JP2008059968A - Fuel cell system - Google Patents

Abstract

A fuel cell system capable of continuing stable power generation when an abnormality in instantaneous voltage drop occurs in a system power supply voltage.
A fuel cell, a DC / AC converter connected to a system power source, converts DC power from the fuel cell into AC power, and supplies AC power to a home load 13 together with the system power source, and from startup An operation control means includes an operation control means for controlling a series of operations until power generation, a system power supply voltage measurement means 15 for measuring a voltage waveform at the system power supply, and a voltage waveform storage means 16 for storing the power supply voltage waveform. 14, the system power supply voltage measuring means 15 measures the voltage waveform at the system power supply, the voltage waveform is stored in the voltage waveform storage means 16, and the instantaneous voltage drop occurrence in the system power supply is detected with the voltage waveform storage means 16. Priority is given to output current reduction control in response to a reduction in power supply voltage, detected by data comparison.
[Selection] Figure 1

Description

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

  As a conventional fuel cell system, there is a fuel cell system that performs failure diagnosis control of an on-off valve provided in a fuel gas supply pipe that communicates a fuel gas supply source and a fuel cell main body (see, for example, Patent Document 1). FIG. 8 shows a conventional fuel cell system described in Patent Document 1. In FIG.

In FIG. 8, a first on-off valve 2 and a second on-off valve 3 are provided in a fuel gas supply pipe 4 between the fuel gas supply source 1 and the fuel cell main body 6, and the pressure of the fuel gas is detected between the on-off valves. A gas sensor 5 is provided. At the time of start-up, when the first and second on-off valves 2 and 3 are closed by the control of the control unit 7, the gas sensor 5 performs failure diagnosis control of the first on-off valve, and then turns on the first on-off valve. After opening the valve, the valve is closed and the gas sensor 5 performs failure diagnosis control of the second on-off valve.
Japanese Patent Application Laid-Open No. 09-022711

  However, the conventional configuration has a problem that failure diagnosis control of a part between the fuel gas supply source and the fuel cell main body cannot be performed, and failure diagnosis control subsequent to the fuel cell cannot be performed.

  The present invention solves the above-described conventional problems, and performs failure diagnosis control at the latter stage of the fuel cell, that is, at the output of the DC / AC converter, so that the system power supply is stable even if an abnormality occurs temporarily. An object of the present invention is to provide a fuel cell system capable of continuously generating power.

  In order to solve the above-mentioned conventional problems, the fuel cell system of the present invention performs fault diagnosis control at the output of the DC / AC conversion means by including system power supply voltage measuring means and voltage waveform storage means.

  With this configuration, by performing failure diagnosis control at the output of the DC / AC converter downstream of the fuel cell, a fuel that can continuously perform stable power generation even if a temporary abnormality occurs in the system power supply A battery system can be provided.

  According to the fuel cell system of the present invention, the failure diagnosis control at the output of the DC / AC converter means downstream of the fuel cell is determined not to be a failure of the DC / AC converter means even if an abnormality occurs temporarily in the system power supply. Thus, stable power generation can be continuously performed.

  The first invention is a fuel cell, a DC / AC converting means connected to a system power source for converting DC power from the fuel cell to AC power, an operation control means for controlling a series of operations from startup to power generation, System power supply voltage measuring means for measuring the voltage waveform at the system power supply, the operation control means detects the pressure of the system power supply by measuring the voltage waveform at the system power supply by the system power supply voltage measurement means, When the voltage in the system power supply decreases, the output current is controlled so that even if an instantaneous voltage drop occurs in the system power supply, it is determined that there is no failure in the DC / AC conversion means, and the fuel cell Without stopping system power generation, instantaneous output overcurrent caused by instantaneous voltage drop can be prevented, and stable power generation can be continued.

  In the second invention, in particular, the operation control means of the first invention periodically compares the current output power with the command power and corrects the output power, so that the system power supply voltage continues to decrease for a long time. However, by correcting, it is possible to continuously and stably output electric power close to the command value, and it is possible to perform an ideal operation that is efficient and balanced in the entire fuel cell system.

