JPH04222465A - Voltage variable power supply equipment - Google Patents

Abstract

PURPOSE:To make it possible to vary the output voltage at a constant distortion factor highly efficiently in a wide range by controlling the output phase of two inverter power circuits and by composing the output of these inverter power supply circuits vectorially for obtaining the line voltage of the specified level. CONSTITUTION:The phase of inverter power supply circuits 11, 12 is controlled by a phase control circuit 15 for controlling the output voltage V3. At that time, the outputs V1, V2 of these inverter power supply circuits 11, 12 are subjected to vector addition by transformers 13, 14 and such output voltage V3 as to be suited to a phase difference between the inverter power supply circuits 11 and 12 is obtained. The output level of the inverter power supply circuits 11, 12 is constant and good and the output voltage V3 can be varied at the fixed distortion ratio. In addition, the level can be changed to a linear state with the phase angle of the voltage V3 against a reference signal being fixed, or the phase angle of the voltage V3 against the reference signal V can be freely controlled by the phase of the inverter power supply circuits 11, 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable voltage power supply device.

0002

[Prior Art] In order to test current transformers and a large number of watt-hour meters, the test current range is wide (120% to 20% of the rating).
．． 5%), coarse adjustment using a tapped transformer and fine adjustment using a slip transformer have been used to adjust the test power supply.

FIG. 6 shows the circuit configuration thereof. In this figure, 1 is a tapped transformer, T is its tap,
S is a switch connected to each tap T, and tap T
are connected in parallel, and the switches S of those taps T, T,...
is selectively turned on, thereby causing the corresponding tap T
It obtains a secondary voltage with a value corresponding to the switch S, S,
The secondary voltage is intermittently made variable by selective control of...

2 is a slip transformer, 3 is a servo motor, the secondary voltage of the tapped transformer 1 is applied to the primary winding of this slip transformer 2; The sliding contact is driven by a servo motor 3 to be continuously variable.

With this configuration, the output voltage Vout is
The coarse adjustment is made by on/off control of the switch S, and the fine adjustment is made by controlling the drive of the servo motor 3.

However, in the case of this type of variable voltage power supply, the voltage variable control is controlled by mechanical contacts such as opening and closing of the switch S and driving of the sliding contact by the servo motor 3, so the control speed is slow. It is slow and the circuit configuration of the control system is complicated, so it is desirable to make it stationary from the viewpoint of longevity.

Furthermore, although linear power amplifiers have already been widely used as devices that can vary the voltage by electrical control rather than mechanical contact control, their multi-KVA units generate heat and generate heat. It is also necessary to drive a fan or the like for cooling, which results in poor efficiency and increases the size of the device.

[0008] Against this background, as an efficient device in which variable voltage control is performed exclusively electrically,
An inverter power supply was considered. FIG. 7 shows the circuit configuration of this inverter power supply. In this figure, 4~
7 is a switch transistor, and FIGS. 8(a) and (b)
As shown in FIG. 8(c), each set of transistors 4, 5 and transistors 6, 7 is controlled to be turned on/off alternately, so that currents i1 and i2 are caused to flow alternately, and a voltage signal v0 as shown in FIG. 8(c) is generated. get. 8 is a filter circuit, and this filter circuit 8 removes harmonic components from the voltage signal v0 to obtain a sine wave. According to this configuration, when the transistor switch is on, the voltage is several [V] or less, and when it is off, the current is zero, so there is an advantage that power consumption is small in any case.

However, with this configuration, the signal v0
contains many harmonics, so a filter with high selectivity must be used in order to lower the distortion rate, resulting in an increase in the scale of the filter circuit. Therefore, as shown in FIG. 9, modulated wave signals C' and C'' with pulse widths corresponding to the instantaneous value of the sine wave are obtained from a modulation circuit that operates as a comparator at a modulation frequency C higher than that of the sine wave, and these signals are used to drive the inverter. An inverter power supply using a pulse width modulation method was considered, which drives the oscilloscope and demodulates it with a low-pass filter to obtain the fundamental wave.In this case,
Since the low-order harmonic components are small, a beautiful sine wave with less distortion can be obtained without using a large-scale filter.

0010

[Problem to be Solved by the Invention] However, although the output voltage can be adjusted by changing the level of the reference signal, as the output voltage becomes smaller, the height of the switched pulse remains constant, so the output voltage becomes smaller relative to the fundamental wave. The harmonic components become large. Therefore, adjusting the output voltage by changing the reference signal makes it impossible to operate the output voltage at a constant distortion rate, and thus cannot be used as a test power supply.

