JP6408356B2 - Distributed power system independent operation determination method, distributed power system, and power conditioner - Google Patents

Description

  The present invention relates to an isolated operation determination method for a distributed power supply system, a distributed power supply system, and a power conditioner.

  Patent Document 1 describes a technique related to an isolated operation determination method for a distributed power supply system. This system includes a distributed power supply device, a system power supply, and a power conditioner that determines whether a single operation of the distributed power supply system is performed by active detection means and passive detection means. In this system, it is determined by the active detection means and the passive detection means that the system power supply is stopped at the time of a power failure and the distributed power supply system is operating independently.

JP 2009-77612 A

  Here, the frequency of the system power supply is, for example, disturbance in the operation of the power plant, load fluctuations in neighboring factories that use a lot of power, problems with the impedance of low-voltage distribution lines, problems with the capacity of the pole transformer, etc. It may vary depending on the cause of. Therefore, when the frequency fluctuates greatly due to such a cause, in the above system, it is erroneously determined that the distributed power supply system is operating independently even though no power failure etc. has actually occurred. There is.

  Accordingly, an object of the present invention is to provide a method for determining an isolated operation of a distributed power system, a distributed power system, and a power conditioner that can accurately determine an isolated operation by the distributed power system.

The isolated operation determination method for a distributed power system according to the present invention can execute a grid-connected operation for supplying power in conjunction with a system power supply. In the isolated operation determination method of the distributed power supply system disconnected from the power supply, a frequency detection step for detecting the frequency of the voltage of the system power supply, and a determination value based on the detection frequency detected in the frequency detection step are predetermined determinations. When not included in the range, the isolated operation determination step for determining that the isolated operation by the distributed power system is being performed, and the degree of fluctuation of the detected frequency calculated based on the high frequency component and the low frequency component A frequency fluctuation detection step for detecting a frequency fluctuation degree to be represented, and a determination range for changing the determination range in the isolated operation determination step based on the detected frequency fluctuation degree Comprising further a step.

  An isolated operation determination method for a distributed power system according to the present invention includes a variation range setting step for setting a variation range of a determination range based on the frequency variation detected in the frequency variation detection step. The determination range is changed according to the fluctuation range set in the fluctuation range setting step.

  In the isolated operation determination method for a distributed power system according to the present invention, in the frequency variation detection step, the frequency variation is detected based on the high frequency component and the low frequency component of the detected frequency.

  In the isolated operation determination method for a distributed power supply system according to the present invention, in the determination range change step, the determination range is changed by providing at least one of an upper limit value or a lower limit value with respect to the change amount of the determination range.

  In the isolated operation determination method for a distributed power supply system according to the present invention, in the determination range changing step, the determination range is changed by expanding and contracting the determination range.

  In the isolated operation determination method for the distributed power system according to the present invention, the isolated operation determination step determines the isolated operation when the determination value based on the main component of the detected frequency is not included in the determination range.

In the isolated operation determination method of the distributed power supply system according to the present invention, in the determination range changing step, a variation factor that fluctuates the frequency variation is detected, and the determination range is changed according to the variation factor .

  In the isolated operation determination method for a distributed power system according to the present invention, the determination range change step learns the change of the determination range according to the frequency fluctuation occurrence state, and the isolated operation determination step learns in the determination range change step. The single operation is determined based on the determination range changed in advance.

  In the isolated operation determination method of the distributed power system according to the present invention, in the isolated operation determination step, the determination range changed in the determination range change step based on the detection frequency detected in the frequency detection step is the frequency. Used after a predetermined waiting time has elapsed since detection.

The distributed power supply system according to the present invention can execute a grid-connected operation for supplying power in conjunction with a grid power supply. In the distributed power system, the frequency detection unit for detecting the frequency of the voltage of the system power supply and the determination value based on the detection frequency detected by the frequency detection unit are not included in the predetermined determination range. A single operation determination unit that determines that the operation is being performed, a frequency variation detection unit that detects a frequency variation degree representing a degree of variation in the detection frequency calculated based on the high frequency component and the low frequency component, and detection A determination range changing unit that changes the determination range in the isolated operation determination unit based on the frequency fluctuation level.

The power conditioner according to the present invention is capable of executing grid-connected operation for supplying power in linkage with the system power supply, and is disconnected from the system power supply when an isolated operation associated with the stoppage of the system power supply is detected. In a power conditioner that controls the output of a distributed power supply system, a frequency detection unit that detects the frequency of the voltage of the system power supply and a determination value based on the detection frequency detected by the frequency detection unit are included in a predetermined determination range Frequency variation indicating the degree of variation in the detection frequency calculated based on the high frequency component and the low frequency component, and the single operation determination unit that determines that the single operation by the distributed power supply system is being performed. A frequency variation detection unit that detects the degree, and a determination range change unit that changes the determination range in the isolated operation determination unit based on the detected frequency variation.

