JPH0919057A - Method and apparatus for controlling load power - Google Patents

Abstract

PURPOSE: To minimize voltage variation at customers by adjusting feeding power of a heavy power load corresponding to excessive value and reducing the variation of the voltage value at the predetermined point on the power distribution line when the measured voltage value of the predetermined point on the power distributing line within the premises becomes higher or lower than the reference value. CONSTITUTION: When an output voltage of a receiving voltage setting function 18 which is the reference voltage is, for example, a minus voltage and an input characteristic of a comparing function 19 is the subtraction function, a voltage level outputted from a rectifying function 16 is a minus voltage and it is matched with the adjusted output voltage of the receiving voltage setting function 18 when the voltage of power distribution line 1 is equal to the receiving voltage to be set by the receiving voltage setting function 18. When the input characteristic of the comparison function 19 is the adding function, the voltage level outputted from the rectifying function 16 is a positive voltage and it is matched with the adjusted output voltage of the receiving voltage setting function 18 when the voltage of the power distribution line 1 is equal to the receiving voltage to be set by the receiving voltage setting function 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control function for heavy power loads such as a high frequency induction furnace, and in particular, it is connected from a substation in a remote place via an automatic voltage regulator (SVR: hereinafter referred to as SVR). And a load power control method for reducing a voltage change caused by a change in current flowing through a transmission line forming a system and an impedance of the transmission line and an operation delay of an SVR. The present invention relates to a load power control device.

[0002]

2. Description of the Related Art The power control function of a high frequency induction furnace, which is a heavy power load, is constructed as shown in FIG. 6, for example.
In FIG. 6, the AC power transmitted by the three-phase distribution line 1 in the premises of the power user who forms the power system is converted into DC by the controllable rectification function 2A, and then is converted to DC by the inverter 2B. It is converted into electric power and supplied to the high frequency induction furnace 3. The controllable rectification function 2A is
For example, a rectification output is controlled by a power control device (hereinafter referred to as a control device) 4 for a high-frequency induction furnace, which is composed of a controllable rectifying element such as a thyristor and has a main function of adjusting the power supplied to the high-frequency induction furnace. Is configured to. Further, the current flowing through the distribution line 1 is detected by the instrument current transformer 5, and the converter 6 having a rectifying function obtains a supply current equivalent value which is a low-voltage DC. The supply voltage of the high-frequency induction furnace 3 is supplied to the first input terminal a of the PI adjusting function 9 by obtaining a low-voltage DC supply voltage equivalent value by the transformer 7 and the rectifying function 8.

A load composed of a switch 11 and a three-terminal variable resistor or the like between the common line 17 and the transmission line 10 of a DC voltage having a stable predetermined value created by the rectification function having a rectification stabilization function (not shown). The power setting function 12 is connected, and the adjustment terminal output of the load power setting function 12 is the PI adjustment function 9 described above.
Is input to the second input terminal b. Therefore, the PI adjustment function 9 compares the supply voltage equivalent value of the high frequency induction furnace 3 with the adjusted output voltage of the load power setting function 12, and the deviation value is PI.
It is processed by the characteristics of the adjusting function 9 and input to the control device 4. Here, the PI adjusting function 9 is composed of an amplifier having a predetermined gain, which compares signals input from two input terminals, and has a comparison result with a PI function (proportional amplification and integration function) and a differentiation function depending on conditions. Has been done. In the control device 4, the controllable rectification function 2A is controlled by the processing function configured in the control device 4 from the supply current equivalent value indicating the current value flowing through the distribution line 1 and the output value of the PI adjustment function 9. Creating and outputting signals. That is,
If the controllable rectification function 2A is configured by a thyristor, the output timing of the pulse signal supplied to the gate that determines the firing phase of the thyristor is controlled to control the rectified output of the controllable rectification function 2A. With the above-described configuration, the power supplied to the high frequency induction furnace 3 is controlled according to the adjustment of the load power setting function 12.

[0004]

