KR20020087583A - Step down AC regulator and its control method - Google Patents

Abstract

PURPOSE: An automatic voltage-drop regulator and method for controlling operation of the same is provided to reduce power consumption and improve response time and efficiency, while reducing size of an AC power saving device. CONSTITUTION: An automatic voltage-drop regulator comprises an AC chopper unit(100) serving as a switching unit for switching and chopping an input AC voltage(Vi); a wave filtering unit(200) for wave filtering an output voltage(VIO) of the AC chopper unit; a voltage compensating unit(300) for voltage-drop compensating the input AC voltage into an output voltage(Vo), by the voltage(Vfo) filtered through the wave filtering unit; a first switch(SW1) for switching a current path between the output terminal of the AC chopper unit and the input terminal of the wave filtering unit; a second switch(SW2) for forming a current path for the current returning from the voltage compensation unit through the wave filtering unit, and switching the current path; and a control unit(400) for comparing the output voltage of the voltage compensation unit with a preset value, controlling switching operation of the AC chopper unit in accordance with the result of comparison, and controlling switching operation of first and second switches.

Description

Step-down AC regulator and its control method

The present invention relates to an automatic step-down regulator and a control method thereof, and more particularly, in a field in which a precise voltage is required as an input power supply, when the input voltage rises above the reference voltage, it is stepped down to compensate for a constant voltage output. It relates to an automatic step-down regulator for and a control method thereof.

As shown in FIG. 1, a conventional automatic voltage regulator for controlling an AC voltage has a multi-tap transformer T as a basic configuration such that a constant voltage Vo is output regardless of a change in an input voltage Vi. When the operation is briefly described, a change in the input voltage Vi is detected, and the transformer T secondary-side power strip is interrupted using a semiconductor switching element S such as a triac based on the detected change value. Thus, a constant voltage is output.

However, according to the conventional automatic voltage regulator as described above, the number of semiconductor switching elements increases according to the number of taps and the number of taps for precise voltage control, and the intermittent operation of the semiconductor switch element for tap switching causes the input voltage to be '0. Because the response time is limited, the output voltage is controlled discretely with respect to the input voltage fluctuation.

The present invention has been made to solve the above-mentioned conventional problems, and its object is to automatically compensate for voltage drop when the input AC voltage rises above the reference voltage so that the AC power applied to the load is always a constant voltage. Provides an automatic step-down regulator and its method of controlling the step-down regulator, which enable precise linear voltage control when compensating the step-down, and realize size reduction, efficiency improvement and fast response time according to the input voltage. I would like to.

1 is a circuit diagram of an automatic voltage regulator incorporating a conventional multi-tap transformer,

2 is a circuit diagram of an automatic step-down regulator according to an embodiment of the present invention,

3 is a circuit diagram of an automatic step-down regulator according to another embodiment of the present invention,

4 is a circuit diagram in which the automatic step-down regulator for the single phase of FIG. 2 is applied to the automatic step-down regulator for three phases (U, V, W),

5 is a waveform diagram of the main part of FIG.

6 is a pulse width modulation control signal waveform diagram for controlling the AC chopper of the control unit of FIG.

FIG. 7 is a signal waveform diagram illustrating sequence logic performed by a controller during initial driving of the present invention of FIG. 2.

FIG. 8 is a signal waveform diagram illustrating sequence logic when the input AC voltage is bypassed through the second winding of a transformer in the present invention of FIG. 2.

※ Explanation of code for main part of drawing

100: AC chopper part 200: filter part

300: voltage compensation unit 400: control unit

S1.S2, S3, S4: Semiconductor Switch SW1, SW2: Switch

L: Inductor C: Capacitor

T: transformer

In order to achieve the above object, the automatic step-down regulator according to the present invention includes an interruption means for interrupting the AC input voltage; Filtering means for filtering the output voltage of said interrupting means; Voltage compensating means for step-down compensating the AC input voltage to the output side according to the output voltage of the filtering means; A first switch for interrupting a current path between an output end of the interrupting means and an input end of the filter means; A second switch which forms a passage of current returned from the voltage compensating means through the filtering means and interrupts the current passage; And control means for comparing the output voltage of the voltage compensating means with a set command value and controlling the interruption operation of the interruption means and controlling the interruption operation of the first and second switches according to the result. And the interrupting means comprises two bidirectional switching units connected in series with both ends of the AC input voltage, and the voltage compensating means includes a first winding and an AC input voltage terminal having an output voltage of the filter means connected to both ends. It is preferably configured as a transformer having a second winding connected to one side and the other side connected to the output side.

In order to achieve the above object, a control method of an automatic step-down regulator according to the present invention includes the steps of: opening the first and second switches in the voltage regulator of the present invention configured as described above; A first step of initially driving by sequentially turning on the first switch, turning off and opening the second switch, and controlling the interruption operation of the interruption means sequentially; After the initial driving, in the selection of a specific mode for stopping the compensation of the AC input voltage, stopping control of the interruption operation of the interruption means, turning on the second switch, and turning off the first switch. Performing a step sequentially to reflux current induced in the first winding through the filter means and the second switch in sequence; And performing a normal operation by sequentially turning on the first switch, turning off the second switch, and controlling an interruption operation of the interruption means when the selected specific mode is released. Characterized in that it comprises a step.

The present invention configured as described above is applied to industrial lighting such as road lighting, manufacturing plants, workshops, supermarkets, and office lighting such as government offices, so as to properly reduce the input voltage input to the lighting device at a time when high illumination is not required. In order to achieve this, an AC chopper as the interrupting means and a series compensating transformer as the voltage compensating means are added to the AC chopper to generate a compensating voltage corresponding to the amount of input voltage to be saved. This compensates for the input alternating voltage and the output voltage is stepped down to achieve power savings. Therefore, it is possible to control high-quality voltage that always outputs a constant voltage even within the fluctuation range of input voltage, and has the advantage of excellent response time and efficiency. In the control of the AC compensator of the series compensation method, since a high voltage may be generated on the primary side of the serial compensating transformer when all the switches are turned off, measures to protect the AC chopper switch are required. Since the main current flows to the vehicle side, the Pulse Width Modulation was created and introduced to operate the switch so that the current can be fed back to the input power side at all times. Implement proper sequence logic to completely protect the switch element from the high voltage generation on the transformer primary side, and configure the pulse width modulation method applied to each switch according to the polarity of input voltage and the polarity of PWM applied waveform. To keep the current flowing.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the automatic step-down regulator and its control method according to a preferred embodiment of the present invention.

2 is a circuit diagram of an automatic step-down regulator according to an embodiment of the present invention, an AC chopper unit 100 as an intermittent means for intercepting and chopping an AC input voltage Vi; A filter unit 200 for filtering the output voltage V _IO of the AC chopper unit 100; A voltage compensator 300 for step-down compensating the AC input voltage by the voltage V _fo filtered through the filter part 200 to produce an output voltage Vo; A first switch (SW1) for controlling a current path between an output terminal of the AC chopper unit 100 and an input terminal of the filter unit 200; A second switch (SW2) for forming a current path that flows back from the voltage compensator (300) through the filter unit (200) and intercepts the current path; And compares the output voltage Vo of the voltage compensator 300 with a set command value and controls the AC chopper unit 100 intermittent operation according to the result, and controls the first and second switches SW1 and SW2. It is comprised by the control part 400 which controls an interruption operation.

The AC chopper unit 100 includes first and second switching units 110 and 120 connected in series to both ends (+,-) of the AC input voltage Vi, and the first and second switching units ( The common connection point of 110 and 120 has an output terminal. The first bidirectional switching unit 110 includes a first semiconductor switch S1 having a current inlet connected to a positive pole of the power supply, and a current outlet connected to a current outlet of the first semiconductor switch S1. A second semiconductor switch S2) and first and second diodes D1 and D2 connected in anti-parallel, respectively, between the current inlet and the current outlet of the first and second semiconductor switches S1 and S2. . The second bidirectional switching unit 120 may include a third semiconductor switch S3 connected to a current inflow terminal of the second semiconductor switch S2, and a current outlet of the third semiconductor switch S3. A current inflow end is connected, and a current inflow end is connected between the fourth semiconductor switch S4 connected to the cathode (-) of the power supply, and between the current inflow end and the current outflow end of the third and fourth semiconductor switches S3 and S4. It is composed of third and fourth diodes D3 and D4 connected in anti-parallel, respectively.