[0011] Even when the output voltage is small, the distortion of the output waveform can be reduced by controlling the DC voltage supplied to the switching elements. However, controlling the DC voltage etc. will reduce efficiency and damage the circuit. It gets complicated.

The present invention has been made in view of the above circumstances, and its purpose is to efficiently vary the output voltage at a constant distortion rate using a pulse width modulation type inverter power supply circuit. Another object of the present invention is to provide a variable voltage power supply device in which the phase angle of the output voltage can be arbitrarily adjusted.

[0013]

[Means for Solving the Problems] A variable voltage power supply device of the present invention as set forth in claim 1 comprises two inverter power supply circuits of a pulse width modulation type, and vector synthesis of the outputs of these two inverter power supply circuits to obtain an output voltage. and a phase control circuit that controls the output phase from the two inverter power supply circuits.

In the variable voltage power supply device of the present invention as set forth in claim 2, in particular, the phase control circuit is configured such that the outputs from the two inverter power supply circuits lag and lead symmetrically with respect to a predetermined phase angle with respect to the reference signal phase. The output phases of the two inverter power supply circuits are controlled.

[0015]

[Operation] When the vector sums of the outputs from the two inverter power supply circuits are combined, a voltage signal of a predetermined level is obtained depending on the phase difference between the two. Therefore, by controlling the output phases of the two inverter power supply circuits, the output voltage can be varied.

According to the present invention, the output phases of the two inverter power supply circuits are controlled, and the outputs of both inverter power supply circuits are vector-combined to obtain a voltage at a predetermined level. may be constant, and therefore the output voltage can be varied with a constant distortion factor.

According to the second aspect of the present invention, the output phases are controlled so that the outputs from the two inverter power supply circuits lag and lead symmetrically with respect to the reference signal phase at a predetermined phase angle. Therefore, it is possible to linearly change the output voltage while keeping the phase angle of the synthesized voltage signal with respect to the reference signal constant.

Since the predetermined phase angle can also be changed by changing the output phase of the inverter power supply circuit, it is possible to arbitrarily control the phase angle of the output voltage with respect to the reference signal.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of a variable voltage power supply device according to a first embodiment of the present invention. In FIG. 1, 11 and 12 are pulse width modulation type inverter power supply circuits, and 13 and 14 are transformers. The output of inverter circuit 11 is applied to the primary winding of transformer 13 , and the output of inverter circuit 12 is applied to the primary winding of transformer 14 . The secondary windings of these transformers 13 and 14 are connected in series, and both ends of the series circuit are used as output terminals, and the output voltages V1 and V2 of the inverter power supply circuits 11 and 12 are
3 and 14, vector sums are taken and combined, and the combined voltage is output as the output voltage V3.

The inverter circuits 11 and 12 can be externally synchronized, and 15 is a phase control circuit that controls their output phase angles. Here, each inverter power supply circuit 11
, 12 output voltages V1, V2 are θ1, θ
2, the output voltage V3 becomes V3 = V1 cos θ1 + V2 cos θ2. The phase control circuit 15 controls the output phases θ1 and θ2 of the two inverter power supply circuits 11 and 12. Here, as a simple example of this phase control circuit 15, one as shown in FIG. 3 can be considered. This device inputs the reference signal V and shifts the phase of this signal according to the time constant of the time constant circuit 16. For example, when keeping the phase of the output voltage V1 of the inverter power supply circuit 11 consistent with the reference signal V and controlling the output phase of the other inverter power supply circuit 12, this can be achieved with a single transfer circuit as shown in FIG. can.

By controlling θ1 in this way,
As shown in FIG. 4, the value of V3 can be changed.

However, since the phase angle of the output voltage V3 changes as the voltage value changes, this is fine if the phase of the output voltage signal V3 changes, but it is not suitable for power meter testing. When using it as a power source for other purposes, the following control is required.

The control is performed so that the outputs V1 and V2 from the two inverter power supply circuits 11 and 12 are delayed and symmetrical with respect to the phase of the reference signal V at a predetermined phase angle θ3, as shown in FIG. It is becoming more and more popular. Specifically, the reference signal V is input to this phase control circuit 15, and the phase control circuit 15 converts this reference signal V into (θ3 −
Two different types, θ1 ) and (θ3 −(−θ2 )), are applied to each inverter power supply circuit 11, 12.

As a result, as shown in FIG. 2, it is possible to linearly change the output voltage V3 while keeping the phase angle θ3 of the combined voltage signal with respect to the reference signal constant.

