JP2005513722A - Control of hybrid fuel cell system - Google Patents

Abstract

  A fuel cell with a battery utilizes a first stage that regulates the current through the series pass element in response to a large value of battery charge current error, battery voltage error, and stack current error. The fuel cell system utilizes a second stage that controls the partial pressure of the reactant flow to the fuel cell stack based on the voltage deviation across the series pass element or based on the battery condition. The fuel cell system may use either stage or both stages. Individual fuel cells can be combined in series and / or in parallel to produce a composite fuel cell system having the desired output voltage and current.

Description

  The present invention relates generally to fuel cell systems, and more particularly to control of the output voltage of a fuel cell system.

  Electromechanical fuel cells convert fuel and oxidants to electricity. Solid polymer electromechanical fuel cells typically use a membrane electrode assembly (“MEA”), which typically comprises a porous, conductive sheet material layer such as carbon fiber paper or carbon cloth. It includes an ion exchange membrane or solid polymer electrolyte disposed between two provided electrodes. The MEA includes a catalyst layer, typically in the form of finely divided platinum, at each membrane electrode to induce the desired electrochemical reaction. In operation, the electrodes are electrically coupled to conduct electrons between the electrodes via an external circuit. Typically, several MEAs are electrically coupled in series to form a fuel cell stack with the desired power output.

  In the case of a standard fuel cell, the MEA is placed between two conductive liquid flow field plates. The liquid flow field plate has flow paths for sending fuel and oxidant to the electrodes, ie the anode and cathode, respectively. Liquid flow field plates function as current collectors, support electrodes, provide access channels for fuel and oxidants, and channels for removing reaction products such as water generated during fuel cell operation I will provide a. The fuel cell system may utilize a reaction product in maintaining the reaction. For example, reaction water can be utilized to hydrate the ion exchange membrane and / or maintain the temperature of the fuel cell stack.

  Stack current is a linear function of reactant flow, and stack current increases with increasing reactant flow. The stack voltage is a non-linear mathematical relationship and changes inversely with the stack current. The relationship between stack voltage and stack current at a given flow of reactant is typically expressed as a polarization curve for the fuel cell stack. A set or group of polarization curves can represent the relationship between stack voltage and stack current at various flow rates of reactants.

  In most applications, it is desirable to keep the voltage output from the fuel cell stack nearly constant. One approach is to use a battery in the fuel cell system to supply additional current when the load demand exceeds the output of the fuel cell stack. This approach often requires a separate battery charging power source to maintain the battery charge, resulting in unnecessary cost and complexity for the system. Other challenges arise from attempts to place the battery in parallel with the fuel cell stack to eliminate the need for a separate battery charging power source. These challenges include, for example, prevention of battery overcharging, increased efficiency, and the need for voltage, current, or power conversion or matching components between the fuel cell stack, battery, and / or load. A lower cost, less complex and / or more efficient approach is desirable.

  In one aspect, a fuel cell system includes a fuel cell stack, a battery, a series pass element electrically coupled between at least a portion of the fuel cell stack and a portion of the battery, a battery charging current error, a battery And a regulation circuit for regulating the current through the series pass element in response to a large value of the voltage error and the stack current error.

  In another aspect, the fuel cell system includes a reactant supply system for supplying a reactant to the fuel cell, wherein the reactant supply system reduces the partial pressure of the reactant flow to at least some of the fuel cells. At least a first control element adjustable to control and a control circuit coupled to the first control element. The control circuit may also control the first control element based on a deviation of the voltage across the series pass element from some desired value, such as about 75% and 95% of the saturation level for the series pass element. Good. Alternatively, or in addition, the control circuit may be based on a predetermined operating state of the battery, such as current inflow and outflow to or from the battery over time, battery voltage, or battery charge state. The first control element may be controlled.

  In another aspect, the fuel cell system may include a series pass element and a regulator circuit as the first stage, and a reactant supply system and a control circuit as the second stage. The first and second stages work in concert and even at the same time with parallel coupled batteries to achieve efficient and continuous output voltage control while protecting the battery from damage . The first stage is a relatively quick reaction stage, while the second stage is a slower reaction stage compared to the first stage. The first stage ensures that the battery is properly charged and discharged efficiently without damage. The second stage controls the efficiency of the fuel cell stack operation (i.e., the efficiency expressed as a specific polarization curve on which the fuel cell is operating). In this way, the second stage limits the amount of heat dissipated by the series pass element by dissipating more energy through the fuel cell stack (ie, through less efficient operation).

  In yet another aspect, a composite fuel cell system includes two or more individual fuel cell systems electrically coupled in series and / or in parallel to generate a desired current at a desired voltage. It is out.

  In the drawings, identical reference numbers identify similar elements or operations. The element sizes and relative positions in the drawings are not necessarily to scale. For example, the shapes and angles of the various elements are not to scale, and some of these elements are arbitrarily enlarged and arranged to increase the clarity of the drawing. Furthermore, the particular shapes of elements shown are not intended to convey any information about the actual shapes of particular elements, but are merely selected to facilitate recognition in the drawings.

  In the following description, certain specific details are disclosed in order to provide a thorough understanding of various embodiments of the invention. However, those skilled in the art will appreciate that the invention may be practiced without these details. In other instances, well-known structures for fuel cells, fuel cell stacks, batteries, and fuel cell systems have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the invention. .

Unless the context requires otherwise, the term “comprise” and its variants, such as “comprises” and “comprising”, include and include throughout the following specification and claims. It should be construed to have an open and comprehensive meaning of “not limited”.
(Overview of fuel cell system)
FIG. 1 illustrates a fuel cell system 10 for supplying power to a load 12 according to an illustrated embodiment of the present invention. The load 12 typically constitutes a device powered by the fuel cell system 10, such as a vehicle, equipment, computer, and / or associated peripheral equipment. Although the fuel cell system 10 is typically not considered to be part of the load 12, a part of the fuel cell system 10, such as control electronics, may be part of the load 12 in certain possible embodiments. Or it may constitute everything.

  The fuel cell system 10 includes a fuel cell stack 14 consisting of a number of individual fuel cells electrically coupled in series. The fuel cell stack 14 receives the reactants indicated by arrows 9, such as hydrogen and air, via the reactant supply system 16. The reactant supply system 16 may include one or more reactant supply tanks or sources 11, a reformer (not shown), and / or one or more compressors, pumps, and / or valves 18, or other reactant conditioning elements. One or more control elements may be included. In the operation of the fuel cell stack 14, a reaction product indicated by an arrow 20 that typically contains water is generated. The fuel cell system 10 may reuse a part or the remainder of the reaction product. For example, as shown by arrows 22, water and air are moistened at the proper temperature and / or water is used to hydrate the ion exchange membrane (not shown) or control the temperature of the fuel cell stack 14. A part or the whole may be returned to the fuel cell stack 14.

The fuel cell stack 14 can be modeled as an optimal battery having an open circuit voltage and a voltage equivalent to the series resistance R _s . The series resistance R _s varies according to the polarization curve for a particular fuel cell stack 14. The series resistance R _s can be adjusted by controlling the availability of the reactants so as to lower the desired voltage for any given current, it substantially uniform stack voltage in the entire range of stack current I _s by V _s Is possible. The relationship between the flow of reactants and the series resistance R _s is shown in FIG. However, simply reducing the overall reactant pressure and reaction pressure within the fuel cell system 10 may interfere with overall system operation, for example, ion exchange membrane hydration and / or fuel cell stack temperature control. There is. In order to avoid such undesirable results, the fuel cell system 10 can adjust the partial pressure of the reactants as will be described in detail later.

The fuel cell stack 14 generates the stack voltage V _s across the high voltage bus formed by positive and negative voltage rails 19a, 19b. Stack current I _s flows to the load 12 through the high-pressure bus from the fuel cell stack 14. As used herein, “high voltage” refers to the voltage (eg, 5V) to the power load 12 generated by the conventional fuel cell stack 14 and is used by the fuel cell system 10 for control and / or communication. It is used to distinguish from the voltage. Thus, the high voltage is not necessarily “high” relative to other electrical systems.

The fuel cell system 10 includes a battery 24 that is electrically coupled in parallel with the fuel cell stack 14 across the rails 19a, 19b of the high voltage bus to power the addition 12. The open circuit voltage of the battery 24 is selected to be the same as the full load voltage of the fuel cell stack 14. The internal resistance R _B of the battery 24 is selected to be considerably lower than the internal resistance of the fuel cell stack 14. In this way, the battery 24 absorbs excess current when the fuel cell stack 14 generates more current than the load 12 requires, and loads when the fuel cell stack 14 generates less current than the load 12 requires. 12 functions as a buffer for supplying current. High bus 19a, the voltage 24 across the 19b subtracts the battery discharge current from the open-circuit voltage, a value obtained by multiplying the value of the internal resistance R _B of the battery 24. The smaller the internal resistance R _B of the battery 24, the variation of the bus voltage decreases.

An optional reverse current blocking diode D 1 can be electrically coupled between the fuel cell stack 14 and the battery 24 to prevent current from flowing from the battery 24 to the fuel cell stack 14. The disadvantage of reverse current blocking diode D1 is the associated diode voltage drop. The fuel cell system 10 may further include other diodes and other surge protection elements to prevent fuses or short circuits and / or surges.
(stage)
As shown in FIG. 1, the fuel cell system 10 includes two control stages. That is, a first stage that uses a series pass element 32 and a regulator circuit 34 that regulates the current through the series pass element, and a flow of reactants to control the series resistance R _s to the fuel cell stack 14. And a second stage for controlling the pressure. The first and second stages cooperate in cooperation with the battery 24 coupled in parallel and even at the same time to achieve efficient and continuous output voltage control while protecting the battery 24 from damage. Operate. In some embodiments, the fuel cell system 10 includes only the first stage or only the second stage, providing a simple and low cost alternative embodiment.