  According to a third aspect of the present invention, in particular, the operation control means of the first aspect of the invention controls power generation by a chemical reaction by continuing power generation from the fuel cell and stopping output from the DC / AC conversion means when the system power supply fails. However, once the power generation is stopped, it takes time to return, but the DC / AC conversion means can immediately resume the conversion from DC power to AC power. It is possible to resume power generation.

  In the fourth aspect of the invention, in particular, the operation control means of the first aspect of the present invention minimizes the supply of hydrogen to the fuel cell by stopping the power generation from the fuel cell when the system power supply continues the power failure for a certain time or more. Even if it is limited to the limit, the burden on the fuel cell due to stopping the output from the fuel cell for a long time without stopping the supply of hydrogen is large, so the burden on the fuel cell can be reduced and the life can be extended. Can do.

  According to the fifth aspect of the invention, in particular, the operation control means of the first aspect of the present invention instantaneously maintains a constant power output without following the voltage fluctuation, even when an instantaneous voltage waveform fluctuation occurs in the system power supply. Output overcurrent can be prevented and stable power generation can be continued.

  In addition to the fuel cell system of the fifth invention, the sixth invention is provided with voltage distortion waveform storage means for storing a distortion waveform of the power supply voltage, and the operation control means generates instantaneous voltage waveform fluctuations in the system power supply. If it occurs, it is stored in the voltage distortion waveform storage means, and if it occurs for the second time or later, by performing output current control ignoring the generated voltage fluctuation, the DC power conversion side is not a failure. With respect to the voltage waveform distortion generated in step 1, an instantaneous output overcurrent can be prevented and stable power generation can be continued.

  In addition to the fuel cell systems of the first to sixth inventions, the seventh invention is provided with communication means, and the operation control means is capable of causing an abnormality in the system power supply and returning from the abnormality by the communication means. By sending information to the fuel cell system, it is possible to continue the optimum power generation control with minimum damage by sharing information on the system power supply in advance.

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

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

  In FIG. 1, power generation is performed in a fuel cell 11 using a fuel containing a hydrocarbon such as methane such as city gas as a raw material. The DC / AC conversion means 12 is connected to a commercial power supply, converts DC power from the fuel cell 11 into AC power, and supplies AC power to the home load 13 together with the system power supply. The operation control means 14 controls a series of operations from startup to power generation. The system power supply voltage measuring means 15 measures a voltage waveform at the system power supply. Further, the voltage waveform storage means 16 stores the power supply voltage waveform measured by the system power supply voltage measurement means 15. Here, the power supply voltage waveform to be stored is a voltage waveform that is measured for each cycle and is mainly measured in a normal state.

  Here, the operation control means 14 measures the voltage waveform at the system power supply one by one by the system power supply voltage measuring means 15, stores the voltage waveform at the voltage waveform storage means 16, and generates an instantaneous voltage drop at the system power supply. Priority is given to output current reduction control according to a reduction in power supply voltage, which is detected by data comparison with the voltage waveform storage means 16. That is, the system power supply voltage measuring means 15 measures the voltage waveform at the system power supply to detect the pressure of the system power supply, and controls to reduce the output current when the voltage at the system power supply decreases. .

  The waveform of FIG. 2 shows a voltage waveform when an instantaneous voltage drop of the system power supply voltage occurs. Usually, the DC / AC converter 12 generates power in accordance with a power command from the operation controller 14. That is, control is performed so that the output power value matches the command power value, that is, the sine wave current output is maintained, as indicated by command power = system voltage × output current, that is, output power = command power. . However, when an instantaneous voltage drop of the system power supply voltage as shown in FIG. 2 occurs, the output current instantly responds to the voltage drop, and the output current is reduced by the reduced voltage so as to maintain the output power. As a result, an instantaneous overcurrent such as the current waveform in FIG. 3 is generated.

