JP2018007320A - System interconnection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a malfunction of an operation continuation function at the time of an accident and improve the detection accuracy of independent operation when a momentary power failure occurs in an electric power system to which the power generation device is connected. Provide the device. According to the grid interconnection control device of the present invention, the control device (16) includes an independent operation detection sensitivity changing unit (41). The independent operation detection sensitivity change unit (41) detects the independent operation of the power generation device when a momentary power failure occurs in the power system to which the power generation device is connected, as compared with the case where the momentary power failure does not occur. At least one of the detection threshold and the detection time is lowered to increase the detection sensitivity of the isolated operation. [Selection diagram] Fig. 4

Description

  The present invention relates to a grid interconnection control device that detects a single operation of a power generator.

  As an example of the above-mentioned invention, the invention described in Patent Document 1 is cited. In the isolated operation detection device described in Patent Document 1, both the operation frequency calculated by the first PLL processing unit and the system frequency measured by the system frequency measurement unit change in one direction at a plurality of continuous system cycles. It is determined that it is in a single operation state. Thus, the invention described in Patent Document 1 tries to avoid unnecessary detection of an isolated operation at the time of a sudden phase change of the system power supply or a sudden phase change due to an instantaneous voltage drop.

JP2015-133785A

  Single operation detection function for disconnecting the power generator from the power system when the single operation of the power generator is detected, and continuation of operation at the time of an accident (FRT: Fault Ride Through) for continuing the operation of the power generator against disturbance of the power system The function is a contradictory function, and there is a concern about these control interferences. In particular, there is a concern that the accident-time operation continuation function malfunctions in a situation where the isolated operation detection function should operate.

  For example, it is assumed that a power failure occurs in a power system in which a plurality of power generation devices are connected. It is assumed that, for example, the detection of the single operation of one power generation apparatus is delayed due to the variation in the detection of the single operation of the plurality of power generation apparatuses. In this case, the system voltage drops because the majority of the power generation devices are disconnected from the power system, but the AC power supplied from the power generation device for which the detection of the isolated operation is delayed may cause a state similar to an instantaneous power failure. There is sex. For this reason, in the power generation device in which the detection of the isolated operation is delayed, the operation continuation function during an accident may malfunction, and it may be difficult to detect the isolated operation.

  The invention described in Patent Document 1 is intended to suppress malfunction of the isolated operation detection function in a situation where the operation continuation function during an accident should operate. However, the invention described in Patent Document 1 is not an invention that attempts to suppress the malfunction of the accident-time operation continuation function in a situation where the above-described isolated operation detection function should operate.

  The present invention has been made in view of such circumstances, and when an instantaneous power failure occurs in the power system to which the power generation apparatus is connected, the malfunction of the operation continuation function at the time of an accident is suppressed. It is an object of the present invention to provide a grid interconnection control device capable of improving the operation detection accuracy.

  A grid interconnection control device according to the present invention includes a power generation device including a power source and a power converter that converts power output from the power source into AC power and outputs the AC power to a load connected to the system power source, and the system And a control device for paralleling or disconnecting the power generation device with respect to the power system of the power source, wherein the control device is connected to the power system to which the power generation device is connected. When an instantaneous power failure occurs, compared to the case where the instantaneous power failure does not occur, at least one of a detection threshold and a detection time when detecting the isolated operation of the power generation device is reduced to reduce the isolated operation. A single operation detection sensitivity changing unit for increasing detection sensitivity is provided.

  According to the grid interconnection control device according to the present invention, the control device includes the isolated operation detection sensitivity changing unit. Therefore, the grid connection control device according to the present invention can increase the detection sensitivity of isolated operation when an instantaneous power failure occurs in the power system connected to the power generation device, and the operation continuation function during an accident malfunctions. Before doing so, it is possible to easily detect the isolated operation of the power generation device. That is, the grid interconnection control device according to the present invention can improve the detection accuracy of the isolated operation by suppressing the malfunction of the accident-time operation continuation function.

It is a block diagram which shows an example of a grid connection control apparatus. FIG. 2 is a configuration diagram illustrating an example of a control device 16. It is a figure which shows an example of a voltage drop tolerance with respect to the driving | operation continuation requirement at the time of an accident. It is a figure which shows an example of the frequency fluctuation tolerance of a step raise regarding the driving | operation continuation requirement at the time of an accident. It is a figure which shows an example of the frequency fluctuation tolerance of a lamp raise or a lamp fall in connection with the driving | operation continuation requirement at the time of an accident. 3 is a block diagram illustrating an example of a control block of a control device 16. FIG. It is a flowchart which shows an example of the control procedure of a grid connection control apparatus. 3 is a schematic diagram illustrating an example of a storage area that stores a detected value of a physical quantity (system frequency) related to AC power of the system power supply 20. FIG. It is a figure which shows an example of the time-dependent change of the detected value of the physical quantity (system frequency) regarding the alternating current power of the system power supply.

  Hereinafter, the grid connection control apparatus of this embodiment is demonstrated based on drawing. In addition, drawing is a conceptual diagram and does not prescribe | regulate to the dimension of a detailed structure.

<Configuration of grid interconnection control device>
As shown in FIG. 1, the grid interconnection control device of the present embodiment includes a power generation device 1, switches 15 a and 15 b, a control device 16, and a detector 18. The power generation apparatus 1 includes a power source 10 and a power converter 11, and the power converter 11 includes a converter 12, a capacitor 13, and an inverter 14. The detector 18 includes a DC voltage detector 18a and a system voltage detector 18b.

(Power supply 10)
Although the power supply 10 is not limited, For example, a fuel cell can be used as the power supply 10. The fuel cell is a distributed power source that generates electric power using fuel and an oxidant gas. For example, various fuel cells such as a known solid oxide fuel cell (SOFC) can be used. The power supply 10 can also use a distributed power supply (for example, a solar power generation device) other than the fuel cell. When the above-described distributed power source is used as the power source 10, the power source 10 outputs DC power.

  The power supply 10 may be a gas engine generator. When a gas engine generator is used as the power source 10, the AC generator of the gas engine generator outputs AC power. In order to output DC power as in the above-described distributed power supply, it is preferable to generate DC power by rectifying the AC power output from the AC generator with a known smoothing circuit such as a diode bridge. As shown in the figure, the power source 10 includes output side terminals 10a and 10b. The output terminal 10 a is connected to the positive electrode (+) of the power supply 10, and the output terminal 10 b is connected to the negative electrode (−) of the power supply 10. Further, the output state (information such as output power) of the power supply 10 is transmitted to the control device 16 described later.

