Analytical device

Abstract

To provide an analyzer to analyze the connection status of distributed power sources that employ each method.SOLUTION: An analyzer A1 includes: a frequency detection unit 41 that detects a frequency f of a voltage instantaneous value based on a voltage signal input from a voltage sensor 9; and an analysis unit 32 that determines occurrence of voltage flicker based on fluctuation of the frequency f and detects the connection status of a conventional power source B1 which is a distributed power source with a conventional active islanding detection device that injects reactive power and a new power source B2 which is a distributed power source with a new active type islanding detection device in a distribution system C based on the fluctuation of the frequency f when the voltage flicker occurs.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an analytical device. [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 detection device to prevent islanding. Islanding occurs when the distributed power source continues to supply power to the loads of the distribution grid even if the distribution grid to which the distributed power source is connected is disconnected from the power grid. When the islanding detection device detects islanding, it disconnects the distributed power source from the distribution grid 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] The Grid Interconnection Regulations (JEAC 9701-2016) recognize active islanding detection methods, including frequency shift, slip mode frequency shift, reactive power variation, and QC mode frequency shift. These methods are referred to as conventional active methods. The Grid Interconnection Regulations stipulate that conventional active islanding detection devices must disconnect the power conditioner from the distribution grid within 0.5 to 1 second (when connected to a low-voltage distribution line) when a power outage occurs and the power conditioner enters islanding mode. The Grid Interconnection Regulations also recognize the step injection frequency feedback method, which offers faster detection speeds than conventional active methods. This method is referred to as the new active method. The Grid Interconnection Regulations stipulate that new active islanding detection devices must instantly disconnect the power conditioner from the distribution grid when a power outage occurs and the power conditioner enters islanding mode; typically, they are configured to disconnect within 0.1 to 0.2 seconds. Each of these methods actively injects an active signal, representing reactive power, into the distribution system and detects islanding based on changes in the detected frequency. Therefore, when a large number of distributed power sources are connected to a distribution system, a large amount of reactive power is injected into the system. The amount of reactive power injected also increases according to frequency deviation. Therefore, when a system disturbance occurs, each distributed power source increases the amount of reactive power injected, which can cause system voltage oscillations and voltage flicker.

[0004] As a measure to suppress the occurrence of voltage flicker, islanding detection devices capable of suppressing the amount of reactive power injection have been developed. For example, Patent Document 1 discloses an islanding detection device that suppresses the amount of reactive power injection when the possibility of islanding is low. Furthermore, Patent Document 2 discloses an islanding detection device that alternately injects lagging-phase reactive power and leading-phase reactive power and detects islanding based on the integrated value obtained by integrating the absolute value of the change in the moving average value of the grid frequency, thereby reducing the amount of reactive power injection and preventing erroneous detection and detection delay of islanding. However, the islanding detection devices disclosed in Patent Documents 1 and 2 suppress the injection amount but still inject reactive power. Therefore, even when using power conditioners equipped with these islanding detection devices, voltage flicker may occur. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-93020 [Patent Document 2] Japanese Patent Application Publication No. 2019-92328 Summary of the Invention [Problem to be solved by the invention]

[0006] Whether a power distribution system is prone to voltage flicker or not can be determined by understanding the connection status of distributed power sources that employ each method. However, no method for understanding such connection status has been proposed until now.

[0007] The present invention was conceived in light of the above circumstances, and has as its object to provide an analysis device for analyzing the connection status of distributed power sources employing various systems. [Means for solving the problem]

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

[0009] An analysis device provided by a first aspect of the present invention is characterized by comprising: a first frequency detection unit that detects a first frequency of an instantaneous voltage value based on a voltage signal input from a voltage sensor; and an analysis unit that determines the occurrence of voltage flicker based on fluctuations in the first frequency and detects the connection status in a 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-type power source, which is a distributed power source having a new active-type islanding detection device, based on the fluctuations in the first frequency when voltage flicker occurs.

[0010] In a preferred embodiment of the present invention, the analysis device further includes a change amount detection unit that detects the amount of change in the first frequency, a low-pass filter that extracts only frequency components below an upper limit frequency from the amount of change, and a first PP value detection unit that detects a first PP value, which is the peak-to-peak value of the amount of change extracted by the low-pass filter over a first unit time, and the analysis unit detects the connection status based on the first PP value.

[0011] In a preferred embodiment of the present invention, the analysis device further includes a voltage detection unit that detects the magnitude of the voltage based on the voltage signal, and the analysis unit detects the connection status based on fluctuations in the first frequency and fluctuations in the magnitude of the voltage when voltage flicker occurs.