  The current waveform in FIG. 3 shows an example of an output current waveform when an instantaneous overcurrent is generated from the DC / AC conversion means 12. Here, the effective value of the normal output current Iac is Iac (rms) = 5.5A, and the peak value is √2 times Iac (peak) = 7.8A, but the peak value Iac (peak) is An example in which the overcurrent peak Iaco of 11.7 A or more corresponding to 150% is output and the output of the DC / AC converting means 12 is stopped is shown.

  Here, even if there is a temporary malfunction of the system power supply, control is performed so as not to follow the instantaneous voltage drop and to prevent transient output such as instantaneous overcurrent. That is, the voltage waveform storage means 16 stores the normal voltage waveform as an ideal voltage waveform, and constantly compares the stored waveform with the waveform measured by the system power supply voltage measurement means 15 to obtain a voltage. When it is determined that a reduction has occurred, the output current is also reduced, that is, the output power is also reduced according to the voltage drop, without performing the constant output power control corresponding to the command power.

  Here, as a criterion for occurrence of the voltage drop, when the peak value of the voltage waveform, that is, the voltage amplitude is lowered, it is instantaneously reduced by 5 V or more or within a certain time (for example, 1 second, 10 seconds, 30 seconds, 1 minute) It is assumed that the voltage drops by 10V or more. Then, the ratio of the voltage drop is calculated from the normal value to reduce the output current.

  Here, the operation will be described with reference to the flowchart of FIG. In step 1, the operation control means 14 performs constant output power control. In step 2, the system power supply voltage measuring means 15 measures and inputs the system power supply voltage waveform data. In step 3, the measured power supply voltage waveform data is stored in the voltage waveform storage means 16. In step 4, the voltage waveform measured and inputted by the system power supply voltage measuring means 15 is compared with the waveform data stored in the voltage waveform storage means 16. In step 5, it is detected whether there is an instantaneous voltage drop based on the voltage comparison data.

  If an instantaneous voltage drop is detected, the output power constant control is canceled in step 6 to facilitate control of the output current. In step 7, the power supply voltage drop rate is calculated based on the waveform data stored in the voltage waveform storage means 16. In step 8, the output current is controlled to decrease in accordance with the calculated power supply voltage drop rate.

  As a result, the instantaneous output overcurrent as shown in FIG. 3 is not generated to stop the power generation.

  According to such a configuration, even when an instantaneous voltage drop occurs in the system power supply, it is determined that there is no failure in the DC / AC conversion means, and the instantaneous voltage drop is caused without stopping the power generation of the fuel cell system. Instantaneous output overcurrent can be prevented and stable power generation can be continued.

  Further, the operation control means 14 periodically compares the current output power with the command power, and corrects the output power. That is, the output current is corrected.

  Every time an instantaneous voltage drop occurs in the system power supply voltage, the output current also decreases. Therefore, the output power decreases as shown by the expression of system voltage × output current = output power. In other words, the power is not output according to the command power. When the voltage drop frequently occurs, the output power is greatly reduced with respect to the command power.

  Here, the term “periodic” refers to every 10 wavelengths (0.2 seconds at 50 Hz), every 1 second, every 10 seconds, or the like. In order to suppress the energy loss as much as possible, it is necessary to always increase the output current by comparing the output power with the command power to correct the output decrease, for example, every 10 wavelengths.

  The system voltage is measured by the system power supply voltage measuring means 15, the output current value is detected on the circuit, the current output power is calculated by calculating the measured voltage value and current value, and the corrected power value = Command power-current output power is calculated, output current value to be corrected = corrected power value / output current value to be corrected by system voltage, and the output current value is corrected.

  In the first place, the command power value is a value calculated based on the balance between the amount of raw material gas, the amount of air, etc. and the amount of power generated by the fuel cell 11, so if the output power is deviated, the aforementioned balance is lost and the efficiency is poor. Thus, since the durability of the fuel cell 11 is adversely affected, it is necessary to make the output power as close as possible to the command power value.

  According to such a configuration, even if the drop in the system power supply voltage continues for a long time, it is possible to continuously and stably output electric power close to the command value by correcting it, and to an efficient fuel cell system as a whole. A well-balanced ideal operation is possible.