  ADVANTAGE OF THE INVENTION According to this invention, it can determine accurately that the independent operation by the distributed power supply system is performed.

1 is a block configuration diagram of a distributed power supply system and a power conditioner according to an embodiment of the present invention. It is a graph which shows the relationship between progress of time in each situation, and the fluctuation | variation of a frequency. It is a graph which shows the relationship between the threshold value of a determination range, and a frequency variation degree. It is a flowchart which shows an example of the control processing of the distributed power supply system which concerns on embodiment of this invention, and a power conditioner. 5 is a flowchart illustrating an example of a control process of determination range change control illustrated in FIG. 4. It is a figure which shows the timeline of determination range change control. It is a graph which shows an example of a judgment range.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a block configuration diagram of a distributed power supply system 100 and a power conditioner according to the present embodiment. The distributed power supply system 100 is a system in which a distributed power supply 1 that is a power generation unit and a system power supply 3 are connected to supply power to a load 4. As shown in FIG. 1, the distributed power supply system 100 includes a distributed power supply device 1 and a power conditioner 2.

  The distributed power supply device 1 is a power supply having a function of generating power. Examples of the distributed power supply device 1 include a power generator for a distributed power supply such as a fuel cell, a solar cell, and a storage battery. In addition, when a fuel cell is applied as the distributed power supply device 1, the type of the fuel cell is not particularly limited. For example, a solid oxide fuel cell (SOFC), a polymer electrolyte fuel cell (PEFC) : Polymer Electrolyte Fuel Cell), Phosphoric Acid Fuel Cell (PAFC), Molten Carbonate Fuel Cell (MCFC), and other types can be employed.

  In the present embodiment, the distributed power supply system 100 can execute a grid-connected operation in which power is supplied to the load 4 in conjunction with the grid power supply 3. In addition, the distributed power supply system 100 is used when the voltage of the system power supply 3 is lost (for example, a power failure of the system power supply 3 is stopped due to an emergency such as a system failure, maintenance work, or a fire). A single operation for charging the system electric circuit L1 occurs. Therefore, when the isolated operation of the distributed power supply system 100 is determined, the distributed power supply system 100 needs to be disconnected from the system power supply 3. The distributed power supply device 1 is connected to a load 4 via a power conditioner 2 through a power supply line L0 and a system power line L1. The system power supply 3 is connected to the system electric circuit L1 outside the power conditioner 2.

  The power conditioner 2 converts and adjusts the power from the distributed power supply device 1 and supplies it to the load 4 according to the power usage state at the outside (load 4). The power conditioner 2 includes a conversion unit 11, a grid connection switching unit 12, a measurement unit 13, an isolated operation monitoring unit 14, a grid connection protection unit 15, and a storage unit 16.

  The converter 11 performs a process of converting the output voltage of the distributed power supply device 1 and a process of converting DC power to AC power. The converter 11 includes a DC / DC converter that boosts DC power from the distributed power supply device 1 and a DC / AC inverter that converts DC power boosted by the DC / DC converter into AC power. The conversion unit 11 is provided in a power supply line L0 having one end connected to the distributed power supply device 1 and the other end connected to the system power line L1 via the system interconnection switching unit 12.

  The grid connection switching unit 12 switches the connection and disconnection between the distributed power supply system 100 and the grid power supply 3. The grid connection switching unit 12 is configured by, for example, a relay, a breaker, or the like. The grid connection switching unit 12 is provided so that the other end of the power supply line L0 on the downstream side of the conversion unit 11 and one end of the grid circuit L1 can be connected. Switching of the grid interconnection switching unit 12 is controlled by receiving a signal from the grid interconnection protection unit 15.

  The measuring unit 13 is provided in a monitoring line L3 that is drawn from between the one end connected to the grid connection switching unit 12 and the connection unit of the system power supply 3 in the grid circuit L1 and connected to the isolated operation monitoring unit 14. A value related to the voltage generated in the system electric circuit L1 is measured. The measuring unit 13 may measure any value as long as it can derive the frequency of the voltage generated in the grid circuit L1 in the isolated operation monitoring unit 14, for example, the distributed power system 100 You may measure the frequency information by the communication means which communicates the voltage information inside. The measuring unit 13 transmits the measurement result to the isolated operation monitoring unit 14 via the monitoring line L3. In addition, the measurement position of the measurement part 13 is not limited to the part shown in FIG. 1, You may change suitably according to the system of an independent operation detection.

  The isolated operation monitoring unit 14 monitors whether the distributed power supply system 100 is performing an isolated operation. When the isolated operation monitoring unit 14 detects the isolated operation, the isolated operation monitoring unit 14 transmits the detection result to the grid interconnection protection unit 15 via the signal line L4. The isolated operation monitoring unit 14 includes a frequency detection unit 21, an isolated operation determination unit 22, a frequency variation detection unit 23, a variation range setting unit 24, a determination range change unit 25, and a storage unit 16.

