Photovoltaic module
A photovoltaic module includes a solar cell module including multiple solar cells, and first and second conductive lines connected respectively to first and second solar cells among the solar cells, and a junction box attached to the solar cell module. The junction box includes a power conversion unit including a capacitor unit located between the first and second conductive lines, a converter unit to change the level of a DC voltage at opposite ends of the capacitor unit and to output the DC voltage, and a controller to control the converter unit. When shading occurs in some of the solar cells, the power conversion unit supplies a second current, the level of which is lower than the level of a first current supplied before shading occurs, whereby the possibility of generation of a hot spot may be reduced despite the absence of bypass diodes when shading occurs.
1. A photovoltaic module comprising:
a solar cell module including a plurality of solar cells, a first conductive line connected to a first solar cell among the plurality of solar cells, and a second conductive line connected to a second solar cell among the plurality of solar cells; and
a power conversion unit including a capacitor unit located between the first conductive line and the second conductive line,
wherein, when shading occurs in some of the plurality of solar cells, the power conversion unit selects a second current, a level of which is lower than a level of a first current that was selected before the shading occurs, without bypass for at least one of the first conductive line and the second conductive line,
wherein the power conversion unit further includes:
an input voltage detector to detect an input voltage at opposite ends of the capacitor unit; and
a controller configured to select the first current, and
wherein, when a voltage variation rate of the input voltage detected by the input voltage detector is a predetermined value or more, the controller determines that the shading occurs, and selects the second current.
2. The photovoltaic module according to claim 1 , wherein the power conversion unit further includes:
an input current detector to detect an input current flowing to the capacitor unit, and
wherein the controller is configured to determine whether or not the shading occurs in some of the plurality of solar cells based on the input current detected by the input current detector, and when determining the occurrence of the shading, to perform a control operation to select the second current, the level of which is lower than the level of the first current that was selected before the shading occurs.
3. The photovoltaic module according to claim 1 , wherein, when the shading occurs, the controller controls the solar cell module so as to output a second voltage, a level of which is higher than a level of a first voltage that was output from the solar cell module before the shading occurs.
4. The photovoltaic module according to claim 1 , wherein, when the shading occurs, the controller performs a control operation to prevent generation of a hot spot in the solar cell module.
5. The photovoltaic module according is claim 1 , wherein the power conversion unit further includes a converter unit to change a level of a DC voltage at the opposite ends of the capacitor unit and to output the level-changed DC voltage.
6. The photovoltaic module according to claim 1 , wherein the power conversion unit further includes:
a converter unit to change a level of a DC voltage at the opposite ends of the capacitor unit and to output the level-changed DC voltage; and
an inverter unit to convert the level-changed DC voltage into an AC voltage and to output the AC voltage, and
wherein the controller controls the converter unit and the inverter unit.
7. The photovoltaic module according to claim 5 , wherein, when the shading occurs in the solar cell module, the controller performs a control operation to calculate a plurality of maximum power points with respect to a range of DC voltages supplied from the solar cell module in which the shading occurs, to determine a maximum value of the calculated maximum power points to be a maximum power point, and to select the second current corresponding to the maximum power point.
8. The photovoltaic module according to claim 7 , wherein the controller an inflection point of a voltage-power curve within the range of DC voltages, and determines the calculated inflection point to be the maximum power point.
9. The photovoltaic module according to claim 6 , wherein, when the shading occurs in the solar cell module, the controller performs a control operation to calculate a plurality of maximum power points with respect to a range of DC voltages supplied from the solar cell module in which the shading occurs, to determine a maximum value of the calculated maximum power points to be a maximum power point, and to select the second current corresponding to the maximum power point.
10. The photovoltaic module according to claim 9 , wherein the controller calculates an inflection point of a voltage-power curve within the range of DC voltages, and determines the calculated inflection point to be the maximum power point.
11. The photovoltaic module according to claim 1 , wherein the solar cell module further includes:
a first sealing member and a second sealing member formed respectively on a lower surface and an upper surface of the plurality of solar cells;
a back substrate formed on a lower surface of the first sealing member; and
a front substrate formed on an upper surface of the second sealing member.
12. The photovoltaic module according to claim 1 , wherein the solar cell module further includes a bus ribbon connected to an end of a solar cell string, which is formed by interconnecting some of the plurality of solar cells in a line, and
wherein each of the first conductive line and the second conductive line is connected to an end of the solar cell string that is not connected to the bus ribbon, extends to the back surface of the solar cell module through an opening formed in the solar cell module, and is connected to each end of the capacitor unit disposed on the back surface of the solar cell module.
13. The photovoltaic module according to claim 1 , wherein, when the shading occurs, the controller controls the solar cell module so as to output second power, which is less than first power that was output from the solar cell module before the shading occurs.
14. The photovoltaic module according to claim 13 , wherein, when shading occurs in some of the plurality of solar cells, the controller performs a control operation to cause a temperature of the solar cell module to be reduced from a time when the second power is supplied.
15. A photovoltaic module comprising:
a solar cell module including a plurality of solar cells, a first conductive line connected to a first solar cell among the plurality of solar cells, and a second conductive line connected to a second solar cell among the plurality of solar cells; and
a power conversion unit, which includes a capacitor unit located between the first conductive line and the second conductive line, a converter unit to change a level of a DC voltage at opposite ends of the capacitor unit and to output the level-changed DC voltage, and a controller to control the converter unit,
wherein, when shading occurs in some of the plurality of solar cells, the power conversion unit selects a second current, a level of which is lower than a level of a first current that was selected before the shading occurs,
wherein the power conversion unit further includes:
an input voltage detector to detect an input voltage at opposite ends of the capacitor unit; and
the controller configured to select the first current, and
wherein when a voltage variation rate of the input voltage detected by the input voltage detector is a predetermined value or more, the controller determines that the shading occurs, and selects the second current.
16. The photovoltaic module according to claim 15 , wherein the power conversion unit further includes:
an input current detector to detect an input current flowing to the capacitor unit, and
wherein the controller determines whether or not shading occurs in some of the plurality of solar cells based on the input current detected by the input current detector, and when determining the occurrence of the shading, performs a control operation to select the second current, the level of which is lower than the level of the first current that was selected before the shading occurs.
17. A photovoltaic module comprising:
a solar cell module including a plurality of solar cells, a first conductive line connected to a first solar cell among the plurality of solar cells, and a second conductive line connected to a second solar cell among the plurality of solar cells; and
a power conversion unit, which includes a capacitor unit located between the first conductive line and the second conductive line, a converter unit to change a level of a DC voltage at opposite ends of the capacitor unit and to output the level-changed DC voltage, an inverter unit to convert the level-changed DC voltage into an AC voltage and to output the AC voltage, and a controller to control the converter unit and the inverter unit,
wherein, when shading occurs in some of the plurality of solar cells, the power conversion unit selects second current, a level of which is lower than a level of first current that was selected before the shading occurs,
wherein the power conversion unit further includes:
an input voltage detector to detect an input voltage at opposite ends of the capacitor unit; and
the controller configured to select the first current, and
wherein, when a voltage variation rate of the input voltage detected by the input voltage detector is a predetermined value or more, the controller determines that the shading occurs, and selects the second current.
18. The photovoltaic module according to claim 17 , wherein the power conversion unit further includes:
an input current detector to detect an input current flowing to the capacitor unit, and
wherein the controller determines whether or not shading occurs in some of the plurality of solar cells based on the input current detected by the input current detector, and when determining the occurrence of the shading, performs a control operation to select the second current, the level of which is lower than the level of the first current that was selected before the shading occurs.