GB2534596A - A voltage waveform generator - Google Patents

A voltage waveform generator Download PDF

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Publication number
GB2534596A
GB2534596A GB1501470.7A GB201501470A GB2534596A GB 2534596 A GB2534596 A GB 2534596A GB 201501470 A GB201501470 A GB 201501470A GB 2534596 A GB2534596 A GB 2534596A
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United Kingdom
Prior art keywords
output terminal
fuel cells
voltage waveform
voltage
controller
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GB1501470.7A
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GB201501470D0 (en
Inventor
Elliott Zachary
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Intelligent Energy Ltd
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Intelligent Energy Ltd
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Priority to GB1501470.7A priority Critical patent/GB2534596A/en
Publication of GB201501470D0 publication Critical patent/GB201501470D0/en
Publication of GB2534596A publication Critical patent/GB2534596A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/501—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode sinusoidal output voltages being obtained by the combination of several pulse-voltages having different amplitude and width
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0438—Pressure; Ambient pressure; Flow
    • H01M8/04388—Pressure; Ambient pressure; Flow of anode reactants at the inlet or inside the fuel cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0438—Pressure; Ambient pressure; Flow
    • H01M8/04395—Pressure; Ambient pressure; Flow of cathode reactants at the inlet or inside the fuel cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04544—Voltage
    • H01M8/04559—Voltage of fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04574—Current
    • H01M8/04589—Current of fuel cell stacks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
    • H01M2250/10—Fuel cells in stationary systems, e.g. emergency power source in plant
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/30—The power source being a fuel cell
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Abstract

A voltage waveform generator comprises a first output terminal 102, a second output terminal 104, and a plurality of fuel cells 106a-d. Each fuel cell is configured to provide a DC output voltage. The voltage waveform generator also includes a switching module 112 connected to the first output terminal, the second output terminal and the plurality of fuel cells, and a controller 114. The controller is configured to control the switching module in order to selectively connect one or more of the plurality of fuel cells to the first output terminal and the second output terminal in order to provide an output signal with a time-varying voltage waveform between the first output terminal and the second output terminal. The fuel cells may be proton exchange membrane (PEM) fuel cells.

