JP3517260B2 - Fuel cell power generator and control method for fuel cell power generator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator for supplying hydrogen gas using a reformer and a control method for the fuel cell power generator.

[0002]

2. Description of the Related Art A conventional fuel cell using a reformer usually uses city gas as a raw material gas and reacts the city gas with steam to obtain hydrogen gas to be supplied to the fuel cell.
The output control method of such a fuel cell device calculates the required fuel flow rate from the actual fuel cell output that meets the load request, and controls the opening of the fuel flow rate control valve provided in the fuel supply system passage. To do. The outline of the configuration of the fuel cell power generator using the reformer will be described with reference to FIG. The fuel cell power generation device includes a fuel cell 1, a hydrogen gas supply system 2 for supplying hydrogen to the fuel cell, an oxygen gas supply system 3 for supplying oxygen (air) to the fuel cell, an inverter device 4, and a fuel. The load 5 includes a control system that controls the output of each system and the inverter device so as to supply fuel and oxygen commensurate with the battery output, and is connected to a commercial power source through a circuit breaker.
Is supplying power to.

The fuel gas supply system 2 includes a reformer 6, an injector 7, a steam control valve 8, and a fuel flow rate control valve 9 for controlling the flow rate of hydrogen gas input to the reformer and supplied to the fuel cell. Composed of and. The oxygen gas supply system 3 is
It is composed of a blower 10 and an oxygen gas flow rate control valve 11. The control system includes a controller 12, a steam flow meter 15 for detecting the flow rate of steam supplied from the steam drum to the reformer, and a raw material gas flow meter 16 for detecting the flow rate of raw material gas supplied to the injector 7. An air flow meter 17 for detecting the flow rate of the air supplied to the fuel cell, and a direct current detector 18 including a direct current transformer for detecting the output of the fuel cell.
And an active power detector 19 for detecting the active power amount of the power supplied to the load 5.

FIG. 4 is a control block diagram showing a control method of the fuel cell power generator as described above, and the fuel cell control method based on the conventional technique executed by the control device 12 will be described with reference to FIG. This method sets the active power supplied to the load as a target value, controls the output of the inverter device by monitoring the active power actually supplied to the load with this target value, and responds to the load demand. This is a method of calculating and controlling the amount of gas to be supplied to the fuel cell based on the actual fuel cell output and the amount of fuel actually supplied to the fuel cell.

The active power target value PS set in the control device 12 and the active power detection value PR which is the actual active power detected by the active power detector 19 are constituted by a subtractor provided in the control device. It is input to the error amplifying means 21, and its deviation ΔP is an inverter phase control means 25 composed of a PI calculator.
Is output to. The inverter phase control means 25
Calculates the phase angle for firing the gate of the inverter device 4 based on the deviation ΔP, and outputs the calculation result to the gate drive circuit 26. That is, the inverter phase control means 25 determines that the active power detection value PR is the active power target value PS.
When the deviation ΔP is 0, the phase angle signal φ for controlling the gate is output while maintaining the phase angle at the current state, and the active power detection value PR is equal to the active power target value PS.
When it is larger, that is, when the deviation ΔP is negative, the phase angle signal φ that reduces the phase angle from the current state is output, and when the active power detection value PR is smaller than the active power target value PS,
That is, when the deviation ΔP is positive, the phase angle signal φ that increases the phase angle from the current state is output. The gate drive circuit 26 outputs a firing signal for firing the gate of the inverter device 4 to the inverter device 4 according to the phase angle signal φ.

