JP7328544B2 - power system - Google Patents

Description

The present invention relates to power supply systems.

The power supply system is an uninterruptible power supply system that compensates for important loads by disconnecting from the commercial power system in the event of a power failure or momentary voltage drop (hereinafter also referred to as a momentary sag). It is classified as a distributed power supply system that realizes load leveling such as cut/peak shift.

In recent years, due to the improvement in performance of storage batteries, especially in storage battery systems of large capacity (500 kW capacity class or higher), systems that achieve both an uninterruptible power supply function and a load leveling function are 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. The system is configured to disconnect and supply power to critical loads in the event of a power outage or voltage drop.

By the way, the number of distributed power sources connected to the commercial power system is increasing, and if all of these distributed power sources are disconnected at the same time during a momentary sag, it will have a large impact on maintaining the voltage and frequency of the entire commercial power system. may give For this reason, continuous operation of the distributed power supply without disconnection from the commercial power system is required even during a momentary sag (fault continuous operation (FRT) requirement).

However, in the power supply system described above, the FRT requirement cannot be satisfied because the power supply system is disconnected at the moment of voltage drop. In addition, as shown in Patent Document 2, it is conceivable to use a storage battery for uninterruptible power supply and a storage battery for load leveling in a power supply system to achieve each function individually, but the cost and size are high. increase. In addition, none of the power supply systems described above take into consideration the quality of the power supply during self-sustained operation.

Japanese Patent No. 3402886 Japanese Patent Application Laid-Open No. 2004-289980

Therefore, the present invention has been made to solve the above problems, and a power supply that satisfies the FRT requirements and uses a common distributed power supply to achieve both the uninterruptible power supply function and the load leveling function of the constant commercial power supply system. The main task of the system is to improve the quality of the power supply during isolated operation.

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 for supplying power to the important load, and comprising a power line for supplying power from the commercial power system to the important load. a distributed power supply connected to a switch for opening and closing the power line; an impedance element connected in parallel to the switch; a parallel-off switch provided closer to the commercial power system than the switch; a switching circuit for switching a connection point of the distributed power supply between a first connection point between the changeover switch and the important load and a second connection point between the changeover switch and the parallel-off switch; A system abnormality detection unit that detects a system abnormality of the power system, and a control unit that controls the changeover switch and the changeover circuit. Then, when the system abnormality is detected, the control unit opens the changeover switch in a state where the connection point of the distributed power supply is set to the first connection point, and the distributed power supply and the commercial power system are connected to each other. is connected via the impedance element, the distributed power supply continues the interconnection operation including the reverse power flow, and when the system abnormality satisfies a predetermined parallel-off condition, the parallel-off switch is opened, A connection point of the distributed power sources is set to the second connection point by the switching circuit, and the switching circuit is turned on to perform self-sustained operation by the distributed power sources.

In such a power supply system, when a system abnormality is detected, the changeover switch is opened with the connection point of the distributed power supply as the first connection point, and the impedance between the distributed power supply and the commercial power system is reduced. By connecting via elements and continuing grid-connected operation including reverse power flow with a distributed power supply, it is possible to satisfy both the uninterruptible power supply function and the load leveling function using a common distributed power supply while satisfying the FRT requirements. can be done. When the system abnormality satisfies the predetermined parallel-off conditions, the switch for parallel-off is opened, the connection point of the distributed power sources is set to the second connection point by the switching circuit, and the switch is turned on to make the distributed power sources self-sustaining. Since the operation is performed, it is possible to improve the quality of the power supply in the self-sustained operation.

Specifically, the effect of the present invention becomes significant when the power supply system further includes a power supply unit having an energy storage unit on the important load side of the changeover switch. That is, when the system abnormality is detected, the control unit opens the changeover switch and supplies power from the power supply unit to the important load, and then supplies power from the distributed power supply to the important load. It is desirable to As a result, the power supply unit can supply power to the important load until the voltage of the distributed power supply is established, so that the voltage quality of the power supply can be improved.

The power supply system further includes a redundant power supply separate from the distributed power supply, and the control unit opens the changeover switch and disconnects the important power supply from the power supply unit when an abnormality is detected in the distributed power supply during the self-sustained operation. It is desirable to supply power to a load, then connect the redundant power supply to the second connection point and turn on the changeover switch to supply power from the redundant power supply to the critical load.
With this configuration, since redundant power sources are provided separately from distributed power sources, the reliability of power supply to important loads during self-sustained operation can be improved. In addition, when switching from a distributed power supply to a redundant power supply, the power supply unit can supply power to important loads until the voltage of the redundant power supply is established, so the voltage quality of the power supply during self-sustained operation can be improved. .

The power supply system further includes a grid-side voltage detection unit that detects a voltage on the commercial power grid side rather than the changeover switch, and the control unit detects that the grid abnormality resolves the predetermined parallel-off condition and that the grid When the detected voltage of the side voltage detection unit satisfies the synchronization test condition, it is preferable that the switching circuit sets the connection point of the distributed power supply as the first connection point and turns on the parallel-off switch. Here, the predetermined synchronization test condition is that the magnitude, frequency, and phase of the voltage detected by the grid-side voltage detector match the magnitude, frequency, and phase of the grid voltage of the commercial power grid. . The system voltage of the commercial power system is detected by a power supply side voltage detection unit that detects the voltage on the distributed power supply side rather than the parallel-off switch on the power line.

In the present invention, the demand side equipment is connected to the commercial power system via the impedance element in response to a system abnormality, preventing unnecessary disconnection of the distributed power supply and preventing adverse effects on important loads at the time of system abnormality. can be prevented. Here, it is desirable that the system anomaly detector detects at least one of instantaneous voltage drop and frequency fluctuation, voltage rise, phase fluctuation, voltage imbalance, harmonic anomaly, and flicker.

Here, it can be read from the interconnection regulations that the above-mentioned phase fluctuation, voltage unbalance, harmonic abnormality, or flicker can be considered as system abnormal elements. In the β-0-transformed complex number, the α component (which is assumed to be the real number component) and the β component (which is assumed to be the imaginary number component) are expressed by Equation 1.

ここで各要素は以下である。
v：系統電圧
Ｖ_１：系統電圧振幅
ｆ：系統電圧周波数
θ：系統電圧位相、位相跳躍との位相変動はこの要素の変化である。
Σ_ｎ≠１ｖ_ｎ：基本波正相分以外の成分、ｎ＝－１の逆相成分と｜ｎ｜≠１の高調波成分がある。
なお、フリッカはＶ_１の数～数十Ｈｚの低周期変動である。

where each element is:
v: system voltage V ₁ : system voltage amplitude f: system voltage frequency θ: system voltage phase, phase fluctuation with phase jump is a change of this element.
Σ _n≠1 v _n : There are components other than the positive phase component of the fundamental wave, the negative phase component of n=−1, and the harmonic component of |n|≠1.
Note that flicker is a low-period fluctuation of several to several tens of Hz of _V1 .

As a result of the addition of system abnormal elements based on this consideration, even in the uninterruptible power supply system of the continuous commercial power supply system, in the same way as the uninterruptible power supply system of the continuous inverter power supply system, which is more expensive can also handle.

In the present invention, the system abnormality element detected by the system abnormality detection unit is also applied to the abnormality detection of the distributed power supply in the self-sustained operation. As an example, it is possible to prevent abnormalities during self-sustained operation of the power supply system (for example, occurrence of uneven rotation of the induction motor (important load) due to imbalance caused by disconnection of one phase of the output circuit of the distributed power supply).

According to the present invention configured in this way, in a power supply system that satisfies the FRT requirements and functions as an uninterruptible power supply system and a function as a distributed power supply using a common distributed power supply, the power supply in the self-sustained operation quality can be improved.