Description

A Voltage Waveform Generator The present disclosure relates to voltage waveform generators, and in particular to voltage waveform generators that comprise a plurality of fuel cells.
According to a first aspect of the invention, there is provided a voltage waveform generator comprising: a first output terminal; a second output terminal; a plurality of fuel cells, each fuel cell configured to provide a DC output voltage; a switching module connected to the first output terminal, the second output terminal and the plurality of fuel cells; and a controller; wherein the controller is configured to control the switching module in order to selectively connect one or more of the plurality of fuel cells to the first output terminal and the second output terminal in order to provide an output signal with a time-varying voltage waveform between the first output terminal and the second output terminal.
The time-varying voltage waveform may comprise a sinusoidal waveform, or an AC 20 waveform.
The controller may be configured to selectively connect two or more of the plurality of fuel cells in series or parallel with each other between the first output terminal and the second output terminal.
The controller may be configured to control the number of fuel cells that are in series with each other between the first output terminal and the second output terminal in order to set a desired current and / or voltage level of the output signal. The controller may be configured to control the number of fuel cells that are in parallel with each other between the first output terminal and the second output terminal in order to set a desired current and / or voltage level of the output signal.
The controller may be configured to: connect two or more of the plurality of fuel cells in parallel for providing the time-varying waveform when its intended instantaneous voltage level is below a threshold level; connect the two or more of the plurality of fuel cells in series for providing the time-varying waveform when its intended instantaneous voltage level is above a threshold level.
The controller may be configured to selectively disconnect one or more of the plurality of fuel cells from the first output terminal and the second output terminal.
A first subset of the plurality of fuel cells may be configured to provide a positive voltage across the first output terminal and the second output terminal. A second subset of the plurality of fuel cells may be configured to provide a negative voltage across the first output terminal and the second output terminal.
The controller may be configured to control the switching module such that: the plurality of fuel cells are connectable between the first output terminal and the second output terminal in a first polarity in order to provide a positive voltage across the first output terminal and the second output terminal; and the plurality of fuel cells are connectable between the first output terminal and the second output terminal in a second polarity, which is opposite to the first polarity, in order to provide a negative voltage across the first output terminal and the second output terminal.
The controller may be configured to control one or more of the plurality of fuel cells in order to provide the output signal with the time-varying voltage waveform. The controller may be configured to control an amount of fuel or oxygen supplied to one or more of the plurality of fuel cells such that the one or more fuel cells provide a desired output voltage. The controller may be configured to control the amount of fuel or oxygen supplied to the one or more of the plurality of fuel cells such that the one or more fuel cells provide either full power or zero power.
The controller may be configured to provide a fuel cell control signal for controlling a fuel supply or an oxygen supply to one or more of the plurality of fuel cells, wherein the fuel cell control signal has a duty cycle such that the one or more fuel cells provide a DC output voltage that corresponds to at least part of the desired time-varying voltage waveform.
The time-varying voltage waveform may comprise at least 8 discrete voltage levels. The plurality of fuel cells may comprises at least 3, 4, 5, 8 or 10 fuel cells.
The voltage waveform generator of claim 1 may include a fuel cell stack that comprises the plurality of fuel cells. The plurality of fuel cells may be accessible / engagable at positions within the stack.
The voltage waveform generator may comprise a planar fuel cell array that comprises the plurality of fuel cells. The plurality of fuel cells may be accessible / engagable at positions within the planar fuel cell array.
The controller may be configured to receive a sensor input signal that provides information associated with a system that uses the output signal. The controller may be configured to control the switching module and / or the plurality of fuel cells in accordance with the received sensor input signal.
According to a further aspect, there is provided a method of generating a time-varying voltage waveform, the method comprising: selectively connecting one or more of a plurality of fuel cells to a first output terminal and a second output terminal in order to provide an output signal with a time-varying voltage waveform between the first output terminal and the second output terminal.
There may be provided a computer program, which when run on a computer, causes the computer to configure any apparatus, including a circuit, voltage waveform generator, controller, switching matrix, or device disclosed herein or perform any method disclosed herein. The computer program may be a software implementation, and the computer may be considered as any appropriate hardware, including a digital signal processor, a microcontroller, and an implementation in read only memory (ROM), erasable programmable read only memory (EPROM) or electronically erasable programmable read only memory (EEPROM), as non-limiting examples. The software may be an assembly program.
The computer program may be provided on a computer readable medium, which may be a physical computer readable medium such as a disc or a memory device, or may be embodied as a transient signal. Such a transient signal may be a network download, including an internet download.
Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 shows a voltage waveform generator, and Figure 2 shows an example of an output signal that can be generated by the voltage waveform generator of figure 1.
Examples disclosed herein relate to a voltage waveform generator that comprises a plurality of fuel cells and a switching matrix. Each of the fuel cells can provide a DC (direct current) output voltage, which the switching matrix can sequentially and selectively connect to a first output terminal and a second output terminal in order to provide an output signal with a time-varying voltage waveform, such as a sinusoidal, AC or sawtooth waveform. The fuel cells can be selectively connected in series or parallel in order to provide the desired output voltage waveform.
