JPH08126336A - Low-loss snubber circuit for power converter - Google Patents

Abstract

PURPOSE: To improve conversion efficiency of a power converter without increasing the number or the capacity of regenerating means by utilizing the energy stored in a voltage snubber circuit using no regenerating means as the snubber energy of a pair of arms through an energy transferring means consisting of a reactor and a diode. CONSTITUTION: The energy stored in the snubber capacitor CS2 of an upper arm GTO2 is utilized for the recovery of the free wheel diodes DF3 and DF4 of lower arms and for charging a lower-arm snubber circuit through an energy transferring means ET2 composed of a reactor LT2 and diode DT2 when upper arms GTO1 and GTO2 are turned on. The energy stored in the snubber capacitor CS3 of a lower arm GTO3 is utilized for the recovery of the free wheel diodes DF1 and DF2 of upper arms and for charging an upper-arm snubber circuit through an energy transferring means ET1 composed of a reactor LT1 and diode DT1 when lower arms GTO3 and GTO4 are turned on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-loss snubber circuit for a power converter which is constructed by using a plurality of self-turn-off devices.

[0002]

2. Description of the Related Art An apparatus for constructing a power converter using a plurality of self-extinguishing elements and converting power from alternating current to direct current or from direct current to alternating current is used in many fields. In particular,
Voltage-type inverters that use GTO thyristors are being put to practical use in the fields of electric railways, rolling mills, and electric power, and are being made even larger in capacity and higher in frequency. Resistance loss of a voltage snubber circuit (a snubber circuit configured by a capacitor or the like and connected in parallel to the GTO) and a current snubber circuit (a snubber circuit configured by a reactor or the like and connected in series with the GTO) provided for Conventionally, the energy stored in these circuits has been consumed by resistance, and the reduction thereof has become a very important problem.

Therefore, various so-called low-loss snubber circuits (hereinafter referred to as low-loss snubber circuits) in which the resistance loss of these voltage / current snubber circuits is reduced are considered variously.

For example, FIG. 3 shows a conventional low-loss snubber circuit provided with a means for regenerating the stored energy of the voltage / current snubber circuit to a DC power source. One example of application to a three-phase voltage type inverter is shown in FIG. It is shown in a circuit diagram.

In FIG. 3, GTO1 and GTO2 are GTO thyristors as an example of self-extinguishing elements. P and N are positive and negative terminals of the DC power supply, CF is a power supply filter capacitor, and UP and UN are U-phase positive and negative wirings, and V
P, VN and WP, WN respectively indicate positive and negative wirings of V phase and W phase. In the U phase showing the circuit for one phase,
LA1 and LA2 are anode reactors (constituting a current snubber circuit) connected in series to GTO1 and GTO2, respectively, and CS1 and DS1 and CS2 and DS2 are GT, respectively.
Snubber capacitors and diodes connected in parallel to O1 and GTO2 (configure voltage snubber circuit), DF1 and DF2 are freewheel diodes connected in parallel to GTO1 and GTO2, respectively, and DR1 and CR1, DR2 and CR2 are voltage and current snubber circuits. Stored energy of GTO1, GT
These are a diode and a capacitor for forming a circuit for temporarily storing electricity according to on / off control of O2. Rg
Reference numerals 1 and Rg2 are means for regenerating the energy of the storage capacitors CR1 and CR2 to the DC power supply, and here, the self-extinguishing element GTOg1, the reactor Lg1 and the diode, respectively.
This is a chopper circuit composed of Dg1, a self-extinguishing element GTOg2, a reactor Lg2, and a diode Dg2.

Here, the regenerative operation of the energy stored in the voltage / current snubber circuit will be briefly described by taking the upper arm as an example.
The stored energy of the upper arm snubber capacitor CS1 is GT
When O1 turns on, CS1-CR1-LA1-GT
The energy stored in the closed circuit of O1-CS1 and in the upper arm anode reactor LA1 is stored in the storage capacitor CR1 in the closed circuit of LA1-DS1-DR1-CR1-LA1 when GTO1 is turned off. The energy stored in the storage capacitor CR1 is used for the chopper operation by the on / off control of the self-extinguishing element GTOg1 of the regenerative means Rg1.
That is, when GTOg1 is turned on, energy is stored in the reactor Lg1, and when GTOg1 is turned off, the energy of the reactor Lg1 is recovered to the power supply side filter capacitor CF via the diode Dg1. The regenerative operation of the lower arm can be considered in the same way.

