Relay and series-parallel switching circuit of power supply system

Abstract

The invention relates to a relay and a series-parallel switching circuit of a power supply system, and belongs to the technical field of battery charging control. According to the invention, a pair of normally-closed moving and static contact groups is added on the basis of a plurality of pairs of moving and static contact groups included in an existing relay, and the pair of normally-closed moving and static contact groups are used for being arranged at two ends of a pre-charging resistor in an output loop of a battery system; and the displacement stroke of the process of switching from the unclosed state to the closed state is larger than that of the other two pairs of normally-closed movable and static contact groups, so that the normally-closed movable and static contact groups cannot be switched immediately at the moment when a battery system loop is switched from a series charging state to a parallel discharging state, and a pre-charging resistor in the loop is connected in series in the loop, so that the battery system loop is prevented from being damaged. The device is used for balancing the voltage of the two systems and playing a role in current limiting. According to the invention, by setting the pre-charging resistor and different contact strokes, the problem of large current impact caused by voltage difference when two battery systems are connected in parallel is solved, so that electrical parts or battery cells in a loop are prevented from being damaged.

Description

Technical Field

[0001] The invention relates to a relay and a power supply system series-parallel switching circuit, belonging to the technical field of battery charging control. Background Art

[0002] With the increasing development of the new energy market, the requirements for vehicle endurance and charging speed are becoming higher and higher. The three main factors affecting this problem are: ①Increasing the power of the whole vehicle; ②Increasing the current carrying capacity of the battery system; ③Increasing the system platform voltage. Among them, increasing the power of the whole vehicle can effectively improve the endurance of the whole vehicle, but the accompanying problem is that the increase in power will pose a great challenge to the cost and layout space of the whole vehicle, and the increase in power may cause slower charging speed. Increasing the current carrying capacity of the battery system requires the selection of cells and electrical connectors that support high-rate charging and discharging, which can effectively improve the charging speed and discharge capacity of the system, but the accompanying problem is that it will cause more heat loss and will pose a great challenge to battery thermal management. On the premise that the power of the battery system remains unchanged, increasing the system platform voltage can reduce the cell capacity required by the battery system, and a small cell capacity is more conducive to high-rate charging and can also reduce the heat loss of the system.

[0003] From the above analysis, it can be seen that increasing the system platform voltage is more conducive to improving the charging rate of the system, but it has little effect on the endurance of the vehicle. In addition, the improvement of the voltage platform requires the simultaneous improvement of high-voltage devices (battery system, DCDC, MCU, motor, etc.) in the entire circuit, which requires relatively expensive development costs and a relatively long development cycle. However, to improve the system voltage platform only when charging, it is only necessary to improve several devices such as charging batteries, charging sockets, charging cables, DCDC, etc., which can greatly save development costs and development cycles. At present, some manufacturers in the industry realize the series and parallel connection of two battery systems by controlling the on and off of three independent relays, thereby realizing the series connection of the two systems for high-voltage charging during charging, and the parallel connection of the two systems for large-capacity discharge during discharge.

[0004] For two battery systems, the series-parallel switching of the two battery systems is currently achieved by controlling three independent relays (K1 / K2 / K3), such as Figure 1 The specific operation is as follows: When the system is discharging, the control relays K1 / K2 are closed, and K3 is disconnected, at which time the battery system 1 and the battery system 2 are discharged in parallel. When the system is charging, the control relays K1 / K2 are disconnected, and K3 is closed, at which time the battery system 1 and the battery system 2 are discharged in series.

[0005] However, this solution has the following problems: the control of the on and off of three independent relays (K1 / K2 / K3), and the closing or closing of the three relays has high requirements on the timing, and the BMS drive circuit and control accuracy are required to be high; if the closing timing of the three independent relays is wrong or the relays are stuck, it will cause safety risks such as short circuit in the system, such as K1 and K3 are closed at the same time or K2 and K3 are closed at the same time. For this reason, someone proposed a relay that can realize multiple pairs of moving contact groups, such as the Chinese patent application document with application publication number CN118571712A, which discloses a relay, a power battery pack and a vehicle, wherein the relay includes at least three pairs of moving and static contact groups, and the linkage mechanism drives the moving contact group to move, so that one of the multiple moving contact groups can be located in the combined position, and at least two of the remaining moving contact groups are located in the disconnected position, that is, the combination or disconnection of some moving and static contact groups is realized, and the on and off of multiple circuits can be controlled by this relay to realize the series-parallel switching of multiple circuits.

