JPS6194523A - Load distribution system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the load current shared by each power source when a plurality of AC power sources, for example, inverters, are operated in parallel to supply power.

[Conventional technology]

Inverters are widely used as AC power sources for computer equipment, and a plurality of inverters are generally operated in parallel when increasing power supply capacity or to improve supply reliability.

Two conditions must be satisfied to operate AC power supplies in parallel. One of them is to match the respective power supply frequencies and phases.

If there is a phase mismatch, a cross current occurs due to the difference in instantaneous power supply voltage values, and power is exchanged between the power supplies. Since this power is not supplied to the load, the power supply may be overloaded even when the actual load is light.

The second condition is to match the levels of the power supply output voltages. If a voltage level difference exists, the load sharing may be concentrated on the higher voltage power supply, causing this power supply to become overloaded. In order to equalize the load shared by each power source according to the power source capacity, it is necessary to match the power source voltages.

By the way, in the conventional load distribution method for a plurality of inverters, the output currents of the inverters operating in parallel are compared with each other, and the ratio of the current values is made to match a predetermined value.

[Problem that the invention seeks to solve]

In such a conventional load apportioning method, the information exchange and processing means for mutually comparing the output currents of the inverters have a complicated configuration, so a power supply system using this method has the disadvantage that the reliability of the power supply decreases.

The present invention solves these problems, and aims to provide a load distribution method that is highly reliable and realizes stable parallel operation of AC power supplies.

[Means for solving problems]

The present invention provides a power supply system that is connected to a power supply system that includes a plurality of AC power supply devices operated in parallel, and means for generating a total current signal corresponding to the output current of the AC power supply device or a combined current. As a means for solving the above-mentioned problems, the load distribution method includes an output current control means that automatically controls the current value of each output current of the AC power supply device individually based on the signal. means for generating a signal at a level corresponding to a current value obtained by dividing the current value proportionally based on each rated capacity of the AC power supply; and circuit means for supplying this signal to each of the output current control means as the reference signal. The invention is characterized in that it comprises a reference signal generating means including:

Further, the reference signal generating means includes a current transformer having a primary winding through which the total current signal passes and a secondary winding corresponding to each of the AC power supply devices, and a current transformer connected in parallel to each of the secondary windings. A series circuit including a connected impedance and a switching means, and means for outputting a reference signal from a voltage generated in this impedance, and further includes a circuit for closing the corresponding switching means during operation of the AC power supply. A configuration may also be provided that includes means for making this happen.

Further, the reference signal generating means is connected in parallel to a current transformer through which the total current signal passes through its primary winding, and a secondary winding of this current transformer, and has a number of sets corresponding to the AC power supply device. a DC circuit including a first impedance, a second impedance, and a switching means; and means for outputting a reference signal from a voltage generated in the first impedance; The configuration may include means for closing the switching means.

Further, the reference signal generating means is provided corresponding to the first current transformer through which the total current signal passes through its primary winding, and the AC power supply device, and is provided in correspondence with the secondary winding of the first current transformer. a second current transformer having its primary winding connected in parallel to the line; a series circuit of a set of impedances and switching means connected in parallel to the secondary winding of this second current transformer; It may also be configured to include means for outputting a reference signal from the voltage generated in this impedance, and further include means for closing the corresponding switching means during operation of the AC power supply.

[For production]

The reference signal generating means generates a level corresponding to a current value that is obtained by dividing the total current obtained by combining the output power of the AC power supplies operating in parallel, based on the rated capacity of the AC power supplies supplying power. When a reference signal is generated and this reference signal is applied manually to the output current control means that controls the corresponding AC power supply, the AC power supply outputs a current whose current value has changed by the ratio of the change in the reference signal. As a result, load distribution between the plurality of AC power supply devices according to their respective rated capacities is realized.

〔Example〕

Hereinafter, an embodiment of the present invention and a reference signal generator used in this embodiment will be explained based on the drawings.

FIG. 1 is a block configuration diagram showing the configuration of this embodiment system. FIG. 2 is a connection diagram showing the configuration of the first embodiment circuit of the reference signal generator. FIG. 3 is a connection diagram showing the configuration of a second embodiment circuit of the reference signal generator. FIG. 4 is a connection diagram showing the configuration of a third embodiment circuit of the reference signal generator.

First, the configuration of this embodiment system will be explained based on FIG. This embodiment system includes inverters 1) to in, output current control circuits 1) to lnl, reference signal generator 2,
The power output of the inverters 1) to 1n is connected to the power input of the reference signal generator 2, and the power output of the reference signal generator 2 is connected to the power input of the load 3. riJ of the reference signal generator 2 (however, Fil is "1" to rn
The control signal output (a natural number up to J) is output from the output current control circuit 1.
i1, and the output of the output current control circuit 1i1 is connected to the control signal input of the inverter 1).

Next, the operation of this embodiment system will be explained based on FIG.

