Active equalization system and method based on bidirectional isolation converter

Abstract

The invention relates to the technical field of battery management, in particular to an active equalization system and method based on a bidirectional isolation converter. Comprising a voltage detection unit, a control logic unit, a bidirectional isolation converter, a first switch matrix and a second switch matrix. The first switch matrix is electrically connected with the batteries one by one from the cathode to the anode of the battery pack; the second switch matrix is electrically connected with the batteries one by one from the anode to the cathode of the battery pack; the voltage detection unit can detect the battery voltage to select an extreme value battery and a to-be-balanced battery and integrate the extreme value battery and the to-be-balanced battery into a detection result; the bidirectional isolation converter is electrically connected with the first switch matrix and the second switch matrix; and the control logic unit can control the first switch matrix and the second switch matrix to act according to the detection result so as to electrically connect the extreme value battery and the to-be-equalized battery with the bidirectional isolation converter. Compared with the prior art, direct transfer of electric quantity can be realized, the equalization speed and efficiency are effectively improved, and the overall size is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management, and in particular to an active balancing system and method based on a bidirectional isolation converter. Background Art

[0002] With the gradual maturity and market promotion of new energy technologies, more and more devices, from power tools to electric vehicles, from small appliances to energy storage power stations, are powered by lithium batteries. Lithium batteries are usually connected in series or in parallel to form battery packs. Due to differences in manufacturing processes and application conditions, battery cells will have inconsistencies in voltage, capacity, internal resistance, self-discharge rate and other characteristics. This inconsistency will increase with the number of cycles, thereby accelerating the aging and performance degradation of the battery pack, and even creating the risk of thermal runaway. At present, equalization technology is widely used to improve the inconsistency of battery cells, increase the available charge and discharge capacity of the battery pack, and extend the battery life, so as to improve the performance and safety characteristics of the battery pack.

[0003] Specifically, the battery pack balancing architecture can be divided into two categories: passive balancing and active balancing. Active balancing has the significant advantage of high efficiency compared to passive balancing, so this technology has become a major trend in the development of battery pack balancing architecture. For example, a battery pack active balancing system based on supercapacitor and its working method disclosed in a Chinese patent [Application number: CN201910285493.0, Publication number: CN109980741A], a lithium-ion battery active balancing implementation method [Application number: CN202111023731.4, Publication number: CN113708456A], and a lithium battery protection board based on supercapacitor to achieve active balancing of battery packs [Application number: CN201920479589.6, Publication number: CN209462059U]. This type of active balancing architecture uses a switch matrix to charge an energy storage capacitor from the battery with the highest voltage through a bidirectional non-isolated DC-DC converter (hereinafter referred to as DC-DC). After transferring a certain amount of electricity, the DC-DC is connected to the battery with the lowest voltage, and the electricity in the energy storage capacitor is charged to this battery through the DC-DC. This is repeated until the voltage difference between all batteries reaches the expected range. This type of active balancing architecture transfers the electricity from the battery with the most electricity to the battery with the least electricity. It seems to be more efficient, but in fact, when the electricity is transferred from the battery with the highest voltage to the battery with the lowest voltage, it needs to pass through the DC-DC twice instead of once, and there will be a certain amount of energy loss in each transfer. Therefore, the efficiency of its energy transfer is relatively insufficient. At the same time, due to the aforementioned two transfer processes, the balancing time of this type of active balancing architecture is relatively long. On the other hand, this type of active balancing architecture also needs to be equipped with large-capacity capacitors or supercapacitors, and the overall volume is relatively large. Summary of the invention

[0004] In view of the technical problems in the prior art, the present invention provides an active balancing system based on a bidirectional isolation converter.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] An active balancing system based on a bidirectional isolation converter comprises: a voltage detection unit, a control logic unit, a bidirectional isolation converter, a first switch matrix, a second switch matrix, and a battery connection unit; the first switch matrix is ​​electrically connected to the battery interface positions one by one by the negative interface positions of the battery connection unit in ascending order of number; the second switch matrix is ​​electrically connected to the battery interface positions one by one by the positive interface positions of the battery connection unit in descending order of number; the voltage detection unit is capable of detecting the voltages of each adjacent battery interface position of the battery connection unit and integrating them into a first detection result; the bidirectional isolation converter is electrically connected to the first switch matrix and the second switch matrix; the control logic unit is capable of obtaining the connection status of each battery interface position according to the first detection result and obtaining the second detection result after excluding the vacant battery interface position; the control logic unit is also capable of calculating, comparing, and searching the first detection result and the second detection result; the control logic unit is also capable of controlling the first switch matrix and the second switch matrix to electrically connect several battery interface positions to the bidirectional isolation converter.

[0007] In actual application, the first switch matrix and the second switch matrix are electrically connected to each battery in the battery pack through each battery interface position of the battery connection unit at the same time. The voltage of the battery interface position is detected by the voltage detection unit and calculated and compared by the control logic unit. The control logic unit controls the operation of the first switch matrix and the second switch matrix according to the detection situation of the single cell voltage detection unit, so as to electrically connect the battery at the corresponding battery interface position with the bidirectional isolation converter, and then use the bidirectional isolation converter to transfer the electricity between the batteries. In this way, the balance of electricity between the batteries is achieved. In summary, through the above process, the electricity transfer process of the present invention is only once, which effectively improves the balancing efficiency and shortens the balancing time. At the same time, there is no need to equip large-capacity capacitors or supercapacitors, which effectively reduces the overall volume of the device.

[0008] Furthermore, the negative electrode interface position of the battery connection unit is electrically connected to the negative electrode of the battery pack; the equipotential points of the battery pack are electrically connected to the battery interface positions one by one in order from low to high potential starting from the negative electrode; the number of battery interface positions of the battery connection unit is greater than or equal to the number of equipotential points of the battery pack.

