JPH0628518B2 - Inverter parallel device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Use of the Invention The present invention uses an inverter set using a self-extinguishing type semiconductor device in which conduction and non-conduction can be controlled by transmitting an ignition and extinction signal to a control electrode. , A device in which the inverter sets are connected in parallel.

[Prior art]

FIG. 1 shows an inverter set parallel apparatus using a gate turn-off thyristor (GTO) which is one of self-extinguishing type semiconductor devices. This circuit is an inverter device in which a single-phase inverter using a two-divided DC power supply is connected in parallel in a set via a current balancing interphase reactor.

In the figure, 1 and 2 are single-phase inverter sets,
3, 4 are DC power supplies, 5 is a load, 51 is a resistor, and 52 is a reactor. Reference numerals 11 and 12 are GTOs forming the positive and negative arms of the inverter set 1, 11 'and 12' are feedback diodes connected in parallel to the respective GTOs 11 and 12 with opposite polarities, and 21 and 22 are feedback diodes of the inverter set 2. The GTOs 21 'and 22' constituting the side and negative side arms are feedback diodes connected in parallel to the respective GTOs 21 and 22 with opposite polarities. Reference numeral 7 is an interphase reactor for balancing the output currents of the inverter sets 1 and 2.

In this device, the turn-on time, turn-off time, and forward voltage drop (hereinafter referred to as FVD) of GTO 11 and 21.
A voltage corresponding to the difference between the GTOs 12 and 22 and the turn-on time and turn-off time of the GTOs 12 and 22 and the FVD.
Therefore, when GTO is arbitrarily selected, a voltage in only one direction may be applied between the interphase reactor terminals.

FIG. 2 shows an example in which a unidirectional voltage is applied to the interphase reactor. In the figure, CS is a control signal, INV1 is the operation of the inverter set 1, INV2 is the operation of the inverter set 2, i _u
Indicates load current, and v _ipx indicates inter-phase reactor terminal voltage. The operation of the inverter is based on GTO11 and GTO
21 turn-on is delayed and turn-off is advanced,
With the GTO 12 as a reference, the turn-on of the GTO 22 advances and the turn-off of the GTO 22 delays. Further, comparing the FVDs of the corresponding elements, the FVDs of GTO21 rather than GTO11
, The FVD of GTO 12 is larger than that of GTO 22, the FVD of 11 'is larger than that of feedback diode 21', and the FVD of 22 'is larger than 12'. On the contrary to the case of FIG. 2, when the operation is the opposite of the above operation, a voltage only in the negative direction is applied to the interphase reactor.

FIG. 3 shows the operation waveform of each part in the period A in FIG. In the figure, GTO11 and GTO21 are GTO11 and GTO, respectively.
The operation of TO21, e _u1 and e _u2 are the inverter sets 1 and 2.
, And the output phase voltage v _Ipx is the inter-phase reactor voltage. The t _{O N11,} t _ON21 is Delta] t _ON by the turn-on time of GTO11, GTO21 is the difference, t _OFF11, t
_OFF21 is the turn-off time of GTO11 and GTO21, Δt.
_OFF is the difference. Further, V ₁₁ and V ₂₁ are GTO ₁₁ ,
In FVD of GTO21, ΔV _GTO is the difference,
V ₁₂ ′ and V ₂₂ ′ are FVs of the feedback diodes 12 ′ and 22 ′.
ΔV _{FD in} D is the difference.

As shown in Fig. 2 and Fig. 3, when the voltage of the same polarity is continuously applied between the interphase reactor terminals, the magnetic flux of the interphase reactor is saturated and the current balance cannot be maintained. I can't do it. Alternatively, in order to maintain the current balance in this state, the interphase reactor becomes very large.

[Object of the Invention]

SUMMARY OF THE INVENTION The present invention aims to maintain the output current balance of each inverter set in an inverter set parallel apparatus in which the above-mentioned drawbacks are eliminated and to further reduce the size of the current balancing interphase reactor.

[Outline of Invention]

The present invention that achieves the above object is such that a feedback diode is connected in series with a circuit in which a self-arc-extinguishing type semiconductor device in which reverse polarities are connected in parallel is used for the positive and negative arms, and a series connection circuit. An inverter including a DC power source and an output terminal at a positive / negative arm connection portion of the series connection circuit, wherein the inverter includes at least two units, and the output terminals of each inverter are connected via an interphase reactor, The semiconductor element forming the arm on the same side of
In a parallel device of inverters that controls ignition based on the same ignition signal and supplies electric power from each of the inverters to a load connected to the midpoint of the reactor, self-extinguishing of arms on the same side of each of the inverters. The arc-shaped semiconductor element and the feedback diode have switching characteristics and forward voltage drop characteristics, in which the turn-on time of the semiconductor element of one of the inverters is A1, the turn-off time is B1, the forward voltage drop is C1, and the forward direction of the feedback diode. The voltage drop is D1, the turn-on time of the semiconductor element of the other inverter is A2, and the turn-off time is B.
2, where C2 is the forward voltage drop and D2 is the forward voltage drop of the feedback diode, A1 <A2, B1 <B2
The characteristics of the self-arc-extinguishing semiconductor device and the feedback diode are selected so that the inequalities of C1> C2 and D1 <D2 are simultaneously satisfied.