1 is a schematic diagram showing the configuration of a power supply system according to an embodiment of the present invention; FIG. It is a schematic diagram which shows the structure of the system|strain abnormality detection part of the same embodiment. FIG. 4 is a diagram showing a connection state of distributed power sources when the system is healthy according to the same embodiment; It is a figure which shows the connection state of the distributed power supply above a system|strain, such as a voltage sag of the same embodiment. It is a figure which shows the connection state of the distributed power supply in the self-sustaining operation of the same embodiment. FIG. 4 is a diagram showing a time chart until switching from distributed power sources to redundant power sources in self-sustained operation of the same embodiment; FIG. 10 is a diagram showing a list of operating states of the power supply system when a distributed power supply is abnormal during self-sustained operation of the embodiment; It is a schematic diagram which shows the structure of the power supply system of deformation|transformation embodiment.

An embodiment of a power supply system according to the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the power supply system 100 of the present embodiment is provided between the commercial power system 10 and the important load 30, and supplies power to the important load 30 when the commercial power system 10 malfunctions. function (uninterruptible power supply function) and a function (load leveling function) as a distributed power supply system that levels the load by forward and reverse power flow to the commercial power system 10 .

Here, the commercial power system 10 is a power supply network of an electric power company (electric utility), and has a power plant, a power transmission system, and a power distribution system. Further, the important load 30 is a load to which electric power should be stably supplied even in the event of a system abnormality such as a power failure or a momentary voltage drop.

Specifically, the power supply system 100 includes, as shown in FIG. 3, a grid-side voltage detector 5 that detects the voltage on the commercial power grid 10 side rather than the changeover switch 3, and a grid-side voltage detector 5 that detects a grid abnormality from the detected voltage. An abnormality detection unit 6 and a control unit 7 for opening the changeover switch 3 in response to a detection signal from the system abnormality detection unit 6 are provided.

Distributed power supply DP is connected to power line L1 for supplying power from commercial power system 10 to important load 30 . This distributed power supply DP is interconnected to the commercial power system 10, and includes, for example, AC power generation facilities such as synchronous generators and induction generators, DC power generation facilities such as solar power generation and fuel cells, and power converters. , or a power generation facility (not shown) that rectifies the electric energy output by AC such as wind power generation and micro gas turbine to DC and is connected to the grid using a power converter.

This distributed power supply DP is connected to the power line L1 via a switching circuit SC. In the switching circuit SC, the connection points of the distributed power supply DP are the first connection point between the changeover switch 3 and the important load 30 (hereinafter also referred to as "L point"), the changeover switch 3 and the parallel-off switch 8. and a second connection point (hereinafter also referred to as "point D") between the two. Specifically, the switching circuit SC includes a first connection line L2 connected to the point L, a second connection line L3 connected to the point D, and a switch SC1 that switches between the lines L2 and L3 connected to the distributed power supply DP. have. The switch SC1 is, for example, a mechanical switch, and is controlled to be opened or closed by the controller 7. FIG.

A redundant power supply RP is connected in parallel to the distributed power supply DP separately from the distributed power supply DP to the switching circuit SC. For example, an emergency power generator can be used as the redundant power supply RP. The distributed power supply DP and redundant power supply RP are configured to be selectively connectable to the switching circuit SC. Specifically, an open/close switch S1 is provided between the distributed power supply DP and the switching circuit SC, and an open/close switch S2 is provided between the redundant power supply RP and the switching circuit SC. The opening/closing switches S1 and S2 are mechanical switches, for example, and are controlled to be opened/closed by the control unit 7 .

The power supply unit 2 is connected to the important load 30 side of the changeover switch 3 on the power line L1. The power supply unit 2 is connected to the commercial power system 10 and has an energy storage unit 21 such as a secondary battery (storage battery) and a power converter (power conditioner) 22 .

Further, in the power supply system 100 of the present embodiment, a parallel-off switch (power receiving point switch) 8 is provided on the commercial power system 10 side of the power line L1 relative to the distributed power supply DP. Further, in the power supply system 100 of the present embodiment, the power receiving point voltage detection unit 9 is provided to detect the voltage on the commercial power system 10 side rather than the parallel-off switch 8 in the power line L1.

