RU2368997C1 - Converter of three-phase voltage into dc voltage - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: converter of three-phase voltage into DC voltage is intended for supply of DC loads with increased requirements to reliability of converter. Suggested converter ar p-multiple frequency of rectified voltage pulsation comprises p/6 three-phase sources of power supply, identical voltages of which are serially shifted by phase by 2 π/p electric degrees, and n=(p/6)+1 serially located valve groups, extreme of which comprises three valves combined into anode and cathode valve stars, common points of which create outlet leads of device, and other groups represent six valve rings with three pairs of diametrically installed points of identical valve electrodes connection, extreme valve groups are connected to adjacent groups in three units, every of which is created by free electrode of anode (cathode) valve star and free point of connection of valve electrodes in adjacent valve ring, created by electrodes of another name, adjacent valve rings are connected in three units, every of which is created by free pair of connection points of valve electrodes in adjacent rings, besides in these units electrodes of valves in one adjacent ring have one name, and valve electrodes of the second ring - another one, moreover, one of phases of one of three-phase sources of supply is connected to each unit of adjacent valve groups connection, besides each of phases of any supply source is connected via valves of rings only with phases of adjacent sources of supply, having phase shifts

electric degrees, relative to this phase. Overvoltage protection device is connected to each pair of diametral points of six valve rings. Overvoltage protection devices may comprises asymmetrical limiters of voltage, electrodes of which are connected with identical electrodes of ring valves.

EFFECT: suggested converter of three-phase voltage into DC voltage has higher reliability.

2 cl, 8 dwg

Description

The invention relates to the field of converter technology and may find application for supplying direct current consumers with increased requirements for converter reliability.

Known converters of three-phase voltage to DC, built according to series-type circuits (A.S. No. 57985 of the USSR. Device for rectifying and inverting three-phase alternating current. / Ya. M. Chervonenkis, registered 03.06.39, publ. 01.01.1940; and No. 801204, USSR, AC to DC Converter / A.A. Yatsenko, 4N02M7 / 06, Bull.No. 4, 01/30/1981).

The disadvantages of these converters are the high power losses in the valves.

Known converter of three-phase voltage to DC, having a ring circuit for switching valves, providing loss reduction in valves (External characteristics and operating modes of a twelve-phase converter with reduced losses. Kolev Sv.N., Kalchev AK / ref. Journal "Electrical Engineering and Electric Power" 21 Yu, No. 9, 1977 // (bulg.) "Scientific Traffic Institute of Mechanical Engineering, Mechanics and Electricity, Rural Stop - Ruse", 1974, ser. 6, 17, P.117 -120).

Three-phase DC to DC converters are also known (private implementations of the aforementioned converter) having ring circuits for connecting valves (AS No. 1356153, USSR. High-voltage power supply A.M. Repin / A.M. Repin, Bull. No. 44, 1987).

These converters contain two sources of three-phase voltage systems, mutually shifted by 30 el. hail., and three groups of valves: anodic, cathodic, and six-valve ring (ring group).

The disadvantage of the above converters is the difficulty of protecting the groups of valves from overvoltage.

/p эл. град., и n=(р/6)+1 последовательно расположенных вентильных групп, каждая из которых включает m²=9 вентилей, соединенных в 2m=6 вентильных звезд с циклическим соединением лучей, при этом каждая вентильная звезда имеет к=3!=6 контуров из шести вентилей, образующих шестивентильное кольцо с тремя парами диаметрально расположенных точек соединения одноименных электродов вентилей, при этом точки соединения лучей вентильных звезд образуют по три входных (анодных) и по три выходных (катодных) узла вентильной группы, причем каждый из трех незадействованных одноименных узлов одной из смежных вентильных групп соединен с одним из трех незадействованных узлов другого наименования второй смежной вентильной группы, а к каждой точке попарного соединения узлов смежных вентильных групп подключена одна из фаз одного из трехфазных источников питания, причем в каждой вентильной группе, связывающей смежные источники питания, всегда найдется шесть вентилей, соединенных попарно одноименными электродами в замкнутое шестивентильное кольцо, через пару вентилей которого каждая из фаз одного из смежных источников питания соединена с фазами другого смежного источника питания, имеющими фазовые сдвиги