Alternatively, in the same device, the characteristics of the self-extinguishing semiconductor device and the feedback diode are selected so that the inequalities of A1 <A2, B1> B2, C1> C2 and D1> D2 are simultaneously satisfied.

As a result, the voltage between the interphase reactor terminals does not become a unidirectional voltage, but if the voltage is applied in both the positive and negative directions, the excitation voltage of the interphase reactor will always be positive and negative.
The magnetic flux never saturates. Therefore, the amount of excitation of the interphase reactor is reduced, and the current balance can be maintained with a small reactor.

Therefore, positive between the interphase reactor terminals. It suffices to select the switching characteristics of the GTO used in the inverter set parallel apparatus, the magnitude of FVD, and the magnitude of FVD of the feedback diode so that negative and bidirectional voltages are applied.

Example of Invention

FIG. 4 shows one embodiment of the present invention in the single-phase inverter set parallel apparatus of FIG. This figure shows the GTO1 where the output current balance state of the inverter sets 1 and 2 is the best.
1 shows an example of a combination of characteristics of the GTO 21 and the feedback diodes 12 'and 22'. The symbols in the figure correspond to those in FIG. 3, respectively, and also when the inverter load current i _u is positive. Turn on GTO11,
If the turn-off is faster than the turn-on and turn-off of GTO21, GTO21 is turned on and then GTO21
A positive voltage is applied to the interphase reactor before the turn-on, and a negative voltage is applied until the GTO 21 turns off after the GTO 11 turns off. Also GTO
If the FVD of 11 is larger than the FVD of GTO21, the GTO
A negative voltage corresponding to the difference is applied to the interphase reactor during the conduction between 11 and the GTO 21, and the feedback diode 2
When the FVD of 2'is larger than the FVD of 12 ', a forward voltage corresponding to the difference is applied between the conduction of both diodes.
At this time, the reverse voltage is applied to the reactor immediately after the positive voltage is applied, and immediately after the negative voltage is applied, the positive voltage is applied in the opposite direction, so that the interphase reactor is not saturated and the current balance is improved. Can be kept very good. Positive and negative voltages are applied alternately, and the magnetic flux is sufficiently reset, so that the reactor can be made extremely small.

Next, FIG. 5 shows another embodiment. The symbols in the figure are shown in Fig. 3,
Corresponding to FIG. 4, the load current i _u is positive. Fifth
In the figure, the turn-on of GTO11 is faster than the turn-on of GTO21, and the turn-off of GTO11 is GTO2.
GTO11 and GTO21 due to slower than 1 turn-off
During switching, a positive voltage is applied to the interphase reactor. However, the FVD of the GTO 11 is larger than the FVD of the GTO 21, and the FVD of the feedback diode 12 'is 2
By selecting the element characteristics so as to be larger than the FVD of 2 ', a negative voltage is applied to the reactor when the GTOs 11 and 21 are conducting and the feedback diodes 12' and 22 'are conducting. Therefore, the reactor is not saturated and the current balance can be kept good.

When the combination of GTO11 and GTO21 is determined, the applied voltage to the interphase reactor becomes as shown in FIG. 5 due to the switching characteristics, and unlike FIG.
When the FVD of O11 is smaller than the FVD of GTO 21, a forward voltage is applied to the reactor when the GTOs 11 and 21 are conducting. In such a case, the FV of the feedback diode 12 '
If the element characteristics are selected so that the FVDs of D and 22 'are larger than the FVD difference shown in FIG. 5, a large reverse voltage is applied to the reactor when the feedback diodes 12' and 22 'are conducting, and the reactor is not saturated. Therefore, good current balance can be maintained.

The above is the same even when the characteristics of the GTOs 11 and 21 and the feedback diodes 12 'and 22' in FIGS. 4 and 5 are reversed, and when the load current i _u is negative.
The same applies to the TOs 12 and 22 and the feedback diodes 11 'and 21'.

The present invention is not limited to the single-phase inverter shown in FIG. 1, but can be applied to the three-phase inverter shown in FIG. In the figure, reference numerals 1 and 2 are three-phase inverter sets, 3 is a DC power supply, and 5 is a load, which is generally an AC motor. The DC power supply 3 is common to the inverter sets 1 and 2, and the output terminals of the u-phase, v-phase, and w-phase of each inverter set are connected to the interphase reactors 7, 8, and 9, and the respective output currents are applied to the load. Supply. 11, 12, 13, 14,
15, 16 and 21, 22, 23, 24, 25, 26
Is GTO 11 ', 12', 13 ', 14', 15 ',
16 ', 21', 22 ', 23', 24 ', 25', 2
6'is a respective feedback diode. Two GTOs corresponding to each of the inverter sets 1 and 2 and two corresponding feedback diodes of the paired arms, that is, the GTOs 11 and 21 and the feedback diode 12 'in FIG.
And 22 ', GTO 12 and 22, and feedback diode 1
1'and 21 ', GTO 13 and 23 and feedback diodes 14' and 24 ', GTO 14 and 24 and feedback diodes 13' and 23 ', GTO 15 and 25 and feedback diodes 16' and 26 ', GTO 16 and 26 and feedback diode 15'. And 25 ', as shown in the above single-phase inverter, the switching characteristics of the two GTOs, the FVD and the FV of the two feedback diodes.
If the element characteristics are selected such that positive and negative voltages are alternately applied to the interphase reactor as shown in FIGS. 4 and 5 for D, the same effect as in the case of the single-phase inverter can be obtained.