Figure 1 shows a voltage waveform generator 100. The waveform generator 100 comprises a first output terminal 102 and a second output terminal 104, which will be used to provide an output signal with a time-varying voltage waveform. The voltage waveform generator 100 also includes a plurality of fuel cells 106a, 106b, 106c, 106d. In this example, four fuel cells are shown, although it will be appreciated that fewer or more fuel cells could be used, in accordance with the requirements of a specific application. The fuel cells may be proton exchange membrane (PEM) fuel cells. Each fuel cell 106a, 106b, 106c, 106d can provide a DC output voltage, in this example between a first fuel cell output terminal 108 and a second fuel cell output terminal 110. One of the first fuel cell output terminal 108 and the second fuel cell output terminal 110 may be a reference terminal, such as a ground terminal.
The voltage waveform generator 100 also includes a switching matrix 112 that is connected to the first output terminal 102, the second output terminal 104 and the plurality of fuel cells 106a, 106b, 106c, 106d. The switching matrix is an example of a switching module. In this example the switching matrix 112 is connected to the first fuel cell output terminal 108 and the second fuel cell output terminal 110 of each of the plurality of fuel cells 106a, 106b, 106c, 106d.
Figure 1 also shows a controller 114. The controller 114 is configured to control the switching matrix 112 in order to sequentially / selectively connect one or more of the plurality of fuel cells 106a, 106b, 106c, 106d to the first output terminal 102 and the second output terminal 104 in order to provide an output signal between the first output terminal 102 and the second output terminal 104, wherein the output signal is a time-varying voltage waveform. The time-varying voltage waveform may be a sinusoidal waveform (that may or may not pass through zero), a combination of multiple sinusoidal waveforms, an alternating current (AC) waveform, which may be single phase or 3-phase signalling, or a sawtooth waveform, as non-limiting examples.
This control is illustrated in figure 1 by the controller 114 providing a switching control signal 116 to the switching matrix 112. The switching control signal 116 can set the state of the switches within the switching matrix 112 such that, over time, the individual DC output voltages of the fuel cells 106a, 106b, 106c, 106d are combined in such a way that the output signal at the first and second output terminals 102, 104 is a desired time-varying waveform. That is, the way in which the fuel cells 106a, 106b, 106c, 106d are connected to the first and second output terminals 102, 104 is changed over time. The controller 114 may have access to a data file that contains information that characterises the desired time-varying waveform -for example, frequency, amplitude, waveform shape, etc. The information may be hard-coded such that the controller 114 does not necessarily require any input during operation in order to control the switching matrix 112. The information may be used by the controller 114 to determine present and future instantaneous values for the voltage and / or current of the output signal so that the switching matrix 112 can be controlled accordingly.
The time-varying waveform can be considered as a synthesized time-varying waveform inasmuch as it is made up of a discrete number of DC levels, depending upon how the plurality of fuel cells 106a, 106b, 106c, 106d are connected through the switching matrix 112. The plurality of fuel cells 106a, 106b, 106c, 106d may comprise at least 3, 4, 5, 8 or 10 fuel cells The time-varying waveform comprises at least 3, 4, 5, 8 or 10 discrete voltage levels.
The controller 114 can selectively connect two or more of the plurality of fuel cells 106a, 106b, 106c, 106d in series or parallel with each other between the first output terminal 102 and the second output terminal 104. This can involve controlling the number of fuel cells 106a, 106b, 106c, 106d that are in series with each other between the first output terminal 102 and the second output terminal 104. Additionally or alternatively, this can also involve controlling the number of fuel cells 106a, 106b, 106c, 106d that are in parallel with each other between the first output terminal 102 and the second output terminal 104. In this way, the current and / or voltage level of the output signal can be set. It will be appreciated that connecting fuel cells in series can increase the voltage level of the output signal, and that connecting fuel cells in parallel can increase the current level of the output signal.
In some examples, the controller 114 can selectively connect two or more of the plurality of fuel cells 106a, 106b, 106c, 106d in parallel with each other for providing the time-varying voltage waveform when its desired instantaneous voltage level is below a threshold level. Also, the controller 114 can selectively connect the two or more of the plurality of fuel cells in series for providing the sinusoidal waveform when its desired instantaneous voltage level is above a threshold level. In this way, the voltage and current levels of the time-varying waveform can be set in accordance with the desired instantaneous voltage level of the time-varying waveform. In an example where the voltage waveform generator is used to provide power to a motor, the controller 114 can use an expected current consumption of the motor to set how many fuel cells 106a, 106b, 106c, 106d are connected in parallel, and therefore appropriately control the current level of the time-varying waveform. Such an expected current consumption may relate to whether or not the motor is starting up and therefore requires more current, or whether or not the motor has already been started up and therefore requires less current. This functionality may be particularly beneficial for load devices that have non-linear behaviour.
The expected current consumption is an example of expected-use data, which can be used by the controller to control the voltage waveform generator 100. The controller 114 can, in some examples, modify any determined present and future instantaneous values for the voltage and / or current of the output signal in accordance with the expected-use data.
The controller 114 can control the switching matrix 112 in order to selectively disconnect one or more of the plurality of fuel cells 106a, 106b, 106c, 106d from the first output terminal 102 and the second output terminal 104. That is, the controller 114 can operate the voltage waveform generator 100 such that not all of the plurality of fuel cells 106a, 106b, 106c, 106d are used at the same time. This can advantageously enable an efficient system to be provided. The controller 114 can selectively disconnect a fuel cell 106a, 106b, 106c, 106d in accordance with desired characteristics of the time-varying waveform, such as current, voltage or power. This may involve comparing the output characteristics of each of the plurality of fuel cells 106a, 106b, 106c, 106d with the desired characteristics of the time-varying waveform in order to determine which, if any, of the fuel cells to disconnect.