The parallel-off switch 8 of the present embodiment is an open/close switch for paralleling off the commercial power system 10 and the distributed power supply DP, and is, for example, a mechanical switch. In FIG. 1 , it is provided on the commercial power system 10 side of the changeover switch 3 , but it may be provided on the distributed power supply DP side of the changeover switch 3 . The parallel-off switch 8 is controlled to open and close by the controller 7 .

The changeover switch 3 is provided closer to the commercial power system 10 than the first connection point (point L) of the distributed power supply DP on the power line L1, and opens and closes the power line L1. A changeover switch capable of high-speed switching, such as a hybrid switch combined with a mechanical switch, can be used. For example, if a semiconductor switch is used, the switching time can be reduced to 2 milliseconds or less, and cutoff can be performed regardless of the zero point. In addition, when a hybrid switch is used, the switching time can be reduced to 2 milliseconds or less, and not only can it be cut off regardless of the zero point, but also the conduction loss can be reduced to zero. The changeover switch 3 is controlled to be opened/closed by the controller 7 .

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

The system-side voltage detection unit 5 detects the voltage on the commercial power system 10 side of the changeover switch 3 via the voltage transformer 51 in the power line L1. Specifically, the grid-side voltage detector 5 is connected to the commercial power grid 10 side through a voltage transformer 51 with respect to the parallel circuit composed of 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 rather than the changeover switch 3 from the detected voltage detected by the system side voltage detection unit 5 . System abnormalities in the present embodiment are voltage drop including momentary sag, voltage rise, frequency fluctuation, phase fluctuation, voltage unbalance, abnormal harmonics, and flicker.

For this reason, as shown in FIG. 2, the system abnormality detection unit 6 includes a voltage drop detection unit 61 that detects a voltage drop including an instantaneous drop, a frequency fluctuation detection unit 62 that detects frequency fluctuations, and a voltage rise detection unit 62 that detects voltage rises. A voltage rise detector 63, a phase fluctuation detector 64 that detects phase fluctuation, a voltage unbalance detector 65 that detects voltage imbalance, an abnormal harmonic detector 66 that detects abnormal harmonics, and a flicker detector. and a flicker detection unit 67 for detecting the flicker.

The voltage drop detector 61 detects a voltage drop by comparing the voltage detected by the grid voltage detector 5 with a predetermined set value. Here, the set value for detecting a voltage drop is a voltage value for detecting an instantaneous drop, for example, a residual voltage of 20%.

The frequency variation detector 62 detects frequency variation (frequency increase (OF), frequency decrease (UF)) from the voltage detected by the system side voltage detector 5 . Note that the frequency variation is, for example, a step-up or a ramp-up/down.

The voltage rise detection section 63 detects a voltage rise by comparing the voltage detected by the grid side voltage detection 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 change detector 64 detects a phase change such as a 10° phase jump from the phase of the voltage detected by the system side voltage detector 5 .

The voltage unbalance detection section 65 detects that the voltage detected by the system side voltage detection section 5 is different in magnitude of amplitude or phase difference 120° between the three phases.

The abnormal harmonic detector 66 detects a harmonic voltage from the voltage detected by the grid voltage detector 5 . The flicker detector 67 detects a voltage fluctuation (flicker) from the voltage detected by the grid-side voltage detector 5 .

The control unit 7 outputs a control signal to the changeover switch 3 and the changeover circuit SC based on each detection signal and the like detected by the system abnormality detection unit 6 to control the changeover switch 3 and the changeover circuit SC. The control unit 7 of the present embodiment accepts the detection signals from the detection units 61 to 67 and opens the changeover switch 3 when any one of the detection signals satisfies the condition (OR condition).

Specifically, when the voltage sag tolerance of the important load 30 or the distributed power supply DP does not satisfy a predetermined settling range, the control unit 7 detects that the voltage sag detected by the voltage drop detection unit 61 is equal to or greater than the voltage sag tolerance, and , the change-over switch 3 is opened when it is within a predetermined settling range. The set value for the instantaneous sag determined by the control unit 7 has a voltage level element and a time limit element. It is to be. The same applies to other system abnormality elements determined by the control unit 7 . As a result, the commercial power system 10 , the distributed power supply DP, and the important load 30 are connected via the impedance element 4 . In this state, the distributed power sources DP continue interconnected operation including reverse power flow.

Further, when the frequency fluctuation tolerance of the important load 30 or the distributed power supply DP does not satisfy a predetermined settling range, the frequency fluctuation detected by the frequency fluctuation detector 62 is equal to or greater than the frequency fluctuation tolerance, and When it is within the predetermined settling range, the changeover switch 3 is opened. In this state, the distributed power sources DP continue interconnected operation including reverse power flow.

Further, the control unit 7 opens the changeover switch 3 when other system abnormalities detected by the system abnormality detection units 63 to 67 are greater than or equal to the tolerance of the important load 30 or the distributed power supply DP against other system abnormalities. As a result, the commercial power system 10 , the distributed power supply DP, and the important load 30 are connected via the impedance element 4 . In this state, the distributed power sources DP continue interconnected operation including reverse power flow.

Then, the control unit 7 opens the parallel-off switch 8 when the voltage detected by the grid-side voltage detection unit 5 or the system abnormality satisfies a predetermined parallel-off condition. Here, the predetermined parallel-off condition is that the duration of the voltage drop in the system voltage (the state in which the detected voltage is equal to or lower than the set value) is equal to or greater than a predetermined value (longer than the voltage sag duration). . With the parallel-off switch 8 opened, the distributed power supply DP enters the self-sustained operation mode and supplies power to the important load 30 . Since the selector switch 3 has already been released, the overcurrent due to the opening of the parallel-off switch 8 is suppressed by the reactor 4 .

Further, the controller 7 ensures that the detected voltage of the grid-side voltage detector 5 satisfies the predetermined parallel off condition, and that the detected voltage of the grid-side voltage detector 5 and the detected voltage of the power supply-side voltage detector 9 meet the synchronization test condition. The parallel-off switch 8 is turned on when the following is satisfied. Here, the synchronization test condition is, for example, that the magnitude, frequency, and phase of the voltage of the distributed power supply DP and the magnitude, frequency, and phase of the voltage of the commercial power system 10 match.

In addition, the control unit 7 also opens the parallel-off switch 8 when another system abnormality such as frequency fluctuation satisfies a predetermined parallel-off condition. At this time, the control unit 7 turns on the parallel-off switch 8 when the detected system abnormality falls within the normal range.

Next, specific opening/closing control of the changeover switch 3 and switching control of the changeover circuit SC of the control unit 7 and operation of the distributed power supply DP will be described with reference to FIGS. 3 to 7. FIG.

(1) When the commercial power system is healthy (see Fig. 3)
In the power supply system 100, the changeover switch 3 is normally closed, and the connection point of the distributed power supply DP is set to the L point by the changeover circuit SC. As a result, the power supply system 100 is in a state where the distributed power supply DP and the important load 30 are connected to the commercial power system 10 via the changeover switch 3 . Although the reactor 4 is connected in parallel to 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/peak shift can be realized by reverse power flow by the distributed power source DP.

(2) When an abnormality occurs in the commercial power system (see Fig. 4)
When the system abnormality detection unit 6 detects a system abnormality in the commercial power system 10, the control unit 7 opens the changeover switch 3 while keeping the connection point of the distributed power supply DP at the L point. Then, the distributed power supply DP and the important load 30 are connected to the commercial power system 10 via the reactor 4 . Here, when the changeover switch 3 is opened, the control unit 7 activates the power supply unit 2 and supplies power from the power supply unit 2 to the important load 30 until the voltage of the distributed power supply DP is established. , and then supplies power to the critical load 30 from the distributed power supply DP. Then, the distributed power sources DP continue interconnected operation including reverse power flow. Note that the distributed power sources DP continue to operate within the range of the critical load 30 or the distributed power source DP, whichever has the smaller system anomaly tolerance.

