JP2009043522A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the degradation of an operating condition of a system, in relation to a fuel cell system. <P>SOLUTION: The fuel cell system includes: a fuel cell 11; a D.C.-A.C. conversion means 12 converting D.C. power generated by the fuel cell 11 to A.C. power to supply the A.C. power to a load; an A.C. output current waveform measurement means 15 measuring output waveform from the D.C.-A.C. conversion means 12 to a domestic load 13 side; a detection circuit 23 detecting a D.C. component in the output waveform from the D.C.-A.C. conversion means 15; and an operation control means 14 controlling the operations of the fuel cell 13, the D.C.-A.C. conversion means 12, the A.C. output current waveform measurement means 15 and the detection circuit 23, wherein the fuel cell system is configured such that the output of the detection circuit 23 is substantially invalidated for a predetermined period after detecting an overcurrent by the A.C. output current waveform measurement means 15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system that generates power using a fuel cell.

  As a conventional fuel cell system, there has been a fuel cell system in which an output waveform from a DC / AC conversion unit is measured step by step by an AC power output waveform measurement unit to diagnose a failure of the DC / AC conversion unit. (For example, refer to Patent Document 1).

  FIG. 9 shows a conventional fuel cell system described in Patent Document 1. In FIG.

  In FIG. 9, power generation is performed in the fuel cell 1 using a fuel containing a hydrocarbon such as methane such as city gas as a raw material. The DC / AC converting means 2 converts the DC power from the fuel cell 1 into AC power and supplies the AC power to the home load 3 together with the commercial power supply.

  The operation control means 4 controls a series of operations from startup to power generation in this fuel cell system.

  The AC power output waveform measuring means 5 is connected to the output terminal of the DC / AC converting means 2, the output current waveform of AC power output from the DC / AC converting means 2 to the home load 3, and the voltage waveform of the commercial power supply. And measure.

The operation control means 4 measures the output current waveform of the alternating current power output from the direct current alternating current conversion means 2 to the home load 3 by the alternating current power output waveform measuring means 5 one by one, and the voltage waveform from the commercial power source is normal. In spite of the fact, when the output current waveform is abnormal, it is determined that the internal circuit of the DC / AC converting means 2 is faulty.
JP 2006-310116 A

  In the conventional configuration, when the output overcurrent is detected by the AC power output waveform measuring unit 5, the operation control unit 4 temporarily stops the operation of the fuel cell system.

  When the DC component is detected during the output from the DC / AC converting means 2, the operation control means 4 causes the operation of the fuel cell system to be continuously stopped.

  However, if the fuel cell system is stopped continuously even though only a direct current component is detected due to a disturbance in the voltage waveform on the commercial power supply side that does not cause a problem, an unnecessary operation will occur. The system will be stopped and the system operation status will be deteriorated.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress deterioration of the operating state of the system.

  In order to achieve this object, the present invention provides a fuel cell, DC / AC conversion means for converting DC power generated in the fuel cell into AC power, and supplying AC power to a load, and DC / AC conversion means. AC output current waveform measuring means for measuring an output waveform to the load side, a detection circuit for detecting a DC component in the output waveform from the DC to AC conversion means to the load side, the fuel cell, DC to AC conversion means, AC Output current waveform measuring means, and operation control means for controlling the operation of the detection circuit, and for a predetermined time after the overcurrent detection by the AC output current waveform measurement means, the output from the detection circuit is substantially reduced. It is configured to be invalidated, thereby achieving the intended purpose.

  As described above, the present invention is configured such that the output from the detection circuit is substantially invalidated for a predetermined time after the overcurrent predetermined is detected by the AC output current waveform measuring means. In such a case, since the system is not continuously stopped, the deterioration of the operating state of the system can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention.

  In FIG. 1, hydrogen reformed from a fuel containing a hydrocarbon such as methane such as city gas and oxygen in the atmosphere are reacted in a fuel cell 11 to generate power.

  The DC / AC converting means 12 converts the DC power from the fuel cell 11 into AC power and supplies the AC power to the home load 13 together with the commercial power supply.

  The AC output current waveform measuring means 15 is connected to the output end of the DC / AC converting means 12 and measures AC power (AC current output waveform) output from the DC / AC converting means 12 to the home load 13. is there.

  The DC component detection invalidating means 16 is configured to substantially invalidate the output from the detection circuit (23 in FIG. 2) for a predetermined time after the overcurrent detection by the AC output current waveform measuring means 15. Thus, in the temporary DC component outflow detection, the operation control means 14 prevents the system from being continuously stopped.

  The operation control unit 14 controls a series of operations from start-up to power generation and operation stop. The operation control of the fuel cell 11, the DC / AC conversion unit 12, the AC output current waveform measurement unit 15, and the DC component detection invalidation unit 16 is performed. Is to do.

  Here, the direct current component in the alternating current will be described.

  In the DC component outflow principle diagram in the AC output current of FIG. 2, the hatched portions A and B usually have the same area when A = B, and the DC component is zero.

