JPH03223911A - Automatic ac voltage controller - Google Patents

Abstract

PURPOSE:To compensate continuously the output voltage against the disturbance by the PWM control to ensure the high accuracy and high stability by connecting a protection part to a control part to output a signal in order to stop the output of a pulse width modulation control signal when the current of a current detector exceeds a limit level. CONSTITUTION:A secondary winding 2-2 of a serial transformer is connected between an input terminal 1-1 and an output terminal 4-1, and two diagonal points of a bridge circuit containing the AC switches 3-1 - 3-4 are connected between the output terminals 4-1 and 4-2. A voltage suppressing element 11 is connected between other diagonal points of the bridge circuit, then to a primary winding 2-1 of the serial transformer via a current detector 10-4 and a filter 9. At the same time, a control part 6 is connected to the switches 3-1 - 3-4 to detect an error between the output voltage and the reference voltage and to output a PWM control signal to stabilize the output voltage. Then a protection part 10 is connected to the part 6 to output a signal which stops the output of the PWM control signal when the current of the detector 10-4 exceeds a limit level. In such constitution, the output voltage is stabilized with high accuracy and the protection of a device is attained despite the disturbance and the accidents.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an AC automatic voltage regulator (hereinafter referred to as A
(abbreviated as C-AVR).

(Prior Art) Conventional AC-AVRs include, for example, those that apply magnetic amplifiers, fero-resonance, or thyristor phase control, but all of them are heavy and large in size.

Recently, switching systems aiming at compactness and light weight include those using thyristors as shown in FIG. 7 and those using transistors as shown in FIG. 8.

First, let's explain from what is shown in Figure 7: 1, 1 is an input terminal, 2 is a series transformer, 3 is a regulator and a bridge circuit of an AC switch using a thyristor, 4, 4 is an output terminal, 5 is a load, and 6 is a control It consists of a department.

In the circuit diagram shown in FIG. 7, when the output voltage between the output terminals 4 and 4 decreases due to fluctuations in the power supply voltage or load input between the input terminals 1 and 1, that is, due to disturbance, the control unit 6 compares it with the reference value. Based on the comparison signal, the AC switch of the regulator 3 is selected to have a polarity such that the voltage of the secondary winding 2-2 of the series transformer 2 is superimposed on the input voltage, and the decreased output voltage is compensated to the specified value.

Conversely, when the output voltage increases, the AC switch of the regulator 3 is selected to have a polarity such that the voltage of the secondary winding 2-2 of the series transformer 2 is subtracted from the input voltage by the function of the control unit 6.
The increased output voltage is compensated to the specified value.

When the power supply voltage and the output voltage are approximately equal, the AC switch of the regulator 3 is selected to short-circuit the primary winding 2-1 of the series transformer 2 by the function of the control unit 6, and the power supply voltage is output as is. Become.

Next, what is shown in FIG. 8 will be explained. Components having the same or similar functions as the blocks in FIG. 7 are given the same reference numerals, and their explanations will be omitted. Reference numeral 3 denotes a regulator, which includes a switching circuit of transistors and diodes, 7 a power transformer, 8 a feedback circuit, and 9 a filter.

In the circuit diagram shown in FIG. 8, when the output voltage decreases due to disturbance, the control unit 6 compares it with the reference voltage, and uses pulse width modulation (hereinafter abbreviated as PWM) as the comparison signal.
The switching of the regulator 3 is caused by the control signal so that the voltage of the secondary winding 2-2 of the series transformer 2 is superimposed on the input voltage. The output voltage is compensated to the specified value.

Conversely, when the output voltage increases, the switching of the regulator 3 is controlled by the function of the control unit 6 such that the on-time of the transistor on the subtraction side is adjusted so that the voltage of the secondary winding 2-2 of the series transformer 2 is subtracted from the input voltage. The on-time of the addition side is shortened, and the increased output voltage is compensated to the specified value.

Even when the load 5 is inductive and there is a phase difference between voltage and current, a feedback circuit 8 is provided as a route for the current from the primary winding of the series transformer 2.

(Problem to be solved by the invention) The circuit shown in FIG. 7 has the following problems.

