CN104362921B - Control circuit of on-load tap changing transformer - Google Patents

Abstract

The invention discloses a control circuit of an on-load voltage regulating transformer. The control circuit includes a voltage sampling circuit, a single-chip microcomputer circuit, and a motor power supply circuit; the voltage sampling circuit is connected to any phase of the low-voltage side of the transformer to detect and convert It is a low-voltage DC voltage; the single-chip circuit is provided with a voltage comparison module, and the single-chip circuit converts the low-voltage DC voltage detected by the voltage sampling circuit into an AC voltage represented by a digital signal, and the voltage comparison module compares the AC voltage with the valve Value voltages are compared and output control signals to the motor power supply circuit according to the comparison results. The motor power supply circuit is provided with a motor forward and reverse control module. If the AC voltage is greater than the threshold upper limit voltage, the motor is controlled to rotate forward; if the AC voltage If the voltage is lower than the threshold lower limit, the motor is controlled to reverse. The invention achieves the function of automatically controlling the on-load voltage regulating switch to adjust the tap.

Description

A kind of on-load voltage regulating transformer control circuit

technical field

The invention relates to an automatic control technology of a power grid, in particular to a control circuit of an on-load voltage regulating transformer.

Background technique

At present, ordinary transformers are widely used in public transformers in rural areas. Every summer and winter or when the load changes greatly during operation, it is necessary to manually go to the site to carry out power outages, and adjust the transformer taps to complete the transformer speed drop and increase. Downgrade from time to time.

There are many problems in this way, such as increasing the workload of power supply enterprises; operating safety risks during voltage regulation; and the time difference between discovery and voltage regulation will cause the quality of power supply voltage to decline, and users complain a lot; the location of voltage regulation is only an empirical practice, which is difficult to control.

Contents of the invention

The technical problem to be solved by the present invention is to provide a control circuit of an on-load voltage-regulating transformer to solve the problem of automatic voltage regulation of the on-load voltage-regulating transformer in rural public transformers.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions: a control circuit of an on-load tap changer, a motor is installed on the transformer, and the control circuit includes a DC power supply, a voltage sampling circuit, a single-chip microcomputer circuit, and a motor power supply circuit; The DC power supply is used as the power supply of the control circuit, and the voltage sampling circuit is connected to any phase on the low-voltage side of the transformer to detect the voltage on the low-voltage side of the transformer and convert it into a low-voltage DC voltage; a voltage comparison module is provided in the single-chip microcomputer circuit, and the single-chip microcomputer The circuit converts the low-voltage DC voltage detected by the voltage sampling circuit into an AC voltage represented by a digital signal. The voltage comparison module compares the AC voltage with the threshold voltage and outputs a control signal to the motor power supply circuit according to the comparison result. The motor A motor forward and reverse control module is installed in the power supply circuit. If the AC voltage is greater than the upper threshold voltage, the motor is controlled to rotate forward; if the AC voltage is lower than the lower threshold voltage, the motor is controlled to reverse.

Preferably, the DC power supply includes a power transformer, a rectifying and filtering circuit, and a DC voltage stabilizing circuit. The power transformer steps down the AC 220V, rectifies and filters it into DC through the rectifying and filtering circuit, and the DC stabilizing circuit stabilizes the DC voltage to 5V.

Preferably, the voltage sampling circuit includes a voltage transformer and a rectification and filtering circuit, the voltage transformer isolates and steps down one phase voltage of the transformer into a low-voltage AC voltage, and then rectifies and filters it into a low-voltage DC voltage through the rectification and filtering circuit.

Preferably, the forward and reverse control module of the motor includes a current limiting resistor, a thyristor optocoupler, and a triac connected in sequence.

Preferably, the control circuit further includes a gear control circuit, the gear control circuit is provided with at least two gear contacts for adjusting the voltage of the transformer, and the gear contacts are controlled to be closed by the transformer gear switch.

The advantage of the present invention is: after the motor-type on-load tap changer has been installed on the public transformer in rural areas, using the on-load tap-changer control circuit of the present invention, the voltage of any phase can be selected according to the low-voltage side of the transformer to control the transformer. Automatic voltage regulation control, when the voltage exceeds the upper limit threshold value, the motor is controlled to rotate forward, and when the voltage is lower than the lower limit threshold value, the motor is controlled to rotate reversely, so as to achieve the function of automatically controlling the on-load tap changer to adjust the tap.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

Fig. 1 is a schematic circuit diagram of the present invention;

Figure 2 is a schematic diagram of a DC power supply circuit;

Figure 3 is a schematic diagram of the voltage sampling circuit;

Fig. 4 is the schematic diagram of the single-chip microcomputer control circuit;

Figure 5 is a schematic diagram of the motor power supply circuit;

Figure 6 is a schematic diagram of the gear position control circuit;

Fig. 7 is the circuit principle diagram of LCD liquid crystal screen;

Figure 8 is a schematic diagram of the keyboard circuit.

detailed description

The present invention will be described in detail below in conjunction with FIGS. 1 to 8 .

A control circuit for an on-load tap changer, in which a motor is installed on the transformer, and the control circuit includes a DC power supply, a voltage sampling circuit, a single-chip microcomputer circuit, and a motor power supply circuit;

The DC power supply is used as the power supply of the control circuit, and the voltage sampling circuit is connected to any phase of the low-voltage side of the transformer to detect the voltage on the low-voltage side of the transformer and convert it into a low-voltage DC voltage; the single-chip circuit is provided with a voltage comparison module, and the The single-chip microcomputer circuit converts the low-voltage DC voltage detected by the voltage sampling circuit into an AC voltage represented by a digital signal, and the voltage comparison module compares the AC voltage with a threshold voltage and outputs a control signal to the motor power supply circuit according to the comparison result. The motor power supply circuit is provided with a motor forward and reverse control module. If the AC voltage is greater than the threshold upper limit voltage, the motor is controlled to rotate forward; if the AC voltage is lower than the threshold lower limit voltage, the motor is controlled to reverse.

As shown in Figure 2, the DC power supply includes a power transformer, a rectification and filtering circuit, and a DC voltage stabilizing circuit. The power transformer steps down the AC 220V, rectifies and filters the DC power through the rectifying and filtering circuit, and the DC voltage stabilizing circuit stabilizes the DC voltage. is 5V. Specifically, the power transformer T4 is used to step down the AC 220, rectified and filtered by the rectifier bridge BG and capacitor C7 to DC, and the three-terminal regulator G2 and capacitor C8 stabilize the DC voltage to 5V for use by various circuits.

As shown in FIG. 3 , the voltage sampling circuit includes a voltage transformer and a rectification and filtering circuit. The voltage transformer isolates and steps down one-phase voltage of the transformer into a low-voltage AC voltage, and then rectifies and filters it into a low-voltage DC voltage through the rectification and filtering circuit. Specifically, select any phase voltage on the three phases A, B, and C on the low-voltage side of the transformer to connect to the voltage sampling circuit through the voltage transformer T3, and then step down the voltage through isolation to a low-voltage AC voltage and rectify it through the diode D1, capacitor C3, and resistor R10. The filter is a DC voltage VAC, which is proportional to the output voltage of the transformer.

The forward and reverse control module of the motor includes a current-limiting resistor, a thyristor optocoupler, and a bidirectional thyristor connected in sequence. The control circuit also includes a gear control circuit, the gear control circuit is provided with at least two gear contacts for adjusting the voltage of the transformer, and the gear contacts are closed by the transformer gear switch.

The DC voltage VAC is sent to the 8th pin of the single-chip microcomputer control circuit U2. The analog-to-digital converter of U2 converts the analog DC voltage into an AC voltage represented by a digital signal. Compared with the internal adjustment threshold, when the AC voltage is greater than the upper limit voltage,

The 12th pin of the microcontroller outputs a high level to the motor power supply circuit 4, the current is limited by the resistor R14, the thyristor optocoupler Q1 is turned on and the bidirectional thyristor G1 is turned on, and the motor rotates forward; if the AC voltage is lower than the lower limit voltage , when the pin 13 of the microcontroller U2 outputs a high level, the current is limited by the resistor R15, the thyristor optocoupler Q2 is turned on and the bidirectional thyristor G2 is turned on, and the motor reverses; the resistor R17, the capacitor C5, and the varistor RV1 form The forward buffer circuit protects the triac GS1; the resistor R18, capacitor C6, and piezoresistor RV2 form a reverse buffer circuit to protect the triac GS2.

