Electric vehicle charging and discharging circuit, electric vehicle and control method

Abstract

The application provides an electric vehicle charging and discharging circuit, an electric vehicle and a control method, wherein the circuit comprises: a battery pack, a fuse, a current sensor, a main negative relay, a main positive relay, a fast charging negative relay, a fast charging positive relay, a first semiconductor and a second semiconductor; when the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are all in a closed state, the main negative relay and the fast charging negative relay are connected in parallel through the first semiconductor, and the main positive relay and the fast charging positive relay are connected in parallel through the second semiconductor; when the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are all in an open state, the current output by a direct current charging pile flows from the positive pole of the charging pile to the distribution box through the second semiconductor, and then flows to the negative pole of the charging pile through the first semiconductor. The application can improve the fast charging performance, reduce the cost and enhance the pre-heating reliability.

Description

Technical Field

[0001] The present invention relates to the automotive field, and in particular to an electric vehicle charging and discharging circuit, an electric vehicle, and a control method. Background Art

[0002] With the development of electric vehicle technology, more and more users begin to use electric vehicles. Existing electric vehicles are equipped with charging and discharging circuits to meet the power supply and charging needs of the vehicles.

[0003] However, in the existing technology, in order to shorten the charging time, the charging current is increased, and the current carrying capacity of the fast charging relay needs to be improved accordingly. The use of a larger relay will lead to an increase in weight and cost. The increase in heat generated by a single relay carrying a large amount of electricity will increase the temperature rise of the relay, posing a reliability risk. At the same time, the main circuit and fast charging circuit of the battery pack are usually equipped with a pre-charging circuit, which requires the configuration of a pre-charging relay and a pre-charging resistor. The pre-charging circuit takes up more space and increases the cost. In addition, the low-temperature charging process requires the battery to be preheated by the thermal management system before charging. Under the existing technology, the main circuit relay remains closed during the preheating period. During the preheating process, the current output by the charging pile may partially charge the battery cell, which is not good for the life and safety of the battery cell. Summary of the Invention

[0004] In view of the defects in the prior art, the purpose of the present invention is to provide an electric vehicle charging and discharging circuit, an electric vehicle and a control method, which can realize the transmission of a larger charging current without increasing the current-carrying capacity of the fast-charging relay, thereby improving the fast-charging performance, reducing costs and enhancing the preheating reliability.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solution:

[0006] According to a first aspect of the present invention, there is provided an electric vehicle charging and discharging circuit, comprising: a battery pack, a fuse, a current sensor, a main negative relay, a main positive relay, a fast charge negative relay, a fast charge positive relay, a first semiconductor, and a second semiconductor;

[0007] The power distribution box is used to distribute electrical energy to the electrical load of the entire vehicle, and the main negative relay and the main positive relay are electrically connected to the power distribution box respectively;

[0008] The fast charge negative relay is connected to the negative pole of the charging pile, and the fast charge positive relay is connected to the positive pole of the charging pile;

[0009] The two ends of the first semiconductor are electrically connected to the main negative relay and the fast charging negative relay respectively, and the two ends of the second semiconductor are electrically connected to the main positive relay and the fast charging positive relay respectively;

[0010] The first semiconductor and the second semiconductor are unidirectionally conductive;

[0011] When the main negative relay, main positive relay, fast charging negative relay and fast charging positive relay are all in the closed state, the main negative relay and the fast charging negative relay are connected in parallel through the first semiconductor, and the main positive relay and the fast charging positive relay are connected in parallel through the second semiconductor;

[0012] When the main negative relay, main positive relay, fast charging negative relay and fast charging positive relay are all in the disconnected state, the current output by the DC charging pile flows from the positive pole of the charging pile through the second semiconductor to the distribution box, and then passes through the first semiconductor to connect to the negative pole of the charging pile.

[0013] Preferably, the forward resistance values ​​of the first semiconductor and the second semiconductor are positively correlated with the magnitude of the forward current.

[0014] According to a second aspect of the present invention, there is provided an electric vehicle comprising the above-mentioned electric vehicle charging and discharging circuit.

[0015] According to a third aspect of the present invention, there is provided a method for controlling the above-mentioned electric vehicle charging and discharging circuit, comprising:

[0016] determining an operating mode of the electric vehicle;

[0017] When the electric vehicle is in fast charging mode, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed, the main negative relay and the fast charging negative relay are connected in parallel through the first semiconductor, and the main positive relay and the fast charging positive relay are connected in parallel through the second semiconductor;

[0018] When the electric vehicle is in the preheating mode, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed first, so that the distribution box supplies power to the thermal management system of the entire vehicle. After the charging pile outputs current normally, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are disconnected. The current output by the DC charging pile flows from the positive pole of the charging pile through the second semiconductor to the distribution box, and then passes through the first semiconductor to be connected to the negative pole of the charging pile. When the temperature of the battery pack rises to the threshold temperature allowing charging, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed again.

