JPH0937468A - Static reactive power compensator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self exciting static reactive power compensator which can easily and accurately adjust the excitation impedance ratio of transformers connected in plural numbers in series, and further which can be downsized. SOLUTION: This compensator is provided with a series multiple transformer 4, where each high-voltage-side windings 41a and 42a of plural transformers 41 and 42 are connected in series and the line is connected to a system power source 1, inverters 5 and 6, which are connected to each low-voltage-side winding 41b and 42b of the series multiple transformer 4, and reactors 9 and 10, on the high voltage side or low voltage side of the series multiple transformer 4, and/or a gap, at the iron core of the transformer, and the impedance ratio of each transformer 41 and 42 is adjusted by the adjustment of this reactor and/or the gap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to adjustment of excitation impedance of a transformer device such as a self-excited static var compensator in which a plurality of transformers are connected in series.

[0002]

2. Description of the Related Art As one of reactive power compensators for stabilizing a power system, there is a large-capacity, low-loss self-excited static var compensator (SVC) equipped with a series multiple transformer.
An example thereof will be described with reference to FIG. 5. Reference numeral 4 is a series multiplex transformer, and in the figure, it is composed of a first transformer 41 and a second transformer 42, and high-voltage side windings of the first and second transformers 41 and 42. 41
a and 42a are connected in series and the system bus 2 is connected via the circuit breaker 3.
It is connected to the. System bus 2 is system impedance X
s, is connected to the power supply 1 and has a bus voltage Vs.

Throughout the specification and drawings, the self-excited static var compensator (SVC) has the same configuration for each phase when the power supplies are multi-phase, and therefore only the single-phase component will be described. .

The low voltage side winding 41b of the first transformer 41 is connected to the first inverter 5, and the low voltage side winding 42b of the second transformer 42 is connected to the second inverter 6. First
A capacitor 7 is connected to the inverter 5, and the capacitor 7 is charged with a current converted into a direct current by a converter or the like.
Is a low-loss, large-capacity inverter that generates a fixed rectangular wave base voltage Vp having a fundamental frequency (50, 60 Hz) by using as a power source.

The second inverter 6 is connected to a capacitor 8 and uses a capacitor 8 charged by a DC-converted current by a converter or the like as a power source to compensate a fluctuation of the reactive power. It is a high-loss, small-capacity inverter that generates

According to the self-excited static var compensator (SVC) having the above structure, when the system bus voltage Vs rises due to the reduction of the reactive power of the load, the first and second inverters generate the voltages Vp and Vq. Then, it is delayed to the system bus 2 via the first and 241, 42, and the reactive power θ
(Θ> 0) is supplied, and when the system bus voltage Vs decreases due to an increase in the reactive power of the load, similarly, the reactive power θ (θ <0) that advances to the system bus 2 is supplied, and the system changes due to load reactive power fluctuations. Stabilize the bus voltage Vs. The reactive power Q is determined by Q = Vs × (Vs− (Vp + Vq) / Xs, and the voltage component Vq of the second inverter 6 is variably controlled and set appropriately.

In the self-excited static var compensator as described above, for example, the circuit breaker 3 is turned on to connect the high voltage sides 41a and 42b of the first and second transformers 41 and 42 to the system bus 2. However, when the first and second inverters 5 and 6 are about to start operating, or when the reactive power compensator is stopped, after the output of the first and second inverters 5 and 6 is stopped, the breaker 3 is turned on. Although the first and second inverters 5 and 6 are stopped when they are turned off, the system bus voltage Vs may be applied to the first and second transformers 41 and 42 to excite them. By this excitation, the first and second transformers 4
Induced voltages Va and Vb on the low voltage side 41b and 42b
Occurs.

At this time, the voltage sharing applied to the first and second transformers 41 and 42 is determined by the first and second transformers 41 and 42.
When the exciting impedance ratio of the first and second transformers 41 and 42 is different from a predetermined value, the voltage sharing is not as predetermined and is biased to one side, and one induced voltage Va or Vb Is too large. This excessive voltage is applied to the inverter, and there is a risk of destroying the inverter if an overvoltage that is equal to or higher than the rating, for example, a voltage that is 1.2 times or more the rating is applied.

