JPH0284018A - Snubber circuit provided with power regenerative circuit - Google Patents

Abstract

PURPOSE:To improve the efficiency by recovering the energy stored in a snubber capacitor through a regenerative transformer, a rectifier and the like to a DC power source. CONSTITUTION:Upon application of firing pulses, with same timing, onto the gates of a gate turn-off thyristor GTO2 and a thyristor Thy2, a snubber capacitor Cs2 discharges through a regenerative transformer T. Upon application of firing pulses, with same timing, onto the gates of a GTO1 and a thyristor Thy1, a snubber capacitor Cs1 starts to discharge through the regenerative transformer T. Consequently, AC voltage is induced in the output winding N0 of the regenerative transformer T through resonant current, then the AC voltage is rectified through a rectifier 3 and fed through a reactor L to a DC circuit. By such arrangement, energy stored in the snubber capacitors Cs1, Cs2 is recovered to a DC power source CCD.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a snubber circuit with a power regeneration function used in a semiconductor switching element such as a GTO (gate turn-off thyristor) constituting a power conversion device.

(Prior Art) Conventionally, as this type of snubber circuit, a CR snubber circuit with a diode shown in FIG. 7 is known.

This snubber circuit 21 connects a snubber diode Ds and a snubber capacitor Cs in series.
It is constructed by connecting a snubber resistor Rs in parallel to s. Here, the snubber diode Ds is used by being connected in the forward direction to the gate turn-off thyristor GT○. In addition, in the same figure, the snubber circuit 2 is connected to the GTO in which the freewheel diode Dv is connected in antiparallel.
1 is applied.

Next, FIGS. 8 and 10 show the snubber circuit 21 of FIG.
FIG. 2 is a partial circuit diagram of two units of a normal bridge type single-phase inverter or three-phase inverter connected to each other. First, the operation when the GTO 8 is cut off from the on state while the GTO 2 is in the off state will be described with reference to FIGS. 8 and 9 (operation waveform diagrams).

First, assume that a current is flowing in the path Coc (DC power supply) → GTO, → point N → point n (Figure 8: path ■).Here, when GTO1 is cut off, the current flowing through GTO
aTab begins to decrease, and the current shifts to the path Coc → snubber diode Dsz → snubber capacitor Csx → point N → point n (Figure 8: path ■, Figure 9: t1-t2),
Charging of the snubber capacitor Csx is started by the ffi source voltage Ed of the DC power supply Coc and the back electromotive force of the inductance of the circuit. When the charging voltage 13C8t of the snubber capacitor C81 exceeds Ed (Fig. 9: t3), the freewheel diode DFz becomes conductive (Fig. 9: t4).
), Coc-) Current flows through the path from Drz → point N → point n, and the commutation ends (Figure 8: path ■). In Figure 9, i C8L and L C12 are snubber capacitors Cs. , Cs*, i, DFz is the #i current flowing through the freewheeling diode DFz.

fElcll, ecsz are snubber capacitors C!
11, shows the charging voltage of C8z.

Next, the operation when GTOz is in the off state and G T 01 is fired from the off state will be described with reference to FIGS. 10 and 11 (operation waveform diagrams).

First, CDc-+DF! Assume that four streams are flowing through the path from → point N → point n (Figure 10: route), where GT
When o is ignited (Fig. 11: 11), the current is Cnc→
As the path moves from GTO → point N → point n, the freewheel diode DF2 turns off and Co
Charging of the snubber capacitor Csz (terminal voltage of Cs2 is ecsz) starts on the path c-eGTOx-+ point N-+D Sz → Csx (Fig. 1O: path ■, 1st
Figure 1: t□), and the charge f of the snubber capacitor Csa
The Li flow j CBz becomes zero (2tx in the same figure), and the commutation ends.

(Problem to be Solved by the Invention) However, in the commutation process shown in FIG. 9, the charge in the snubber capacitor Cs2 that was initially charged in Ed is discharged through the snubber resistor R52. ), also fl! The snubber capacitor Csx, which has been charged to a voltage higher than the source voltage Ed, is discharged through the snubber resistor R91 until its voltage becomes equal to Ed (Fig. 8: Path ■
, the 9th d8.

Of these losses. The loss in the snubber resistor Rsx is due to the release of energy stored in the wiring inductance of one circuit. In addition, the loss in the snubber resistor Rsz is increased in order to change the charging voltage ecBz of the snubber capacitor C82 from Ed to zero in response to changes in the conduction mode. This is generated when charges are discharged through the snubber resistor Rsz, and is a completely unnecessary loss.

