Analytical device and program

Abstract

To provide an analyzer and a program that analyze a connection status of distributed power sources that adopt each method.SOLUTION: An analyzer A1 includes a frequency detection unit 11 that detects a system frequency of a distribution system C, a recording control unit 14 that records a system frequency f detected by a frequency detection unit 11 in a storage unit 3, a change rate calculation unit 12 that calculates a change rate Δf of the system frequency f, a change point detection unit 13 that detects timing at which the change rate Δf changes as a change point, and an analysis unit 16 that analyzes a connection status in the distribution system C of a conventional power supply B1 which is a distributed power supply having a conventional active type islanding detection device that injects reactive power and a new type power source B2 which is a distributed power source having a new active type islanding detection device on the basis of the system frequency f recorded between a plurality of change points detected by the change point detection unit 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an analysis device and a program. [Background technology]

[0002] When a distributed power source is connected to a power grid, the power conditioner of the distributed power source must be equipped with an islanding operation detection device to prevent islanding. Islanding operation occurs when the distributed power source continues to supply power to the load of the distribution system when the distribution system to which the distributed power source is connected is disconnected from the power system. When the islanding operation detection device detects islanding, it disconnects the distributed power source from the distribution system and stops the supply of power from the distributed power source to the load. There are passive and active methods for detecting islanding, and various detection methods have been developed.

[0003] In the Grid Interconnection Regulations (JEAC 9701-2016), the frequency shift method, slip mode frequency shift method, reactive power fluctuation method, and QC mode frequency shift method are recognized as active methods for detecting islanding. These methods are called conventional active methods. In the Grid Interconnection Regulations, it is stipulated that the conventional active method of islanding detection device should disconnect the power conditioner from the distribution system within 0.5 to 1 second (in the case of connection with a low-voltage distribution line) when a power outage occurs and the system enters an islanding state. In addition, the Grid Interconnection Regulations recognize the frequency feedback method with step injection as a method that detects the islanding state faster than the conventional active method. This method is called the new active method. In the Grid Interconnection Regulations, it is stipulated that the new active method of islanding detection device should instantly disconnect the power conditioner from the distribution system when a power outage occurs and the system enters an islanding state, and is generally set to disconnect within 0.1 to 0.2 seconds. Each of these methods actively injects an active signal, which represents reactive power, into the power distribution system and detects islanding according to changes in the detected frequency. Therefore, when many distributed power sources are connected to a power distribution system, a large amount of reactive power is injected into the power distribution system. Furthermore, the amount of reactive power injected is increased according to the frequency deviation. Therefore, when a system disturbance occurs, each distributed power source increases the amount of reactive power injected, which may cause the system voltage to oscillate and result in a voltage flicker phenomenon.

[0004] As a measure to suppress the occurrence of the voltage flicker phenomenon, an islanding detection device capable of suppressing the injection amount of reactive power has been developed. For example, Patent Document 1 discloses an islanding detection device that suppresses the injection amount of reactive power when the possibility of islanding is low. Patent Document 2 discloses an islanding detection device that can prevent false detection and detection delay of islanding while reducing the injection amount of reactive power by alternately injecting lagging phase reactive power and leading phase reactive power and detecting islanding based on an integrated value obtained by integrating the absolute value of the amount of change in the moving average value of the system frequency. However, the islanding detection devices disclosed in Patent Documents 1 and 2 suppress the injection amount, but still inject reactive power. Therefore, even when a power conditioner equipped with these islanding detection devices is used, the voltage flicker phenomenon may occur. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-93020 A [Patent Document 2] JP 2019-92328 A Summary of the Invention [Problem to be solved by the invention]

[0006] Whether a power distribution system is prone to voltage flicker can be confirmed by understanding the connection status of distributed power sources that adopt each method. However, no method for understanding such connection status has been proposed in the past.

[0007] The present invention has been devised in light of the above circumstances, and has an object to provide an analysis device and a program for analyzing the connection status of distributed power sources that employ each method. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following technical solutions.

[0009] An analysis device provided by a first aspect of the present invention includes a detection unit that detects electrical characteristics related to a power distribution system, a recording control unit that records the detection values ​​detected by the detection unit in a memory unit, a change rate calculation unit that calculates a rate of change of the detection value, a change point detection unit that detects the timing at which the change rate changes as a change point, and an analysis unit that analyzes the connection status in the power distribution system of a conventional power source, which is a distributed power source having a conventional active type islanding detection device that injects reactive power, and a new power source, which is a distributed power source having a new active type islanding detection device, based on the detection values ​​recorded between a plurality of change points detected by the change point detection unit.

[0010] The "electrical characteristics" include voltage, current, power (active power, reactive power), and frequency. They also include the voltage, current, power, and frequency of a specified harmonic component. The "detected value detected by the detection unit" includes not only the magnitude of the voltage, current, power, and frequency, but also the deviation (amount of change from a reference) and the rate of change.

[0011] In a preferred embodiment of the present invention, the change point detection unit detects a first change point, a subsequent second change point, and a subsequent third change point, and the analysis unit estimates a new type ratio, which is the ratio of the total capacity of the new type power sources to the total capacity of the entire distribution system, based on detection values ​​recorded between the first change point and the second change point, and estimates a conventional ratio, which is the ratio of the total capacity of the conventional power sources to the total capacity of the entire distribution system, based on detection values ​​recorded between the second change point and the third change point.

