News Column

Patent Application Titled "Energy Recovery Circuit for Distributed Power Converters in Solar Cells" Published Online

May 23, 2014



By a News Reporter-Staff News Editor at Energy Weekly News -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors POTHARAJU, Suryanarayana (San Jose, CA); JAYARAMAN, Vijay Shankar (San Jose, CA), filed on December 31, 2012, was made available online on May 8, 2014.

The assignee for this patent application is SunEdison Microinverter Products LLC.

Reporters obtained the following quote from the background information supplied by the inventors: "The present disclosure generally relates to integrated circuits. More particularly, the present disclosure provides a method and system for inverter device including an energy recovery circuit architecture configured for a solar module. Merely by way of example, the inverter device can be coupled to a backplane of a solar module, including a plurality of solar cells. Of course, there can be other variations, modifications, and alternatives.

"Since the discovery of the photoelectric effect, solar inverters have been designed to convert direct current (DC) electricity produced by solar cells or panels into alternating current (AC). The circuits termed inverters originally refer to the process of constantly inverting the incoming signal from a DC source have been performing the DC to AC conversion from watts to megawatts. Since the resurgence of the PV solar panel technologies in the early 2000's, inverters have become the point of focus as they defined the cost, performance and reliability of solar installations. Clubbed with other components as part of the Balance-of-System (BOS) components the inverter plays a significant role in defining the lifetime of the installation.

"As an example, the US Department of Energy has launched the SunShot.TM. initiative to achieve the goal of an installed cost of $1/watt (DC) for solar systems for residential, commercial and utility-scale photovoltaic (PV) solar installations. With panel costs rapidly falling, the inverter, BOS costs and installation costs have been the focus for the PV industry. In addition the lower system efficiencies (Solar-panel to grid/end point of load), hovering around 80%, have been an area of concern as they contribute to significant capital expenditure and O&M costs. Efficient power conversion topologies that would lower the cost, improve system efficiency and performance have been sought to achieve the goal of grid parity for Leveraged cost of electricity (LCOE) for PV Solar power."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "The present disclosure generally relates to integrated circuits. More particularly, the present disclosure provides a method and system for an inverter device including an energy recovery circuit architecture configured for a solar module. Merely by way of example, the inverter device can be coupled to a backplane of a solar module, including a plurality of solar cells. Of course, there can be other variations, modifications, and alternatives.

"In a specific embodiment, the present invention provides an inverter device configured on a back plane of a solar module. In an example, the inverter device comprises an energy recovery circuit device. The energy recover circuit a storage device coupled to a rectifier output from a rectifier circuit device. The energy recovery circuit is configured to temporarily store a reverse recovery charge and transfer the reverse recovery charge to an output of a DC bus structure to reduce a diode recovery loss in the rectifier circuit.

"In an example, the storage device comprises a capacitor configured between a first terminal and a second terminal of the rectifier output. In an example, the second terminal is at a ground terminal. In an example, the energy recovery circuit further comprises a node between the capacitor and the second terminal. The node is at an output voltage of the output of the DC bus structure. In an example, the energy recovery circuit includes a first p-n diode configured between the node and the second terminal. The first p-n diode is configured to maintain the node at the output voltage. In an example, the rectifier circuit device comprises a full bridge diode circuit coupled with the energy recovery circuit. In an example, the energy recovery circuit further comprising an inductor coupled to the first terminal. The inductor is in parallel to the storage capacitor and in series with the first p-n junction diode. In an example, the energy recovery circuit further comprising a second p-n junction diode provided between the first p-n junction diode and the storage capacitor. The second p-n junction diode is coupled to an output terminal of the DC bus structure. In an example, the second p-n junction diode is configured to allow a switching current to flow to the output terminal. In an example, the energy recovery circuit is configured with the inverter device, which is coupled to a group of solar cells. In an example, the group of solar cells is provided in a solar module. In an example, the storage capacitor is metal or ceramic filled capacitor structure having a capacitance determined by a frequency of switching on the rectifier circuit, the reverse recovery charge, and a voltage across the rectifier output.

"In an alternative specific embodiment, the present invention provides a method of operating an inverter device configured on a back plane of a solar module, the inverter device comprising an energy recovery circuit device coupled to a rectifier circuit, the method comprising transferring a charge from a rectifier output to a storage capacitor configured in an energy recovery circuit; storing the charge at the storage capacitor for a time period associated with a reverse recovery time; and transferring the charge to an output of a DC bus structure to reduce a diode recovery loss in the rectifier circuit. Further details of the present method can be found throughout the present specification and more particularly below.

"Many benefits are achieved by ways of present invention. For example, the present invention uses an integrated solar inverter device, having a master/slave architecture, on a back plane coupled to a solar module. The present solar module is efficient and less costly than conventional solar modules with external inverters connected through a junction box. Additionally, the inverter device comprises a slave circuit and master circuit. Depending on the embodiment, one or more of the benefits can be achieved. These and other benefits will be described in more detailed throughout the present specification and particularly below.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a simplified top view diagram of a solar module comprising a plurality of cells and associated inverters according to an embodiment of the present disclosure;

"FIG. 2 is a simplified top view diagram of a module backplane coupled to a slave inverter according to an embodiment of the present disclosure;

"FIG. 3 is a simplified diagram of a master chip module according to an embodiment of the present disclosure.

"FIG. 4 is a simplified diagram of a slave chip module according to an embodiment of the present disclosure.

"FIG. 4A is a simplified flow diagram of a master chip module and slave chip module operation according to an embodiment of the present invention.

"FIG. 4B is a simplified flow diagram of a master chip module and slave chip module operation according to an embodiment of the present invention.

"FIG. 5 is a more detailed of the slave circuit of FIG. 4, including filter, phase shifter, RERC, and boost circuit (including phase shifter and RERC) according to an embodiment of the present disclosure.

"FIGS. 6, 7, and 8 are examples of inverter circuits according to an embodiment of the present disclosure.

"FIG. 9 is a waveform derived from a slave circuit according to an embodiment of the present disclosure.

"FIG. 10 is an overall diagram of a master circuit coupled to a plurality of slave circuits according to an embodiment of the present disclosure.

"FIG. 11 illustrates each of the voltage and current waveforms from each of the slave circuits and an aggregation of each of the voltage and current wave forms according to an embodiment of the present disclosure.

"FIG. 12 illustrates solar cell elements, including a glass member, a plurality of cells, a backplane, and an inverter according to an embodiment of the present disclosure.

"FIGS. 13 and 14 illustrate waveforms with switching voltages across rectifier bridge diodes with and without the RERC circuitry according to an embodiment of the present disclosure.

"FIG. 15 illustrates a voltage/current plotted against time for the circuitry of FIGS. 13 and 14.

"FIG. 16 illustrates waveforms of a wave shaper circuit according to an embodiment of the present disclosure."

For more information, see this patent application: POTHARAJU, Suryanarayana; JAYARAMAN, Vijay Shankar. Energy Recovery Circuit for Distributed Power Converters in Solar Cells. Filed December 31, 2012 and posted May 8, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4273&p=86&f=G&l=50&d=PG01&S1=20140501.PD.&OS=PD/20140501&RS=PD/20140501

Keywords for this news article include: Oil & Gas, Energy Recovery, SunEdison Microinverter Products LLC.

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Source: Energy Weekly News