Electric power conversion systems – Frequency conversion without intermediate conversion to d.c. – By semiconductor converter
Reexamination Certificate
2001-05-30
2002-09-10
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Frequency conversion without intermediate conversion to d.c.
By semiconductor converter
C363S037000, C363S059000
Reexamination Certificate
active
06449181
ABSTRACT:
The invention relates to a frequency converter for converting electrical energy, in particular for the electrical energy produced by a generator for an electrical system of a vehicle.
PRIOR ART
The frequency conversion of electrical energy, for example in an electrical system of a vehicle, usually takes place today by means of a static inverter. In these electronic power circuits, often direct quantities are converted into alternating quantities of a particular frequency or conversely, alternating quantities are converted into direct quantities. The alternating or direct quantities are, for example, voltages or currents. For conversion of quantities, it is also possible for direct quantities to be converted into direct quantities, for example a direct current is converted into a direct current with a different voltage level. With this voltage conversion, an energy flux in both directions can also take place.
Frequency converters with an intermediary voltage circuit (voltage converters) and autonomous bridge circuits, for example rectifier bridge circuits in a vehicle electrical system, are currently the standard design for nearly all frequency converter application areas. In this connection, the intermediary circuit can also be constituted directly by a direct current network. The intermediary circuit is required for temporarily storing the energy. A capacitor with the greatest possible capacitance serves as a temporary storage.
The required capacitance of the intermediary circuit capacitor is determined by the energy which it must temporarily store and by the alternating current resulting from it. Usually, an electrolytic capacitor is used for the intermediary circuit; if the temporary storage must hold larger quantities of energy, several electrolytic capacitors are used. These have a particularly high capacitance in relation to their volume, but due to their design they are very sensitive to high temperatures. Particularly at high temperatures, this leads to an aging of the electrolytic capacitors and to early failure. Other disadvantages of electrolytic capacitors are their low current carrying capacity, their relatively high internal resistance, and the parasitic inductances in series to the capacitance.
A frequency converter for converting electrical energy, which converts the electrical voltage supplied by a three-phase generator in a vehicle electrical system, is known, for example, from DE-OS 196 46 043. In this known system, the three-phase generator is simultaneously also operated as a starter. As a result, the machine can operate both as a starter and as a generator and, in order to optimally regulate the output voltage during generator operation, the electrical machine is connected to the vehicle electrical system, including the battery, via a controlled rectifier bridge and via an intermediary circuit capacitor. In this connection, the rectifier bridge includes six pulse inverter elements which are triggered by a control unit of the vehicle electrical system.
OBJECT OF THE INVENTION
The intermediary circuit capacitances required in the known voltage converters and the input capacitance in direct current converters (DC/DC converters) require a not inconsiderable amount of structural space. Frequently the intermediary circuit capacitor, for example an electrolytic capacitor, is the component with the greatest volume. Since this is a disadvantage, the object of the invention is to considerably reduce the value of the intermediary circuit capacitance and in particular also the size of the intermediary circuit capacitance and the intermediary circuit capacitor or the input capacitance in a voltage converter and as a result, to reduce the structural volume and the costs. Another object is to achieve a possibility of reducing the capacitance so far that electrolytic capacitors customarily used in the intermediary circuit can be forsaken for other capacitor principles. A further object of the invention is to embody choke devices so that the different branches of the frequency converter are decoupled from one another.
ADVANTAGES OF THE INVENTION
The frequency converter for converting electrical energy, with the characteristics of claim
1
, has the advantage that one capacitor, whose capacitance is considerably reduced in comparison to conventional systems, suffices as the intermediary circuit capacitance. As a result, it is advantageously possible to reduce the size of the intermediary circuit capacitor and thereby to reduce the structural volume and the attendant costs. In a particularly advantageous manner, it is possible to design the frequency converter, which contains at least one high-side switch and one low-side switch, so that the required capacitance can be reduced so much that the customarily used electrolytic capacitors can be forsaken for other capacitor principles. This achieves the particular advantages that the low current carrying capacity of electrolytic capacitors and their sensitivities to temperature and aging can be circumvented.
Other advantages of the invention are achieved by means of the measures taken in the dependent claims. It is thereby advantageous that the frequency converter and/or the DC/DC converters can be designed as separate half bridges with semiconductor valves, which can also be advantageously combined to form a complete frequency converter module, which can be integrated in a particularly advantageous manner into the generator housing or the machine housing.
Through suitably offset triggering of the half bridges, a particularly low voltage ripple can be advantageously obtained. Short circuits are reliably prevented through simultaneous triggering of parallel connected semiconductor valves or semiconductor switches of a half bridge.
The use of coupled chokes permits a particularly advantageous decoupling of different branches of the frequency converter. The machine winding, for example for a delta connected claw-pole generator, can be embodied through advantageous disposition of the chokes so that a decoupling of two partial branches is achieved.
REFERENCES:
patent: 5132898 (1992-07-01), Nishizawa et al.
patent: 5142439 (1992-08-01), Huggett et al.
patent: 5576943 (1996-11-01), Keir
patent: 5726557 (1998-03-01), Kusase
patent: 5903121 (1999-05-01), Maier
patent: 196 46 043 (1996-11-01), None
patent: 0 683 560 (1995-11-01), None
patent: 0 740 394 (1996-10-01), None
patent: 0 777 309 (1997-06-01), None
Patent Abstracts of Japan vol. 1995, No. 10, Nov. 30, 1995 & JP 07 170746 A, Jul. 4, 1995.
Reutlinger Kurt
Rieger Reinhard
Patel Rajnikant B.
Robert & Bosch GmbH
Striker Michael J.
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