JP3733791B2 - Output correction control device for vehicle fuel cell system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an output correction control device for a vehicle fuel cell system that accurately determines the power generation state of a fuel cell and performs control so that an actual output from the fuel cell becomes a required output.
[0002]
[Prior art]
Conventionally, an output correction control device for a fuel cell system for a vehicle corrects an output that can be taken out according to a power generation state of the fuel cell when controlling the actual output from the fuel cell to be a required output. Are known.
[0003]
In this output correction control device, when the required output requested from the vehicle controller is taken out from the fuel cell, if there is a difference between the required output and the actual output, the current of the fuel cell stack monitored during traveling Using the instantaneous data such as voltage, reformed gas pressure, and temperature, the output that can be taken out is corrected according to the power generation state of the fuel cell.
[0004]
[Problems to be solved by the invention]
However, in the conventional fuel cell vehicle, the power generation state of the fuel cell is obtained by using a sampled detection current signal or detection voltage signal of the fuel cell that constantly fluctuates during traveling.
[0005]
For this reason, especially when the vehicle is frequently accelerated and decelerated, and sampling is performed in a situation where the current and voltage output from the fuel cell fluctuate greatly, the deviation from the current-voltage characteristics of the fuel cell during steady state becomes large. It was. As a result, there is a problem that it is difficult to accurately determine the power generation state of the fuel cell.
[0006]
In this case, the correction amount used for controlling the fuel cell is also shifted, so that there is a problem that the response time until the required output required for the fuel cell is increased.
[0007]
The present invention has been made in view of the above, and an object thereof is to provide an output correction control device for a fuel cell system for a vehicle that can accurately determine the power generation state of the fuel cell.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 is a storage means for storing in advance initial output characteristics representing current characteristics corresponding to the required output required for the fuel cell, and a required output from the initial output characteristics. Based on the current and voltage output from the fuel cell, output current fixing means for temporarily fixing the output current output from the fuel cell to the required current, , the actual output calculating means for calculating an actual output, the comparison between the actual output and the required output and the power generation state determining means for determining the power generation state of the fuel cell, the power generation state of the fuel cell is determined by the power generation state determination means And a control means for controlling the actual output to be the required output .
[0009]
According to a second aspect of the present invention, there is provided a correction coefficient calculating means for calculating a correction coefficient relating to an output that can be taken out from the fuel cell according to the pressure and temperature applied to the fuel cell, and The required output correcting means for correcting the required required output using a correction coefficient, and when the corrected required output does not match the required output before correction, the initial output characteristics are corrected using the correction coefficient. Output characteristic correcting means, and second required current calculating means for calculating a second required current corresponding to the required output from the corrected second output characteristic, are output from the fuel cell by the output current fixing means. The gist is to temporarily fix the output current to the second required current.
[0010]
According to a third aspect of the present invention, in order to solve the above-mentioned problem, when the second required current calculation unit cannot calculate the second required current, the maximum value that can be calculated from the corrected second output characteristic And a maximum pressure calculating means for calculating a settable maximum pressure that becomes a required output at the maximum required current, and the pressure applied to the fuel cell becomes the maximum pressure. The gist is to temporarily fix the output current output from the fuel cell to the maximum required current by the output current fixing means.
[0011]
In order to solve the above-mentioned problem, the invention according to claim 4 is provided with notifying means for notifying that the output of the fuel cell is restricted when the pressure of the fuel cell cannot be increased. To do.
[0012]
In order to solve the above problem, the power generation state determination means determines that the fuel cell is deteriorated when the actual output of the fuel cell does not match the required output, and The gist is to provide a degradation coefficient calculation means for calculating a degradation coefficient of the fuel cell based on the current and voltage output from the battery and the required output, and to correct the correction coefficient calculated by the correction coefficient calculation means. .
[0013]
【The invention's effect】
According to the first aspect of the present invention, the initial initial output characteristic representing the current characteristic corresponding to the required output required for the fuel cell is stored in advance, and the required current corresponding to the required output is determined from the initial output characteristic. And the output current output from the fuel cell is temporarily fixed at this required current. Here, the actual output is calculated based on the current and voltage output from the fuel cell, and the power generation state of the fuel cell is determined by comparing the actual output with the required output, thereby accurately determining the power generation state of the fuel cell. It is possible to control the actual output to be the required output based on the power generation state of the fuel cell.
