JP2008193827A - Isolated operation detecting method, controller for detecting isolated operation of distributed power supply, isolated operation detecting apparatus, and distributed power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the level of power fluctuation and to prevent the power fluctuation from becoming so excessive as to cause problem of flickering, and thereby eliminate or reduce flickering. <P>SOLUTION: A method is used to detect whether a dispersed power supply is isolated from a power system and is operating in an isolated manner, based on the power fluctuations injected into a power system. The method includes a first step of injecting power fluctuation into the power system; a second step of detecting the state of power of the power system; and a third step of reducing the level of power fluctuation to a fixed upper limit or lower, according to the result of the detection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an isolated operation detection method for detecting whether or not a distributed power source is isolated from a power system based on various power fluctuations such as reactive power injected into the power system, and an isolated operation of the distributed power source. The present invention relates to a detection control device, an isolated operation detection device, and a distributed power source.

  Independent operation is a state in which a distributed power source supplies power to a local system load in a state where an accident or the like has occurred in the power system and stopped. A distributed power source is one that generates power by installing a power source at or near a demand location. Currently, such distributed power sources are mainly cogeneration systems using gas turbines, gas engines, sunlight, and the like. In the future, in addition to these systems, power generation systems that use renewable energy such as wind power, small-scale hydropower, biomass, etc., or waste, and micro gas turbines and fuel cells that are technically under development are expected to become popular. Has been. Among them, fuel cells are expected to be the mainstream of distributed power sources, and are expected to be introduced not only to large-scale facilities such as factories but also to small-scale facilities such as ordinary houses.

  Typical small distributed power sources include gas engines, gas turbines, micro gas turbines, sunlight, fuel cells, and the like. Until now, electric power companies have invested enormously in a place far from the demand area to construct a power plant and transmit power to the demand area, so there is a transmission loss and the power generation efficiency is only around 30%.

  In the isolated operation detection device for detecting the isolated operation of the distributed power source described above, the detailed description of the isolated operation detection method is omitted, but the reactive power variation method, the active power is determined by the power variation injection method. Various methods (power fluctuation method) such as a fluctuation method and a harmonic injection method have already been proposed.

  In isolated operation detection using such a power fluctuation method, if a large number of isolated operation detectors inject power fluctuations into the power system irregularly, the power fluctuations may cancel each other out in the power system. Operation detection is affected. Therefore, when a large number of isolated operation detection devices inject power fluctuations into the power system all at once in synchronization with a standard time radio signal etc., the load connected to the power system into which these power fluctuations are injected For example, flickering of a fluorescent lamp, malfunction of a microcomputer, and flicker (periodic fluctuation of voltage) that may cause motor rotation control failure may occur. Of course, even if one or several independent operation detection devices are used, if the level of power fluctuation is excessive, the same flicker problem as in the case of multiple units occurs. There are many techniques related to isolated operation, and representatives of the patent documents are listed below.

  On the other hand, flickering of lighting due to fluctuations in the effective voltage value in the voltage system, so-called flicker, is an important problem in power quality, and there is ΔV10 as shown in the equation (1) as one of the management indexes. .

In equation (1), ΔVn represents the fluctuation (effective value) of the voltage fluctuation component of the fluctuation frequency fn obtained as a result of frequency analysis of the voltage fluctuation, for example, as shown in FIG. 1, and an represents the flicker visibility shown in FIG. The flicker visibility coefficient corresponding to the fluctuation frequency fn when 10 Hz in the curve is set to 1 is shown. ΔV10 is a fluctuation value of 10 Hz in the flicker visibility curve. This ΔV10 is compared with a predetermined allowable value, and if it is equal to or smaller than the allowable value, it is determined that the power quality is good, and if it is equal to or larger than the allowable value, it is determined as defective.
Japanese Patent Laid-Open No. 08-98411 Japanese Patent No. 3397912 Japanese Patent No. 3424443

