US 8842454

Here's a concise summary of US patent 8842454:

US Patent 8842454: Inverter array with localized inverter control

• Title: Inverter array with localized inverter control
• Assignee: GRIDSCALE SOLUTIONS, LLC. (Current Assignee as of 2026-04-21)
• Inventors: Brian Johnson, Philip Krein, Alexander Gray, Patrick L. Chapman
• Filing Date: 2011-02-17
• Issue Date: 2014-09-23
• Abstract: An apparatus delivers AC power to an AC load using multiple inverters, each receiving DC power from a respective source. A primary controller generates a primary control signal based on the total AC current and voltage supplied to the load. Each of several secondary controllers receives this primary signal and produces a unique secondary control signal. This individual secondary control signal then governs a corresponding inverter to provide its portion of the AC power.

Plain-Language Overview of Independent Claims:

• Independent Claim 1 (Apparatus): This claim describes an apparatus designed to deliver AC power to an AC load. It includes:

  • Multiple inverters, each taking DC power from a separate DC source and converting it to AC power for the load.
  • A main (primary) controller that generates a primary control signal. This signal is determined by the overall AC current and AC voltage being supplied to the load by all the inverters.
  • Multiple secondary controllers, each receiving the primary control signal. Each secondary controller then creates its own specific (respective) secondary control signal, which is also based on the primary control signal.
  • Crucially, each individual secondary control signal from a secondary controller is used to control one or more of the corresponding inverters, directing it to produce its share of the AC power.

• Independent Claim 10 (Method): This claim outlines a method for controlling AC power supplied to an AC load. The steps include:

  • Generating AC power using an array of inverters, with each inverter's output based on the DC power it receives.
  • Creating a first control signal in response to the overall AC power being produced.
  • Generating multiple second control signals, each in response to the first control signal.
  • Controlling the individual AC power output of each inverter in the array. This control is based on a corresponding one of the second control signals, with the total AC power being the combined output of all the inverters.

• Independent Claim 17 (Computer-Readable Medium): This claim describes a computer-readable medium containing instructions for a processor to perform the control method. The instructions include:

  • Directing an array of inverters to generate AC power, based on the DC power they receive.
  • Generating a first control signal in response to the AC power.
  • Generating multiple second control signals in response to the first control signal.
  • Controlling the individual AC power output of each inverter in the array, based on a corresponding one of the second control signals. The total AC power is the combination of each inverter's output.

CAFC 2026 Dockets:

A search of CAFC 2026 dockets for US Patent 8842454 did not return any specific cases or mentions of this patent number. While there are several patent-related decisions and filings in 2026, none of the available snippets explicitly refer to US8842454. Therefore, there is no authoritative information from the provided search results to indicate active litigation or appeals concerning this patent in the CAFC dockets for 2026.

A search for litigation involving US patent 8842454 on Unified Patents and through general web searches did not yield any specific district court litigation cases, CAFC cases, or PTAB cases directly citing this patent number. The search results primarily contained information about other patents or general information about Unified Patents' services.

Therefore, as of April 26, 2026, no known litigation involving US patent 8842454 could be identified based on the provided search results.

Proceedings overview

There is no PTAB activity on file for US Patent 8842454.

Strategic summary

There are no AIA trial proceedings (Inter Partes Review, Post-Grant Review, or Covered Business Method) on file for US Patent 8842454. This means that all claims of the patent (claims 1-20) are currently untested by the PTAB.

Since there are no PTAB proceedings, there is no estoppel landscape to consider under § 315(e)(2). All prior-art grounds remain available to a potential petitioner. The absence of PTAB activity could suggest that the patent has not been extensively asserted, or that previous challenges have not taken the form of AIA trials.

Recommended next steps

Since no PTAB activity exists for US Patent 8842454, a defendant facing assertion of this patent would have the full range of prior art and statutory grounds available for an AIA trial challenge (e.g., IPR, PGR). This absence of PTAB history means the patent has not been subjected to the scrutiny of an administrative trial, and its claims have not been challenged or confirmed by the PTAB.

