JPS5820237B2 - Current source inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a large capacity current source inverter device used as a current source.

In general, current source inverter devices are as shown in Figure 1.
It is composed of a rectifier 12 provided on the AC input terminal 11 side, an inverter 14 connected to the rectifier 12 via a DC reactor 13, and a load 15 provided on the output side thereof.

The maximum rated current is determined for the main thyristor and diode, which are the main circuit switching elements of such a current source inverter device, and there is a limit on the maximum load current that can be passed through them.

Therefore, in order to configure a large capacity current source inverter device that exceeds the maximum rated current of the main circuit, (1) as shown in FIG.
(2) As shown in FIG. 2, the inverter groups 141 to 144 are connected in parallel by inserting AC reactors 161 to 164 as balancers on their output sides, respectively. Traditional.

However, the former type is often used to increase the capacity of the rectifier 12, but the inverter circuit 14 requires a balancer because the number of elements increases and it is impossible to connect directly in parallel with a thyristor, etc. However, this is rarely used to increase the capacity of an inverter because the operating frequency becomes higher than the commercial frequency, making it difficult to design a balancer.

In the latter case, AC reactors 161 to 1 are operated in parallel for each inverter and provided on the output side.
64 can respectively limit the load current,
The balancing effect is significant.

However, even in this case, when the output frequency is controlled over a wide range and operation is performed near zero frequency, it is necessary to provide AC reactors 161 to 164 with relatively large inductance in order to maintain balance.

On the other hand, in the forced commutation circuit of a current source inverter circuit, the commutation operation changes due to the influence of the inductance on the inverter output side. Therefore, if the inductance value of the AC reactors 161 to 164 is large, the commutation operation time increases and the commutation capacitor This has the disadvantage of causing a voltage increase.

The present invention has been made in consideration of the above points, and provides a circuit configuration for balancing the load current flowing through each of the main sirisks when increasing the capacity of a current source inverter device, and also The present invention provides a large-capacity current source inverter device that eliminates the adverse effects of AC reactance.

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

In FIG. 3, the current source inverter device according to the present invention is provided with DC reactors 131 and 132 on the positive and negative sides of the output of the rectifier 12, respectively, and a unit inverter connected to this DC circuit via impedance elements 171 and 172 on the positive side. 141 is also the impedance element 17
The unit inverter 142 is connected to the unit inverter 142 through impedance elements 175 and 176.
3 are connected in parallel, and each inverter 141 to 14
It is constructed by directly connecting loads 151 to 153 to the common output side of No. 3.

In the inverter device configured in this way, the load current flowing through each unit inverter 141 to 143 is limited by each impedance element 171 to 176, so that it is necessary to maintain a sufficiently good balance of current in a steady state. I can do it.

In addition, impedance elements (for example, inductance) 171 to 176 as a balancer are inserted only in the DC circuit,
Since no AC reactor is provided on the output side of each unit inverter 141 to 143, there is no adverse effect on the commutation operation of the inverter.

Furthermore, in the event of a DC short circuit accident due to failure of commutation in each unit inverter 141 to 143, fault currents from other inverters will flow into the positive and negative sides of the inverter input that first caused the fault, so different fault currents will be generated. impedance elements 171 to 17 are installed on the positive and negative sides of each unit inverter input.
6, it is possible to obtain the effect that the DC short circuit fault current of each inverter is limited.

FIG. 4 shows another embodiment of the current source inverter device according to the present invention, in which a part of the DC reactor is divided into unit inverters 141 to 143 connected in parallel.
DC reactor 1 on the positive and negative sides of the input.
31 to 136, respectively, and each of the divided reactors 131 to 136 is configured to function as the impedance elements 171 to 176 shown in FIG. 3.

In a current source inverter device having such a Q configuration, effects equivalent to those shown in Fig. 3 can be obtained. can be done.

As described above, in the current source inverter device according to the present invention, when a plurality of unit current source inverters are installed together, a current balancer can be provided so as not to have any adverse effect on the commutation operation of each inverter, and the load current Since the capacitance of the commutation capacitor can be made variable according to the amount of electricity, the stability of the inverter operation can be greatly improved. Since it is possible to change the number of auxiliary silis bridges, it has various excellent advantages such as the ability to significantly reduce the size and cost of the device.

[Brief explanation of drawings]

FIGS. 1 and 2 are electrical wiring diagrams each showing a configuration example of a conventional current source inverter device, and FIGS. 3 and 4 are electrical wiring diagrams showing an embodiment of the present invention, respectively. 11... AC input, 12... Rectifier,
13゜131~136・・・DC reactor, 1
4...Inverter, 141-144...
・Unit inverter, is, isi~153...
Load, 161-164... AC reactor, 1
71-176... Impedance element, 111
~116...Lord Cyrisk.

Claims (1)

[Scope of Claims] 1. A multi-unit inverter that drives a load motor by connecting a plurality of forced commutation type unit inverters made of thyristor bridges in parallel, connecting their midpoints and operating in the same phase as each of the unit inverters. A current source inverter device for extracting phase alternating current power, characterized in that impedance elements are provided on each of the positive side and negative side ζ of the input of each unit inverter to balance the load current between each unit inverter. 2. A current source inverter device according to item 1 above, characterized in that a part of the DC reactor provided in the DC circuit is divided into impedance elements for each unit inverter.