Electric power conversion systems – Current conversion – With voltage multiplication means
Patent
1993-03-24
1998-04-07
Wong, Peter S.
Electric power conversion systems
Current conversion
With voltage multiplication means
307110, H02M 318
Patent
active
057372012
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an electronic device for converting electric energy between a voltage source and a current source, comprising n controllable switching cells, each comprised of at least two switches working in a complementary manner, with n.gtoreq.2.
BACKGROUND AND OBJECTS OF THE INVENTION
According to the definition provided in "Techniques de l'Ingenieur," Electronic Volume, pp D3-150 and following; by the term "voltage source" is meant an electric dipole (generator or receiver) of which the voltage at the terminals can not undergo a discontinuity by reason of the circuit exterior to said dipole (examples: storage battery, alternating distribution networks, high value capacitor . . . ); by the term "current source" is meant an electric dipole (receiver or generator) which is traversed by a current which cannot undergo a discontinuity by reason of the circuit external to said dipole (examples: inductive load, coil, direct current machine . . . ).
In a conventional manner, static converting devices are comprised of a combination of switching cells, each formed from two switches of complementary operation, that is, one being conducting when the other is blocked or non-conducting. Each cell has an associated control logic which assures the complementary status and manages the exchanges of energy as a function of the application.
A variation of these prior converting devices, known as a "three level converter" is known and has been in use since 1981 in the high voltage field (references: Ch. Bachle et al, "Requirements on the Control of a Three-Level Four Quadrant Power Converter in a Traction Application," Proceeding E.P.E. Aachen 1989, pp 577 to 582; B. Velaerts et al, "New Developments of 3-Level PWM Strategies," Proceeding E.P.E. Aachen 1989, pp 411 to 416.) Devices of this type are comprised of modules with four switches and these latter are imbricated to form two series, and no longer operate in a complementary manner. Two diodes are connected to a capacitative mid-point connected to the voltage source in order to limit the value of the voltages supported by each of the 4 switches to the half-voltage and to furnish three levels of voltage output, (from which comes the name "three level invertor" for these devices). A specific control is necessary in this type of device to permit the set of diodes to carry out its role of clipping and dividing the voltage, but this control is incompatible with a complementary operation of the switches of the two series. Under these conditions; such a device provides at the output a voltage wave in which the amplitude and the frequency are related:
this wave is accomplished either between the level of intermediate voltage and one of the extreme levels and thus has an amplitude which is only a fraction (V/2) of the overall supply voltage (V), the frequency of this wave being then equal to the control frequency (F) of the switches,
or this wave overlays the three voltage levels and thus has an amplitude equal to the overall supply voltage (V), but in this case, the frequency of this wave is a multiple of the control frequency of each switch (2F).
In the first case, the limited value (V/2) of the wave amplitude of the output voltage would tend to facilitate its filtering, but this would eliminate a low frequency F, which limits this advantage. Conversely, in the second case, the high frequency (2F) of the output voltage wave would tend to facilitate its filtering, but the high value of the amplitude thereof (V) limits this advantage. As a result, by their own nature, these devices do not permit benefitting from the advantages associated with a reduction of amplitude (V/2) and a multiplication of frequency (2F).
In other words, the very specific character of the control of these devices, the switches of which do not operate in a complementary manner, limits to four the number of switches which can make up a module.
It is to be noted that certain conventional converters (converters with greater pulse modulation) are comprised of combinations of switching cells which
REFERENCES:
patent: 3596369 (1971-08-01), Dickerson et al.
patent: 5159543 (1992-10-01), Yamawaki
patent: 5179289 (1993-01-01), Sridharan
IEEE Trans. On Aerospace and Electronic Systems, vol. 24, No. 6, Nov. 1988, New York, pp. 743-754; Tymerski `Generation and Classification of PWM DC-to-DC Converter` p. 750, config N2.
International Journal of Electronics; vol. 68, No. 1, Jan. 1990, London, pp. 143-160; Nakaoka "New efficient high-frequency power inverter . . . " pp. 146-151, figs 1, 3, 11.
Foch Henri
Meynard Thierry
Dutton, Jr. Harold H.
Han Y. J.
Jamison W. Charles L.
Liebman Diane F.
Wong Peter S.
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