The first stage is a relatively quick reaction stage, while the second stage is a slower reaction stage compared to the first stage. As described above, the battery 24 responds very quickly to changes in load demand, supplying current to the load 12 when demand is greater than or equal to the output of the fuel cell stack 14, and the output of the fuel cell stack 14 is If the demand is exceeded, the redundant current is reduced. By controlling the flow of current through the series pass element 32, the first stage ensures that the battery is properly charged and discharged efficiently without damage. By controlling the partial pressure of the reactants, and thus the series resistance R _s , the second stage allows the efficiency of operation of the fuel cell stack 14 (ie, the efficiency expressed as a specific polarization curve on which the fuel cell is operating based). ) To control. In this way, the second stage limits the amount of heat dissipated by the series pass element 32 by dissipating more energy through the fuel cell stack 14 (ie, through less efficient operation).

  If the fuel cell stack 14 dissipates energy as heat, this energy can be regenerated in various parts of the fuel cell system and thus reused in other parts of the fuel cell system (ie, cogeneration). For example, energy dissipated as heat can be recycled to the fuel cell stack 14 via airflow, stack refrigerant, or reactants. Additionally or alternatively, the energy dissipated as heat may be recycled to the riff (not shown), to other parts of the fuel cell system 10, or to some external system. In addition, by limiting the amount of energy that the series pass element 32 must dissipate, the size and associated cost of the series pass element 32 and any associated heat sink can be reduced.

Details of the first and second stages will be described later.
(Outline of the first stage, series pass element regulator)
With continued reference to FIG. 1, the first stage of the fuel cell system 10 is electrically between the fuel cell stack 14 and the battery 24 to control the flow of current I _s from the fuel cell stack 14 to the battery 24 and the load 12 A series pass element 32 coupled thereto. The first stage of the fuel cell system 10 further includes an adjustment circuit 34 coupled to adjust the series pass element 32 based on various operating parameters of the fuel cell system 10. Series pass element 32 has a drain and source electrically coupled between fuel cell stack 14 and battery 24, and a field effect transistor having a gate electrically coupled to the output of regulator circuit 34 (“ FET ").

The first stage of the fuel cell system 10 includes several sensors for determining various operating parameters of the fuel cell system 10. For example, the fuel cell system 10 includes a battery charging current sensor 36 coupled to determine the battery current I _B. Furthermore, for example, the fuel cell system 10 includes a fuel cell stack current sensor 38 coupled to determine the stack current I _s. Further, for example, the fuel cell system 10 includes a battery current sensor 40 for determining the voltage V _B across the battery 24. In addition, the fuel cell system 10 may include a battery temperature sensor 42 arranged to determine the temperature of the battery 24 or the vicinity of the battery 24. Although the sensors 36-42 are shown as being discrete from the adjustment circuit 34, in some embodiments, one or more sensors 36-42 may be integrally formed as part of the adjustment circuit 34.

The first stage of the fuel cell system 10 may include a soft start circuit 15 for slowly raising the voltage during startup of the fuel cell system 10. The fuel cell system 10 may further include a quick shut-off circuit 17 for quickly turning off the power to prevent damage to the battery 24, for example when there is no load or when the load 12 does not consume power. .
(Outline of the second stage, reactant partial pressure controller)
The second stage of the fuel cell system 10 includes a reactant flow regulator such as a controller 28, an actuator 30, and a valve 18. The controller 28 receives a first voltage value V ₁ from the input side of the series pass element 32 and a second voltage value V ₂ from the output side of the series pass element 32. Based on the difference between the first voltage V ₁ and the second voltage V ₂ , the controller 28 regulates the flow of reactant to the fuel cell stack 14 via the valve 18 or other reactant flow regulating element. A control signal is supplied to the actuator 30.

Since the battery 24 covers any short-term mismatch between available reactants and consumed reactants, the reaction rate required for the fuel cell reactant supply system 16 is significantly greater than the rate of change of the electrical load. It may be late. The reaction rate required for the fuel cell reactant supply system 16 primarily affects the depth of the charge / discharge cycle of the battery 24 and the energy dissipation through the series pass element 32.
(Explanation of the first stage, series pass element adjustment)
FIG. 2 illustrates an adjustment including components for determining battery charge current error, stack current error, and battery voltage error, and generating an output to series pass element 32 in response to a large value of the determined errors. One embodiment of circuit 34 is shown.

  The adjustment circuit 34 includes a battery charging current error integrating circuit 44 for determining a battery charging current error, and a battery charging current limiting circuit 46. The battery charging current limiting circuit 46 supplies the battery charging current limit value to the inverting terminal of the battery charging current error integrating circuit 44, while the battery charging current sensor 36 supplies the battery charging current value to the non-inverting terminal. A capacitor C9 is coupled between the inverting terminal and the output terminal of the battery charging current error integrating circuit 44. The battery charging current limit error integrating circuit 44 integrates the difference between the battery charging current value and the battery charging current limit value.

  The adjustment circuit 34 includes a stack current error integrating circuit 50 for determining a stack current error, and a stack current limiting circuit 52. The stack current limit circuit 52 supplies the stack current limit value to the inverting terminal of the stack current error integrating circuit 50, while the stack current sensor 38 supplies the stack current value to the non-inverting terminal. Capacitor C8 is coupled between the inverting terminal and output terminal of stack current error integrating circuit 50. The stack current limit error integration circuit 50 integrates the difference between the stack current value and the stack current limit value. The limiting effect of the second stage on the stack current limit is indicated by the dashed arrow 53.

  The adjustment circuit 34 includes a battery voltage error integration circuit 56 and a battery voltage setting circuit 58. The battery voltage setting circuit 58 supplies the battery voltage limit value to the inverting terminal of the battery voltage error integrating circuit 56, while the battery voltage sensor 40 supplies the battery voltage value to the non-inverting terminal. Capacitor C7 is electrically coupled between the inverting terminal and output terminal of battery voltage error integrating circuit 56. The battery voltage error integration circuit 56 integrates the difference between the battery voltage value and the battery voltage set value.

  The adjustment circuit 34 may further include a temperature compensation circuit 62 that generates a compensation value using battery temperature measurement by the battery temperature detector 42. The battery voltage setting circuit 58 uses the compensation value to determine the battery voltage setting value.

  The adjustment circuit 34 further includes an OR circuit 64 for selecting a larger value among the output values of the error integrators 44, 50 and 56. The OR circuit 64 can take the form of three diodes (not shown) having cathodes coupled in common. The anode of each diode is electrically coupled to a respective one of error integrating circuits 44, 50, 56.

  The adjustment circuit 34 further includes a charge pump 66 for applying a voltage to a control terminal (eg, gate) of the series pass element 32 by a level shifter such as an inverting level shifter 68. The inversion level shifter 68 supplies a linear output value that is inverted from the input value.

  FIG. 3 shows an alternative embodiment of the first stage of the fuel cell system 10 that uses a microprocessor 70 as the conditioning circuit. This alternative embodiment and the other alternatives and embodiments described herein are substantially similar to the previous embodiment, and common operations and structures are identified by the same reference numerals. Only significant differences in operation and structure are described below.

  Microprocessor 70 is programmed or configured to perform the functions of conditioning circuit 34 (FIG. 1). For example, the microprocessor 70 can perform error integration of some or all of the battery charge current, stack current, and battery voltage values. The microprocessor 70 can store some or all of the battery charge current limit value, the stack current limit value, and / or the battery voltage limit value. The microprocessor 70 can further determine temperature compensation based on the battery temperature determined by the battery temperature detector 42. Furthermore, the microprocessor 70 can select a large value among the error values and supply an appropriate signal to the control terminal of the series pass element 32.

  FIG. 4 shows an example of a first stage operating method 100 of the fuel cell system 10 of FIGS. During operation, the method 100 repeats continuous adjustment of the operating parameters of the fuel cell system 10.

In step 102, a battery charging current sensor 36 (FIG. 1-3) determines the value of the battery charging current _{I B.} In step 104, the battery charging current error integration circuit 44 (FIG. 2) or the microprocessor 70 (FIG. 3) determines the value of the battery charging current error.

  In step 106, the stack current sensor 38 (FIGS. 1-8) determines the value of the stack current. At step 108, the stack current error integration circuit 50 (FIG. 20) or the microprocessor 70 (FIG. 2) determines the value of the stack current error.

In step 110, the battery voltage sensor 40 (FIGS. 1-3) determines the voltage V _B across the battery 24. In operation step 112, the battery temperature sensor 42 determines the temperature of the battery 24 or a space near the battery 24. In operational step 114, the temperature compensation circuit 62 (FIG. 2) or the microprocessor 70 (FIG. 3) determines a battery current limit value based on the determined battery temperature. At step 116, battery current error integration circuit 56 (FIG. 2) or microprocessor 70 (FIG. 3) determines the battery voltage error value.

  The fuel cell system 10 performs steps 102, 106, and in a different order, eg, performing step 106 before step 102, or performing step 110 before step 102 and / or step 106. 110 may be executed. Steps 102, 106, 110, 112 may be performed simultaneously or nearly simultaneously so that the sensors 36, 38, 40, 42 appear to operate in parallel. Thus, the above list of actions does not specify any particular sequence, ie order.

