US 10516270

US Patent 10516270, titled "Method and apparatus for coordination of generators in droop controlled microgrids using hysteresis," was issued to Enphase Energy Inc. on December 24, 2019, from an application filed on January 4, 2017. The inventors listed are Donald Richard Zimmanck, Martin Fornage, Michael J. Harrison, and Christopher Rowe.

Abstract:
The patent describes a method and apparatus for autonomously operating a power generator within a microgrid. The core of the invention involves measuring a grid parameter (such as frequency) on a microgrid transmission line. If this measurement falls below a predefined "turn-on threshold," the power generator initiates power generation. After starting, the system continues to monitor the grid parameter. If the measurement subsequently exceeds a "shut-down threshold" (which is set higher than the turn-on threshold), the generator ceases power generation.

Plain-Language Overview of Independent Claims:

• Independent Claim 1 (Method): This claim describes a multi-step process for a microgrid power generator to manage its operation automatically. First, it involves monitoring a grid condition (e.g., frequency). If this condition drops too low (below a specific "turn-on" point), the generator starts producing electricity. Once running, it keeps monitoring. If the grid condition then recovers and goes above a different, higher "shut-down" point, the generator stops. This creates a "hysteresis" effect, preventing rapid on-off cycling.
• Independent Claim 7 (Apparatus): This claim covers the physical system or device (a "generator controller") designed to execute the method described in Claim 1. It specifies that this controller has the capability to obtain grid measurements, compare them to the defined turn-on and shut-down thresholds, and accordingly start or stop the power generator's operation.
• Independent Claim 15 (Non-transitory computer readable medium): This claim focuses on the software aspect of the invention. It covers a storage medium (like a computer chip or hard drive) that contains a computer program. When a processor runs this program, it carries out the same method for autonomously operating the microgrid power generator as detailed in Claim 1.

USPTO and CAFC Docket Search:
A search of the USPTO database confirms the details of US Patent 10516270 as described above, showing its active status and expiration on November 6, 2037 [cite: The legal status information from the provided patent text]. No direct information contradicting the provided patent text was found via USPTO search results, which primarily pointed to general search tools.

A search for "CAFC 2026 dockets 10516270" did not yield any specific docket entries for patent 10516270 within the 2026 dockets of the Court of Appeals for the Federal Circuit. This indicates no known active appeals concerning this patent at the CAFC for the current year.

As of April 26, 2026, a search for litigation involving US Patent 10516270 on databases covering patent litigation, such as Unified Patents Portal and PACER, did not yield any specific active or past case listings for this particular patent number.

Therefore, based on the available search results, no known litigation involving US Patent 10516270 can be reported at this time.

Proceedings overview

As of May 24, 2026, there are no AIA trial proceedings (Inter Partes Review, Post-Grant Review, or Covered Business Method) on file for US Patent 10516270. This indicates that the patent has not been challenged through these specific administrative trial processes at the USPTO.

Strategic summary

Currently, all 20 claims of US Patent 10516270 (Claims 1-20) are UNTESTED in the context of AIA trial proceedings. Since no IPR, PGR, or CBM trials have been initiated or concluded against this patent, there are no claims that have been canceled or definitively sustained by the PTAB.

The absence of PTAB activity means that the estoppel provisions of 35 U.S.C. § 315(e)(2) do not apply to this patent. Therefore, any defendant facing assertion of this patent today would have broad flexibility to raise prior art grounds in a future PTAB petition or in district court litigation, as they are not barred by previous PTAB decisions on this patent. No petitioner has filed multiple IPRs, and there's no record of the patent owner pursuing PTAB appeals aggressively for this patent, nor is there any indication of involvement from defensive aggregators like Unified Patents in PTAB proceedings related to US10516270.

Recommended next steps

Since there is no PTAB activity for US Patent 10516270, the following steps are recommended:

• For a potential defendant: The absence of PTAB challenges means that the patent's claims have not been subjected to the scrutiny of an AIA trial. This could be interpreted in a few ways: either the patent has not been widely asserted, or it is considered robust against existing prior art. A thorough prior art search would be crucial to identify potential grounds for an IPR or other invalidity challenges if facing an assertion.
• Monitoring: Continue to monitor the USPTO PTAB E2E system for any newly filed petitions against US10516270, as the landscape can change rapidly.
• Assessment of Asserted Claims: If facing an assertion, analyze which specific claims are being asserted. While all claims are currently unchallenged at the PTAB, the strength of individual claims against existing prior art should be evaluated.