[0009] Furthermore, the first switch matrix also includes a first single-pole double-throw switch (SW1A) and a second single-pole double-throw switch (SW2A); the second switch matrix also includes a third single-pole double-throw switch (SW1B) and a fourth single-pole double-throw switch (SW2B); the contact of the first single-pole double-throw switch (SW1A) is electrically connected to the first positive pin (VCC1) of the bidirectional isolation converter; the contact of the second single-pole double-throw switch (SW2A) is electrically connected to the first negative pin (GND1) of the bidirectional isolation converter; the contact of the third single-pole double-throw switch (SW1B) is electrically connected to the second positive pin (VCC2) of the bidirectional isolation converter; and the contact of the fourth single-pole double-throw switch (SW2B) is electrically connected to the second negative pin (GND2) of the bidirectional isolation converter.

[0010] An active balancing method based on a bidirectional isolation converter is applied to an active balancing system based on a bidirectional isolation converter as described above, and includes the following steps: an operating mode judgment step: judging the current operating mode, when the operating mode is judged as a mode that does not require complementarity, executing a non-complementary balancing step, which includes a deviation measurement step and a balancing operation step; when the operating mode is judged as a mode that requires complementarity, executing a complementary balancing step, which includes a deviation measurement step, a complementary judgment step, a complementary operation step, and a balancing operation step.

[0011] Furthermore, the "working mode determination step" includes the following steps: obtaining the connection status of each battery interface position, and when the two battery interface positions connected to the positive pole of the battery pack and the second highest equipotential point in the battery pack are electrically connected to the first switch matrix and the second switch matrix at the same time, determining that the current working mode is a mode that does not require complementation; when the battery interface position connected to the positive pole of the battery pack is only electrically connected to the second switch matrix, determining that the current working mode is a mode that requires complementation.

[0012] Furthermore, the "deviation measurement step" includes the following steps: calculating the mean value of the voltages of each adjacent battery interface position according to the second detection result to obtain a third detection result; subtracting the third detection result from the second detection result to obtain the voltage deviation of each adjacent battery interface position, that is, the fourth detection result, and comparing the fourth detection result with the balancing threshold. If the absolute values ​​of all voltage deviations are less than the balancing threshold, it is considered that the entire battery pack is balanced; comparing the voltage deviations in the fourth detection result to find the voltage deviation of each adjacent battery interface position with the largest absolute value to obtain the extreme value battery; determining the search range for searching the battery to be balanced. If the two adjacent battery interface positions corresponding to the extreme value battery are not electrically connected to the first switch matrix and the second switch matrix at the same time, the search range is the battery interface positions corresponding to the switch matrix different from the switch matrix where the extreme value battery is located. If two adjacent battery interface positions corresponding to the extreme value battery are electrically connected to the first switch matrix and the second switch matrix at the same time, the search range is all battery interface positions in the second detection result; the positive and negative values ​​of the voltage deviation of the extreme value battery are judged. If the voltage deviation of the extreme value battery is positive, the voltage deviation of each adjacent battery interface position is found in the range with a negative and minimum value, and the battery to be balanced is obtained. If it cannot be found and the complementary operation step has not been performed before, the complementary operation step is performed, otherwise the deviation measurement step is performed again from the beginning; the positive and negative values ​​of the voltage deviation of the extreme value battery are judged. If the voltage deviation of the extreme value battery is negative, the voltage deviation of each adjacent battery interface position is found in the range with a positive and maximum value, and the battery to be balanced is obtained. If it cannot be found and the complementary operation step has not been performed before, the complementary operation step is performed, otherwise the deviation measurement step is performed again from the beginning.

[0013] Further, the "complementary judgment step" includes the following steps: executing the criterion acquisition step to obtain the upper complementary criterion and the lower complementary criterion; and judging whether the complementarity is ready based on the upper complementary criterion and the lower complementary criterion. If the absolute value of the sum of the upper complementary criterion and the lower complementary criterion is less than the complementary threshold, it is deemed that the complementarity is ready; if the judgment result of "whether the complementarity is ready" is yes, then judge whether the absolute value of the deviation of the battery to be balanced is less than any one of the absolute value of the upper complementary criterion and the absolute value of the lower complementary criterion; if the judgment result of "whether the absolute value of the deviation of the battery to be balanced is less than any one of the absolute value of the upper complementary criterion and the absolute value of the lower complementary criterion" is yes, then execute the complementary operation step; if the judgment result of "whether the absolute value of the deviation of the battery to be balanced is less than any one of the absolute value of the upper complementary criterion and the absolute value of the lower complementary criterion" is no, then execute the balancing operation step; if the judgment result of "whether the complementarity is ready" is no, then execute the balancing operation step.

[0014] Furthermore, the "balancing operation step" includes the following steps: the control logic unit controls the first switch matrix and the second switch matrix, so that the extreme value battery is electrically connected to the positive and negative poles of the bidirectional isolation converter through the first switch matrix and the second switch matrix, and the battery to be balanced is electrically connected to the positive and negative poles of the bidirectional isolation converter through the first switch matrix and the second switch matrix; the control logic unit controls the power transfer direction of the bidirectional isolation converter and enables the bidirectional isolation converter, so that the power of the battery with higher voltage among the extreme value battery and the battery to be balanced is transferred to the battery with lower voltage, until the absolute value of the voltage deviation of one of the extreme value battery and the battery to be balanced is less than the balancing threshold. When the absolute value of the voltage deviation is less than the balancing threshold, it is deemed that the balancing is completed and returns to the deviation measurement step.

[0015] Further, the "complementary operation step" includes the following steps: judging the positive or negative value of the upper complementary criterion; if the value of the upper complementary criterion is positive, selecting any balanced battery as the first battery to be complementary at each adjacent battery interface position that is not electrically connected to the first switch matrix, and selecting the battery with the positive and largest value in the voltage deviation at each adjacent battery interface position that is not electrically connected to the second switch matrix as the second battery to be complementary; if the value of the upper complementary criterion is negative, selecting any balanced battery as the first battery to be complementary at each adjacent battery interface position that is not electrically connected to the second switch matrix, and selecting the battery with the positive and largest value in the voltage deviation at each adjacent battery interface position that is not electrically connected to the first switch matrix. as the second battery to be complementary; the control logic unit controls the first switch matrix and the second switch matrix, so that the first battery to be complementary is electrically connected to the positive and negative poles of the bidirectional isolation converter correspondingly through the switch matrix, and the second battery to be complementary is electrically connected to the positive and negative poles of the bidirectional isolation converter correspondingly through the switch matrix; the control logic unit controls the power transfer direction of the bidirectional isolation converter and enables the bidirectional isolation converter, so that the power of the battery with higher voltage in the first battery to be complementary and the second battery to be complementary is transferred to the battery with lower voltage, until the sum of the absolute values ​​of the upper complementary criterion and the lower complementary criterion is less than the complementary threshold value, and the complementary operation is deemed to be completed; the working mode is switched to the mode without complementary, and the non-complementary balancing step is performed.