Inventors

• Brian Johnson: Employer at time of filing unknown.
• Philip Krein: Employer at time of filing unknown.
• Alexander Gray: Employer at time of filing unknown.
• Patrick L. Chapman: Employer at time of filing unknown.

It is difficult to determine the inventors' employers at the time of filing from the provided patent text. The original assignee is Solarbridge Technologies Inc.

Original assignee

Solarbridge Technologies Inc. was the original assignee named on the issued patent.

Based on available information, Solarbridge Technologies Inc. developed microinverters for solar panels. They did ship products embodying the claims, specifically microinverters designed for photovoltaic applications. Solarbridge Technologies Inc. was acquired by SunPower Corporation in 2014.

Assignment timeline

• 2011-03-25 (executed) / recorded 2011-03-25 — Reel 026135/0508
  • Conveyance: Assignment
  • Assignor: KREIN, PHILIP; CHAPMAN, PATRICK L.; GRAY, ALEXANDER; JOHNSON, BRIAN
  • Assignee: SolarBridge Technologies
  • Correspondent: Jeffrey C. Handley, Patent Law Group LLP, 2800 Bridgepark Dr, Suite 100, Redwood City, CA, 94065-1133
  • Context: Transfer of inventors' interest to original assignee
• 2014-09-02 (executed) / recorded 2014-09-02 — Reel 032227/0268
  • Conveyance: Security Interest
  • Assignor: SOLARBRIDGE TECHNOLOGIES, INC.
  • Assignee: SILICON VALLEY BANK
  • Correspondent: Gregory P. Brown, Baker & McKenzie LLP, 2 Embarcadero Center, 24th Floor, San Francisco, CA, 94111
  • Context: Securitization of assets by a bank
• 2014-12-19 (executed) / recorded 2014-12-19 — Reel 032646/0001
  • Conveyance: Assignment of Assignor's Interest
  • Assignor: SOLARBRIDGE TECHNOLOGIES, INC.
  • Assignee: SUNPOWER CORPORATION
  • Correspondent: Scott B. MacDonald, Law Office of Scott B. MacDonald, 1500 Hamilton Ave., Suite 201, San Jose, CA, 95125
  • Context: Acquisition of Solarbridge Technologies, Inc. by SunPower Corporation
• 2014-12-19 (executed) / recorded 2014-12-19 — Reel 032646/0010
  • Conveyance: Release by Secured Party
  • Assignor: SILICON VALLEY BANK
  • Assignee: SOLARBRIDGE TECHNOLOGIES, INC.
  • Correspondent: Jeffrey P. Kushan, Sidley Austin LLP, 1501 K Street N.W., Washington, DC, 20005
  • Context: Release of security interest due to acquisition
• 2018-09-10 (executed) / recorded 2018-09-10 — Reel 044031/0950
  • Conveyance: Assignment of Assignors Interest
  • Assignor: SUNPOWER CORPORATION
  • Assignee: ENPHASE ENERGY, INC.
  • Correspondent: Matthew N. Bernstein, Sheppard Mullin Richter & Hampton LLP, 379 Lytton Ave., Palo Alto, CA, 94301
  • Context: Transfer of assets from SunPower to Enphase Energy
• 2026-04-21 (executed) / recorded 2026-04-21 — Reel 060595/0306
  • Conveyance: Assignment of Assignor's Interest
  • Assignor: POWERBRIDGE NETWORKS, LLC
  • Assignee: GRIDSCALE SOLUTIONS, LLC
  • Correspondent: Jason B. Komorsky, Carstens & Cahoon, LLP, P.O. Box 741639, Dallas, TX, 75374-1639. This correspondent has appeared on other tracked patents on this site.
  • Context: Transfer of patent ownership.

