JP2020018028A - Electrical power system - Google Patents

Abstract

To dispense with a dedicated electric power conversion device for detecting individual operation in an electrical power system performing an uninterruptible power supply function and a load leveling function of a constant commercial-power feeding type using a common dispersion type power source.SOLUTION: In an electrical power system 100 performing an uninterruptible power supply function and a load leveling function of a constant commercial-power feeding type using a common dispersion type power source 2, the dispersion type power source 2 generates an active signal for actively detecting individual operation, and has tolerance dose with respect to the range of an inactive area of a linkage protection element against voltage and frequency of a commercial power system 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply system.

  The power supply system has an uninterruptible power supply system that disconnects from the commercial power system and compensates for important loads in response to a power failure or instantaneous voltage drop (hereinafter also referred to as an instantaneous voltage drop). It is classified as a distributed power supply system that realizes load leveling such as cut / peak shift.

  In recent years, due to the high performance of storage batteries and the like, particularly in a storage battery system having a large capacity (500 kW capacity class or more), a battery system having both an uninterruptible power supply function and a load leveling function is being considered. For example, as shown in Patent Literature 1, a secondary battery system having both an uninterruptible power supply function and a load leveling function has been considered. This system is configured to supply power to an important load by disconnecting from a power failure or a sag.

  By the way, the number of distributed power sources connected to the commercial power system is increasing, and if these distributed power sources are disconnected at the same time during a sag, the maintenance of the voltage and frequency of the entire commercial power system will be greatly affected. Could give. For this reason, there is a demand for continuous operation of the distributed power supply without disconnection from the commercial power system even during an instantaneous sag (the requirement for continuation of operation during an accident (FRT)).

  However, in the above-described power supply system, the FRT requirement cannot be satisfied because the power supply system is disconnected at the moment of voltage sag. Further, as shown in Patent Document 2, it is conceivable to use a storage battery for an uninterruptible power supply and a storage battery for load leveling in a power supply system to individually perform each function, but cost and size are reduced. Will increase. Further, when there is a reverse power flow in load leveling, a power converter for generating an active signal for detecting islanding operation in an active manner is separately required, and this addition increases the cost. Would.

Japanese Patent No. 3402886 JP 2004-289980 A

  Therefore, the present invention has been made to solve the above problems, and in a power supply system in which an uninterruptible power supply function and a load leveling function of a regular commercial power supply system are compatible using a common distributed power supply, an isolated operation is performed. It is a main object of the present invention to eliminate the need for a dedicated power converter for generating an active signal for detection.

That is, a power supply system according to the present invention is a power supply system provided between a commercial power system and an important load and supplying power to the important load, and a power line for supplying power from the commercial power system to the important load. A distributed power supply connected to the power line, a switch provided on the commercial power system side of the distributed power supply in the power line, and a switch for opening and closing the power line, and an impedance element connected in parallel to the switch in the power line. A system-side voltage detection unit that detects the voltage of the commercial power system than the changeover switch, and a system abnormality detection unit that detects a system abnormality of the commercial power system from a detection voltage of the system-side voltage detection unit. The changeover switch is opened based on the system abnormality detected by the system abnormality detection unit, and the distributed power supply and the commercial power system are A control unit connected via an impedance element, wherein the distributed power supply continues operation including reverse power flow in a state where the distributed power supply and the commercial power system are connected via the impedance element. Wherein the distributed power supply generates an active signal for detecting islanding operation in an active manner, and the range of the inoperative area of the interconnection protection element with respect to the voltage and frequency of the commercial power system is Characterized by having a withstand capability.
Here, the non-operation area of the grid connection protection element is defined as overvoltage (OV), undervoltage (UV), overfrequency (OF), and underfrequency (UF) which are protection elements for localization of islanding operation. This is a non-operation area.