The filter unit 200 has a capacitor (C) having one side connected to a common connection point of the first and second switching units (110, 120) and one end connected to the other side of the capacitor (C), and the other end of the negative electrode of the power source ( It consists of an LC filter with an inductor (L) connected to-).

The voltage compensator 300 includes a first winding connected in parallel to the capacitor C and a second winding having one end connected to the positive pole (+) of the power supply behind the AC chopper 100 and the other end being an output terminal. It consists of the transformer T included.

The first switch SW1 is provided on a connection line between the common connection point of the first and second switching units 110 and 120 and the capacitor C and is configured to interrupt a current flowing through the connection line. The switch SW2 is provided on a connection line between the common connection point of the first switch SW1 and the capacitor C and the negative electrode (-) of the power supply, and is configured to interrupt the reflux current flowing through the connection line. In particular, the second switch SW2 is preferably configured as a magnetic contactor in the form of a latch.

3 is a circuit diagram of the automatic step-down regulator according to another embodiment of the present invention, there is a difference only in the connection relationship between the components of the filter unit 200 and the voltage compensator 300 compared to FIG. The configuration and the connection relationship are all the same. Referring to the drawings, one end of the inductor L is connected to the common connection point of the first and second switches SW1 and SW2, and the other end of the inductor L and the A capacitor C is connected between the negative pole of the power supply, and a first winding of the transformer T is connected in parallel to the capacitor C, and one end of the second winding of the transformer T is connected to the capacitor C. It is connected to the negative (-) of the power supply and the other end forms an output terminal.

As such, when the position of the transformer T of the voltage compensator 300 is moved to the negative (−) side of the power source, the transformer T may be adopted as a single winding transformer, thereby achieving cost reduction.

FIG. 4 is a circuit diagram in which the automatic step-down regulator for the single phase of FIG. 2 is applied to the automatic step-down regulator for three phases (U, V, and W). And two three-phase switching legs in which two bidirectional switching units identical to the configurations of the second bidirectional switching units 110 and 120 are connected in series, respectively, between the arm and the ground of each leg, such as the filter unit 200 of FIG. 2. An LC filter is provided, and a three-phase transformer such as the voltage induction part 300 of FIG. 2 is provided to guide the output signal of each LC filter to the output terminal of the power line of each phase.

Subsequently, the control method of the automatic step-down regulator according to the present invention will be described, but the method will be described in parallel with the operation because it is applied to the apparatus of the present invention configured as above.

According to the present invention, when a change occurs in the input AC voltage (Vi) and rises above the reference voltage (Vref), the control unit 400 is based on the difference between the set command voltage and the detected output voltage command value. The semiconductor switch S1-S4 of the AC chopper unit 100 on / off by a pulse width modulation (PWM) method based on the generated compensation voltage command value to control the input AC voltage Vi. By directly chopping, the chopped voltage V _IO is output from the AC chopper unit 100, and the chopped voltage V _IO is filtered through the filter unit 200 to provide the input AC voltage. then made of the compensation voltage (V _fo) corresponding to the variation of the (Vi), a compensation voltage (Vfo) is induced to the secondary side from the primary side of the transformer (T) of the voltage compensation unit 300, the first In the two windings, the input alternating voltage Vi is stepped down by the compensation voltage Vfo. After the output, the operation will be described in more detail below.

First, the state in which the first switch SW1 is turned on and the second switch SW2 is turned off is a normal operation state. As described above, when the input AC voltage Vi rises above the reference voltage Vref, the on / off control process of each semiconductor switch S1-S4 of the AC chopper unit 100 will be described.