Here, each detection unit 62, 64 to 67 detects each system abnormality of the commercial power system 10 regardless of whether the changeover switch 3 is opened or closed, and the control unit 7 detects each system abnormality of the commercial power system 10. The changeover switch 3 is closed when it becomes less than the smaller system abnormality tolerance.

(3) During self-sustaining operation (see Fig. 5)
When the system abnormality satisfies a predetermined parallel-off condition, the control unit 7 opens the parallel-off switch 8, sets the connection point of the distributed power supply DP to point D by the switching circuit SC, and turns on the switch 3. As a result, the power supply system 100 is in a state where the important load 30 is connected to the distributed power supply DP via the changeover switch 3 . In this state, self-sustaining operation is performed by the distributed power supply DP.

(4) When an abnormality (isolated system abnormality) occurs during isolated operation When an abnormality (isolated system abnormality) such as distributed power supply DP is detected during isolated operation, the changeover switch 3 is opened as shown in FIGS. Then, the distributed power supply DP (switching source generator) is paralleled off, and the power supply unit 2 is activated to supply power from the power supply unit 2 to the important load 30 . At the same time, the redundant power supply RP (switch destination generator) is activated, the redundant power supply RP is connected to the point D, and the switch 3 is turned on to supply power from the redundant power supply RP to the important load 30 . Further, when the connection of the redundant power supply RP is completed, the power supply unit 2 is stopped.

The isolated system abnormality is detected by the system abnormality detection unit 6, and the system abnormality of the commercial power system 10 (voltage drop including voltage drop, voltage rise, frequency fluctuation, phase fluctuation, voltage imbalance, abnormality harmonics, flicker). In addition, failure of the isolated system includes failure of the distributed power supply DP, running out of fuel, and the like.

Here, when the controller 7 detects an abnormality in the distributed power supply DP, the control unit 7 opens the open/close switch S1 of the distributed power supply DP and turns on the open/close switch S2 of the redundant power supply RP to switch the switching circuit SC. Switch the connected power supply. As a result, the redundant power supply RP is connected to the D point. Since the power supply unit 2 is configured to supply power to the important load 30 during switching to the redundant power supply RP after detecting an abnormality in the distributed power supply DP, the reliability of the power supply to the important load 30 is improved. The voltage quality of the power supply can be improved.

(5) Reconnection from isolated operation to the commercial power system The control unit 7 switches when the system abnormality eliminates the predetermined parallel-off condition and the detected voltage of the system-side voltage detection unit 5 satisfies the synchronization verification condition. The connection point of the distributed power supply DP is set to point L by the circuit SC, and the parallel-off switch 8 is turned on. As a result, the power supply system 100 is in a state in which the distributed power supply DP and the important load 30 are connected to the commercial power system 10 via the changeover switch 3 .

<Effects of this embodiment>
According to the power supply system 100 of the present embodiment configured in this way, when a system abnormality is detected, the changeover switch is opened with the connection point of the distributed power sources as the point L, and the distributed power sources and the commercial The power system is connected via an impedance element, and the distributed power supply continues the interconnected operation including the reverse power flow. can be compatible with When the system abnormality satisfies the predetermined parallel-off conditions, the switch for parallel-off is opened, the connection point of the distributed power sources is set to the point D by the switching circuit SC, and the switch is turned on to allow the distributed power sources to operate independently. Therefore, it is possible to improve the quality of the power supply in the isolated operation.

Specifically, since the power supply system has a redundant power supply in addition to the distributed power supply, it is possible to improve the reliability of the power supply to the important loads during the self-sustained operation. Furthermore, when switching from a distributed power supply to a redundant power supply, the power supply unit supplies power to the important load until the voltage of the redundant power supply is established, so that the voltage quality of the power supply during self-sustained operation can be improved. .

<Other Modified Embodiments>
It should be noted that the present invention is not limited to the above embodiments.

For example, in the above-described embodiment, the redundant power supply is switchably connected to the switching circuit SC in addition to the distributed power supply. However, as shown in FIG. Also good.

Moreover, as the redundant power supply RP, a commercial power system different from the commercial power system that is paralleled off by the parallel-off switch 8 may be used.