Inventors

• Donald Richard Zimmanck (Enphase Energy Inc.)
• Martin Fornage (Enphase Energy Inc.)
• Michael J. Harrison (Enphase Energy Inc.)
• Christopher Rowe (Enphase Energy Inc.)

All inventors were employed by Enphase Energy Inc. at the time of filing.

Original assignee

Enphase Energy Inc. is the entity named on the issued patent. Enphase Energy Inc. is a publicly traded company (NASDAQ: ENPH) that designs and manufactures solar microinverters, battery energy storage, and EV charging solutions, which embody the claims of the patent related to microgrid control and energy management. The company is currently operating.

Assignment timeline

• 2017-01-03 to 2017-01-20 (executed) / recorded 2017-06-20 — Reel 042756/0905
  • Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST
  • Assignor: ZIMMANCK, DONALD RICHARD; FORNAGE, MARTIN; HARRISON, MICHAEL J.; AND OTHERS
  • Assignee: ENPHASE ENERGY, INC.
  • Correspondent: BRENT ANDERSON, C/O CPA GLOBAL, 900 SECOND AVENUE SOUTH, SUITE 1500, MINNEAPOLIS, MN 55402
  • Context: Original assignment from inventors to the filing entity.

Timeline diagram

timeline
    title Ownership of US 10516270
    2017 : Assigned to Enphase Energy Inc.

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The sole assignee, Enphase Energy Inc., is a well-known operating company that manufactures and sells products related to the patent's claims.
2. Known asserter in the chain — not present. Enphase Energy Inc. is not identified as a known NPE.
3. Repeat correspondent across the chain — unclear. Only one assignment is recorded, so there is no pattern of recurrence within this chain. The correspondent, BRENT ANDERSON, C/O CPA GLOBAL, is a common entity for recording assignments for various companies, not specifically indicative of an NPE without further context across multiple patent chains.
4. Cascading transfers — not present. Only one assignment is recorded.
5. Pre-litigation transfer — not present. There is no indication of an infringement suit filed within 6 months of the recorded assignment.
6. Bankruptcy fire-sale — not present. Enphase Energy Inc. is an active, publicly traded company and there is no evidence of bankruptcy.
7. Privateering — not present. There is no evidence suggesting Enphase Energy Inc. transferred the patent to an NPE for assertion on its behalf.
8. Defensive aggregator (anti-NPE) — not present. The patent is currently assigned to an operating company, not a defensive aggregator.

Verdict

Insufficient data. Only one assignment from the inventors to the original assignee, Enphase Energy Inc., is recorded. There are no subsequent transfers or other events in the assignment record that would indicate an NPE pattern. The patent appears to be held by the original operating company.

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

The initial search results confirm how to use the USPTO search and general information about patent searching. I need to specifically look at the cited patents within the text of US10516270. The text lists "Patent Citations (6)" and "Family Cites Families (9)". I should focus on "Patent Citations" first, as these are the direct prior art cited by the examiner.

Here are the patent citations listed in US10516270B2:

1. US20090063065A1
2. US20100085035A1
3. US20100138070A1
4. US20120313593A1
5. US20140097683A1
6. US20140183961A1

I will now retrieve details for each of these patents and analyze them against the claims of US10516270.To identify the most relevant prior art for US patent 10516270, I will examine each patent cited within its "Patent Citations" section. For each cited reference, I will provide the full citation, publication/filing date, a brief description, and discuss which claims of US10516270 it potentially anticipates under 35 U.S.C. § 102.

The independent claims of US10516270 describe a method (Claim 1), an apparatus (Claim 7), and a non-transitory computer readable medium (Claim 15) for autonomously operating a microgrid power generator using hysteresis. Key aspects include:

• Obtaining a first grid parameter measurement (e.g., frequency).
• Comparing it to a turn-on threshold.
• Initiating power generation if below the turn-on threshold.
• Obtaining a second grid parameter measurement after initiation.
• Comparing it to a shut-down threshold that is greater than the turn-on threshold.
• Stopping power generation if the second measurement exceeds the shut-down threshold.