In other words, the inverter power supply circuit 11,1
By changing the output phase of 2, it becomes possible to arbitrarily control the phase angle θ3 of the output voltage with respect to the reference signal.

[0026] Here, in order to use the power supply for power meter testing, it is necessary to control the phases of both the voltage generator and the current generator. The voltage circuit only requires the rated voltage, but the phase and magnitude of the current circuit voltage must be controlled. For example, a current of 120 [A] with a lagging power factor of 0.5,
When controlling a load impedance of 1.0 ohm, the combined voltage should be 120 [V] and the phase angle should be 53.13.
(θ1 = θ2), and the power factor is the reference signal V
The phase angle of V1 is 60-53.13°=6.8
Delayed by 7°, V2 is 60 + 53.13° = 113
．． It is possible to set a delay of 13 degrees, a composite voltage of 120 [V], and a power factor of 0.5.

In this way, the magnitude of the output voltage V3 and the phase angle θ3 with respect to the reference voltage V can be controlled only by the output phase angles of the inverter power supply circuits 11 and 12.

FIG. 5 shows a circuit configuration of a second embodiment of the present invention, and its feature is that the outputs of the two inverter power supply circuits 21 and 22 are configured to take the difference and synthesize the outputs. However, only one combining transformer 23 is required. Even in this case, the phase control circuit 2
The phase control No. 4 performs the same control as the phase control circuit 15, thereby achieving the above-mentioned effects.

In the present invention, two inverter power supplies are used, but since their output voltages are combined and used, each output can be used effectively, and even if the output voltage is small, the power is always maintained at the rated power. The output capacity can be obtained.

[0030]

[Effects of the Invention] As explained above, according to the present invention, the output phases of two inverter power supply circuits are controlled, and the outputs of both inverter power supply circuits are vector-combined to obtain a voltage at a predetermined level. The output level of the inverter power supply circuit may be constant, and therefore the output voltage can be varied over a wide range with high efficiency at a constant distortion rate. In particular, since the inverter power supply circuit can be operated at the rated output voltage, considerable efficiency can be expected.

According to the second aspect of the present invention, the output phases are controlled such that the outputs from the two inverter power supply circuits lag and lead symmetrically with respect to the reference signal phase at a predetermined phase angle. Therefore, it is possible to linearly change the output voltage while keeping the phase angle of the synthesized voltage signal with respect to the reference signal constant.

Since the above-mentioned predetermined phase angle can also be changed by changing the output phase of the inverter power supply circuit, it becomes possible to arbitrarily control the phase angle of the output voltage with respect to the reference signal.

Overall, it is possible to provide a low-loss, compact, and inexpensive device as a power source for various tests.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a variable voltage power supply device according to a first embodiment of the present invention.

FIG. 2 is a vector diagram for explaining the concept of more preferable phase control of the variable voltage power supply device shown in FIG. 1;

FIG. 3 is a circuit diagram showing an example of a simple transfer circuit applicable as a phase control circuit of the variable voltage power supply shown in FIG. 1;

FIG. 4 is a vector diagram for explaining the concept of phase control when one transfer circuit shown in FIG. 3 is used.

FIG. 5 is a circuit diagram of a variable voltage power supply device according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional variable voltage power supply device using mechanical contact control.

FIG. 7 is a circuit diagram of a variable voltage power supply device comprising a conventional switching inverter power supply.

FIG. 8 is a time chart diagram illustrating a simple operation of the inverter section of the variable voltage power supply device shown in FIG. 7;

9 is a time chart diagram illustrating the operation of the inverter section of the variable voltage power supply shown in FIG. 7 using a pulse width control method.

[Explanation of symbols]

11 Inverter power supply circuit 12 Inverter power supply circuit 13 Vector synthesis transformer 14 Vector synthesis transformer 15 Phase control circuit 21 Inverter power supply circuit 22 Inverter power supply circuit 23 Vector synthesis transformer 24 Phase control circuit

Claims (2)

[Claims] 1. Two inverter power supply circuits using a pulse width modulation method, a transformer that performs vector synthesis on the outputs of the two inverter power supply circuits to obtain an output voltage, and controlling the output phase from the two inverter power supply circuits. A variable voltage power supply device equipped with a phase control circuit. 2. The phase control circuit controls the output phases of the two inverter power supply circuits so that the outputs from the two inverter power supply circuits lag and lead symmetrically with respect to a reference signal phase at a predetermined phase angle. The variable voltage power supply device according to claim 1, wherein: