SU1534691A1 - Three-phase-to-three-phase frequency converter with quasisingle-sideband modulation - Google Patents

Abstract

The invention relates to power converter technology and can be used in the construction of various controlled machine-valve systems. The goal is to increase efficiency and expand the scope. The converter contains four three-phase sets connected in a star of secondary windings A _I X _I , B _I Y _I , C _I Z _I , where I = 1.4. Four valve groups of nine thyristors each are connected to the windings with the corresponding polarity. The switching node is made in the form of two thyristors 1, 2, connected between the zero points of the respective pairs of windings, and two switching capacitors 3, connected between the electrodes of the same name of these thyristors. A quasi-single-band modulation algorithm is implemented in the converter. 1 hp f-ly, 3 ill.

Description

windings, and two switching capacitors 3, connected between the same electrodes of these thyristors. AT

the converter implements an algorithm of quasi-one-band modulation, 1 hp f-ly, 3 ill.

The invention relates to the field of Conversion Technique and Yacheno technology for converting a 3-phase pregnant voltage into a 3-phase alternating voltage of adjustable frequency for powering AC electric machines and other consumers.

The aim of the invention is to increase the efficiency and expansion of the field of application.

Fig. I is represented in principle by an electrical circuit of the proposed converter; Fig. 2a shows timing diagrams explaining its operation (supply and output voltage curves); on - the timing diagram of the control pulses of the converter valves; in Fig. 2b, graphs of the output voltage {phase A, B, C) of the converter in the vicinity of time t (Fig. 2a) with inductive type of load (cos CfH

R

3 -C); on fig.Z - structural scheme

$ local control

| Fig. 1 shows the principle of the electrical circuit of the proposed converter, which contains four 3-phase supply windings aJ-xl bi-ylj cl-zl-; a2-x2 ;; B2-y2 c2 - z2 ,; AZ-xZ; B3-FB; c3-z3; A4-x4; B4 –y4; c4-z4, controlled unidirectional switches 1 and 2 with two switching capacitors 3 connected between their electrodes of the same name, controlled unidirectional switches 4-15. The phases of each of the 3-phase power windings are connected by one pin to a star, with the first and second phases being connected to a star by leads XI, U1, Z1 and X2, Y2, Z2, respectively, and the third and fourth phases by leads a3s LZ C3 and a4, b4, c4. Between the neutrals of the first and second 3-phase supply windings, a fully controllable unidirectional switch 1 can be switched on, and between the third and fourths neutrals, a call 2 can be turned. As fully controlled unidirectional switches, in Fig. 1, artificial switching thyristors are shown. the implementation of which between the anodes and between the cathodes of the thyristors 1 and 2 includes switching capacitors 3. The thyristor 1 is connected by the anode to the neutral of the first 3-phase winding and the cathode to the neutral of the second 3-phase winding, and the thyristor 2 is connected by the anode to it Raleigh third 3-phase winding and the cathode to the neutral of the fourth 3-phase winding. The controllable unidirectional keys 4-15, for which thyristors are used in Fig. 1, are divided into twelve 3-phase groups, each of which are connected into a star. Neutral stars of 3-phase key groups are connected to the phase terminals of the power windings. Moreover, in 3-phase groups containing keys 4.8 and 12, the thyristors are connected to neutrals by cathodes, and neutrals are connected to pins al, b1, cl of the first 3-phase supply winding, in 3 phase groups containing keys 5.9 and 13, thyristors are connected to neutrals by anodes, and neutrals are connected to terminals a2, b2, c2 of the second 3-phase supply winding, in 3-phase groups consisting of keys 6,10 and 14, thyristors are connected to leads x3, ultrasonic, The z3 of the third supply winding and in 3-phase groups consisting of keys 7, 11 and 15, the thyristors are connected to the neutrals by anodes, and the neutrals are connected with enes pin a4, 4, c4 fourth three-phase windings. The other terminals of the keys 4-15 are interconnected according to the circular phase alternation scheme and the points of their connection are provided with the terminals A, B, C for connecting a 3-phase load 6 "

The operation of the circuit is as follows.

