JPH06338428A - Transformer provided with one pair of magnetic cores and string of dispersed power supply and system power supply using it - Google Patents

Abstract

PURPOSE:To prevent the interterminal voltage of one out of a primary-side winding and a secondary-side winding from being generated due to a reverse induction from the other, out of the windings, to which a voltage has been applied when the voltage of either one out of the windings is vanished by a method wherein one out of one pair of magnetic cores performs a normal voltage transformation operation when a normal voltage is applied to both of the primary-side and secondary-side windings. CONSTITUTION:Magnetic cores at least on one side are saturable magnetic cores 11, 12, primary windings and secondary windings on one side for each unit transformer 10 are connected in series, and those on the other side are connected in reverse series. When a prescribed voltage is applied to both of the primary windings and the secondary windings, one of the saturable magnetic cores 11, 12 is saturated, and only the residual magnetic core performs a voltage transformation action. When the voltage is applied to only one out of the primary windings and the secondary windings, the saturable magnetic cores 11, 12 become unsaturated, the number of turns of the individual windings and the BH characteristic of the magnetic cores are selected in such a way that values of voltages induced in the individual windings which have been connected in reverse series become equal and of reverse polarity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for linking a distributed power supply and a system power supply, and a transformer suitable for use in the device.

[0002]

2. Description of the Related Art There has been developed a technique for operating a distributed power source such as a private power generator, particularly a solar cell or a fuel cell, in cooperation with a system power source such as a distribution line having a commercial frequency.

FIG. 11 is a block diagram showing a specific example thereof. The DC output of the solar cell 1 as a distributed power source is DC /
The AC inverter 2 converts the AC into a commercial frequency AC, which is linked to the commercial power source 4 via the coupling transformer 3. The commercial power supply 4 to which the load 42 is connected is provided with a power failure (or / and short-circuit) detection device 6, and the detected outputs open the breakers 7 and 8 on the solar cell side and the commercial power supply side.

FIG. 12 is a block diagram showing another conventional example of a solar cell linked to a system power supply. In this example, DC
After the DC output of the solar cell 1 is converted to a high frequency (for example, several tens of KHz) by the / AC inverter 2A, it is converted into a commercial frequency AC through the high frequency transformer 3A and the bidirectional AC / AC converter 9. It is converted and linked to the commercial power supply 4. Other configurations are the same as in the case of FIG.

In the conventional example as shown in FIGS. 11 and 12, as the power failure (or short circuit) detection device 6, a frequency relay, a voltage relay, a current relay, etc. are used. When a short-circuit accident occurs in the system power supply or when the power supply to the distribution line is stopped for the purpose of repairing or repairing the failure, the detection output of the detection device causes a blur on the solar cell side and commercial power supply side.
The powers 7 and 8 are opened, and the distributed power source 1 is disconnected from the system. As a result, there is no fear of generating electric voltage to the distribution line or the like due to the induction from the distributed power source 1 even if the system power source 4 is cut off at the time of maintenance and electric shock to the worker.

However, there are problems that the breaker and the relay are operated with a time delay and the reliability is low. Further, when a plurality of distributed power sources 1 are linked to the system power source 4, there is also a problem that the disconnection timing of each distributed power source 1 is shifted due to the variation in the time delay. As a countermeasure, a linking transformer using an orthogonal magnetic core as shown in FIG. 13 has been proposed (February 1992, Institute of Electrical Engineers of Japan, Magnetics Research Group, MAG-92-57, “Orthogonal Magnetic Core Type DC-AC Conversion”). About the photovoltaic power generation system that applies the device ").

In the figure, in a transformer for connection 3B using orthogonal magnetic cores, a pair of u-shaped magnetic cores 31 and 32 are combined so that their magnetic circuits rotate 90 ° spatially and are orthogonal to each other. Transformer cores are configured, and primary (distributed power supply 30) side and secondary (system power supply 40) side windings are wound around each u-shaped magnetic core, and the magnetic fluxes Φ1, Φ2 are generated by the currents flowing through the windings. Is induced. Obviously, in the state where the magnetic core is not saturated, these magnetic fluxes do not interlink with the windings on the opposite side, and thus do not function as a normal transformer.

However, as can be easily understood from the figure,
The magnetic circuits on the primary and secondary sides are partly a common magnetic path, and this common magnetic path is configured to have saturation characteristics.Since the magnetic flux of the sum of the magnetic fluxes Φ1 and Φ2 passes through this part, When the magnetic flux Φ1 on the primary side increases, the common magnetic path becomes saturated,
The effective inductance of the secondary winding is reduced. Therefore, when an alternating current is supplied to the primary winding, the inductance of the secondary winding changes periodically and the secondary current is modulated. This phenomenon is used to convert and transmit electric power. In such an orthogonal magnetic core transformer, when the system voltage is cut off or short-circuited, the common magnetic path portion of the magnetic core is not saturated, and the orthogonal magnetic core does not originally have a normal transformer function. The induction does not generate a voltage on the system side 40. Therefore, the induced voltage is not applied to both ends of the load, and electric shock during work can be prevented without using a power failure (or short circuit) detection device, relay, or breaker.

[0009]

As can be easily inferred from FIG. 13, the linking transformer using the orthogonal magnetic core has the following problems.

(1) Since the cross-sectional area of the magnetic path is limited by the area of the joint surface of the pair of magnetic cores, the utilization efficiency of the magnetic cores is poor and it is difficult to reduce the size.

(2) Leakage magnetic flux is easily generated from the joint to cause an eddy current loss, and the loss is increased in peripheral devices and electromagnetic induction damage to the surrounding environment is easily generated. It is easy to generate noise.

(3) It is difficult to increase the frequency.

(4) Since the shape of the magnetic core is peculiar, theoretical analysis and design are difficult.

The present invention has been made to solve the above-mentioned problems, and it is possible to insulate a distributed power source and a system power source from each other only by using commercially available components, and even if no special measures are taken, (EN) Provided are a linking transformer that can theoretically prevent a voltage from being applied to a load by reverse induction from a distributed power source when the system voltage disappears, and a system linking device using the distributed power source and a commercial power source. It is in.

[0015]

The transformer of the present invention is a combination of a pair of unit transformers each comprising a primary and a secondary winding and a magnetic core around which these windings are wound. Yes, at least one of the magnetic cores is a saturable magnetic core, and one of the primary and secondary windings of each unit transformer is connected in series and the other is connected in anti-series. When a predetermined voltage is applied to both the primary and secondary windings, 1
When one saturable magnetic core is saturated and the remaining magnetic core performs a transforming action, when a voltage is applied to only one of the primary and secondary windings, the saturable magnetic core becomes unsaturated,
The number of windings of each winding and the BH characteristic of the magnetic core are selected so that the voltages induced in the windings connected in anti-series are equal and have opposite polarities.

Further, in the linking device of the distributed power source and the system power source of the present invention, the transformer and one of the primary and secondary windings have a frequency equal to the frequency of the system power source to be linked. Means for connecting to the AC output of the power supply, means for connecting the other of the primary and secondary windings to the system power supply, means for detecting the phase difference between the system power supply voltage and the distributed power supply voltage, and the detected phase difference And means for adjusting the phase of the dispersed power supply voltage so as to be equal to a preset value.

Still another distributed power supply and system power supply linking device is supplied with the output of the distributed power supply to be linked with the transformer, converts the output to high frequency AC, and transforms the primary winding of the transformer. And a means for connecting the secondary winding of the transformer to its input, for converting the high frequency alternating current induced in the secondary winding into alternating current of the system power supply frequency and connecting it to the system power supply. A means for detecting one of the phase difference between the system power supply voltage and the distributed power supply voltage and the phase difference between the primary and secondary windings of the transformer, and the detected phase difference being equal to a preset value And means for adjusting the phase of the primary side voltage of the transformer.

[0018]

When a predetermined voltage is applied to both the primary and secondary windings of the transformer of the present invention, one saturable magnetic core saturates in a certain phase range of the AC half-wave, so that other saturable cores are not saturated. The core and the windings perform the usual transformation. On the other hand, when a voltage is applied to only one of the primary and secondary windings, the saturable core becomes unsaturated, so
The voltage induced in the other winding wound around the pair of magnetic cores is
The values are equal and have opposite polarities, and the voltage between the terminals of the other winding is zero.

When a distributed power source is linked to a system power source such as a distribution line through such a transformer, if the system power source is opened or short-circuited and voltage is not applied to one winding of the transformer, Since the pair of magnetic cores are both unsaturated and exhibit a transformer action, the voltage induced in one winding by the voltage applied to the other winding is one pair of magnetic cores, and its value is Equal and opposite polarities. Therefore, the voltage between the terminals of one of the windings becomes zero, and accidents such as electric shock are prevented. Further, when a predetermined voltage is applied to both the primary and secondary windings, it is 1 in a certain phase range of the AC half-wave.
As one saturable core saturates, the other transformers and windings that do not saturate perform the normal transformation action.

