An electric energy discharge device and method for electric vehicle bus capacitor

Abstract

The present invention relates to an electric energy discharge device and method for a bus capacitor of an electric vehicle, wherein the bus capacitor and the power battery of the electric vehicle are both arranged in a discharge circuit of the electric vehicle. The discharge circuit is controlled to be on and off by at least one discharge contactor. The electric energy discharge device comprises an active discharge circuit and a discharge control circuit. The active discharge circuit comprises a discharge switch and a discharge resistor, and the discharge switch, the discharge resistor and the bus capacitor are connected in series to form an active discharge circuit. The discharge control circuit is used to control the closing or opening of the discharge switch by its own on and off. The discharge control circuit is connected in series with at least one discharge interlock switch. The auxiliary contact of the discharge contactor is used to control the on and off of the control circuit of the discharge interlock switch corresponding thereto. The present invention realizes hardware interlocking between the active discharge circuit and the discharge circuit, and the electric energy discharge of the bus capacitor is more stable and safe.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and in particular to an electric energy discharge device and method for a bus capacitor of an electric vehicle. Background Art

[0002] In electric vehicles, DC support bus capacitors (bus capacitors) are applied on the DC input side of inverters and converters (motor controllers, oil pump controllers, etc.) to buffer the energy exchange between the DC power supply and the load, stabilize the DC bus voltage, prevent large fluctuations in the DC bus voltage due to sudden load changes such as acceleration and deceleration and the induced electromotive force generated by parasitic inductance, and suppress the harmonic voltage on the DC side. When the vehicle is powered off, the bus capacitor stores a large amount of energy. To prevent operators from getting electric shock during routine maintenance or overhaul, the vehicle is usually equipped with an active discharge circuit, which quickly discharges the voltage on the capacitor to below the safe voltage through resistor heating. During the discharge process, it is necessary to ensure that the high-voltage contactor of the discharge circuit is in the disconnected state, otherwise the active discharge circuit of the active discharge circuit is directly connected to the power battery, which will cause the discharge resistor to burn out or even burn through, causing the filler to splash, and there is a risk of arcing and fire.

[0003] In the prior art, the contactor status is usually determined by monitoring the voltage difference across the contactor main contacts. When the power is off, the active discharge needs to be turned on after the contactor is disconnected. The voltage drops slowly, and the contactor status cannot be quickly and accurately determined. Therefore, it is only detected during the power-on process, and not detected during power-off. If the control software of the active discharge circuit is abnormal or the high-voltage contactor is stuck, the structure has the problem of directly connecting the active discharge circuit to the power battery.

[0004] For example, the solution disclosed in the Chinese invention patent with the authorization announcement number CN106199409B relies on the voltage sampling accuracy and the discharge curve of the bus capacitor, but it is still essentially judged by the voltage difference method. This structure has the problems of poor timeliness and accuracy in the detection of the power-off process, and there is still the possibility that the bus capacitor active discharge circuit is directly connected to the power battery discharge circuit. And the solution disclosed in the Chinese invention patent with the application number 201610166360.8, which uses key signals, charging signals, etc. to control the on and off of the active discharge circuit, also has the problem of direct connection between the active discharge circuit and the power battery due to abnormal control software or adhesion of the high-voltage contactor. Although the above solution also proposes protection measures such as fuses, the structure is complex and the fuse also has limitations. Summary of the invention

[0005] The present invention provides an electric energy discharge device and method for a bus capacitor of an electric vehicle to solve the above problems.

[0006] The present invention adopts the following technical solution:

[0007] An electric energy discharge device for a bus capacitor of an electric vehicle, wherein the bus capacitor and the power battery of the electric vehicle are both arranged in a discharge circuit of the electric vehicle. The discharge circuit is controlled to be on and off by at least one discharge contactor, and the main contact of the discharge contactor is used to control the on and off of the discharge circuit. The electric energy discharge device includes an active discharge circuit and a discharge control circuit. The active discharge circuit includes a discharge switch and a discharge resistor, and the discharge switch, the discharge resistor and the bus capacitor are connected in series to form an active discharge circuit. The discharge control circuit is used to control the closing or opening of the discharge switch by its own on and off. The discharge control circuit is connected in series with at least one discharge interlock switch, and the discharge interlock switch is arranged in a one-to-one correspondence with the discharge contactor. The discharge interlock switch is a discharge interlock switch of a normally closed structure, and the discharge interlock switch is used to disconnect the discharge control circuit by its own disconnection. The auxiliary contact of the discharge contactor is used to control the on and off of the control circuit of the corresponding discharge interlock switch.

