the BMS executes the user's instruction to stop the reflux restriction. At this time, the vehicle is restored to allow powering on and off.

[0033] When the battery cells in the battery string are limiting the backflow, the switch K2 is closed, and the variable resistor R2 is adjusted to the maximum resistance through K1 to quickly consume the voltage, and then the resistance value of the variable resistor R2 is lowered through the switch K1 to achieve fine adjustment of the consumed voltage. After the adjustment is completed, the K1 and K2 switches of all the battery cells are disconnected to complete the current limiting control in the battery string; then after the current limiting of each battery string is completed, the total voltage and total internal resistance of each battery string are acquired through the BMS, and then the voltage difference and internal resistance difference between the battery strings are compared again, and the voltage difference between each battery string is further controlled by K1 and K2 to be less than 1mv, and then K3 is allowed to close, otherwise K3 is prohibited from closing, thereby prohibiting the parallel connection of the battery strings to avoid the backflow caused by the parallel connection.

[0034] The present invention relates to the field of new energy power battery pack systems, and discloses a multi-stage parallel circuit battery system reflux control strategy, including hardware schematic diagram introduction and software control strategy flow. The present invention can solve the problem that when the battery system, battery module, and battery cell are connected in parallel at multiple levels, the battery voltage platform is inconsistent (pressure difference), which causes a large current (sparking phenomenon) to be generated in an instant when the parallel connection is connected, thereby causing safety hazards. At the same time, this strategy can also be used to balance the parallel circuits, solving the defect of low available energy caused by inconsistent battery attenuation in multi-stage parallel circuits.

[0035] In view of this, the purpose of the present invention is to provide a multi-stage parallel loop battery system backflow control strategy to solve the problems raised in the above background technology.

[0036] In order to achieve the purpose of the above invention, the technical solution adopted by the present invention is:

[0037] 1) There are total circuit MOS tube K1 and power resistor control MOS tube K2 on the same series circuit of V1, V2...Vn batteries, where K1 controls the total circuit of power resistor, K2 controls the resistance value of power resistor (sliding rheostat), and MOS tube K3 between parallel circuits controls the connection of adjacent circuits and controls the circuit on and off between parallel circuits;

[0038] 2) When V1, V2, ... Vn batteries are in the process of charging / discharging, the battery management system (BMS) recognizes that the voltage difference between V1, V2, ... Vn batteries exceeds 1mv or the internal resistance exceeds 1mΩ, then the MOS is closed.

[0039] 3) The battery management system (BMS) recognizes that the voltage difference between the parallel circuits exceeds 5mv, and prohibits the parallel circuits from forming a loop by controlling the on and off of K3, effectively reducing the backflow caused by the pressure difference in the parallel circuits, thereby avoiding the large current caused by the instantaneous connection of the parallel circuits.

[0040] Software Strategy Process Description:

[0041] 1) After the BMS (battery management system) is activated, the system starts self-checking, reads the circuit voltage value V, and automatically calculates the voltage difference △U or internal resistance difference △R between each parallel circuit. If △U ≥ 10mv or internal resistance difference △R ≥ 10mΩ, the BMS closes the MOS tube K1 on the corresponding circuit;

[0042] 2) After closing the MOS tube K1, the BMS will close and open the MOS tube in stages according to the set time, and perform periodic technical calculations to compare the voltage difference △U or internal resistance difference △R between each parallel circuit until △U < 10mv or internal resistance difference △R < 10mΩ, and the system will enter the secondary control mechanism;

[0043] 3) After closing MOS tube K2, the secondary control mechanism is entered, and periodic technical calculations are performed to compare the voltage difference △U or internal resistance difference △R between each parallel circuit until △U < 1mv or internal resistance difference △R < 1mΩ, and the same-level series circuit exits the mechanism;

[0044] 4) When the battery △U of all circuits is less than 1mv or the internal resistance difference △R is less than 1mΩ, the MOS tube K3 is closed and a system parallel circuit is formed.