[0020]

1 is a block diagram of an embodiment of the present invention.
The link transformer 10 comprises two independent saturable unit transformers 21 and 22 with saturable magnetic cores 11 and 12, respectively.
As shown in the figure, the primary winding 1 of each saturable unit transformer
3, 14 are connected in anti-series and connected to the distributed power supply 30, while the secondary windings 15, 16 are connected in series and the distribution line 3
8 to be connected to the system (commercial) power supply 40. Distribution line 3
A load 42 is connected to 8. The distributed power source 30 is an alternating current whose phase is controlled at the same frequency as the system power source 40, and is, for example, an output of a solar cell converted into an alternating current by an inverter. The number of turns of each of the windings is such that at least one of the saturable magnetic cores 11 and 12 is in the middle of the positive or negative half cycle of the alternating current when the alternating voltage of both the distributed power source 30 and the system power source 40 is applied at the same time. It saturates, but when only one of the voltages is applied, the saturable magnetic cores 11 and 12 are set so as not to saturate during the half cycle. As a material of such a saturable magnetic core, for example, a grain-oriented silicon steel sheet commercially available under the trade name of "Semper-Sil" can be used.

In operation, when the AC voltages of both the distributed power supply 30 and the system power supply 40 are normally applied simultaneously and the two saturable magnetic cores 11 and 12 are not saturated, the transformer is operated. The flowing current is only the exciting current, and its value is very small. Therefore, the number of turns N12, N22 of the primary winding in each magnetic core is equal to each other, the ratio of these to the number of turns N11, N21 of the secondary winding is n, and the voltages of the distributed power supply 30 and the system power supply 40 are V1 and V2,
When Faraday's law is applied to find the voltages V21 and V22 induced on the secondary side of the magnetic cores 11 and 12, they are as follows.

V21 = (V2 + nV1) / 2 V22 = (V2-nV1) / 2 That is, the distributed power source 3 is provided in the above two magnetic cores 11 and 12.
One half of the sum or difference between the voltage nV1 obtained by converting the output voltage V1 of 0 to the system side and the system voltage V2 is added.

Since the amount of magnetic flux of each magnetic core 11 and 12 depends on the integrated value of the voltage applied thereto, one of the magnetic cores is saturated during the positive or negative half cycle of the applied AC. The reactance of the winding wound around the magnetic core on the saturated side becomes substantially zero, and this winding can be regarded as a short circuit. Therefore, assuming that the magnetic core 12 is saturated now, the device of FIG. 1 has an equivalent circuit configuration of FIG. 2, and the entire voltage is applied to the windings 13 and 15 of the magnetic core 11 on the unsaturated side. Electric power is transmitted. The magnetic cores 11 and 12 are alternately saturated for each positive and negative half cycle of the AC voltage, and are saturated from the middle thereof. As will be easily understood from the above description, when the magnetic core 11 is saturated, the magnetic core 12 is transformed. Electric power is transmitted by the action.

When the system power supply is normal, the distributed power supply voltage V1 and the system power supply voltage V2 are simultaneously applied to the primary and secondary sides of the linkage transformer 10 while maintaining a certain phase difference θ. At this time, if the impedance between the two power sources is X, as is well known, a power flow represented by P = (V1 .V2 sin .theta.) / X occurs. Therefore, the direction and amount of power transmission can be controlled as desired by adjusting the phase difference θ. When a magnetic core with a small saturation inductance and excellent squareness is used as the saturable magnetic core,
Since a large circulating current flows from the distributed power source (inverter) 30 through the transformer to the distributed power source 30 through the system power source 40, one of the magnetic cores is deeply saturated, which causes an increase in iron loss. In this case, it is preferable to insert a linking reactor between the output of the distributed power source 30 and the transformer 10 or use a current source inverter on the output side of the distributed power source.

FIG. 3 is an equivalent circuit when an open accident occurs in the system power supply. When the system power supply 40 is opened, the voltage of the distributed power supply 30 is independently applied to the linkage transformer 10.
As described above, in this state, it is assumed that the magnetic core does not saturate throughout the positive and negative cycles of the alternating current, and the number of turns N12 and N22 of the primary winding in each magnetic core 11 and 12 is equal to each other. Half of the output voltage V1 of the distributed power source is always applied to the windings 13 and 14, and the secondary winding 1
5 and 16 have the opposite polarities and have the same absolute value V21,
V22 is induced. As a result, the voltage V2 appearing on the secondary side of the linkage transformer 10, that is, the voltage applied to the load becomes zero, and since there is no power transmitted from the distributed power source 30 to the system power source 40 side, the system side is not charged. . In this case, the distributed power source 30 only supplies the exciting current of the linkage transformer 10.

FIG. 4 is an equivalent circuit when a short circuit accident occurs in the system power supply. Even when the system power supply 40 is short-circuited as indicated by the dotted arrow, the voltage of the distributed power supply 30 is applied to the linkage transformer 10 alone, as in the case of FIG. The voltage V2 appearing at 1), that is, the voltage applied to the load becomes zero, and an overcurrent does not flow out from the distributed power source 30 due to a short circuit on the system side. Also in this case, the distributed power source 30 only supplies the exciting current of the linkage transformer 10.

Further, as will be easily understood from the above description, conversely, when an accident such as an open or a short circuit occurs on the distributed power source side, a voltage is induced on the dispersed power source side by the system power source side, or an overcurrent occurs. Will no longer flow.

Since the device of FIG. 1 operates as described above, when one of these is short-circuited or opened for the purpose of accident, repair, or maintenance of the system power source or distributed power source, the circuit break of a relay or the like is interrupted. Without using any device, voltage induction and reverse charging on the other power supply side are automatically prevented only by the original physical properties of the link transformer,
It is possible to reliably prevent electric shock accidents and the like caused by these.

FIG. 5 shows the phase difference between the system power supply and the distributed power supply voltage and the power supplied from each power supply in the apparatus of FIG. 1 using a saturable magnetic core sold under the trade name "Semper-Sil". It is a graph which shows an example of a relation, a horizontal axis is the phase difference of the primary side and the secondary side voltage of cooperation transformer 10, and a vertical axis is electric power. In this example, the distributed power source 30 is a solar cell,
The output voltage of the inverter, that is, the distributed power supply voltage V1 and the system power supply voltage V2 are 70V, and the load resistance is 4V.
0Ω, constant power consumption of load PL (= 122.5W)
And Phase difference θ between system power supply and distributed power supply voltage is 0
To 360 °, the electric powers P2 and P3 supplied from the system power source and the distributed power source change as shown in the figure.

That is, the magnetic core 12 is saturated in the range of the phase difference θ of 90 to 165 °, and the magnetic core 11 is saturated in the range of 270 to 345 ° in the middle of the positive or negative half cycle of the alternating current. Distributed power source 30 to system power source 4
The power is transmitted to the 0 side, and the power flow becomes opposite at other phase differences. Then, the amount of power transmitted changes depending on the phase difference. Therefore, it is possible to control the power transmission direction and the power transmission amount by adjusting the phase difference. For example, in FIG. 5, the maximum power can be taken out from the solar cell by setting the phase difference that maximizes the power P3.

FIG. 6 shows the same apparatus as in FIG. 5, in which the primary and secondary side power supplies are held at 70 V and the phase difference θ is changed, and the respective shared powers P2 and P3 of the primary and secondary side power supplies.
Is a diagram showing a change state of load resistance RL, that is, load power as a parameter. Load resistance RL is 40Ω, 80
The load power at that time is represented by curves PL1 and PL2, and the power burden on the commercial power source is represented by curves P21 and P22. In this figure, the power of P3 shared by the solar cell
The curves do not change even if the parameters (load power) change, and they all overlap. That is, distributed power source (solar cell)
It can be seen that the electric power supplied from the device hardly changes even if the load resistance changes, and depends only on the phase difference θ. Therefore, the phase difference θ between the primary and secondary power supply voltages is detected,
If the phase of the output voltage of the primary side, that is, the distributed power source 30 is adjusted so that this phase difference is maintained at the set value, the planned (desirably maximum) power can be supplied from the dispersed power source 30 to the load.

FIG. 7 is a block diagram of an embodiment of a device for linking distributed power sources and system power sources according to the present invention. In the figure, the same reference numerals as those in FIG. 1 indicate the same or equivalent portions.
The phase difference detector 25 detects the phase difference θ between the primary and secondary side power supply voltages of the link transformer 10, and detects the phase difference θ.
Supply to. The phase control circuit 26 compares the value set by the phase difference setting unit 27 with the phase difference θ, and adjusts the phase of the trigger signal of the DC / AC inverter 2, for example, so that the deviation becomes zero. . In this way, the device of FIG. 7 operates with the set phase difference maintained.

