Patent Publication Number: US-2007114850-A1

Title: Power system and method for supplying electrical power to a load

Description:
TECHNICAL FIELD  
      The present invention relates to a power system and a method for supplying electrical power to a load, and more specifically to a power system. having a plurality of DC power sources and which provides a smooth power output to a load when one of the DC power sources is intermittently electrically decoupled from the load.  
     BACKGROUND OF THE INVENTION  
      In U.S. Pat. Nos. 6,030,718 and 6,468,682, a fuel cell power system is disclosed, and which includes a plurality of fuel cell modules which can be operably detached and removed from the fuel cell power system while the remaining fuel cell modules continue to operate; The removal of the fuel cell modules may be for purposes of repair, replacement or the like. Further, the electrical shunting of the same fuel cell modules as more fully disclosed in U.S. Pat. No. 6,096,449 is effective for increasing the performance of such fuel cell power systems.  
      As should be understood, when any of a plurality of DC power sources are intermittently and periodically interrupted, for whatever reason, (whether it be for shunting as disclosed in U.S. Pat. No. 6,096,449 or removed from the fuel cell power system as described more fully in the earlier patents noted above), a by-product of this process is a ripple or interruption in the overall power system output voltage caused by the periodic shorting of one or many modules. This ripple or momentary interruption in the output voltage must be, according to the prior art practices, smoothed out by a DC to DC power converter which then supplies the resulting DC voltage to the load.  
      While the prior art practice has operated with a great degree of success, it has shortcomings which have detracted from its usefulness. More specifically, the prior art practice as briefly described above increases the complexity and cost of a fuel cell power system by adding additional equipment to the fuel cell power system. While this additional equipment is somewhat costly, there are also power losses attendant with the use of equipment such as a DC to DC power converter.  
      A power system and method for supplying power to a load which avoids the shortcomings attendant with the prior art practices employed heretofore, is the subject matter of the present application.  
     SUMMARY OF THE INVENTION  
      A first aspect of the present invention relates to a power system which includes a plurality of serially electrically coupled DC power sources each having an electrical power output which is supplied to a load; a charge storage device electrically coupled with the plurality of DC power sources, and having a maximum electrical charge which is substantially equal to the electrical power output of one of the plurality of DC power sources; and means for electrically decoupling at least one of the plurality of DC power sources while simultaneously electrically discharging the charge storage device to the load.  
      Another aspect of the present invention relates to a power system which includes a plurality of DC power sources which provide a source of electrical power to service a requirement of the load; a charge storage device having a maximum electrical charge which is less than the amount of electrical power which is necessary to service the requirement of the load; and means for selectively decoupling the individual DC power sources from the load while simultaneously electrically discharging, and electrically coupling the charge storage device to the load in a manner which provides uninterrupted electrical power to meet the electrical power requirement of the load.  
      Still another aspect of the present invention relates to a power system which includes a plurality of fuel cells each having a predetermined electrical power output, and which are serial electrically coupled together, and which produce a cumulative power output which substantially meets the electrical power requirements of the load; a controller which is electrically coupled with the respective plurality of fuel cells, and which periodically electrically decouples individual fuel cells from the load; and a charge storage device which is electrically coupled with the controller, and which is selectively electrically coupled to the load when the controller electrically decouples one of the plurality of fuel cells from the load, and wherein the charge storage device provides an amount of electrical power to the load which is not greater than the electrical power output of the decoupled fuel cell.  
      Yet still another aspect of the present invention relates to a power system which includes a plurality of fuel cells which each have anode and cathode, and which, when rendered operable, supply electrical power of a given amount to meet the electrical power requirements of a load; a controller electrically coupled to the anode and cathode of each of the fuel cells, and which is operable to periodically shunt the anode to the cathode of each of the respective fuel cells, and wherein the shunting of the respective fuel cells results in a reduced amount of electrical power provided to the load; and a charge storage device which is controlled by the controller and which is periodically electrically coupled to the load during the shunting of the respective fuel cells, and which is operable to deliver electrical power which is substantially equal to the reduced amount of electrical power as caused by the shunting.  
