Abstract:
A fault-tolerant device is kept functioning in an alternating-current inverter for fuel cell even if an inverter unit in the device is malfunctioned. The malfunctioned inverter unit is rep laced with a backup inverter unit to keep the device functioning.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a fault-tolerant device; more particularly, relates to keeping a fuel cell AC (alternating current) inverter functioning even when an inverter unit in the fuel cell AC inverter is malfunctioned. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    A prior art as shown in  FIG. 4 , is a patent of US RE37,126 E “Multilevel cascade voltage source inverter with separate DC sources”. The prior art has a plurality of inverter circuits  41  having a series connection; and each inverter circuit  41  comprises a plurality of switch diodes  411  and a capacitor  42 . And the prior art can be used as a step-up and commutation circuit for a fuel cell (not shown in the figure) for compensating reactive power and voltage balancing. 
         [0003]    Although the above prior art is capable of compensating reactive power and voltage balancing, the inverter circuits  41  are in a series connection; and so, when any one of the switch diodes  411  or the capacitors  42  is malfunctioned, the whole inverter circuit  41  is malfunctioned as well, which in turn makes the fuel cell malfunctioned or even broken. This surely results in somewhat a sum of cost in applying such an expansive fuel cell. Hence, the prior art does not fulfill users requests on actual use. 
       SUMMARY OF THE INVENTION 
       [0004]    The main purpose of the present invention is to replace an inverter unit in a fuel cell AC inverter with a backup inverter unit when the inverter unit is malfunctioned; and, by doing so, a whole fuel cell AC inverter keeps functioning regardless of the malfunctioned inverter unit. 
         [0005]    To achieve the above purpose, the present invention is a fault-tolerant circuit device in a fuel cell AC inverter, comprising a plurality of inverter units each comprising a capacitor and a plurality of switch diodes and having a series connection; a dispatching and time-series control system connecting to the inverter units and a plurality of fuel cells; a plurality of backup inverter units connecting to the dispatching and time-series control system and having a series connection with the inverter units and each comprising a capacitor and a plurality of switch diodes; a control unit connecting to the dispatching and time-series control system; a detection unit connecting to the inverter units, the backup inverter units and the control unit; and a switch unit connecting to the inverter units, the backup inverter units and the control unit. Accordingly a novel fault-tolerant circuit device in a fuel cell AC inverter is obtained. 
     
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0006]    The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
           [0007]      FIG. 1  is the view showing the structure of the preferred embodiment according to the present invention; 
           [0008]      FIG. 2  is the view showing the connections in the dispatching and time-series control system; 
           [0009]      FIG. 3  is the view showing the operating process; and 
           [0010]      FIG. 4  is the view of the circuit of the prior art. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]    The following description of the preferred embodiment is provided to understand the features and the structures of the present invention. 
         [0012]    Please refer to  FIG. 1 , which is a view showing a structure of a preferred embodiment according to the present invention. As shown in the figure, the present invention is a fault-tolerant circuit device in a fuel cell AC (alternating current) inverter, comprising a plurality of inverter units  11 , a dispatching and time-series control system  12 , a plurality of backup inverter units  13 , a control unit  14 , a detection unit  15  and a switch unit  16 . 
         [0013]    Each inverter unit  11  has a capacitor and a plurality of switch diodes. 
         [0014]    The dispatching and time-series control system  12  is connected with each inverter unit  11 ; and the dispatching and time-series control system  12  is connected with a plurality of fuel cells  121 . 
         [0015]    Each backup inverter unit  13  comprises a capacitor and a plurality of switch diodes and is connected with the dispatching and time-series control system  12 ; the backup inverter units  13  have a series connection in themselves; and the backup inverter units  13  have a series connect ion with the inverter units  11 . 
         [0016]    The control unit  14  is connected with the dispatching and time-series control system  12 . 
         [0017]    The detection unit  15  is connected with the inverter units  11 , the backup inverter units  13  and the control unit  14 . 
         [0018]    The switch unit  16  is connected with the inverter unit  11 , the backup inverter units  13  and the control unit; and the switch unit  6  has a plurality of switch components  161  each separately located between the switch unit  6  and one of the inverter units  11  as well as between the switch unit  6  and one of the backup inverter units  13 . 
         [0019]    Thus a novel fault-tolerant circuit device in a fuel cell AC inverter is obtained. 
         [0020]    Please refer to  FIG. 2 , which is a view showing connections in a dispatching and time-series control system. As shown in the figure, inverter units  11 , backup inverter units  13 , and fuel cells  121  are connected through circuits  122 . In a normal operation, each fuel cell  121  is connected with a corresponding inverter unit  11 . When anyone of the inverter units  11  is malfunctioned, its output waveform does not conform with a default waveform. The corresponding fuel cell  121  changes its connection to a backup inverter unit  13 ; and a full bridge time-series of the malfunctioned inverter unit  11  is applied to the backup inverter unit  13  as a replacement. 
