RU2056692C1 - Transformer-thyristor reactive-power corrector - Google Patents

Abstract

FIELD: a.c. voltage regulation and reactive-power correction in devices using stepless control of load voltage amplitude and phase. SUBSTANCE: corrector has transformer, inverter, reversing rectifier, sensors of reactive component of supply mains current or power and load voltage, switch. Setting signal and signal picked off load voltage sensor are applied to subtractor inputs. Differential signal is sent to inverter control system. Amplitude of combined load voltage vector is regulated by varying control angle of inverter thyristors. Signal coming from supply mains current or power reactive component sensor goes to pulse-phase control system of reversing rectifier and controls reactive power consumed from mains by varying control angle of rectifier thyristors. EFFECT: provision for correcting reactive power with desired load voltage stability irrespective of external characteristic of supply mains and magnitude and type of load. 3 dwg

Description

 The invention relates to electrical engineering, in particular to reactive power compensation devices, and can be used to create power units of industrial and agricultural facilities with high efficiency of use and consumption of electricity and stable voltage.

 Known transformer-thyristor regulating device [1] which contains a first three-phase transformer including a primary, one control and two secondary windings, a second three-phase transformer including a primary, control and secondary windings, and a thyristor switch. The primary windings of the transformers are connected in series and connected to the load, and the two secondary windings of the first transformer are interconnected, connected to the network and the secondary winding of the second transformer, while the control windings of both transformers are closed by means of a thyristor switch.

 The device provides interconnected regulation of the amplitude and phase of the output voltage. In this case, only one of these parameters can be purposefully acted upon, while the nature of the change in the other is determined by the winding switching circuit.

 The main disadvantages of the device include the large weight and dimensions, installed power and cost of transformers. The device requires special, complex transformers in design, which complicates its production.

 A transistor-thyristor device for controlling reactive power [2] is also known, which contains two three-phase transformers and two thyristor switches with control systems. The primary windings of both transformers are connected in series and connected between the network and the load, and the secondary windings are combined through the first thyristor switch, while the second thyristor switch switches only sections of the secondary winding of the first three-phase transformer. This device is designed to control the phase of the load voltage relative to the mains voltage.

 However, this device also has drawbacks, including a large weight and dimensions, installed power and cost of transformers, as well as the need to design and manufacture special transformers.

 The known transistor-thyristor reactive power compensator, taken as a prototype [3] contains two three-phase transformers, two inverters with control systems and a rectifier. The primary windings of both transformers are connected in series to the load circuit, and the secondary are connected to a star and connected respectively to the first and second inverters, the inputs of which are combined and connected through the rectifier to the network or to the load. The synchronizing inputs of the control systems of the first and second inverters are connected to the network, and their control inputs, respectively, to the output of the reactive power sensor of the network and to the output of the subtractor. The inputs of the subtractor are respectively connected to the block of the driving signal and the output of the voltage sensor.

 The device provides full compensation of the input reactive power and stabilization of the effective value of the output voltage, regardless of the external characteristics of the network, as well as the magnitude and nature of the load.

 However, it also has drawbacks, which primarily include the need to use special transformers that require experimental design, as well as the large weight, dimensions and installed power of the transformers, which makes both the development and manufacture of such devices more expensive. These shortcomings are caused by two circumstances. Firstly, these transformers, when quickly controlling the reactive power and the actual value of the output voltage, are prone to one-sided magnetization due to the large amplitude of the phase of the output voltage of the first and second inverters and, to avoid saturation at the required speed, they require the use of magnetic cores with a calculated induction underestimated by about 20-25% those. the next size from the standard range. Secondly, two transformers are used in the device.

 The purpose of the invention is the improvement of overall dimensions and a reduction in the installed capacity of transformer equipment and, as a result, a reduction in the cost of the device while maintaining speed and functionality.

 The goal is achieved in that the other terminals of the primary winding of the transformer are connected to the network and a reversible rectifier is used as a rectifier, which includes a valve block, an output inductance-capacitive filter and a pulse-phase control system synchronized with the voltage at the output terminals of the rectifier, the control input being pulse-phase control system is connected to the output of the reactive power sensor (reactive current) of the network.