      Moreover, another aspect of the present invention relates to a method for supplying electrical power to a load which includes the steps of providing a plurality of fuel cells which individually produce an electrical power output; serially electrically coupling the plurality of fuel cells together to provide a resulting electrical power output which is not greater than the electrical power requirements of a load; supplying the resulting electrical power output of the serially electrically coupled fuel cells to the load; providing a controller which is controllably electrically coupled to the respective plurality of fuel cells; periodically electrically decoupling at least one of the fuel cells from the plurality of serially electrically coupled fuel cells with the controller; providing a charge storage device which is selectively electrically coupled with resulting electrical power output of the plurality of fuel cells, and the load, and which is controllably electrically coupled with the controller; electrically charging the charge storage device to a maximum charge with the resulting electrical power output while the plurality of fuel cells simultaneously meet the electrical needs of the load; and electrically discharging the charge storage device during a time period where the controller has electrically decoupled at least one of the fuel cells from the plurality of fuel cells, and wherein the discharged charge storage device provides electrical power in an amount which is substantially equal to the electrical power output of the electrically decoupled fuel cell.  
      These and other aspects of the present invention will be discussed in greater detail hereinafter.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred embodiments of the invention are described below with reference to the following accompanying drawings.  
       FIG. 1  is a greatly simplified depiction of the power system of the present invention.  
       FIG. 2  is a greatly simplified depiction of a portion of the circuitry employed in the present invention and which is shown in a first electrical state.  
       FIG. 3  is a greatly simplified depiction of a portion of the circuitry employed in the present invention and which is shown in a second electrical state.  
       FIG. 4  is a greatly simplified depiction of a portion of the circuitry employed in the present invention and which is shown in a third electrical state.  
       FIG. 5  is a greatly simplified depiction of a portion of the circuitry employed in the present invention and which is shown in a fourth electrical state.  
       FIG. 6  is a greatly simplified depiction of a portion of the circuitry employed in the present invention and which is shown in a fifth electrical state.  
       FIG. 7  is a graphical depiction of the power output provided by a plurality of DC power sources and which is seen by a load when individual DC power sources are electrically decoupled from the load.  
       FIG. 8  is a graphical depiction showing the DC power output of a plurality of DC power sources provided to a load employing the features of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).  
      Referring now to  FIGS. 1 and 2 , the present invention relates to a power system and a method for supplying electrical power to a load, and which is generally indicated by the numeral  10 . As seen therein, the present invention  10  includes, as seen in  FIG. 1  and  2 , for example, a plurality of serially electrically coupled DC power sources each having an electrical power output which is supplied to a load. The plurality of DC power sources are herein indicated as first, second, third and fourth DC power sources DC 1 -DC 4  and which are indicated by the numerals  11 ,  12 ,  13 , and  14 , respectively. Each of the plurality of DC power sources may have substantially the same electrical power output, or alternatively may have different electrical power outputs. Still further, the respective individual DC power sources may include fuel cells having multiple modules as described in prior art U.S. Pat. Nos. 6,030,718 and 6,468,682. The teachings of these patents are incorporated by reference herein. Further, and as seen in  FIG. 1 , one of the DC power sources, that being  14 , may include shunt control circuitry  20  similar to that described in U.S. Pat. No. 6,096,449 and which periodically shunts the electrical power output of individual fuel cell modules, for example, in order to increase the performance of same. The individual DC power sources  11 - 14 , respectively, each provide an electrical power output which is supplied to a load  30  in order to energize same. The present invention  10  further includes a controller  40  which is controllably electrically coupled to the respective plurality of DC power sources  11 - 14 , and in electrical sensing relation relative to the load  30 . The controller  40  provides a means for electrically decoupling at least one of the plurality of DC power sources  11 - 14  from the load  30  for the purposes which will be described in greater detail hereinafter.  