[0006] Although the above solution can solve the risks brought by multiple relays, since the two battery systems are connected in series and then switched to parallel after charging, there will be a pressure difference between the two systems and then they will be directly closed to generate an instant short-circuit impact current, which will seriously affect the service life of the power system battery and relays. After long-term use, it will cause the relays to stick together, resulting in a system short-circuit safety risk. In addition, the two ends of the multiple sets of moving and static contacts of the relay in the above solution are reused by two sets of electrical connection circuits, so that the same contact needs to bear double the arc energy damage caused by the contact being attracted or disconnected under load, which will affect its normal service life. Summary of the invention

[0007] The purpose of the present invention is to provide a relay and a power system series-parallel switching circuit to solve the problem of short relay service life and high safety risk caused by impact current generated when two battery systems are connected in series and then switched to parallel.

[0008] In order to solve the above technical problems, the present invention provides a series-parallel switching circuit for a power system, comprising at least two battery systems and a relay for realizing series-parallel switching of multiple battery systems, wherein the relay comprises three pairs of moving and static contact groups, two pairs of which are normally closed and used for realizing parallel connection of two battery systems, and the other pair is normally open and used for realizing series connection of two battery systems, wherein the relay further comprises a pair of normally closed moving and static contact groups, wherein the pair of normally closed moving and static contact groups are arranged at both ends of a pre-charging resistor, wherein the pre-charging resistor is arranged in an output circuit of the battery system, and wherein the displacement stroke of the pair of normally closed moving and static contact groups in the process of switching from an unclosed state to a closed state is greater than that of the other two pairs of normally closed moving and static contact groups.

[0009] Furthermore, the elastic coefficient of the normally closed type moving and static contact group with a larger displacement stroke is greater than the elastic coefficient of other normally closed type moving and static contact groups.

[0010] Furthermore, each movable contact in each movable and static contact group is driven by the same push rod.

[0011] Furthermore, the push rod is connected to a driving assembly, which includes a coil and a spring. The spring is used to drive the push rod to move under the force of the magnetic field generated when the coil is energized, thereby realizing the state switching of each moving and static contact group.

[0012] Furthermore, the series-parallel switching circuit also includes a current sensor arranged in each battery system loop.

[0013] The present invention also provides a relay, comprising three pairs of moving and static contact groups, two pairs of which are normally closed and used to realize parallel connection of two battery systems, and the other pair is normally open and used to realize series connection of two battery systems. The relay also includes a pair of normally closed moving and static contact groups, which are used to be arranged at both ends of a pre-charging resistor, and the pre-charging resistor is used to be arranged in an output circuit of the battery system, and the displacement stroke of the pair of normally closed moving and static contact groups in the process of switching from an unclosed state to a closed state is greater than that of the other two pairs of normally closed moving and static contact groups.

[0014] Furthermore, the elastic coefficient of the normally closed type moving and static contact group with a larger displacement stroke is greater than the elastic coefficient of other normally closed type moving and static contact groups.

[0015] Furthermore, each movable contact in each movable and static contact group is driven by the same push rod.

[0016] Furthermore, the push rod is connected to a driving assembly, which includes a coil and a spring. The spring is used to drive the push rod to move under the force of the magnetic field generated when the coil is energized, thereby realizing the state switching of each moving and static contact group.