With such a power supply system, a changeover switch is provided on the commercial power system side of the distributed power supply in the power line, and an impedance element is connected in parallel to the changeover switch, and the changeover switch is detected by the system abnormality detection unit. Since the changeover switch is opened based on the system abnormality, even when the system is abnormal, the demand-side facility is connected to the commercial power system via the impedance element.
According to the present invention, the demand-side equipment is connected to the commercial power system via the impedance element with respect to the system abnormality including the instantaneous voltage drop and the frequency fluctuation, and while satisfying the FRT requirement of the distributed power supply, It is possible to prevent a voltage drop and a frequency fluctuation to an important load at the time. As a result, the uninterruptible power supply function and the load leveling function can be compatible using the common distributed power supply while satisfying the FRT requirement.
In particular, in the present invention, the distributed power supply generates an active signal for detecting the islanding operation in an active manner, so that a dedicated power converter for generating the active signal can be omitted. As a result, it is possible to achieve both the distributed power supply function with reverse power flow and the uninterruptible power supply function for important loads while reducing costs and installation locations.
In addition, since the distributed power supply has a tolerance to the range of the inoperative region of the interconnection protection element with respect to the voltage and frequency of the commercial power system, the operation including the reverse power flow of the distributed power supply can be stably performed. .

  It is preferable that the distributed power supply has a tolerance against a step-like or lamp-like change in the range of the non-operating region with respect to the frequency of the commercial power system.

  The controller, when the tolerance of the important load or the distributed power supply to the system abnormality does not satisfy a predetermined settling range, the system abnormality detected by the system abnormality detection unit is the important load or the distributed load. It is desirable to open the changeover switch when the power supply is equal to or more than the tolerance of the power supply to the system abnormality and is within the predetermined settling range.

  In a state in which the distributed power supply and the commercial power system are connected via the impedance element, the distributed power supply is reversed within a range of a smaller tolerance of the important load or the distributed power supply to a system abnormality. It is desirable to continue operation including tidal current.

  According to the present invention configured as described above, in a power supply system in which an uninterruptible power supply function and a load leveling function of an always commercial power supply system are compatible using a common distributed power supply, a dedicated power conversion for detecting an isolated operation is performed. The device can be eliminated.

It is a schematic diagram which shows the structure of the uninterruptible power supply of this embodiment. FIG. 4 is a diagram showing a non-operation area of a protection element for localization of islanding operation. It is a table | surface which shows the list | wrist of the operation | movement state in the interconnection rule protection element of the embodiment. 4 is a table showing a list of operation states according to FRT requirements of the embodiment. It is a figure showing a simulation model of the whole system of the embodiment. It is a figure showing a simulation model of a distributed power supply of the embodiment. It is a simulation result which shows the voltage change at the time of entering into a non-operation area | region of a protection element at the time of islanding operation. It is a simulation result which shows the frequency change at the time of entering into a non-operation area | region of a protection element at the time of an isolated operation. It is a simulation result which shows the modification of an active signal, and the frequency fluctuation at that time. It is a simulation result which shows the voltage change at the time of entering the operation area of a protection element at the time of occurrence of an islanding operation (entering the operation range of a UV element). It is a simulation result which shows the frequency change at the time of entering into the operation area of the protection element (in the case of entering the operation range of the UV element) when the isolated operation occurs.

  Hereinafter, an embodiment of a power supply system according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a power supply system 100 according to the present embodiment is provided between a commercial power system 10 and an important load 30, and supplies power to the important load 30 when the commercial power system 10 is abnormal. (Uninterruptible power supply function), and a function as a distributed power supply system (load leveling function) for load leveling by flowing forward power and reverse power to the commercial power system.

  Here, the commercial power system 10 is a power supply network of a power company (an electric power company) and includes a power plant, a power transmission system, and a power distribution system. In addition, the important load 20 is a load to which power is to be stably supplied even in the event of a system failure such as a power failure or an instantaneous drop, and is one in FIG. 1, but may be plural.

  Specifically, the power supply system 100 includes a distributed power supply 2, a changeover switch 3 connecting the commercial power system 10 to the distributed power supply 2 and the important load 30, an impedance element 4 connected in parallel to the changeover switch 3, A system voltage detector 5 for detecting a voltage on the commercial power system 10 side of the switch 3; a system abnormality detector 6 for detecting a system abnormality from a detected voltage of the system voltage detector 5; A first control unit that opens the changeover switch according to the detection signal.