  The frequency detector 21 detects the frequency of the voltage generated in the system electrical circuit L1. The frequency detection unit 21 detects the frequency based on the measurement result of the value related to the voltage generated in the system electric circuit L1 transmitted from the measurement unit 13. The frequency detection unit 21 performs component analysis of the value related to the supplied power, deposits a peak value, a quasi-peak value, an average value, and the like, detects the frequency of the main component that becomes the peak value, It is possible to detect the peak value and quasi-peak value of the noise region on the high frequency side and the low frequency side with respect to the frequency of. Further, the frequency detection unit 21 transmits the detected frequency together with time data to the storage unit 16 for storage.

  The isolated operation determination unit 22 stops the power supply of the system power supply 3 due to a power failure or the like when the frequency of the main component based on the analysis of the detection frequency detected by the frequency detection unit 21 is not included in the predetermined determination range. Therefore, it is determined that the isolated operation by the distributed power supply system 100 is being performed. The kind of determination method by the independent operation determination unit 22 is not particularly limited, and any known method may be used. For example, passive methods such as a voltage phase jump detection method, a frequency change rate detection method, a third harmonic voltage distortion rapid increase detection method, etc. may be adopted, and a frequency shift method, reactive power fluctuation method, active power fluctuation method, load fluctuation method, etc. An active method such as the above may be adopted. A plurality of detection methods may be combined. The determination value is a parameter having a correlation with the detection frequency, and any parameter may be employed based on the determination method employed. The determination range is a range determined by a predetermined threshold set for the determination value. The isolated operation determination unit 22 determines that the frequency of the main component, which is the determination value, is within the determination range, and determines that it is not an isolated operation, and if the determination value is below the lower limit value of the determination range, or the upper limit of the determination range When it exceeds the value, it is determined that the vehicle is operating alone.

  As shown in FIG. 7, the isolated operation determination unit 22 uses the detected frequency as a determination value and sets a predetermined frequency range as the determination range. As shown in FIG. 7, the determination range DA is set as a frequency range of “50 ± α Hz” with respect to the reference frequency (here, 50 Hz) of the system power supply 3 by the power company in the corresponding region. . In this example, the absolute value of the threshold value on the low frequency side and the threshold value on the high frequency side with respect to the reference frequency are the same value (α), but the absolute value of the threshold value may be different between the high frequency side and the low frequency side. The isolated operation determination unit 22 determines the isolated operation when the main component frequency of the detection frequency that is the determination value is not included in the determination range DA. The isolated operation determination unit 22 may convert the detected frequency into another parameter by calculation or the like and employ it as a determination value.

  The frequency variation detector 23 detects a frequency variation representing the degree of variation in the detected frequency detected by the frequency detector 21. Here, as the “frequency fluctuation degree”, any index may be adopted as long as it is an index indicating the degree of fluctuation of the detected frequency, that is, the degree of disturbance, the degree of scattering, the degree of variation, and the like. For example, an index calculated by statistical processing such as standard deviation, variance, variation coefficient, probability distribution, moving average, exponential average, etc. may be detected as the frequency variation. Here, the frequency variation detector 23 detects the frequency variation based on the high frequency component and the low frequency component of the detected frequency. Specifically, in the example shown in FIG. 7, the high-frequency noise component NH and the low-frequency noise component NL based on the high-frequency noise component NH and the low-frequency noise component NL that are quasi-peak values on the higher frequency side and the lower frequency side among the detection frequencies. Frequency variability such as a difference from the low frequency noise component NL and a deviation of each noise component NH, NL with respect to a reference frequency (50 Hz) may be detected.

  The fluctuation range setting unit 24 sets the fluctuation range of the determination range based on the frequency fluctuation level detected by the frequency fluctuation level detection unit 23. The variation range setting unit 24 may set the variation range of the determination range of the determination range used by the isolated operation determination unit 22 to be larger as the frequency variation rate is larger, and the variation range of the determination range as the frequency variation rate is smaller. You may set small.

  The determination range changing unit 25 changes the determination range in the isolated operation determination unit 22 based on the fluctuation range set by the fluctuation range setting unit 24. The isolated operation monitoring unit 14 transmits the detection result to the grid interconnection protection unit 15 when the isolated operation determination unit 22 detects (detects) the isolated operation using the determination range changed by the determination range change unit 25. To do.