[0014]
According to the second aspect of the present invention, the correction coefficient related to the output that can be taken out from the fuel cell is calculated according to the pressure and temperature applied to the fuel cell, and the required output required for the fuel cell is calculated as the correction coefficient. Use to correct. If the corrected required output does not match the required output before correction, the initial output characteristic is corrected using the correction coefficient, and the second output characteristic after correction corresponds to the required output. By calculating the required current, the output current output from the fuel cell is temporarily fixed at the second required current. Therefore, even when the required output is corrected, the power generation state of the fuel cell is accurate. Can judge well. Moreover, the responsiveness at the time of vehicle driving can be improved.
[0015]
According to the third aspect of the present invention, when the second required current cannot be calculated, the maximum required current that can be calculated from the corrected second output characteristic is calculated, and this maximum required current is calculated. By calculating the settable maximum pressure that becomes the required output in step 1, the pressure applied to the fuel cell is controlled to become the maximum pressure, and the output current output from the fuel cell is temporarily set to this maximum required current. Since it is fixed, for example, even when the correction coefficient is too small to calculate the second required current, the power generation state of the fuel cell can be accurately determined.
[0016]
According to the fourth aspect of the present invention, when the pressure of the fuel cell cannot be increased, the power generation state of the fuel cell is notified to the driver by notifying that the output of the fuel cell is limited. Can be notified.
[0017]
According to the fifth aspect of the present invention, when the actual output of the fuel cell does not match the required output, it is determined that the fuel cell has deteriorated, and the current and voltage output from the fuel cell, the required By calculating the deterioration factor of the fuel cell based on the output, the correction factor related to the output that can be taken out from the fuel cell is corrected. Therefore, even if the fuel cell deteriorates, the driving performance of the fuel cell vehicle A decrease can be prevented.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a diagram showing a configuration of a fuel cell system mounted on a fuel cell vehicle according to an embodiment of the present invention.
[0020]
In the fuel reformer 11, a reformed gas containing hydrogen is generated from hydrocarbon, alcohol, or the like. On the other hand, the compressor 13 compresses air and supplies it to the fuel cell stack 15 and the fuel reformer 11.
[0021]
The fuel cell stack 15 generates power using hydrogen contained in the reformed gas from the fuel reformer 11 and oxygen contained in the air from the compressor 13. The power distributor 17 distributes the power generated by the fuel cell stack 15 to the vehicle load 19 and the secondary battery 21.
[0022]
The vehicle load 19 is a load generated when a motor driving the vehicle and other auxiliary machines are driven. The secondary battery 21 is connected in parallel with the vehicle load, charges the power collected from the motor by regeneration during braking, and assists the power supplied to the motor during sudden acceleration.
[0023]
A pressure adjusting valve 31 is provided in the middle of the exhaust air piping discharged from the fuel cell stack 15 to the fuel reformer 11 in order to adjust the pressure of the exhaust air flowing into the fuel cell stack 15. Further, a pressure adjusting valve 33 for adjusting the pressure of the reformed gas flowing into the fuel cell stack 15 is provided in the middle of the exhaust reformed gas discharged from the fuel cell stack 15 to the fuel reformer 11. .
[0024]
The stack voltage sensor 35 and the stack current sensor 37 detect the voltage and current generated by the fuel cell stack 15 and output them to the fuel cell control device 51.
[0025]
The pressure sensor 41 is provided in the middle of the piping of the reformed gas flowing into the fuel cell stack 15 from the fuel reformer 11, detects the pressure of the reformed gas, and outputs it to the fuel cell control device 51. The pressure sensor 43 is provided in the middle of the piping for the air flowing into the fuel cell stack 15 from the compressor 13, detects the pressure of the air, and outputs it to the fuel cell control device 51.
[0026]
The temperature sensors 45 and 47 are provided in the middle of the piping of exhaust reformed gas and exhaust air discharged from the fuel cell stack 15 to the fuel reformer 11, respectively, and detect the temperature of the exhaust reformed gas and exhaust air to detect the fuel cell. Output to the control device 51.
[0027]
The fuel cell control device 51 includes a RAM that stores control data, a ROM that stores a control program, an initial output characteristic OPini, and a hydrogen utilization rate table, and a CPU that controls the fuel cell system according to the control program. Yes.
[0028]
The drive control device 53 calculates the vehicle load power by summing the power required by each auxiliary machine constituting the vehicle load 19, and based on the power capacity remaining in the secondary battery 21 and the vehicle load power, the fuel cell stack 15 is calculated and transmitted to the fuel cell control device 51, and a distribution ratio for distributing the electric power generated by the fuel cell stack 15 to the vehicle load 19 and the secondary battery 21 is calculated. It transmits to the distributor 17.
[0029]
Next, FIG. 2 is a diagram showing the relationship between the current that can be extracted from the fuel cell stack 15 and the power.
[0030]
As shown in FIG. 2, the stack current and the stack power have a one-to-one correspondence in the region of the voltage of about 300 V and the current of about 300 A, which is a power source for the electric vehicle. This relationship indicates that the higher the reformed gas, the air pressure, and the higher the stack temperature, the greater the power for the same current value.
[0031]
Next, FIG. 3 is a diagram showing the relationship of the correction coefficient to the required output required when calculating the output that can be taken out with respect to the pressure or temperature applied to the fuel cell stack 15.
[0032]
The correction coefficient has current dependency, and as shown in FIG. 3, it indicates that the correction coefficient shifts in a direction of lowering as the current increases.
[0033]
Next, FIG. 4 is a diagram showing an initial output characteristic and a corrected output characteristic of the fuel cell stack 15 used when performing the output correction control process.
[0034]
When the output from the drive control device 53 is output at a current value calculated from the initial output characteristic OPini without considering the power generation state of the fuel cell stack 15, the request is output when the fuel cell stack 15 deteriorates. The output is not satisfied. Therefore, the correction output characteristic is calculated by correcting the initial output characteristic OPini with the correction coefficient, and further, the correction current for the requested output is calculated from the correction output characteristic, and the output current from the fuel cell stack 15 is output with this correction current. Control may be performed as follows.
[0035]
Next, FIG. 5 is a diagram showing that the ratio of the target voltage of the fuel cell stack 15 to the actual detection voltage can be converted into a hydrogen utilization rate.
[0036]
The hydrogen utilization rate indicates the ratio of consumed hydrogen to the total amount of hydrogen flowing into the fuel cell stack 15. As shown in FIG. 5, the fuel cell vehicle is assumed to be used at a hydrogen utilization rate of about 70 to 80%.
[0037]
Next, normal output correction control processing by the fuel cell control device 51 and output correction control processing according to the power generation state of the stack will be described with reference to FIGS.
[0038]
First, normal output correction control processing by the fuel cell control device 51 will be described.
[0039]
In step S5, the pressure of the reformed gas is detected from the pressure sensor 41, the stack temperature is detected from the temperature sensor 45, and the current correction coefficient Kr, as shown in FIG. Based on the correction coefficient Kt by, and the deterioration coefficient Kd representing the degree of stack deterioration,
[Expression 1]
Kr = Kp x Kt x Kd
As shown in FIG.
[0040]
If the calculation process in step S5 is the first time, the calculation process is performed with the deterioration coefficient Kd = 1.
[0041]
In step S10, when the request output Pout is received from the drive control device 53, the request output Pout from the drive control device 53 is held in the internal RAM. If the request output Pout cannot be received from the drive control device 53, the request output Pout at the time of the previous reception held in the internal RAM is read out.
[0042]
In step S20, referring to FIG. 4, the initial output characteristic OPini is converted into a required output conversion current Iout_1 corresponding to the required output Pout. At the same time, the requested output Pout is multiplied by the current correction coefficient Kr to correct it, thereby obtaining a corrected requested output Pout_1.
[0043]
In step S30, it is determined whether the correction request output Pout_1 and the request output Pout match. If they match, the process proceeds to step S40, the output current from the fuel cell stack 15 is output as the required output conversion current Iout_1 obtained in step S20, and the process proceeds to step S110.