[0045] The present invention solves the problem that when there are many parallel circuits in the battery system & battery module (N>3), the parallel circuits form a backflow due to the consistent battery voltage platform of each circuit and the inconsistent internal resistance of the battery circuit, which can easily cause safety risks and quality problems of inconsistent battery attenuation. A power resistor is added to each parallel circuit. If there is a pressure difference in each parallel circuit, the peak current generated when the parallel circuit is connected can be reduced by intervening through the resistor (the maximum can reach more than 500A). For each parallel circuit, a software calculation strategy is added to automatically calculate the internal resistance of the single cell circuit through the real-time single cell voltage / current. If the battery internal resistance deviation is large, the industry difficulty of inconsistent battery attenuation rate can be controlled through the backflow control strategy.

[0046] 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 battery reflux control circuit, characterized in that: The battery is a parallel battery pack, which is formed by connecting multiple battery strings in parallel; each battery string includes multiple battery cells connected in series, and a reflux limiting unit is arranged in parallel at both ends of each battery cell. The output end of the battery management system BMS is connected to the reflux limiting unit. The battery management system BMS obtains the voltage and internal resistance of each battery cell to determine whether the reflux limiting unit at both ends of each battery cell is activated.

2. A battery reflux control circuit as claimed in claim 1, characterized in that: When multiple battery strings are connected in parallel to form a parallel battery pack, a switch K3 is provided in the parallel circuit between the battery strings; the battery management system BMS collects and obtains the voltage and / or resistance value of each battery string, and the output end of the battery management system is connected to the switch K3, which is used to control the opening and closing of the switch K3 to control whether the battery strings are connected in parallel.

3. A battery reflux control circuit as claimed in claim 1, characterized in that: The backflow limiting unit includes a switch K2, a variable resistor R, and a switch K1 that controls the resistance value of the variable resistor R. The variable resistor R and the switch K2 are connected in series and then arranged in parallel at both ends of the corresponding battery cell; the output end of the battery management system BMS is connected to the switches K1 and K2, which are used to control the operation of the backflow limiting unit and the resistance value of the variable resistor R respectively.

4. A battery reflux control circuit as claimed in any one of claims 1 to 3, characterized in that: The battery management system BMS is connected to the human-machine interaction module of the vehicle to realize interactive control of human-machine control signals.

5. A battery reflux control circuit as claimed in any one of claims 1 to 3, characterized in that: The switches K3, K2 and / or K1 are implemented by MOS tubes.

6. A control method for a battery reflux control circuit according to any one of claims 1 to 5, characterized in that: The steps include: The BMS detects the voltage difference and internal resistance difference between the battery cells in each battery string in the battery pack, as well as the overall voltage of each battery string, and determines whether there is a backflow risk. If not, it controls the power on and off of the battery pack according to the received power on and off signals. If so, the state of the vehicle at this time is determined and the operation of the backflow restriction unit is started according to the state of the vehicle.

7. The control method of the battery reflux control circuit as claimed in claim 6, characterized in that: When it is detected that the voltage difference or internal resistance difference between battery cells in the battery string exceeds 1mv or 1mΩ respectively, it is judged that there is a backflow risk at this time.

8. A control method for a battery reflux control circuit as claimed in claim 6, characterized in that: Collecting the current state of the vehicle includes collecting whether the vehicle is in a driving state, and if not, directly starting the backflow restriction unit and sending corresponding backflow restriction reminder information through the vehicle-mounted human-computer interaction unit; If so, wait until the vehicle is in a parked state before starting the backflow restriction unit and giving the corresponding backflow restriction reminder information.

9. A control method for a battery reflux control circuit as claimed in claim 8, characterized in that: When the reflux limiting unit is working to limit the reflux of the battery pack, the vehicle is prohibited from powering on. At the same time, the BMS obtains the user's operation signal in real time. When the user actively inputs the stop signal, the BMS executes the user's instruction to stop the reflux restriction. At this time, the vehicle is restored to allow power on.

10. A control method for a battery reflux control circuit according to any one of claims 6 to 9, characterized in that: When the battery cells in the battery string are limiting the backflow, the switch K2 is closed, and the variable resistor R2 is adjusted to the maximum resistance through K1 to quickly consume the voltage, and then the resistance of the variable resistor R2 is lowered through the switch K1 to achieve fine adjustment of the consumption voltage. After the adjustment is completed, the K1 and K2 switches of all the battery cells are disconnected.

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