DETAILED ACTION
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 .
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
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.
Claim(s) 1-8, 11, 13-18, 20-21 is/are rejected under 35 U.S.C. 103 as being unpatentable over Wang (CN114498710A; specific reference is made to attached English machine translation) in view of Agirman (US2017/0288574).
Re claim 1. Wang teaches a power conversion device (see Wang: Figs. 2-3), comprising:
a three-level inverter (three-level inverter <203>, see Wang: [56-58], [61-62], Figs. 2-3 regarding bidirectional AC-DC conversion between respective DC terminals and at least two AC terminals for L1,L2), having a first AC terminal, a second AC terminal and two DC terminals, wherein the three-level inverter is configured for AC- DC power conversion;
a first positive DC terminal and a first negative DC terminal (positive and negative DC terminals between inverter <203> and DC-DC converter <205>, see Wang: [61-63], Fig. 3), coupled to the two DC terminals of the three-level inverter respectively;
a first capacitor and a second capacitor (bus capacitors <CBH,CBL>, see Wang: [63], Fig. 3 regarding connection between positive and negative DC terminal with midpoint <Y1> therebetween), wherein a capacitor midpoint (<Y1>) is between the first capacitor and the second capacitor, two terminals of the first capacitor are coupled to the first positive DC terminal and the capacitor midpoint respectively, and two terminals of the second capacitor are coupled to the capacitor midpoint and the first negative DC terminal respectively;
a bidirectional DC-DC converter (bidirectional DC-DC converter <205>, see Wang: [56-58], [64], Figs. 2-3 regarding bidirectional DC-DC conversion between respective sides with the corresponding bidirectional DC-AC conversion flow), configured for DC-DC voltage conversion, wherein a first side of the bidirectional DC-DC converter is electrically connected to the first positive DC terminal and the first negative DC terminal, when the three-level inverter receives an AC power, a second side of the bidirectional DC-DC converter provides a DC power correspondingly, and when the second side of the bidirectional DC-DC converter receives a DC power, the three-level inverter provides an AC power correspondingly; and
a controller (signal processing unit <206>, see Wang: [56-59], Fig. 2 regarding respective converter switch control), configured to control the three-level inverter and the bidirectional DC-DC converter. See Wang: [54-70], Figs. 2-3.
Wang does not explicitly disclose providing a separate balance circuit for the capacitors. One of ordinary skill in the art of multi-level power converters would know, however, that use of various active balance circuits to balance voltage across midpoint coupled capacitors is well-known in the art. Agirman, for example, teaches that it is known in the art of three-level converter systems with capacitors coupled with midpoint of the three-level inverter (see Agirman: [0019-0020], Figs. 1, 3) to further include a balance circuit (balancing circuit <18>, see Agirman: [0021-0022], Fig. 3 regarding balancing circuit coupled across DC bus and to the midpoint/neutral), electrically connected between the first positive DC terminal and the first negative DC terminal, wherein the balance circuit has a neutral terminal electrically connected to the capacitor midpoint; and corresponding controller (see Agirman: [0023-0025], Figs. 3-4 regarding controller <32> monitoring capacitor voltage imbalance and controlling switches to balance/equalize the voltages between the capacitors), configured to control the balance circuit, wherein the controller controls switches of the balance circuit according to a first capacitor voltage across the first capacitor and a second capacitor voltage across the second capacitor to keep the first capacitor voltage and the second capacitor voltage equal. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the system of Wang to incorporate the teachings of Agirman by including the known balancing circuit and controller for NPC three-level inverter for purposes of providing known means to predictably ensure the capacitors of the NPC three-level inverter remain balanced such that the neutral does not fluctuate to unacceptable levels and cause converter failure (see Agirman: [0005], [0022], [0025]). Note generally, a variety of other cited prior art of record may also teach a balance circuit as is currently broadly recited.
Re claim 2. Wang in view of Agirman teaches the power conversion device according to claim 1, wherein the three- level inverter (<203>) comprises a first switch, a second switch, a third switch and a fourth switch (switches <T11,T12,T13,T14>, see Wang: [62], [76], [81], Fig. 3 regarding TNPC three-level inverter topology with switches arranged as recited), two terminals of the first switch are electrically connected to the first positive DC terminal and a first switch midpoint respectively, two terminals of the second switch are electrically connected to the first switch midpoint and the first negative DC terminal respectively, two terminals of the third switch are electrically connected to the first positive DC terminal and a second switch midpoint respectively, two terminals of the fourth switch are electrically connected to the second switch midpoint and the first negative DC terminal respectively, the first switch midpoint is coupled to the first AC terminal, and the second switch midpoint is coupled to the second AC terminal.