FIG. 8 is a block diagram showing an example of a control circuit for digitally performing the above-mentioned phase control. The zero-cross detector 43 detects the zero-cross point of the voltage waveform of the secondary side, that is, the commercial power supply 40, generates a signal having a frequency twice the commercial frequency, and supplies the signal to the PLL circuit 43. PL
The L circuit 43 generates a clock signal having a frequency of 256 times that of this signal and supplies it to the counter 45. The count value of the counter 45 is sent to the comparator 46, where a value set in advance by the phase setter according to the planned phase difference θ (for example, if the commercial frequency is 60 Hz and the advance phase is 130 °, the value is 13).
0). When the count value exceeds the set value, the comparator 46 generates a pulse to trigger the flip-flop 48, so that the flip-flop 48 obtains a pulse with a duty ratio of 50%. This pulse is used as a drive signal for the DC / AC inverter 2 which converts the DC output of the solar cell 1 into AC. In this case, the output of the inverter 2 is pulsed, and the output of the linkage transformer 10 contains harmonic components. Therefore, in order to suppress the inflow to the system, the output of the linkage transformer 10 is connected to the output side of the linkage transformer 10. It is necessary to insert a low pass filter.

In the above, the example in which the primary and secondary power supplies are directly linked at the commercial frequency has been described, but in this case, the following problems are expected.

(1) The device is large and tends to be expensive.

(2) Since the magnetic core is saturated, low frequency vibration due to magnetostriction is likely to occur and cause noise.

In order to solve such a problem, it is advantageous to operate the link transformer in a high frequency band higher than the audible frequency band. FIG. 9 is a principle block diagram of an embodiment of the present invention using an associative transformer operating in the high frequency band. The DC / AC inverter 2A converts the direct current output of the solar cell 1 into a high frequency alternating current (for example, 20 KHz) and supplies the high frequency alternating current transformer 10H with the primary side. Linking high-frequency transformer 10H has the same configuration as that of linking transformer 10 and the saturation characteristic of the magnetic core. Bidirectional AC / AC converter 9
Converts the high frequency output of the linked high frequency transformer 10H into a commercial frequency AC. The phase comparison / control circuit 29 detects the phase difference between the input and output side voltages of the associated high frequency transformer 10H and compares it with a set value so that the detected phase difference matches the set value. It controls the operation of 2H and may have the same configuration as that of FIG. 7 or 8.

FIGS. 10 (A) and 10 (B) are conceptual diagrams showing a concrete configuration example of the primary and secondary windings of the transformer of the present invention. In the same figure (A), when a voltage equal to each primary winding is applied to a pair of magnetic cores 11 and 12, at least one of which is made of a saturable magnetic material, the voltage induced in the secondary winding is equal. The winding transformers 13 to 16 are wound around the respective magnetic cores at such a winding ratio that the unit transformers are individually configured.
After that, the pair of magnetic cores 11 and 12 are superposed on each other, and the respective windings are connected so as to have polarities as shown in the drawing. In this configuration, when a voltage of V1 is applied to the primary windings 13 and 14, no voltage appears between the terminals of the secondary windings 15 and 16 connected in series, but to the individual windings 15 and 16, Since the voltages V21 and V22 are generated respectively, there is still a risk of electric shock, and it is not sufficient to ensure safety during work.

FIG. 2B is to improve this point, and a pair of magnetic cores 1 of which at least one is made of a saturable magnetic material 1 is used.
First, only the primary windings 13 and 14 are wound on 1 and 12, then two magnetic cores are superposed, and one secondary winding 19 is commonly wound on the two superposed magnetic cores. With this configuration, the voltage between the terminals of the secondary winding as well as the voltage itself induced in the winding can be reduced to zero, so there is no risk of electric shock, and safety during work can be further ensured. it can.

[0040]

In the transformer of the present invention, when a normal voltage is applied to both the primary and secondary windings, one of the pair of magnetic cores performs a normal transformer operation. When the voltage of one winding disappears, the generation of the terminal voltage of the one winding due to the reverse induction from the other winding to which the voltage is applied is prevented. This eliminates the risk of electric shock and ensures safety during work. Further, the transformer is capable of exhibiting the above-mentioned effects as its own characteristics, and can be configured only with commercially available components, and does not require additional components such as a sensor and a protection circuit.
Not only is the structure simple and inexpensive to manufacture, but it is also highly reliable.