  In step 118, the OR circuit 64 (FIG. 2) or the OR circuit configured in the microprocessor 70 (FIG. 3) determines a larger value among the determined values. The OR circuit may be wired within the microprocessor 70 or may take the form of executable instructions. At step 120, charge pump 66 (FIG. 2) generates charge. Although not shown, the embodiment of FIG. 3 may further include a charge pump, or the microprocessor 70 may generate appropriate signal values. In step 122, the level shifter 68 (FIG. 2) or the microprocessor 70 (FIG. 3) charges the series pass element 32 (FIGS. 1-3) as an input voltage in proportion to the larger error value determined. Apply.

Thus, the first stage of the fuel cell system 10 basically operates in three modes. That is, a battery voltage limit mode, a stack current limit mode, and a battery charge current limit mode. For example, when the battery 24 is discharged, the fuel cell system 10 enters a battery charging current mode to prevent damage to the battery 24 and limits the battery charging current. When the battery 24 is recharged, the fuel cell system 10 enters a voltage limiting mode to maintain the battery's floating voltage (eg, about 75-95% of full charge) without sulfating the battery 24, Trickle charge the battery 24. When the load 12 draws more current than the fuel cell stack 14 can supply, the fuel cell system 10 enters the stack current limit mode, and there is a fourth “saturation” mode. In this mode, as load 12 draws more current, stack voltage V _S drops below battery voltage V _{B. In} this “saturation” mode, battery 24 is discharged and battery 24 is If the battery is sufficiently discharged, the battery charging current limiting mode is entered in some cases.
(Explanation of the second stage, partial pressure control of reactants)
FIG. 5A shows the second stage of the fuel cell system 10 in more detail using the voltage difference across the series pass element 32 as an operating condition.

More specifically, the controller 28 includes a first comparator 90 </ _b > A that receives the first voltage value V ₁ from the input side of the series pass element 32 and the second voltage value V ₂ from the output side of the series pass element 32. Contains. The first comparator 90A generates a processing variable ΔV corresponding to the difference between the first and second voltages V ₁ and V ₂ .

  The controller 28 further includes a second comparator 92 that receives the processing variable ΔV and the set value from the first comparator 90A. The comparator 92 compares the processing variable ΔV with the set value and generates the first control voltage CV1. The set value reflects the desired maximum operating level of the series pass element 32 and is typically between about 75% and about 95% of the saturated series pass element for the series pass element 32. A setting of 80% of the saturation value is particularly suitable and provides some kind of solution in the circuit even when the fuel cell stack 14 is operating under partial load.

Comparator 92 supplies the resulting control variable CV1 to actuator 30, which adjusts compressor or valve 18 accordingly. The valve 18 adjusts the partial pressure of the reactants to the fuel cell stack 14 that serves as the second control variable CV2 for the fuel cell system 10. As described above, the internal resistance _RS of the fuel cell stack 14 is adjusted by controlling the partial pressure of the reactant, and at the same time, the power output of the fuel cell stack 14 is adjusted. The first and second comparators 90a, 92 may be discrete components or may be implemented as a microprocessor, microcontroller, or other integrated circuit.

  The controller 28 further includes a first switch 96 that electrically couples the battery 24 in parallel with the fuel cell 14 and a second switch 98 that electrically couples the load 12 in parallel with the fuel cell stack 14 and the battery 24. Logic 94 may be included for controlling various switches.

  FIG. 6A shows an example of a second stage operating method 200 of the fuel cell system 10 of FIGS. 1 and 5A. At step 102, the battery 24 is electrically coupled in parallel with the fuel cell stack 14. At step 204, load 12 is electrically coupled with battery 24 and fuel cell stack 14. In step 206, at least one of the battery 24 and the fuel cell stack 14 supplies current to the load 12. If the fuel cell stack 14 is generating enough current to meet the demand of the load 12, the fuel cell stack 12 supplies current to the load 12. The redundant current from the fuel cell stack 14 recharges the battery 24. If the fuel cell stack 14 does not generate enough current to meet demand, the battery 24 may supply some or all of the power to the load 12.

In step 208, the second stage of the fuel cell system 10 determines the first voltage V ₁ on the input side of the series pass element 32. In step 210, the second stage of the fuel cell system 10 determines the second voltage V ₂ on the output side of the series pass element 32. The order of steps 208 and 210 is not important and can be performed in any order or even simultaneously.

In step 212, the first comparator 90A compares the difference between the first and second voltages V ₁ and V ₂ . In step 214, the difference ΔV determined by the second comparator 92 is compared with a set value. In step 216, the second stage of the fuel cell system 10 adjusts the partial pressure of at least one reactant flow to the fuel cell stack 14 via the actuator 30 and valve 18 based on the determined deviation. For example, the fuel cell system 10 can adjust the partial pressure of hydrogen, the partial pressure of an oxidant (eg, air), or the partial pressure of both hydrogen and oxygen. As described above, the internal series resistance R _S inherent in the fuel cell stack 14 is changed by changing the partial pressure of the fuel and / or oxidant to control the voltage dropping at any given stack output current. can do. By changing the partial pressure in this way, the maximum voltage effect across the series pass element 32 can be reduced.

  FIG. 5B illustrates in further detail another embodiment of the second stage of the fuel cell system 10 that utilizes battery current as an operating condition. This particular embodiment and the other particular embodiments described herein are substantially similar to the previous embodiments, and common operations and structures are identified by the same reference numerals. Only significant differences in operation and structure are described below. The embodiment shown in FIG. 5B may be implemented in the fuel cell system 10 with the adjustment circuit (FIGS. 1-4) forming the second stage, or used independently without the adjustment circuit of the first stage. May be.

  In the embodiment of FIG. 5B, the battery condition sensor takes the form of a current sensor 26b coupled to detect current to and from the battery 24. Controller 28 includes a battery charge current integrator 90. Integrator 90 may be a discrete component or may be implemented in a microprocessor or microcontroller. Integrator 90 integrates the battery charge current to determine the approximate overall charge of battery 24. The integrator 90 is supplied with an initial battery charge that is appropriate for the starting embodiment and needs to be rationalized from time to time. The resulting process variable (“PV”) is sent to the comparator 92.

Comparator 92 may be a discrete comparator or may be implemented in a microprocessor or microcontroller. The comparator 92 compares the PV with the set value and generates a first control voltage (“CV1”). The set value reflects the desired nominal battery charge at the start of operation and can typically be between about 75% and about 95% of the full battery charge. Comparator 92 supplies the resulting CV1 to actuator 30, which adjusts compressor or valve 18 accordingly. The valve 18 regulates the reactant partial pressure to the fuel cell stack, which serves as a second control variable (“CV2”) for the fuel cell system 14. As described above, by controlling the partial pressure of the reactant, the internal resistance _RS of the fuel cell stack 14 is adjusted, and at the same time, the power output of the fuel cell stack 14 is adjusted.

  The controller 28 further includes a first switch 96 that electrically couples the battery 24 in parallel with the fuel cell 14 and a second switch 98 that electrically couples the load 12 in parallel with the fuel cell stack 14 and the battery 24. Logic 94 may be included for controlling various switches.

  FIG. 6B shows an example of a second stage operating method 300 of the fuel cell system 10 of FIG. 5B. At step 302, the battery 24 is electrically coupled in parallel with the fuel cell stack 14. At step 304, sensor 26b determines the flow of current to and from battery 24. At step 306, integrator 90b integrates the battery current flow to determine the total charge of battery 24.

  At step 308, the comparator 92 also compares the integrated battery current flow with the setpoint. This set value is selected to trickle charge the battery 24 by holding the battery 24 at an appropriate floating voltage, for example to prevent damage to the battery 24 due to sulfation. A suitable range for this may be between about 75% and 95% of the desired battery charge, with about 80% of the desired nominal battery charge being particularly suitable.

  At step 310, the fuel cell system 10 adjusts the partial pressure of the fuel flow to the fuel cell stack 14 to maintain the desired battery charge. For example, the actuator 30 can adjust the partial pressure of hydrogen via one or more valves 18. Alternatively, the actuator 30 can adjust the speed of one or more compressors (not shown). At step 312, the fuel cell system 10 adjusts the partial pressure of the oxidant (eg, air) flow to the fuel cell stack to maintain the desired battery charge. Again, the fuel cell system 10 can use one or more numerical values 18 and / or one or more compressors (not shown) to adjust the oxidant partial pressure. The controller 28 may make an attempt to maintain an appropriate stoichiometric relationship between the fuel and the oxidant.

FIG. 5C shows another embodiment of the second stage of the fuel cell system 10 in more detail, utilizing the voltage V _B across the battery 24 as an operating condition. The embodiment shown in FIG. 5C may be implemented in the fuel cell system 10 with the adjustment circuit (FIGS. 1-4) forming the second stage, or used independently without the adjustment circuit of the first stage. May be.

In the embodiment of FIG. 5C, the battery condition sensor takes the form of a voltage sensor 26 c that detects the voltage V _B across the battery 24. The controller 28 takes the form of a field controller 90c. Field controllers are commonly found in automotive systems as well as other electrical systems. The field controller 90c supplies an output CV1 to the actuator 30 in order to control the partial pressure of the reactants to the fuel cell stack 14.

FIG. 6C shows a method 400 of operation of the fuel cell system 10 of FIG. 5C. In step 402, the voltage sensor 26c determines the voltage V _B across the battery 24. In step 404, the field controller 90c determines deviation from desired battery voltage of the battery voltage V _B. At step 406, the controller 28 adjusts the partial pressure of the fuel flow to the fuel cell stack 14 to maintain the desired battery voltage. In step 408, the controller 28 adjusts the partial pressure of the oxidant flow to the fuel cell stack 14 to maintain the desired battery voltage. As mentioned above, the fuel cell system 10 may use one or more valves, compressors, pumps and / or regulating means to regulate the partial pressure of the fuel and / or oxidant.