(Power converter 11)
The power converter 11 converts the power output from the power supply 10 into AC power and outputs it to the load 30 connected to the system power supply 20. In the present embodiment, the power converter 11 boosts the DC power output from the power supply 10, converts the boosted DC power into AC power, and outputs the AC power to the load 30. Therefore, the power converter 11 includes a converter 12, a capacitor 13, and an inverter 14.

(Converter 12 and capacitor 13)
Converter 12 boosts the DC power output from power supply 10 and outputs it to inverter 14. The converter 12 includes input side terminals 12a and 12b and output side terminals 12c and 12d. An electric circuit 17 a is formed between the output side terminal 10 a of the power supply 10 and the input side terminal 12 a of the converter 12. Further, an electric circuit 17 b is formed between the output-side terminal 10 b of the power supply 10 and the input-side terminal 12 b of the converter 12. The DC power output from the power supply 10 is input to the converter 12 via the electric paths 17a and 17b. The DC power boosted by the converter 12 is output from the output side terminals 12c and 12d. As the electric paths 17a and 17b, for example, a known power cable can be used. The same applies to the electric circuit described later.

  The converter 12 includes a reactor 12e, a diode 12f, and a switching element 12g. As these elements, known power devices can be used. For example, a known field effect transistor (FET), an insulated gate bipolar transistor (IGBT), or the like can be used as the switching element 12g.

  An electric path 17c is formed between the input side terminal 12a and the output side terminal 12c of the converter 12. Further, an electric circuit 17 d is formed between the input side terminal 12 b and the output side terminal 12 d of the converter 12. In the electric circuit 17c, a reactor 12e and a diode 12f are provided in this order from the input side terminal 12a side. Further, a connection point 12h is provided in the electric circuit 17c between the reactor 12e and the diode 12f, and the drain 12g1 of the switching element 12g is connected to the connection point 12h. The source 12g2 of the switching element 12g is connected to a connection point 12i provided in the electric circuit 17d, and an electric circuit 17e is formed between the connection point 12h and the connection point 12i. Note that the gate 12g3 of the switching element 12g is connected to a control device 16 to be described later via a drive circuit 16e. A known driver circuit can be used for the drive circuit 16e. Moreover, the converter 12 should just be able to step up DC power output from the power supply 10, and is not limited to the above-mentioned configuration.

  An electric circuit 17 f is formed between the output side terminal 12 c of the converter 12 and the input side terminal 14 a of the inverter 14. An electric circuit 17 g is formed between the output side terminal 12 d of the converter 12 and the input side terminal 14 b of the inverter 14. A capacitor 13 and a DC voltage detector 18a are provided between the electric circuit 17f and the electric circuit 17g.

  A connection point 13a is provided in the electric circuit 17f, and one end side (positive electrode side) of the capacitor 13 is connected to the connection point 13a. A connection point 13b is provided in the electric circuit 17g, and the other end side (negative electrode side) of the capacitor 13 is connected to the connection point 13b. As the capacitor 13, a known electrolytic capacitor can be used, and the ripple of the DC power boosted by the converter 12 can be reduced. The DC voltage detector 18 a detects the DC voltage of the DC power boosted by the converter 12. Specifically, the DC voltage detector 18 a detects a DC voltage applied between the input side terminals 14 a and 14 b of the inverter 14.

  For example, the DC voltage detector 18a divides the DC voltage Vdc between the electric circuit 17f and the electric circuit 17g by a plurality of resistors having known resistance values, and the input side of the inverter 14 is based on the divided voltage value. The DC voltage Vdc applied between the terminals 14a and 14b can be detected. Specifically, the DC voltage divided by the resistor described above is input to the control device 16. Then, the control device 16 obtains the DC voltage divided by a known A / D converter (not shown) and calculates the DC voltage Vdc applied between the input terminals 14a and 14b of the inverter 14. can do.

  The control device 16 determines a duty ratio of a pulse width modulation (PWM) signal that is a control signal of the switching element 12g that drives the converter 12 based on the target value of the output power. The control device 16 applies a pulse signal based on the duty ratio to the gate 12g3 of the switching element 12g via the drive circuit 16e which is a driver circuit. For example, when the voltage applied to the gate 12g3 of the switching element 12g is at a high level (a state exceeding a predetermined voltage value), the drain 12g1 and the source 12g2 of the switching element 12g are electrically connected. Thus, electromagnetic energy is stored in the reactor 12e.

  When the voltage applied to the gate 12g3 of the switching element 12g is at a low level (a state equal to or lower than a predetermined voltage value), the drain 12g1 and the source 12g2 of the switching element 12g are electrically disconnected, and the reactor 12e The capacitor 13 is charged with the electromagnetic energy stored in, and the output power of the converter 12 increases. Thus, control device 16 can control the output power of converter 12 to a desired power value (target value of output power).

(Inverter 14)
The inverter 14 converts the DC power boosted by the converter 12 into AC power and outputs the AC power to the load 30 connected to the system power supply 20. The inverter 14 includes input terminals 14a and 14b and output terminals 14c and 14d. An electric circuit 21 a is formed between the output side terminal 14 c of the inverter 14 and the power system 22 of the system power supply 20. Further, an electric circuit 21 b is formed between the output side terminal 14 d of the inverter 14 and the power system 22 of the system power supply 20. Connection terminals 20 a and 20 b of the system power supply 20 are connected to the power system 22. Thereby, the alternating current power output from the inverter 14 is output to the load 30 via the electric circuits 21a and 21b. The AC power of the system power supply 20 can be supplied to the load 30 via the power system 22 of the system power supply 20 and the electric paths 21a and 21b. In addition, as the system power source 20, for example, a commercial AC power source supplied from a distribution network owned by an electric power company can be used. The load 30 is a load that uses electric power as a drive source, and examples thereof include household electric appliances (such as home appliances) and industrial electric appliances (such as robots).

  The inverter 14 includes a plurality (four in this embodiment) of switching elements (first switching element 14e to fourth switching element 14h). As the first switching element 14e to the fourth switching element 14h, similar to the switching element 12g of the converter 12, a known field effect transistor (FET), an insulated gate bipolar transistor (IGBT), or the like can be used.

  As shown in FIG. 1, an electric circuit 17h is formed between the input side terminal 14a of the inverter 14, the drain 14e1 of the first switching element 14e, and the drain 14g1 of the third switching element 14g. In addition, an electric circuit 17i is formed between the input side terminal 14b of the inverter 14, the source 14f2 of the second switching element 14f, and the source 14h2 of the fourth switching element 14h.