  The distributed power supply 2 is connected to a power line L1 for supplying power from the commercial power system 10 to the important load 30. The distributed power supply 2 is connected to the commercial power system 10 and includes, for example, a DC power generation facility 21a such as a photovoltaic power generator or a fuel cell and a power converter 22, a secondary battery (storage battery), and the like. That has a power storage device (power storage device) 21b and a power converter 22, rectifies AC output from an AC power source such as wind power generation or a micro gas turbine into DC power, and then uses the power converter to connect the system to the system. It is a power generation facility (not shown) provided with a system or an AC power generation facility 21c such as a synchronous generator or an induction generator. The power supply system 100 may include at least the power storage device 21b, and may include any of the above-described distributed power supplies 2.

  The changeover switch 3 is provided on the commercial power system 10 side of the power line L1 with respect to the connection point of the distributed power supply 2 and opens and closes the power line L1. For example, a semiconductor switch or a combination of a semiconductor switch and a mechanical switch is used. A changeover switch capable of high-speed switching, such as a hybrid switch, can be used. For example, when a semiconductor switch is used, the switching time can be reduced to 2 milliseconds or less, and the switching can be performed regardless of the zero point. Further, when a hybrid switch is used, the switching time can be reduced to 2 milliseconds or less, and the switching can be performed irrespective of the zero point, and the conduction loss can be reduced to zero. The switch 3 is controlled to be opened and closed by the first controller 7.

  The impedance element 4 is connected in parallel to the changeover switch 3 on the power line L1, and in the present embodiment, is a current limiting reactor.

  The system-side voltage detection unit 5 detects a voltage on the power line L <b> 1 on the commercial power system 10 side from the changeover switch 3 via the instrument transformer 51. Specifically, the system-side voltage detection unit 5 is connected to the commercial power system 10 via the instrument transformer 51 rather than the parallel circuit including the changeover switch 3 and the impedance element 4.

  The system abnormality detection unit 6 detects each system abnormality on the commercial power system 10 side from the changeover switch 3 based on the detection voltage detected by the system side voltage detection unit 5. The system abnormalities of the present embodiment include voltage drop including voltage sag, voltage rise, frequency fluctuation, phase fluctuation, voltage imbalance, abnormal harmonic, and flicker.

  Therefore, the system abnormality detecting unit 6 includes a voltage drop detecting unit 61 that detects a voltage drop including an instantaneous voltage drop, and a frequency fluctuation detecting unit 62 that detects a frequency fluctuation.

  The voltage drop detection unit 61 detects a voltage drop by comparing the detection voltage of the system-side voltage detection unit 5 with a predetermined set value. Here, the set value for detecting a voltage drop is a voltage value for detecting an instantaneous voltage drop, and is, for example, a remaining voltage of 20%.

  The frequency fluctuation detection unit 62 detects a frequency fluctuation (frequency rise (OF), frequency decrease (UF)) from the detection voltage of the system-side voltage detection unit 5. The frequency fluctuation is, for example, a step rise or a ramp rise / fall.

  The first control section 7 outputs a control signal to the changeover switch 3 based on each detection signal detected by the system abnormality detection section 6 to open the changeover switch 3. The first control unit 7 of the present embodiment receives the detection signals from the detection units 61 and 62 and opens the changeover switch 3 when any one of the detection signals satisfies the condition (OR condition).

  Specifically, the first control unit 7 determines that the instantaneous sag detected by the voltage drop detecting unit 61 is equal to or greater than the instantaneous sag tolerance when the sag tolerance of the important load 30 or the distributed power supply 2 does not satisfy the predetermined settling range. The switch 3 is opened when it is within the predetermined set range. As a result, the commercial power system 10 is connected to the distributed power supply 2 and the important load 30 via the impedance element 4. In this state, the distributed power supply 2 continues the operation including the reverse power flow.

