JPH0433113A - Reactive power compensator - Google Patents

Abstract

PURPOSE:To prevent the overload on a transformer and to prevent detachment from a power system by providing an overload prevention limitter limiting output reactive power. CONSTITUTION:The setting unit 16 of the overload prevention limitter 21 sets the limitation value of leading reactive power to -1.0pu and the like A subtracter 9-3 calculates a difference -0.1pu with the set point -1.0pu of the setter 16 and adds it to a negative value passage circuit 18 when a reactive power detection circuit 15 detects reactive power -1.1pu based on respective detection values of a transformer for meter 5-2 and a current transformer for meter 6-2. Since an operation value is negative, it passes through the negative value passage circuit 18 and it is added to a primary delay circuit 20-1. In such a case, the effect of a limitter is large when the gain K of the primary delay circuit 20-1 is large and the output of an invalid power compensation device is immediately limited to less than -1.0pu. Delay reactive power is similarly limited. Thus, the overload of the transformer is prevented, detachement from the power system can be prevented and the power system can be stabilized much more with constitution provided with the overload prevetion limitter limitting output reactive power to less than the set point which is set in the upper limit part of a range where the transformer is not overloaded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a reactive power compensator used for stabilizing a power system.

(Prior Art) A reactive power compensator is a reactive power supply device using a semiconductor switch such as a thyristor, and adjusts its output amount to stabilize the voltage of a power system and improve its stability.

FIG. 2 shows the configuration of this type of conventional reactive power compensator, which combines a thyristor-controlled reactor and a capacitor. Here, thyristors 1-1 and l-2
are connected in series to the reactor 2, thereby forming a thyristor-controlled reactor. This thyristor-controlled reactor is connected in parallel with the capacitor 3 between the secondary side of the transformer 4 and a ground point (not shown).

Note that the primary side of the transformer 4 is connected to the power system.

On the other hand, an instrument transformer 5 is used to detect the current of the power system.
-1 is provided, and an instrument current transformer 6-1 is further provided to detect the primary current of the transformer 4. Among these, the instrument transformer 5-1 is connected to the voltage detection circuit 7, the output of this voltage detection circuit 7 is added as the subtracted input of the subtracter 9-1, and the set value of the reference voltage setter 8 is subtracted. It is added as a subtraction input to the unit 9-1. Also, the subtractor 9-
The output of 1 is added as the subtracted input of another subtractor 9-2. On the other hand, the instrument current transformer 6-1 is connected to a current detection circuit 10, and the output of this current detection circuit 10 is applied via a proportional circuit U as a subtraction input to a subtracter 9-2. The output of the subtracter 9-2 is then added to the proportional-integral circuit 12 with a limiter, and the proportional-integral circuit 12 with a limiter
2 is applied to the firing angle determining circuit 13, and further, the output of this firing angle determining circuit 13 is applied to the gate pulse generating circuit 1.
Added to 4. An instrument transformer 5-1 is also connected to the gate pulse generation circuit 14, and here, the thyristor 1-1
, 1-2 control signals are generated.

Next, the operation of this reactive power compensator will be explained.

A system voltage V is detected by an instrument transformer 5-1 connected to the power system and a voltage detection circuit 7.

The subtracter 9-1 calculates an error voltage ΔV, which is the difference between the detected voltage (2) and the reference voltage vref' of the reference voltage setter 8.

On the other hand, the output current I of the reactive power compensator is detected by the meter current transformer 6-1 and the current detection circuit 10. This detected current I is multiplied by vC by K by the proportional circuit 11 and converted into a voltage. The subtracter 9-2 calculates the difference between this voltage and the error voltage ΔV (ΔV-, .l5Ve) and adds it to the proportional-integral circuit 12 with a limiter.

The proportional-integral circuit 12 with a limiter
), the thyristor control reactor current Itar is calculated so that the difference becomes zero by performing proportional and integral calculations on vC. The firing angle determination circuit 13 determines the firing angle α of the thyristor so that this current Itcr flows. A gate pulse generation circuit 14 generates a gate pulse having a firing angle α and applies it to the gates of thyristors l-1 and l-2. As a result, the calculation current Itcr of the proportional-integral circuit with limiter 12 flows through the thyristor control reactor, and this current is supplied to the power system.

FIG. 3 shows an example of the voltage-current characteristics of this reactive power compensator. In the figure, the vertical axis shows the system voltage V, and the horizontal axis shows the output current I of the var power compensator SvC. Here, the broken line ◎-■-vC ■ is the reference voltage v, 8. 1. This is the voltage-current characteristic when set to Opu. Moreover, the broken line ◎-@-◎ is the voltage-current characteristic when the reference voltage Vref' is set to 1.1 pu. Incidentally, the slopes of the straight line portions ■-■ and ◎-◎ are determined by the gain K of the proportional circuit 11.