  The first switching element 14e and the second switching element 14f are connected in series between the electric circuit 17h and the electric circuit 17i, and between the source 14e2 of the first switching element 14e and the drain 14f1 of the second switching element 14f. The electric circuit 17j is formed. The third switching element 14g and the fourth switching element 14h are connected in series between the electric circuit 17h and the electric circuit 17i, and the source 14g2 of the third switching element 14g and the drain 14h1 of the fourth switching element 14h are connected. An electric circuit 17k is formed between them. That is, the first switching element 14e and the second switching element 14f connected in series and the third switching element 14g and the fourth switching element 14h connected in series are connected in parallel between the electric circuit 17h and the electric circuit 17i. Yes.

  A connection point 14 i is provided in the electric circuit 17 j, and an electric circuit 17 l is formed between the connection point 14 i and the output side terminal 14 c of the inverter 14. Further, a connection point 14j is provided in the electric circuit 17k, and an electric circuit 17m is formed between the connection point 14j and the output side terminal 14d of the inverter 14. As described above, the first switching element 14e to the fourth switching element 14h are full-bridge connected.

  The gates 14e3 to 14h3 of the first switching element 14e to the fourth switching element 14h are connected to the control device 16 via the drive circuit 16f. A known driver circuit can be used as the drive circuit 16f. The first switching element 14e to the fourth switching element 14h are drive-controlled based on a drive signal (open / close signal) output from the control device 16.

  For example, when the voltage applied to the gate 14e3 of the first switching element 14e is at a high level (in a state exceeding a predetermined voltage value), the drain 14e1 and the source 14e2 of the first switching element 14e are electrically connected. It will be in the state. On the other hand, when the voltage applied to the gate 14e3 of the first switching element 14e is at a low level (state below a predetermined voltage value), the drain 14e1 and the source 14e2 of the first switching element 14e are electrically disconnected. It becomes a state. The same applies to the second switching element 14f to the fourth switching element 14h. For example, the control device 16 can vary the duty ratio by pulse width modulation (PWM) control, and can control the opening and closing of the first switching element 14e to the fourth switching element 14h based on the duty ratio.

  The inverter 14 is in a state in which both the first switching element 14e and the fourth switching element 14h are electrically conducted, and both the second switching element 14f and the third switching element 14g are electrically cut off. The first state which is the state, the first switching element 14e and the fourth switching element 14h are both electrically disconnected, and both the second switching element 14f and the third switching element 14g are electrically The DC power input from the input terminals 14a and 14b of the inverter 14 can be converted into AC power by alternately repeating the second state, which is a state of being electrically connected to each other.

  A known filter circuit can be provided between the inverter 14 and the load 30. For example, a known LC circuit can be used as the filter circuit. Thereby, the harmonic component contained in the output current of the inverter 14 output from the output side terminals 14c and 14d of the inverter 14 is reduced, and the output current of the inverter 14 is shaped into a sine wave.

(Switches 15a and 15b)
The switches 15 a and 15 b parallel or disconnect the power generator 1 with respect to the power system 22 of the system power supply 20. The switches 15 a and 15 b are respectively provided on a plurality (two in this embodiment) of electric circuits 21 a and 21 b that connect the power converter 11 of the power generation device 1 and the power system 22 of the system power supply 20. Specifically, the switch 15 a is provided in the electric circuit 21 a between the inverter 14 and the load 30, and the switch 15 b is provided in the electric circuit 21 b between the inverter 14 and the load 30. As the switches 15a and 15b, for example, a known normally open type switch can be used. The switches 15a and 15b can mechanically disconnect the power generating device 1 from the electric paths 21a and 21b when the power generating device 1 is disconnected from the power system 22, and maintain a completely insulated state electrically. can do.

  The switches 15a and 15b are connected to the control device 16 via a drive circuit 16g. A known driver circuit can be used for the drive circuit 16g. The switches 15a and 15b are controlled to be opened and closed by the control device 16 and switched to an open state or a closed state. The open state refers to a state in which a plurality (two) of electric circuits 21a and 21b are both electrically disconnected. The closed state refers to a state in which a plurality (two) of electric circuits 21a and 21b are electrically connected to each other. The control device 16 can cause the power generation device 1 to be parallel to the power system 22 of the system power supply 20 by switching the switches 15 a and 15 b from the open state to the closed state. On the other hand, the control device 16 can disconnect the power generation device 1 from the power system 22 by switching the switches 15a and 15b from the closed state to the open state. In addition to the power generator 1 described above, one or a plurality of various power generators (not shown) can be connected to the power system 22.

(Detector 18)
The detector 18 includes a DC voltage detector 18a and a system voltage detector 18b. The DC voltage detector 18a is as described above, and a duplicate description is omitted. The system voltage detector 18b detects the system voltage Vs (voltage between the electric circuit 21a and the electric circuit 21b shown in FIG. 1). A known voltage detector can be used as the system voltage detector 18b. The system voltage detector 18b can detect the system voltage Vs based on the voltage value obtained by stepping down the system voltage Vs with a transformer, for example. The detector 18 is not limited to the detector described above, and can include various detectors used in grid interconnection control. Each detection value of the detector 18 is transmitted to the control device 16.

  The system voltage detector 18 b can detect a physical quantity related to the AC power of the system power supply 20. The system voltage Vs described above is included in a physical quantity related to the AC power of the system power supply 20. In addition to this, as physical quantities related to AC power of the system power supply 20, for example, system frequency, rate of change of system frequency (for example, amount of change of system frequency per unit time), harmonics included in system voltage Vs, system voltage Examples include the phase of Vs.

  The system frequency, the rate of change of the system frequency, and the phase of the system voltage Vs can be calculated based on, for example, the change over time of the detected value of the system voltage Vs detected by the system voltage detector 18b. For example, the system frequency can be calculated based on the period (zero cross period) in which the polarity (positive / negative) of the detected value of the system voltage Vs is inverted.

  In addition, the harmonics included in the system voltage Vs can be calculated by, for example, fast Fourier transform (FFT). Fast Fourier transform (FFT) is an algorithm for computing discrete Fourier transform at high speed on a computer, and can speed up computation processing for extracting a desired harmonic component from a detected value of system voltage Vs. In addition, although the order of the harmonic to detect is not limited, For example, the 2nd-7th harmonic can be detected. In addition, the harmonics included in the system voltage Vs can be represented by, for example, total harmonic distortion (THD) of these harmonics.

(Control device 16)
As shown in FIG. 2, the control device 16 includes a known central processing unit 16a, a storage device 16b, and an input / output interface 16c, which are electrically connected via a bus 16d. . The control device 16 can perform various arithmetic processes using these, and can exchange input / output signals with an external device.

