JP3031108B2 - Three-phase power supply including inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A plurality of three-phase inverter devices are connected in parallel to supply power to a load.

[0003]

A conventional three-phase inverter device connected in parallel to supply power to a load is a three-phase inverter device.
Because of the phase batch control, stable operation was not possible in the case of an unbalanced load. In other words, if the load becomes unbalanced and the output voltage also becomes unbalanced, if it is attempted to correct this, each phase voltage (or each line voltage) will interfere with each other and change, resulting in a stable balance. Could not be taken.

Accordingly, an object of the present invention is to provide a three-phase power supply using an inverter even if the load is unbalanced.
An object of the present invention is to provide a three-phase power supply capable of supplying a phase-balanced voltage.

According to the present invention, there is provided a three-phase power supply comprising first and second three-phase inverter power supplies connected in parallel with each other to supply power to a common load. the first three-phase inverter power supply first, a combination of the second and third single-phase inverter, said second three-phase inverter power source apparatus fourth, fifth
And a combination of single-phase inverter device according to the sixth, before
The first, second, third, fourth, fifth and sixth single-phase inverters
Each of the D-devices for converting DC to AC.
A C-AC conversion circuit, and an output transistor connected to the conversion circuit.
A primary winding of a lance, and a secondary winding electromagnetically coupled to the primary winding.
Secondary winding, connected between the secondary winding and the load
A smoothing reactor, and between the reactor and the load;
Current detector connected to the, and detected by the current detector
Current and the voltage on the load side of the reactor
Effective current detecting means for detecting an effective current Ip by means of
Reactive current based on the current and voltage of the output stage of the actuator
Reactive current detecting means for detecting,
Controlling the output voltage of the conversion circuit to a predetermined value based on the output
Voltage control circuit, and the active current detection means detects
The effective current Ip to a first constant K1 (where K1 is ωL / 2V
Is a constant according to K, where ω is the angular frequency and L is
Actuator inductance value, V is the inverter device
Is an output voltage, and K is a constant. ) Multiplied by the phase difference signal
a first arithmetic circuit for determining φp and the first arithmetic circuit
The obtained phase difference signal φp has a second constant K2 (where K
2 is a value smaller than 1. ) To calculate the phase difference
A second arithmetic circuit for obtaining a signal K2φp;
A waveform shaping circuit for shaping the voltage on the load side into a rectangular wave,
A base for generating a reference rectangular wave having the same frequency as the output voltage
A quasi-rectangular wave generating circuit, and a rectangular wave obtained from the waveform shaping circuit.
Shape wave and reference square wave obtained from the reference square wave generation circuit
Phase to output the measured phase difference signal φ1
A comparison circuit; and the actual positioning obtained from the phase comparison circuit.
The operation obtained from the second arithmetic circuit from the phase difference signal φ1
The corrected phase difference signal is obtained by subtracting the calculated phase difference signal K2φp.
A subtraction circuit, and a corrected phase difference signal obtained from the subtraction circuit.
The correction is performed so that the corrected phase difference signal becomes zero based on
From the phase control circuit that controls the phase of the output voltage of the conversion circuit.
The first and second inverters of the first three-phase inverter power supply.
And secondary winding of the output transformer of the third single-phase inverter device
The lines are Y-connected, and the second three-phase inverter power supply
Output of the fourth, fifth and sixth single-phase inverter devices
The secondary winding of the transformer is Y-connected, and the first and second
And the secondary winding of the Y-connection of the third single-phase inverter device.
Neutral point and the fourth, fifth and sixth single-phase inverter devices
The neutral point of the Y-connected secondary winding is
The first, second, third, fourth, fifth and sixth single-phase inverters.
The present invention relates to a three-phase power supply, wherein the power supply devices are configured to be controlled independently of each other. It is to be noted that the output of the second arithmetic circuit can be converted into a digital signal as described in claim 2.