Further, the control device 12 includes a direct current detector 1
The detected value IR of No. 8 is calculated by the amplification means 23 composed of a proportional calculator, and the flow rate of fuel required to obtain this current value IR is set as the fuel gas flow rate target value GS, and the target value GS and the fuel gas flow rate are also set. The fuel flow rate detection value G from the meter 13 is calculated by the error amplifying means 24 composed of a subtractor, and the gas flow rate deviation ΔG is output to the gas flow rate control means 22 composed of a PI calculator. When the hydrogen gas flow rate detection value G is equal to the gas flow rate target value GS, that is, when the gas flow rate deviation ΔG is 0, the gas flow rate control means 22 holds the opening degree of the fuel flow rate control valve 9 at the present state. D
When the detected value G is larger than the target value GS, that is, when the gas flow rate deviation ΔG is negative, a valve opening signal D for decreasing the opening degree of the control valve 9 is set so that the detected value G is greater than the target value GS. When it is small, that is, when the gas flow rate deviation ΔG is positive, a valve opening signal D for increasing the opening degree of the control valve 9 is output to the fuel gas flow rate control valve 9 to control the fuel gas flow rate.

As described above, in the output control system of the fuel cell power generator using the reformer, it is possible to change the fuel supply amount according to the slow load fluctuation, but the actual fuel The required fuel flow rate from the cell output, that is, the fuel flow rate target value is set, and the deviation from the actual fuel flow rate is calculated to control the fuel supply amount, so the response of the gas flow rate control is slow, It becomes impossible to deal with the fluctuation of the fast frequency fuel flow rate due to the fluctuation of the source pressure of the raw material gas, the rapid frequency fuel flow rate fluctuation due to the temperature change of the steam drum, and the fast frequency fuel flow rate fluctuation due to the back pressure fluctuation. ,
There is a problem that the fuel cells are deteriorated due to insufficient fuel flow rate.

The change in the original pressure of the raw material gas is due to the change in the load (gas engine, gas turbine, etc.) connected to the fuel supply line of the fuel cell. Also,
Since the raw material gas is mixed with steam using the injector 7 and supplied to the reformer 6, fuel gas corresponding to the pressure of the steam is supplied. However, water vapor is supplied from the steam drum, and when water vapor is supplied to lower the water level in the drum, water having a lower water temperature than the water temperature in the drum is replenished. At times, the temperature inside the drum drops, causing pressure fluctuations. Therefore, the temperature change of the drum breaks the stability of the pressure of the water vapor, and the supply amount of the fuel gas fluctuates. Usually, about 80% of the hydrogen gas generated in the reformer 6 is supplied to the fuel cell, and the remaining 20% is returned to the reformer and used as a heat source. When the supply amount of the fuel gas sharply decreases, there occurs a moment when the hydrogen gas amount required by the fuel cell cannot be satisfied. This causes deterioration of the electrodes and must be avoided. To address this, traditionally,
This problem was dealt with by setting the utilization rate to a slightly lower value without setting the hydrogen gas utilization rate limit value, but this coping method causes a reduction in the utilization rate of hydrogen gas,
It was a factor that pushed up the power generation cost.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the above-mentioned conventional control method, and involves fluctuations in the drum pressure of the steam generating drum, fluctuations in the back pressure of the reformer, fluctuations in the gas source pressure, and the like. An object of the present invention is to provide a control method of a fuel cell power generation device that can improve the utilization rate of hydrogen gas without increasing the utilization rate of hydrogen gas when there is a disturbance with a rapid cycle and without taking an excessive margin in the utilization rate. .

[0010]

In order to solve the above problems, the present invention is directed to a fuel cell, a reformer for supplying hydrogen gas to the fuel cell, and the output of the fuel cell to AC power for conversion to a commercial power grid. In a fuel cell power generator including an interconnected inverter device and a control device for controlling the fuel cell, the control device sets an effective power target value of the output of the fuel cell set in the control device and the actual fuel cell from the fuel cell. Means for controlling the fuel flow rate supplied to the fuel cell from the active power supplied to the load, and the output current target value of the fuel cell calculated based on the fuel flow rate actually supplied to the fuel cell and the actual fuel And a means for controlling the output of the inverter device based on the output current value of the battery.

Further, in the fuel cell power generator of the present invention, the means for controlling the fuel flow rate comprises a PI calculator for calculating the supplied fuel based on the active power deviation, and the means for controlling the output of the inverter is a direct current. The PI calculator for calculating the phase angle of the inverter based on the phase angle deviation signal calculated based on the deviation.

