RU2052845C1 - Device for pulse regulation of three-phase voltage - Google Patents

Abstract

FIELD: converters. SUBSTANCE: device has three-phase stepping- up transformer, which secondary winding is connected between corresponding phase terminals for connection of supply line and load. Primary winding of stepping-up transformer is connected between corresponding phase input terminals of two three-phase rectifying bridges. Output of each bridge is by-passed by controlled thyristor or transistor direct current circuit breaker. Starts and ends of phase primary windings of stepping-up transformer are connected to corresponding phase of supply line or load through six triacs. Said six triacs of device are switched off by current break in primary winding of stepping-up transformer by means of direct current circuit breakers at output of three-phase rectifying bridges. Design of device uses minimal number of controlled thyristor or transistor direct current circuit breakers. Device provides smooth regulation of voltage in load up and down with respect to supplying voltage. EFFECT: decreased size and weight, simplified design, simplified control algorithm, decreased cost. 2 dwg

Description

 The invention relates to a converter technique and is intended to regulate or stabilize a three-phase voltage.

 A device for pulse regulation of three-phase voltage [1] which in each phase contains a boost booster double-winding transformer, an additional autotransformer and a semiconductor switch made on five fully controllable keys with two-side conductivity, each of which is, for example, two counter-parallel lockable thyristors or transistor switch.

 The disadvantages of the device are the large weight, dimensions and cost of both the transformer part containing six single-phase transformers and the semiconductor made on fifteen keys with two-sided conductivity.

 It is also known a device for pulse regulation of three-phase voltage [2] containing in each phase a boost transformer, an additional step-down transformer and a bridge switch made on four fully controllable keys with two-side conductivity, each of which is, for example, two counter-parallel lockable thyristors or transistor switch.

 However, this device also has a large weight, dimensions and cost due to the use of three single-phase boost transformers, three single-phase additional transformers and twelve fully controlled keys with two-sided conductivity in it.

 Closest to the claimed one is a device for pulse regulation of three-phase voltage [3] containing several three-phase rectifier bridges, the output of each of which is shunted with a fully controlled key with one-side conductivity, for example, a lockable thyristor, transistor or single-phase thyristor with an artificial switching unit, and a three-phase voltage-boosting multi-winding transformer the secondary winding of which is connected between the network and the load, one of the primary windings is connected between the input of the two three-phase rectifier bridges, and the remaining primary windings are connected between the inputs of the additional three-phase rectifier bridge and the terminal of the secondary windings of additional three-phase transformer.

 The disadvantages of the prototype include the large weight, dimensions and cost of both transformer equipment and a semiconductor switch.

 The purpose of the invention is the improvement of overall dimensions, cost reduction and simplification of the device.

 The goal is achieved by the fact that six triacs are introduced into the device, each of which is connected between the corresponding phase input of the corresponding rectifier bridge and the corresponding phase outputs intended for connection to the network or to the load, and a control pulse shaper with a frequency higher than the network frequency.

 In FIG. 1 shows a schematic diagram of a device; in FIG. 2 timing diagrams for two operating modes.

 The device contains triacs 1-6, DC choppers, for example lockable thyristors 7 and 8, included in the diagonals of the corresponding three-phase rectifier bridges, a high-frequency driver 9 of the control pulses, a three-phase boost transformer 10, input and output terminals 11 and 12, intended for connection to network and load.

 The inputs of two three-phase rectifier bridges, between which the primary winding of the three-phase boost transformer is turned on, are connected to the network through six triacs, the secondary winding of the three-phase boost transformer is connected between the mains and the load, the output of each three-phase rectifier bridge is shunted by a DC chopper, such as a lockable thyristor, and high-frequency outputs control pulse shapers are connected to control electrodes of both lockable thyristors, so and triacs.

 The device in accordance with the proposed control algorithm (Fig. 2) works as follows.

 Regulation of the load voltage upward relative to the mains voltage is performed in the voltage boost mode, which is provided when the DC chopper (lockable thyristor) 8 is turned on at intervals of the high-frequency alternation of the conductive state of the triacs 1, 3, 5 with the conductive state of the DC chopper (lockable thyristor) 7 (Fig. 2a). The triacs 1, 3, 5 are turned on by short-term interruption of the current in the primary winding of the boost transformer 10 by turning off the direct current breaker (lockable thyristor) 8 for the time of restoring the blocking properties of these triacs, and voltage regulation of the boost voltage by changing the duration of the conductive state of the triacs 1, 3, 5.

 Voltage regulation downward relative to the mains voltage is performed in the voltage mode, in which the DC breaker (lockable thyristor) 7 is turned on and triacs 2, 4, 6 are switched from the DC chopper (lockable thyristor) 8 (Fig. 2b). The triacs 2, 4, 6 are turned off by short-term interruption of the current in the primary winding of the boost transformer 10 by turning off the DC breaker (lockable thyristor) 7 for the time of restoring the locking properties of these triacs, and the voltage regulation of the voltage circuit is done by changing the duration of the conducting state of the triacs 2, 4, 6 .

 The device is switched from the voltage boost mode to the voltage mode and vice versa through the intermediate mode, in which three-phase fully controllable switches on three-phase rectifier bridges with DC breakers (lockable thyristors) 7 and 8, the primary winding of the three-phase voltage boost transformer 10 is shorted and the load voltage is equal to the mains voltage.

The voltage at the load is determined by the expression
U ₂ U ₁ 1 + K _t [± Φ (K ωt)] (1) where U ₁ and U _{2 are the} input and output voltages;
K _t transformation ratio;
± Φ (K ωt) is the unit switching function of the reverse switch;
To the multiplicity of increasing the control frequency relative to the network frequency.

From the expression (1) it follows that when Φ (Kωt) changes from +1 to 0 and then from 0 to -1, the output voltage U _{2 is} regulated from (1 + K _t ) U ₁ to U ₁ and then from U ₁ to ( 1 K _t ) U ₁ .

The key switching algorithm of the device for smooth regulation of U ₂ in accordance with expression (1) can be realized by comparing the control voltage U _y with two triangular reference voltages U _op1 and U _{op2 of the} same amplitude (Fig. 2), one of which is shifted up and the other down by an amount exceeding the amplitude value of these reference voltages relative to zero, creating a deadband of the device on the control signal. In FIG. 2 dead zone is hatched. Its value is insignificant and does not exceed the value at which the deviation of the output voltage goes beyond the specified control accuracy. With small values of U _у lying in the dead zone (in the zero region), the device operates in an intermediate mode, in which only DC breakers (lockable thyristors) 7 and 8 are turned on. With a smooth increase in U _y in the positive direction (Fig. 2a) the device smoothly switches to the voltage boost mode, and to the negative (Fig. 2b) in the voltage mode.

 The proposed device as more advanced, made with a minimum number of lockable thyristors, can replace the known AC voltage regulators. The most appropriate use of a device for regulating or stabilizing a three-phase voltage in pro-power units with a capacity of 100-1000 kVA.

Claims (1)

 DEVICE FOR PULSE CONTROL OF THREE-PHASE VOLTAGE, containing a three-phase boost transformer with a secondary winding connected between the corresponding phase terminals for connecting the network and the load, and with a primary winding connected between the corresponding phase inputs of two three-phase rectifier bridges, each of which is controlled by a shunt connected to the corresponding or a transistor DC chopper, characterized in that six triacs are introduced, each of which is switched on by the corresponding phase input of the corresponding rectifier bridge and the corresponding phase output, intended for connection to the network or the load, and a control pulse shaper with a frequency higher than the network frequency.

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