  The central processing unit 16a is a CPU (Central Processing Unit) and can perform various arithmetic processes. The storage device 16b includes a first storage device 16b1 and a second storage device 16b2. The first storage device 16b1 is a readable / writable volatile storage device (RAM: Random Access Memory), and the second storage device 16b2 is a read-only nonvolatile storage device (ROM: Read Only Memory). is there. The input / output interface 16c exchanges input / output signals with an external device.

  For example, the central processing unit 16a reads the drive control program for the inverter 14 stored in the second storage device 16b2 to the first storage device 16b1, and executes the drive control program. The central processing unit 16a generates a drive signal for the inverter 14 (opening / closing signals of the first switching element 14e to the fourth switching element 14h) based on the drive control program. The generated drive signal is applied to the gates 14e3 to 14h3 of the first switching element 14e to the fourth switching element 14h of the inverter 14 via the input / output interface 16c and the drive circuit 16f. In this way, the inverter 14 is driven and controlled by the control device 16. The same applies to the converter 12, and the converter 12 is driven and controlled by the control device 16. Further, the control device 16 causes the power generation device 1 to be parallel or disconnected from the power system 22 of the system power supply 20.

<Control by grid interconnection control device>
As an example of the protection function in the grid connection, there are an isolated operation detection function and an accident continuation operation (FRT: Fault Ride Through) function. The isolated operation detection function is a function for detecting the isolated operation of the power generation device 1, and disconnects the power generation device 1 from the power system 22 when the isolated operation of the power generation device 1 is detected. Here, the independent operation is a power generation device (for example, the power generation device 1 shown in FIG. 1) that is connected in a state where the power system 22 connected to the plurality of power generation devices is disconnected from the system power supply 20. ) Refers to a state in which power generation is continued only by driving and power is supplied to the premises load. Examples of the disconnection of the power system 22 and the system power source 20 include an accident in the power system and a power failure due to the opening of a relay for the purpose of maintenance.

  On the other hand, the operation continuation function at the time of an accident is a function that suppresses the simultaneous disconnection of a plurality of power generation devices connected to the power system due to disturbance of the power system. The operation of the power generator 1 is continued with respect to the frequency fluctuation. Thereby, the system voltage Vs and the system frequency can be stabilized, and the power quality can be ensured. In addition, the operation continuation requirement at the time of an accident means the requirement to continue the driving | operation of the electric power generating apparatus 1 with respect to the disturbance of the electric power system mentioned above, for example, the requirements defined by a grid connection rule (JEAC 9701-2012) are mentioned. .

  Thus, the isolated operation detection function disconnects the power generation apparatus 1 from the power system 22, whereas the accident-time operation continuation function continues the operation of the power generation apparatus 1. Therefore, the isolated operation detection function and the accident operation continuation function are contradictory functions, and there is concern about these control interferences. In particular, there is a concern that the accident-time operation continuation function malfunctions in a situation where the isolated operation detection function should operate.

  FIG. 3A is a diagram illustrating an example of the voltage drop withstand capability in relation to the operation continuation requirement at the time of an accident. A curve L11 shows an example of a voltage drop tolerance of the system voltage Vs. The vertical axis represents the remaining voltage when the effective value of the system voltage Vs at time t0 when the system voltage Vs starts to decrease is 100%, and the horizontal axis represents the time. A region R11 indicates a region in which the voltage drop time is equal to or less than the predetermined time TP1 from time t0 to time t1, and the remaining voltage is V1% or more. In the region R11, as a general rule, the operation of the power generator 1 is continued. A region R12 indicates a region where the voltage drop time is equal to or less than the predetermined time TP1 from time t0 to time t1, and the remaining voltage is less than V1%. In the region R12, as a rule, the operation of the power generator 1 is continued or the gate block (the output of the inverter 14 is stopped). When the voltage drop continues for a predetermined time TP1 or more, in principle, the power generator 1 is disconnected from the power system 22.

  For example, it is assumed that a power failure occurs in the power system 22 in which a plurality of power generation devices are connected. It is assumed that, for example, the detection of the single operation of one power generation apparatus is delayed due to the variation in the detection of the single operation of the plurality of power generation apparatuses. In this case, the system voltage Vs decreases because the majority of the power generation devices are disconnected from the power system 22, but the AC power supplied from the power generation device for which the detection of the isolated operation is delayed causes a state similar to the instantaneous power failure ( For example, there is a possibility that the state of the region R12 in which the voltage drop time is equal to or less than the predetermined time TP1 and the remaining voltage is less than V1%. For this reason, in the power generation device in which the detection of the isolated operation is delayed, the operation continuation function during an accident may malfunction, and it may be difficult to detect the isolated operation.

  The same can be said for the frequency fluctuation tolerance. FIG. 3B is a diagram illustrating an example of the step-up frequency variation tolerance in relation to the accident continuation requirement. A curve L21 shows an example of a frequency fluctuation tolerance when the system frequency is stepped up. The vertical axis represents frequency, and the horizontal axis represents time. The region R21 indicates a region where the upper limit value of the step increase with respect to the rated frequency F0 (for example, 50 Hz or 60 Hz) is the frequency F11 and the frequency increase time is equal to or less than the predetermined time TP2 from the time t0 to the time t2. In area | region R21, the driving | operation of the electric power generating apparatus 1 is continued. Note that when at least one of the increase in frequency is equal to or higher than the frequency F11 and the increase in frequency is continued for a predetermined time TP2 or more is established, the power generation device 1 is disconnected from the power system 22.

  FIG. 3C is a diagram illustrating an example of a frequency fluctuation tolerance of ramp up or ramp down in relation to the requirement for continuation of operation during an accident. The vertical axis represents frequency, and the horizontal axis represents time. A curve L31a indicates the upper limit of the rate of change in lamp rise (for example, the amount of increase in frequency per unit time). Further, the upper limit value of the frequency is the frequency F21, and can be set to a set value of a frequency increasing relay (OFR), for example. A curve L31b indicates the lower limit of the rate of change in ramp drop (for example, the amount of decrease in frequency per unit time). Further, the lower limit value of the frequency is the frequency F22, and can be, for example, a settling value of a frequency lowering relay (UFR). As in FIG. 3B, the rated frequency is indicated by the rated frequency F0.

  A region R31 indicates a region surrounded by the curves L31a and L31b. In area | region R31, the driving | operation of the electric power generating apparatus 1 is continued. That is, when the frequency change rate is larger than the slope indicated by the curve L31b and smaller than the slope indicated by the curve L31a, the operation of the power generator 1 is continued. However, the frequency is not less than the frequency F22 and not more than the frequency F21. When the change with time in frequency deviates from the region indicated by region R <b> 31, power generation device 1 is disconnected from power system 22.