[0012] In a preferred embodiment of the present invention, when the change-point detection section does not detect the third change-point, the analysis section estimates the new type proportion based on detection values ​​recorded between the first change-point and the second change-point if the second change-point is before a predetermined time, and estimates the conventional type proportion if the second change-point is after the predetermined time.

[0013] In a preferred embodiment of the present invention, the detection unit detects a frequency of a system voltage of the power distribution system as the detection value.

[0014] In a preferred embodiment of the present invention, the system includes a second detection unit that detects a second detection value different from the detection value, a second recording control unit that records the second detection value in the memory unit, a second change rate calculation unit that calculates a rate of change of the second detection value, a second change point detection unit that detects a timing at which the rate of change of the second detection value changes as a change point, and a second analysis unit that analyzes the connection status of the conventional power source and the new power source in the power distribution system based on the second detection value recorded between multiple change points detected by the second change point detection unit, and performs analysis based on the analysis result of the analysis unit and the analysis result of the second analysis unit, and the memory unit further records the second detection value.

[0015] A program provided according to a second aspect of the present invention causes a computer to function as a detection unit that detects electrical characteristics related to a power distribution system, a recording control unit that records the detection values ​​detected by the detection unit in a memory unit, a change rate calculation unit that calculates the rate of change of the detection value, a change point detection unit that detects the timing at which the change rate changes as a change point, and an analysis unit that analyzes the connection status in the power distribution system of a conventional power source, which is a distributed power source having a conventional active type islanding detection device that injects reactive power, and a new power source, which is a distributed power source having a new active type islanding detection device, based on the detection values ​​recorded between multiple change points detected by the change point detection unit. Effect of the Invention

[0016] According to the present invention, the change point detection unit detects the timing at which the rate of change of the detection value changes as a change point. Then, the analysis unit analyzes the connection status of the conventional power source and the new power source in the power distribution system based on the detection value recorded between the multiple change points. This makes it possible to determine whether the power distribution system is prone to voltage flicker based on the analyzed connection status of the conventional power source and the new power source.

[0017] Other features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram for explaining an analysis device according to a first embodiment, and is a diagram showing the overall configuration of a power distribution system. [Diagram 2] 2 is a time chart showing changes in system frequency when the power distribution system shown in FIG. 1 experiences a power outage and each power conditioner enters an isolated operation state. [Diagram 3] 2 is a time chart showing a change in system frequency when the power distribution system C shown in FIG. 1 goes into a power outage state and each power conditioner goes into an isolated operation state. [Figure 4] 1 is an example of a flowchart for explaining an analysis process performed by a control unit 1. [Diagram 5] FIG. 11 is a block diagram for explaining an analysis device according to a second embodiment, and is a diagram showing the overall configuration of a power distribution system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0020] [First embodiment] FIG. 1 is a block diagram for explaining an analysis device A1 according to the first embodiment, and shows the overall configuration of a power distribution system C.

[0021] The power distribution system C is a high-voltage power distribution system, to which a load L, a conventional power source B1, a new power source B2, and a voltage sensor 9 are connected. The load L is a consumer that receives power supply. The conventional power source B1 is a distributed power source equipped with a power conditioner having an islanding detection device of a type that injects reactive power for detection among conventional active methods. Conventional active methods for injecting reactive power include, for example, a frequency shift method and a slip mode frequency shift method. The conventional power source B1 injects reactive power so as to shift the frequency by positive feedback against frequency fluctuations. The detection method of the islanding detection device of the conventional power source B1 is not limited. The new power source B2 is a distributed power source equipped with a power conditioner having an islanding detection device of a new active method. The power distribution system C (and the low-voltage power distribution system connected to the power distribution system C via a transformer) is connected with a plurality of loads L, conventional power sources B1, and new power sources B2. Note that in FIG. 1, only one load L is shown as a representative. Distribution system C is connected to the power system via a circuit breaker. In the event of an accident in the power system, the circuit breaker is opened by a protective device installed on the power system side, and distribution system C is isolated from the power system (power outage state). As a result, each power conditioner connected to distribution system C, which has been isolated from the power system, goes into isolated operation state.

[0022] The voltage sensor 9 detects the voltage of the power distribution system C and inputs the detected voltage signal to the analysis device A1. The location of the voltage sensor 9 is not limited. The voltage sensor 9 does not have to be dedicated to the analysis device A1, and may be a voltage sensor for controlling a power conditioner of any of the conventional power source B1 or new power source B2, or a voltage sensor of other power equipment connected to the power distribution system C.

[0023] When a power outage occurs, the analysis device A1 analyzes the connection status of the conventional power source B1 and the new power source B2 in the power distribution system C. Specifically, the analysis device A1 detects the frequency of the voltage of the power distribution system C (hereinafter referred to as "system frequency") based on a voltage signal input from the voltage sensor 9, and analyzes the connection status of the conventional power source B1 and the new power source B2 in the power distribution system C based on a change in the system frequency when a power outage occurs.