  Here, an example of the operation of the determination range changing unit 25 will be described with reference to FIGS. 2 and 3. When power supply by the system power supply 3 is stopped due to a power failure, the power balance between the load 4 and the distributed power supply system 100 is lost and a frequency shift occurs. At this time, the frequency of the voltage generated in the system circuit L1 is displaced in one direction of increase or decrease. Therefore, when the power supply of the system power supply 3 is stopped and the distributed power supply system 100 is in a single operation state, the voltage measured by the measurement unit 13 as shown by the broken line graph in FIG. The value changes with the passage of time, and as shown by the broken line graph in FIG. 2D, the voltage frequency (the frequency of the voltage generated in the system circuit L1) gradually increases with the passage of time, or FIG. As shown in the dashed line graph in (b), the voltage value is displaced with the passage of time, and the voltage frequency gradually decreases with the passage of time as shown in the dashed line graph in FIG. That is, when the power supply by the system power supply 3 is actually stopped, the voltage frequency is gradually (slowly) displaced to one of the high frequency side and the low frequency side. On the other hand, due to disturbances in the operation of the power plant, load fluctuations in nearby factories that use a lot of power, problems with the impedance of low-voltage distribution lines, problems with the capacity of pole transformers, etc. The system frequency of the system power supply 3 may be disturbed by affecting the power. In this case, the voltage value is displaced with time as shown by the two-dot chain line in FIG. 2C, and the voltage frequency is not stabilized as shown by the two-dot chain line in FIG. As a result, the frequency variation increases and the frequency fluctuation increases.

  Based on such a frequency fluctuation degree, the fluctuation range setting unit 24 changes the determination range by correcting a threshold value that determines the determination range, as indicated by a solid line in FIG. The fluctuation range setting unit 24 performs correction so that the threshold value increases as the frequency fluctuation degree increases. The threshold correction method is not particularly limited, and a value corresponding to the increase in the frequency fluctuation degree may be added to or multiplied by the initial threshold value (threshold value when the frequency does not vary) α0. Correction may be performed by the calculation method. In addition, as shown by a dotted line in FIG. 3, the threshold value is a constant value of the lower limit value α0 when the frequency variation is in the range of the predetermined value v1 or less, and a constant value of the upper limit value αm in the range of the frequency variation is the predetermined value v2 or more. May be set to be.

  In the present embodiment, for example, as shown in FIG. 7A, when the determination range in which the width is set by the initial threshold value α0 is indicated by “determination range DA0”, the fluctuation range setting unit 24 A variation range larger than the determination range DA0 is set by correcting the threshold value of the determination range based on the frequency variation detected by the variation detection unit 23. The determination range changing unit 25 changes the determination range DA1 and the determination range DA2 wider than the determination range DA0 based on the threshold value α corrected to obtain the fluctuation range. Further, the determination range changing unit 25 may change the determination range by providing at least one of an upper limit value and a lower limit value with respect to a change amount (corrected threshold value) of the determination range. That is, an upper limit value may be provided so that detection of an isolated operation due to an actual power failure is not hindered by making the determination range too large. In addition, a lower limit value may be provided so that erroneous detection of isolated operation is not performed by making the determination range too narrow. Further, the determination range changing unit 25 changes the determination range by performing expansion / contraction of the determination range. For example, as shown in FIG. 7A, the determination range changing unit 25 may extend from the determination range DA0 to the determination range DA1 according to the threshold value corrected based on the detected frequency fluctuation degree, and from the determination range DA2. You may shorten to determination range DA1. Further, the determination range changing unit 25 may change the determination range DA3 by contracting the lower limit side and extending the upper limit side with respect to the determination range DA1. In this way, as in the case of changing from the determination range DA1 to the determination range DA3, the size of the determination range itself is maintained, and expansion and contraction is performed so that the position of the determination range is slid to the high frequency side or the low frequency side. Also good.

  The grid interconnection protection unit 15 suppresses charging to the grid circuit L1 by disconnecting the distributed power supply system 100 from the grid power supply 3 based on the detection result of the isolated operation monitoring unit 14. Note that the distributed power supply system 100 may be stopped at the time of disconnection. The grid connection protection unit 15 is connected to the conversion unit 11 and the grid connection switching unit 12 via the transmission line L5. When the grid connection protection unit 15 receives the detection result that the single operation is performed from the single operation monitoring unit 14, the grid connection protection unit 15 stops the output of the conversion unit 11 by transmitting a signal via the transmission line L5. At the same time, the grid connection switching unit 12 is disconnected.

  The storage unit 16 is configured by a memory or the like, and stores and reads data used in the control process in the power conditioner 2. The storage unit 16 stores data received from the isolated operation monitoring unit 14 and transmits data in response to a request from the isolated operation monitoring unit 14.

  Next, with reference to FIG. 4 to FIG. 7, a description will be given of an isolated operation determination method for the distributed power supply system 100 by the distributed power supply system 100 and the power conditioner 2 according to the present embodiment. FIG. 4 is a flowchart illustrating an example of control processing of the distributed power supply system 100 according to the present embodiment. FIG. 5 is a flowchart illustrating an example of a control process of the determination range change control illustrated in FIG. The control processing shown in FIGS. 4 and 5 is repeatedly executed at a predetermined timing in the power conditioner 2 during the operation of the distributed power supply system 100. However, the control processing shown in FIGS. 4 and 5 is merely an example of the control processing of the distributed power supply system 100 and is not limited to the processing content.

