JP5330089B2 - Fuel cell power generation system and control method thereof - Google Patents

Description

  The present invention relates to a fuel cell power generation system and a control method thereof, and more particularly to a fuel cell power generation system capable of continuing operation even when power supplied from a DC voltage converter to an auxiliary machine temporarily increases and a control method thereof. About.

  A conventional typical fuel cell power generation system includes a fuel cell main body that generates DC electric energy, a DC power-driven auxiliary machine, a DC voltage converter for supplying a DC voltage to the auxiliary machine, and a system controller. (See Patent Document 1).

  Here, the DC power-driven auxiliary machines include rotating machines such as blowers, pumps and fans, electric heaters, electromagnetic valves, CPU power supplies, inverter gate power supplies, and the like. In addition, an inverter connected to an AC power supply system by converting DC power generated from the fuel cell body into AC is provided.

JP 2006-288024 A

  In the fuel cell main body, the generated battery voltage gradually decreases due to cell deterioration due to long-time operation and the like. Therefore, in order to maintain a predetermined output power, the battery current is increased and the operation is continued. On the other hand, the DC power necessary for the auxiliary machine may fluctuate depending on the operating condition of the fuel cell power generation system and may increase rapidly.

  In particular, when the battery direct current is increasing at the end of operation or the like, and the auxiliary power for such DC power driving is increased, the possibility that the auxiliary power exceeds the capacity of the DC voltage converter is increased. When the auxiliary power actually exceeds the capacity of the DC voltage converter, the voltage output of the DC voltage converter is cut off, and the fuel cell power generation system has come to a failure stop. If there is such a failure stop, not only an extra maintenance cost is required, but also the reliability of the fuel cell power generation system as a product is reduced. In order to suppress the occurrence of such a failure stop, it is necessary to employ a large-capacity DC voltage converter, which requires extra cost.

  An object of the present invention is to solve the above-described problems, and an object of the present invention is to make it possible to continue a power generation operation by suppressing a failure stop of a fuel cell power generation system without increasing the capacity of a DC voltage converter. To do.

In order to achieve the above object, a fuel cell power generation system according to the present invention includes a fuel cell body that takes in a fuel gas and an oxidant gas and generates DC electric energy by an electrochemical reaction, and is generated in the fuel cell body. A DC voltage converter for converting a direct current voltage, at least one auxiliary device driven by direct current power obtained by the DC voltage converter, an inverter for converting direct current generated in the fuel cell body to alternating current, Means for calculating the current or power supplied from the DC voltage converter to the auxiliary machine based on the operating state of the auxiliary machine; and the current or power supplied from the DC voltage converter to the auxiliary machine is a predetermined value. Control means for reducing the output power of the inverter when a threshold value is exceeded.

The fuel cell power generation system control method according to the present invention includes a fuel cell body that takes in fuel gas and an oxidant gas to generate direct current electric energy through an electrochemical reaction, and a direct current voltage generated in the fuel cell body. A fuel cell having a DC voltage converter for conversion, at least one auxiliary device driven by direct current power obtained by the DC voltage converter, and an inverter for converting direct current generated in the fuel cell main body to alternating current A method for controlling a power generation system, wherein a current or power supplied from the DC voltage converter to the auxiliary machine is calculated based on an operating state of the auxiliary machine, and is supplied from the DC voltage converter to the auxiliary machine. The output power of the inverter is reduced when the current or power to be output exceeds a predetermined threshold value.

  According to the present invention, it is possible to continue the power generation operation by suppressing the failure stop of the fuel cell power generation system without increasing the capacity of the DC voltage converter.

1 is a block diagram showing an overall configuration of an embodiment of a fuel cell power generation system according to the present invention. It is a block diagram which shows the control apparatus of the fuel cell power generation system of FIG. It is a graph which shows typically the relation between auxiliary machine current (current supplied to an auxiliary machine from a DC voltage converter) and battery current.

  Hereinafter, an embodiment of a fuel cell power generation system according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of an embodiment of a fuel cell power generation system according to the present invention. FIG. 2 is a block diagram showing a control device of the fuel cell power generation system of FIG.