By the way, in general, as shown in FIG. 7, electric power consumers are supplied with electric power by electric power distribution lines to form an electric power system. In FIG. 7, A is a three-phase transmission line, and the transmission power of the transmission line A is converted into a predetermined voltage at the substation 20 and the first distribution line 1
A is transmitted for a predetermined distance. In addition, after branching for distribution to the electricity consumers, SVR corrects the voltage lowered by the impedance of the first distribution line 1A,
Electric power is distributed to each electric power consumer by the second distribution line 1B. In other words, SVR measures about 7% of voltage fluctuations on the distribution line due to load fluctuations.
It is controlled to keep it within the range. The second distribution line 1B shown in FIG. 7 corresponds to the distribution line 1 shown in FIG. In FIG. 7, 22A _{1 to} 22A _n are loads of electric power consumers connected to the first distribution line 1A, 22B _{1 to} 22B _n are loads of electric power consumers connected to the second distribution line 1B, and 3 is 7 shows a heavy power load such as the high frequency induction furnace described in FIG. 6. When a heavy power load such as a high frequency induction furnace is turned on and off in such a transmission system, the voltage drop value due to the distribution line fluctuates due to the current change and the impedance of the distribution line. That is, both the first distribution line 1A and the second distribution line 1B correspond to conditions such as the location of the substation 20 and the location of a power consumer business establishment having a heavy power load, for example, between the two. Are installed at a long distance of about 4 km. Further, the SVR 21 sets the output voltage to a high value in order to correct the voltage drop at the business place of the electric power consumer, and has an operation delay of 20 seconds to 120 seconds.
For example, when a heavy power load such as a high frequency induction furnace is turned on and off, a large voltage fluctuation as illustrated in FIG. 8 occurs at the terminal of the second distribution line 1B.

That is, in FIG. 8, the distribution line voltage is 6825 volts while the heavy power load is off, but when the heavy power load is turned on, the distribution line voltage instantaneously drops to 5925 volts. Then, after the SVR operation delay, the distribution line voltage rises to 6405 volts and stabilizes. When the heavy power load is turned off, the distribution line voltage instantaneously rises to 7140 volts, and after the SVR operation delay, the distribution line voltage becomes 6
Drop to 825 volts. In this way, the SVR may cause a variation of about 20% when the variation is large. The transient characteristics shown in FIG. 8 are simplified. A delay characteristic may be given to the change in the electric power load when the high frequency induction furnace is turned on and off, but this is not practical because the operation time of the induction furnace is extended. Therefore, if it is supplied by a distribution line whose voltage value fluctuates as described above,
Electricity consumers have a problem that the supplied voltage fluctuates greatly. As a measure against the above-mentioned problems, conventionally, a function of supplying reactive power so as to suppress voltage fluctuations by using a reactive power compensator has been taken, but the reactive power compensator is an expensive device, There has been a demand for a function that is inexpensive and prevents voltage fluctuations. The present invention solves the above-mentioned problems (problems) of the conventional one, and when a heavy power load such as a high frequency induction furnace is used in a weak power system, the function of the SVR in the middle of the system is utilized to the maximum extent. An object of the present invention is to provide an inexpensive load power control method and load power control device for minimizing voltage fluctuations in power consumers.

[0006]

In order to solve the above problems, in a load power control method according to the present invention, a voltage measuring function at a predetermined point of a premises distribution line and a measured value of this voltage measuring function are preset. When the value exceeds the standard value, the control function to adjust the supply power of the heavy power load according to the excess value is provided, and the voltage of the predetermined point of the distribution line generated with the operation of the heavy power load is provided. The variation of the value is reduced. In this case, when the measured value of the voltage measurement function exceeds the preset reference value by plus or minus, the excess level value is converted by a step function having a predetermined characteristic corresponding to the excess value, and the converted value is used as a weight. It is desirable to adjust the power supply of the power load. Further, it is desirable to reduce the changing speed of the control signal via a delay element by a ramp function having a predetermined characteristic. Furthermore, when the measured value of the voltage measurement function exceeds the preset reference value by plus or minus, the excess level value is converted by the step function of the predetermined characteristic corresponding to this excess value, and the weight is converted by the converted value. It is more desirable to provide a control function for adjusting the supply power of the power load and reduce the changing speed of the control signal of this control function via a delay element by a ramp function having a predetermined characteristic.

Further, the load power control device according to the present invention calculates the load power setting function, the voltage measuring function at a predetermined point of the premises distribution line, and the deviation between the measured value of this voltage measuring function and a preset reference value. The deviation value detection function that determines and outputs the comparison result according to a predetermined condition, the function that superimposes the detection value of this deviation value detection function and the setting value of the load power setting function, and this superposition value If the measured value of the voltage measurement function exceeds the reference value set in advance by plus or minus, the supply power of the heavy power load is responded to by this excess value. It may be configured such that the fluctuation of the voltage value at the predetermined point on the premises caused by the operation of the heavy power load is reduced by adjusting

[0008]

According to the present invention, as described above, when the voltage measuring function at a predetermined point of the premises distribution line and the measured value of this voltage measuring function exceeds the reference value set in advance by plus or minus, it corresponds to this excess value. In order to reduce the fluctuation of the voltage value at a predetermined point on the premises that occurs with the operation of the heavy power load, the control function to adjust the supply power of the heavy power load is provided. Even if the power load is turned on and off, voltage fluctuations in the system to which the distribution line is connected will be minimized. When the measured value of the above voltage measurement function exceeds the preset reference value by plus or minus, the excess level value is converted by the step function of the predetermined characteristic corresponding to this excess value, and the heavy power load is converted by this converted value. In the case where the power supply to the control circuit is adjusted, it is possible to prevent the control characteristic from hunting.

