JPH077958A - Power converter - Google Patents

Abstract

PURPOSE:To make shared currents of semiconductor elements uniform by making wiring inductances uniform in the case of unbalance in the shared currents of the elements due to a difference of the wiring inductances in many parallel connection circuits of the elements for constituting an output circuit of an inverter. CONSTITUTION:An inverter has power converting switching semiconductor elements 3-12 connected in parallel by conductors with a DC power source 1 and an electrolytic capacitor 2 as inputs. Parallel connecting conductors 17-19 are used to make wiring inductances uniform to make shared currents of the elements 3-12 uniform. Thus, a difference of current loads of the elements is eliminated, many parallel connections can be performed, a capacity of an inverter output circuit using the elements can be easily increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device,
The present invention relates to a power conversion device that outputs an AC power or a DC power by PWM control by connecting an arbitrary DC power supply to a semiconductor element group configured by connecting a large number of switching semiconductor elements for power conversion in parallel with an arbitrary conductor.

[0002]

2. Description of the Related Art In general, a power conversion system in which a large number of switching semiconductor devices for power conversion are connected in parallel by arbitrary conductors to connect a direct current power supply to a semiconductor device group and output alternating current power or direct current power by PWM control. In the device, no consideration was given to variations in the wiring inductance and wiring resistance of each semiconductor element, and the current was concentrated in the element having the smallest wiring impedance with respect to the current path, resulting in current imbalance between the semiconductor elements. It was

Japanese Laid-Open Patent Publication No. 1-85570 proposes a method of connecting a saturable reactor in series with a power conversion switching semiconductor element to prevent current imbalance during switch operation.

[0004]

In the above-mentioned prior art, a saturable reactor is connected in series with a switching semiconductor element for power conversion to prevent current imbalance. However, like the PWM inverter which has been spreading recently, When the high frequency switching operation of the semiconductor element is required, there is a problem that power loss becomes large and stable and high quality power cannot be supplied, and there is a problem that the device becomes large.

An object of the present invention is to connect an arbitrary DC power source to a semiconductor element group formed by connecting a large number of switching semiconductor elements for power conversion in parallel with an arbitrary conductor, and output AC power or DC power by PWM control. In the power converter, the current imbalance is suppressed, that is, the current imbalance of each switching semiconductor element for power conversion during the switching operation is suppressed.

[0006]

In order to achieve the above object, the current path length and the wiring impedance per unit length of each power conversion switching semiconductor element connected in parallel are obtained, and the current path of each element is calculated. Achieved by moving the branch connection point so that the wiring impedance becomes equal, and by connecting the DC wiring and the switching semiconductor element for power conversion with the same wiring length so that the impedance of the current path becomes equal. To be done.

[0007]

With the parallel connection method of the semiconductor elements, the wiring impedances of the respective current paths are equalized and equalized. Thereby, the currents of the respective semiconductor elements are equalized and the current imbalance can be suppressed.

[0008]

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIG.
~ It demonstrates by FIG. The circuit connection diagram of the present invention is shown in FIG. 1, and the configuration diagram is shown in FIG. An equivalent circuit of the present invention is shown in FIG.
4 (a), (b) and (c). The conventional parallel connection simulation result is shown in FIG. 5, and the parallel connection simulation result of the present invention is shown in FIG. The overall sequence of the power conversion device is shown in FIG. In FIG. 7, DC power supply 1, electrolytic capacitor 2, inverter module 13,
This is a power conversion device configured by an AC filter 14, and converts DC power into AC power or DC power and supplies energy to the load 15.

In FIG. 2, the collectors of the power conversion switching semiconductor elements 3 to 7 are connected by a parallel connection conductor 17, and the emitters of the power conversion switching semiconductor elements 3 to 7 and the collectors of the semiconductor elements 8 to 12 are connected in parallel. Conductor 18
And the switching semiconductor element for power conversion 8 to
The twelve emitters are connected by the parallel connection conductor 19. The present invention relates to a method of constructing the parallel connection conductors 17 and 19.

Next, the operation of the present invention will be described to find the optimum configuration of the parallel conductor connections 17 and 19. 1 and 2, when the power conversion switching semiconductor elements 3 to 7 are ignited, a current flows through the power conversion switching semiconductor elements 3 to 7 and the output terminal, but at that time, the power conversion switching semiconductor elements on the opposite side. The diode recovery currents of 8 to 12 are so large as to short-circuit the current terminals P and N.

If the influence of the lead lines from the parallel elements to the current does not affect the current sharing, the equivalent circuit at the time of ignition is as shown in FIG. Compared with the wiring inductance in the inverter module 13, which is a group of parallel connection of power conversion switching semiconductor elements, the wiring resistance is a negligible value, and the current sharing is negligible because it is negligible, and only the semiconductor elements 3 to 7 are fired. The equivalent circuit is shown in Fig. 4 (a).
It becomes like. Here, the constant k is the length ratio of the connection points. Further, since this circuit is bilaterally symmetric, assuming that equal currents flow into the central semiconductor elements 5 and 10 from the left and right, the equivalent circuit is as shown in FIG. That is, from the symmetry, half of the shared current of 5 parallels may be considered.

Now

[0013]

## EQU00001 ## If L0 = a.times.L1 (Equation 1), the equivalent circuit of the half part is as shown in FIG. 4C, and the sharing current will be examined.

