JPH11143561A - Voltage variation suppressing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the capacity of a self-excited converter as well as its cost by limiting the level and duration of an overload exceeding the rated capacity and compensating for the load variation. SOLUTION: When the power of a fluctuating load exceeds the rated capacity of a self-excited converter, a limiting value of a limiter circuit 12B is reduced in response to the level and duration of the overload. Thus, a temporary output occurs in an overload area when the power of the fluctuating load exceeds the rated capacity of the self-excited converter by the change of limiting value of the circuit 12B. When the above temporary output continues, the output is temporarily reduced less than the rated capacity. That is, if the power of the fluctuating load exceeds the rated capacity of the self-excited converter and an overload state is caused, the level and duration of overload of the self-excited converter are limited in response to the power variation of the fluctuating load. Thus, the converter is available for a short time in the overload area and the rated capacity of the converter is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power supply system (hereinafter, referred to as a power supply system).
The present invention relates to an improvement of a voltage fluctuation suppressing device that suppresses a voltage fluctuation of a power supply system caused by a power fluctuation of a load in a system that supplies power from a power supply to a load having a large power fluctuation.

[0002]

2. Description of the Related Art FIG. 9 is a schematic diagram showing an example of a configuration in which a conventional voltage fluctuation suppressing device is provided in a system for supplying power from a power supply to a load having a large power fluctuation (hereinafter referred to as a variable load). is there.

In FIG. 9, power is supplied from a power supply 1 via a power transmission line 2 to a system. This system is configured by connecting a variable load 3 which is a cause of voltage fluctuation and a self-excited converter 4 which is voltage fluctuation suppressing means in parallel, and the self-excited converter 4 is controlled by a control circuit 10 thereof. It is supposed to be.

The self-excited converter 4 and the control circuit 10
Thus, the voltage fluctuation suppressing device is configured. In such a system, when the self-excited converter 4 is not provided, the bus voltage fluctuates due to the power fluctuation of the variable load 3. It is known that voltage fluctuation is mainly caused by reactive power fluctuation.

[0005] The magnitude ΔVL is the variable load 3
Is the reactive power fluctuation of ΔQL and the reactance of transmission line 2 is X
If S, it is expressed by the following equation. ΔVL = XS · ΔQL (1) In the above formula, unless otherwise specified, the expression is expressed by using the PU method, and PU is used as a unit of voltage, reactance, and power.

[0006] This voltage fluctuation adversely affects the general load connected to the same system, for example, flickering of lighting,
This may cause a malfunction or the like of the electronic device. The self-excited converter 4 serving as a voltage fluctuation suppressing means is provided with the reactive power fluctuation Δ
By compensating for QL, voltage fluctuation ΔVL is suppressed. The self-excited converter 4 has various circuit types. A typical example thereof is a voltage source PW described in Japanese Patent Application Laid-Open No. 3-183324.
There is a device using an M inverter.

As shown in FIG. 9, the reactive power fluctuation ΔQ is calculated by using a bus voltage detected by the instrument transformer 6 and a current of the variable load 3 output by the current transformer 7.
By controlling the output reactive power QC of the self-excited converter 4 so as to detect L and cancel it, the variation ΔQS of the reactive power supplied from the power supply 1 is reduced,
This is to suppress the voltage fluctuation ΔVS.

This can be expressed by the following equation. QC = −ΔQL (2) ΔQS = ΔQL + QC = 0 (3) ΔVS = XS · ΔQS = 0 (4) Similarly, the fluctuation of the bus voltage also occurs for the negative-phase current and the harmonic current of the variable load 3. Which can be suppressed by the self-excited converter 4.

[0009] Here, the power caused by the reactive power, the negative-phase current and the harmonic current will be collectively referred to as power fluctuation. The control circuit 10 of the self-excited converter 4 for performing the above-described compensation functions as described below.

The instantaneous real power and imaginary power of the fluctuating load 3 are detected by the p and q detection detection circuit 11. This instantaneous real power,
The imaginary power is described in “IEEJ Transactions 5160, pp. 41-48”.
It is defined in "Generalized Theory of Instantaneous Reactive Power and Its Application", and includes the power caused by the reactive power, the negative-phase current, and the harmonic current.

The compensation current calculation circuit 12 calculates a current reference _ic ^* of the self-excited converter 4. FIG. 10 is a block diagram showing a configuration example of a conventional compensation current calculation circuit 12, and its function will be described below.

