The present invention relates generally to electrical power conversion, and more particularly to multiple-input power converters implementing soft-switching techniques thereby reducing the converter switching losses and increasing the converter efficiency while using fewer components than presently designed multiple-input power converters.
Most electrical systems are supplied by one kind of energy source, e.g., batteries, wind energy, solar energy, or utility energy. Certain special cases are supplied by two sources, such as uninterruptible power supplies. Electrical systems would beneficially be supplied by energy sources of all kinds. Renewable sources are of particular interest, as resources are further distributed about the terrestrial power grid. In islanded power systems, interfacing of multiple sources allows for improved reliability, flexibility, and use of preferred energy sources. The different sources, such as photovoltaic cells, fuel cells, and batteries, generally have different voltage and current characteristics. In some cases, one source is preferential to others; in other cases, a simultaneous combination of sources is appropriate for energy or resource use. Typically, each different source requires a different power converter. As a result, a single-input power converter may be utilized for converting the energy of a particular power source. However, a system with multiple single-input power converters can become complex with a large number of energy sources. As a result, multiple-input power converters may be used to convert energy from multiple energy sources. By integrating all the energy sources through a single conversion device, the structure is simplified resulting in a low cost, unified control and compact system.
Multiple-input power converters can be divided into the following categories: time-sharing multiple-input power converters, multiple-input power converters with pulsating current source cells; multiple-input power converters with pulsating voltage source cells; multiple-input power converters with alternative pulsating current source cells; multiple-input power converters with alternative pulsating voltage source cells; multiple-winding magnetic coupled multiple-input power converters; and multiple-input direct-connected push-pull power converters. Unfortunately, energy conversion using such multiple-input power converters either involves the utilization of a significant number of components or limited voltage conversion ratios which result in significant switching losses, a reduction in converter efficiency, and a limit in the scope of multiple-input power converter applications.
In one embodiment of the present invention, a multiple-input power converter transferring energy from multiple input sources to a load comprises a plurality of voltage inputs. The power converter further comprises a first plurality of serially connected switches coupled to a first voltage input of the plurality of voltage inputs in a first input leg. The power converter additionally comprises a second plurality of serially connected switches coupled to a second voltage input of the plurality of voltage inputs in a second input leg. Furthermore, the power converter comprises a first capacitor inserted between the first input leg and the second input leg. Additionally, the power converter comprises a load. In addition, the power converter comprises a transformer isolating the load from the plurality of voltage inputs, where the first capacitor is coupled to a primary winding of the transformer.
In another embodiment of the present invention, a multiple-input power converter transferring energy from multiple input sources to a load comprises a plurality of voltage inputs. The power converter further comprises a first inductor coupled to a first voltage input of the plurality of voltage inputs in a first input leg. The power converter additionally comprises a second inductor coupled to a second voltage input of the plurality of voltage inputs in a second input leg. Furthermore, the power converter comprises a first capacitor inserted between the first input leg and the second input leg. Additionally, the power converter comprises a load. In addition, the power converter comprises a transformer isolating the load from the plurality of voltage inputs, where the capacitor is coupled to a primary winding of the transformer.
The foregoing has outlined rather generally the features and technical advantages of one or more embodiments of the present invention in order that the detailed description of the present invention that follows may be better understood. Additional features and advantages of the present invention will be described hereinafter which may form the subject of the claims of the present invention.
A better understanding of the present invention can be obtained when the following detailed description is considered in conjunction with the following drawings, in which:
In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits have been shown in block diagram form in order not to obscure the present invention in unnecessary detail. For the most part, details considering timing considerations and the like have been omitted inasmuch as such details are not necessary to obtain a complete understanding of the present invention and are within the skills of persons of ordinary skill in the relevant art.
As stated in the Background section, multiple-input power converters can be divided into the following categories: time-sharing multiple-input power converters, multiple-input power converters with pulsating current source cells; multiple-input power converters with pulsating voltage source cells; multiple-input power converters with alternative pulsating current source cells; multiple-input power converters with alternative pulsating voltage source cells; multiple-winding magnetic coupled multiple-input power converters; and multiple-input direct-connected push-pull power converters. Unfortunately, energy conversion using such multiple-input power converters either involves the utilization of a significant number of components or limited voltage conversion ratios which result in significant switching losses, a reduction in converter efficiency, and a limit in the scope of multiple-input power converter applications.