〔The invention's effect〕

As described above, according to the present invention, in the inverter set parallel apparatus to which the GTO is applied, the inverter set 1
The switching characteristics of the GTO such that positive and negative voltages are applied to the phase-to-phase reactor, FVD, and FVD of the feedback diode to the GTO, with respect to the two GTOs corresponding to 1 and 2 and the feedback diodes corresponding to the paired arms, respectively. By selecting the combination of the feedback diodes, it becomes easy to maintain the current balance state of the inverter, the current balancing interphase reactor can be downsized, and the device can be downsized. Although the present invention has been described in the case of being applied to a GTO inverter, it can be similarly applied to a self-extinguishing element such as a transistor or FET, and can be applied to an inverter using a thyristor.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a single-phase inverter set parallel circuit, FIG. 2 is an operation explanatory diagram when a unidirectional voltage is applied to an interphase reactor, and FIG. 3 is an enlarged operation diagram of period A in FIG. ,
FIG. 4 and FIG. 5 are enlarged operation diagrams when positive and negative bidirectional voltages are applied to the interphase reactor, and FIG. 6 is a diagram showing another embodiment of the present invention. 1, 2 ... Inverter set, 11, 12, 13, 1
4, 15, 16, 21, 22, 23, 24, 25, 26
... GTO, 11 ', 12', 13 ', 14', 1
5 ', 16', 21 ', 22', 23 ', 24', 2
5 ', 26' ... Feedback diode, 7, 8, 9 ... Reactor between phases.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsunori Suzuki 3-1-1 Hitachi-machi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Miki Kajita 3-chome, Hitachi City, Ibaraki Prefecture No. 1 in Hitachi Engineering Co., Ltd. (56) References Japanese Patent Publication 4-52068 (JP, B2)

Claims (2)

[Claims] 1. A circuit in which self-extinguishing semiconductor elements in which feedback diodes are connected in parallel with opposite polarities are used in positive and negative arms for series connection, and a DC power supply connected to both ends of the series connection circuit. An inverter provided with an output terminal at a positive / negative arm connection portion of the series connection circuit, wherein the inverter has at least two units, and the output terminals of the respective inverters are connected via an interphase reactor, and are connected on the same side of the respective inverters. In the parallel device of the inverters, the semiconductor elements forming the arms are controlled to be fired based on the same firing signal to supply electric power from the respective inverters to the load connected to the midpoint of the reactor. The self-extinguishing type semiconductor device and the feedback diode of the arm on the same side of the Let A1 be the turn-on time of the semiconductor element of the burner, B1 be the turn-off time, C1 be the forward voltage drop and D1 be the forward voltage drop of the feedback diode, and A2 be the turn-on time of the semiconductor element of the other inverter. B
2, where C2 is the forward voltage drop and D2 is the forward voltage drop of the feedback diode, A1 <A2, B1 <B2
A parallel device of an inverter, wherein the characteristics of the self-turn-off semiconductor element and the feedback diode are selected so that the inequalities of C1> C2 and D1 <D2 are simultaneously satisfied. 2. A circuit in which self-arc-extinguishing type semiconductor elements in which feedback diodes are connected in parallel with opposite polarities are used in the positive and negative arms and are connected in series, and a DC power source is connected to both ends of the series connection circuit. An inverter provided with an output terminal at a positive / negative arm connection portion of the series connection circuit, wherein the inverter has at least two units, and the output terminals of the respective inverters are connected via an interphase reactor, and are connected on the same side of the respective inverters. In the parallel device of the inverters, the semiconductor elements forming the arms are controlled to be fired based on the same firing signal to supply electric power from the respective inverters to the load connected to the midpoint of the reactor. The self-extinguishing type semiconductor device and the feedback diode of the arm on the same side of the Let A1 be the turn-on time of the semiconductor element of the burner, B1 be the turn-off time, C1 be the forward voltage drop and D1 be the forward voltage drop of the feedback diode, and A2 be the turn-on time of the semiconductor element of the other inverter. B
2, where C2 is the forward voltage drop and D2 is the forward voltage drop of the feedback diode, A1 <A2, B1> B2
A parallel device of an inverter, wherein the characteristics of the self-turn-off semiconductor element and the feedback diode are selected so that the inequalities of C1> C2 and D1> D2 are simultaneously satisfied.