Further, in the control method of the fuel cell power generator of the present invention, the output of the fuel cell, the reformer for supplying hydrogen gas to the fuel cell, and the output of the fuel cell are converted into AC power and connected to the commercial power grid. In a method for controlling a fuel cell power generation device including an inverter device and a control device for controlling the fuel cell, active power that can be output from the fuel cell is set as a target value The process of adjusting the fuel flow rate supplied to the fuel cell based on the actual active power value, and the direct current value that the fuel cell can output based on the actual fuel flow rate supplied to the fuel cell And a step of controlling the output of the inverter device based on the DC current target value and the DC current value actually output from the fuel cell.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a method for controlling the output of the fuel cell power generator shown in FIG. This control method detects the fuel flow rate at the fuel cell inlet, controls the inverter device inserted on the output side of the fuel cell so as to extract the current (electric power) based on the fuel flow rate and the output of the fuel cell, and The fuel gas flow rate to be supplied to the fuel cell is controlled based on the active power target value supplied from the fuel cell to the load connected to the power source and the detected actual power value actually supplied from the fuel cell to the load. It has a feature in the point.
In this method as well, the current fluctuates according to the fluctuation of the gas amount, but when viewed from the side using the electric power (load side) when the electric power is connected to the system, the fluctuation is not a problem in practical use.

The control method of the present invention is shown in FIG. 2 and FIG.
Will be explained. FIG. 2 is a block diagram showing a control aspect of the present invention, and FIG. 3 is a flowchart of a control method according to the method of the present invention.

The error amplifying means 21 composed of a subtracter provided in the control device 12 actually supplies the active power target value PS set in the control device and the fuel cell detected by the active power detector 19 to the load. The active power deviation ΔP obtained by calculation from the detected detected active power PR is output to the fuel flow rate control means 22 including a PI calculator. The control means 22 calculates the opening degree of the fuel flow rate control valve 9 based on the deviation ΔP, and outputs a valve opening degree signal D to the fuel flow rate control valve 9. When the active power detection value PR is equal to the active power target value PS, that is,
When the active power deviation ΔP is 0, a valve opening signal D for maintaining the current opening of the fuel flow rate control valve 9 is output,
When the active power detection value PR is larger than the active power target value PS, that is, when the deviation ΔP is negative, a valve opening signal D for decreasing the opening of the fuel flow rate control valve 9 is output, and the active power detection value PR is When it is smaller than the active power target value PS, that is, when the deviation ΔP is positive, a valve opening signal D for increasing the opening of the fuel flow rate control valve 9 is output to the fuel flow rate control valve 9.

Further, the control device 12 calculates a direct current target value IS indicating the fuel cell output corresponding to the fuel flow rate from the fuel flow rate detection value G detected by the fuel flow meter 13 by the amplifying means 23 composed of a proportional calculator. Then, from the DC current target value IS and the DC current detection value IR representing the actual output of the fuel cell detected by the DC current detector 18 by the error amplification means 24 composed of a subtractor, the ignition angle of the gate in the inverter device 4 is determined. Phase angle deviation Δφ is calculated, and this phase angle deviation signal Δφ is calculated as P
It outputs to the inverter phase control means 25 which consists of an I arithmetic unit.

When the detected direct current value IR is equal to the desired direct current value IS, that is, when the phase angle deviation Δφ is 0, the inverter phase control means 25 keeps the ignition phase angle of the gate of the inverter device at the current state. When the DC current detection value IR is larger than the DC current target value IS, the phase angle signal φ that reduces the phase angle is calculated as the DC current detection value IR.
Is smaller than the DC current target value IS, a phase angle signal φ for increasing the phase angle is supplied to the gate drive circuit 2 of the inverter.
Output to 6.

The gate drive circuit 26 outputs the phase signal φ.
Based on the above, a firing signal which is a firing sequence and timing for firing the gate of the inverter device 4 is calculated, and the firing signal is output to the inverter device.