(1) Since the switch combination of the regulator 3 has only three stages of compensation: addition, short circuit, and depolarization, it is not possible to stabilize output voltage fluctuations due to disturbances by more than -3.

(2) Since the switch combination of the regulator 3 is in three stages, for example, when the switch combination changes from short circuit to added polarity, the voltage applied to the series transformer 2 will change greatly, resulting in a DC bias phenomenon and excessive Since a large current flows, a circuit is required to determine when the combination is switched.

(3) Since the thyristor of the regulator 3 does not have a self-turn-off function, when an excessive current flows through this circuit, even if the gate signal of the thyristor is turned off, it cannot be protected for a maximum of half a cycle.

The circuit shown in FIG. 8 has the following problems.

(1) The main purpose of adopting a high-frequency PWM control method is to make the device smaller and lighter, but since the power transformer 7 is required, the smaller and lighter weight cannot be fully utilized.

(2) Since both the series transformer 1 and the power transformer 7 have center-tapped windings, the utilization rate is low and the reduction in size and weight cannot be fully utilized.

(3) Since the filter 9 is connected to the main circuit, a filter with a large current capacity is required, and the reduction in size and weight cannot be fully utilized.

(4) When excessive current flows due to a load short circuit accident, etc.
Since there is no protection part, semiconductor elements such as transistors cannot be protected.

(5) Feedback circuit 8 is required depending on the power factor of load 5.

Users have been requesting smaller, lighter weight and higher performance static AC-AVHs, but it has been difficult to apply and develop devices and circuit systems suitable for the various conditions and loads of AC power supplies. However, it has not been possible to commercialize it until now.

(Objective of the Invention) The object of the present invention is to eliminate or significantly improve the above-mentioned problems, to stabilize the output voltage with high accuracy and to protect the device even in the event of anticipated disturbances or accidents, and to be compact and lightweight. The object of the present invention is to provide an AC-AVR that has good efficiency and power factor, has little waveform distortion of output voltage, has fast response speed, is highly reliable, and is inexpensive.

(Means for Solving the Problems) The means of the present invention to achieve the above object will be explained with reference to FIG.

A secondary winding 2-2 of a series transformer is connected between the input terminal 1-1 and the output terminal 4-1, and a secondary winding 2-2 is connected between the input terminal 1-2 and the output terminal 4-2.

AC switch 3-1.3- between output terminals 4-1.4-2
2. Connect the two diagonal points of the bridge circuits in 3-3 and 3-4.

A voltage suppressing element 11 is connected between the other diagonal points of the bridge circuit, and a current detector 0-4 is connected between the same points, and then the next winding 2- of the series transformer is passed through the filter 9.
Connect to 1.

A control section 6 is connected to each of the AC switches, which detects an error between the output voltage and the reference voltage and outputs a PWM control signal to stabilize the output voltage.

The control section 6 is connected to a protection section 10 which outputs a signal to stop outputting the PWM control signal when the current of the current detector 10-4 exceeds a limit value.

(Function) The power supply voltage Vin is output as an output voltage Vout from between the input terminals to the load between the output terminals via the secondary winding of the series transformer.

When the output voltage Vout fluctuates to the lower side, 1, each of the AC switches switches while adjusting the time to short-circuit the input side of the filter and the time to connect to the output side of the filter according to the PWM control signal, and the switched AC voltage is Smooth it with a filter and input it to the primary side of the series transformer. The voltage Vts of the secondary winding of the series transformer is generated with a polarity superimposed on the power supply voltage Vin, and the low output voltage Vout is appropriately increased to compensate.

When the power supply voltage Vin is equal to the output voltage Vout, each AC switch switches so as to always short-circuit the input side of the filter and isolate it from the output side by the PWM control signal, so that the voltage of the secondary winding of the series transformer Vts also becomes zero, and the power supply voltage Vin is output as is.

When the output voltage Vout changes to a higher side, each of the AC switches adjusts the time to short-circuit the input side of the filter and the time to connect the output side of the filter, and further performs switching so that the opposite polarity occurs. Therefore, the voltage Vts of the secondary winding of the series transformer is generated with a polarity subtracted from the power supply voltage Vin, and the high output voltage Vout is appropriately lowered to compensate.

