JPH0678549A - Circuit system of inverter - Google Patents

Abstract

PURPOSE:To balance currents without uniformizing the characteristics of the connected-in-parallel elements of an inverter or converter strictly. CONSTITUTION:The parallel elements U1 and U2 of the upper arm of an inverter and those X1 and X2 of the lower arm are connected in series respectively. To their connected points (a1) an (a2) AC wires W1 and W2 of large impedance, with the other ends (a) connected to each other, are connected, and the current burden between the parallel elements is made even. The parallel elements X1 and X2 of the lower arm are controlled by a common gate circuit Gx. While, the gates of the parallel elements U1 and U2 of the upper arm are controlled by gate circuits GU1 and GU2 insulated respectively, and shortcircuiting of the connected points (a1) and (a2) by the gate circuits is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter circuit system in which semiconductor elements such as IGBT transistors are used in parallel.

[0002]

2. Description of the Related Art Conventionally, a circuit example of a single-phase inverter using semiconductor elements in parallel is shown in FIG. In this case, the currents flowing through the semiconductor elements T ₁ and T ₂ connected in parallel are made uniform by aligning the voltage drop V _FF characteristics when the elements are turned on in the forward direction and equalizing the wiring impedance of the electric circuit.

[0003]

The above-mentioned inverter having a well-balanced semiconductor element current has a practical problem when it is applied as a DC / AC converter to a load having a relatively high power factor such as a commercial frequency. Does not occur.

However, when it is used from a low frequency such as motor control, or when it is used in a regenerative region such as interconnection with a system, the current is unbalanced for the following reasons.

(1) Case of low frequency When used for motor control The frequency range of the inverter is from several Hz to several hundred Hz. When it is used at a low frequency such as several Hz, the wiring impedance is almost eliminated, the current sharing is determined only by the V _FF characteristic of the element, and high-precision element characteristic is required, which causes a trouble in manufacturing.

(2) In case of regeneration area The inverter connected to the grid is used in the drive and regeneration areas. In the case of driving, the current flowing through the element flows in the forward direction, and in the case of regeneration, it flows in the reverse direction. Therefore, it is necessary to select the elements so that the voltage characteristic V _FR characteristic when the current flows in the opposite direction to the V _FF characteristic is made uniform.

Even in motor control, when the current is large in the regenerative region, it is necessary to make both the characteristics of V _FF and V _FR of the element uniform. For this reason, it becomes difficult to select conditions for the elements, which causes a practical problem. In particular, when using elements composed of two arms of U-phase and X-phase in parallel, it is necessary to match the V _FF and V _FR characteristics of the P-phase and the N-phase, respectively, and the selection conditions become more severe.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a circuit system of an inverter capable of balancing currents without strictly aligning characteristics of parallel-connected elements. To provide.

[0009]

In order to achieve the above object, the circuit system of the converter according to the present invention is based on the main circuit:
In an inverter that uses a plurality of semiconductors in parallel in the lower arm, each semiconductor element of the upper and lower arms is connected in series, and each semiconductor element of the upper arm is commonly connected to the positive pole, Each semiconductor element is commonly connected to the negative pole.

A plurality of alternating current lines, the other ends of which are connected, are connected to the connection points of the respective semiconductor elements connected in series.
Each semiconductor element on the lower arm side is controlled by a common gate circuit, and each semiconductor element on the upper arm is controlled by each insulated gate circuit.

[0011]

A plurality of semiconductor elements, which are parallel elements of the upper arm and the lower arm, are connected in series, and a plurality of alternating current lines whose other ends are connected are connected to the respective connection points. The AC side impedance of is increased by the wiring impedance of the AC line.

Since this wiring impedance is larger than the impedance of the semiconductor element, the current sharing of the paralleled semiconductor elements is balanced even if there are many differences in the characteristics of each semiconductor.

Since the semiconductors of the lower arm are commonly connected to the negative pole, they can be controlled by a common gate circuit.