  As in the case of the voltage drop tolerance shown in FIG. 3A, it is assumed that, for example, the detection of the single operation of one power generation apparatus is delayed due to the variation in the detection of the single operation of the plurality of power generation apparatuses. In this case, since the majority of the power generation devices are disconnected from the power system 22, the frequency changes suddenly. However, the sudden change in frequency is suppressed by the AC power supplied from the power generation device whose detection of the isolated operation is delayed. As a result, the frequency may change with time in the region R21 shown in FIG. 3B. The same applies to the frequency fluctuation tolerance shown in FIG. 3C, and the frequency may change over time in the region R31. For this reason, in the power generation device in which the detection of the isolated operation is delayed, the operation continuation function during an accident may malfunction, and it may be difficult to detect the isolated operation. Therefore, when the instantaneous power failure occurs in the power system 22 to which the power generator 1 is connected, the grid interconnection control device of the present embodiment suppresses the malfunction of the operation continuation function at the time of the accident and detects the isolated operation. Improve accuracy.

(Configuration of each control unit)
As shown in FIG. 4, the control device 16 includes an isolated operation detection sensitivity changing unit 41 and an isolated operation detection unit 42 when viewed as a control block. Further, the control device 16 executes the control program according to the flowchart shown in FIG. The isolated operation detection sensitivity changing unit 41 performs the determination of step S11 and the processing of step S12 and step S13. The isolated operation detection unit 42 performs the determination in step S14 and the process in step S15. Hereinafter, each control unit and control flow will be described in detail with reference to FIGS.

(Single operation detection sensitivity changing unit 41)
The isolated operation detection sensitivity changing unit 41 detects the isolated operation of the power generation device 1 when an instantaneous power failure occurs in the power system 22 to which the power generation device 1 is connected, compared to the case where no instantaneous power failure occurs. At least one of the detection threshold TH and the detection time TD at the time of performing is lowered to increase the detection sensitivity of the isolated operation.

  Specifically, the isolated operation detection sensitivity changing unit 41 determines whether or not an instantaneous power failure has occurred in the power system 22 to which the power generator 1 is connected (step S11 shown in FIG. 5). The method for detecting an instantaneous power failure is not limited. The isolated operation detection sensitivity changing unit 41 preferably determines that an instantaneous power failure has occurred when the effective value of one cycle of the system voltage Vs or the effective value of the half cycle of the system voltage Vs becomes less than a predetermined voltage value. . The predetermined voltage value can be set, for example, to a voltage level included in the region R12 illustrated in FIG. 3A. That is, the predetermined voltage value can be set to a voltage level equivalent to the operating condition of the operation continuation function during an accident. In addition, a predetermined voltage value when determining the effective value of one cycle of the system voltage Vs is a first voltage value, and a predetermined voltage value when determining the effective value of a half cycle of the system voltage Vs is a second voltage value. . At this time, it is preferable that the first voltage value is set smaller than the second voltage value.

  When determining whether or not an instantaneous power failure has occurred based on the effective value of one period of the system voltage Vs, the calculation load associated with calculating the effective value is reduced compared to determining based on the effective value of the half period of the system voltage Vs. This makes it easy to grasp voltage fluctuations over a plurality of periods of the system voltage Vs. On the other hand, when determining whether or not an instantaneous power failure has occurred based on the effective value of the half cycle of the system voltage Vs, a steep instantaneous power failure during one cycle of the system voltage Vs (for example, the remaining of the system voltage Vs within the half cycle). (When the voltage disappears) can be detected quickly.

  According to the grid interconnection control device of the present embodiment, the isolated operation detection sensitivity changing unit 41 is configured such that the effective value of one cycle of the system voltage Vs or the effective value of the half cycle of the system voltage Vs becomes less than a predetermined voltage value. It is determined that an instantaneous power failure occurred. Therefore, the isolated operation detection sensitivity changing unit 41 can appropriately determine the presence or absence of the instantaneous power failure in the power system 22 according to the calculation load accompanying the effective value calculation and the required detection accuracy of the instantaneous power failure.

  When the instantaneous power failure has not occurred (Yes in step S11), the detection threshold value TH when detecting the independent operation of the power generator 1 is set to the detection threshold value TH0. Further, the detection time TD when detecting the independent operation of the power generator 1 is set to the detection time TD0 (step S12). On the other hand, when an instantaneous power failure occurs (in the case of No in step S11), the isolated operation detection sensitivity changing unit 41 detects when detecting the isolated operation of the power generator 1 as compared to the case where no instantaneous power failure occurs. At least one of the threshold value TH and the detection time TD is lowered to increase the detection sensitivity of the isolated operation. When an instantaneous power failure occurs, by increasing the detection sensitivity of the isolated operation, it becomes easier to detect the isolated operation of the power generator 1 before the accident-time operation continuation function malfunctions.

  In the present embodiment, the isolated operation detection sensitivity changing unit 41 reduces both the detection threshold value TH and the detection time TD when an instantaneous power failure occurs (step S13). The detection threshold that has been lowered and changed by the isolated operation detection sensitivity changing unit 41 is defined as a detection threshold TH1. In addition, the detection time that is lowered and changed by the isolated operation detection sensitivity changing unit 41 is set as a detection time TD1. The detection threshold value TH1 and the detection time TD1 are such that, when an instantaneous power failure occurs in the power system 22, the operation continuation function during an accident does not malfunction, and single operation can be detected, for example, by simulation, verification by an actual machine, It is good to obtain in advance. The detection threshold value TH1 can be, for example, 90%, 85%, 80%, 75%, or 70% of the detection threshold value TH0. Further, the detection time TD1 can be set to 90%, 85%, 80%, 75%, or 70% of the detection time TD0, for example.

  Note that the detection threshold value TH1 and the detection time TD1 are preferably set according to the detection target when the single operation of the power generation device 1 is detected. The detection target is preferably a physical quantity (system frequency, rate of change of system frequency, system voltage Vs, harmonics included in system voltage Vs, phase of system voltage Vs) related to the AC power of the system power supply 20 described above. . The detection threshold TH1 and the detection time TD1 may be acquired in advance according to these detection targets, for example, by simulation, verification with an actual machine, or the like.

(Single operation detection unit 42)
The isolated operation detection unit 42 determines whether or not the generator 1 is operated independently (step S14 shown in FIG. 5). The method for detecting an isolated operation is not limited. The isolated operation detection unit 42 can detect the isolated operation of the power generator 1 by various known methods. As a detection method for an isolated operation, there are a passive method and an active method. In the passive method, for example, the single operation of the power generation device 1 is detected by detecting a sudden change in the voltage phase, the frequency, or the like when the power generation device 1 shifts to the single operation. Examples of the passive method include a voltage phase jump detection method, a third harmonic voltage distortion rapid increase detection method, and a frequency change rate detection method.

  On the other hand, in the active method, fluctuations such as voltage and frequency are periodically given to the control system of the power converter 11 (inverter 14), the external resistor, and the like, and the power generator 1 shifts to the single operation. By detecting a sudden change in these fluctuation ranges, the single operation of the power generator 1 is detected. Examples of the active method include a frequency shift method, an active power fluctuation method, a reactive power fluctuation method, a load fluctuation method, and a frequency feedback method with step injection. In addition, it is preferable that the isolated operation detection unit 42 detects the isolated operation of the power generator 1 by combining one or more of the passive method and the active method.

  When the isolated operation of the power generation device 1 is detected (Yes in step S14), the isolated operation detection unit 42 disconnects the power generation device 1 from the power system 22 (step S15). And control is once complete | finished. On the other hand, when the isolated operation of the power generation device 1 is not detected (No in step S14), the control is temporarily terminated. The control program is repeatedly executed every predetermined time.

  The single operation detection unit 42 determines that the power generation device 1 is in a single operation when at least one of the first condition and the second condition is satisfied, and disconnects the power generation device 1 from the power system 22. It is preferable to do so. The first condition is that the change amount ΔD of the detected value of the physical quantity related to the AC power of the system power supply 20 immediately after the instantaneous power failure occurs is equal to or greater than the detection threshold TH1 changed by the isolated operation detection sensitivity changing unit 41. The second condition means that the increase or decrease in the detected value of the physical quantity related to the AC power of the system power supply 20 immediately after the occurrence of the instantaneous power failure continues for the detection time TD1 changed by the isolated operation detection sensitivity changing unit 41.

  Further, the physical quantity related to the AC power of the system power supply 20 is at least one of the system frequency and the rate of change of the system frequency, the system voltage Vs, the harmonics included in the system voltage Vs, and the phase of the system voltage Vs. Is preferred. Hereinafter, a system frequency will be described as an example of a physical quantity related to AC power of the system power supply 20. The system frequency is an object to be detected when an isolated operation is detected by a frequency shift method, a frequency feedback method with step injection, or the like.

  As shown in FIG. 6, the isolated operation detection unit 42 has a plurality (20 in this embodiment) of continuous storage areas (M1) that store detection values of the system frequency in the first storage device 16b1 shown in FIG. To M20). The storage areas (M1 to M20) are configured in, for example, a first-in first-out (FIFO) system.

  Specifically, the detection value of the system frequency detected by the system voltage detector 18b is first stored in the storage area M1. Next, when the detection value of the system frequency is detected by the system voltage detector 18b, the detection value of the system frequency stored in the storage area M1 is moved to the storage area M2. Then, the newly detected detection value of the system frequency is stored in the storage area M1. Next, when the detection value of the system frequency is detected by the system voltage detector 18b, the detection value of the system frequency stored in the storage area M2 is moved to the storage area M3 and stored in the storage area M1. The detected value of the system frequency is moved to the storage area M2. Then, the newly detected detection value of the system frequency is stored in the storage area M1. This is repeated every time a detection value of the system frequency is detected.

  In all the storage areas (M1 to M20), when the detection value of the system frequency is detected by the system voltage detector 18b after the detection value of the system frequency is stored, the storage area that is the oldest detection value The detection value of the system frequency stored in M20 is discarded, and the detection value of the system frequency stored in the storage area M19 which is the next oldest detection value is moved to the storage area M20. Similarly, the detection values of the system frequency stored in the storage areas M18 to M1 are also moved one by one. Then, the newly detected detection value of the system frequency is stored in the storage area M1. This is repeated every time a detection value of the system frequency is detected.

  In addition, after averaging the detection values of a plurality of system frequencies (for example, 10) to calculate the average value, the average value can be stored in the storage area M1. Next, when the average value of the detected values of a plurality (10) of system frequencies is calculated, the average value of the detected values of the plurality (10) of system frequencies stored in the storage area M1 is stored in the storage area M2. Moved to. Then, the newly calculated average value of the detected values of a plurality of (ten) system frequencies is stored in the storage area M1. Thereafter, in the same manner as described above, the average value of the detected values of a plurality of (10) system frequencies can be stored in the storage area (M1 to M20).

  The isolated operation detection unit 42 calculates the change amount ΔD of the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20. The method for calculating the change amount ΔD is not limited. It is preferable that the isolated operation detection unit 42 subtracts the second moving average value Fave2 from the first moving average value Fave1 to calculate the change amount ΔD of the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20. .

  As shown in FIG. 6, the first moving average value Fave1 is a physical quantity (system frequency) related to AC power of the system power supply 20 that is sequentially detected from the reference time t30 to the first time t31 after the first time T1 has elapsed. This is a moving average of a plurality (10 in this embodiment) of detected values. The second moving average value Fave2 is a plurality of physical quantities (system frequencies) related to AC power of the system power supply 20 sequentially detected from the first time t31 to the second time t32 when the same time as the first time T1 has elapsed. In the embodiment, it means a moving average of 10 detection values.

  In the example illustrated in FIG. 6, the isolated operation detection unit 42 calculates a moving average of detection values of a plurality (10) of system frequencies stored in the storage area (M11 to M20), and sets the calculation result as the first. The moving average value is Fave1. In addition, the isolated operation detection unit 42 calculates a moving average of detection values of a plurality of (10) system frequencies stored in the storage areas (M1 to M10), and the calculation result is referred to as a second moving average value Fave2. To do.

  The moving average described above is not limited as long as time series data can be smoothed. For example, the moving average may be a simple moving average that does not weight individual data or may be a weighted moving average that weights individual data. The weighted moving average may be a linear weighted moving average or an exponential weighted moving average. In the linear weighted moving average, the weight of the newest data is the heaviest, and the weight is decreased in order as the old data becomes old, and the weight of the oldest data is set to zero. The exponential weighted moving average exponentially reduces the weight of the linear weighted moving average. Furthermore, the weighting of the individual data can be selected in accordance with the change in the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20. For example, the weight of data in a region where the variation in the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20 is large is weighted, and the variation in the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20 is small It is possible to reduce the weight of the data.

  In the present embodiment, the isolated operation detection unit 42 subtracts the second moving average value Fave2 from the first moving average value Fave1 to obtain the change amount ΔD of the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20. calculate. And the independent operation detection part 42 judges that it is the independent operation of the electric power generating apparatus 1 when at least one of the first condition and the second condition is satisfied, and determines the electric power generating apparatus 1 from the electric power system 22. Disconnect. First, the first condition will be described. As described above, the first condition is that the change amount ΔD of the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20 immediately after the instantaneous power failure occurs is changed by the isolated operation detection sensitivity changing unit 41. It means that it is more than the detection threshold TH1.