[0006]

According to the present invention, the secondary windings of the output transformers of the first, second and third single-phase inverters are connected in a Y-connection, and the neutral point is set in the second three-phase inverter. Since the first, second and third single-phase inverters are connected independently to the neutral point of the phase power supply and independently controlled, even if the load becomes unbalanced, each phase voltage and each line voltage are balanced. And stable supply of three-phase power can be achieved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an apparatus in which two three-phase inverter power supplies according to an embodiment of the present invention are connected in parallel will be described with reference to FIGS. FIG. 1 schematically shows a power supply device, which is configured by connecting first and second three-phase inverter power supply devices 1 and 2 in parallel. To connect two three-phase inverter power supplies 1 and 2 in parallel,
A neutral line 6 is provided in addition to the power lines 3, 4, and 5 of the second and third phases. The loads 7a, 7b, 7c are connected between the power supply lines 3, 4, 5, respectively.

[0008] The first three-phase inverter power supply 1 has a first
It consists of a combination of the second and third single-phase inverter devices 8a, 8b, 8c. Each single-phase inverter device 8a, 8b,
8c is a primary winding 10a, 10b, 10c and a secondary winding 11a, 11 of an output transformer connected to a bridge type DC-AC conversion circuit (inverter circuit) 9a, 9b, 9c.
b, 11c. The first, second and third secondary windings 11a, 11b and 11c are Y-connected, and their output terminals are connected to the three-phase power supply via reactors 12a, 12b and 12c and thyristor AC switches 13a, 13b and 13c. Lines 3, 4 and 5 are connected to these neutral points
It is connected to the. Here, control circuits 14a, 14b, 14 are independently provided corresponding to conversion circuits 9a, 9b, 9c of each phase.
Although c is provided, the control circuit may be shared and independently controlled. . Although the connection is omitted in FIG. 1, the control circuits 14a, 14b, and 14c are connected to each other to operate with a phase difference of 120 degrees, and are connected to the respective conversion circuits 9a, 9b, and 9c. ing. The current detectors 15a, 15b, and 15c of each phase are connected to the control circuits 14a, 14b, and 14c, and voltage detection lines on the input and output sides of the switches 13a, 13b, and 13c are connected. The reactors 12a, 1
The output stages of 2b and 12c have capacitors 16a, 16b,
16c is connected.

Since the second three-phase inverter power supply 2 has the same configuration as the first three-phase inverter power supply 1, many parts are omitted, and the primary windings 17a, 17 of the output transformer are omitted.
b, 17c and only the secondary windings 18a, 18b, 18c are shown. The secondary windings 18a, 18b and 18c are Y-connected, and their output terminals are connected to the three-phase power supply lines 3, 4 and 5, and their neutral points are connected to the neutral line 6.

Since the first, second and third single-phase inverter devices 8a, 8b and 8c of FIG. 1 have the same structure, FIGS.
The first single-phase inverter device 8a will now be described in detail with reference to FIG. 9, and the second and third single-phase inverter devices 8b,
The description of 8c is omitted. In FIG. 2, the control circuit 1 of FIG.
4a is shown in detail. The inverter circuit controlled by the control circuit 14a, that is, the DC-AC conversion circuit 9a
As shown in FIG. 3, first to fourth transistors Q1, Q2, Q3 and Q4 as switching elements are bridge-connected,
This is connected to a DC power supply 19 composed of a rectifier and the like via DC power supply lines 17 and 18. In order to control the value of the output voltage between the output lines 20 and 21, a transistor S1 as a chopper switch element is connected in series with the power supply line 17. The transistor S1 is on / off controlled at a frequency (for example, 20 KHz) sufficiently higher than the frequency of the inverter output voltage (for example, 50 Hz) as shown in FIG. 4A, and controls the inverter output voltage by adjusting the duty ratio. . The transistors Q1 to Q4 are controlled as shown in FIGS. 4B, 4C, 4D and 4E.
The output shown in (F) is obtained.

In FIG. 2, a current detector 15a and a voltage detector 22 are provided between a reactor 12a and a switch 13a. Current detector 15a and voltage detector 22
The active current detection circuit 23 and the reactive current detection circuit 24 respectively connected to the inverter are configured to detect the active current component and the reactive current component of the output current of the inverter by a known method.

The phase difference signal forming circuit 25 connected to the active current detecting circuit 23 comprises a first arithmetic circuit 26 and a second arithmetic circuit 27. The first arithmetic circuit 26 applies a first signal to the signal IP indicating the active current detected by the active current detection circuit 23,
Is converted to a phase difference signal φp. The second arithmetic circuit 27 adds a constant K2 to the phase difference signal φp.
(For example, 0.99) to obtain a signal K corresponding to the phase difference.
This is a circuit to obtain 2 φp.