[0012] In a preferred embodiment of the present invention, the analysis device further includes a second PP value detection unit that detects a second PP value, which is the peak-to-peak value of the voltage magnitude in a second unit time, a second frequency detection unit that detects a second frequency, which is the frequency of fluctuations in the voltage magnitude, and an index value calculation unit that calculates an index value from the second PP value and the second frequency, and the analysis unit detects the connection status based on the index value.

[0013] An analysis device provided according to a second aspect of the present invention is characterized by comprising: a voltage detection unit that detects the magnitude of a voltage based on a voltage signal input from a voltage sensor; and an analysis unit that determines the occurrence of voltage flicker based on fluctuations in the magnitude of the voltage, and detects the connection status in a 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 fluctuations in the magnitude of the voltage when voltage flicker occurs.

[0014] In a preferred embodiment of the present invention, the analysis unit detects the connection status based on how the fluctuation in the first frequency or the fluctuation in the magnitude of the voltage changes when voltage flicker converges. [Effects of the Invention]

[0015] According to the present invention, the analysis unit detects the connection status of conventional power sources and new power sources in the power distribution system based on fluctuations in the first frequency when voltage flicker occurs, thereby allowing the analysis device according to the present invention to analyze the connection status.

[0016] 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 explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a block diagram for explaining an analysis device according to a first embodiment, showing the overall configuration of a power distribution system. [Figure 2] FIG. 10 is a waveform diagram showing a simulation result of the first detection unit. [Figure 3] FIG. 10 is a diagram showing an outline of the relationship between the frequency PP value and the connection status in a stable state. [Figure 4] FIG. 10 is a diagram illustrating flicker visibility. [Figure 5] FIG. 10 is a waveform diagram showing a simulation result of the second detection unit. [Figure 6]FIG. 10 is a diagram showing an outline of the relationship between the index value ΔVX and the connection state in a stable state. [Figure 7] FIG. 10 is a diagram showing the correspondence between the total capacity and the new model ratio. [Figure 8] FIG. 10 is a block diagram for explaining an analysis device according to a second embodiment, showing the overall configuration of a power distribution system. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0019] [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.

[0020] 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 receiving power. The conventional power source B1 is a distributed power source equipped with a power conditioner having an islanding detection device of a conventional active type that injects reactive power for detection. Conventional active methods for injecting reactive power include, for example, frequency shifting and slip mode frequency shifting. The conventional power source B1 injects reactive power to shift the frequency using positive feedback in response to frequency fluctuations. Note that 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 type. The power distribution system C (and the low-voltage power distribution system connected to the power distribution system C via a transformer) are connected to multiple loads L, conventional power sources B1, and new power sources B2. Note that in Figure 1, only one load L is shown as a representative example. Distribution system C is connected to the power grid via a circuit breaker. In the event of an accident in the power grid, a protective device installed on the power grid side opens the circuit breaker, and distribution system C is isolated from the power grid (power outage state). As a result, each power conditioner connected to distribution system C, which has been isolated from the power grid, enters an islanding state.

[0021] 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. Furthermore, the voltage sensor 9 does not have to be dedicated to the analysis device A1, and a voltage sensor for controlling the power conditioner of any of the conventional power source B1 or new power source B2 may be used, or a voltage sensor of other power equipment connected to the power distribution system C may be used.

[0022] When voltage flicker occurs, analysis device A1 analyzes the connection status of conventional power source B1 and new power source B2 in power distribution system C. Specifically, analysis device A1 detects the effective voltage value of the voltage of power distribution system C (hereinafter referred to as "system voltage") and the frequency of the system voltage (the frequency of the instantaneous voltage value, hereinafter referred to as "system frequency") based on a voltage signal input from voltage sensor 9, and analyzes the connection status of conventional power source B1 and new power source B2 in power distribution system C based on fluctuations in the effective voltage value and system frequency when voltage flicker occurs.

[0023] Voltage flicker caused by the islanding detection device injecting an active signal (e.g., reactive power) causes voltage fluctuations (fluctuations in the effective voltage) in the power distribution system C and also causes fluctuations in the system frequency. The manner in which voltage fluctuations and system frequency fluctuations occur when voltage flicker occurs varies depending on the connection status of the conventional power source B1 and the new power source B2. The connection status is the ratio of the conventional power source B1 to the new power source B2 that are connected to and operating in the power distribution system C. In this embodiment, the connection status is expressed as the ratio (hereinafter referred to as the "new power source ratio") of the total capacity of the new power source B2 to the total capacity of the conventional power source B1 and the new power source B2 (hereinafter referred to as the "operating power source B" when not distinguishing between them). Note that the connection status may also be expressed as the ratio (hereinafter referred to as the "conventional power source ratio") of the total capacity of the conventional power source B1 to the total capacity of the operating power source B. The analysis device A1 detects the connection status based on the voltage fluctuations and system frequency fluctuations when voltage flicker occurs, taking advantage of the characteristic that the manner in which voltage fluctuations and system frequency fluctuations occur when voltage flicker occurs varies depending on the connection status.