Timeline diagram

timeline
    title Ownership of US 8842454
    2011 : Inventors to SolarBridge Tech
    2014 : Security interest to SVB
         : SolarBridge to SunPower
         : SVB releases interest
    2018 : SunPower to Enphase Energy
    2026 : PowerBridge Networks to Gridscale Solutions

NPE / troll-pattern signals

1. Shell-entity transfer — Present. The transfer from POWERBRIDGE NETWORKS, LLC to GRIDSCALE SOLUTIONS, LLC in 2026 (Reel 060595/0306) suggests a shell entity transfer. PowerBridge Networks, LLC, and Gridscale Solutions, LLC do not appear to be operating companies producing products embodying the claims, and the recurring correspondent further supports this.
2. Known asserter in the chain — Unclear. While Enphase Energy Inc. and Sunpower Corporation are operating companies, the most recent assignee, GRIDSCALE SOLUTIONS, LLC, is not a publicly known operating company or a listed NPE at present. Further research would be needed to definitively confirm its status.
3. Repeat correspondent across the chain — Present. Jason B. Komorsky of Carstens & Cahoon, LLP is listed as the correspondent for the 2026-04-21 assignment to GRIDSCALE SOLUTIONS, LLC (Reel 060595/0306). This correspondent has been flagged as appearing on other tracked patents on this site.
4. Cascading transfers — Not present. There are no multiple consecutive assignments through chained LLCs in a short period (<24 months) with shared correspondent addresses or attorneys. The transfers are spaced out over several years.
5. Pre-litigation transfer — Unclear. Without litigation data, it's impossible to determine if the 2026 transfer to Gridscale Solutions, LLC is pre-litigation.
6. Bankruptcy fire-sale — Not present. Solarbridge Technologies Inc. was acquired by SunPower Corporation, not sold in bankruptcy proceedings.
7. Privateering — Unclear. There is no available information to suggest privateering.
8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at a known defensive aggregator.

Verdict

NPE — moderate confidence. The transfer to GRIDSCALE SOLUTIONS, LLC in 2026 (Reel 060595/0306), coupled with the presence of a known repeat correspondent (Jason B. Komorsky of Carstens & Cahoon, LLP) for this transfer, suggests an NPE pattern. However, without confirmed litigation data or more explicit information about Gridscale Solutions, LLC's business model, it remains at moderate confidence.

USPTO Assignment Center search: https://assignmentcenter.uspto.gov/

To find the most relevant prior art for US patent 8842454, I will use the patent's own citations. The full patent text provided lists a "Citations" section. I will analyze these cited patents to identify those most relevant to the claims of US8842454. I will then extract the required information for each.

Based on the provided patent text, I will now list the patent citations for US8842454, along with the requested details. Since I do not have direct access to the USPTO database for real-time searching and claim-by-claim analysis against each prior art, I will focus on providing the available information from the "Citations" section within the patent document itself. I will identify potential anticipation under 35 U.S.C. § 102 based on the brief descriptions and the claims of US8842454.

Please note that a definitive anticipation analysis under 35 U.S.C. § 102 requires a detailed review of each prior art document's full disclosure and a comparison with each claim element of US8842454, which goes beyond the scope of a brief summary. The "which claim(s) it potentially anticipates" will be an informed estimation based on the titles and descriptions provided in the patent itself.

Here are some of the patent citations from US8842454, along with the requested information:

Most Relevant Prior Art for US Patent 8842454

• US4994953A

  • Full Citation: US4994953A, "DC power supply for high power applications"
  • Publication Date: 1991-02-19
  • Filing Date: 1989-08-15
  • Brief Description: This patent describes a DC power supply system for high-power applications.
  • Potential Anticipation (35 U.S.C. § 102): Potentially relevant to the general concept of DC power supply and conversion, particularly as it relates to the input stage of the inverters in US8842454 (e.g., receiving DC power from a DC power source). Might be relevant to claims 1, 10, and 17 in their broadest sense of handling DC power.

• US5677833A

  • Full Citation: US5677833A, "Power conditioning system for a four quadrant photovoltaic array with an inverter for each array quadrant"
  • Publication Date: 1997-10-14
  • Filing Date: 1995-05-16
  • Brief Description: This patent describes a power conditioning system specifically for photovoltaic arrays, where an inverter is provided for each quadrant of the array.
  • Potential Anticipation (35 U.S.C. § 102): Highly relevant to US8842454, especially the concept of a plurality of inverters associated with photovoltaic cells. This could potentially anticipate aspects of claims 1, 10, and 17, particularly where the DC power source is explicitly a photovoltaic source (as detailed in the description of US8842454). The distributed inverter architecture is a key overlap.

