JP4161253B2 - Multiphase AC voltage regulator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable AC voltage source that outputs a multiphase AC voltage by turning on and off a semiconductor switching element, and more particularly to a multiphase AC voltage adjustment device that adjusts the magnitude of an output voltage.
[0002]
[Prior art]
FIG. 7 shows a three-phase V-connection chopper composed of two AC choppers as a conventional variable AC voltage source that outputs a multiphase AC voltage.
In FIG. 7, R, S, and T are AC input terminals connected to a three-phase AC power source, U, V, and W are AC output terminals connected to a load, CH ₁ and CH ₂ are choppers, and chopper CH ₁ Is composed of bidirectional AC switches S ₁ and S ₃ , and chopper CH ₂ is composed of bidirectional AC switches S ₂ and S ₄ .
[0003]
FIG. 8 shows the configuration of the AC switches S _{1 to} S ₄ . FIG. 8A shows two switches S _A and S _B such as IGBTs connected in series in the reverse direction, S _a and S _b are switching elements, and D _af and D _bf are _free- wheeling diodes. According to this configuration, by using the free-wheeling diodes D _af and D _bf built in the switches S _A and S _B , it is possible to pass current bidirectionally without an external diode.
[0004]
Further, FIG. 8 (b), in which a series circuit of a switching element S _a and the diode D _a, are connected in parallel a series circuit of a switching element S _b and a diode D _b in the reverse direction, the switching element S _a , by using those having a reverse breakdown voltage performance as S _b, diode D _{a shown,} it is possible to omit the D _b.
Further, FIG. 8 (c), the diode _D a, is obtained by connecting _{D b} of the series circuit and a diode _D c, the series circuit and the switching element _{S a} of _{D d} in parallel, a plurality of diodes and one is realized AC switch bidirectional by the combination of the switching element S _a.
[0005]
In the three-phase V-connection chopper shown in FIG. 7, in order to adjust the magnitude of the AC output voltage, the AC switches S ₁ and S ₂ are switched at the same timing, and the AC switches S ₃ and S ₄ are the same timing. Switch with. That is, when the AC switches S ₁ and S ₂ are simultaneously turned on, the AC switches S ₃ and S ₄ are simultaneously turned off. When the AC switches S ₁ and S ₂ are simultaneously turned off, the AC switches S ₃ and S ₄ are simultaneously turned on. To switch.
These AC switches S _1, S ₂ of the pair of on-time ratio of off, in other words AC switch S _3, S ₄ pairs off, by varying the time ratio of the on, to adjust the magnitude of the output voltage be able to. This voltage adjustment operation is the same as that of a normal DC chopper.
[0006]
The three-phase V-connection chopper described above is used, for example, as an AC voltage regulator that is a starting device for an induction motor.
The AC voltage regulator reduces the output voltage at the time of starting to suppress the inrush current of the induction motor and contributes to stabilization of the system and reduction of the equipment capacity. After the induction motor is started, the AC switch S ₁ , the switching losses to zero by turning on constantly S _2, thereby achieving a high efficiency of the device.
[0007]
Note that a single-phase AC chopper that is the basis of the three-phase V-connection chopper shown in FIG. 7 is described in the following non-patent document.
[0008]
[Non-Patent Document 1]
"Semiconductor power conversion circuit" edited by the Institute of Electrical Engineers of Japan, 6th edition, 11.3 AC switch control methods and functions, 11.3.2 AC chopper control, The Institute of Electrical Engineers of Japan, issued April 1, 1992 , P.267-p.268
[0009]
[Problems to be solved by the invention]
In the three-phase V-connection chopper of FIG. 7, for example, as shown in FIGS. 8A and 8B, the AC switches S _{1 to} S ₄ have two switching elements S _a and S _b , respectively. As a whole, eight switching elements are required, the drive circuit is complicated, and the switching loss is increased.
Further, when the configuration of FIG. 8C is used as the AC switches S _{1 to} S ₄ , the number of switching elements can be reduced, but when the AC switches S ₁ and S ₂ are always on in FIG. There is a problem that the conduction loss increases due to the large number of passing diodes.