  FIG. 7 is a diagram illustrating an example of a change over time of a detected value of a physical quantity (system frequency) related to AC power of the system power supply 20. A curve L41 shows an example of a change over time of a physical quantity (system frequency) related to the AC power of the system power supply 20 in the case of a normal power failure (when the frequency variation is fast). A curve L42 shows an example of a change over time of a physical quantity (system frequency) related to the AC power of the system power supply 20 in the case of an instantaneous power failure (when the frequency fluctuation is slow). In either case, it is assumed that the frequency starts to change at time t0. The vertical axis indicates the frequency, and the horizontal axis indicates the time.

  First, as shown by a curve L41, a case of a normal power failure (a case where a change in frequency is fast) is assumed. At this time, the change amount ΔD of the detected value of the system frequency during the period from time t0 to time t41 is set as the change amount ΔD0. Further, the change amount ΔD of the detected value of the system frequency during the period from time t41 to time t42 is set as a change amount ΔD1. The amount of change ΔD1 is assumed to be larger than the amount of change ΔD0. Furthermore, it is assumed that the detection threshold value TH0 when detecting the independent operation of the power generation device 1 is set to the same value as the change amount ΔD1. In this case, the isolated operation detection unit 42 detects the isolated operation of the power generator 1 when the change amount ΔD of the detected value of the system frequency becomes equal to or greater than the change amount ΔD1 (that is, at time t42).

  Next, it is assumed that the detection threshold TH is not lowered or changed by the isolated operation detection sensitivity changing unit 41 in the case of an instantaneous power failure (when the frequency fluctuation is slow) (comparative form). At this time, as indicated by a curve L42, the change amount ΔD of the detected value of the system frequency during the period from time t43 to time t44 is set as a change amount ΔD0. Further, the change amount ΔD of the detected value of the system frequency during the period from time t44 to time t45 is defined as a change amount ΔD1. The relationship between the change amount ΔD0, the change amount ΔD1, and the detection threshold value TH0 is the same as that described above. In this case, the isolated operation detection unit 42 detects the isolated operation of the power generator 1 when the change amount ΔD of the detected value of the system frequency becomes equal to or greater than the change amount ΔD1 (that is, at time t45). The time from the time t0 to the time t45 is longer than the time from the time t0 to the time t42, and the accident-time operation continuation function may malfunction before the isolated operation detection unit 42 detects the isolated operation of the power generator 1. There is sex.

  Next, it is assumed that the detection threshold TH is lowered and changed by the isolated operation detection sensitivity changing unit 41 in the case of an instantaneous power failure (when the frequency fluctuation is slow) (this embodiment). As described above, when the instantaneous power failure occurs, the isolated operation detection sensitivity changing unit 41 lowers the detection threshold value TH when detecting the isolated operation of the power generator 1 and changes the detection threshold value TH1. For example, the detection threshold value TH1 is set to the same value as the above-described change amount ΔD0. In this case, the isolated operation detecting unit 42 changes the detected value change ΔD of the physical quantity (in this case, the system frequency) related to the AC power of the system power supply 20 immediately after the occurrence of the instantaneous power failure by the isolated operation detection sensitivity changing unit 41. When the first condition that is equal to or greater than the detected threshold value TH1 (change amount ΔD0) is satisfied (that is, at time t44), the single operation of the power generator 1 is detected.

  It can be seen that the time from time t0 to time t44 is shorter than the time from time t0 to time t45, and the isolated operation detection sensitivity changing unit 41 increases the isolated operation detection sensitivity of the power generator 1. By setting the detection threshold TH1 to be smaller than the change amount ΔD0, it is possible to further reduce the time required to detect the isolated operation of the power generation apparatus 1. That is, the time until detecting the single operation of the power generator 1 can be set to a time equivalent to or less than that in the case of the normal power failure shown in the curve L41 (when the frequency change is fast). Therefore, the isolated operation detection unit 42 can easily detect the isolated operation of the power generator 1 before the accident-time operation continuation function malfunctions.

  The same can be said for the second condition. As described above, in the second condition, the increase or decrease in the detected value of the physical quantity (system frequency) related to the AC power of the system power supply 20 immediately after the occurrence of the instantaneous power failure is changed by the isolated operation detection sensitivity changing unit 41. It means to continue for the detection time TD1 or more. In the example described above, the detection time TD0 when detecting the single operation of the power generation device 1 corresponds to the time from time t0 to time t42. The detection time TD1 when detecting the independent operation of the power generator 1 when an instantaneous power failure occurs is set shorter than the detection time TD0. Thereby, the isolated operation detection part 42 becomes easy to detect the isolated operation of the electric power generating apparatus 1 before the operation continuation function at the time of an accident malfunctions.

  FIG. 7 shows an example when the detected value of the system frequency decreases. As an example of the case where the detection value of the system frequency increases, there is a case where only the delayed reactive current flows into the open point (not shown) of the power system 22. Since the inverter 14 is controlled by a power factor of 1, no reactive power is output from the inverter 14 (it is 0). Therefore, in order to eliminate the reactive power imbalance, the inverter 14 needs to increase the frequency to increase the reactance of the load 30 and reduce the delayed reactive power consumed by the load 30. In this case, the detected value of the system frequency increases for a certain time after the shift to the independent operation.

  In addition, the above can be similarly applied to the case where the physical quantity related to the AC power of the system power supply 20 is the rate of change of the system frequency, the system voltage Vs, the harmonics included in the system voltage Vs, or the phase of the system voltage Vs. That is, when an instantaneous power failure occurs, these changes are smaller than in a normal power failure. Therefore, the isolated operation detection unit 42 can detect the isolated operation of the power generator 1 in the same manner as in the case of the system frequency.

  According to the grid interconnection control device of the present embodiment, the control device 16 includes the isolated operation detection sensitivity changing unit 41. For this reason, the grid interconnection control device of the present embodiment can increase the detection sensitivity of an isolated operation when an instantaneous power failure occurs in the power system 22 to which the power generation device 1 is linked. It is possible to easily detect the single operation of the power generation device 1 before the malfunction occurs. That is, the grid interconnection control apparatus of the present embodiment can improve the detection accuracy of the isolated operation by suppressing the malfunction of the accident-time operation continuation function.