In examples that provide an AC time-varying waveform, a first subset of the plurality of fuel cells 106a, 106b, 106c, 106d can provide a positive voltage across the first output terminal 102 and the second output terminal 104, and a second, different, subset of the plurality of fuel cells 106a, 106b, 106c, 106d can provide a negative voltage. Having subsets of the fuel cells that are designated as either providing a positive or negative component of the AC signal can simplify the implementation of the switching matrix 112 because fewer switching combinations are required.
In other examples that provide an AC time-varying waveform, the controller 114 can control the switching matrix such that the plurality of fuel cells 106a, 106b, 106c, 106d are connectable between the first output terminal 102 and the second output terminal 104 in a first polarity in order to provide a positive voltage. When a negative voltage of the AC waveform is required, the controller 114 can control the switching matrix 112 in order to connect the plurality of fuel cells 106a, 106b, 106c, 106d between the first output terminal 102 and the second output terminal 104 in a second polarity, which is opposite to the first polarity. In this way fewer fuel cells may be required to achieve an AC waveform with a to given accuracy / resolution.
The plurality of fuel cells 106a, 106b, 106c, 106d may be provided by one or more fuel cell stacks. The plurality of fuel cells may be accessible / engagable at positions within the one or more fuel cell stacks. For example, a single stack may have multiple take-off points, and the fuel cells in the stack between a first pair of take-off points may be isolated or isolatable from fuel cells in the stack between a second, different, pair of take-off points.
Alternatively or additionally, the plurality of fuel cells 106a, 106b, 106c, 106d may be provided by one or more planar fuel cell arrays. Again, the plurality of fuel cells may be accessible / engagable at positions within the one or more planar fuel cell arrays.
In some examples, the controller 114 can be used to control one or more of the fuel cells 106a, 106b, 106c, 106d in order to provide the time-varying waveform at the first output terminal 102 and the second output terminal 104. Such control is illustrated in figure 1 by the controller 114 providing optional fuel cell control signalling 118 to the fuel cells 106a, 106b, 106c, 106d. The controller 114 can control an amount of fuel or oxygen that is supplied to a fuel cell such that it provides a desired output voltage. For example, the amount of fuel or oxygen supplied can be controlled such that an associated fuel cell either provides full power or zero power. Advantageously, the controller 114 may cause a fuel supply to a disconnected fuel cell to be temporarily stopped whilst the fuel cell is not providing a voltage to the first and second output terminals 102, 104. This can advantageously enable an efficient system to be provided because fuel is not used by fuel cells that are not essential to providing an output signal with the required characteristics.
The fuel cell control signalling 118 for controlling fuel or oxygen supplied to a fuel cell can be set with a duty cycle such that the fuel cell provides a DC output voltage that corresponds to at least part of the desired time-varying waveform at the first and second output terminals 102, 104.
Alternatively or additionally, the switching matrix can be controlled such that the individual fuel cells 106a, 106b, 106c, 106d can be considered as being connected to the first and second output terminals 102, 104 over a period of time with a fuel cell connection profile that defines a duty cycle. When all of the fuel cells are connected to the output terminals 102, 104 in accordance with their respective duty cycles, the net effect is a time-varying output voltage signal with a desired time-varying profile. The controller 114 can control the switching matrix 112 such that the frequency of the fuel cell connection profiles can be set so as to achieve a desired result with a load that is connected to the first and second output terminals 102, 104; for example, to control the speed of a motor.
In some examples, one or more transformers (not shown) can be used to increase the voltage level of the output signal provided at the first and second output terminals 102, 104. A transformer can be provided at the output of the switching matrix 112 in order to increase the voltage of the time-varying waveform. Alternatively, or additionally, a transformer can be associated with each of the fuel cells 106a, 106b, 106c, 106d in order to increase the voltage of the individual DC voltages before they are combined to provide the time-varying waveform.
In some examples, the controller 114 can receive a sensor input signal (not shown). The sensor input signal can provide information associated with a system that uses the time-varying signal that is output by the voltage waveform generator 100. For example, the sensor input signal may be representative of an operating parameter of a motor that is connected to the voltage waveform generator 100 as a load. The controller 114 can then control the switching matrix 112 and I or the fuel cells 106a, 106b, 106c, 106d in accordance with the received sensor input signal. For example, the number of fuel cells that are connected in parallel, and therefore the current level of the time-varying waveform, can be set in accordance with the measured operating conditions of the load.
In some examples, the switching matrix 112 may be provided on a single integrated circuit (IC), for example as a transistor array. In other examples, at least some of the functionality of the switching matrix 112 may be distributed such that switches are associated with each fuel cell 106a, 106b, 106c, 106d. For example, switches for reversing the polarity of the DC voltage provided between the first fuel cell output terminal 108 and the second fuel cell output terminal 110 of a fuel cell may be individually associated with each fuel cell.
It will be appreciated that any components that are described or illustrated herein as being coupled or connected could be directly or indirectly coupled or connected. That is, one or more components could be located between two components that are said to be coupled or connected whilst still enabling the required functionality to be achieved.
Figure 2 shows an example of an output signal that can be generated by the voltage waveform generator of figure 1. In this example the output signal is a sinusoidal time-varying voltage waveform 202. As can be seen, the sinusoidal time-varying voltage waveform 202 has seven discrete DC voltage levels.