A current flowing into the load 3 passes through the standard signal generator 2, and a signal having a frequency and phase matching the fundamental frequency of this current and its phase is generated, and based on this signal, The ratio between the levels of the generated and output control signals is determined to match the ratio between the rated capacities of the inverters that input the control signals.

Therefore, when the combination of inverters operated in parallel changes, the output level of this control signal changes. The inverter li is controlled by its output current control circuit 1) 1 based on the signal level of this control signal, and outputs a current according to the capacity of the inverter, thereby performing load sharing according to the rated capacity of the inverter. .

Next, the configurations of the circuits of the first to third embodiments of the reference signal generator will be explained with reference to FIGS. 2 to 4.

As shown in FIG. 2, this first embodiment circuit 2a includes a current transformer 200, switches 21) to 21n, and a resistor 221.
~22n. Here, the current transformer 200 is a current transformer having one primary winding and n secondary windings having the same number of turns, and the current transformation ratio is defined as rTJ. In addition, the resistor 221
The resistance values of ~22n are equal to each other, and their value is rRJ. One terminal of the primary winding of the current transformer 200 is connected to the inverter 1.
) ~ 1n, and the other terminal of the primary winding of the dt transformer 200 is connected to the input of the load 3. One terminal of the first secondary winding of the current transformer 200 is connected to the switch 21i.
is connected to one end of the resistor 22i through the current transformer 20
The other terminal of the first secondary winding 0 is connected to one end of the resistor 22i, and the two ends of the resistor 22i are connected to the control input of the corresponding inverter 1).

Further, as shown in FIG. 3, the second embodiment circuit 2b includes a current transformer 200, switches 21) to 2In, and a resistor 22I.
a to 22na, and resistors 221b to 22nb.

Here, the resistance values of the resistors 221a to 22na are equal to each other, and the resistance values of the resistors 221b to 22nb are also equal to each other. One terminal of the primary winding of the current transformer 200 is connected to the inverter 1.
)=In, and the other terminal of the primary winding of the current transformer 200 is connected to the input of the load 3. current transformer 2
One terminal of the secondary winding 00 is connected to one end of the resistor 22ia, the other end of the resistor 22ib is connected to one end of the resistor 22ib, and the other end of the resistor 22ih is connected to one end of the resistor 22ia through the switch 21i. It is connected to the other terminal of the secondary winding of the current transformer 200, and the two ends of the resistor 22ib are connected to the control power of the corresponding inverter 1).

Further, as shown in FIG. 4, the third embodiment circuit 2c includes current transformers 200 to 20n and switches 21) to 20n. 2in
and resistors 221 to 22n, one terminal of the primary winding of the current transformer 200 is connected to the power output of the inverter 1) to 1n, and the other terminal of the primary winding of the current transformer 200 is 9,
Connected to load 3's human power. One terminal of the secondary winding of current transformer 200 is connected to one terminal of the primary winding of current transformer 20i, and the other terminal of the primary winding of current transformer 20i is connected to current transformation via switch 21i. It is connected to the other terminal of the secondary winding of the device 200. One terminal of the secondary winding of current transformer 20i is connected to one end of resistor 22i, the other end of resistor 22i is connected to the other terminal of the secondary winding of current transformer 20i,
The two ends of the resistor 22i are connected to the control input of the corresponding inverter li. Here, in the first to third embodiment circuits, the rated outputs of the inverters 1) to 1n are equal to each other, and the resistance values of the resistors 221 to 22n are equal to each other.

Next, the operation of the first to third embodiment circuits of the reference signal generator will be explained based on FIGS. 2 to 4.

In the first to third embodiment circuits, a load current I passes through the primary winding of the current transformer 200. In addition, the switch 21
i is closed when the inverter 1) is in operation.

In the first embodiment circuit, when only the inverter 1) is operated, only the switch 21) is closed, and the load current I flowing into the load 3 is transformed by the current transformer 200 and the resistor 2
An i1j: signal with a value of rI R/TJ is generated at both ends of 21. The level of this reference signal is aimed at at a level that causes the inverter 1) to bear 100% of the negative current I. The inverter 1) is current controlled in accordance with the voltage level of this reference signal. Here, other resistors 222 to 22
No voltage is generated across the output current control circuit 12.
No voltage signal is output from 1 to lnl.

Next, when the inverter 1) and the inverter 12 are operated, the switch 21) and the switch 212 are closed, and the load current I flowing into the load 3 is transferred to the current transformer 200.
A reference signal having a value of rlR/2TJ is generated across the resistor 221 and the resistor 222. The voltage level of this reference signal is inverter 1) and inverter 1).
1 is aimed at a level at which 50% of the load current I is applied to 2 and 2, respectively. Inverter 1) and inverter 12 are current controlled in accordance with the voltage level of this reference signal,
Cross current between inverter 1) and inverter 12 is suppressed and synchronous operation is maintained.