(Problem to be Solved by the Invention) In the conventional reactive power compensator described above, the reference voltage vr8f is normally set to, for example, 1.0 pu. Now, if this reference voltage Vref is set to a high value such as 1.1 pu, the reactive power compensator will adjust the system voltage to 1.1 pu.
It outputs reactive power in an attempt to maintain it at 1 pu. In this case, the iron loss and copper loss of the transformer 4 become very large values, and if these values exceed the standard values of the transformer, it is necessary to disconnect it from the reactive power compensator.

Therefore, in the conventional reactive power compensator, the reference voltage v, 8. If it is set too high, there is a problem that the disconnection leaves nothing to compensate for the reactive power, making the power system unstable.

This invention was made to solve the above-mentioned problems, and includes reactive power compensation that prevents transformers from being overloaded and disconnected from the power system, thereby further stabilizing the power system. The purpose is to obtain equipment.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a reactive power compensator connected to an electric power system via a transformer, in which the transformer is set at an upper limit of a range in which the transformer does not become overloaded. , is equipped with an overload prevention limiter that limits the output reactive power.

(Function) In this invention, since the output reactive power value is limited to a value set at the upper limit of the range in which the transformer is not overloaded, the output is slightly limited compared to the ideal value. , compared to being disconnected from the grid due to overload.
It is much more effective in stabilizing the grid.

(Embodiment) FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, the same elements as those in FIG. 2 showing the conventional device are given the same reference numerals, and the explanation thereof will be omitted. Moreover, an overload prevention limiter 21 surrounded by a broken line is newly added to the conventional device.

Here, an instrument transformer 5-2 is provided to detect the secondary voltage of the transformer 4, and an instrument current transformer 6-2 is provided to detect the secondary current of the transformer 4. , each secondary side is connected to a reactive power detection circuit 15. The output of this reactive power detection circuit 15 is added as the subtracted input of the subtracter 9-3, and the output of the setting device 16 that sets the regulation value of the advanced reactive power flowing into the transformer 4 is added as the subtracted input of the subtracter 9-3. Added as input.

The output of this reactive power detection circuit 15 is also added as the subtracted input of another subtractor 9-4, and the output of the setting device 17 that sets the regulation value of delayed reactive power flowing into the transformer 4 is subtracted. It is added as a subtraction input to the unit 9-4. The output of the subtracter 9-3 is then applied to a negative value passing circuit 18 that passes only negative values.

Furthermore, the output of this negative value passing circuit 18 is passed through a first-order lag circuit 20-1 with a gain of 1 time constant T to a subtracter 9-5.
is added as a subtraction input. Note that this subtracter 9-5
The output of the proportional-integral circuit 12 with a limiter is added as the human power to be subtracted. On the other hand, the output of the subtracter 9-4 is applied to a positive value passing circuit 19 that passes only positive values. moreover,
The output of this positive value passing circuit 19 is added to the gain as a subtraction input of a subtracter 9-6 via a first-order lag circuit 20-2 with a time constant of 1 T. The output of the subtracter 9-5 is added as the subtracted input of the subtracter 9-6, and the output of the subtracter 9-6 is added to the firing angle determining circuit 13.

The operation of this embodiment configured as described above will be explained below.

The setter 16 sets the reactive power regulation value to -1.0pu, and the setter 17 sets the reactive power regulation value to +1.0pu.
Assume that it is set to 0pu. On the other hand, the voltage-current characteristics (◎
-■-◎), at 0 points and 0 points, VXI-±1
．． 1 pu exceeds VXI-±1.0 pu.

First, consider the case where the 0 point, that is, the leading reactive power exceeds -1.0 pu.

At this time, the instrument transformer 5-2 and the instrument current transformer 6-
Based on each detected value of 2, the reactive power detection circuit 15 detects reactive power Vx I--1, 1pu. The subtracter 9-3 calculates the difference between this reactive power -1,1 pu and the set value -1, Opu of the setter 16, calculates -0,1 pu, and adds it to the negative value passing circuit 18. Since the calculated value is negative, it passes through the negative value passing circuit 18 and is applied to the first-order lag circuit 20-1. In this case, if the gain K of the -order lag circuit 20-1 is large, the effect of the limiter is large, and the output of the reactive power compensator immediately becomes -1.0 pu or less (the absolute value is 1.0 pu).
pu).