A voltage detecting transformer 28 connected to the line 3 on the output side of the AC switch 13a is for detecting the voltage on the load side of the reactor 12a, that is, the phase of the load terminal voltage V0. A waveform shaping circuit 29 connected to the transformer 28 shapes the sine wave output voltage into a rectangular wave.

The reference rectangular wave generating circuit 30 includes an oscillator 31 and a frequency divider 32, and generates a rectangular wave at the same frequency as a required output voltage. The reference rectangular wave generation circuit 30 is connected to the switch control circuit 33 and to the phase comparison circuit 34.

The phase comparison circuit 34 outputs a signal indicating the phase difference φ 1 between the reference rectangular wave and the rectangular wave corresponding to the output voltage obtained from the waveform shaping circuit 29.

The subtraction circuit 35 is connected to the phase comparison circuit 34 and the second arithmetic circuit 27, and subtracts K2 φp corresponding to the phase difference φp obtained by calculation from the actually measured phase difference φ1 obtained from the phase comparison circuit 34. Then, the phase shift signal φ is supplied to the control circuit 33. The control circuit 33 shifts the phase of the control signal of the conversion circuit 9 a by φ with respect to the output of the reference rectangular wave generation circuit 30. If the phase of the output voltage of the conversion circuit 9a is controlled based on only the phase difference φ1 so as to eliminate the actually measured phase difference φ1 obtained from the phase comparison circuit 34, a sudden phase change may occur. On the other hand, in the present embodiment, the phase difference φ1 obtained by multiplying the phase difference φp multiplied by the calculation by a constant K2 smaller than 1 is obtained, and the actually measured phase difference φ1
And the difference (φ1 −K2
Since the phase is corrected by φp), no abrupt phase change occurs.

To form a control signal for adjusting the output voltage of the conversion circuit 9a, a third arithmetic circuit 36 is provided in the reactive current detection circuit 24. The reactive current IQ obtained from the reactive current detection circuit 24 obtains a value corresponding to the voltage adjustment value. The third arithmetic circuit 36 obtains a voltage value to be adjusted by multiplying the reactive current IQ by a coefficient K3. The arithmetic circuit 36 is connected to the addition circuit 37, and the voltage detection circuit 3 connected to the output line of the reactor 12a.
8 is also connected. Therefore, a value obtained by adding the voltage IQ K3 to be adjusted to the output voltage V0 is output from the addition circuit 37. A signal obtained from the adding circuit 37 is compared with a reference voltage of a reference voltage source 40 by an error amplifier 39, and an error signal is sent to the control circuit 33.

As shown in FIG. 5, the control circuit 33 includes a triangular wave generation circuit 41, a voltage comparator 42, and a phase shift circuit 4
3 and a switching control signal forming circuit 44. One input terminal of the comparator 42 is connected to the triangular wave generation circuit 41, and the other input terminal is connected to the output terminal of the error amplifier 39 of FIG. The triangular wave generation circuit 41 outputs the frequency (50 Hz) of the output voltage of the conversion circuit 9a.
A triangular wave having a frequency sufficiently higher than the triangular wave (for example, 20 KHz) is generated, and the level of the error signal on the line 39a is set to cross the triangular wave. Therefore, when the level of the error signal changes, the duty ratio of the output pulse of the comparator 42 changes. The output terminal of the comparator 42 is coupled to the base of the transistor S1 contained in the conversion circuit 9a of FIG. When the transistor S1 is turned on / off in response to the pulse width-controlled pulse train obtained from the comparator 42, the DC voltage E of the power supply 19 is turned on and off as shown in principle in FIG. A DC voltage is obtained. FIG.
(A) shows a pulse with a long period for the sake of illustration, but a pulse is actually obtained with a very short period. The bases of the transistors Q1 to Q4 constituting the conversion circuit of FIG. 3 are connected to the switching control signal forming circuit 44 of FIG. The switching control signal forming circuit 44 forms a switching control signal of each of the transistors Q1 to Q4 shown in principle in FIGS. 4B, 4C, 4D, and 4E according to a known method. The transistors Q1 to Q4 are shown in FIG.
When ON / OFF control is performed as shown in (C), (D), and (E), an AC output voltage shown in FIG. Since this AC output voltage corresponds to the pulse shown in FIG. 4A, if the duty ratio of the pulse shown in FIG. 4A is changed, the AC output voltage also changes.