Let at time t, unload the thyristors 4 and 5 and 1, then the voltages 1) d, Ujj, Uc of the first and second 3-phase supply windings of the power transformer are applied to the phases A, B, C, depending on from the instantaneous values of these voltages and from the parameters of the load, one or two of the windings al-xl will conduct the current; cl-zl / bl-yl, with the corresponding thyristors 4, thyristor 1 and two or one of the windings a2-x2; c2-z2; B2-y2 with the corresponding of thyristors 5 Then, with some lead in relation to the time t2 t, + t (fig. 2a), the unlocking of the thyristors 6 and 7 and the charge of capacitors 3 occur. The charge currents of the capacitors flow through successive pairs of power windings corresponding to their thyristor switches 4–7 and thyristor 1, and the input current of those pairs of phase windings, the instantaneous values of the voltages of which are maximum and directed according to the conductivity of the thyristor switches, enters the charge current circuit. As a result of charging, the sum of the voltages of the capacitors Vits equal to the maximum of the instantaneous values of linear voltage 3-phase windings feeding te "close to the line voltage amplitude. The polarity of the capacitor voltage is positive for thyristor 2.

At time te, the thyristor 2 is unlocked and the sum of the voltages of capacitors 3 is applied to the thyristor 1 in the opposite direction, as a result of which the thyristor 1 is turned off. The capacitors 3 are first discharged through the thyristor 2, the first and second 3-phase supply windings and keys 4 and 5, and then recharging through successive pairs of supply windings, keys 4-7 and thyristor 2 up to a voltage close to the amplitude of the linear voltage of the feeding windings at its opposite polarity, i.e.

wives ,, Uc first and second 350

for thyristor 1. After the end .e moment of time ts - thyristor 1, charging capacitors thyristors 4 and 5 of the switch to phases A, B, C of the load, for example, are switched off to phases A, B, C of the load through the thyristor keys 6 and 7 and thyristor 2 are applied respectively to the voltages Uz, Uu, Ux of the third and fourth 3-phase supply windings

Further, with some lead in relation to the time t9 tЈ + Ј, the thyristor keys 8 and 9 are unlocked. In this case, the discharging of capacitors 3 can occur, if the largest of the instantaneous values is 55

phase supply windings. In advance of the time t6 ts + момент, the thyristor switches 14 and 15 are unlocked, and at time t the thyristor 2 is turned on and the third and fourth 3-phase supply voltages U, x and U2 are applied to the A, B, C phases. windings

Then, keys 4 and 5 and thyristor I are unlocked again and a new switching cycle begins.

3-phase line voltage supply:

the windings are closer to the amplitude value than at time point c.

At time t, t ristor 1 is turned off and capacitor 3 is applied to thyristor 2 in the opposite direction, as a result of which thyristor 2 is turned off and capacitors 3 are discharged through thyristor 1, the third and fourth 3-phase supply windings and thyristor switches 6 and 7. After discharge of the capacitors, they are recharged through a series of

5 pairs of supply windings, keys 6 and 9 and thyristor 1 up to a voltage close to the amplitude of the linear voltage of the supply windings, with a polarity positive for the thyristor

0 2o At the moment of termination of the recharge current, the capacitors thyristors 6 and 7 are turned off, and to the phases A, B, C the loads through the thyristor switches 8 and 9 and the thyristor 1 remain connected, respectively, to the voltage U, UQ, Uc of the first and second 3-phase feed windings.

Then, with respect to the time t t 3 + “, the thyristor switches 10 and I are unlocked

providing the possibility of dosing (capacitors 3, and at time t ,, the thyristor 2 is turned on, ensuring the switching off of the thyristor 1, discharge,

, and recharge of capacitors 3 and connection to the phases A, B, C of the load voltage Ux, U2, Uu, the third and fourth 3-phase supply windings,

In a similar way, two subsequent stages of the switching cycle proceed, with a pre-emption, in relation to the time t t, + Ј, the thyristor keys 12 and 13 are unlocked, and

wives ,, Uc first and second 30

.e moment of time ts - thyristor 1, podklyuch to the phases A, B, C load napr -

five

phase supply windings. In advance of the time t6 ts + момент, the thyristor switches 14 and 15 are unlocked, and at time t the thyristor 2 is turned on and the third and fourth 3-phase supply voltages U, x and U2 are applied to the A, B, C phases. windings

Then, keys 4 and 5 and thyristor I are unlocked again and a new switching cycle begins.

