JP3319111B2 - Static var compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stationary system for controlling a thyristor circuit in a power system to which a load causing a variation in reactive power is connected to compensate for the variation in reactive power caused by the operation of the load. The present invention relates to a reactive power compensator.

[0002]

2. Description of the Related Art Generally, in a power system to which a load whose reactive power fluctuates greatly is connected, a voltage at a connection point of the load fluctuates according to a reactive current flowing through the load.
It may adversely affect other power consumers connected to the same power system. A static var compensator is provided to suppress such voltage fluctuations.

FIG. 7 shows a three-phase connection diagram of a conventional static var compensator. 1 is a first reactor, 2 is a second reactor, 3 is a capacitor, 4 is a thyristor circuit in which a thyristor 11 is connected in anti-parallel and whose conduction angle is adjustable, and 5 is a control device that regulates the conduction angle of the thyristor circuit 4 , 6 are connection terminals, and 11 is a thyristor.

FIG. 8 shows a single-phase connection diagram for explaining a conventional static var compensator. 7 is a power supply, 8 is a load,
9 is a harmonic current prevention device, and 10 is a static var compensator. 8, since the first reactor 1 exists on the power supply 7 side of the capacitor 3 including the second reactor 2, when the thyristor circuit 4 stops, the terminal voltage VC of the capacitor 3 becomes maximum, and the first reactor 1 And the terminal voltage VR2 of the second reactor 2 becomes minimum, so that the advanced reactive power becomes maximum. On the other hand, when the control device 5 makes the thyristor circuit 4 conductive at a certain delay control angle, the second reactor 2 and the capacitor 3 are short-circuited only during that period, and the terminal voltage VR1 of the first reactor 1 rises. The leading reactive power supplied by the capacitor 3 decreases, and the lag reactive power by the first reactor 1 increases. The thyristor circuit 4
, The charge of the capacitor 3 is inverted and charged through the second reactor 2 and the thyristor circuit 4. After the thyristor circuit 4 is turned off, the inverted charge flows into the power supply 7 as a lagging current, and the delay becomes invalid. Generate power. If the delay control angle of the thyristor circuit 4 is further advanced, the overall reactive power decreases and the delay reactive power increases. As described above, by controlling the phase of the thyristor circuit 4, it is possible to continuously control from the leading reactive power to the lag reactive power.

As described above, by controlling the phase of the thyristor circuit 4, the voltage applied to the capacitor 3 is controlled to suppress the generation of the leading reactive power, and the delay reactive power due to the charge inversion of the capacitor 3. Is generated, and at the same time, the delay reactive power generated in the first reactor 1 is increased or decreased, so that the total reactive power can be continuously controlled from the delay reactive power to the delay reactive power.

[0006]

Since the conventional static var compensator has the above configuration, the thyristor circuit 4
, A harmonic current flows out of the static var compensator. For this reason, other devices connected to the power system to which the static var compensator is connected may be adversely affected, or a separate harmonic wave prevention device may need to be provided to prevent this. There was a point.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and suppresses harmonic currents of a plurality of frequencies flowing out of a static var compensator, which is a problem, inside the static var compensator. It aims to improve practicality.

[0008]

Means for Solving the Problems The present invention to achieve the above object, a first reactor, the first React
A thyristor circuit connected in series with the thyristor and a thyristor connected in anti-parallel, a control device for adjusting a conduction angle of the thyristor , the first reactor and the thyristor circuit,
Parallel to the connection point, one set was a circuit in series connected capacitors and a second reactor, at least two or more sets
And a circuit connected to the
A circuit in which the sensor and the second reactor are connected in series,
Reactive power is adjusted, and each set of
Resonance set by the combination of the sensor and the second reactor
The frequency of the harmonic current
Separately set to any of the target frequencies
To suppress harmonic currents at multiple frequencies.
It is characterized by that .

[0009]

According to the present invention, a plurality of harmonic currents can be suppressed by adjusting the resonance frequency of the capacitor and the reactor to the frequency of the plurality of harmonic currents flowing out of the static var compensator. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail.

FIG. 1 is a three-phase connection diagram of a static var compensator showing an embodiment according to the present invention. 21 is a first reactor, 22a, 22b and 22c are second reactors, 23a, 23b and 23c are capacitors, 31 is a thyristor, 24 is a thyristor circuit in which the thyristor 31 is connected in anti-parallel and the conduction angle is adjustable, and 25 is a thyristor circuit. A control device for adjusting the conduction angle of the thyristor circuit 24 connected in anti-parallel, 26
Is a connection terminal. Thyristor circuit 2 connected in reverse parallel
4 and the first reactor 21, a series-connected capacitor 23 a, which also serves to absorb harmonic current and supplies reactive power, and a second reactor 22 a and a capacitor 23.
b and the second reactor 22b, and the capacitor 23c and the second reactor 22c. The resonance frequency adjusted to the frequency of the fifth harmonic current is set to the capacitor 23a and the second reactor 22a, and the resonance frequency adjusted to the frequency of the seventh harmonic current is set to the capacitor 23b and the second reactor 22.
b, The resonance frequency matched to the frequency of the eleventh harmonic current is constituted by the capacitor 23c and the second reactor 22c.