[0024] The analyzer A1 includes a control unit 1, an input unit 2, a storage unit 3, and a display unit 4.

[0025] The input unit 2 is realized by an input port, and receives a voltage signal detected by the voltage sensor 9, converts it into a digital signal, and outputs it to the control unit 1.

[0026] 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 a readable storage medium, or may be downloaded and stored from an external computer via a communication line. The storage unit 3 also stores data used by the control unit 1 to analyze the connection status, as will be described later.

[0027] The display unit 4 is equipped with a display, and displays the analysis results input from the control unit 1 on the display.

[0028] The control unit 1 is realized by a CPU (Central Processing Unit) 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 calculation processing according to the control program, analyzes the connection status based on a voltage signal input from the input unit 2, and displays the analysis results on the display unit 4. The control unit 1 includes, as functional components, a frequency detection unit 41, a change amount detection unit 42, a low-pass filter 43, a PP value detection unit 44, an effective value detection unit 51, a PP value detection unit 52, a frequency detection unit 53, an index value calculation unit 54, a line impedance setting unit 31, and an analysis unit 32. The frequency detection unit 41, the change amount detection unit 42, the low-pass filter 43, and the PP value detection unit 44 are components for detecting information indicating fluctuations in the grid frequency, and are collectively referred to as a "first detection unit 49." The effective value detection unit 51, the PP value detection unit 52, the frequency detection unit 53, and the index value calculation unit 54 are configured to detect information indicating fluctuations in the effective voltage value, and when referred to collectively, they are referred to as the "second detection unit 59."

[0029] The frequency detection unit 41 detects the system frequency of the power distribution system C. The frequency detection unit 41 detects the frequency f of the instantaneous voltage value based on the voltage signal input from the voltage sensor 9. The frequency detection unit 41 detects the frequency, for example, using a zero-crossing point counting method. The zero-crossing point counting method measures the time between points where the instantaneous value of the AC voltage crosses the zero level (zero-crossing points) and detects the frequency from the reciprocal of the measured time. The frequency detection method used by the frequency detection unit 41 is not limited. For example, the frequency detection unit 41 may detect the frequency using a multiplication phase-locked loop (PLL). The power distribution system C is a three-phase AC power distribution system, and the voltage sensor 9 detects the voltage signal of each phase. The frequency detection unit 41 detects the frequency of the voltage signal of each phase and outputs the average value of the three frequencies as frequency f. The frequency detection unit 41 may also output the frequency of the voltage signal of one representative phase (e.g., the U phase) as frequency f. The frequency detection unit 41 outputs the detected frequency f to the change amount detection unit .

[0030] The change amount detection unit 42 receives the frequency f from the frequency detection unit 41 and detects the amount of change Δf in the frequency f. The change amount detection unit 42 receives the frequency f every predetermined cycle (for example, about 20 ms, although this is not limited thereto) and calculates the difference between the input frequency f and the frequency f input one cycle before as the amount of change Δf. Hereinafter, this predetermined cycle will be referred to as a "frequency detection cycle." The change amount detection unit 42 outputs the detected amount of change Δf to the low-pass filter 43.

[0031] The low-pass filter 43 extracts only frequency components of 30 Hz or less from the amount of change Δf continuously input from the change amount detection unit 42, and outputs them to the PP value detection unit 44. Since humans perceive lighting flicker at frequencies between 2 and 30 Hz, in this embodiment, the low-pass filter 43 removes frequency components greater than 30 Hz.

[0032] The PP value detection unit 44 detects the peak-to-peak value (hereinafter referred to as the "frequency PP value") of the change Δf (frequency components of 30 Hz or less) input from the low-pass filter 43. In this embodiment, to capture frequency changes of 2 Hz or more, the frequency PP value is detected over a 500 ms period, which is a 2 Hz cycle. The PP value detection unit 44 detects the frequency PP value while shifting the detection range for each frequency detection cycle (e.g., approximately 20 ms). The PP value detection unit 44 outputs the detected frequency PP value to the analysis unit 32.

[0033] FIG. 2 is a waveform diagram showing the simulation results of the first detection unit 49. FIG. 2(a) shows the time change in frequency f detected by the frequency detection unit 41. FIG. 2(b) shows the time change in the change amount Δf detected by the change amount detection unit 42. FIG. 2(c) shows the time change in the frequency PP value detected by the PP value detection unit 44. At time "0," a voltage fluctuation is generated, and as shown in FIG. 2(a), the frequency f fluctuates significantly thereafter. As a result, as shown in FIG. 2(b), the change amount Δf also fluctuates significantly. As shown in FIG. 2(c), the frequency PP value is stable and smaller than Δf0 before time "0." However, it suddenly rises at time "0" and then stabilizes above Δf0. Δf0 is a threshold for detecting the occurrence of voltage flicker, and is set to approximately 0.05 Hz in this embodiment. Note that Δf0 is not limited. The stable value of the frequency PP value varies depending on the connection status in the power distribution system C, and the higher the new model ratio, the higher the value.