FIG. 7 shows an example of a polarization curve for the fuel cell stack 14 corresponding to the partial pressures of the five different reactants. The stack voltage V _S is shown along the vertical axis, and the stack current I _S is shown along the horizontal axis. The first curve 59 shows the polarization when the reactant partial pressure is low. Curves 61, 62, 63, and 65 show the polarization as the partial pressure of the reactants increases continuously. Dashed line 69 shows a constant nominal output voltage of 24 volts. Vertical broken lines 71, 723, 75, 77, 79 indicate stack currents corresponding to voltage outputs at the respective partial pressure curves 59, 61, 63, 65, 67.
(Embodiment of Fuel Cell System Interconnected with Battery Part / Fuel Cell Part)
FIG. 8 illustrates yet another embodiment of the fuel cell system 10 in which a portion of the battery 24 is interconnected with a portion of the fuel cell stack 14.

  Specifically, the fuel cell stack 14 can include several groups or portions 14a, 14b, ... 14n interconnected with each group or portion of the batteries 24a, 24b, ... 24n. Although shown as one battery cell 24a, 24b, ... 24n for each fuel cell set 14a, 14b, ... 14n, the fuel cell system 10 can use other ratios of battery cells and fuel cells. .

  The fuel cell system 10 can include a capacitor, such as a supercapacitor 140, electrically coupled in parallel across the load 12. The fuel cell system 10 of FIG. 8 can operate according to the methods 100 and 200 of FIGS. 4 and 6A.

Although not shown in FIG. 8, separate control elements such as valve 18, controller 28 and / or actuator 30 are connected to fuel cell sets 14a, 14b,. . . 14n can be connected to each one.
(Fuel cell system and load current, voltage, and resistance)
FIGS. 9A-9F illustrate various currents, voltages, and resistances of the fuel cell system in single-phase AC operation when the fuel cell stack is sufficiently powering the load without draining or recharging the battery. It is a series of graphs showing the relationship. The various graphs of FIGS. 9A-9F share a common horizontal time axis.

FIG. 9A is a graph 150 showing the actual stack current _IS and the average stack current _IS-AVG as a function of time. Figure 9B is a graph 152 showing the actual battery current I _B as a function of time. FIG. 9C is a graph 154 showing actual battery voltage V _B and average battery voltage V _{B -AVG} as a function of time. FIG. 9D is a graph 156 showing the actual current _IL and average load current _IL-AVG conducting the load as a function of time. FIG. 9E is a graph 158 showing the actual load resistance _RL as a function of time. FIG. 9F is a graph 160 showing the AC voltage V _ac across the load 12 as a function of time.

  FIGS. 10A-10C illustrate various currents, voltages, and currents of the fuel cell system in single-phase AC operation, where the battery supplies current to the load to cover the shortage from the fuel cell stack and then recharges the battery. It is a series of graphs showing the relationship of resistance. The various graphs of FIGS. 10A-10C share a common horizontal time axis.

Figure 10A is a graph 162 showing the stack current _{I S} as a function of time. Figure 10B is a graph 164 showing the battery current _{I B} as a function of time. Figure 10C is a graph 166 showing the load current _{I L} as a function of time. As can be seen from FIGS. 10A-10C, as the demand for load 12 increases, battery 24 supplies current to make up for the shortage from fuel cell stack 14. As the demand for load 12 decreases, fuel cell stack 14 recharges battery 24 until battery 24 returns to floating voltage.
(Fuel cell system as a component block of a composite fuel cell system)
FIG. 11 shows several fuel cell systems 10a-10f that form an electrically coupled composite fuel cell system 10g for powering the load 12 with the desired voltage and current. The fuel cell systems 10a-10f may take the form of any fuel cell system 10, such as the fuel cell system 10 shown in FIGS.

  The composite fuel cell system 10 utilizes polarization curve matching between the fuel cell stack 14 and each battery 24. One approach to achieving polarization curve matching includes the first stage adjustment scheme generally described above. Another approach involves controlling the partial pressure of one or more reactant streams based on the deviation of the voltage across battery 24 from the desired voltage across battery 24. Yet another approach involves controlling the partial pressure of the one or more reactant streams based on the deviation of the battery charge from the desired battery charge. Battery charge can be determined by integrating the flow of charge from or to the battery 24. Another approach includes phase or pulse switching adjustment or control schemes.

  As an example, each fuel cell system 10a-10f is capable of supplying a current of 50A at 24V. When the first pair of fuel cell systems 10a and 10b are electrically coupled in series, 50A is supplied at 48V. Similarly, when the second pair of fuel cell systems 10c and 10d are electrically connected in series, 50A is supplied at 48V. When these two pairs of fuel cell systems 10a, 10b, and 10c, 10d are electrically coupled in series, 100A is supplied at 48V. When the third pair of fuel cell systems 10e and 10f are electrically connected in series, 50A is supplied at 48V. When the third pair of fuel cell systems 10e and 10f are electrically connected in parallel with the first pair of fuel cell systems 10a and 10b and the second pair of fuel cell systems 10c and 10d, 150A is supplied at 48V.

FIG. 11 shows only one possible configuration. Those skilled in the art will appreciate that other configurations are possible to achieve the desired voltage and current. The composite fuel cell system 10g may include a smaller number or a larger number of fuel cell systems 10a-10f than shown in FIG. Other numbers of electrical coupling combinations of individual fuel cell systems 10 can be utilized to provide power at other desired voltages and currents. For example, one or more additional fuel cell systems (not shown) may be electrically coupled in parallel with one or more fuel cell systems 10a-10b. Additionally or additionally, one or more additional fuel cell systems (not shown) are electrically in series with any pair of illustrated fuel cell systems 10a: 10b, 10c: 10d, 10e: 10f. Can be combined. Further, the fuel cell systems 10a-10f may have different voltage and / or current ratings. The individual fuel cell systems 10a-10f can be combined to create an "n + 1" array to obtain the desired amount of redundancy and high reliability.
(Power supply system)
FIG. 11 illustrates one embodiment of a power supply system 550, which is collectively indicated at 10, including a one-dimensional array 552 of fuel cell systems, which includes a power bus 556 for supplying power to the load 12. Each of the positive and negative voltage rails 556a and 556b to be formed can be electrically coupled in series. Each diode, indicated collectively as 558, is electrically coupled between the positive and negative outputs of each fuel cell system 10. The illustrated power supply system 550 includes M + 1 fuel cell systems, indicated individually as 10 (1) -10 (M + 1), and the numbers in parentheses indicate the number of fuel cell systems 10 in the array 10. Indicates the position. The ellipse in FIG. 11 indicates that the power supply system 550 includes an additional fuel cell system (not explicitly shown) between the third fuel cell system 10 (3) and the Mth fuel cell system 10 (M). It may be included. One or more fuel cell systems (eg, 10 (M + 1)), for example, if one of the other fuel cell systems 10 (1) -10 (M) fails or the load 12 requires additional power or voltage It can function as a “redundant” fuel cell system electrically coupled in series to the power bus 556.

  The power supply system 550 may use a contactor or one or more failure switches such as a transistor 560 that can automatically shut off the respective fuel cell system 10 in the event of a defect or failure. For example, the failure-time transistor 560 may be opened upon a failure or failure of the fuel cell system 10 itself, or upon a failure or failure of the power supply system 550.

  The power supply system 550 can electrically couple each fuel cell system 10 (M + 1) to the power bus 556 manually or automatically based on a state other than the operating state of the fuel cell system 10 (M + 1) itself. One or more redundant switches such as contactors or transistors 562 may be used. For example, if another fuel cell system 10 fails, redundant transistor 562 is closed to hold redundant fuel cell system 10 (M + 1) to power bus 556 to retain power, voltage, and current to load 12. Can be combined. Further, for example, if higher output power is desired, redundant transistor 562 is closed to regulate redundant fuel cell system 10 (M + 1) to power bus 556 in order to regulate power, voltage, and current to load 12. Can be combined.

  Although manual operation is possible, the power supply system 550 may also include control logic 564 to automatically control the operation of redundant switches (eg, transistor 562).

The control logic 564 receives inputs relating to the operating state of each fuel cell system 10 (1) -10 (M + 1) (ie, “connected when unit 1 to M fails”) to one or more other fuel cell systems 10 (1). It can be received from -10 (M). For example, the control logic 564 can receive voltage, current, and / or power measurements for the fuel cell stack 14 and / or the storage battery 24 of the fuel cell system 10. Such measurements include, but are not limited to, may include stack current I _S, the stack voltage VI _S, and / or the temperature. Further, for example, the control logic 564 is a logical value relating to the operating status of various systems of the fuel cell system 10 including, but not limited to, ambient hydrogen levels, ambient oxidant levels, and reactant flow. Can receive. In this regard, US patent application Ser. No. 09 / 916,240 “Methods, Apparatus and Scheduling of Fuel Cell Systems,” filed on June 25, 2001, assigned to a common applicant, No. 130109.409).

In addition, or alternatively, control logic 564 is from other components of power supply system 550 such as voltage and current sensors coupled to determine voltage or current at various points on power bus 556. Can receive input. For example, the control logic 564 can receive a voltage measurement corresponding to the voltage across the power bus measured at the “top” of the one-dimensional array 552, whereby the control logic 564 is a measurement less than the predicted threshold. (Ie, connected when V _X <M × 24V ″), it is possible to indirectly detect a failure of one or more fuel cell systems 10. The threshold for detecting a failure condition is It may be predefined within the control logic 564 or may be set by a user or operator via a user interface such as a dedicated or general purpose computer analog or digital control, or a graphical user interface 566.

