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DEVICES AND METHODS OF ECONOMY AND PRESERVATION OF ELECTRICITY
INVENTION
Patent of the Russian Federation RU2187185

DEVICE FOR COMPENSATION OF REACTIVE POWER

DEVICE FOR COMPENSATION OF REACTIVE POWER

The name of the inventor: Kulinich Yu.M .; Litovchenko VV; Savos'kin A.N.
The name of the patent holder: Far Eastern State Transport University
Address for correspondence: 680021, Khabarovsk, ul. Serysheva 47, Far Eastern State Transport University
Date of commencement of the patent: 2000.02.21

The device for reactive power compensation can be used on the electric AC train to increase the power factor of the locomotive, which is the technical result. The device for reactive power compensation compensates the reactive power with sinusoidal and nonsinusoidal form of the supply voltage and current, as well as with different operating modes of the electric locomotive due to both improving the shape of the input current and by compensating the reactive component of the input current in operating modes different from the nominal ones. The device for reactive power compensation contains a load, a reactive power source consisting of inductively coupled inductance, capacitance and two counter-parallelly connected thyristors, a network mode sensor including a voltage transformer and a current transformer, a synchronizing pulse unit, wherein the load is connected to a supply Network through the network mode sensor and parallel to the reactive power source, the first output of the network mode sensor is connected to the input of the clock pulse unit. A new one is the device for calculating a predetermined current, a subtracter, a four-quadrant converter control unit, a four-quadrant converter, a constant-voltage source, a key element control device, in which the first output of the network mode sensor is connected to the first inputs of the device for calculating the preset current and the device The second output of the network mode sensor is connected to the second input of the current current calculating device and the first input of the subtracter, the output of the predetermined current calculator is connected to the second input of the subtracter whose output is connected to the first input of the four-quadrant converter control unit whose second input is connected to the output Synchronous pulse source, a constant-voltage source through a four-quadrant converter whose input is connected to the output of the control unit of a four-quadrant converter is connected in parallel with the load, the second input of the control device of the key element is connected in parallel to the capacitor of the reactive power source, and its output is connected to the key element. Tests of the device for compensation of reactive power on the locomotive VL65 showed a decrease in electric power consumption by 5-7%.

DESCRIPTION OF THE INVENTION

The device belongs to the electrical engineering and is intended to increase the power factor of consumers, in particular the electric rolling stock of alternating current with thyristor converters.

One of the disadvantages of current AC electric locomotives with smooth voltage regulation (VL65, VL85) is a low power factor, reaching, at best, 0.84. The power factor is one of the main energy indicators of an electric locomotive, which determines its consumption of non-productive reactive power. The operation of an electric locomotive with a low power factor leads to significant energy losses.

When the voltage and current are not sinusoidal, the power factor Km of an electric locomotive is determined by the formula [1]

K m = cos · , (1)

Where - angle of shear between current and voltage;

Is the distortion factor.

The latter coefficient characterizes the degree of distortion of the input current and is determined by the ratio of the first current harmonic to its effective value:



When calculating by the formula (1), the higher harmonic components, characteristic for non-sinusoidal currents and voltages, are taken into account. This relationship is also valid for sinusoidal currents, since = 1 expression (1) takes the form:

K m = cos (3)

Thus, the power factor K m is characterized by the degree of consumption by the electric locomotive of the active and accordingly reactive power, i.e. An increase in K m contributes to an increase in active power and a simultaneous decrease in reactive power.

To increase the power factor due to cos Apply compensating installations in the form of LC-circuits located on the locomotive and connected directly to the secondary winding of its traction transformer. The compensating device increases the power factor by creating a capacitive load and shifting the primary current of the electric locomotive in the direction of advancing the supply voltage.

