A circuit and method for switching a hydrogen fuel cell vehicle to a pure electric operation mode

Abstract

The present invention belongs to the field of fuel cell technology, and discloses a circuit for switching a hydrogen fuel cell vehicle to a pure electric operation mode, wherein the positive output end of a DC / DC boost converter is directly connected to a lithium battery, and the negative output end of the DC / DC boost converter is connected to the lithium battery through a negative contactor K2; the DC / DC boost converter also includes an on-off control circuit U1, wherein the bus capacitor C2 is connected across the output ends of the DC / DC boost converter, and the bus capacitor discharge resistor R1 is connected in series with the on-off control circuit U1 to form a series branch connected across the output ends of the DC / DC boost converter, and the on-off control circuit U1 is used to control the on or off of the series branch; and also discloses a method for switching a hydrogen fuel cell vehicle to a pure electric operation mode. The present invention realizes the ability to reduce product volume and save product cost, and is conducive to promoting the miniaturization design of DC / DC boost converter products.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a circuit and method for switching a hydrogen fuel cell vehicle to a pure electric operation mode. Background Art

[0002] The power of hydrogen fuel cell vehicles comes from two parts: one is the hydrogen fuel cell and the other is the lithium-ion power battery. Under normal operating conditions, the two components provide power for the entire vehicle at the same time, and this operating mode is the hybrid mode. When the hydrogen fuel cell system is abnormal, the vehicle needs to switch to the pure electric mode with pure lithium-ion battery power output to continue driving.

[0003] Figure 1 The connection relationship between the hydrogen fuel cell stack (hydrogen stack for short), DC / DC boost converter and lithium-ion power battery in most hydrogen fuel cell vehicles. When the insulation failure occurs at the negative electrode of the hydrogen stack, since the hydrogen stack is directly connected to the negative electrode of the lithium-ion power battery, the insulation failure of the hydrogen stack will affect the insulation detection of the lithium-ion power battery, and the vehicle system will be unable to switch to pure electric mode to continue driving due to the insulation failure of the hydrogen stack.

[0004] To solve the problem that the vehicle cannot switch to pure electric mode due to hydrogen stack insulation failure, some vehicles will Figure 1 On the basis of, add negative contactor K2 at the output end of DC / DC boost converter, such as Figure 2 When an insulation failure occurs in the hydrogen stack, the positive contactor K1 and the negative contactor K2 are used to completely disconnect the hydrogen stack to prevent the hydrogen stack insulation failure from affecting the insulation detection of the lithium-ion power battery. The vehicle can then switch to pure electric mode to continue driving. Currently, this solution has disadvantages: the DC / DC boost converter requires two output contactors, which increases the product size and cost, especially under high current conditions, and is not conducive to the miniaturization design of vehicle-mounted products. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide a circuit and method for switching a hydrogen fuel cell vehicle to a pure electric operation mode, which can reduce product volume and save product cost, and is conducive to promoting the miniaturization design of DC / DC boost converter products.

[0006] The embodiment of the present invention is implemented as follows:

[0007] A circuit for switching a hydrogen fuel cell vehicle to a pure electric operation mode, comprising a hydrogen stack, a DC / DC boost converter and a lithium battery, wherein the hydrogen stack is connected to the input end of the DC / DC boost converter, the output end of the DC / DC boost converter is connected to the lithium battery, the DC / DC boost converter comprises a bus capacitor discharge resistor R1 and a bus capacitor C2, the positive output end of the DC / DC boost converter is directly connected to the lithium battery, and the negative output end of the DC / DC boost converter is connected to the lithium battery via a negative contactor K2; the DC / DC boost converter further comprises an on-off control circuit U1, the bus capacitor C2 is connected across the output ends of the DC / DC boost converter, the bus capacitor discharge resistor R1 is connected in series with the on-off control circuit U1 to form a series branch connected across the output ends of the DC / DC boost converter, and the on-off control circuit U1 is used to control the conduction or disconnection of the series branch;

[0008] Among them, the on-off control circuit U1 is automatically turned on or off by the voltage of the bus capacitor C2;

[0009] The resistance of the bus capacitor discharge resistor R1 is less than or equal to 1 MΩ.

