Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Reexamination Certificate
2000-05-23
2001-03-27
Nguyen, Matthew (Department: 2838)
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
C363S132000
Reexamination Certificate
active
06208540
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to electric vehicles and, more particularly, to power generating apparatus including a power inverter and auxiliary power supply that employs space vector modulation and a voltage generation method for use in electric vehicles.
The assignee of the present invention designs and develops electric vehicles and power supplies that are used to convert power from a power source (such as batteries) at one voltage level for use by subsystems of such vehicles that operate at different voltage levels. This different voltage level is related to the auxiliary DC power supply.
In order to utilize power semiconductor devices to generate an auxiliary DC power supply in addition to the primary task of controlling a motor of an electric vehicle, the conventional approach is to build a completely separate DC/DC power supply that converts voltage derived from a power source to an output voltage for use by various loads in the vehicle. The conventional approach has a higher cost, uses additional components, takes up additional space, and requires additional semiconductor devices and a controller, which results in lower overall reliability.
It would, therefore, be desirable to have power generating apparatus and a voltage generation method for use in electric vehicles that eliminates additional components, improves reliability, and lowers costs.
SUMMARY OF THE INVENTION
The present invention comprises power generating apparatus and a voltage generation method that may advantageously be used with an electric vehicle. Exemplary power generating apparatus comprises a DC power source coupled by way of a three-phase voltage source power inverter to a three-phase load, such as an AC motor used in an electric vehicle. An auxiliary power supply is coupled to one output of the three-phase voltage source power inverter and ground. The auxiliary power supply comprises a single-phase transformer whose primary is coupled to the one output of the three-phase voltage source power inverter by way of a DC rejection capacitor. The secondary of the single-phase transformer is coupled to a rectifier and a low pass filter that produces a predetermined DC output voltage.
The input to and output of the auxiliary power supply are coupled to inputs of a controller. The controller manipulates or controls semiconductor switches in the three-phase voltage source power inverter to generate an AC voltage across the single-phase transformer that is not seen by the AC motor. This allows for independent control of the line-to-line voltage at the motor as well as the DC voltage produced by the auxiliary power supply.
The three-phase voltage applied to the motor is constructed from one of two null vectors. Each phase of the motor may be connected to the +DC voltage or to the −DC voltage. Although the resultant voltage on the motor is zero, the single phase transformers see either 2 DC volts or 0 volts. By alternating the frequency of selection between these two null (zero voltage) vectors, an AC current is passed through the DC transformer.
In the voltage generation method, a DC power supply voltage is provided or generated. The DC power supply voltage is inverted by controlling semiconductor switches, for example, to generate three phase AC. The three phase AC is supplied to an AC motor. One phase of the three phase AC is filtered and transformed to generate an AC voltage. The AC voltage is rectified and filtered to produce a DC output voltage. The one phase of the three phase AC and the DC output voltage are processed and controlled by frequencies of null line-to-line zero voltage vectors during inversion so that the transformed AC voltage does not affect the AC motor.
REFERENCES:
patent: 5367448 (1994-11-01), Carroll
patent: 5627447 (1997-05-01), Unsworth et al.
patent: 5710698 (1998-01-01), Lai et al.
O'Meara Thomas P.
Stancu Constantin C.
DeVries Christopher
General Motors Corporation
Nguyen Matthew
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