FIG. 2 is a single-phase connection diagram for explaining the operation of the above embodiment according to the present invention. In FIG. 2, when the thyristor circuit 24 is stopped, the capacitors 23a, 23b, 2
Since the terminal voltage of the terminal 3c becomes maximum and the terminal voltage of the first reactor 21 and the terminal voltage of the second reactors 22a, 22b, 22c become minimum, the leading reactive power becomes maximum. On the other hand, when the thyristor circuit 24 is turned on by the control device at a certain delay control angle, the second reactor 22a, the capacitor 23a, and the second reactor 22
b, the capacitor 23b, the second reactor 22c, and the capacitor 23c are short-circuited, and the terminal voltage of the first reactor 21 increases.
The leading reactive power supplied by 3b and 23c decreases, and the lag reactive power by the first reactor 21 increases. Further, due to the conduction of the thyristor circuit 24, the electric charges of the capacitors 23a, 23b and 23c are respectively transferred to the second reactors 22a, 22b and 22c and the thyristor circuit 24.
After the thyristor circuit 24 is turned off, the inverted charge flows out of the static var compensator as a lag current to generate lag reactive power. If the delay control angle of the thyristor circuit 24 is further advanced, the advance reactive power decreases as a whole, and the delay reactive power increases. The fifth, seventh, and eleventh harmonic currents are connected to a series-connected capacitor 23a and a second reactor 22a, a capacitor 23b and a second reactor 22b, and a capacitor 23c and a second capacitor 22c having respective resonance frequencies. Reactor 22
absorbed by c.

FIG. 3 shows the fifth static order, FIG. 4 shows the seventh order, and FIG. 5 shows the eleventh order.
Next, FIG. 6 shows a comparison of the 13th harmonic current. The horizontal axis indicates the amount of reactive power, and the vertical axis indicates the harmonic current value. From these figures, it can be seen that the static var compensator according to the embodiment has a higher harmonic current flowing out of the static var compensator when operating at the same reactive power than the conventional static var compensator. For the fifth, seventh, and eleventh harmonic currents, a series-connected capacitor 23a and a second reactor 22a having respective resonance frequencies,
This shows that the harmonic current is absorbed by the capacitor 23b and the second reactor 22b and the capacitor 23c and the second reactor 22c, and the harmonic current is greatly reduced as compared with the 13th harmonic current.

In the above description, an example in which the fifth, seventh, and eleventh harmonic currents are suppressed has been described. However, a series connection having a resonance frequency matching the frequency of the other harmonic currents is described. By providing the capacitor and the second reactor, a plurality of arbitrary harmonic currents flowing out of the static var compensator can be suppressed, and the present invention can be applied not only to a three-phase circuit but also to a single-phase circuit. Needless to say.

[0015]

As is apparent from the above description, according to the present invention, the first reactor, the thyristor circuit in which the thyristors are connected in anti-parallel, and the control device for adjusting the conduction angle of the thyristor circuits are provided. At least two sets of capacitors and second reactors connected in series at a connection point between the first reactor and the thyristor circuit; and a resonance frequency of each combination of the capacitor and the second reactor. Is set to the frequency of the harmonic current that is to be reduced, so that harmonic currents at multiple frequencies flowing out of the static var compensator that poses a problem can be suppressed inside the static var compensator. ,
Resolves problems such as adverse effects on other equipment connected to the power system to which the static var compensator is connected, and the need to provide a separate harmonic eliminator to prevent this. However, the practical value of the static var compensator can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a three-phase connection diagram of a static var compensator according to an embodiment of the present invention.

FIG. 2 is a single-phase connection diagram of the static var compensator according to one embodiment of the present invention;

FIG. 3 is a diagram showing a comparison of the fifth harmonic current between the conventional static var compensator and the embodiment according to the present invention;

FIG. 4 is a diagram showing a comparison between the conventional static var compensator and the seventh harmonic current of the embodiment according to the present invention.

FIG. 5 is a diagram showing a comparison of the eleventh harmonic current between the conventional static var compensator and the embodiment according to the present invention.

FIG. 6 is a diagram showing a comparison of the 13th harmonic current between the conventional static var compensator and the embodiment according to the present invention.

FIG. 7 is a three-phase connection diagram showing a conventional static var compensator.

FIG. 8 is a single-phase connection diagram of a conventional static var compensator on a power system.

[Explanation of symbols]

 1, 21 First reactor 2, 22a, 22b, 22c Second reactor 3, 23a, 23b, 23c Capacitor 4, 24 Thyristor circuit 5, 25 Controller 6, 26 Connection terminal 7 Power supply 8, Load 9, Harmonic current prevention Device 10 Static var compensator 11, 31 Thyristor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05F 1/70 H02J 3/18

Claims (1)

(57) [Claims] And 1. A first reactor connected to an electric power system, the series-connected to the first reactor, and a thyristor circuit thyristor is connected in anti-parallel, a control unit for adjusting the conduction angle of the thyristors, The first reactor
Wherein the connection point between the thyristor circuit, a circuit in which a pair serially connected capacitors and a second reactor and,
And at least two sets of circuits connected in parallel.
Each pair of the capacitor and the second reactor
The circuits connected in series adjust the reactive power and
Each set of the capacitor and the second reactor
The harmonic current has the resonance frequency set by the combination of
Any of multiple frequencies whose frequency is to be suppressed
By setting each of them separately,
A static reactive power device characterized by suppressing a number of harmonic currents .