The gear control circuit is provided with at least two gear contacts DW1, DW2, and DW3 for adjusting the transformer voltage. When the transformer voltage is adjusted to a certain gear, the corresponding gear contacts are closed, and the corresponding optocoupler is turned on. The control circuit is connected with the I/O port of the single-chip microcomputer control circuit.

In addition, the above-mentioned on-load tap changer control circuit is also equipped with an LCD display circuit and a keyboard circuit. When the I/O port of the microcontroller detects that the corresponding gear contact is closed, that is, when the gear changes, the LCD display is controlled to display, that is, For the specific gear position, the keyboard circuit is connected to the I/O port of the single-chip microcomputer U2, which is used to input the upper and lower limit voltages of the threshold, and transmits them to the LCD display circuit to display the upper and lower limit voltages.

Claims (1)

1. a kind of ULTC control circuit, on the transformer motor is installed it is characterised in that: described control circuit Including dc source, voltage sampling circuit, single chip circuit, motor power circuit；Described dc source is as control circuit Power supply, described voltage sampling circuit accesses in the arbitrary phase of step down side, and detection step down side voltage is simultaneously converted to low Pressure DC voltage；It is provided with voltage comparison module, voltage sampling circuit is detected by described single chip circuit in described single chip circuit To low-voltage dc voltage be converted into the alternating voltage that data signal represents, described voltage comparison module is by this alternating voltage and valve Threshold voltage is compared and according to comparative result output control signal to motor power circuit, is provided with described motor power circuit Motor positive and inverse control module, if this alternating voltage is more than threshold values upper voltage limit, controlled motor rotates forward；If this alternating voltage Less than lower threshold voltage, controlled motor inverts, and it is steady that described dc source includes power transformer, current rectifying and wave filtering circuit, direct current Volt circuit, described power transformer will exchange 220v step-down, and rectified filter circuit rectifying and wave-filtering is direct current, DC voltage-stabilizing electricity Direct current voltage stabilizing is 5v by road, and described voltage sampling circuit includes voltage transformer and current rectifying and wave filtering circuit, described mutual induction of voltage One phase voltage isolated buck of transformer is that rectified filter circuit rectifying and wave-filtering is low-voltage direct to low-voltage ac voltage again by device Voltage, described motor positive and inverse control module includes the current-limiting resistance being sequentially connected, and controllable silicon optocoupler, bidirectional triode thyristor are described Control circuit also includes gear control circuit, and the gear that described gear control circuit is provided with least two adjustment transformer voltages connects Point, described gear contact is closed by transformer gear switch control rule；220 step-downs will be exchanged using power transformer t4, rectified Bridge bg, electric capacity c7 rectifying and wave-filtering are direct current, and direct current voltage stabilizing is used for each circuit by three terminal regulator g2 electric capacity c8 for 5v；Single To motor power circuit, through resistance r14 current limliting, controllable silicon optocoupler q1 conducting controls bidirectional triode thyristor to piece machine circuit output high level Gs1 turns on, and motor rotates forward；If when alternating voltage is less than lower threshold voltage, when the high electricity of 13 pin outputs of single chip circuit At ordinary times, through resistance r15 current limliting, controllable silicon optocoupler q2 conducting controls bidirectional triode thyristor gs2 conducting, motor reversal；Resistance r17, electricity Hold c5, piezo-resistance rv1 constitutes rotating forward buffer circuit protection bidirectional triode thyristor gs1；Resistance r18, electric capacity c6, piezo-resistance rv2 Constitute reversion buffer circuit protection bidirectional triode thyristor gs2, be additionally provided with lcd display screen circuit and keyboard circuit, single chip circuit i/o Mouth detects corresponding gear junction closure, controls lcd display screen to show the i/ of specific gear, keyboard circuit and single chip circuit O mouth connects, and for inputting threshold values upper and lower limit voltage, and transmits and shows this threshold values upper and lower limit voltage to lcd display screen circuit.