  In addition, when the frequency fluctuation tolerance of the important load 30 or the distributed power supply 2 does not satisfy the predetermined settling range, the first controller 7 determines that the frequency fluctuation detected by the frequency fluctuation detector 62 is equal to or greater than the frequency fluctuation tolerance. The switch 3 is opened when it falls within the predetermined settling range, whereby the commercial power system 10 is connected to the distributed power supply 2 and the important load 30 via the impedance element 4. In this state, the distributed power supply 2 continues the operation including the reverse power flow.

  The power supply system 100 of the present embodiment has a system interconnection protection function. Specifically, the power supply system 100 detects a protection element for localizing the isolated operation, and opens the power receiving point switch (disconnecting switch) 8 to disconnect it. Protective elements for localization of islanding are overvoltage (OV), undervoltage (UV), frequency rise (OF) and frequency fall (UF).

  The power receiving point switch 8 is, for example, a mechanical switch, and is provided on the power line L1 closer to the commercial power system 10 than the distributed power source 2. In the power supply system 100 of the present embodiment, a power receiving point voltage detection unit 9 that detects a voltage on the commercial power system 10 side of the power receiving point switch 8 on the power line L1 is provided.

  Specifically, the power supply system 100 detects an overvoltage and an undervoltage from the detection voltage detected by the system-side voltage detection unit 5 and determines whether to disconnect the OV / UV disconnection determination unit 111, An OF / UF disconnection determination unit 112 that detects frequency rise and frequency decrease from the detected voltage to determine whether or not to disconnect, and detects and disperses an active signal (disturbance signal) injected into a commercial power system. Method for determining the isolated operation of the distributed power supply 2 by an active method and the voltage and frequency of the commercial power system to detect the isolated operation of the distributed power supply 2 by the passive method. And a passive system disconnection judging section 114.

  In addition, the power supply system 100 has a second control unit 12 that outputs a control signal to the power receiving point switch 8 and opens the power receiving point switch 8 based on each determination signal from the disconnection determination units 111 to 114. are doing. The second control unit 12 of the present embodiment receives the determination signals from the respective parallel-off determination units 111 to 114 and opens the power receiving point switch 8 when any one of the determination signals satisfies a condition (OR condition). . In the present embodiment, a detection signal from a disconnection element detection unit that uses an element other than the line voltage such as a ground fault abnormality is also used for opening / closing control of the power receiving point switch 8.

  Then, the distributed power supply 2 of the present embodiment generates an active signal (disturbance signal) for detecting the islanding operation in an active manner and injects it into the commercial power system. Note that the active system may be a frequency shift system, an active power fluctuation system, or a reactive power fluctuation system.

  Specifically, the power converter 22 as a power conditioner provided in each distributed power supply 2 has a function of generating an active signal. The fluctuation of the detection voltage or the frequency due to the active signal is detected by the active system disconnection judging section 113, and the islanding is detected.

  Here, in the present embodiment, in order to synchronize the active signals generated by the respective distributed power supplies 2 having the plurality of distributed power supplies 2, any one of the distributed power supplies 2 is used as the master power supply, Is configured to transmit a synchronization signal for synchronizing an active signal from the master power supply to the slave power supply.

  As shown in FIG. 2, the distributed power supply 2 is provided with interconnecting protection elements (protection elements (OV, UV, OF, UF) for localization of islanding operation) for the voltage and frequency of the commercial power system. Withstands the range of the non-operating region (the hatched portion in FIG. 2).

  Furthermore, the distributed power supply 2 has a tolerance against a step-like or lamp-like change in the inoperative region of the protection element (OV, UV, OF, UF) for localization of the islanding in the case of frequency fluctuation. . Here, as a sufficient condition, it is sufficient to have a tolerance in a state of a continuous fluctuation time period (0.5 to 1.0) with at least a step fluctuation to the OF set value and the UF set value. Further step changes continue into the operating area of the protection element for localization. Also in the ramp change, the reaching value to the OF set value and the UF set value is the fastest severe change.

  Next, the operation of the distributed power supply 2 as well as the opening / closing control of the changeover switch 3 and the power receiving point switch 8 of each of the control units 7 and 12 will be described with reference to FIGS.