[0016] Furthermore, the "criterion acquisition step" includes the following steps: obtaining the fourth detection result, and after excluding the batteries whose two adjacent battery interface positions are electrically connected to the first switch matrix and the second switch matrix at the same time: finding out all the negative voltage deviation values ​​among the batteries electrically connected to the second switch matrix and calculating their sum, finding out all the positive voltage deviation values ​​among the batteries electrically connected to the first switch matrix and calculating their sum, adding the two sums to obtain an upper complementary criterion; finding out all the positive voltage deviation values ​​among the batteries electrically connected to the second switch matrix and calculating their sum, finding out all the negative voltage deviation values ​​among the batteries electrically connected to the first switch matrix and calculating their sum, adding the two sums to obtain a lower complementary criterion.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] Through the present invention, the power of a battery can be directly transferred to another battery through a bidirectional isolation converter to achieve a balancing process, that is, there is only one power transfer process during one balancing operation, thereby effectively reducing energy loss.

[0019] Since there is only one power transfer process during one balancing operation, the present invention effectively shortens the time required for balancing.

[0020] Since the electric quantity is directly transferred between the two batteries, the present invention does not need to assemble a large-capacity capacitor or supercapacitor or the like as a temporary energy storage device for electric quantity transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Overall structure diagram.

[0022] Figure 2 : Flowchart of the method.

[0023] Figure 3 : Schematic diagram of connection method of embodiment 1.

[0024] Figure 4 : Schematic diagram of connection method of embodiment 2.

[0025] Figure 5 : Schematic diagram of voltage change in embodiment 1.

[0026] Figure 6 : Schematic diagram of the balancing process of embodiment 1.

[0027] Figure 7 : Schematic diagram of voltage change in embodiment 2.

[0028] Figure 8 : Schematic diagram of the balancing process of embodiment 2. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the embodiments, but it does not constitute any limitation to the present invention. Any limited number of modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0030] Embodiment 1:

[0031] An active balancing system based on a bidirectional isolation converter includes: a voltage detection unit, a control logic unit, a bidirectional isolation converter, a first switch matrix, a second switch matrix, and a battery connection unit. In this embodiment, a plurality of battery cells are connected in parallel in the same number, and each multi-parallel cell is connected in series in turn to form a battery pack. Since the voltage of each battery cell connected in parallel is the same and the capacity is equal to the sum of the capacities of each cell, it is actually equivalent to the properties of a single large cell. Therefore, the multi-parallel cells between every two adjacent (not simply representing the spatial orientation) equipotential points in the battery pack are regarded as a whole. At the same time, in the accompanying drawings, these wholes are coded one by one from B1 to B12, and these wholes are collectively referred to as batteries below. Since the battery connection unit only serves as a connection, it is not drawn in the accompanying drawings.

[0032] In this embodiment, the battery connection unit includes 14 battery interface positions, and every two adjacent battery interface positions correspond to a single cell or multiple single cells connected in series, that is, the battery connection unit corresponds to a total of 13 single cells or multiple single cells connected in series, commonly known as 13 strings of batteries.

[0033] It should be noted that, in the implementation process, it is not required that the number of battery strings completely corresponds to the battery connection unit, but the number of battery interface positions of the battery connection unit should be greater than or equal to the number of equipotential points of the battery pack, that is, the number of strings corresponding to the battery connection unit should be greater than or equal to the number of strings of the connected battery pack. This makes it easier for the active balancing system with a fixed number of battery interface positions to adapt to battery packs with multiple numbers of strings.

[0034] In this embodiment, the battery groups to be balanced are B1 to B12, that is, 12 strings, which do not correspond to the number of battery interface positions. The first 13 battery interface positions are electrically connected to the equipotential points of B1 to B12 one by one, and the positive electrode interface position that should be connected to the positive electrode of B13 is vacant due to the insufficient number of battery strings, but this does not prevent the switch matrix from being electrically connected to the battery interface position.

[0035] Each equipotential point of the battery pack is electrically connected to each battery interface position one by one according to the potential from the negative pole to the high potential. The first switch matrix is ​​electrically connected to the battery interface position one by one by the negative pole interface position of the battery connection unit in ascending order of number. The first switch matrix includes 7 single-pole single-throw switches (hereinafter referred to as switches unless otherwise specified), which are coded one by one from S0A to S6A. One end of each switch is electrically connected to the corresponding battery interface position. These switches are divided into two groups, and the other ends of each group are electrically connected to each other. Specifically, in the accompanying drawings, the battery range included in the first switch matrix is ​​from B1 to B6. The switches of the first switch matrix are coded one by one from S0A to S6A. Among them, the switch that is electrically connected to the battery interface position corresponding to the positive pole of a battery coded as an odd number or the negative pole of a battery coded as an even number is defined as an odd switch. The other ends of the odd switches are electrically connected to each other, and for the convenience of distinction and expression, this connection node is defined as ENA. A switch whose one end is electrically connected to the positive electrode of a battery coded as an even number or to the battery interface corresponding to the negative electrode of a battery coded as an odd number is defined as an even switch. The other ends of the even switches are electrically connected to each other, and for the convenience of distinction and description, this connection node is defined as EPA.

