SU1480062A1 - Twelve-phase converter control method - Google Patents

Abstract

The invention relates to a converter technique and can be used in direct current drives. The purpose of the invention is to improve the power factor. In the method of controlling a twelve-phase converter, consisting in the formation of three-phase systems of currents at the input of the first and second bridges, shifted relative to each other by 30 °, current curves at the input of bridges are proposed to be unlocked and locked by the gate shaper according to the given law, according to which the harmonic of any current at any rectified voltage at the inputs of the bridges, it coincides in phase with the corresponding EMF curve, and at any time the load current is carried out either by a pair of first valves or a pair of veins Ile second bridge. 6 Il.

Description

one

The invention relates to electrical engineering, in particular to converter equipment, and can be used in direct current drives.

The aim of the invention is to increase the power factor.

Figure 1 shows a twelve-phase converter circuit; figure 2 is a functional diagram of the device that implements the proposed method; fig. 3 shows the dependence of the EMF of phase a, the first bridge and the currents of all the gates on the time expressed in angular measurement.

The converter (Fig. 1) contains a transformer 1 with a power winding 2 and a valve winding 3. The valve winding 3 consists of two parts:

part 4, connected in a star, and part- 5, connected in a triangle. In addition, the converter contains two parallel-connected bridges 6, 7, a converter control unit 8, a control pulse driver unit 9. The first bridge 6 is connected in three phases (a, b, c) with part 4 of the valve winding 3. The first bridge contains two groups of thyristors, a cathode group 10 and an anode group 11. Group 10 consists of ns thyristors 12-14, interconnected by cathodes, group 11 - from thyristors 15 - 17, connected by anodes.

The second bridge 7 also contains two groups of thyristors, a cathode group 18 and an anode group 19. The first group

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their gates consist of 20-22, the second consists of gates 23-25.

At the output of the converter, load 26 is turned on.

The device (Fig. 2) consists of a block for isolating the highest voltage, a logic unit 28, a timer 29, a clock circuit 30, electronic switches 31-40, a power supply 4. Block 9 consists of pulse shapers 42–46. The number of keys for the entire converter is 24, and the number of pulse shapers is 12. In FIG. 2 shows five thyristors 12, 15, 16, 21, 24 and the corresponding number of pulse shapers and electronic switches operating on the Q time interval (-45 Ј b -15). In the subsequent 30-degree zones, over the period of the supply voltage 0, only the composition of the thyristor rails changes. For example, the second packet includes thyristors 12, 15, 20, 23, 24 (range -15 ° 9–15 °). A total of 12 thyristor circuits can be identified over the period. Block 27 serves to allocate 30-degree intervals, each of which corresponds to

It is responsible for the work of the next thyristor stack. The inputs of block 27 are supplied with a twelve-phase system of instantaneous line voltages from parts 4 and 5 of winding 3. Block 27 forms a logical signal at the corresponding output at an interval when one of the voltages exceeds the others. We call this interval a zone. At the beginning of each zone, pulses are formed by a chain 30. The same chain provides a reference to the beginning of time. According to the signal of the AOR circuit, the timer 29 generates pulses of duration Q, which may vary depending on the external setpoint. Block 28, logically combining the signals of block 27 and timer 29, generates short pulses of key control 31-40. These keys provide the connection of the formers 42-46 to the source 41. When the keys 31, 33, 35, 37 and 39 are closed, the formers 42-46 form pulses that turn on the corresponding thyristor, and the closure of the keys 32, 34, 36, 38 and 40 causes the formation pulses. The switching order of thyristors of bridges 6 and 7 of the converter is given in the table.

At the first / table interval of the converter, the load current is conducted by thyristors 12, 15. The duration of the first interval is 15/1-X. At the end of the first interval, the electronic switch 35 closes the signal of block 28, which causes the pulse 44 to open and the thyristor unlocks 16 Simultaneously with the unlocking of the thyristor 16, the switch 34 closes, which causes the actuator 43 to operate and lock the thyristor 15. From the moment of unlocking the thyristor 16 and locking the thyristor 15, the second interval starts, at which the load current is conducted by the thyristor Chaps 12 and 16. The duration of the second interval is 30ft.

At intervals of 30, electronic switches 33 and 36 are closed, which leads to unlocking of the thyristor 15 and locking of the thyristor 16. From this moment, the third interval of operation of the converter occurs. At this interval, the load current is carried out by thyristors 12 and 15. The duration of the third interval is equal to the duration of the first, i.e. 15 / 1-.

The processes described for the first zone -45 ° 9 Ј 15 ° are repeated in the next zone (-15 0 Ј 15 °), etc. until the end of the period.

A change in the value of the output voltage is achieved by setting the value via timer 29.

All electronic switches are opened after locking at a certain time interval, measured in microseconds and sufficient to unlock and lock the thyristors.

The current of each phase is equal to the difference of the currents of the corresponding thyristors: on / example, the current of the phase a of the bridge is equal to the difference of the currents of the thyristors 12 and 15 and is shown in FIG. 3. The main harmonic of the phase current coincides in phase with the emf of the phase regardless of the value of the rectified voltage, which leads to an increase in the power factor equal to the ratio of the effective values of the active component of the main harmonic of the current and the current at the converter input. In addition, when controlling the converter according to this method, the input of the converter eliminates

the harmonics are 5, 7, 17, 19, ..., i.e., 6k + 1, where k is an odd number, since symmetrical three-phase current systems shifted by 30 are formed at the input of bridges. At the same time, the current distribution between the bridges is evenly distributed due to the fact that at any moment of time all the load current flows either through a pair of thyristors of bridge 6, or through a pair of thyristors of bridge 7, i.e. bridges are loaded with equal currents.

Claims (1)

Invention Formula Twelve-phase control method a converter on fully controlled thyristors containing two three-phase bridges with anode and cathode thyristors connected in parallel to the load; the inputs of the first bridge are connected to the transformer windings connected in a star; the inputs of the second to the transformer windings connected in a triangle, consisting in that the ratio b of the required value of the rectified voltage to its maximum value, sets the beginning of the time reference and turns on and off the thyristors of both bridges differing from in that, in order to improve the power factor above the reference time is set at the time of the maximum voltage phase and the network, and said activation and deactivation of the thyristors T is produced at the following times: Cactic and First Anodic -30 / (1+ Anodic - and Cathodic and Second anode - b AnodicFirst Table continuation  l FU (f # / h m / b / 14 / J / JV / v A / v 27 / K A / TV / T / Jv / TV / | R F / Tv / J A / ------- ffWcW U ab off ace and bs 6 c to fa1 with cV. Figg J R nineteen , G. F 1 7 & -Ј- / J / jv / v A / v f / tv / j a / J D T Js7 3 30 ° (1 + &