JPS586078A - Inverter - Google Patents

Abstract

PURPOSE:To reduce a loss of an inverter by storing the charged charge of a snubber capacitor in a GTO, a snubber capacitor and an auxiliary capacitor forming a closed loop, thereby eliminating a snubber resistor. CONSTITUTION:When a GTO1 is turned ON, the charge of a snubber condenser C1 is charged through a GTO1, a current limiting reactor L1 and a diode D13 in an auxiliary capacitor C5. When the GTO1 is then turned OFF, a current continuously flows in a closed loop of a GTO4, a flywheel diode D1 and a current limiting reactor L2 by the energy of a load. Accordingly, the terminal voltage of the GTO2 becomes substantially zero, and the charged of the capacitor C5 is thus discharged through the closed loop. In this manner, a snubber resistor can be eliminated, thereby reducing the loss of an inverter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter, and more particularly to an inverter in which a converter for converting direct current to alternating current is composed of switching elements.

Conventionally, switching elements such as gate turn-off thyristors (hereinafter referred to as GTOs) have been used as converters for converting direct current into alternating current in inverters. When configuring an inverter using this GTO, a snubber circuit is provided to absorb the voltage at turn-off/turn-off of the GTO.

FIG. 1 shows a configuration diagram of a single-phase inverter using GTO. In the figure, a single-phase inverter can convert direct current supplied from a direct current power source E into alternating current and supply the alternating current to a load. GTO1 is used as a converter to convert this DC to AC.

2.3.4 are provided between the DC power supply E and the AC output terminals T, T2. Diode D1, resistor R1, and capacitor C are connected between the anode and cathode of GTOI.
1 constitutes a snubber circuit. A capacitor C1 of the snubber circuit (hereinafter referred to as a snubber capacitor) is provided to absorb the voltage when the GTOI is turned off and to reduce the switching power when the GTOI is turned off. Diode D is provided to block discharge current from snubber capacitor C1 when fdGTO1 is turned on. That is, when the snubber capacitor C1 discharges, the current flows through the resistance R of the snubber circuit (hereinafter referred to as snubber resistance). A snubber resistor R1 is provided to consume the discharge energy of the snubber capacitor C1.

Also, the current rise when GTOl turns on 9
A current limiting reactor L is provided to suppress the rate of increase d i /d t and to limit the current when the arm is short-circuited. A diode D2 and a resistor R2 are connected in parallel to the current limiting reactor L1. This diode D2 is provided to prevent overvoltage from being applied to CTOl when the GTOI is turned on and turned off9, and the resistor R12 is generated in the current limiting reactor L from when the GTO1 is turned off until it is turned off again. It is provided to consume energy and to increase suppression of the rise rate di/dt of the current at turn-off of the GTol.

In addition, the snubber resistor R provided in GTO2, 3, and 4
3, R5, R7, snubber capacitor C2+C3, C4,
Diodes D3, D,, D,, D6.

D7. D, , resistors R4, R6, Rs, time-limiting reactor L2. L3. L, respectively have the same functions as those used in GTOI.

Also, a flyhole diode D g r D 1o + D is installed between the anode and cathode of GTOI, 2, 3.4.
I+'+D1□ is connected.

According to the above configuration, in the inverter shown in FIG. 1, by controlling the switching of GTOIs 2 and 3.4, DC is converted to AC, and AC output terminals T, .
It can be supplied to the load connected between T2. The snubber circuit can reduce the switching power when turning off GTOI, 2, 3.4, and ensure good switching operation.

However, when GTOI, 2 and 3.4 turn on, the discharge energy of the snubber capacitor CI + C2T c, +04 reaches the snubber resistor R1, respectively.

Since it is consumed by R8, R,, R7,
The drawback is that the snubber circuit consumes power. Furthermore, as the operating frequency of the GTO switching operation increases, the loss increases.

Furthermore, inductance due to the wiring occurs in the DC power supply E and the power supply line of GTOI, 2.3.4, as shown by the reference numerals in FIG. Therefore, this inductance L
, at both ends of GTOl.

2.3.4 is turned off, a back emf is generated. The energy of this inductance L is added to the DC voltage VD and the snubber capacitors C, , C2, C3,
C, so the snubber capacitors c, , c2 .
c8. C4 is overcharged. In particular, in a large-capacity inverter, each component constituting the inverter becomes large, and the distance between the DC power source E and the GTO becomes long, resulting in a large value of inductance. Therefore, in such a case, as shown in FIG. 2, the peak value of the voltage Vc applied to the snubber capacitor becomes more than twice the DC voltage VD. Then, the overcharged snubber capacitors c,,c2.
c3. The charge on snubber resistor R,,R,3,R,,R,when GTOI,2,3.4,respectively turns off.
, which has the disadvantage that the loss due to the snubber circuit further increases.

