JPS6168618A - Automatic voltage regulator - Google Patents

Abstract

PURPOSE:To prolong the life of an in-loading tap changeover transformer by storing a target voltage for each tap position, and deriving the difference between said voltage and an actual input value and comparing the result with a predetermined blind sector set value. CONSTITUTION:The output of a three-phase AC power source 1 is fed to a load through the in-loading tap changeover transformer (LRT)2 under the automatic control of the automatic voltage regulator (AVR)15 using the LRT2, whose tap is driven by an in-loading tap switch 3. For the purpose, a tap position switch 8 is provided and the actual tap position signal of the LRT2 is inputted to the signal converter in the AVR5. Then, the AVR5 samples the primary-side instantaneous voltage value of the LRT2 inputted from a transformer 4 for measurement at a constant period to calculate the mean value VA within a constant time. Further, a target voltage VSET stored C for every tap position is selected (b) to calculate the difference DELTAV from the actual value. This is compared with the predetermined blind sector set value and a switching command is issued to said switch 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an automatic electrical regulator (8E) regulating system voltage using an on-load tap-changing transformer.

[Technical background of the invention and its problems]

Figure 4 shows the configuration of an automatic voltage regulator (AVR) using a conventional on-load tap changer (LRT). In the figure, 1 is a three-phase AC power supply, 2 is 1. RT and 3 are electric operating mechanisms for the tap changer, which have tap control circuits I and RT2 and drive the taps. 4 is an instrument transformer, and 5 is an AVR, which has an integrating circuit 7 and has a function of integrating the difference between the kVVS2 set value and the adjusted magnetic pressure. Reference numeral 6 denotes a signal contact that is turned on during tap switching, and is linked to the operation of the tap changer electric operating mechanism 3.

Next, the conventional operation will be explained with reference to FIG. When the transformer secondary voltage fluctuates and exceeds the set value of AVR5, the excess amount is integrated by the integrating circuit 7, and it is determined whether the value after the integration exceeds the dead band set value set in advance by AVR51ζ. do. As a result, if the set value is exceeded, a tap change signal is transmitted from the input VR 5 to the tap changer electric operating mechanism 3.

When the tap switching electric operation mechanism 3 operates, the integral circuit 7 of the human VR 5 is reset by the driving signal generated by the ON operation of the contact 6. Also, I, BT 2 tap is 1
The tap changes, and the tap change is completed. After the tap change, the deviation value between the transformer secondary voltage and the set value of the person VR5 is newly integrated, and the above-mentioned operation is repeated according to the fluctuation of the transformer secondary voltage.

However, when this method is applied to a power system that causes sudden load fluctuations due to the operation of steelmaking arc furnaces, etc. or flickers in the grid voltage, the flicker voltage input to AIL5 and the reference value set for AVR are The deviation from the LRT is integrated, and when this integrated value exceeds the dead zone setting value, the LRT tap switching signal is output from the human VR, and the LRT tap is switched. In this way, the LRT taps are changed frequently in accordance with the load operation period due to the flicker voltage accompanying the load operation, rather than the system voltage fluctuating continuously. Such switching is an unnecessary switching operation and also has the effect of shortening the life of the tap switching mechanism.

[Purpose of the invention]

The purpose of the present invention is to provide a power system for steelmaking arc furnace equipment, for example, in which the secondary voltage of a transformer fluctuates rapidly or flickers during equipment operation. An object of the present invention is to provide an automatic voltage regulator that enables stable LRT tap switching control without performing LFLT tap switching.

[Summary of the invention]

As shown in FIG. 1, the present invention relates to an automatic voltage regulator using a tap-changing transformer 2 on load. Means C for storing a value corresponding to the primary side voltage E to be applied at a tap position as a target voltage vsM for each tap, and a detector 8 for detecting the tap position of the on-load tap change transformer 2. The target voltage vfin? corresponding to this tap position is input by inputting the tap position signal from Vfin? The means for selecting Vall? is selected by inputting the primary side voltage of the on-load tap changing transformer and selecting a target value Vall? corresponding to that value Vm and the tap position E. A means a for calculating the difference ΔV between the two is compared with a preset dead zone setting value V, and if ΔV>Vl, the difference ΔV is integrated, and this integral value ΔVΣ becomes the preset operating value. means (d) for giving a tap change command to the on-load tap changer 3 when the on-load tap changer 3 is exceeded, and maintains high stability without being affected by sudden load fluctuations, flickers, etc. on the secondary side of the on-load tap transformer. Moreover, it is designed to reliably capture continuous fluctuations in system voltage and perform adjustment operations.

[Embodiments of the invention]

The present invention will be described in detail below with reference to an embodiment shown in the drawings. In Figure 1, 8 is a tap position switch;
A tap position signal corresponding to the actual tap position of LRT2 is input to a signal converter within AVR5. Human VR5
is composed of a microcomputer, etc., and samples the instantaneous voltage value on the primary side of the LRT 2 inputted via the instrument transformer 4 at a constant period, and
Means (not shown) for calculating and determining the average value Vmu (seconds)
has.

Below, various functions performed by the input vFL5 will be explained as means.

C is a storage means in which respective set values vsat are set in advance for each tap position of the LRT2.

Here, the setting value Vlte for each tap position is LR
This is a target voltage corresponding to the primary voltage that should be applied to each tap in order to maintain the secondary side of T2 at a certain constant voltage. For example, as shown in Figure 2, LRT2 with the number of taps "15"
In the case of , the target voltage of "tap position mark" is 220KV (1
If the rated voltage of 220 KV is applied at this tap position "8", a predetermined voltage (for example, 5 Q KV) is obtained on the secondary side. In addition, the target voltage for tap position is 215KV, 1. R
Even if the primary side voltage of T 2 drops by 215 KV Ic, the secondary side voltage is maintained at a predetermined voltage by setting the tap position to "7". Target voltage for tap position “9” is 225KV
and LRT (1) primary side 4 EE 75E 225
Even if the voltage increases to KV, if the tap position is set to "9", the secondary voltage is maintained at the predetermined value mentioned above. Similarly, the target voltage is set as 81τ for each tap position, and even if the primary voltage of LRT2 fluctuates, by switching to the tap position of the corresponding target voltage,
The secondary voltage is maintained at a predetermined voltage.

b is Vllll〒 selection means, and the tap position switch 8
Input the LRT 2 tap position signal input from
Among the target voltages set for each tap position, which target voltage v81 corresponds to the tap position signal? is selected and read out from the storage means C. a is a ΔV calculation means,
Target voltage Vsm selected corresponding to the above tap position〒
and the average value VA of the primary side voltage of LRT2 is calculated. d is a tap switching output means that outputs the above difference ΔV and a preset dead zone setting value ΔV (for example, 1.RT
If ΔV>ΔV, then the voltage difference ΔV is calculated as ΔV,=ΔV−ΔV. Then, this voltage difference ΔV2 is integrated, and the integral value ΔV
Σ is compared with a preset operating value, and if this operating value is exceeded, a tap switching command for one tap is output to the tap changer 3f of the LRT 2.

Next, this operation will be explained according to the flowchart shown in FIG. In the above configuration, the AVR 5 receives the primary voltage of the LRT 2 and the tap position signal of the LRT 2, respectively.

Here, a steelmaking arc furnace, etc. is installed on the secondary side of LRT2.
If provided, flicker will occur in the grid electricity during operation. In other words, for arc furnaces etc., a reactive power compensation device such as a capacitor or an acdle is installed,
Although the influence on the system voltage is suppressed as much as possible, the system having an arc furnace (secondary side of LRT 2) voltage (flicker phenomenon occurs).The purpose of the present invention is to prevent the AVFL 5 from operating due to this flicker. Therefore, the primary side voltage of LRT 2, which causes almost no flicker even when the arc furnace is operated, is input to AVR 5. In this case, it is necessary to control the fluctuation of the primary side voltage of LRT 2 to keep the secondary side magnetic aEe constant, but this cannot be done by setting a constant reference voltage for AVR1 as in the past. is difficult, and the tap position of LRT2 is
It is necessary to control the tap value so that the tap value is the same as the primary side voltage (input voltage of AVR 5). This system will be explained in detail below.

First, as mentioned above, LfL input to AVR5
By detecting the tap position signal of T2, the corresponding setting value (tap position) is selected (step ■).
. Furthermore, the primary voltage of the LFLT is sampled at a constant cycle, and 1. Find the average value VA in seconds (step ①). Next, find the difference ΔV between this value VA and the set value VS*T selected in step ■ above (step ■)
. This difference ΔV is compared with a preset dead zone setting value ΔV1 (step ■), and in this comparison, ΔV, )Δ
If it is V, return to step ■.

Ru.

ΔV, if < ΔV, the difference ΔV2 (= ΔV - ΔVI)
becomes integral data (step ■). The integral value ΔVΣ is updated by this integral data (step ■), and the integral value ΔVΣ is updated (step ■).
VΣ and the operating set value are compared (step ■).

As a result of this comparison (here, if the integral value ΔVΣ is less than the operation setting value, the process returns to step ■), and if the integral value ΔVΣ is greater than the operation setting value, it is determined that LRT tap switching is necessary (step ■) and one tap is performed. At the same time as outputting a switching command, the integral value of the step ■ is cleared (STEP ■).As a result, L
RT tap switching is performed. (Step 0). If further tab switching is required, the taps are switched in the same manner according to the flow of steps ① to 0.

〔Effect of the invention〕

As described above, according to the present invention, the tap of the LFLT does not change due to sudden load fluctuations or flicker voltage on the secondary side of the transformer, unlike in the past, and stable tap switching control becomes possible. Since the tap switching frequency of the LRT is also reduced, it is also effective for the life of the LRT.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the automatic voltage regulator according to the present invention; Fig. 2 is a characteristic diagram showing the relationship between the tap of the LRT and the target field in the present invention; and Fig. 3 is the diagram shown in Fig. 1. FIG. 4 is a block diagram showing the conventional device, and FIG. 5 is a flow chart showing the operation. 1... Three-phase AC 4 sources 2... Load tap changer transformer (LRT) 3... Tap changer electric operation mechanism 4... Instrument transformer 5... Automatic pressure regulator (AVR) ) 8...Tap position switch (7317) Agent Patent attorney Noriyuki Chika Right (
(1 other person) Figure 2 7/7'4 standing Figure 3

Claims (1)

[Claims] In an automatic voltage regulator using an on-load tap-changing transformer, it corresponds to the primary voltage that should be applied at each tap position in order to maintain the secondary voltage of the on-load tap-changing transformer at a certain constant value. The value is set to the target voltage V_ for each tap.
means for storing the on-load tap-changing transformer as S_E_T; means for detecting the tap position of the on-load tap-changing transformer and selecting the target voltage V_S_E_T corresponding to this tap position; and inputting the primary side voltage of the on-load tap-changing transformer. Shiso value V
Target value V_S_ selected corresponding to _A and tap position
A means for calculating the difference ΔV from E_T, and compares this difference ΔV with a preset dead zone setting value V_1, and if ΔV>V_1, integrates the difference ΔV_2, and this integrated value ΔVΣ exceeds the preset operating value. and means for giving a tap change command to an on-load tap changer.