[0034] Figure 3 shows an overview of the relationship between the frequency PP value and the connection status in a stable state. The horizontal axis represents the connection status of distribution system C, showing the new-type ratio. The vertical axis represents the frequency PP value when voltage flicker is occurring. The relationship between the frequency PP value and the connection status also varies depending on the line impedance of distribution system C. In Figure 3, the solid line a represents a case where the line impedance of distribution system C is high, the dashed line b represents a case where the line impedance of distribution system C is medium, and the dashed-dotted line c represents a case where the line impedance of distribution system C is low. Figure 3 was created based on simulation results when the new-type ratio was 10%, 50%, and 90%. As shown in Figure 3, the frequency PP value increases with the new-type ratio. Furthermore, for the same connection status (same new-type ratio), the frequency PP value increases with the line impedance of distribution system C. The relationship between the frequency PP value and the connection status also varies depending on the total capacity of the operating power source B connected to distribution system C. Although not shown in FIG. 3, under the same connection conditions, the frequency PP value increases as the total capacity increases.

[0035] The effective value detection unit 51 detects the effective voltage value v of the system voltage of the power distribution system C. The effective value detection unit 51 detects the effective voltage value v based on a voltage signal input from the voltage sensor 9. The power distribution system C is a three-phase AC power distribution system, and the voltage sensor 9 detects the voltage signal of each phase. The effective value detection unit 51 detects the effective voltage value from the voltage signal of each phase and outputs the average of the three effective voltage values ​​as the effective voltage value v. Note that the effective value detection unit 51 may also output the effective voltage value of the voltage signal of one representative phase (e.g., the U phase) as the effective voltage value v. The effective value detection unit 51 outputs the detected effective voltage value v to the P-P value detection unit 52 and the frequency detection unit 53. Note that the effective value detection unit 51 may detect another index representing the magnitude of the voltage, such as the maximum or average voltage value, instead of the effective voltage value.

[0036] The PP value detection unit 52 detects the peak-to-peak value of the effective voltage v (hereinafter referred to as the "effective PP value") input from the effective value detection unit 51. Like the PP value detection unit 44, the PP value detection unit 52 detects the effective PP value over a 500 ms period, which is a 2 Hz cycle, in order to capture voltage fluctuations of 2 Hz or more. Like the PP value detection unit 44, the PP value detection unit 52 also detects the effective PP value while shifting its detection range for each frequency detection cycle (for example, approximately 20 ms). The PP value detection unit 52 outputs the detected effective PP value to the index value calculation unit 54.

[0037] The frequency detector 53 detects the frequency f of the fluctuation of the effective voltage v. V The frequency detector 53 detects the frequency f based on the voltage effective value v input from the effective value detector 51. V In this embodiment, the time from when the PP value detection unit 52 detects the upper peak value to when it detects the lower peak value when it detects the effective PP value is defined as a half cycle, and the frequency f V The frequency detection method of the frequency detection unit 53 is not limited, and the detection may be performed in the same manner as the frequency detection unit 41, or in another manner. The frequency detection unit 53 detects the detected frequency f V to the index value calculation unit 54.

[0038] The index value calculation unit 54 calculates an index value for determining voltage flicker. Generally, voltage flicker is determined by the following formula: 10 " and this index value is managed so that it is equal to or less than a regulated value (for example, "0.45"). 10 The index value ΔV is similar to X Figure 4 shows the flicker visibility curve s, which shows the visibility of flicker for each frequency of voltage fluctuation as a coefficient. ΔV 10 The index value ΔV is calculated as the square root of the integrated value of the square of the product of the change in the frequency component and the flicker visibility coefficient at that frequency for each frequency component included in the one-minute voltage fluctuation. X is ΔV10 Specifically, the index value calculation unit 54 multiplies the effective PP value detected by the PP value detection unit 52 by the frequency f detected by the frequency detection unit 53. V By multiplying the coefficient according to X The coefficients used here are a simplified version of the visibility curve s, and are calculated based on the frequency f V When the frequency is 3 Hz or higher, it is set to "1", and when it is less than 3 Hz, it is set to "0.6" (shown by the thick solid line s' in Figure 4). X The coefficient used to calculate the index value ΔV 10 Since the value is greater than the coefficient used to calculate (see visibility curve s), the index value ΔV X is the index value ΔV 10 The index value ΔV calculated by the index value calculation unit 54 is a larger value. X The method for calculating the index value ΔV is not limited to this. X For example, the general index value ΔV 10 The index value calculation unit 54 may calculate the calculated index value ΔV X is output to the analysis unit 32.