AC side (emitter) of each semiconductor of the upper arm
Is connected via an AC line, but since each semiconductor is controlled by each insulated gate circuit, control can be performed without any trouble.

[0015]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an inverter main circuit, and FIG. 2 shows a gate circuit.

1 and 2, U ₁ and U ₂ are parallel semiconductor elements of the upper U-phase arm, X ₁ and X ₂ are parallel semiconductor elements of the lower X-phase arm, and collectors of the elements U ₁ and U ₂ . Is connected to the positive bus P, and the emitters of the elements X ₁ and X ₂ are connected to the negative bus N.

The emitters of the upper arm elements U ₁ and U ₂ are connected to the collectors of the lower arm elements X ₁ and X ₂ , respectively, and their connection points a
₁ and a ₂ are not directly connected to each other to form an AC terminal, but two AC lines W ₁ and W _{2 are respectively} drawn out and connected a to the load L side.

The emitters of the elements X ₁ and X ₂ are the negative bus N
The gates of the elements X ₁ and X ₂ are driven by the common gate circuit G _X because they are connected to each other and have a common potential.

The element U ₁ and line W ₁ is between the emitters of U _2, W ₂
Since there is a potential difference due to, the insulated gate circuit G _U1 ,
G _U2 is used to drive the gates of devices U ₁ and U ₂ separately.

The V-phase and Y-phase arm circuits and gate circuits are constructed similarly to the U-phase and X-phase arm circuits and gate circuits.

In the figure, TR is an insulating transformer, R _{f1 to} R
_f3 denotes a rectifier circuit that outputs the power of the secondary winding n ₁ ~n ₃ rectifies the voltage gate circuit G _U1, G _U2, G _X of the transformer TR.

With the above-mentioned structure, the AC side wiring impedance of each element is increased by the AC lines W ₁ and W ₂ , and the current sharing of the parallel elements in each phase can be easily balanced. Further, since each element of the U-phase and V-phase arms is driven by the insulated gate circuit, there is no influence even if the emitter potential is different.

In the above embodiment, the number of parallel elements is 2. However, the number of parallel elements is not limited to this, and any number of parallel elements of 3 or more can be similarly applied. Further, the single-phase inverter is shown, but the same can be applied to a multi-phase inverter. The present invention can also be applied to converters.

[0025]

Since the present invention is configured as described above, it has the following effects.

(1) It becomes easy to balance the currents of the parallel elements of the inverter main circuit.

(2) Therefore, it becomes easy to select the elements to be connected in parallel.

(3) Since the current balance is improved, the number of parallel elements can be reduced.

(4) From the above, the inverter device can be made compact and economical.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main circuit of an inverter according to an embodiment.

FIG. 2 is a circuit diagram showing a gate circuit of the inverter.

FIG. 3 is a circuit diagram showing a main circuit of a conventional inverter.

[Explanation of symbols]

_{T 1, T 2, U 1} , U 2, X 1, X 2 ... semiconductor element _{G U, G U1, G U2} , G X ... gate circuit W _1, W ₂ ... AC line

Claims (3)

[Claims] 1. An inverter using a plurality of semiconductors in parallel in upper and lower arms of a main circuit, wherein each semiconductor element of the upper and lower arms is connected in series and each semiconductor element of the upper arm is positively connected. Commonly connected to the pole, each semiconductor element of the lower arm is commonly connected to the negative pole, the plurality of alternating current lines whose other ends are connected to each other are connected to the connection point of the semiconductor elements connected in series, An inverter circuit system characterized in that each semiconductor element on the arm side is controlled by a common gate circuit, and each semiconductor element on the upper arm is controlled by each insulated gate circuit. 2. A circuit system of an inverter according to claim 1, wherein a current transformer for detecting an alternating current is provided so that a plurality of alternating current lines whose other ends are connected to each other are common. 3. The circuit system of an inverter according to claim 1, wherein the semiconductor element is a self-turn-off element such as an IGBT transistor.