A device for controlling a compensated rectifier-inverter converter of an electric rolling stock is known [2], which compensates for the reactive power consumed by the load with sinusoidal and non-sinusoidal supply voltage. Compensation is achieved by connecting an inductive capacitive LC compensator to the secondary winding of the electric locomotive transformer with fixed inductance and capacitance parameters. With an inductive load, this causes the appearance of a capacitive current component that compensates for the inductive component. In this case, the phase of the current consumed approaches the supply voltage, contributing to an increase in the power factor of the electric locomotive.

The device comprises a voltage transformer, a load, an LC compensator, a key element, a key element generation device, a trigger trigger, an AND element, a pulse generator, a network voltage sensor, a protection unit, a command unit.

The LC-compensator through the key element is connected in parallel with the load and secondary winding of the voltage transformer, the primary winding of which is connected to the network. The first input of the AND element is connected to the output of the network voltage sensor whose input is connected to the network. The protection unit is connected to the second input of the AND element, whose output is connected to the input "R" of the trigger of the trigger. The inputs of the pulse driver are connected to the capacitor of the compensator and the secondary winding of the transformer, and the output is connected to the input "C" of the trigger of the trigger, the output of which is connected to the control input of the key element via the key element generation unit, the command block is connected to the input "D" of the trigger.

The function of the key element is to turn on the device compensator. In this case, the key element is made in the form of two counter-parallelly connected thyristors. The thyristor of the compensator is activated by the signal from the trigger output triggered through the pulse element generation device of the key element. At the same time, a trigger signal "C" of the trigger triggers a signal from the output of the pulse generator which is generated at the moments of equal voltage on the capacitor of the compensator and the secondary winding of the voltage transformer. The signal at the output of the trigger trigger is formed after the command signal is input to its input "D". In this case, the appearance of the voltage at the output of the flip-flop coincides with the closest moment of equality of the voltages on the capacitor and the transformer.

Closing of the thyristors of the key element occurs either in case of exceeding the allowed voltage in the network, or when the protection is activated. The trip signals are formed respectively by the network voltage sensor and the protection unit. If there is at least one of these signals at the input of the AND element, a signal is input at its input to the trigger "R" input of the trigger trigger reset. This signal leads to the formation of a signal at the output of the flip-flop to close the thyristors of the key element.

Thus, through the key element, the LC compensator is permanently connected to the load, with the main purpose of the control units being to prevent overcurrents that are possible when the LC-compensator is connected to the secondary winding of the transformer and to provide high-speed protection. The converter is protected by removing the control pulses from the thyristors in the event of dangerous currents and voltages.

Tests of the compensation device on the V85 electric locomotive [3] showed that at a compensator power of 520 kVAr (C = 1475 μF), the average power factor of the locomotive is 0.92. With such an increase in the power factor of the electric locomotive, an almost twofold reduction in the consumption of reactive energy for the traction of trains is ensured.

Thus, the use of the LC-compensator of reactive power makes it possible to significantly increase the power factor of an electric locomotive and reduce power losses by reducing the consumption of reactive power.

However, the use of an LC compensator with a constant compensation current increases the power factor of an electric locomotive only at certain (nominal) load currents. The deviation of the electric locomotive load from the nominal results in incomplete compensation of the reactive power, which reduces the efficiency of the device application and the power factor is 0.82-0.85.

In addition, the value of the compensation current in the device is not affected by the higher harmonic components of the current and voltage of the contact network. It is known, however, that the values ​​of these harmonics determine the phase shift between the supply voltage and the electric current consumed by the electric locomotive. Therefore, these quantities must be taken into account when choosing the value of the compensator current.

The device for automatic control of reactive power [4] is also known, which allows changing the compensator current by adjusting the opening angle of the thyristors. In this case, the angle of opening of thyristors is determined by the phase angle of the shift between the main harmonics of the mains current and voltage. The compensator current is regulated in such a way as to ensure a minimum phase shift between the current consumed and the mains voltage. This makes it possible to increase the power factor of an electric locomotive at various load currents.