  The control process shown in FIG. 4 is executed during the operation in the grid interconnection operation in which the distributed power supply system 100 and the grid power supply 3 are linked to supply power. As shown in FIG. 4, the frequency detection unit 21 of the isolated operation monitoring unit 14 detects the frequency of the voltage generated in the grid circuit L1 (step S10: frequency detection step). Next, the isolated operation determination unit 22 determines whether or not the isolated operation by the distributed power supply system 100 is performed based on the detected frequency detected in S10 (step S20: isolated operation determination step). Specifically, the isolated operation determination unit 22 determines that the isolated operation is being performed when the determination value based on the detected frequency detected in S10 is not included in the determination range. In S20, when it is determined that the single operation is not performed, the process proceeds to a determination range change control process for changing the determination range (step S30). Details of the processing of S30 will be described later.

  On the other hand, if it is determined in S20 that the determination value based on the detected frequency is not included in the determination range due to a power failure or the like of the system power supply 3, the grid connection protection unit 15 converts the determination. The output of the unit 11 is stopped, and the grid interconnection switching unit 12 is disconnected to cancel the grid interconnection operation (step S40). Thereafter, the power conditioner 2 waits for a predetermined time (step S50) and determines whether the system power supply 3 has recovered from the power failure (step S60). Specifically, at least one of the voltage and the voltage frequency generated in the grid circuit L1 in the disconnected state of the grid connection switching unit 12 has returned to a normal value (a value in the normal operation state of the grid power supply 3). Is detected and return is determined. This return determination may use another determination method. If it is determined in step S60 that the power has not recovered from the power failure, the return determination in step S60 is repeated. In addition, when recovery is not determined even if the determination of power failure recovery is repeated a predetermined number of times, the distributed power supply device 1 is activated by power supplied from a storage battery or the like built in the distributed power supply system 100 to perform independent operation. You may do it. On the other hand, if it is determined in step S60 that the power has returned from the power failure, the grid interconnection operation is started and continued (step S80). When the process of S80 ends, the control process shown in FIG. 4 ends.

  Next, the determination range change control process will be described in detail with reference to FIG. In the determination range change control process, a plurality of tracks whose time is shifted from each other are processed in parallel as in the timeline shown in FIG. Note that the example of FIG. 6 shows 1 minute per square, and the calculation is performed on 6 tracks by shifting the time by 1 minute. In one cycle composed of 6 tracks, data recording is performed for 1 minute, calculation and waiting are performed for 5 minutes, and then the next cycle is started. The flowchart of FIG. 5 shows the contents of control processing for one cycle.

  As shown in FIG. 5, the frequency detection unit 21 acquires and associates the detected frequency data and time data with each other and records them in the storage unit 16 (step S100: frequency detection step). In addition, the isolated operation monitoring unit 14 determines whether or not the recording time has reached 1 minute (step S110). If it is determined that the recording time has not reached 1 minute, the process of S100 is repeated again.

  On the other hand, when it is determined that the recording time has reached 1 minute, the frequency variation detector 23 detects the frequency variation based on the recorded value of the frequency recorded in S100 (step S120: frequency variation). Degree detection step). Further, the fluctuation range setting unit 24 sets the fluctuation range of the determination range based on the frequency fluctuation degree detected in S120 (step S130: fluctuation range setting step). Further, the determination range changing unit 25 acquires the fluctuation range set in S130 as the threshold calculation value αt (step S140: determination range changing step). The threshold calculation value αt is provisionally determined as a value for calculation for determining whether or not it can be adopted as the threshold operation value α for performing actual isolated operation determination.

  A specific example of the processing of S120 to S140 will be described with reference to FIG. However, this processing is an example and can be changed as appropriate. For example, which value is adopted as the frequency fluctuation degree and which value is adopted as the fluctuation range may be appropriately changed. The frequency variation detector 23 detects the frequency variation based on the high frequency noise component NH and the low frequency noise component NL of the detected frequency detected based on the component analysis. The high frequency noise component NH is a peak value (or quasi-peak value) of noise on the high frequency side of the main component frequency, and the low frequency noise component NL is a peak of noise on the low frequency side of the main component frequency. The peak price (or quasi-peak value). The frequency fluctuation detection unit 23 detects the total width W of the fluctuation width of the high frequency noise component NH and the fluctuation width of the low frequency noise component NL with respect to the main component F at the detection frequency as the frequency fluctuation degree. Specifically, the frequency variation is expressed as “| NL−F | + | NH−F |”. That is, the frequency variation is represented by “NH-NL”. In the present embodiment, the fluctuation range setting unit 24 sets the same value as the total width W of the detection frequencies as the total width of the determination range (however, a value adjusted from the total width W of the detection frequencies may be adopted). . In this embodiment, the fluctuation range of the determination range is set to the same value on the high frequency side and the low frequency side with respect to the reference frequency (here, 50 Hz). Therefore, the fluctuation range with respect to the reference frequency is expressed as “(NH−NL) / 2”. The determination range changing unit 25 acquires the value of the fluctuation range as the threshold calculation value αt. Therefore, it is expressed as “αt = (NH−NL) / 2”.