  Further, the operation control means 14 continues power generation from the fuel cell 11 and stops output from the DC / AC conversion means 12 when the system power supply fails.

  The fuel cell 11 outputs DC power by a chemical reaction between hydrogen obtained from city gas and oxygen in the air. Once such a chemical reaction is stopped, it takes time to restart power generation, such as the time to generate hydrogen and the time to reach the appropriate temperature in each part of the system. The power generation from the fuel cell 11 is continued, and only the output of the DC / AC conversion means 12 is stopped.

  Once the system power supply is restored, the DC power from the fuel cell 11 continues to be output. Therefore, when only the DC / AC conversion means 12 is activated, the DC power from the fuel cell 11 is immediately converted to AC power. It is possible to resume doing.

  According to such a configuration, the fuel cell that generates power through a chemical reaction takes time to recover once power generation is stopped, but the DC / AC conversion means can immediately resume the conversion from DC power to AC power. Immediately after the return, power generation from the fuel cell system can be resumed.

  Moreover, the operation control means 14 stops the electric power generation from the fuel cell 11 when the system power supply continues the power failure for a predetermined time or more.

  When the system power supply fails, the output from the DC / AC conversion means 12 must be stopped. If the power outage is short, the output from the fuel cell 11 does not need to be stopped. However, for example, when the power failure continues for a long time such as 30 minutes or more, the burden on the fuel cell 11 increases unless the output from the fuel cell 11 is stopped. Since the supply of hydrogen to the fuel cell 11 is not stopped, but only the DC power output is stopped, the power in the fuel cell 11 is accumulated, and the life is shortened. That is, it is necessary to stop the fuel cell system itself. The operation continuation time after a power failure is a problem of durability in the fuel cell 11, and it is better that the time is as short as possible. Even if power is restored after a long power outage in this way, the time required for the stop process in the fuel cell system and the time required for restart are required, which increases energy loss, but maintains the life and durability of the fuel cell 11. Is intended.

  According to such a configuration, even if the supply of hydrogen to the fuel cell is minimized, the burden on the fuel cell due to stopping the output from the fuel cell for a long time without stopping the supply of hydrogen is reduced. Since it is large, the burden on the fuel cell can be reduced and the life can be extended.

  Further, the operation control means 14 continues constant power output without following the voltage fluctuation even when an instantaneous voltage waveform fluctuation occurs in the system power supply.

  The waveform of FIG. 5 shows a voltage waveform when instantaneous waveform fluctuation (distortion) of the system power supply voltage occurs. When the output power constant control is performed for such a voltage waveform fluctuation accompanied with a rapid change in high frequency, the voltage waveform fluctuation is followed and an overcurrent is generated in the output current as shown in FIG. As a result, the fuel cell system stops because the abnormality detection level is exceeded.

  In this case, constant power is continuously output without following the power supply fluctuation that occurs on a daily basis within a half cycle of the sine wave of the system power supply (10 ms at 50 Hz). That is, the output current is controlled by ignoring instantaneous voltage fluctuation and assuming that the voltage waveform is an ideal sine waveform. The followability with respect to the voltage is deteriorated. For this purpose, an ideal sine waveform of a voltage waveform and a current waveform must be built in the memory.

  According to this configuration, instantaneous output overcurrent can be prevented and stable power generation can be continued.

(Embodiment 2)
FIG. 6 is a block configuration diagram of the fuel cell system according to Embodiment 2 of the present invention. In FIG. 6, the same components as those in FIG.

  In FIG. 6, the voltage distortion waveform storage means 17 stores the voltage distortion waveform when the power supply voltage obtained by the system power supply voltage measurement means 15 is distorted in the system power supply. Specifically, information such as the phase, amplitude, frequency, duration, and the like of the location where the distortion occurs in the voltage distortion occurrence time and the voltage distortion waveform is stored.

  Here, the operation control means 14 stores in the voltage distortion waveform storage means 17 if an instantaneous voltage waveform fluctuation occurs in the system power supply, and ignores the generated voltage fluctuation if it occurs for the second time or later. Output current control is performed.

