JPH0793825B2 - Inverter parallel connection circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a circuit for connecting a plurality of inverters in parallel in order to increase output capacity.

[Conventional technology]

As a parallel connection method of the inverters, a method of connecting a reactor to the output of each inverter is conventionally known as shown in FIG.

The DC input terminals (P, N) of the three inverters 2, 3, 4 are respectively connected in parallel, and further connected to the DC power supply 1. Also, the AC output (U, V) of each inverter 2, 3, 4 is a reactor 5 respectively.
They are connected in parallel through ~ 10 and further connected to the load 11.

The current imbalance is caused by the difference in the output impedance of each inverter 2,3,4, but it is sufficiently larger than the output impedance of the inverter, and the impedance (reactor) with the same value is connected to the output of each inverter, so The difference between the impedances of the paths to the load 11 is reduced to balance the currents of the inverters.

[Problems to be solved by the invention]

However, in this method, it is necessary to have a sufficiently large impedance as the reactor compared to the output impedance of the inverter, and the reactor itself becomes large, and at the same time, the capacity of the inverter increases as the reactor is inserted, and the entire device becomes large. Will end up. In addition, since each reactor needs to be manufactured so that the inductances are equal, it becomes expensive.

An object of the present invention is to provide a parallel connection circuit of inverters which eliminates the disadvantages of the conventional example, can balance the output currents of the respective inverters without increasing the capacity of the inverters, and is inexpensive.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention connects the first output terminals (U-phase) of a plurality of single-phase inverters to the first terminal of a common load via an AC output line, respectively. Second output terminal (V-phase) of each of them is connected to the second terminal of the common load via an AC output line, and is connected to some of the plurality of single-phase inverters and to the first of the inverter itself.
In a parallel connection circuit in which a first magnetic coupling unit is provided between AC output lines connected to the output terminal and the second output terminal, and the plurality of inverters are operated in parallel by an in-phase signal, the plurality of single phase A gist is that the AC output line connected to the first output terminal and the AC output line connected to the second output terminal of another inverter between the inverters are magnetically coupled by the second magnetic coupling means. To do.

[Action]

According to the present invention, the magnetic coupling means is one in which two windings are magnetically coupled, and when the currents in the two windings are equal, the induced voltage in each winding is zero and the current in one winding is , The current is reduced in this winding, and the voltage is induced in the other winding in the direction of increasing current. As a result, the output current of each inverter is balanced.

〔Example〕

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of a parallel connection circuit of inverters according to the present invention, in which three DC inputs (P, N) of single-phase inverters 2, 3, 4 are connected in parallel, respectively. DC power supply 1
Connected to.

The magnetic coupling means used in the present invention is one in which two windings are magnetically coupled, and the current balancer 12 serves as the first magnetic coupling means and the current balancer 14 serves as the second magnetic coupling means. 15,16 are used.

The AC output lines U and V of the inverter 2 are driven by the current balancer 12, and the U-phase output line of the inverter 2 is driven by the V-phase output line of the inverter 3 and the current balancer 15 after passing through the current balancer 12.
The V-phase output line of the inverter 2 passes through the current balancer 12 and the U-phase output line of the inverter 3 and the current balancer 14, and the V-phase output line of the inverter 3 passes through the current balancer 15 and the U-phase output line of the inverter 4 and the current. Each is magnetically coupled by the balancer 16.

The output lines U, V of each inverter are connected to the current balancers 12, 14, 1
After passing through 5,16, they are connected in parallel and then connected to the load 11.

Next, the usage and operation will be described. The current balancer
With 12,14,15,16, two windings are magnetically coupled, and when the currents in the two windings are equal, the induced voltage in each winding becomes zero, and if the current in one winding increases, this A voltage is induced in the winding in the direction of decreasing the current and in the other winding in the direction of increasing the current.

Here, the output current of each inverter is i ₁ as shown in FIG.
Equilibrium conditions of the current when the through i ₆ is _{i 1 = i 3 = i 5} = -i 2 = -i 4
= -I ₆ . The condition of i ₁ = −i ₂ is due to the current balancer 12, and the condition of i ₃ = −i ₂ is due to the current balancer 14, i ₁ = −i ₄
Is established by the current balancer 15, and the condition i ₅ = −i ₄ is established by the current balancer 16. As a result, the conditional expression is i ₁
= I ₃ = i ₅ = −i ₂ = −i _{4 is} established, but according to Kirchhoff's law i ₁ + i ₂ + i ₃ + i ₄ + i ₅ + i ₆ = 0, and the conditional expression obtained for this is Substituting for i ₅ = -i ₆ , all current equilibrium conditions are established.

FIG. 2 shows a second embodiment of the present invention. The difference from the first embodiment of FIG. 1 lies in the positions at which the first magnetic coupling means and the second magnetic coupling means are inserted and the number of each. Is different.

As described above, many combinations can be considered for the insertion method of the first magnetic coupling means and the second magnetic coupling means, and a simple combination of structural arrangements can be freely selected.

〔The invention's effect〕

As described above, in the circuit in which the inverters of the present invention are connected in parallel, the first output terminals of the plurality of single-phase inverters operated by the in-phase signal are respectively connected to the first terminals of the common load via the AC output line. Connect the second output terminals of a plurality of single-phase inverters to the second of the common load via an AC output line.
In a parallel connection circuit of inverters that are connected in parallel by connecting to respective terminals, an AC output that is connected to a first output terminal and a second output terminal of the inverter itself in several negative-phase single-phase inverters A first magnetic coupling means is provided between the lines, and a second magnetic coupling is provided between the plurality of single-phase inverters and between the AC output lines connected to the first output terminal and the second output terminal of another inverter. By simultaneously providing the means, the output currents of the respective inverters are balanced.

Then, the first and second magnetic coupling means need only be provided with an impedance capable of correcting the difference in the output impedance between the respective inverters, and the capacity of the magnetic coupling means itself is small, which is small in size and low in cost. Further, the capacity of the inverter is hardly increased, and the entire apparatus can be downsized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a parallel connection circuit of inverters of the present invention, FIG. 2 is a circuit diagram showing the embodiment of FIG. 2 of the above, and FIG. 3 is a circuit diagram showing a conventional example. . 1 ... DC power supply 2, 3, 4 ... Inverter 5-10 ... Reactor, 11 ... Load 12-16 ... Current balancer

Claims (1)

[Claims] 1. A first output terminal (U phase) of a plurality of single-phase inverters is connected to a first terminal of a common load via an AC output line, respectively, and a second output terminal of the plurality of single-phase inverters. (V phase) via the AC output line to the second of the common load
First magnetic coupling means is provided between the AC output lines connected to the first output terminal and the second output terminal of the inverter itself in some of the plurality of single-phase inverters. A parallel connection circuit for operating the plurality of inverters in parallel by an in-phase signal, wherein an AC output line connected to the first output terminal between the plurality of single-phase inverters and a second output terminal of another inverter A parallel connection circuit of inverters, characterized in that the AC output line connected to is magnetically coupled by a second magnetic coupling means.