JPH06348349A - Voltage control method for power supply system - Google Patents

Abstract

PURPOSE:To ensure the stable and highly accurate control of voltage by performing a tap switching operation according to the deviation from a reference voltage level when it is decided that the level of the secondary voltage gets out of a blind sector that is set previously. CONSTITUTION:A tap switching transformer 3A is provided with a voltage controller 10, and the upper/lower limit value alpha/beta and the allowable value gammaof a blind sector are previously set to the controller 10. Then the secondary voltage level V2 of the transformer 3A is measured and then compared with both value alpha and beta. If it is decided that the level V2 gets out of the blind sector, a deviation is calculated against a reference voltage level V2S. Then a tap switch 9 is actuated according to the deviation and via a voltage control relay 11 so that a tap switching operation is carried out. The tap switching operation is discontinued when the level V2 is included in a prescribed range of the value gammaagainst the level V2S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage control method for a power supply system.

[0002]

2. Description of the Related Art Conventionally, external power is supplied through a substation as a drive source for various power equipment in a manufacturing facility such as a steel mill. However, as shown in FIG. In general, the voltage is transformed into a predetermined voltage by the tap change transformer 3 provided between the system 2 and the system.

Normally, electrical equipment and facilities used in the load system 2 are guaranteed to have normal performance as a permissible value up to ± 10% in voltage fluctuation according to JIS or JEC standards. However, on the use side, in order to ensure stable operation or high-quality operation of these devices and equipment, the voltage fluctuations at the upper substations are, for example, ± 5 in consideration of the voltage drop in the midway transmission system. It is generally controlled within%.

FIG. 4 shows the outline of the configuration of the tap change transformer 3, but the primary side coil 4 connected to the external power system 1 and supplied with the primary voltage V ₁ is changed over. The taps 5 are provided in a plurality of stages, and are operated by the secondary voltage V ₂ detected by the voltage detector 7 provided on the secondary coil 6 side via the dead zone voltage adjusting relay 8 It is made switchable by means of 9. At this time,
It is general that the secondary voltage V ₂ controlled by the dead zone-equipped voltage adjusting relay 8 has a dead zone with respect to the reference voltage V _2S . If the secondary voltage V ₂ falls within this dead zone, the voltage adjusting operation is performed. The control method is considered to be terminated.

[0005]

However, the above-mentioned conventional techniques have the following problems.
That is, when the secondary voltage is out of the dead zone, the control is finished and the control ends at the moment when the voltage value returns to the dead zone. There is a risk that

Therefore, as a method of preventing such a phenomenon, for example, the width of the dead zone may be widened. If this is done, the frequency of the dead zone may certainly decrease, but the deviation from the reference voltage may occur. May increase, resulting in a new problem that the accuracy of the secondary voltage supplied to the load system decreases with respect to the reference voltage.

On the contrary, if the width of the dead zone is narrowed, a cycle in which the secondary voltage deviates from the dead zone or returns frequently occurs, that is, a so-called hunting phenomenon occurs, and electrodes such as the switching tap 5 and the tap switching device 9 are generated. May cause another trouble such as exhaustion. It is an object of the present invention to provide a voltage control method for a power supply system, which solves the above-mentioned problems of the prior art.

[0008]

SUMMARY OF THE INVENTION The present invention is a method for controlling the voltage of a power supply system using a tap change transformer and a voltage adjusting relay, in which the secondary voltage of the tap change transformer is measured, and this measurement is performed. When the voltage value goes out of the dead zone of the preset reference voltage, the tap switching of the tap switching transformer is performed so that the voltage falls within a predetermined allowable range of the reference voltage value. This is a voltage control method.

[0009]

[Operation] According to the present invention, first, the secondary voltage is measured and the voltage value is compared with the preset upper and lower limit values of the dead zone, and when it is determined that the dead zone is exceeded, the deviation from the reference voltage is determined. Calculated, taps are switched according to the deviation, and tap switching is stopped at the stage of entering a predetermined allowable range from the reference voltage. It does not come off.

The procedure of the present invention will be described in detail with reference to FIG. The upper and lower limit values α and β of the dead zone for the reference voltage V _{2S in} advance
And the allowable value γ for the reference voltage V _2S is set. First, it is determined by the following equation (1) whether the secondary voltage V ₂ exceeds the dead zone upper limit value α.

V ₂ ≧ α (1) When the expression (1) is not satisfied, that is, when the expression is not exceeded, the process proceeds to the next step. When it is determined that the time has exceeded, the process proceeds to the next step. Next, it is determined whether the secondary voltage V ₂ exceeds the dead zone lower limit value β by the following equation (2).

V ₂ ≦ β (2) If it does not exceed V ₂ , the process returns to the previous step. When it is determined that the number has exceeded, the process proceeds to the next step. Taps are switched according to steps or instructions of steps. With respect to the result of tap switching, it is determined by the following equation (3) whether the allowable value γ is satisfied.

| V ₂ −V _2S | ≦ γ (3) If the equation (3) is not satisfied, the process returns to the previous step and the tap switching operation is continued until it is satisfied. If Eq. (3) is satisfied, the procedure returns to the first step to prepare for the next voltage fluctuation.

[0014]

EXAMPLES Examples of the present invention will be described below.
As shown in FIG. 1, a voltage control device 10 is provided in the tap change transformer 3A of the present invention. Then, the voltage control device 10 is provided with the upper and lower limit values α,
[beta] and the allowable value [gamma] are set, then step and step are sequentially executed, and at the step execution step, the tap changer 9 is operated via the voltage adjustment relay 11.
Is operated to switch the taps, and the control is continued so that the voltage fluctuation at the step falls within the allowable value γ range.

FIG. 2 shows the transition of voltage fluctuation when the present invention is applied when the secondary voltage V ₂ exceeds the dead zone upper limit value α. For comparison, the characteristic of the conventional example is shown by a dotted line. As shown in this figure, in the conventional example, frequent control is performed by entering and exiting the vicinity of the dead zone upper limit value α, whereas in the method of the present invention, it is only within the reference voltage V _2S . It can be seen that even if there is a voltage change, the voltage changes gently and good voltage control is performed.

In the above embodiment, the dead zone function is provided in the voltage control device 10, but the present invention is not limited to this. For example, as in the conventional example, the dead zone voltage adjusting relay 8 is provided. May be used, or the dead zone function may be configured independently.

[0017]

As described above, according to the present invention, 2
When the next voltage is measured and the voltage value is compared with the preset upper and lower limits of the dead zone, and when it is determined that it is out of the dead zone, it is calculated by calculating the deviation from the reference voltage, and the tap Since the switching is performed and the tap switching is stopped when the voltage is within the predetermined allowable range from the reference voltage, it is possible to perform stable and highly accurate voltage control.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a characteristic diagram showing changes in voltage fluctuation when the present invention is applied.

FIG. 3 is an explanatory diagram of a conventional power supply system.

FIG. 4 is a schematic diagram showing a configuration of a conventional tap switching transformer.

FIG. 5 is a flowchart showing the procedure of the present invention.

[Explanation of symbols]

 1 External power system 2 Load system 3A Tap switching transformer 4 Primary coil 5 Switching tap 6 Secondary coil 7 Voltage detector 8 Dead zone voltage adjustment relay 9 Tap switching device 10 Voltage control device 11 Voltage adjustment relay

Claims (1)

[Claims] 1. A method for controlling a voltage of a power supply system using a tap change transformer and a voltage adjustment relay, wherein a secondary voltage of the tap change transformer is measured, and the measured voltage value is a preset reference value. When the voltage goes out of the dead zone,
A voltage control method for a power supply system, wherein tap switching of the tap switching transformer is performed so that the reference voltage value falls within a predetermined allowable range.