[0010]
As described above, an increase in the number of switching elements causes an increase in cost and a complexity of the drive circuit, and an increase in loss causes a decrease in efficiency and an obstruction to downsizing of the entire apparatus due to an increase in size of the cooling device. It becomes.
Therefore, the present invention aims to provide a polyphase AC voltage regulator that reduces the number of AC switches and reduces losses, thereby reducing the cost and reducing the size of the device.
[0011]
In order to solve the above problems, the invention according to claim 1 is a multiphase AC voltage regulator that adjusts and outputs the magnitude of a multiphase AC input voltage by turning on and off a semiconductor switching element.
Among the AC input terminals and AC output terminals for the number of phases, at least one phase AC input terminal and AC output terminal are directly connected, and bidirectionality is provided between the AC input terminal and AC output terminal of each other phase. Each of the AC switches is connected, and includes a short-circuit means for short-circuiting each phase at once by a single switch means,
The collective short-circuit means is connected to an AC input terminal of each phase at an AC input side, and is connected to a DC output side of the diode bridge circuit, and is turned on when the AC switch is turned off to connect the DC output side. A semiconductor switching element as the switch means for short-circuiting,
A voltage clamping means as a DC snubber circuit is connected in parallel to the semiconductor switching element as the switching means, and a surge voltage generated when the semiconductor switching element is turned off is rectified by the diode bridge circuit and absorbed by the voltage clamping means. Is.
[0012]
The invention according to claim 2 is the multiphase AC voltage regulator according to claim 1,
A semiconductor switching element in a bidirectional AC switch connected between an AC input terminal of one phase and an AC output terminal using an output pulse of a pulse transformer to which a common pulse is input, and another phase The semiconductor switching element in the bidirectional AC switch connected between the AC input terminal and the AC output terminal is driven .
[0013]
The invention according to claim 3 is a multiphase AC voltage regulator that adjusts and outputs the magnitude of the multiphase AC input voltage by turning on and off the semiconductor switching element.
Collective switching means connected between the multi-phase AC input terminal and the AC output terminal, and collectively turning on and off between the AC input terminal and the AC output terminal of each phase;
And a short circuit means for short-circuiting each phase at once by a single switch means,
The collective switching means includes a semiconductor switching element connected between an AC input terminal and an AC output terminal of each phase, and a free-wheeling diode connected in reverse parallel to each of these semiconductor switching elements,
The collective short-circuit means is connected to an AC input side of each phase of the AC output terminal and connected to the DC output side of the diode bridge circuit, and is turned on when the semiconductor switching element of the collective switching means is turned off. A semiconductor switching element as the switch means for short-circuiting the DC output side,
A voltage clamping means as a DC snubber circuit is connected in parallel to the semiconductor switching element as the switching means, and a surge voltage generated when the semiconductor switching element is turned off is rectified by the diode bridge circuit and absorbed by the voltage clamping means. Is.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing a first embodiment of the present invention.
In FIG. 1, R, S, and T are AC input terminals connected to a three-phase AC power source, U, V, and W are AC output terminals connected to a load. An AC switch S ₁ is connected between the AC output terminal U, an AC switch S ₂ is connected between the AC input terminal T and the AC output terminal W, and the AC input terminal S and the AC output terminal. V is directly connected. The AC switch _S 1, _{S 2,} for example FIG. 8 (a), the configured as shown in (b).
[0020]
Further, a three-phase collective short-circuit means 10 is connected between the AC output terminals U, V, and W. The three-phase collective short-circuit means 10 operates in the same manner as the AC switches S ₃ and S ₄ in FIG. 7 by the operation of a single switch means, as will be described later, and outputs AC when the AC switches S ₁ and S ₂ are off. The terminals U, V and W are short-circuited, and the AC output terminals U, V and W are opened when the AC switches S ₁ and S ₂ are on.
The voltage adjustment operation in this embodiment is substantially equivalent to the three-phase V-connection chopper of FIG. 7, and the pair of AC switches S ₁ and S ₂ is turned on (the AC output terminals U and V are connected by the three-phase collective short-circuit means 10). , W is opened) and off (also the AC output terminals U, V, W are short-circuited), and the magnitude of the output voltage is adjusted.