  In the power supply system 100 of the present embodiment, each distributed power supply 2 switches from the interconnection operation mode to the voltage control type independent operation mode by the FRT operation signal or the interconnection protection operation signal.

  The power supply system 100 normally closes the switch 3, and the distributed power supply 2 and the important load 30 are connected to the commercial power system 10 via the switch 3. Although the reactor 4 is connected in parallel with the changeover switch 3, the impedance of the changeover switch 3 is smaller than the impedance of the reactor 4. Exchange power on the side. Peak cut and peak shift can be realized by the reverse power flow by the distributed power supply 2.

(A) Opening / closing control of the power receiving point switch 8 and the changeover switch 3 with respect to the interconnection protection elements (voltage fluctuation, frequency fluctuation) of the system interconnection regulations and operation of the distributed power supply 2

(1) When the size (displacement) of the interconnection protection element is larger than the disconnection requirement ((1) in FIG. 3), the second control unit 12 continues the power receiving point switch 8 and the switching to the timed set value. The switch 3 is opened. At this time, the distributed power supply 2 operates in the independent operation mode. The second control unit 12 may open only the power receiving point switch 8.

(2) When the size (displacement) of the interconnection protection element is smaller than the disconnection requirement ((2) in FIG. 3), the second control unit 12 keeps the power receiving point switch 8 turned on. At this time, the distributed power supply 2 operates in the system interconnection mode.

  In addition, the second control unit 12 determines that the detection voltage of the system-side voltage detection unit 5 eliminates a predetermined disconnection condition, and that the detection voltage of the system-side voltage detection unit 5 and the detection voltage of the power receiving point voltage detection unit 9 are synchronized. When the verification condition is satisfied, the receiving point switch 8 is turned on. Here, the synchronization verification condition is, for example, that the magnitude, frequency, and phase of the voltage of the distributed power supply 2 and the magnitude, frequency, and phase of the voltage of the commercial power system 10 match.

(B) Open / close control of the changeover switch 3 and operation of the distributed power supply 2 with respect to the elements (voltage sag and frequency fluctuation) described in the FRT requirements of the system interconnection regulations

(1) A case in which the system abnormal tolerance (withstand voltage sagging, frequency fluctuation tolerance) of the distributed power supply 2 and the important load 30 satisfies the range (predetermined settling range) of the FRT requirement, and the change of the interconnection protection element is In the case of being within the range of the FRT requirement ((1) in FIG. 4), the first control unit 7 maintains the state where the changeover switch 3 is turned on. At this time, the distributed power supply 2 follows the system abnormality (voltage sag, frequency fluctuation) of the commercial power system 10 and continuously operates in the interconnection operation mode.

(2) A case where at least one of the distributed power source 2 and the important load 30 does not satisfy the range of the FRT requirement in the system abnormal tolerance (voltage sag tolerance, frequency variation tolerance), and the change of the interconnection protection element causes the critical load 30 to fail. Alternatively, when the withstand voltage of the interconnection protection element of the distributed power source 2 is smaller than the withstand voltage of the smaller of the interconnection protection elements ((2) in FIG. 4), the first control unit 7 maintains the state in which the changeover switch 3 is turned on. I do. At this time, the distributed power supply 2 continuously operates in the interconnection operation mode following changes in the interconnection protection elements (voltage fluctuations, frequency fluctuations).

(3) A case where at least one of the distributed power supply 2 and the important load 30 does not satisfy the range of the FRT requirement for the system abnormality tolerance (voltage sag tolerance, frequency variation tolerance), and the change of the interconnection protection element is smaller. In this case, the first control unit 7 opens the changeover switch 3 when it is equal to or more than the interconnection protection element tolerance and is within the range of the FRT requirement ((3) in FIG. 4). Then, the distributed power supply 2 and the important load 30 are connected to the commercial power system 10 via the reactor 4. In this state, the distributed power supply 2 continues to operate in the self-sustained operation mode in the range of the critical load 30 or the limit withstand power of the distributed power supply 2 where the system abnormality tolerance is smaller (see FIG. 5).

