DETAILED ACTION
This Office action is in response to the amendment filed on 21 November 2025.
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Response to Arguments
Applicant's arguments filed 21 November 2025 have been fully considered but they are not persuasive.
Applicant argues, see Remarks at p. 9, that Cai (full citation is found below in this Office action) discloses magnitude control of voltage components to achieve power setpoints, and more particularly that Cai generates d- and q-axis reference values udref and uqref from power commands and controls magnitudes of the d-axis and q-axis voltage components, ud and uq, to match the references. Based on this, Applicant concludes that Cai does not disclose controlling the phase angle of capacitor voltage vector relative to grid voltage vector, to regulate active power transfer.
Examiner respectfully disagrees with the assertions, however, because based on the vector transformations being performed, the phase angle of the capacitor voltage vector is defined or determined from the d-axis and q-axis components thereof. Moreover, it is respectfully submitted that based on the high level of skill in the relevant arts, the ordinary artisan would find this to be an implicit teaching of the Cai reference because it is evident from the vector mathematics involved, such as the conventional use of the Park transformation and the dq-coordinate system, which as routinely used in the field of electrical power systems.
To illustrate what is common knowledge with respect to this subject, an excerpt of the academic textbook, Advances in Power System Modelling, Control and Stability Analysis, 2nd edition, ed. F. Milano (hereinafter “Milano”) has been cited and provided with this Office action. Milano at pp. 394-398 discusses the Park transformation matrix for converting static, three-phase electric quantities to the corresponding d- and q-axis coordinates in the synchronous or rotating reference frame. More specifically, at p. 395, Milano states that, “the d and q components of the voltage describe, in steady state, a vector rotating at the speed of the network frequency”; in the vector diagram shown in Figure 11.4, this is illustrated as components vd, vq in the dq-coordinates defining a three-phase voltage quantity vabc in three-phase or abc-coordinates. As shown, the vector vabc is defined by an angle (not specifically labeled) relative to the a, b, and c axes.
It is respectfully asserted that, based on the above mathematical relationships being part of the common knowledge in the relvant arts, the person of ordinary skill would understand that by controlling the d- and q-axis components, ud, uq, of the capacitor voltage vector to conform to the reference values udref, uqref that were derived from the power commands, Pref, Qref, the Cai reference is also controlling the phase angle of the capacitor voltage vector relative to the grid angle.
Applicant further argues, see Remarks at p. 9, that there is no motivation to combine the Cai reference with the Rocabert reference (citation below) as proposed in the previous Office action, which Applicant asserts provided only a generic rationale in support of the finding of obviousness. More specifically, Applicant argues that the rationale does not explain why one would add multiple operating modes to the working system of Cai when, “Cai’s single approach adequately addresses its stated problem (weak grid conditions)” (Remarks, p. 9, penultimate paragraph).
Examiner respectfully disagrees, however, because while Cai’s system may be adequate to solve one problem, which is that of weak grid operation, the combination with Rocabert was proposed because it would enable the power system as a whole to address additional problems with respect to the grid system. That is, while the grid-supporting mode taught by Rocabert analogously corresponds to the weak grid situation described in Cai, Rocabert additionally discloses grid-forming as well as grid-feeding operations.
According to Rocabert (see sec. II. Classification of power converters in AC microgrids, p. 4735, right column, through p. 4736, left column), grid-forming operation enables setting the voltage amplitude and frequency of the local grid, grid-feeding (corresponding to grid-following) operation enables power delivery to an energized grid, and grid-supporting (corresponding to grid-firming) operation is intended to deliver proper values of active and reactive power to contribute to the regulation of the grid frequency and voltage. Furthermore, Rocabert teaches the use of each of these converter operation control modes in a hierarchical control of an AC microgrid including energy storage systems, among other systems, for the stated reasons of enhancing performance and reliability of such a system (Rocabert, Abstract).
That is, the combination of Cai and Rocabert would enable the person of ordinary skill in the art to obtain the specific benefits associated with grid-supporting or grid-firming control of a single converter to address weak-grid issues as taught by Cai (Abstract), as part of a larger AC microgrid system, in which a hierarchical load manager directs the operational functions of the microgrid as a whole, to include additional power converters which operate, or are capable of being operated, in each of the grid-forming, -following, and -supporting modes (Rocabert at sec. V. Hierarchical control of AC microgrids, pp. 4742, right column through p. 4744, right column).
Finally, Applicant argues (Remarks at bottom p. 9 through top p. 10) that the combination of Cai and Rocabert would change the principle of operation of the Cai system. Examiner respectfully disagrees, however, because as explained above, the proposed combination of the teachings of the prior art would place Cai’s single converter system into the context of a broader, AC microgrid system, having a load manager as taught by Rocabert for coordinating control of several converters for the various grid-support services as part of a hierarchical control scheme. Thus, the converter system of Cai may continue to function in the grid-supporting role, as part of the broader microgrid system and as managed by the hierarchical load manager control of Rocabert, without significant change to its principle of operation.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 1-2, 7, 13-14 and 18 are rejected under 35 U.S.C. 103 as being unpatentable over CN 105958548 with inventors Cai et al. (hereinafter “Cai”; machine translation provided with the present Office action) in view of “Control of Power Converters in AC Microgrids” by Rocabert et al. (hereinafter “Rocabert”).
In re claims 1 and 13-14, Cai discloses a system and corresponding method for managing power transfer with a power grid (Fig. 2), the system including a direct current (DC) link (Udc), and a load manager coupled between the DC link and the power grid (load manager including the inverter, filter, and all control blocks as shown), the load manager including a firming operating mode (see below), in support of the firming operating mode the system comprises:
a DC-to-alternate current (AC) inverter (see Fig. 2) configured to output an output voltage (uabc);
an output filter including a first inductor (L1), a second inductor (L2), and a capacitor (C) electrically coupled between the first inductor and the second inductor, the output filter configured to:
receive an output voltage (uabc); and
generate a capacitor voltage vector (uabc after the Park transformation to dq coordinates: ud and uq) across the capacitor, the capacitor voltage vector including a second axis component capacitor voltage (ud or uq) and a first axis component capacitor voltage (uq or ud); and
a load controller (control blocks of Fig. 2; see also Figs. 4-6) operable to regulate an active power supplied to the power grid by controlling the second axis component capacitor voltage (Figs. 2, 4: active power P regulated to command Pref through control of a second axis capacitor voltage, e.g. uq by generating command uqref; see [0012]) and a reactive power supplied to the power grid by controlling the first axis component capacitor voltage (Figs. 2, 4: reactive power Q regulated to command value Qref through control of a first axis capacitor voltage, e.g. ud by generating command udref; see [0012]);
wherein the load controller regulates the active power by altering a phase angle of the capacitor voltage vector (uabc after the Park transformation to dq coordinates: ud and uq) relative to a grid voltage vector by controlling a magnitude of the second axis component capacitor voltage of the capacitor voltage vector (as explained above in response to Applicant’s arguments, it is understood to be implicit in the Cai reference that the phase angle of the capacitor voltage vector is directly determined from the d- and q-axis components thereof, and active power transfer is thus regulated by controlling these components ud and uq (and thus the phase angle of the voltage vector) to conform to the reference quantities udref, uqref that were calaculated based on the power commands Pref and Qref).
Cai discloses the claimed invention as explained above, except for an energy storage system (ESS) that stores DC power, and the load manager further including a following operating mode, a forming operating mode. Whereas Rocabert discloses the use of energy storage systems in AC grids and/or microgrids (see last paragraph of right-hand column on first page of Rocabert (p. 4734)). In addition, Rocabert discloses the use of a load manager controller scheme (see sec. V., Hierarchical control of AC microgrids; the load manager may correspond to either the secondary or tertiary control layers) for managing power transfer on the grid, including the management or control of inverter-based distributed generation sources (id., Abstract) which may operate in grid-forming, grid-feeding (i.e., “following”), and grid-supporting (i.e., “firming”) modes of operation (See Abstract and sec. II: classification of power converters in AC microgrids, sub-sections A, B, and C).
Rocabert teaches that these and other known features of AC grids and/or microgrids increase the performance and reliability of the electrical system through various grid-support services and continuity of operations (see Abstract).
Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the system of Cai by including an energy storage system (ESS) that stores DC power, as well as a following operating mode and a forming operating mode to the load manager as taught by Rocabert, in order to increase the performance and reliability of the electrical system.
In re claim 2, Cai discloses wherein the first axis component capacitor voltage is aligned with the capacitor output voltage vector (Fig. 3: since the capacitor voltage vector U is defined according to its first- (d- or q-) and second- (q- or d-) axis components Ud and Uq), and wherein the second axis component is orthogonal to the first axis component capacitor voltage (Fig. 3: Ud and Uq are orthogonal).
In re claims 7 and 18, Cai discloses wherein regulating the reactive power by controlling the first axis component capacitor voltage determines a load nominal voltage through a grid tie inductor of the power grid (see [0035]-[0036]).