[0017] The beneficial effects of the present invention are as follows: as an improved invention, the present invention adds a pair of normally closed moving and static contact groups on the basis of multiple pairs of moving and static contact groups included in the existing relay, and the pair of normally closed moving and static contact groups are used to be set at both ends of the pre-charge resistor in the output circuit of the battery system, and the displacement stroke of the pair of normally closed moving and static contact groups in the process of switching from an unclosed state to a closed state is greater than that of the other two pairs of normally closed moving and static contact groups. In this way, when the battery system circuit is switched from a series charging state to a parallel discharge state, since the normally closed moving and static contact groups connected in parallel at both ends of the pre-charge resistor have a large stroke, at the moment when the two battery systems are switched to parallel, the normally closed moving and static contact groups are not switched immediately, and the pre-charge resistor in the circuit will be connected in series in the circuit, thereby balancing the voltages of the two systems and playing a current limiting role. After the moving and static contacts of the normally closed moving and static contact groups are in place, the pre-charge resistor is bypassed, and the system can start parallel discharge normally. It can be seen that the present invention solves the large current impact caused by the voltage difference when two battery systems are connected in parallel by setting the pre-charging resistance and different contact strokes, thereby avoiding damage to the electrical parts or cells in the circuit and improving the life of the relay and the battery system. At the same time, each pair of dynamic and static contact groups is provided with an electrical connection circuit, and there is no situation where multiple electrical connection circuits share one contact group, thereby ensuring the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the electrical schematic diagram of the series-parallel switching circuit of the current power supply system; Figure 2 is a front view of the relay used in the present invention in an undriven state; Figure 3 is a side view of the relay used in the present invention in an undriven state; Figure 4 It is an electrical schematic diagram of parallel discharge of the series-parallel switching circuit of the power supply system of the present invention; Figure 5 It is an electrical schematic diagram of series charging of the series-parallel switching circuit of the power supply system of the present invention; Figure 6 It is an electrical principle diagram of the instant when the series-to-parallel switching circuit of the power supply system of the present invention switches from series to parallel; Figure 7 is a front view of the relay structure adopted by the present invention; Figure 8 is a side view of the relay structure adopted by the present invention; Among them, 1 is a spring, 2 is a coil, 3 is an insulating component, 4 is a push rod, 5 is static contact No. 1, 6 is moving contact No. 1, 7 is static contact No. 2, 8 is moving contact No. 2, 9 is static contact No. 5, 10 is moving contact No. 5, 11 is static contact No. 6, 12 is moving contact No. 6, 13 is static contact No. 3, 14 is moving contact No. 3, 15 is static contact No. 4, 16 is moving contact No. 4, 17 is static contact No. 7, 18 is moving contact No. 7, 19 is static contact No. 8, and 20 is moving contact No. 8. DETAILED DESCRIPTION

[0019] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0020] The present invention adds a pair of normally closed moving and static contact groups on the basis of multiple pairs of moving and static contact groups included in existing relays. The pair of normally closed moving and static contact groups is used to be set at both ends of pre-charging resistance in the output circuit of the battery system, and the displacement stroke of the pair of normally closed moving and static contact groups in the process of switching from an unclosed state to a closed state is greater than that of the other two pairs of normally closed moving and static contact groups. In this way, at the moment when the battery system circuit switches from a series charging state to a parallel discharge state, the normally closed moving and static contact groups will not switch immediately, and the pre-charging resistance in the circuit will be connected in series in the circuit to balance the voltages of the two systems and play a current limiting role.

[0021] Embodiment of series-parallel switching circuit of power supply system like Figure 4 As shown, the series-parallel switching circuit of the power system of the present invention includes two battery systems and relays for realizing series-parallel switching of multiple battery systems, wherein the relays include four pairs of moving and static contact groups, three pairs of which are normally closed, two pairs of which are normally closed and are used to realize parallel connection of two battery systems, and another pair is normally open and is used to realize series connection of two battery systems, and the remaining pair of normally closed moving and static contact groups are arranged at both ends of pre-charging resistors, wherein the pre-charging resistors are arranged in the charging circuit of the series battery system, and the displacement stroke of the pair of normally closed moving and static contact groups in the process of switching from an unclosed state to a closed state is greater than that of the other two pairs of normally closed moving and static contact groups.