If a distributed power source such as a solar cell is linked to a system power source such as a distribution line using the transformer, a linking device having a simple structure and high reliability can be realized. There is no fear of electric shock even when the power is cut off during maintenance and inspection.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an equivalent circuit during normal operation of the device of FIG.

FIG. 3 is an equivalent circuit when an open accident occurs in the system power supply of the device of FIG.

4 is an equivalent circuit when a short circuit accident occurs in the system power supply of the device of FIG.

FIG. 5 is a graph showing an example of the relationship between the phase difference between the system power supply and the distributed power supply voltage and the power supplied from each power supply.

FIG. 6 is a diagram showing a change state of each shared power of a system power supply and a distributed power supply, using load power as a parameter.

FIG. 7 is a block diagram of an embodiment of a device for linking a distributed power supply and a system power supply according to the present invention.

8 is a block diagram showing an example of a control circuit suitable for the linking device of FIG. 7. FIG.

FIG. 9 is a block diagram of another embodiment of the linking device of the distributed power supply and the system power supply according to the present invention.

FIG. 10 is a conceptual diagram showing a configuration example of primary and secondary windings of the transformer of the present invention.

FIG. 11 is a block diagram showing a conventional example of a solar cell linked to a system power supply.

FIG. 12 is a block diagram showing another conventional example of a solar cell linked to a system power supply.

FIG. 13 is a perspective view of a conventional linking transformer using an orthogonal magnetic core.

[Explanation of symbols]

1 ... Solar cell 2, 2A ... DC / AC inverter 4,
40 ... System (commercial) power supply 9 ... AC / AC converter
10 ... Link transformer 11, 12 ... Saturable magnetic core 21, 22 ... Saturable unit transformer 29 ... Phase comparison / control circuit 30 ... Distributed power supply 42 ... Load

Claims (8)

[Claims] 1. A transformer comprising a pair of unit transformers each comprising a magnetic core and primary and secondary windings wound around the respective magnetic cores, wherein the primary and secondary windings are connected to each other. One of them is connected in series and the other is connected in anti-series,
At least one of the magnetic cores is a saturable magnetic core, and when a predetermined voltage is applied to both the primary and secondary windings, the saturable magnetic core is saturated, and only one of the primary and secondary windings is saturated. A transformer characterized in that the saturable magnetic core becomes unsaturated when a voltage is applied. 2. The transformer according to claim 1, wherein the saturable magnetic core is saturated in a part of a half cycle of an applied voltage. 3. The voltage induced in each winding connected in anti-series when the alternating voltage is applied to both ends of the winding connected in series, and the values are equal and opposite in polarity. Transformer. 4. The pair of unit transformers are both made of saturable magnetic cores, and the BH characteristics of the respective magnetic cores are substantially equal.
The transformer according to any one of 1 to 3. 5. A pair of magnetic cores, at least one of which has a saturable characteristic, a first winding which is commonly wound around the pair of magnetic cores, and a first winding which is separately wound around each magnetic core and connected in series. And a second and a third winding, and the currents flowing through the first winding cancel the voltages induced in the second and the third windings. 6. A distributed power supply having the same frequency as the system power supply frequency to be linked with the transformer according to claim 1 and one of the primary and secondary windings. Means for connecting to the AC output, means for connecting the other of the primary and secondary windings to the system power supply, means for detecting the phase difference between the system power supply voltage and the distributed power supply voltage, and the detected phase difference is preset And a means for adjusting the phase of the distributed power supply voltage so as to be equal to the specified value. 7. The distributed power source is a direct current power source, and further comprises a DC / AC inverter for converting the output of the direct current power source into an alternating current having the same frequency as the system power source frequency and outputting the alternating current. A device that links distributed power sources and system power sources. 8. A primary winding of the transformer, which is supplied with an output of a distributed power source which is about to be linked with the transformer according to any one of claims 1 to 5 and converts the output into a high frequency alternating current. And a means for connecting the secondary winding of the transformer to its input, for converting the high-frequency alternating current induced in the secondary winding into alternating current of the system power supply frequency, and connecting it to the system power supply. ,
A means for detecting one of the phase difference between the system power supply voltage and the distributed power supply voltage and the phase difference between the primary and secondary windings of the transformer, and the detected phase difference being equal to a preset value And a means for adjusting the phase of the primary side voltage of the transformer, wherein the distributed power supply and the system power supply are linked together.