In this way, when the number of inverters in operation is m (1<m<n), the voltage level of the reference signal is 1/m of the load current.
The inverter in operation is controlled in accordance with this signal to achieve equal load sharing.

Next, in the second embodiment circuit, the load current I is the current transformer 20
0 to its secondary current, which is shunted into the closed branch circuits of the switches 21) to 21n. A reference voltage is generated by this shunted current passing through the resistors 221b to 22nb. The voltage level of this reference signal is a value obtained by dividing the load current by the number of operating inverters, and the inverters in operation are controlled in accordance with this signal to achieve equal load sharing.

Next, in the third embodiment circuit, the n secondary windings of the current transformer 200 used in the first embodiment circuit are connected to the n current transformers 201.
2On, and switches 21) to 21n are connected in series to the primary windings of the n current transformers 201 to 2On, and the operation is similar to that described in the first embodiment circuit. As a result, equal load sharing is achieved between the inverters in operation.

In the first embodiment circuit, each secondary winding of current transformer 200, and in the third embodiment circuit, current transformers 201-2
When each terminal is turned on, the terminals that output the reference signal are electrically isolated from each other.

In this example circuit, the circuit is configured so that the voltage levels of the reference signals are equal to each other, but in the first example circuit, the number of turns of the n secondary windings and the resistor 221 are
In the second embodiment circuit, the values of the resistors 2218 to 22na are changed, and in the third embodiment circuit, the current transformation ratio of the current transformers 201 to 2On and the resistance 221 are changed.
By changing the value of ~22n, the voltage level of the reference signal is set to a different value depending on the rated capacity of the inverter to which this reference signal is output, so that the load current is distributed to the inverter proportionally according to the rated capacity of the inverter. The present invention can be implemented even if the configuration is configured.

Further, in this embodiment circuit, the inverter is an AC power supply device, but the present invention can also be implemented even if this device is an AC generator.

Further, although an electromagnetic relay is used as the switching means in this embodiment circuit, the present invention can also be practiced using a semiconductor switching element.

〔Effect of the invention〕

The present invention has a simple and robust structure, has a low output impedance and is not affected by external noise, and can DC-isolate the output terminals of the 15 signals connected to the AC power supply. This prevents malfunctions due to mutual interference, and has the effect of realizing a load apportioning device with remarkable high reliability.

[Brief explanation of drawings]

The first part is a block configuration diagram showing the configuration of an embodiment system of the present invention. FIG. 2 is a connection diagram showing the configuration of the circuit of the first embodiment of the J9 signal generator. FIG. 3 shows [1) i of the second embodiment circuit of the reference signal generator.
Connection diagram showing the configuration. Figure 4 shows the third embodiment circuit of the reference signal generator +1)
Connection diagram showing the configuration. 2...Reference signal generator, 3...Load, 1)~1n・
...Inverter, 1) 1-lnl... Output current control circuit, 200-2In-current transformer, 21)-2In-switch, 221-22n. 221a-22na, 221b-22nb-j anti.

Claims (4)

[Claims] (1) Connected to a power supply system including a plurality of AC power supply devices operated in parallel and means for generating a total current signal corresponding to a current in which the output currents of the AC power supply devices are combined, the output current of the AC power supply devices is connected to a reference signal. Based on this, in a load apportioning method that includes an output current control means that automatically controls the current value of each output current of the AC power supply, the current value of the total current signal is determined based on the rated capacity of each of the AC power supplies. Load apportionment characterized by comprising reference signal generation means including means for generating a signal at a level corresponding to the apportioned current value, and circuit means for supplying this signal as the reference signal to each of the output current control means. method. (2) The reference signal generation means includes a current transformer having a primary winding through which the total current signal passes and a secondary winding corresponding to each AC power supply, and connected in parallel to each of the secondary windings. a series circuit of a set of impedances and switching means, and means for outputting a reference signal from the voltage generated in the impedance, and means for closing the corresponding switching means during operation of the AC power supply. A load apportioning method according to claim (1), comprising: (3) The reference signal generating means includes a current transformer through which the total current signal passes through its primary winding, and a reference signal generating means connected in parallel to the secondary winding of this current transformer and having a number of sets corresponding to the AC power supply. a DC circuit including a first impedance, a second impedance, and a switching means; a means for outputting a reference signal from a voltage generated in the first impedance; and the switching means corresponding to the operation of the AC power supply. The load apportioning system according to claim 1, further comprising means for closing the load distribution system. (4) The reference signal generating means is provided in correspondence with a first current transformer through which the total current signal passes through its primary winding, and an AC power supply device, and includes a secondary winding of the first current transformer. a second current transformer having its primary winding connected in parallel to the second current transformer; a series circuit of a set of impedance and switching means connected in parallel to the secondary winding of this second current transformer; Claim 1, further comprising means for outputting a reference signal from a voltage generated in an impedance, and further comprising means for closing the corresponding switching means during operation of the AC power supply. Load distribution method.