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

Furthermore, the grid-side voltage detector of the above-described embodiment may be included in the grid-connection protective device. Examples of grid interconnection protection devices stipulated in grid interconnection regulations include overvoltage relays (OVR), undervoltage relays (UVR), short-circuit direction relays (DSR), ground fault overvoltage relays (OVGR), overfrequency relays ( OFR), under-frequency relays (UFR), transfer interrupters, and the like. In this case, it is conceivable that the control unit opens the parallel-off switch when any one of the linked protection devices operates. Further, the control unit controls the parallel-off switch when all the grid connection protection devices are in an inoperative state and the detection voltage of the grid side voltage detection unit and the detection voltage of the power supply side voltage detection unit satisfy the synchronization verification condition. can also be put in. With this configuration, since the voltage detection section provided in the interlocking protective device is used, there is no need to provide a separate grid-side voltage detection section, and the device configuration can be simplified.

In addition, the power supply side voltage detection unit in the above-described embodiment is provided between the parallel-off switch and the changeover switch, but it may be replaced by the function of measuring the system connection point voltage of the distributed power supply. .

Furthermore, in the above-described embodiments, a storage battery such as a secondary battery is used as an energy storage device. A multilayer capacitor or the like may be used.

In addition, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

100 Power supply system 10 Commercial power system 30 Important load L1 Power line DP Distributed power supply RP Redundant power supply SC Switching circuit 2 Power supply unit 3 ... Changeover switch 4 ... Impedance element 5 ... System side voltage detector 6 ... System abnormality detector 7 ... Control section 8 ... Parallel switch

Claims (6)

A power supply system provided between a commercial power system and a critical load to supply power to the critical load,
a distributed power supply connected to a power line for supplying power from the commercial power system to the critical load;
a changeover switch that opens and closes the power line;
an impedance element connected in parallel to the changeover switch;
a parallel-off switch provided closer to the commercial power system than the selector switch;
a switching circuit for switching a connection point of the distributed power supply between a first connection point between the changeover switch and the important load and a second connection point between the changeover switch and the parallel-off switch;
a system abnormality detection unit that detects a system abnormality in the commercial power system;
A control unit that controls the switch and the switching circuit,
The control unit
When the system abnormality is detected, the changeover switch is opened with the connection point of the distributed power supply as the first connection point, and the distributed power supply and the commercial power system are connected via the impedance element. and continue interconnected operation including reverse power flow by the distributed power source,
When the system abnormality satisfies a predetermined parallel-off condition, the switch for parallel-off is opened, the connection point of the distributed power supply is set to the second connection point by the switching circuit, and the switch is turned on to turn on the switch. A power supply system that performs independent operation with a distributed power supply. 2. The power system according to claim 1, further comprising a power supply unit connected to said critical load side of said changeover switch and having an energy storage unit. When the system abnormality is detected, the control unit opens the changeover switch and supplies power from the power supply unit to the important load, and then supplies power from the distributed power supply to the important load. 3. The power system of claim 2. A redundant power supply is further provided separately from the distributed power supply,
When the control unit detects an abnormality in the distributed power supply during the self-sustained operation, the control unit opens the changeover switch, supplies power from the power supply unit to the important load, and then connects the redundant power supply to the second connection. 4. The power supply system according to claim 2, wherein power is supplied from said redundant power supply to said important load by connecting to a point and turning on said changeover switch. further comprising a grid-side voltage detection unit that detects a voltage on the commercial power grid side rather than the changeover switch,
When the system abnormality eliminates the predetermined parallel off condition and the detected voltage of the system side voltage detection unit satisfies the synchronization verification condition, the control unit switches the connection point of the distributed power supply to the above by the switching circuit. 5. The power supply system according to any one of claims 1 to 4, wherein the parallel-off switch is turned on as a first connection point. 6. The system anomaly detection unit detects at least one of instantaneous voltage drop and frequency fluctuation, voltage rise, phase fluctuation, voltage imbalance, harmonic anomaly, or flicker. The power system described in .