[0008] Further:

[0009] The above-mentioned discharge contactor is a normally open high-voltage contactor structure.

[0010] The discharge switch is a normally open high-voltage contactor structure, and the discharge control circuit controls the discharge switch through a control coil in the normally open high-voltage contactor structure of the discharge switch.

[0011] The discharge switch is a power electronic switch tube structure, and the power electronic switch tube structure is a power electronic switch tube in the form of MOSFET or IGBT.

[0012] The above-mentioned discharge interlock switch is set as a normally closed low-voltage contactor structure, and the control circuit of the discharge interlock switch is the circuit where the control coil of the normally closed low-voltage contactor structure is located.

[0013] When at least two discharge contactors are provided, at least two discharge contactors are connected in parallel to the discharge circuit. At least two discharge interlock switches are connected in series to the discharge control circuit.

[0014] An energy discharge device for an electric vehicle bus capacitor also includes a pressure difference collection component, which is connected to both ends of the main contacts of the above-mentioned discharge contactor and is used to obtain the voltage difference between the two ends of the main contacts of the discharge contactor.

[0015] An electric energy discharge method using the electric energy discharge device for an electric vehicle bus capacitor comprises the following steps:

[0016] Ⅰ. When the electric vehicle is powered off, the above-mentioned discharge contactors are all controlled to be disconnected, that is, the main contacts and auxiliary contacts of the discharge contactors are all disconnected.

[0017] Ⅱ. The above-mentioned discharge interlock switches corresponding to the discharge contactor are all controlled to be closed.

[0018] III. Control the discharge control switch attached to the discharge control circuit to close, turn on the discharge control circuit, and make the discharge switch in a closed state. The active discharge circuit is connected, and the voltage of the bus capacitor is reduced to below the safe voltage through the discharge resistor.

[0019] IV. When the electric vehicle is in the power-off state and at least one discharge contactor is mistakenly in the closed state, or when the electric vehicle is in the power-on state and the above-mentioned discharge control switch is mistakenly controlled to be closed, since at least one discharge contactor is in the closed state, the auxiliary contact of the discharge contactor is also closed accordingly, that is, the discharge interlock switch corresponding to the discharge contactor in the closed state is disconnected. In this state, the discharge control switch is controlled to be closed. Since the discharge interlock switch is disconnected, the discharge control circuit is disconnected, that is, the discharge switch is in the disconnected state, the active discharge circuit is disconnected, and the active discharge fails. When the active discharge fails, the electric vehicle triggers a fault alarm.

[0020] Further:

[0021] In the electric energy discharge method using the electric energy discharge device for the bus capacitor of an electric vehicle, the electric energy discharge device for the bus capacitor of an electric vehicle is provided with the above-mentioned pressure difference acquisition component, and the above-mentioned step III also includes: when the active discharge circuit is connected, the voltage difference between the two ends of the main contacts of the discharge contactor is obtained through the above-mentioned pressure difference acquisition component, and if there is no voltage difference within the specified range, the electric vehicle triggers a fault alarm.

[0022] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following advantages:

[0023] Firstly, the present invention realizes hardware interlocking between the active discharge circuit and the discharge circuit by setting a discharge interlock switch corresponding to the discharge contactor one by one, connecting the discharge interlock switch in series to the discharge control circuit, and using the auxiliary contact of the discharge contactor to control the setting mode of the corresponding discharge interlock switch. Regardless of the control software abnormality of the active discharge circuit or the adhesion of the discharge contactor, the active discharge circuit will not be directly connected to the power battery, that is, the discharge resistor will not burn out or even burn through to splash the filler, and the electric energy discharge of the bus capacitor will be more stable and safe, thereby improving the reliability and safety of the electric vehicle.