  Next, the determination range changing unit 25 determines whether or not the threshold calculation value αt acquired in S140 is larger than the lower limit value α0 (step S150: determination range changing step). The lower limit value α0 is a minimum threshold value in the threshold operation value α employed for actual determination, and is an initial threshold value set when there is no fluctuation in frequency. If it is determined in S150 that the calculated threshold value αt is greater than the lower limit value α0, the determination range changing unit 25 determines whether or not the calculated threshold value αt acquired in S160 is smaller than the upper limit value αm (step S160). : Judgment range changing step). The upper limit value αm is the maximum threshold value in the threshold operation value α that is adopted for actual determination. When it is determined in S160 that the threshold calculation value αt is smaller than the upper limit value αm, the determination range changing unit 25 rewrites the threshold operation value α from the current value to the threshold calculation value αt (step S170: determination range change). Step). On the other hand, when it is determined in S150 that the threshold calculation value αt is equal to or lower than the lower limit value α0, the determination range changing unit 25 rewrites the threshold operation value α from the current value to the lower limit value α0 (step S180: determination range). Change step). When it is determined in S160 that the threshold calculation value αt is equal to or greater than the upper limit value αm, the determination range changing unit 25 rewrites the threshold operation value α from the current value to the upper limit value αm (step S190: determination range) Change step).

  After the rewriting of the threshold operation value α is completed, the isolated operation monitoring unit 14 waits until 6 minutes have elapsed from the start of the process in this cycle (step S200). After S200, the isolated operation determination unit 22 starts to operate the rewritten threshold operation value α (step S210). That is, the isolated operation determination unit 22 uses the determination range changing unit 25 based on the threshold operating value α rewritten by the fluctuation range setting unit 24 based on the processing from step S120 to step S190, instead of the determination range currently used for determination. An isolated operation is determined using a predetermined determination range. When the process of S210 ends, the control process shown in FIG. 5 ends. After the elapse of 6 minutes, the independent operation is determined with the rewritten threshold operation value α for 1 minute. For example, as shown in FIG. 6, the cycle ends 6 minutes after the start of the first cycle of the track 1, and the independent operation is determined based on the rewritten threshold operation value α1. On the other hand, since the first cycle of track 2 has started one minute after the start of the first cycle of track 1, the threshold value of track 2 is one minute after the start of operation with the threshold operation value α1 of track 1. The operation with the operation value α2 starts. By repeating such a cycle on six tracks, the determination of the isolated operation in the determination range based on the new threshold is performed at intervals of 1 minute.

  Further, in one cycle of one track, between the timing at which the frequency is detected and the timing at which the independent operation determination unit 22 performs determination based on the determination range changed based on the detected frequency. A predetermined waiting time is provided. That is, when the isolated operation determination unit 22 determines the isolated operation, the isolated operation determination unit 22 is determined by the determination range change unit 25 based on the detection frequency detected by the frequency detection unit 21. Is used after a predetermined waiting time has elapsed since the frequency was detected. For example, in the first cycle of track 1, the detection frequency is detected and recorded in “Record 1”, and the determination of the isolated operation based on the threshold set based on “Record 1” is “Threshold 1”. Done in Thus, a waiting time is provided so that there is an interval of 5 minutes between them. Note that the standby time is set so that there is an interval longer than at least the time required for frequency detection.

  As shown in FIG. 7A, when the threshold operation value α is rewritten to the lower limit value α0, the determination range is changed to “determination range D0”. When the threshold operation value α is rewritten to the upper limit value αm, the determination range is changed to “determination range DA2”. When the threshold operation value α is rewritten to the threshold calculation value αt, the determination range is changed to “determination range DA1” that is wider than the determination range D0 and narrower than the determination range DA2. In this case, the isolated operation determination unit 22 determines the isolated operation depending on whether or not the main component F of the detected frequency is included in the determination range DA1. When there is no power failure or the like, the main component F of the frequency is 50 Hz (if it is eastern Japan), so that the main component F is included in the determination range DA1 as shown in FIG. The part 22 determines that it is not a single operation. On the other hand, when a power failure occurs, the main component F of the frequency fluctuates greatly. Therefore, as shown in FIG. 7B, when the main component F is not included in the determination range DA1, the isolated operation determination unit 22 operates independently. It is determined that

  Next, functions and effects of the isolated operation determination method for the distributed power supply system 100 according to the present embodiment, the distributed power supply system 100, and the power conditioner 2 will be described.