Further, if the rate of change of the control signal of the control function for adjusting the supply power of the heavy power load is reduced via the delay element due to the ramp function of the predetermined characteristic, the function of the present invention functions smoothly. To do. The measured value of the voltage measurement function exceeds the preset reference value by plus or minus, and the excess level value is converted by the step function of a predetermined characteristic corresponding to this excess value, and the heavy power load is supplied by this converted value. By providing a control function for adjusting the electric power and reducing the fluctuation of the control signal of this control function via the delay element due to the ramp function of a predetermined characteristic, the above-mentioned hunting prevention function can be more reliably exhibited. Since the load power control device is configured as described above, even when a heavy power load such as a high frequency induction furnace is turned on and off, the voltage fluctuation of the system to which the heavy power load is connected can be minimized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a load power control apparatus to which a load power control method according to the present invention is applied will be described in detail with reference to FIGS. FIG. 1 shows an example in which the present invention is applied to a high frequency induction furnace which is an example of the heavy power load device described in the related art with reference to FIG. Therefore, in FIG. 1, the same or corresponding element functions as those shown in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG.
4A is a load power control device configured as a control function for adjusting the supply power of a heavy power load to which the load power control method according to the present invention is applied. The load power setting function 12 described above with reference to FIG. 6 in the load power control device 4A is configured by, for example, a first variable resistor of two triple terminal variable resistors,
The reference numeral is 12a. The adjustment terminal output of the load power setting function 12a is input to the first input terminal a of the addition function 13. The output of the addition function 13 is input to the delay function 14, which is a delay element of the ramp function, the details of which will be described later, and the output of the delay function 14 is input to the second input terminal b of the PI adjustment function 9 described above with reference to FIG. ing. The output of the PI adjusting function 9 is a control device (power control device for a high frequency induction furnace) having the same function as described with reference to FIG. 6 in the prior art.
4 and the output of the control device 4 is input to the controllable rectification function 2A to control the power of the high frequency induction furnace. The voltage of the distribution line 1 on the premises of the power consumer is stepped down to a predetermined voltage by the transformer 15, converted to a DC voltage by the rectification function 16, and input to the first input terminal a of the comparison function 19. There is. The transformer 15 and the rectifying function 16 constitute a voltage measuring function. At the second input terminal b of the comparison function 19, a stabilized DC voltage connected to the switch 11 and the load power setting function 12a, for example, a transmission line 10 of -10 volts, and a common wire 17 of 0 volt, for example. The output of the adjusting terminal of the power receiving voltage setting function 18 that determines the reference value of the power receiving voltage configured by a three-terminal variable resistor or the like connected between is connected. The voltages and polarities of the transmission line 10 and the common line 17 having the stable voltage described above may be appropriately set in correspondence with the voltages for other circuits not described so that the function described later in detail is satisfied. The output of the comparison function 19 is input to the level conversion function 20 having a step function whose details will be described later. To the level conversion function 20, the output voltage of the adjustment terminal of the voltage setting function 12b configured by the second variable resistor that is interlocked with the load power setting function 12a described above is input as the adjustment signal. The output of the level conversion function 20 is connected to the second input terminal b of the addition function 13 described above. The voltage setting function 12b includes the load power setting function 12a.
The transmission line 10 of the same stabilized DC power source as is directly connected. The voltage level and the polarity output from the rectification function 16 described above are, as will be described in detail later, the output of the received voltage setting function 18 which is a reference voltage, the voltage of the distribution line 1 to be controlled, and the comparison function 19. It is set in advance so as to correspond to the characteristics and the like. That is, when the output voltage of the power receiving voltage setting function 18 is a negative voltage as described above and the input characteristic of the comparing function 19 is the subtracting function, the voltage of the distribution line 1 is the power receiving voltage to be set by the power receiving voltage setting function 18. When the voltage is equal to the voltage, the voltage level output from the rectification function 16 is a negative voltage and is matched with the voltage of the regulated output voltage of the power reception voltage setting function 18. When the input characteristic of the comparison function 19 is the addition function and the voltage of the distribution line 1 is equal to the power reception voltage to be set by the power reception voltage setting function 18, the voltage level output from the rectification function 16 is a positive voltage. The voltage is adjusted to match the adjusted output voltage of the setting function 18.