[0019]

[Explanation of Principle] The following describes that phase and voltage control can be performed by the method shown in FIG. An equivalent circuit for one phase of the first and second three-phase inverter power supply devices 1 and 2 in FIG. 1 can be shown in FIG. Note that the first inverter power supply 2
The phase inverter device is indicated by 8a 'and the conversion circuit 9a'
And a reactor 12a '. Now, let the output voltages of the first and second conversion circuits 9a and 9a 'be V1 and V2, and if they are in phase and have the same voltage value, no cross current flows. In addition, in order to simplify the description, the case of no load will be described. As shown in FIG. 8, the first inverter output voltage V1
And the second inverter output voltage V2 are in phase and differ only in voltage value (amplitude), a voltage V1 -V2 which is the difference between the two voltages V1 and V2 is applied to both ends of the two reactors 12a and 12a '. A current I with a delay of 90 degrees flows. That is, only the reactive current Iq flows and the effective current Ip does not flow.

On the other hand, as shown in FIG. 9, if the first and second inverter output voltages V1 and V2 have the same voltage value (amplitude) and a slight phase difference φa, the difference between V1 and V2 is obtained. Of the cross current I based on the voltage ΔV. Since this cross current I is delayed by 90 degrees with respect to the difference voltage ΔV, it has a phase intermediate between V1 and V2. That is, it has the same phase as the load terminal voltage V0. Since the phase difference φa between V1 and V2 can be reduced in advance, if φa is small, there is not much problem even if it is assumed that the cross current I is in phase with V1 and V2. As a result, the cross current I can be regarded as the effective current Ip. The magnitude of the cross current I in FIG. 9 changes in proportion to the phase difference φa, that is, the difference voltage ΔV. Therefore, by detecting the cross current I, that is, the effective current Ip, the phase difference φa can be known.

Next, a description will be given using equations. First and second
When the inverter output voltages V1 and V2 are in phase and have different amplitudes, V1 and V2 can be expressed by the following equations. V1 = Va sin ωt (1) V2 = Vb sin ωt (2) In formulas (1) and (2), Va and Vb indicate maximum values. A voltage having a difference between V1 and V2 is applied to both ends of the two reactors 4, and a cross current I with a delay of 90 degrees flows. This cross current I is expressed by the following equation. I = ｛(Va−Vb) / 2ωL｝ sin (ωt−π / 2) (3)

Since this cross current is a current delayed by 90 degrees,
The reactive current Iq. The voltage drop generated in one reactor 12a based on the cross current I is IωL. In the vector diagram of FIG. 8, it can be seen that the load voltage V0 can be obtained by lowering the first inverter output voltage V1 by IωL and increasing the second inverter output voltage V2 by IωL. Therefore, the voltage value to be adjusted can be known based on the reactive current component Iq of the cross current (reactive current) I.

Therefore, in FIG. 2, the reactive current detection circuit 24
, And rectifies and smoothes the reactive current component Iq to obtain a DC reactive current signal IQ. In the third arithmetic circuit 36, the constant K3 = {V0 / ( _IQmax )}. Times.0.01 is converted to IQ. The voltage adjustment IQ K3 is obtained by the multiplication. This voltage adjustment IQ K3 is added to the voltage V01 detected by the voltage detection circuit 38 and becomes an input to the error amplifier 39, where it is compared with a reference voltage Vr (target voltage) to generate an error signal.

On the other hand, as shown in FIG. 9, when the first and second inverter output voltages V1 and V2 have the same amplitude and slightly different phases, the voltages V1 and V2 can be expressed by the following equations. V1 = Vsin (.omega.t + .phi.a) (4) V2 = Vsin .omega.t (5) The cross current at this time is as follows.

[0025]

(Equation 1)

According to the formula sin (α + β) = sin αcos β + cos αsin β, the following relationship is established. sin (ω + φa) −sin ωt = sin ωcos φa + cos ωtsin φa−sin ωt = sin φa cos ωt− (1−cos φa) sin ωt (7) By substituting, the following equation is obtained.

