A fuel cell system

Abstract

The application relates to a fuel cell system and belongs to the technical field of new energy automobile fuel cell buses. The fuel cell system comprises a fuel cell and further comprises a relay, wherein the normally open contact of the relay is arranged in the fuel cell system and at the outgoing line end of the fuel cell; a current sensor is arranged between the fuel cell and the normally open contact of the relay and is used for measuring the output current of the fuel cell; a voltage sensor is arranged in the fuel cell and is used for measuring the output voltage of the fuel cell; a protector is connected with the input end of the current sensor and the voltage sensor; the output end of the protector is connected with the control coil of the relay; when normally operating, the protector controls the normally open contact of the relay to be closed; when overcurrent / under-voltage failure occurs, the protector controls the normally open contact of the relay to be disconnected. When overcurrent / under-voltage failure occurs, the fuel cell is directly disconnected with the outside from the inside of the fuel cell, so that the fuel cell is more timely and comprehensively protected.

Description

Technical Field

[0001] This invention relates to a fuel cell system, belonging to the field of new energy vehicle fuel cell bus technology. Background Technology

[0002] Fuel cells have advantages such as high power generation efficiency, low environmental pollution, high specific energy, low noise, wide range of fuels, and high reliability. They are increasingly used in the field of new energy vehicles and have become one of the main driving power sources for automobiles.

[0003] Currently, fuel cell systems in automobiles or other applications employ, for example... Figure 1 The system employed involves the fuel cell system in the vehicle generating electrical energy, which is then boosted by a BOOST DC-DC converter before being sent to the power battery. The fuel cell system itself lacks internal protection devices. To protect the fuel cell, the voltage and current at the DC-DC converter input are typically collected and transmitted via the CAN bus to the fuel cell controller, which in turn sends the data to the vehicle controller. The vehicle controller assesses the current and voltage; if they exceed a certain threshold, it disconnects a relay at the power battery input, thus protecting the fuel cell.

[0004] However, the above protection process has the following drawbacks:

[0005] 1. For buses, which have a long communication range, timely protection is not possible;

[0006] 2. When the current and voltage are abnormal, the fuel cell is protected only by disconnecting the power battery. If the DC-DC converter fails, the connection between the DC-DC converter and the fuel cell is not disconnected, which leads to damage to the fuel cell. Therefore, the fuel cell cannot be fully protected. Summary of the Invention

[0007] The purpose of this application is to provide a fuel cell system that addresses the problem of incomplete protection provided by existing protection methods.

[0008] To achieve the above objectives, this application proposes a technical solution for a fuel cell system, which includes a fuel cell and further includes:

[0009] The normally open contacts of the relay are located inside the fuel cell system, at the output terminal of the fuel cell;

[0010] A current sensor is located between the fuel cell and the normally open contact of the relay to measure the output current of the fuel cell.

[0011] A voltage sensor, located inside the fuel cell, is used to measure the output voltage of the fuel cell;

[0012] The protector's input terminals are connected to current and voltage sensors; the protector's output terminals control the control coil of a relay; during normal operation, the protector controls the normally open contacts of the relay to close; in the event of an overcurrent / undervoltage fault, the protector controls the normally open contacts of the relay to open.

[0013] The beneficial effects of the technical solution of the fuel cell system of the present invention are as follows: The present invention sets up a relay, a current sensor, a voltage sensor and a protector inside the fuel cell. When the protector determines that an overcurrent / undervoltage fault has occurred by receiving the current signal and voltage signal output by the fuel cell, it directly cuts off the connection between the fuel cell and the outside from the inside of the fuel cell, so as to protect the fuel cell more timely and comprehensively.

[0014] Furthermore, the protector is a fuel cell controller, and the input terminal of the fuel cell controller is connected to a current sensor and a voltage sensor; the first control terminal of the fuel cell controller controls the control coil of a relay.

[0015] Furthermore, to improve the timeliness of protection, the protector is a protection circuit, which includes:

[0016] The voltage comparator has its inverting input connected to a first reference voltage corresponding to the undervoltage threshold, and its non-inverting input connected to a voltage sensor.

[0017] The current comparator has its inverting input connected to a current sensor and its non-inverting input connected to a second reference voltage corresponding to the overcurrent threshold.

[0018] The input of the AND gate is connected to the output of the voltage comparator and the current comparator; the output of the AND gate controls the control coil of the relay.