      It will be seen from a study of, for example,  FIG. 2 , and following, that the present invention  10  includes first circuitry  51  for serially electrically coupling the plurality of DC power outputs of the plurality of DC power sources  11 - 14 , respectively, to the load  30 . The first circuitry  51  is further operable to selectively electrically disconnect or decouple individual DC power sources from the load  30 , as will be described in greater detail, hereinafter. The present invention  10  further includes, in addition to the first circuitry  51 ; second circuitry  52  which is electrically coupled to the first circuitry  51 , and which supplies a portion of the DC power provided by the plurality of DC power sources  11 - 14  to electrically charge a charge storage device which is generally indicated by the numeral  60 . Still further, the controller  40 , in combination with the second circuitry  52 , electrically discharges the charge storage device  60  when at least one of the plurality of DC power sources  11 - 14  is electrically disconnected or decoupled from the load  30  by means of the controller  40  acting upon the first circuitry  51 . As should be appreciated from a study of  FIGS. 1 and 2 , the first and second circuitry  51  and  52  is electrically controlled by means of the controller  40 . In addition to the foregoing, the present invention  10  includes a charging circuit which is generally indicated by the numeral  70 , and which is further made integral with the second circuitry  52 . The charging circuit  70  is of conventional design, and is operable to provide a charging current which is supplied to the charge storage device  60 . In the arrangement as seen in  FIG. 1 , and following, the charge storage device  60  may comprise a plurality of charge storage devices. If a plurality of charge storage devices is provided, the controller  40  is operable to select the appropriate number of charge storage devices to electrically discharge in order to provide a cumulative amount of electrical power which is then supplied to the first circuitry which is electrically coupled to the load  30  and which replaces the amount of DC power which has been disconnected from the load  30 .  
      In the arrangement as seen in  FIG. 1  and following, the controller  40  which represents the means for electrically decoupling the individual DC power sources from the load  30 , is further electrically coupled with the first and second circuitry  51  and  52 , and further is disposed in electrical charge sensing relation relative to the charge storage device  60 , and is additionally in electrical power output sensing relation relative to the individual DC power sources  11 - 14 , respectively. In this arrangement, the controller  40  provides a convenient means for selectively decoupling the individual DC power sources  11 - 14  from the load  30 , while simultaneously electrically discharging and electrically coupling the charge storage device  60  to the load  30  in a manner which provides uninterrupted electrical power to meet the electrical power requirements of the load. This is best understood by a study of  FIG. 8 .  
      Referring now to  FIG. 1 , the present invention  10  includes a plurality of switches here indicated as SW 1 -SW 11 , respectively, and which are made integral with the respective first and second circuitry  51  and  52 , respectively as seen in  FIG. 2 . As noted above, the first and second circuitry  51  and  52  are electrically coupled together in a fashion to provide the features of the invention and which have been described herein. As seen in  FIG. 1 , the respective switches are controllably electrically coupled by the controller  40  to alternately place them into the open or closed electrical state as will be described below. As will be seen by a study of  FIG. 2  and following, switch SW 4 -SW 11  are incorporated within the first circuitry  51 ; and SW 1 -SW 3  are incorporated within the second circuitry  52 . It should be understood that an actual power system could include many more switches if more than four DC power sources are employed.  
      As seen in FIGS.  2  and following, the power system  10  of the present invention includes a plurality of serially electrically coupled DC power sources  11 - 14  each having a DC electrical power output which is supplied to a load  30 . Still further, the power system  10  includes a charge storage device  60  which is electrically coupled with the plurality of DC power sources, and which has a maximum electrical charge which is substantially equal to the electrical power output of at least one of the plurality of DC power sources  11 - 14 . Still further, the power system  10  includes a means  40  ( FIG. 1 ) which acts upon the first circuitry  51  and which electrically decouples at least one of plurality of DC power sources  11 - 14  while simultaneously electrically discharging the charge storage device  60  to the load  30 . As earlier described, the plurality of DC power sources  11 - 14  may have substantially the same electrical power output or further may have different electrical power outputs. Additionally, a plurality of DC power sources may comprise a plurality of fuel cells which have substantially the same electrical output or different electrical outputs. In the arrangement as seen, in  FIG. 1  and  2 , for example, the charge storage device  60  may include a plurality of charge storage devices, and wherein the means  40  for electrically decoupling the plurality of DC power sources decouples a plurality of DC power sources from the load while simultaneously electrically discharging a number of charge storage devices  60  by means of the second electrical circuitry  52 , and which has an accumulative electrical charge which is substantially equal to the cumulative electrical power output previously provided by the electrically disconnected DC power sources  11 - 14 .  