In particular, in a self-excited static var compensator in which a plurality of transformers having greatly different capacities are connected in series, it is necessary to adjust the exciting impedance of each transformer so as to meet a predetermined ratio. is there. And this adjustment is conventionally performed by adjusting the usage of the iron core which comprises each transformer.

[0010]

However, the adjustment of the amount of iron cores constituting a transformer not only greatly limits the degree of freedom in designing a transformer, but also excites magnetism depending on the processing accuracy such as the joining condition of the iron cores. There is a problem that the impedance changes greatly, and there is no method for correcting it after fabrication, and as a result, it is difficult to obtain a desired excitation impedance.

The present invention has been made in view of the above-mentioned problems, and it is possible to easily and accurately adjust the exciting impedance ratio of a plurality of transformers connected in series, and further, a self-excited static type that can be made compact. An object is to provide a type reactive power compensator.

[0012]

The above object of the present invention can be achieved by the following items (1) to (5). (1) A series multiple transformer in which each high voltage side winding of a plurality of transformers is connected in series and is connected to a system power supply, and an inverter connected to each low voltage side winding of the series multiple transformer, A static var compensator comprising an exciting impedance ratio adjusting reactor connected in parallel to the high voltage side or the low voltage side of at least one transformer of the series multiple transformer.

(2) A series multiple transformer in which the high voltage side windings of a plurality of transformers are connected in series and connected to a system power supply,
A static characterized in that it comprises an inverter connected to each low-voltage side winding of the series multiple transformer, and an exciting impedance ratio adjusting gap is provided in the iron core of at least one transformer of the series multiple transformer. Type reactive power compensator.

(3) A series multiple transformer in which each high-voltage side winding of a plurality of transformers is connected in series and is connected to a system power supply,
An inverter connected to each low voltage side winding of the series multiple transformer, and an exciting impedance ratio adjusting reactor connected in parallel to the high voltage side or the low voltage side of at least one transformer of the series multiple transformer. A static var compensator according to claim 1, wherein an exciting impedance ratio adjusting gap is provided in an iron core of at least one of the series multiple transformers.

(4) A series multiple transformer in which each high voltage side winding of a plurality of transformers is connected in series and is connected to each phase of a multiphase system power source, and each low voltage of the series multiple transformer. An inverter connected to the side winding, and an exciting impedance ratio adjusting reactor connected in parallel to each high-voltage side or low-voltage side of the corresponding series multiplex transformer of at least one of each phase, each reactor being respectively A static var compensator formed by a single-phase device.

(5) A series multiple transformer in which each high voltage side winding of a plurality of transformers is connected in series and is connected to each phase of a multiphase system power source, and each low voltage of the series multiple transformer An inverter connected to the side winding, and an exciting impedance ratio adjusting reactor connected in parallel to each high-voltage side or low-voltage side of the corresponding series multiplex transformer of at least one of each phase, each reactor is Each of them is formed as a separate single-phase device, and at least one series multiple transformer corresponding to each of the phases and each of the reactors are housed in the same tank. Reactive power compensation device.

[0017]

According to the configuration of the present invention, the excitation impedance required for each transformer constituting a series multiple transformer is adjusted by connecting a reactor in parallel to the high voltage side or the low voltage side of the transformer, By changing the thickness of the transformer core gap, or by combining the parallel connection of reactors and changing the thickness of the core gap, it is possible to easily and accurately determine the exciting impedance ratio of transformers connected in series. Can be adjusted. Further, there is no restriction on the usage amount of the iron core of each transformer, the degree of freedom in designing the transformer is expanded, more optimal design is possible, and it is possible to reduce the size and cost.

Even when the transformer has a three-phase three-leg structure, by forming the reactors connected to the respective transformers separately from the single-phase transformers, the output of the inverter is unbalanced. Even if there is one, it is possible to prevent the generation of leakage magnetic flux from the reactor iron core to the outside by designing reactors corresponding to each, and the height of the reactor is formed low, and the transformer and the reactor are the same tank. The multi-transformer with a reactor can be formed compactly.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals are given to corresponding parts throughout the drawings.

FIG. 1 is a circuit diagram of a self-excited static var compensator according to a first embodiment of the present invention. In FIG. 1, 4 is a series multiple transformer, and the series multiple transformer 4 is composed of two transformers, a first transformer 41 and a second transformer 42 in this embodiment. 41 a and the high voltage side winding 42 a of the second transformer 42 are connected in series and connected to the system bus 2 via the circuit breaker 3.

The low voltage side winding 41b of the first transformer 41 is provided with the first inverter 5 which uses the capacitor 7 as a power source, and the low voltage side winding 42b of the second transformer 42 is provided with the capacitor 8 as a power source. Two inverters 2 are connected to each. The above configuration is the same as that of the conventional self-excited static var compensator described with reference to FIG. 5, and a more detailed description of the operation and the like will be omitted.

Reference numerals 9 and 10 denote reactors. The reactors 9 and 10 have the first and second inverters 5 and 6 stopped but have a system voltage Vs of the first and second transformers 4.
1st and 2nd when applied to Nos. 1 and 42 and excited
In order to make the voltage distribution applied to the transformers 41 and 42 a predetermined value, that is, to adjust the exciting impedance ratio of the first and second transformers 41 and 42, the first transformer is used in this embodiment. Low voltage side winding 41b of the transformer 41 and the second transformer 42
By connecting in parallel to both of the low voltage side windings 42b, the exciting impedances of the first and second transformers 41 and 42 are adjusted so that the voltage sharing becomes a predetermined value.

In this embodiment, the reactor is connected in parallel to both the low voltage side winding 41b of the first transformer 41 and the low voltage side winding 42b of the second transformer 42, but the reactor is an exciting impedance. It is for adjusting the ratio and can be similarly adjusted by connecting it in parallel with the high voltage side windings 41a, 42a of the first and second transformers 41, 42, or by providing only one of the transformers. If the reactor is provided with a tap for fine adjustment of the excitation impedance, the excitation impedance ratio can be adjusted more precisely.

In the self-excited static var compensator having such a structure, the reactor is inserted and connected even if the exciting impedances of the first and second transformers 41 and 42 of the series multiple transformer 4 are greatly different. By doing the first
And the excitation impedance of the second transformers 41 and 42 can be easily set to a desired value, and the sharing of the induced voltages Va and Vb generated in the first and second transformers 41 and 42 can be prevented from being biased. be able to. That is, the excitation impedance ratio can be set precisely.

Further, there is no restriction on the usage amount of the iron core of the series multiple transformer 4, the degree of freedom in design of the series multiple transformer 4 is increased, the transformer can be optimally designed, and the size and cost can be reduced. Become.

FIG. 2 is an explanatory view of a main part of a self-excited static var compensator according to a second embodiment of the present invention, in which the reactor having the circuit configuration including the connection shown in FIG. 1 described in the first embodiment. Instead of the first and second transformers 4 of the series multiple transformer 4.
Gap 41g, 42 in the iron cores 41c, 42c of 1, 42
g is formed, and the excitation impedance is adjusted by adjusting the thickness of the gaps 41g and 42g.

The series multiple transformer 4 provided with the gaps 41g and 42g in this way has an equivalent circuit similar to the circuit configuration shown in FIG. 1 of the first embodiment. 2 Even if the capacitance of the transformer 42 is greatly different from that of the exciting impedance, the voltage sharing of each voltage is changed by changing the thicknesses of the gaps 41g and 42g.
The exciting impedance of the transformers 41, 42 can be easily set to a desired value, and the first and second transformers 41, 4
It is possible to prevent uneven distribution of the induced voltages Va and Vb generated in No. 2. That is, the excitation impedance ratio can be set precisely.

Further, according to the second embodiment, the number of devices can be reduced because the reactor is not separately provided, and the structure can be simplified and downsized.

In this embodiment, the gap is formed in both the iron cores 41c and 42c of the first transformer 41 and the second transformer 42, but the gap is for adjusting the exciting impedance ratio, and the first and the second transformers 42 and 42c are used. The same adjustment can be performed by providing only one of the two transformers 41 and 42. Further, the gap may be provided at any position on the iron core leg, and may be plural.

FIG. 3 is an explanatory view of a main part of a self-excited static var compensator according to a third embodiment of the present invention. A reactor is used for adjusting the exciting impedance ratio shown in FIG. 1 described in the first embodiment. What is provided and FIG. 2 described in the second embodiment.
The first and second series multiple transformers 4 are combined by combining the excitation impedance ratio adjustment shown in FIG.
The excitation impedance of the transformers 41 and 42 is adjusted.

In the self-excited static var compensator of the third embodiment, the first transformer 41 has a structure in which a gap 41g is provided in an iron core 41c, and a low voltage side winding 42b of a second transformer 42 is provided.
In addition, the excitation impedance adjusting reactor 10 is connected in parallel with the above.

As described above, even if the self-excited static var compensator is constructed, the exciting impedance ratio can be precisely set as described in the first and second embodiments. .

The reason why the reactor is provided to adjust the exciting impedance ratio and the gap is provided in the iron core is that the iron core with the gap has a drawback that noise and vibration due to the magnetic attraction force become large. However, the gap has an effect of suppressing DC bias excitation of the iron core. On the other hand, when the reactor is provided, noise is not increased, but there is no effect of suppressing DC bias excitation. This 2
This is because the two advantages and disadvantages have been complemented.

That is, in this embodiment, the transformer 41 connected to the inverter 5 (FIGS. 1 and 5) that constantly forms the base voltage is provided with a gap in the iron core to prevent DC bias excitation, and to prevent high-speed load. For variations, eg PWM
Since the transformer 42 connected to the controlled inverter 6 (FIGS. 1 and 5) does not require DC bias excitation,
An exciting impedance adjusting reactor is installed in parallel with the transformer to reduce noise.

FIG. 4 shows an embodiment of the arrangement structure in which the reactor and the series multiple transformer are arranged in the same tank. The transformer 43 is a three-phase three-leg iron core 43c.
And the high voltage side winding 43 for each phase on each leg.
a and the low-voltage side winding 43b are wound (note that the reference numeral is attached to one phase in the drawing), are fastened to a predetermined metal fitting in the tank 50, and are immersed in insulating oil. . Further, above the transformer 43 in the tank 50, the reactor 11 for exciting impedance adjustment (for voltage adjustment) of a single-phase device connected in parallel to each of the low voltage side windings 43b of the transformer 43 is installed. It is fixedly arranged by fastening to a metal fitting or the like for fixing 43.

The arrangement of this embodiment is for a load such as an arc furnace, and the inverter and the transformer for generating a three-phase unbalanced voltage are added to the circuit of the self-excited static var compensator shown in FIG. The layout of the reactor and the series multiple transformer of the added part is shown. In this case, the transformer 43
Converts a zero-phase current into a reciprocating current by adding a delta winding to the three-phase unbalance. Therefore, the transformer 43
The iron core 43c can be composed of three phases and three legs.

However, when the reactor 11 is composed of a three-phase device, since the reactor has no delta winding, the magnetic flux corresponding to the zero phase is leaked to the outside of the iron core 11c and is emitted as a magnetic flux. Due to the leakage magnetic flux, structures such as the tank 50 are overheated, and there is a problem that a positive phase impedance and a zero phase impedance are different due to different magnetic flux distributions. When the two are stored in the same tank, the height of the tank becomes high, and in some cases, the problem that they cannot be built in occurs.
Is a single-phase transformer, the reactor 11 is transformed into the transformer 4
It is possible to dispose it on the upper part of 3, so that the structure can be made compact, and even if the output of the inverter is unbalanced, the problem can be solved by designing the reactor corresponding to it.

In the arrangement structure of this embodiment, a part of the self-excited static var compensator for a load such as an arc furnace and the series multiple transformer are arranged in the same tank. You may make it arrange | position the reactor and serial multiple transformer of all three-phase machines in the same tank.

