CIRCUIT ARRANGEMENTS FOR REDUCING POTENTIAL-INDUCED DEGRADATION IN PHOTOVOLTAIC MODULES

Abstract

The invention relates to circuit arrangements for reducing potential-induced degradation in photovoltaic modules of a photovoltaic generator, said circuit arrangements comprising an insulation monitoring device for a temporally continuous insulation monitoring of the photovoltaic generator. Furthermore, the invention relates to a photovoltaic system comprising a circuit arrangement for reducing potential-induced degradation in photovoltaic modules, said photovoltaic system comprising a photovoltaic generator and an insulation monitoring device for a temporally continuous insulation monitoring of the photovoltaic generator. Different solutions are proposed which enable reducing potential-induced degradation while simultaneously continuously monitoring insulations. The circuit arrangements according to the invention rest upon an insulation monitoring device interacting with measures based circuit technology for influencing potentials in a photovoltaic module.

Claims

1. A circuit arrangement (4) for reducing potential-induced degradation in photovoltaic modules (8) of a photovoltaic generator (6), comprising an insulation monitoring device (12) for a temporally continuous insulation monitoring of the photovoltaic generator (6), characterized in that the insulation monitoring device (12) is connected symmetrically between a positive pole (L+) of the photovoltaic generator (6) and ground and between a negative pole (L−) of the photovoltaic generator (6) and ground and that the circuit arrangement (4) comprises an impulse coupling circuit (14), which is symmetrically connected between the positive pole (L+) of the photovoltaic generator (6) and ground and between the negative pole (L−) of the photovoltaic generator (6) and ground for coupling positive voltage impulses.

2. The circuit arrangement according to claim 1, characterized in that the impulse coupling circuit (14) is realized as a capacitive coupling circuit.

3. The circuit arrangement according to claim 1, characterized in that the impulse coupling circuit (14) is integrated into the insulation monitoring device (12).

4. A circuit arrangement (24) for reducing potential-induced degradation in photovoltaic modules (8) of a photovoltaic generator (6), comprising an insulation monitoring device (26) for a temporally continuous insulation monitoring of the photovoltaic generator (6), characterized in that the insulation monitoring device (26) is connected asymmetrically between either a positive pole (L+) or a negative pole (L−) of the photovoltaic generator (6) and ground and that a low-impedance voltage source (28) is connected serially to the coupling of the insulation monitoring device (26) and serially to the photovoltaic modules (8) of the photovoltaic generator (6).

5. A circuit arrangement (34) for reducing potential-induced degradation in photovoltaic modules (8) of a photovoltaic generator (6), comprising an insulation monitoring device (36) for a temporally continuous insulation monitoring of the photovoltaic generator (6), characterized in that the insulation monitoring device (36) is connected asymmetrically between either a positive pole (L+) or a negative pole (L−) of the photovoltaic generator (6) and ground and that a low-impedance voltage source (38) is connected serially to the insulation monitoring device (36) to ground.

6. The circuit arrangement according to claim 5, characterized in that the low-impedance voltage source (38) is integrated into the insulation monitoring device (36) as an offset voltage source for measuring the voltage of the insulation monitoring device (36).

7. A circuit arrangement (44) for reducing potential-induced degradation in photovoltaic modules (8) of a photovoltaic generator (6), comprising an insulation monitoring device (46) for a temporally continuous insulation monitoring of the photovoltaic generator (6), characterized in that the insulation monitoring device (46) is connected symmetrically between a positive pole (L+) of the photovoltaic generator (6) and ground and between a negative pole (L−) of the photovoltaic generator (6) and ground and that the circuit arrangement (44) comprises an insulation fault location device (48) having a test current source and a control device (45), said insulation fault location device (48) being connected symmetrically between the positive pole (L+) of the photovoltaic generator (6) and ground and between the negative pole (L−) of the photovoltaic generator (6) and ground and said control device (45) controls the functional sequence of the insulation monitoring device (46) and the insulation fault location device (48) such that a temporally continuous or a nearly temporally continuous insulation monitoring is carried out and that the potential-induced degradation is reduced by controlling a test current of the test current source.

8. The circuit arrangement according to claim 7, characterized in that the test current of the insulation fault location device (48) is carried out at such a high impedance that the test current of the test current source serves as a measurement current for insulation monitoring.

9. The circuit arrangement according to claim 7, characterized in that the insulation monitoring device (46), the insulation fault location device (48) and the control device (45) are arranged so as to be integrated in a combination device.