At point 0 in FIG. 3, the output of the limiter-equipped proportional-integral circuit 12 is originally "0", but when the output current of the thyristor control reactor is set to "0", the lead reactive power output from the capacitor 3 is -1.0 pu. As a result, the transformer 4 is overloaded.

Therefore, the output of the -order lag circuit 20-1 increases in negative value until the output reactive power of the reactive power compensator reaches -1.0 pu. That is, the output of the subtractor 9-5 increases in positive value, increasing the output current of the thyristor-controlled reactor. The effect of increasing the current of the thyristor control reactor is that the reactive power output from the reactive power compensator is -1,
Until it becomes 0pu or less, that is, reactive power detection circuit 1
This continues until the output of 5 becomes equal to or less than the set value of the setter 16 by -1.0.

As a result, the reactive power output by the reactive power compensator is −
It can be suppressed to 1.0 pu or less. As a result, the voltage-current characteristic in Figure 3 becomes ◎-■-■-〇 instead of ◎-■-◎, and the leading reactive power output by the reactive power compensator is always -1
, 0 and pu or less.

Next, the delayed reactive power output by the reactive power compensator is +1
．． The operation when the value exceeds Opu will be explained.

In FIG. 3, if the output of the reactive power compensator is +1.1 pu at point 0, it exceeds the regulation value of 1.0.

At this time, the instrument transformer 5-2 and the instrument current transformer 6-
Based on each detected value of 2, the reactive power detection circuit 15 detects reactive power Vx I −+1.1 pU. For this reactive power +1.1 pu, the subtracter 9-4 is set by the setter 16.
Calculate the difference from the set value of +1.0 pu, +o, tp
u is calculated and added to the positive value passing circuit 19. Since this calculated value is positive, it passes through the positive value passing circuit 19 and is added to the first-order lag circuit 20-2.

At point 0 in FIG. 3, the output of the limiter-equipped proportional-integral circuit 12 is designed to maximize the output current of the cyrisk control reactor.

Therefore, the output of the -order lag circuit 20-2 increases in positive value until the output reactive power of the reactive power compensator reaches +1.0 pu. In other words, since the output of the proportional-integral circuit 12 with limiter is maximum on the positive side, the -th lag circuit 2
The output of 0-2 is added to the subtraction input of the subtracter 9-8 to cause the subtracter 9-6 to output a value smaller than that of the proportional-integral circuit with limiter 12, thereby reducing the output current of the thyristor-controlled reactor. In this way, the action of reducing the current of the thyristor control reactor continues until the reactive power output from the reactive power compensator becomes +1.0 pu or less, that is, the output of the reactive power detection circuit I5 reaches the setting value of the setting device 16 +
This continues until it becomes 1.0 or less.

As a result, the reactive power output by the reactive power compensator is +
It can be suppressed to 1.0 pu or less. As a result, the voltage-current characteristic in Figure 3 is not ◎-◎-◎, but ◎-■-■-■-
H, and the advanced reactive power output by the reactive power compensator is always less than +1.0 pu.

Thus, according to this embodiment, it is possible to prevent overload of the transformer 4, which may occur when the reactive power is increased.

In addition, in the above embodiment, the regulation value of reactive power is set to ±1.
．． Although it is set to 0 pu, this value may be set to any other value as long as it is at the upper end of the range within which the transformer will not be overloaded.

〔Effect of the invention〕

As is clear from the above explanation, according to this invention,
Equipped with an overload prevention limiter that limits the output reactive power below a set value at the upper limit of the range within which the transformer will not be overloaded. Disconnection can be prevented, thereby further stabilizing the power system.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure is a block diagram showing the configuration of a conventional reactive power compensator.
FIG. 3 is a current-voltage characteristic diagram in the reactive power compensator. 1-1, l-2... Thyristor, 2... Reactor, 3-... Capacitor, 4... Transformer, 5-1
, 5-2-...Instrument transformer, e-t, 8-2-
...Instrument current transformer, 7...Voltage detection circuit, 8...Reference voltage setter, 9-1 to 9-6...Subtractor, Engineering 0...
・Current detection circuit, 11 proportionality circuit, I2... proportional integral circuit with limiter, 13... firing angle determination circuit, 14...
・Gate pulse generation circuit, 15... Reactive power detection circuit, 18.17... Setting device, I8... Negative value passing circuit,
I9...Positive value passing circuit, 20-120-2...-Next delay circuit, 21...Overload prevention limiter. Figure 3, applicant's agent Mr. Sato

Claims (1)

[Claims] A reactive power compensator connected to a power grid via a transformer, comprising an overload prevention limiter that limits output reactive power to a value set at the upper limit of a range in which the transformer does not become overloaded. A reactive power compensator characterized by: