Method for converting direct voltage into three phase alternating voltage

Abstract

A method of converting a direct voltage generated by a decentralized power supply system into three-phase alternating voltage by means of a plurality of single-phase inverters (WR 1 -WR 3 ), said alternating voltage being provided for supplying an electric mains, is intended to avoid inadmissible load unbalances using single-phase inverters. This is achieved in that, upon failure of one inverter (WR 1 -WR 3 ), an asymmetrical power supply distribution is reduced by limiting the output of the other inverters. The method makes it possible to simplify three-phase voltage monitoring.

We claim: 
     
       1. A method of converting direct voltage generated by a mains connected system for decentralized power supply into a three-phase alternating voltage by means of a plurality of single-phase inverters (WR 1 -WR 3 ) connected to a different phase (L 1 , L 2 , L 3 ), said alternating voltage being provided for supplying an electric the mains and for decentralized power supply, whereby wherein upon failure of one inverter (WR 1 -WR 3 ) of the plurality of inverters, an asymmetrical power supply distribution is reduced by limiting the output of the other inverters of the plurality of inverters, whereby wherein the failure of the one inverter (WR 1 -WR 3 ) is registered by a measurement signal of an additional circuit of each of the inverter other inverters, a communication signal resulting from the measurement signal being provided for limiting the output or for disconnecting the other inverters from the mains, whereby wherein the measurement signal is generated by a current of a constant current source, said current of said constant current source being in the a milliampere range. 
     
     
       2. The method as set forth in  claim 1 , whereby that wherein the output of each inverter (WR 1 -WR 3 ) of the other inverters is durably limited to 2-20 kVA, more specifically to about 4.6 kVA. 
     
     
       3. The method as set forth in  claim 1 , whereby wherein the output of each inverter (WR 1 -WR 3 ) of the other inverters is limited temporarily, more specifically for about 10 minutes, to about 5 kVA. 
     
     
       4. The method as set forth in  claim 1 , whereby wherein the communication signal is communicated to the processors of each of the other inverters (WR 1 -WR 3 ) for limiting the output of each of the other inverters by means of processor control. 
     
     
       5. The method as set forth in  claim 1 , whereby the wherein a communication takes place between the plurality of inverters (WR 1 -WR 3 ), through which each inverter communicates through one or a plurality of external cables that it is ready for supply. 
     
     
       6. The method as set forth in  claim 1 , whereby the wherein a communication takes place between the plurality of inverters (WR 1 -WR 3 ), each inverter communicating by radio that it is ready for supply. 
     
     
       7. A circuit arrangement comprising means for implementing the method as set forth in  claim 1 , with a plurality of single-phase inverters (WR 1 -WR 3 ) of a decentralized power supply system, wherein each inverter has a failure measuring circuit ( 1 ) for reducing the power of the other inverters inverter upon an asymmetrical power supply resulting from the failure of one of the inverter inverters. 
     
     
       8. The circuit arrangement as set forth in  claim 7 , whereby wherein each measuring circuit includes a direct current source ( 3 ), more specifically a constant current source, that may be additionally but only one constant current source is connected through an electrically conductive bridge ( 4 ), so that only one of the current sources ( 3 ) delivers the in order to deliver a measurement current, each measuring circuit comprising a connection for a measurement and/or output signal in such a manner that a failure or an OK signal can be communicated to the other two inverters. 
     
     
       9. The circuit arrangement as set forth in  claim 7 , whereby wherein each inverter is implemented with an external communication line ( 2 ). 
     
     
       10. The circuit arrangement as set forth in  claim 7 , whereby wherein a plurality of groups (GR 1 , GR 2 ) of three single-phase inverters ( 11 - 16 ) is connected to the an output side of a three-phase protection switchgear, said switchgear being adapted to be switched off through the a manual, external clearing means ( 18 ). 
     
     
       11. The circuit arrangement as set forth in  claim 10 , whereby wherein the switchgear is a contactor ( 19 ). 
     
     
       12. The circuit arrangement as set forth in  claim 7 , whereby an implementation such that wherein, upon failure of the one inverter of the inverters, all the inverters are disconnected from the mains when the voltage of one phase exceeds, or falls short of, imposed limit values. 
     
     
       13. The circuit arrangement as set forth in claim  12  whereby an implementation such that 10 wherein all the inverters are disconnected from the mains by directly switching them off, a manual, external clearing means ( 18 ) being directly connected to all the inverter plurality of groups. 
     