, при котором устройство обеспечивает полную компенсацию среднестатистического значения коэффициента мощности пром- и агропромпредприятий. В предлагаемом устройстве высвобождается один инвертор и возможно применение стандартного рекуперативного тиристорного преобразователя со звеном постоянного тока, что также относится к снижению затрат на такие изделия. За счет изменения в устройстве способа амплитудно-фазового формирования напряжения вольтодобавки устраняется подмагничивание трансформатора и уменьшается его установленная мощность и, как следствие, улучшаются массогабаритные показатели устройства в целом.The advantage of the device is that, while maintaining speed, it requires lower costs for transformer equipment both in design and in production. It can be used widespread dry conversion transformer protected or unprotected execution with a transformation ratio equal to 1/1 /

, in which the device provides full compensation of the average value of the power factor of industrial and agricultural enterprises. In the proposed device, one inverter is released and it is possible to use a standard regenerative thyristor converter with a DC link, which also relates to reducing costs for such products. Due to a change in the method of the method of amplitude-phase formation of voltage boost voltage, the magnetization of the transformer is eliminated and its installed power is reduced and, as a result, the overall dimensions of the device are improved.

 In FIG. 1 is a schematic diagram of the power section of a transistor-thyristor reactive power compensator; in FIG. 2 and 3 vector diagrams of the compensator operating modes.

 The compensator includes a transformer 1, an inverter 2 with a control system 3 synchronized with the network, a reversible rectifier 4, which includes a valve block 5, an output inductance-capacitive filter 6 and a pulse-phase control system 7 synchronized with the voltage at the input terminals of the rectifier. In addition, the compensator comprises a sensor 8 for reactive power or network current, a load voltage sensor 9, a subtractor 10, and a load 11.

,

и

соответственно напряжения сети, нагрузки и инвертора;

,

и

соответственно токи потребления сети, нагрузки и выпрямителя; Φ₁ и Φ₂ углы между током и напряжением соответственно сети и нагрузки; α_в и α_и углы управления тиристорами соответственно выпрямителя и инвертора; К_т коэффициент трансформации.In FIG. 2 and 3

,

and

respectively, the mains voltage, load and inverter;

,

and

respectively, the currents of the network, load and rectifier; Φ ₁ and Φ _{2 are the} angles between current and voltage, respectively, of the network and load; α _in and α _{and the} control angles of the thyristors, respectively, of the rectifier and inverter; K _t transformation ratio.

 Transformer-thyristor reactive power compensator operates as follows.

формируется из напряжения сети

и напряжения инвертора 2

регулируемого по величине и фазе соответственно углами α_в и α_и Напряжение на выходе инвертора 2

= K_в•K_и•U₁•F(α_в)

(1) где F( α_в) передаточная функция реверсивного выпрямителя 4;
К_в и К_п коэффициенты передачи напряжения соответственно выпрямителя 4 и инвертора 2.Compensator output voltage

formed from mains voltage

and voltage inverter 2

adjustable in magnitude and phase, respectively, the angles α _in and α _{and the} voltage at the output of the inverter 2

= K _in • K _and • U ₁ • F (α _in )

(1) where F (α _in ) the transfer function of the reversing rectifier 4;
K _in and K _p the transmission coefficients of the voltage, respectively, of the rectifier 4 and inverter 2.

уменьшается в коэффициент трансформации К_т раз и прибавляется к напряжению сети

В результате этого выражение для напряжения нагрузки 11

имеет вид

=

+K_т•K_п•U₁•F(α_в)e

-

(2) где

сопротивление короткого замыкания трансформатора;
K_п=K_в·K_и коэффициент передачи напряжения тиристорного преобразователя со звеном постоянного тока.Using transformer 1, the output voltage of inverter 2

decreases in the transformation coefficient K _t times and is added to the mains voltage

As a result, the expression for load voltage 11

has the form

=

+ K _t • K _p • U ₁ • F (α _c ) e

-

(2) where

short circuit resistance of the transformer;
K _p = K _in · K _and the voltage transfer coefficient of the thyristor converter with a DC link.

=U

1+K_т•F(α_в)e

-

Из выражения (2) и векторных диаграмм (фиг. 2 и 3) видно, что модуль и аргумент вектора напряжения нагрузки

можно регулировать изменением углов управления выпрямителем α_в и инвертором α_и В компенсаторе изменение угла α_в осуществляется в функции отклонения реактивной мощности сети от нулевого уровня, а изменение угла α_и в функции отклонения напряжения нагрузки от заданного уровня, например, равного минимальному напряжению сети. При активно-индуктивной нагрузке и потреблении (генерации) компенсатором реактивной мощности сигнал с выхода датчика 8 реактивной мощности (тока) сети поступает на управляющий вход системы 7 импульсно-фазового управления реверсивным выпрямителем 4 и, уменьшая (увеличивая) угол управления реверсивного выпрямителя α_в осуществляет увеличение (уменьшение) действующего значения выходного напряжения инвертора

и соответственно увеличивая (уменьшая) фазу вектора выходного напряжения

, опережающего вектор напряжения сети

. При этом датчик 9 напряжения, осуществляя контроль за изменением напряжения нагрузки 11, подает сигнал обратной связи на первый вход вычитателя 10, характеризующего уменьшаемое, на второй вход которого, характеризующего вычитаемое, подается сигнал, пропорциональный заданному значению напряжения нагрузки, например соответствующему номинальному напряжению сети. Разность этих сигналов с выхода вычитателя 10 подается на управляющий вход системы 3 управления инвертором 2, которая, изменяя угол управления тиристорами инвертора 2 α_и осуществляет регулирование фазы выходного напряжения инвертора 2

и действующего значения выходного напряжения

. В результате такого амплитудно-фазового воздействия на выходное напряжение инвертора 2 вектор этого напряжения

так формирует свой модуль и аргумент, и что вектор напряжения нагрузки 11

. является радиусом заданной окружности.Bearing in mind that for bridge circuits of the rectifier and inverter with the same number of phases K _p ≈ 1, get

= U

1 + K _t • F (α _in ) e

-

From the expression (2) and vector diagrams (Fig. 2 and 3) it can be seen that the module and the argument of the load voltage vector

can be controlled by changing the control angles of the rectifier α _in and the inverter α _and In the compensator, the change in the angle α _{in is} performed as a function of the deviation of the reactive power of the network from the zero level, and the change in the angle α _and in the function of the deviation of the load voltage from a given level, for example, equal to the minimum network voltage. When the active-inductive load and consumption (generation) by the reactive power compensator, the signal from the output of the reactive power (current) sensor 8 of the network is supplied to the control input of the pulse-phase control system 7 of the reverse rectifier 4 and, decreasing (increasing) the angle of control of the reverse rectifier α _in increase (decrease) in the actual value of the inverter output voltage

and accordingly increasing (decreasing) the phase of the output voltage vector

leading the voltage vector

. In this case, the voltage sensor 9, monitoring the change in the load voltage 11, feeds a feedback signal to the first input of the subtractor 10, characterizing the decrease, the second input of which characterizing the subtracted signal, is proportional to the set value of the load voltage, for example, corresponding to the rated voltage of the network. The difference of these signals from the output of the subtractor 10 is fed to the control input of the control system 3 of the inverter 2, which, by changing the angle of control of the thyristors of the inverter 2 α _and regulates the phase of the output voltage of the inverter 2

and the actual value of the output voltage

. As a result of this amplitude-phase effect on the output voltage of the inverter 2, the vector of this voltage

thus forms its module and argument, and that the load voltage vector 11

. is the radius of the given circle.

 With an active capacitive load, the compensator works similarly, but at the same time, the output voltage of the inverter 2 is formed in the region of the lag of this voltage from the mains voltage.

 In the process of stabilizing the output voltage at a lower (increased) value of the mains voltage relative to a predetermined, for example, rated value, reversible rectifier 4 operates in the rectifier (inverter) mode, providing the transformer 1 and the entire device with operation in the voltage boost mode (voltage isolation) with the consumption of additional energy from the network (with energy recovery in the network).

 During the process of transition of the reversible rectifier 4 from the rectifier mode to the inverter mode and vice versa, the energy supplied to the DC link is accumulated in the filter 6 and then discharged through the inverter 2 and transformer 1 to the load 11 in the voltage mode, in the voltage mode through the reversed rectifier 4 returns to the network.

 Using a compensator allows full compensation of reactive power in various alternating current systems to ensure a given stability of the effective value of the output voltage, regardless of the rigidity of the external characteristics of the network, as well as the magnitude and nature of the load.

Claims (1)

 A REACTIVE POWER TRANSFORMER-THYRISTOR COMPENSATOR containing a rectifier with input terminals connected to a network or a load, an inverter with a control system synchronized with the network, a transformer with a primary winding connected by one output to the load and a secondary winding connected to the star and connected to the output inverter a sensor for the reactive component of the current or power of the network, which includes two single-phase current transformers with primary windings included in the gap of the two phases of the network, load voltage sensor, the output of which is connected to the first subtraction input characterizing the deductible, and its second input characterizing the deductible, connected to the driving signal, the output characterizing the difference is to the control input of the inverter control system, characterized in that the other terminals of the transformer primary winding connected to the network, a reversible rectifier is used as a rectifier, which includes a valve block with a system synchronized with the voltage at the input terminals of the rectifier pulse-phase control and an inductive-capacitive filter is introduced, connected between the output of the rectifier and the input of the inverter, and the control input of the pulse-phase control system of the reverse rectifier is connected to the output of the sensor of the reactive component of the current or power of the network.

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