эл. град. относительно данной фазы, при этом незадействованные узлы первой и последней вентильных групп соединены с одноименными им выходными выводами устройства, образуя при этом из вентилей групп три анодных и три катодных вентильных звезды.Closest to the invention adopted as a prototype is a m-phase voltage to DC converter (AS No. 729777, USSR. M-phase AC to DC converter / Yu.V. Potapov, Bull. No. 15, 1980), in which for m = 3 and p-times the ripple voltage of the rectified voltage, there are p / 6 three-phase power supplies, the voltage of the same name being sequentially phase-shifted by 2

/ p email hail., and n = (p / 6) +1 consecutively located valve groups, each of which includes m ² = 9 valves connected in 2m = 6 valve stars with a cyclic connection of rays, with each valve star having k = 3! = 6 circuits of six gates forming a six-valve ring with three pairs of diametrically located connection points of the same valve electrodes, while the connection points of the rays of the valve stars form three input (anode) and three output (cathode) nodes of the valve group, each of three idle of the same nodes of one of the adjacent valve groups is connected to one of three unused nodes of another name of the second adjacent valve group, and to each point of pairwise connection of nodes of adjacent valve groups is connected one of the phases of one of the three-phase power supplies, and in each valve group connecting adjacent power sources, there are always six gates connected in pairs by the same electrode in a closed six-valve ring, through a pair of gates of which each of the phases of one of the adjacent s power supply is connected with the phases of the other adjacent power supply having phase shifts

email hail. relative to this phase, while the unused nodes of the first and last valve groups are connected to the output terminals of the same name with the device, forming three anode and three cathode valve stars from the group valves.

This converter is not critical to the order of connecting the phase outputs of the supply systems to the corresponding connection points of adjacent valve groups. However, this is ensured by the redundancy of the valves in the groups connecting adjacent power systems.

The disadvantage of this converter is the relatively low reliability due to the lack of protection of the valve groups from overvoltage.

The objective of the invention is to increase the reliability of the Converter.

/p эл. град., и n=(р/6)+1 последовательно расположенных вентильных групп, крайние из которых содержат по три вентиля, соединенных в анодную и катодную вентильные звезды, общие точки которых образуют выходные выводы устройства, а остальные группы представляют собой шестивентильные кольца с тремя парами диаметрально расположенных точек соединения одноименных электродов вентилей, крайние вентильные группы соединены со смежными группами в трех узлах, каждый их которых образован свободным электродом анодной (катодной) вентильной звезды и свободной точкой соединения электродов вентилей смежного вентильного кольца, образованной электродами другого наименования, смежные вентильные кольца соединены в трех узлах, каждый из которых образован свободной парой точек соединения электродов вентилей смежных колец, причем в данных узлах электроды вентилей одного смежного кольца имеют одно наименование, а электроды вентилей второго кольца другое наименование, причем к каждому узлу соединения смежных вентильных групп подключена одна из фаз одного из трехфазных источников питания, при этом каждая из фаз любого источника питания соединена через вентили колец только с фазами смежных источников питания, имеющими фазовые сдвиги

эл. град. относительно данной фазы, причем к каждой паре диаметрально расположенных точек соединения электродов вентилей колец подключено устройство защиты от перенапряжений.This problem is achieved by the fact that the three-phase voltage to DC converter contains, at a p-fold frequency of the ripple voltage of the rectified voltage, p / 6 three-phase power supplies, the voltage of the same name being sequentially phase shifted by 2

/ p email hail., and n = (p / 6) +1 in series of valve groups, the last of which contain three valves connected to the anode and cathode valve stars, the common points of which form the output terminals of the device, and the remaining groups are hexagonal rings with three pairs of diametrically located connection points of the same valve electrodes, the extreme valve groups are connected to adjacent groups in three nodes, each of which is formed by a free electrode of the anode (cathode) valve star and a free the connecting point of the valve electrodes of an adjacent valve ring formed by electrodes of another name, adjacent valve rings are connected in three nodes, each of which is formed by a free pair of connection points of the valve electrodes of adjacent rings, and in these nodes the valve electrodes of one adjacent ring have one name, and the valve electrodes the second ring is a different name, and to each node of the connection of adjacent valve groups is connected one of the phases of one of the three-phase power sources, while Each phase of any power source is connected through ring valves only to phases of adjacent power sources having phase shifts.

email hail. relative to this phase, moreover, to each pair of diametrically located points of connection of the electrodes of the valves of the rings is connected a surge protection device.

Also, the task is achieved in that the overvoltage protection devices may contain asymmetric voltage limiters, the electrodes of which are connected with the same electrodes of the valve rings.

