Electric power conversion systems – Current conversion – Having plural converters for single conversion
Patent
1996-10-08
1998-04-21
Krishnan, Aditya
Electric power conversion systems
Current conversion
Having plural converters for single conversion
H02M 545
Patent
active
057424950
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for providing electrical power conversion and, in particular, to a process which enables controllable transfer of power across a link between electrical systems.
The present invention also provides apparatus for carrying out such a power conversion, and, in particular, for enabling controllable transfer of power across a link between electrical systems.
Processes that result in a change in electric power form, or electrical isolation, or both, are known as "power conversions", and devices that carry out such processes are known as "power converters". This term is reserved for power converters which use "active" devices. An active device is one that can behave as a switch and can change state either by external command signal or according to conditions within the circuit. Thus, transformers are not classified as "power converters", even though they can change voltage amplitudes and provide isolation, since they are not switches. Power conversion processes are well known and described in the Power Electronics" Addison-Wesley Publishing Company, Inc., 1991. ISBN 0-201-09689-7.
An electric circuit which carries out the rectification process is termed a "rectifier". An electric circuit which can execute the inversion process is termed an "inverter". Some implementations of these circuits are capable of performing both processes, in which case they may be termed "bi-directional inverters", although they are often referred to as just "inverters". Circuits which perform DC to DC conversion are called "DC to DC converters" and "bi-directional DC to DC converters", depending if power flow can be bi-directional.
These circuits may be implemented in many ways, using many different circuit designs and electronic component technologies. Power conversion efficiency is a major consideration in the design of power conversion circuits. For this reason, designers use switching techniques in the circuits of power converters. The switches dissipate very little power since they are either on or off. By configuring the switches within a circuit in a certain manner, and operating the switches in a prescribed way, power may be converted from a low frequency form to a high frequency form. By applying filters, which may include inductors and/or capacitors, the high frequency output may be smoothed into the desired form. The switches may be implemented in many ways, including semiconductors such as Bipolar Junction Transistors (BJT) and Silicon Controlled Rectifiers (SCR). These techniques are well known to those versed in the art.
However, the switching techniques commonly employed result in significant energy being lost while the switch is changing state from off to on and vice versa. This switching action is termed "hard-switching" and the energy loss is termed "switching loss". There are a number of circuit techniques that can alleviate switching stresses while at the same time reducing switching power losses. Such "soft-switching" techniques result in improved power conversion efficiency, allow higher frequency of operation, and reduce electromagnetic interference (EMI). There are two types of soft-switching: Zero-Voltage-Switching (ZVS) and Zero-Current-Switching (ZCS), both of which are well known by those skilled in the art. A discussion of ZVS will be found in the United States Lossless Switching Converter") column 4 line 35 onwards. An explanation of the type of soft-switching exhibited by embodiments of the present Inverter", Proc. of a Workshop on "PV in Grid-Connected and Remote Area Stand-Alone Systems", University of New South Wales, 12-13 May, 1992, pp High-Efficiency, Bi-Directional, Lightweight Inverter/Charger.", Proc. Australasian Universities Power Engineering Conference, October 1993, pp. 202-209.
The present invention is an improvement to the inventions described in the above references by Barone et al. The present invention provides a power conversion apparatus, comprising first and second switching networks, the first switching network being arranged to be connected
REFERENCES:
patent: 5552695 (1996-09-01), Schwartz
patent: 5559685 (1996-09-01), Lauw et al.
patent: 5574636 (1996-11-01), Lee et al.
Krishnan Aditya
Unisearch Limited
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