      As should be understood, the charge storage device  60  may comprise a battery, or an ultracapacitor which are well understood in the art. It should be further understood that the power system  10  of the present invention includes first circuitry  51  for serially electrically coupling the plurality of DC power outputs of the plurality of DC power sources  11 - 14  to the load  30 . The first circuitry is further operable by means of the controller  40  to selectively electrically disconnect or decouple the individual DC power sources from the load  30 . Still further, the present invention  10  includes second circuitry  52  which is electrically coupled to the first circuitry, and which supplies a portion of the DC power output provided by the plurality of DC power sources  11 - 14  to electrically charge the charge storage device  60 . Additionally, the second circuitry  52  electrically discharges the charge storage device by means of the controller  40  when at least one of the plurality of DC power sources  11 - 14  is electrically disconnected from the load  30 .  
      In another aspect of the present invention, the power system  10  includes a plurality of DC power sources  11 - 14  which provide a source of electrical power to service a requirement of a load  30 ; and a charge storage device  60  having a maximum electrical charge which is less than the amount of electrical power which is necessary to service the requirement of the load  30 . Still further, the power system  10  includes a means  40  for selectively decoupling the individual DC power sources from the load  30  while simultaneously electrically discharging and electrically coupling the charge storage device  60  to the load  30  in a manner which provides uninterrupted electrical power to meet the electrical power requirements of the load. This is best understood by reference to  FIG. 8 .  
      In the arrangement as seen in  FIG. 2  and following, the respective plurality of DC power sources  11 - 14  each produce an electrical power output, and wherein the maximum electrical charge of the charge storage device  60  is substantially equal to the electrical power output of the DC power sources  11 - 14  which have been selectively decoupled from the load  30 . In the event that there is a plurality of charge storage devices  60 , the means  40  for selectively decoupling the individual DC power sources from the load simultaneously electrically discharges a given number of charge storage devices  60  which have an accumulative electrical charge which is substantially equal to the power output of the DC power sources  11 - 14  which have been selectively disconnected from the load  30  by means of the controller  40 . In the event that the DC power sources comprise a plurality of fuel cells, for example, it should be understood that each fuel cell has an anode and a cathode  15  and  16 , respectively, and the means  40  for selectively electrically decoupling the individual DC power sources  11 - 14  comprises a controller  40  which shunts the anode to the cathode of at least one of the plurality of DC power sources  11 - 14 , respectively. This is achieved by means of the shunt control circuit  20  as seen in  FIGS. 1 . The shunt control circuit is more fully described in U.S. Pat. No. 6,096,449, the teachings of which are incorporated by reference herein.  
      Referring now to  FIG. 7 , a graphical depiction of the power output that might be provided by a power system which does not include the teachings of the present invention is illustrated, and wherein the power system providing this output voltage includes four DC power sources each producing approximately  10  volts each collectively, these four sources provide  40  volts DC to the load. As should be understood, individual DC power sources are electrically decoupled from the load at time intervals T 1 , T 3  and T 5 . This decoupling of one of the sources of DC power from the load produces a ripple, variation or power interruption of  10  volts, as it were, in the electrical power output provided to the load. As should be understood, this may be an unacceptable electrical power output for certain types of equipment which must have a substantially continuous and smooth electrical power supply. As seen in that view, at time intervals T 2 , T 4  and T 6 , all four DC power sources are supplying electrical power to the load. Therefore, the load is receiving an electrical output of 40 volts.  