[0019] Furthermore, to improve the reliability of the protection, the protector includes:

[0020] The fuel cell controller has input terminals connected to current and voltage sensors.

[0021] Protection circuit, including:

[0022] The voltage comparator has its inverting input connected to a first reference voltage corresponding to the undervoltage threshold, and its non-inverting input connected to a voltage sensor.

[0023] The current comparator has its inverting input connected to a current sensor and its non-inverting input connected to a second reference voltage corresponding to the overcurrent threshold.

[0024] The AND gate circuit has its input connected to the outputs of the voltage comparator and the current comparator, as well as the first control terminal of the fuel cell controller; the output of the AND gate circuit controls the control coil of the relay.

[0025] Furthermore, the relay includes a first relay and a second relay, with the first relay disposed on the positive terminal branch of the fuel cell output and the second relay disposed on the negative terminal branch of the fuel cell output.

[0026] Furthermore, to prevent prolonged overload of the fuel cell, a hysteresis range is set. The second control terminal of the fuel cell controller is used to connect to the DC-DC converter to achieve the following steps:

[0027] When the first set current < the measured current ≤ the overcurrent threshold, or the undervoltage threshold ≤ the measured voltage < the first set voltage, the second control terminal of the fuel cell controller controls the DC-DC converter to operate with reduced current.

[0028] When the measured current exceeds the overcurrent threshold or the measured voltage is less than the undervoltage threshold, and an overcurrent / undervoltage fault occurs, the normally open contact of the control relay at the first control terminal of the fuel cell controller will open.

[0029] Furthermore, both the first reference voltage and the second reference voltage are implemented using a voltage divider circuit. Attached Figure Description

[0030] Figure 1 This is a protection schematic diagram of a fuel cell system in the prior art;

[0031] Figure 2 This is a structural diagram of Embodiment 1 of the fuel cell system of the present invention;

[0032] Figure 3 This is a control flowchart of the fuel cell controller of the present invention;

[0033] Figure 4 This is a structural diagram of embodiment 2 of the fuel cell system of the present invention;

[0034] Figure 5 This is a structural diagram of embodiment 3 of the fuel cell system of the present invention. Detailed Implementation

[0035] Fuel cell system example 1:

[0036] The main concept of this invention is to install a protection device inside the fuel cell system to protect the fuel cell. In the event of abnormal current or voltage, the connection between the fuel cell system and the outside world will be cut off in a timely manner, thus ensuring the safety of the fuel cell in all aspects.

[0037] Specifically, such as Figure 2As shown, the fuel cell system includes a fuel cell and a fuel cell system protection device. The fuel cell system protection device includes a fuel cell controller (FCU), a current sensor, a voltage sensor, a relay K1, and a relay K2.

[0038] The output terminal of the fuel cell is connected to the input terminal of the DC-DC converter through a positive branch and a negative branch; and a normally open contact of relay K1 is set on the positive branch of the fuel cell output terminal inside the fuel cell system; a normally open contact of relay K2 is set on the negative branch; so as to control the connection status between the inside and outside of the fuel cell through the state of relay K1 and relay K2.

[0039] The current sensor is a Hall sensor, located between the fuel cell and the normally open contact of relay K1, used to measure the output current of the fuel cell; the voltage sensor is located inside the fuel cell, used to collect the output voltage of the fuel cell; the voltage collected by the voltage sensor is called the measured voltage.

[0040] Hall sensors and voltage sensors are connected to the acquisition terminal of the fuel cell controller (FCU) to send the acquired measured current and voltage to the FCU; the first control terminal of the FCU controls the control coils of relays K1 and K2; the second control terminal of the FCU is connected to the DC-DC converter via CAN communication.

[0041] The fuel cell controller (FCU) includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements... Figure 3 The protection method shown includes:

[0042] When the measured current is less than or equal to the first set current, and when the measured voltage is greater than or equal to the first set voltage, the first control terminal of the fuel cell controller outputs a high level, the control coils of relay K1 and relay K2 are energized, and the normally open contacts of relay K1 and relay K2 are closed; the normally open contacts of the control relays are opened, and the second control terminal of the fuel cell controller controls the DC-DC converter to operate normally.

[0043] When the first set current < the measured current ≤ the overcurrent threshold, or the undervoltage threshold ≤ the measured voltage < the first set voltage, the second control terminal of the fuel cell controller controls the DC-DC converter to operate with reduced current.