The operation of the ramp function provided in the delay function 14 will be described with reference to FIG. FIG. 3 shows the concept of the delay function 14, in which the abscissa axis represents the passage of time, the ordinate axis represents the delay output, and A in FIG. 3 represents the output level change after inputting a signal of a predetermined level, B shows the change in output level after the signal is cut off. That is, it shows that the output level when a square signal is input from the addition function 13 changes with a ramp function. Therefore, the output signal for the input signal of the delay function 14 changes according to the function set in the delay function 14. That is, although not shown, the output level of the portion A in FIG. 3 becomes equal to the input level with a small delay time when the input level is small, and becomes equal to the input level with a large delay time when the input level is large. Also, delay function 1
Regarding the level of the portion B in FIG. 3 showing the case where the signal input to 4 is cut off, if the original input level is small, the output is lost with a small delay time, and if the input level is large, the output is lost with a large delay time. The characteristic of the ramp function is the addition function 13
Output level and this heavy power load equipment (high frequency induction furnace)
And the characteristics of the control device 4 and the characteristics of the SVR connected in front of the distribution line 1 may be appropriately set. For example, 2 if the input level changes by 5 volts.
Second, if the input level changes by 10 volts, set it as 4 seconds.

The operation of the step function provided in the level conversion function 20 will be described with reference to FIG. In FIG. 4, the horizontal axis represents the input level of the level conversion function 20, the center is the reference level, that is, the set value of the received voltage setting function 18 input to the comparison function 19 and the output value from the rectification function 16 are equal. It corresponds to. To the left and right, the right side is the direction in which the input signal level of the a terminal of the comparison function 19 is higher than the reference voltage, that is, the direction in which the output (α) of the comparison function 19 is increased to the positive side, and the left side is the a of the comparison function 19 The direction in which the input signal level of the terminal becomes lower than the reference voltage, that is, the comparison function 1
The directions in which the output (α) of 9 increases to the negative side are shown respectively. On the other hand, the vertical axis indicates the level conversion function 2 set in advance.
The output level of 0 is shown. Therefore, for example, the reference level on each of the horizontal axis and the vertical axis is set to 0 volt, the output level in the lower direction of the vertical axis is equal to the voltage level (-β volt) output from the voltage setting function 12b, and the upper direction is set to Assuming the same voltage level with inverted polarity + β volts, comparison function 1
0 volt is output while the voltage output from 9 and input to the level conversion function 20 is low, and -β volt is output when the input voltage to the level conversion function 20 rises to the plus side and becomes + α volt or more. . On the contrary, when the input voltage to the level converting function 20 becomes negative and becomes higher than -α volt, + β volt is output. The method of determining the response characteristic of the level conversion function 20 described above is an example, and the comparison function 1
It may be set appropriately so as to correspond to the output condition of No. 9 and the function described later in detail is satisfied. The output level of the level conversion function 20 is also an example, and the load power setting function 1
It may be set appropriately so that the operation, the details of which will be described later, is satisfied corresponding to the output condition of 2a.

Next, the operation of the load power control device 4A, which is an example in which the present invention as described above is applied to the control of a high frequency induction furnace, will be described in detail with reference to FIGS. FIG. 2 shows a time course of operating the high frequency induction furnace, and FIG. 2A shows the output of the load power setting function 12a at 0 V at the upper part and the set voltage at the lower part, that is, a negative voltage. B) shows the output of the level conversion function 20 in the central part with 0 volt, the upper part with a positive voltage and the lower part with a negative voltage, and FIG. 7C shows the output of the delay function 14 without the upper part, that is, 0 volt. At the bottom, there is an output, that is, a negative voltage is shown.

Before the operation of the high frequency induction furnace 3, the load power setting function 12a and the received voltage setting function 18 are set in advance. In the following description, the set voltage of the load power setting function 12a is set to -P.
And the set voltage of the received voltage setting function 18 is -E volt. The set output of the load power setting function 12a described above is used to control the output of the controllable rectification function 2A as in the conventional case. Therefore, the output of the inverter 2B, that is, the input of the high frequency induction furnace 3 is set. The set output of the power receiving voltage setting function 18 corresponds to a predetermined power receiving voltage of the distribution line 1, for example, 6600 volts. That is, distribution line 1
When the voltage of 6 is 6600 volts, the voltage level output from the rectifying function 16 is -E volts. The level conversion function 20 also corresponds to the characteristic of the comparison function 19, and when the value corresponding to the received voltage output from the rectification function 16 changes by a predetermined ratio of the set voltage, for example, ± 4% or more, that is, changes by α volt or more. In this case, it is set to output ± β volts (see FIG. 4).