When an excessive switching current Isw flows through the current detector, the regulator instantly turns it off and holds it, and the current in the next winding of the series transformer flows through the voltage suppressing element to suppress the generation of excessive voltage. It is protected from overcurrent and overvoltage, and resumes normal operation from the zero-crossing point of the waveform of power supply voltage Vin.

(Example) The present invention will be described in detail below with reference to FIGS. 1 to 6.

<Main circuit> Power supply is connected between input terminal 1 (, 1-2), load 5 is connected between output terminal 4-1, 4-2, and secondary winding 2-2 of the series transformer is connected between input terminal 1-1 and output. Between terminals 4-1,
The input terminals 1-2 are connected to the output terminals 4-2, respectively, to supply power to the load.

Regulator> The regulator 3 has a capacitor 3-5 between the output terminals 4-1 and 1-2, and a field effect transistor (hereinafter FET).
) are connected in series with opposite polarity to form an AC switch, and the AC switches 31 and 3-2.3-3 are
and 3-4 are connected in series, and their respective ends are connected, and adjustment is performed by switching operation in accordance with the PWM control signal.

<Filter etc.> AC switches 3-1 and 3-2.3-
Voltage suppressing element 11, current transformer 1 from between the connection points of 3 and 3-4
0-4, is connected to the primary winding 2-1 of the series transformer via a filter 9 for overvoltage protection, overcurrent detection, and waveform smoothing.

Control unit> The control unit 6 outputs the output voltage Vout to the output terminal 4.
-1.4-2, the output detection voltage Vo of the detection section 6-1 and the reference voltage Vref of the reference voltage section 6-2 are inputted to the comparison and amplification section 6-3, and the calculation voltage Vop is converted to the inverting circuit 6-4. A comparator circuit 6-6 compares the triangular wave voltage Vtr of the triangular wave oscillator 6-5 and the Vop with the same Vtr.
and the above-mentioned -Vop, and here the voltage value is P
The signals A and B are input into a pulse shaping circuit network 6-7 (hereinafter abbreviated as PFN).

Create signals Al and Bl by inverting B, and write A, Al,
B, A2 with slightly delayed rise time of Bl signal
．． A3. B2. The PWM control signal of B3 is passed through the start/stop circuit 6-8 and the insulation/drive section 6-9 to the FET of the AC switch 3-1゜3-2.3-3.3-4.
The output voltage Vout is stabilized by outputting between the gate and source of the Vout.

Protection unit> The protection unit 10 inputs the voltage detected by the current transformer 10-4 to the reset circuit 10-3, inputs the output to the 1-noset terminal of a flip-flop circuit (hereinafter abbreviated as FF circuit), On the other hand, the waveform of the input power supply voltage Vin is input to the set circuit 10-1, the output is input to the set terminal of the FF circuit 1, and the output is input to the control terminal of the start/stop circuit 6-8 of the control section. Protective action is performed by cutting off excessive switching current.

The power supply voltage Vin is applied from input terminal 1-1.1-2 to output terminal 4-1.4 via the secondary winding 2-2 of the series transformer.
-2 as the output voltage Vout.

When the output voltage Vout fluctuates to the lower side>Output detection voltage proportional to the output voltage Vout■0 is the reference voltage Vre
f, and as shown in FIG. 2 (2L), the calculation voltage Vop of the comparison amplification section 6-3 is 0 (V) of the triangular wave voltage Vtr.
and the positive peak value, and the calculation voltage V.

At this time, the inversion voltage of p -Vop is 0 of the triangular wave voltage Vtr.
They are in symmetrical positions with (V) as the border.

By the functions of the comparator circuit 6-6 and the PFN 6-7, each AC switch 3-1.3-2.3 of the regulator 3 is adjusted as shown in FIG. 2(c), (d), (e), and (f). -3.3-4 is the time t1 to t2. t2~t3°t3~t4. t4~
The four-time pattern of t5 is -repeated, and the output voltage V
Adjustment is performed by PWM switching using out as a power source.

