Power generation system and inverter for feeding power into a three-phase grid
A power generation system for feeding electrical power from a generation unit into a three-phase grid via three AC terminals is disclosed. The system includes a relay arrangement for disconnecting the system from the grid having at least three relays. Each of the three relays includes a control coil and two switching contacts operated by the corresponding control coil. Each of the AC terminals is connectable to the grid via a first and a second switching contact, each of which is assigned to a different one of the relays. Further disclosed are a relay arrangement and an inverter with a relay arrangement.
1. A power generation system for feeding electrical power from a generation unit into a three-phase grid via three AC terminals, the system comprising:
a relay arrangement for disconnecting the system from the grid, wherein:
the relay arrangement comprises at least three relays,
each of the three relays comprises a control coil and two switching contacts operated by the corresponding control coil, and
each of the AC terminals is connectable to the grid via a first switching contact and a second switching contact, wherein each of the first switching contact and the second switching contact is within a different one of the relays.
2. The system of claim 1 , wherein the system further comprises an inverter configured to receive the electrical power from the generation unit and convert a DC power into an AC power.
3. The system of claim 2 , wherein the inverter is a photovoltaic inverter.
4. The system of claim 3 , wherein the generation unit comprises photovoltaic generators.
5. The system of claim 2 , wherein the inverter is a transformerless inverter.
6. The system of claim 1 , wherein each of the relays is separately operable by a corresponding relay driver.
7. The system of claim 6 , wherein each relay driver is configured to operate the corresponding relay only upon presence of a setting signal of a control unit and an interrupt signal of a watchdog arrangement.
8. The system of claim 7 , wherein the control unit is monitored by the watchdog arrangement.
9. The system of claim 7 , wherein each relay driver is configured to be monitored by a test signal of the control unit.
10. The system of claim 9 , wherein control signals for the control coils are interrupted upon presence of the test signal, a duration of the interruption is selected to be short enough to prevent an opening of switches for disconnecting the system from the grid, and a response of the control coils to the test signal is evaluated by the control unit.
11. The system of claim 1 , wherein the relay arrangement comprises automatic switches for preventing unintended connection of the system to the grid.
12. The system of claim 1 , wherein the relay arrangement is integrated into a housing of the system.
13. The system of claim 1 , wherein the relays are arranged on a circuit board.
14. An inverter for converting a DC power into an AC power provided to a three-phase grid via three AC terminals, the inverter comprising:
a relay arrangement for disconnecting the inverter from the grid, wherein:
the relay arrangement comprises at least three relays,
each of the three relays comprises a control coil and two switching contacts operated by the corresponding control coil, and
each of the AC terminals is connectable to the grid via a first switching contact and a second switching contact, wherein each of the first switching contact and the second switching contact is within a different one of the relays.
15. The inverter of claim 14 , wherein the inverter is a photovoltaic inverter.
16. The inverter of claim 14 , wherein the relay arrangement is integrated into a housing of the inverter.
17. A relay arrangement for disconnecting an inverter from a three-phase grid with three active conductors, the relay arrangement comprising:
at least three relays, wherein:
each of the three relays comprises a control coil and two switching contacts operated by the corresponding control coil, and
each switching contact is connected to another switching contact that is within a different one of the relays.
18. The relay arrangement of claim 17 , wherein the relay arrangement further comprises automatic switches for preventing unintended connection of the inverter to the grid.
19. The relay arrangement of claim 17 , wherein each of the relays is separately operable by a corresponding relay driver.
20. The relay arrangement of claim 19 , wherein each relay driver is configured to operate the corresponding relay only upon presence of a setting signal of a control unit and an interrupt signal of a watchdog arrangement.
21. The relay arrangement of claim 20 , wherein the control unit is monitored by the watchdog arrangement.
22. The relay arrangement of claim 20 , wherein each relay driver is configured to be monitored by a test signal of the control unit.
23. The relay arrangement of claim 22 , wherein control signals for the control coils are interrupted upon presence of the test signal, a duration of the interruption is selected to be short enough to prevent an opening of switches for disconnecting the inverter from the grid, and a response of the control coils to the test signal is evaluated by the control unit.