RU2642519C1 - Electronic transformer - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: electronic transformer comprises a first AC voltage network, a first LC filter, a nine-key transducer, a second LC filter, a second alternating voltage network connected in cascade, characterized in that a storage reactor is introduced, and a nine-key transducer is made on fully controllable key with double-ended conductivity. The storage reactor is connected by its clamps to the upper and lower three keys of the nine-key transducer.

EFFECT: invention makes it possible to increase the voltage conversion factor, since now both stages of the electronic transformer contribute to an increase in the output voltage of the electronic transformer.

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Description

The invention relates to semiconductor converters and can be used as an electronic transformer with a smooth change in the transformation coefficient in smart networks when converting AC voltage to AC in magnitude and frequency. Such converters can be used in alternating current generation systems when galvanic isolation of two alternating voltage networks is not required.

An electronic transformer is known for which a converter can be used (S. M. Dehghan, M. Mohamadian, A. Yazdian, F. Ashrafzadeh, A Novel Space Vector Modulation for Nine-Switch Converters, 885-891, 2009 IEEE Energy Conversion Congress and Exposition, San Jose, CA).

It contains two stages of conversion: the first is a Z-filter and a 9-key converter (second stage of the transformer). The second stage is a dual voltage inverter and generates an adjustable voltage on the load in frequency and magnitude, and the magnitude is adjustable only in the direction of decrease.

Such an electronic transformer allows you to adjust the value of the output voltage both below and above the value of the input voltage. Regulation in the direction of increase is possible here only due to one step, namely the first - Z-filter.

The increase in voltage at the load occurs due to the first stage of the converter (Z-filter) by accumulating voltage on the filter capacitor. In the second stage, voltage regulation is possible only in the direction of reduction.

This electronic transformer does not have a sufficiently high voltage conversion coefficient due to an increase in voltage in only one stage of the converter.

An electronic transformer is also known, which can be used as a converter, which is the prototype of Congwei Liu, BinWu, Navid R. Zargari, Dewei (David) Xu and Jiacheng Wang, A Novel Three-Phase Three-Leg AC / AC ConverterUsing Nine IGBTs. IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 24, NO. May 5, 2009.

It also contains a 9-key converter, made on keys with one-way controllability, consisting of counter-parallel connected transistor and diode, with a capacitor on between common points of connection of the upper and lower keys of the 9-key converter.

Such an electronic transformer allows, in addition to regulating the frequency of the output voltage, to regulate the value of the output voltage both lower and higher than the input voltage. Regulation in the direction of increase is possible here only due to the accumulation of voltage on the capacitor mentioned above. Therefore, such an electronic transformer also has a rather low voltage conversion coefficient.

The objective (technical result) of the present invention is the creation of an electronic transformer with a higher voltage conversion ratio.

This is achieved by the fact that the electronic transformer containing the first AC voltage network, the first LC filter, a 9-key reversible converter on controlled keys, the second LC filter, the second AC voltage network, cascaded, characterized in that the 9-key converter is made On fully controllable keys with two-sided conductivity, a storage reactor was also introduced, which is connected with its clamps to the upper and lower three keys of the 9-key converter.

In FIG. 1. a diagram of the proposed electronic transformer is presented, considered as an example of a transformer that converts a three-phase input voltage into a three-phase output voltage, and FIG. 2. - diagrams of his work.

The proposed electronic transformer (Fig. 1.) contains the first network (PS) 1; the first LC filter (F1) 2, included after the first network, 9-key reversing transducer (RP) 3; storage reactor (HP) 4, connected with its clamps to the upper and lower three keys of the 9-key converter, a second LC filter (Ф2) 5, connected between the output of the 9-key reversing converter and the second network (BC) 6.

In FIG. 2 shows voltage plots in the proposed electronic transformer circuit. In FIG. 2 a) are shown: u _in - voltage of the first network 1 and u _o - voltage at the output of the electronic transformer. In FIG. 2. b) i ₄ is the current in the storage reactor 4. In FIG. 2 c) u _in is the voltage of the first network, i _in is the current of the first network 1 and i _rp is the input current of the 9-key reversing converter.

The principle of operation of the proposed electronic transformer is as follows. The 9-key reversing converter is controlled using pulse-width modulation. The clock interval of pulse-width modulation is divided into two sub-intervals. At the first sub-interval, the 9-key reversing converter operates as a rectifier (when transmitting power from the first network to the second). A three-phase bridge rectification circuit is formed from the three top and three middle keys RP. In order for the reactor to be connected to the output of the rectifier, the control pulses of the middle keys are duplicated to the lower keys of the 9-key reversing converter. In this case, a current builds up in the reactor 4 and electromagnetic energy is stored. In the second sub-interval, the rectifier key control pulses are removed, and a three-phase current inverter circuit is formed from the middle and lower keys of the 9-key reversing converter, and now the reactor 4, in which the electromagnetic energy is stored, will act as a current source for the formed current inverter circuit. In order for the storage reactor 4 to be connected to the input of the current inverter, the middle-key control pulses are duplicated on the upper keys of the 9-key reversing converter. The created current inverter circuit generates voltage in the second network. The accumulator reactor 4, which is now disconnected from the first network, acts as a current source for it. At the same time, the stored energy in the storage reactor, the value of which can be adjusted, is transmitted through the keys of the current inverter to the capacitors of the second filter, increasing the voltage on them. In this case, power is transferred from the first network to the second. To transfer power from the second network to the first one, the rectifier and current inverter must be interchanged.

Thus, when forming the voltage on the capacitors of the second filter, two factors are used: the regulated current of the storage reactor 4 and the principle of forming the voltage of the current inverter (moving the operating point along the steeply increasing external characteristics of the reversing current inverter), which makes the voltage conversion coefficient higher than in the prototype.

This became possible due to the fact that the 9-key reversing converter is made on fully controllable keys with two-sided conductivity, and a storage reactor is introduced, which is connected by its clamps to the upper and lower three of the keys of the 9-key converter.

Claims (1)

An electronic transformer containing a first alternating voltage network, a first LC filter, a nine-key converter, a second LC filter, a second alternating voltage network, cascaded, characterized in that a storage reactor is introduced, and the nine-key converter is made on fully controllable keys with two-side conductivity, while the storage reactor is connected with its clamps to the upper and lower three keys of the nine-key converter.

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