[0024] When a power outage occurs, the islanding detection devices of the conventional power source B1 and the new power source B2 connected to the power distribution system C increase the reactive power injected to change the system frequency, and detect an islanding operation when the detected system frequency exceeds a threshold. The analysis device A1 analyzes the connection status of the conventional power source B1 and the new power source B2 based on the change in the system frequency at this time. The islanding detection device of the conventional power source B1 and the islanding detection device of the new power source B2 have different deadlines from the occurrence of a power outage to isolation, as stipulated in the system interconnection regulations. Therefore, the change in the system frequency differs depending on how much the conventional power source B1 and the new power source B2 are connected to the power distribution system C.

[0025] 2 and 3 are time charts showing changes in system frequency when the power distribution system C shown in FIG. 1 goes into a power outage and each power conditioner goes into an isolated operation state. The horizontal axis of each diagram indicates the time elapsed after the power outage occurs, with 0 seconds as the time. The vertical axis of each diagram indicates the system frequency. Note that the vertical and horizontal axes of the waveform diagrams and time charts referred to in this specification are appropriately enlarged or reduced for ease of understanding, and each waveform shown is simplified, exaggerated, or emphasized for ease of understanding.

[0026] FIG. 2(a) shows a case where the ratio of the total capacity of conventional power source B1 to the total capacity of the entire power distribution system C (hereinafter referred to as the "conventional ratio") and the ratio of the total capacity of new type power source B2 to the total capacity of the entire power distribution system C (hereinafter referred to as the "new type ratio") are both large. The total capacity of the entire power distribution system C includes the total capacity of conventional power source B1, the total capacity of new type power source B2, and the total capacity of other power sources. The other power sources include, for example, distributed power sources equipped with power conditioners having islanding detection devices of a conventional active type that does not inject reactive power to shift the frequency by positive feedback in response to frequency fluctuations, and generators.

[0027] When a power outage occurs, the system frequency of the power distribution system C changes slightly. The new power source B2 detects the frequency change and injects reactive power to raise or lower the system frequency. Figure 2(a) shows the case where the system frequency rises. Note that Figures 2(b)-(d) and Figures 3(a) and (b) also show the case where the system frequency rises. The new power source B2 generally detects islanding within 0.1 to 0.2 seconds after a power outage and is disconnected from the power distribution system C. Therefore, reactive power is rapidly injected after the power outage occurs, and the system frequency rises rapidly. Therefore, as shown in Figure 2(a), the system frequency rises rapidly after the power outage occurs (see point a). In addition, the new power source B2 detects islanding within 0.2 seconds and stops injecting reactive power, so at this time, the rate of change of the system frequency (corresponding to the slope of the waveform in Figure 2) decreases. However, since the conventional power source B1 continues to inject reactive power, the reduction in the rate of change is limited. Therefore, as shown in FIG. 2(a), the rate of change of the system frequency decreases when the elapsed time is between time T1 and time T2 (see point b). In this embodiment, time T1 is 0.1 seconds and time T2 is 0.2 seconds, but time T1 and time T2 are not limited. Since the conventional power source B1 detects the islanding operation within 1 second and stops injecting reactive power, the rate of change of the system frequency also decreases at this time. When all the conventional power sources B1 stop injecting reactive power and power is no longer supplied to the power distribution system C, the voltage of the power distribution system C is no longer detected, and the system frequency is no longer detected. Therefore, as shown by the solid line in FIG. 2(a), the system frequency starts to decrease when the elapsed time is between time T3 and time T4 (see point c), and is no longer detected. Note that, as shown by the dashed line in FIG. 2(a), the change of the system frequency varies, and there are cases where the system frequency continues to increase instead of decreasing from point c. However, when any of the conventional power sources B1 stops injecting reactive power, the rate of change of the grid frequency decreases. In this embodiment, the time T3 is 0.5 seconds and the time T4 is 1 second, but the times T3 and T4 are not limited. Then, by 1 second, all of the conventional power sources B1 stop injecting reactive power, and the grid frequency is no longer detected.

[0028] Figure 2(b) shows a case where the proportion of conventional power is small and the proportion of new power is large. As shown in Figure 2(b), the system frequency in this case rises rapidly from the occurrence of the blackout (point a), as in the case of Figure 2(a), and the rate of change up to point b is large. On the other hand, after the rate of change decreases at point b, the rate of change until it decreases at point c is smaller than in the case of Figure 2(a).

[0029] Figure 2(c) shows a case where the conventional-type ratio is large and the new-type ratio is small. As shown in Figure 2(c), the system frequency in this case rises rapidly from the occurrence of the blackout (point a), but the rate of change up to point b is smaller than in the case of Figure 2(a). On the other hand, after the rate of change decreases at point b, the rate of change decreases until the rate of change decreases at point c, which is about the same as in the case of Figure 2(a).

[0030] Figure 2(d) shows a case where both the conventional and new type ratios are small. As shown in Figure 2(d), the system frequency in this case rises rapidly from the occurrence of the blackout (point a), but the rate of change up to point b is smaller than in the case of Figure 2(a). In addition, the rate of change after decreasing at point b until it decreases to point c is also smaller than in the case of Figure 2(a).

[0031] As can be seen from Figs. 2(a) to (d), when the new type ratio is large, the rate of change between points a and b is large. Also, when the conventional type ratio is large, the rate of change between points b and c is large. Therefore, when a power outage occurs and an islanding state occurs, the new type ratio can be estimated based on the rate of change between points a (the point of change in the system frequency due to the power outage) and point b (the point of change in the rate of change in the system frequency due to the stop of new type power source B2), i.e., the rate of change in the system frequency mainly due to the reactive power injection of new type power source B2. Also, the conventional type ratio can be estimated based on the rate of change between points b and c (the point of change in the rate of change in the system frequency due to the stop of conventional power source B1), i.e., the rate of change in the system frequency due to the reactive power injection of conventional power source B1.

[0032] FIG. 3(a) shows a case where the conventional power source B1 is not connected to the power distribution system C, and only the new power source B2 is connected. As shown in FIG. 3(a), the system frequency in this case rises rapidly from the occurrence of a power outage (point a) to the change point (point b) where the change rate changes, as in the case of FIG. 2(a). However, since the conventional power source B1 is not connected, the change rate at point b decreases significantly. Then, when all the new power sources B2 stop injecting reactive power and power is no longer supplied to the power distribution system C, the voltage of the power distribution system C is no longer detected, and the system frequency is no longer detected. In this case, the change point at point c shown in FIG. 2(a) to (d) is not detected. Also in this case, the new type ratio can be estimated based on the change rate between point a and point b.

[0033] FIG. 3(b) shows a case where the new power source B2 is not connected to the power distribution system C, and only the conventional power source B1 is connected. As shown in FIG. 3(b), the system frequency in this case also rises rapidly from the occurrence of a power outage (point a). However, since the new power source B2 is not connected, the rate of change is smaller than that in the cases of FIG. 2(a)-(d) and FIG. 3(a), and is approximately the same as the rate of change between points b and c in FIG. 2(a). And, the rate of change does not change between time T1 and time T2, and the change point of point b shown in FIG. 2(a)-(d) is not detected. On the other hand, between time T3 and time T4 (point c), the conventional power source B1 stops injecting reactive power, so the rate of change changes. And when all the conventional power sources B1 stop injecting reactive power and power is no longer supplied to the power distribution system C, the voltage of the power distribution system C is no longer detected, and the system frequency is no longer detected. In this case, the conventional ratio can be estimated based on the rate of change between points a and c.

[0034] The analysis device A1 includes a control unit 1, an input unit 2, a storage unit 3, and a display unit 4.

[0035] The input unit 2 is realized by an input port, and receives a voltage signal detected by a voltage sensor 9, converts it into a digital signal, and outputs it to the control unit 1.

[0036] The storage unit 3 is realized by a memory such as a ROM (Read Only Memory), a RAM (Random Access Memory), a flash memory, or a hard disk, and various programs and data are stored in advance. The various programs and data stored in the storage unit 3 may be read and stored from various programs and data stored in a readable storage medium, or may be downloaded and stored from an external computer via a communication line. The storage unit 3 also records the system frequency calculated by the control unit 1.

[0037] The display unit 4 is equipped with a display, and displays the analysis results input from the control unit 1 on the display.

[0038] The control unit 1 is realized by a CPU (Central Processing Unit) or the like, and controls the analysis device A1. The control unit 1 performs control processing by reading and executing a control program stored in the storage unit 3. In this embodiment, the control unit 1 performs arithmetic processing according to the control program, calculates a system frequency based on a voltage signal input from the input unit 2, records and reads out the system frequency in the storage unit 3, and displays the analysis result on the display unit 4. The control unit 1 includes, as functional components, a frequency detection unit 11, a change rate calculation unit 12, a change point detection unit 13, a recording control unit 14, a power outage determination unit 15, and an analysis unit 16.

[0039] The frequency detection unit 11 detects the system frequency f of the power distribution system C. The frequency detection unit 11 detects the frequency based on the voltage signal input from the input unit 2. The frequency detection unit 11 detects the frequency by, for example, a zero-crossing point counting method. The zero-crossing point counting method is a method of measuring the time between points (zero-crossing points) where the instantaneous value of the AC voltage crosses the zero level, and detecting the frequency from the inverse of the measured time. The frequency detection method of the frequency detection unit 11 is not limited. For example, the frequency detection unit 11 may detect the frequency using a multiplication PLL (Phase Locked Loop). In this embodiment, the frequency detection unit 11 calculates the average value of the detected frequency for a predetermined time in order to eliminate minute fluctuations and detection errors, and outputs the calculated average value as the system frequency f. The frequency detection unit 11 outputs the detected system frequency f to the change rate calculation unit 12. The frequency detection unit 11 corresponds to the "detection unit" of the present invention, and the system frequency f corresponds to the "detection value" of the present invention.

[0040] The change rate calculation unit 12 calculates the change rate Δf of the system frequency based on the system frequency f detected by the frequency detection unit 11. The change rate Δf is the amount of change in the system frequency f per unit time. The system frequency f detected by the frequency detection unit 11 is stored for a predetermined time in the storage unit 3, and the change rate calculation unit 12 calculates the change rate Δf based on the stored system frequency f for the predetermined time. Note that the method of calculating the change rate Δf is not limited.

