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 .
Response to Arguments
Applicant’s amendments, filed 01/16/2026, are accepted.
Claims 1-17 are pending. Claims 16-17 are added.
Examiner notes new claims 16 and 17 present matter which has not been previously reviewed, and which requires further search and evaluation.
Regarding rejection of Claims 1-15 under 35 USC § 103
Examiner has fully reviewed applicant arguments regarding rejections made over prior art in previous office action (Non-Final Rejection, dated 04/07/2026), but finds arguments unpersuasive as detailed below.
With attention to independent Claim 1, Applicant argues (Remarks, Pg7, ¶2) that references as cited by JIA (), LAAKSONEN (), SOONEE (), and KHODAPARASTAN () do not teach or render obvious each and every element of claim 1. Examiner respectfully disagrees. Applicant specifically argues that the combination of references fails to teach the limitations of “determining a detection parameter from the rate of change of frequency and the rate of change of reactive power, wherein determining the detection parameter comprises forming a quotient of the rate of change of frequency and the rate of change of reactive power ...” and “changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value”
Applicant notes, as presented in previous office action, primary reference by JIA does teach a method of islanding detection in an AC power grid, based on monitoring frequency, reactive power, and time-rate of change in frequency and reactive power, in passive and active detection modes, does not teach the limitations recited direction above. Applicant further notes, as presented in previous office action, reference by LAAKSONEN explicitly teaches the inventive concept of using a derived “detection parameter” involving rate of change in frequency and rate of change in reactive power, but does not explicitly teach a ratio (i.e., “quotient”) of the cited rates of change. Applicant further notes, as presented in previous office action, SOONEE does explicitly teach use of a parameter formed by a ratio (i.e., “quotient”), specifically the ratio “dQ/df” for analysis of power grid behavior and performance. Applicant argues that the ratio as taught by SOONEE is not analogous to the claim limitation reciting “forming a quotient of the rate of change of frequency and the rate of change of reactive power”. As discussed in previous office action, Examiner respectfully disagrees. Applicant further argues that the ratio dQ/dF as taught by SOONEE is “not a ratio of two time derivatives”. Examiner respectfully disagrees. Based on SOONEE disclosure, with frequency and reactive power are known to be time-dependent functions, such that if both are differentiable quantities, “df” and “dQ” would be considered differential expressions, such that,
d
f
d
t
=
d
f
d
Q
d
Q
d
t
, and
d
f
d
Q
=
d
f
d
t
d
Q
d
t
, where generally known differential calculus (chain rule) is used to understand the recited ratio. The quantity recited by SOONEE and monitored for analysis of a power grid, is a ratio of time rates of change, given by:
d
Q
d
f
=
d
Q
d
t
d
f
d
t
, i.e., the mathematical inverse quantity of the quantity
d
f
d
Q
. Moreover, Examiner notes claim limitation, as presented by Applicant and evaluated in previous office action, recites only that a ratio is formed: “forming a quotient of the rate of change of frequency and the rate of change of reactive power”, as is taught by SOONEN. Examiner notes application of broadest reasonable interpretation (BRI) and plain meaning in interpretation of claims, with specification used to guide understanding of limitations. However, limitations may not be imported from the specification. (See MPEP 2111.01, II.)
Applicant further argues that reference by KHODAPARASTAN fails to teach “changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value." Examiner respectfully disagrees. KHODAPARASTAN is relied upon in obvious combination with JIA, as modified by LAAKSONEN and SOONEN as teaching the concept of thresholding for analysis of a detection parameter. Applicant argues that reactive power is not considered in the analysis method taught by KHODAPARASTAN. Examiner respectfully disagrees, see KHODAPARASTAN in at least Pg 2166, Col.1, Section A. “System Evaluation Under UL1741 Test Condition”, wherein Case 1)-5) are described using consideration of reactive power in each case in a method directed to determination of islanded conditions. Examiner asserts one of ordinary skill would find rational cause to consult the method of KHODAPARASTAN, which teaches thresholding as a trigger for passive/active monitoring, as recited in previous office action, see
Examiner asserts that prior art as applied in previous office action and discussed above teaches each and every element of Claim 1, such that Applicant arguments are unpersuasive. Rejections for Claims 1-15 over prior art, as presented in previous office action, are maintained, as presented below where in additional remarks are included for clarification. Further, Applicant’s amendments, specifically new claims 16 and 17, necessitate further search and evaluation, with new grounds of rejection under 35 U.S.C §103. Examiner finds claims as currently amended do not differentiate claimed invention over prior art available before effective filing date of the claimed invention, as detailed below.
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, 4-6, and 15 are rejected under 35 USC § 103 as being unpatentable over JIA (CN 109861278 A), in view of LAAKSONEN (US 9784781 B2) and SOONEE ("REACTIVE POWER AND SYSTEM FREQUENCY RELATIONSHIP:A CASE STUDY", 7th International R&D Conference, 4-6 February 2009), and further in view of KHODAPARASTAN (“A Novel Hybrid Islanding Detection Method for Inverter-Based DGs Using SFS and ROCOF”, IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 32, NO. 5, OCTOBER 2017).
With regard to Claim 1, JIA teaches:
A method of detecting an islanding operation of an electrical power generating system coupled to a power grid, (Refer to English translation provided in previous office action, JIA is in same technical field, see Abstract.)
and the method comprising: monitoring a frequency that is indicative of an AC frequency on the power grid; (JIA teaches monitoring AC frequency on grid: [0015]: “collecting the electrical characteristic quantities (i.e., “monitoring”) of the system when it is connected to the grid”, with [0016]: “characteristic electrical quantities include…frequency”; Examiner interprets “monitoring” analogous to reference term “collecting the electrical characteristic quantities”; Examiner interprets “AC frequency” as a term generally known by one of ordinary skill in the art, and analogous to reference [0016]: “frequency and rate of change of frequency over time”)
monitoring reactive power on a coupling of the electrical power generating
system to the power grid; (JIA teaches monitoring reactive power, see [0016]: “characteristic electrical quantities…reactive power”; and [0053]: “detecting the active and reactive power of the PCC point and its rate of change over time.", and [0050]: “reactive power of the load is all provided by the power grid”.)