• US6169678B1

  • Full Citation: US6169678B1, "Photovoltaic power generation apparatus and control method thereof"
  • Publication Date: 2001-01-02
  • Filing Date: 1999-01-28
  • Brief Description: This patent describes a photovoltaic power generation apparatus and its control method.
  • Potential Anticipation (35 U.S.C. § 102): Very relevant due to its focus on photovoltaic power generation and control. Aspects of this patent describing conversion of DC to AC power and overall system control could potentially anticipate elements of claims 1, 10, and 17, especially regarding the generation of control signals and managing output power from PV sources.

• US6259017B1

  • Full Citation: US6259017B1, "Solar power generation apparatus and control method therefor"
  • Publication Date: 2001-07-10
  • Filing Date: 1998-10-15
  • Brief Description: This patent describes a solar power generation apparatus and its control method.
  • Potential Anticipation (35 U.S.C. § 102): Similar to US6169678B1, this patent is highly relevant to the core subject matter of US8842454. It could potentially anticipate the elements of claims 1, 10, and 17 that relate to controlling AC power from solar sources using inverters and control signals.

• US20030231517A1

  • Full Citation: US20030231517A1, "System and method for regenerative PWM AC power conversion"
  • Publication Date: 2003-12-18
  • Filing Date: 2001-01-02
  • Brief Description: This patent describes a system and method for regenerative Pulse Width Modulation (PWM) AC power conversion.
  • Potential Anticipation (35 U.S.C. § 102): Relevant to the "controlling respective output AC power of each inverter... based on a corresponding one of the second control signals" aspect of US8842454 (claims 1, 10, 17), especially where PWM signals are used for control (as described in the detailed description of US8842454).

• US20040208029A1

  • Full Citation: US20040208029A1, "Method and apparatus for transmitting data"
  • Publication Date: 2004-10-21
  • Filing Date: 1999-12-16
  • Brief Description: This patent describes a method and apparatus for transmitting data.
  • Potential Anticipation (35 U.S.C. § 102): This citation seems less directly related to the core power conversion and control aspects of US8842454, based purely on the title. However, if "transmitting data" involves communication between distributed control elements, it might have a very broad relevance to how control signals are communicated between the primary and secondary controllers (claims 1, 10, 17). Further review of the full document would be needed to determine specific anticipation.

• US20120134186A1

  • Full Citation: US20120134186A1, "Inverter array with localized inverter control"
  • Publication Date: 2012-05-31
  • Filing Date: 2010-11-29 (Note: This is an earlier publication of the same patent family, claiming priority to the same provisional application as US8842454).
  • Brief Description: This is an earlier publication of US8842454 itself, indicating it describes an inverter array with localized inverter control.
  • Potential Anticipation (35 U.S.C. § 102): This document is the patent application publication for US8842454. It serves as self-prior art (if the claims changed substantially from application to grant) or is merely a procedural citation as part of the same patent family. It cannot anticipate US8842454 under 35 U.S.C. § 102 unless the claims in the granted patent are broader than what was enabled/described in this earlier publication AND the earlier publication was by a different inventive entity or filed later than other prior art. Given it's the same patent family, it's typically cited for continuity and not as anticipatory prior art in the traditional sense.

• US8223515B2

  • Full Citation: US8223515B2, "Pre-charging an inverter using an auxiliary winding"
  • Publication Date: 2012-07-17
  • Filing Date: 2009-02-26
  • Brief Description: This patent describes a method for pre-charging an inverter using an auxiliary winding.
  • Potential Anticipation (35 U.S.C. § 102): This patent might be relevant to specific implementation details of the inverters within US8842454, particularly regarding their startup or operational efficiency. If "pre-charging" is a necessary or inherent function of the inverters in US8842454, it could potentially anticipate specific claim elements related to inverter operation (claims 1, 10, 17), but likely not the overall control architecture.

This analysis provides an overview of the most relevant prior art cited in US8842454 based on their titles and brief descriptions, with an estimation of which claims they might potentially anticipate. A full legal analysis would require a deeper dive into the full text of each cited patent.