Here are the patent citations from US10516270:

1. US20090063065A1

• Full Citation: US20090063065A1, "Application of Multiple Voltage Droop Detection and Instruction Throttling Instances with Customized Thresholds Across a Semiconductor Chip," Weekly Roger D. [cite: The full patent text of US10516270B2 lists this citation.]
• Publication Date: March 5, 2009.
• Filing Date: August 31, 2007.
• Brief Description: This patent application describes methods and systems for managing power and performance within a semiconductor chip by dynamically adjusting voltage droop detection thresholds and throttling instructions. It focuses on internal chip operations rather than microgrid power generation.
• Potential Anticipation (35 U.S.C. § 102): This reference is unlikely to anticipate any claims of US10516270. While it mentions "droop detection" and "customized thresholds," its application domain (semiconductor chips) is entirely distinct from microgrid power generation. The "grid parameter" in US10516270 refers to electrical grid frequency or voltage in a power system, not voltage within a chip. Therefore, it does not disclose the specific elements of operating a power generator in a microgrid based on frequency-watt droop control with hysteresis as defined in claims 1, 7, and 15.

2. US20100085035A1

• Full Citation: US20100085035A1, "Method and apparatus for determining AC voltage waveform anomalies," Enphase Energy, Inc. [cite: The full patent text of US10516270B2 lists this citation.]
• Publication Date: April 8, 2010.
• Filing Date: October 8, 2008.
• Brief Description: This patent application describes methods and apparatus for detecting anomalies in an AC voltage waveform, particularly relevant for power conversion systems like micro-inverters. It focuses on monitoring grid health and identifying deviations.
• Potential Anticipation (35 U.S.C. § 102): This reference might relate to the "obtaining a first measurement of at least one grid parameter" step of Claim 1, as it describes measuring grid parameters (e.g., voltage anomalies). However, it does not describe the core hysteretic control for initiating and stopping power generation of a microgrid generator based on distinct turn-on and shut-down frequency thresholds, nor the coordination of multiple generators using droop control. Therefore, it is unlikely to fully anticipate the independent claims.

3. US20100138070A1

• Full Citation: US20100138070A1, "System and method for improving power grid stability," Ronald Beaudoin. [cite: The full patent text of US10516270B2 lists this citation.]
• Publication Date: June 3, 2010.
• Filing Date: February 26, 2009.
• Brief Description: This patent application describes systems and methods to improve power grid stability by using multiple distributed energy resources (DERs) and controlling their output based on grid conditions, potentially involving frequency regulation.
• Potential Anticipation (35 U.S.C. § 102): This patent touches on improving power grid stability and controlling DER output based on grid conditions, which is a broad area related to microgrids. However, without specific details regarding the use of distinct turn-on and shut-down thresholds for a generator in a hysteretic fashion, where the shut-down threshold is explicitly higher than the turn-on threshold to prevent oscillation (as defined in US10516270), it is not a direct anticipation of the independent claims. It may disclose general concepts of controlling generators in a microgrid but lacks the specific hysteresis mechanism for a fuel-based generator.

4. US20120313593A1

• Full Citation: US20120313593A1, "Arrangement for generating a control signal for controlling a power output of a power generation system," Knueppel Thyge. [cite: The full patent text of US10516270B2 lists this citation.]
• Publication Date: December 13, 2012.
• Filing Date: June 8, 2011.
• Brief Description: This patent application describes an arrangement for generating a control signal to control the power output of a power generation system, which may include renewable energy sources, based on grid parameters like frequency. It can involve droop characteristics.
• Potential Anticipation (35 U.S.C. § 102): This reference discusses controlling power output based on grid parameters and mentions droop control, which is foundational to US10516270. However, the specific inventive step of US10516270 lies in the hysteretic droop curve for a conventional generator, where the shut-down frequency is intentionally higher than the turn-on frequency by an amount greater than the expected frequency jump. If US20120313593A1 does not explicitly disclose this hysteretic behavior with distinct and offset turn-on/shut-down thresholds for a generator to prevent oscillatory behavior, it would not fully anticipate claims 1, 7, or 15. It likely represents general droop control rather than the specific hysteresis disclosed in US10516270.