       FIG. 8  is a depiction of a DC power output provided by the present invention  10 . As seen at time intervals T 1 , T 3  and T 5 , respectively, individual DC power sources  11 - 14 , respectively are individually decoupled from the load  30 . However, during the same time interval (T 1 ; T 3 ; and T 5 ), the controller  40  is operable to electrically discharge the charge storage device  60  in a fashion so as to provide an amount of electrical power (10 V) which is equal to that which was previously supplied by the decoupled DC power source. The power from the charge storage device  50  is provided to the load  30  in a fashion which prevents any ripple or disruption from being experienced by the load  30 . The load  30  therefore receives a constant 40 volts notwithstanding the decoupling of the individual DC power sources  11 - 14 . Referring now to  FIG. 2 , and  FIG. 8 , and in a first electrical state, and at time T 0 , or the initial state, it will be understood that the electrical switches identified as SW 1 , SW 3 , SW 4 , SW 6 , SW 8  and SW 10  are closed by the controller  40 , and further, electrical switches SW 5 , SW 7 , SW 9  and SW 11  are electrically opened by the same controller. In this first electrical state, the charge storage device  60  is charged to about 10 volts. As should be understood, this voltage is about equal to the DC power output of at least one of the plurality of DC power sources  11 - 14 , respectively. The voltage output of the power system  10  as seen and illustrated in  FIG. 2  is approximately 40 volts, that being, the sum of the DC voltage output of the  4  DC power sources  11 - 14 , respectively.  
      Referring now to  FIG. 3 , a second electrical state of the power system  10  is shown, and wherein at time period T 1  as seen in  FIG. 8 , a single DC power source  11  is electrically decoupled from the load  30  by the controller  40 . In order to achieve this electrical state, electrical switches SW 1 , SW 3 , SW 4 , SW 7 , SW 9 , and SW 11  are opened and electrical switches SW 2 , SW 5 , SW 6 , SW 8  and SW 10  are closed by the controller  40 . The voltage output as provided by the power system  10  is 40 volts, that being, the sum of the DC power sources  12 ,  13  and  14 , respectively and the DC power output of the charged storage device  60  which is electrically discharged by the controller  40  for the time period during which the DC power source  11  is electrically decoupled from the load  30 . During time period T 2 , the circuitry  51  and  52  and the respective switches referenced above revert by means of the controller  40  to the initial or first electrical state as seen in  FIG. 2 , and wherein all four DC power sources are collectively supplying power to energize the load  30 , and the charge storage device is being electrically charged and readied for another electrical discharge.  
      Referring now to  FIG. 4 , and  FIG. 8 , a third electrical state of the power system  10  is shown at time period T 3 , and wherein a single DC power source, here indicated as the second DC power source  12 , is electrically decoupled from the load  30  by the controller  40 . In this regard, the electrical switches SW 1 , SW 3 , SW 5 , SW 6 , SW 9 , and SW 11  are electrically opened; and electrical switches SW 2 , SW 4 , SW 7 , SW 8  and SW 10  are electrically closed by the same controller  40 . The voltage output which is provided to the load  40  remains at  40  volts and which is equal to the sum of the DC power output of the first, third and fourth DC power sources  11 ,  13  and  14 , respectively, and the electrical power provided by the charge storage device  60 . As will be appreciated, during time period T 4 , the power system  10  and all the above discussed electrical switches return to the first electrical state as shown in  FIG. 2 , and wherein the charging circuit  70  is operable to charge the charge storage device  60  with an amount of electricity from the DC power sources  11 - 14  thereby returning the charge storage device to a state where it can be selectively discharged by the controller  40  during another cycle, and the four DC power sources  11 - 14  are supplying electrical power to energize the load  30 .  