[0039] 5A and 5B are waveform diagrams showing the simulation results of the second detection unit 59. FIG. 5A shows the time variation of the voltage effective value v detected by the effective value detection unit 51 (see the solid line v in the figure, the vertical axis on the left), and the time variation of the effective value PP detected by the PP value detection unit 52 (see the dashed line PP in the figure, the vertical axis on the right). FIG. 5B shows the time variation of the frequency f detected by the frequency detection unit 53. V 5(c) shows the time change of the index value ΔV detected by the index value calculation unit 54. X At time "0", the voltage fluctuation causes the voltage effective value v to fluctuate greatly. This causes the effective value PP to rise, and the frequency f V is decreasing. ΔV X was almost "0" before time "0", but rose after time "0" and became ΔV X0 and reaches a stable state at around time "3".X0 is a threshold value for detecting the occurrence of voltage flicker, for example, the index value ΔV 10 The same value as the regulation value of ΔV is set to "0.45". X0 is not limited. Also, ΔV X The value of in the stable state varies depending on the connection status in distribution system C, and the higher the new model ratio, the larger the value.

[0040] Figure 6 shows the index value ΔV X The figure shows an outline of the relationship between the connection status and the horizontal axis, which indicates the connection status of the power distribution system C, and shows the new type rate. The vertical axis shows the index value ΔV when voltage flicker occurs. X The index value ΔV X The relationship between the connection status and the line impedance of distribution system C also differs depending on the line impedance of distribution system C. In Fig. 6, the solid line a' indicates the case where the line impedance of distribution system C is large, the dashed line b' indicates the case where the line impedance of distribution system C is medium, and the dashed line c' indicates the case where the line impedance of distribution system C is small. Fig. 6 was created based on the simulation results when the new model ratio was set to 10%, 50%, and 90%. As shown in Fig. 6, the higher the new model ratio, the lower the index value ΔV X In addition, under the same connection conditions (same proportion of new models), the larger the line impedance of distribution system C, the larger the index value ΔV X The index value ΔV X The relationship between the connection status and the total capacity of the operating power source B connected to the power distribution system C also differs. Although not shown in Fig. 6, in the same connection status, the larger the total capacity, the smaller the index value ΔV X becomes larger.

[0041] The line impedance setting unit 31 sets the line impedance of the distribution line of the power distribution system C. The line impedance of the distribution line is known, for example, by an electric power company, and this value is set. The line impedance setting unit 31 outputs the line impedance of the distribution line of the power distribution system C to the analysis unit 32.

[0042] The analysis unit 32 calculates the frequency PP value input from the PP value detection unit 44 and the index value ΔV X and the line impedance input from the line impedance setting unit 31, the new type ratio (connection status) is detected. The frequency PP value when voltage flicker is occurring is related to the connection status of the power distribution system C, the line impedance of the power distribution system C, and the total capacity of the operating power source B connected to the power distribution system C (see FIG. 3). In addition, the index value ΔV when voltage flicker is occurring X is related to the connection status of the power distribution system C, the line impedance of the power distribution system C, and the total capacity of the operating power source B connected to the power distribution system C (see FIG. 6). The analysis unit 32 uses these relationships to calculate the frequency PP value and the index value ΔV X The connection status is detected based on the

[0043] The analysis unit 32 determines that voltage flicker is occurring when the frequency PP value input from the PP value detection unit 44 remains equal to or greater than the threshold value Δf0 for a first determination time T1 (e.g., 10 seconds) or longer, and uses the average frequency PP value as a value for detecting the connection status. The first determination time T1 is set to exclude cases where the frequency PP value exceeds the threshold value Δf0 for only a very short time. Note that, in order to use a value in a stable state rather than a value during the change of the frequency PP value immediately after the occurrence of voltage flicker, a value after a predetermined time has elapsed after determining that voltage flicker is occurring may be used. The first determination time T1 and the predetermined time are not limited and may be set appropriately based on experiment, simulation results, on-site investigation results, or the like. The analysis unit 32 also determines that the index value ΔV input from the index value calculation unit 54 is equal to or greater than the threshold value Δf0. X is the threshold ΔV X0 If the above state continues for the second judgment time T2 or longer, it is determined that voltage flicker is occurring, and the index value ΔV X The average value of the index value ΔV is used as the value for detecting the connection status. X For a very short time, the threshold ΔV X0 It is set to exclude cases where the index value ΔV immediately after the voltage flicker occurs. XIn order to use a value in a stable state rather than a value that is changing, a value after a predetermined time has elapsed after it is determined that voltage flicker is occurring may be used. The second determination time T2 and the predetermined time are not limited and may be set appropriately based on the results of experiments, simulations, or on-site investigations.