By the way, considering that such a low-loss snubber circuit is applied to a circuit in which each upper and lower arm of a voltage type inverter has two self-extinguishing elements connected in series, the circuit shown in FIG. 4 is obtained. . That is, in comparison with the conventional circuit of FIG. 3, the number of GTO thyristors, which are self-extinguishing elements, is increased by one in each of the upper and lower arms, and the upper arms are GTO1 and GTO2.
, And the lower arm is composed of GTO3 and GTO4 connected in series, and GTO1 is the GTO1 of the conventional embodiment shown in FIG.
Further, the GTO 4 is made to correspond to the GTO 2 of the conventional embodiment shown in FIG. Therefore, the stored energy of the anode reactor LA1 and the snubber capacitor CS1 is controlled by the ON / OFF control of the GTO1, and the anode reactor LA2 and the snubber capacitor CS is controlled by the ON / OFF control of the GTO4.
The stored energy regeneration operation of No. 4 is performed by the regeneration means Rg1 and Rg2 as in the conventional circuit example of FIG. However, the snubber capacitor CS of the GTO inside each upper and lower arms
Since the stored energy of 2 and CS3 is consumed by the resistor R as it is, another set of regenerating means is required.

[0008]

As described above, in the conventional circuit of FIG. 3, the energy stored in the voltage / current snubber circuit of the GTO can be regenerated to the DC power source by the two sets of regenerating means, so that it can be converted with a low loss. Although it can be an efficient power converter, the conventional circuit of FIG. 4 requires three or more sets of regenerative means, especially three or more sets of self-extinguishing elements that require auxiliary devices such as gate drivers and snubbers. Since it is necessary, the regenerating means becomes complicated and expensive. Therefore, the power converter also becomes expensive. Although the regenerative means shown in FIGS. 3 and 4 is shown as a chopper circuit, a DC-DC converter circuit using a transformer, for example, requires a plurality of self-extinguishing elements such as transistors, which is also complicated and expensive. It is inevitable that

The problem is that as the capacity and frequency of the power converter increase, the number of regenerative means increases and the capacity increases, so the power converter becomes more expensive. For this reason, simplification of regenerative means and price reduction are very important issues.

An object of the present invention is, in a power converter composed of a plurality of self-extinguishing elements, without increasing the stored energy regeneration means of a voltage / current snubber circuit more than necessary.
An object of the present invention is to provide a low-loss snubber circuit that can be configured without making it complicated and expensive.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a power converter composed of a plurality of self-extinguishing elements, in which the energy stored in a voltage / current snubber circuit is regenerated by self-extinguishing elements. At the same time, the stored energy of another voltage snubber circuit to which the regeneration means is not connected is utilized for snubber energy supply to the pair of arms via the energy transfer means composed of a reactor and a diode.

[0012]

Therefore, the stored energy of the voltage snubber circuit without the regeneration means can be utilized for the snubber energy supply of the anti-arm via the energy transfer means composed of the reactor and the diode, so that the complicated and expensive self A power converter with good conversion efficiency can be obtained without increasing the number or capacity of the regenerative means composed of arc extinguishing elements.

[0013]

1 shows an embodiment of a low-loss snubber circuit according to the present invention, which is an example applied to the conventional circuit of FIG. In the embodiment shown in FIG. 1, similarly to the conventional circuit shown in FIG. 4, the upper arm is composed of GTO1 and GTO2 connected in series and the lower arm is composed of GTO3 and GTO4 connected in series, and the anode reactor LA1 and the snubber capacitor are controlled by the ON / OFF control of GTO1. The stored energy regeneration operation of CS1 and the stored energy regeneration operation of the anode reactor LA2 and the snubber capacitor CS4 by the ON / OFF control of the GTO 4 are performed by the regeneration means Rg1 and Rg2 as in the conventional circuit example of FIG. On the other hand, in the present invention, the energy stored in the snubber capacitor CS2 of the upper arm GTO2 is equal to the upper arm GTO2.
1, when the GTO2 is turned on, it is used for recovery of the lower arm free wheel diodes DF3, DF4 and charging of the lower arm snubber circuit which have been in the freewheel state through the energy transfer means ET2 composed of the reactor LT2 and the diode DT2. In addition, the energy stored in the snubber capacitor CS3 of the GTO3 is
3, when the GTO 4 is turned on, it is used for recovery of the upper arm free wheel diodes DF1 and DF2, which were in the freewheel state until then, and charging of the upper arm snubber circuit, through the energy transfer means ET1 composed of the reactor LT1 and the diode DT1. As described above, according to the embodiment of FIG. 1, the two GTs added to the conventional circuit example of FIG.
There is an effect that the energy stored in the snubber capacitor of O can be used for the recovery of the anti-arm freewheel diode and the charging of the upper arm snubber circuit without increasing the capacity or the number of the regenerative means composed of the self-extinguishing element. In this embodiment, in order to prevent the recovery of the anti-arm freewheel diode at light load, the resistor R shown by the dotted line in the figure (value larger than the normal snubber resistor) is connected, It is also conceivable to consume the resistance R.

As described above, according to this embodiment of FIG. 1, even if the number of self-extinguishing elements forming the upper and lower arms is increased in series, the self-extinguishing element can regenerate the stored energy of the voltage / current snubber circuit. Since it is performed by the configured regenerative means, the stored energy of the other voltage snubber circuit to which the regenerative means is not connected can be used for the snubber energy supply of the anti-arm via the energy transfer means composed of the reactor and the diode. The regenerating means can be made inexpensive, that is, the power converter can be made inexpensive, without increasing the capacity or the number of the regenerating means composed of the self-extinguishing element.

FIG. 2 shows still another embodiment of the low-loss snubber circuit of the present invention, which is an example of application to a three-level voltage type inverter circuit. The operation of the three-level voltage type inverter is publicly known (for example, Japanese Patent Laid-Open No. 55-43996) and will not be described. In the embodiment of the present invention shown in FIG. 2, the voltage of the upper and lower arms
As shown in FIG. 1, the connection of the regenerative means constituted by the self-extinguishing element for regenerating the stored energy of the current snubber circuit and the energy transfer means for utilizing the stored energy of the other voltage snubber circuit for the snubber energy supply of the anti-arm is implemented. Same as the example. The stored energy regenerating operation of the anode reactor LA1 and the snubber capacitor CS1 by the ON / OFF control of the GTO1 and the stored energy regenerating operation of the anode reactor LA2 and the snubber capacitor CS4 by the ON / OFF control of the GTO4 are regenerated as in the embodiment of FIG. By means Rg1 and Rg2. Also, GTO
2 or when the GTO3 is turned on, the stored energy of the snubber capacitors CS3, CS2 of the GTO3 or GTO2 of the opposite arm is used to supply the snubber energy of the opposite arm via the energy transfer means ET1, ET2. The same is done as in the example.

As described above, according to the present embodiment shown in FIG. 2, the power conversion device can be made inexpensive as in the embodiment shown in FIG.

[0017]

According to the present invention, in the power conversion device composed of a plurality of self-extinguishing elements, the stored energy regenerating means of the voltage / current snubber circuit connected to the plurality of self-extinguishing elements is required. As described above, the power conversion device can be inexpensive because it can be configured without making it complicated and expensive.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a low-loss snubber according to the present invention.

FIG. 2 is a circuit diagram of another embodiment of the low loss snubber according to the present invention.

FIG. 3 is a circuit diagram of a conventional low-loss snubber.

FIG. 4 is another circuit diagram of a conventional low-loss snubber.

[Explanation of symbols]

P ... DC power source positive side terminal, N ... DC power source negative side terminal, U
P ... U-phase positive side power supply wiring, UN ... U-phase negative side power supply wiring,
VP ... V phase positive side power supply wiring, VN ... V phase negative side power supply wiring, WP ... W phase positive side power supply wiring, WN ... W phase negative side power supply wiring.

Claims (2)

[Claims] 1. A first self-extinguishing element in which a DC power supply and a current snubber composed of a reactor are connected in series, and a first voltage snubber composed of a series body of a capacitor and a diode is connected in parallel, and a first self-extinguishing element of the above construction. In a power converter in which upper and lower arms are respectively formed of a series body of a second voltage snubber and a second self-extinguishing element connected in parallel, a current / voltage snubber in each of the first self-extinguishing elements of the upper and lower arms is provided. Stored energy of each of the stored energy and a stored energy regenerating means comprising a self-extinguishing element connected in parallel with the energy storage capacitor, and stored energy of a voltage snubber in the second self-extinguishing element of each of the upper and lower arms. An energy transfer means composed of a reactor and a diode when the second self-extinguishing element is turned on. Low-loss snubber circuit for a power converter which is characterized by utilizing a snubber energy supply of the pair arms and. 2. The three-level power converter according to claim 2, wherein the DC power supply is divided into two, and diodes are respectively connected from the dividing points to connection points of the first and second self-extinguishing elements in the upper and lower arms. Power converter low loss snubber circuit consisting of.