Under the above-mentioned conditions, the switch 11 is not turned on before the high frequency induction furnace 3 is operated, so that the input voltage of the first input terminal a of the addition function 13 is 0 volt. Further, since the high frequency induction furnace 3 is not loaded on the distribution line 1, the reference voltage of the distribution line 1 does not fluctuate greatly. Therefore, the amount of deviation between the output voltage of the rectifying function 16 and the set voltage of the power receiving voltage setting function 18 is small, and the output level of the level converting function 20 is 0 volt. Therefore, the output level of the delay function 14 is also 0 volt. Therefore, naturally, the high frequency induction furnace is not functioning. When the switch 11 is turned on at the timing t1 shown in FIG. 2, the setting output −P volt of the load power setting function 12a is input to the addition function 13. Since the output of the level conversion function 20 does not change from 0 volt until the voltage of the distribution line 1 changes by a predetermined value or more, the addition function 13 outputs -P volt. However, since the output level of the delay function 14 is low due to the function of the delay function 14, the controllable rectification function 2
The control device 4 for controlling the output of A does not suddenly change from a predetermined initial state. When the output level of the delay function 14 increases, the load power increases due to the function of the control device 4, the voltage of the distribution line 1 decreases, and the output of the rectifying function 16 decreases. When the deviation between the output level of the rectification function 16 and the set voltage of the power receiving voltage setting function -E volt exceeds α volt and the output of the comparison function 19 exceeds -α volt, the level conversion function 2
The output of 0 becomes + β volt (timing t shown in FIG.
2). After that, it operates as described below.

(1) The output of the addition function 13 decreases because + β volt is added to the set output -P volt of the load power setting function 12a, and the absolute values of ± β volt and -P volt are made equal to each other. In this case, it becomes 0 volt (hereinafter, description will be made assuming that the absolute values of + β volt and −P volt are equal). (2) Therefore, the changing direction of the output voltage of the delay function 14 is reversed, and its output functions to reduce the load power. (3) Therefore, the output of the inverter 2B (high frequency induction furnace) is attenuated and the voltage of the distribution line 1 is increased. (4) Therefore, when the deviation between the output level of the rectifying function 16 and the set voltage of the power receiving voltage setting function −E volt becomes α volt or less and the output of the comparison function 19 becomes within −α volt, the level converting function is performed. The output from 20 becomes 0 volt (timing t3 shown in FIG. 2). (5) Therefore, the input of the addition function 13 is only -P volt, and the output is -P volt. (6) Therefore, the output of the inverter 2B (high frequency induction furnace) rises and the voltage of the distribution line 1 decreases to a drooping state (hereinafter referred to as drooping). (7) Therefore, the output voltage of the rectifying function 16 becomes lower than the set voltage -E of the power receiving voltage setting function 18 by α volt or more again, and the level converting function 20 outputs + β volt (timing t4 shown in FIG. 2). (8) Therefore, the output of the adding function 13 becomes 0 volt, and the changing direction of the output voltage of the delay function 14 is reversed. (9) Therefore, the output of the inverter 2B (high frequency induction furnace) is attenuated, and the voltage of the distribution line 1 rises again. (10) Therefore, the output from the level conversion function 20 becomes 0 volt (timing t5 shown in FIG. 2). (11) Therefore, the output of the addition function 13 becomes -P volt. (12) Therefore, the output of the inverter 2B (high frequency induction furnace) rises and the voltage of the distribution line 1 drops. However, at this stage, the output voltage of the rectification function 16 due to the delay function of the SVR and the voltage drop of the distribution line 1 due to the input current to the inverter 2B (high frequency induction furnace) and the set output of the power reception voltage setting function 18 Since the deviation voltage is lower than α volt, the level conversion function 20 does not output + β volt, and the output of the delay function 14 changes to −P volt according to a predetermined delay characteristic. As a result of the above-mentioned operation, the voltage of the distribution line 1 does not drop below the voltage determined by the setting condition of the input voltage at which the step output of the level conversion function 20 operates, and the inverter 2B (high frequency induction furnace) has a time determined by the delay function. Completely rises to the set power with. In the above description, the state in which + β volt is output from the level conversion function 20 is repeated twice, but it is natural that the number of repetitions differs depending on the load power, the characteristics of the distribution line 1, and the like.

When the operation of the high frequency induction furnace is stopped, the load power control device according to the present invention operates in the opposite direction to the above. At timing t6 shown in FIG. 2, the switch 11
When the power is cut off, the load power setting function 12 is added to the addition function 13.
The set output of a-P volt disappears and becomes 0 volt.
Since the output of the level conversion function 20 does not change until the voltage of the distribution line 1 changes by a predetermined value or more, the addition function 13 outputs 0 volt. However, delay function 1
Since the output of the delay function 14 is not immediately attenuated by the action of 4, the control device 4 of the high frequency induction furnace 3 continues to operate. The output level of the delay function 14 decreases, that is, the output level of the delay function 14 changes upward in FIG.
Starts to reduce the output. Therefore, since the output of the controllable rectification function 2A decreases, the output of the inverter 2B attenuates and the voltage of the distribution line 1 starts to increase. When the detected voltage of the voltage of the distribution line 1, that is, the output voltage of the rectifying function 16 increases and the deviation from the set voltage of the power receiving voltage setting function 18 −E volt becomes α volt or more, the output of the comparison function 19 outputs + α volt. , The output of the level conversion function 20 becomes −β volt (timing t7 shown in FIG. 2). After that, it operates as described below.