         [0021]    Please refer to  FIG. 3 , which is a view showing an operating process. As shown in the figure a fault-tolerant circuit device in a fuel cell AC inverter according to the present invention has an operating process, comprising the following steps: 
         [0022]    (a) Starting a device and activating a timer interrupt process  31 : A fault-tolerant circuit device in a fuel cell AC inverter according to the present invention is started and a timer interrupt process is activated as well. 
         [0023]    (b) Acquiring waveform data  311 ; Waveform data are acquired by a detection unit  15 . 
         [0024]    (c) Detecting voltage drop for each inverter unit  312 : After a rating time of the timer interrupt process, a voltage drop for each inverter unit  11  is separately obtained through the detection unit  15 . 
         [0025]    (d) Comparing output voltage of the inverter unit with a default output voltage  313 : A comparison between the output voltage of each inverter unit  11  and a default output voltage is done. When the output voltage of the inverter unit  11  is equal to the default output voltage, step (e)  32  is then processed. When the output voltage of the inverter unit  11  is not equal to the default output voltage, step (f1)  331  is then processed. 
         [0026]    Hence, when the output voltage of the inverter unit  11  is equal to the default output voltage, the operating process continues with the following step: 
         [0027]    (e) After returning report, looping back to step (b)  32 : A report is returned to the control unit  14  and then step (b)  311  is processed. 
         [0028]    In the other hand, when the output voltage of the inverter unit  11  detected in step (d)  313  is not equal to the default output voltage, the operating process continues with the following steps: 
         [0029]    (f1) Ceasing the timer interrupt process  311 : the timer interrupt process is ceased. 
         [0030]    (f2) Searching for backup inverter unit in the device  332 : A backup inverter unit  13  is searched for. When the backup inverter unit  13  is found, step (g1)  341  is then processed. When the backup inverter unit  13  is not found, step (h)  35  is then processed. 
         [0031]    When the backup inverter unit  13  is found, the operating process continues with the following steps: 
         [0032]    (g1) Cutting a connecting circuit of a malfunctioned inverter unit and applying the malfunctioned inverter unit&#39;s time-series to a backup inverter unit  341 : A malfunctioned inverter unit is found by the dispatching and time-series control system according to a mismatching waveform; a connecting circuit between the malfunctioned inverter unit and a corresponding fuel cell is cut; and a time-series of the malfunctioned inverter unit is applied to a backup inverter unit  13 . 
         [0033]    (g2) Replacing the malfunctioned inverter unit with the backup inverter unit  342 : The malfunctioned inverter unit  11  is replaced with the backup inverter unit  13  by an open circuit between the backup inverter unit  13  and a switch component  161  of a switch unit  16  as well as a short circuit between the malfunctioned inverter unit  13  and the switch component  161  of the switch unit  16 . 
         [0034]    In the beginning, when the switch unit  16  successfully activates the inverter units  11 , the connection between any one of the inverter units  11  and the switch component  161  of the switch unit  16  is in an open circuit state; and the connection between any one of the backup inverter unit  13  and the switch component  161  of the switch unit  16  is in a short circuit state. Yet, when the inverter unit  11  is malfunctioned, the connection between the malfunctioned inverter unit  11  and the switch component  161  of the switch unit  16  is turned to a short circuit state; the connection between the backup inverter unit  13  and the switch component  161  of the switch unit  16  is turned to an open circuit state; and, by doing so, the malfunctioned inverter unit  11  is replaced with the backup inverter unit  13 . 
         [0035]    (g3) Connecting the backup inverter unit with the corresponding fuel cell, activating the timer interrupt process and processing step (b)  343 : A new connecting circuit between the backup inverter unit  13  and the corresponding fuel cell  121  is built; the timer interrupt process is activated again; and then step (b)  311  is processed. 
         [0036]    However, when the backup inverter unit  13  is not found, the operating process continues with the following step: 
         [0037]    (h) Stopping the device  35 : The whole device is stopped. 
         [0038]    Consequently, with the above steps, an operation process for the present invention is obtained, where the inverter unit  11  and the backup inverter unit  13  is a three-phase and wye-connected circuit or a three-phase and delta-connected circuit. 
         [0039]    To sum up, the present invention is a fault-tolerant circuit device in a fuel cell AC inverter where a backup inverter unit replaces a malfunctioned inverter unit in a fuel cell so that a fuel cell AC inverter keeps functioning even when an inverter unit in the fault-tolerant circuit device is malfunctioned. 
         [0040]    The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.