[0036] The second switch matrix is ​​electrically connected to the battery interface bit one by one by the positive electrode interface bit of the battery connection unit in descending order of number. The second switch matrix includes 11 single-pole single-throw switches, which are encoded one by one from S3B to S13B. Like the first switch matrix, one end of each switch of the second switch matrix is ​​electrically connected to the corresponding battery interface bit. These switches are divided into two groups, and the other ends of each group are electrically connected to each other. Specifically, in the accompanying drawings, the battery range included in the second switch matrix is ​​from B4 to B12, and B13 which is not actually connected. The switches of the second switch matrix are encoded one by one from S3B to S13B. Similarly, the switch whose one end is electrically connected to the battery interface bit corresponding to the positive electrode of the battery encoded as an odd number or the negative electrode of the battery encoded as an even number is defined as an odd switch. The other ends of the odd switches are electrically connected to each other, and for the convenience of distinction and description, this connection node is defined as ENB. The switch whose one end is electrically connected to the battery interface bit corresponding to the positive electrode of the battery encoded as an even number or the negative electrode of the battery encoded as an odd number is defined as an even switch. The other ends of the even switches are electrically connected to each other. For the convenience of distinction and description, this connection node is defined as EPB.

[0037] Therefore, the first switch matrix and the second switch matrix form two sets in mathematical concepts, and each battery is an element therein. Specifically, batteries whose positive and negative poles are both electrically connected to the first switch matrix are considered to be included in the first switch matrix; batteries whose positive and negative poles are both electrically connected to the second switch matrix are considered to be included in the second switch matrix. The union of the two sets is the full set, that is, all batteries; the intersection of the two sets is referred to as shared batteries. Based on this, for the sake of convenience, the set of batteries included in the first switch matrix is ​​referred to as the A end, and the set of batteries included in the second switch matrix is ​​referred to as the B end. Batteries only included in the A end, that is, the complement of the B end, are referred to as the A' end; batteries only included in the B end, that is, the complement of the A end, are referred to as the B' end.

[0038] The first and second switch matrices also each include two single-pole double-throw switches, both of which are electrically connected to the bidirectional isolation converter. The single-pole double-throw switches are also electrically connected to the odd and even switch nodes of their respective switch matrices. Among them, the first single-pole double-throw switch (SW1A) and the second single-pole double-throw switch (SW2A) belong to the first switch matrix. The contact of SW1A is electrically connected to the first positive pin (VCC1) of the bidirectional isolation converter, one contact is electrically connected to ENA at the A end, and the other contact is electrically connected to EPA at the A end. The contact of SW2A is electrically connected to the first negative pin (GND1) of the bidirectional isolation converter, one contact is electrically connected to ENA at the A end, and the other contact is electrically connected to EPA at the A end. The third single-pole double-throw switch (SW1B) and the fourth single-pole double-throw switch (SW2B) belong to the second switch matrix. The contact of SW1B is electrically connected to the second positive pin (VCC2) of the bidirectional isolation converter, one contact is electrically connected to ENB at the B end, and the other contact is electrically connected to EPB at the A end. The contact of SW2B is electrically connected to the second negative pin (GND2) of the bidirectional isolation converter, one contact is electrically connected to ENB at the B end, and the other contact is electrically connected to EPB at the A end.

[0039] The two negative pins of the bidirectional isolation converter are electrically isolated, and the bidirectional isolation converter can both step up and step down the voltage. Preferably, the bidirectional isolation converter operates in a constant current mode.

[0040] The control logic unit controls the bidirectional isolation converter through its pins. Specifically, the pin used to control whether the bidirectional isolation converter works, namely EN, and the pin used to control the direction of power transfer of the bidirectional isolation converter, namely DIR, are respectively controlled by the control logic unit or directly electrically connected to the control logic unit. The voltage detection unit can measure the voltage of each adjacent battery interface through the electrical connection of the battery connection unit, which is the first detection result, which is read by the control logic and further processed.

[0041] In actual normal operation, if there is an empty battery interface position, the voltage of the adjacent battery interface position will be measured as zero by the voltage detection unit. After the control logic reads the first detection result, these zero values ​​are identified as empty batteries and excluded. The excluded empty batteries do not participate in the subsequent calculation and operation steps. The voltage of all adjacent battery interface positions after exclusion is the second detection result. For the convenience of distinction and expression, the voltage of the adjacent battery interface position is referred to as the battery voltage below; the "all batteries" and "each battery" mentioned below are regarded as the remaining batteries after the above exclusion, that is, the batteries in the second detection result. In this embodiment, the positive pole of the battery pack and the equipotential point with the second highest potential in the battery pack are not electrically connected to the first switch matrix and the second switch matrix at the same time, that is, the current working mode is a complementary mode. The average voltage of all batteries is obtained by averaging the voltages of all batteries to obtain the mean voltage, which is the third detection result. Next, the difference between the voltage of each battery and the mean voltage is calculated, and the obtained value is its voltage deviation, which is the fourth detection result. If the deviation is a positive value, it is called a positive deviation, and if the deviation is a negative value, it is called a negative deviation. At this time, the battery with the largest absolute value of deviation is obtained according to the fourth detection result, that is, the extreme value battery. Correspondingly, the switch matrix in which the extreme value battery is located is different from the switch matrix in which the extreme value battery is contained, and the numerical sign of the voltage deviation is also different. The battery with the largest absolute value of voltage deviation that meets these two conditions is used as the battery to be balanced. For example: if the extreme value battery is a battery with a positive deviation in the A end, the battery to be balanced should be the battery with the largest absolute value of negative deviation in the B end. If the extreme value battery is a battery with a negative deviation in the A end, the battery to be balanced should be the battery with the largest positive deviation in the B end. In particular, when the intersection of the A end and the B end is not an empty set, that is, there are shared batteries, if the extreme value battery is a shared battery, the battery to be balanced can be a battery in the A end or a battery in the B end.

[0042] In the balanced stop state, the switches are all in the disconnected state. Preferably, in the balanced stop state, the single-pole double-throw switches are all in the disconnected state.