      Referring now to  FIG. 5 , the power system  10  is shown in a fourth electrical state during time period T 5 , and wherein a single DC power source here shown as  13  is electrically decoupled from the load  30  by the controller  40 . In this third electrical state, electrical switches SW 1 , SW 3 , SW 5 , SW 7 , SW 8  and SW 11  are opened; and electrical switches SW 2 , SW 4 , SW 6 , SW 9 , and SW 10  are closed by the same controller. As with the previous examples, the voltage output of the power system  10  during this fourth electrical state equals 40 volts, that being, the sum of the electrical power outputs of the first, second and fourth DC power sources  11 ,  12  and  14 , respectively, and the electrical power output provided by the charge storage device  60 , and which is selectively discharged by the controller  40  during the time period T 5  as seen in  FIG. 8 . Again, at time period T 6  as seen in  FIG. 8 , the power system  10  of the present invention returns to the electrical state as seen in  FIG. 2  under the influence of controller  40 , and wherein the charging circuit  70  is operable to impart an electrical charge to the charge storage device  60  thereby rendering it capable of delivering an electrical discharge of 10 V during the next cycle.  
      As seen in  FIG. 8  and referring now to  FIG. 6 , the power system  10  of the present invention includes a fifth electrical state during time period T 7 , and wherein the fourth DC power source  14  is electrically decoupled from the load  30  by the controller  40 . In this electrical state, electrical switches SW 1 , SW 3 , SW 5 , SW 7 , SW 9 , and SW 10  remain electrically open; and electrical switches SW 2 , SW 4 , SW 6 , SW 8  and SW 11  are electrically closed by the same controller. Again, the voltage output as experienced by the load  30  remains 40 volts, that is, the sum of the DC power output of the three DC power sources  11 ,  12 , and  13 , respectively, and the voltage provided by the charge storage device  60  which is electrically discharged by the controller  60  during the time period T 7 . Again, after the time period T 7 , the fourth DC power source is again electrically coupled to the load, and the power system  10  is operable by means of the controller to return to the first electrical state as seen in  FIG. 2 . In the first electrical state, the charging circuit  70  is operable to electrically charge the charge storage device  60  thereby rendering it available to electrically discharge during another cycle as previously described.  
     Operation  
      The operation of the described embodiment of the present invention is believed to be readily apparent and is briefly summarized at this point.  
      As best understood by a study of  FIGS. 1 , a power system  10  is disclosed and which includes a plurality of DC power sources  11 - 14 , respectively such as a plurality of fuel cells, and wherein each of the DC power sources have a predetermined electrical power output, and which are serially electrically coupled together to produce a cumulative power output which substantially meets the electrical power requirements of the load  30 . A controller  40  is provided and which is electrically coupled with the respective plurality of DC power sources  11 - 14 , which may include a plurality of fuel cells, and which periodically electrically decouples the individual fuel cells from the load. Still further, the power system  10  includes a charge storage device  60  which is electrically coupled with the controller, and which is selectively electrically coupled to the load  30  when the controller decouples one of the plurality of DC power sources  11 - 14  from the load  30 . The charge storage device  60  provides an amount of electrical power to the load  30  which is not greater than the electrical power output of the decoupled individual DC power sources  11 - 14 . In the arrangement as seen, the controller  40  couples the charge storage device  60  to the load  30  in a manner wherein the load experiences substantially no interruption or reduction in the electrical power being supplied to same. This is best seen in  FIG. 8 .  
      In the arrangement as seen in FIGS.  2  and following, first circuitry  51  is provided and which couples the plurality of fuel cells  11 - 14  to the load  30 . Still further, the power system  10  includes second circuitry  52  which is electrically coupled to the first circuitry  51 , and which delivers a portion of the electrical power output of the respective fuel cells  11 - 14  to electrically charge the charge storage device  60  while the first circuitry  51  delivers the electrical power to meet the power requirements of the load  30 . In the arrangement as seen in  FIG. 1 , the controller  40  is coupled in electrical power sensing relation relative to the respective plurality of DC power sources  11 - 14 , respectively and the charge storage device  60 . The controller is further controllably electrically coupled with the electrical switches SW 1 -SW 11 , respectively. As should be understood, the power system  10  of the present invention may be utilized with a plurality of fuel cells which each have an anode  15  and a cathode  16 , and which, when rendered operable, supply electrical power of a given amount to meet the electrical power requirements of the load  30 . In the arrangement as illustrated, and when a plurality of fuel cells are utilized as the DC power sources  11 - 14 , the controller  40  is electrically coupled to the anode and cathode of each of the fuel cells and which is operable to periodically shunt the anode and cathode of each of the respective fuel cells by utilizing the shunt control circuitry  20  as indicated in  FIGS. 1 and 2 . Upon accomplishing the shunting, the respective DC power sources or fuel cells  11 - 14  in this case, results in a reduced amount of electrical power provided to the load  30 . In this arrangement, a charge storage device  60  is provided, and which is controlled by the controller  40 , and which is periodically electrically coupled to the load  30  during the shunting of the respective fuel cells, and which is operable to deliver electrical power which is substantially equal to the reduced amount of electrical power as caused by the shunting. In this arrangement as described, the electrical power output of the plurality of fuel cells is further utilized to charge the charge storage device during time periods between the shunting. As earlier discussed, the charge storage device  10  may comprise a plurality of ultracapacitors.  
      The present invention also relates to a method for supplying electrical power to a load  30  and which includes, in its broadest sense, the steps of providing a plurality of serially electrically coupled DC power sources  11 - 14  which individually produce an electrical power output; periodically removing the electrical power output of at least one of the DC power sources  11 - 14 ; and replacing the electrical power output which has been removed with another source of DC electrical power, such as provided by a charge storage device  60 , in a fashion such that the electrical power supplied to the load  30  is substantially uninterrupted. In the methodology as described above, the method further includes the steps of sensing the electrical power output of the respective DC power sources by means of a controller  40 , and providing a charge storage device  60  which is further electrically coupled with the controller. The method further includes the step of electrically charging the charge storage device  60  by means of a charging circuit  70 , and which is supplied with the electrical power from of the plurality of DC power sources  11  and  14 , respectively. Still further, the methodology includes the step of sensing the electrical charge of the charge storage device  60  by means of the controller  40 ; and electrically discharging the charge storage device  60  to replace the electrical power output of one of the DC power sources  11 - 14  which has been removed or electrically decoupled from the load  30 .  
      More specifically, the methodology for supplying electrical power to a load  30  includes the steps of providing a plurality of DC power sources  11 - 14  which may include a plurality of fuel cells, and which individually produce an electrical power output; and serially electrically coupling the plurality of fuel cells together to provide a resulting electrical power output which is not greater than the electrical power requirements of the load  30 . The methodology as described above includes a further step of supplying the resulting electrical power output of the serially electrically coupled DC power sources or fuel cells  11 - 14  to the load  30 . Still further, the methodology includes a step of providing a controller  40  which is controllably electrically coupled to the respective plurality of DC power sources  11 - 14 . Still further, the methodology includes a step of periodically electrically decoupling at least one of the plurality of DC power sources  11 - 14  from the plurality of serially electrically coupled DC power sources  11 - 14  with the controller  40 . Additionally, the methodology includes the step of providing a charge storage device  60  which is selectively electrically coupled with the resulting electrical power output provided by the plurality of DC power sources, and which may include a plurality of fuel cells, and the load  30 . As described herein, this step includes a further step wherein the charge storage device  60  is controllably electrically coupled with the controller  40 . The methodology as described includes a further step of electrically charging the charge storage device  60  by use of a charging circuit  70  with the resulting electrical power output as provided by the plurality of DC power sources  11 - 14  while the plurality of DC power sources simultaneously meet the electrical power requirements of the load  30 . The methodology as described further includes a step of electrically discharging the charge storage device  60  during a time period where the controller  40  has electrically decoupled at least one of the DC power sources from the plurality of DC power sources, and wherein the charge storage device  60  is discharged to provide electrical power in an amount which is substantially equal to the electrical power output of the electrically decoupled DC power source.  
      Therefore it will be seen that the present invention provides a convenient means whereby individual DC power sources may be selectively electrically decoupled from a load in a fashion whereby the resulting electrical power supplied to the load is substantially maintained without any ripple or significant interruption of any kind.  
      In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.