processing the frequency to determine a rate of change of frequency; (JIA, see [0013]: “Collect and calculate (i.e., “processing”) the current characteristic electrical quantities”, and [0016]: “characteristic electrical quantities…frequency, rate of change of frequency over time”)
processing the reactive power to determine a rate of change of reactive power; (JIA teaches “processing”, as above, [0013]; and [0016]: “characteristic electrical quantities…reactive power, and the rate of change of reactive power over time”.)
operating in a passive detection mode while monitoring the frequency and monitoring the reactive power, (JIA, as above, Abstract: “relates to an intelligent passive island detection method”; and, as above, [0015]-[0016].)
the passive detection mode without injecting a disturbance into the electrical power provided by the power generating system to the power grid; (JIA, recites known definition of passive detection used in disclosed method, see [0006]: “passive island detection method performs island detection without injecting disturbance signals”, FIG. 6 step 5 “system's current characteristic electrical quantities are collected and calculated in real time”, with [0039]: “flow chart of an intelligent passive island detection method for a photovoltaic grid-connected power generation system”.)
operation in passive detection mode and active detection mode (JIA teaches both active and passive detection methods, see [0043]: “collected data are divided into two categories according to the system passive/active island detection method”;)
operating in the active detection mode while monitoring the frequency and monitoring the reactive power, (JIA teaches active detection mode, [0005]: "active detection method”, and monitoring frequency and reactive power, as above, [0015]-[0016].)
wherein the active detection mode comprises injecting a disturbance into electrical power provided by the power generating system to the power grid; (JIA teaches injection method, see[0005]: "active detection method injects disturbance signals into the power grid”; )
JIA does not explicitly teach:
determining a detection parameter from the rate of change of frequency and the rate of change of reactive power;
determining the detection parameter comprises forming a quotient of the rate of change of frequency and the rate of change of reactive power;
in the passive detection mode the detection parameter is determined without injecting a disturbance into the electrical power provided by the power generating system to the power grid;
changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value;
detecting the islanding operation of the electrical power generating system if the detection parameter exceeds an islanding threshold value.
injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid
LAAKSONEN teaches:
determining a detection parameter from the rate of change of frequency and the rate of change of reactive power (LAAKSONEN in same technical field, see Abstract: “device for detecting an islanding condition in an electricity distribution network”; teaches method involving frequency, time rates of change, see Col2L1: “detection methods include monitoring of frequency (f), rate-of-change-of-frequency (ROCOF/df/dt)”, and Col3L60, Col4: “islanding detection method can be based, for example, on measurement of one or more of the following parameters …rate-change-of-reactive-power (dQ/dt)”; and see COL3L; Applying BRI and plain meaning, Examiner interprets “determining a detection parameter” as analogous to “detection methods” with a list of “parameters” as taught by reference.)
in the passive detection mode the detection parameter is determined without injecting a disturbance into the electrical power provided by the power generating system to the power grid; (LAAKSONEN, Col2L1: “detection methods”, and Col1,L65-Col2: “ Passive methods are based on monitoring one or more system parameters … without directly interacting (i.e., “ without injecting a disturbance”) with the network”)
detecting the islanding operation of the electrical power generating system if the detection parameter exceeds an islanding threshold value. (LAAKSONEN, as above, teaches monitoring islanding detection parameters, see Col3L60-Col4: “islanding detection method can be based, for example, on measurement of one or more of the following parameters”, and teaches analysis based on thresholding method, see Col4L59-60:"monitoring can be based on a predetermined threshold value”; and Col7L38-42: “comparison of a current value is done to an earlier value…if the change rate exceeds a threshold value, a trigger is given.”, (i.e., “detecting the islanding operation”))
It would be obvious for one of ordinary skill on or before the effective filing date of the claimed invention to combine the islanding detection method of JIA with the technique of determining a detection parameter from the rate of change of frequency and the rate of change of reactive power and to use a passive detection with no disturbance injection; to include, in a passive detection mode, determining a detection parameter without injecting a disturbance into the electrical power provided by the power generating system to the power grid, and to include detecting the islanding operation of the electrical power generating system if the detection parameter exceeds an islanding threshold value, as taught by LAAKSONEN because these additional details in the method of JIA would be seen as obvious ways to leverage the system taught by JIA to include steps that would result in more accurate and reliable determination of islanding in a power grid. As LAAKSONEN suggests (see for example, COL3L52), using the steps as describe above, incorporated into a similar system, as disclosed by JIA, would improve islanding detection reliability and also substantially improve loss-of-mains (LOM) protection, which would be understood by one of ordinary skill in the art as an obvious advantage for an islanding detection method/system.
JIA, as modified by LAAKSONEN and taught above, does not teach:
determining the detection parameter comprises forming a quotient of the rate of change of frequency and the rate of change of reactive power
changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value;
injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid
SOONEE teaches:
determining the detection parameter comprises forming a quotient of the rate of change of frequency and the rate of change of reactive power; (SOONEE is in same technical field ABSTRACT: “describes the impact of System frequency on Reactive power”, directed to understanding of power grid, see Pg2/8,§3: “generating stations in the grid”; SOONEE teaches use of detection parameter ratio, see P3,Table 1: “dQ/dF” (i.e., “quotient of the rate of change of frequency and the rate of change of reactive power), where Q, reactive power, and F, frequency, are defined as time dependent functions, see Pg 2/8,§4, and “dQ” and “dF” are differentials representing change in these parameters, as discussed above; See FIG. 4.2, depicting graphical analysis of dQ/dF; As explained above, Examiner applies BRI and plain meaning, to interpret “quotient of rate of change of frequency and the rate of change of reactive power” to be analogous to reference ratio of “dQ/df” to mean a parameter representing a rate of change in reactive power in a comparative ration with rate of change in frequency.)
It would be obvious for one of ordinary skill on or before the effective filing date of the claimed invention to combine the islanding detection method of JIA as modified by using a detection parameter based on time rate of change of frequency and reactive power as taught by LAAKSONEN to further include determining the detection parameter comprises forming a quotient of the rate of change of frequency and the rate of change of reactive power as taught by SOONEE because the ratio would reveal additional insight with increased sensitivity to islanding phenomena, based on the strong frequency dependence of reactive power. One of ordinary skill would see the advantage of using a ratio that combines the two monitored parameters of frequency and reactive power, specifically their time dependence, as a way to understand the impact of the relationship between frequency and reactive power in a power grid, as is pointed out by SOONEE (see P7§12: Conclusion: “strong impact of frequency on Reactive power”. One of ordinary skill would find use of a quotient as taught be SOONEE as a way to leverage a sensitive detection parameter without significant change to the system as taught by JIA and modified by LAAKSONEN taught above.