[0027]

(Equation 2)

When φa is near zero, the second term of equation (8) becomes extremely small, so that this can be ignored, and the cross current I can be approximately expressed by the following equation. I = (V / ωL) sin φa sin ωt (9) When φa is near zero, sin φa and φa in equation (9)
Is in a proportional relationship, so that equation (9) can be approximated to the following equation. I = (V / .omega.L) K.phi.asin.omega.t (10) In the first term of the equation (8), the equations (9) and (10) represent a current in phase with the voltage, that is, an effective current component Ip. The maximum value (V / ω) of the amplitude of the cross current I (active current component Ip) in equation (10)
L) Kφa includes the phase difference φa. Therefore, the active current component Ip is detected by the active current detection circuit 23 of FIG. 2, and the maximum value of the amplitude is output as the active current signal IP.
By multiplying by 1, the phase difference signal φp can be obtained.
In FIG. 9, the phase difference φp between the load terminal voltage V0 and the first and second inverter output voltages V1 and V2 is φa / 2.
Therefore, the constant K1 in the first arithmetic circuit 26 is
L / 2VK. Thus, the phase difference signal φp is obtained by the following equation. φp = K1 · Ip · · · (11)

The phase difference signal φp is approximately obtained in the form of a DC signal from the first arithmetic circuit 26 in FIG. 2 based on the arithmetic operation. The subtraction circuit 35 outputs the calculated phase difference signal φ
When p is input, it may coincide with the phase difference signal φ1 obtained by measurement, and control may be impossible. Therefore, a constant K2 (for example, 0.
99) is multiplied by φp and added to the subtraction circuit 35.

FIG. 6 is a waveform diagram showing an operation when the phase difference φ1 between the first inverter output voltage V1 and the load terminal voltage V0 is reduced. The load terminal voltage V0 shown in FIG.
The waveform is shaped by the waveform shaping circuit 19 as shown in FIG. Phase comparison circuit 3
In FIG. 4, the reference rectangular wave shown in FIG.
A DC signal corresponding to the phase difference φ1 from the detected rectangular wave of (B) is obtained. The phase of the reference rectangular wave generating circuit 30 is determined in advance so as to match the voltage phase of the bus (load terminal) before the parallel operation starts. Therefore, no significant phase difference occurs.
The signal indicating the phase difference φ1 measured by the control
3, the signal is converted by a subtraction circuit 35 into a signal corresponding to .phi.1-K2 .phi.p and added. FIG. 6D shows the first
6C shows a rectangular wave having a phase difference φp of the output stage of the arithmetic circuit 26, and FIG. 6C shows a rectangular wave having a phase difference of K2 φp. The subtraction circuit 35 outputs a signal indicating the correction phase difference φ = φ1−K2 φp to the phase shift circuit 4 shown in FIG.
Give to 3. The phase shift circuit 43 converts the rectangular wave shown in FIG. 6 (E) of the reference rectangular wave generating circuit 30 given by the line 30a into a signal shown in FIG. Shift. Thus, a part of the phase difference φ1 between the load terminal voltage V0 and the reference rectangular wave is corrected. The phase difference φ1 is gradually corrected without being corrected all at once, and the phase of the load terminal voltage V0 approaches the reference rectangular wave.

When the parallel operation of the first and second inverter power supply units 1 and 2 is started, even if the output phase of the reference rectangular wave generation circuit 30 is set to match the load terminal voltage V 0, The phases of the output voltages V1 and V2 of the conversion circuits 9a and 9a 'of the two inverter devices 8a and 8a' may be shifted, and this is corrected by the phase shift circuit 43.

When both the voltage value (amplitude) and the phase of the first and second output voltages V1 and V2 are different, both the voltage control and the phase control are performed based on the reactive current component and the active current component. Done.

Although the above description is for a case where there is no load, a correction operation such that the cross current becomes zero occurs even when there is a load, and the voltage and phase are corrected. That is, when a resistor is connected to the load, an effective current always flows, so that K2 φp always occurs, and a phase shift operation always occurs. However, with respect to the load terminal voltage V0, the first and second output voltages V
1 and V2 operate so that they have the same phase. As a result, the phases of the first and second output voltages V1 and V2 are almost the same.
The current is almost balanced and the cross current is suppressed to a small value.