  However, as shown in FIG. 2, when the zero point is shifted to the plus side, A <B is established, and a negative DC component is generated. Conversely, when the zero point is shifted to the minus side, A> B, and a positive DC component is generated.

  According to the standard, the direct current component is ± 1% or less of the alternating current. If the effective value of the alternating current is 5 A, it is determined that the direct current component is abnormal if a direct current component of ± 50 mA or more occurs. If the direct current component flows out to the commercial power source side, there is a risk of inconvenience to the pole transformer in the utility pole, so this outflow must be prevented.

  Therefore, in the present embodiment, the means shown in FIG. 4 is provided in the DC / AC conversion means 12 to detect the DC component, and when the DC component is detected, the operation control unit 14 basically stops the system operation immediately. It has a configuration like this.

  Next, detection of the DC component in the AC output current from the DC / AC converting means 12 will be described with reference to FIG.

  The main circuit 21 of the DC / AC conversion means 12 is a circuit through which the DC current and the AC current in the DC / AC conversion means 12 actually flow, and the DC component sensor 22 is provided near the output end of the DC / AC conversion means 12. A sensor for detecting a direct current component in an alternating current.

  The detection circuit 23 is a circuit that amplifies a minute signal of the DC component sensor 22, and the CPU 24 that is a part of the detection circuit 23 is an integrated circuit composed of a microcomputer or the like. Judging.

  That is, the signal of the DC component sensor 22 in the DC / AC converting means 12 is input to the detection circuit 23, and after input such as amplification, it is input to the CPU 24 such as a microcomputer to determine the generation and magnitude of the DC component. .

  In order to detect a minute DC component, the DC component sensor 22 uses a shunt resistor in which two resistors of 0.01Ω are connected in parallel, that is, a resistance value of 0.005Ω, but this is not restrictive. A sensor may be used.

  The detection circuit 23 amplifies the minute voltage of the DC component sensor 22 and cuts high-frequency components by an active low-pass filter (here, a fourth-order filter) via an insulated amplifier circuit such as an isolation amplifier. Are output to a CPU 24 such as a microcomputer which is a part of the detection circuit 23.

  Further, in a CPU 24 such as a microcomputer which is a part of the detection circuit 23, a correction bias for a direct current is set by an input signal, and a bias limiter for the direct current is provided to reflect it in actual output current waveform generation. Is.

  Returning to FIG. 1 again, the DC component detection invalidating means 16 connected to the DC / AC converting means 12 is software-directed in a CPU 24 such as a microcomputer which is a part of the detection circuit 23. In the following specific situation (immediately after an overcurrent is detected by the AC output current waveform measuring means 15) by performing an operation such as determining that the minute is zero and ignoring the input signal itself to the CPU 24. Only, it is configured to avoid the continuous operation stop of the system by the operation control means 14.

  In the configuration shown in FIG. 1, under the control of the operation control unit 14, the AC output current waveform measurement unit 15 outputs AC power (output of AC current) from the DC / AC conversion unit 12 to the home load 13. Waveform) is measured one by one.

  When an overcurrent is detected by the AC output current waveform measuring means 15, the operation control means 14 immediately puts the system into a temporary operation stop state.

  Further, when the overcurrent is detected by the AC output current waveform measuring means 15 as described above, the DC component detection invalidating means 16 invalidates the DC component detection in the AC output current only for a predetermined time from that point. And prevent the system from entering the continuous shutdown mode.

  The current waveform in FIG. 3 shows the output current waveform from the DC / AC converter 12. Here, the effective value of the normal output current Iac is Iac (rms) = 5A, and the peak value is √2 times Iac (peak) = 7.07A, but 150% of the peak value Iac (peak). Immediately after detecting that the corresponding overcurrent peak Iaco (threshold level) of 10.6 A or more is detected, the system is immediately put into a temporary operation stop state by the operation control means 14 as described above.

  Therefore, thereafter, as shown in FIG. 3, the output current is attenuated.

  However, as shown in FIG. 3, the output current waveform from the DC / AC conversion means 12 is out of balance between positive and negative until the output current stops after the overcurrent occurs, as if the DC component is It behaves as if it occurred.

At this time, in actuality, although the above-described DC component is not generated due to a circuit or control failure of the DC-AC converting means 12, it is erroneously determined that the DC component is out of flow, so the AC output When the overcurrent is detected by the current waveform measuring means 15, the direct current component detection invalidating means 16 causes the direct current detection invalidating means 16 during tr ₀ from the overcurrent detection until the output is stopped, that is, for several ms to several tens of ms. The system is prevented from shifting to the continuous operation stop mode of the unnecessary system by minute detection.

  As described above, in the present embodiment, the AC output current waveform measuring means 15 disables the DC component detection in the AC output current for a predetermined time after the DC component exceeding the predetermined value is detected, and the system operates continuously. Since the transition to the stop mode is prevented, deterioration of the operating state of the system can be suppressed.