  Therefore, the problem to be solved by the present invention is that the level of power fluctuation is controlled so that the power fluctuation does not become excessive to the extent that the flicker problem occurs, and the flicker is eliminated or suppressed to a small level. To satisfy the provisions of

  An isolated operation detection method according to the present invention is a method for detecting whether or not a distributed power source is isolated from an electric power system based on electric power fluctuations injected into the electric power system at each fluctuation frequency fn of the electric power system. The first step of measuring the voltage fluctuation ΔVn, the second step of converting the voltage fluctuation ΔVn to the fluctuation value ΔV10 of 10 Hz by the flickering visibility curve, and the converted fluctuation value ΔV10 are determination criteria for flicker countermeasures. And a third step of injecting power fluctuations into the power system so as not to exceed the allowable value.

  In the above, the injection of the power fluctuation may be arbitrary such as periodic or irregular.

  The power fluctuation includes reactive power fluctuation, active power fluctuation, harmonic power fluctuation, and the like, and is not particularly limited.

  The allowable value is 0.23V (0.46V in 202V conversion) for new generator equipment, and 0.45V (0.9V in 202V conversion) when considering voltage flicker before interconnection.

  According to the present invention, when the power fluctuation is injected into the power system, the fluctuation value ΔV10 is prevented from exceeding the allowable value which is a criterion for countermeasures against flicker. Even when power fluctuations are injected into the power system all at once, the power fluctuations are suppressed to a value that does not cause flickering problems, and there is no possibility of causing the flickering problems, and at the same time, the ΔV10 regulation is satisfied. be able to.

  In a preferred aspect of the present invention, the power fluctuation injected in the third step is the amount of power fluctuation.

  In a preferred aspect of the present invention, the power fluctuation injected in the third step is a change in the fluctuation frequency.

  According to a preferred aspect of the present invention, when the power fluctuation injected in the third step is small, the fluctuation frequency is increased, and when the fluctuation of the system voltage is large, the amount of power fluctuation.

  One preferred aspect of the present invention is that power fluctuations (changes in quantity and fluctuation frequency) are suppressed to a certain upper limit until ΔV10 exceeds a certain value, and after ΔV10 exceeds a certain value, power is increased or decreased with respect to ΔV10. The level of fluctuation is to be cycle controlled with hysteresis.

  According to the present invention, flicker can be detected while satisfying the ΔV10 rule.

  Hereinafter, an isolated operation detection method, its control device, an isolated operation detection device, and a distributed power supply according to embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 3 shows a configuration of a power control system including a distributed power source and an isolated operation detection device. Referring to FIG. 3, 10 is a distributed power source such as sunlight, wind power, micro gas turbine, and fuel cell, 15 is a power conditioner, 20 is an independent operation detection device, and 30 is a power system. The details of the power system 30 are omitted because they do not require any particular explanation in the present embodiment. Also, the illustration of the load is omitted. The isolated operation detection device 20 includes interconnection relays 21 and 25, a control device 22, an inverter control unit 23, an inverter 24, and a current detector 26.

  The control device 22 has a built-in microcomputer and can execute a control operation by a software program of the microcomputer. In this case, the control device 22 can be configured by hardware other than the microcomputer.

(Embodiment 1)
FIG. 4 shows the main functions of the control device 22 relating to the first embodiment in a block configuration. In FIG. 4, reference numeral 29 denotes a radio timepiece that operates with a standard time radio signal, and reference numeral 31 denotes a periodic power fluctuation signal S 3 for controlling minute fluctuations (power fluctuation) of the electric power system 30 periodically in synchronization with the radio timepiece 29. It is an electric power regular fluctuation part which outputs'.

  Reference numeral 32 denotes a flicker detection processing unit for detecting flicker of power fluctuation in the power system 30 and outputting a flicker detection signal (power fluctuation amount) S3 ″.

  33 is a product of the periodic power fluctuation signal S3 ′ from the periodic fluctuation section 31 and the flicker detection signal (amount of power fluctuation) S3 ″ from the flicker detection processing section 32, and the result is multiplied by the power fluctuation command signal S3 (the reactive current itself). Rather than as a control signal to the inverter controller 23).