Also, in the commutation process shown in Figure 11. The charging charge of the snubber capacitor Cat, which was initially charged to Ed, is
At the same time as GTO□ is turned on (Fig. 11: t), it is discharged through the snubber resistor Rsx (Fig. 10: path ■).

Also, since the charge of the snubber capacitor Csx charged to a voltage higher than the 'Wi source voltage Ed is discharged through the snubber resistor Rsz until the charging voltage becomes equal to Ed (10th
Figure: path ■), the snubber resistor R 81 1 R 3z causes a large loss even in this commutation mode.

Here, the loss in the snubber resistor Rsm due to the discharge of the snubber capacitor Csx is. If the capacitance of the snubber capacitor Csi is C, then per firing time of G −r O,
CXEd''/2 (joules), resulting in a large loss proportional to the size of the snubber capacitor Cst, causing a decrease in inverter efficiency.

Furthermore, conventionally, there was a problem in that a large-capacity cooling device had to be provided in order to alleviate the heat generated by the snubber resistor Rslg Rsz.

The present invention was proposed in order to solve the above problems, and prevents power loss in the listener circuit by regenerating the energy generated during commutation of semiconductor switching elements into the DC power supply, thereby generating highly efficient power. The object of the present invention is to provide a snubber circuit with a power regeneration function that realizes a conversion device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides one or two or more in series in each of the upper and lower arms of a power converter,
and a snubber circuit applied to a semiconductor switching element in which freewheeling diodes are connected in antiparallel to each other, the snubber circuit comprising a series circuit of a snubber diode and a snubber capacitor oriented in the same polarity as the semiconductor switching element. One power regeneration transformer connected in parallel and shared by each arm, multiple power regeneration transformers independent for each arm, or multiple power regeneration transformers provided independently for each semiconductor switching element. A unidirectional coil that operates in synchronization with each of the semiconductor switching elements is connected between both terminals of each of the snubber capacitors through each input winding that is a winding and is wound with opposite polarity for each of the upper and lower arms. The output winding provided in the power regeneration transformer is connected to the AC side of the rectifier, and the DC side is connected to the DC side of the power converter. Connected to a power source, using the snubber capacitor as a power source, the energy stored in the capacitor is regenerated into the DC power source of the power converter via the power regeneration transformer and the rectifier by the operation of the unidirectional switching element. It is characterized by

(Function) When one or more semiconductor switching elements provided in the - arm of the power conversion device transition from a conductive state to an off state, current is applied to the snubber capacitor via the snubber diode at the same time as the switching element is turned off. flows and the snubber capacitor is charged. When the semiconductor switching element transitions from an off state to a conductive state, the unidirectional switching element is turned on in synchronization with the on operation of the semiconductor switching element. Simultaneously with this ON operation, the charged tn charge in the snubber capacitor begins to flow through the input winding of the power regeneration transformer, exciting the power regeneration transformer.

The above operation is performed for each upper and lower arm, but since the input windings of each arm are wound with opposite polarities to excite the power regeneration transformer, the output winding of the power regeneration transformer is An alternating current is generated in the line, and this alternating current is converted into direct current by a rectifier and supplied to the direct current circuit of the power converter. That is.

The energy stored in the snubber capacitor is regenerated into the DC power supply of the power converter via the regeneration transformer and rectifier by the operation of the unidirectional switching element.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial circuit diagram in the case where one snubber circuit IA with a power regeneration function according to the present invention is applied to two upper and lower arms of a single-phase or multi-phase inverter constituted by semiconductor switching elements.

In FIG. 1, gate turn-off thyristors GTO, GTO have freewheeling diodes DFx and DDO2 connected in parallel in opposite directions.

In contrast, the input side circuit 1 of the snubber circuit IA with power regeneration function
a, lb are connected, and the output side circuit 2 of the snubber circuit IA
is the DC power supply (capacitor C in Figure 1).

C).

The input side circuit 1a (Ib) has 9 snubber diodes DSL (
Dst) and a snubber capacitor C11x (c92), a one-way switching element (thyristor Thyz (Thya) in Fig. 1), and the input winding (minus winding) of the regenerative transformer T Ntz (Ntz ) and a series circuit. Here, the series circuit of snubber diode Dst and snubber capacitor Css is as follows.