That is, the instantaneous real power p _L and the instantaneous imaginary power q _{L of} the variable load 3 detected by the p, q detection circuit 11
Are input to the compensation component extraction circuit 12A, and the components p _L ′ and q _L ′ to be compensated by the self-excited converter 4 are extracted.

The extracted components p _L ′ and q _L ′ differ depending on the type of the variable load 3 and the purpose of suppressing the voltage variation.
A component to be compensated is selected from the reactive power, the power resulting from the negative phase current, and the power resulting from the harmonic current.

The components p _L ′ and q _L ′ are input to a limiter circuit 12 B, and are subjected to a limiter so as not to exceed the rated capacity of the self-excited converter 4, thereby obtaining components p _c ^* and q _c ^*. Can be

Further, by the instantaneous current calculation circuit 12C,
Component p _c ^*, by using the q _c ^* and the system voltage, p, by the inverse operation of q detection circuit 11, the self-excited converter 4 in the current reference i _c ^* is calculated.

On the other hand, the error detecting circuit 13 detects a deviation between the current reference _ic ^* and the output current _ic of the self-excited converter 4 detected by the current transformer 8 so that the deviation becomes zero. to calculates the control signal E _c of the voltage source PWM inverter by the current control circuit 14. The PWM circuit 15 generates a gate signal of the PWM inverter constituting the self-excited converter 4.

[0017]

In such a conventional voltage fluctuation suppressing device, in order to completely suppress the voltage fluctuation of the power supply system, as shown in the above equation (2), the variable load 3 A device capacity equivalent to the power fluctuation is required.

However, since the amount of power fluctuation of the variable load 3 is not constant but changes, if a voltage fluctuation suppressing device corresponding to the maximum load power fluctuation is installed,
There is a problem in that the capacity of the self-excited converter 4 is large and is not economical, and when the load fluctuation is small, the voltage fluctuation suppressing device is not fully utilized.

FIG. 11 is a waveform diagram showing an example of the fluctuation of the reactive power of the variable load 3 and the fluctuation of the voltage caused by the fluctuation. This is a measurement result of an AC arc furnace for steelmaking. It can be seen that there is a difference of about twice in the magnitude of the reactive power fluctuation and the voltage fluctuation between the melting period and the refining period.

In the melting period, a short circuit occurs between the electrode and the scrap, and the reactive power and the voltage fluctuation may suddenly increase. In this case, since the purpose of the voltage fluctuation suppressing device is to suppress a large voltage fluctuation during the melting period, the capacity of the self-excited converter 4 is commensurate with the maximum reactive power fluctuation of the variable load 3, and a large device is required. Required,
The equipment price increases.

Further, in the refining period, since the power fluctuation of the variable load 3 is small, the output of the self-excited converter 4 is about one half of the rated value, and the voltage fluctuation suppressing device is not fully utilized. An object of the present invention is to provide a voltage fluctuation suppressing device capable of reducing the capacity of a self-excited converter and reducing the cost.

[0022]

According to a first aspect of the present invention, there is provided an apparatus for suppressing voltage fluctuation of a power supply system in a system for supplying power from a power supply system to a load having large power fluctuations. In the self-excited converter, which is a voltage fluctuation suppressing means provided in parallel with the load, and by limiting the magnitude and duration of overload exceeding the rated capacity of the self-excited converter according to the power fluctuation of the load, Control means for compensating for power fluctuations of the load.

Therefore, in the voltage fluctuation suppressing device according to the first aspect of the present invention, when the load power fluctuation exceeds the rated capacity of the self-excited converter and becomes overloaded, the load is overloaded in accordance with the load power fluctuation. Acts to limit the size and the duration of the self-commutated converter in the overload region for a short time, and the rated capacity of the self-excited converter can be reduced.

According to the second aspect of the present invention, the difference between the power fluctuation of the load and the rated capacity of the self-excited converter is integrated with the self-excited converter as voltage fluctuation suppressing means provided in parallel with the load, Control means for controlling the compensation power of the self-excited converter by multiplying the power fluctuation amount of the load by a coefficient determined in inverse proportion to the magnitude of the integral output.