     
       14. A method comprising:
 applying a measurement current in a milliampere range from a constant current source to an inverter system comprising a first single phase inverter, a second single phase inverter and a third single phase inverter;   monitoring the inverter system through a first circuit in the first single phase inverter;   monitoring the inverter system through a second circuit in the second single phase inverter;   monitoring the inverter system through a third circuit in the third single phase inverter;   upon a failure of the third single phase inverter, measuring the failure in the first single phase inverter and the second single phase inverter;   reducing a first output power of the first single phase inverter based on the measured failure in the first single phase inverter; and   reducing a second output power of the second single phase inverter based on the measured failure in the second single phase inverter   thereby reducing an asymmetrical power supply.   
     
     
       15. The method according to claim 14, wherein measuring the failure comprises communicating a first communication signal to a first processor of the first single phase inverter and communicating a second communication signal to a second processor of the second single phase inverter. 
     
     
       16. The method according to claim 14, wherein reducing the first output power and the second output power comprises limiting the first output power and the second output power to 2 kVA-20 kVA, respectively. 
     
     
       17. A method of converting a direct voltage into a three phase alternating voltage for supplying into a mains, each single phase inverter of a plurality of single phase inverters having a different phase, the method comprising:
 monitoring a plurality of single phase inverters by measuring a constant current in a milliampere range at a circuit of each single phase inverter;   upon measuring a failure of one of the single phase inverters, communicating the failure to a processor of each of the other single phase inverters; and   reducing an asymmetrical power supply by limiting an output power of each of the other single phase inverters.   
     
     
       18. The method according to claim 17, wherein reducing the output power comprises limiting the output power to 2 kVA-20 kVA, respectively. 
     
     
       19. A method comprising:
 monitoring an operating condition of a first single phase inverter, a second single phase inverter and a third single phase inverter by measuring a constant current in a milliampere range;   upon measuring a failure of the first single phase inverter in circuits of the second single phase inverter and the third single phase inverter; and   reducing an asymmetrical power supply by reducing output powers of the second single phase inverter and the third single phase inverter by communicating to processors of the second single phase inverter and the third single phase inverter the failure of the first single phase inverter.   
     
     
       20. The method according to claim 19, wherein reducing the output power comprises limiting the output power to 2 kVA-20 kVA. 
     
     
       21. A system comprising:
 a plurality of single-phase inverters, each single phase inverter configured to provide a different single phase and each single-phase inverter comprising
 a monitoring circuit configured to measure a constant current in a milliampere range; and 
 a controller configured to control a power output of the respective single phase inverter; and 
   a connection connecting the monitoring circuits of the plurality of the single phase inverters,   wherein upon a failure of one of the single phase inverters, the monitoring circuits of the other single phase inverters send a communication signal to their respective controllers, and   wherein the controllers of the other single-phase inverters reduce the power outputs of the other single-phase inverters to reduce an asymmetrical power supply.   
     
     
       22. The system according to claim 21, wherein the power outputs of the other single-phase inverters are limited to 2 kVA-20 kVA. 
     
     
       23. The system according to claim 21, further comprising a communication circuit having one or a plurality of external cables. 
     
     
       24. The system according to claim 21, further comprising a wireless communication circuit. 
     
     
       25. A system comprising:
 a first single phase inverter configured to produce a first single phase, the first single phase inverter comprising
 a first monitoring circuit; 
 a first constant current source configured to provide a current in a milliampere range; and 
 a first controller configured to control a first power output of the first single phase inverter; 
   a second single phase inverter configured to produce a second single phase, the second single phase inverter comprising
 a second monitoring circuit; and 
 a second controller configured to control a second power output of the second single phase inverter; 
   a third single phase inverter configured to produce a third single phase, wherein the first, second and third single phase are different; and   a connection connecting the first single-phase inverter, the second single-phase inverter and the third single phase inverter,   wherein the monitoring circuit of the first single phase inverter is configured to send, upon detection of a failure of the third single phase inverter, a first communication signal to the controller of the first single phase inverter,   wherein the monitoring circuit of the second single phase inverter is configured to send, upon detection of the failure of the third single phase inverter, a second communication signal to the controller of the second single phase inverter,   wherein the first single phase inverter reduces a first output power,   wherein the second single phase inverter reduces a second output power, and   wherein an asymmetrical power supply is reduced.   
     
     
       26. The system according to claim 25, wherein the first output power comprises 2 kVA-20 kVA, and wherein the second output power comprises 2 kVA-20 kVA. 
     
     
       27. The system according to claim 25, wherein the first output power comprises about 4.6 kVA, and wherein the second output power comprises about 4.6 kVA. 
     
     
       28. The system according to claim 25, further comprising a communication circuit comprises one or a plurality of external cables. 
     
     
       29. The system according to claim 25, further comprising a wireless communication circuit. 
     
     
       30. The system according to claim 25, wherein the first single phase inverter comprises a conductive bridge between the constant current source and the monitoring circuit.