  In FIG. 1, a fuel cell power generation system 50 is a fuel cell power generation system for home use, for example. The fuel cell main body 1 generates DC electric energy, and a part of the DC power generated by the fuel cell main body 1 (large And an inverter 2 connected to an external AC power supply system. In addition, this fuel cell power generation system includes a DC voltage converter 3 that converts a part of DC power generated in the fuel cell main body 1 and a plurality of DC power that is driven by the DC power converted by the DC voltage converter 3. An auxiliary machine 4, an ammeter 6 for measuring a direct current supplied from the DC voltage converter 3 to the plurality of auxiliary machines 4, and a control device 5 for controlling the fuel cell power generation system are provided.

  The auxiliary machine 4 includes a rotating machine such as a blower, a pump, and a fan, and a plurality of devices such as an electric heater, a solenoid valve, a CPU power supply, and an inverter gate power supply. The fuel cell main body 1 takes in the fuel gas and the oxidant gas, and generates electric power by the electrochemical reaction between them.

  When the fuel cell power generation system 50 is in a normal power generation operation, most of the DC power generated in the fuel cell main body 1 is converted into AC by the inverter 2 and supplied to the AC power system, which is connected to the commercial power source. Used together with a power source (not shown) for a household load (not shown). At that time, a part of the DC power generated in the fuel cell main body 1 is converted by the DC voltage converter 3 into a DC voltage (for example, DC 24V) suitable for the auxiliary machine 4 driven by DC power. The direct current supplied from the DC voltage converter 3 to the plurality of auxiliary machines 4 is measured by an ammeter 6.

  At this time, the DC current supplied from the DC voltage converter 3 to the auxiliary device 4 may increase temporarily due to some cause caused by some of the devices constituting the plurality of auxiliary devices 4. For example, in the case of a system that recovers heat generated in the fuel cell main body 1 as warm water and stores the warm water in a warm water storage tank (not shown), a hot water pump (not shown) for circulating the warm water has a plurality of auxiliary units. It constitutes a part of the machine 4. Here, until the hot water storage tank is filled with hot water, cold water is supplied and used for cooling the fuel cell main body 1, so the flow rate of the hot water pump is relatively small, but when the hot water storage tank is full of hot water, Since the fuel cell body 1 is cooled by the relatively high temperature water, the flow rate per unit time of the hot water pump increases. At that time, the DC power necessary for driving the hot water pump increases rapidly.

  In this way, when the direct current supplied from the DC voltage converter 3 to the plurality of auxiliary machines 4 temporarily increases, if the direct current exceeds the maximum allowable current of the DC voltage converter 3, the fuel cell power generation system 50 is determined to be a failure, and stops. Therefore, in this embodiment, when the current of the DC voltage converter 3 exceeds a predetermined current threshold, the control device 5 controls the output power of the inverter 2 to be reduced. In this case, the reduced output power of the inverter 2 is supplemented by power supply from a power generation facility (not shown) such as a commercial power source connected to the AC power system.

  As a specific control method, as shown in FIG. 2, a DC voltage converter current threshold is set in the proportional-plus-integral controller (PI) 10 and a DC voltage converter current (measured value) as a control value is input. Then, the difference (DC voltage converter current threshold-DC voltage converter current) is input to the adder 11 as an output power setting correction value. However, the output power setting correction value is valid only when it is negative. The adder 11 adds the output power setting reference value and the output power setting correction value, and uses the output as the output power setting value.

  Most of the DC power necessary for the plurality of auxiliary machines 4 decreases in accordance with the reduction of the output power of the inverter 2. Therefore, even if the direct current of a specific one of the plurality of auxiliary machines 4 increases rapidly, the increase in the DC power of the plurality of auxiliary machines 4 is suppressed by reducing the output power of the inverter 2. . Thereby, it is possible to avoid the current of the DC voltage converter 3 from exceeding the maximum allowable current. As a result, the fuel cell power generation system can continue the power generation operation without stopping the failure.

  FIG. 3 is a graph schematically showing a relationship between an auxiliary machine current (current supplied to a plurality of auxiliary machines from the DC voltage converter) and a battery current (total supply current of the fuel cell main body) in this embodiment. .