[0041] The change point detection unit 13 detects that the rate of change Δf has changed, and detects the timing of the change as a change point. The change point detection unit 13 compares the rate of change Δf input from the rate of change calculation unit 12 with a threshold value, and determines that the rate of change Δf has changed when the rate of change Δf exceeds the threshold value. The change point detection unit 13 has a functional configuration for detecting points a, b, and c shown in FIG. 2. The threshold value compared with the rate of change Δf varies depending on which change point is detected, and also varies depending on the previous rate of change Δf. The rate of change Δf is determined to have changed, for example, when it exceeds a range (Δfx-Δx≦Δf≦Δfx+Δx) set around the rate of change Δfx, which is the previous rate of change Δf. An appropriate value is set for Δx based on an experiment, a simulation result, or an investigation result at the site. The method for determining the change in the rate of change Δf is not limited. Before the occurrence of a power outage, the system frequency f is constant, so the rate of change Δf is approximately "0". Therefore, the occurrence of a power outage (point a in FIG. 2) is detected based on a threshold value Δf0 for identifying the occurrence of a power outage, and is determined based on whether the rate of change Δf exceeds a range (−Δf0≦Δf≦Δf0). The change point detection unit 13 determines that a power outage has occurred and the rate of change Δf has changed when the rate of change Δf is greater than Δf0 or smaller than −Δf0. An appropriate value is set for Δf0 based on an experiment, a simulation result, or a survey result at the site. The change point detection unit 13 may determine that a power outage has occurred and the system frequency f has started to change (the rate of change Δf has changed) when the system frequency f exceeds a range (f0-f1≦f≦f0+f1) set around a reference value f0 (for example, 50 Hz or 60 Hz). An appropriate value is set for f1 based on an experiment, a simulation result, or a survey result at the site.

[0042] The recording control unit 14 controls the recording of the system frequency f in the storage unit 3 in response to the detection of the change by the change point detection unit 13. Specifically, the recording control unit 14 starts recording the system frequency f when it detects a change point (point a shown in FIG. 2) of the system frequency f due to the occurrence of a power outage. In addition, the recording control unit 14 temporarily stops recording the system frequency f when it detects a change point (point b shown in FIG. 2) of the system frequency change rate Δf due to the stop of the new power source B2, changes the storage area, and resumes recording the system frequency f. In addition, the recording control unit 14 stops recording the system frequency f when it detects a change point (point c shown in FIG. 2) of the system frequency change rate Δf due to the stop of the conventional power source B1. As a result, the system frequency f between points a and b and the system frequency f between points b and c are distinguished and recorded in the storage unit 3.

[0043] The power outage determination unit 15 determines whether or not a power outage has actually occurred. The power outage determination unit 15 determines that a power outage has occurred when a voltage signal is no longer input from the input unit 2. The power outage determination unit 15 may determine whether or not a power outage has occurred using other methods. When the power outage determination unit 15 determines that a power outage has not occurred, it determines that the detection of the power outage occurrence (point a) by the change point detection unit 13 was an erroneous detection, and the recording control unit 14 erases the data of the system frequency f recorded in the memory unit 3. On the other hand, when the power outage determination unit 15 determines that a power outage has occurred, the analysis unit 16 performs analysis using the data of the system frequency f recorded in the memory unit 3.

[0044] The analysis unit 16 analyzes the connection status of the conventional power source B1 and the new power source B2 in the power distribution system C. The analysis unit 16 estimates the conventional ratio and the new type ratio based on the system frequency f recorded in the storage unit 3. More specifically, the analysis unit 16 estimates the new type ratio based on the system frequency f recorded from point a to point b, and estimates the conventional ratio based on the system frequency f recorded from point b to point c.

[0045] In this embodiment, the analysis unit 16 calculates the rate of change Δf between point a and point b based on the system frequency f recorded from point a to point b. abThe analysis unit 16 calculates the rate of change from each system frequency f excluding those recorded around the points a and b, and calculates the average value of the calculated rates of change to obtain the rate of change Δf ab The system frequency f recorded around points a and b is a detection value in the transient state of the rate of change, so by excluding this, the rate of change when the system is in a steady state can be calculated. The rate of change Δf ab The method of calculating the change rate Δf is not limited. ab The analysis unit 16 estimates the new type ratio based on, for example, the rate of change Δf ab The new type ratio is estimated by multiplying the new type ratio by a preset coefficient. The coefficient is set to an appropriate value based on the results of experiments, simulations, or on-site investigations. There are no limitations on the method for estimating the new type ratio.

[0046] In addition, the analysis unit 16 calculates the rate of change Δf between points b and c based on the system frequency f recorded from point b to point c. bc The analysis unit 16 calculates the rate of change from each system frequency f excluding those recorded around points b and c, and calculates the average value of the calculated rates of change to obtain the rate of change Δf bc The system frequency f recorded around points b and c is a detection value in the transient state of the rate of change, so by excluding this, the rate of change when the system is in a steady state can be calculated. Note that the rate of change Δf bc The method of calculating the change rate Δf is not limited. bc The analysis unit 16 estimates the conventional ratio based on, for example, the rate of change Δf bc The conventional ratio is estimated by multiplying by a preset coefficient. The coefficient is set to an appropriate value based on the results of experiments, simulations, or on-site investigations. The method of estimating the conventional ratio is not limited.

[0047] The analysis unit 16 may create a graph as shown in Fig. 2 from the system frequency f recorded in the storage unit 3, and estimate the new type ratio and the conventional type ratio from the graph using image recognition technology. The analysis unit 16 causes the display unit 4 to display the estimated new type ratio and conventional type ratio.