  Reference numeral 34 denotes a power fluctuation monitoring unit that monitors the power fluctuation of the power line 27 based on the signal S5.

  35 determines based on the monitoring signal from the power fluctuation monitoring unit 34 whether the distributed power source 10 is disconnected from the power system 30 and is operating independently, and the control signals S1, S2, S6 corresponding to the determination. Is an independent operation determination unit that outputs to the interconnection relays 21 and 25 and the inverter control unit 23.

  The radio clock 29 and the periodic power fluctuation unit 31 output a periodic power fluctuation signal S3 ′ to the multiplier 33, and output a power fluctuation command signal S3 from the multiplier 33. In response to the power fluctuation command signal S3, the inverter Through the control unit 23 and the inverter 24, a power fluctuation injection unit that injects a power fluctuation into the power system 30 can be configured.

  In the flicker detection processing unit 32, 32a is a measurement unit that analyzes the fluctuation of the system voltage shown in FIG. 1 and measures the voltage fluctuation ΔVn (fluctuation of the effective value of the system voltage) at the fluctuation frequency fn of the power system, 32b A conversion processing unit (filter processing unit) that converts (filters) the voltage fluctuation amount ΔVn into a fluctuation value ΔV10 of 10 Hz according to the flicker visibility curve shown in FIG. 2, and 32c is a few seconds of the converted fluctuation value ΔV10. In the embodiment, an effective value processing unit for calculating an effective value for 5 seconds, 32d calculates a power fluctuation amount according to FIG. 5 so that the effective fluctuation value ΔV10 does not exceed an allowable value that is a criterion for countermeasures against flicker, and detects a flicker detection signal. It is a calculating part which outputs as S3 ''. This permissible value can be determined based on the grid connection regulations (JEAC9701-2006). For example, 0.23V (0.46V in 202V conversion) for new generator equipment, and voltage flicker before connection is taken into consideration Then, it is 0.45V (0.9V in terms of 202V). In FIG. 5, the horizontal axis represents the voltage deviation (V) (ΔV10), and the vertical axis represents the injected power fluctuation amount (Var).

  The effective value processing unit 32c performs effective value processing on the horizontal axis in FIG. 5 and outputs the effective value processing result to the calculation unit 32d. With respect to the horizontal axis in FIG. 5, the effective value processing unit 32 c calculates the effective value calculation for 5 seconds as the voltage deviation (ΔV10) on the horizontal axis in FIG. 5.

  In the calculation part 32d, even if the voltage deviation (ΔV10) increases or decreases between 0 and 0.45 in the hysteresis curve W1 indicated by the one-dot chain line in FIG. 5, the power fluctuation amount is maintained at the upper limit of 40 (Var), When the deviation (ΔV10) increases or decreases between 0.45 and 0.9, when the current power fluctuation amount exceeds W1, the power fluctuation amount fluctuates in the range of 0 to 40 (Var). Clip to W1. Then, once the voltage deviation (ΔV10) becomes 0.9, when the voltage deviation (ΔV10) decreases, the power fluctuation amount is maintained at zero. When the voltage deviation (ΔV10) becomes 0.85, when the voltage deviation (ΔV10) increases or decreases, the power fluctuation amount is increased or decreased by 0 to 40. That is, control is performed by a hysteresis operation in which the current power fluctuation amount is clipped to W2 when it falls below the hysteresis curve W2 indicated by the dotted line.

  In the above, since the output of the calculation unit 32d is output to the multiplier 33 as the flicker detection signal S3 ″, the power fluctuation amount can be suppressed to 40 (Var) or less according to the function shown in FIG. Since the power fluctuation command signal S3 for suppressing the power fluctuation amount to 40 (Var) or less is output to the inverter control section 23 to the inverter control section 23, flicker is suppressed.