From FIG. 4C, the element currents I1, I2, I
When the time rate of change of 3 is represented by I1 ', I2', I3 '

[0015]

[Equation 2] I1 ′ = (k × L1 + a × L1) = (I2 ′ + 0.5 × I3 ′) × (1-k) × L1 + I2 ′ × a × L1 (Equation 2)

[0016]

[Equation 3] I2 ′ × a × L1 = 0.5 × I3 ′ (L1 + 2 × a × L1) (Equation 3) From Equation 3

[0017]

[Equation 4]

From equations 3 and 4

[0019]

[Equation 5]

Now, let k0 be k for a such that I1 '= I2'.

[0021]

[Equation 6]

It becomes I3 for a is obtained from the equation 4.

From the above examination, it is possible to equalize the shared currents by setting k0 to an appropriate value.

In this embodiment, k0 = 0.6 and the parallel connection conductors 17 and 19 shown in FIG.

FIGS. 5 and 6 are simulation results in current sharing between the conventional parallel connection method and the parallel connection method of the present invention. As can be seen from this, it can be seen that the present embodiment has the effect of making the shared currents of the power conversion switching semiconductor elements 3 to 7 uniform. Further, since the di / dt at the turn-on of the switching operation of the inverter circuit becomes uniform, the current imbalance of each power conversion switching semiconductor element can be eliminated. This eliminates the difference in the currents of the power conversion switching semiconductor elements and enables a large number of parallel connections.

(Embodiment 2) Another embodiment of the present invention will be described below with reference to FIG.

FIG. 8 is an example of a connection diagram in which the present invention is expanded and developed. A connection group in which a DC power supply 1, an electrolytic capacitor 2 and a switching semiconductor element for power conversion, which are parallel connection groups, are further connected in parallel. It is composed of 16.

The inverter module 13 is considered as one element and is connected as in the first embodiment. As a result, a large number of power conversion switching semiconductor elements can be connected in parallel without any difference in current between the power conversion switching semiconductor elements, and the capacity can be easily increased.

(Embodiment 3) Another embodiment of the present invention will be described below with reference to FIG.

FIG. 9 is another example of a connection diagram in which the present invention is expanded and developed. The DC power supply 1, the electrolytic capacitor 2, the power conversion switching semiconductor elements 3 to 12, and the parallel connection conductor 2 are shown.
It is composed of 0-29.

In FIG. 3, the DC power supply 1 and the power conversion switching semiconductor elements 3 to 12 are connected in parallel through the electrolytic capacitor 2 by the parallel connection conductors 20 to 29. Here, the parallel connection conductors 20 to 29 are connected to each individual power conversion switching semiconductor element with the same length. Thereby, the DC power supply 1 and the power conversion switching semiconductor elements 3 to 12 are individually connected with the same wiring length, so that the impedances of the current paths of the DC power supply 1 and the power conversion switching semiconductor elements 3 to 12 are equal. become,
This has the effect of suppressing current imbalance.

[0032]

According to the present invention, the currents of the switching semiconductor elements for power conversion are equalized, and the current imbalance of each element can be eliminated. This eliminates the difference in the current burden of the power conversion switching semiconductor elements, allows a large number of parallel connections, and easily increases the capacity of the power conversion device using the power conversion switching semiconductor elements.

[Brief description of drawings]

FIG. 1 is a connection diagram of five switching semiconductor elements for power conversion of the present invention when connected in parallel.

FIG. 2 is a configuration diagram of the power conversion switching semiconductor element of the present invention when connected in parallel with 5;

FIG. 3 is an equivalent circuit diagram of the power conversion switching semiconductor element of the present invention when 5 parallel connections are made.

FIG. 4 is a simplified equivalent circuit diagram of the power conversion switching semiconductor element of the present invention when 5 parallel connections are made.

FIG. 5 is a diagram showing a simulation result when five switching semiconductor elements for power conversion are connected in parallel in a conventional power conversion device.

FIG. 6 is a diagram showing simulation results when five switching semiconductor elements for power conversion are connected in parallel in the power conversion device of the present invention.

FIG. 7 is a diagram showing an example of an overall sequence of a power conversion device.

FIG. 8 is an expanded and expanded connection diagram of the present invention.

FIG. 9 is another connection diagram in which the present invention is expanded and developed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2 ... Electrolytic capacitor, 3-12 ... Switching semiconductor element for power conversion, 13 ... Inverter module, 14 ... AC filter, 15 ... Load, 16 ... Inverter which is a parallel connection group of switching semiconductor elements for power conversion Connection group in which module 13 is further parallelized, 17-
29 ... Parallel connection conductor.

Claims (3)

[Claims] 1. A power conversion system in which a large number of switching semiconductor elements for power conversion are connected in parallel by arbitrary conductors to connect a desired DC power supply to a semiconductor element group and output AC power or DC power by PWM control. In the device, the wiring length of any conductor that connects the DC power supply and the semiconductor element group is minimized, and the wiring impedance of each switching semiconductor element for power conversion and the impedance inside the element are taken into consideration for each power conversion. An electric power converter characterized in that an arbitrary conductor is branched and connected at two points so that the impedance of the current path of the switching semiconductor element becomes equal. 2. The power converter according to claim 1, wherein in the parallel semiconductor element group formed by connecting a large number of the semiconductor element groups in parallel with an arbitrary conductor, the DC power source and the parallel semiconductor element group are connected. Set the minimum wiring length of any conductor, and consider the wiring impedance of each semiconductor element group and the impedance inside the semiconductor element group, and use two arbitrary conductors so that the impedance of the current path of each semiconductor element group becomes equal. A power converter characterized by being branched and connected. 3. The power conversion device according to claim 1, wherein a large number of power conversion switching semiconductor elements connected in parallel are connected by an arbitrary conductor, and the DC power source and the current path of each power conversion switching semiconductor element are connected. Impedance is
A power conversion device characterized in that they are individually connected with the shortest conductors having the same wiring length so as to be even.