[0048] 4 is an example of a flowchart for explaining the analysis process performed by the control unit 1. The analysis process is a process for analyzing the connection status of the conventional power source B1 and the new power source B2 in the power distribution system C, and estimates the conventional ratio and the new ratio when a power outage occurs. The analysis process starts when the analysis device A1 is started up.

[0049] First, the system frequency f is acquired (S1). Specifically, the frequency detection unit 11 detects the system frequency f based on the voltage signal input from the input unit 2. Next, the change rate Δf is calculated (S2). Specifically, the change rate calculation unit 12 calculates the change rate Δf based on the detected system frequency f. Next, it is determined whether or not a power outage has occurred (S3). Specifically, the change point detection unit 13 determines whether or not the change rate Δf has exceeded the range (-Δf0≦Δf≦Δf0). This corresponds to the detection of point a in FIG. 2. If it is determined that the change rate Δf is within the range (-Δf0≦Δf≦Δf0) and no power outage has occurred (S3: NO), the process returns to step S1, and the processes of steps S1 to S3 are repeated.

[0050] When it is determined that a power outage has occurred because the rate of change Δf exceeds the range, i.e., Δf0<Δf or Δf<-Δf0 (S3: YES), it is determined whether or not a variable X for counting the number of times is "0" (S4). The variable X is initialized to "0" at the start of the analysis process. When the variable X is "0" (S4: YES), recording of the system frequency f is started (S5). Specifically, the recording control unit 14 starts recording the system frequency f in the storage unit 3. When the variable X is not "0" (S4: NO), recording has already started, so the process of step S5 is not performed.

[0051] Next, it is determined whether or not a change point of the rate of change Δf is detected (S6). Specifically, the change point detection unit 13 determines whether or not the rate of change Δf exceeds a threshold for detecting point b in FIG. 2. If a change point of the rate of change Δf is not detected (S6: NO), the variable X is incremented by 1 (S7). Next, it is determined whether or not the variable X exceeds a threshold X1 (S8). The threshold X1 is a value for determining whether or not the isolation deadline (T2 in FIG. 2, for example, 0.2 seconds) of the islanding detection device of the new power source B2 has elapsed, and a number according to the isolation deadline is set. Note that instead of incrementing the variable X and comparing it with the threshold, it is also possible to measure time and determine whether or not the time has elapsed. If the variable X does not exceed the threshold X1 (S8: NO), the process returns to step S1 and the processes of steps S1 to S8 are repeated.

[0052] In step S6, if a change point of the rate of change Δf is detected (S6: YES), the recording of the system frequency f is temporarily stopped and then resumed (S9). Specifically, the recording control unit 14 temporarily stops recording the system frequency f in the storage unit 3, changes the storage area, resumes recording the system frequency f, and proceeds to step S10. On the other hand, in step S8, if the variable X exceeds the threshold value X1 (S8: YES), since the rate of change Δf has not changed by the time limit for disconnection of the islanding detection device of the new power source B2, it is determined that the new power source B2 is not connected. In this case, the process of step S9 is not performed, that is, the recording of the system frequency f is continued, and the process proceeds to step S10. Next, the system frequency f is acquired (S10), and the rate of change Δf is calculated (S11).

[0053] Next, it is determined whether or not a change point of the rate of change Δf is detected (S12). Specifically, the change point detection unit 13 determines whether or not the rate of change Δf exceeds a threshold for detecting point c in FIG. 2. If a change point of the rate of change Δf is not detected (S12: NO), the variable X is incremented by 1 (S13). Next, it is determined whether or not the variable X exceeds a threshold X2 (S14). The threshold X2 is a value for determining whether or not the cutoff deadline of the islanding detection device of the conventional power source B1 (T4 in FIG. 2, for example, 1 second) has elapsed, and a number according to the time until the cutoff deadline of the islanding detection device of the conventional power source B1 is set. If the variable X does not exceed the threshold X2 (S14: NO), the process returns to step S11, and the processes of steps S10 to S14 are repeated.

[0054] In step S12, if a change point of the rate of change Δf is detected (S12: YES), the recording of the system frequency f is terminated (S15). Specifically, the recording control unit 14 terminates the recording of the system frequency f in the storage unit 3. Also, in step S14, if the variable X exceeds the threshold value X2 (S14: YES), the rate of change Δf has not changed by the time the isolation detection device of the conventional power source B1 is disconnected, so it is determined that the conventional power source B1 is not connected. In this case, the recording of the system frequency f is also terminated (S15). Next, it is determined whether or not a power outage has actually occurred (S16). Specifically, the power outage determination unit 15 determines whether or not a power outage has actually occurred. If a power outage has occurred (S16: YES), the conventional type ratio and the new type ratio are estimated, and the conventional type ratio and the new type ratio are displayed on the display unit 4 (S17), and the analysis process is terminated. Specifically, the analysis unit 16 estimates the conventional type ratio and the new type ratio based on the system frequency f recorded in the storage unit 3.