  FIG. 6 shows an image in which injection power fluctuation is suppressed by the above. FIG. 6A shows the fluctuation of power injected periodically, and FIG. 6B shows the state where the fluctuation of injected power is suppressed by the first embodiment.

  Note that the calculation unit 32d may control the power fluctuation amount with a hysteresis curve shown in FIG. When the voltage deviation (ΔV10) is small compared to the hysteresis curve of FIG. 5, that is, when the power fluctuation of the power system is small, a large amount of power fluctuation can be injected, and the load power and the generated power are perfectly balanced. It is possible to detect the single operation at a high speed by rapidly breaking.

(Embodiment 2)
FIG. 8 shows a block configuration of the control device 22 according to the second embodiment. In the control device 22 shown in FIG. 8, the multiplier 33 is omitted, and the output of the flicker detection processing unit 32 is directly input to the periodic power fluctuation unit 31, and the calculation unit of the flicker detection processing unit 32. 32d is that the calculation is performed according to the hysteresis curve shown in FIG. The vertical axis in FIG. 9 represents the injection power fluctuation frequency (Hz).

  In the calculation unit 32d described above, in the hysteresis curve W1 shown by the one-dot chain line in FIG. 9, even if the voltage deviation (ΔV10) increases or decreases between 0 and 0.45, the power fluctuation frequency is maintained at the upper limit of 2 (Hz). When the voltage deviation (ΔV10) increases or decreases between 0.45 and 0.9, by changing the power fluctuation frequency in the range of 0.1 to 2 (Hz), the current power fluctuation amount becomes W1. If it exceeds, W1 is clipped. Once the voltage deviation (ΔV10) reaches 0.9, the power fluctuation frequency is maintained at 0.1 when the voltage deviation (ΔV10) decreases. When the voltage deviation (ΔV10) becomes 0.85, when the voltage deviation (ΔV10) increases or decreases, the power fluctuation frequency is increased or decreased by 0.1 to 2. That is, control is performed by a hysteresis operation in which the current power fluctuation amount is clipped to W2 when it falls below the hysteresis curve W2 indicated by the dotted line.

  In the first embodiment described above, in order to satisfy the voltage flicker ΔV10, the system voltage ΔV10 is calculated and the periodic power fluctuation amount is suppressed, whereas the implementation shown in FIGS. 8 and 9 is performed. In form 2, the effect on ΔV10 is the maximum at 10 Hz as shown in FIG. 2, and the effect decreases as the distance from 10 Hz decreases. By changing the power fluctuation frequency to be injected by the calculated ΔV10, The voltage flicker was kept within the allowable value.

  In this case, even if the injected power fluctuation frequency is low and the period of power fluctuation is long, if there is fluctuation in the system voltage, it is possible to break the perfect balance between the generated power and the load power, The detection time of detection is not affected.

  FIG. 10 shows an image in which injection power fluctuation is suppressed by the above. FIG. 10A shows periodic power fluctuation injection, and FIG. 10B shows a state in which the power fluctuation is suppressed by extending the cycle of the injected power fluctuation.

(Embodiment 3)
FIG. 11 shows a block configuration of the control device 22 according to the third embodiment. In the control device 22 shown in FIG. 11, the output of the flicker detection processing unit 32 is input to the multiplier 33 and the periodic power fluctuation unit 31, and the calculation unit 32d of the flicker detection processing unit 32 is shown in FIG. (A) The calculation is performed in accordance with the hysteresis curves shown in (b), the multiplier 33 has the corresponding power fluctuation amount in FIG. 12 (a), and the power periodic fluctuation unit 31 has the fluctuation corresponding in FIG. 12 (b). This means that the flicker detection signal S3 ″ is output for each frequency change. 12A corresponds to FIG. 5, and FIG. 12B corresponds to FIG. These descriptions are omitted.

  In the control device 22 shown in FIG. 11, when ΔV10 is 0 to 0.4, the power fluctuation frequency is changed according to the hysteresis curve shown in FIG. 12B, and when ΔV10 is 0.4 to 0.9, the injected power fluctuation amount is shown. The voltage flicker is kept within the allowable value of ΔV10 by changing according to the hysteresis curve indicated by 12 (a). In the first embodiment, when the system voltage fluctuation is small, a large power fluctuation is injected, so that the complete balance state between the load power and the generated power can be rapidly broken to perform the isolated operation detection at high speed. However, since the large power fluctuation is injected, the apparatus becomes large and expensive, and the loss also increases. Therefore, in the third embodiment, when the system voltage fluctuation is small, it is possible to rapidly collapse the perfect balance state between the load power and the generated power by increasing the fluctuation frequency of the injected power fluctuation. Compared to 1, it is advantageous from the viewpoints of a small device size, cost reduction, and small loss.

  FIGS. 13A and 13B show the case where ΔV10 is 0.4 to 0.9, and FIGS. 13C and 13D show the case where ΔV10 is 0 to 0.4. FIGS. 13 (a) and 13 (c) are cases where periodic power fluctuations are injected, FIG. 13 (b) is a case where the power fluctuation amount and FIG. 13 (d) are cases where the fluctuation frequency is changed. In both cases, fluctuations in injected power are suppressed.

  As described above, in the isolated operation detection device 20 of the first to third embodiments, the power fluctuation is injected from the control device 22 into the power system. As a result, a large number of isolated operation detection devices inject the power fluctuation into the power system all at once. However, the power fluctuation can be suppressed so as not to cause the problem of flicker while satisfying ΔV10.

  Returning to FIG. 3, in the isolated operation detection device 20 externally attached to the distributed power source 10, a control command S <b> 3 for periodically injecting power fluctuations from the control device 22 to the inverter control unit 23 into the power system is provided. Entered. As a result, the inverter control unit 23 outputs the control signal S4 to the inverter 24 to drive the inverter 24 and inject power fluctuation into the power line 27. Note that the interconnection relays 21 and 25 are closed by the control device 22.

  The control device 22 monitors the power fluctuation from the power line 27 by the power fluctuation monitoring unit 34 by the signal S5 from the system. The power fluctuation monitoring unit 34 inputs monitoring data of power fluctuations to the isolated operation determination unit 35. If the isolated operation determination unit 35 determines that the operation is independent from the monitoring data, the control signals S1 and S2 for turning off the interconnection relays 21 and 25 and the control signal S6 for causing the inverter control unit 23 to stop the operation of the inverter 24. Is output. Thereby, the independent operation is stopped.

  On the other hand, the flicker detection processing unit 32 of the control device 22 detects the voltage and frequency of the system so that the power fluctuation level for the independent operation determination does not exceed a certain value, controls the level of power fluctuation, and suppresses the occurrence of flicker. To do.

  FIG. 14 shows a power conditioner incorporating a stand-alone operation detection device. This distributed power source includes a power source body 50 such as a solar cell or a fuel cell, and a power conditioner 60. The power conditioner 60 includes an inverter 61, a current detector 62, an interconnection relay 63, an inverter control unit 64, and the control device 65 of the embodiment.

  In the above configuration, in the power conditioner 60, a control command for periodically injecting power fluctuations into the power system is input from the control device 65 to the inverter control unit 64. Thereby, the inverter control unit 64 drives the inverter 61 to inject power fluctuations into the power line 66. Note that the interconnection relay 63 is closed by the control device 65.

  The control device 65 monitors the power fluctuation from the power line 66 by the power fluctuation monitoring unit 34. The power fluctuation monitoring unit 34 inputs monitoring data of power fluctuations to the isolated operation determination unit 35. When it is determined from the monitoring data that the islanding operation determination unit 35 is the islanding operation, it outputs a control signal for driving the interconnection relay 63 off and a control signal for causing the inverter control unit 64 to stop the operation of the inverter 64. Thereby, the independent operation is stopped.

  On the other hand, the flicker detection processing unit 32 of the control device 65 detects the voltage and frequency of the system so that the power fluctuation level for the independent operation determination does not exceed a certain value, controls the power fluctuation level, and generates flicker. Suppress.