[0039]

As described in detail above, according to the present invention,
To adjust the exciting impedance required for each transformer that constitutes a series multiple transformer, connect a reactor in parallel to the high voltage side or low voltage side of the transformer, change the thickness of the transformer core gap, or change the reactor thickness. By combining the parallel connection of and the change of the thickness of the gap of the iron core,
The exciting impedance ratio of a plurality of transformers connected in series can be adjusted easily and accurately. Further, there is no restriction on the usage amount of the iron core of each transformer, the degree of freedom in designing the transformer is expanded, more optimal design is possible, and it is possible to reduce the size and cost.

Even when the transformer has a three-phase three-leg structure, the output of the inverter is unbalanced by forming the reactors connected to the respective transformers separately from the single-phase transformer. Even if there is one, it is possible to prevent the generation of leakage magnetic flux from the reactor iron core to the outside by designing reactors corresponding to each, and the height of the reactor is formed low, and the transformer and the reactor are the same tank. The multi-transformer with a reactor can be formed compactly.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a self-excited static var compensator according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part of a self-excited static var compensator according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a main part of a self-excited static var compensator according to a third embodiment of the present invention.

FIG. 4 is an arrangement structure diagram in the case where the reactor and the series multiple transformer of the self-excited static var compensator of the embodiment of the present invention are arranged in the same tank.

FIG. 5 is a circuit diagram of a conventional self-excited static var compensator.

[Explanation of symbols]

 1 Power Supply 2 System Bus 3 Breaker 4 Series Multiple Transformer 5, 6 Inverter 7, 8 Capacitor 9, 10, 11 Reactor 41, 42, 43 Transformer 41c, 42c, 43c, Iron Core 41g, 42g Gap 50 Tank Vs System Voltage Xs system impedance

Front page continued (72) Inventor Takeshi Yoshida 47 Umezu Takaunecho, Ukyo-ku, Kyoto City Nissin Electric Co., Ltd. (72) Inventor Kunio Yamaguchi 47 Umezu Takaune-cho, Ukyo-ku, Kyoto City Nissin Electric Co., Ltd.

Claims (5)

[Claims] 1. A series multiple transformer in which each high voltage side winding of a plurality of transformers is connected in series to be connected to a system power supply, and an inverter connected to each low voltage side winding of the series multiple transformer. And an exciting impedance ratio adjusting reactor connected in parallel to the high voltage side or the low voltage side of at least one transformer of the series multiple transformer. 2. A series multiple transformer in which each high voltage side winding of a plurality of transformers is connected in series to be connected to a system power supply, and an inverter connected to each low voltage side winding of the series multiple transformer. The static var compensator according to claim 1, wherein an exciting impedance ratio adjusting gap is provided in the iron core of at least one transformer of the series multiple transformer. 3. A series multiple transformer in which each high voltage side winding of a plurality of transformers is connected in series to be connected to a system power supply, and an inverter connected to each low voltage side winding of the series multiple transformer. And an exciting impedance ratio adjusting reactor connected in parallel to the high voltage side or the low voltage side of at least one transformer of the series multiplex transformer, and in the iron core of at least one transformer of the series multiplex transformer. A static var compensator having a gap for adjusting an excitation impedance ratio. 4. A series multi-transformer in which windings on the high-voltage side of a plurality of transformers are connected in series and connected to each phase of a multi-phase system power source, and low-voltage sides of the series multi-transformer. An inverter connected to the winding and an exciting impedance ratio adjusting reactor connected in parallel to each high-voltage side or low-voltage side of the corresponding series multiplex transformer of at least one phase, and each reactor is a single reactor. A static var compensator formed of a phaser. 5. A series multi-transformer in which windings on the high-voltage side of a plurality of transformers are connected in series and connected to each phase of a multi-phase system power source, and low-voltage sides of the series multi-transformer. An inverter connected to the winding, and an exciting impedance ratio adjusting reactor connected in parallel to each high-voltage side or low-voltage side of the corresponding series multiplex transformer of at least one of each phase, each of the reactors respectively. A static invalid, which is formed as a separate body of a single-phase device, and in which at least one series multiple transformer corresponding to each phase and each reactor are housed in the same tank. Power compensator.