CN201142343Y - Self-starting and self-adaptive control circuit for air supply of fuel cell stack - Google Patents

Abstract

The utility model relates to a self-starting and self-adaptive control circuit for air supply of a fuel battery pack, which is characterized by comprising a voltage stabilizing circuit unit, a control circuit unit, a signal acquisition unit and a field effect transistor G; the voltage stabilizing circuit unit is used for providing a stable power supply for the control circuit; the control circuit unit takes the currents of the battery pack and the fan as comparison signals and controls the conduction size of the field effect transistor G in a feedback comparison control mode; the signal acquisition unit is used for acquiring the current output by the battery pack and the current used by the fan and transmitting the acquired current to the control circuit unit; the control circuit not only solves the problem that the direct current fan is easy to burn out when the direct current fan is used for supplying air because the output voltage of the fuel cell changes greatly, but also solves the contradiction of inconsistent air quantity supply and demand and improves the performance of the fuel cell set; the structure is simple, the used components are few, the production is convenient, the cost is very low, and the method is suitable for wide popularization.

Description

Self-starting and self-adaptive control circuit for fuel cell stack air supply

technical field

The utility model relates to an air supply device for a fuel cell group, in particular to a self-starting and self-adaptive control circuit for the air supply of a fuel cell group.

Background technique

Medium and small power fuel cell stacks generally choose a very low working pressure, and in order to reduce the cost and simplify the system, usually a DC fan is directly connected to the output of the fuel cell stack to provide air for the fuel cell stack and dissipate the heat consumed in it. Take away program. However, this solution obviously has some disadvantages: the output voltage of the fuel cell stack decays as the load increases, and the output voltage at rated power is only 60-70% of the no-load output voltage, or even lower. If the fan is not controlled, it may cause damage to the fan due to the high voltage at no-load; even if the fan can work, if it is not controlled, the no-load air volume will be the largest, and the air supply volume will be the smallest when the power output is maximum; this is in line with the requirements of the fuel cell group. Quite the opposite. So there is an urgent need for a new type of fan control system to come out.

Contents of the invention

The purpose of the utility model is to develop a fuel cell group air supply control circuit with easy realization, high reliability and low cost in view of the deficiencies in the prior art. The control idea adopted is: use DC fan or DC blower to supply air to the fuel cell stack, and build a fan-following control circuit with the output current of the fuel cell stack as an independent variable; when the fuel cell stack is turned on, the control circuit uses The fan is at the lowest speed; when the load of the fuel cell increases, the control circuit increases the speed of the fan; when the fuel cell group reaches the rated power output, the control circuit makes the fan reach the highest speed. The technical means adopted are as follows:

A self-starting and self-adaptive control circuit for fuel cell stack air supply, characterized in that it includes a voltage stabilizing circuit unit, a control circuit unit, a signal acquisition unit and a field effect transistor G;

The voltage stabilizing circuit unit is used to provide a stable power supply for the control circuit; the control circuit unit uses the current of the battery pack and the fan as a comparison signal, and uses a feedback comparison control method to control the conduction of the field effect tube G; The above-mentioned signal acquisition unit is used to collect the current output by the battery pack and the current used by the fan, and transmit the collected current to the control circuit unit; when in use, connect the I and II terminals to the positive and negative poles of the load, and pass the battery pack through the signal acquisition unit. The output current and the current used by the fan are collected, and the collected current is transmitted to the control circuit unit. After being processed by the control circuit unit, the control current is input to the driving end of the field effect tube G to realize the control of the fan. The voltage stabilizing chip in the voltage stabilizing circuit unit adopts a 7812 chip; the signal acquisition unit is mainly composed of resistors, wherein the resistor R1 completes the detection of the output current of the battery pack, and the resistor R2 completes the detection of the current used by the fan.

The control circuit unit is composed of an operational amplifier and discrete components; wherein the resistor _R1 is a sampling resistor for the output current of the battery pack, and constitutes the detection of the output current of the fuel cell with the operational amplifier IC ₁ ; the output of the operational amplifier IC ₁ is sent to the transport Put the positive input terminal of IC ₃ , so that if the output current of the battery pack increases, the output of the operational amplifier IC ₃ will be high, which drives the field effect tube G, thereby controlling the fan speed to increase; the current detection of the fan is detected by the resistor R ₂ Sampling and operational amplifier IC ₂ are completed, which will lead to the increase of the output voltage of operational amplifier IC ₂ , and this signal is added to the negative terminal of operational amplifier IC ₃ to form a negative feedback, thereby restraining the rise of the output of operational amplifier IC ₃ ; thus Each change in the output current of the battery pack will cause a corresponding change in the fan current and be in a new stable state. The IC ₁ , IC ₂ and IC ₃ are three operational amplifiers in the LM324 integrated circuit; the fan is a DC axial fan or a DC fan.

Due to the adoption of the above-mentioned technical scheme, the control method of the medium and small power fuel cell group air supply fan provided by the utility model has clear ideas, simple design, few components and parts, easy to purchase and cheap, easy to manufacture and debug, and not only solves the problem of Due to the large change in the output voltage of the fuel cell, the DC fan is directly used to supply air, which is easy to burn out the fan. It also solves the contradiction between the supply and demand of the air volume and improves the performance of the fuel cell stack.