[0043] The control logic unit controls the first switch matrix and the second switch matrix to operate according to the positions of the extreme value battery and the battery to be balanced on the battery string, so as to electrically connect the extreme value battery, the battery to be balanced and the bidirectional isolation converter. For example, in this embodiment: the extreme value battery is B2 at the beginning, the battery voltage deviation is -0.266V and is located at the A end, then the battery with a positive deviation and the largest absolute value is found at the B end as the battery to be balanced, that is, B11. The control logic unit controls switch S1A and switch S2A to close. At the same time, the SW1A toggle contact is controlled to be electrically connected to EPA, and the SW2A toggle contact is controlled to be electrically connected to ENA. As a result, the positive pole of B2 is electrically connected to VCC1 of the bidirectional isolation converter, and the negative pole of B2 is electrically connected to GND1 of the bidirectional isolation converter. On the other hand, the control logic unit controls switch S10B and switch S11B to close. At the same time, the SW1B toggle contact is controlled to be electrically connected to ENB, and the SW2B toggle contact is controlled to be electrically connected to EPB. As a result, the positive electrode of B11 is electrically connected to the VCC2 of the bidirectional isolation converter, and the negative electrode of B11 is electrically connected to the GND2 of the bidirectional isolation converter. The control logic unit controls the DIR pin of the bidirectional isolation converter accordingly and pulls the EN pin of the bidirectional isolation converter to a high level, so that the bidirectional isolation converter transfers the electricity on the VCC2 and GND2 sides to the VCC1 and GND1 sides, that is, the electricity of B11 is transferred to B2 through the bidirectional isolation converter. On the contrary, if the extreme value battery has a positive deviation, the electricity is transferred from the extreme value battery to the battery to be balanced.

[0044] At the same time, the voltage detection unit monitors the voltage of the extreme value battery and the battery to be balanced periodically or in real time. Preferably, the control logic unit also updates the second and third detection results and the voltage deviation at the same frequency. When the absolute value of the voltage deviation of the battery to be balanced is less than the balancing threshold, it indicates that the balancing of the battery to be balanced is completed. The balancing threshold is a preset value and a positive value close to zero, and the complementary threshold is also the same. For the convenience of explanation, the balancing threshold and the complementary threshold are both 0 in this embodiment. At this time, the voltage deviation of B11 becomes 0, and the voltage deviation of B2 becomes -0.045V; the value of the upper complementary criterion is deviation (B1+B3+B9+B12)=0.031V+0.032V+(-0.055V)+(-0.035V)=-0.027V, and the value of the lower complementary criterion is deviation (B2+B4+B5+B10+B11)=(-0.266V)+(-0.088V)+(-0.008V)+0.009V+0.221V=-0.131V, and the complementarity is not ready.

[0045] Next comes the second operation, and the control logic unit controls the switches in the two switch matrices that were closed during the last operation to open. Look for the extreme value battery and the battery to be balanced again. At this time, the extreme value battery is B8, the voltage deviation is 0.156V and it is a shared battery, then find the battery with a negative deviation and the largest absolute value among B1 to B12 as the battery to be balanced, that is, B6. The control logic unit controls the corresponding switches to change the connection state according to the aforementioned logic, so that B8 and B6 are connected to both sides of the bidirectional isolation converter, and controls the bidirectional isolation converter to transfer the power of B8 to B6 until B8 and B6 are balanced. At this time, the voltage deviation of B6 becomes 0, and the voltage deviation of B8 becomes 0.04V; the upper complementary criterion is -0.027V, and the lower complementary criterion is -0.131V, and the complementarity is not ready.

[0046] Repeat the above process several times. After the fifth operation, the voltage deviation of B7 becomes 0, and the voltage deviation of B2 becomes -0.014V; the upper complementary criterion is 0.012V, and the lower complementary criterion becomes -0.012V. At this time, the absolute value of the sum of the upper complementary criterion and the lower complementary criterion is 0, and the complementarity is ready.

[0047] The above process is then repeated. The difference from the previous times is that until the complementary operation step is completed, a judgment operation is added each time, that is, whether the absolute value of the deviation of the battery to be balanced is less than any one of the absolute values ​​of the upper complementary criterion and the absolute value of the lower complementary criterion: for example, in the 7th operation, the extreme value battery is B1, the voltage deviation is 0.031V and is located at the A end, then the battery with a negative deviation and the largest absolute value is found at the B end as the battery to be balanced, that is, B9. Its deviation is -0.016V, and its absolute value is 0.016V, which is greater than the absolute value of the current upper complementary criterion 0.012V and the absolute value of the lower complementary criterion 0.012V, so the balancing operation step is still performed next, which will not be repeated here. After this operation, the voltage deviation of B9 becomes 0, and the voltage deviation of B1 becomes 0.015V; the upper and lower complementary criteria are still 0.012V and -0.012V respectively. At this time, the absolute value of the sum of the upper complementary criterion and the lower complementary criterion is still 0, and the complementarity is ready.

[0048] In the 8th operation, the extreme value battery is B1, the voltage deviation is 0.015V and it is located at the A end, then the battery with the negative deviation and the largest absolute value is found at the B end as the battery to be balanced, that is, B12. Its deviation is -0.003V, and its absolute value is 0.003V, which is less than the absolute value of the current upper complementary criterion 0.012V and the absolute value of the lower complementary criterion 0.012V, so the complementary operation step is performed next.

[0049] At this time, the upper complementary criterion is 0.012V, which is a positive value. Therefore, any balanced battery is selected at the B' end as the first complementary battery, and B9 is selected in this embodiment; the battery with the positive and largest value in the voltage deviation is selected at the A' end as the second complementary battery, that is, B1. The control logic unit controls the corresponding switch to change the connection state according to the aforementioned logic, so that B9 and B1 are connected to both sides of the bidirectional isolation converter, and controls the bidirectional isolation converter to transfer the power of B1 to B9 until the sum of the absolute values ​​of the upper complementary criterion and the lower complementary criterion is less than the complementary threshold. In this embodiment, after this power transfer, the upper and lower complementary criteria are both changed to 0, and the complementary operation is completed. At this time, the voltage deviation of B9 becomes 0.012V, and the voltage deviation of B1 becomes 0.003V.