[0022] Specifically, the three-dimensional structure of the relay used in this embodiment is as follows Figure 7 and Figure 8 As shown, its internal structure is as follows Figure 2 and Figure 3As shown, it includes a spring 1, a coil 2, an insulating component 3 and a push rod 4, wherein the insulating component 3 is arranged between the push rod 4 and the moving contact piece, and functions to isolate the electrical connection between different moving contact pieces and between the push rod 4, so as to prevent different moving contact pieces from being connected to each other and insulation failure; the push rod 4 is connected to each moving contact in the four pairs of moving and static contact groups, and can simultaneously drive all the moving contacts in the four pairs of moving and static contact groups to move, and the four pairs of moving and static contact groups include a first moving and static contact group, a second moving and static contact group, a third moving and static contact group and a fourth moving and static contact group. The first static and moving contact group includes static contact No. 1 5, dynamic contact No. 1 6, static contact No. 2 7 and dynamic contact No. 2 8; the second static and moving contact group includes static contact No. 3 13, dynamic contact No. 3 14, static contact No. 4 15 and dynamic contact No. 4 16; the third static and moving contact group includes static contact No. 5 9, dynamic contact No. 5 10, static contact No. 6 11 and dynamic contact No. 6 12; the fourth static and moving contact group includes static contact No. 7 17, dynamic contact No. 7 18, static contact No. 8 19 and dynamic contact No. 8 20. The first static and moving contact group, the second static and moving contact group and the third static and moving contact group are all normally closed static and moving contact groups, and the fourth static and moving contact group is a normally open static and moving contact group.

[0023] In order to achieve the purpose of voltage balancing and current limiting of the large impact current generated when two battery systems are connected in series and parallel, the pull-in displacement stroke of one group of the three normally closed moving and static contact groups is greater than that of the other two groups. In this embodiment, the displacement stroke of the first moving and static contact group during the process of switching from an unclosed state to a closed state is greater than that of the second moving and static contact group and the third moving and static contact group. Since the displacement strokes of the push rod 4 are consistent, and the displacement stroke of the moving contact of the first moving and static contact group is greater than that of the other two normally closed contact groups, it can be concluded that the spring compression amount on the moving contact of the first moving and static contact group is relatively small. In order to ensure that the positive pressure between different moving and static contacts is consistent when closing, the spring elasticity coefficient on the contact of the first moving and static contact group can be increased (a spring with a large elasticity coefficient can be directly selected when selecting the spring) to achieve the first moving and static contact group. When the contact spring compression amount is low, it can still ensure the same elasticity as other contact groups, thereby ensuring the reliability of electrical connection.

[0024] The pre-charge resistor needs to be connected in parallel between the two battery systems. Its main function is: after the two systems are charged in series, the pre-charge resistor needs to intervene in the parallel circuit at the moment of switching to the parallel circuit. This prevents two systems with a voltage difference from being directly connected in parallel to generate a large current. Figure 4 As shown, the first moving and static contact group is set at both ends of the pre-charging resistor, the second moving and static contact group is set between the positive poles of the two battery systems, the third moving and static contact group is set between the positive poles of the two battery systems, and the fourth moving and static contact group is set between the positive pole of one battery system and the negative pole of another battery system.

[0025] In this way, when two battery systems need to be discharged in parallel, it is only necessary to control the second and third moving and static contact groups to be in a closed state, and the fourth moving and static contact group to be in an open state. To avoid unnecessary energy loss, the first moving and static contact group is also in a closed state at this time, and the pre-charge resistor is bypassed. Figure 4 When two battery systems need to be connected in series for discharge, it is only necessary to control the first moving and static contact group, the second moving and static contact group, and the third moving and static contact group to be in an open state, and the fourth moving and static contact group to be in a closed state, as shown. Figure 5 As shown, the two battery systems can now be charged in series.

[0026] When the two battery systems are switched from series charging to parallel discharge, due to the different distribution of the internal resistance of the two battery systems, there will be voltage inconsistency during the charging process. When the relay state is switched from the driven state to the undriven state, it is equivalent to the first moving and static contact group, the second moving and static contact group and the third moving and static contact group switching from the non-closed state to the closed state, and the fourth moving and static contact group switching from the closed state to the non-closed state. And because the two moving contacts of the second moving and static contact group have a larger travel displacement than the four moving contacts in the second moving and static contact group and the third moving and static contact group, at the moment the two battery systems are switched to parallel, the pre-charging resistance in the circuit will be connected in series in the circuit to balance the voltage of the two systems and perform current limiting, such as Figure 6 After the moving and static contacts of the first moving and static contact group are in contact, the pre-charge resistor is bypassed, and the two battery systems can start parallel discharge normally.