Description of drawings

Fig. 1 is a schematic circuit diagram of the utility model;

Fig. 1 is the accompanying drawing of the specification abstract of the utility model.

Detailed ways

The key to the control method of the air supply of the fuel cell stack is the follow-up control of the fan current with the output current of the fuel cell stack; respectively detect the output current of the fuel cell stack 4 and the current of the fan 5, and unify the scale (completed by separate sampling and amplifiers) , and then sent to the positive terminal and negative terminal of the differential amplifier, so the output of the differential amplifier naturally increases with the output current of the fuel cell stack; this signal drives the fan to increase speed, and the current of the fan increases and is fed back to the differential The negative terminal of the amplifier, thus achieving the balance of the new higher bit.

Figure 1 is a control circuit diagram of the present utility model, including a voltage stabilizing circuit unit 1, a control circuit unit 2,

Signal acquisition unit 3 and field effect tube G; voltage stabilizing circuit unit 1 is used to provide stable power for the control circuit through the voltage stabilizing chip 7812; The control mode is used to control the size of the conduction of the field effect tube G; the signal acquisition unit 3 is used to collect the current output by the battery pack 4 and the current used by the fan 5, and pass the collected current to the control circuit unit 2; Terminals I and II are connected to the positive and negative poles of the load, and the current output by the battery pack 4 and the current used by the blower fan 5 are collected through the voltage stabilizing circuit unit 1, and the collected current is passed to the control circuit unit 2, and passed through the control circuit unit After the processing of 2, the control current is input to the driving end of the field effect tube G, so as to realize the control of the fan 5.

In the figure, operational amplifiers IC ₁ , IC ₂ and IC ₃ are three operational amplifiers in the LM324 integrated circuit, and G is a field effect transistor. The signal acquisition unit 3 is mainly composed of resistors, wherein the resistor R1 completes the detection of the output current of the battery pack 4 , and the resistor R2 completes the detection of the current used by the fan 5 . The control circuit unit 2 is composed of an operational amplifier and discrete components; the resistor R ₁ is the sampling resistor for the output current of the battery pack 4, and forms the detection of the output current of the fuel cell with the operational amplifier IC ₁ ; the output of the operational amplifier IC ₁ is sent to the transport Put the positive input end of IC ₃ , if the output current of battery pack 4 increases like this, the output of operational amplifier IC ₃ will be high, and it drives field effect tube G, thereby controls fan 5 speed to increase; The current detection of fan 5 is by The sampling of the resistor R ₂ and the completion of the op amp IC ₂ will lead to the increase of the output voltage of the op amp IC ₂ , and the signal is added to the negative terminal of the op amp IC ₃ to form a negative feedback, thereby restraining the rise of the output of the op amp IC ₃ ; Thus, every change in the output current of the battery pack 4 causes a corresponding change in the current of the fan 5 and is in a new stable state.

When the battery pack is started, how to ensure that the fan is running at a low speed? When the fuel cell pack is supplying hydrogen, because there is no load at startup, the voltage of the fuel cell rises rapidly, the circuit consumes little power, and can enter the working state immediately. R ₃ and R ₄ divide the output voltage _of the fuel cell stack, and introduce it to the positive input terminal of IC 1 through R ₉ , so that IC ₁ has a certain output voltage, resulting in a larger output voltage of IC ₃ to drive the field effect tube and cause the fan to run; Fan current detection amplifies and feedbacks the negative terminal of IC ₃ to make it reach a stable state; select a suitable DC axial fan or DC fan according to the output voltage, output power and geometric size of the fuel cell stack.

Fuel cell stacks are ever-changing, so it’s inconvenient to go into details, but the following principles must be followed: meet the air demand requirements of fuel cell stacks; geometric dimensions correspond to both; when rated power output, the output voltage of fuel cell stacks is greater than and close to that of axial flow fans or DC The rated voltage of the fan.

R ₁ and IC ₁ are used to detect the output current of the fuel cell group, R ₂ and IC ₂ are used to detect the current of the fan, so the magnification of IC ₁ and IC ₂ is not important, but the unity of the two signals is the most important important. Let the rated output current of the fuel cell set be I _1H , and the rated current of the fan be I _2H , then R ₁ ·I _1H ·K ₁ =R ₂ ·I _2H ·K ₂ is important. The value of R ₁ ·I _1H ·K ₁ is generally 5V. Because R ₁ is the sampling resistance of the output current of the fuel cell group, the current flowing through it is relatively large, so the power consumption should be as small as possible, and the sampling resistance R ₂ of the fan current should be selected as small as possible. Ten milliohm level. After selecting _R1 and _R2 and knowing the rated output current of the fuel cell group and the rated current of the fan, _K1 and _K2 can be calculated. The magnification of IC ₃ affects the sensitivity of the follow-up; the larger K ₃ is, the more sensitive it is, and the smaller K _{3 is} , the more stable it is. If it is too active, it will be unstable, and if it is too stable, it will not work; experience has proved that 50<K ₃ <100 is all right. C ₁ and R ₁₅ are not negligible, they affect the stability of the drive; the smaller the value of R ₁₅ ·C ₁ is, the faster the fan current follows the output current of the fuel cell; the value of R ₁₅ ·C ₁ is too small It will cause a large overshoot of the fan current, and even cause oscillation. Generally, R ₁₅ chooses 1KΩ, and C ₁ chooses 47цf.