[0044]
On the other hand, if the two do not match, the process proceeds to step S50, and referring to FIG. 4, it corresponds to the required output Pout from the corrected output characteristic OPini_r obtained by multiplying the initial output characteristic OPini by the current correction coefficient Kr. The correction current Iout_2 to be read is read.
[0045]
In step S60, with reference to FIG. 4, it is determined whether the correction current Iout_2 has been read from the initial output characteristic OPini. If the correction current Iout_2 can be read, the process proceeds to step S70, the output current from the fuel cell stack 15 is output as the correction current Iout_2 obtained in step S50, and the process proceeds to step S110.
[0046]
On the other hand, if the correction current Iout_2 cannot be read, the current correction coefficient Kr is too small and the correction current Iout_2 does not exist on the correction output characteristic OPini_2, so the process proceeds to step S80 and is provided at the inlet of the fuel cell stack 15. The pressure of the reformed gas is read from the pressure sensor 41, and it is determined whether the current pressure is in a state where it can be increased without exceeding a predetermined value.
[0047]
When the pressure of the reformed gas can be increased, the process proceeds to step S90, the maximum output current Iout_2max that can be output on the corrected output characteristic OPini_2 is read, and the maximum settable pressure that becomes the required output Pout with this maximum output current Iout_2max Is calculated backward. The pressure control valve 33 provided at the outlet of the fuel cell stack 15 is controlled up to the maximum settable pressure calculated by the pressure of the reformed gas while being detected by the pressure sensor 45 provided at the inlet of the fuel cell stack 15. Increase the pressure. As a result, the output current from the fuel cell stack 15 is output at the maximum output current Iout_2max obtained, and the process proceeds to step S110.
[0048]
In this case, control is performed to raise the pressure of the reformed gas while compensating for the shortage of the output current by discharging from the secondary battery 21. Also,
[Expression 2]
Iout_2 = Iout_2max
When reaching the value, output compensation from the secondary battery 21 is stopped.
[0049]
On the other hand, when the pressure of the reformed gas cannot be increased, the process proceeds to step S100, and an output restriction warning signal is transmitted to the drive control device 53. Then, the output current from the fuel cell stack 15 is output at the maximum output current Iout_2max obtained as described above, and the process proceeds to step S110.
[0050]
In this case, since the drive control device 53 receives the output restriction warning signal from the fuel cell control device 51, a warning is displayed on the display unit provided on the meter panel to indicate that the driver has entered the output restriction region. Inform.
[0051]
In addition,
[Equation 3]
Iout_2> Iout_2max
When the pressure reaches the upper limit value during the period, the output compensation by the secondary battery 21 is continued. However, if the output compensation cannot be continued because there is no power capacity of the secondary battery 21, similarly, a warning is displayed and notified that the output limit area has been entered.
[0052]
Further, since the correction coefficient Kr is updated every fixed time, the correction current Iout_2 is also updated at the same time. As a result, when the updated correction current Iout_2 returns from the output restriction region to the output possible region, a warning cancellation signal is transmitted to the drive control device 53 in order to cancel the warning display described above. In this case, since the drive control device 53 receives the warning release signal from the fuel cell control device 51, the warning display is released from the display unit on the meter panel, and the driver is notified that the output enabled region has been entered.
[0053]
As described above, the output current output from the fuel cell stack 15 is temporarily fixed by steps S40, S70, S90, and S100.
[0054]
Next, output correction control according to the state of the fuel cell stack 15 by the fuel cell control device 51 will be described.
[0055]
First, in step S110, the stack voltage Vsen and the stack current Isen detected by the stack voltage sensor 35 and the stack current sensor 37 are input. Until the detection process in step S110 is executed next time, the detected value of this time is held in the RAM in the fuel cell control device 51, and the excess / deficiency during that time is compensated by charging / discharging by the secondary battery 21. I will do it.
[0056]
In step S120,
[Expression 4]
Iout_2 ≦ Iout2_max
Assuming that the output current permissible width ΔP is subtracted from the detected stack current Isen, the actual output by the stack voltage Vsen, and the required output Pout at the start of sampling,
[Equation 5]
Isen × Vsen <(Pout−ΔP)
Compare whether or not.