(1) As a result of the above, the output of the addition function 13 is −
It becomes β volt, and since −β volt and −P volt are made equal, it becomes −P volt. (2) Therefore, the changing direction of the output voltage of the delay function 14 is reversed. (3) Therefore, since the output of the controllable rectification function 2A increases, the output of the inverter 2B (high frequency induction furnace) increases,
The voltage of the distribution line 1 drops. (4) Therefore, when the deviation between the output voltage of the rectifying function 16 and the set voltage of the power receiving voltage setting function 18 becomes α volt or less, the output from the level converting function 20 becomes 0 volt (timing t8 shown in FIG. 2). . (5) Therefore, the output of the addition function 13 becomes 0 volt. (6) Therefore, the output of the controllable rectification function 2A decreases, so the output of the inverter 2B (high frequency induction furnace) decreases,
The voltage of the distribution line 1 rises. (7) Therefore, the deviation between the output voltage of the rectifying function 16 and the set voltage −E of the power receiving voltage setting function 18 becomes α volt or more and outputs + α volt or more. Therefore, the level converting function 20 outputs −β volt. Output (timing t9 shown in FIG. 2). (8) Therefore, the output of the addition function 13 becomes -β volt (-P volt because -β volt and -P volt are made equal to each other), and the change direction of the output voltage of the delay function 14 is reversed. (9) Therefore, since the output of the controllable rectification function 2A increases, the output of the inverter 2B (high frequency induction furnace) rises,
The voltage of the distribution line 1 drops again. (10) Therefore, the output from the level conversion function 20 becomes 0 volt (timing t10 shown in FIG. 2). (11) Therefore, the output of the addition function 13 becomes 0 volt. (12) Therefore, the output of the high frequency induction furnace is decreased and the voltage of the distribution line 1 is increased. However, at this stage, the output voltage of the rectification function 16 accompanying the delay function of the SVR and the voltage increase of the distribution line 1 due to the input current attenuation to the inverter 2B (high frequency induction furnace),
Since the deviation voltage from the set output of the power receiving voltage setting function 18 is lower than α volt shown in FIG. 4, the level converting function 20 does not output −P volt and the delay function 1
The output of 4 changes to 0 volt according to a predetermined delay characteristic, and the output of the controllable rectification function 2A is attenuated, so that the inverter 2B (high frequency induction furnace) returns to a predetermined initial state.
That is, as a result of the above-described operation, the voltage of the distribution line 1 does not rise above the voltage determined by the setting condition of the input voltage at which the step of the level conversion function 20 operates, and the inverter 2B
The (high frequency induction furnace) returns to a predetermined initial state within a time determined by the delay function 14. Also in the above description, the state in which + β volt is output from the level conversion function 20 is repeated twice, but the number of repetitions naturally varies depending on the load power, the characteristics of the distribution line 1, and the like.
In the above description, the output of the level conversion function 20 ± β
The case where the absolute value of the volt and the absolute value of -P volt which is the set output of the load power setting function 12a are equal has been described. Good. Therefore, the level conversion function 20
In the above description, the output level of 1 is interlocked with the setting of the load power setting function 12a, but it may be fixed depending on the conditions.

A sequence for setting a program when the above-described functions are applied to a computer or a computer application device such as a sequencer will be described with reference to FIG.
However, for convenience of description, it is assumed that the function corresponding to the control device 4 described in FIGS. 1 and 6 is configured separately from the computer that executes the following sequence.
In FIG. 5 (A), when the high frequency induction furnace is started, the output level of the load power setting function 12a is delayed by the ramp function in the closing process of the switch 11 (the explanation function of FIG. 3 is executed by software. Then, the inverter 12
It is compared with the output of B, processed corresponding to the PI adjustment function, and input to the power control device (corresponding to the control device 4 shown in FIGS. 1 and 6). The control device creates a control signal for the controllable rectification function 2A and controls the controllable rectification function 2A (corresponding to t1 and later shown in FIG. 2). In step 1A, the voltage of the rectifying function 16 indicating the voltage of the distribution line 1 (referred to as a feedback voltage value) is higher than the set voltage of the power receiving voltage setting function 18 by α (the unit volt is omitted. The same applies hereinafter). When it becomes smaller, a level + P (corresponding to β shown in FIG. 4) (the description of the unit of bolt is omitted. The same applies hereinafter) is created and output (step 2A). Feedback voltage value and power receiving voltage setting function 18
While the deviation from the set voltage of is less than α, the operation up to that point is continued. In step 3A, the level P is added to the output (-P) of the load power setting function 12a and superposed. The result of the addition is delayed by the delay function having the ramp function (step 4A). The delayed signal is compared with the output of the inverter 2B, and signal processing corresponding to the PI adjustment function is performed (step 5).
A). The signal of the processing result in step 5A is input to the power control device and a predetermined function is executed to control the controllable rectification function 2A (step 6A). After step 6A, the process returns to step 1A and the above operation is repeated.
As a result, the inverter 2B (high frequency induction furnace) starts up in a predetermined time and continues its operation without causing a large voltage fluctuation in the distribution line 1.