2. In the interval t1 to t2, as shown in FIG. 2(C), the AC switches 3-1.3-4 are on and the AC switches 3-2.3-3 are off, and the output voltage Vout is the same as that of the AC switches 3-1.3-4. 3-4 and is applied to the input side of the filter 9.

In the section t2 to t3, as shown in FIG. 2(d), the AC switches 3-1 and 3-2 are reversed, and AC switch 3-2.3"4 is turned on, and AC switch 3-1.3-3 is turned on. is off, AC switch 3
The input side of the filter 9 is short-circuited through -2°3-4 and separated from the output voltage Vout by an AC switch 3-1.3-3.

In the period t3 to t4, as shown in FIG. 2(e), the AC switches 3-1 and 3-2 are inverted again, and the state is the same as in FIG. 2(C), and the output voltage Vout is applied to the input of the filter 9. Apply.

In the section t4 to t5, as shown in FIG. 2(f), the AC switches 3-3 and 3-4 are reversed, and the AC switch 3-1.3-3 is turned on, and the AC switch 3-2.3 is turned on. -4 is turned off, and the effect is the same as that shown in FIG. 2(d), with the input side of the filter 9 being short-circuited and separated from the output voltage Vout.

In the interval t5-t6, as shown in FIG. 2(C), the AC switches 3-3 and 3-4 are reversed again, and the interval t1-t2 is
Then, the four-time PWM switching pattern completes one cycle.

In this way, the input side of the filter 9 has an output voltage Vo
A voltage whose on time ton is continuously variable PWM-controlled within a period T time is applied to ut using the calculation voltage Vop of the comparison amplification section 6-3 as shown in FIG. The voltage Vtp applied to the primary winding 2-1 of the series transformer and the voltage Vts of the secondary winding 2-2 are expressed by the following formula, Vtp= (ton/T) ・VoutVts= (t
on/T-N) = Vout Also, since the voltage Vts of the secondary winding 2-2 is generated with a polarity superimposed on the power supply voltage Vin, the output voltage Vout is calculated by the following formula, Vout=Vin+Vt5 =Vin/ (1-ton /T-N), and by continuously varying the on-time ton from 0 to the period T, a low output voltage Vou can be obtained.
Compensate by increasing t appropriately.

Here, on-time ton=t2-tl-t4-t3 period T=t
3-tl=t5-t3 Turns ratio N=Number of turns of primary winding 2-1 of series transformer/Number of turns of secondary winding 2-2, and other detailed circuit constants are omitted.

When the power supply voltage Vin is equal to the output voltage Vout> The output detection voltage Vo and the reference voltage Vref are equal, and the operation voltage Vop of the comparison amplification section 6-3 becomes 0 as shown in FIG. 3(a).
(V).

In the section tl=t2 to t3=t4, in FIG. 3(C), the section t
3=t4 to t5=t6, the AC switches 3-1.3-2 and 3-3.3-4 repeat reversal in the same direction at the same timing as shown in FIG. 3(d), so the filter 9 The input side of is always short-circuited and isolated from the output voltage Vout.

As shown in FIG. 3(b), there is no voltage applied to the input of the filter, and since the on-time cutoff n=0, the output voltage Vo in the above equation
ut becomes equal to the power supply voltage Vin.

5. When the output voltage Vout fluctuates to a higher side> The output detection voltage Vo becomes higher than the reference voltage Vref, and the calculation voltage Vop of the comparison amplification section 6-3 and the triangular wave voltage Vtr are as shown in FIG.
It will be like a).

The AC switch 3-1.3-2.3-3.3-4 is as shown in FIG. 4(C) in the section t1 to t2, as shown in FIG. 4(d) in the section t2 to t3, and as shown in FIG. 4(d) in the section t3 to t4. Figure (e), the interval t4-t5 as in Figure 4(f), the interval t5-t6 as in Figure 4(C), the interval t1-t.
The state is the same as in 2, and the pattern of four PWM switching cycles completes.

In this way, a voltage as shown in FIG. 4(b) is applied to the input side of the filter 9 with a polarity opposite to that in FIG. 2(b), and the voltage Vts of the secondary winding 2-2 of the series transformer is applied. is the power supply voltage V
The output voltage Vout is generated because the polarity is subtracted from in.
is the following formula.

