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 .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission(s) filed on 01/16/2026 and 02/10/2026 have been entered.
Response to Amendment
Applicant’s amendments, filed 01/16/2026, are accepted.
Claims 1-15 are pending.
Claims 1 and 5 are amended.
Applicant's arguments filed 01/16/2026 have been reviewed and fully considered.
With regard to rejection of Claims 1-15 under 35 U.S.C. § 103, over obvious
combination of prior art, based on further consideration and search as necessitated by amendments, Examiner finds arguments are not persuasive. Further consideration and search as necessitated by amendments, with new grounds for rejection is detailed below.
Specifically, Applicant argues (REMARKS, Pg3, Paragraph1) regarding rejection of Claims 1, 4, 6, and 15 35 U.S.C. § 103, over obvious combination of prior art by JIA (CN 109861278 A) in view of LAAKSONEN (US 9784781 B2) and further in view of SOONEE ("REACTIVE POWER AND SYSTEM REQUENCY RELATIONSHIP:A CASE STUDY", 7th International R&D Conference, 4-6 February 2009), that the cited references do not teach or render obvious each and every limitation recited in independent Claim 1, as currently amended. Examiner notes that amended language in claim 1 adds specificity that has not previously been considered in examination and requires further search and evaluation. Examiner acknowledges Applicant’s concerns regarding specific details of passive detection methods, evaluation of relationship between of frequency and reactive power in terms or ratios or inverse of ratios found in cited references, and use of these ratios as the parameter for triggering from passive detection to active detection. Examiner respectfully disagrees that the claimed invention would not result from an obvious combination of discovered prior art, based on claim interpretation using plain meaning and broadest reasonable interpretation, and reminds Applicant that specification can only be used to guide interpretation. Specifically, Applicant argues (REMARKS, Pg.8) that identified prior art does not teach use of a quotient parameter for islanding detection. Examiner respectfully disagrees and finds that the inventive concept of using a ratio-type parameter for evaluation of power grid behavior, specifically occurrence of islanding phenomena is discussed in the general exposition of SOONEE, as discussed in detail below. SOONEE teaches the advantage of using a ratio of change in frequency and change in reactive power based on the significant frequency dependence of reactive power response to perturbation. Using the inventive idea of SOONEE to enhance and broaden the sensitivity and accuracy of the islanding detection method of the of the invention of JIA (as modified), provides a proper case of prima facie obviousness that would result in the claimed invention, as discussed below.
Examiner finds claims as currently amended are not distinguishable over prior art available before effective filing date of the claimed invention. Detailed response addressing Applicant arguments, with attention to reasoning and rationale as applied to establish a prima facie case of obviousness in determination that the claimed invention does not distinguish over prior art is presented below with new grounds of rejection as necessitate by amendment.
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 respect to Claim 1, JIA teaches:
A method of detecting an islanding operation of an electrical power generating system coupled to a power grid, (Referring to English translation provided in previous office action, JIA is in same technical field, 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 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”; 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 [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, [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, 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, [0015]-[0016], as above.)
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, [0006]: “passive island detection method performs island detection without injecting disturbance signals”, FIG. 6 step 5 “The 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 [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, [0005]: "active detection method injects disturbance signals into the power grid”; )
JIA does not 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, Abstract; LAAKSONEN Col2L1: “detection methods include monitoring of frequency (f), rate-of-change-of-frequency (ROCOF/df/dt)”, and Col3L60, Col4: “detection method can be based…rate-change-of-reactive-power (dQ/dt)”; Examiner interprets “determining a detection parameter” as analogous to “detection methods include”.)
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 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, islanding detection parameters, Col3L60-Col4: “islanding detection method can be based, for example, on measurement of one or more of the following parameters” and 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., islanding is detected.)
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 using rate of change of frequency and rate of change of reactive power for determining a detection parameter, and to use a passive detection with no disturbance injection, and to detect the islanding operation using a threshold method, as taught by LAAKSONEN because these additional details in the method of JIA would add accuracy and reliability to an islanding detection system.
JIA, as modified by LAAKSONEN as 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; SOONEE teaches use of “ratio” , i.e., “quotient”, P3,Table 1: “dQ/df”, where “dQ” is change in reactive power and “df” is change in frequency, and FIG. 4.2; Examiner interprets “quotient of rate of change of frequency and the rate of change of reactive power” analogous to reference ratio of “dQ/df, rate of change in reactive power to rate of change in frequency”, as the two ratios are composed of same variable quantities, with reference ratio is expressed as a simple mathematical inverse.)
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 LAAKSONEN with the detection parameter determination using ratios of rate of change of frequence and rate of change of reactive power because the ratio would reveal additional insight with increased sensitivity to islanding phenomena, based on the strong frequency dependence of reactive power. This is pointed out by SOONEE, P7: “strong impact of frequency on Reactive power”.)
The combination of 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, 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 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…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”; Examiner interprets “detection parameter” analogous to reference “signal for island detection” and flow chart box “trip” indicates signal to begin active detection method, Pg3Col2,SectionC “Proposed Hybrid Method: When the ROCOF relay detects any variation in df/dt, a trip signal will be sent to a multiple switch which activates the SFS signal(i.e., changes operation to active mode)”; and Pg6Col2, Section E: “If this frequency deviation exceeds the ROCOF relay threshold, the SFS method will be initiated”)
injecting a disturbance ([Symbol font/0x71]SFS, [Symbol font/0x71]FS) into electrical power grid (KHODAPARASTAN recites Pg1, “dominant active techniques are: active frequency drift method (AFD)… Sandia frequency-shift method (SFS)” Examiner notes FS disturbance method is also known as Frequency Shift (FS) / Active Frequency Drift (AFD) method as would be understood by one of ordinary skill in the art, where both [Symbol font/0x71]SFS would be known as dominant active perturbation methods for island detection, as taught by KHODAPARASTAN)
It would be obvious for one of ordinary skill on or before the effective filing date of the claimed invention to combine the method of island detection of JIA as modified with the detection techniques taught by LAAKSONEN and ratio/quotient parameter technique of SOONEE with explicit teaching of a hybrid method with a thresholding method of changing from a passive mode to an active mode, as taught by KHODAPARASTAN because it would provide more robust and accurate data by using both active and passive methods, thereby taking advantage of the strengths of each method. 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 operating status a system.
With respect to Claim 4, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN teaches the method according to 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, 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 respect to Claim 5, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, teaches the method according to claim 1.
KHODAPARASTAN further teaches:
the activation threshold value is lower than the islanding threshold value (KHODAPARASTAN suggests, a lower islanding threshold, Pg2164, Col2: “If the threshold is set too low, it may lead to nuisance trips of DG; and if the threshold is set too high, islanding may not be detected…relay calculates df/dt, then if islanding is suspected, an activation signal will be sent to SFS”; Examiner interprets “activation threshold” to system is switched to active detection mode, which must be lower than the threshold indication of islanding, analogous to reference teaching.)
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 as taught above to ensure 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.
With respect to Claim 6, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN teaches the method according to claim 1.
JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN, does not teach:
operating in the active detection mode occurs continuously.
LAAKSONEN further teaches:
operating in the active detection mode occurs continuously (LAAKSONEN Fig. 3, method steps, depicts loop structure with repeating measurements, 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 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.
With respect to Claim 15, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, teaches the method according to 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 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 modify JIA, s modified by LAAKSONEN, SOONEE and KHODAPARASTAN 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, such as that of LAAKSONEN because, while JIA does not explicitly recite use of a computer with program instructions, does imply 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. The invention of JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN would be more efficiently carried out by including the computational programming technique taught by the LAAKSONEN disclosure in order to make control, calculations, including comparative analysis efficient and accessible.
Claim 2 is rejected under 35 USC § 103 as being unpatentable over JIA, in view of LAAKSONEN, SOONEE, and KHODAPARASTAN, 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 respect to Claim 2, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN teaches the method according to claim 1, but does not 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, 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, 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…” 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, in view of LAAKSONEN and SOONEE, as taught above, to determine a rate of change of frequency by using a predetermined first window length, and a rate of change of reactive power is by using a predetermined second window length, such as that of ALAM because the window-based method for data acquisition provides increased understanding of system dynamics. ALAM teaches the value of using window based collection protocol because careful choice of timing for gathering data to evaluate frequency or reactive power behavior for fluctuations indicating islanding ensures more accurate identification, 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, 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 respect to Claim 3, JIA as modified by LAAKSONEN, SOONEE and KHODAPARASTAN teaches the method according to claim 1.
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, 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” Examiner interprets “predetermined amount of time” as 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, 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, 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 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, 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.(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 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, 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 as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and further modified by REIGOSA, as taught above, teaches the method according to 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, (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. (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 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 as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and further modified by REIGOSA as taught above, teaches the method according to 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. (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).)
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 a as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and further modified by REIGOSA as taught above, teaches the method according to 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. (As above, 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 a as modified by LAAKSONEN, SOONEE and KHODAPARASTAN and further modified by REIGOSA as taught above, teaches the method according to claim 10.
KHODAPARASTAN further teaches:
a phase angle of the grid voltage determined by a phase locked loop (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 is a well known and proven method for accurate phase control and determination.
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 (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, in combination with LAAKSONEN, SOONEE, KHODAPARASTAN and REIGOSA 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, 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 as taught above, teaches the method according to claim 7.
JIA, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA as taught above, does not 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 is in same technical field, title; 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. (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 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, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA as taught above, 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” )
JIA, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA as taught above, does not 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 (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 JIA, as modified by LAAKSONEN, SOONEE , KHODAPARASTAN, and REGIOSA 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 wide 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, and further in view of 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, (Combination of JIA with LAAKSONEN, SOONEE and KHODAPARASTAN, discussion, Claims 1, 15 above.)
JIA, as modified by LAAKSONEN, SOONEE and KHODAPARASTAN as taught above, does not 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”; [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.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure.
BICKEL (US 20130169309 A1) – teaches buffering for acquisition of frequency and rate of change in frequency over pre-determined time intervals to determine event occurrence.
SAMET (Samet, et al., “Islanding detection method for inverter-based distributed generation with negligible non-detection zone using energy of rate of change of voltage phase angle”, IET Gener. Transm. Distrib., 9: 2337-2350, 2015) – teaches a simplified method for islanding detection based on rate of change of voltage phase angle with phase-locked loop, and use of both passive and active detection modes.
TRAN (Tran, et al., “Islanding Detection Method Based on Injecting Perturbation Signal and Rate of Change of Output Power in DC Grid-Connected Photovoltaic System” Energies 2018, 11(5), 1313
ZAMANIA (Zamani, et al., “A novel hybrid islanding detection method using dynamic characteristics of synchronous generator and signal processing technique”, Electric Power Systems Research 175 (2019) 105911. – teaches both active and passive methods for island detection.
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/TONI D SAUNCY/Examiner, Art Unit 2857
/Catherine T. Rastovski/Supervisory Primary Examiner, Art Unit 2857