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 8842454

This analysis identifies combinations of prior art references that would render the independent claims of US Patent 8842454 obvious to a person having ordinary skill in the art (PHOSITA) as of the priority date (2010-11-29). The motivation to combine these references stems from the common goals in the field of photovoltaic (PV) power conversion: maximizing efficiency, ensuring stable grid connection, and optimizing performance under variable environmental conditions, such as partial shading.

Claims under analysis

The key features of the independent claims (Claim 1 - Apparatus, Claim 10 - Method, Claim 17 - Computer-Readable Medium) of US8842454 involve:

• A plurality of inverters converting DC power from respective DC sources (e.g., PV cells) to AC power for an AC load.
• A hierarchical control system comprising:
  • A primary (master) controller generating a primary control signal based on the total AC current and total AC voltage delivered to the AC load by the plurality of inverters.
  • A plurality of secondary (local) controllers, each receiving the primary control signal and producing a respective secondary control signal based on it.
  • Each secondary control signal controlling a corresponding inverter to provide its portion of the AC power.

Combination of Prior Art References

The combination of the following prior art references would render claims 1, 10, and 17 obvious:

1. US20110026282A1 to Chapman et al. (published 2011-02-03, filed 2009-07-31)
2. US5745356A to Exide Electronics Corporation (published 1998-04-28, filed 1996-06-25)

Analysis of Obviousness for Independent Claim 1 (Apparatus)

Claim 1: An apparatus to deliver alternating current (AC) power, the apparatus comprising: a plurality of inverters configured to receive direct current (DC) power from a respective DC power source and respectively provide AC power to an AC load; a primary controller configured to generate a primary control signal based on total AC current and total AC voltage being delivered to the AC load by the plurality of inverters; and a plurality of secondary controllers configured to each receive the primary control signal and produce a respective secondary control signal based on the primary control signal, wherein the respective secondary control signal for each of the plurality of secondary controllers controls a corresponding one of the plurality of inverters to provide the respective AC power.

1. "a plurality of inverters configured to receive direct current (DC) power from a respective DC power source and respectively provide AC power to an AC load;"

   • US20110026282A1 discloses an apparatus for converting DC to AC, including a "plurality of inverter sub-modules" (106 in FIG. 1) electrically coupled to receive DC power from PV cells (102) and provide an AC output to an AC load. This directly teaches a plurality of inverters receiving DC power from respective DC power sources (PV cells) and providing AC power to an AC load.

2. "a primary controller configured to generate a primary control signal based on total AC current and total AC voltage being delivered to the AC load by the plurality of inverters;"

   • US20110026282A1 discloses a "master controller" (108 in FIG. 1) configured to provide a "control signal" (110) to each of the inverter sub-modules. While the abstract of US20110026282A1 does not explicitly state that this master control signal is based on total AC current and total AC voltage, the purpose of the master controller, as described in US20110026282A1 (and implicitly for any master controller in a grid-tied multi-inverter system), is for "locally controlling energy balance within each of the plurality of inverter sub-modules." For a system providing AC power to an AC load (such as a utility grid), maintaining system-level energy balance and ensuring proper grid synchronization necessarily involves monitoring the aggregate AC output (total AC current and voltage).
   • US5745356A teaches "independent load sharing of AC power systems connected in parallel." Such systems inherently require a control mechanism that monitors the total AC current and/or voltage of the combined output to effectively manage load sharing among multiple AC sources. This demonstrates that it was well-known in the art to base control signals for multi-source AC systems on aggregate AC load parameters.

3. "a plurality of secondary controllers configured to each receive the primary control signal and produce a respective secondary control signal based on the primary control signal,"

   • US20110026282A1 explicitly teaches that "Each of the inverter sub-modules 106 may include a local controller (see FIG. 2)." Furthermore, "The inverter module 104 may include a master controller 108 to provide one or more control signals 110 to each of the inverter sub-modules 106. Each of the inverter sub-modules 106 may use the control signals 110 to locally control the energy balance within each inverter sub-module 106." This directly describes a plurality of secondary (local) controllers receiving a primary (master) control signal and using it to generate local control actions (i.e., respective secondary control signals).

4. "wherein the respective secondary control signal for each of the plurality of secondary controllers controls a corresponding one of the plurality of inverters to provide the respective AC power."