[0024] Secondly, the structure and method of the present invention are scientific, reasonable, reliable and easy to implement, and the installation, use and maintenance costs of the present invention are lower.

[0025] Thirdly, the present invention monitors the discharge contactor using the pressure difference method through the arrangement and application of the pressure difference acquisition component, thereby further improving the reliability and safety of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The circuit diagram of the electric energy discharge device for the bus capacitor of an electric vehicle according to the present invention.

[0027] Figure 2 The present invention is a flowchart of a method for discharging electric energy from a bus capacitor of an electric vehicle. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0029] refer to Figure 1 , an electric energy discharge device for an electric vehicle bus capacitor 41, the bus capacitor 41 and the power battery 42 of the electric vehicle are both located in the discharge circuit of the electric vehicle. The above-mentioned discharge circuit is controlled by at least one discharge contactor, and the main contact of the discharge contactor is used to control the discharge circuit. The electric energy discharge device includes an active discharge circuit 1, a discharge control circuit 2 and a pressure difference acquisition component 3. The above-mentioned active discharge circuit 1 includes a discharge switch and a discharge resistor 12, and the discharge switch, the discharge resistor 12 and the above-mentioned bus capacitor 41 are connected in series to form an active discharge circuit. The above-mentioned discharge control circuit 2 is used to control the closing or opening of the above-mentioned discharge switch through its own on-off. The above-mentioned pressure difference acquisition component 3 is connected to the two ends of the main contact of the above-mentioned discharge contactor, and the pressure difference acquisition component 3 is used to obtain the voltage difference between the two ends of the main contact of the discharge contactor. The discharge control circuit 2 is provided with a discharge control switch, and the discharge control switch is used to perform the discharge of the electric energy of the bus capacitor 41 by being controlled by the vehicle controller. The above structure is basically consistent with the conventional technical means of existing electric vehicles, and will not be described in detail here. Among them, the discharge resistor 12 can adopt the commonly used multi-resistance combination method in the field, Figure 1 The illustration of the discharge resistor 12 is for illustration only. Figure 1 The discharge control circuit 2 only involves the circuit of the improved part of the present invention.

[0030] Continue to refer Figure 1, the above-mentioned discharge control circuit 2 is connected in series with at least one discharge interlock switch, and the discharge interlock switch is set in one-to-one correspondence with the above-mentioned discharge contactor. The discharge interlock switch is a discharge interlock switch of a normally closed structure, and the discharge interlock switch is used to disconnect the discharge control circuit 2 by disconnecting itself. The auxiliary contact of the discharge contactor is used to control the on-off of the control circuit of the above-mentioned discharge interlock switch corresponding to it. Specifically, the above-mentioned discharge contactor is set as a normally open high-voltage contactor structure, the above-mentioned discharge interlock switch is set as a normally closed low-voltage contactor structure, and the above-mentioned discharge switch is a normally open high-voltage contactor structure. The discharge switch includes a discharge main contact 111 and a discharge control coil 112. The discharge control coil 112 is energized or de-energized to control the closing or disconnection of the discharge main contact 111. The discharge control coil 112 is connected to the above-mentioned discharge control circuit 2, that is, the discharge control circuit 2 is used to control the discharge control coil 112 to be energized or de-energized by its own on-off. Among them, the discharge switch can also be a power electronic switch tube structure in the form of MOSFET, IGBT, etc. Correspondingly, when the discharge switch is a power electronic switch tube structure in the form of MOSFET, IGBT, etc., technical personnel in this field can adaptively modify the discharge control circuit 2 according to the above structure and the driving circuit structure of the power electronic switch tube as needed.