[0057]
However, if the lower limit voltage of the stack voltage Vsen is the stack lower limit voltage Vlow,
[Formula 6]
Vsen ≧ Vlow
It is.
[0058]
here,
[Expression 7]
Isen × Vsen ≧ (Pout−ΔP)
Is satisfied, there is no problem such as deterioration in the power generation state of the fuel cell stack 15, so that the output is continued to return to step S5 and the process is repeated.
[0059]
On the other hand, when this inequality (7) is not satisfied, it is determined that the hydrogen flow rate to the fuel cell stack 15 is insufficient and the prescribed hydrogen utilization rate is not obtained.
[0060]
In step S130, as the voltage target value,
[Equation 8]
Vout = Pout / Isen
Is calculated.
[0061]
Furthermore, as a voltage ratio between the detection voltage Vsen and the target voltage Vout,
[Equation 9]
Voltage ratio = Vsen / Vout
Is calculated.
[0062]
Here, referring to FIG. 5, the current hydrogen utilization rate is calculated from the hydrogen utilization rate table with respect to the voltage ratio Vsen / Vout stored in advance in the ROM in the fuel cell control device 51.
[0063]
In step S140, a hydrogen increase request is output to the fuel reformer 11 so as to achieve the target hydrogen utilization rate. The fuel reformer 11 that has received the hydrogen increase request from the fuel cell control device 51 increases the amount of reformed gas produced in response to the hydrogen increase request.
[0064]
After the correction of the hydrogen flow rate, in step S150, the actual output represented by the stack current Isen and the stack voltage Vsen is again compared with the required output Pout.
[Expression 10]
Pout = Isen × Vsen
Judge whether both match.
[0065]
If the two match, the process returns to step S5 and the above-described reception determination process is repeated.
[0066]
On the other hand, if they do not match, it is determined that the fuel cell stack 15 has deteriorated because the actual output is insufficient even after the hydrogen flow rate is corrected.
[0067]
In step S160, as the deterioration coefficient Kd,
## EQU11 ##
Kd = Vsen / Vout
Is calculated.
[0068]
At this time, a warning signal indicating that the output is likely to be restricted due to deterioration of the fuel cell stack 15 and a warning signal for prompting inspection or replacement when the deterioration coefficient Kd is 0.8 or less are driven and controlled. Call the device 53. In this case, since the drive control device 53 receives a warning signal from the fuel cell control device 51, a warning is displayed on the display unit on the meter panel to notify the driver of the above-described content.
[0069]
And it returns to step S5 and repeats a process. In this case, in step S5, the current correction coefficient Kr is corrected using a new deterioration coefficient Kd of less than 1.
[0070]
As described above, the initial initial output characteristic representing the current characteristic corresponding to the required output required for the fuel cell stack is stored in advance, the required current corresponding to the required output is calculated from the initial output characteristic, and the fuel cell The output current output from the stack is temporarily fixed at this required current. Here, the actual output is calculated based on the current and voltage output from the fuel cell stack, and the power generation state of the fuel cell stack is determined by comparing the actual output with the required output. The state can be determined with high accuracy.
[0071]
Further, a correction coefficient related to the output that can be taken out from the fuel cell stack is calculated according to the pressure and temperature applied to the fuel cell stack, and the required output required for the fuel cell stack is corrected using the correction coefficient. If the corrected required output does not match the required output before correction, the initial output characteristic is corrected using the correction coefficient, and the second output characteristic after correction corresponds to the required output. Since the output current output from the fuel cell stack is temporarily fixed to the second required current by calculating the required current, the power generation state of the fuel cell stack is corrected even when the required output is corrected. Can be accurately determined. Moreover, the responsiveness at the time of vehicle driving can be improved.
[0072]
Further, when the second required current cannot be calculated, the maximum required current that can be calculated from the corrected second output characteristic is calculated, and the maximum settable pressure that becomes the required output at this maximum required current is calculated. By calculating, the pressure applied to the fuel cell stack is controlled to be the maximum pressure, and the output current output from the fuel cell stack is temporarily fixed to the maximum required current. Even when the correction coefficient is too small to calculate the second required current, the power generation state of the fuel cell stack can be accurately determined.