[0021]
2 that shows the configuration of the three-phase short-circuit means 10.
In FIG. 2, the AC output terminals U, V, and W are connected to the AC input side of a three-phase diode bridge circuit composed of diodes 12 to 17, and the DC output side has an IGBT as a single switch means. A semiconductor switching element 11 such as is connected.
By turning on the switching element 11 at the same timing as the AC switches S ₃ and S ₄ in FIG. 7, the output voltage of the diode bridge circuit becomes zero, and the diodes 12 to 17 are turned on and off according to the polarity of the load current. By doing this, the AC output terminals U, V, W can be short-circuited, and the magnitude of the AC output voltage can be adjusted by the same operation as in FIG.
[0022]
According to this embodiment, even if the AC switches S ₁ and S ₂ are configured as shown in FIG. 8 (a) or (b), the total number of switching elements including the three-phase collective shorting means 10 is five. The number of switching elements in the case of FIG. 7 (eight) can be greatly reduced. The reduction in the number of switching elements not only reduces the cost of the switching elements themselves, but also contributes to the reduction and simplification of the drive circuit. Therefore, the cost reduction effect is also great in this respect. Further, the conduction loss due to the diode is small as compared with the case where the configuration of FIG. 8C is used as the AC switches S ₁ and S ₂ .
Further, when the AC switches S ₁ and S ₂ are configured as shown in FIG. 8C, the conduction loss increases as compared with FIG. 8A or 8B, but the number of switching elements in the entire apparatus is 3 It becomes a piece.
[0023]
Next, FIG. 3 shows a second embodiment of the present invention.
In this type of AC voltage regulator, when an inductive load is connected as a load, when the switching element is turned off, a surge voltage is generated at both ends of the switching element due to the energy accumulated in the inductive load, and the switching element is destroyed. There is a fear.
For this reason, an AC snubber circuit is generally connected to a switching element to absorb a surge voltage.
[0024]
In the second embodiment shown in FIG. 3, voltage clamp means 20, which is a kind of DC snubber circuit, is integrated with three-phase collective short-circuit means 10 and connected to both ends of switching element 11 as surge voltage absorbing means. Here, the voltage clamp means 20 is, for example, a Zener diode, and its cathode is connected to the collector of the switching element 11 and its anode is connected to the emitter of the switching element 11.
With such a configuration, when the switching element 11 is turned off, the surge voltage caused by the stored energy of the inductive load is rectified from the AC output terminals U, V, and W through the diode bridge circuit and absorbed by the voltage clamp means 20. I did it.
[0025]
Next, FIG. 4 is a circuit diagram showing a third embodiment of the present invention. This embodiment relates to a switching element drive circuit in the first and second embodiments.
In FIG. 4, 31 is a PWM pulse generating means for outputting a PWM pulse by comparing a voltage command with a carrier, 32 to 34 are AC switches S ₁ and S ₂ of FIG. ₁ and FIGS. 2 and 3 based on the PWM pulse. Gate pulse generators 35 to 37 for outputting gate pulses for driving the switching elements 11 are pulse transformers in which primary windings 351, 361 and 371 are connected to the gate pulse generators 32 to 34, respectively.
[0026]
The secondary winding 352 of the pulse transformer 35 is connected between the gate and the emitter of one of the switching elements S _1a of the AC switch S ₁ in FIG. 1 _(e.g. corresponding to S _a in FIG. 8 (a)), the pulse transformer tertiary winding 353 of 35 is connected between the gate and the emitter of one of the switching elements _{S 2a} of the AC switch _{S 2} in FIG. 1 (also corresponding to _{S a} in FIG. 8 (a)).
The secondary winding 362 of the pulse transformer 36 is connected between the gate and emitter of the other switching element S _1b (for example, equivalent to S _b in FIG. 8A) of the AC switch S ₁ of FIG. The tertiary winding 363 of the pulse transformer 36 is connected between the gate and emitter of the other switching element S _2b (also corresponding to S _b in FIG. 8A) of the AC switch S ₂ of FIG.
