Device for feeding electrical energy from an energy source

Abstract

A device ( 1 ) for feeding electrical energy from an energy source with variable source voltage into an electric power supply network ( 15 ), said device ( 1 ) including a transformer ( 112 ) for galvanic isolation, a resonant inverter ( 11 ) with semi-conductor switches (a-d; A, B), one or several resonant capacitors ( 17; 18, 19; 20, 21 ) and one rectifier ( 113 ), is intended to provide high efficiency and have galvanic isolation. This is achieved in that the resonant inverter ( 11 ) is operated in the full resonant mode if the operating voltage is in an operation point (MPP) and in the hard-switching mode if the voltages exceed the operation point (MPP).

I claim: 
     
       1. A device ( 1 ) for feeding electrical energy from an energy source with variable source voltage into an electric power supply network ( 15 ), said the device ( 1 ) including comprising:
 a transformer ( 112 ) for galvanic isolation,; 
 a resonant high frequency inverter ( 11 ) with semi-conductor comprising first switches (a-d; A, B), and one or several resonant capacitors ( 17 ;  18 ,  19 ;  20 ,  21 ); and 
 onea rectifier ( 113 ), characterized in that 
 wherein the device ( 1 ) does not comprise a boost chopper or a buck chopper, and that 
 wherein the resonanthigh frequency inverter ( 11 ) is operated configured to operate in a full resonant mode if an operating voltage is in a maximum power operation point (MPP) that exists in normal operation, whereby wherein in the maximum power point (MPP) the a current from the transformer ( 112 ) is a current made from comprises sinusoidal half-waves, and 
 wherein the resonanthigh frequency inverter ( 11 ) is operated configured to operate in a hard-switching mode if the voltages exceed the maximum operation power point (MPP), so that the current from the transformer ( 112 ) comprises sine-wave portions, whereby wherein the hard-switching mode only occurs in a start-up phase. 
 
     
     
       2. The device as set forth in  claim 1 ,
 characterized in that, in the operation point (MPP), the semi-conductor switches (a-d; A, B) of the resonant inverter ( 111 ) are operated with a duty cycle that is more than half a period of a resonance frequency of an oscillating circuit comprising one resonant capacitor or several resonant capacitors and of a transformer leakage inductance, at pulse widths ranging between 30 and 50% of a period of a pulse frequency, so that a voltage at an intermediate circuit capacitor ( 12 ) will not fall below a minimum value needed for feeding the network ( 15 ), even if a voltage at the maximum power point (MPP) of the energy source adopts a minimum voltage value imposed by the device, and that, if the voltages of the energy source are higher than the maximum power point voltage, said semi-conductor switches are operated at pulse widths of between zero and 50% so that the voltage at the intermediate circuit capacitor ( 12 ) will not exceed a maximum value given by an electric strength of the semi-conductor switches (a-d, A, B) of a regen-capable inverter ( 13 ), even if the voltage of the energy source is higher than the (MPP) voltage.   
     
     
       3. The device as set forth in  claim 1 , characterized in that further comprising a regen-capable inverter comprising second switches, and wherein the first switches and the second switches have about semi-conductor switches of the same electric strength as semi-conductor switches (a-d; A,B) are used in the resonant inverter ( 11 ) and in the regen-capable inverter ( 13 ). 
     
     
       4. The device as set forth in  claim 1 ,
 characterized by an implementation such that, in the hard-switching operation above the operation point (MPP), a transformer current of the transformer ( 112 ) consists of sine-wave portions.   
     
     
       5. The device as set forth in  claim 1 ,
 characterized in thatwherein the transformer ( 112 ) is a high-frequency transformer ( 112 ) and is operated at a frequency that is higher than a frequency of the energy electric power supply network ( 15 ). 
 
     
     
       6. The device as set forth in  claim 1 , characterized in that a wherein the switches of the high-frequency inverter ( 111 ), which is part of the inverter ( 11 ) and comprises the semi-conductor switches (a-d; A, B), which are performed as MOS transistors, IGBT's, or GTO's, is mounted upstream of the transformer ( 112 ) IGBTs or GTOs. 
     
     
       7. The device as set forth in claim  2  3,
 characterized in thatwherein the regen-capable inverter ( 13 ) is a one-phase or a three-phase inverter. 
 
     
     
       8. The device as set forth in  claim 1 ,
 characterized in thatwherein the transformer, the high frequency inverter and the rectifier form a resonant inverter ( 11 ), and wherein the resonant inverter comprises a full bridge. 
 
     
     
       9. The device as set forth in  claim 1 ,
 characterized in thatwherein the transformer, the high frequency inverter and the rectifier form a resonant inverter ( 11 ), and wherein the resonant inverter comprises a half-bridge. 
 
     
     
       10. The device as set forth in  claim 9 ,
 characterized in thatwherein the resonant inverter ( 11 ) is performed ascomprises a centrecenter tap connection circuit. 
 
     
     
       11. The device as set forth in  claim 1 ,
 characterized in thatwherein the rectifier ( 113 ) is devised ascomprises a half-bridge. 
 
     
     
       12. The device as set forth in  claim 1 ,
 characterized in thatwherein the one or several resonant capacitors ( 17 ;  16 ,  19 ;  20 ,  21 ) are connected in series or in parallel with a resonant circuit with respect to a primary winding of the transformer ( 112 ). 
 