[0019] Preferably, it also includes:

[0020] When the electric vehicle is powered on, the main negative relay and the fast charging positive relay are closed, and pre-charging is performed through the second semiconductor. After the pre-charging is completed, the main positive relay is closed again, and the fast charging positive relay is disconnected after the main positive relay is closed.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention utilizes the main relay to jointly carry the current during the fast charging process, and can achieve a larger charging current through a small fast charging relay, reducing the cost / weight and space occupancy of the fast charging relay. At the same time, connecting multiple relays in parallel is beneficial to the heat dissipation of the relay, reducing temperature rise, and improving fast charging performance.

[0023] 2. The present invention uses reusable fast-charging relays and semiconductors to replace existing pre-charging relays and pre-charging resistors, reducing the cost and space occupied by the pre-charging circuit and improving the pre-charging performance.

[0024] 3. During fast charging preheating, the present invention can power the heating management system through semiconductors, thereby preventing the battery pack from being unexpectedly charged or discharged to the power supply, while improving the reliability of low-temperature charging conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0026] Figure 1 This is a schematic structural diagram of the existing electric vehicle charging and discharging circuit described in Example 1 of the present invention;

[0027] Figure 2 This is a schematic structural diagram of the electric vehicle charging and discharging circuit described in Example 1 of the present invention.

[0028] The figure shows:

[0029] 1-Battery pack;

[0030] 2-Distribution box

[0031] 3-Fuse

[0032] 4-Current sensor

[0033] 51-Main negative relay

[0034] 52-Main positive relay

[0035] 53-Fast charging negative relay

[0036] 54-Fast charging positive relay

[0037] 55-Precharge relay

[0038] 61-Charging pile positive electrode

[0039] 62-Charging pile negative pole

[0040] 7-Pre-charge resistor

[0041] 81-First Semiconductor

[0042] 82-Second Semiconductor DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for clear, complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0045] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, all directional indications (such as up, down, left, right, front, back, bottom, etc.) in the present application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain specific posture (as shown in the drawings), if the specific posture changes, the directional indications also change accordingly. Further, the description involving "first", "second" and the like in the application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. The technology, method and equipment known to those skilled in the relevant art can not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as part of the specification.

[0046] Embodiment 1

[0047] The electric vehicle charging and discharging circuit provided in the present embodiment is improved on the basis of the existing electric vehicle charging and discharging circuit as shown in Figure 1 The prior art vehicle charging and discharging circuit is as shown in Figure 1As shown, the battery pack is provided with a battery pack 1, a fuse 3, a current sensor 4, a main negative relay 51 and a main positive relay 52. Among them, the main negative relay 51 and the main positive relay 52 are respectively electrically connected to the distribution box 2, and the distribution box 2 distributes electric energy to the whole vehicle electric load. For example, the distribution box 2 can be electrically connected to the motor controller, the air conditioner compressor and the electric heater and other electric loads, and usually the motor controller and the air conditioner compressor are provided with a capacitor, and when the main negative relay 51 and the main positive relay 52 are closed, there will be a large impact current. The main circuit is provided with a pre-charging circuit connected in series by a pre-charging relay 55 and a pre-charging resistor 7. The power-on process first closes the main negative relay 51, and then closes the pre-charging relay 55 to connect the pre-charging resistor 7 in series, and the pre-charging resistor 7 plays a role in reducing the impact current. For example, the resistance value of the pre-charging resistor 7 is 40-100Ω, the voltage of the battery pack 1 is 300-450V, and the introduction of the pre-charging resistor 7 makes the impact current less than 15A in the pre-charging relay 55 closing moment, thereby avoiding the sintering of the relay contact. The pre-charging process takes about 400ms, and after the pre-charging is completed, the voltage at both ends of the capacitor of the electric load is approximately equal to the voltage of the battery pack 1, so the main positive relay 52 is closed after the pre-charging is completed. The main positive relay 52 will not have an impact current in the closing moment. After the main positive relay 52 is closed, the pre-charging relay 55 is disconnected, and the power-on process is completed. The battery pack 1 can transmit electric energy to the whole vehicle electric load through the distribution box 2.

