RU1781794C - 2@-phase compensated converter of ac voltage to dc voltage and backwards - Google Patents

Abstract

Usage: the invention can be used as a direct or alternating current power source. SUMMARY OF THE INVENTION: the converter consists of two six-phase units with a zero rectification circuit constructed using a converter transformer, the network windings of which 2, 3, equipped with switching devices, are connected to a star and a triangle, and the valve windings 4,5,6,7 are connected by direct star and reverse star schemes. Between the zero points of the corresponding stars, equalization reactors 8.9 are included, the midpoints of which are connected to the negative output terminal. The inputs of the rectifier devices 10, 11 are connected to the valve windings 4-7, and the outputs 12 with a positive output terminal. The first 12 and second 13 three-phase windings of the reactor of the compensating device are connected in series with the network windings of the transformer on the side of the supply network. A third 14 and a quarter 15 of the reactor winding are connected in a star, connected in series according to and the capacitor battery 16 is connected to the points of their connection. The specified embodiment of the device simplifies it and reduces the installed power of the equipment with deep regulation of the rectified voltage. 2 s.p. f-ly, 1 ill. Ј 00 t-A O .N

Description

The invention relates to power conversion technology and can be used in electrolysis, electrothermal, railway transport, etc. to power the load with direct current. It can also be used to invert DC to AC.

A twelve-phase compensated AC / DC converter is known. It contains two six-phase converter blocks formed by a converter transformer, the network windings of which are connected to the input terminals for connecting a three-phase supply network, and the secondary phase voltages of one of the blocks are shifted by 30 electric degrees. with respect to the similar voltages of the other unit by connecting the valve windings to a star and a triangle, and two rectifier devices with a bridge rectifier circuit, each of which is connected to the valve windings of the transformer with a secondary phase voltage system of the corresponding unit by the output and - to the output terminals for connecting the load, as well as a compensating device including a reactor made on two magnetic cores, on the first of which there are an unconnected first and connected star third three-phase winding, and the second - similar to the first unbound second and fourth bonded delta three phase windings, and third and fourth three-phase windings are connected in series, and to compound them points connected three phase capacitor bank

The disadvantage of the prototype is that the reactor of the compensating device is made of two structurally different parts. One of them contains a third winding connected to a star, and the other contains a fourth winding connected to a triangle. The number of turns of the fourth winding is V3 times greater than that of the third winding. The structural difference of the reactor parts of the compensating device substantially complicates the practical implementation of the compensated converter. Another disadvantage of the prototype is manifested in transformer regulation of rectified voltage, which in a large number of electrical engineering installations is carried out to maintain rectified current. Regulation, as a rule, is carried out by changing the number of turns of the network

windings using a switching device. As the number of turns of the network winding increases, the rectified voltage of the converter decreases, since

the voltage across the valve windings decreases. With a constant capacitance of the battery capacitors, the direct current in the prototype corresponds to the unchanged voltage across the capacitors. They are practically independent of the transformer ratio. Reducing the voltage across the valve windings of the transformer and maintaining the switching voltage of the capacitors leads to

5 to generating positive voltages on the converter valves in the non-conductive part of the period. The valves re-conduct the operating current during the supply voltage period. Appearance of a lagging wave

0 valve currents leads to a shift in the direction of the lag of the inverter currents to reduce power factor. To maintain it, it is necessary to reduce the natural frequency of the circuit

5 switching valves by additionally connecting capacitor banks in a capacitor bank. As a result, its installed capacity increases.

The aim of the invention is to simplify the design and reduce the installed power of the converter equipment by deeply regulating the rectified voltage using switching devices in the main windings of the transformer.

The goal is achieved in that the fourth three-phase winding of the reactor of the compensating device of the prototype is made with the number of turns equal to the number

0 turns of the third winding and connected to a star. In addition, the first and second reactor windings are connected in phase in series with the network windings of the converter transformer on the side

5 of the supply network. As a result, the design of both parts of the reactor of the compensating device becomes the same, which greatly simplifies the implementation of the compensated converter,

0 The inclusion of a compensating device on the mains side with respect to the regulated network windings of the conversion transformer while decreasing the rectified voltage AB5 thematically reduces the natural frequency of the switching circuit of the valves, since with increasing transformer ratio the capacitance of the capacitor bank brought into the switching circuit in the proposed the converter is reduced. The latter provides a detuning from the repeated conductivity of the valves without additional connection of capacitors in the capacitor bank of the compensating device, which reduces the required power of the capacitor bank with deep transformer voltage control at the load.

In order to increase the constant load and load, the m-phase converter blocks with respect to it are connected in series. In order to increase the direct current value, the blocks with respect to the load are switched on in parallel. Rectifier devices can be performed both on diodes and on thyristors. By using the inverse conversion of direct voltage to ac, they can be performed with the forward and reverse sets of thyristors.

The figure shows a schematic diagram of one of the possible variants of the proposed compensated converter, namely, a 12-phase converter, consisting of two six-phase blocks with a zero rectification circuit. It contains a converter transformer 1, the network windings of which 2 and 3, equipped with switching devices, are connected to a star and a delta, and the valve windings 4,5,6 and 7 are connected according to the direct star and reverse star schemes. Between zero points in pairs of antiphase valve windings, equalization reactors 8 and 9 are included, the conclusions from the midpoints of which are connected to the negative pole of the load. Rectifier devices 10 and 11 are connected by input terminals to valve windings 4, 5, 6, and 7, and output terminals to a positive load pole. The first and second three-phase windings of the reactor of the compensating device 12 and i3 are connected in series with the network windings of the transformer from the supply network. The third and fourth windings of the reactor 14 and 15, both connected to a star, are connected in series according to, and a capacitor bank 16 is connected to their connection points. Other options for the converter may have a different phasing, other connection schemes for the network and valve transformer windings, and rectifier devices may also have a bridge design.

The work of the proposed compensated rectifier is carried out as follows. When connecting the transformer 1 to the mains

valve coils 4, 5 and 6.7 generate voltages forming two six-phase symmetrical voltage systems. Since these systems are shifted by 30 degrees due to the connection of the network windings of transformer 2 and 3 into a star and a delta, a rectified voltage corresponding to the twelve-phase conversion mode is created at the load using rectifier devices 10 and 11. In the mains, the currents also correspond to twelve-phase conversion. The currents in the first and second windings of the reactor 4 of the compensating device 12 and 13 contain 1,5,7,11,13,17,19 it.p. harmonics. The harmonics are also contained in the currents of the third and fourth 14 and 15 windings. Harmonics 1, 11, 13, etc. closed in the circuits of the windings 14 and 15, pass capacitors, harmonics 5, 7, 17, 19, etc. fall into capacitors and recharge them. The voltage of the capacitors of the battery 16 having the same spectrum, being transformed into the switching circuits of the valves of the devices 10 and 11, causes the leading artificial switching of the valves. As a result, the valve and, consequently, the mains currents of the converter are shifted ahead of them, which leads to an increase in its power factor. The rectified voltage of the converter is controlled by switching devices of the windings 2 and 3. In order to reverse convert the direct voltage to alternating voltage, the devices 10 and 11 are put into inverter operation mode. The technical and economic efficiency of the proposed compensated converter is determined by the simplification of the reactor of the compensating device, since both its parts become identical. In addition, with deep transformer regulation in the proposed converter, the installed capacity of the capacitor bank of the compensating device is reduced. With a control depth of 70%, as is the case with graphitization furnaces, the installed battery power can be almost halved.

Claims (3)

SUMMARY OF THE INVENTION 1. A 2 m-phase compensated AC / DC converter, comprising two two-phase converter blocks formed by a converter transformer, the network windings of which are connected to the input terminals for connecting a three-phase supply network, moreover, the secondary phase voltages of one converter unit are shifted by an angle of l / t el. in relation to the similar voltages of the other unit, and two rectifier devices, each of which is connected to the valve windings of the transformer with a secondary phase voltage system of the corresponding unit with an input, and an output to the output terminals for connecting the load, as well as a compensating device, comprising a reactor made on two magnetic cores, on the first of which there is an unconnected first and a third three-phase windings connected to a star, and on the second - similar to the first unconnected second and fourth the mouth of the three-phase windings, and the third and fourth three-phase windings are connected in series according to, and a three-phase capacitor bank is connected to the points of their connection, characterized in that, in order to constructively simplify and reduce the installed power of the equipment while deeply regulating the rectified voltage using switching devices in the transformer network windings, the fourth three-phase reactor winding is made with the number of turns equal to the number of turns of the third winding, and connected to a star, and VA and the second windings of the reactor are connected in phase with the network windings of the transformer transformer on the supply side. i 2. The converter pop. 1, from the key, and so that, in order to increase constant voltage, m-phase converter blocks with respect to the load are connected in series. 3. The converter pop. 1, distinguished by the fact that, in order to increase DC, m-phase converter blocks are connected in parallel with respect to the load.