FIG. 1 is a diagram for explaining the flicker fluctuation voltage. FIG. 2 is a diagram for explaining the flicker visibility coefficient. FIG. 3 is a diagram showing a configuration of a power control system including a distributed power source and an isolated operation detection device to which the isolated operation detection method according to Embodiment 1 of the present invention is applied. FIG. 4 is a block diagram of the control device of FIG. FIG. 5 is a diagram for explaining the operation of the control device of FIG. FIG. 6 is an image diagram in which the injection power fluctuation is suppressed by the periodic power fluctuation injection and the first embodiment. FIG. 7 is a diagram illustrating a modification of the calculation of the calculation unit according to the first embodiment. FIG. 8 is a block diagram of the control device of the second embodiment. FIG. 9 is provided for explaining the operation of the control device of FIG. 8, and is a diagram showing the relationship between the voltage deviation (ΔV10) and the injected power fluctuation amount. FIG. 10 is an image diagram in which injected power fluctuation is suppressed by the periodic power fluctuation injection and the first embodiment. FIG. 11 is a block diagram of the control device according to the third embodiment. FIG. 12A is a diagram for explaining the operation of the control device in FIG. 11 and shows a relationship between the voltage deviation (ΔV10) and the amount of fluctuation in injected power. FIG. 12B is a diagram for explaining the operation of the control device in FIG. It is a figure which provides and shows the relationship between voltage deviation ((DELTA) V10) and injection | pouring electric power fluctuation frequency. FIG. 13 is an image diagram in which the injection power fluctuation is suppressed by the periodic power fluctuation injection and the third embodiment. FIG. 14 is a diagram showing a configuration of another power control system including a distributed power source and an isolated operation detection device to which the isolated operation detection method according to the embodiment of the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Distributed type power supply 20 Independent operation detection apparatus 30 Electric power system

Claims (8)

In a method for detecting whether a distributed power source is disconnected from a power system and operating independently based on power fluctuations injected into the power system,
A first step of measuring a voltage variation ΔVn at each variation frequency fn of the power system;
A second step of converting the voltage fluctuation ΔVn into a fluctuation value ΔV10 of 10 Hz in the flicker visibility curve;
A third step of injecting power fluctuations into the power system so that the converted fluctuation value ΔV10 does not exceed an allowable value that is a criterion for flicker countermeasures;
An islanding operation detection method comprising:   The islanding operation detection method according to claim 1, wherein the power fluctuation injected in the third step is an amount of power fluctuation.   The isolated operation detection method according to claim 1, wherein the power fluctuation injected in the third step is a change in a fluctuation frequency.   2. The single power supply according to claim 1, wherein the power fluctuation injected in the third step depends on a fluctuation frequency when the fluctuation of the system voltage is small, and depends on an amount of the power fluctuation when the fluctuation of the system voltage is large. Driving detection method. In the control device that controls the detection operation for the single operation detection device that detects whether the distributed power source is disconnected from the power system and is operating alone,
A first means for measuring a voltage variation ΔVn at each variation frequency fn of the power system;
A second means for converting the voltage fluctuation ΔVn into a fluctuation value ΔV10 of 10 Hz by a flickering visibility curve;
Third means for injecting power fluctuations into the power system so that the converted fluctuation value ΔV10 does not exceed an allowable value that is a criterion for countermeasures against flicker;
A control device comprising:   In the control device that controls the detection operation with respect to the single operation detection device that detects whether or not the distributed power source is disconnected from the power system and is operating alone, the control device includes a microcomputer, A control device comprising a microcomputer provided with a software program for executing the method according to claim 1.   An isolated operation detection device for detecting whether or not a distributed power source is disconnected from an electric power system and operated independently, comprising the control device according to claim 5 or 6. In the distributed power supply which incorporates the isolated operation detection device which detects whether or not the isolated operation is performed from the electric power system, the isolated operation detection device is the isolated operation detection device according to claim 7. Distributed power supply.

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