  In the isolated operation determination method for the distributed power supply system 100 according to the present embodiment, in the frequency variation detection step (S120), a frequency variation representing the degree of variation in the detected frequency is detected. In the determination range changing step (S130 to S190), the determination range used for determination in the isolated operation determination step (S20) is changed based on the detected frequency fluctuation degree. Thus, in the isolated operation determination step, it is possible to determine the isolated operation by the distributed power supply system 100 based on the determination range changed based on the frequency fluctuation degree. Therefore, the voltage frequency of the power line L1 is reduced due to disturbances in the operation of the power plant, load fluctuations in neighboring factories that use a lot of power, problems with the impedance of low-voltage distribution lines, problems with the capacity of the pole transformer, etc. When it fluctuates, the determination range used for the isolated operation determination can be changed in accordance with the variation, so that it is possible to suppress erroneous determination that the distributed power supply system 100 is performing the isolated operation. As described above, isolated operation by the distributed power supply system 100 can be accurately determined, and unnecessary stoppage of the distributed power supply system 100 can be suppressed.

  The isolated operation determination method for the distributed power supply system 100 according to the present embodiment includes a variation range setting step (S130) for setting a variation range of the determination range based on the frequency variation detected in the frequency variation detection step. In the determination range changing step, the determination range is changed according to the fluctuation range set in the fluctuation range setting step. According to such a configuration, it is possible to easily change the determination range by changing the determination range according to the fluctuation range set based on the frequency fluctuation degree.

  In the isolated operation determination method for the distributed power supply system 100 according to the present embodiment, in the frequency variation detection step, the frequency variation is detected based on the high frequency component and the low frequency component of the detected frequency. According to such a configuration, for example, as in the control process described with reference to FIG. 5, the frequency fluctuation degree can be indicated using the fluctuation range between the high-frequency component and the low-frequency component of the detection frequency. The frequency variation can be easily detected without performing a simple calculation.

  In the isolated operation determination method of the distributed power supply system 100 according to the present embodiment, in the determination range change step, the determination range is changed by providing at least one of an upper limit value or a lower limit value with respect to the change amount of the determination range (threshold value α). doing. According to such a configuration, the determination range can be changed within an appropriate range, so that the isolated operation can be determined with higher accuracy. For example, by providing a lower limit value, it is possible to prevent the determination range from becoming too narrow and easy to make an erroneous determination of isolated operation, and by providing an upper limit value, it is difficult to determine isolated operation during an actual power failure. Can be prevented.

  In the isolated operation determination method of the distributed power supply system 100 according to the present embodiment, in the determination range change step, the determination range is changed by expanding and contracting the determination range. According to such a configuration, the size of the determination range can be easily changed by expanding and contracting according to the frequency fluctuation degree.

  In the isolated operation determination method of the distributed power supply system 100 according to the present embodiment, in the isolated operation determination step, the isolated operation is determined when the determination value based on the main component of the detected frequency is not included in the determination range. The main component of frequency fluctuates greatly during an actual power outage. Therefore, according to such a configuration, the determination can be easily made by determining the isolated operation based on the main component of the detected frequency.

  In the isolated operation determination method of the distributed power supply system 100 according to the present embodiment, the timing at which the frequency is detected in the frequency detection step and the timing at which the determination range changed based on the detected frequency is used in the isolated operation determination step. In the meantime, a predetermined waiting time is provided. For example, when the judgment range is changed by immediately reflecting the frequency fluctuation degree of the detected frequency, when the frequency fluctuates greatly, the judgment range also expands accordingly, so that it is actually necessary to judge the isolated operation. Nevertheless, the determination may be delayed. On the other hand, according to the present embodiment, the isolated operation determination unit can determine using a determination range based on a detection frequency that is traced back by a predetermined standby time. Therefore, it is possible to suppress a delay in the determination of the isolated operation.

  The present invention is not limited to the embodiment described above.

  For example, in the determination range changing step, the frequency fluctuation occurrence state may be detected, and the determination range may be changed in accordance with the fluctuation occurrence state. The frequency fluctuation occurrence status includes location, date and environment (temperature, etc.). The degree of change in the determination range may be adjusted based on the frequency of occurrence and the like depending on the occurrence status. According to such a configuration, it is possible to perform the isolated operation with high accuracy in accordance with the frequency fluctuation occurrence state.

  In addition, in the determination range changing step, the change of the determination range according to the frequency fluctuation occurrence state is learned, and in the isolated operation determining step, the isolated operation is determined based on the determination range changed in advance by the learning in the determination range changing step. You can do it. For example, when the determination range is changed due to frequency fluctuation, the changed determination range and the occurrence status are associated with each other and stored in the storage unit 16, and stored in the future when the same occurrence status is obtained. The range may be used to determine the isolated operation. According to such a configuration, the isolated operation can be easily performed by determining the isolated operation based on the determination range changed in advance based on the learning.

  In the above-described embodiment, the threshold value α is rewritten based on the high frequency component and the low frequency component of the detection frequency in the control process shown in FIG. Instead, for example, a value (for example, standard deviation) obtained by statistically processing the detected frequency may be set as the threshold value α, and “reference frequency ± threshold value α” may be set as the determination range.