Re claim 3. Wang in view of Agirman teaches the power conversion device according to claim 2, wherein the three- level inverter further comprises a first regulation switch and a second regulation switch (switches <Q11,Q12>) electrically connected in series between the first switch midpoint and the capacitor midpoint, the three-level inverter further comprises a third regulation switch and a fourth regulation switch (switches <Q13,Q14>, see Wang: [62], [76], [81], [90-92], Fig. 3 regarding TNPC three-level inverter topology and operation to control AC output) electrically connected in series between the second switch midpoint and the capacitor midpoint, and the controller regulates potentials at the first AC terminal and the second AC terminal by controlling the first regulation switch, the second regulation switch, the third regulation switch and the fourth regulation switch.
Re claim 4. Wang in view of Agirman teaches the power conversion device according to claim 2, wherein the three- level inverter further comprises a first bidirectional regulation switch (switches <Q11,Q12> functioning together as a bidirectional switch) electrically connected between the first switch midpoint and the capacitor midpoint, and the three-level inverter further comprises a second bidirectional regulation switch (switches <Q13,Q14> functioning together as bidirectional switch, see Wang: [62], [76], [81], [90-92], Fig. 3 regarding TNPC three-level inverter topology and operation to control AC output via switches allowing controlled current flow in both directions generally) electrically connected between the second switch midpoint and the capacitor midpoint, and the controller regulates potentials at the first AC terminal and the second AC terminal by controlling the first bidirectional regulation switch and the second bidirectional regulation switch. Wang in view of Agirman does not explicitly disclose use of bidirectional GaN switch components for the regulation switches, but Official Notice is hereby taken that it is well-known in the art of converter circuitry that GaN switches are well-known, equivalent switch components that can be used for converter bidirectional switches. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to substitute the regulation switch components of Wang with the known GaN switch components for purposes of providing known, equivalent electronic switching devices predictably being able to be controlled in the same manner to allow for electronic converter switching operation.
Re claim 5. Wang in view of Agirman teaches the power conversion device according to claim 1, wherein the balance circuit comprises a first balance switch (switch <22>), a second balance switch (switch <28>) and an inductor (inductor <20>; see Agirman: [0021-0022], Fig. 3 and discussion of claim 1 above regarding providing balance circuit across the DC input of the three-level inverter and coupled to the capacitor midpoint for balancing purposes), a first terminal of the first balance switch is electrically connected to the first positive DC terminal, a second terminal of the first balance switch is electrically connected to a first terminal of the second balance switch and a first terminal of the inductor, a second terminal of the second balance switch is electrically connected to the first negative DC terminal, and a second terminal of the inductor is electrically connected to the neutral terminal.
Re claim 6. Wang in view of Agirman teaches the power conversion device according to claim 5, wherein a control signal of the first balance switch is complementary to a control signal of the second balance switch, and the controller compares the first capacitor voltage with the second capacitor voltage and regulates a duty ratio of the control signal of the first balance switch according to a comparison result, wherein the duty ratio is less than 0.5 when the first capacitor voltage is greater than the second capacitor voltage, and the duty ratio is greater than 0.5 when the first capacitor voltage is less than the second capacitor voltage (see Agirman: [0023-0025], Figs. 3-4 regarding alternately/complementary switching based on comparison of Vupper to Vlower to regulate duty cycle value to be respectively higher/lower between the two alternately switched components).
Re claim 7. Wang in view of Agirman teaches the power conversion device according to claim 6, wherein a magnitude of the duty ratio of the control signal of the first balance switch depends on a difference between the first capacitor voltage and the second capacitor voltage (see Agirman: [0023-0025], Figs. 3-4 regarding duty cycle value dependent on difference <34> between Vupper and Vlower).
Re claim 8. Wang in view of Agirman teaches the power conversion device according to claim 6, wherein a magnitude of the duty ratio of the control signal of the first balance switch depends on a difference between the first capacitor voltage and the second capacitor voltage, and the magnitude of the duty ratio of the control signal of the first balance switch further depends on an average current of the inductor (see Agirman: [0023-0025], Figs. 3-4 regarding duty cycle value dependent on difference <34> between Vupper and Vlower and current of inductor <38>).
Re claim 11. Wang in view of Agirman teaches the power conversion device according to claim 1, further comprising a filter circuit (filtering unit <201>, precharge unit <204>, see Wang: [161-162], [164-165], Figs. 2-3), wherein the filter circuit comprises two filter capacitors (capacitors <C3,C2>) and a resistor (resistor <R2>), the two filter capacitors are electrically connected in series between the first AC terminal and the second AC terminal (see Wang: [161-162], Fig. 3 regarding capacitors connected in series via neutral point). Wang in view of Agirman does not explicitly describe respective switches in series with each AC terminal as recited, but Official Notice is hereby taken that it is very well-known in the art of power distribution and conversion systems to provide series AC disconnect switches at converter output for purposes of providing means to disconnect the converter from AC source in response to emergencies or faults. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the system of Wang in view of Agirman to further include first and second filter switches arranged as recited at the AC terminals for purposes of providing known means to enable the power converter to disconnect for AC output or source to prevent damage to components in case of emergencies or faults. Note the combination would result in the first filter switch is electrically connected to the first AC terminal, and two terminals of the second filter switch are electrically connected to the second AC terminal and the resistor respectively by placing the switches in series with <L1> and <L2> terminals of Wang.
Re claim 13, the claim recites a control method of a power conversion device comprising operating essentially the same components in the same manner recited in claim 1, and therefore is rejected by the same reasoning applied to claim 1 above.
Re claims 14-18, the further recited limitations essentially correspond to the limitations recited in claims 2-8, respectively, and are therefore rejected by the same reasoning applied above. See claim discussions above for corresponding limitations.
Re claim 20. Wang in view of Agirman teaches the control method according to claim 16, wherein the sub-step (bl) comprises: comparing the first capacitor voltage with the second capacitor voltage to obtain a difference between the first capacitor voltage and the second capacitor voltage (difference element <34>); processing the difference to generate a first comparison result (regulator <36>), and comparing the first comparison result with an average current of the inductor to generate a second comparison result (difference element <38>); and generating the control signal of the first balance switch according to the second comparison result (see Agirman: [0024-0025], Fig. 4). Wang in view of Agirman does not explicitly disclose the regulator <36> comparing the difference with a reference voltage to generate the first comparison result, but Official Notice was previously taken and hereby made of record that it is well-known in the art of signal processing circuitry that a regulator may be designed to receive reference voltage for comparison for purposes of allowing electronic control to regulate to the desired reference voltage. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the system of Wang in view of Agirman to have the control circuit receive reference voltage as recited for purposes of providing known means to allow the control circuit to receive settable reference voltage for regulation and providing equivalent, known circuit means for predictably implementing a signal regulator.
Re claim 21. Wang in view of Agirman teaches the control method according to claim 20, and sensing of the capacitor voltages for control (see Agirman: [0023-0025], Figs. 3-4), but does not explicitly disclose steps to filter the voltage signals before processing. Official Notice was previously taken and hereby made of record, however, that it is well known in power conversion circuits using voltage sensing to include filtering of the sensed voltage signals before processing for purposes of filtering out unwanted noise signals produced in the power distribution system which may throw off accuracy of voltage measurements. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the system of Wang in view of Agirman to further include steps of filtering the first capacitor voltage and the second capacitor voltage before comparing the first capacitor voltage with the second capacitor voltage for purposes of providing known technique for improving accuracy of voltage signal measurement by predictably removing noise from the measurement signal that may occur due to power system operation.
Claim(s) 9, 19 is/are rejected under 35 U.S.C. 103 as being unpatentable over Wang in view of Agirman, as applied respectively above, further in view of Yamashita (US2018/0019685).
Re claim 9. Wang in view of Agirman teaches the power conversion device according to claim 6, but does not explicitly disclose control to restrict operation of the balance circuit based on a threshold. Yamshita, however, teaches that it is known in the art of balance circuits for multi-level inverters wherein the controller regulates the duty ratio of the control signal of the first balance switch when an absolute value of a difference between the first capacitor voltage and the second capacitor voltage is greater than a preset threshold, and the controller controls the balance circuit to stop operating when the absolute value of the difference is less than the preset threshold (see Yamashita: [0004], [0059-0062], Figs. 1, 7, 15-16 regarding only performing balancing control if absolute value of capacitor voltage difference exceeds a threshold). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the system of Wang in view of Agirman to further incorporate the teachings of Yamashita by having operation of balance occur based on the recited condition for purposes of providing known, predictable means to determine whether an unbalanced condition is present requiring correction and otherwise not performing balance operation if not needed (see Yamashita: [0004], [0059-0062]).