It can be expressed as Vout=Vin-Vts Vin/(1+ton/TN), and by continuously varying the on-time ton by 6 times as described above, the high output voltage Vout is appropriately lowered and compensated for.

Protective part during normal operation> The protective part 10 is located on the primary side of the current transformer 10-4 at t in FIG. 5(a).

When a switching current Isw such as the time from The reset signal Vre of the output of the reset circuit 10-3
s is at a low level as shown in FIG. 5(b), and the output VQ of the FF circuit 10-2 remains unchanged as shown in FIG. 5(e).

On the other hand, the waveform of the power supply voltage Vin in FIG. 5(c) is input to the set circuit 10-1, and the set signal Vset is as shown in FIG. 5(d).
The output VQ of the FF circuit 10-2 is maintained at a high level, and when the control terminal signal of the start/stop circuit 6-8 of the control section is at a high level, it is started. /Input signal A2 of stop circuit 6-8.
A3. B2. B3. is the following insulation/drive section 6-9
is transmitted to continue normal operation.

Protective part At the time of overcurrent
When an excessive switching current Isw flows, such as during the period of With higher priority, the output VQ of the FF circuit 10-2 is set to a low level,
The input signals of the start/stop circuit 6-8 set all outputs to the next block at low level, and each AC switch 3 of the regulator 3
-1.3-2.3-3.3-4 is turned off instantaneously, and the switching current Isw is also turned off and held.

The current in the series transformer-next winding 2-1 is transferred to the voltage suppressing element 11.
The AC switches of the regulator 3 are protected from excessive current and excessive voltage, and when the output signal Vset of the set circuit 10-1 becomes high level, the FF circuit 10 The output VQ of -2 also becomes high level again, and normal operation starts from the zero-crossing point of the waveform of the power supply voltage Vin.

Other Embodiments (1) The configuration of the main circuit is shown in FIG. 1 as an embodiment, but as shown in FIG. 6(a), the regulator 3 is connected to the output terminals 4-1.
A similar effect can be obtained by connecting between input terminals 4-2 and 1-1 and 1-2.

(2) A no-fuse breaker is installed on the input terminal 1-1.1-2 side and the output terminal 4-1.4-2 side of the main circuit to turn on and off the power supply and load, and to protect against excessive current. Depending on the usage environment of this AC-AVR, a line filter or isolation transformer may be connected to reduce the influence of conduction noise.

(3) Regarding the winding structure of the series transformer 2, there is also a method of separating the windings so that excessive current such as a load short circuit decreases transmission from the secondary winding 2-2 to the primary winding 2-1. Alternatively, the smoothing filter 9 can be omitted by utilizing the low transmission of high frequency components of the voltage waveform switched by the regulator 3.

(4) A capacitor is connected between the output terminals 4-1, 4-2 to the series transformer 2 via the regulator 3 to further reduce the influence on the output voltage when the power is transferred by PWM switching to the series transformer 2. A reactor can also be inserted between the output terminal 3-5 and the output terminal 4-1.4-2.

(5) Each AC switch of the regulator 3 is an FET shown in FIG.
As an example, an AC switch is constructed by connecting the FETs in series with opposite polarities, but as shown in FIGS. 6(b) and (C), a semiconductor element with a self-turn-off function such as a transistor or Gate turn-off thyristor (G
(abbreviated as TO) with a high-speed diode connected in parallel in the opposite direction to the current direction of the element, or a high-speed diode rectifier as shown in Figures 6(d), (e), and (f). FE between the positive and negative terminals of the bridge
The same function can be achieved by connecting the drain and source of a T, the collector and emitter of a transistor, or the anode and cathode of a GTO, respectively, and using an AC switch between the AC terminals of the rectifier bridge.

r1 (6) When the AC switches 3-1 and 3-2 and the AC switches 3-3 and 3-4 of the regulator 3 are inverted, the control unit 6 is used to prevent short circuits caused by the upper and lower elements due to the switching characteristics of each element. A dead time is provided to slightly delay turn-on at P F N 6-7, and a snubber circuit that absorbs the surge voltage generated between the elements at this time can be connected in parallel to each AC switch.

(7) Although the current transformer 10-4 is used as an example of detecting the switching current Isw of the protection unit 10, the same function can be obtained even if a resistor or a Hall element is used.

(8) In the signals input from the detection section 6-1 and the reference voltage section 6-2 of the control section 6 to the comparison amplification section 6-3, in the DC mode, the absolute value of the output voltage Vout is integrated, and the DC voltage is sampled and held. ■This is a method of inputting 0 and DC reference voltage Vref, and AC mode is the method of inputting AC output detection voltage Vref.
There is a method of inputting an AC reference voltage Vref synchronized with O and the power supply voltage, and FIG. 1 describes the case of DC mode.

(9) At the start of operation of the AC-AVR of the present invention and the protection unit 10
When recovering after operation, the reference voltage Vref is instantly lowered and raised to the steady-state value Vref over a certain period of time, so that the output voltage Vout smoothly rises from a low voltage to the steady-state value Vout according to the reference voltage Vref. You can also do it.

10) Control section 6, insulation/drive section 6-9, and protection section 1
A set circuit 10 for the auxiliary power supply and protection unit 10 that operates the 0
The power supply voltage waveform inputted to -1 can also be supplied by providing a power transformer.

(Effects of the Invention) Since the present invention is configured as described above, it has the following effects.

(1) Continuously variable PWM control continuously compensates the output voltage from disturbances such as input fluctuations to achieve high accuracy (±
0.1 to ±1.0%) is obtained.

(2) Since PWM control is performed at an extremely high frequency (>20Hz) compared to the frequency of the power supply (50/60Hz), a high-speed response (1 to 200 m5ec) can be obtained even when there is a disturbance, reducing the effect on the output voltage. It can be done very little.

(3) The main components constituting the main circuit only need to be a series transformer, and the circuit configuration allows good utilization of the series transformer, so the entire device can be made small and lightweight (volume ratio 175 to 1/2).

(4) Since the voltage waveform switched by the regulator is smoothed on the primary side of the series transformer with a small current value, a small filter is required, so the entire device can be made smaller and lighter.

(5) High reliability can be obtained in the use of semiconductor devices because the protection action is activated instantaneously against excessive currents and surge voltages such as load short-circuit accidents related to AC switch elements.

(6) Since the current loop of the regulator is always established for any load with any power factor, no special power factor countermeasures are required.

(7) The frequency of the voltage waveform switched by the regulator is in the ultrasonic band, so the noise is extremely low.Moreover, the switching frequency of the AC switch can be set to half of that, which reduces loss and improves efficiency.

It is understood that because of the above effects, the present invention is extremely superior compared to other systems.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the AC-AVR related to the present invention, FIGS. 2, 3, 4, and 5 are waveform diagrams and circuit diagrams of the AC-AVR related to the present invention, FIG. 6 is a partial circuit diagram showing another embodiment of the AC-AVH according to the present invention, and FIGS. 7 and 8 are respectively the conventional AC-AVH.
FIG. DESCRIPTION OF SYMBOLS 1... Input terminal, 2... Series transformer, 3... Regulator, 4... Output terminal, 5... Load, 6... Control part, 7... Power transformer, 8... ...Feedback circuit, 9...
- Filter, 10...Protective section, 11... Voltage suppression element. 4

Claims (1)

[Claims] In an AC power supply circuit, a secondary winding of a series transformer is connected between a power supply input terminal and an output terminal, two diagonal points of a bridge circuit of four AC switches are connected between the output terminals, and other than the bridge circuit Connect a voltage suppressing element between the diagonal points of
Further, a pulse width modulation control signal is connected between the same points to the primary winding of the series transformer via a current detector and a filter, and is sent to each AC switch to detect the error between the output voltage and the reference voltage and stabilize the output voltage. Connect the control unit that outputs
An AC automatic voltage regulator, characterized in that the control unit is connected to a protection unit that outputs a signal that stops outputting the pulse width modulation control signal when the current of the current detector exceeds a limit value. .