The snubber diode Dsx is connected between the anode and cathode of the GTO in the same direction as the GTO, and the series circuit of the thyristor rhyt and the human winding Nil is connected in parallel to the snubber capacitor Csx ( The same applies to the input side circuit 1b).

On the other hand, the output side circuit 2 is composed of a rectifier (a diode bridge circuit in FIG. 1) 3, a reactor L, and an output winding (secondary winding) Na of a regenerative transformer T. Both terminals of the output winding No are connected, and the output side is connected to the DC power supply Coc via an inductance L. Here, the leakage inductance of the regenerative transformer T and the wiring inductance are the output current of the regenerative transformer T (
If the smoothing of the regenerative current (regenerative current) can be sufficiently compensated for, the inductance L may not be provided. Note that the input winding N ix
and N iJ have opposite polarities.

Next, the operation of the above embodiment will be explained along the operation waveform diagram of FIG. 2. In addition, in Figure 2, the load current is commutated to the freewheel diode DF2 due to the disconnection operation from the conduction state m of GTO
It shows the operation until commutation from DFz to GTOl due to the ignition of x (see period ■ in the figure).

First, when GTO is in a conductive state and GTOt is in a reverse blocking state, when an extinguishing pulse is applied to the gate of GTO (time tl in FIG. 2), the anode current ia of GTO1 becomes 0. begins to decrease, and at the same time charging current i C9L begins to flow through the snubber capacitor Csx, the terminal voltage e C3z (e [lTO+) of Csz gradually increases, and at the same time, the anode-cathode voltage GGTO2 of G TOz gradually decreases. .

And 7. When the jd pressure easl exceeds the power supply voltage Ed, the freewheel diode D F 2 is turned on (time 2 in the figure), and the voltage eGTOx drops to the power supply voltage Ed. During this time, charging 111f of snubber capacitor C92
Since the fi load cannot be discharged because the snubber diode DS2 is reversely connected, the terminal voltage ecsz of C82 does not change.

Next, when an ignition pulse is applied to each gate of GTO□ and thyristor Thyz at the same timing (time ta in Figure 2), the charge in the snubber capacitor Ccsz becomes a current L C82 in the regenerative transformer T and is discharged. be done. Conventionally, power was consumed by passing this discharge current through a snubber resistor, but in the snubber circuit according to this embodiment, this power consumption is eliminated.

Here, it is preferable that the capacitance of the snubber capacitor Csz is set so as to cause resonance with the inductance of the regenerative transformer T. When the voltage 0C5z becomes zero due to the above discharge, the current based on the inductance of the first regeneration transformer T flows along the path DFz→Dsz(GTOz)→Tt+yZ, so the current iDFz flowing through the freewheeling diode DFz is A part of the above current is superimposed on the current that was flowing (Figure 2: time t4)
(Above, Figure 2: Period ■).

Next, when firing pulses are applied to each gate of the GTO and the thyristor Thyx at the same timing (FIG. 2: time tg), the electric current 1iaro□ flowing through the GTOt begins to increase. At the same time, the snubber capacitor C81 starts discharging, the current i C8t flows through the regenerative transformer T as a resonant current, and the current i DFz flowing through the freewheel diode DFi starts to decrease. Then, when the voltage eC5i reaches the power supply voltage Ed, charging of the snubber capacitor C82 is started, and the current i cs
s begins to flow (time L6 in FIG. 2).

After this, when the voltage e csl becomes zero, the current based on the inductance of the first regeneration transformer T changes from DF1 to GTou.
Since the current flows along the path of (Dst)+Thyt, the current i GTOz flowing through the GTO8 is a part of the above-mentioned current superimposed on the current flowing from a single source (period ■ in FIG. 2). In addition, in Fig. 2, the thyristor L' hyt
, T hyz , each current IThy of reactor L
, +i Thy2, iL and the electromotive force of the regenerative transformer T are also shown.

As described above, in this embodiment, the regenerative transformer T
An alternating current voltage is generated in the output winding No. This alternating voltage is rectified by the rectifier 3, and a direct current flows through the reactor L into the direct current circuit. As a result, the snubber capacitor Ccs
The energy stored in CC8z and CC8z will be regenerated to the DC power supply Coc.

In addition, in this embodiment, each input person l1AN 5-, N i for the upper arm and the lower arm of the regenerative transformer T
Since z is alternately excited with opposite polarity, the regenerative transformer '
The magnetic saturation phenomenon of r can be reduced.