[0044] When the measured current exceeds the overcurrent threshold or the measured voltage is less than the undervoltage threshold, an overcurrent / undervoltage fault occurs. The first control terminal of the fuel cell controller outputs a low level, the control coils of relay K1 and relay K2 are de-energized, and the normally open contacts of relay K1 and relay K2 are disconnected.

[0045] In the above embodiments, two current nodes and voltage nodes are set to achieve phased protection of the fuel cell. In other implementations, the relay can be directly disconnected when an overcurrent / undervoltage fault occurs, without the need for the DC-DC converter to reduce current.

[0046] In the above embodiments, in order to improve the reliability of protection, a relay is provided on both the positive and negative branches. In other embodiments, a relay may be provided on only one branch.

[0047] This invention provides comprehensive and reliable protection for the fuel cell by promptly disconnecting the fuel cell system from external connections in the event of an overcurrent / undervoltage fault.

[0048] Fuel cell system example 2:

[0049] The fuel cell system proposed in this embodiment differs from that in Embodiment 1, the fuel cell controller FCU is used as a protector to protect the fuel cell, while in this embodiment, a protection circuit is used to protect the fuel cell in order to improve the timeliness of protection.

[0050] Specifically, protection circuits such as Figure 4 As shown, it includes comparator U1, comparator U2, and AND gate circuit.

[0051] Comparator U1 is used as a voltage comparator. The inverting input of comparator U1 is connected to the first reference voltage corresponding to the undervoltage threshold, and the non-inverting input of comparator U1 is connected to a voltage sensor. The voltage collected by the voltage sensor is the measured voltage.

[0052] Comparator U2 serves as a current comparator. Its inverting input is connected to a current sensor, and its non-inverting input is connected to a second reference voltage corresponding to the overcurrent threshold. The current sensor is a Hall sensor that collects the output current of the fuel cell and converts the current signal into a voltage signal for output. The voltage collected by the Hall sensor is referred to as the Hall voltage.

[0053] The AND gate circuit has its input connected to the outputs of comparators U1 and U2; the output of the AND gate circuit controls the control coil of the relay.

[0054] The protection principle of the protection circuit is as follows:

[0055] When the measured voltage is greater than or equal to the first reference voltage, comparator U1 outputs a high level; when the Hall voltage is less than or equal to the second reference voltage, comparator U2 outputs a high level; after passing through the AND gate circuit, the AND gate circuit outputs a high level, the control coils of relay K1 and relay K2 are energized, and the normally open contacts of relay K1 and relay K2 are closed.

[0056] When the measured voltage is less than the first reference voltage, comparator U1 outputs a low level; when the Hall voltage is greater than the second reference voltage, comparator U2 outputs a low level; if either comparator U1 or comparator U2 outputs a low level, that is, when an overcurrent / undervoltage fault occurs, the AND gate circuit outputs a low level, the control coils of relay K1 and relay K2 are de-energized, and the normally open contacts of relay K1 and relay K2 open.

[0057] In this embodiment, the first and second reference voltages are set using a voltage divider circuit. The voltage divider circuit includes resistors R1, R2, and R3 connected in series. One end of the voltage divider circuit is connected to the reference voltage VCC, and the other end is grounded. The connection point of resistors R1 and R2 in the voltage divider circuit is the first voltage divider point, i.e., the first reference voltage; the connection point of resistors R2 and R3 is the second voltage divider point, i.e., the second reference voltage. Alternatively, the first and second reference voltages can also be implemented using their own voltage divider circuits. This ensures that the two voltages are not affected by each other and allows for easier adjustment of the reference voltage.

[0058] The other structures of the fuel cell system in this embodiment are the same as those in Embodiment 1, and will not be described in detail here.

[0059] Fuel cell system example 3:

[0060] The fuel cell system in this embodiment is proposed in conjunction with the fuel cell systems in Embodiments 1 and 2. This fuel cell system can protect the fuel cell controller (FCU) through a protection circuit in the event of a malfunction, thereby improving the reliability of the protection.

[0061] Specifically, such as Figure 5 As shown, the fuel cell system includes a fuel cell and a fuel cell system protection device. The fuel cell system protection device includes a fuel cell controller FCU, a current sensor, a voltage sensor, relays K1 and K2, comparators U1 and U2, and an AND gate circuit.

[0062] The connection relationships and settings of the current sensor, voltage sensor, comparator U1, comparator U2, and gate circuits have been described in Example 2, and will not be repeated here.