Implementation points of the present utility model: 1) the fuel cell stack must select a suitable air supply fan. 2) The output current signal of the fuel cell group and the fan current signal have a uniform variation range, generally 0-5V. 3) When the load of the fuel cell group changes, the fan current changes accordingly; when the follow-up is too slow, reduce R ₁₅ or C ₁ ; when the load changes cause the fan current to fluctuate, increase R ₁₅ or C ₁ . 4) Adjust R ₄ when it is no-load, so that the fan can start reliably and run at the lowest speed, and adjust R ₁₁ when it is full-load, so that the fan is in the rated working state. They affect each other, so repeated adjustments must be made at least twice. 5) If the fuel cell stack uses a DC shaft fan for air supply, use a FET to control the fan as shown in the circuit diagram. The field effect transistor is selected according to its working voltage and current. Pay attention to the heat dissipation of the field effect tube. If the fuel cell stack uses a DC fan, and the DC fan has a controller to control the speed, the output of IC ₃ can be used to replace the speed given signal of the controller. The signal is generally 0-5V and can be directly replaced.

Such as a 7.0KW fuel cell pack; use a 48V DC fan (the fan has a speed controller). The fuel cell pack charges the battery through DC/DC, and the battery supplies power to the motor and fan. The experimental data are as follows:

Battery pack voltage V 90.5 84.9 79.8 75.1 69.7 64.9 60.1 Battery pack current A 0 19.1 38.9 61.5 83.5 103 125.2 Fan speed given voltage IC ₃ output V 1.6 2.1 2.6 3.2 3.8 4.4 5.0 Fan current A 6.0 6.9 8.0 10.1 13.2 18.4 25.1

The above is only a preferred embodiment of the present utility model, but the scope of protection of the present utility model is not limited thereto. Any equivalent replacement or change of the technical solutions and their inventive concept shall be covered by the protection scope of the present utility model.

Claims (6)

1. A self-starting and self-adaptive control circuit for fuel cell stack air supply, characterized in that it comprises a voltage stabilizing circuit unit (1), a control circuit unit (2), a signal acquisition unit (3) and a field effect tube G; The voltage stabilizing circuit unit (1) is used to provide a stable power supply for the control circuit; The control circuit unit (2) uses the current of the battery pack (4) and the fan (5) as a comparison signal, and adopts a feedback comparison control mode to control the conduction of the field effect tube G; The signal acquisition unit (3) is used to collect the current output by the battery pack (4) and the current used by the fan (5), and transmit the collected current to the control circuit unit (2); When in use, connect the I and II terminals to the positive and negative poles of the load, collect the current output by the battery pack (4) and the current used by the fan (5) through the signal acquisition unit (3), and transmit the collected current to the control circuit In the unit (2), after being processed by the control circuit unit (2), the control current is input to the driving end of the field effect tube G, so as to realize the control of the fan (5). 2. The self-starting and self-adaptive control circuit for fuel cell stack air supply according to claim 1, characterized in that the voltage stabilizing chip in the voltage stabilizing circuit unit (1) is a 7812 chip. 3. The self-starting and self-adaptive control circuit for air supply of the fuel cell stack according to claim 1, characterized in that the signal acquisition unit (3) is mainly composed of resistors, wherein the resistor R1 completes the output to the battery pack (4) For current detection, the resistor R2 completes the detection of the current used by the fan (5). 4. The self-starting and self-adaptive control circuit for fuel cell stack air supply according to claim 1, characterized in that the control circuit unit (2) is composed of operational amplifiers and discrete components; wherein the resistor _R1 is the fuel cell stack (4) The sampling resistor of the output current forms the detection of the output current of the fuel cell together with the operational amplifier IC ₁ ; the output of the operational amplifier IC ₁ is sent to the positive input terminal of the operational amplifier IC ₃ , so that the output current of the battery pack (4) if If it increases, the output of the operational amplifier IC ₃ will be high, and it drives the FET G, thereby controlling the speed of the fan (5) to increase; the current detection of the fan (5) is sampled by the resistor R ₂ and completed by the operational amplifier IC ₂ , This must cause the output voltage of op-amp IC ₂ to rise, and this signal is added to the negative terminal of op-amp IC ₃ to form negative feedback, thereby restraining the rise of op-amp IC ₃ output; thus forming each battery pack (4) Changes in the output current cause corresponding changes in the current of the fan (5) and are in a new stable state. 5. The self-starting and self-adaptive control circuit for fuel cell stack air supply according to claim 4, characterized in that said IC ₁ , IC ₂ and IC ₃ are three operational amplifiers in an LM324 integrated circuit. 6. The self-starting and self-adaptive control circuit for fuel cell stack air supply according to claim 1, characterized in that the fan (5) is a DC axial fan or a DC fan.

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