Re claim 19, the further recited limitations essentially correspond to the limitations recited in claim 9, and are therefore rejected by the same reasoning applied above.
Claim(s) 10, 22 is/are rejected under 35 U.S.C. 103 as being unpatentable over Wang in view of Agirman, as applied respectively above, further in view of Hayashi (US2021/0257919), further in view of Yamashita (US2018/0019685).
Re claim 10. Wang in view of Agirman teaches the power conversion device according to claim 5, wherein the controller compares the first capacitor voltage with the second capacitor voltage, when the first capacitor voltage is not equal to the second capacitor voltage, the controller controls a control signal of the second balance switch to be complementary to a control signal of the first balance switch for balancing (see Agirman: [0023-0025], Figs. 3-4). Wang in view of Agirman does not explicitly discuss the further recited balancing control for the balance circuit, including specific duty ratio and stopping switching when balanced. Hayashi, however, teaches that it is known in the art of multi-level inverter balancing circuits using complementary switches to perform balancing by controlling a duty ratio of the control signal of the first balance switch to be maintained at 0.5 (see Hayashi: [0005], [0030], [0035], Fig. 1 regarding known control of converter structure to balance capacitor voltages by operating at 50% duty ratio; note broadly the control includes switching off both switches at some point during and once balancing is achieved). Additionally, Yamashita teaches that it is known in the art of balance circuits for multi-level inverters for the controller to control the balance circuit to stop operating when the capacitor voltages are equal (see Yamashita: [0004], [0059-0062], Figs. 1, 7, 15-16 regarding only performing balancing control if absolute value of capacitor voltage difference exceeds a threshold; note that it is understood stopping/not performing balancing would mean the balancing switches are not operated, i.e. off). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the system of Wang in view of Agirman to incorporate the teachings of Hayashi and Yamashita by having the recited control operation of the balance circuit for purposes of providing known control means for the balance circuit to provide balancing of the capacitor voltages (see Hayashi: [0005], [0030], [0035], Fig. 1) and for purposes of providing known, predictable means to determine whether an unbalanced condition is present requiring correction and otherwise not performing balance operation if not needed (see Yamashita: [0004], [0059-0062]).
Re claim 22, the further recited limitations essentially correspond to the limitations recited in claims 5 and 10, and are therefore rejected by the same reasoning applied above.
Claim(s) 12 is/are rejected under 35 U.S.C. 103 as being unpatentable over Wang in view of Agirman, as applied respectively above, further in view of Phillips (WO2024/016056).
Re claim 12. Wang in view of Agirman teaches the power conversion device according to claim 1, wherein the three-level inverter for delivering power to an electrical grid (see Wang: [3], [6], [54], Fig. 2 regarding inverter for grid coupling) and the bidirectional DC-DC converter for delivering power to an on-board power supply (see Wang: [3], [6], [58], Fig. 2 regarding bidirectional DC/DC <205> providing power to electric vehicle battery) but does not explicitly discuss the system further incorporating a photovoltaic system. Phillips, however, teaches that it is known in the art of grid coupled power conversion and distribution systems using multi-level grid coupled inverter to further comprise a photovoltaic system (solar PV array, see Phillips: [0040], Figs. 4A), wherein the photovoltaic system is electrically connected to the first positive DC terminal and the first negative DC terminal, the photovoltaic system comprises a photovoltaic array, a photovoltaic EMI filter, and a boost circuit electrically connected to each other, a voltage generated by the photovoltaic array is filtered by the photovoltaic EMI filter and then is boosted by the boost circuit (see Phillips: [0040], Fig. 4A regarding PV array coupled via EMI filters and then boost-buck circuits), and the voltage after being filtered and boosted is provided to the three-level inverter for delivering power to an electrical grid (see Phillips: [0017], [0040], Figs. 4A-B regarding coupling PV system to DC input of multi-level grid coupled inverter). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the system of Wang in view of Agirman to further incorporate the teachings of Phillips by further including a PV system with components coupled as recited for purposes of providing known power grid coupled arrangement predictably allowing for local renewable power sources such as solar to contribute to providing power to loads/batteries while also capable of feeding power back to the grid (see Phillips: [0001], [0017], [0024], [0030]).