[0055] When the new type power source B2 is not connected, as shown in FIG. 3(b), a change point is not detected between time T1 and time T2, so the process proceeds to "YES" in step S8, and the recording of the system frequency f is continued without being terminated. Then, when a change point of the rate of change Δf (see point c in FIG. 3(b)) is detected in step S12 (S13: YES), the recording is terminated. That is, after point a is detected, point c corresponding to the next change point is detected after time T2. In this case, in step S17, only the conventional ratio is estimated based on the recorded system frequency f. On the other hand, even if the conventional power source B1 is not connected, a change point is detected between time T1 and time T2, as shown in FIG. 3(a), so the process proceeds to "YES" in step S6, and the recording of the system frequency f is temporarily terminated. Thereafter, recording of the system frequency f is restarted, and since no change point is detected between time T3 and time T4, the process proceeds to "YES" in step S14 and recording ends. In other words, after point a is detected, point b, which corresponds to the next change point, is detected before time T2. In this case, in step S17, only the new type proportion is estimated based on the system frequency f recorded up to point b. In this embodiment, time T2 corresponds to the "predetermined time" of the present invention.

[0056] In step S16, if no power outage has occurred (S16: NO), the power outage detection in step S3 was a false detection, so the system frequency f recorded in the storage unit 3 is erased (S18), the variable X is initialized to "0" (S19), and the process returns to step S1. Note that the process shown in the flowchart of Fig. 4 is an example, and the analysis process performed by the control unit 1 is not limited to the one described above.

[0057] The analysis device A1 may be a general-purpose computer with a program installed thereon, or may be a dedicated device.

[0058] Next, the effects of the analysis device A1 according to this embodiment will be described.

[0059] According to this embodiment, the change point detection unit 13 detects that the rate of change Δf has changed, and detects the timing of the change as a change point. Then, the analysis unit 16 estimates the new type ratio based on the system frequency f recorded from the change point of the system frequency f due to the occurrence of a power outage (point a shown in FIG. 2) to the change point of the rate of change Δf of the system frequency due to the stop of the new type power source B2 (point b shown in FIG. 2). The analysis unit 16 also estimates the conventional type ratio based on the system frequency f recorded from point b to the change point of the rate of change Δf of the system frequency due to the stop of the conventional power source B1 (point c shown in FIG. 2). This makes it possible to analyze the connection status of the conventional power source B1 and the new type power source B2 in the distribution system C, so it is possible to determine whether the distribution system C is a distribution system in which the voltage flicker phenomenon is likely to occur. For example, if the new type ratio is large, the voltage flicker phenomenon is likely to occur, so the manager of the distribution system C can take measures such as adjusting each islanding detection device to reduce the reactive power injected.

[0060] Furthermore, according to this embodiment, if the change point detection unit 13 cannot detect the third change point, the analysis unit 16 estimates only the conventional ratio based on the recorded system frequency f if the second change point was detected after time T2. Furthermore, if the second change point was detected before time T2, the analysis unit 16 estimates only the new type ratio based on the recorded system frequency f. This allows the analysis unit 16 to estimate the conventional ratio even if the new type power source B2 is not connected to the power distribution system C, and to estimate the new type ratio even if the conventional power source B1 is not connected to the power distribution system C.

[0061] Furthermore, according to this embodiment, the analysis device A1 performs analysis based on the rate of change Δf of the system frequency f of the power distribution system C. In order to detect islanding, the islanding detection devices for the conventional power source B1 and the new power source B2 inject reactive power according to the frequency deviation to further change the system frequency f. Therefore, the system frequency f is suitable as an electrical characteristic to be used in analyzing the connection status of the conventional power source B1 and the new power source B2.

[0062] In the present embodiment, the analysis device A1 performs analysis based on the system frequency f, which is the frequency of the voltage of the power distribution system C detected by the frequency detection unit 11, but the present invention is not limited to this. The analysis device A1 may use the frequency of the current or power of the power distribution system C. The analysis device A1 may perform analysis based on electrical characteristics such as the voltage, current, and power (active power, reactive power) of the power distribution system C. The analysis device A1 may perform analysis based on the voltage, current, power, and frequency of predetermined harmonic components such as the third, fifth, and seventh orders. The analysis device A1 is not limited to the detection values ​​that detect the magnitudes of the detected voltage, current, power, and frequency, and may use deviations (amounts of change from a reference) and change rates.

[0063] Second Embodiment 5 is a block diagram for explaining the analysis device A2 according to the second embodiment, and shows the overall configuration of a power distribution system C. In the figure, elements that are the same as or similar to those in the analysis device A1 according to the first embodiment (see FIG. 1) are given the same reference numerals and overlapping descriptions will be omitted.

[0064] The analysis device A2 according to this embodiment differs from the analysis device A1 in that it performs analysis using two types of detection values.

[0065] The control section 1 of the analysis device A2 further includes a voltage detection section 21, a second change rate calculation section 22, a second change point detection section 23, a second recording control section 24, and a second analysis section .

[0066] Voltage detection unit 21 detects the effective voltage value v of the power distribution system C. Voltage detection unit 21 detects the effective voltage value v based on a voltage signal input from voltage sensor 9. Voltage detection unit 21 outputs the detected effective voltage value v to second change rate calculation unit 22. In this embodiment, voltage detection unit 21 corresponds to the "second detection unit" of the present invention, and the effective voltage value v corresponds to the "second detection value" of the present invention. Note that voltage detection unit 21 may detect the maximum value or average value of the voltage, etc.