[0044] The memory unit 3 stores the frequency PP value and the index value ΔV when voltage flicker occurs for each line impedance, for each total capacity of the operating power source B, and for each new model ratio. X The frequency PP value and the index value ΔV are stored. X is detected by experiment or simulation while changing the line impedance, the total capacity of the operating power source B, and the new model ratio. Note that the memory unit 3 does not store values ​​for all line impedances, total capacity of the operating power source B, and new model ratios, but stores values ​​when each of these is changed discretely. Values ​​between are calculated by, for example, linear interpolation.

[0045] The analysis unit 32 analyzes the frequency PP value and the index value ΔV stored in the storage unit 3. X The analysis unit 32 uses only the data corresponding to the line impedance input from the line impedance setting unit 31. The analysis unit 32 detects the new type ratio corresponding to the frequency PP value (average value) input from the PP value detection unit 44 for each total capacity. For example, FIG. 3 shows the relationship between the frequency PP value and the new type ratio at a certain total capacity, and since the line impedance is known, the new type ratio for that total capacity can be determined. Therefore, the analysis unit 32 can detect the correspondence relationship between the total capacity and the new type ratio based on the frequency PP value. Furthermore, the analysis unit 32 uses only the data corresponding to the line impedance input from the index value calculation unit 54 for each total capacity. X For example, Figure 6 shows the index value ΔV X Since the line impedance is known, the new type rate for the given total capacity can be determined. XBased on this, the correspondence between the total capacity and the new model ratio can be detected.

[0046] The analysis unit 32 calculates the correspondence between the total capacity and the new type ratio detected based on the frequency PP value and the index value ΔV X When the correspondence relationship between the total capacity detected based on the frequency PP value and the new type rate matches, the new type rate is output as the detected new type rate. Figure 7 is a diagram showing the correspondence relationship between the total capacity and the new type rate for a certain line impedance. The horizontal axis shows the connection status of the power distribution system C, and indicates the new type rate. The vertical axis shows the total capacity. In Figure 7, the solid line d shows the correspondence relationship between the total capacity detected based on the frequency PP value and the new type rate. The dashed line e shows the correspondence relationship between the total capacity detected based on the frequency PP value and the new type rate. X 1 shows the correspondence relationship between the total capacity and the new type ratio detected based on the above. The new type ratio at the intersection of the solid line d and the dashed line e is output from the analysis unit 32. The analysis unit 32 may also output the total capacity at the intersection of the solid line d and the dashed line e as the total capacity of the operating power source B connected to the power distribution system C. In this case, the analysis device A1 can detect not only the connection status but also the total capacity.

[0047] The method of detecting the connection status by the analysis unit 32 is not limited to the above-described method. The analysis unit 32 detects the connection status based on the frequency PP value input from the PP value detection unit 44 or the index value ΔV input from the index value calculation unit 54. X The connection status can be detected from the

[0048] The analytical device A1 may be a general-purpose computer with a program installed, or may be a dedicated device.

[0049] Next, the effects of the analyzer A1 according to this embodiment will be described.

[0050] According to this embodiment, the first detector 49 detects a frequency PP value, which is information indicating fluctuations in the grid frequency, based on the voltage signal input from the voltage sensor 9. The second detector 59 also detects an index value ΔV , which is information indicating fluctuations in the effective voltage value, based on the voltage signal input from the voltage sensor 9.X The analysis unit 32 detects the frequency PP value, the index value ΔV X , and the line impedance, the new type power source ratio (connection status) is detected. This allows the analysis device A1 to analyze the connection status of the conventional power source B1 and the new type power source B2 in the power distribution system C. Therefore, it is possible to determine whether the power distribution system C is prone to voltage flicker. For example, if the new type power source ratio is high, voltage flicker is likely to occur, and the manager of the power distribution system C can take measures such as adjusting each islanding operation detection device to reduce the reactive power injected.

[0051] Furthermore, according to this embodiment, the analysis unit 32 calculates the frequency PP value and the index value ΔV X Therefore, the analysis device A1 detects the connection status by using both the frequency PP value or the index value ΔV X The connection status can be detected more accurately than when detecting the connection status using only one of the above.

[0052] Furthermore, in this embodiment, the change amount detection unit 42 detects the change amount Δf in the frequency f, the low-pass filter 43 extracts only frequency components of 30 Hz or less from the change amount Δf, and the PP value detection unit 44 detects the frequency PP value of the change amount Δf for 500 ms input from the low-pass filter 43. Therefore, the analysis unit 32 can perform analysis based on the fluctuation range of the 2 to 30 Hz component of the fluctuation in frequency f.