Response to Arguments
Applicant's arguments filed 16 September 2025 have been fully considered but they are not persuasive.
Regarding Applicant’s remarks concerning Objections and previous rejection under 35 USC 112(a) of claims 10 and 22, the remarks are persuasive given Applicant’s explanation together with amendments to the claim language for clarity, and the Objections and 35 USC 112(a) rejection have been withdrawn. See updated prior art rejection above.
Regarding Applicant’s arguments against 35 USC 103 rejection of claim 1 in view of Wang and Agirman, Applicant’s arguments are unpersuasive on all grounds.
Regarding Applicant’s allegation that Wang does not mention its capacitors are required to be equal or balanced and thus has no motivation to combine with Agirman, the examiner recognizes that obviousness may be established by combining or modifying the teachings of the prior art to produce the claimed invention where there is some teaching, suggestion, or motivation to do so found either in the references themselves or in the knowledge generally available to one of ordinary skill in the art. See In re Fine, 837 F.2d 1071, 5 USPQ2d 1596 (Fed. Cir. 1988), In re Jones, 958 F.2d 347, 21 USPQ2d 1941 (Fed. Cir. 1992), and KSR International Co. v. Teleflex, Inc., 550 U.S. 398, 82 USPQ2d 1385 (2007). In this case and as previously indicated, Agirman explicitly suggests that capacitors being unbalanced is a common issue for neutral point multi-level inverters, such as Wang’s neutral point multi-level inverter, and that providing a balancing circuit ensures the capacitors of the NPC three-level inverter remain balanced such that the neutral does not fluctuate to unacceptable levels and cause converter failure (see Agirman: [0005], [0022], [0025]). The motivation to combine is therefore clearly stated in Agirman and clearly applicable to the similar neutral point capacitors of the multi-level inverter in Wang which would predictably benefit in the same way from the known balancing technique. Wang’s silence on need for balancing does not constitute teaching away from the combination, and there appears to be no further disclosure in Wang or Agirman that would otherwise teach away from their combination. Applicant should also consider the other cited prior art of record which shows many examples of how balancing circuits are frequently applied to neutral-point inverter applications.
Regarding Applicant’s discussion of paragraphs [0003-0005] of Agirman, the arguments appear to mischaracterize the disclosure of Agirman and are also generally not applicable to the rejection at hand. An examination of Agirman: [0003-0004] appears to merely be a background discussion of why multi-level inverters are generally used in some high power applications. Agirman: [0005] then mentions that a known issue with neutral-point three-level inverters is that their neutral point requires balancing. Wang’s silence on the issue again does not constitute teaching away from the combination, and one of ordinary skill would instead find that Agirman’s disclosure suggests a reason that a balancing circuit would predictably benefit the neutral-point multi-level inverter of Wang.
Regarding Applicant's argument that Applicant’s Specification: [0003-0007] discloses solving other issues than those described by Agirman, the fact that the inventor has recognized another advantage which would flow naturally from following the suggestion of the prior art cannot be the basis for patentability when the differences would otherwise be obvious. See Ex parte Obiaya, 227 USPQ 58, 60 (Bd. Pat. App. & Inter. 1985). Applicant’s disclosure in the Specification does not appear to affect the manner of interpretation and scope of the claimed features. Although Agirman may describe the negative effects of unbalanced midpoint voltage differently, one of ordinary skill would still generally recognize the issue of unbalance is still overall the same, and provides sufficient reason to predictably combine the references as discussed.
The same reasoning applies to independent claim 13 as discussed.
At present, it remains unapparent what aspects of the invention would be considered distinguished and nonobvious over the prior art. As discussed, overall arrangement of bidirectional and multi-port power conversion systems with known converter circuits appears to be known, and the use and circuit topology/operation of the described balancing circuits also appear known and obvious to apply. It is recommended that if Applicant believes a specific combination of features is distinguished and nonobvious over the prior art that the claims be amended to explicitly recite the corresponding circuit structure and manner of operation with explanation of reasons for nonobviousness and citation to the disclosure for support.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, 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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/DAVID A SHIAO/Examiner, Art Unit 2836
/DANIEL CAVALLARI/Primary Examiner, Art Unit 2836