[0050] Switch the working mode to the non-complementary mode and perform the non-complementary balancing step. After the 12th operation, all the batteries in the battery pack are balanced. Figure 5 The voltage variation of each battery cell after multiple operations in a certain simulation is shown, which is the present embodiment.

[0051] In summary, in the aforementioned process, the electric power is directly transferred between the extreme value battery and the battery to be balanced through the bidirectional isolation converter, rather than charging the energy storage capacitor through the DC-DC and then transferring the electric power from the energy storage capacitor to the corresponding battery through the DC-DC. That is, through the present invention, the electric power only needs one transfer process to meet the balancing demand. In terms of numerical values, almost every electric power transfer is accompanied by a reduction in the total deviation. In other words, almost every electric power transfer makes the entire battery group more inclined to complete balance. Only the electric power transfer in the complementary operation step does not cause a reduction in the total deviation. On the one hand, the present invention effectively reduces the energy loss in the balancing process; on the other hand, because the electric power is directly transferred from one battery to another, the time required for balancing is effectively shortened. At the same time, the present invention does not need to assemble large-capacity capacitors or supercapacitors, thereby effectively reducing the overall volume of the device.

[0052] It is worth noting that the aforementioned switches and single-pole double-throw switches represent devices or circuits that can realize the on / off or gating function of the circuit through the control of the control logic unit, which can be one or more transistors with a certain connection method, or optoelectronic semiconductor devices, magnetic coupling devices, integrated circuits, or even relays, reed switches, etc. As long as they can realize the on / off control function of the aforementioned circuit, they are included.

[0053] It is worth noting that, in actual conditions, the aforementioned electrical connection depends on the actual device. For example, when the aforementioned switch uses a solid-state relay, the control pin of the solid-state relay is electrically connected to the control logic unit, while the solid-state relay uses light as the control medium, and there is no direct electrical connection between the control logic unit and the aforementioned switch.

[0054] It is worth noting that, since there are many possible shapes of the bidirectional isolation converter during implementation, the above-mentioned pins of the bidirectional isolation converter may also be pins, pads, terminals, or even metal bonding pads, etc. The control logic of the bidirectional isolation converter is not limited to controlling it by directly electrically connecting its DIR and EN pins, but may also indirectly control it by indirectly connecting isolation devices such as optoelectronic semiconductor devices and magnetic coupling devices. As long as the corresponding control can be achieved, it is included.

[0055] It is worth noting that the pin used to control whether the bidirectional isolation converter works is EN, and the pin used to control the direction of power transfer of the bidirectional isolation converter is DIR. These two names EN and DIR are only named for convenience and in accordance with relevant industry practices, but are not limited to these names. For example, the pin used to control whether the bidirectional isolation converter works can also be named CE, OE, nSLEEP, etc., and the pin used to control the direction of power transfer of the bidirectional isolation converter can also be named CTRL, SEL, etc.

[0056] It is worth noting that the application objects of the present invention include secondary battery (i.e., rechargeable battery) groups that need to be balanced, in addition to common lithium battery groups, it can also be battery groups such as sodium batteries and aluminum batteries that have not yet been widely used. Since the properties of battery groups are similar to those of supercapacitor groups and electrochemical hybrid capacitors (such as lithium-ion capacitors), the application objects of the present invention can be supercapacitor groups and electrochemical hybrid capacitor groups in addition to battery groups. The control logic unit represents a device and peripheral circuit with a control function, which can be an MCU, a SoC, or even an integrated circuit such as a CPLD or FPGA.

[0057] Embodiment 2:

[0058] An active balancing system based on a bidirectional isolation converter comprises: a voltage detection unit, a control logic unit, a bidirectional isolation converter, a first switch matrix, a second switch matrix, and a battery connection unit.

[0059] This embodiment provides an implementation in which the number of battery strings and the battery connection unit completely correspond, that is, there is no vacant battery interface position and no shared battery. Moreover, the voltage of each battery in this embodiment is more special than that in the first embodiment, which will lead to the occurrence of special operations. This embodiment will focus on explaining this special situation.

[0060] In this embodiment, the battery connection unit includes 11 battery interface positions, and every two adjacent battery interface positions correspond to a monomer connected in series, that is, the battery connection unit corresponds to a total of 10 monomers connected in series, commonly known as 10 strings of batteries, which are numbered B1 to B10 in sequence. The 11 battery interface positions are electrically connected to each equipotential point from B1 to B10 one by one. Among them, the battery range included in the first switch matrix is ​​from B1 to B5, that is, the A end, that is, the A' end; the battery range included in the second switch matrix is ​​from B6 to B10, that is, the B end, that is, the B' end. For the convenience of explanation, in this embodiment, the balance threshold and the complementary threshold are both 0, but each value is rounded off: specifically, rounded to millivolts.

[0061] After the connection is identified, it is determined that the complementary mode is required, and the deviation measurement and complementary judgment are performed: after obtaining all battery voltages, the average voltage is calculated, and then the deviation of each battery and each judgment criterion are obtained. Since there is no shared battery, the complementary mode is ready in the initial situation.

[0062] Perform the first operation: At this time, the extreme value battery is B2, the voltage deviation is 0.343V and is located at the A end, then find the battery with negative deviation and the largest absolute value at the B end as the battery to be balanced, that is, B6. Its deviation is -0.278V, and its absolute value is 0.278V, which is not less than the absolute value of the current upper complementary criterion of 0.058V and the absolute value of the lower complementary criterion of 0.058V, so the next balancing operation step is performed. After the operation, the voltage deviation of B6 becomes 0, and the voltage deviation of B2 becomes 0.066V.

[0063] Second operation: At this time, the extreme value battery is B10, the voltage deviation is -0.272V and is located at the B end, then the battery with positive deviation and the largest absolute value is found at the A end as the battery to be balanced, that is, B4. Its deviation is 0.215V, and its absolute value is 0.215V, which is not less than the absolute value of the current upper and lower complementary criteria, so the next balancing operation step is performed. After the operation, the voltage deviation of B4 becomes 0, and the voltage deviation of B10 becomes -0.057V.