[0010] The on-off control circuit U1 includes an N-type MOS transistor Q2, a voltage regulator transistor Z1, an upper driving resistor R2 and a lower driving resistor R3, one end of the discharge resistor R1 is connected to the positive pole of the bus of the DC / DC boost converter, the drain D of the MOS transistor Q2 is connected to the other end of the connected bus capacitor discharge resistor R1, the source S of the MOS transistor Q2 is connected to the negative pole of the bus of the DC / DC boost converter, the voltage regulator transistor Z1 and the lower driving resistor R3 are connected in parallel between the gate G and the source S of the MOS transistor Q2, and the upper driving resistor R2 is connected between the gate G of the MOS transistor Q2 and the positive pole of the bus of the DC / DC boost converter; wherein the total resistance of the upper driving resistor R2 and the lower driving resistor R3 is greater than or equal to 5MΩ.

[0011] Among them, when the residual voltage of the bus capacitor C2 is greater than or equal to 60V, the on-off control circuit U1 is turned on, and the bus capacitor discharge resistor R1 quickly discharges the bus capacitor; when the bus capacitor is discharged to less than 60V, the on-off control circuit U1 is turned off.

[0012] A method for switching a hydrogen fuel cell vehicle to a pure electric operation mode, using the circuit as described above for switching.

[0013] The embodiment of the present invention solves the problem that the system cannot switch to pure electric mode operation due to hydrogen stack insulation failure by using only one output contactor, reduces product volume and saves product cost, and is conducive to promoting the miniaturization design of DC / DC boost converter products. The present invention uses a negative contactor and a bus capacitor discharge resistor control circuit to disconnect the hydrogen stack from the system, ensuring that the insulation detection of the lithium-ion power battery system is not affected by the hydrogen stack insulation failure, and the system can smoothly switch to pure electric mode operation; the bus capacitor discharge resistor control circuit is composed of passive devices, which can automatically control the opening and closing according to the voltage of the bus capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the connection diagram of hydrogen stack, DC / DC boost converter and lithium-ion power battery;

[0015] Figure 2 It is a circuit diagram for switching to pure electric mode in the prior art;

[0016] Figure 3 This is a circuit diagram for switching to pure electric mode in the present invention;

[0017] Figure 4 yes Figure 3 Circuit diagram of the on-off control circuit U1 of the bus discharge resistor R1. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] The embodiment of the present invention adopts a Boost circuit through a DC / DC boost converter, and the input negative electrode and the output negative electrode are not isolated. Delete the existing solution ( Figure 2 ) The DC / DC boost converter outputs the positive contactor K1, retains the negative contactor K2, and adds the on-off control circuit U1 of the bus capacitor discharge resistor R1, such as Figure 3 As shown. When a negative pole grounding fault occurs in the hydrogen stack, the DC / DC boost converter disconnects the negative pole connection of the hydrogen stack through the negative pole contactor K2 to ensure that the insulation detection of the negative pole of the lithium-ion power battery is not affected. At this time, the insulation resistance of the positive pole of the lithium-ion power battery to the ground is equal to R1, and R1 is the discharge resistance of the bus capacitor C2. According to the safety specifications of the equipment, the voltage of the bus capacitor C2 needs to be discharged to less than 60V within 5 minutes after the equipment is powered off. Limited by this requirement, the resistance of R1 will generally be less than 1MΩ, so the insulation of the positive pole of the lithium-ion power battery to the ground will also be less than 1MΩ and cannot meet the system operation requirements. The system insulation monitoring module will trigger an insulation fault, causing the vehicle to stop due to a fault and unable to continue driving.

[0020] When the insulation of the negative electrode of the hydrogen stack is abnormal, the DC / DC boost converter will stop running and the output negative electrode contactor will be disconnected to ensure that the insulation detection of the negative electrode of the lithium-ion power battery is not affected; the on-off control circuit U1 of the discharge resistor R1 disconnects the R1 resistor from the loop to ensure that the insulation detection of the positive electrode of the lithium-ion power battery is not affected by the R1 resistor. The hydrogen stack can be disconnected from the system through K2 and U1 to ensure that the insulation detection of the lithium-ion power battery system is not affected by the hydrogen stack insulation fault, and the system can smoothly switch to pure electric mode operation.