[0019]

EFFECTS OF THE INVENTION It is possible to cope with gas flow rate fluctuations of a short cycle which could not be conventionally coped with, and it is possible to always keep the hydrogen utilization rate within an appropriate range. In this way, the PI control of the fuel flow rate is performed based on the active power supplied from the fuel cell to the load and the active power target value, and the DC output current target value calculated from the fuel flow rate supplied to the fuel cell and the actual Since the output of the inverter is PI-controlled based on the DC current value, even if the fuel flow rate suddenly decreases, it is possible to prevent the deterioration of the fuel cell by burdening the connected commercial power grid with a load. Furthermore, when the flow rate of fuel supplied to the fuel cell changes due to changes in the temperature of the steam drum or changes in the source pressure of the raw material, the DC current target value that is the DC current value that can be output by the fuel cell in response to this change. Changes, the output of the inverter can be changed to a value corresponding to the fuel flow rate. Therefore, it is possible to quickly respond to the disturbance with a fast cycle and suppress the fuel cell output,
The adverse effect on the fuel cell can be reduced. Also,
For a disturbance with a slow cycle due to clogging of a filter provided in the fuel supply path, the gas flow rate can be PI controlled based on the active power target value and the actual active power value supplied to the load.

[0020]

[Brief description of drawings]

FIG. 1 is a diagram showing the concept of a fuel cell power generator including a reformer according to the present invention.

FIG. 2 is a block diagram showing a control mode of the fuel cell power generator according to the present invention.

FIG. 3 is a flowchart showing a control mode of the fuel cell power generator according to the present invention.

FIG. 4 is a block diagram showing a control mode of a fuel cell power generator according to a conventional technique.

[Explanation of symbols]

1 fuel cell 2 Hydrogen gas supply system 3 Oxygen gas supply system 4 Inverter device 5 load 6 reformer 7 injectors 8 Steam flow control valve 9 Fuel flow control valve 10 Blower 11 Oxygen gas flow control valve 12 Control device 15 Water vapor flow meter 16 Raw material gas flow meter 17 Air flow meter 18 DC current detector 19 Active power detector 21 Error amplification means 22 Gas flow rate control means 23 Amplification means 24 Error amplification means 25 Inverter phase control means 26 Gate drive circuit

Claims (3)

(57) [Claims] 1. A fuel cell, a reformer for supplying hydrogen gas to the fuel cell, an inverter device for converting the output of the fuel cell into AC power and connecting it to a commercial power grid, and a controller for controlling the fuel cell. In the fuel cell power generation device, the control device supplies the fuel cell with the active power target value of the output of the fuel cell set in the control device and the active power actually supplied from the fuel cell to the load. Means for controlling the fuel flow rate, and controlling the output of the inverter device based on the output current target value of the fuel cell calculated based on the fuel flow rate actually supplied to the fuel cell and the actual output current value of the fuel cell A fuel cell power generation device comprising: 2. The means for controlling the fuel flow rate comprises a PI calculator for calculating the supply fuel flow rate based on the active power deviation, and the means for controlling the output of the inverter calculates the phase angle based on the deviation of the direct current. The fuel cell power generator according to claim 1, comprising a PI calculator that calculates the phase angle of the inverter based on the deviation signal. 3. A fuel cell, a reforming device for supplying hydrogen gas to the fuel cell, an inverter device for converting the output of the fuel cell into AC power and connecting it to a commercial power grid, and a control device for controlling the fuel cell. In the method for controlling a fuel cell power generation device, the active power that can be output from the fuel cell is supplied to the fuel cell based on the active power target value set as a target value and the actual active power value supplied from the fuel cell to the load. The step of adjusting the fuel flow rate, the step of calculating a direct current value that the fuel cell can output as a direct current target value based on the actual fuel flow rate being supplied to the fuel cell, and the direct current target value. A method of controlling a fuel cell power generation device, which comprises a process of actually controlling the output of an inverter device based on a direct current value output from a fuel cell.