  Additionally or alternatively, the control logic 564 can receive input from the user or operator via the user interface 566, which includes operating parameters such as power, voltage, and / or current thresholds. Set and set desired parameters, such as desired power, desired voltage, or desired current nominal values, provide electrical configuration information, and / or automatic operation aspects of control logic 564 Includes a set of user controls to get over. User interface 566 may be remote from the rest of power supply system 550. The control logic 564 can be implemented with one or more of wired circuitry, firmware, microcontrollers, application specific processors, programmed general purpose processors, and / or instructions to a computer readable medium.

  When the output voltage of the fuel cell system 10 can be strictly controlled as in the operation in the first stage and / or the second stage described above, the fuel cell systems 10 can be connected in series. In this manner, any desired number of fuel cell systems 10 can be electrically coupled in series to achieve any integer multiple voltage output of individual fuel cell systems 10. For example, if each fuel cell system 10 generates 24 volts across the rails 19a, 19b, three fuel cell systems 10 (1) -10 (3) may be electrically coupled to generate 72 volts. it can. More generally, a number M of fuel cell systems 10 can be electrically coupled in series to produce a voltage M times the nominal voltage of the fuel cell system across power bus 556. In addition, the position of the redundant fuel cell system 10 (M + 1) within the one-dimensional array 552 is less important due to the series coupling.

  FIG. 12 shows a two-dimensional array 568 of the fuel cell system 10 arranged in M rows and N columns for powering the load 12 via the power bus 556. The fuel cell system 10 is individually indicated by 10 (1,1) -10 (M, N), the first number in parentheses indicates the position of the row, and the second number in parentheses indicates the fuel cell system 10 Indicates the position of the column. The ellipse in FIG. 12 indicates that the various rows and columns of the two-dimensional array 568 may include additional fuel cell systems (not explicitly shown). Diode 558, fault and redundant switches 560, 562, control logic 564, and user interface 566, respectively, have been omitted for clarity of the drawing.

Each fuel cell system 10 (1,1) -10 (M, N) can be individually coupled to a power bus 556 to provide various desired output powers. The fuel cell systems 10 (1-M, 1), 10 (1-M, 2), 10 (1-M, 3) -10 (1-M, N) in each row 1-M are electrically in series with each other. Can be combined. The fuel cell systems 10 (1, 1-N), 10 (2, 1-N), 10 (3, 1-N) -10 (M, 1-N) in each row 1-N are electrically parallel to each other. Can be combined. From FIG. 12 and this description, those skilled in the art will appreciate that the two-dimensional array 568 allows series coupling of the fuel cell system 10 to adjust the output power of the power supply system 550 by adjusting the output voltage. . Further, those skilled in the art will appreciate that the two-dimensional array 568 allows parallel coupling of the fuel cell system 10 to adjust the output power of the power supply system 550 by adjusting the output current. Further, those skilled in the art will appreciate that the two-dimensional array 568 allows the fuel cell system 10 to be connected in series and in parallel to adjust the output power of the power supply system 550 by adjusting both the output current and the output voltage. Let's be done. Thus, in the illustrated case where each fuel cell system produces 1 Kw at, for example, 24 volts and 40 amps, a maximum output power of N × NkW is possible. Further, the one-dimensional and two-dimensional array structures described herein are indicative of mutually connectable mutual positions, and the fuel cell system 10 need not necessarily be physically arranged in rows and / or columns. Those skilled in the art will understand that this is not the case.
(Example)
13-15 is a fuel cell system of the two-dimensional array 568 of FIG. 12 for generating the desired output power, eg, 4 kW, where each fuel cell system 10 is capable of generating 1 Kw at 24 volts and 40 amps. Ten different three electrical configurations are shown. Specifically, FIG. 13 shows four fuel cell systems 10 (1, 1) -10 (from the first row of two-dimensional array 568 that are electrically coupled in series to provide 4 Kw at 96 volts and 40 amps. 4 shows an embodiment using 1). FIG. 14 shows four fuel cell systems 10 (1,1) -10 (1,4) in a first row two-dimensional array 568 that are electrically coupled in parallel to provide 4 Kw at 24 volts and 160 amps. One example used is shown. FIG. 15 shows two pairs of fuel cell systems 10 (1, 1), 10 (2, 1) and 10 (1, 2), 10 (2, 2) electrically connected in series electrically in parallel. Four fuel cell systems 10 (1,1), 10 (1,2), 10 (2,1), 10 (2,2,2) in a two-dimensional array 568 that are combined to provide 4 Kw at 48 volts and 80 amps. ), An example using the above is shown. Those skilled in the art will appreciate from these teachings that other combinations and tandems of the two-dimensional array 568 fuel cell system 10 are possible.
(Operation of power supply system)
FIG. 16 illustrates a method 600 of operating the power supply system 550 according to one embodiment described with reference to FIG. This method 600 is implemented within the control logic 564 described above.

  At step 602, control logic 564 selectively activates one of the switches 560, 562 to electrically connect M fuel cell systems 10 (1) -10 (M) on power bus 566. In series. At step 604, control logic 564 determines whether there is a failure. For example, is the control logic 564 whether any one parameter of the fuel cell system 10 (1) -10 (M) is out of an acceptable range, or exceeds an acceptable threshold or falls below it? Determine whether or not. As described above, the control logic 564 can receive voltage, current and / or power measurements for the fuel cell stack 14 and / or the storage battery 24 of the fuel cell system 10. In addition or alternatively, the control logic 564 can also receive logic values relating to the operating state of various systems of the fuel cell system 10. In addition or alternatively, control logic 564 may provide other power supply system 550 features, such as voltage or current sensors coupled to determine voltages or currents at various points on power bus 556. Can receive input from components. The control logic 564 can include a comparison circuit, such as a comparator, for example, to compare the received numerical value with a specified range and / or threshold, or an instruction, where the total voltage across the power bus 556 is a specified threshold. It is ensured that it is above or within the prescribed range. Alternatively, or in addition, control logic 564 may provide individual fuels such as “1” or “0” corresponding to one or more operating states of each fuel cell system 10 (1) -10 (M). The set of logic values returned from the battery system 10 (1) -10 (M) can be relied upon.

  If there are no faults, the method 600 returns to step 604 to perform a monitor loop. If there is a fault, the control logic 564 in step 606, for example, by sending an appropriate signal to the corresponding redundant switch, for example, by applying a signal to the gate of the redundant transistor 562, the redundant fuel cell system 10 (M + 1). Are electrically coupled in series on the power bus 556. Since the fuel cell system 10 (1) -10 (M + 1) is “hot swappable”, the power supply system 550 need not be shut off.

  In operational step 608, the control logic 564 sends a faulty fuel cell system, eg, 10 (3), for example by sending a signal to the corresponding fault switch, eg, by applying a signal to the gate of the fault transistor 560. Electrically disconnected from the power bus 556. In operational step 610, the user or service technician replaces the failed fuel cell system 10 (3) in the array 552 of the power supply system 550. The replacement fuel cell system 10 serves as a redundant fuel cell system in case another fuel cell system 10 fails in some cases.

  FIG. 17 illustrates an optional step 612 that may be included in the method 600. At step 612, the additional fuel cell system 10 is electrically coupled in series with one or more fuel cell systems 10 (1) -10 (M) on the power bus 550. For example, after the failed fuel cell system 10 (3) is replaced, the replacement fuel cell system may be electrically coupled in series to increase the power output of the power supply system 550.

  FIG. 18 illustrates an optional step 614 that may be included in the method 600. At step 614, the additional fuel cell system 10 is electrically coupled in parallel with one or more fuel cell systems 10 (1) -10 (M) on the power bus 552. From this description, those skilled in the art will appreciate that the method 600 may utilize any of a variety of series and / or parallel combinations of springs 10.

  FIG. 19 illustrates a method 630 of operation of the power supply system 550 according to the additional or alternative illustrated embodiment described with reference to the two-dimensional array 568 of FIG. As such, power supply system 550 may use method 630 in addition to or instead of method 600.

At step 632, control logic 564 determines at least one of the desired power, voltage, and current output from power supply system 550. The desired value may be defined in the control logic 564, or the control logic 564 may receive the desired value (s) from the user or operator via the user interface 566. At step 634, control logic 564 provides a series and / or parallel combination of several fuel cell systems 10 (1,1) -10 (M, N) to provide the desired power, voltage and / or current. Determine the electrical configuration. At step 636, control logic 564 activates several redundant switches (only one is shown in FIG. 11) such as transistor 560, each one fuel cell system 10 (1,1) -10 (M , N) are electrically coupled to the determined electrical configuration.
(Conclusion)
In the foregoing description, any number of fuel cell systems 50 can be electrically coupled in series and / or in parallel to form a combined power supply system 550 for powering the load 12 with a desired voltage and current. It is shown.

  The fuel cell system 10 may take the form of any of the fuel cell systems described above, such as the fuel cell system 10 shown in FIG. As described above, the power supply system 550 utilizes matching of polarization curves between the fuel cell stack 14 and the respective storage batteries 24 so that the fuel cell systems can be connected in series. One approach to achieving polarization curve matching generally involves the first stage adjustment scheme described above. Another approach is to control the partial pressure of one or more reactant flows based on the deviation of the voltage across a storage element, such as a battery 24, from the desired voltage across the storage element 24. It is included. Yet another approach includes controlling the partial pressure of one or more reactant flows based on the deviation of the stored charge from the desired stored charge. The amount of stored charge can be determined by integrating the flow of charge to and from the storage battery 24. Other approaches include phase or pulse switching adjustment or control schemes. Reasons for using a series structure include cost advantages and a structure that provides maximum efficiency at full output power if the stack voltage is equal to the battery's floating voltage at that point, eg , Efficiency is 24V system and R.E. It can exceed 97% without the problem of F noise. Although the fuel cell system 10 is described as having two stages, the power supply system 550 may include one or more fuels having only a single stage, either the first stage or the second stage, depending on the embodiment. The battery system 10 may be incorporated.