[0031] Continue to refer Figure 1, the number of the above-mentioned discharge contactors is set by the needs of the electric vehicle. This specific embodiment adopts the discharge contactor composed of a first discharge contactor and a second discharge contactor connected in parallel to each other for description. Those skilled in the art can increase or decrease the number of the discharge contactors as needed. The above-mentioned discharge interlock switch and the above-mentioned discharge contactor correspond to each other and are composed of a first discharge interlock switch and a second discharge interlock switch connected in series. The above-mentioned first discharge contactor includes a first main contact 511, a first auxiliary contact 512 and a first discharge control coil 513. The first discharge control coil 513 controls the first main contact 511 and the first auxiliary contact 512 to close or disconnect synchronously by its own power-on or power-off. The above-mentioned second discharge contactor includes a second main contact 521, a second auxiliary contact 522 and a second discharge control coil 523. The second discharge control coil 523 controls the second main contact 521 and the second auxiliary contact 522 to close or disconnect synchronously by its own power-on or power-off. The first discharge interlock switch includes a first interlock contact 211 and a first interlock control coil 212. The first interlock control coil 212 controls the first interlock contact 211 to open or close by being energized or de-energized. The second discharge interlock switch includes a second interlock contact 221 and a second interlock control coil 222. The second interlock control coil 222 controls the second interlock contact 221 to open or close by being energized or de-energized. The first auxiliary contact 512 is connected to the circuit setting where the first interlock control coil 212 is located. The closing or opening of the first auxiliary contact 512 is used to control the first interlock control coil 212 to be energized or de-energized. The second auxiliary contact 522 is connected to the circuit setting where the second interlock control coil 222 is located. The closing or opening of the second auxiliary contact 522 is used to control the second interlock control coil 222 to be energized or de-energized.

[0032] refer to Figure 2 , an energy discharging method using the above-mentioned energy discharging device for the electric vehicle bus capacitor 41 comprises the following steps:

[0033] Ⅰ. When the electric vehicle is powered off, the above-mentioned discharge contactors are all controlled to disconnect, that is, the first discharge control coil 513 and the second discharge control coil 523 lose power, and the first main contact 511, the first auxiliary contact 512, the second main contact 521, and the second auxiliary contact 522 are all disconnected.

[0034] II. Since the first auxiliary contact 512 and the second auxiliary contact 522 are disconnected, the first interlock control coil 212 and the second interlock control coil 222 are both de-energized, and the first interlock contact 211 and the second interlock contact 221 are both closed.

[0035] III. Control the discharge control switch attached to the discharge control circuit 2 to close, connect the discharge control circuit 2, energize the discharge control coil 112, close the discharge main contact 111, that is, the discharge switch is in a closed state. The active discharge circuit is connected, and the voltage of the bus capacitor 41 is reduced to below the safety voltage through the discharge resistor 12.

[0036] When the active discharge circuit is connected, the voltage difference across the main contacts of the discharge contactor is obtained through the pressure difference acquisition component 3. If the voltage difference does not exist within the specified range, the electric vehicle triggers a fault alarm.

[0037] IV. When the electric vehicle is in the power-off state and at least one discharge contactor is mistakenly in the closed state or when the electric vehicle is in the power-on state and the above-mentioned discharge control switch is mistakenly controlled to be closed, since at least one discharge contactor is in the closed state, the auxiliary contact of the discharge contactor is also closed accordingly, that is, the discharge interlock switch corresponding to the discharge contactor in the closed state is disconnected. In this state, the discharge control switch is controlled to be closed. Since the discharge interlock switch is disconnected, the discharge control circuit 2 is disconnected, that is, the discharge switch is in the disconnected state, the active discharge circuit is disconnected, and the active discharge fails. When the active discharge fails, the electric vehicle triggers a fault alarm.

[0038] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. An electric energy discharge device for a bus capacitor of an electric vehicle, wherein the bus capacitor and the power battery of the electric vehicle are both arranged in a discharge circuit of the electric vehicle; the discharge circuit is controlled by at least one discharge contactor; the electric energy discharge device comprises an active discharge circuit and a discharge control circuit; the active discharge circuit comprises a discharge switch and a discharge resistor, and the discharge switch, the discharge resistor and the bus capacitor are connected in series to form an active discharge circuit; the discharge control circuit is used to control the closing or opening of the discharge switch by its own on-off; characterized in that: The discharge control circuit is connected in series with at least one discharge interlock switch, which is arranged in a one-to-one correspondence with the discharge contactor, and the discharge interlock switch is a discharge interlock switch with a normally closed structure; the auxiliary contact of the discharge contactor is used to control the on-off of the control circuit of the corresponding discharge interlock switch.

