A dc system unit current sharing circuit and battery system

Abstract

The application provides a direct current system unit current sharing circuit, n parallel direct current system units, wherein n is a positive integer greater than or equal to 2; a first bus bar connected to a first end of the direct current system unit through a connecting wire; a second bus bar connected to a second end of the direct current system unit through a connecting wire; and the configuration principle of the wire length between the first bus bar, the second bus bar and the direct current system unit is that the resistance of each direct current system unit to the bus node of the first bus bar and the second bus bar is the same. The above scheme sets the length of the wire between the direct current system unit E3 and the bus bar, so that the equivalent resistance between the input and output nodes of each direct current system unit and the bus node on the bus bar is the same, thereby keeping the output electric quantity of each direct current system unit in the direct current system unit current sharing circuit consistent.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, specifically to a current sharing circuit for a DC system unit and a battery system. Background Technology

[0002] DC system unit: an energy storage unit that can be charged and discharged, such as a battery, but not limited to a battery, or an electrical unit that can support DC input and output.

[0003] With the application of various types of energy storage units in DC power systems, a single energy storage unit often cannot meet the needs of the power system. Therefore, multiple DC system units or energy storage units need to be used in parallel to meet the redundancy and capacity expansion requirements of the power system. The voltage and current output of each DC system unit in the parallel system to the total output port need to be consistent to ensure the stability of the DC system and avoid circulating current in each DC system. Therefore, current sharing among the units in the DC parallel system is particularly important.

[0004] Currently, when multiple battery modules and battery systems are connected in parallel, such as Figure 1 As shown, Figure 1 In the diagram, E1 is the positive bus, the positive input and output of the DC system; E2 is the positive connection wire to the bus; E3 is the DC system unit; E4 is the negative connection wire to the bus; and E5 is the negative bus, the negative input and output of the DC system. Figure 1 In this process, the two ends of wires E2 and E4 of equal length are connected to the terminals on the DC system unit and busbars E1 and E5, respectively. Since the busbar terminals are distributed at equal intervals with equal resistance (R... Bus_n )like Figure 2 As shown, Figure 2 In the middle, R Bus_n R is the resistance value between two adjacent busbar connection terminals. Cabel_1-n The resistance value of the wires corresponding to each DC system unit is determined, therefore, each DC system unit E3 is connected to the input / output terminals on E1 and E5. The resistance is inconsistent due to the inconsistency of the busbar resistance.

[0005] Because the line resistance from each DC system unit E3 to the busbar is not equal, such as... Figure 2 As shown, the DC system unit voltages are equal. However, uneven current distribution occurs during the charging and discharging process of the DC system unit, i.e., the battery module. The shortest line resistance (R) between the front-end DC system unit BAT_SYS_n and the input / output terminals is... Bus_n +R Cabel_n The current is at its minimum during charging and discharging, and at its maximum during charging and discharging. Conversely, the distance from the DC system unit BAT_SYS_1 at the rear end to the input / output terminals is the greatest, and the line resistance (R) is the lowest. Bus_1 +R Bus_2 +RBus_3 +…+R Cabel_n The current is at its maximum during charging and discharging, and at its minimum during charging and discharging. Therefore, the current of each DC system unit E3 is inconsistent during the input and output processes, which will cause system errors and some control problems. Summary of the Invention

[0006] In view of this, embodiments of the present invention provide a current sharing circuit and a battery system for a DC system unit to solve the problem of inconsistent power during the input and output process of a DC system unit.

[0007] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0008] A current sharing circuit for a DC system unit, comprising:

[0009] n parallel DC system units, where n is a positive integer greater than or equal to 2;

[0010] The first bus is connected to the first terminal of the DC system unit via a connecting wire;

[0011] The second bus is connected to the second terminal of the DC system unit via a connecting wire;

[0012] The principle for configuring the wire lengths between the first bus, the second bus, and the DC system unit is as follows:

[0013] The resistances from each DC system unit to the bus nodes of the first and second busbars are the same.

[0014] Optionally, in the current sharing circuit of the DC system unit described above, the length of the conductors between the first bus, the second bus and the DC system unit is inversely proportional to the node distance, where the node distance is the distance between the node of the DC system unit on the first bus and the second bus and the bus node.

[0015] Optionally, in the current sharing circuit of the DC system unit described above, the connection nodes of the N parallel DC system units are distributed at equal intervals on the first busbar and the second busbar.

[0016] Optionally, in the current sharing circuit of the DC system unit described above, the DC system unit is directly connected to the first bus and the second bus via a wire;

[0017] The angle between the first busbar, the second busbar and the extension of the conductor is θ, where θ is less than 90°.

[0018] Optionally, in the current sharing circuit of the DC system unit described above, the first busbar and the second busbar are mounted on the busbar fixing part via hinges or rotatable fixing points.

[0019] Optionally, in the current sharing circuit of the DC system unit described above, the free portions of the first busbar and the second busbar are engaged with the travel guide rail via a snap-fit ​​part. When the first busbar and the second busbar rotate around the busbar fixing part, the snap-fit ​​part travels within the travel guide rail.

[0020] Optionally, in the current sharing circuit of the above-mentioned DC system unit, the lengths of the wires between the first bus, the second bus, and the DC system unit are:

[0021] L_Bi=L_B1+(i-1)·(ρ Bus ·S cabel ·(1+α Bus ·T)) / (ρ cabel ·s Bus ·(1+α cabel ·T))·ΔL Bus Where 2≤i≤n;

[0022] The i represents the conductor corresponding to the i-th DC system unit, and the L_Bi represents the conductor length corresponding to the i-th DC system unit;

[0023] L_B1 is the conductor length corresponding to the DC system unit farthest from the main node;

[0024] The ρ Bus The resistivity of the busbar;

[0025] The ρ cabel The resistivity of the conductor;

[0026] The s Bus The cross-sectional area of ​​the busbar;

[0027] The S cabel The cross-sectional area of ​​the conductor;

[0028] The α Bus The temperature coefficient of the busbar;

[0029] The α cabel The temperature coefficient of the conductor;

[0030] T is the set operating ambient temperature of the current sharing circuit of the DC system unit;

[0031] The ΔL Bus The spacing between the connection nodes of the DC system unit on the first busbar and the second busbar.

[0032] Optionally, in the current sharing circuit of the above DC system unit, the value of θ is:

[0033] θ=arccos[((ρ Bus ·s cabel ·(1+α Bus ·T)) / (ρcabel·sBus·(1+αcabel·T))]

[0034] The ρ Bus The resistivity of the busbar;

[0035] The ρ cabel The resistivity of the conductor;

[0036] The s Bus The cross-sectional area of ​​the busbar;

[0037] The S cabel The cross-sectional area of ​​the conductor;

[0038] The α Bus The temperature coefficient of the busbar;

[0039] The α cabel The temperature coefficient of the conductor;

[0040] T is the set operating ambient temperature of the current sharing circuit of the DC system unit.

[0041] A battery system comprising: a current sharing circuit for a DC system unit as described in any one of the preceding claims.

[0042] Optionally, in the above battery system, the battery system is a stationary energy storage system or a mobile energy storage system.

[0043] Based on the above technical solution, the solution provided by the embodiments of the present invention sets the length of the wire between the DC system unit E3 and the bus so that the equivalent resistance value between the input and output nodes of each DC system unit and the bus node on the bus is the same, thereby making the output power of each DC system unit in the current sharing circuit of the DC system unit consistent. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the current sharing circuit in a DC system unit in the prior art;

[0046] Figure 2 This is a schematic diagram of the equivalent resistance of the current sharing circuit in a DC system unit.

[0047] Figure 3 This is a schematic diagram of the current sharing circuit of the DC system unit disclosed in the embodiments of this application;

[0048] Figure 4 This is a schematic diagram of the busbar fixing method in the DC system unit disclosed in the embodiments of this application. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] To address the issue of inconsistent electrical quantities in DC system units E3 during input and output processes due to varying electrical connection distances between their input / output nodes and bus terminals on the bus when DC system units E3 are connected in parallel, which can cause system errors and control problems, this application provides a DC system unit current sharing circuit. By configuring the length of the wires between the DC system units E3 and the bus, the equivalent resistance values ​​between the input / output nodes of each DC system unit E3 and the bus terminals on the bus are made the same, thereby solving the aforementioned problem.

[0051] See Figure 3 This application discloses a current sharing circuit for a DC system unit, which may include:

[0052] n parallel DC system units E3, where n is a positive integer greater than or equal to 2;

[0053] The first bus E1 is connected to the first end of the DC system unit E3 via a connecting wire E2;

[0054] The second bus E5 is connected to the second end of the DC system unit E3 via a connecting wire E4;

[0055] Specifically, the positive terminal of the DC system unit E3 is connected to the first bus E1, and the negative terminal of the DC system unit E3 is connected to the second bus E5. The first bus E1 and the second bus E5 are provided with equally spaced terminals. The positive and negative terminals of the DC system unit E3 are connected to the first bus E1 and the second bus E5 through these terminals. The first bus E1 and the second bus E5 have bus nodes, which are connected to the bus of an external system. The bus node on the first bus E1 is designated as the total positive terminal E6, and the bus node on the second bus E5 is designated as the total negative terminal E7.

[0056] The conductor length L_B between the first bus E1, the second bus E5, and the DC system unit E3 1-n The configuration principle is as follows:

[0057] The resistances of each DC system unit E3 to the bus nodes of the first bus E1 and the second bus E5 are the same. Specifically, the equivalent resistance between the positive terminal of the DC system unit E3 and the total positive terminal E6 is the same, and the equivalent resistance between the negative terminal of the DC system unit E3 and the total negative terminal E7 is the same.

[0058] In the above scheme, since the resistance of each DC system unit E3 to the bus node of the first bus E1 and the second bus E5 is the same, the electrical quantities of the DC system unit E3 during the input and output process are consistent.

[0059] In an optional embodiment of this application, the connection nodes of the N parallel DC system units E3 on the first bus E1 and the second bus E5 are equally spaced, with a distance of ΔL. That is, the terminals on the first bus E1 and the second bus E5 are equally spaced. Therefore, the equivalent resistance between each terminal and the bus node should be in an arithmetic progression. Thus, by configuring the wire lengths between the nodes (positive or negative terminals of DC system units E3) and the terminals on the bus, the wire lengths corresponding to each DC system unit E3 can be equally spaced, making the wire lengths of DC system units E3 closer to the bus node shorter and the wire lengths of DC system units E3 further from the bus node longer. In other words, the wire lengths between the first bus E1, the second bus E5, and each DC system unit E3 are inversely proportional to the node distance, where the node distance is the distance between the node of the DC system unit E3 on the first bus E1, the second bus E5, and the bus node. The length of the conductor corresponding to the DC system unit E3 is inversely proportional to the distance between its corresponding terminal and the bus node. The shorter the distance between the terminal and the bus node, the longer the distance of the conductor connected to the terminal. The longer the distance between the terminal and the bus node, the shorter the distance of the conductor connected to the terminal. This makes the equivalent resistance between the nodes and the bus nodes of each DC system unit E3 the same.

[0060] In an optional embodiment of this application, to facilitate wiring, maintain neatness within the circuit, and facilitate maintenance and installation, in the above scheme, the DC system unit E3 is directly connected to the first bus E1 and the second bus E5 via a wire. That is, the wire between the DC system unit E3 and the first bus E1 and the second bus E5 is a straight line, and the axes of the straight lines corresponding to multiple DC system units E3 are parallel to each other. The angle between the first bus E1, the second bus E5, and the extension line of the wire is θ, where θ is less than 90°. At this time, the extension lines of the first bus E1 and the second bus E5 also have a certain angle.

[0061] Of course, in another embodiment of the technical solution disclosed in this application, the first bus E1 and the second bus E5 can also be arranged in parallel. In this case, the wires between the first bus E1, the second bus E5 and the DC system unit E3 need to follow a curved path or a spiral path. Of course, these wires can also be set as spirals. Since the length of the spiral wire can be stretched or contracted arbitrarily, it will not cause the wiring in the circuit system to be too complicated and cumbersome.

[0062] In an optional embodiment of this application, see [link to relevant documentation]. Figure 4The fixed ends of the first bus E1 and the second bus E5 are mounted to the bus fixing part E8 via hinges or rotatable fixing points, so that the first bus E1 and the second bus E5 can rotate around the bus fixing part E8. The included angle θ can be adjusted by rotating, and the wire length between the DC system unit E3 and the first bus E1 and the second bus E5 can be adjusted by adjusting the included angle θ.

[0063] See Figure 4 To facilitate the fixation of the first busbar E1 and the second busbar E5, ensuring a constant included angle θ, a travel guide rail E10 can be provided in this design. The fixed end of the travel guide rail E10 is hinged to a fixed position E9 and can rotate freely around E9. The free portions of the first busbar E1 and the second busbar E5 are engaged with the travel guide rail E10 via a snap-fit ​​part E11. When the first busbar E1 and the second busbar E5 rotate around the busbar fixed part E8, the snap-fit ​​part E11 moves within the travel guide rail E10. By adjusting the snap-fit ​​part E11, the free ends of the first busbar E1 and the second busbar E5 can be fixed on the travel guide rail E10. The travel guide rail E10 is a slidable busbar. The slidable busbar can be made of the same material as the first busbar or the second busbar, or it can be made of an insulating material. When its material is the same as that of the first busbar or the second busbar, the bus node is located at the end of the slidable busbar away from the first busbar E1 and the second busbar E5 connected to it. Of course, it can also be located on the first busbar E1 and the second busbar E5. When the slidable busbar is made of an insulating material, the bus node is located on the first busbar E1 and the second busbar E5.

[0064] The following is based on Figure 3 Taking this as an example, the calculation of each parameter in the above scheme will be explained in detail.

[0065] Where 1-n represents units from 1 to n.

[0066] R BAT_SYS_1-n R represents the resistance between each DC system unit E3 and the positive terminal E6 and negative terminal E7 of busbars E1 and E5. BAT_SYS_1-n The resistance values ​​are described below.

[0067] R BAT_SYS_1 =R Cabel_1 +R Bus_1 +R Bus_2 +R Bus_3 +…+R Bus_n (1)

[0068] R BAT_SYS_2 =R Cabel_2 +R Bus_2 +R Bus_3 +…+R Bus_n (2)

[0069] R BAT_SYS_3 =R Cabel_3 +R Bus_3 +…+R Bus_n (3)

[0070] …

[0071] R BAT_SYS_n =R Cabel_n +R Bus_n (4)

[0072] In formulas (1) to (4), the connection terminals on the busbar used to connect the DC system unit are equidistant from each other. Figure 3 The distance ΔL between each connection terminal of the busbar is equal, so the resistance values ​​of each RBus_1-n are equal. RBus_1-n is the resistance value between two adjacent connection terminals on busbars E1 and E5.

[0073] R Bus_1-n =R Bus_1 =R Bus (5)

[0074] In this scheme, even if the distance from the connection terminal on the bus corresponding to the nth DC system unit E3 to the total positive terminal E6 and the total negative terminal E7 is greater than ΔL, RBus_n is still regarded as having the same resistance value as other bus terminals for ease of calculation.

[0075] This invention uses wires of unequal length to connect DC system unit E3 to busbars E1 and E5. The resistance difference between the corresponding wires of two adjacent DC system units is ΔR. cabel_i =R Cabel_i -R Cabel_i-1 Where i > 1. (6)

[0076] The design and configuration method of this invention can make the port resistance of each DC system unit E3 consistent.

[0077] R BAT_SYS_1 =R BAT_SYS_2 =R BAT_SYS_3 =…=R BAT_SYS_n (7)

[0078] To make formula (7)R BAT_SYS_i All resistance values ​​are equal so that R Cabel_i =R Cabel_i -1+R Bus_i-1 Where i > 1 (8)

[0079] Substituting formula (6) into formula (8) yields ΔR. cabel_i =R Bus_i-1 =R Bus Where i > 1 (9)

[0080] Therefore, R Cabel_i =R Cabel_1 +(i-1)*R Bus Where i > 1 (10)

[0081] Calculate the length of the conductor

[0082]

[0083] In the above formula:

[0084] R represents the resistance value;

[0085] ρ is the resistivity;

[0086] L is the conductor length;

[0087] s is the cross-sectional area of ​​the conductor;

[0088] α is the temperature coefficient;

[0089] The ρ Bus The resistivity of the busbar;

[0090] The ρ cabel The resistivity of the conductor;

[0091] The s Bus The cross-sectional area of ​​the busbar;

[0092] The S cabel The cross-sectional area of ​​the conductor;

[0093] The α Bus The temperature coefficient of the busbar;

[0094] The α cabel The temperature coefficient of the conductor;

[0095] T is the set operating ambient temperature of the current sharing circuit of the DC system unit.

[0096] After determining the formulas (6) and (9) for the difference in resistance between unequal-length wires, the difference in length between unequal-length wires can be derived from formulas (11) and (12).

[0097]

[0098]

[0099] The value of θ is:

[0100]

[0101] As can be seen from the above formula, the magnitude of angle θ depends on the resistivity ρ of the bus and the conductor. Bus , ρ cabel Temperature coefficient α Bus α cabel That is, the cross-sectional area s cabel s Bus .

[0102] The lengths of the conductors connecting the first bus E1, the second bus E5, and the DC system unit E3 are:

[0103]

[0104] Where 2≤i≤n;

[0105] The i represents the wire corresponding to the i-th DC system unit E3, and the L_Bi represents the length of the wire corresponding to the i-th DC system unit E3;

[0106] L_B1 is the conductor length corresponding to the DC system unit E3 that is farthest from the main node;

[0107] The ΔL Bus The spacing between the connection nodes of the DC system unit E3 on the first busbar E1 and the second busbar E5.

[0108] Corresponding to the circuit described above, this application also discloses a battery system that can apply the DC system unit current sharing circuit described in any of the above claims.

[0109] Specifically, the battery system is a stationary energy storage system or a mobile energy storage system, and the energy storage units in the system are lead-acid batteries, lithium batteries, nickel-metal hydride batteries or supercapacitors.

[0110] For ease of description, the above system is described by dividing it into various modules based on their functions. Of course, in implementing this invention, the functions of each module can be implemented in one or more software and / or hardware components.

[0111] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. Components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0112] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0113] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0114] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A current sharing circuit for a DC system unit, characterized in that, include: n parallel DC system units, where n is a positive integer greater than or equal to 2; The first bus is connected to the first terminal of the DC system unit via a connecting wire; The second bus is connected to the second terminal of the DC system unit via a connecting wire; The principle for configuring the wire lengths between the first bus, the second bus, and the DC system unit is as follows: The resistance from each DC system unit to the bus node of the first bus and the second bus is the same; The DC system unit is directly connected to the first bus and the second bus via a conductor, and the axes of the conductors corresponding to the plurality of DC system units are parallel to each other; The angle between the first bus, the second bus and the extension of the conductor is θ, where θ is less than 90°. The conductor length is shorter for DC system units closer to the bus node and longer for DC system units farther from the bus node. The fixed ends of the first busbar and the second busbar are mounted to the busbar fixing part by hinges or rotatable fixing points; the free parts of the first busbar and the second busbar are engaged with the travel guide rail by snap-fit ​​parts. When the first busbar and the second busbar rotate around the busbar fixing part to adjust the included angle θ, the snap-fit ​​parts travel within the travel guide rail. The fixed end of the walking guide rail is hinged to a fixed position and can rotate freely around the fixed position; the walking guide rail is a slidable busbar, the slidable busbar is made of the same material as the first busbar or the second busbar, and the bus node is located at the end of the slidable busbar away from the first busbar or the second busbar connected to it.

2. The current sharing circuit of the DC system unit according to claim 1, characterized in that, The length of the conductors between the first bus, the second bus and the DC system unit is inversely proportional to the node distance, which is the distance between the node of the DC system unit on the first bus and the second bus and the bus node.

3. The current sharing circuit of the DC system unit according to claim 1, characterized in that, The n parallel DC system units are distributed at equal intervals on the first busbar and the second busbar.

4. The current sharing circuit of the DC system unit according to claim 1, characterized in that, The lengths of the conductors connecting the first bus, the second bus, and the DC system unit are: Where 2≤i≤n; The i represents the conductor corresponding to the i-th DC system unit. This represents the conductor length corresponding to the i-th DC system unit; The The length of the conductor corresponding to the DC system unit furthest from the bus node; The The resistivity of the busbar; The The resistivity of the conductor; The The cross-sectional area of ​​the busbar; The The cross-sectional area of ​​the conductor; The The temperature coefficient of the busbar; The The temperature coefficient of the conductor; T is the set operating ambient temperature of the current sharing circuit of the DC system unit; The The spacing between the connection nodes of the DC system unit on the first busbar and the second busbar.

5. The current sharing circuit of the DC system unit according to claim 1, characterized in that, The value of θ is: The The resistivity of the busbar; The The resistivity of the conductor; The The cross-sectional area of ​​the busbar; The The cross-sectional area of ​​the conductor; The The temperature coefficient of the busbar; The The temperature coefficient of the conductor; T is the set operating ambient temperature of the current sharing circuit of the DC system unit.

6. A battery system, characterized in that, include: The current sharing circuit of the DC system unit according to any one of claims 1-5.

7. The battery system according to claim 6, characterized in that, The battery system is a stationary energy storage system or a mobile energy storage system, and the energy storage units in the system are lead-acid batteries, lithium batteries, nickel-metal hydride batteries or supercapacitors.

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