[0027] In addition, there are only two current sensors in the circuit. At the same time, a charging contactor is provided in the charging circuit to realize charging control, and an MSD is also provided in the discharging circuit.

[0028] Therefore, the present invention sets a pre-charging resistor in the circuit of the battery system, and makes the moving contact stroke of the first moving and static contact group connected in parallel at both ends of the pre-charging resistor greater than the moving contact stroke of the second moving and static contact group and the third moving and static contact for realizing parallel switching of the battery system. In this way, the large current shock caused by the pressure difference when two battery systems are connected in parallel can be solved, thereby avoiding damage to electrical components or battery cells in the circuit and improving the life of the relay and the battery system.

[0029] Relay Example The relay of this embodiment includes three pairs of moving and static contact groups, two of which are normally closed and used to realize the parallel connection of two battery systems, and the other pair is normally open and used to realize the series connection of two battery systems. The relay also includes a pair of normally closed moving and static contact groups, which are used to be set at both ends of the pre-charging resistor, and the pre-charging resistor is used to be set in the output circuit of the battery system, and the displacement stroke of the normally closed moving and static contact group from the unclosed state to the closed state is greater than that of the other two pairs of normally closed moving and static contact groups. The specific structure has been described in detail in the embodiment of the series-parallel switching circuit of the power supply system, and will not be repeated here.

Claims

1. A power system series-parallel switching circuit, comprising at least two battery systems and a relay for realizing series-parallel switching of multiple battery systems, wherein the relay comprises three pairs of moving and static contact groups, two pairs of which are normally closed and used to realize parallel connection of two battery systems, and the other pair is normally open and used to realize series connection of two battery systems, characterized in that: The relay also includes a pair of normally closed moving and static contact groups, which are arranged at both ends of the pre-charging resistor, and the pre-charging resistor is arranged in the output circuit of the battery system, and the displacement stroke of the pair of normally closed moving and static contact groups in the process of switching from an unclosed state to a closed state is greater than that of the other two pairs of normally closed moving and static contact groups.

2. The power supply system series-parallel switching circuit according to claim 1, characterized in that: The elastic coefficient of the normally closed type moving and static contact group with a larger displacement stroke is greater than the elastic coefficient of other normally closed type moving and static contact groups.

3. The power system series-parallel switching circuit according to claim 1, characterized in that: Each moving contact in each moving and static contact group is driven by the same push rod.

4. The power supply system series-parallel switching circuit according to claim 3, characterized in that: The push rod is connected to a driving assembly, which includes a coil and a spring. The spring is used to drive the push rod to move under the force of the magnetic field generated when the coil is energized, so as to achieve state switching of each moving and static contact group.

5. The power system series-parallel switching circuit according to claim 1, characterized in that: The series-parallel switching circuit also includes a current sensor arranged in each battery system loop.

6. A relay, comprising three pairs of moving and static contact groups, two pairs of which are normally closed and used to realize the parallel connection of two battery systems, and the other pair is normally open and used to realize the series connection of two battery systems, characterized in that: The relay also includes a pair of normally closed moving and static contact groups, which are used to be set at both ends of the pre-charging resistor, and the pre-charging resistor is used to be set in the output circuit of the battery system, and the displacement stroke of the pair of normally closed moving and static contact groups in the process of switching from an unclosed state to a closed state is greater than that of the other two pairs of normally closed moving and static contact groups.

7. The relay according to claim 6, characterized in that: The elastic coefficient of the normally closed type moving and static contact group with a larger displacement stroke is greater than the elastic coefficient of other normally closed type moving and static contact groups.

8. The relay according to claim 6, characterized in that: Each moving contact in each moving and static contact group is driven by the same push rod.

9. The relay according to claim 8, characterized in that: The push rod is connected to a driving assembly, which includes a coil and a spring. The spring is used to drive the push rod to move under the force of the magnetic field generated when the coil is energized, so as to achieve state switching of each moving and static contact group.

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