The controller 400 turns on the second and fourth semiconductor switches S2 and S4 as shown in FIG. 6 during a half period of the positive (+) of the input AC voltage Vi as shown in FIG. While maintaining the ON state, the first semiconductor switch S1 and the third semiconductor switch S3 are controlled in a pulse width modulation (PWM) manner so as to be alternately turned on / off, and then the input alternating current Vi The second and fourth semiconductor switches S2 and S4 alternate with each other while the first and third semiconductor switches S1 and S3 are kept on during the negative half period of By controlling in a pulse width modulation (PWM) manner to turn on / off, the positive / negative (+ /-) section of the AC input voltage (Vi) directly through the AC chopper unit 100 as a pulse signal chopped Figure 5 AC pulse width modulation compensation voltage (VIO) as shown in (b) is generated and output.

Thereafter, the AC pulse width modulation compensation voltage VIO as shown in FIG. 5B output from the AC chopper unit 100 is filtered through the filter unit 200 and input as shown in FIG. 5C. The sinusoidal AC compensation voltage Vfo corresponding to the voltage variation value is converted, and the sinusoidal AC compensation voltage Vfo is induced from the primary winding of the transformer T of the voltage compensator 300 to the secondary winding. By step-compensating AC input voltage Vi by the sinusoidal AC compensation voltage Vfo. The output voltage Vo is kept constant at the reference voltage Vref level as shown in FIG. At this time, a constant current is regenerated from the transformer T to achieve power saving.

On the other hand, in the normal operation state (ie, SW1 is on and SW2 is off), the present invention is initially driven as it is, or the input AC voltage Vi is bypassed through the second winding of the transformer T. In case of bypass, the semiconductor switches S1-S4 of the AC chopper unit 100 are driven by energy induced from the second winding of the transformer T of the voltage compensator 300 to the first winding side. Since the burnout is described, the control method of the present invention for preventing the burnout will be described below.

FIG. 7 is sequence logic performed by the controller 400 during initial driving of the present invention. As shown in the figure, initial power (Power) in a state in which the first and second switches SW1 and SW2 are opened. ), The second switch SW2 and the first switch SW1 are sequentially turned on, and then the second switch SW2 is turned off and opened, and then each semiconductor of the AC chopper 100 is opened. By outputting a PWM signal for controlling the switches (S1-S2) to control the intermittent operation of the AC chopper 100 as described above, to enter the operation of the steady state.

That is, when the power is initially turned on, the second switch SW2 is first introduced while the first and second switches SW1 and SW2 are open, and the voltage across the second switch SW2 is reduced. If it is made 0, the current induced from the secondary side to the primary side through the transformer T does not flow to the AC chopper part 100 side because the first switch SW1 is open, and thus the filter part 200 ) And the second switch SW2 is refluxed and regenerated, after which the first switch SW1 is inserted to regenerate the AC chopper unit 100 via the filter unit 200. ), And by opening the second switch SW2 and outputting a PWM signal to control each semiconductor switch S1-S4 of the AC chopper unit 100, the semiconductor switch elements S1-S4. To protect.

FIG. 8 is a sequence logic in the case of bypassing the input alternating current Vi through the second winding of the transformer T in the present invention, and as shown in FIG. In the normal operation state, when the bypass switch Bypass SW is applied to stop the compensation of the AC input voltage Vi, the semiconductor switches S1-S4 of the AC chopper unit 100 are first selected when the bypass mode is selected. Stopping the PWM output for controlling the control, turn on the second switch (SW2), and turn off the first switch (SW1) in sequence to perform the transformer through the second switch (SW2) The current induced in the first winding of T) is allowed to flow to the ground side. Subsequently, when the selected bypass mode is released through the bypass switch Bypass SW, the first switch SW1 is first turned on, the second switch SW2 is turned off, and the PWM signal is output. By sequentially performing the control process for controlling each semiconductor switch (S1-S4) of the AC chopper unit 100 to re-enter the normal operating state.

That is, when bypass is required during the normal operation as described above, the state of the bypass switch (Bypass SW) is detected and the PWM output is stopped first as shown in FIG. After the switch SW2 is inserted to configure the reflux circuit, the first switch SW1 is opened, and since the bypass is not necessary, the first switch SW1 is first introduced in the reverse order when the bypass switch is opened. After that, the second switch SW2 is opened, and then the PWM output is applied to each of the semiconductor devices S1-S4 of the AC chopper unit 100. In this case, the second switch SW2 uses a latch type magnetic contactor so that the bypass state can be maintained even when the power is cut off and re-powered during the bypass.