JIA, as modified by LAAKSONEN and SOONEE as taught above, does not explicitly teach:
changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value;
injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid
KHODAPARASTAN teaches:
changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value; (KHODAPARASTAN is in same technical field, see Abstract: “aimed at proposing a new hybrid method for the islanding detection of distributed-generation (DG)units.”; and teaches “SFS” method, generally known as an “active method”, and teaches passive method, see Abstract: “optimized Sandia frequency shift (SFS) method is used as the selected active method, and rate of change of frequency relay (ROCOF) is used as the passive method”; and see Pg3,Col1 and Fig.4: “B. Rate of Change of the Frequency Method (ROCOF)…df/dt is measured over a few cycles…by ROCOF relay, then the required signal for islanding is computed” and “flowchart diagram, which describes the operation of the ROCOF method, is shown in Fig. 4…output signal of the low-pass filter is compared to the ROCOF relay setting ([Symbol font/0x62])…In the case that the rate of change of frequency is bigger than [Symbol font/0x62], a trip signal will be sent (i.e., “exceeding an activation threshold value”)”; Examiner notes in first decision box shown in Fig. 4, parameter [Symbol font/0x62] is explicitly referred to as “threshold”. Further, the term “trip”, the result of the decision process depicted in Fig. 4, is taught as the signal to enter active mode, see P2164 Col2: “trip signal will be sent to a multiple switch which activates the SFS signal”, where, as taught above, SFS method is a known active method for power grid analysis, and see Pg6Col2, Section E: “deviation exceeds the ROCOF relay threshold, the SFS method will be initiated”; Applying BRI and plain meaning, Examiner interprets “detection parameter” analogous to reference “signal for island detection”)
injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid (KHODAPARASTAN teaches, as above use of SFS as active methods, see Pg2162,COL2: “active techniques are…active frequency drift method (AFD)… Sandia frequency-shift method (SFS)”; Applying BRI and plain meaning as would be familiar to one of ordinary skill in the art, Examiner interprets “[Symbol font/0x71]FS” to be injection using disturbance/perturbation (active) method of AFD, and “[Symbol font/0x71]SFS” as disturbance in SFS method.)
It would be obvious for one of ordinary skill on or before the effective filing date of the claimed invention to combine the system/method of island detection of JIA as modified with the detection-parameter based techniques taught by LAAKSONEN and ratio/quotient parameter analysis method of SOONEE with explicit teaching of a hybrid method with a thresholding method of changing from a passive mode to an active mode, and injection of disturbances as shown above while in active method, as taught by KHODAPARASTAN because these steps would be an efficient way to improve accuracy of islanding detection by providing broader analysis of both active and passive method signals. One of ordinary skill would be motivated to leverage the strengths of both methods, where KHODAPARASTAN teaches both AFD and SFS are generally known as dominant active perturbation methods for island detection to provide a more comprehensive understanding of grid behavior, which would be seen as advantageous, particularly when combined with the features taught by LAAKSONEN and SOONE, including thresholding, so that the active method is used effectively. One of ordinary skill would be motivated to combine these references to arrive at the claimed invention because hybrid data integrates the characteristics of the feature quantities of active and passive detection systems to result in a more accurate real-time evaluation of the system status.
With regard to Claim 4, JIA, in view of LAAKSONEN, SOONEE and KHODAPARASTAN, teaches the limitations of claim 1.
JIA further teaches:
the disturbance comprises a disturbance of an AC frequency of the electrical power provided by the power generating system to the power grid. (JIA teaches disturbance as feature of active method in an AC system, see Fig. 1, AC power symbol, with [0005]:”active detection method injects disturbance signals into the power grid and uses the changes in electrical quantities caused by the disturbance signals to determine the occurrence of islanding”; [0043]: “frequency-reactive feedback islanding detection systems”)
With regard to Claim 5, JIA, in view of LAAKSONEN, SOONEE and KHODAPARASTAN, teaches the limitations of claim 1.
JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and taught above, does not explicitly teach:
the activation threshold value is lower than the islanding threshold value
KHODAPARASTAN further teaches:
the activation threshold value is lower than the islanding threshold value (KHODAPARASTAN suggests lower islanding threshold, see Pg2164,COL2: “care should be taken while setting the thresholds for the ROCOF relay (i.e. “activation threshold”)…key point about merging ROCOF and SFS is keeping the ROCOF threshold level as low as possible, which makes it possible to detect islanding occurrence”; and see Pg2167,COL2 “if this frequency deviation exceeds the ROCOF relay threshold, the SFS method will be initiated”; Applying BRI and plain meaning, Examiner interprets “activation threshold”, consistent with Claim 1, to mean the signal point where system is switched from passive to active detection mode, where reference teaches ROCOF as passive mode and SFS as active mode, and that ROCOF activation threshold is lower than islanding threshold as islanding is detected after initiating active.)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify over JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and as taught above, to include an activation threshold value lower than an islanding threshold value, as suggested by KHODAPARASTAN because, as taught in reference, this allows for a switch to active mode for more reliable detection of an islanding even, and avoids the shortcomings of false detection in the passive mode. KHODAPARASTAN points out the benefits of using the criteria as above to improve discrimination between islanding events and other system anomalies (See Pg2169,§ V “Conclusion”) and can detect islanding events quickly, such that it would be considered as advantageous to include in the invention taught by JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and taught above.
With regard to Claim 6, JIA, in view of LAAKSONEN, SOONEE and KHODAPARASTAN, teaches the limitations of claim 1.
JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and taught above, does not teach:
operating in the active detection mode occurs continuously.
LAAKSONEN further teaches:
operating in the active detection mode occurs continuously (LAAKSONEN, see Fig. 3, method steps, depicting loop structure with repeating measurements during active mode, and Col8L65-col9L1: “step 314, where the functionality is reset and the evaluation of loss of mains condition and fault condition is restarted”; Examiner interprets “occurs continuously” to be analogous to reference teaching islanding detection method loop structure with a “reset” and “restarted” operating continuously.)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and as taught above, to include continuously operating in the active detection mode, as that further taught by LAAKSONEN because this step would provide on-going real time monitoring to ensure accurate detection of an islanding event and leverage automated data collection system as found in JIA.
With regard to Claim 15, JIA, in view of LAAKSONEN, SOONEE and KHODAPARASTAN, teaches the limitations of claim 1
JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, does not explicitly teach:
A computer program product for detecting an islanding operation of a power generating system, wherein the computer program product comprises control instructions which, when executed by a processing unit of a control unit of the power generating system;
LAAKSONEN further teaches:
A computer program product (LAAKSONEN, FIG. 4, “unit 440”, with Col12, L37: “specially programmed processor to execute a computer program”) for detecting an islanding operation of a power generating system, (LAAKSONEN, as above, see Abstract)
wherein the computer program product comprises control instructions which, when executed by a processing unit of a control unit of the power generating system (as above, Col12, L37 “execute a computer program”) cause the control unit to perform the method of claim 1. (addressed with combination of JIA with LAAKSONEN, SOONEE and KHODAPARASTAN teaches method of claim 1.)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and as taught above, to use the explicitly taught computer program product for detecting an islanding operation of a power generating system, such that the computer program product comprises control instructions which, when executed carry out the method of Claim 1, as further taught by LAAKSONEN because, while JIA does not explicitly recite use of a computer with program instructions, JIA does suggest such a system to carry out the method of islanding detection therein, and it would be an obvious combination for implementing an advanced islanding detection method. One of ordinary skill in the art would see an advantage to improve the invention of JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and taught above, by enabling a system to efficiently collect and analyze system data by using computational programming methods as taught by the LAAKSONEN, to make control, calculations, and comparative analysis more efficient and accessible.
Claim 2 is rejected under 35 USC § 103 as being unpatentable over JIA, in view of LAAKSONEN, SOONEE, and KHODAPARASTAN, as applied to Claim 1 above, and further in view of ALAM (ALAM, et al., “A Short Length Window-Based Method for Islanding Detection in Distributed Generation”, WCCI 2012 IEEE World Congress on Computational Intelligence, 2012).
With regard to Claim 2, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN teaches the method according to claim 1, but the obvious combination does not explicitly teach:
the rate of change of frequency is determined by using a predetermined first window length, and wherein the rate of change of reactive power is determined by using a predetermined second window length, wherein the first window length is different from the second window length.
ALAM teaches:
the rate of change of frequency is determined by using a predetermined first window length, (ALAM in same technical field, see Abstract: “detection method of one such crucial event which is “islanding”…network parameters such as rate of change of frequency (ROCOF)…have been extracted from the voltage and current signal”; ALAM teaches windowing method for frequency determination, see Pg1,Col2,second paragraph: “technique which introduces a short length window-based Mahalanobis Distance (MD) method for detection of islanding”; and Pg4Col1SectionV-Col2: “PROPOSED MAHALANOBIS DISTANCE BASED CLASSIFICATION METHOD”, “ROCOF…measured for 10 cycles of window length”, and FIG. 5; Examiner asserts Mahalanobis Distance method would be known and understood by one of ordinary skill in the art.)
and wherein the rate of change of reactive power is determined by using a predetermined second window length, (ALAM, as above, Pg4,Col2: “ROCOQ are measured”, Pg5,Col1,Section VI. COMPUTATIONAL RESULTS AND THE EFFECT OF WINDOW LENGTH…” followed by discussion of variation in window lengths.)
wherein the first window length is different from the second window length. (ALAM, Pg5,Col2, “very short window length (3 cycles, 4cycles, 5 cycles etc.) are also analysed”)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify JIA, as modified by LAAKSONEN and SOONEE, and KHODAPARASTAN and as taught above, to include as part of the method, determination of rate of change of frequency using a predetermined first window length, and wherein the rate of change of reactive power is determined by using a predetermined second window length, wherein the first window length is different from the second window length, as taught by ALAM because the window-based method for data acquisition provides increased understanding of system dynamics and allows for efficiently organized data collection and analysis. ALAM teaches the value of using window based collection protocol because a careful choice of timing for gathering data to evaluate frequency or reactive power behavior for fluctuations to indicate islanding provides more accurate and reliable system anomaly identification, specifically islanding, and a better estimate of trending, and ability to rule out short term fluctuations caused by noise.
Claim 3, is rejected under 35 U.S.C. 103 as being unpatentable over as being unpatentable over JIA, in view of LAAKSONEN, SOONEE, and KHODAPARASTAN, as applied to Claim 1 above, and further in view of WRIGHT ("Field Measurement of Frequency and ROCOF in the Presence of Phase Steps"", IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 68, NO. 6, JUNE 2019).
With regard to Claim 3, JIA in view of LAAKSONEN, SOONEE and KHODAPARASTAN teaches the method according to claim 1, but does not explicitly teach:
determining the detection parameter further comprises buffering the rate of change of frequency for a first predetermined amount of time and using a minimum value of the buffered rate of change of frequency in the determination of the detection parameter, and/or buffering the rate of change of reactive power for a second predetermined amount of time and using a maximum value of the buffered rate of change of reactive power in the determination of the detection parameter, wherein the first predetermined amount of time is smaller than the second predetermined amount of time.
WRIGHT teaches at least:
determining the detection parameter further comprises buffering the rate of change of frequency for a first predetermined amount of time (WRIGHT is in same technical field, see ABSTRACT: “rate of change of frequency (ROCOF)… operation of electricity networks”, with P1689: “ROCOF algorithm on any given instrument measures an absolute value above a preset threshold, a rolling buffer of raw waveform data before and after the trigger event is saved”; buffer timing shown in Fig. 5, with P1692: “data are delayed in a first-in first-out (FIFO) buffer by n-cycles…n-cycle latency is added to give sufficient time to process data to decide whether a phase step has occurred”; Applying BRI and plain meaning, Examiner interprets “predetermined amount of time” to be analogous to reference teaching “n-cycle latency” to mean predetermined time to acquire a predetermined quantity of data buffered for analysis.)
and using a minimum value of the buffered rate of change of frequency in the determination of the detection parameter (WRIGHT, Pg1690, Fig.1: “Recording of an ROCOF event”, with “Measured frequency…(bottom)”, depicting minimum frequency at event, where it would be known by one of ordinary skill in the art that a frequency dip (i.e., minimum) would signify an event; Examiner notes “ROCOF” refers to detection parameter of reference.)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify over JIA, in combination with LAAKSONEN, SOONEE, and KHODAPARASTAN and as taught above, to use the technique of buffering the rate of change of frequency for a first predetermined amount of time and using a minimum value of the buffered rate of change of frequency in the determination of the detection parameter, and using minimum value of ROCOF for determination of detection parameter, such as that taught by WRIGHT because collecting and storing the rate of change of frequency over a specific duration allows for a more detailed and accurate analysis of frequency behavior and a minimum in a rate of change in frequency signals an event of interest, which would reduce false tripping and improve reliability of identification of an islanding event. Using comparative analysis of frequency behavior over pre-determined prescribed time interval and considering a buffered rate of change to pre-defined thresholds provides an enhanced ability to reliably identify patterns or events of interest, an advantageous way to better the invention of JIE, as modified above.