The first three-phase inverter power supply device 1 shown in FIG. 1 is constructed by combining single-phase inverter devices 8a, 8b, 8c, and the second three-phase inverter power supply device 2 also has three single-phase inverter devices. And the neutral points are connected to each other, so that it is possible to control each phase and to make each phase voltage or line voltage the same without being affected by other phases. be able to.

[0035]

Another Embodiment The inverter device 8a of FIG. 2 can be modified as shown in FIG. The main circuit of this embodiment is the same as that of FIG. 1 except for the control circuit. Therefore, in FIG. 10, portions common to FIG. In this embodiment, a signal indicating the phase difference K2 φp based on the operation result is converted into a digital signal by the A / D converter 51 and input to the subtraction and frequency dividing circuit 52. On the other hand, the output of the waveform shaping circuit 29 is output to a multiplier 53.
Is connected to the counter 54 via the.

The multiplication circuit 53 multiplies the waveform shaping output shown in FIG. 12A to a frequency sufficiently higher than that shown in FIG. 12B. The counter 54 is shown in FIG.
As shown in (C), counting is started in synchronization with the output waveform of the waveform shaping circuit 29, and reset in synchronization with the end of one cycle. Therefore, the counter 54 outputs the phase information of the load terminal voltage V0 as a digital value.

The subtraction and frequency dividing circuit 52 comprises a digital subtractor 55 having a plurality of frequency dividing output terminals as shown in FIG. The output line 54 of the counter 54 is provided to the subtractor 55.
a and the output line 51a of the A / D converter 51 are connected. This subtractor 55 is, for example, SN542 of Texas Company.
Was 83, when it is 12 a value from the count value 65536 by subtracting the phase difference corresponding value 1820 obtained from the A / D converter 51 corresponding to one period of the waveform of (A) 63716, 2 ¹⁶ output terminals Are inverted as shown in FIG. Since the output terminal of the 2 ¹⁵ is a 1/2 frequency-divided output, and outputs the waveform of FIG. 12 (E). FIG. 12 (A)
12E and the waveform of FIG. 12E, the waveform of FIG. 12E corresponds to a waveform obtained by shifting the phase of the waveform of FIG. 12A by the phase angle φ. FIG.
The waveform 2 (E) is supplied to the control signal forming circuit 56 and becomes, for example, the signals (base signals of Q1 and Q4) shown in FIGS. The control signals for the transistors Q2 and Q3 are formed by the phase inversion signal shown in FIG. When the transistors Q1 to Q4 of the conversion circuit 8a are controlled based on the waveform of FIG. 12E, the phase of the load terminal voltage V0 changes, and the rectangular wave of FIG. 12A is replaced with a new one. As a result, each inverter operates so that the output phase of the first and second conversion circuits 9a and 9a 'coincides with the phase of the load terminal voltage V0, and a current balance is obtained. If the load is a resistor, in addition to the active current component (cross current) based on the phase difference, the active current of the load flows, and the phase correction operation is always performed, and the frequency slightly decreases. There is no problem in a circuit where the load does not require a constant frequency.

The voltage control in the circuit of FIG. 10 is performed by the pulse width control circuit 57 at the output stage of the error amplifier 39. This pulse width control circuit 57 includes a triangular wave generation circuit 41 shown in FIG. 5 and a comparator 42 for forming a pulse for controlling the switch S1 shown in FIG.

The rectangular wave generating circuit 59 shown in FIG. 10 is necessary for the start-up, and generates a reference rectangular wave as shown in FIG. Send to

According to the embodiment of FIG. 10, it is possible to easily form the control signals for the transistors Q1 to Q4 as the switching elements of the inverter by the signals obtained from the subtraction and frequency dividing circuit 52.