[0067] The second change rate calculation unit 22 has a functional configuration similar to that of the change rate calculation unit 12, and calculates the rate of change Δv of the effective voltage value based on the effective voltage value v detected by the voltage detection unit 21. The second change point detection unit 23 has a functional configuration similar to that of the change point detection unit 13, and detects that the rate of change Δv has changed, and detects the timing of the change as a change point. The second recording control unit 24 has a functional configuration similar to that of the recording control unit 14, and controls the recording of the effective voltage value v in the memory unit 3 in response to the detection of a change by the second change point detection unit 23. The second analysis unit 26 has a functional configuration similar to that of the analysis unit 16, and analyzes the connection status of the conventional power source B1 and the new power source B2 in the power distribution system C.

[0068] The control unit 1 determines an overall analysis result based on the analysis result by the analysis unit 16 and the analysis result by the second analysis unit 26, and displays it on the display unit 4. For example, the control unit 1 calculates the average value of the new type ratio estimated by the analysis unit 16 and the new type ratio estimated by the second analysis unit 26, and outputs the calculated average value as the new type ratio. The control unit 1 also calculates the average value of the conventional type ratio estimated by the analysis unit 16 and the conventional type ratio estimated by the second analysis unit 26, and outputs the calculated average value as the conventional type ratio. Note that the method of calculating the overall analysis result by the control unit 1 is not limited.

[0069] In this embodiment, the same effects as those in the first embodiment can be achieved. Furthermore, according to this embodiment, the control unit 1 can determine a comprehensive analysis result based on the analysis result based on the system frequency f and the analysis result based on the effective voltage value v. This allows the analysis device A2 to output a more reliable analysis result.

[0070] In the present embodiment, the control unit 1 performs the analysis based on the system frequency f and the analysis based on the effective voltage value v, but the present invention is not limited to this. The control unit 1 may perform the analysis based on other electrical characteristics. Moreover, the control unit 1 may perform the analysis based on three or more types of electrical characteristics.

[0071] The analytical device and the program according to the present invention are not limited to the above-described embodiment. The specific configurations of the components of the analytical device and the program according to the present invention can be freely designed in various ways. [Explanation of symbols]

[0072] A1, A2: analysis device, 11: frequency detection unit, 12: change rate calculation unit, 13: change point detection unit, 14: recording control unit, 16: analysis unit, 21: voltage detection unit, 22: second change rate calculation unit, 23: second change point detection unit, 24: second recording control unit, 26: second analysis unit, B1: conventional power source, B2: new power source, C: power distribution system

Claims

1. A detection unit that detects an electrical characteristic related to the power distribution system; a recording control unit that causes a detection value detected by the detection unit to be recorded in a storage unit; A change rate calculation unit that calculates a change rate of the detection value; a change point detection unit that detects a timing at which the rate of change changes as a change point; an analysis unit that analyzes a connection status in the power distribution system of a conventional power source, which is a distributed power source having an islanding detection device of a conventional active type that injects reactive power, and a new power source, which is a distributed power source having an islanding detection device of a new active type, based on detection values ​​recorded between a plurality of change points detected by the change point detection unit; An analytical device comprising:

2. the change point detection unit detects a first change point, a subsequent second change point, and a subsequent third change point; the analysis unit estimates a new-type ratio, which is a ratio of a total capacity of the new-type power sources to a total capacity of the entire power distribution system, based on the detection values ​​recorded between the first change point and the second change point, and estimates a conventional-type ratio, which is a ratio of a total capacity of the conventional power sources to a total capacity of the entire power distribution system, based on the detection values ​​recorded between the second change point and the third change point; The analytical device of claim 1 .

3. If the change point detection unit does not detect the third change point, the analysis unit estimates the new type ratio if the second change point occurs before a predetermined time based on the detection value recorded between the first change point and the second change point, and estimates the conventional type ratio if the second change point occurs after the predetermined time. The analytical device according to claim 2 .

4. The detection unit detects a frequency of a system voltage of the power distribution system as the detection value.

4. The analysis device according to claim 1.

5. A second detection unit that detects a second detection value different from the detection value; a second record control unit that causes the second detection value to be recorded in the memory unit; a second change rate calculation unit that calculates a change rate of the second detection value; a second change point detection unit that detects a timing at which a rate of change of the second detection value changes as a change point; a second analysis unit that analyzes a connection status of the conventional power source and the new power source in the power distribution system based on a second detection value recorded between a plurality of change points detected by the second change point detection unit; Equipped with performing an analysis based on the analysis result of the analysis unit and the analysis result of the second analysis unit; 5. The analysis device according to claim 1.

6. Computer, A detection unit that detects an electrical characteristic related to the power distribution system; a recording control unit that causes a detection value detected by the detection unit to be recorded in a storage unit; A change rate calculation unit that calculates a change rate of the detection value; a change point detection unit that detects a timing at which the rate of change changes as a change point; an analysis unit that analyzes a connection status in the power distribution system of a conventional power source, which is a distributed power source having an islanding detection device of a conventional active type that injects reactive power, and a new power source, which is a distributed power source having an islanding detection device of a new active type, based on detection values ​​recorded between a plurality of change points detected by the change point detection unit; A program that makes it work.

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