[0048] The battery pack is further provided with a fast-charging negative relay 53 and a fast-charging positive relay 54, the fast-charging negative relay 53 is connected to the negative pole 62 of the charging pile, and the fast-charging positive relay 54 is connected to the positive pole 61 of the charging pile; during the fast-charging process, the charging pile outputs current through the positive pole 61 of the charging pile, the current flows into the battery pack 1 through the fast-charging positive relay 54 and the fuse 3, and further flows through the current sensor A1 and the fast-charging negative relay 53 to the negative pole 62 of the charging pile. For example, if the charging current is 400A, the fast-charging negative relay 53 and the fast-charging positive relay 54 need to continuously bear 400A current; as the performance of the battery cell and the charging pile improves, the fast-charging current becomes larger and larger, and the charging current of the super-fast-charging battery pack can exceed 600A. The improvement of the current-carrying capacity of the fast-charging relay will bring a substantial increase in cost, weight and volume, and how to cool the relay during the fast-charging process is also difficult, which further limits the improvement of the fast-charging performance of the battery pack.

[0049] In addition, the charging of the battery pack 1 under low temperature conditions is limited. For example, charging the battery pack 1 at -20°C will cause lithium precipitation, thereby reducing the cycle life and safety of the battery pack 1. Therefore, in the prior art, the battery pack 1 is usually heated by the vehicle thermal management system until the temperature of the battery pack 1 rises to above 0°C before charging. During the process of plugging in the gun to charge and preheat the battery pack 1, the fast charge negative relay 53 and the fast charge positive relay 54 remain closed, and the current input by the charging pile is transmitted to the battery pack 1 and the distribution box 2 through the fast charge negative relay 53 and the fast charge positive relay 54. The distribution box 2 supplies power to the vehicle thermal management system. During the preheating process, the charging pile is a DC power supply, and the battery pack 1 and the vehicle thermal management system are connected in parallel. The power of the vehicle thermal management system will fluctuate, and it is difficult to ensure that there is no current continuously flowing into the battery pack 1. The fast charge preheating under the prior art has the risk of abuse of the battery pack 1.

[0050] like Figure 2 As shown, based on the existing technology, the electric vehicle charging and discharging circuit provided in this embodiment has been improved. Specifically, a first semiconductor 81 is introduced to electrically connect the rear end of the contact of the main negative relay 51 to the rear end of the contact of the fast charging negative relay 53; a second semiconductor 82 is introduced to electrically connect the rear end of the contact of the main positive relay 52 to the rear end of the contact of the fast charging positive relay 54. The first semiconductor 81 and the second semiconductor 82 can be high-power diodes or other controllable semiconductors to achieve unidirectional conductivity or controllable conduction. That is, when current passes through the first semiconductor 81 or the second semiconductor 82 in the forward direction, the first semiconductor 81 and the second semiconductor 82 exhibit low resistance; conversely, the first semiconductor 81 and the second semiconductor 82 exhibit high resistance, that is, they have reverse blocking characteristics. Preferably, the forward resistance of the first semiconductor 81 and the second semiconductor 82 is positively correlated with the forward current value. When the forward current of the first semiconductor 81 and the second semiconductor 82 changes, their forward resistance will also change accordingly. The larger the forward current, the smaller the forward resistance, and vice versa.

[0051] During the fast charging process, the main negative relay 51 and the main positive relay 52, as well as the fast charging negative relay 53 and the fast charging positive relay 54 are all in the closed state. The main negative relay 51 and the fast charging negative relay 53 are connected in parallel through the first semiconductor 81, and the main positive relay 52 and the fast charging positive relay 54 are connected in parallel through the second semiconductor 82. On the positive side of the battery pack 1, the fast charging current simultaneously flows through the circuit in which the fast charging positive relay 54, the second semiconductor 82 and the main positive relay 52 are connected in series. The main positive relay 52 shunts part of the current for the fast charging positive relay 54. On the negative side of the battery pack 1, the fast charging current simultaneously flows through the circuit in which the fast charging negative relay 53, the first semiconductor 81 and the main negative relay 51 are connected in series. The main negative relay 51 shunts part of the current for the fast charging negative relay 53.