The nature of the distortions of the output direc- tions UQ, U {,, Uc at one of the moments of switching t1 is reflected in Fig. 2c.

Switching algorithms for converter keys (–C5 and Φ, 2 are shown in FIG. 26, Digital indexes with designations of algorithms correspond to key numbers.

The block diagram of the control system (Fig. 3) includes a series-connected master oscillator fg-17 and a six-bit shift register 18 (RG) with outputs p, -p6. The correspondence between the outputs P, P6 and the switching algorithms of the thyristors - ($, 5 is set to 4 ”3”. To control the switching thyristors 1 and 2, two logic elements ZILI 19 and 20 and g are used, respectively, delayed delay elements 21 and 22. It allowed the implementation of the same functions of the conversion to significantly simplify the power part of the converter, increase the efficiency and expand the scope of application due to the possibility of connecting a three-wire (and not six-wire) three-phase load.

F o

rmula invention

Claims (1)

1. Three-phase-three-phase frequency converter with quasi-single-sided modulation, containing a transformer node with four sets of three-phase secondary windings, twelve valve groups, at least two fully controlled valves installed in the circuit between the opposite poles of the corresponding valve groups, as well as a control unit containing sequentially connected frequency control and pulse distributor, made in the form of a six-bit shift register, whose outputs are connected with control the inputs of the corresponding gates, as well as at least two delay elements and two OR elements, characterized in that, in order to increase the efficiency and expand the field of application, the windings in each of the above sets are connected according to a star circuit, and the zero points of these stars windings are formed for the first and second sets of ends, and for the third and fourth S 0 0 five five . 55 Moreover, between the zero points of the first and second, third and fourth sets two fully controlled valves are connected, the anode and the cathode of one valve are connected respectively to the zero points of the first and second sets, the anode and cathode of the other are connected to the zero points of the third and fourth sets, respectively. windings, each of the mentioned valve groups containing 3 single-stage thyristors with common anodes, is connected last to one of the free ends of the second and fourth coils each of the valve groups with common cathodes are connected by these cathodes to one of the free ends of the windings of the first and third sets, and the free terminals of the first, second and third thyristors of the valve groups are connected to one phase of the first and second sets of windings and to another phase e of the third and fourth sets of windings are connected respectively to the output terminals A, B and C of the converter, the first, second and third free terminals of the thyristors of valve groups connected to phase B of the first and second sets of windings and to phase a of the third and fourth sets of windings are connected respectively to output terminals C, A and B of the converter, the first, second and third free terminals of thyristors of valve groups connected to phase C of the first and second sets of windings and to phase B of the third and the fourth winding sets, respectively, are connected to phases B, C, and A of the converter; the control inputs of the first, second, and third thyristors of the valve groups connected to the first and second sets of windings are connected respectively About to the outputs of the pp RZ, ps of the pulse distributor, the control inputs of the first, second and third thyristors of the valve groups connected to the third and fourth sets of windings are connected respectively to the outputs of p2, p4, rb of the pulse distributor, and the control inputs of the fully controlled valves are connected to the pulse distributor via a series-connected element 3 OR and a delay element, with the inputs of element 3 OR located in the control circuit of the fully controlled valve and connected between the left points of the first and second sets of windings are connected to the outputs P3 and pF of the pulse distributor, and the inputs of the OR element 3 located in the control circuit of another fully controlled valve, when Iff Uc Of, f j-h f connected to the outputs of the p, p, p pulse distributor " 2о The converter according to claim 1, о t - which is characterized by the fact that fully controlled valves are made in the form of single-operation thyristors, between which of the same power electrodes the switching capacitors are switched on. I l CD