10. A photovoltaic system (52) comprising a circuit arrangement (54) for reducing potential-induced degradation in photovoltaic modules (57), comprising a photovoltaic generator (55) and comprising an insulation monitoring device (56) for a temporally continuous insulation monitoring of the photovoltaic generator (55), characterized in that the insulation monitoring device (56) is connected symmetrically between a positive pole (L+) of the photovoltaic generator (55) and ground and between a negative pole (L−) of the photovoltaic generator (55) and ground and that the photovoltaic generator (55) comprises a shielding (53), which is laid on a positive potential by means of a high-impedance voltage source (58).

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0043] Further advantageous embodiments can be taken from the following description and the drawing, which describe a preferred embodiment of the invention at hand by way of examples. In the figures,

[0044] FIG. 1 shows a photovoltaic system comprising a circuit arrangement according to the invention and according to a first solution;

[0045] FIG. 2 shows a photovoltaic system comprising a circuit arrangement according to the invention and according to a second solution;

[0046] FIG. 3 shows a photovoltaic system comprising a circuit arrangement according to the invention and according to a third solution;

[0047] FIG. 4 shows a photovoltaic system comprising a circuit arrangement according to the invention and according to a fourth solution;

[0048] FIG. 5 shows a photovoltaic system according to the invention comprising a photovoltaic generator and a circuit arrangement according to a fifth solution.

[0049] FIG. 1 shows a photovoltaic system 2 comprising a circuit arrangement 4 according to the invention and according to a first solution. The photovoltaic system 2 comprises a photovoltaic generator 6 made of photovoltaic modules 8, an inverter 10 and the circuit arrangement 4 for reducing potential-induced degradation in photovoltaic modules 8.

[0050] The circuit arrangement 4 consists of an insulation monitoring device 12 and an impulse coupling circuit 14. The ground connection of the insulation monitoring device 12 and the ground connection of the impulse coupling circuit 14 are laid on a ground potential and the corresponding system connections of the insulation monitoring device 12 and the impulse coupling circuit 14 are symmetrically connected to the positive pole L+ and the negative pole L− of the photovoltaic generator 6.

[0051] In FIG. 2, a photovoltaic system 22 comprising a circuit arrangement 24 according to the invention and according to a second solution is shown.

[0052] The circuit arrangement 24 consists of an insulation monitoring device 26 and a low-impedance voltage source 28. The insulation monitoring device 26 is connected asymmetrically to the photovoltaic generator 6, i.e. only with the negative pole L− of the photovoltaic generator 6, and the voltage source 28 is serially connected to the conductor of the negative pole L−.

[0053] FIG. 3 shows a photovoltaic system 32 comprising a circuit arrangement 34 according to the invention and according to a third solution.

[0054] The circuit arrangement 34 consists of an insulation monitoring device 36 and a low-impedance voltage source 38 connected serially to the insulation monitoring device 36. The circuit arrangement 34 is connected asymmetrically to the negative pole L− of the photovoltaic generator 6.

[0055] FIG. 4 shows a photovoltaic system 42 comprising a circuit arrangement 44 according to the invention and according to a fourth solution.

[0056] The circuit arrangement 44 consists of an insulation monitoring device 46, an insulation fault location device 48 having a test current source and a control device 45, these functionalities being integrated in a combined device. The insulation monitoring device 46 and the insulation fault location device 48 are each symmetrically connected to the photovoltaic generator 6, i.e. to the positive conductor L+ of the photovoltaic generator 6 as well as to the negative conductor L− of the photovoltaic generator 6.

[0057] The control device 45 controls the test current source of the insulation fault location device 48 in such a manner that the PID inhibiting effect arises via an increase in potential of the photovoltaic module to ground. In the example showing the separation of measuring current for insulation monitoring from the test current, the control device 45 controls the mode of operation by alternatingly activating the insulation monitoring device 46 and the insulation fault location device 48 such that a nearly temporally continuous insulation monitoring and a reduction of potential-induced degradation takes place.

[0058] FIG. 5 shows a photovoltaic system 52 according to the invention comprising a photovoltaic generator 55 and a circuit arrangement 54 according to a fifth solution.

[0059] The photovoltaic generator 55 is provided with a shielding 53 which is realized as a conductive shielding foil and inhibits charge carriers from moving between the photovoltaic modules 57 and the grounded module frame 59.

[0060] The circuit arrangement 54 comprises an insulation monitoring device 56 symmetrically connected to the positive pole L+ and the negative pole L− of the photovoltaic generator 55 and a high-impedance voltage source 58, which lays the shielding 53 of the photovoltaic generator 55 on a high positive potential to ground.