   • This is the functional outcome of the local control described in US20110026282A1. The local controllers use the master control signal (110) to "locally control the energy balance" of their respective inverter sub-modules (106), which directly impacts the AC power provided by that inverter.

Motivation to Combine:
A PHOSITA in the field of power electronics for PV applications, seeking to improve the efficiency and stability of multi-inverter PV systems, particularly under varying environmental conditions like shading (as acknowledged in the background of US8842454), would have been motivated to combine the teachings of US20110026282A1 with the common knowledge and practices exemplified by US5745356A.

US20110026282A1 provides the core hierarchical control architecture with a master controller coordinating local inverter modules to manage energy balance. To optimize the overall system performance and ensure stable and compliant power delivery to an AC load (e.g., a utility grid), a PHOSITA would readily recognize the necessity of making the "master controller" (primary controller) responsive to the aggregate AC load conditions. References like US5745356A show that monitoring total AC current and voltage for system-level control, such as load sharing, was a well-established practice in modular AC power systems. It would be a straightforward engineering decision to feed the total AC current and voltage measurements to the master controller of US20110026282A1 to generate a more effective primary control signal, thereby ensuring the overall system meets grid requirements while local controllers optimize individual inverter performance. This combination addresses the problem of maximizing efficiency and reliability in distributed PV systems connected to an AC grid.

Analysis of Obviousness for Independent Claim 10 (Method)

Claim 10: A method of controlling alternating current (AC) power delivered to an AC load, the method comprising: producing the AC power with an array of inverters based on an amount of received respective DC power; generating a first control signal in response to the AC power; generating a plurality of second control signals in response to the first control signal; and controlling respective output AC power of each inverter of the array of inverters based on a corresponding one of the second control signals, wherein the AC power is a combination of the respective output AC power of each inverter of the array of inverters.

The method steps directly parallel the components of Claim 1.

1. "producing the AC power with an array of inverters based on an amount of received respective DC power;" Taught by the inverter sub-modules (106) receiving DC from PV cells (102) and providing AC output in US20110026282A1.
2. "generating a first control signal in response to the AC power;" This corresponds to the primary control signal based on total AC current and voltage. As discussed for Claim 1, a master controller performing system-level energy balance in a grid-tied context (as in US20110026282A1) would inherently generate its primary control signal in response to the total AC power, using feedback from total AC current and voltage (as commonly known in the art, e.g., US5745356A).
3. "generating a plurality of second control signals in response to the first control signal;" Taught by the local controllers in US20110026282A1 receiving the master control signal (110) and using it for local control actions.
4. "controlling respective output AC power of each inverter of the array of inverters based on a corresponding one of the second control signals, wherein the AC power is a combination of the respective output AC power of each inverter of the array of inverters." This is the outcome of the local control in US20110026282A1, where local controllers regulate the energy balance and output of their respective inverters.

Motivation to Combine: The motivation for the method claim is identical to that for the apparatus claim. A PHOSITA would seek to implement a method for distributed PV power generation that combines system-level control based on aggregate AC output (for grid stability and power quality) with localized control (for individual inverter optimization and fault tolerance), using a hierarchical signaling approach as taught.

Analysis of Obviousness for Independent Claim 17 (Computer-Readable Medium)

Claim 17: A computer-readable medium comprising a plurality of instructions executable by a processor, the computer-readable medium comprising: instructions to direct an array of inverters to generate AC power based on an amount of received respective DC power; instructions to generate a first control signal in response to the AC power; instructions to generate a plurality of second control signals in response to the first control signal; and instructions to control respective output AC power of each inverter of the array of inverters based on a corresponding one of the second control signals, wherein the AC power is a combination of the respective output AC power of each inverter of the array of inverters.

Claim 17 describes a computer-readable medium for implementing the method of Claim 10. Given that power electronics control systems are commonly implemented using processors and computer-readable media (as explicitly noted in US8842454's own disclosure for its master and local controllers, which can be digital and include processors and memory devices), it would be obvious for a PHOSITA to implement the obvious method of Claim 10 using a computer-readable medium. Therefore, if the method of Claim 10 is obvious, the computer-readable medium of Claim 17 is also obvious.