  As described above, the plurality of auxiliary machines 4 include a plurality of devices such as a rotating machine such as a blower, a pump, and a fan, an electric heater, a solenoid valve, a CPU power source, an inverter gate power source, and the like. Most of the current supplied to each auxiliary machine is controlled so as to increase as the battery current increases. This relationship is shown by a straight line 20 rising to the right in FIG. Assume that the battery current is IFC1 and the auxiliary current is IA1 when the battery is steadily operated at point P1 in FIG. At this time, it is assumed that the direct current of a specific one of the plurality of auxiliary machines 4 temporarily increases for some reason. In that case, since the control for reducing the load current is not performed in the prior art, the auxiliary current increases to IAX. At that time, the maximum allowable current of the auxiliary machine current may be exceeded. However, in this embodiment, when the auxiliary machine current exceeds the threshold value IAT, the control for reducing the output power of the inverter 2 is activated, and the battery current is reduced to IFC2 accordingly. As the battery current decreases, an increase in auxiliary current is suppressed (operating point P2). Then, although the cause of the temporary increase in the auxiliary machine current among the plurality of auxiliary machines 4 is solved, the output power of the inverter 2 is increased to return to the original state after the cause is solved. This returns to the original operating point P1.

  Here, the battery current during normal operation gradually increases due to cell deterioration due to continued operation of the fuel cell body 1. When the battery current IFC1 during normal operation in the initial operation of the fuel cell body 1 increases to the battery current IFC3 during normal operation at the end of the operation, the fuel cell body 1 moves from the operation point P1 to the operation point P3 in FIG. At this time, the auxiliary machine current IA3 is larger than the auxiliary machine current IA1 at the initial stage of operation, and there is a high possibility that the maximum allowable current of the auxiliary machine current will be exceeded. However, the possibility of the auxiliary machine current exceeding the maximum allowable current is kept low, the fuel cell power generation system can be continued without generating a failure, and the fuel cell can be operated without increasing the capacity of the DC voltage converter. The reliability of the power generation system can be increased.

  The above embodiment is merely an example, and the present invention is not limited to this.

  For example, as a control method used for load reduction, not only the above-described PI control, but also P control (proportional control), PID control (proportional integral differential control), step reduction control, lamp reduction control, and the like may be used.

  In addition, auxiliary power may be used as a control value instead of auxiliary current. Also, instead of measuring the auxiliary machine current or auxiliary machine power, the current or power of each auxiliary machine is estimated by calculation based on the operating state of each auxiliary machine, and these are added together to obtain the auxiliary machine at that time. It can also be current or auxiliary power. For example, the current or power of each auxiliary machine can be estimated based on the open / close state of the switches of each auxiliary machine, the excitation non-excited state, and the rotational speed of the auxiliary machine if the auxiliary machine is a rotating machine.

  Further, in the above example, there are a plurality of auxiliary machines, but there may be only one auxiliary machine.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body 2 ... Inverter 3 ... DC voltage converter 4 ... Auxiliary machine 5 ... Control apparatus 6 ... Ammeter 10 ... Proportional integral controller 11 ... Adder 50 ... Fuel cell power generation system

Claims (3)

A fuel cell body that takes in fuel gas and oxidant gas to generate DC electric energy through an electrochemical reaction;
A DC voltage converter for converting a DC voltage generated in the fuel cell body;
At least one auxiliary machine driven by DC power obtained by the DC voltage converter;
An inverter that converts direct current generated in the fuel cell body into alternating current;
Means for calculating a current or power supplied from the DC voltage converter to the auxiliary machine based on an operating state of the auxiliary machine;
Control means for reducing output power of the inverter when current or power supplied from the DC voltage converter to the auxiliary machine exceeds a predetermined threshold;
A fuel cell power generation system comprising: 2. The fuel cell power generation system according to claim 1, wherein the operation state of the auxiliary machine includes at least one of an open / close state of the auxiliary machine, an excitation non-excitation state, and a rotation speed . A fuel cell body that takes in fuel gas and oxidant gas to generate DC electric energy through an electrochemical reaction;
  A DC voltage converter for converting a DC voltage generated in the fuel cell body;
  At least one auxiliary machine driven by DC power obtained by the DC voltage converter;
  An inverter that converts direct current generated in the fuel cell body into alternating current;
  A control method for a fuel cell power generation system having
  Calculate the current or power supplied from the DC voltage converter to the auxiliary machine based on the operating state of the auxiliary machine,
  A fuel cell power generation system control method, comprising: reducing output power of the inverter when current or power supplied from the DC voltage converter to the auxiliary device exceeds a predetermined threshold.

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