Claims 7-11 are rejected under 35 USC § 103 as being unpatentable over JIA, in view of LAAKSONEN, SOONEE, and KHODAPARASTAN, as applied to Claim 1 above, and further in view REIGOSA ("Active Islanding Detection Using High-Frequency Signal Injection", October 2012IEEE Transactions on Industry Applications 48(5):1588 -1597, 2012).
With respect to Claim 7, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, teaches the method according to claim 1.
JIA, in combination with LAAKSONEN, SOONEE, and KHODAPARASTAN teaches, as discussed above, active detection method including injected disturbance (For example, JIA [0005] and [0043]) but does not explicitly teach:
the power generating system comprises a power converter configured to control an AC frequency of the electrical power provided by the power generating system to the power grid,
injecting the disturbance comprises controlling the power converter so as to disturb the AC frequency of the electrical power provided to the power grid.
REIGOSA teaches:
the power generating system comprises a power converter configured to control an AC frequency of the electrical power provided by the power generating system to the power grid, (REIGOSA in same technical field, see Abstract: “new active islanding-detection method…injection of a high-frequency voltage…adaptive control of the power converter” with Fig. 1.”)
injecting the disturbance comprises controlling the power converter so as to disturb the AC frequency of the electrical power provided to the power grid. (REIGOSA, P1589 Col2§III: “ Voltage-source inverters (VSIs) present in the microgrid [e.g.,…power converters, etc.] can easily inject a low-magnitude high-frequency voltage…variety of forms of high-frequency excitation can be used…reliable implantations obtained by injecting either a rotating or pulsating voltage vector”)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify over JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and as taught above, to include the specific details of a power generating system with a power converter configured to control an AC frequency of the electrical power provided by the power generating system to the power grid, and to use the technique of controlling the power converter so as to disturb the AC frequency of the electrical power provided to the power grid for injecting a disturbance in active mode operation, as taught by REIGOSA because it would improve the invention of JIA, as modified and taught above, by using proven and efficient methods for AC frequency control, and standard reliable methods for carrying out an active mode inspection of system behavior to determine islanding in a distributed power system.
With respect to Claim 8, JIA in view of LAAKSONEN, SOONEE and KHODAPARASTAN and further in view of REIGOSA, teaches the limitations of claim 7.
REIGOSA further teaches:
the power converter is controlled by determining control parameters for the power converter in a rotating reference frame that is synchronous with a grid frequency of the power grid, (REIGOSA teaches rotating frame of reference, P1589§III: “implantations obtained by injecting either a rotating or pulsating voltage vector” and Section A “Rotating High-Frequency Signal Injection”)
in the active detection mode, the disturbing of the AC frequency comprises disturbing the determination of the control parameters such that the determined control parameters are no longer synchronous with the grid frequency. (REIGOSA, see P1589§III, FIG. 2 illustrating determining differences between frequencies to distinguish grid mode from island modes.)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify JIA as modified by LAAKSONEN, SOONEE, KHODAPARASTAN, REIGOSA and as taught above, to include the technique of determining control parameters for the power converter in a rotating reference frame synchronous with grid frequency to control the power converter, and to determine control parameters so that they are no longer synchronous with grid frequency when in active detection mode , such as that further taught by REIGOSA because it is an accurate and reliable way to discern a response related to an islanding event if detection parameter was asynchronous with power grid frequency. This would improve the accuracy of the invention of JIA as modified and discussed above.
With respect to Claim 9, JIA inv view of LAAKSONEN, SOONEE and KHODAPARASTAN and further inv view of REIGOSA teaches the limitations of Claim 8.
REIGOSA further teaches:
the determination of the control parameters is disturbed by rotating the control parameters determined in the synchronous reference frame by a disturbance angle. (REIGOSA, see P1589, §III.A “Rotating High-Frequency Signal Injection”: “inject a low-magnitude high-frequency voltage… simple and reliable implantations obtained by injecting either a rotating or pulsating voltage vector”; Equation (1) defining injection, “where [Symbol font/0x77]f is frequency of injected signal”; P.1590, “principle of operation…shown in Fig. 2”; Examiner notes REIGOSA uses a different detection parameter (impedance) but is considered to be analogous art relevant to the problem of the claimed invention.)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify JIA, in combination with LAAKSONEN, SOONEE, KHODAPARASTAN and REIGOSA as taught above, to include the determination of the control parameters is disturbed by rotating the control parameters determined in the synchronous reference frame by a disturbance angle, such as that of REIGOSA because the comparison of the synchronous reference frame with the injected rotational disturbance angle would allow for more accurate identification of an islanding event independent of random noise or other non-islanding fluctuation. This is made obvious by REIGOSA in Fig.2 illustrating how the method allows for identification of islanding by using variant frequency rotating method.
With respect to Claim 10, JIA inv view of LAAKSONEN, SOONEE and KHODAPARASTAN and further in view of REIGOSA, teaches the limitations of claim 9.
REIGOSA further teaches: disturbing the determination of the control parameters comprises disturbing the
determination of the rotating reference frame by a disturbance angle such that the rotating reference frame is no longer synchronous with the grid frequency. (REIGOSA, as above, see P1589, §III.A “Rotating High-Frequency Signal Injection”, teaching details of rotating reference frame method of active mode and importance of asynchronous, “high frequency” for injection frequency, with details Pg1592,Col1, “VI. HIGH-FREQUENCY SIGNAL SELECTION”)
It would have been obvious to one of ordinary skill in the art before effective
filing date of the claimed invention to further modify JIA, in combination with LAAKSONEN, SOONEE, KHODAPARASTAN and REIGOSA as taught above, to use the method of disturbing the determination of the control parameters is done by disturbing the determination of the rotating reference frame by an disturbance angle such that the rotating reference frame is no longer synchronous with the grid frequency, such as that of REIGOSA because the comparison of the synchronous reference frame with the injected rotational disturbance angle, when it is no longer synchronous with the grid frequency would allow for more accurate identification of an islanding event independent of random noise or other non-islanding fluctuation.
With respect to Claim 11, JIA inv view of LAAKSONEN, SOONEE and KHODAPARASTAN and further in view of REIGOSA teaches the limitations of claim 10.
KHODAPARASTAN further teaches:
a phase angle of the grid voltage determined by a phase locked loop (KHODAPARASTAN, see P2163,Col2,“Fig. 3 SFS Block” and A. Sandia Frequency Shift Method (SFS), Equation (1), “inverter phase angle, dependent on “f is the frequency of the system”, with P2164, C. Proposed Hybrid Method…SFS is used as the active method…System frequency is estimated using the phase-locked loop (PLL)”)
It would have been obvious to one of ordinary skill in the art before effective
filing date of the claimed invention to further modify JIA, in combination with LAAKSONEN, SOONEE, KHODAPARASTAN and REIGOSA as taught above, to use a phase locked loop technique for determination of phase angle because it would be understood by one of ordinary skill in the art as a way to leverage a well-known and proven method for accurate phase control and determination in AC electrical system analysis.
REIGOSA further teaches:
the determination of the rotating reference frame is based on a phase angle of the grid voltage wherein disturbing the determination of the rotating reference frame comprises introducing the disturbance angle in the determination of the phase angle (REIGOSA teaches, as above, P1589, §III.A “Rotating High-Frequency Signal Injection”, Equation (5), phase angle.)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify JIA, as modified by LAAKSONEN, SOONEE, KHODAPARASTAN and REIGOSA and as taught above, to use the technique of determination of the rotating reference frame based on a phase angle and where disturbing the determination of the rotating reference frame comprises introducing the disturbance angle in the determination of the phase angle, as further taught by REIGOSA because it would allow for accurate determination of small changes in phase would lead to a more reliable discernment of an islanding issue distinct from other fault events or fluctuations.
Claims 12-13 are rejected under 35 USC § 103 as being unpatentable over JIA, in view of LAAKSONEN, SOONEE, KHODAPARASTAN, and REIGOSA, as applied to Claim 7 above, and further in view of BARAVANI ("Nine Switch Back To Back Converter- Design and Simulation for Wind Turbines Based on Doubly Fed Induction Generator”, International Journal of Recent Technology and Engineering (IJRTE), Volume-8 Issue-5, January 2020 ).
With respect to Claim 12, JIA, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA and as taught above, teaches the limitations of claim 7, but does not explicitly teach:
the power generating system comprises a doubly fed induction generator, wherein the power converter is coupled to a rotor of the doubly fed induction generator and is configured to control rotor currents in the rotor to thereby control the AC frequency of AC electrical power provided by the doubly fed induction generator to the power grid.
BARAVANI teaches:
the power generating system comprises a doubly fed induction generator (BARAVANI in same technical field, see Title and Abstract: “Doubly Fed Induction Generator (DFIG)”, and Fig.2 “DFIG”)
the power converter is coupled to a rotor of the doubly fed induction generator and is configured to control rotor currents in the rotor to thereby control the AC frequency of AC electrical power provided by the doubly fed induction generator to the power grid. (BARAVANI, see Fig.2, Fig.3, with P5501,Col1, “II. DOUBLY FED INDUCTION GENERATOR”: “RSC controls the stator active power, electrical torque and stator reactive power creation, by controlling rotor current and RSC output voltage.”)
It would have been obvious to one of ordinary skill in the art before effective
filing date of the claimed invention JIA, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA and as taught above, to include a doubly fed induction generator and a power converter connected as described above in a power generating system to be analyzed for islanding issues, as taught BARAVANI because the doubly fed generation system is well-understood as a standard arrangement of incorporating wind-powered energy resources into a distributed electric grid and this would make the invention of JIA, as modified, applicable to a wider range of systems.
With respect to Claim 13, JIA, in view of LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA, teaches the method according to claim 7.
JIA further teaches:
the disturbance comprises a disturbance of the AC frequency of AC electrical power provided by the grid side converter to the power grid. (JIA, [0005]: “active method”: Examiner notes “disturbance” is associated with active mode detection technique.)
JIA, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA as taught above, does not explicitly teach:
the power converter is a full power converter coupled to an output of a generator and configured to convert the power generated by the generator, wherein the power converter comprises a grid side converter
BARAVANI teaches:
the power converter is a full power converter coupled to an output of a generator and configured to convert the power generated by the generator, wherein the power converter comprises a grid side converter (BARAVANI, as above, and see structure depicted in Fig.2 or Fig. 3)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify JIA, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA and as taught above, to include a power converter is a full power converter coupled to an output of a generator and configured to convert the power generated by the generator where the power converter comprises a grid side converter, as taught by BARAVANI, because it this structure would be well understood as a standard arrangement of incorporating wind-powered energy resources into a distributed electric grid, and ensure that the invention of JIA, as modified, would be applicable to a broad range of known and used electrical grid systems.
Claim 14 is rejected under 35 USC § 103 as being unpatentable over JIA, in view of LAAKSONEN, SOONEE, and KHODAPARASTAN, as applied to Claim 1 above, and further in view of FARESE (US 20160301328 A1).
With respect to Claim 14, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, teaches the method according to claim 1.
A control system for detecting an islanding operation of a power generation system, wherein the control system comprises a processing unit and a memory storing control instructions which when executed by the processing unit, cause the control system to perform the method according to claim 1, (As noted, this limit is taught by obvious combination JIA in view of LAAKSONEN, SOONEE and KHODAPARASTAN, discussed in Claim 1, as above)
JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, does not explicitly teach:
the power generation system is a wind turbine or a wind farm.
FARESE teaches:
the power generation system is a wind turbine or a wind farm (FARESE in same technical field, Abstract: “detecting an islanding condition of a grid”; and see [0003]: “systems are adapted to generate electrical power for direct delivery to the power grid…renewable sources…wind turbines.”)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify the invention of JIA, JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, to include implementation in a wind turbine or wind farm power generation system, as taught by FARESE because including a renewable power generation source, such as wind turbine/farm would strengthen the usefulness of the invention of JIA, as modified, by considering a more unpredictable source, since wind farm generation would be known to commonly exhibit technical problems, including system stability and reliability, islanding and voltage regulation. Combining the technique of FARESE with the modified invention of JIA would broaden applicability to a prime candidate for implementation of a detection method to identify unintentional islanding which is common in wind-energy resourced power systems.
Claim 16 is rejected under 35 USC § 103 as being unpatentable over JIA, in view of LAAKSONEN, SOONEE, and KHODAPARASTAN, as applied to Claim 1 above, and further in view of RAZA (Raza, et al., “A Sensitivity Analysis of Different Power System Parameters on Islanding Detection”, IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, VOL. 7, NO. 2, APRIL 2016).
With regard to Claim 16, JIA, as modified by LAAKSONEN, SOONEE, and KHODAPARASTAN and taught above teach the limitations of Claim 1, but does not teach:
forming the quotient comprises dividing the rate of change of frequency by the rate of change of reactive power.
RAZA teaches:
forming the quotient comprises dividing the rate of change of frequency by the rate of change of reactive power. (RAZA is in same technical field, see Abstract: “work analyzes the sensitivity of 16 power system parameters that can be used in passive techniques to detect islanding and nonislanding events”; and teaches use of detection parameters, see Title, and Abstract: “rate of change of frequency over reactive power (df /dq) can effectively detect minute disturbances in power supply”, and see Pg461,COL2, last paragraph: “work aims to analyze the sensitivity of different passive
parameters in the form of frequency, …reactive power, and their respective derivatives”; and see Pg. 462,COL1: “”Based on observations, a unique passive technique utilizing the rate of change of frequency over reactive power (df /dq) as a parameter for islanding detection is proposed”; also see Pg462,TableII, listing parameters “2 Rate of chang of frequency df/dt…3 Rate of change of reactive power dq/dt…7 Rate of change of frequency over reactive power df/dq”)
It would have been obvious to one of ordinary skill in the art before effective filing date of the claimed invention to further modify the invention of JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, to include forming the quotient comprises dividing the rate of change of frequency by the rate of change of reactive power, as taught by RAZA because, as disclosed by RAZA, the technique of using the rate of change of frequency over reactive power has the ability to differentiate islanding from non-islanding events. One of ordinary skill would be motivated to combine this ratio based on the results of RAZA’s work showing that of the 16 ratio-based parameters studied, the ratio df/dq resulted in superior sensitivity and accuracy (See Pg.269,§IX. Conclusion), and as taught explicitly Pg464,COL2,P2: “the change in frequency with respect to reactive power (df /dq) reveals the minute variations expeditiously”
Examiner Note
Prior art discovered for evaluation of Claim 16 provides alternate rejection for limitations of Claim 1 to include RAZA in place of SOONEE and LAAKSONEN. Revised rejection, based on obvious combination of references by JIA, RAZA and KHODAPARASTAN is as follows:
With regard to Claim 1, JIA teaches (cited portions of JIA reference are discussed more fully above/)
A method of detecting an islanding operation of an electrical power generating system coupled to a power grid, (JIA, Abstract)
and the method comprising: monitoring a frequency that is indicative of an AC frequency on the power grid; (JIA, [0015-16])
monitoring reactive power on a coupling of the electrical power generating system to the power grid; (JIA, [0016], [0050])
processing the frequency to determine a rate of change of frequency; processing the reactive power to determine a rate of change of reactive power; (JIA, [0013]. [0016])
operating in a passive detection mode while monitoring the frequency and monitoring the reactive power; (JIA, Abstract, and [0015-16]))
the passive detection mode without injecting a disturbance into the electrical power provided by the power generating system to the power grid; (JIA, [0006], and FIG. 6 step 5 with [0039])
operation in passive detection mode and active detection mode; (JIA, [0043]
operating in the active detection mode while monitoring the frequency and monitoring the reactive power, (JIA, [0005], and [0015-16]) wherein the active detection mode comprises injecting a disturbance into electrical power provided by the power generating system to the power grid; (JIA, [0005])
As discussed above, JIA does not explicitly teach:
determining a detection parameter from the rate of change of frequency and the rate of change of reactive power;
determining the detection parameter comprises forming a quotient of the rate of change of frequency and the rate of change of reactive power;
in the passive detection mode the detection parameter is determined without injecting a disturbance into the electrical power provided by the power generating system to the power grid;
changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value;
the active detection mode comprises injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid
detecting the islanding operation of the electrical power generating system if the detection parameter exceeds an islanding threshold value.
RAZA teaches:
determining a detection parameter from the rate of change of frequency and the rate of change of reactive power (RAZA Abstract, Pg461,COL2, last paragraph; and see Pg. 462,COL1)
determining the detection parameter comprises forming a quotient of the rate of change of frequency and the rate of change of reactive power; (RAZA Pg. 462,COL1)
in the passive detection mode the detection parameter is determined without injecting a disturbance into the electrical power provided by the power generating system to the power grid; (RAZA disclosure is directed to studies of parameters during passive detection, defined as method that does not include an injected perturbation, as taught by JIA above, and repeated by RAZA, as above, see Pg461,COL¶2-COL2; RAZA teaches determination of detection parameter with highest sensitivity, df/dq, as above, Abstract, Pg461,COL2, and Pg462,COL1.)