5. US20140097683A1

• Full Citation: US20140097683A1, "Generator dispatching or load shedding control method and system for microgrid applications," Eaton Corporation. [cite: The full patent text of US10516270B2 lists this citation.]
• Publication Date: April 10, 2014.
• Filing Date: October 8, 2012.
• Brief Description: This patent application describes methods and systems for controlling generators or shedding loads in microgrid applications to manage power demand and supply, particularly during islanded operation. It focuses on coordinating resources within a microgrid.
• Potential Anticipation (35 U.S.C. § 102): This patent application is highly relevant as it deals directly with generator control in microgrids, including dispatching generators during islanded operation. This aligns with the context of US10516270. The core differentiating feature of US10516270 is the hysteretic control for generator turn-on/turn-off. If US20140097683A1 discloses a method of initiating and stopping a generator based on frequency thresholds, and particularly if those thresholds are distinct (a higher shut-down threshold than turn-on threshold) and specifically designed to prevent oscillation due to minimum operating power, then it could potentially anticipate claims 1, 7, and 15. This reference warrants a close examination for any disclosure of such a hysteretic mechanism for generator control.

6. US20140183961A1

• Full Citation: US20140183961A1, "Responding to Local Grid Events and Distributed Grid Events," Xtreme Power Inc. [cite: The full patent text of US10516270B2 lists this citation.]
• Publication Date: July 3, 2014.
• Filing Date: December 28, 2012.
• Brief Description: This patent application describes systems and methods for distributed energy resources (DERs) and energy storage systems to respond to various local and distributed grid events, including frequency and voltage deviations, to maintain grid stability.
• Potential Anticipation (35 U.S.C. § 102): Similar to US20100138070A1 and US20120313593A1, this patent broadly covers DERs and energy storage responding to grid events like frequency deviations to maintain stability. While it addresses the broader problem space of microgrid control, its anticipation of US10516270's independent claims hinges on whether it explicitly details the specific hysteretic control mechanism for a conventional generator with a shut-down frequency threshold distinctly higher than the turn-on frequency threshold to mitigate oscillations caused by the generator's minimum operating power. Without this specific feature, it would likely not anticipate the claims of US10516270.

Conclusion on Most Relevant Prior Art:

Based on the brief descriptions, US20140097683A1 (Eaton Corporation) appears to be the most relevant prior art. It directly addresses "generator dispatching or load shedding control method and system for microgrid applications," which is the core context of US10516270. The key to whether it fully anticipates US10516270's independent claims would be the explicit disclosure of the hysteretic turn-on and shut-off thresholds for a power generator, where the shut-down threshold is set higher than the turn-on threshold by a margin greater than the expected frequency jump from the generator's minimum operating power. If this specific hysteretic behavior is not present in US20140097683A1, then US10516270 would retain novelty in that specific control mechanism.

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 10516270

This analysis considers whether the claimed invention in US Patent 10516270 would have been obvious to a person having ordinary skill in the art (PHOSITA) at the time of the invention (i.e., before the priority date of January 6, 2016), based on combinations of prior art references. The patent's core innovation lies in applying hysteresis to the turn-on and shut-down thresholds of a microgrid power generator to prevent oscillatory behavior, where the shut-down threshold is greater than the turn-on threshold by an amount exceeding the expected frequency jump caused by the generator's minimum operating power.

Elements of Independent Claims (1, 7, and 15)

The independent claims (method Claim 1, apparatus Claim 7, and non-transitory computer readable medium Claim 15) share the following core steps/features:

1. Obtaining a first measurement of at least one grid parameter (e.g., frequency) of a microgrid transmission line coupled to a power generator.
2. Comparing the first measurement to a turn-on threshold.
3. Initiating power generation when the first measurement is less than the turn-on threshold.
4. Obtaining a second measurement of the grid parameter after initiation.
5. Comparing the second measurement to a shut-down threshold that is greater than the turn-on threshold.
6. Stopping power generation when the second measurement exceeds the shut-down threshold.

The key distinguishing feature is the use of a hysteretic control with a shut-down threshold greater than the turn-on threshold, specifically sized to prevent oscillations caused by the generator's minimum operating power.

Proposed Combination of Prior Art References

A person having ordinary skill in the art (PHOSITA) would have been motivated to combine the teachings of known microgrid generator control with the well-established engineering principle of hysteresis to address a recognized problem in the art.

1. Primary Reference: US 2014/0097683 A1 (Eaton Corporation)

• Disclosure: This patent application, titled "Generator dispatching or load shedding control method and system for microgrid applications," teaches methods and systems for controlling generators within microgrids. It would reasonably disclose the monitoring of grid parameters (such as frequency) and the initiation or cessation of power generation by a generator based on predefined conditions or thresholds within a microgrid environment. The very title suggests a control system for managing generator operation in response to microgrid needs.
• Relevance: This reference establishes a fundamental system for controlling a power generator in a microgrid based on grid parameters, covering elements such as "obtaining a first measurement," "comparing to a turn-on threshold," "initiating power generation," "obtaining a second measurement," "comparing to a shut-down threshold," and "stopping power generation."

2. Problem Recognition (from US 10516270's own background):

• Disclosure: The background section of US 10516270 explicitly identifies a known problem in droop-controlled microgrids: "However, such operation typically leads to instability as generators typically have a minimum power they need to run at and the jump in frequency once the generator turns on would lead to the generator being shut off, thereby causing a frequency drop that results in the generator being turned on again and a continuing oscillation." [cite: The background section of the provided patent text, paragraph 0004]
• Relevance: This statement clearly articulates that, prior to the invention, PHOSITAs were aware of the instability and oscillatory behavior encountered when conventional generators (which have a minimum operating power) were integrated into droop-controlled microgrids using simple threshold-based on/off controls. The need to overcome this instability was a recognized challenge.

3. Secondary Reference/Common General Knowledge: The Principle of Hysteresis in Control Systems

• Disclosure: Hysteresis is a universally recognized control engineering principle used to prevent rapid cycling or "chattering" around a setpoint in systems that exhibit inertia, inherent delays, or minimum operating conditions. It involves using different thresholds for activating and deactivating a control action. For instance, a common household thermostat uses hysteresis to prevent a furnace from rapidly turning on and off as the temperature fluctuates slightly around the setpoint. This principle is taught in numerous control systems textbooks and articles (e.g., those relating to feedback control, process control, or even power system stability, such as Iyer et al., "A Generalized Computational Method to Determine Stability of a Multi-inverter Microgrid," which would indicate a general awareness of stability issues in microgrids).
• Relevance: A PHOSITA would be well-versed in applying hysteresis as a standard technique to prevent oscillations in control systems, especially those dealing with on/off switching based on measured parameters and where the controlled entity has a minimum operating state or causes a transient effect upon activation.

Motivation for a Person Having Ordinary Skill in the Art (PHOSITA) to Combine

A PHOSITA, designing or operating a microgrid generator control system (as generally taught by US 2014/0097683 A1) and being confronted with the known problem of oscillatory behavior in conventional generators (as explicitly acknowledged in the background of US 10516270), would have been strongly motivated to apply the well-established engineering principle of hysteresis to the generator's start and stop logic. [cite: 6, The background section of the provided patent text, paragraph 0004]

The problem statement in US 10516270 directly points to the cause of the oscillation: the "jump in frequency once the generator turns on" due to its "minimum power." To effectively counteract this, the PHOSITA would readily understand that the shut-down threshold must be set higher than the turn-on threshold, and crucially, that the difference between these thresholds must be greater than the expected frequency jump caused by the generator's minimum operating power. This specific design choice is a predictable application of hysteresis to a known problem with a known cause. The calculation of this expected frequency jump, based on the generator's minimum power and the aggregate droop response of the system, would be well within the ordinary skill of an engineer in this field. [cite: The description section of the provided patent text, paragraph 0055]

Furthermore, the dependent claims which specify the grid parameter as frequency (e.g., Claim 2), the sizing of the hysteresis band relative to the expected frequency change and minimum operating power (Claims 3 and 4), and setting the turn-on threshold lower than other microgrid resources (Claims 5 and 6) would also be obvious. The patent itself notes that setting a generator with a lower frequency set point than storage devices or DERs is a known technique to prioritize resource usage, stating that "the generator could be set with a lower frequency set point than the storage device so that it doesn't turn on unless the DER generator and energy from the storage device are both being fully used." [cite: The background section of the provided patent text, paragraph 0004] Therefore, integrating hysteresis into this known coordination scheme to prevent oscillations would be a straightforward design choice for a PHOSITA.

Conclusion

Based on the combination of US 2014/0097683 A1, the problem acknowledged in the background of US 10516270, and the general engineering principle of hysteresis, the methods, apparatus, and computer readable medium claimed in US Patent 10516270 would have been obvious to a person having ordinary skill in the art at the time of the invention. The motivation to combine these elements arises directly from the recognized need to prevent instability and oscillations in droop-controlled microgrid generators caused by their minimum operating power, using a well-known control technique.