The principles of the present invention provide a means for implementing soft-switching techniques thereby reducing the converter switching losses and increasing the converter efficiency while using fewer components than presently designed multiple-input power converters as discussed below in connection with
As stated above,
Referring to
Converter 100 further includes a load (identified as “Load” in
A pulsating voltage is applied to the corresponding input transformer or coupled-inductor winding of an isolated converter. In general, the pulsating voltage can be generated either by a single pulsating voltage or by two different pulsating voltages as shown in
Furthermore, transformer T1 isolates the load from the sources thereby increasing the safety of converter 100 and providing a wider range of source-to-load voltage transfer ratios. The characteristic can be examined through the topology operational analysis. For example, the continuous current mode (CCM) operations of the first type of a dual-input phase-shift full-bridge power converter 100 can be divided into six states, shown in
Referring to
State 1 (t0<t<t1) shown in
State 2 (t1<t<t2) shown in
State 3 (t2<t<t3) shown in
State 4 (t3<t<t4) shown in
State 5 (t4<t<t5) shown in
State 6 (t5<t<t6) shown in
The dynamic equations of the capacitors remain the same in the six states:
It is noted that the average current of input winding, ipri, is zero in states 3 and 6, which means that the energy at the input side does not transfer to the output side in these states.
The related key waveforms for deriving the sources-to-load voltage transfer ratio (shown in
where ø2=ø1+D2−D1, n=NP1:(NS1=NS2), and VCb=D1Vin1−D2Vin2. The duty cycle losses can be represented as (EQ 4):
Moreover, in the topologies of the present invention (
Referring to
When the following condition is satisfied, soft-switching can be achieved on input switches (EQ 5):
LriLr2(0)≧CeqvCeq2(0)
where Ceq equals to 2Coss (Coss is the parasitic capacitance of input switches); vCeq(0) equals the input voltage, and iLr(0) and vCeq(0) are the initial conditions of Lr and Ceq, respectively. Soft-switching can mitigate some of the mechanisms of switching losses (e.g., losses due to high voltage and high current present in the switch during transitions and losses due to shorting device capacitances) and possibly reduce the generation of EMI. In implementing soft-switching, semiconductor devices are switched on or off at the zero crossing of their voltage or current waveforms thereby eliminating the switching loss caused by IGBT (Insulated-Gate Bipolar Transistor) current tailing and by stray inductances as well as eliminating the switching loss induced by diode stored charge and device output capacitances.
In addition, the topologies of the present invention (
Other multiple-input converters implementing the principles of the present invention are discussed below in connection with
A second type of a dual-input phase-shift full-bridge power converter 500 implementing the principles of the present invention is shown in
Referring to
A third type of a dual-input phase-shift full-bridge power converter 600 implementing the principles of the present invention is shown in
Referring to
A first type of a multiple-input phase-shift full-bridge power converter 700 implementing the principles of the present invention is shown in
Referring to
A second type of a multiple-input phase-shift full-bridge power converter 800 implementing the principles of the present invention is shown in
Referring to
A third type of a multiple-input phase-shift full-bridge power converter 900 implementing the principles of the present invention is shown in
Referring to
A first type of a dual-input parallel resonant power converter 1000 implementing the principles of the present invention is shown in
Referring to
A second type of a dual-input parallel resonant power converter 1100 implementing the principles of the present invention is shown in
Referring to
A third type of a dual-input parallel resonant power converter 1200 implementing the principles of the present invention is shown in
Referring to
A multiple-winding magnetic coupled multiple-input phase-shift full-bridge power converter 1300 implementing the principles of the present invention is shown in
Referring to
A first type of a dual-input series resonant power converter 1400 implementing the principles of the present invention is shown in
Referring to
A second type of a dual-input series resonant power converter 1500 implementing the principles of the present invention is shown in
Referring to
A third type of a dual-input series resonant power converter 1600 implementing the principles of the present invention is shown in
Referring to
The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
This application is related to the following commonly owned co-pending U.S. patent application: Provisional Application Ser. No. 61/665,999, “Multiple Input Soft-Switching Power Converters,” filed Jun. 29, 2012, and claims the benefit of its earlier filing date under 35 U.S.C. §119(e).
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Number | Date | Country | |
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20140001858 A1 | Jan 2014 | US |
Number | Date | Country | |
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61665999 | Jun 2012 | US |