Claims (23)

  1. Claims 1. A voltage waveform generator comprising: a first output terminal; a second output terminal; a plurality of fuel cells, each fuel cell configured to provide a DC output voltage; a switching module connected to the first output terminal, the second output terminal and the plurality of fuel cells; and a controller; wherein the controller is configured to control the switching module in order to selectively connect one or more of the plurality of fuel cells to the first output terminal and the second output terminal in order to provide an output signal with a time-varying voltage waveform between the first output terminal and the second output terminal.
  2. 2. The voltage waveform generator of claim 1, wherein the time-varying voltage waveform comprises a sinusoidal waveform.
  3. 3. The voltage waveform generator of claim 1, wherein the time-varying voltage waveform comprises an AC waveform.
  4. 4. The voltage waveform generator of claim 1, wherein the controller is configured to selectively connect two or more of the plurality of fuel cells in series or parallel with each other between the first output terminal and the second output terminal.
  5. 5. The voltage waveform generator of claim 4, wherein the controller is configured to control the number of fuel cells that are in series with each other between the first output terminal and the second output terminal in order to set a desired current and / or voltage level of the output signal.
  6. 6. The voltage waveform generator of claim 4, wherein the controller is configured to control the number of fuel cells that are in parallel with each other between the first output terminal and the second output terminal in order to set a desired current and / or voltage level of the output signal.
  7. 7. The voltage waveform generator of claim 1, wherein the controller is configured to: connect two or more of the plurality of fuel cells in parallel for providing the time-varying waveform when its intended instantaneous voltage level is below a threshold level; connect the two or more of the plurality of fuel cells in series for providing the time-varying waveform when its intended instantaneous voltage level is above a threshold level.
  8. 8. The voltage waveform generator of claim 1, wherein the controller is configured to selectively disconnect one or more of the plurality of fuel cells from the first output terminal and the second output terminal.
  9. 9. The voltage waveform generator of claim 1, wherein a first subset of the plurality of fuel cells are configured to provide a positive voltage across the first output terminal and the second output terminal, and a second subset of the plurality of fuel cells are configured to provide a negative voltage across the first output terminal and the second output terminal.
  10. 10. The voltage waveform generator of claim 1, wherein the controller is configured to control the switching module such that: the plurality of fuel cells are connectable between the first output terminal and the second output terminal in a first polarity in order to provide a positive voltage across the first output terminal and the second output terminal; and the plurality of fuel cells are connectable between the first output terminal and the second output terminal in a second polarity, which is opposite to the first polarity, in order to provide a negative voltage across the first output terminal and the second output terminal.
  11. 11. The voltage waveform generator of claim 1, wherein the controller is configured to control one or more of the plurality of fuel cells in order to provide the output signal with the time-varying voltage waveform.
  12. 12. The voltage waveform generator of claim 1, wherein the controller is configured to control an amount of fuel or oxygen supplied to one or more of the plurality of fuel cells such that the one or more fuel cells provide a desired output voltage.
  13. 13. The voltage waveform generator of claim 12, wherein the controller is configured to control the amount of fuel or oxygen supplied to the one or more of the plurality of fuel cells such that the one or more fuel cells provide either full power or zero power.
  14. 14. The voltage waveform generator of claim 12, wherein the controller is configured to provide a fuel cell control signal for controlling a fuel supply or an oxygen supply to one or more of the plurality of fuel cells, wherein the fuel cell control signal has a duty cycle such that the one or more fuel cells provide a DC output voltage that corresponds to at least part of the desired time-varying voltage waveform.
  15. 15. The voltage wavefomi generator of claim 1, wherein the time-varying voltage waveform comprises at least 8 discrete voltage levels.
  16. 16. The voltage waveform generator of claim 1, wherein the plurality of fuel cells comprises at least 3, 4, 5, 8 or 10 fuel cells.
  17. 17. The voltage waveform generator of claim 1, comprising a fuel cell stack that comprises the plurality of fuel cells, wherein the plurality of fuel cells are accessible / engagable at positions within the stack.
  18. 18. The voltage waveform generator of claim 1, comprising a planar fuel cell array that comprises the plurality of fuel cells, wherein the plurality of fuel cells are accessible / engagable at positions within the planar fuel cell array.
  19. 19. The voltage waveform generator of claim 1, wherein the controller is configured to receive a sensor input signal that provides information associated with a system that uses the output signal, and wherein the controller is configured to control the switching module and / or the plurality of fuel cells in accordance with the received sensor input signal.
  20. 20. A method of generating a time-varying voltage waveform, the method comprising: selectively connecting one or more of a plurality of fuel cells to a first output terminal and a second output terminal in order to provide an output signal with a time-varying voltage waveform between the first output terminal and the second output terminal.
  21. 21. A computer program, which when run on a computer, causes the computer to configure the voltage waveform generator of claim 1, or perform the method of claim 20.
  22. 22. A voltage waveform generator substantially as herein described, and as illustrated in the accompanying drawings.
  23. 23. A method substantially as herein described, and as illustrated in the accompanying drawings.
GB1501470.7A 2015-01-29 2015-01-29 A voltage waveform generator Withdrawn GB2534596A (en)