In order to stop the operation of the high frequency induction furnace (inverter 2B), the output level of the load power setting function 12a becomes 0 volt by the interruption processing of the switch 11 in FIG. After the delay processing is performed, the output voltage of the inverter 2B is compared, signal processing corresponding to the PI adjustment function is performed, and the signal is input to the control device 4. The control device 4 creates a control signal for the controllable rectification function 2A and controls the controllable rectification function 2A (corresponding to t6 and thereafter shown in FIG. 2). Next, in step 1B, when the feedback voltage value becomes larger than the set voltage of the power receiving voltage setting function 18 by α or more, level-P is created and output (step 2B). While the feedback voltage value is less than or equal to α with respect to the set voltage of the power receiving voltage setting function 18, the operation up to that point is continued. In step 3B, level-P is added to the output (0) of the load power setting function 12a and superposed. The added result is delayed by a delay function having a ramp function (step 4B). The delayed signal is compared with the output of the inverter 2B, and signal processing corresponding to the PI adjusting function is performed (step 5B). The signal of the processing result in step 5B is input to the power control device, a predetermined function is executed, and the controllable rectification function 2A is controlled (step 6B). After step 6B, the process returns to step 1B and the above-described operation is repeated. As a result, the inverter 2 can be operated within a predetermined time without causing a large voltage fluctuation in the distribution line 1.
B (high frequency induction furnace) is stopped. During the operation of the high frequency induction furnace, etc., in the flow described above with reference to FIG. 5, the process returns from step 6A to X, and therefore to step 1A or step 1B, and from step 6B to step 1B.
Alternatively, the process may return to step 1A.

The above description shows an example to which the technical idea based on the present invention is applied. Depending on the starting characteristics of the high frequency induction furnace, the condition of the distribution line, the condition of the SVR delay time, etc. The element level conversion function may be omitted. In that case, a dead zone of a predetermined width may be provided in the PI adjustment function, or a step element having a characteristic other than the above may be used. For example, the positive and negative operating points with respect to the input level may be unbalanced, or the ramp function and the step function may be mixed. Similarly, the delay function, which is a delay element, may be omitted, and the characteristics of the delay element may be different from those described above. For example, different lamp characteristics may be used when there is input and when there is no input. Further, when the load power control method based on the present invention is applied to the conventional power control apparatus, the above conditions may be modified appropriately in accordance with the constituent element conditions of the conventional power control apparatus. For example, when the conventional power control device is configured by a computer as its signal processing unit, an appropriate program may be created and incorporated by referring to the above-described flow (see FIG. 5). Even in the case of being configured, the above-mentioned technical idea may be achieved corresponding to the configuration. Further, since the configuration of the above-described embodiment is one example, any elemental function may be used and any configuration may be adopted as long as the technical idea of the present invention is achieved. Needless to say. Further, although the above-described embodiment has been described as an example applied to the control of the high frequency induction furnace, it is needless to say that it can be applied to other heavy power loads. Further, the case of one set of high-frequency induction furnace has been described, but when a plurality of heavy power load devices are connected to the same power system of the power consumer, the above description is appropriate for each heavy power load device. It is natural that it can be applied to.

[0022]

Since the present invention has the above-mentioned method and is constructed, the following excellent effects can be obtained. Instead of simply delaying the fluctuation of the power setting, the setting of the output power is changed according to the voltage fluctuation width of the distribution line, which is the received voltage, so the start time and stop time of heavy power loads such as high frequency induction furnaces can be minimized. The length can be shortened and the fluctuation of the distribution line voltage can be suppressed. Without introducing expensive equipment such as a reactive power compensator as in the past, by adding a few functions to the conventional power control device, there is almost no cost increase, and the intended distribution line voltage fluctuation. Can be suppressed. If the conventional power control device for heavy power load (for example, high-frequency induction furnace) is configured by the application of a computer such as a sequencer, it is cheaper than the above because the main body of the required function can be realized by adding a program. The above effect can be realized at a cost. When the measured value of the voltage measurement function exceeds the preset reference value by plus or minus, the excess level value is converted by the step function with a predetermined characteristic corresponding to the excess value, and the converted value supplies the power supplied to the heavy power load. If the control is adjusted, it is possible to prevent the control characteristic from hunting. When the change of the input control signal of the power control device is reduced via the delay element by the ramp function having the predetermined characteristic, the function of the present invention operates smoothly. By providing the delay element by the ramp function and the level conversion element by the step function, the above-mentioned hunting prevention function can be more reliably exhibited.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a load power control device in which a load power control method according to the present invention is applied to a control device for a high frequency induction furnace which is an example of a heavy power load device.