Note that 1A is the anode current, and VAK is the voltage between the anode and cathode of the GTO.

In addition, in conventional inverters, in order to increase the capacity of the inverter and increase the operating frequency, the snubber resistor must have a large capacity, which has the disadvantage of increasing the size and cost of the inverter. .

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an inverter that can reduce loss.

In order to achieve the above object, the present invention stores the electric charge accumulated in the snubber capacitor when the switching element is turned off in another capacitor when the switching element is turned on, and the electric charge accumulated in this capacitor is transferred to the snubber capacitor when the switching element is turned on. The device is characterized in that it is configured to discharge through the load at turn-off.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 3 shows a preferred embodiment of the invention. Note that the same reference numerals are given to the same or corresponding members as those shown in FIG.

This embodiment differs from the case of FIG. 1 in that GTOI is used.

2.3.4 Current limiting reactor L1゜L2 connected in series
, L3. L4 is the AC output terminal T1. Is it connected to T2 and is it a snubber capacitor? C,,C,,5zGTOI,3
Snubber capacitors C2 and C4 are connected to the anode side of GTO.
They are connected to the cathode sides of Nos. 2 and 4, respectively. And snubber capacitors c,,c2. c3. c, respectively, are diodes D, , D3. D6. Via D7-CGTOI
, 2°3.4 is connected to the cathode side.

Also, snubber capacitors C1, C2 and diodes D1. D
The connecting portions 3 are connected to the AC output terminal T1 via diodes D13°D, 4 and auxiliary capacitors C6, C, which are used to store the charges of snubber capacitors C, , C2, respectively. Snubber capacitor C3, C, and diode D,
, D7 are connected to diodes D, , , D, respectively.
6 and snubber capacitors C3, C, are connected to the AC output terminal T2 via auxiliary capacitors C, , C, for storing charges.

Diode D, 3. Dl, and auxiliary capacitor C5+C
7 connection part is each diode DI? e It is connected to the negative otherity side of the DC power supply E via D,8.

Diode D, 4. Dl, and auxiliary capacitor C0゜C
The connection portions 6 are each connected to the positive polarity side of the DC power supply E via a diode DIQ + D20.

The reason why each GTO is provided with a current limiting reactor is to strengthen the current limiting effect when an arm short circuit occurs. Also, auxiliary capacitors C,,C,.

C7 and C8 are snubber capacitors CI + c2#c,
.

A larger capacity than C4 is used.

With the above configuration, in this embodiment, as in the case of FIG. 1 described above, direct current can be converted into alternating current and the converted alternating current can be supplied to the load connected to the alternating current output terminal.

This embodiment differs from the case in which the charge charged in the snubber capacitor when the GTO is turned on is consumed by the snubber resistor in FIG. It is designed to be stored in

That is, when GTol is turned on, the discharge current of the snubber capacitor C1 is GTOI, I'l flow! It flows through a loop of the J accelerator L1, the auxiliary capacitor C6, and the diode D13, and the charge of the snubber capacitor c1 is charged to the auxiliary capacitor C6. At this time, since GTO2 is turned off, DC voltage VD is applied to GTO2.

Next, when GTO1 is turned off, a circulating current continues to flow through the closed loop of GTO4, flyhole diode D10% current limiting reactor L2 due to the energy of the load, and the terminal voltage of GTO2 becomes approximately 0. Therefore, the charge stored in the auxiliary capacitor C3 is discharged through the closed loop.

Depending on the GTO switching control method, the flyhole diode D, 1 or GTO3 forms part of the closed loop instead of the GTO4 forming the closed loop.

Also, when the charge of the auxiliary capacitor C6 is discharged, GT
The charge of the O2 snubber capacitor c2 is discharged through the diode D1, the auxiliary capacitor C6, and the load. This charge is then stored in the auxiliary capacitor C6. The charge stored in this auxiliary capacitor c6 is discharged through the load and the diode I)to when the GTOI is next turned on.

Note that when GTol is turned off and GTO2 is turned on, the same operation as described above is repeated. Also, G
When TO3 and TO4 are turned on and turned off, respectively, the same operation as described above occurs.

According to this embodiment, when the GTO is turned on, the charge stored in the snubber capacitor is transferred to the GT
Since it can be stored in an auxiliary capacitor that forms a closed loop with O and the snubber capacitor, there is no need for a conventional snubber resistor. Therefore, the device can be made smaller and losses can be reduced.

Further, the charge stored when the GTO turns on can be supplied as energy to the load when the GTO turns off, reducing losses and making effective use of power.

Further, in this embodiment, the electric charge of the snubber capacitor that is overcharged by the energy of the inductance caused by the wiring can be regenerated into the power source.

That is, if snubber capacitor C1 is overcharged, this charge is transferred to diodes D, 7. D,..., is regenerated to the power source through the loop of the snubber capacitor C1 and the DC power source E, and when the snubber capacitor C2 is overcharged, is regenerated to the power source via the diodes DI4 r DI9.

Note that even if the snubber capacitor C3+04 is overcharged, the charged charge is similarly regenerated to the power source.

As described above, according to this embodiment, even if the inductance value due to the wiring is large, the charge overcharged in the snubber capacitor is regenerated to the power supply, so that the loss can be reduced and the GTO can be protected.

Figure 4 shows the anode current iA flowing from the snubber capacitor and the anode voltage V A when the GTO is turned on.
A waveform diagram of N is shown. In the same figure, the chain line is a waveform diagram of the conventional inverter, and the solid line is a waveform diagram of the present embodiment.

Although the anode current lA according to this embodiment has a large peak value, the anode current iA at the initial turn-on of the GTO
The value of is getting smaller. This is because the rise rate di/dt of the current at the initial turn-on of the GTO is suppressed by the current limiting reactor. On the other hand, in the conventional case, the value of the anode current ■A is small.

This is because the leading value of the anode current i is suppressed by the snubber resistor. However, the anode current iA and anode voltage V A at the initial turn-on of the GTO
The KO value is larger than that of this example.

This indicates that the local concentration of current inside the GTO element is greater than in the case of this embodiment. That is, when the GTO is turned on, a narrow region inside the device first becomes conductive, and the on region becomes wider as time passes. Therefore, the rise rate di of the anode current iA when the GTO is turned on is
If /dt is constant, the maximum value of the current density inside the GTO element decreases with time. One to follow? :The fact that the value of the anode current iA at the initial stage of turn-on of the GTO is small means that the local concentration of current inside the GTO element is small. This means that in this embodiment, even if the value of the anode current iA increases, the anode voltage V
This is also clear from the fact that the value of AK has become smaller.

As described above, according to this embodiment, local concentration of current inside the GTO element can be suppressed, so that the reliability of the inverter can be improved.

In this embodiment, a single-phase inverter has been described, but it goes without saying that this embodiment can be applied to a three-phase inverter.

As explained above, according to the present invention, there is an excellent effect that loss in an inverter can be reduced.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional single-phase inverter, and Figure 2 is:
The operating waveform diagram of GTO shown in Fig. 1 and Fig. 3 are as follows.
FIG. 4, which is a configuration diagram showing an embodiment of the present invention, is an operational waveform diagram of the GTO for comparing the present invention and a conventional example. 1.2, 3.4...GTO, C,, C2, C3°C4
... Snubber capacitor, L1# L2 + L3 +
L4...Current limiting reactor, E...DC power supply, T. T2... AC output terminal, c, , c, , c7. c...
・Auxiliary capacitor, DI~D,,D,3~D20...
Diode, D9. D, o, D7. , I)1□
,,・Fly holder Fig. 1 ＼ Fig. 2

Claims (1)

[Claims] 1. The switching unit has at least two sets of series circuits in which two switching elements and a snubber circuit in which a capacitor and a rectifying element are connected in series are connected in parallel, and each of these series circuits has a DC current. In an inverter that is connected in parallel to a power supply and configured with the connection point between each switching unit as an AC output terminal, an auxiliary capacitor that includes at least a switching element and a capacitor of a snubber circuit in a loop and constitutes a first closed loop, and at least an auxiliary A rectifying element that includes a capacitor and a load connected to the AC output terminal in a loop and forming a second closed loop is provided in each of the switching parts, and when the switching element is turned off, the charge accumulated in the capacitor of the snubber circuit is transferred to the switching element. An inverter characterized in that the charge is accumulated in a first closed loop auxiliary capacitor when turned on, and the charge accumulated in the auxiliary capacitor is discharged via a second closed loop when a switching element is turned off.