[0052] For example, the continuous current carrying capacity of the first semiconductor 81 and the second semiconductor 82 is 300A, and when the forward current of the first semiconductor 81 and the second semiconductor 82 is 10A, the resistance is about 40Ω; when the forward current is 200A, the resistance is about 0.4mΩ; when the forward current is 300A, the resistance is about 0.2mΩ. The reverse resistance of the first semiconductor 81 and the second semiconductor 82 is greater than 500kΩ. The rated current of the fast charging negative relay 53 and the fast charging positive relay 54 is 200A, and the contact resistance is 0.6mΩ; the rated current of the main negative relay 51 and the main positive relay 52 is 300A, and the contact resistance is 0.2mΩ. If the DC charging pile output current is 400A, the current passing through the fast-charge negative relay 53 and the fast-charge positive relay 54 is 200A, the current passing through the second semiconductor 82 and the main positive relay 52 is 200A, and the current passing through the first semiconductor 81 and the main negative relay 51 is 200A. If the DC charging pile output current is 500A, the current passing through the fast-charge negative relay 53 and the fast-charge positive relay 54 is 200A, the current passing through the second semiconductor 82 and the main positive relay 52 is 300A, and the current passing through the first semiconductor 81 and the main negative relay 51 is 300A. However, it should be noted that the above parameters do not constitute a limitation on the technical solution of this embodiment.

[0053] The first semiconductor 81 diverts part of the current through the main negative relay 51, and the second semiconductor 82 diverts part of the current through the main positive relay 52. ​​This reduces the current in the fast-charge negative relay 53 and the fast-charge positive relay 54. During high-current fast charging, smaller relays can be used to meet the current carrying requirements, reducing manufacturing costs. Furthermore, since the fast-charge current is carried by multiple relays, the heat dissipation and temperature rise of the relays are easier to control.

[0054] When charging and preheating the battery pack 1 at -20°C, first the main negative relay 51 and the main positive relay 52 are closed, and the fast charge negative relay 53 and the fast charge positive relay 54 are closed. At this time, the current input by the charging pile is transmitted to the battery pack 1 and the distribution box 2 through the fast charge negative relay 53 and the fast charge positive relay 54, and the distribution box 2 supplies power to the thermal management system of the whole vehicle. After successful communication with the DC charging pile and the charging pile outputs current normally, the main negative relay 51 and the main positive relay 52 are disconnected, and then the fast charge negative relay 53 and the fast charge positive relay 54 are disconnected. The current output by the DC charging pile flows from the positive pole 61 of the charging pile through the second semiconductor 82 to the distribution box 2, and then through the first semiconductor 81 to the negative pole 62 of the charging pile. This ensures that during the preheating process, all the electric energy output by the charging pile is transmitted to the thermal management system of the whole vehicle through the distribution box 2, and no current continues to flow into the battery pack 1. When the temperature of the battery pack 1 rises to a threshold temperature allowing charging, the main negative relay 51 and the main positive relay 52 are closed, and the fast charge negative relay 53 and the fast charge positive relay 54 are closed.

[0055] The charge and discharge circuit provided in this embodiment is as follows: Figure 2 As shown, the Figure 1 The pre-charge relay 55 and pre-charge resistor 7 commonly used in the prior art are shown, and can also achieve no impact current at the moment the main positive relay 52 is closed. Specifically, the power-on process first closes the main negative relay 51, and then closes the fast-charge positive relay 54. The second semiconductor 82 plays the role of a pre-charge resistor. The capacitor of the electrical load is pre-charged through the pre-charge circuit composed of the fast-charge positive relay 54 and the second semiconductor 82. At this time, the second semiconductor 82 can play a role in reducing the impact current. After the pre-charge is completed, the voltage across the capacitor of the electrical load is roughly equal to the voltage of the battery pack 1; after the pre-charge is completed, the main positive relay 52 is closed again, and there will be no impact current at the moment the main positive relay 52 is closed; after the main positive relay 52 is closed, the fast-charge positive relay 54 is disconnected, and the power-on process is completed.

[0056] Example 2

[0057] This embodiment provides an electric vehicle, which includes the electric vehicle charging and discharging circuit according to embodiment 1.

[0058] According to the electric vehicle of this embodiment, the fast-charging process utilizes the main relay to jointly carry the current, and a larger charging current is achieved through a small fast-charging relay; the cost / weight and space occupied by the fast-charging relay are reduced, and multiple relays connected in parallel are beneficial to the heat dissipation of the relay, reducing temperature rise and improving fast-charging performance. The fast-charging relay and semiconductor are reused to replace the existing pre-charging relay and pre-charging resistor, reducing the cost and space occupied by the pre-charging circuit and improving pre-charging performance. During fast-charging preheating, the semiconductor is used to power the heating management system, preventing the battery pack from being unexpectedly charged or discharged to the feeder; and improving the reliability of low-temperature charging conditions.

[0059] Specifically, electric vehicles include but are not limited to pure electric vehicles and hybrid electric vehicles.

[0060] It should be noted that the explanation of the implementation method and beneficial effects of the electric vehicle charging and discharging circuit in the above embodiment 1 is also applicable to the electric vehicle of this embodiment. To avoid redundancy, it will not be elaborated here.

[0061] Example 3

[0062] The present invention proposes a control method for a charging and discharging circuit of an electric vehicle according to any of the above embodiments, the control method comprising: firstly determining an operating mode of the electric vehicle;

[0063] When the electric vehicle is in the fast charging mode, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed, the main negative relay and the fast charging negative relay are connected in parallel through the first semiconductor, and the main positive relay and the fast charging positive relay are connected in parallel through the second semiconductor;

[0064] When the electric vehicle is in the pre-heating mode, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are first closed, so that the power distribution box supplies power to the vehicle thermal management system, then the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are disconnected, the current output by the direct current charging pile flows from the positive pole of the charging pile to the power distribution box through the second semiconductor, and then is connected to the negative pole of the charging pile through the first semiconductor, when the temperature of the battery pack rises to the threshold temperature allowing charging, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed again.

[0065] Preferably, when the electric vehicle is powered on, the main negative relay and the fast charging positive relay are closed, pre-charging is performed through the second semiconductor, after the pre-charging is completed, the main positive relay is closed again, and after the main positive relay is closed, the fast charging positive relay is disconnected.

[0066] Specifically, the working mode of the electric vehicle can include the fast charging mode and the pre-heating mode. It should be noted that the above embodiment 1 and embodiment 2 are also applicable to the control method of the present embodiment, and the implementation and beneficial effects of the electric vehicle charging and discharging circuit are explained and described, and to avoid redundancy, they will not be expanded here.

[0067] The above describes the specific embodiments of the present application, and through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application.

Claims

1. An electric vehicle charging and discharging circuit, characterized in that: include: Battery pack, fuse, current sensor, main negative relay, main positive relay, fast charge negative relay, fast charge positive relay, first semiconductor, second semiconductor; The power distribution box is used to distribute electrical energy to the electrical load of the entire vehicle, and the main negative relay and the main positive relay are electrically connected to the power distribution box respectively; The fast charge negative relay is connected to the negative pole of the charging pile, and the fast charge positive relay is connected to the positive pole of the charging pile; The two ends of the first semiconductor are electrically connected to the main negative relay and the fast charging negative relay respectively, and the two ends of the second semiconductor are electrically connected to the main positive relay and the fast charging positive relay respectively; The first semiconductor and the second semiconductor are unidirectionally conductive; When the main negative relay, main positive relay, fast charging negative relay and fast charging positive relay are all in the closed state, the main negative relay and the fast charging negative relay are connected in parallel through the first semiconductor, and the main positive relay and the fast charging positive relay are connected in parallel through the second semiconductor; When the main negative relay, main positive relay, fast charging negative relay and fast charging positive relay are all in the disconnected state, the current output by the DC charging pile flows from the positive pole of the charging pile through the second semiconductor to the distribution box, and then passes through the first semiconductor to connect to the negative pole of the charging pile.

2. The electric vehicle charging and discharging circuit according to claim 1, characterized in that: The forward resistance values ​​of the first semiconductor and the second semiconductor are positively correlated with the magnitude of the forward current.

3. An electric vehicle, characterized in that: The electric vehicle charging and discharging circuit comprises the electric vehicle charging and discharging circuit according to any one of claims 1-2.

4. A control method for an electric vehicle charging and discharging circuit according to any one of claims 1-2, characterized in that: include: determining an operating mode of the electric vehicle; When the electric vehicle is in fast charging mode, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed, the main negative relay and the fast charging negative relay are connected in parallel through the first semiconductor, and the main positive relay and the fast charging positive relay are connected in parallel through the second semiconductor; When the electric vehicle is in the preheating mode, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed first, so that the distribution box supplies power to the thermal management system of the entire vehicle. After the charging pile outputs current normally, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are disconnected. The current output by the DC charging pile flows from the positive pole of the charging pile through the second semiconductor to the distribution box, and then passes through the first semiconductor to be connected to the negative pole of the charging pile. When the temperature of the battery pack rises to the threshold temperature allowing charging, the main negative relay, the main positive relay, the fast charging negative relay and the fast charging positive relay are closed again.

5. The control method of the electric vehicle charging and discharging circuit according to claim 4, characterized in that: Also includes: When the electric vehicle is powered on, the main negative relay and the fast charging positive relay are closed, and pre-charging is performed through the second semiconductor. After the pre-charging is completed, the main positive relay is closed again, and the fast charging positive relay is disconnected after the main positive relay is closed.

Images