Claims 3-6, 8-11, 15-17 and 19-20 are rejected under 35 U.S.C. 103 as being unpatentable over Cai (CN 105958548) and Rocabert (“Control of …”) as applied to claims 1-2, 7, 13-14 and 18 above, and further in view of Yuan et al. (US 2013/0207622; hereinafter “Yuan”).
In re claims 3 and 15, Cai discloses wherein to regulate the second axis component capacitor voltage, the load controller comprises (see annotated version of Figs. 4 and 5 of Cai, below):
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a second axis component capacitor voltage summation node (as annotated above);
a second axis component capacitor voltage regulator (as annotated above) operable to control the second axis component capacitor voltage (uq; see above) based at least in part on the second axis component capacitor voltage summation node ([0038]).
The combination of Cai and Rocabert do not disclose a second axis component capacitor voltage limiter operable to limit the second axis component capacitor voltage to a pre-determined level. Whereas Yuan discloses a controller for a grid-connected power converter (Figs. 2-16) including limiter circuits (e.g., Fig. 8: 80, Fig. 9: 74, Fig. 10: 104, Fig. 11: 112, etc.) for limiting the control command quantities (and thus, the actual controlled quantities) so that the commanded parameters do not exceed the capabilities of the converter ([0046], [0047]).
Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the combined system of Cai and Rocabert by including a second axis component capacitor voltage limiter operable to limit the second axis component capacitor voltage to a pre-determined level as taught by Yuan so as to not exceed the capabilities of the converter/inverter under control.
In re claims 4 and 16, Cai discloses wherein the second axis component capacitor voltage summation node comprises:
a real power reference value (Fig. 4: Pref); and a real power measured voltage measured at a connection point to the power grid (Fig. 4: P).
In re claim 5, Cai discloses wherein to further regulate the first axis component capacitor voltage, the load controller comprises (see the annotated version of Figs. 4 and 5 of Cai, below):
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a second axis component inductor voltage summation node (as annotated above) including:
a reactive inductor reference value (ilq); and
a reactive inductor measured voltage measured at a connection point to the power grid (igq; see Fig. 2);
a second axis component inductor voltage regulator (as annotated above) operable to control a second axis component inductor voltage based at least in part on the second axis component inductor voltage summation node (Figs. 4, 5; [0038]).
Cai, as modified, does not disclose a second axis component inductor voltage limiter operable to limit the second axis component inductor voltage to a pre-determined level. Whereas Yuan discloses a controller for a grid-connected power converter (Figs. 2-16) including limiter circuits (e.g., Fig. 8: 80, Fig. 9: 74, Fig. 10: 104, Fig. 11: 112, etc.) for limiting the control command quantities (and thus, the actual controlled quantities) so that the commanded parameters do not exceed the capabilities of the converter ([0046], [0047]).
Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the combined system of Cai and Rocabert by including a second axis component inductor voltage limiter operable to limit the second axis component inductor voltage to a pre-determined level as taught by Yuan so as to not exceed the capabilities of the converter/inverter under control.
In re claims 6 and 17, Cai, as modified, discloses a capacitor voltage regulator coupled between the second axis component capacitor voltage limiter and the power grid operable to provide pulse-width modulation to the power grid (the PWM modulation referred to at end of [0038]).
In re claims 8-11 and 19-20, the claims represent substantially the same features as claims 3-6 and 15-17, only with the various recitiations “first axis component” and “second axis component” interchanged. However, it is noted that neither the “first axis” or “second axis” are explicitly defined in the claims when referring to either a capacitor voltage or an inductor voltage, etc.. As such, the combination of Cai, Rocabert, and Yuan, as proposed above for claims 3-6 and 15-17, is likewise applicable, mutatis mutandis, to claims 8-11 and 19-20, and is not being copied here for brevity.
Claim 12 is rejected under 35 U.S.C. 103 as being unpatentable over Cai (CN 105958548) and Rocabert (“Control of …”) as applied to claim 1, above, and further in view of Li (US 2024/0258934).
In re claim 12, Cai and Rocabert disclose the claimed invention as explained above except for an AC output transformer coupled between the output filter and the power grid. Whereas Li discloses the use of a transformer (Fig. 1: 103) to connect a power converter (110) to the grid (101) in order to match the power converter terminal voltage to that of the grid according to the turns ratio of the transformer windings (see [0027]).
Therefore it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to have modified the combined system of Cai and Rocabert by including an AC output transformer coupled between the output filter and the power grid as shown by Li in order to match the power converter terminal voltage to that of the grid according to the turns ratio of the transformer windings.
Conclusion
THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/FRED E FINCH III/Primary Examiner, Art Unit 2838