Further, the secondary winding 372 of the pulse transformer 37 is connected between the gate and emitter of the switching element 11 of the three-phase collective short-circuit means 10 in FIGS.
[0027]
The AC switches S ₁ and S ₂ perform switching at the same timing. Specifically, the switching elements S _a (S _1a and S _2a ) in the AC switches S ₁ and S ₂ , S _b (S _1b , S _2b ) are switched at the same timing.
Therefore, as shown in FIG. 4, the two switching elements S _1a and S _2a are driven through the pulse transformer 35 by one common gate pulse output from the gate pulse generating means 32, and the gate pulse generating means is similarly processed. The two switching elements S _1b and S _2b can be driven via the pulse transformer 36 by one common gate pulse output from the 33.
Thereby, the drive circuit (drive power supply) of the switching element can be simplified.
[0028]
In each of the above embodiments, the three-phase collective short-circuit means 10 is connected to the load side (AC output terminals U, V, W side) of the AC voltage regulator as shown in FIG. A reactor may be inserted in series in each phase of the AC input terminals R, S, and T), and the three-phase collective short-circuit means 10 may be connected between these reactors and the AC switches S ₁ and S ₂ . In this case, the operation of the entire apparatus is a multiphase AC boost chopper.
[0029]
Next, FIG. 5 is a circuit diagram showing a fourth embodiment of the present invention.
In this embodiment, instead of the AC switches S ₁ and S ₂ in the first embodiment, the three-phase collective switching means 40 is connected between the AC input terminals R, S, T and the AC output terminals U, V, W. It is a thing.
[0030]
The three-phase collective switching means 40 includes AC switches 41, 42, and 43 as shown in FIG. 6, and the AC switch 41 is a semiconductor switching device such as an IGBT connected between the AC input terminal R and the AC output terminal U. The AC switch 42 is configured by an antiparallel circuit of a semiconductor switching element 42S and a freewheeling diode 42D connected between the terminals S and V, and the AC switch 43 is configured by an antiparallel circuit of the element 41S and the freewheeling diode 41D. Similarly, it is constituted by an antiparallel circuit of a semiconductor switching element 43S and a free-wheeling diode 43D connected between the terminals T and W.
The configuration of the three-phase batch short-circuit means 10 is the same as that shown in FIG .
[0031]
Three-phase switching device 40 of the switching elements 41S, 42S, 43S, the switching AC switch S _1, S ₂ in FIG. 7 is turned on, off timing of the same timing on, collectively a three-phase by turning off In addition, the switching element 11 of the three-phase collective short-circuit means 10 is turned on at the same timing as the timing when the AC switches S ₃ and S ₄ in FIG. Short-circuit between V and W.
[0032]
In the AC switches 41, 42, and 43 shown in FIG. 6, the switching elements 41S, 42S, and 43S can control only a unidirectional current. However, when the switching elements 41S, 42S, and 43S are turned on, the freewheeling diode 41D, Currents in both directions can be passed by 42D and 43D, and when the switching elements 41S, 42S, and 43S are turned off, diodes are all connected in the same direction with respect to the power supply. Therefore, the bidirectional AC switch S of FIG. _1, S ₂ and it is possible to prevent current in the same manner. That is, by switching the three phases at once, even a unidirectional switch as shown in the figure can block current similarly to the AC switches S ₁ and S ₂ .
In FIG. 6, the emitters of the switching elements 41S, 42S, and 43S are on the load side and the collector is on the power supply side. However, the emitter may be on the power supply side and the collector may be on the load side.
[0033]
According to the present embodiment, the total number of semiconductor switching elements included in the three-phase collective switching means 40 and the three-phase collective short-circuit means 10 is four, and the number of switching elements in the case of FIG. be able to. In addition, since only one switching element and one diode exist in the path from the power source to the load, and the diode generally has less conduction loss than the switching element, this embodiment also reduces conduction loss compared to the prior art. It is possible.
The reduction in the number of semiconductor switching elements in this way greatly contributes not only to the cost of the elements themselves but also to the cost reduction due to the reduction of drive circuits.