  The disclosed embodiment proposes a “building block” or “component” approach to the power supply system, and a variety of power supply systems, even from a single basic type of fuel cell system 10 with few or even fewer manufacturers. 550 can be manufactured. This approach can result in low design, manufacturing, and inventory costs, and redundancy that extends the average time to failure of the resulting user finished product (ie, power supply system). This approach can further simplify maintenance or repair and reduce its cost.

  While specific embodiments of the fuel cell system and method have been described herein for purposes of illustration, various equivalents may be used without departing from the spirit and scope of the invention, as will be appreciated by those skilled in the relevant art. Correction is possible. For example, the teachings presented herein may be applied to fuel cell systems including other types of fuel cell stacks or fuel cell assemblies, not necessarily the polymer exchange membrane fuel cell assemblies generally described above. In addition or alternatively, the fuel cell system 10 may interconnect a portion of the fuel cell stack 14 with a portion of the batteries B1, B2. The fuel cell system can employ various other approaches and elements for adjusting the reactant partial pressure. The various embodiments described above can be combined to provide further embodiments.

US patent application Ser. No. 10/017470, filed Dec. 14, 2001, entitled “METHOD AND APPARATUS FOT CONTROLLING VOLTAGE FROM AFUEL CELL SYSTEM” (method and apparatus for controlling voltage from a fuel cell system). No. 130109.436), filed December 14, 2001, with the name “METHOD AND APPARATUS FOR MULTIPLE MODE CONTROL OF VOLTAGE FROM A FUEL CELL SYSTEM” (multiple voltage from fuel cell system) And US Patent Application No. 10/017462 (Attorney Docket No. 130109.442), December 14, 2001 U.S. Patent Application No. 10/017461 (Attorney Docket No. 130109.) filed on the same day and whose name is "FUEL CELL SYSTEM MULTIIPLE VOLTAGE CONTROL METHOD AND APPARATUS" (multi-stage voltage control method and apparatus for fuel cell system). 446), and US Patent Application No. _____ (Express Mail Number EV0649990705US), named “ADJUSTABLE ARRAY OF FUEL CELL SYSTEMS IN POWER SUPPLY” (adjustable array of fuel cell systems in power supply) No. 130109.449) are all incorporated herein by reference. In order to provide further embodiments of the present invention, aspects of the present invention can be modified to utilize various patent, application, and publication systems, circuits, and concepts as needed. For example, in addition or as an alternative, the fuel cell system 10 may have a battery voltage V _B , a current flow to or from the battery 24, or a battery as taught in US patent application Ser. No. 10/017470. The partial pressure of the reactant can be controlled as a function of either charge.

  These or other changes can be made in light of the above description. In general, in the following claims, the terms are not to be construed as limiting the invention to the specific embodiments disclosed herein, but include all fuel cell systems operating according to the claims. It should be interpreted. Accordingly, the invention is not limited by the disclosure, but the scope of the invention is to be determined entirely by the following claims.

FIG. 1 is a schematic diagram of a fuel cell system for powering a load, the fuel cell system adjusting a fuel cell stack, a battery, a series pass element, and a current flow through the series pass element. In order to reduce the energy dissipated by the series pass element by controlling the partial pressure of the reactants according to the illustrated Japanese embodiment of the present invention and the first stage comprising the circuit, between the ends of the series pass element. And a second stage including a controller that utilizes the voltage difference. FIG. 2 is a schematic diagram of the first stage of the fuel cell system of FIG. 1 including a conditioning circuit used with or without the second stage. FIG. 3 is an alternative embodiment of the first stage of a fuel cell system that uses a microprocessor as a regulator circuit used with or without the second stage. FIG. 4 is a flowchart of an example of a method of operating the first stage of the fuel cell system of FIGS. FIG. 5A includes a control circuit for controlling the partial pressure of the reactant based on the change in voltage across the series pass element relative to the desired value, used with or without the first stage. 2 is an electrical schematic diagram of a second stage of one fuel cell system. FIG. FIG. 5B shows the second stage electricity of the fuel cell system showing an alternative control circuit for controlling the reactant partial pressure based on the battery charge current, used with or without the first stage. FIG. FIG. 5C shows an alternative control circuit for controlling the reactant partial pressure based on battery voltage, used with or without the first stage, in the second stage of the fuel cell system. FIG. FIG. 6A is a flowchart of an example of a method of operating the second stage of the fuel cell system of FIG. 5A. FIG. 6B is a flowchart of an example of a method of operating the second stage of the fuel cell system of FIG. 5B. 6C is a flowchart of an example of an operation method of the second stage of the fuel cell system of FIG. 5C. FIG. 7 is a graphical representation of the polarization curve of an example fuel cell stack for five examples of partial pressure. FIG. 8 is a schematic diagram of an alternative embodiment of the fuel cell system of FIG. 1, wherein a portion of the fuel cell stack is interconnected to a portion of the battery. 9A-9F illustrate fuel cell system stack current, battery current, and load current, battery voltage and bus voltage, and load when the fuel cell stack is sufficiently powering the load without draining or recharging the battery. It is a series of graphs regarding resistance. FIGS. 10A-10C show the stack current, battery current, and load current for a fuel cell system, where the battery supplies load current to make up for the shortage from the fuel cell stack, and the fuel cell stack later recharges the battery. It is a series of graphs over time. FIG. 11 illustrates power to a load including several individual fuel cell systems that form a one-dimensional array of fuel cell systems that can be electrically coupled in series to power a load at a desired voltage and current. It is the schematic of the electric power supply system which supplies FIG. 12 is a schematic diagram of a power supply system including several fuel cell systems that form a two-dimensional array of fuel cell systems that can be electrically coupled in various series and parallel combinations. 13 is a schematic diagram illustrating several of the fuel cell systems of FIG. 12 electrically coupled in series to provide a desired output power at a first output voltage and a first output current. FIG. 14 is a schematic diagram illustrating several fuel cell systems of FIG. 12 electrically coupled in parallel to provide a desired output power at a second output voltage and a second output current. FIG. 15 is a schematic diagram illustrating several fuel cell systems of FIG. 12 electrically coupled in series to provide a desired output power at a third output voltage and a third output current. FIG. 16 is a flowchart of a method of operating the power supply system of FIGS. 11 and 12 according to one embodiment, including replacing a failed fuel cell system with a redundant fuel cell system. FIG. 17 is a flowchart of operational steps for incorporation into the method of FIG. FIG. 18 is a flowchart of operational steps for incorporating the method of FIG. FIG. 19 includes additional or including electrically coupling several fuel cell systems in a determined series and / or parallel combination to produce the desired power, voltage, and current output. 13 is a flow diagram of a method of operation of the power supply system of FIGS. 11 and 12, according to an alternative embodiment.

Claims (79)