  FIG. 8 illustrates the operation after the overcurrent is detected by the AC output current waveform measuring means 15 and the system is immediately put into a temporary operation stop state by the operation control means 14.

  That is, after the system is temporarily stopped, the system is automatically restarted by the operation control means 14, but so-called soft start is performed so that the output from the DC / AC conversion means 12 gradually increases. Is supposed to do.

(Embodiment 2)
FIG. 5 is a configuration diagram of a fuel cell system according to Embodiment 2 of the present invention. In FIG. 5, the same components as those in FIG.

  In FIG. 5, the DC component detection invalidating means 17 is configured to increase the threshold level of the detection level for detecting the DC component in the AC output current.

  Here, immediately after the output overcurrent is detected by the AC output current waveform measuring means 15, the operation control means 14 increases the DC component detection level threshold by the DC component detection invalidating means 17 to detect the DC component. As a result, the continuous operation stop mode by the operation control means 14 is substantially invalidated, and the system is not continuously stopped immediately, so that deterioration of the operating state of the system is suppressed. I can do it.

(Embodiment 3)
FIG. 6 is a configuration diagram of a fuel cell system according to Embodiment 3 of the present invention. In FIG. 6, the same components as those in FIG. 1 or FIG.

  In FIG. 6, DC component detection invalidating means 18 increases the gain of the correction bias for the detected DC component.

  Here, immediately after the output overcurrent is detected by the AC output current waveform measuring means 15, the operation control means 14 detects a DC component equal to or greater than a predetermined value by the AC output current waveform measuring means 15. The time / DC component detection invalidating means 18 is configured to lower the DC component detection level in the AC output current below the threshold level, thereby substantially disabling the continuous operation stop mode by the operation control means 14. Since the system is not continuously stopped from operating immediately, deterioration of the operating state of the system can be suppressed.

(Embodiment 4)
FIG. 7 is a configuration diagram of a fuel cell system according to Embodiment 4 of the present invention. In FIG. 7, the same components as those in FIG.

  In the present embodiment, a single-layer three-wire 1: 1 insulating transformer 19 is provided between the AC output current waveform measuring means 15 and the household load 13.

  In other words, if a 1: 1 insulation transformer 19 of single-layer three-wire is provided, the direct current component can be cut by separating the primary side and the secondary side.

  The fuel cell system of the present invention is configured to substantially invalidate the output from the detection circuit for a predetermined time after the overcurrent predetermined is detected by the AC output current waveform measuring means, In this case, since the operation of the system is not continuously stopped, the deterioration of the operating state of the system can be suppressed.

  Therefore, economical and safe power generation is performed using the fuel cell, which greatly contributes to the suppression of deterioration of the global environment.

1 is a block configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. DC component outflow principle diagram in the AC output current of the fuel cell system according to Embodiment 1 of the present invention The wave form diagram which shows an example of the alternating current output current waveform of the fuel cell system in Embodiment 1 of this invention 1 is a block configuration diagram of a DC component detection circuit of a fuel cell system according to Embodiment 1 of the present invention. Block diagram of a fuel cell system according to Embodiment 2 of the present invention Block configuration diagram of a fuel cell system according to Embodiment 3 of the present invention Block configuration diagram of a fuel cell system according to Embodiment 4 of the present invention Waveform diagram for explaining the operation of the fuel cell system according to Embodiment 1 of the present invention Block diagram of a conventional fuel cell system

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fuel cell 12 DC / AC conversion means 13 Domestic load 14 Operation control means 15 AC output current waveform measurement means 16 DC component detection invalidation means 17 DC component detection invalidation means 18 DC component detection invalidation means 21 DC / AC conversion means 21 Main circuit 22 DC component sensor 23 Detection circuit 24 CPU

Claims (4)

A fuel cell, DC / AC conversion means for converting DC power generated in the fuel cell into AC power and supplying AC power to a load, and AC output current for measuring an output waveform from the DC / AC conversion means to the load side Controls the operation of the waveform measurement means, the detection circuit for detecting the DC component in the output waveform from the DC / AC conversion means to the load side, the fuel cell, the DC / AC conversion means, the AC output current waveform measurement means, and the detection circuit A fuel cell system configured to substantially invalidate the output from the detection circuit for a predetermined time after the overcurrent is detected by the AC output current waveform measuring means. The operation control means is connected to DC component detection invalidating means for substantially invalidating the output from the detection circuit for a predetermined time after the overcurrent is detected by the AC output current waveform measuring means. 2. The fuel cell system according to 1. 3. The DC component detection invalidating unit is configured to increase a DC component detection threshold level in the detection circuit for a predetermined time after the DC output current waveform measuring unit detects a DC component equal to or greater than a predetermined value. The fuel cell system described. The DC component detection invalidating unit is configured to lower the DC component detection level of the detection circuit below a threshold level for a predetermined time after the overcurrent is detected by the AC output current waveform measuring unit. Fuel cell system.

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