Reducing risk of reverse bias in partially-shaded solar modules
A controller for a solar power generation system comprising a plurality of photovoltaic cells, the controller comprising: a meter instrument configured for determining an electrical parameter representative of an open circuit voltage of at least one photovoltaic cell of the plurality of photovoltaic cells; and at least one control unit configured for: calculating a limit voltage based on the open circuit voltage; and performing maximum power point tracking of the plurality of photovoltaic cells, between the limit voltage and the open circuit voltage.
1 . A controller for a solar power generation system, the controller comprising:
a meter instrument configured for determining an electrical parameter representative of an open circuit voltage of at least one photovoltaic cell of a plurality of photovoltaic cells, wherein the electrical parameter representative is based on voltage values and current values measured under a set of operating conditions using the meter instrument, wherein the electrical parameter representative includes at least one of an IV curve or a PV curve based on the voltage values and the current values measured under the set of operating conditions using the meter instrument; and
at least one control unit configured for:
calculating a limit voltage by multiplying the open circuit voltage by a predetermined ratio of a maximum power point (MPP) voltage to the open circuit voltage, wherein the open circuit voltage is a maximum voltage value of the voltage values measured when a current value of the current values measured is zero, wherein the MPP voltage is a point on at least one of the IV curve or the PV curve where the voltage values and the current values measured are maximized; and
determining an operating voltage of the plurality of photovoltaic cells by performing maximum power point tracking (MPPT) of the plurality of photovoltaic cells, between the limit voltage and the open circuit voltage,
wherein the at least one control unit is configured to select the MPP voltage as the operating voltage of the plurality of photovoltaic cells when the MPP voltage is greater than or equal to the limit voltage,
wherein the at least one control unit is configured to select the limit voltage as the operating voltage of the plurality of photovoltaic cells when the MPP voltage is less than the limit voltage.
2 . The controller of claim 1 , wherein the at least one control unit is configured for performing the MPPT based on a perturb and observe, P&O, method.
3 . The controller of claim 1 , wherein the limit voltage is calculated to be in a range of 80% to 110% of the ratio of the predetermined MPP voltage to the open circuit voltage.
4 . The controller of claim 1 , wherein the predetermined ratio of the MPP voltage to the open circuit voltage is in a range of 0.700-0.850.
5 . The controller of claim 4 , wherein the limit voltage is calculated as circa 0.750-0.800 of the open circuit voltage.
6 . The controller of claim 1 , wherein the MPPT is iterated over a plurality of iterations.
7 . The controller of claim 1 , wherein the photovoltaic cells comprise tandem cells.
8 . The controller of claim 1 , wherein the photovoltaic cells comprise the photovoltaic cells comprise, crystalline silicon (CIGS), Perovskite or Cadmium telluride cells.
9 . The controller of claim 1 , wherein the controller is implemented digitally.
10 . A solar power generation system comprising:
a plurality of photovoltaic cells; and
a controller, wherein the controller comprises:
a meter instrument configured for determining an electrical parameter representative of an open circuit voltage of at least one photovoltaic cell of the plurality of photovoltaic cells, wherein the electrical parameter representative is based on voltage values and current values measured under a set of operating conditions using the meter instrument, wherein the electrical parameter representative includes at least one of an IV curve or a PV curve based on the voltage values and the current values measured under the set of operating conditions using the meter instrument; and
at least one control unit configured for:
calculating a limit voltage by multiplying the open circuit voltage by a predetermined ratio of a maximum power point (MPP) voltage to the open circuit voltage, wherein the open circuit voltage is a maximum voltage value of the voltage values measured when a current value of the current values measured is zero, wherein the MPP voltage is a point on at least one of the IV curve or the PV curve where the voltage values and the current values measured are maximized; and
determining an operating voltage of the plurality of photovoltaic cells by performing maximum power point tracking (MPPT) of the plurality of photovoltaic cells, between the limit voltage and the open circuit voltage,
wherein the at least one control unit is configured to select the MPP voltage as the operating voltage of the plurality of photovoltaic cells when the MPP voltage is greater than or equal to the limit voltage,
wherein the at least one control unit is configured to select the limit voltage as the operating voltage of the plurality of photovoltaic cells when the MPP voltage is less than the limit voltage.
11 . A method of controlling a solar power generation system comprising a plurality of photovoltaic cells, the method comprising:
determining an electrical parameter representative of an open circuit voltage of at least one photovoltaic cell of the plurality of photovoltaic cells, wherein the electrical parameter representative is based on voltage values and current values measured under a set of operating conditions, wherein the electrical parameter representative includes at least one of an IV curve or a PV curve based on the voltage values and the current values measured under the set of operating conditions;
calculating a limit voltage by multiplying the open circuit voltage by a predetermined ratio of a maximum power point (MPP) voltage to the open circuit voltage, wherein the open circuit voltage is a maximum voltage value of the voltage values measured when a current value of the current values measured is zero, wherein the MPP voltage is a point on at least one of the IV curve or the PV curve where the voltage values and the current values measured are maximized;
determining an operating voltage of the plurality of photovoltaic cells by performing maximum power point tracking (MPPT) of the plurality of photovoltaic cells, between the limit voltage and the open circuit voltage,
wherein the at least one control unit is configured to select the MPP voltage as the operating voltage of the plurality of photovoltaic cells when the MPP voltage is greater than or equal to the limit voltage,
wherein the at least one control unit is configured to select the limit voltage as the operating voltage of the plurality of photovoltaic cells when the MPP voltage is less than the limit voltage.
12 . The method of claim 11 , wherein performing the MPPT comprises a perturb and observe (P&O) method.
13 . The method of claim 11 , wherein the limit voltage is calculated to be in a range of 80% to 110% of the ratio of the predetermined MPP voltage to the open circuit voltage.
14 . The method of claim 11 , wherein the predetermined ratio of the MPP voltage to the open circuit voltage is in a range of 0.700-0.850.
15 . The method of claim 14 , wherein the limit voltage is calculated as circa 0.750-0.800 of the open circuit voltage.
16 . The method of claim 11 , wherein the MPPT is iterated over a plurality of iterations.
17 . The method of claim 11 , wherein the photovoltaic cells comprise tandem cells.
18 . The method of claim 11 , wherein the photovoltaic cells comprise crystalline silicon (CIGS), Perovskite or Cadmium telluride cells.