[0073]
Furthermore, when the pressure of the fuel cell stack cannot be raised, the driver can be notified of the power generation state of the fuel cell stack by notifying that the output of the fuel cell stack is limited.
[0074]
If the actual output of the fuel cell stack does not match the required output, it is determined that the fuel cell stack has deteriorated, and based on the current and voltage output from the fuel cell stack and the required output, the fuel cell stack By calculating the deterioration coefficient of the fuel cell, the correction coefficient related to the output that can be taken out from the fuel cell stack is corrected. Therefore, even if the fuel cell stack deteriorates, the deterioration of the driving performance of the fuel cell vehicle can be prevented. Can do.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a fuel cell system mounted on a fuel cell vehicle according to an embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between current and power that can be taken out from a fuel cell stack.
FIG. 3 is a diagram showing a relationship of a correction coefficient with respect to a required output necessary for calculating a removable output with respect to a pressure or temperature applied to a fuel cell stack.
FIG. 4 is a diagram showing an initial output characteristic and a corrected output characteristic of a fuel cell stack used when performing an output correction control process.
FIG. 5 is a diagram showing that a ratio of an actual detection voltage to a target voltage of a fuel cell stack can be converted into a hydrogen utilization rate.
FIG. 6 is a flowchart for explaining normal output correction control processing by the fuel cell control device and output correction control processing according to the power generation state of the stack.
[Explanation of symbols]
11 Fuel reformer 13 Compressor 15 Fuel cell stack 19 Vehicle load 21 Secondary battery 31, 33 Pressure regulating valve 35 Stack voltage sensor 37 Stack current sensors 41, 43 Pressure sensor 45, 47 Temperature sensor 51 Fuel cell control device 53 Drive control apparatus

Claims (5)

Storage means for storing in advance initial output characteristics at the initial stage representing current characteristics corresponding to required output required for the fuel cell;
Request current calculation means for calculating a request current corresponding to the request output from the initial output characteristics;
Output current fixing means for temporarily fixing the output current output from the fuel cell to the required current;
Actual output calculation means for calculating the actual output based on the current and voltage output from the fuel cell;
Power generation state determining means for determining the power generation state of the fuel cell by comparing the actual output and the required output ;
An output correction control device for a fuel cell system for a vehicle, comprising: control means for controlling an actual output to be a required output based on the power generation state of the fuel cell determined by the power generation state determination means . Correction coefficient calculating means for calculating a correction coefficient related to the output that can be taken out from the fuel cell according to the pressure and temperature applied to the fuel cell;
Requested output correction means for correcting the required output required for the fuel cell using a correction coefficient;
If the required output after correction does not match the required output before correction, output characteristic correction means for correcting the initial output characteristic using a correction coefficient;
A second required current calculating means for calculating a second required current corresponding to the required output from the corrected second output characteristic;
2. The output correction control device for a fuel cell system for a vehicle according to claim 1, wherein the output current output from the fuel cell by the output current fixing means is temporarily fixed to the second required current. The second required current calculation means includes:
If the second request current cannot be calculated, maximum request current calculation means for calculating the maximum request current that can be calculated from the corrected second output characteristic;
A maximum pressure calculating means for calculating a settable maximum pressure that becomes a required output at the maximum required current,
The pressure applied to the fuel cell is controlled to be a maximum pressure, and the output current output from the fuel cell is temporarily fixed to the maximum required current by the output current fixing means. 3. The output correction control device for a fuel cell system for vehicles according to 2.   4. The output correction control for a fuel cell system for a vehicle according to claim 3, further comprising an informing means for informing that the output of the fuel cell is restricted when the pressure of the fuel cell cannot be increased. apparatus. The power generation state determination means includes
If the actual output of the fuel cell does not match the required output, it is determined that the fuel cell has deteriorated, and the deterioration factor of the fuel cell is determined based on the current and voltage output from the fuel cell and the required output. A deterioration coefficient calculating means for calculating,
The output correction control apparatus for a fuel cell system for a vehicle according to claim 2, wherein the correction coefficient calculated by the correction coefficient calculation means is corrected.

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