A fuel cell system,
A fuel cell stack having several fuel cells;
A battery having a number of battery cells that can be electrically coupled in parallel across the fuel cell stack;
A series pass element electrically coupled between at least a portion of the fuel cell stack and a portion of the battery;
A reactant delivery system for delivering reactant to the fuel cell, comprising at least a first control element adjustable to control a partial pressure of the reactant flow to at least some of the fuel cells;
A control circuit coupled to control the at least the first control element based on at least one of the determined operating state of the battery and the determined deviation of the voltage across the series pass element; Fuel cell system provided. The adjustment circuit
A battery charge current error integrator having a first input coupled to receive a battery charge current signal and a second input coupled to receive a battery charge current limit signal;
A battery voltage error integrator having a first input coupled to receive a battery voltage signal and a second input coupled to receive a battery voltage limit signal;
The stack current error integrator according to claim 1, comprising a stack current error integrator having a first input coupled to receive a stack current signal and a second input coupled to receive a stack current limit signal. Fuel cell system. The adjustment circuit is
A charge pump,
A level shifter coupled between the charge pump and the series pass element;
The fuel cell system according to claim 1, comprising: The adjustment circuit is
2. An input side and an output side, the input side comprising an OR circuit coupled to the battery charge current error integrator, a battery voltage error integrator, and the stack current error integrator. Or 4. The fuel cell system according to 3. The series pass element comprises a field effect transistor;
The fuel cell system of claim 1, comprising a blocking diode electrically coupled between the fuel cell stack and the series pass element.   The fuel cell system according to claim 1, wherein at least a part of the battery is electrically coupled in parallel with at least a part of the fuel cell stack. The adjustment circuit is
Integrating the difference between the battery current and the battery current limit;
Integrating the difference between the battery voltage and the battery voltage limit;
Integrating the difference between the stack current and the stack current limit;
Selecting a larger value of the integrated differences;
Applying a control signal to said value in proportion to a large value of the integrated difference, and comprising a microprocessor programmed to adjust the current through said series pass element. The fuel cell system described. The adjustment circuit is
A battery charge current sensor for supplying a battery charge current signal proportional to the battery charge current;
A battery voltage sensor for supplying a battery voltage signal proportional to the battery voltage;
The fuel cell system according to claim 2, 3 or 4, further comprising: a stack current sensor that supplies a stack current signal proportional to the stack current.   The circuit of claim 1 wherein the conditioning circuit comprises any of a number of discrete integrators or microprocessors.   A voltage sensor for determining a voltage across the series pass element; and a comparator coupled to compare the determined voltage across the series pass element with a desired voltage. The fuel cell system according to claim 1, comprising:   The fuel cell system of claim 14, wherein the desired voltage corresponds to between about 75% and 95% of a saturation level for the series pass element.   The fuel cell system of claim 1, wherein the control circuit is coupled to control at least the first control element based only on at least one predetermined operating state of the battery.   The fuel cell system of claim 1, wherein the control circuit is coupled to control at least the first control element based solely on a determined deviation between the ends of the series pass element. A circuit for a fuel cell system having a fuel cell stack, a battery, and a series pass element,
Means for determining a larger value of the difference between the battery charge current and the battery charge current limit value, the difference between the battery voltage and the battery voltage limit value, and the difference between the stack current and the stack current limit value;
A series pass adjustment means for adjusting the flow of the stack current through the blocking diode in proportion to the determined large difference;
Means for controlling the partial pressure of the flow of the at least one reactant in proportion to at least one of the determined operating state of the battery and the determined voltage deviation between both ends of the series pass element; circuit. Integrating means for determining the difference between the battery charging current and the battery charging current limit value;
Integrating means for determining the difference between the battery voltage and the battery voltage limit value;
15. The circuit of claim 14, further comprising integrating means for determining a difference between the stack current and the stack current limit value.   16. The circuit according to claim 14, further comprising means for determining a voltage deviation between both ends of the series pass element. A method for operating a fuel cell system, comprising:
Supplying current at several output terminals from at least one of a fuel cell stack and a battery electrically coupled in parallel to the fuel cell stack;
In the first stage, in proportion to at least a larger value of the difference between the battery charge current and the battery charge current limit value, the difference between the battery voltage and the battery voltage limit value, and the difference between the stack current and the stack current limit value Adjusting the current through the series pass element;
Adjusting a partial pressure of a reactant flow to at least a portion of the fuel cell stack in a second stage to maintain at least one of an operating state of the battery and a desired saturation level of the series pass element; , Including methods.   The method of claim 17, wherein the first stage and the second stage are performed simultaneously. Determining a first potential on the input side of the series pass element;
Determining a second potential on the output side of the series pass element;
Determining a voltage across the series pass element from the first and second potentials;
Determining a quantity of deviation of the voltage across the series pass element from a value corresponding to the desired saturation level, and including the operating state of the battery and the desired saturation level of the series pass element. Adjusting the reactant flow partial pressure to at least a portion of the fuel cell stack to maintain at least one adjusts the reactant flow partial pressure based on the determined quantity of deviations; The method according to claim 17 or 18, comprising a step. Determining the difference between the battery charge current and the battery charge current limit value by integrating the difference between the battery charge current over time and the battery charge current limit value;
Determining the difference between the battery voltage and the battery voltage limit value by integrating the difference between the battery voltage over time and the battery voltage limit value;
The method of claim 17, 18, or 19, further comprising: determining a difference between the tack current and the stack current limit value by integrating a difference between the stack current over time and the stack current limit value. . Selecting a larger value of the difference between the battery charge current and the battery charge current limit value, the difference between the battery voltage and the battery voltage limit value, and the difference between the stack current and the stack current limit value;
Level shifting one of the selected differences;
21. The method of claim 17, 18, 19, or 20, further comprising: applying one of the level shifted selected differences to a control terminal of the series pass element. Determining a neighboring temperature of the battery;
Determining a battery voltage limit value based at least in part on the determined temperature;
The method of claim 17, 18, or 19, further comprising: integrating a time-dependent difference between the battery voltage and the determined battery voltage limit value to determine a battery voltage error.   Responds first to the determined difference between battery charge current and battery charge current limit, second to respond to determined difference between battery voltage and battery voltage limit, and third to stack current and stack current limit The method of claim 17, further comprising selectively coupling charge from a charge pump to a control terminal of the series pass element in response to the determined difference from the value.   The method of claim 17, wherein the desired saturation level is between about 75% and 95% of full saturation.   The method of claim 17, wherein the desired operating state of the battery is at least one of a current flow to or from the battery over time, a voltage across the battery, and a battery charge.   Adjusting the partial pressure of the reactant flow to at least a portion of the fuel cell stack includes adjusting the partial pressure of the fuel flow to at least a portion of the fuel cell stack; 20. A method according to claim 17 or 19, comprising adjusting the partial pressure of the oxidant stream to at least some parts.   27. The method of claim 17, 19 or 26, further comprising maintaining a pressure of at least one reactant stream while adjusting a partial pressure of the reactant stream. A fuel cell system,
A fuel cell stack having several fuel cells;
Several batteries that can be electrically coupled in parallel across the fuel cell stack. A battery having a cell;
A series pass element electrically coupled between at least a portion of the fuel cell stack and a portion of the battery;
A fuel cell system comprising: an adjustment circuit for adjusting a current through the series pass element in response to a large value of a battery charging current error, a battery voltage error, and a stack current error. The adjustment circuit is
A battery charge current error integrator having a first input coupled to receive a battery charge current signal and a second input coupled to receive a battery charge current limit signal;
A battery voltage error integrator having a first input coupled to receive a battery voltage signal and a second input coupled to receive a battery voltage limit signal;
30. A stack current error integrator having a first input coupled to receive a stack current signal and a second input coupled to receive a stack current limit signal. Fuel cell system. The adjustment circuit is
A charge pump,
A level shifter coupled between the charge pump and the series pass element;
30. The fuel cell system according to claim 28 or 29, further comprising an OR circuit. A circuit for a fuel cell system,
Means for determining a larger value of the difference between the battery charge current and the battery charge current limit value, the difference between the battery voltage and the battery voltage limit value, and the difference between the stack current and the stack current limit value;
A series pass adjustment means for adjusting the flow of the stack current through the blocking diode in proportion to the determined large difference. A method for operating a fuel cell system, comprising:
Supplying current at several output terminals from at least one of a fuel cell stack and a battery electrically coupled in parallel to the fuel cell stack;
Pass through the series pass element in proportion to at least the largest of the difference between the battery charge current and the battery charge current limit, the difference between the battery voltage and the battery voltage limit, and the difference between the stack current and the stack current limit. Adjusting the current. Selecting a larger value of the difference between the battery charge current and the battery charge current limit value, the difference between the battery voltage and the battery voltage limit value, and the difference between the stack current and the stack current limit value;
Level shifting one of the selected differences;
33. The method of claim 32, further comprising: applying one of the level shifted selected differences to a control terminal of the series pass element. A fuel cell system,
A fuel cell stack having several fuel cells;
Several batteries that can be electrically coupled in parallel across the fuel cell stack. A battery having a cell;
A reactant delivery system for delivering reactant to the fuel cell, comprising at least a first control element adjustable to control a partial pressure of the reactant flow to at least some of the fuel cells;
Coupled to receive a signal corresponding to the input and output potentials of the series pass element, and based on the received signal, a voltage across the series pass element from a desired operating voltage. A fuel cell system comprising: a control circuit configured to determine a deviation and coupled to control at least the first control element based on the determined deviation.   A voltage sensor for determining the voltage across the series pass element and a comparator coupled to compare the voltage across the opposite series pass element with a desired voltage; A fuel cell system according to claim 34, comprising:   The control circuit comprises a comparator that compares the determined voltage across the series pass element to a desired voltage corresponding to between about 75% and 95% of the saturation level of the series pass element. Item 36. The fuel cell system according to Item 34 or 35. A circuit for a fuel cell system,
Means for determining a difference between a voltage across the series passage adjustment means and a desired operating state of the series passage adjustment means;
Means for controlling the partial pressure of the flow of at least one reactant in proportion to the determined difference between the voltage across the series pass regulator and the desired operating state of the series pass regulator. Circuit. A method of operating a fuel cell system having series pass elements,
Supplying current at several output terminals from at least one of a fuel cell stack and a battery electrically coupled in parallel to the fuel cell stack;
Adjusting a partial pressure of the reactant to at least a portion of the fuel cell stack to maintain a series pass element at a desired saturation level. Determining a first potential on the input side of the series pass element;
Determining a second potential on the output side of the series pass element;
Determining a voltage across the series pass element from the first and second potentials;
Determining a quantity of deviation of the voltage across the series pass element relative to a value corresponding to the desired saturation level, and maintaining the fuel in order to maintain the series pass element at the desired saturation level. The method of claim 38, wherein adjusting a reactant flow partial pressure to at least a portion of the battery stack includes adjusting a reactant flow partial pressure based on the determined quantity of deviations. Method.   Determining a quantity of the determined voltage deviation includes determining a difference between the determined voltage and a value corresponding to a ratio of a saturation level of the series pass element, wherein the ratio is about 75. 40. The method of claim 38, wherein the method is between about 95% and about 95%. A fuel cell system for supplying power to a load,