  As shown in FIG. 5, the fluctuation (distortion) of the system power supply voltage is likely to occur repeatedly over a plurality of cycles once it occurs. In a similar place, even if the sine waveform is restored to normal, there is a high possibility that it will repeatedly occur. Here, the output current control based on the ideal sine wave voltage waveform is ignored if it matches any information such as phase, amplitude, frequency, duration, etc. Do.

  Therefore, if the voltage waveform is stored in the voltage distortion waveform storage means 17, the voltage waveform distortion occurs at the second time, for example, every cycle as shown in FIG. By ignoring the fluctuation (distortion), stable power generation can be continued.

  According to such a configuration, an instantaneous output overcurrent can be prevented and a stable power generation can be continued for a voltage waveform distortion generated on the system power supply side, not a failure of the DC / AC conversion means.

(Embodiment 3)
FIG. 7 is a block diagram of a fuel cell system according to Embodiment 3 of the present invention. In FIG. 7, the same components as those in FIGS. 1 and 6 are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 7, the communication means 18 exchanges various information between a plurality of fuel cell systems, and is constituted by a telephone line or the like regardless of wired or wireless.

  Here, the operation control means 14 sends information about the occurrence of an abnormality in the system power supply and the recovery from the abnormality to the nearby fuel cell system by the communication means 18. For example, when instantaneous voltage fluctuations occur in the system power supply, the information can be shared with other fuel cell systems to control the operation of the system predicting voltage fluctuations and prevent unnecessary system shutdowns. Is possible. Moreover, if information indicating that the system power supply has recovered from an abnormality can be obtained, efficient and optimal control can be continued without performing unnecessary control for avoiding the abnormality.

  According to such a configuration, by sharing information on the system power supply in advance, it is possible to keep the optimum power generation control with minimal damage.

  The fuel cell system of the present invention is useful for stationary fuel cell systems installed for home use, and can also be used in power generation systems for industrial purposes.

1 is a block configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. The figure which shows an example of the waveform which shows the system power supply voltage fall of the fuel cell system in Embodiment 1 of this invention The figure which shows an example of the output current waveform of the fuel cell system in Embodiment 1 of this invention Flowchart of output current control of fuel cell system in Embodiment 1 of the present invention The figure which shows an example of the system power supply voltage fluctuation | variation (distortion) waveform of the fuel cell system in Embodiment 1 of this 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 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 System power supply voltage measurement means 16 Voltage waveform storage means 17 Voltage distortion waveform storage means 18 Communication means

Claims (7)

A fuel cell; a DC / AC converter connected to a system power source for converting DC power from the fuel cell to AC power; an operation control unit for controlling a series of operations from start-up to power generation; and a voltage waveform at the system power source A power supply voltage measuring means for measuring the power supply, and the operation control means detects the pressure of the system power supply by measuring the voltage waveform at the system power supply by the system power supply voltage measuring means, and the voltage at the system power supply decreases. In such a case, a fuel cell system that controls the output current to decrease. 2. The fuel cell system according to claim 1, wherein the operation control means periodically compares the current output power with the command power and corrects the output power. 2. The fuel cell system according to claim 1, wherein the operation control means continues to generate power from the fuel cell and stops output from the DC / AC conversion means when the system power supply fails. 2. The fuel cell system according to claim 1, wherein the operation control means stops the power generation from the fuel cell when the system power source continues the power failure for a predetermined time. 2. The fuel cell system according to claim 1, wherein the operation control means continues the constant power output without following the voltage fluctuation even when an instantaneous voltage waveform fluctuation occurs in the system power supply. Voltage distortion waveform storage means for storing the distortion waveform of the power supply voltage is provided, and the operation control means stores the voltage distortion waveform storage means when an instantaneous voltage waveform fluctuation occurs in the system power supply, and after the second time 6. The fuel cell system according to claim 5, wherein when it occurs, output current control is performed ignoring the generated voltage fluctuation. The communication means is provided, and the operation control means sends information on the occurrence of an abnormality in the system power supply and the recovery from the abnormality to a nearby fuel cell system by the communication means. The fuel cell system described in 1.

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