detecting the islanding operation of the electrical power generating system if the detection parameter exceeds an islanding threshold value. (RAZA teaches thresholding for islanding detection, based on detection parameter df/dq, see Pg462,Col2, last paragraph: “df /dq show significant changes during the islanding scenario…also observed that there are maximums and minimums of df /dq that can be used as thresholds for distinguishing islanding from non-islanding events”)
It would be obvious for one of ordinary skill on or before the effective filing date of the claimed invention to combine the system/method of island detection of JIA to include the detailed detection-parameter taught by RAZA, because, as disclosed by RAZA, the technique of using the rate of change of frequency over reactive power has the ability to differentiate islanding from non-islanding events with superior sensitivity. One of ordinary skill would be motivated to combine this ratio based on the results of RAZA’s work showing that of the 16 ratio-based parameters studied, the ratio df/dq resulted in superior sensitivity and accuracy (See Pg.269,§IX. Conclusion), and as taught explicitly Pg464,COL2,P2: “the change in frequency with respect to reactive power (df /dq) reveals the minute variations expeditiously”
JIA, as modified by RAZA and taught above, does not teach:
changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value;
the active detection mode comprises injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid
KHODAPARASTAN teaches:
changing operation from the passive detection mode to an active detection mode in response to the detection parameter exceeding an activation threshold value; (KHODAPARASTAN Abstract, Pg3,Col1 and FIG4, as discussed and interpreted above)
the active detection mode comprises injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid (KHODAPARASTAN teaches, as above use of SFS as active methods, see Pg2162,COL2: “active techniques are…active frequency drift method (AFD)… Sandia frequency-shift method (SFS)”; Applying BRI and plain meaning as would be familiar to one of ordinary skill in the art, Examiner interprets “[Symbol font/0x71]FS” to be injection using disturbance/perturbation (active) method of AFD, and “[Symbol font/0x71]SFS” as disturbance in SFS method.)
It would be obvious for one of ordinary skill on or before the effective filing date of the claimed invention to combine the system/method of island detection of JIA as modified with the detection-parameter techniques taught by RAZA to include a hybrid method using thresholding, there a threshold is used to determine changing from a passive mode to an active mode, and injection of disturbances as shown above while in active method, as taught by KHODAPARASTAN because these steps would be an efficient way to improve accuracy of islanding detection by providing broader analysis of both active and passive method signals. One of ordinary skill would be motivated by the advantage of leveraging the strengths of both methods to provide a more comprehensive understanding of grid behavior, particularly when combined with the passive mode features taught by RAZA, including thresholding, so that the active method is used effectively. One of ordinary skill would be motivated to combine these references to arrive at the claimed invention because hybrid data integrates the characteristics of the feature quantities of active and passive detection systems to result in a more accurate real-time evaluation of the system status.
With regard to Claim 17, JIA, as modified by LAAKSONEN, SOONEE, and KHODAPARASTAN* teach the limitations of Claim 1.
JIA, as modified by LAAKSONEN, SOONEE, and KHODAPARASTAN* does not explicitly teach:
determining the rate of change of frequency comprises deriving a rate of change from a monitored frequency value and one or more previously monitored frequency values and taking an absolute value of the rate of change, and wherein
determining the rate of change of reactive power comprises deriving a rate of change from a monitored reactive power value and one or more previously monitored reactive power values and taking an absolute value of the rate of change.
RAZA teaches:
determining the rate of change of frequency comprises deriving a rate of change from a monitored frequency value and one or more previously monitored frequency values (RAZA, as above, see Pg462,Table II: “2 Rate3 of change of frequency df/dt”; and see Pg463,§IV. “Analysis of Selected Parameters”, ¶1; “)necessary to analyse the relation between the variations in frequency”, see Eq(3) and – Pg464COL1,¶2: “it can also be inferred from (3) that the variation in frequency (Δf) due to islanding condition is dependent on both active and reactive power mismatches…relation between ΔQ and Δf is described by [25]*” followed by Eq(5); and see Pg464,Col2,¶2: “ “reactive power mismatch causes the frequency to deviate from the nominal value”; Applying BRI and plain meaning, Examiner interprets “previously monitored frequency” as analogous to reference “nominal value” to mean a frequency known or measured at a time prior to a change in frequency; Also so *Examiner notes reference [25], ZEINELDIN, et al., is included below as pertinent art.
and taking an absolute value of the rate of change, (RAZA teaches “absolute” change, Pg464,COL2,§V.,¶2, “proposed passive technique measures the absolute df /dq at every half cycle.”; Examiner interprets “absolute” as analogous to “absolute value”, based on further disclosure of only positive magnitude, see, for example FIG. 6(b),7(b),8(b)“Magnitude vs. Time” of df/dt, showing only positive values.)
and wherein determining the rate of change of reactive power comprises deriving a rate of change from a monitored reactive power value and one or more previously monitored reactive power values and taking an absolute value of the rate of change. (RAZA, as above, teaches consideration of magnitudes, suggesting use of absolute value for all 16 parameters, see Pg462,TableII, Pg463, FIG.3 with Pg462,§III.: “performance analysis of multiple passive parameters, such as …rate of change of reactive power (dq/dt), rate of change of frequency (df /dt)…Table II list details of these parameters…magnitudes of these parameters were observed”; and see PG464, COL1, ¶2 – COL2¶2, with equations (5), (7),(9),(11), discussion of “delta Q”, where reactive power rate of change is expressed in terms of known “QDER”; Examiner interprets “previously monitored” as above.)
It would be obvious for one of ordinary skill on or before the effective filing date of the claimed invention to combine the system/method of island detection of as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above*, to include determining the rate of change of frequency comprises deriving a rate of change from a monitored frequency value and one or more previously monitored frequency values and taking an absolute value of the rate of change, and determining the rate of change of reactive power comprises deriving a rate of change from a monitored reactive power value and one or more previously monitored reactive power values and taking an absolute value of the rate of change, as taught by RAZA, because RAZA explicitly teaches these steps to result in a detection parameter for detecting islanding which has superior sensitivity when compared with monitoring other parameters. One of ordinary skill would see the benefit and utility of using magnitudes of change rates to better examine variations in a detection parameter because it would simplify data analysis, relying on comparative size of change without regard for the sign of the change, as taught by RAZA.
*or alternately using newly discovered art, JIA, RAZA and KHODAPARASTAN, as noted above.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure.
MAHAT, et al., “Review on islanding operation of distribution system with distributed generation,” in Proc. IEEE Power Energy Soc. Gen. Meeting, 2011, pp. 1–8 – teaches background and support details for a variety of techniques as applied to islanding detection in a power grid. This work is references by RAZA.
ZEINELDIN, et. al., “Impact of DG interface control on islanding detection and non-detection zones,” IEEE Trans. Power Del., vol. 21, no. 3, pp. 1515–1523, Jul. 2006. – teaches relative change in frequency, as used by RAZA in analysis of sensitivity parameter df/dq, with further motivation for using the relationship between frequency and reactive power for analysis.
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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/TONI D SAUNCY/Examiner, Art Unit 2857
/YOSHIHISA ISHIZUKA/Primary Examiner, Art Unit 2857
