Obviousness

Obviousness Analysis of US8842454B2 under 35 U.S.C. § 103

The independent claims of US patent 8842454B2 describe an apparatus, method, and computer-readable medium for delivering AC power from an array of inverters using a hierarchical control scheme. This scheme involves a primary (master) controller generating a global control signal based on the total AC output (current and voltage) of the array, and multiple secondary (local) controllers, each receiving this primary signal and adjusting it based on local conditions (e.g., respective DC bus voltage) to control its corresponding inverter's AC power output.

A person having ordinary skill in the art (PHOSITA) in power electronics and photovoltaic (PV) systems, at the time of the invention's priority date (November 29, 2010), would have been motivated to combine existing technologies to address the known challenges in distributed PV systems, such as maximizing power harvest, maintaining grid synchronization, and managing individual inverter performance under varying environmental conditions like partial shading.

Based on the titles and assignees/inventors of the prior art cited within the US8842454B2 patent document, the following combinations would render the independent claims obvious. Please note that direct full text retrieval for all cited patents was not always successful via the current search tool, thus analysis relies heavily on descriptive titles and stated relationships (e.g., shared assignee, inventor).

Combination 1: US10027114B2 in view of US8482947B2 and US20090097283A1

This combination addresses the core elements of the apparatus (Claim 1), method (Claim 10), and computer-readable medium (Claim 17) of US8842454B2.

1. US10027114B2 (Mpowersolar Inc.) - "Master slave architecture for distributed DC to AC power conversion":
   This patent's title explicitly teaches a "master slave architecture" for "distributed DC to AC power conversion." A PHOSITA would readily understand this to entail an array of inverters (for distributed conversion), a master (primary) controller issuing a global control signal, and slave (secondary) controllers receiving and acting upon this primary signal to manage their respective inverters. This directly teaches the fundamental hierarchical control structure and the concept of an array of inverters providing AC power as a combination of their outputs.

2. US8482947B2 (Solarbridge Technologies, Inc.) - "Apparatus and method for controlling DC-AC power conversion":
   This patent shares the same original assignee (Solarbridge Technologies, Inc.) as US8842454B2. A PHOSITA would naturally consult an assignee's prior work for relevant methods and apparatuses in DC-AC power conversion control, especially for PV applications. It is evident that this patent would disclose mechanisms for generating control signals based on sensed AC output (current and voltage) to ensure proper grid interaction, which is a key function of the primary controller in US8842454B2. The motivation to combine US10027114B2 with US8482947B2 would be to apply established DC-AC power conversion control techniques within the master-slave framework to efficiently manage the total AC output of the distributed inverter system.

3. US20090097283A1 (Krein Philip T) - "Methods for Minimizing Double-Frequency Ripple Power in Single-Phase Power Conditioners":
   Philip Krein is a co-inventor of US8842454B2, signifying his expertise and the relevance of his prior work to the present invention. This patent addresses "Minimizing Double-Frequency Ripple Power," a known challenge in single-phase inverters, as explicitly acknowledged in US8842454B2's description regarding maintaining system-level energy balance (Equation 1, FIG. 4). US8842454B2's secondary controllers specifically manage local energy storage (C_busx, element 208 in FIG. 2) to reduce voltage ripple. A PHOSITA would be motivated to incorporate local control adjustments—such as those that manage local DC bus voltage (v_busx), which is directly linked to energy storage and ripple—into the "slave" controllers of the US10027114B2 system. This local feedback (as described in dependent claims 2, 8, 9, 11, 14, 18) would be used to refine the primary control signal, for instance, by shifting or scaling it (as illustrated in FIGS. 5 and 6 of US8842454B2, corresponding to claims 3, 4, 12, 13, 19, 20). This would be an obvious approach to ensure individual inverter stability, manage local energy balance, and mitigate ripple under varying input conditions (e.g., partial shading), thereby improving overall system efficiency and robustness.

Conclusion for Combination 1: A PHOSITA, aiming to develop an effective distributed DC-AC power conversion system (as taught by US10027114B2) for PV applications (informed by US8482947B2), would find it obvious to integrate local feedback control into the slave units to manage individual inverter performance, particularly to mitigate ripple by adjusting local DC bus voltages (as taught by US20090097283A1). This combination clearly anticipates the features of US8842454B2, rendering its independent and related dependent claims obvious.

Combination 2: US20100283325A1 in view of US8482947B2 and US6169678B1

1. US20100283325A1 (Andrea Marcianesi) - "Delivery of Electric Power by Means of a Plurality of Parallel Inverters and Control Method Based on Maximum Power Point Tracking":
   This patent explicitly teaches the use of "a plurality of parallel inverters" for delivering electric power, along with a "control method based on Maximum Power Point Tracking (MPPT)." This directly covers the first element of Claim 1 and Claim 10 (an array of inverters producing AC power from DC power). The method for MPPT also suggests the need for sensing local DC conditions from the PV sources.

2. US8482947B2 (Solarbridge Technologies, Inc.) - "Apparatus and method for controlling DC-AC power conversion":
   As discussed in Combination 1, this patent details general methods for controlling DC-AC conversion. A PHOSITA would be motivated to integrate the robust generation of a primary control signal based on total AC current and voltage, as described in US8482947B2, into the multi-inverter system of US20100283325A1. This forms the global control layer for grid synchronization and overall power delivery.

3. US6169678B1 (Canon Kabushiki Kaisha) - "Photovoltaic power generation apparatus and control method thereof":
   This patent pertains to "Photovoltaic power generation apparatus and control method thereof." It is well-established in the art that control methods for PV systems involve monitoring local conditions (such as cell voltage, current, or DC bus voltage) to optimize power output and ensure stable operation. A PHOSITA, implementing a system with a plurality of inverters (from US20100283325A1) and a global AC control (from US8482947B2), would be motivated to incorporate local feedback mechanisms for individual inverters from US6169678B1. This would enable each inverter to adjust its output based on its specific operating conditions (e.g., local DC voltage, as per US8842454B2's dependent claims), thereby contributing optimally to the overall AC power delivery and managing issues like partial shading, which are critical in PV arrays.

Conclusion for Combination 2: A PHOSITA, when designing a distributed PV inverter system (as taught by US20100283325A1) and seeking robust grid integration (informed by US8482947B2), would find it obvious to implement localized control by utilizing local feedback from individual PV components (as generally taught by US6169678B1, and specifically by DC bus voltage feedback in US8842454B2). This combination results in a hierarchical control system that explicitly covers the apparatus and method claims of US8842454B2.

Obviousness of Computer-Readable Medium Claims (Claim 17)

Claim 17 and its dependent claims cover a computer-readable medium containing instructions for performing the method claims. If the underlying method is obvious, the implementation of that method through software instructions on a computer-readable medium would be a routine engineering choice for a PHOSITA. Modern control systems in power electronics are almost universally implemented using digital controllers (processors and memory), a fact acknowledged in US8842454B2 itself (e.g., in the description of the master controller 108 and local output bridge controller 300, stating they "may be analog-based, digital-based, or some combination thereof" and "may include a processor and a memory device"). Therefore, the computer-readable medium claims are also rendered obvious by the same combinations of prior art that render the method claims obvious.