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Publication number Priority date Publication date Assignee Title
DE102021123774A1 (en) 2021-09-14 2023-03-16 Stack Hydrogen Solutions Gmbh CONNECTION AND FUEL CELL DEVICE FOR EFFICIENT CONNECTION OF FUEL CELLS AND MOTOR VEHICLES

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US6198178B1 (en) * 1999-12-21 2001-03-06 International Power Systems, Inc. Step wave power converter
US20050127853A1 (en) * 2003-12-12 2005-06-16 Gui-Jia Su Multi-level dc bus inverter for providing sinusoidal and pwm electrical machine voltages
US7808125B1 (en) * 2006-07-31 2010-10-05 Sustainable Energy Technologies Scheme for operation of step wave power converter
US20140117770A1 (en) * 2012-10-25 2014-05-01 Mcmaster University Power converter

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6198178B1 (en) * 1999-12-21 2001-03-06 International Power Systems, Inc. Step wave power converter
US20050127853A1 (en) * 2003-12-12 2005-06-16 Gui-Jia Su Multi-level dc bus inverter for providing sinusoidal and pwm electrical machine voltages
US7808125B1 (en) * 2006-07-31 2010-10-05 Sustainable Energy Technologies Scheme for operation of step wave power converter
US20140117770A1 (en) * 2012-10-25 2014-05-01 Mcmaster University Power converter

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102021123774A1 (en) 2021-09-14 2023-03-16 Stack Hydrogen Solutions Gmbh CONNECTION AND FUEL CELL DEVICE FOR EFFICIENT CONNECTION OF FUEL CELLS AND MOTOR VEHICLES

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