Patent Publication Number: US-9906024-B2

Title: Power management between sources and load

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/IB2014/059712, filed on Mar. 13, 2014, which claims the benefit of U.S. Provisional Patent Application No. 61/804,305, filed on Mar. 22, 2013. These applications are hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a device for coupling sources to a load. The invention further relates to a system, to a method, to a computer program product and to a medium. 
     Examples of such a device are power conversion devices, and examples of such a system are sources and loads and parts thereof. 
     BACKGROUND OF THE INVENTION 
     US 2012/0173031 A1 discloses a real time power point calibration system. To determine, as disclosed in its abstract, operating points of a photovoltaic array, an amount of power supplied by an alternate power source is adjusted. Thereto, as shown in  FIG. 3  and as discussed in paragraph 0084, an indication of a current or a voltage at the photovoltaic array is used to determine whether an output of the photovoltaic array has reached a target current or voltage. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved device. It is a further object of the invention to provide a system, an improved method, a computer program product and a medium. 
     According to a first aspect, a device is provided for coupling sources to a load, the device comprising 
     a first converter for converting a first input signal originating from a first source into a first output signal, the first converter comprising a control input for receiving a control signal, a control value of the control signal defining a first parameter of the first output signal, 
     a circuit for receiving the first output signal and for receiving a second output signal originating from a second source or from a second converter coupled to the second source and for providing a power signal destined for the load, the second source comprising a solar panel, and 
     a controller for in response to a detection of a change in a second parameter of the first input or output signal adapting the control value of the control signal. 
     A first converter converts a first input signal originating from a first source such as for example a battery or a mains supply into a first output signal. The first converter has a control input for receiving a control signal. A control value of the control signal defines a first parameter of the first output signal. A circuit receives the first output signal and receives either a second output signal originating from a second source or receives a second output signal from a second converter coupled to the second source and provides a power signal to the load. The second source comprises a solar panel. 
     The device further comprises a controller for adapting the control value of the control signal in response to a detection of a change in a second parameter of the first input or output signal. In other words, contrary to the system in US 2012/0173031 A1 that detects a current or a voltage at the second source (the photovoltaic array) to determine whether an output of the second source has reached a target current or voltage, the improved device detects a change in a second parameter of the first input or output signal, at the input or the output of the first converter. In response to a detection, the control value of the control signal is adapted. 
     As a result, an improved device has been created, that, compared to the system in US 2012/0173031 A1, no longer needs two disadvantageous sensors at the output of the second source (the photovoltaic array) and no longer needs to concentrate on the second source and no longer needs any calibration, but that concentrates on the first input or output signal. By concentrating on the first converter instead of concentrating on the second source, the complexity is reduced much. These are all great advantages. 
     The circuit may receive the second output signal from the second source, that may comprise the second converter or not, or from the second converter coupled to the second source. Such a circuit may for example comprise two diodes or two resistors for combining the two output signals into the power signal. Each output signal is to be supplied to one side of its diode/resistor, with the other sides of the diodes/resistors being coupled to each other for providing the power signal. Other kinds of circuits are not to be excluded. 
     US 2012/0173031 A1 discloses in paragraphs 0036 and 0064 that indications of currents and voltages at the output of the first converter and at the output of the circuit may be used as well. However, these indications are only used for supporting calculations and calibrations performed in response to photovoltaic sensor results. These indications are not used for adapting the control value of the control signal in response to detections of changes in these currents and voltages. 
     A second source comprising a solar panel is also known as and/or comprises a photovoltaic array and can be any kind of solar-dependent-generator. 
     An embodiment of the device is defined by the change in the second parameter of the first input or output signal comprising in a first situation an increase of this second parameter and an adaptation of the control value of the control signal then defining the first parameter of the first output signal to be decreased, and the change in the second parameter of the first input or output signal comprising in a second situation a decrease of this second parameter and the adaptation of the control value of the control signal then defining the first parameter of the first output signal to be increased. When the second parameter of the first input or output signal is increased (decreased), the control value of the control signal should define the first parameter of the first output signal to be decreased (increased). So, when the second parameter of the first input or output signal is increased (decreased), the amount of power delivered by the first converter should be decreased (increased). Preferably, by adapting the control value of the control signal, the amount of power supplied via the first converter is minimized. 
     An embodiment of the device is defined by the adaptation of the control value of the control signal defining the first parameter of the first output signal to be increased in any situation when the second parameter of the first input or output signal is smaller than a threshold value. When the second parameter of the first input or output signal is smaller than a threshold value, the control value of the control signal should define the first parameter of the first output signal to be increased. So, when the second parameter of the first input or output signal is too low/too small, the power delivered via the first converter should be increased. 
     An embodiment of the device is defined by the first input or output signal comprising a first input or output current signal and the second parameter of the first input or output signal comprising a root mean square value of the first input or output current signal, the control signal comprising a control voltage signal and the control value of the control signal comprising an amplitude of the control voltage signal, and the first output signal comprising a first output voltage signal and the first parameter of the first output signal comprising an amplitude of the first output voltage signal. Preferably, by adapting the first amplitude of the control voltage signal, the amount of power supplied via the first converter is minimized. The power signal is also known as grid signal. Other kinds of signals, parameters and values are not to be excluded. 
     An embodiment of the device is defined by further comprising 
     a memory for storing the second parameter of the first input or output signal. By storing (a value of) an old, earlier second parameter, by detecting (a value of) a new, present second parameter and by comparing them, the change in (the value of) the second parameter can be detected. The memory may form part of the controller or not. 
     An embodiment of the device is defined by further comprising 
     a monitor for monitoring the first input or output signal and/or the second parameter of the first input or output signal. By monitoring the first input or output signal and/or the second parameter of the first input or output signal, (the values of) the second parameters can be stored/detected. The monitor may form part of the controller or not. 
     An embodiment of the device is defined by further comprising 
     the second converter. Such a device can be coupled directly to a second source that itself does not need to comprise the second converter. 
     An embodiment of the device is defined by the first converter comprising an AC-DC-converter and the first source comprising a mains supply. Preferably, an alternating-current-to-direct-current-converter is used to convert the first input signal into the first output signal. However, other kinds of converters are not to be excluded. For example, for a first source in the form of a battery, a direct-current-to-direct-current-converter might be required. 
     An embodiment of the device is defined by the second converter comprising a DC-DC-converter for converting a second input signal originating from the second source into the second output signal. Preferably, a direct-current-to-direct-current-converter is used to convert the second input signal into the second output signal. Usually, a second source in the form comprising a solar panel or a photovoltaic array or another kind of solar-dependent-generator will produce a direct-current-signal. However, other kinds of converters are not to be excluded. For example, for a second source that generates an alternating-current-signal, an alternating-current-to-direct-current-converter might be required. 
     An embodiment of the device is defined by the controller operating independently from the second output signal and/or from the second input signal. Contrary to the system in US 2012/0173031 A1 that detects currents and voltages at the output of the second source (the photovoltaic array) and that detects incoming light entering the second source and that fully depends on these individual signals, the improved device should preferably operate relatively independently from the second output signal and from the second input signal and only use the first input or output signal as a basis for decisions. 
     An embodiment of the device is defined by the controller adapting the control value of the control signal once per time-interval. Preferably, either the change in the second parameter of the first input or output signal is detected once per time-interval and in response the control value of the control signal is adapted, or the change in the second parameter of the first input or output signal is detected more often and in response the control value of the control signal is adapted once per time-interval. The time-interval may be fixed or flexible. 
     According to a second aspect, a system is provided comprising the device as defined above and further comprising the second converter and/or the second source and/or the load. 
     According to a third aspect, a method is provided for a device for coupling sources to a load, the device comprising a first converter for converting a first input signal originating from a first source into a first output signal, the first converter comprising a control input for receiving a control signal, a control value of the control signal defining a first parameter of the first output signal, and the device comprising a circuit for receiving the first output signal and for receiving a second output signal originating from a second source or from a second converter coupled to the second source and for providing a power signal destined for the load, the second source comprising a solar panel, the method comprising a step of 
     adapting the control value of the control signal in response to a detection of a change in a second parameter of the first input or output signal. 
     According to a fourth aspect, a computer program product is provided for, when run on a computer, performing the step of the method as defined above. 
     According to a fifth aspect, a medium is provided for storing and comprising the computer program product as defined above. 
     A basic idea is that a detection of a change in a second parameter of a first input or output signal should be used for adapting a control value of a control signal destined for a first converter coupled to a first source. 
     A problem to provide an improved device has been solved. A further advantage is that the device is more robust and more efficient and low-cost. 
     These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  shows an embodiment of a device, and 
         FIG. 2  shows a flow chart. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In the  FIG. 1 , an embodiment of a device  20  is shown. The device  20  comprises a first converter  21  having inputs coupled to a first source  11  such as a mains supply for receiving a first input signal originating from the first source  11  and having outputs coupled to first inputs of a circuit  23  for providing a first output signal. The first converter  21  comprises a control input for receiving a control signal. A control value of the control signal defines a first parameter of the first output signal. The circuit  23  has second inputs coupled to outputs of a second converter  22  for receiving a second output signal originating from the second source  12 . Inputs of the second source  12  are coupled to a second source  12  comprising a solar panel for receiving a second input signal from the second source  12 . 
     Alternatively, the second converter  22  may be left out or may form part of the second source  12 , in which case the second inputs of the circuit  23  will be coupled to the second source  12  more directly. The circuit  23  comprises for example two diodes, with their anodes being coupled to the outputs of the converters  21 ,  22  and with their cathodes being coupled to each other. Alternatively, the circuit  23  may comprise two resistors each one replacing one of the diodes etc. The circuit  23  combines the output signals from the converters  21 ,  22  and provides a power signal destined for the load  13 . In the circuit  23 , further circuitry may be present. 
     The device  20  comprises a controller  24  for in response to a detection of a change in a second parameter of the first input or output signal adapting the control value of the control signal. As also explained at the hand of the flow chart shown in the  FIG. 2 , in a first situation, the change in the second parameter of the first input or output signal may comprise an increase of this second parameter and an adaptation of the control value of the control signal may then define the first parameter of the first output signal to be decreased. In a second situation, the change in the second parameter of the first input or output signal may comprise a decrease of this second parameter and the adaptation of the control value of the control signal may then define the first parameter of the first output signal to be increased. When the second parameter of the first input or output signal is increased (decreased), the control value of the control signal should define the first parameter of the first output signal to be decreased (increased). So, when the second parameter of the first input or output signal is increased (decreased), the amount of power delivered by the first converter  21  should be decreased (increased). Said adapting of the control value of the control signal is such that the amount of power supplied via the first converter  21  is minimized. 
     In any situation, the adaptation of the control value of the control signal may define the first parameter of the first output signal to be increased when the second parameter of the first input or output signal is smaller than a threshold value. When the second parameter of the first input or output signal is too low/too small, the power delivered via the first converter  21  should be increased. 
     As an example only, the first input or output signal may comprise a first input or output current signal and the second parameter of the first input or output signal may comprise a root mean square value of the first input or output current signal. The control signal may comprise a control voltage signal and the control value of the control signal may comprise an amplitude of the control voltage signal. The first output signal may comprise a first output voltage signal and the first parameter of the first output signal may comprise an amplitude of the first output voltage signal. 
     The controller  24  may further comprise a memory  26  for storing the second parameter of the first input or output signal and/or may further comprise a monitor  27  for monitoring the first input or output signal and/or the second parameter of the first input or output signal. The device  20  may further comprise an interface  25  for providing the control signal to the control input of the first converter  21  and/or may further comprise a processor  28 . Alternatively, one or more of the memory  26  and the monitor  27  and the interface  25  may form part of the processor  28 , or the processor  28  may form part of one or more of the memory  26  and the monitor  27  and the interface  25 . The monitor  27  may for example comprise a current detector and/or a voltage detector and may for example comprise an analog-to-digital-converter. The interface  25  may for example comprise a digital-to-analog-converter. Alternatively, one or more of the memory  26  and the monitor  27  and the interface  25  may be located outside the controller  24 . 
     The first converter  21  may for example comprise an AC-DC-converter and the second converter  22  may for example comprise a DC-DC-converter. The controller  24  in the device  20  preferably operates independently from the second output signal from the second converter  22  and preferably adapts the control value of the control signal once per time-interval. A control input of an AC-DC-converter may for example be a feedback pin also known as FB-pin. The controller  24  adapts the control value of the control signal in response to a detection of a change in a second parameter of the first input signal or in response to a detection of a change in a second parameter of the first output signal or both. 
     In the  FIG. 2 , a flow chart is shown, wherein the following blocks have the following meaning:
     Block  31 : Start, go to block  32 .   Block  32 : Set a default control value of the control signal, go to block  33 .   Block  33 : Measure the second parameter of the first input or output signal and store it as an old second parameter value, go to block  34 .   Block  34 : Increase the control value of the control signal by a first step value, go to block  35 .   Block  35 : Measure the second parameter of the first input or output signal and store it as a new second parameter value, go to block  36 .   Block  36 : Is the new second parameter value smaller than the old second parameter value and is the new second parameter value larger than a threshold value? If yes, give the old second parameter value a value of the new second parameter value and go to block  34 . If no, go to block  37 .   Block  37 : Is the new second parameter value larger than the old second parameter value and is the new second parameter value larger than the threshold value? If yes, give the old second parameter value a value of the new second parameter value and go to block  38 . If no, give the old second parameter value a value of the new second parameter value and go to block  34 .   Block  38 : Decrease the control value of the control signal by a second step value, go to block  35 .   

     So, after a start (block  31 ), a default control value of the control signal is set (block  32 ). The second parameter of the first input or output signal is measured and stored as an old second parameter value (block  33 ). Then the control value of the control signal is increased by a first step value (block  34 ), and the second parameter of the first input or output signal is measured again and stored as a new second parameter value (block  35 ). The new second parameter value is compared with the old second parameter value and with a threshold value (block  36 ), and if smaller and larger respectively, the old second parameter value is given a value of the new second parameter value and the control value of the control signal is increased again by the first step value (block  34 ) etc. If not smaller and larger respectively, the new second parameter value is compared with the old second parameter value and with the threshold value again (block  37 ), and if larger and larger respectively, the old second parameter value is given a value of the new second parameter value and the control value of the control signal is decreased by a second step value (block  38 ) and the second parameter of the first input or output signal is measured again and stored as a new second parameter value (block  35 ) etc. If not larger and larger respectively, the old second parameter value is given a value of the new second parameter value and the control value of the control signal is increased by the first step value (block  34 ) etc. 
     Many alternatives will be possible to this flow chart. For example, the block  36  may be used to only determine whether the new second parameter value is larger than the threshold value. If no, the old second parameter value is given a value of the new second parameter value, and the block  34  is performed again, if yes the block  37  is performed. The block  37  may then be used to determine whether the new second parameter value is larger than the old second parameter value, if yes, the old second parameter value is given a value of the new second parameter value, and the block  38  is performed, if no, the old second parameter value is given a value of the new second parameter value, and the block  34  is performed again etc. The first and second step values may be equal or different and may each have a fixed size or a flexible size. 
     The device  20  does not maximize an amount of power supplied via the second converter  22  to the load  13  directly, but maximizes the amount of power supplied via the second converter  22  to the load  13  indirectly, by minimizing an amount of power supplied via the first converter  21  to the load  13 . The amount of power supplied via the first converter  21  is minimized by regulating the first converter  21  in response to detections of the first input or output signal entering or leaving the first converter  21 . 
     Summarizing, devices  20  for coupling sources  11 ,  12  to loads  13  comprise first converters  21  for converting first input signals from first sources  11  into first output signals. The first converters  21  comprise control inputs for receiving control signals. Control values of the control signals define first parameters of the first output signals. Circuits  23  in the devices  20  receive the first output signals and receive second output signals originating from second sources  12  or from second converters  22  coupled to the second sources  12  and provide power signals to the loads  13 . The second sources  12  comprise solar panels. Controllers  24  adapt the control values of the control signals in response to detections of changes in second parameters of the first input or output signal. The controllers  24  may operate independently from the second output signals and from second input signals. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.