[0041]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) Instead of detecting the active current and the reactive current, the phase and the voltage may be controlled by detecting the active power and the reactive power. In general, since the load terminal voltage does not change so much, the active power substantially corresponds to the active current, and the reactive power substantially corresponds to the reactive current, so that substantially the same control as in the first and second embodiments can be performed. . (2) The adjustment of the inverter output voltage may be performed by controlling the level of the DC voltage E of the power supply 19 instead of the intermittent operation of the transistor S1 in FIG. Further, the inverter composed of the transistors Q1 to Q4 may be operated by pulse width control (PWM control), and the inverter output voltage may be adjusted by controlling each pulse width. (3) The conversion circuits 9a, 9b, 9c of the three single-phase inverter devices 8a, 8b, 8c are not structurally separated, and the conversion circuits 9a, 9b, 9c for three phases are arranged and connected to a common DC power supply. can do. (4) The first and second three-phase inverter power supplies have been described as examples, but the present invention can also be applied to a power supply in which three or more three-phase inverter power supplies are connected in parallel. (5) In addition to the first and second three-phase inverter power supply devices, the present invention can also be applied to a commercial synchronous parallel operation system in which a commercial power supply is put on standby and synchronously operated. (6) The semiconductor switches 13a, 13b, and 13c in FIG. 1 can be replaced with mechanical switches such as an electric circuit breaker and an electromagnetic contactor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a power supply device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing one phase of FIG. 1;

FIG. 3 is a circuit diagram showing a conversion circuit.

FIG. 4 is a diagram showing the state of each part in FIG. 3 in principle.

FIG. 5 is a block diagram showing a control circuit of FIG. 3;

FIG. 6 is a waveform chart showing the principle of phase control in FIG.

FIG. 7 is a block diagram for explaining the principle of phase and voltage control of the device of FIG. 2;

FIG. 8 is a vector diagram when the first and second inverter output voltages are in phase.

FIG. 9 is a vector diagram showing a state in which the first and second inverter output voltages have a phase difference.

FIG. 10 is a block diagram showing a power supply device according to another embodiment of the present invention.

FIG. 11 is a diagram showing a subtraction and frequency division circuit of FIG. 10;

FIG. 12 is a diagram showing a state of each unit in FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st inverter power supply 2 2nd inverter power supply

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-226315 (JP, A) JP-A-4-145837 (JP, A) JP-A-56-58744 (JP, A) 52021 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 3/00-5/00 G05F 1/70 H04M 7/48-7/529

Claims (2)