Therefore, in the voltage fluctuation suppressing device according to the second aspect of the present invention, the overload state is limited by the magnitude and duration of the fluctuation of the load power exceeding the rated capacity of the self-excited converter. Therefore, the self-excited converter can be used for a short time in the overload region, and the rated capacity of the self-excited converter can be reduced.

On the other hand, according to the third aspect of the present invention, a self-excited converter which is a voltage fluctuation suppressing means provided in parallel with the load, and a difference between the output power of the self-excited converter and the rated capacity are integrated, and the integration is performed. Control means for controlling the compensation power of the self-excited converter by multiplying the power variation of the load by a coefficient determined in inverse proportion to the magnitude of the output.

Therefore, in the voltage fluctuation suppressing device according to the third aspect of the present invention, the overload state is limited by the magnitude and duration of the output power of the self-excited converter exceeding its rated capacity. In addition, the self-excited converter can be used for a short time in the overload region, and the rated capacity of the self-excited converter can be reduced.

According to the present invention, a self-excited converter as a voltage fluctuation suppressing means provided in parallel with the load and a coefficient determined in inverse proportion to a cooling medium temperature of the self-excited converter are determined by the load of the load. Control means for controlling the compensation power of the self-excited converter by multiplying the power fluctuation amount.

Therefore, in the voltage fluctuation suppressing device according to the fourth aspect of the present invention, the overload state is limited by the way of increasing the temperature of the cooling medium of the self-excited converter.
The self-excited converter can be used for a short time in the overload region, and the rated capacity of the self-excited converter can be reduced.

Further, according to the invention of claim 5, a self-excited converter as a voltage fluctuation suppressing means provided in parallel with the load,
The difference between the reactive power fluctuation of the load and the rated capacity of the self-excited converter is integrated, and a numerical value determined in inverse proportion to the magnitude of the integrated output is defined as a compensation reactive power limiter value of the self-excited converter. Control means for controlling the compensation power of the exciter converter.

Therefore, in the voltage fluctuation suppressing device according to the fifth aspect of the present invention, the overload state is limited by the magnitude and duration of the reactive power fluctuation exceeding the rated capacity of the self-excited converter. Thus, the self-excited converter can be used for a short time in the overload region, and the rated capacity of the self-excited converter can be reduced.

As described above, the self-excited converter can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter can be reduced to reduce the cost. It becomes possible.

[0033]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment: Corresponding to Claim 1) FIG. 1 is a block diagram showing a configuration example of a compensation current calculation circuit in a voltage fluctuation suppressing device according to this embodiment, and FIGS.
The same parts as those described above are denoted by the same reference numerals and the description thereof will be omitted, and here, only different parts will be described.

That is, as shown in FIG. 1, the compensation current calculation circuit of the present embodiment has a limiter calculation circuit 1 shown in FIG.
2E is newly added, and the limiter value of the limiter circuit 12B is made variable.

The limiter operation circuit 12E limits the magnitude and duration of the overload exceeding the rated capacity of the self-excited converter 4 according to the power fluctuation of the variable load 3, and compensates for the power fluctuation of the variable load 3. Thus, the limiter value of the limiter circuit 12B is determined.

Next, the operation of the voltage fluctuation suppressing device provided with the compensation current calculation circuit of the present embodiment configured as described above will be described. Note that the overall operation of the voltage fluctuation suppressing device is the same as that of FIGS. 9 and 10 described above, and thus the description thereof is omitted, and only the operation of the different portions will be described here.

In FIG. 1, the limiter operation circuit 12E outputs to the limiter circuit 12B a limiter value that changes according to the power fluctuation of the variable load 3. That is, when the power fluctuation of the variable load 3 is smaller than the rated capacity of the self-excited converter 4, the limiter value of the limiter circuit 12B becomes the value of the rated capacity. Exceeds the rated capacity, the limiter value of the limiter circuit 12B decreases according to the magnitude and duration.

As described above, by changing the limiter value of the limiter circuit 12B, when the power fluctuation of the variable load 3 exceeds the rated capacity of the self-excited converter 4, the output temporarily becomes in the overload region. If the state continues, the output temporarily decreases and acts so that the output is equal to or less than the rated capacity.

That is, when the power fluctuation of the variable load 3 exceeds the rated capacity of the self-excited converter 4 and becomes overloaded,
According to the power fluctuation of the variable load 3, the self-commutated converter 4 acts to limit the magnitude and duration of the overload.