The device for automatic control of reactive power contains a load, a reactive power source, a network mode sensor, a synchronizing pulse unit, a control unit and a pulse-phase control unit. The load is a thyristor converter. The reactive power source consists of a series-connected inductance, capacitance and two counter-parallelly connected thyristors.

The network mode sensor includes a voltage transformer and a current transformer.

The load is connected to the mains through a current transformer and in parallel to a reactive power source. The voltage transformer is connected in parallel to the supply network, its output is connected to the input of the synchronizing pulse unit, the output of which is connected to the first inputs of the control unit and the pulse-phase control unit. The output of the current transformer is connected to the second input of the control unit. The output of the control unit is connected to the second input of the pulse-phase control unit. The output of the pulse-phase control unit is connected to the thyristors of the reactive power source.

Compensation for reactive power occurs due to the creation of a capacitive component of the load current, which is carried out with the help of a reactive power source. The magnitude of this current is determined by the opening angle of the thyristors entering the reactive power source.

The change in the load power factor is based on the magnitude of the phase angle of the shift between the current and the voltage of the supply network. Such a measurement method is realized with the help of a reactive power sensor, a control unit and a pulse-phase control unit. At the output of the control unit, a voltage proportional to the load power factor is generated. By means of this voltage and the synchronization voltage pulses arriving at the inputs of the pulse-phase control unit, the voltage is converted into the phase of control of thyristors of the reactive power source.

When the power factor, caused by the appearance of a phase angle of shear between the mains current and the voltage, is reduced, the device automatically changes the thyristor opening phase. Changing the opening angle of thyristors leads to an increase in the capacitive component of the reactive power source current flowing in antiphase with the inductive component of the current consumed by the load. This causes a decrease in the phase angle of shear between the supply voltage and the resulting load current, which leads to an increase in the load power factor. This is how the reactive power of the load is compensated in all operating modes of the electric locomotive.

Thus, the known device allows to compensate reactive power in all operating modes of an electric locomotive.

However, reactive power compensation in the device is only possible with a sinusoidal form of the supply voltage and current. This is due to the fact that with a sinusoidal form of voltage and current, the power factor is determined by the angle of shear between these quantities. In this case, the higher harmonic components of current and voltage are not taken into account. With a distorted (nonsinusoidal) form of the supply current and voltage characteristic of AC railways, the power factor is determined by the ratio of the active and full powers consumed by the load. Therefore, the method of measuring the power factor adopted in the device causes a measurement error with a nonsinusoidal current and voltage form, since the active and full power are determined and the higher harmonic components associated with distortions in the shape of the voltage and current. For this reason, the phase angle of the shift only between the fundamental voltage and current harmonics does not fully determine the load power factor. This leads to incomplete compensation of reactive power and deterioration of the electric locomotive's power parameters, therefore the power factor in this case is 0.85-0.88.

It is an object of the invention to provide a device for compensating reactive power in which cos Is increased both by improving the shape of the input current and by decompensating the reactive component of the input current under various operating conditions of the electric locomotive.

The problem is solved by the fact that a reactive power compensation device comprising a load as a thyristor converter is used, a reactive power source consisting of inductively connected inductance, capacitance and two back-to-back thyristors, a network mode sensor including a transformer Voltage and current transformer, a synchronizing pulse unit, the load being connected to the mains through the network mode sensor and parallel to the reactive power source, the first output of the network mode sensor is connected to the input of the clock pulse unit, the current reference calculating device, the subtracter, the unit A four-quadrant converter, a constant-voltage source, a key element control device, wherein the first output of the network mode sensor is connected to the first inputs of the device for calculating the predetermined current and the control device of the key element, the second output of the network mode sensor is connected to the second input of the current- And the first input of the subtractor, the output of the predetermined current calculator is connected to the second input of the subtracter whose output is connected to the first input of the control unit of the four-quadrant converter whose second input is connected to the output of the clock pulse unit, a constant-voltage source through a four-quadrant converter whose input is connected to the output of the unit Control of the four-quadrant converter is connected in parallel with the load, the second input of the control device of the key element is connected in parallel to the capacitor of the reactive power source, and its output is connected to the key element.

The introduction into the device of a set of new elements (a device for calculating a given current, a subtracter, a four-quadrant converter control unit, a four-quadrant converter, a constant voltage source and a key element control device) and their interrelationships allows one to influence the current distortion factor And cos (1.2). This is due to the approximation of the shape of the current being consumed to the sinusoidal by suppressing the higher harmonics and thereby increasing cos Converter with simultaneous compensation of the reactive component of the input current, leading to an increase in cos In different from the nominal operating modes.

One of the reasons for the appearance of reactive power is the non-sinusoidal form of the electric locomotive input current. Thanks to a four-quadrant converter, the claimed device generates an antiphase current harmonic generated by a four-quadrant converter and approximates the current of the electric locomotive to the sinusoidal form due to compensation of higher harmonics. Contrary to the generally accepted opinion, the suppression of higher harmonics contributing to the approximation of the current to the sinusoidal form in the claimed device leads to an increase in cos . Thus, an increase in the distortion coefficient , Achieved as a result of improving the shape of the input current, changes its phase In the direction of approaching the supply voltage. This in turn increases cos Electric locomotive and increases its power factor [5, рис.30].

Simultaneously, the presence of a four-quadrant converter allows to compensate the reactive component of the input current and increase cos In modes other than the nominal.

Thus, cos In the device of reactive power compensation is increased both by improving the shape of the input current, and by decompensating the reactive component of the input current in different from the nominal operating modes. As a consequence, the power factor of the locomotive K M increases in a new way.

The figure shows the scheme of the device for reactive power compensation.

DEVICE FOR COMPENSATION OF REACTIVE POWER

The device for reactive power compensation contains the load 1, the reactive power source 2, the network mode sensor 3, the synchronizing pulse unit 4, the set current calculator 5, the subtractor 6, the four-quadrant converter control unit 7, the four-quadrant converter 8, the constant voltage source 9, the control device A key element 10. The reactive power source 2 consists of the series-connected inductance 11, the capacitance 12 and two counter-parallelly connected thyristors 13, 14. The network mode sensor 3 includes a voltage transformer 15 and a current transformer 16.

The load 1 is connected to the network via a current transformer 16 and parallel to a circuit of inductively connected inductors 11, capacitors 12 and back-to-back thyristors 13, 14. The voltage transformer 15 is connected in parallel to the network, and its output is connected to the input of the synchronizing pulse 4 and to the first The inputs of the device for calculating the preset current 5 and the control device of the key element 10. The output of the current transformer 16 is connected to the second input of the calculating unit 5 and the first input of the subtracter 6. The output of the device for calculating the preset current 5 is connected to the second input of the subtracter 6 whose output is connected to the first The input of the control unit of the four-quadrant converter 7 whose second input is connected to the output of the synchronizing pulse unit 4. The DC voltage source 9 through the four-quadrant converter 8 whose input is connected to the output of the control unit of the four-quadrant converter 7 is connected in parallel with the load 1. The second input of the control device of the key element 10 Is connected in parallel with the capacitor 12 of the reactive power source 2, and its output is connected to the thyristors 13, 14 of the key element.

As the key elements of the four-quadrant converter power IGBT-transistors, the device for calculating the preset current and the control unit for a four-quadrant converter are made on the basis of operational amplifiers and digital microcircuits of medium integration degree, the synchronizing pulse block is made according to the patent [6].

DEVICE FOR COMPENSATION OF REACTIVE POWER CURRENTLY WORKS AS FOLLOWS:

By means of a circuit of the series-connected inductance 11 and capacitance 12 tuned to the frequency of the third harmonic of the supply voltage, the reactive component of the input current of the electric locomotive is compensated in its nominal operating mode. In addition, the LC circuit suppresses the pulsation of the third harmonic of the input current, improving its shape. The thyristors 13, 14 and the control device of the key element 10 are designed to turn the LC compensator on and off when the voltage on the capacitor 12 is equal and the voltage of the network measured at the output of the voltage transformer 15. At the output of the voltage transformer 15 and current 16, a voltage proportional to the instantaneous values ​​of the supply Voltage and current consumption. At the output of the device for calculating the preset current 5, a sinusoidal waveform is generated whose value is determined by the active component of the input current. With the aid of a subtracter 6, a difference signal is determined that is proportional to the distortion of the input current associated with the higher harmonics, as well as the reactive component of the input current. By the magnitude of this signal, the control unit of the four-quadrant converter 7 generates a control voltage of the key elements of the four-quadrant converter. For synchronous operation of the control unit of a four-quadrant converter with a supply network, a synchronizing pulse unit 4 is provided. Due to the energy of the constant voltage source 9, a current is generated at the output of the four-quadrant converter, the antiphase current of the higher harmonics and the reactive component of the input current.

This is how the reactive component of the input current is compensated and cos Both by improving the shape of the input current, and by compensating the reactive component of the input current in operating modes different from the nominal.

The device for reactive power compensation was tested at the Belogorsk depot of the Trans-Baikal Railway. Experienced trips with an electric locomotive VL 65 showed a decrease in the electric power consumption by (5 - 7)%

INFORMATION SOURCES

1. L.A. Bessonov Theoretical Foundations of Electrical Engineering. - M: High School, 1984.

2. А. 1468791 Device for controlling compensated rectifier-inverter converter of electric rolling stock. The inventors VA Kuchumov, V.A. Tatarnikov, N. Shirochenko, Z.G. Bibineishvili. - Opubl. In the BI 12 1989 MKI V 60 L 9/12.

3. NN Shirochenko, V.A. Tatarnikov, ZG. Bibineishvili. Improving the power of AC electric locomotives. - Rail transport, 1988, 7 C. 33.

4. AS 1674306. Device for automatic control of reactive power. Kopanev, B.M. Naumov. I.K. Yurchenko - Opobl. In the BI 32 1991 г МКИ Н 02 J 3/18.

5. B.N. Tikhmenev. Electric locomotives of alternating current with static converters M: State transport railway publishing house, 1958.

6. Patent 2118038. Synchronizing pulse driver. The authors Yu.M. Kulinich and V.V. Kravchuk.

CLAIM

A reactive power compensation device comprising a load, a reactive power source consisting of a series-connected inductor, a capacitor and a key element of two counter-parallelly connected thyristors, a network mode sensor including a voltage transformer connected in parallel to the network and a current transformer, a unit Synchronizing pulses, and the load is connected to the supply network via a current transformer and parallel to the reactive power source, the output of the voltage transformer is connected to the input of the synchronizing pulse unit, characterized in that it additionally includes a device for calculating a predetermined current, a subtracter, a four-quadrant converter, a four- A voltage source, a key element control device, wherein the output of the voltage transformer is connected to the first inputs of the current current calculating device and the key element control device, the current transformer output is connected to the second input of the current current calculating device and the first input of the subtracter, Current is connected to the second input of the subtracter whose output is connected to the first input of the control unit by a four-quadrant converter whose second input is connected to the output of the synchronizing pulse unit, a constant-voltage source through a four-quadrant converter whose input is connected to the output of the control unit by a four-quadrant converter is connected in parallel with the load, The input of the control device of the key element is connected to the capacitor of the reactive power source, and its output is connected to the key element, with the current generated at the output of the four-quadrant converter, the antiphase current of the higher harmonics and the reactive component of the input current, and the sine- The value of which is determined by the active component of the input current.

print version
Published on February 15, 2007