Patent WO-2012069044-A2 (WO)
Inventor: GOETZ MARCO
Filed: 2011-11-23
Abstract: The invention relates to a photovoltaic generator (40) having a switching system (1) for protecting photovoltaic modules (2), wherein the switching system (1) is connected to an inverter (41) by means of at least one generator string line (6), a generator junction box (42), and a direct-current network (22) in that sequence and the photovoltaic modules (2) are each connected to the generator string line (6) of the photovoltaic generator (40) by means of a module electronics unit (3), wherein the switching system (1) has a module electronics unit (3) associated with the photovoltaic module (2) for each photovoltaic module (2) and a control center (14, 141), which is associated with all the photovoltaic modules (2) and which has a signal connection to the individual module electronics units (3), wherein at least the following assemblies are provided for the module electronics unit (3): - an active switching element (8), which is connected in a short-circuit line (17) between the first position string connection (4) and a second negative string connection (5) of the generator string line (6) and - a module electronics control unit (90), which is connected between the module connections (12, 13) for the photovoltaic module (2) and which comprises - a supply unit (29), which is fed from the photovoltaic module (2) at the first positive module connection (12, 21) and continuously supplies at least the control electronics unit (9) with current, wherein in the switch-off state (39) the supply voltage for the switch-off electronics unit (9) is caused by the generation of a higher supply voltage from the low module residual voltage (UR) by means of the boost chopper (68), - a control electronics unit (9), which has at least one control logic unit (92) and a switch-off controller (94), and - a stationary switch-off control device comprising a switch-off controller (94) and the switching element (8) for the module voltage (U pv ) at the positive string connection (4), in such a way that, in the switch-off state (39), a differential amplifier (53) forms the difference (ΔU ρν ) of the module voltage (U pv  ) at the positive string connection (4) as a control variable with a firmly programmed desired value (U s ) of the module residual voltage (U R ) of a desired voltage source (55) as a reference variable and amplifies said difference to a control deviation (ΔU pv ) on the control line (19), which influences the conductivity of the active switching element (8) by means of the control input (99) of the active switching element (8) in such a way that the module voltage (U pv ) at the positive string connection (4) is reduced in the event of a positive control deviation (ΔU ρν ) and increased in the event of a negative control deviation (ΔU ρν ) regardless of the module short-circuit current (l K ), - at least one measuring electronics unit (10), which is wired to the control electronics unit (9) so as to permit signal exchange and is connected to the supply unit (29) so as to permit energy supply, and - a communication electronics unit (11, 111), which is connected to the control electronics unit (9) and to the control center (14, 141) located outside the module electronics unit (3) by means of a communication segment (23) so as to permit signal exchange and wired to the supply unit (29) so as to permit energy supply, wherein for the module electronics unit (3) having the controllable switching element (8) at least two operating states can be separately set for each individual module electronics unit (3) depending on signals of the measuring electronics unit (10) and the communication electronics unit (11, 111): a) either an activation state (38), caused by the opening of the active switching element (8), with connection of the photovoltaic module (2) and current transfer into the generator string line (6), b) or a switch-off state (39), caused by the closing of the active switching element (8), with short circuit between the string connections (4, 5) at controlled module short-circuit voltage, wherein the control electronics unit (9) has a control connection to the active switching element (8) in such a way that the activation state (38) and switch-off state (39) of the switching element (8) can be separately set for each individual module electronics unit (3) by means of the control logic unit (92), wherein after the end of the switch-off state (39) the active activation state (38) of each individual module electronics unit (3) is enabled by the continuously supplying supply unit (29) by means of the active control logic unit (92) by evaluating the signals of the measuring electronics unit (10) and/or the communication electronics unit (11, 111) by means of the control center (14, 141).