  The voltage drop detecting unit 61 and the frequency fluctuation detecting unit 62 detect the instantaneous voltage drop and the frequency fluctuation of the commercial power system 10 irrespective of whether the changeover switch 3 is opened or closed. When the instantaneous voltage drop and the frequency fluctuation are less than the smaller system abnormal tolerance (the instantaneous voltage tolerance and the frequency fluctuation tolerance), the changeover switch 3 is closed.

  In both the operations (A) and (B), the opening of the changeover switch 3 has priority.

<Simulation of this embodiment>
The system model of this simulation is as shown in FIG. Further, as shown in FIG. 6, the distributed power supply is an example in which a function for generating an active signal of a reactive power fluctuation method as an active signal for detecting an isolated operation is incorporated.

(A) When the protection element for localization enters the non-operation area when the islanding operation occurs (see FIGS. 7 and 8)

The distributed power supply 2 keeps the interconnection operation until the settling time, while observing the requirements of the interconnection protection element. Distributed power, because it has a resistance in dead areas of the protective element for localizing the islanding, amplitude and frequency of between voltage v _L is stable. It can be seen that the distributed power supply and the important load maintain the voltage and the frequency while satisfying the withstand capability including the FRT requirement.

Here, when the step change of the frequency in FIG. 8 (also in the case of a ramp change) results in an abnormality in the tolerance of the distributed power supply or the important load (the case where the protection element for localization has no tolerance in the inoperative area). 9), as shown in FIG. 9, it is conceivable that the step change of the active signal (disturbance signal) is reduced to form, for example, a sine wave. By devising an active signal in this way, in the case of a step change that the frequency v _L has been a more capability of critical loads, it will satisfy the capability of the important load.

(B) When entering the operation area of the protection element for localization at the time of occurrence of the islanding operation (when entering the operation area of UV) (see FIGS. 10 and 11)

  The distributed power supply 2 keeps the interconnection operation until the settling time, while observing the requirements of the interconnection protection element. As a result, it is understood that the distributed power supply and the important load satisfy the withstand voltage including the FRT requirement and maintain the voltage and the frequency.

<Effect of this embodiment>
According to the power supply system 100 of the present embodiment configured as described above, the switch 3 is provided on the power line L1 on the commercial power system side of the distributed power supply 2, and the impedance element 4 is connected to the switch 3 in parallel. Since the changeover switch 3 is opened based on the system abnormality detected by the system abnormality detection units 61 and 62, the distributed power supply 2 is connected to the commercial power system 10 via the impedance element 4 even in the case of system abnormality. It will be in the state that was done.

  In the present embodiment, the distributed power supply 2 is connected to the commercial power system 10 via the impedance element with respect to the system abnormality including the instantaneous voltage drop and the frequency fluctuation, and satisfies the FRT requirement of the distributed power supply 2. In addition, it is possible to prevent a voltage drop to the important load 30 and a frequency fluctuation at the time of a system abnormality. As a result, the uninterruptible power supply function and the load leveling function can be compatible using the common distributed power supply 2 while satisfying the FRT requirement.

  In particular, in the present embodiment, since the distributed power supply 2 generates an active signal for detecting the islanding operation in an active manner, a dedicated power converter for generating the active signal can be omitted. As a result, it is possible to achieve both the distributed power supply function with reverse power flow and the uninterruptible power supply function for important loads while reducing costs and installation locations.

  Further, since the distributed power supply 2 has a tolerance for the range of the inoperative region of the interconnection protection element with respect to the voltage and frequency of the commercial power system 10, the distributed power supply 2 stably performs the operation including the reverse power flow. be able to.

<Other modified embodiments>
Note that the present invention is not limited to the above embodiment.

  For example, in the embodiment, the switch is opened when any one of the system abnormalities satisfies the condition. However, when the combination of two or more system abnormalities satisfies the predetermined condition, the switch is opened. May be opened.

  Further, the system abnormality detection unit 6 may detect at least one of a voltage increase, a phase variation, a voltage imbalance, an abnormal harmonic, and flicker, in addition to a voltage drop including an instantaneous voltage drop and a frequency variation. .