As described in detail above, according to the automatic step-down regulator according to the present invention and a control method thereof, when the input AC voltage rises above the reference voltage by using a new method composed of an AC chopper and an auxiliary transformer, the voltage is compensated by the provisional voltage. By outputting at the level, power can be saved, and response time is improved and efficiency is higher than that of the conventional tap-changing method. In addition, in the conventional tap-changing method, as the voltage fluctuation range is precisely required, more taps and semiconductor switch elements are required, but in the case of the present invention, a precise voltage control is possible with a fixed number of semiconductor switch elements and the transformer is increased in proportion to the capacity. Its size and weight are eliminated, and the size of the AC power saving device can be significantly reduced compared to the conventional method. The control method of the automatic step-down regulator according to the present invention creates the effect that can be stable operation while protecting the switching element of the AC chopper.

Claims (8)

Interrupting means for interrupting the AC input voltage; Filtering means for filtering the output voltage of said interrupting means; Voltage compensating means for compensating the AC input voltage according to the output voltage of the filter means and directing it to an output side; A first switch for interrupting a current path between an output end of the interrupting means and an input end of the filter means; A second switch forming a current path that flows back from the voltage compensating means through the filter means and intercepts the current path; And And controlling means for comparing the output voltage of the voltage compensating means with a set command value and controlling the interrupting operation of the interrupting means and controlling the interrupting operation of the first and second switches according to the result. Automatic step-down regulator. The method of claim 1, And said interrupting means comprises two bidirectional switching units connected in series with both ends of said power supply of said AC input voltage. The method of claim 1, The voltage compensation means, A first winding to which the output voltage of said filtering means is connected at both ends; And And the AC input voltage terminal is connected to one side and the other side is configured as a transformer having a second winding connected to the output side. The method of claim 3, wherein And the second switch forms a current path that flows back from the first winding through the filter means and interrupts the path. The method according to claim 1 or 4, And said second switch comprises a latch type magnetic contactor. The method of claim 1, The control means, during initial driving, sequentially turns on the second switch and the first switch while the first and second switches are open, and then turns off the second switch to open the interruption means. Automatic step-down regulator, characterized in that for controlling the intermittent operation of. The method of claim 1, The control means, during the normal operation with the first switch in the on state and the second switch in the off state, when the compensation action stop signal of the compensation voltage means is input, the interruption control control stop of the interruption means → the second After sequentially controlling the operation of the switch to the first switch off, and then releasing the compensating stop signal, the first switch is turned on and the second switch is turned off. Automatic step-down regulator characterized in that to control the operation of the sequentially. An intermittent means for regulating the AC input voltage, a filter means for filtering the output voltage of the interruption means, a first winding to which the output voltage of the filter means is connected at both ends, and the AC input voltage terminal is connected at one side and the other side is A voltage compensator comprising a transformer having a second winding connected to the output side and compensating the AC input voltage to an output side according to the output voltage of the filter means, an output end of the interruption means and an input end of the filter means In an automatic step-down regulator having a first switch for regulating a current path therebetween, and a second switch for forming a path of current flowing back through the filter means from the transformer primary winding of the voltage compensating means and regulating the passage, In the method for controlling the interruption operation of the interruption means and the first and second switches, Opening the first and second switches, sequentially turning on the second switch and the first switch, turning off and opening the second switch, and controlling the interruption operation of the interruption means. A first step of sequentially performing the steps of performing initial driving; After the initial driving, in the case of selecting a specific mode for stopping the compensation of the AC input voltage, stopping control of the interruption operation of the interruption means, turning on the second switch, and turning off the first switch Sequentially performing a second step of refluxing the current induced in the first winding through the filtering means and the second switch; And A third step of sequentially turning on the first switch, turning off the second switch, and controlling an interruption operation of the interruption means when the selected specific mode is released; Control method of the automatic step-down regulator, characterized in that configured to include.