Next, FIGS. 3 to 6 are circuit diagrams showing other embodiments, and in each of these circuits, IB, Ic, LD, and IE each indicate a snubber circuit with a power regeneration function.

First, in FIG. 3, two regenerative transformers "I",
, T, and each regenerative transformer T1. The output windings of T2 are connected in parallel, and each terminal is connected to the AC terminal of the II current flow device 3, respectively.

In addition, FIG. 4 shows that in the embodiment shown in FIG.
O-1~GTO! , n are connected in series to form the upper arm,
G T 021 to G T Oz n are connected in series to configure the lower arm, respectively, and each GToi, to GTo1n,
The output windings thereof are connected to the rectifier 3 via one regenerative transformer T provided with a plurality of human-powered windings corresponding to GTOhx to GTO-n.

Furthermore, in the embodiment of FIG. 5, in the upper and lower arms having the same configuration as that of FIG. 4, one regeneration transformer T1 is provided for each of the upper arm and the lower arm. The output windings of these regenerative transformers T, , T, are connected in parallel as in the embodiment shown in FIG. In the upper and lower arms similar to Figure 5,
Regenerative transformer Tzz~Tln for each GTO element
, T2x to T2n are the output windings of the respective regenerative transformers connected in parallel.

Although not described in detail, in each of these examples, the first
Similar to the embodiment shown, the energy stored in the snubber capacitor can be recovered to the direct current UIXCDC. Furthermore, although a snubber resistor is not used in each of the above embodiments, the effects of the present invention can be achieved even if a snubber resistor with a small resistance value is connected in parallel to each snubber diode.

(Effects of the Invention) As described above, according to the present invention, a transformer for regenerating the energy stored in a snubber capacitor that is consumed when a semiconductor switching element such as a GTO is on.

I decided to regenerate the power into the DC power supply via a rectifier, etc.
High efficiency of the power conversion device can be achieved. Furthermore, since the snubber resistor can be removed from the conventional snubber circuit or a resistor with a small resistance value can be used in place of the conventional snubber resistor, it is possible to downsize the snubber circuit and the power converter, etc. By reducing the heat generated by the snubber resistor, it is possible to downsize the cooling device.

[Brief explanation of the drawing]

Fig. 1 is a partial circuit diagram of an inverter for explaining one embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the circuit shown in Fig. 1, and Figs. 3 to 6 explain other embodiments. FIG. 7 is a diagram showing a conventional snubber circuit. FIGS. 8 and 10 are partial circuit diagrams of an inverter for explaining the operation of the conventional snubber circuit. 11th
This figure is an explanatory diagram of the operation of the circuit shown in FIGS. 8 and 10. +a, lb...Input side circuit, 2...Output side circuit, 3
... Rectifier, G T Ox, G T Oz ... Gate turn-off thyristor D Ps HD Fz ... Freewheel diode, D 3t, D sz ... Snubber diode, C
Iit, Csz... snubber capacitor, Thyx
l Thyz...Thyristor. T...Regenerative transformer, L...Reactor Cnc...DC power supply (capacitor)

Claims (1)

[Scope of Claims] A snubber circuit that is applied to a semiconductor switching element that is provided in each of the upper and lower arms of a power converter, or two or more in series, and in which freewheeling diodes are connected in anti-parallel to each other, the snubber circuit comprising: A series circuit of a snubber diode and a snubber capacitor oriented in the same polarity as the semiconductor switching element is connected in parallel to each other, and one power regeneration transformer is shared by each arm, and multiple power regeneration units are independent for each arm. or a plurality of power regeneration transformer primary windings provided independently for each of the semiconductor switching elements, and for each upper and lower arm, each input winding is wound with opposite polarity. hand,
A unidirectional switching element that operates in synchronization with each of the semiconductor switching elements and is oriented in the same polarity as each of the snubber diodes is connected between both terminals of each of the snubber capacitors, and is provided in the power regeneration transformer. The output winding is connected to the alternating current side of the rectifier, and the direct current side thereof is connected to the direct current power source of the power converter, and the snubber capacitor is used as a power source to transfer the energy stored in the capacitor to the unidirectional switching element. A snubber circuit with a power regeneration function, wherein the power is regenerated into the DC power source of the power conversion device through the power regeneration transformer and the rectifier upon operation.