[0021] A circuit for switching a hydrogen fuel cell vehicle to a pure electric operation mode, comprising a hydrogen stack, a DC / DC boost converter and a lithium battery, wherein the hydrogen stack is connected to the input end of the DC / DC boost converter, the output end of the DC / DC boost converter is connected to the lithium battery, the DC / DC boost converter comprises a bus capacitor discharge resistor R1 and a bus capacitor C2, the positive output end of the DC / DC boost converter is directly connected to the lithium battery, and the negative output end of the DC / DC boost converter is connected to the lithium battery via a negative contactor K2; the DC / DC boost converter further comprises an on-off control circuit U1, the bus capacitor C2 is connected across the output ends of the DC / DC boost converter, the bus capacitor discharge resistor R1 is connected in series with the on-off control circuit U1 to form a series branch connected across the output ends of the DC / DC boost converter, and the on-off control circuit U1 is used to control the conduction or disconnection of the series branch;

[0022] Among them, the on-off control circuit U1 is automatically turned on or off by the voltage of the bus capacitor C2;

[0023] The resistance of the bus capacitor discharge resistor R1 is less than or equal to 1 MΩ.

[0024] The on-off control circuit U1 includes an N-type MOS transistor Q2, a voltage regulator transistor Z1, an upper driving resistor R2 and a lower driving resistor R3, one end of the discharge resistor R1 is connected to the positive pole of the bus of the DC / DC boost converter, the drain D of the MOS transistor Q2 is connected to the other end of the connected bus capacitor discharge resistor R1, the source S of the MOS transistor Q2 is connected to the negative pole of the bus of the DC / DC boost converter, the voltage regulator transistor Z1 and the lower driving resistor R3 are connected in parallel between the gate G and the source S of the MOS transistor Q2, and the upper driving resistor R2 is connected between the gate G of the MOS transistor Q2 and the positive pole of the bus of the DC / DC boost converter; wherein the total resistance of the upper driving resistor R2 and the lower driving resistor R3 is greater than or equal to 5MΩ.

[0025] Among them, when the residual voltage of the bus capacitor C2 is greater than or equal to 60V, the on-off control circuit U1 is turned on, and the bus capacitor discharge resistor R1 quickly discharges the bus capacitor; when the bus capacitor is discharged to less than 60V, the on-off control circuit U1 is turned off.

[0026] A method for switching a hydrogen fuel cell vehicle to a pure electric operation mode, using the circuit as described above for switching.

[0027] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments:

[0028] The present invention deletes the positive contactor of the DC / DC boost converter output and retains the negative contactor K2, and adds an on-off control circuit U1 of the bus capacitor discharge resistor R1, such as Figure 3 shown.

[0029] The on-off control circuit U1 is composed of: one end of the discharge resistor R1 is connected to the positive electrode of the bus capacitor, and the other end is connected to the drain D of the N-type MOS tube Q2, and the source S of the MOS tube Q2 is connected to the negative electrode of the bus capacitor; the voltage regulator tube Z1 and the resistor R3 are connected in parallel between the gate G and the source S of the MOS tube Q2; the resistor R2 is connected to the gate G of the MOS tube Q2 and the positive electrode of the bus of the DC / DC boost converter, such as Figure 4 shown.

[0030] Working principle: When the bus voltage of the DC / DC boost converter is greater than 60V or lower, the series divided voltage on R3 is greater than the turn-on threshold voltage Vth of the MOS tube, the MOS tube is normally turned on, and the bus resistor R1 discharges the bus capacitor C2; when the bus voltage of the DC / DC boost converter is less than 60V or lower, the series divided voltage on R3 is less than the turn-on threshold voltage Vth of the MOS tube, the MOS tube is disconnected, and the bus resistor stops discharging the bus capacitor; the rated voltage of the voltage regulator Z1 is less than the maximum gate voltage of the MOS tube, which can prevent the gate of the MOS tube Q2 from being damaged due to overvoltage.

[0031] When the negative electrode of the hydrogen stack has insulation abnormalities, the DC / DC boost converter will stop running and the output negative electrode contactor will be disconnected. At this time, the residual voltage of the output bus capacitor C2 is greater than 60V or lower, the MOS tube Q2 is turned on, and the discharge resistor R1 quickly discharges the bus capacitor. When the bus capacitor is discharged to less than 60V or lower, the MOS tube Q2 is disconnected to ensure that the discharge resistor R1 does not affect the insulation of the positive electrode of the lithium battery. MOS tube Q2 is a voltage-type drive, and the drive resistors R2 and R3 can be designed to have high resistance values, and the total resistance value is ensured to be greater than 5MΩ. When the negative electrode of the hydrogen stack is short-circuited to the ground, the insulation detection of the positive electrode of the lithium-ion power battery can meet the insulation resistance requirement of 500Ω / V for the lithium-ion power battery system.

[0032] The embodiment of the present invention solves the problem that the system cannot switch to pure electric mode operation due to hydrogen stack insulation failure by using only one output contactor. The control circuit U1 is used to replace the positive contactor K1, and the volume is increased from 373.8cm 3 Reduced to less than 1cm 3, greatly reducing the product volume and saving product costs, which is conducive to promoting the miniaturization design of DC / DC boost converter products; U1 uses MOS tube to control on and off, replacing the mechanical on and off mechanism of the contactor, solving the problems of arc extinguishing difficulty and high heat generation of the contactor, and improving product reliability. The present invention uses a negative contactor and a bus capacitor discharge resistor control circuit to disconnect the hydrogen stack from the system, ensuring that the insulation detection of the lithium-ion power battery system is not affected by the insulation failure of the hydrogen stack, and the system can smoothly switch to pure electric mode operation; the bus capacitor discharge resistor control circuit is composed of passive devices, which can automatically control the opening and closing according to the voltage of the bus capacitor.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A circuit for switching a hydrogen fuel cell vehicle to a pure electric operation mode, comprising a hydrogen stack, a DC / DC boost converter and a lithium battery, wherein the hydrogen stack is connected to the input end of the DC / DC boost converter, the output end of the DC / DC boost converter is connected to the lithium battery, and the DC / DC boost converter comprises a bus capacitor discharge resistor R1 and a bus capacitor C2, characterized in that: The positive output end of the DC / DC boost converter is directly connected to the lithium battery, and the negative output end of the DC / DC boost converter is connected to the lithium battery through the negative contactor K2; the DC / DC boost converter also includes an on-off control circuit U1, the bus capacitor C2 is connected across the output ends of the DC / DC boost converter, the bus capacitor discharge resistor R1 is connected in series with the on-off control circuit U1 to form a series branch connected across the output ends of the DC / DC boost converter, and the on-off control circuit U1 is used to control the conduction or disconnection of the series branch; Among them, the on-off control circuit U1 is automatically turned on or off by the voltage of the bus capacitor C2; The resistance of the bus capacitor discharge resistor R1 is less than or equal to 1 MΩ.

2. A circuit for switching a hydrogen fuel cell vehicle to a pure electric operation mode according to claim 1, characterized in that: The on-off control circuit U1 includes an N-type MOS transistor Q2, a voltage regulator tube Z1, an upper driving resistor R2 and a lower driving resistor R3, one end of the discharge resistor R1 is connected to the positive pole of the bus of the DC / DC boost converter, the drain D of the MOS transistor Q2 is connected to the other end of the connected bus capacitor discharge resistor R1, the source S of the MOS transistor Q2 is connected to the negative pole of the bus of the DC / DC boost converter, the voltage regulator tube Z1 and the lower driving resistor R3 are connected in parallel between the gate G and the source S of the MOS transistor Q2, and the upper driving resistor R2 is connected between the gate G of the MOS transistor Q2 and the positive pole of the bus of the DC / DC boost converter; wherein the total resistance of the upper driving resistor R2 and the lower driving resistor R3 is greater than or equal to 5MΩ.

3. A circuit for switching a hydrogen fuel cell vehicle to a pure electric operation mode according to claim 1, characterized in that: When the residual voltage of the bus capacitor C2 is greater than or equal to 60V, the on-off control circuit U1 is turned on, and the bus capacitor discharge resistor R1 quickly discharges the bus capacitor; when the bus capacitor is discharged to less than 60V, the on-off control circuit U1 is turned off.

4. A method for switching a hydrogen fuel cell vehicle to a pure electric operation mode, characterized in that: The switching is performed using a circuit as described in any one of claims 1 to 3.

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