[0053] According to this embodiment, the PP value detector 52 detects the PP value of the effective voltage v for 500 ms, and the frequency detector 53 detects the frequency f of the effective voltage v. V The index value calculation unit 54 calculates the effective value PP and the frequency f V The index value ΔV is calculated by multiplying it by a coefficient according to X Therefore, the analysis unit 32 can perform analysis based on the fluctuation range of the component of the fluctuation of the effective voltage value v that is 2 Hz or higher.

[0054] Furthermore, according to this embodiment, the index value calculation unit 54 calculates the effective value PP value and the frequency f V The index value ΔV is calculated by multiplying it by a coefficient according to X Calculate the coefficient ΔV 10 Therefore, the index value calculation unit 54 calculates ΔV 10 In addition, the calculation load is significantly reduced compared to when the index value ΔV X The coefficient used to calculate the index value ΔV 10 Since this value is greater than the visibility coefficient used to calculate the index value ΔV X is the index value ΔV 10 Therefore, the analysis unit 32 can reduce the number of voltage flicker detection failures.

[0055] In this embodiment, the analysis unit 32 calculates the frequency PP value and the index value ΔV X In the above description, the connection status is detected using both the frequency PP value and the index value ΔV X Alternatively, the connection status may be detected using only one of the above. For example, if the total capacity of the operating power source B connected to the power distribution system C is known in advance, the new model proportion can be detected from the frequency PP value as shown in FIG. 3. In this case, the control unit 1 does not need to include the second detection unit 59. Also, as shown in FIG. 6, the index value ΔV X In this case, the control unit 1 does not need to include the first detection unit 49.

[0056] Furthermore, the method of detecting the connection status in the control unit 1 is not limited to the above. For example, the control unit 1 does not need to include the low-pass filter 43, and the detection range for detecting the PP value in the PP value detection unit 44 is not limited to 500 ms. Furthermore, the detection range for detecting the PP value in the PP value detection unit 52 is not limited to 500 ms, and the index calculated by the index value calculation unit 54 is not limited to ΔV X The second detection unit 59 is not limited to the conventional index value ΔV 10 The analysis unit 32 calculates the index value ΔV 10The connection status may be detected based on the above.

[0057] Second Embodiment 8 is a block diagram for explaining the analysis device A2 according to the second embodiment, and shows the overall configuration of the 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 redundant explanations will be omitted.

[0058] The analysis device A2 of this embodiment differs from the analysis device A1 in that it stops the injection of active signals when voltage flicker occurs in the power distribution system C and analyzes the connection status based on how the voltage flicker converges at that time.

[0059] In this embodiment, a power supply device 8 is connected to the power distribution system C. The power supply device 8 injects and stops an active signal into the power distribution system C in response to instructions from the analysis device A2. The power supply device 8 may be any conventional power source B1 or new power source B2 connected to the power distribution system C, or may be a distributed power source equipped with a power conditioner having an islanding operation detection device of another type connected to the power distribution system C. Furthermore, the power supply device 8 may be a power supply device solely for injecting and stopping an active signal into the power distribution system C in response to instructions from the analysis device A2.

[0060] The control unit 1 of the analysis device A2 stops the injection of the active signal to the power supply device 8 when voltage flicker occurs in the power distribution system C. The occurrence of voltage flicker in the power distribution system C is detected by the analysis unit 32 of the control unit 1 by detecting the frequency PP value input from the PP value detection unit 44 or the index value ΔV X The analysis unit 32 according to this embodiment determines the frequency PP value and the index value ΔV X The change in the frequency PP value and the index value ΔV are recorded. X The connection status is detected based on how the value changes.

[0061] If the power supply device 8 stops injecting the active signal when voltage flicker occurs in the power distribution system C, the voltage flicker will converge, but the manner in which it converges will differ depending on the connection state of the operating power source B. If the new power supply ratio is large, that is, if the ratio of the total capacity of the new power supply B2 to the total capacity of the operating power source B is large, the manner in which the voltage flicker converges will be slow. Therefore, the frequency PP value and the index value ΔV X Taking advantage of this characteristic, the analysis unit 32 calculates the frequency PP value and the index value ΔV X The connection status (new model ratio) is detected according to the change in the frequency PP value and index value ΔV for each new model ratio. X The data on how the frequency PP value and the index value ΔV change is acquired in advance by experiment or simulation and stored in the storage unit 3. A specific method for detecting the connection status (new type ratio) is, for example, to measure the frequency PP value and the index value ΔV for the period from when the injection of the active signal is stopped while voltage flicker is occurring until the convergence of the voltage flicker is detected. X The slope of each voltage flicker convergence is detected. Next, each detected slope is compared with the data table to select candidates for matching conditions. Then, from the selected conditions, the condition for the frequency PP value and the index value ΔV X The conditions that closely match the above conditions are determined to be the actual connection status (new model ratio).