  Further, according to the grid interconnection control device of the present embodiment, the control device 16 includes the isolated operation detection unit 42. Therefore, the grid interconnection control apparatus of the present embodiment uses at least one of the detection threshold TH1 and the detection time TD1 changed by the isolated operation detection sensitivity changing unit 41 when an instantaneous power failure occurs in the power system 22. Thus, the single operation detection unit 42 can determine the single operation of the power generator 1. And the grid connection control apparatus of this embodiment can disconnect the electric power generating apparatus 1 from the electric power system 22, when the independent operation detection part 42 judges that it is an independent operation of the electric power generating apparatus 1. FIG.

  Furthermore, according to the grid interconnection control apparatus of the present embodiment, the isolated operation detection unit 42 subtracts the second moving average value Fave2 from the first moving average value Fave1 to detect a physical quantity related to the AC power of the system power supply 20. A change amount ΔD of the value is calculated. Therefore, the grid interconnection control apparatus according to the present embodiment has a wider range (twice the first time T1 than the case where the change amount ΔD is calculated from a plurality of detection values sequentially detected at the first time T1, for example. The change amount ΔD can be calculated using a plurality of detected values of (time). Therefore, the grid interconnection control apparatus of the present embodiment can reduce the influence of disturbance due to noise or the like, and can improve the detection accuracy of the single operation of the power generation apparatus 1.

  Further, according to the system interconnection control device of the present embodiment, the physical quantity related to the AC power of the system power supply 20 includes the system frequency and the rate of change of the system frequency, the system voltage Vs, the harmonics included in the system voltage Vs, and the system It is at least one of the phases of the voltage Vs. Therefore, the isolated operation detection unit 42 can determine the isolated operation of the power generation device 1 using at least one of the physical quantities normally detected in the grid interconnection control. In addition, when the single operation detection unit 42 determines the single operation of the power generation device 1 using a plurality of types of physical quantities, the single operation detection unit 42 determines that the single operation of the power generation device 1 is determined using one type of physical quantity. Erroneous detection can be reduced, and the detection accuracy of isolated operation can be further improved. In this case, the isolated operation detection unit 42 determines that the generator 1 is in the isolated operation when at least one of the first condition and the second condition is satisfied for each of the plurality of types of physical quantities. The power generator 1 is disconnected from the power system 22.

  Furthermore, when the load 30 is an inductive load (for example, an electric motor, a transformer, etc.), the physical quantity related to the AC power of the system power supply 20 is preferably a harmonic contained in the system frequency and the system voltage Vs. In this case, the isolated operation detection unit 42 is the isolated operation of the power generator 1 when both the first condition and the second condition are satisfied for each of the harmonics included in the system frequency and the system voltage Vs. It is preferable that the power generation device 1 be disconnected from the power system 22 by determining that

  For example, when a step-out (out-of-synchronization) occurs in a synchronous motor that is an inductive load, the frequency hunts, and depending on only the amount of change in system frequency and the duration of change, the single operation of the power generator 1 is appropriately detected May not be possible. As a result, it may be difficult to detect the isolated operation of the power generation device 1 within a predetermined time and disconnect the power generation device 1 from the power system 22.

  According to the grid interconnection control device of this embodiment, the load 30 is an inductive load, and the physical quantity related to the AC power of the grid power supply 20 is a harmonic contained in the grid frequency and the grid voltage Vs. Further, the isolated operation detection unit 42 is in the isolated operation of the power generator 1 when both the first condition and the second condition are satisfied for each of the harmonics included in the system frequency and the system voltage Vs. Determination is made to disconnect the power generation device 1 from the power system 22. Therefore, the isolated operation detection unit 42 can improve the detection accuracy of the isolated operation of the power generator 1 when the load 30 is an inductive load.

<Others>
The present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention. For example, the control of the grid interconnection control device can include various arithmetic processes in addition to the processes and determinations shown in FIG. The grid interconnection control device according to the present invention can also be applied to multiphase (for example, three-phase) system power supplies and inverters.

1: power generation device, 10: power supply, 11: power converter, 16: control device,
20: System power supply, 22: Power system,
30: load,
41: Isolated operation detection sensitivity changing unit, 42: Isolated operation detection unit,
TH0, TH1: detection threshold, TD0, TD1: detection time,
ΔD0, ΔD1: The amount of change in the detected value of the physical quantity related to the AC power of the system power supply 20.

Claims (6)

A power generator comprising: a power source; and a power converter that converts power output from the power source into AC power and outputs the AC power to a load connected to the system power source;
A control device for paralleling or disconnecting the power generation device with respect to the power system of the system power supply;
A grid interconnection control device comprising:
When the control device detects an isolated operation of the power generation device when an instantaneous power failure occurs in the power system to which the power generation device is connected, compared to a case where the instantaneous power failure does not occur. A grid interconnection control apparatus including an isolated operation detection sensitivity changing unit that increases at least one of a detection threshold and a detection time to increase the detection sensitivity of the isolated operation.   The independent operation detection sensitivity changing unit determines that the instantaneous power failure has occurred when an effective value of one cycle of the system voltage or an effective value of a half cycle of the system voltage becomes less than a predetermined voltage value. The grid interconnection control apparatus described.   The first condition that the amount of change in the detected value of the physical quantity related to the AC power of the system power supply immediately after the instantaneous power failure occurs is equal to or greater than the detection threshold changed by the isolated operation detection sensitivity changing unit, and the instantaneous power failure At least one of the second conditions in which the increase or decrease in the detected value of the physical quantity related to the AC power of the system power supply immediately after the occurrence continues for the detection time changed by the isolated operation detection sensitivity changing unit is satisfied. 3. The grid interconnection control device according to claim 1, further comprising: an isolated operation detection unit that determines that the power generation device is in the isolated operation and disconnects the power generation device from the power system.   From the first moving average value that is a moving average of a plurality of detected values of physical quantities related to the AC power of the system power supply sequentially detected from the reference time to the first time after the first time has passed. A second moving average value that is a moving average of a plurality of detected values of physical quantities related to AC power of the system power supply sequentially detected from the first time to a second time after the same time as the first time. The grid interconnection control apparatus according to claim 3, wherein the change amount of the detected value of the physical quantity related to the AC power of the grid power supply is calculated by subtraction.   The physical quantity related to the AC power of the system power supply is at least one of a system frequency and a rate of change of the system frequency, a system voltage, a harmonic included in the system voltage, and a phase of the system voltage. 4. The grid interconnection control device according to 4. The load is an inductive load;
The physical quantity related to the AC power of the system power supply is the harmonics included in the system frequency and the system voltage,
The islanding detection unit is configured to perform the islanding operation of the power generator when both of the first condition and the second condition are satisfied for the harmonics included in the grid frequency and the grid voltage. The grid interconnection control apparatus according to claim 5, wherein the grid interconnection control apparatus is configured to determine that the power generation apparatus is present and to disconnect the power generation apparatus from the power system.

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