(57) [Claims] 1. A three-phase power supply comprising first and second three-phase inverter power supplies connected in parallel to each other to supply power to a common load, wherein the first three-phase inverter power supply device first, second and combinations consist of the third single-phase inverter, said second three-phase inverter power source apparatus fourth, fifth and
And the first, second, third, fourth, fifth and sixth single-phase inverters.
Each of the converters includes a DC-AC conversion circuit for converting DC to AC, a primary winding of an output transformer connected to the conversion circuit, and a secondary winding electromagnetically coupled to the primary winding. A secondary winding, and a smoothing rear connected between the secondary winding and the load.
And a current detector connected between the reactor and the load.
From the current detected by the current detector and the reactor.
Also detects the effective current Ip based on the voltage on the load side.
Based on active current detection means and current and voltage of the output stage of the reactor.
A reactive current detecting means for detecting a current, and a conversion circuit based on an output of the reactive current detecting means.
A voltage control circuit for controlling an output voltage to a predetermined value, and a first current applied to the active current Ip detected by the active current detection means.
(Where K1 is a constant according to ωL / 2VK,
Here, ω is the angular frequency, and L is the inductor of the reactor.
Value, V is the output voltage of the inverter, and K is a constant
It is. ) To obtain the phase difference signal φp
Arithmetic circuit and the phase difference signal φp obtained from the first arithmetic circuit.
Second constant K2 (where K2 is a value smaller than 1)
The second arithmetic circuit for obtaining the arithmetic phase difference signal K2φp by multiplying
When, shaping the voltage of the load side to a rectangular wave than the reactor
A waveform shaping circuit, and a base for generating a reference rectangular wave having the same frequency as the output voltage.
A quasi-rectangular wave generating circuit, a rectangular wave obtained from the waveform shaping circuit, and the reference rectangular wave
Compare the phase with the reference square wave obtained from the
A phase comparison circuit that outputs a measured phase difference signal φ1, and the measured phase difference signal φ1 obtained from the phase comparison circuit.
The calculated phase difference signal obtained from the second calculation circuit
Subtraction circuit that subtracts signal K2φp to obtain a corrected phase difference signal
If, before based on the corrected phase difference signal obtained from the subtraction circuit
Output of the conversion circuit so that the corrected phase difference signal becomes zero.
And a phase control circuit for controlling the phase of the voltage. The secondary windings of the output transformers of the first, second and third single-phase inverters of the first three-phase inverter power supply are Y
And the fourth, fifth and fifth power supplies of the second three-phase inverter power supply are connected .
The secondary winding of the output transformer of the single-phase inverter device of No. 6 is Y-connected, and the Y-connection of the first, second and third single-phase inverter devices is connected.
Of the secondary winding and the fourth, fifth and sixth single-phase
The first, second, third, fourth, fifth and sixth single-phase inverters are mutually connected to the neutral point of the Y-connected secondary winding of the inverter. A three-phase power supply, wherein the devices are configured to be controlled independently. 2. A system for powering a common load.
First and second three-phase inverter power supply units connected in parallel to each other
A first three-phase inverter power supply , wherein the first three-phase inverter power supply has first, second and
Three single-phase inverter devices, wherein the second three-phase inverter power supply device comprises a fourth, a fifth and a
And the first, second, third, fourth, fifth and sixth single-phase inverters.
Each of the converters includes a DC-AC conversion circuit for converting DC to AC, a primary winding of an output transformer connected to the conversion circuit, and a secondary winding electromagnetically coupled to the primary winding. A secondary winding, and a smoothing rear connected between the secondary winding and the load.
And a current detector connected between the reactor and the load.
From the current detected by the current detector and the reactor.
Also detects the effective current Ip based on the voltage on the load side.
Based on active current detection means and current and voltage of the output stage of the reactor.
A reactive current detecting means for detecting a current, and a conversion circuit based on an output of the reactive current detecting means.
A voltage control circuit for controlling an output voltage to a predetermined value, and a first current applied to the active current Ip detected by the active current detection means.
(Where K1 is a constant according to ωL / 2VK,
Here, ω is the angular frequency, and L is the inductor of the reactor.
Value, V is the output voltage of the inverter, and K is a constant
It is. ) To obtain the phase difference signal φp
Arithmetic circuit and the phase difference signal φp obtained from the first arithmetic circuit.
Second constant K2 (where K2 is a value smaller than 1)
The second arithmetic circuit for obtaining the arithmetic phase difference signal K2φp by multiplying
And the analog arithmetic phase difference obtained from the second arithmetic circuit
An analog converter that converts a signal into a digital operation phase difference signal
A digital converter and a voltage on the load side of the reactor is shaped into a rectangular wave.
The waveform shaping circuit and a rectangular wave obtained from the
The frequency that forms a signal with a frequency sufficiently higher than the wave number
In synchronization with the leading edge of the square wave obtained from the waveform shaping circuit.
Of the high frequency signal obtained from the frequency multiplier
Start counting and reset at the end of one cycle of the rectangular wave
Counting output corresponding to the time length of one cycle of the rectangular wave
A digital value output from the counter, and the analog value obtained from the digital value obtained from the counter.
Subtract digital value obtained from digital-to-digital converter
To obtain the corrected digital value.
Form a corrected square wave with a period corresponding to the digital value
A subtraction and frequency division circuit, and a correction square wave obtained from the subtraction and frequency division circuit.
Control signal forming the phase control signal of the conversion circuit
Circuit and the output of the inverter only when the converter is activated
A starting rectangular wave is generated at a frequency equal to the desired period of the voltage.
It consists of a startup rectangular wave signal supply means for supplying to the number Tei multiplying circuit, the first three-phase inverter - the first motor power supply, second and third
The secondary winding of the output transformer of the single-phase inverter device of No. 3 is Y
And the fourth, fifth and fifth power supplies of the second three-phase inverter power supply are connected .
The secondary winding of the output transformer of the single-phase inverter device 6 is Y-connected.
Are linear, the first, second and third single-phase inverters - Y connection of data device
Of the secondary winding and the fourth, fifth and sixth single-phase
The first, second, third, fourth, fifth and sixth single-phase inverters are mutually connected to the neutral point of the Y-connected secondary winding of the inverter. A three-phase power supply, wherein the devices are configured to be controlled independently.