  In this case, the system abnormality detection unit detects a voltage rise detection unit that detects a voltage rise, a phase variation detection unit that detects a phase variation, a voltage unbalance detection unit that detects a voltage imbalance, and detects an abnormal harmonic. It has an abnormal harmonic detector and a flicker detector that detects flicker.

  The voltage rise detecting section detects a voltage rise by comparing the detected voltage of the system side voltage detecting section 5 with a predetermined set value. Here, the set value for detecting the voltage rise is, for example, 107% of the system voltage.

  The phase fluctuation detecting section detects a phase fluctuation such as a 10 ° phase jump from the phase of the detection voltage of the system side voltage detecting section 5.

  The voltage unbalance detection unit detects that the amplitude of the three phases or the phase difference of 120 ° is different from the detection voltage of the system-side voltage detection unit 5.

  The abnormal harmonic detection unit detects a harmonic voltage from the detection voltage of the system-side voltage detection unit 5. The flicker detection unit detects voltage fluctuation (flicker) from the detection voltage of the system-side voltage detection unit 5.

  Then, the first control unit 7 opens the changeover switch 3 when the other system abnormality detected by the system abnormality detection unit is equal to or greater than the tolerance of the important load 30 or the distributed power supply 2 against other system abnormality. . As a result, the commercial power system 10 is connected to the distributed power supply 2 and the important load 30 via the impedance element 4. In this state, the distributed power supply 2 continues the operation including the reverse power flow.

  In the embodiment, the first control unit 7 that mainly controls the changeover switch 3 and the second control unit 12 that mainly controls the power receiving point switch 8 are separately provided, but they are configured by one control unit. Is also good.

  Further, a capacitor may be used as the impedance element 4, or a combination of any of a reactor, a resistor, and a capacitor may be used.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist thereof.

100 power supply system 10 commercial power system 30 important load L1 power line 2 distributed power supply 3 changeover switch 4 impedance element 5 system side voltage Detecting unit 6 System abnormality detecting unit 61 Voltage drop detecting unit 62 Frequency fluctuation detecting unit 7 First control unit 8 Power receiving point switch 9 Power receiving point voltage detecting unit 12 ... second control unit

Claims (4)

A power supply system that is provided between a commercial power system and an important load and supplies power to the important load,
A distributed power supply connected to a power line for supplying power to the important load from the commercial power system,
A changeover switch provided on the commercial power system side of the distributed power supply in the power line to open and close the power line,
An impedance element connected in parallel to the changeover switch on the power line;
A system-side voltage detection unit that detects a voltage on the commercial power system side from the changeover switch,
A system abnormality detection unit that detects a system abnormality on the commercial power system side from a detection voltage of the system side voltage detection unit,
A control unit that opens the changeover switch based on a system abnormality detected by the system abnormality detection unit, and connects the distributed power supply and the commercial power system via the impedance element,
In a state where the distributed power supply and the commercial power system are connected via the impedance element, the distributed power supply continues to operate including reverse power flow,
The distributed power supply is for generating an active signal for detecting islanding operation in an active manner, and has a withstand capability with respect to a range of a non-operating region of the interconnection protection element with respect to a voltage and a frequency of the commercial power system. Power system.   2. The power supply system according to claim 1, wherein the distributed power supply has a tolerance against a step-like or ramp-like change in a range of the inoperative region with respect to the frequency of the commercial power system. 3.   The controller, when the tolerance of the important load or the distributed power supply to the system abnormality does not satisfy a predetermined settling range, the system abnormality detected by the system abnormality detection unit is the important load or the distributed load. 3. The power supply system according to claim 1, wherein the switch is opened when the power of the type power supply is equal to or greater than the tolerance to the system abnormality and is included in the predetermined set range. 4.   In a state in which the distributed power supply and the commercial power system are connected via the impedance element, the distributed power supply is reversed within a range of a smaller tolerance of the important load or the distributed power supply to a system abnormality. The power supply system according to any one of claims 1 to 3, wherein the operation including the power flow is continued.