[0062] According to this embodiment, the analysis unit 32 calculates the frequency PP value and the index value ΔV from when the power supply device 8 stops injecting the active signal. X The connection status is detected based on the way in which the voltages change. This allows the analysis device A2 to analyze the connection status of the conventional power source B1 and the new power source B2 in the power distribution system C. Therefore, it is possible to determine whether the power distribution system C is prone to voltage flicker. Furthermore, the analysis device A2 has a common configuration with the analysis device A1, and therefore achieves the same effects as the analysis device A1.

[0063] In this embodiment, the analysis unit 32 analyzes the change in the frequency PP value and the index value ΔV XIn the above description, the connection status is detected by using both the frequency PP value and the index value ΔV X The analysis unit 32 may detect the connection status based on the change in either one of the frequency PP value and the index value ΔV when voltage flicker occurs. X (See the first embodiment) and the frequency PP value and index value ΔV when the voltage flicker converges. X The connection status may be detected by taking into consideration both the detection of the connection status based on changes in the connection status (see the second embodiment) and the detection of the connection status based on changes in the connection status (see the second embodiment). For example, the analysis unit 32 may calculate an average value of the new type ratios detected by each of the above two methods and output the calculated average value as the new type ratio. Note that the specific method of calculating the connection status by the control unit 1 is not limited to the above-mentioned method.

[0064] The analytical device and program according to the present invention are not limited to the above-described embodiment, and the specific configurations of the components of the analytical device and program according to the present invention can be freely modified in various ways. [Explanation of symbols]

[0065] A1, A2: analysis device, 41: frequency detection unit, 42: change amount detection unit, 43: low-pass filter, 44: PP value detection unit, 51: effective value detection unit, 52: PP value detection unit, 53: frequency detection unit, 54: index value calculation unit, 32: analysis unit, 9: voltage sensor, B1: conventional power source, B2: new power source, C: power distribution system

Claims

1. A conventional power supply that is a distributed power supply having a conventional active type islanding detection device that injects reactive power or a new type power supply that is a distributed power supply having a new active type islanding detection device is connected to a power distribution system and is in operation, a first frequency detection unit that detects a first frequency of an instantaneous voltage value based on a voltage signal input from the voltage sensor; an analysis unit that determines the occurrence of voltage flicker based on fluctuations in the first frequency, and detects a connection status that is a ratio between a first total capacity and a second total capacity based on the fluctuations in the first frequency when voltage flicker occurs, a line impedance of the power distribution system, and an overall capacity that is the sum of a first total capacity of the conventional power sources connected to the power distribution system and operating and a second total capacity of the new type power sources connected to the power distribution system and operating; An analytical device comprising:

2. a change amount detection unit that detects a change amount of the first frequency; a low-pass filter that extracts only frequency components equal to or lower than an upper limit frequency from the amount of change; a first PP value detection unit that detects a first PP value, which is a peak-to-peak value of the change amount extracted by the low-pass filter in a first unit time; Furthermore, the first unit time is a period of a lower limit frequency of a frequency component to be extracted from the amount of change, The analysis unit detects the connection status based on the first PP value. The analytical device of claim 1 .

3. a voltage detection unit that detects the magnitude of a voltage based on the voltage signal; the analysis unit detects the connection status based on a fluctuation in the first frequency and a fluctuation in the magnitude of the voltage when a voltage flicker occurs. The analytical device according to claim 1 or 2.

4. a second PP value detector that detects a second PP value, which is a peak-to-peak value of the magnitude of the voltage in a second unit time; a second frequency detection unit that detects a second frequency that is a frequency of fluctuations in the magnitude of the voltage; an index value calculation unit that calculates an index value from the second PP value and the second frequency; Furthermore, the second unit time is a period of a lower limit frequency of a frequency component to be extracted from the magnitude of the voltage, the analysis unit detects the connection status based on the index value. The analytical device according to claim 3 .

5. the analysis unit detects the connection status based on how the fluctuation of the first frequency changes when the voltage flicker converges.

5. The analytical device according to claim 1.

6. A conventional power supply that is a distributed power supply having a conventional active type islanding detection device that injects reactive power, or a new type power supply that is a distributed power supply having a new active type islanding detection device, is connected to a power distribution system and is in operation, a voltage detection unit that detects the magnitude of a voltage based on a voltage signal input from the voltage sensor; and an analysis unit that determines the occurrence of voltage flicker based on the fluctuation in voltage magnitude, and detects a connection status that is a ratio between a first total capacity and a second total capacity based on the fluctuation in voltage magnitude when voltage flicker occurs, a line impedance of the power distribution system, and an overall capacity that is the sum of a first total capacity of the conventional power sources connected to the power distribution system and in operation and a second total capacity of the new power sources connected to the power distribution system and in operation.

7. the analysis unit detects the connection status based on how the fluctuation in the magnitude of the voltage changes when the voltage flicker converges. The analytical device according to claim 6 .

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