2. The electric energy discharge device for the bus capacitor of an electric vehicle according to claim 1, characterized in that: The discharge contactor is a normally open high-voltage contactor structure.

3. The electric energy discharge device for the bus capacitor of an electric vehicle according to claim 1, characterized in that: The discharge switch is a normally open high voltage contactor structure.

4. The electric energy discharge device for the bus capacitor of an electric vehicle according to claim 1, characterized in that: The discharge switch is a power electronic switch tube in the form of MOSFET or IGBT.

5. The electric energy discharge device for the bus capacitor of an electric vehicle according to claim 1, characterized in that: The discharge interlock switch is arranged as a normally closed low-voltage contactor structure, and the control circuit of the discharge interlock switch is the circuit where the control coil of the normally closed low-voltage contactor structure is located.

6. The electric energy discharge device for bus capacitor of electric vehicle according to claim 1, characterized in that: When at least two discharge contactors are provided, at least two discharge contactors are connected in parallel to the discharge circuit; at least two discharge interlock switches are connected in series to the discharge control circuit.

7. The electric energy discharge device for bus capacitor of electric vehicle according to claim 1, characterized in that: It also includes a pressure difference collection component, which is connected to the two ends of the main contacts of the discharge contactor and is used to obtain the voltage difference between the two ends of the main contacts of the discharge contactor.

8. An electric energy discharge method using the electric energy discharge device for electric vehicle bus capacitor according to any one of claims 1 to 6, characterized in that: The following steps are involved: Ⅰ. When the electric vehicle is powered off, the discharge contactors are all controlled to disconnect; Ⅱ. The discharge interlock switches corresponding to the discharge contactors are all controlled to be closed; III. Control the discharge control switch attached to the discharge control circuit to close, turn on the discharge control circuit, and make the discharge switch in a closed state; the active discharge circuit is connected, and the voltage of the bus capacitor is reduced to below the safe voltage through the discharge resistor; IV. When the electric vehicle is in a power-off state and at least one discharge contactor is mistakenly in a closed state, or when the electric vehicle is in a power-on state and the discharge control switch is mistakenly controlled to be closed, since at least one discharge contactor is in a closed state, the auxiliary contact of the discharge contactor is also closed accordingly, that is, the discharge interlock switch corresponding to the discharge contactor in the closed state is disconnected. In this state, the discharge control switch is controlled to be closed. Since the discharge interlock switch is disconnected, the discharge control circuit is disconnected, that is, the discharge switch is in an open state, the active discharge circuit is disconnected, and the active discharge fails; When active discharge fails, the electric vehicle triggers a fault alarm.

9. An electric energy discharge method using the electric energy discharge device for electric vehicle bus capacitor according to claim 7, characterized in that: The following steps are involved: Ⅰ. When the electric vehicle is powered off, the discharge contactors are all controlled to disconnect; Ⅱ. The discharge interlock switches corresponding to the discharge contactors are all controlled to be closed; III. Control the discharge control switch attached to the discharge control circuit to close, turn on the discharge control circuit, and make the discharge switch in a closed state; the active discharge circuit is connected, and the voltage of the bus capacitor is reduced to below the safe voltage through the discharge resistor; When the active discharge circuit is connected, the voltage difference between the two ends of the main contact of the discharge contactor is obtained through the pressure difference acquisition component. If there is no voltage difference within the specified range, the electric vehicle triggers a fault alarm; IV. When the electric vehicle is in a power-off state and at least one discharge contactor is mistakenly in a closed state, or when the electric vehicle is in a power-on state and the discharge control switch is mistakenly controlled to be closed, since at least one discharge contactor is in a closed state, the auxiliary contact of the discharge contactor is also closed accordingly, that is, the discharge interlock switch corresponding to the discharge contactor in the closed state is disconnected. In this state, the discharge control switch is controlled to be closed. Since the discharge interlock switch is disconnected, the discharge control circuit is disconnected, that is, the discharge switch is in an open state, the active discharge circuit is disconnected, and the active discharge fails; When active discharge fails, the electric vehicle triggers a fault alarm.

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