2 is a time flow chart showing the operation of the load power control apparatus shown in FIG. 1, in which FIG. 2 (A) is a diagram showing the output level of the load power setting function that appears when the switch 11 is turned on and off; 2 (B) is a diagram showing an output waveform of the level conversion function 20, and FIG. 2 (C) is a diagram showing an output waveform of the delay function 14.

3A and 3B are explanatory diagrams showing the operation of a delay function 14 of the load power control system shown in FIG. 1, in which A is a case where the input level is high and B is a case where the input level is low. , Respectively.

FIG. 4 is an explanatory diagram showing the operation of a level conversion function 20 of the load power control system shown in FIG.

FIG. 5 is a flow chart showing a schematic time sequence when the load power control method according to the present invention is implemented by a computer program, in which (A) and (B) are the switch closing process side and the switch breaking process side, respectively. Each time sequence of is shown.

FIG. 6 is a block diagram showing a configuration of a control device for a high-frequency induction furnace which is a conventional heavy power load device.

FIG. 7 is a power system diagram illustrating a problem of a conventional power system to which a heavy power load is connected.

FIG. 8 is a schematic time flow chart for explaining the problems of SVR in the power system shown in FIG. 7.

[Explanation of symbols]

 1: Distribution line (electric power system) 2A: Controllable rectification function 2B: Inverter 3: High frequency induction furnace (heavy power load) 4: Power control device 4A: Load power control device 5: Current transformer for instrument 9: PI adjustment function 11: Switch 12a: Load power setting function 13: Addition function 14: Delay function 16: Rectification function 18: Power reception voltage setting function 19: Comparison function 20: Level conversion function

Claims (5)

[Claims] 1. In a power consumer equipped with at least one heavy power load, a voltage measuring function at a predetermined point of a distribution line on a premises and a measured value of the voltage measuring function is plus or minus a reference value set in advance. And a control function that adjusts the supply power of the heavy power load according to the excess value to reduce the fluctuation of the voltage value at the predetermined point on the premises that occurs with the operation of the heavy power load. A load power control method characterized by the above. 2. In a power consumer equipped with at least one heavy power load, a voltage measuring function at a predetermined point of a distribution line in a premises and a measured value of the voltage measuring function is plus or minus a preset reference value. When the excess power value is exceeded, the excess level value is converted by a step function having a predetermined characteristic corresponding to the excess value, and a control function for adjusting the supply power of the heavy power load according to the converted value is provided to operate the heavy power load. The load power control method is characterized in that the fluctuation of the voltage value at the predetermined point on the premises that occurs with the above is reduced. 3. In a power consumer equipped with at least one heavy power load, a voltage measuring function at a predetermined point of a distribution line on a premises and a measured value of the voltage measuring function is plus or minus a reference value set in advance. And a control function that adjusts the supply power of the heavy power load according to the excess value, and reduces the rate of change of the control signal of the control function via a delay element by a ramp function of a predetermined characteristic. A load power control method characterized by the above. 4. A power consumer equipped with at least one heavy power load, wherein a voltage measuring function at a predetermined point of a distribution line on a premises and a measured value of the voltage measuring function are positive or negative than a preset reference value. And a control function for converting the excess level value by a step function having a predetermined characteristic corresponding to the excess value, and adjusting the supply power of the heavy power load according to the conversion value. Is reduced via a delay element due to a ramp function having a predetermined characteristic. 5. An electric power consumer having at least one heavy electric power load, a load electric power setting function, a voltage measuring function at a predetermined point of a premises distribution line, a measured value of the voltage measuring function, and a preset reference. A deviation value detection function that determines the deviation from the value, outputs the comparison result after processing according to a predetermined condition, and a function that superimposes the detection value of the deviation value detection function and the set value of the load power setting function And a function for controlling the amount of electric power supplied to the heavy power load by the superposed value, and when the measured value of the voltage measuring function exceeds the reference value set in advance by plus or minus, it corresponds to the excess value. The load power control device is configured to reduce the fluctuation of the voltage value at the predetermined point on the premises, which is caused by the operation of the heavy power load, by adjusting the power supplied to the heavy power load.