[0064] The third to fifth operations are not described in detail. After the fifth operation, the voltage deviation of B2 becomes 0, and the voltage deviation of B10 becomes -0.036V.

[0065] The sixth operation: At this time, the extreme value battery is B8, the voltage deviation is 0.058V and is located at the B end. Then, a battery with a negative deviation and the largest absolute value is found at the A end as the battery to be balanced. However, there is no battery with a negative deviation at the A end at this time. Because the complementary operation has not been performed before, the complementary operation step is directly performed next. At this time, the upper complementary criterion is -0.058V, which is a negative value. Therefore: any balanced battery is selected at the A' end as the first battery to be complementary. In this embodiment, B5 is selected; at the B' end, the battery with a positive and largest value in the voltage deviation is selected as the second battery to be complementary, that is, B8. The control logic unit controls the corresponding switch to change the connection state according to the above logic, so that B8 and B5 are connected to both sides of the bidirectional isolation converter, and controls the bidirectional isolation converter to transfer the power of B8 to B5 until the sum of the absolute values ​​of the upper complementary criterion and the lower complementary criterion is less than the complementary threshold. After this power transfer, the upper and lower complementary criteria are both changed to 0, and the complementary operation is completed. At this time, the voltage deviation of B8 becomes 0, and the voltage deviation of B5 becomes 0.058V.

[0066] Switch the working mode to the mode without complementary operation and perform the step of non-complementary equalization.

[0067] The seventh and eighth operations are not described in detail. After the eighth operation, the voltage deviation of B7 becomes 0, and the voltage deviation of B1 becomes 0.012V.

[0068] The 9th operation: At this time, the extreme value battery is B9, the voltage deviation is -0.012V and is located at the B end, then the battery with positive deviation and the largest absolute value is found at the A end as the battery to be balanced, that is, B1, whose deviation is 0.012V. Due to rounding, after the balancing operation, the voltage deviation of B1 becomes 0, and the voltage deviation of B9 becomes -0.001V.

[0069] The 10th operation will not be described in detail. After the 10th operation, the voltage deviation of B9 and B5 becomes 0, the voltage deviation of all batteries is 0, and all batteries in the battery pack are balanced.

[0070] The specific embodiments described herein are merely examples of the spirit of the present invention. A person skilled in the art of the present invention may make various modifications or additions to the specific embodiments described or replace them in a similar manner. However, this will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. An active balancing system based on a bidirectional isolation converter, characterized in that: include: A voltage detection unit, a control logic unit, a bidirectional isolation converter, a first switch matrix, a second switch matrix, and a battery connection unit; The first switch matrix is ​​electrically connected to the battery interface positions one by one by the negative electrode interface positions of the battery connection unit in ascending order of number; The second switch matrix is ​​electrically connected to the battery interface positions one by one by the positive electrode interface positions of the battery connection unit in descending order of number; The voltage detection unit is capable of detecting the voltages of adjacent battery interface positions of the battery connection unit and integrating them into a first detection result; The bidirectional isolation converter is electrically connected to the first switch matrix and the second switch matrix; The control logic unit can obtain the connection status of each battery interface position according to the first detection result, and obtain the second detection result after excluding the vacant battery interface position; The control logic unit can also calculate, compare and search the first detection result and the second detection result; The control logic unit can also control the first switch matrix and the second switch matrix to electrically connect a plurality of the battery interface positions to the bidirectional isolation converter.

2. The active balancing system based on a bidirectional isolation converter according to claim 1, characterized in that: The negative electrode interface of the battery connection unit is electrically connected to the negative electrode of the battery pack; Each equipotential point of the battery pack is electrically connected to each battery interface point one by one in order from the negative electrode in order from low to high potential; The number of battery interface positions of the battery connection unit is greater than or equal to the number of equipotential points of the battery pack.

3. The active balancing system based on a bidirectional isolation converter according to claim 1, characterized in that: The first switch matrix also includes a first single-pole double-throw switch (SW1A) and a second single-pole double-throw switch (SW2A); The second switch matrix further includes a third single-pole double-throw switch (SW1B) and a fourth single-pole double-throw switch (SW2B); The contact of the first single-pole double-throw switch (SW1A) is electrically connected to the first positive pin (VCC1) of the bidirectional isolation converter; the contact of the second single-pole double-throw switch (SW2A) is electrically connected to the first negative pin (GND1) of the bidirectional isolation converter; the contact of the third single-pole double-throw switch (SW1B) is electrically connected to the second positive pin (VCC2) of the bidirectional isolation converter; and the contact of the fourth single-pole double-throw switch (SW2B) is electrically connected to the second negative pin (GND2) of the bidirectional isolation converter.

4. An active balancing method based on a bidirectional isolation converter, characterized in that: Applicable to an active balancing system based on a bidirectional isolation converter as claimed in any one of claims 1 to 3, The following steps are involved: Working mode determination step: determining the current working mode, and when the working mode is determined to be a mode that does not require complementary operation, executing a non-complementary equalization step, wherein the non-complementary equalization step includes a deviation measurement step and an equalization operation step; When the working mode is determined to be a complementary mode, a complementary equalization step is executed, and the complementary equalization step includes a deviation measurement step, a complementary judgment step, a complementary operation step, and a balancing operation step.

5. The active balancing method based on a bidirectional isolation converter according to claim 4 is characterized in that: The "operating mode determination step" includes the following steps: Acquire the connection status of each battery interface position, and when the two battery interface positions connected to the positive electrode of the battery pack and the equipotential point with the second highest potential in the battery pack are electrically connected to the first switch matrix and the second switch matrix at the same time, determine that the current working mode is the non-complementary mode; When the battery interface to which the positive electrode of the battery pack is connected is electrically connected only to the second switch matrix, it is determined that the current working mode is the complementary mode.