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 can be reduced.

FIG. 2 is a schematic diagram showing the above-described response.
As described above, in the voltage fluctuation suppressing device according to the present embodiment, the magnitude of the overload exceeding the rated capacity of the self-excited converter 4 provided in parallel with the variable load 3 in accordance with the power fluctuation of the variable load 3 When the power fluctuation of the variable load 3 exceeds the rated capacity of the self-excited converter 4 and becomes overloaded, the fluctuation is suppressed. Since the magnitude and duration of the overload are limited according to the power fluctuation of the load 3, the self-commutated converter 4 can be used for a short time in the overload region, and the rated capacity of the self-commutated converter 4 is reduced. can do.

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 can be reduced.
It is possible to reduce the price.

(Second Embodiment: Corresponding to Claim 2) FIG. 3 is a block diagram showing a configuration example of a compensation current calculation circuit in a voltage fluctuation suppressing device according to the present embodiment.
The same parts as those described above are denoted by the same reference numerals and the description thereof will be omitted, and here, only different parts will be described.

That is, as shown in FIG. 3, the compensation current calculation circuit of the present embodiment employs the limiter circuit 1 shown in FIG.
2B and the limiter operation circuit 12E are connected to the power detection circuit 1
2F, a difference detection circuit 12G, an integration circuit 12H, a time limit characteristic circuit 12I, and a multiplier 12J.

The power detection circuit 12F inputs the instantaneous real power p _L ^′ and the instantaneous imaginary power q _L ^′ detected by the compensation component extraction circuit 12A, and calculates the compensation power P. The difference detection circuit 12G calculates a difference (excess amount) ΔP between the compensation power P calculated by the power detection circuit 12F and the rated capacity of the self-excited converter 4.

The integrating circuit 12H integrates the excess amount ΔP calculated by the difference detecting circuit 12G to determine the degree of overload. The inverse time characteristic circuit 12I inputs the degree of overload determined by the integration circuit 12H and determines a limiter value that is inversely proportional to the magnitude of the overload.

The multiplier 12J includes a compensation component extraction circuit 12A
Real power p _L ^′ and instantaneous imaginary power q _L detected by
^'A, multiplied by the limiter value determined by inverse time characteristic circuit 12I, the compensation amount p to the instantaneous current calculation circuit 12C
_c ^*, to calculate the q _c ^*.

Next, the operation of the voltage fluctuation suppressing device provided with the compensation current calculation circuit of the present embodiment configured as described above will be described. Note that the overall operation of the voltage fluctuation suppression device is the same as that in the case of FIG. 1 described above, and a description thereof will be omitted, and only operations of different portions will be described here.

In FIG. 3, in the power detection circuit 12F,
The instantaneous real power p _L ^′ detected by the compensation component extraction circuit 12A
From the instantaneous imaginary power q _L ^′ , the magnitude is calculated as the compensation power P by the following equation.

P = √ (p _L ^{' 2} + q _L ^{' 2} ) (5) Next, the difference detection circuit 12G calculates the difference between the compensation power P and the rated capacity of the self-excited converter 4, The excess amount ΔP with respect to the rated capacity of the self-excited converter 4 is calculated.

Next, in the integrating circuit 12H, the excess amount Δ
The degree of overload is determined by integrating P, that is, the degree of overload is determined by the magnitude of the excess amount ΔP and its duration, and the overload state of the device is determined.

When the excess amount ΔP is negative, that is, when the compensation power P is smaller than the rated capacity of the self-excited converter 4, a limiter is provided to prevent the integrated output of the integrating circuit 12H from becoming negative. ing.

Next, the time limit characteristic circuit 12I outputs a limiter value with the degree of overload as an input. The characteristic is determined from the overload tolerance of the self-excited converter 4 and shows a characteristic that is inversely proportional to the degree of overload.

The multiplier 12J multiplies the instantaneous real power p _L ^′ and the instantaneous imaginary power q _L ^′ of the compensating component by the limiter value determined by the time limit characteristic circuit 12I in this manner, thereby obtaining a compensation amount. p _c ^*, to calculate the q _c ^*.

As described above, the overload of the self-excited converter 4 is limited by the magnitude and duration of the power fluctuation of the variable load 3 exceeding the rated capacity of the self-excited converter 4.

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 can be reduced.

