Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-04-07
2001-01-23
Han, Jessica (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S132000
Reexamination Certificate
active
06178099
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to resonant power converters and, more particularly, to a series resonant converter controlled to operate in a super-resonant switching mode in order to achieve zero-voltage switching under all operating conditions.
Classical optimal control involves operating a full-bridge switching converter in a full square wave mode of operation. That is, both diagonal pairs of switching devices are switched on and off simultaneously. Unfortunately, classical optimal control results in higher than desirable switching losses and less than desirable dynamic performance for some applications. For example, for x-ray generation, classical optimal control does not meet strict performance criteria. Such criteria include the following: a fast generator voltage rise time in order to avoid an excess radiation dose to patients; minimal generator voltage ripple in order to avoid imaging jitter problems; avoidance of voltage overshoots which would create an additional radiation dose to patients; high audiosusceptibility, or line voltage ripple rejection, to avoid jitter and to ensure a tightly regulated output; independence of generator with respect to line voltage variations for consistent imaging performance; maintenance of a constant output voltage for high-quality successive images; reduction of high frequency currents flowing from the power converter back into the dc bus capacitors; and compliance with electromagnetic interference regulations.
Accordingly, it is desirable to provide a control for a series resonant converter which results in a very fast response time while maintaining zero-voltage switching operation. It is furthermore desirable that such a control meet strict performance criteria such as those set forth hereinabove.
BRIEF SUMMARY OF THE INVENTION
An optimal phase-shifted control for a series resonant converter comprises an instantaneous monitoring of state variables (resonant capacitor voltage, resonant inductor current and dc output voltage) and implementation of a control law for providing a quasi-squarewave-with-maximum-coasting (QSWMC) mode of operation. The control law uses the instantaneous resonant inductor current, the instantaneous resonant capacitor voltage and the dc output voltage to determine the optimal switching events in order to operate on a desired control trajectory. QSWMC operation for optimal phase-shifted control comprises a repetitive set of four forcing functions across the resonant tank circuit and thus four repetitive switching modes. The QSWMC converter operates at a minimized frequency in a super-resonant mode (i.e., above the resonant tank frequency) with zero-voltage switching, minimized electrical stresses, and reduced electromagnetic interference due to nearly sinusoidal resonant tank currents.
REFERENCES:
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patent: 5648705 (1997-07-01), Sitar et al.
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“Resonant Power Processors, Part I-State Plane Analysis,” Ramesh Oruganti; Fred C. Lee; IEEE Transactions on Industry Applications, vol. IA-21, No. 6, Nov./Dec. 1985, pp. 1453-1460.
“Resonant Power Processors, Part II-Methods of Control,” IEEE Transactions on Industry Applications, vol. IA-21, No. 6, Nov./Dec. 1985, pp. 1461-1471.
Schutten Michael Joseph
Vlatkovic Vlatko
Wirth William Frederick
Breedlove Jill M.
General Electric Company
Han Jessica
Stoner Douglas E.
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