6. The active balancing method based on a bidirectional isolation converter according to claim 4, characterized in that: The "deviation measurement step" includes the following steps: Calculate the average value of the voltages of the adjacent battery interface positions according to the second detection result to obtain a third detection result; Subtracting the third detection result from the second detection result to obtain the voltage deviation of each adjacent battery interface position, i.e., the fourth detection result, and comparing the fourth detection result with the balancing threshold. If the absolute values ​​of all the voltage deviations are less than the balancing threshold, it is considered that the balancing of the entire battery pack is completed; Comparing the voltage deviations in the fourth detection result, finding the voltage deviation with the largest absolute value among the voltage deviations of the adjacent battery interface positions, and obtaining the extreme value battery; Determine a search range for searching for batteries to be balanced. If the two adjacent battery interface positions corresponding to the extreme value battery are not electrically connected to the first switch matrix and the second switch matrix at the same time, the search range is the battery interface positions corresponding to the switch matrix different from the switch matrix where the extreme value battery is located. If two adjacent battery interface positions corresponding to the extreme value battery are electrically connected to the first switch matrix and the second switch matrix at the same time, the search range is all battery interface positions in the second detection result; Determine the positive or negative value of the voltage deviation of the extreme value battery. If the voltage deviation of the extreme value battery is positive, find the voltage deviation of each adjacent battery interface position with the negative and smallest value in the range to obtain the battery to be balanced. If it cannot be found and the complementary operation step has not been performed before, perform the complementary operation step, otherwise re-execute the deviation measurement step from the beginning; Determine the positive and negative values ​​of the voltage deviation of the extreme value battery. If the voltage deviation of the extreme value battery is negative, find the voltage deviation of each adjacent battery interface position with a positive and maximum value in the range to obtain the battery to be balanced. If it cannot be found and the complementary operation step has not been performed before, perform the complementary operation step, otherwise re-execute the deviation measurement step from the beginning.

7. The active balancing method based on a bidirectional isolation converter according to claim 6, characterized in that: The "complementary determination step" includes the following steps: Execute the criterion acquisition step to obtain the upper complementary criterion and the lower complementary criterion; and judge whether the complementation is ready according to the upper complementary criterion and the lower complementary criterion. If the absolute value of the sum of the upper complementary criterion and the lower complementary criterion is less than the complementary threshold, it is considered that the complementation is ready; If the result of the judgment of "is complementation ready" is yes, then judging whether the absolute value of the deviation of the battery to be balanced is less than any one of the absolute value of the upper complementation criterion and the absolute value of the lower complementation criterion; If the result of the judgment of "whether the absolute value of the deviation of the battery to be balanced is less than any one of the absolute value of the upper complementary criterion and the absolute value of the lower complementary criterion" is yes, the complementary operation step is performed; If the judgment result of "whether the absolute value of the deviation of the battery to be balanced is less than any one of the absolute value of the upper complementary criterion and the absolute value of the lower complementary criterion" is no, the balancing operation step is performed; If the result of the judgment of "is complementation ready" is no, the balancing operation step is performed.

8. The active balancing method based on a bidirectional isolation converter according to claim 6, characterized in that: The "balancing operation step" includes the following steps: The control logic unit controls the first switch matrix and the second switch matrix, so that the extreme value battery is electrically connected to the positive and negative electrodes of the bidirectional isolation converter through the first switch matrix and the second switch matrix, and the battery to be balanced is electrically connected to the positive and negative electrodes of the bidirectional isolation converter through the first switch matrix and the second switch matrix; The control logic unit controls the power transfer direction of the bidirectional isolation converter and enables the bidirectional isolation converter, so that the power of the battery with a higher voltage among the extreme value battery and the batteries to be balanced is transferred to the battery with a lower voltage, until the absolute value of the voltage deviation between the extreme value battery and one of the batteries to be balanced is less than the balancing threshold. When the absolute value of the voltage deviation is less than the balancing threshold, it is considered that balancing is completed and the process returns to execute the deviation measurement step.

9. The active balancing method based on a bidirectional isolation converter according to claim 7, characterized in that: The "complementary operation step" comprises the following steps: Determining whether the value of the upper complementary criterion is positive or negative; If the value of the upper complementary criterion is positive, any balanced battery is selected as the first battery to be complementary from each adjacent battery interface position that is not electrically connected to the first switch matrix, and the battery with the positive and largest value in the voltage deviation is selected as the second battery to be complementary from each adjacent battery interface position that is not electrically connected to the second switch matrix; If the value of the upper complementary criterion is negative, any balanced battery is selected as the first battery to be complementary from each adjacent battery interface position that is not electrically connected to the second switch matrix, and the battery with the positive and largest value in the voltage deviation is selected as the second battery to be complementary from each adjacent battery interface position that is not electrically connected to the first switch matrix; The control logic unit controls the first switch matrix and the second switch matrix so that the first battery to be complementary is electrically connected to the positive and negative electrodes of the bidirectional isolation converter through the switch matrix, and the second battery to be complementary is electrically connected to the positive and negative electrodes of the bidirectional isolation converter through the switch matrix; The control logic unit controls the power transfer direction of the bidirectional isolation converter and enables the bidirectional isolation converter, so that the power of the battery with a higher voltage among the first battery to be complementary and the second battery to be complementary is transferred to the battery with a lower voltage, until the sum of the absolute values ​​of the upper complementary criterion and the lower complementary criterion is less than the complementary threshold value, and the complementary operation is considered to be completed; The working mode is switched to the non-complementary mode, and the non-complementary equalization step is performed.

10. The active balancing method based on a bidirectional isolation converter according to claim 7, characterized in that: The "criterion acquisition step" includes the following steps: The fourth detection result is obtained, and after excluding batteries whose two adjacent battery interface positions are electrically connected to the first switch matrix and the second switch matrix at the same time: Finding all the negative voltage deviations among the batteries electrically connected to the second switch matrix and calculating their sum, finding all the positive voltage deviations among the batteries electrically connected to the first switch matrix and calculating their sum, and adding the two sums to obtain the upper complementary criterion; All positive voltage deviation values ​​are found in each battery electrically connected to the second switch matrix and their sum is calculated, and all negative voltage deviation values ​​are found in each battery electrically connected to the first switch matrix and their sum is calculated, and the two sums are added to obtain the lower complementary criterion.

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