[0034]
In this embodiment as well , the voltage clamping means 20 can absorb the surge voltage generated when the switching element 11 is turned off by connecting the voltage clamping means 20 shown in FIG. it can.
[0035]
【The invention's effect】
As described above, according to the present invention, the number of AC switches, that is, switching elements can be reduced and loss can be reduced, and the cooling capacity of the cooling device can be reduced.
In addition, since the configuration of the short-circuit means and the drive circuit is simple, it is possible to provide a highly efficient multiphase AC voltage regulator that is small in size and low in cost.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention.
2 is a block diagram of the three-phase collective short-circuit means in FIG. 1. FIG.
FIG. 3 is a circuit configuration diagram showing a second embodiment of the present invention.
FIG. 4 is a circuit configuration diagram showing a third embodiment of the present invention.
FIG. 5 is a circuit configuration diagram showing a fourth embodiment of the present invention.
6 is a circuit diagram showing a specific configuration of FIG. 5. FIG.
FIG. 7 is a circuit configuration diagram of a three-phase V-connection chopper showing the prior art.
FIG. 8 is a configuration diagram of the bidirectional AC switch in FIG. 7 and the present invention.
[Explanation of symbols]
R, S, T: AC input terminals U, V, W: AC output terminals 10: Three-phase collective short-circuit means 11: Semiconductor switching elements 12-17: Diode 20: Voltage clamp means 31: PWM pulse generator means 32-34: Gate pulse generating means 35-37: pulse transformer 40: three-phase collective switching means 41-43: semiconductor switches 41D, 42D, 43D: freewheeling diodes 41S, 42S, 43S: semiconductor switching elements

Claims (3)

In the multi-phase AC voltage regulator that adjusts and outputs the magnitude of the multi-phase AC input voltage by turning on and off the semiconductor switching element,
Among the AC input terminals and AC output terminals for the number of phases, at least one phase AC input terminal and AC output terminal are directly connected, and bidirectionality is provided between the AC input terminal and AC output terminal of each other phase. Each of the AC switches is connected, and includes a short-circuit means for short-circuiting each phase at once by a single switch means,
The collective short-circuit means is connected to an AC input terminal of each phase at an AC input side, and is connected to a DC output side of the diode bridge circuit, and is turned on when the AC switch is turned off to connect the DC output side. A semiconductor switching element as the switch means for short-circuiting,
A voltage clamping means as a DC snubber circuit is connected in parallel to the semiconductor switching element as the switching means, and a surge voltage generated when the semiconductor switching element is turned off is rectified by the diode bridge circuit and absorbed by the voltage clamping means. A multi-phase AC voltage regulator characterized by that. In the multiphase alternating voltage regulator according to claim 1,
A semiconductor switching element in a bidirectional AC switch connected between an AC input terminal of one phase and an AC output terminal using an output pulse of a pulse transformer to which a common pulse is input, and another phase A multi-phase AC voltage regulator characterized by driving a semiconductor switching element in a bidirectional AC switch connected between an AC input terminal and an AC output terminal. In the multi-phase AC voltage regulator that adjusts and outputs the magnitude of the multi-phase AC input voltage by turning on and off the semiconductor switching element,
Collective switching means connected between the multi-phase AC input terminal and the AC output terminal, and collectively turning on and off between the AC input terminal and the AC output terminal of each phase;
And a short circuit means for short-circuiting each phase at once by a single switch means,
The collective switching means includes a semiconductor switching element connected between an AC input terminal and an AC output terminal of each phase, and a free-wheeling diode connected in reverse parallel to each of these semiconductor switching elements,
The collective short-circuit means is connected to an AC input side of each phase of the AC output terminal and connected to the DC output side of the diode bridge circuit, and is turned on when the semiconductor switching element of the collective switching means is turned off. A semiconductor switching element as the switch means for short-circuiting the DC output side,
A voltage clamping means as a DC snubber circuit is connected in parallel to the semiconductor switching element as the switching means, and a surge voltage generated when the semiconductor switching element is turned off is rectified by the diode bridge circuit and absorbed by the voltage clamping means. A multi-phase AC voltage regulator characterized by that.

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