  In the above-described embodiment, the determination range is set by using the upper limit value αm and the lower limit value α0 for the threshold value α that is the variation range of the determination range, but the upper limit for the maximum value and the minimum value of the determination value that defines the determination range. A value and a lower limit value may be set, and the maximum value and the minimum value of the determination range may be set between the upper limit value and the lower limit value.

  In the above-described embodiment, the distributed power supply system 100 using a fuel cell as the distributed power supply device 1 has been described. However, a distributed power supply device for a distributed power supply such as a solar cell or a storage battery (a distributed power generation device). The above-described embodiment may be applied to the distributed power supply system 100 using the power supply as the distributed power supply device 1.

  DESCRIPTION OF SYMBOLS 1 ... Distributed type power supply device, 2 ... Power conditioner, 3 ... System power supply, 14 ... Single operation monitoring part, 21 ... Frequency detection part, 22 ... Single operation determination part, 23 ... Frequency fluctuation detection part, 24 ... Fluctuation width Setting unit, 25 ... determination range changing unit, 100 ... distributed power supply system.

Claims (11)

Isolated operation determination method for a distributed power supply system that can perform grid-connected operation that supplies power in conjunction with the system power supply and that is disconnected from the system power supply when an isolated operation associated with the stoppage of the system power supply is detected In
A frequency detection step for detecting the frequency of the voltage of the system power supply;
A single operation determination step for determining that a single operation by the distributed power supply system is performed when a determination value based on the detection frequency detected in the frequency detection step is not included in a predetermined determination range; ,
A frequency variation detection step for detecting a frequency variation representing a degree of variation in the detected frequency calculated based on a high frequency component and a low frequency component ;
A determination range changing step for changing the determination range in the isolated operation determination step based on the detected frequency fluctuation degree;
An independent operation determination method for a distributed power supply system comprising: A variation range setting step of setting a variation range of the determination range based on the frequency variation detected in the frequency variation detection step;
The method of claim 1, wherein in the determination range changing step, the determination range is changed according to the fluctuation range set in the fluctuation range setting step. 3. The islanding operation determination method for a distributed power supply system according to claim 1, wherein in the frequency fluctuation detection step, the frequency fluctuation is detected based on a high frequency component and a low frequency component of the detection frequency. . 4. The determination range change step according to claim 1, wherein the determination range is changed by providing at least one of an upper limit value and a lower limit value with respect to a change amount of the determination range. Of independent operation of distributed power supply system In the determination range changing step, the determination range is changed by performing expansion and contraction of the determination range, and the independent operation determination of the distributed power supply system according to any one of claims 1 to 4 Method. 6. The islanding operation determination step, wherein the islanding operation is determined when the determination value based on a main component of the detection frequency is not included in the determination range. A method for determining an isolated operation of a distributed power supply system according to claim 1. The said determination range change step detects the fluctuation | variation factor from which the said frequency fluctuation | variation fluctuates, and changes the said determination range according to this fluctuation | variation factor , It is characterized by the above-mentioned. Isolated operation determination method for a distributed power system. In the determination range change step, the change of the determination range according to the occurrence state of the frequency fluctuation is learned,
The islanding operation determination step according to claim 7, wherein the islanding operation is determined based on the determination range changed in advance by learning in the determination range changing step. In the isolated operation determination step, a predetermined standby time elapses after the frequency is detected in the determination range changed in the determination range change step based on the detection frequency detected in the frequency detection step. It uses after having performed, The isolated operation determination method of the distributed power supply system as described in any one of Claims 1-8 characterized by the above-mentioned. In a distributed power supply system that can perform grid-connected operation that supplies power in conjunction with the grid power supply and is disconnected from the grid power supply when an isolated operation associated with the stoppage of the grid power supply is detected,
A frequency detector for detecting the frequency of the voltage of the system power supply;
A single operation determination unit that determines that the single operation is performed when a determination value based on the detection frequency detected by the frequency detection unit is not included in a predetermined determination range;
A frequency variability detector that detects a frequency variability representing the degree of fluctuation of the detected frequency calculated based on a high frequency component and a low frequency component ;
A determination range changing unit that changes the determination range in the isolated operation determination unit based on the detected frequency variation,
A distributed power system comprising: It is possible to perform grid-connected operation that supplies power in conjunction with the grid power supply, and controls the output of the distributed power system that is disconnected from the grid power supply when a stand-alone operation associated with the stoppage of the grid power supply is detected In the inverter
A frequency detector for detecting the frequency of the voltage of the system power supply;
An isolated operation determination unit that determines that an isolated operation by the distributed power supply system is performed when a determination value based on the detected frequency detected by the frequency detection unit is not included in a predetermined determination range; ,
A frequency variability detector that detects a frequency variability representing the degree of fluctuation of the detected frequency calculated based on a high frequency component and a low frequency component ;
A determination range changing unit that changes the determination range in the isolated operation determination unit based on the detected frequency variation,
Power conditioner with

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