[0063] The difference between the fuel cell controller FCU, current sensor, and voltage sensor and the embodiment is that the first control terminal of the fuel cell controller FCU is connected to the input terminal of the gate circuit. The similarities will not be repeated here.

[0064] The current sensor uses a Hall sensor, and the voltage collected by the Hall sensor is referred to as the Hall voltage. The voltage collected by the voltage sensor is the measured voltage, and therefore is defined as follows: the voltage corresponding to the first set current is the first Hall voltage; the voltage corresponding to the overcurrent threshold is the second reference voltage.

[0065] The voltage collected by the voltage sensor is directly called the measured voltage, and the voltage corresponding to the undervoltage threshold is the first reference voltage.

[0066] Based on the fuel cell system proposed in this embodiment, the protection device combines software protection and circuit protection. The purpose of setting up these two protection methods is to prevent the fuel cell controller (FCU) from failing to provide protection due to a malfunction. The protection circuit quickly disconnects relays K1 and K2. The control logic for software protection is as follows: Figure 3 As shown, the overall protection method, combined with circuit protection, includes the following steps:

[0067] 1) When the measured current is less than or equal to the first set current, and when the measured voltage is greater than or equal to the first set voltage (i.e., when the Hall voltage is less than or equal to the first Hall voltage and the measured voltage is greater than or equal to the first set voltage), the output terminals of comparators U1 and U2 output high-level signals; the first control terminal of the fuel cell controller FCU outputs a high level; and the AND gate circuit outputs a high level; the control coils of relays K1 and K2 are energized, the normally open contacts of relays K1 and K2 are closed; and the second control terminal of the fuel cell controller FCU controls the DC-DC converter to operate normally.

[0068] 2) When the first Hall voltage < Hall voltage ≤ second reference voltage, or the undervoltage threshold ≤ measured voltage < first set voltage, the second control terminal of the fuel cell controller FCU controls the DC-DC converter to operate with reduced current. At this time, comparators U1 and U2, as well as the first control terminal of the fuel cell controller FCU, are all outputting at a high level, which does not affect the closed state of the normally open contact of relay K1 and the normally open contact of relay K2.

[0069] 3) When the Hall voltage is greater than the second reference voltage, or the measured voltage is less than the undervoltage threshold (first reference voltage), the first control terminal of the fuel cell controller FCU outputs a low level; the AND gate outputs a low level, the control coils of relay K1 and relay K2 are de-energized, and the normally open contacts of relay K1 and relay K2 are opened; at the same time, comparators U1 and U2 both output a low level; this ensures that when the fuel cell controller FCU continuously outputs a high level due to a fault, the circuit protection will directly make the AND gate output a low level, thus timely disconnecting the fuel cell system from the outside.

[0070] This embodiment includes an internal protection device for the fuel cell system to promptly disconnect the fuel cell system from the external environment and prevent short circuits from damaging the fuel cell. Furthermore, it employs both software protection and circuit protection methods to ensure the safety and lifespan of the fuel cell.

Claims

1. A fuel cell system comprising a fuel cell, characterized by, Also include: A relay, the normally open contact of the relay is arranged inside the fuel cell system, the output terminal of the fuel cell; A current sensor arranged between the fuel cell and the normally open contact of the relay, for measuring the output current I of the fuel cell; A voltage sensor arranged inside the fuel cell, for measuring the output voltage U of the fuel cell; A protector including a fuel cell controller, a voltage comparator, a current comparator and an AND gate circuit, the input end of the fuel cell controller is connected to the current sensor and the voltage sensor; The inverting input end of the voltage comparator is connected to the under-voltage threshold U1, and the non-inverting input end of the voltage comparator is connected to the voltage sensor; The inverting input end of the current comparator is connected to the current sensor, and the non-inverting input end of the current comparator is connected to the over-current threshold I1; The output end of the voltage comparator and the current comparator is connected to the first control end of the fuel cell controller; The output end of the AND gate circuit controls the control coil of the relay; When I≤I2, and U≥U2, the output end of the voltage comparator and the current comparator outputs high level, and the first control end of the fuel cell controller outputs high level; When I2 2. The fuel cell system according to claim 1, characterized by, The relay includes a first relay and a second relay, the first relay is arranged on the positive branch of the fuel cell output; The second relay is arranged on the negative branch of the fuel cell output.

3. The fuel cell system of claim 1, wherein The first reference voltage corresponding to the over-current threshold and the second reference voltage corresponding to the under-voltage threshold are both realized by a voltage dividing circuit.

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