FIG. 4 is a schematic diagram showing the above-described response.
As described above, in the voltage fluctuation suppressing device according to the present embodiment, the difference between the power fluctuation of the variable load 3 and the rated capacity of the self-excited converter 4 provided in parallel with the variable load 3 is integrated, and this integrated output is obtained. Is multiplied by the coefficient determined in inverse proportion to the magnitude of the variable load 3 to control the compensation power of the self-excited converter 4, so that the power fluctuation of the variable load 3 The overload condition is limited by the size and the duration of exceeding the rated capacity of the converter 4, so that the self-excited converter 4 can be used for a short time in the overload region, The capacity can be reduced.

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 is reduced.
It is possible to reduce the price.

(Third Embodiment: Corresponding to Claim 3) FIG. 5 is a block diagram showing a configuration example of a compensation current calculation circuit in a voltage fluctuation suppressing device according to the present embodiment.
The same parts as those described above are denoted by the same reference numerals and the description thereof will be omitted, and here, only different parts will be described.

That is, as shown in FIG. 5, the compensation current calculation circuit of the present embodiment has a p, q detection circuit 12K shown in FIG.
And the output of the p, q detection circuit 12K is sent to the power detection circuit 12F instead of the instantaneous real power p _L ^′ and the instantaneous imaginary power q _L ^′ detected by the compensation component extraction circuit 12A. It is configured to input.

The p, q detection circuit 12K receives the system voltage v detected by the instrument transformer 6 and the output current _{ic of} the self-excited converter 4 detected by the current transformer 8, detecting the instantaneous real power p _c and imaginary power q _c self-excited converter 4.

Next, the operation of the voltage fluctuation suppressing device having the compensation current operation circuit of the present embodiment configured as described above will be described. Note that the overall operation of the voltage fluctuation suppression device is the same as that in the case of FIG. 3 described above, and a description thereof will not be repeated.

In FIG. 5, the p and q detection circuit 12K calculates the system voltage v detected by the instrument transformer 6 and the output current _{ic of} the self-excited converter 4 detected by the current transformer 8.
Detecting the instantaneous real power p _c and imaginary power q _c self-excited converter 4.

[0064] In the power detection circuit 12F, from the self instantaneous real power of commutated converters 4 p _c and imaginary power q _c, calculates an output power P _c of the self-commutated converter 4 by the following equation. P _c = √ (p _c ² + q _c ² ) (6) Next, in the difference detection circuit 12G, the difference between the output power P _c of the self-excited converter 4 and the rated capacity of the self-excited converter 4 is calculated. The calculated excess amount ΔP with respect to the rated capacity of the self-excited converter 4 is calculated.

Next, the excess amount ΔP is determined by the integration circuit 12H
, And operates in the same manner as in the case of FIG. 3 described above. As described above, the output power _Pc of the self-excited converter 4 acts to limit the overload state of the self-excited converter 4 depending on the magnitude and duration of the output power _Pc exceeding its rated capacity.

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 can be reduced.

FIG. 6 is a schematic diagram showing the above-described response.
As described above, in the voltage fluctuation suppressing device according to the present embodiment, the difference between the output power of the self-excited converter 4 provided in parallel with the variable load 3 and the rated capacity is integrated, and the magnitude of this integrated output is calculated. Since the compensation power of the self-excited converter 4 is controlled by multiplying the power fluctuation amount of the variable load 3 by a coefficient determined in inverse proportion, the output power of the self-excited converter 4 exceeds its rated capacity. Since the overload state is limited by the size and duration, the self-commutated converter 4 can be used for a short time in the overload region, and the rated capacity of the self-commutated converter 4 can be reduced. .

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 is reduced.
It is possible to reduce the price.

(Fourth Embodiment: Corresponding to Claim 4) FIG. 7 is a block diagram showing an example of the configuration of a compensation current calculation circuit in a voltage fluctuation suppression device according to the present embodiment.
The same parts as those described above are denoted by the same reference numerals and the description thereof will be omitted, and here, only different parts will be described.

That is, as shown in FIG. 7, the compensation current calculation circuit of the present embodiment uses the power detection circuit 1 shown in FIG.
2F, the difference detection circuit 12G, and the integration circuit 12H are omitted, and the cooling medium temperature of the self-excited converter 4 is replaced with the output of the integration circuit 12H.
Input to I.

The time limit characteristic circuit 12I includes the self-excited converter 4
And determines a limiter value that is inversely proportional to its magnitude. Next, the operation of the voltage fluctuation suppressing device including the compensation current calculation circuit of the present embodiment configured as described above will be described.

Since the overall operation of the voltage fluctuation suppressing device is the same as that of FIG. 3 described above, a description thereof will be omitted, and only the operation of different portions will be described.

In FIG. 7, the time limit characteristic circuit 12I outputs the limiter value by inputting the cooling medium temperature of the self-excited converter 4 as the degree of overload. The characteristic is determined from the temperature of the cooling medium of the self-excited converter 4 and shows a characteristic that is inversely proportional to the degree of overload.

That is, the devices constituting the self-excited converter 4 are mainly inverters and their transformers, and air, water, oil, etc. are used as a medium for cooling them. . Since the temperature is proportional to the output of the self-excited converter 4, by measuring the temperature of the cooling medium, the situation of overload can be known. Therefore, the temperature of the cooling medium is measured and input to the time limit characteristic circuit 121 to output a limiter value.

Then, the time limit characteristic circuit 1
The limiter value determined in 2I is input to the multiplier 12J, and operates in the same manner as in the case of FIG. 3 described above. As described above, the manner in which the temperature of the cooling medium of self-excited converter 4 rises acts to limit the overload state of self-excited converter 4.

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 can be reduced.

As described above, in the voltage fluctuation suppressing device according to the present embodiment, the coefficient determined in inverse proportion to the cooling medium temperature of the self-excited converter 4 provided in parallel with the Since the compensation power of the self-excited converter 4 is controlled by multiplying the amount of power fluctuation, the overload state is limited by the manner in which the temperature of the cooling medium of the self-excited converter 4 rises. Excited converter 4 can be used for a short time in the overload region, and the rated capacity of self-excited converter 4 can be reduced.

As a result, the self-excited converter 4 can be used in the overload region for a short time without causing overheating of the device, and the rated capacity of the self-excited converter 4 is reduced.
It is possible to reduce the price.

(Fifth Embodiment: Corresponding to Claim 5) FIG. 8 is a block diagram showing a configuration example of a compensation current calculation circuit in a voltage fluctuation suppression device according to the present embodiment.
The same parts as those described above are denoted by the same reference numerals and the description thereof will be omitted, and here, only different parts will be described.

That is, as shown in FIG. 8, the compensation current calculation circuit of the present embodiment includes a limiter calculation circuit 12E shown in FIG. 1 and a difference detection circuit 12G and an integration circuit 12H.
And a time limit characteristic circuit 12I, and the instantaneous real power p _L detected by the compensation component extraction circuit 12A.
^'As zero, the compensation component as the reactive power Q _L of variable load 3, the reactive power Q _L of the variable load 3, so that input to the limiter circuit 12B.

The difference detection circuit 12G calculates the reactive power Q _L of the variable load 3 detected by the compensation component extraction circuit 12A.
(Excess amount) ΔQ between the rated capacity and the rated capacity of the self-excited converter 4 is calculated.

The integrating circuit 12H integrates the excess amount ΔQ calculated by the difference detecting circuit 12G to determine the degree of overload. The reverse time limit characteristic circuit 12I inputs the degree of overload determined by the integration circuit 12H, and determines a limiter value of the limiter circuit 12B that is inversely proportional to the magnitude, that is, a compensation reactive power limiter value.

Next, the operation of the voltage fluctuation suppressing device having the compensation current calculation circuit of the present embodiment configured as described above will be described. Note that the overall operation of the voltage fluctuation suppression device is the same as that in the case of FIG. 1 described above, and a description thereof will be omitted, and only operations of different portions will be described here.

In FIG. 8, in the difference detection circuit 12G,
And reactive power Q _L of the detected by the compensation component extraction circuit 12A variable load 3, the difference between the rated capacity of self-commutated converter 4 is calculated, the excess amount ΔQ with respect to the rated capacity of self-commutated converter 4
Is calculated.

Next, in the integrating circuit 12H, the excess amount Δ
The degree of overload is determined by integrating Q, that is, the degree of overload is determined by the magnitude of the excess amount ΔQ and its duration, and the overload state of the device is determined.

Next, the time limit characteristic circuit 12I outputs the limiter value to the limiter circuit 12B with the degree of overload as an input. The characteristic is determined from the overload tolerance of the self-excited converter 4 and shows a characteristic that is inversely proportional to the degree of overload.

[0087] Then, the limiter circuit 12B, thus to by the limiter value determined in inverse time characteristic circuit 12I to, limit the reactive power Q _L of variable load 3 that is detected by the compensation component extraction circuit 12A, Q _c ^It is output as ^* to the instantaneous current calculation circuit 12C.

As described above, the overload state of the self-excited converter 4 is limited by the magnitude and duration of the fluctuation of the reactive power of the variable load 3 exceeding the rated capacity of the self-excited converter 4.

Thus, the self-excited converter 4 can be used for a short time in the overload region without causing overheating of the device, and the rated capacity of the self-excited converter 4 can be reduced.

As described above, in the voltage fluctuation suppressing apparatus according to the present embodiment, the reactive power fluctuation of the variable load 3 and the variable load 3
And the difference between the rated capacity of the self-excited converter 4 provided in parallel and the value determined in inverse proportion to the magnitude of this integrated output is defined as the compensation reactive power limiter value of the self-excited converter 4. Since the compensation power of the self-excited converter 4 is controlled, the reactive power fluctuation of the variable load 3
The state of overload is limited by the size and duration exceeding the rated capacity of the self-excited converter 4, so that the self-excited converter 4 can be used for a short time in the overload region.
Rated capacity can be reduced.

In this case, the power detector 12F is not required as compared with the above-described second embodiment, and the limiter circuit 12B can be used instead of the multiplier 12J. Can be realized.

[0092]

As described above, according to the voltage fluctuation suppressing device of the first aspect of the present invention, the voltage fluctuation suppressing device can
Since the magnitude and duration of the overload exceeding the rated capacity of the self-excited converter, which is a voltage fluctuation suppression means provided in parallel with the load, are limited to compensate for the power fluctuation of the load, The self-excited converter can be used in the overload region for a short time without causing overheating, and the capacity of the self-excited converter can be reduced, and the price can be reduced.

According to the voltage fluctuation suppressing device of the second aspect of the present invention, the difference between the power fluctuation of the load and the rated capacity of the self-excited converter which is a voltage fluctuation suppressing means provided in parallel with the load is integrated. However, since the compensation power of the self-excited converter is controlled by multiplying the power variation of the load by a coefficient determined in inverse proportion to the magnitude of the integral output, the self-commutated converter is controlled without overheating. The exciter can be used for a short time in the overload region, so that the capacity of the self-excited converter can be reduced and the price can be reduced.

On the other hand, according to the voltage fluctuation suppressing device of the third aspect of the present invention, the difference between the output power of the self-excited converter as the voltage fluctuation suppressing means provided in parallel with the load and the rated capacity is integrated. Since the compensation power of the self-excited converter is controlled by multiplying the power fluctuation of the load by a coefficient determined in inverse proportion to the magnitude of the integrated output, the self-excited converter can be used without causing overheating of the device. Can be used for a short time in the overload region, and the capacity of the self-excited converter can be reduced, and the cost can be reduced.

Further, according to the voltage fluctuation suppressing device of the present invention, the coefficient determined in inverse proportion to the cooling medium temperature of the self-excited converter, which is a voltage fluctuation suppressing means provided in parallel with the load, is determined by the load. The compensation power of the self-excited converter is controlled by multiplying the power fluctuation amount of the self-excited converter, so that the self-excited converter can be used in the overload region for a short time without causing overheating of the device. It is possible to reduce the capacity of the exciter-type converter and reduce the price.

Further, according to the voltage fluctuation suppressing device of the present invention, the difference between the reactive power fluctuation of the load and the rated capacity of the self-excited converter as the voltage fluctuation suppressing means provided in parallel with the load is determined. Integrating and controlling the compensation power of the self-excited converter as a value determined in inverse proportion to the magnitude of the integrated output as the compensation reactive power limiter value of the self-excited converter. It is possible to use the self-excited converter in the overload region for a short time without causing the problem, simplify the device configuration, reduce the capacity of the self-excited converter, and reduce the cost. Become.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a compensation current calculation circuit in a voltage fluctuation suppression device according to the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the voltage fluctuation suppressing device according to the first embodiment.

FIG. 3 is a block diagram showing a second embodiment of a compensation current calculation circuit in the voltage fluctuation suppression device according to the present invention.

FIG. 4 is a schematic diagram for explaining the operation of the voltage fluctuation suppressing device according to the second embodiment.

FIG. 5 is a block diagram showing a third embodiment of the compensation current calculation circuit in the voltage fluctuation suppression device according to the present invention.

FIG. 6 is a schematic diagram for explaining the operation of the voltage fluctuation suppressing device according to the third embodiment.

FIG. 7 is a block diagram showing a fourth embodiment of the compensation current calculation circuit in the voltage fluctuation suppression device according to the present invention.

FIG. 8 is a block diagram showing a fifth embodiment of the compensation current calculation circuit in the voltage fluctuation suppression device according to the present invention.

FIG. 9 is a schematic diagram showing a configuration example in a case where a system for supplying power to a variable load includes a conventional voltage fluctuation suppressing device.

FIG. 10 is a block diagram showing a configuration example of a compensation current calculation circuit in a conventional voltage fluctuation suppression device.

FIG. 11 is a waveform chart showing an example of a reactive power fluctuation of a variable load and a voltage fluctuation caused by the fluctuation.

[Explanation of symbols]

 1. Power supply, 2. Transmission line. 3: Variable load, 4: Self-excited converter, 6: Transformer for instrument, 7, 8: Current transformer, 10: Control circuit, 11: p and q detection circuit, 12: Compensation current calculation circuit, 13: Error Detection circuit, 14: current control circuit, 15: PWM circuit, 12A: compensation component extraction circuit, 12B: limiter circuit, 12C: instantaneous current calculation circuit, 12E: limiter calculation circuit, 12F: power detection circuit, 12G: difference detection circuit 12H: integration circuit; 12I: anti-time characteristic circuit; 12J: multiplier; 12K: p, q detection circuit.

Claims (5)

[Claims] In a system for supplying power from a power supply system to a load having a large power fluctuation, an apparatus for suppressing voltage fluctuation of the power supply system, wherein the self-excited conversion means is a voltage fluctuation suppression means provided in parallel with the load. And a control means for limiting the magnitude and duration of an overload exceeding the rated capacity of the self-excited converter in accordance with the power fluctuation of the load, and compensating for the power fluctuation of the load. A voltage fluctuation suppressing device characterized by the above-mentioned. 2. An apparatus for suppressing voltage fluctuation of a power supply system in a system for supplying power from a power supply system to a load having a large power fluctuation, wherein the self-excited conversion means is a voltage fluctuation suppression means provided in parallel with the load. Integrating the difference between the power fluctuation of the load and the rated capacity of the self-excited converter, multiplying the power fluctuation of the load by a coefficient determined in inverse proportion to the magnitude of the integrated output, A voltage fluctuation suppressing device, comprising: control means for controlling compensation power of a self-excited converter. 3. An apparatus for suppressing voltage fluctuations in a power supply system in a system for supplying power from a power supply system to a load having a large power fluctuation, wherein the self-excited conversion means is a voltage fluctuation suppression means provided in parallel with the load. And integrating the difference between the output power and the rated capacity of the self-excited converter, multiplying the power variation of the load by a coefficient determined in inverse proportion to the magnitude of the integrated output, and performing the self-excited conversion. And control means for controlling the compensation power of the device. 4. A device for suppressing voltage fluctuations of the power supply system in a system for supplying power from a power supply system to a load having a large power fluctuation, wherein the self-excited conversion means is a voltage fluctuation suppression means provided in parallel with the load. And control means for controlling the compensation power of the self-excited converter by multiplying the power fluctuation amount of the load by a coefficient determined in inverse proportion to the cooling medium temperature of the self-excited converter. A voltage fluctuation suppressing device characterized by the above-mentioned. 5. An apparatus for suppressing voltage fluctuations of the power supply system in a system for supplying power from a power supply system to a load having a large power fluctuation, wherein the self-excited conversion means is a voltage fluctuation suppression means provided in parallel with the load. And a difference between the reactive power fluctuation of the load and the rated capacity of the self-excited converter, and a value determined in inverse proportion to the magnitude of the integrated output is a compensation reactive power limiter of the self-excited converter. Control means for controlling the compensation power of the self-excited converter as a value.