Methods and Devices for Controlling a Photovoltaic Panel in a Three Phase Power Generation System

A pulse amplitude modulated current converter (“PAMCC”) for generating three phase alternating electrical current from direct electrical current, the device comprising:

• a first input terminal for receiving a positive electrical current from a direct electrical current source;
• a second input terminal for receiving a negative electrical current from the direct electrical current source;
• a main switch connected across the first input terminal and the second input terminal;
• a controller coupled to the main switch, the controller configured to control the main switch to generate a positive pulse amplitude modulated electrical current at the first input terminal and a negative pulse amplitude modulated electrical current at the second input terminal;
• a first unfolding circuit connected across the first input terminal and the second input terminal, the first unfolding circuit coupled to the processor, and an output of the first unfolding circuit connected to a first output terminal;
• a second unfolding circuit connected across the first input terminal and the second input terminal, the second unfolding circuit coupled to the processor, and an output of the third unfolding circuit connected to a second output terminal;
• and
• a third unfolding circuit connected across the first input terminal and the second input terminal, the third unfolding circuit coupled to the processor, and an output of the third unfolding circuit connected to a third output terminal;
• wherein the controller is further configured to control the operation of each unfolding circuit to generate a first phase of power on the first output terminal, a second phase of power on the second output terminal, and a third phase of power on the third output terminal.

A method for determining a scaling factor for a pulse amplitude modulated current converter (“PAMCC”), wherein the PAMCC comprises a memory and a processor couple to the memory, the processor configured to control the operation of the PAMCC, the method comprising:

• connecting a grid power supply to an output terminal of the PAMCC;
• providing a voltage from the grid power supply to the PAMCC equal to a desired nominal three phase voltage;
• connecting a source of direct current to an input terminal of the PAMCC;
• setting a first value of the scaling factor for the PAMCC to a high value;
• scaling a switch time table stored in the memory using the first value of the scaling factor to produce a three phase output from the PAMCC equal to the voltage being supplied by the grid power supply;
• decreasing the scaling factor set in the PAMCC while observing a voltage input from the source of direct current to the PAMCC until the voltage input to the PAMCC equals a desired nominal voltage;
• storing the value of the scaling factor set in the PAMCC when the voltage input to the PAMCC equals a desired nominal voltage as a first scaling factor in the memory;
• changing the value of the scaling factor set in the PAMCC such that the voltage input to the PAMCC is different from the desired nominal voltage;
• storing a second scaling factor in the memory, the second scaling factor determined by dividing the difference between the changed value of the scaling factor set in the PAMCC when the voltage input to the PAMCC is different from the desired nominal voltage and the stored first scaling factor by the difference between the PAMCC voltage at the changed scaling factor and the desired nominal voltage;
• removing the grid power supply from the PAMCC output terminal;
• connecting a variable resistive load to the PAMCC output terminal;
• changing the value of the scaling factor set in the PAMCC and a resistance of the variable resistive load such that the voltage input to the PAMCC equals the desired nominal voltage and the three phase output of the PAMCC is two volts above the desired nominal three phase voltage;
• and
• storing a third scaling factor in the memory, the third scaling factor determined by dividing the difference between the changed value of scaling factor set in the PAMCC after changing the scaling factor and resistive load and the stored first scaling factor by the difference between the three phase output of the PAMCC and the desired nominal three phase voltage.

A system for generating three phase alternating electrical current power, the system comprising:

• a plurality of photovoltaic panels each configured to output direct electrical current from output leads when exposed to light;
• a plurality of pulse amplitude modulated current converters (“PAMCCs”) each connected to the direct electrical current output leads of one of the plurality of photovoltaic panels, each of the plurality of PAMCCs comprising input terminals, first, second and third output terminals, and a controller configured to perform operations comprising outputting a first pulse amplitude modulated current pulse at a first phase from the first output terminal, outputting a second pulse amplitude modulated current pulse at a second phase from the second output terminal, and outputting a third pulse amplitude modulated current pulse at a third phase from the third output terminal,
• wherein the first output terminal of each PAMCC is electrically connected in parallel with the first output terminals of others of the plurality of PAMCCs, the second output terminal of each PAMCC is electrically connected in parallel with the second output terminals of others of the plurality of PAMCCs, and the third output terminal of each converter is electrically connected in parallel with the third output terminals of others of the plurality of PAMCCs, and
• wherein the first, second and third current pulses of at least two of the plurality of PAMCCs are out of phase with respect to the first, second and third current pulses of each other such that the current pulses of each phase of the plurality of PAMCCs are summed in the system so that a signal modulated onto the pulse output of the converters is demodulated to produce three-phase alternating current output from the system.

A method for controlling a pulse amplitude modulated current converter (“PAMCC”) connected to the direct electrical current output leads of a photovoltaic panel, the PAMCC comprising input terminals, first, second and third output terminals, and a controller configured to perform operations comprising outputting a first pulse amplitude modulated current pulse at a first phase from the first output terminal, outputting a second pulse amplitude modulated current pulse at a second phase from the second output terminal, and outputting a third pulse amplitude modulated current pulse at a third phase from the third output terminal, the method comprising:

• retrieving a stored target output voltage for the photovoltaic panel from a memory;
• determining an instant voltage output of the photovoltaic panel;
• and
• controlling the operation of the PAMCC such that the current drawn from the photovoltaic panel causes the instant voltage output of the photovoltaic panel to approach the target output voltage for the photovoltaic panel.

A method for controlling a pulse amplitude modulated current converter (“PAMCC”) connected to the direct electrical current output leads of a photovoltaic panel, the PAMCC comprising input terminals, first, second and third output terminals, and a controller configured to perform operations comprising outputting a first pulse amplitude modulated current pulse at a first phase from the first output terminal, outputting a second pulse amplitude modulated current pulse at a second phase from the second output terminal, and outputting a third pulse amplitude modulated current pulse at a third phase from the third output terminal, the method comprising:

• determining a temperature of the connected photovoltaic panel;
• determining a voltage provided from the photovoltaic panel to the PAMCC;
• determining a parameter based on the voltage and the temperature of the photovoltaic panel;
• populating a first table stored in a memory with values corresponding to a length of time for closing a first switch set, the values for the first switch set closing calculated using, at least in part, the determined parameter;
• populating a second table resident in the memory with values corresponding to a length of time for closing a second switch set, the values for the second switch set closing calculated using, at least in part, the determined parameter;
• determining a first PAMCC switch set opening time duration based on the first table, the voltage, and the parameter;
• determining a second PAMCC switch set opening time duration based on the second table, the voltage, and the parameter;
• opening the first PAMCC switch set for the determined first switch set opening time duration;
• opening the second PAMCC switch set for the determined second switch set opening time duration;
• and
• determining a new parameter based on the parameter, the voltage, and a target voltage output value for the PAMCC.

A method for controlling a pulse amplitude modulated current converter (“PAMCC”) connected to the direct electrical current output leads of a photovoltaic panel, the PAMCC comprising input terminals, first, second and third output terminals, and a controller configured to perform operations comprising outputting a first pulse amplitude modulated current pulse at a first phase from the first output terminal, outputting a second pulse amplitude modulated current pulse at a second phase from the second output terminal, and outputting a third pulse amplitude modulated current pulse at a third phase from the third output terminal, the method comprising:

• determining a temperature of the photovoltaic panel;
• determining an expected output voltage of the photovoltaic panel as a function of the temperature of the photovoltaic panel;
• determining an instant value of the output voltage of the photovoltaic panel;
• comparing the instant value of the output voltage of the photovoltaic panel to the expected value of the output voltage of the photovoltaic panel;
• and
• controlling the operation of the PAMCC such that a value of current drawn from the photovoltaic panel prevents the instant value of the output voltage from exceeding a negative difference value of the expected output voltage.

A method for controlling a pulse amplitude modulated current converter (“PAMCC”) connected to the direct electrical current output leads of a photovoltaic panel, the PAMCC comprising input terminals, first, second and third output terminals, and a controller configured to perform operations comprising outputting a first pulse amplitude modulated current pulse at a first phase from the first output terminal, outputting a second pulse amplitude modulated current pulse at a second phase from the second output terminal, and outputting a third pulse amplitude modulated current pulse at a third phase from the third output terminal, the method comprising:

• determining an initial temperature of the photovoltaic panel;
• determining an instant voltage of the photovoltaic panel;
• determining an instant current of the photovoltaic panel;
• determining a current versus voltage characteristic curve (“IV curve”) for the photovoltaic panel based at least in part on the initial temperature, the instant voltage, the instant current, and a thermal model of the photovoltaic panel;
• determining an expected voltage of the photovoltaic panel as a function of the value of the initial temperature;
• determining a minimum current value, the minimum current value corresponding to the greatest value of current drawn from the photovoltaic panel which will result in the output value of the voltage of the photovoltaic panel exceeding a negative difference value of the expected output voltage of the photovoltaic panel;
• determining a target voltage value that maximizes the power generated by the photovoltaic panel for the determined IV curve;
• controlling the operation of the PAMCC to drive the output voltage of the photovoltaic panel toward the target voltage value;
• determining a new instant current of the photovoltaic panel;
• and
• controlling the operation of the PAMCC to increase the output voltage of the photovoltaic panel if the new instant current is below the minimum current value.

A non-transitory processor-readable medium having stored thereon processor-executable instructions configured to cause a processor of a pulse amplitude modulated current converter (“PAMCC”) connected to the direct electrical current output leads of a photovoltaic panel and comprising input terminals, first, second, and third output terminals to perform operations comprising:

• determining a temperature of the connected photovoltaic panel;
• determining a voltage provided from the photovoltaic panel to the PAMCC;
• determining a parameter based on the voltage and the temperature of the photovoltaic panel;
• populating a first table stored in a memory with values corresponding to a length of time for closing a first switch set, the values for the first switch set closing calculated using, at least in part, the determined parameter;
• populating a second table resident in the memory with values corresponding to a length of time for closing a second switch set, the values for the second switch set closing calculated using, at least in part, the determined parameter;
• determining a first PAMCC switch set opening time duration based on the first table, the voltage, and the parameter;
• determining a second PAMCC switch set opening time duration based on the second table, the voltage, and the parameter;
• opening the first PAMCC switch set for the determined first switch set opening time duration;
• opening the second PAMCC switch set for the determined second switch set opening time duration;
• and
• determining a new parameter based on the parameter, the voltage, and a target voltage output value for the PAMCC.