     
     
       13. A The device for feeding electrical energy as set forth in  claim 1 ,
 characterized in that a resonant capacitor ( 20 ,  21 ) iswherein the one or several capacitors are connected in series or in parallel with a secondary winding of the transformer ( 112 ). 
 
     
     
       14. The device as set forth in  claim 1 ,
 characterized in that thewherein the one or several resonant capacitors ( 18 ,  19 ) of a half-bridge located on the a primary side of the transformer ( 112 ) are utilized configured to operate as resonant capacitors. 
 
     
     
       15. The device as set forth in  claim 1 ,
 characterized in thatwherein the one or several resonant capacitors ( 20 ,  21 ) of a secondary side half-bridge located on a secondary side of the transformer are utilized configured to operate as resonant capacitors. 
 
     
     
       16. The device as set forth in  claim 1 ,
 characterized in that awherein the high-frequency inverter ( 111 ), the transformer ( 112 ) and the rectifier ( 113 ) form a resonant converter that is a DC/DC converter, a natural frequency formed by the one or more resonant capacitors ( 17 ;  18 ,  19 ;  20 ,  21 ) of a leakage inductance of the transformer ( 112 ) being higher than a switching frequency of the resonant inverter ( 11 ) in order to minimize switching losses in the semi-conductor switches (a-d; A, B) of the resonant high frequency inverter ( 11 ) as compared to a hard-switching mode of operation. 
 
     
     
       17. A The device for feeding electrical energy as set forth in  claim 1 ,
 characterized in thatwherein a leakage inductance of the transformer ( 112 ) is complemented by one or several additional inductances in order to achieve a desired resonance frequency. 
 
     
     
       18. The device as set forth in  claim 1 ,
 characterized in that, on a primary side, several resonant inverters ( 11 ) are mounted in parallel at the energy source and, on a secondary side, are connected to a common intermediate circuit capacitor ( 12 ) discrete resonant inverters ( 11 ) being clocked at different times.   
     
     
       19. The device as set forth in  claim 1 ,
 characterized in that thewherein the transformer, the high frequency inverter and the rectifier form a resonant inverter ( 11 ), and wherein the resonant inverter is connected to a regen-capable inverter ( 13 ). 
 
     
     
       20. A system with a comprising the device as set forth in  claim 1  and with the energy source,
 characterized in thatwherein the energy source is a solar generator ( 10 ), a fuel cell, a battery, a wind power plant with a permanent-magnet generator, a combustion engine with a permanent-magnet generator or a water power plant with a permanent-magnet generator (PM-generator). 
 
     
     
       21. Use of a A method for using the device as set forth in  claim 1 , wherein the device is used in a public energy the electric power supply network supplying a plurality of consumers or an island network with one or several consumers. 
     
     
       22. A method of operating a the device as set forth in  claim 1 , wherein the energy source of which is comprises a photovoltaic solar generator with having a solar generator characteristic lineat least one with the maximum power point (MPP) of a solar generator characteristic line, the resonant inverter ( 11 ) device being operated in the full resonant mode in the MPP and in the hard-switching mode when the voltage exceeds the MPP. 
     
     
       23. The device as set forth in  claim 1 ,
 characterized in that high-performance semi-conductors capable of being switched off are mounted in parallel with the diodes D 5  through D 8  of the resonant rectifier ( 113 ) so that a circuit may be operated in both directions if the energy source is an energy accumulating device.   
     
     
       24. A method for feeding electrical energy from an energy source with a variable source voltage to an electrical power supply network, the method comprising:
 converting a first DC power to a second DC power in a resonant converter, wherein the resonant converter operates in a hard switching operation mode, and wherein a current of a transformer of the resonant converter comprises sine-wave portions if a DC voltage exceeds a maximum power point (MPP) of the energy source that occurs only in a start-up phase; and   converting a first DC power to a second DC power in the resonant converter, wherein the resonant converter operates in a soft switching operation mode, and wherein a current of the transformer of the resonant converter comprises sinusoidal half-waves if the DC voltage is in the maximum power point (MPP) of the energy source that exists in normal operation.   
     
     
       25. The method as set forth in claim 24, wherein the resonant converter is buck chopper free and boost chopper free. 
     
     
       26. The method as set forth in claim 25, wherein operating the resonant converter in the soft switching mode comprises operating the converter with a resonance frequency, and wherein the resonance frequency is higher than a clock frequency of switches of an inverter. 
     
     
       27. The method as set forth in claim 25, further comprising
 filtering the second DC power;   inverting the filtered second DC power to an AC power;   filtering the AC power; and   feeding the filtered AC power into the electrical power supply network.   
     
     
       28. The method as set forth in claim 25, wherein the resonant converter comprises an inverter, the transformer and a rectifier, and wherein the inverter is electrically coupled to a primary winding of the transformer, wherein the rectifier is electrically coupled to a secondary winding of the transformer. 
     
     
       29. The method as set forth in claim 28, wherein operating the resonant converter in the soft switching mode comprises operating switches of the inverter at pulse widths between about 30% and about 50% of a period of a clock frequency, and wherein operating the resonant converter in the hard switching mode comprises operating the switches of the inverter at pulse widths between about zero and about 50% of the period of the clock frequency. 
     
     
       30. The method set forth in claim 28, wherein operating the resonant converter in the soft switching mode comprises switching switches of the inverter at a time when a current in the primary winding of the transformer is about zero.