Figure 1 shows the electrical circuit of the proposed Converter, for example, with a 12-fold pulse frequency of the rectified voltage; figure 2 shows a valve ring with surge protection devices (hereinafter protection devices), presented, for example, in the form of asymmetric voltage limiters; figure 3 - vector voltage diagrams represented by the amplitude-phase portraits of the voltages of the secondary phase windings (the triangle is replaced by a star) and detailed vector diagrams explaining the principle of the formation of the resulting voltages, the voltage acting between the diametrically located points of the valve ring, and the reverse voltage on two valves ; figure 4 is a diagram of the formation of the inclusion circuits of the protection devices on the example of two of the six possible positions in the vector diagrams of figure 3; figure 5 - time diagram of reverse voltages on valves of various groups and a voltage diagram between diametrically located points of the valve ring; figure 6 is a timing diagram of the reverse voltages and currents of the valves when exposed to overvoltage in the prototype circuit and in the circuit of the proposed Converter with protection devices made on asymmetric voltage limiters, as well as diagrams of the protection device; 7 is a timing diagram of the reverse voltages and currents of the valves, as well as the rectified voltage when exposed to overvoltage in the prototype circuit and in the circuit of the proposed Converter with protection devices based on a symmetrical voltage limiter; on Fig - one of the specific implementations of the Converter with protection devices having an 18-fold pulse frequency of the rectified voltage.

The Converter (Figure 1) contains a three-phase transformer 1 with secondary windings connected by star and triangle circuits, twelve valves 2-13 and three protection devices 14-16, shown in the diagram, for example, in the form of symmetrical voltage limiters. Gates 5-10 form a six-valve ring connected by three inputs to valves 2-4, forming an anode valve star, and three outputs to valves 11-13, forming a cathode valve star. The common points of the stars 17 and 18 form the output terminals of the converter, to which the load 19 is connected. Each of the protection devices 14-16, shown in figure 1 as symmetrical voltage limiters, or 20-22, shown in figure 2 as asymmetric limiters voltage, connected to one of three pairs of diametrically located points of connection of the valves of the ring and each of the devices connects the same phase terminals of the secondary windings, respectively aa, b-c, c-c.

The principle of operation of the device (Figure 1) is illustrated by vector diagrams of voltages, presented in the form of amplitude-phase portraits of voltages of the secondary phase windings, comprising two symmetric three-phase systems, shifted in the phase plane by 30 el. deg., and deployed on the phase plane of the vector diagrams of the resulting stresses (diagram a-e in Figure 3). From the vector diagrams it can be seen that between the diametrically located connection points of the valve ring valves a unipolar alternating voltage is generated (for example, the voltage on the protection device 14 connected between points aa '), which has the same sign as the reverse voltages on the valves (for example, valves 9, 10). The maximum instantaneous voltage value between diametrically located points of the valve ring for a converter with a 12-fold rectified voltage ripple frequency is less than the maximum value of the working reverse voltage on the ring valves and is greater than the maximum instantaneous value of the working reverse voltage of the valves of the anode and cathode groups. When overvoltages occur, the relations between the magnitudes of the considered voltages remain almost the same. This allows you to include between the diametrically located points of the valve ring of the protection device with a trip setting that is equal to or greater than the maximum instantaneous value of the operating voltage between the diametrically located points, thereby limiting overvoltage both on the ring valves and on the valves of the anode and cathode groups.

Figure 4 schematically shows the process of connecting the protection devices to the secondary windings in two adjacent phases of the conversion cycle. It is seen that the overvoltage limitation is provided on any part of the circuits with a variable structure. In addition to protection devices, the above diagrams show only valves with maximum reverse voltages and valves that conduct current in these conversion phases.

The ratios of the levels of reverse voltages on the valves and the voltages between the diametrical pairs of the connection points of the ring valves for an ideal converter are shown in the diagrams of Figure 5.

The presence of electromagnetic coupling of the windings improves surge protection for the entire converter as a whole. The operation of the protection device is also facilitated because its operating voltage is less than the voltages on the ring valves (undesirable heating, for example, of avalanche valves, occurs precisely in the operating mode by reverse currents). With an increase in the phase of the converter, the difference in these voltages increases.

The choice of protection device circuits is wide enough and is determined by the energy characteristics of the power supply network and the converter, the expected level of overvoltage and their energy. For example, Fig. 6 shows the results of circuit simulation of the prototype and the proposed low-power converter with protection devices in a 220 V network. Overvoltages in the primary windings of such converters can reach 4-5-fold the level of the operating voltage amplitude, which was taken into account when modeling. As protection devices, asymmetrical voltage limiters, such as avalanche diodes, are used. For comparison, the selected valves of the prototype, which correspond to the inclusion in the circuit valves of the proposed device.

In powerful converters operating in high voltage networks, overvoltages usually do not exceed three times the level. The simulation results of the operation of such a converter, in the protection devices of which symmetrical voltage limiters are used, for example varistors, are shown in the diagrams of Fig. 7. For comparison, Fig. 7 shows the operation diagrams of the corresponding valves of the prototype. For valve 10, reverse voltage diagrams are separately shown for triple and single overvoltage levels. Diagrams of rectified voltage and voltage at valve 3 are given at a single level of overvoltage.

A specific implementation of the converter with protective devices having an 18-fold frequency of the ripple voltage of the rectified voltage shown in Fig. 8, and the implementation of the converter with a higher phase conversion, do not have significant differences from the implementation shown in Fig. 1. However, the relationships between the maximum values of the working reverse voltages of the valves of the anode (cathode) group and the valves of the rings change. Therefore, the setting of the protection parameters is carried out taking into account the following ratios common for p-phase converters, valid for an idealized converter.

For valves of the anode and cathode groups, as in bridge rectifiers, the maximum value of the working reverse voltage is

For ring valves

where U _L is the effective value of the linear voltage of a symmetric three-phase voltage system of the secondary windings of the transformer.

Thus, the valves of the anode and cathode groups are affected by the linear voltage of the supply systems, and the valves of the rings are subject to higher reverse voltages, the absolute and relative (relative to the voltages of the valves of the anode and cathode groups) the value of which decreases with increasing phase transformer. The setting of the operation of the protection device must correspond to a level that is equal to or greater than the maximum instantaneous voltage value applied to the diametrical points of the ring, and is determined by the formula:

When using silicon zener diodes, diode avalanche poles or other asymmetrical voltage limiters with a zener diode effect, for example avalanche valves, in the protection devices of the converter converter, the electrodes of the latter are connected (connected) with the ring valve electrodes of the same name. The use of symmetrical voltage limiters in protection devices, for example, silicon symmetric limiters or metal oxide varistors, does not require compliance with the polarity of the connection of the limit device.

Compared with the prototype in the Converter, the total number of valves of the valve groups connecting adjacent power sources is reduced by

вентилей, вместо которых включены устройства защиты от перенапряжений. Сокращено на двенадцать общее число вентилей в анодной и катодной группах.

valves, instead of which surge protection devices are included. Twelve total valves in the anode and cathode groups were reduced.

The proposed Converter in comparison with the prototype reduces the likelihood of failure of the valves when exposed to overvoltages, as protection devices reduce the level of overvoltages.

Thus, the proposed Converter three-phase voltage to DC has increased reliability.

Claims (2)

1. The converter of three-phase voltage to DC, containing at r times the frequency of the ripple of the rectified voltage p / 6 three-phase power supply, the same voltage which is sequentially phase-shifted by 2 π / p el. hail., and n = (p / 6) +1 in series of valve groups, the last of which contain three valves connected to the anode and cathode valve stars, the common points of which form the output terminals of the device, and the remaining groups are hexagonal rings with three pairs of diametrically located connection points of the same valve electrodes, the extreme valve groups are connected to adjacent groups in three nodes, each of which is formed by a free electrode of the anode (cathode) valve star and a free a connecting point of the valve electrodes of an adjacent valve ring formed by electrodes of another name, adjacent valve rings are connected in three nodes, each of which is formed by a free pair of connecting points of the valve electrodes of adjacent rings, while in these nodes the valve electrodes of one adjacent ring have one name, and the electrodes the valves of the second ring are different, moreover, one of the phases of one of the three-phase power sources is connected to each node of the connection of adjacent valve groups, and each of the phases any power source is connected through the valves of the rings only with the phases of adjacent power supplies having phase shifts

email hail. relative to this phase, characterized in that an overvoltage protection device is connected to each pair of diametrically located connection points of the valve electrodes of the rings. 2. The Converter according to claim 1, characterized in that the surge protection device contains asymmetric voltage limiters, the electrodes of which are connected with the same electrodes of the valve rings.

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