A fuel cell stack having several fuel cells;
Several batteries that can be electrically coupled in parallel across the fuel cell stack. A battery having a cell;
A reactant delivery system for delivering reactant to the fuel cell, comprising at least a first control element adjustable to control a partial pressure of the reactant flow to at least some of the fuel cells;
The battery is coupled to receive a signal corresponding to an operating state of the battery, and is configured to determine a deviation of the operating state of the battery from a desired operating state of the battery based on the received signal. And a control circuit coupled to control at least the first control element based on the determined deviation.   A current sensor coupled to measure current flow to and from the battery and to supply the measured current flow to the control circuit as a signal corresponding to the operating state of the battery; 42. A fuel cell system according to claim 41, comprising:   42. A voltage sensor coupled to measure a voltage across the battery and supply the measured voltage to the control circuit as a signal corresponding to an operating state of the battery. Fuel cell system. A method of operating a fuel cell system for supplying power to a load, comprising:
Supplying current to a load from at least one of a fuel cell stack and a battery electrically coupled in parallel to the fuel cell stack;
Determining an operating state of the battery;
Determining a quantity of a deviation of the determined operating state of the battery from a desired operating state of the battery; and a determined deviation for at least one reactant flow to at least a portion of the fuel cell stack. Adjusting the partial pressure of the reactant flow based on the amount.   45. The method of claim 44, wherein determining the operating state of the battery includes determining a current flow to and from the battery over time.   Determining the amount of deviation of the determined operating state of the battery from the desired operating state of the battery includes: defining and specifying a desired nominal charge amount to and from the battery over time. 46. A method according to claim 44 or 45, comprising integrating the difference from the current flow.   Determining the amount of deviation of the determined operating state of the battery from the desired operating state of the battery includes: defining and specifying a desired nominal charge amount to and from the battery over time. 46. The method of claim 44 or 45, comprising integrating a difference from current flow, wherein the desired nominal charge is between about 75% and 85% of full charge of the battery.   45. The method of claim 44, wherein determining the operating state of the battery includes determining a voltage across the battery.   Determining the amount of deviation of the determined operating state of the battery from the desired operating state of the battery comprises comparing the determined battery charge to a defined desired nominal battery charge 46. The method of claim 44 or 45, comprising: A power supply system,
A power bus,
A first fuel cell system;
A second fuel cell system;
A first switch selectively operable to couple the first fuel cell system electrically in series within the power bus;
A second switch selectively operable to couple the second fuel cell system electrically in series within the power bus.   The first fuel cell system includes a first fuel cell stack and a first capacitor electrically connected in parallel to the first fuel cell stack, and the second fuel cell system includes a second fuel cell stack. 51. The power supply apparatus according to claim 50, further comprising: a second battery that is electrically coupled to the second fuel cell stack in parallel.   51. The power supply system according to claim 50, wherein the first fuel cell system and the second fuel cell system are fuel cell systems according to claim 1, 14, 28, or 39.   53. The power supply system according to claim 50 or 52, wherein the first switch is one of a contactor and a transistor. A third fuel cell system;
53. The power supply system of claim 50 or 52, further comprising a third switch selectively operable to couple the third fuel cell system electrically in series within the power bus. A third fuel cell system;
A third switch selectively operable to electrically couple the third fuel cell system in the power bus with at least one of the first fuel cell system and the second fuel cell system; The power supply system according to claim 50 or 52 further provided. The first switch is selectively operable according to the state of the first fuel cell system,
A first redundant switch that is electrically coupled in series with the first switch and is selectively operable to electrically couple the first fuel cell system to the power bus in series with the first switch; 53. The power supply system according to claim 50 or 52, wherein the first redundant switch is selectively operable according to at least an operating state of the second fuel cell system. The first switch is selectively operable according to the state of the first fuel cell system,
A first redundant switch that is electrically coupled in series with the first switch and is selectively operable to electrically couple the first fuel cell system to the power bus in series with the first switch; 53. The power supply system according to claim 50 or 52, wherein the first redundant switch is selectively operable according to at least a voltage of the second fuel cell system. The first switch is selectively operable according to the state of the first fuel cell system,
A first redundant switch that is electrically coupled in series with the first switch and is selectively operable to electrically couple the first fuel cell system to the power bus in series with the first switch; 53. The power supply system according to claim 50 or 52, wherein the first redundant switch is selectively operable according to a voltage across the power bus. The first switch is selectively operable according to the state of the first fuel cell system,
A first redundant switch that is electrically coupled in series with the first switch and is selectively operable to electrically couple the first fuel cell system to the power bus in series with the first switch; 53. The power supply system according to claim 50 or 52, wherein the first redundant switch is selectively operable according to a desired output of the power supply system. The first switch is selectively operable according to the state of the first fuel cell system,
A first redundant switch that is electrically coupled in series with the first switch and is selectively operable to electrically couple the first fuel cell system to the power bus in series with the first switch; The first redundant switch is selectively operable in response to at least one of a desired nominal power output of the power supply system, a desired nominal voltage output of the power supply system, and a desired nominal current of the power supply system. 53. A power supply system according to claim 50 or 52. A power supply system,
A power bus,
A plurality of fuel cell systems each having a fuel cell stack and a capacitor electrically coupled in parallel to the fuel cell stack, the fuel cell system being electrically connectable to a power bus;
A plurality of switches selectively operable to disconnect from the power bus, each responsive to a respective operating condition of the fuel cell system;
Selected to electrically couple each first one of the plurality of fuel cell systems to the power bus in response to a different operating state than the first one of the plurality of fuel cell systems. Power supply system comprising at least one first redundant switch that is operable in a functional manner.   Additional operation each selectively operable to electrically couple each one of the fuel cell systems to the power bus in response to an operating condition different from the operating condition of the respective one fuel cell system. The power supply system of claim 60, further comprising a number of redundant switches.   The operating condition to which the first redundant switch responds is at least one fuel cell system other than the first fuel cell system, each of which is selectively operable to electrically couple the first redundant switch to the power bus. The power supply system according to claim 60, wherein the power supply system is in an operating state.   The operating condition to which the first redundant switch responds is at least one fuel cell system other than the first fuel cell system, each of which is selectively operable to electrically couple the first redundant switch to the power bus. 61. The power supply system of claim 60, wherein the power supply system is a voltage at the output of.   Each of the fuel cell systems further includes a number of sensors for determining a set of operating parameters for the respective fuel cell system and an operation of the respective fuel cell system based on the determined set of operating parameters. 61. The power supply system of claim 60, further comprising: a processor configured to determine a state, wherein the operating condition to which the first redundant switch responds is an operating condition determined by at least one of the processors.   The operating state to which the first redundant switch responds is the power output of the power bus, the voltage across the power bus, the current output of the power bus, the desired nominal power output of the power supply system, the power supply system 61. The power supply system of claim 60, wherein the power supply system is at least one of a desired nominal voltage output of the power supply system and a desired nominal current output of the power supply system.   A controller communicatively coupled to receive a set of operating parameters from each of the plurality of fuel cell systems, further comprising a controller that determines an operating state of the fuel cell system based on the set of operating parameters. The power supply system according to claim 60, wherein the operation state to which the first redundant switch responds is the operation state determined by the controller. At least two fuel cell systems;
Means for selectively electrically connecting the at least two fuel cell systems in series.   The means for selectively electrically connecting the at least two fuel cell systems in series comprises a respective switch for each of the fuel cell systems, each switch being at least one of the other fuel cell systems. 69. The power supply system of claim 68, responsive to an operating condition. A method of operating a power supply system having at least a first and a second fuel cell system comprising:
First electrically coupling the first fuel cell system to the power bus in series;
Determining the presence of a fault condition;
Electrically coupling a second fuel cell system to the power bus in series second automatically in response to the fault condition;
Automatically disconnecting the first fuel cell system from the power bus.   Determining the presence of a fault condition includes output power, output voltage, output current, battery current, battery voltage, stack current, ambient hydrogen level, ambient oxygen level, and reactant to the first fuel cell system. 71. The method of claim 70, comprising monitoring at least one of the flows. A plurality of fuel cell systems, a first number of fuel cell systems electrically coupled in series to the power bus, and a second number of fuel cell systems electrically coupled in series to the power bus A method of operating a fuel cell system comprising:
Determining the presence of a fault condition in at least one of the first several fuel cell systems;
In response to determining the presence of the fault condition, at least one of the second several fuel cell systems is automatically configured to maintain the electrical output on the power bus of the fuel cell system. Electrically connecting to the power bus in series. Replacing at least one of the fuel cell systems having the fault condition with a replacement fuel cell system;
Electrically coupling the replacement fuel cell system to the power bus in series in response to determining the presence of the fault condition to maintain an electrical output on the power bus of the fuel cell system. 75. The method of claim 72, further comprising:   In order to maintain an electrical output on the power bus of the fuel cell system, the second several fuel cell systems are automatically connected to the power bus in response to determining the presence of the fault condition. Coupling in series with said fuel cell in proportion to a decrease associated with at least one fault condition of at least one output power, output current, and output voltage of several fuel cell systems in said first position. 74. A method according to claim 72 or 73, comprising activating a first transistor electrically coupled to the power bus. A method of operating a power supply system having a plurality of fuel cell systems that can be selectively coupled to at least some of the power buses, comprising:
Determining at least one of a desired power, a desired current, and a desired voltage for the power supply system based on a load;
Supply the determined desired power, the determined desired current, and the determined desired voltage when electrically coupled to the power bus in several series and parallel combinations Determining an electrical configuration for a number of fuel cell systems;
Automatically activating a number of switches to electrically couple the number of fuel cell systems to the power bus in the determined electrical configuration.   Automatically activating several switches to electrically couple the number of fuel cell systems to the power bus in the determined electrical configuration comprises electrically connecting at least two of the fuel cell systems. 76. The method of claim 75, further comprising closing at least one of the switches to couple in series.   Automatically activating several switches to electrically couple the number of fuel cell systems to the power bus in the determined electrical configuration comprises electrically connecting at least two of the fuel cell systems. 76. The method of claim 75, further comprising closing at least one of the switches to couple in parallel.   Automatically activating several switches to electrically couple the number of fuel cell systems to the power bus in the determined electrical configuration comprises electrically connecting at least two of the fuel cell systems. Closing at least a first one of the switches to be coupled in series and electrically coupling at least one of the fuel cell systems in parallel with at least two of the fuel cell systems coupled in series 76. The method of claim 75, further comprising closing at least a second one of the switches.   Automatically activating several switches to electrically couple the number of fuel cell systems to the power bus in the determined electrical configuration comprises electrically connecting at least two of the fuel cell systems. The switch for closing at least a first one of the switches to be coupled in parallel and electrically coupling at least one fuel cell with two of the fuel cell systems coupled in parallel 76. The method of claim 75, comprising closing at least a second one of the two.

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