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DEVICES AND METHODS OF ECONOMY AND PRESERVATION OF ELECTRICITY
INVENTION
Patent of the Russian Federation RU2169978

DEVICE FOR AUTOMATIC REGULATION OF REACTIVE POWER

DEVICE FOR AUTOMATIC REGULATION OF REACTIVE POWER

The name of the inventor: Kulinich Yu.M .; Savos'kin AN; Yakimenko V.I.
The name of the patent holder: Far Eastern State Transport University
Address for correspondence: 680021, Khabarovsk, ul. Serysheva, 47, Far Eastern State Transport University, Head of the OPS NF Shcherbakova
Date of commencement of the patent: 1999.04.05

The device for automatic control of reactive power can be used on an AC-powered electromotor composition to increase the power factor of an electric locomotive. The technical result is an increase in the compensation of reactive power with a sinusoidal and non-sinusoidal form of the supply voltage and current, and also for various operating modes of the electric locomotive by approximating the shape of the current consumed to the supply voltage, taking into account higher harmonics and simultaneously reducing the pulsations of the current consumed by the electric locomotive, which reduces the power consumption. The device for automatic control of reactive power contains a load, a reactive power source, a network mode sensor, a synchronizing pulse unit, a pulse-phase control unit, four multipliers, three integrators, a square root calculator and a comparison element. The reactive power source consists of 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 via a current transformer and parallel to the circuit of the series-connected inductors, capacitors and back-to-back thyristors, the voltage transformer is connected in parallel to the network, and its output is connected to the first and second inputs of the first multiplier, the first input of the third multiplier and the input of the pulse synchronization unit . The output of the current transformer is connected to the first and second input of the second multiplier and the second input of the third multiplier. The outputs of the first and third multipliers are connected with the first inputs of the integrators. The outputs of the first and second integrators are connected to the corresponding inputs of the fourth multiplier, whose output through the square root calculation device is connected to the first input of the comparison element. The output of the comparison is connected to the input of the pulse-phase control unit. The output of the pulse synchronization unit is connected to the second inputs of the integrators, the output of the third integrator is connected to the second input of the comparison element, the output of the pulse-phase control unit is connected to the thyristors of the reactive power source.

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. To increase the power factor, compensating installations are used in the form of LC-circuits located on an electric 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 is known for controlling a compensated rectifier-inverter converter of an electric rolling stock [1], which compensates for the reactive power consumed by the load with a 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 consumed current 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. 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 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 enable and disable the device compensator. At the same time, the key element is made in the form of two counter-parallelly connected ti rators. 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 output to the "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, when connecting the LC-compensator to the secondary winding voltage of the transformer and providing high-speed protection. The converter is protected by removing the control pulses from thyristors in the event of dangerous currents and voltages.

Tests of the compensation device on the electric locomotive VL 85 [2] showed that at a compensator power of 520 kVAr (1475 μF) the average value of the 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 [3] is also known, which allows changing the compensator current by adjusting the opening angle of the thyristors. In this case, the opening angle of the thyristors is determined by the phase angle of the shift between the main harmonics of the mains current and the 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 back-to-back 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 load power factor is measured by 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 the 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, full compensation of reactive power in the device is possible only 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 for AC railways, the power factor is determined by the ratio of the active and full powers consumed by the load [4]. 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.

The invention is based on the task of creating an apparatus for automatically regulating reactive power, which allows maximum compensation of reactive power at any (sinusoidal and non-sinusoidal) form of the supply voltage and current, and in various operating modes of the electric locomotive by approximating the shape of the current consumed to the supply voltage Higher harmonics and a simultaneous decrease in the pulsations of the current consumed by the electric locomotive.

The task is achieved by providing a reactive power source comprising a series-connected inductance, capacitance and two counter-parallelly connected thyristors to a device for automatically controlling reactive power, which includes a thyristor converter, a network mode sensor including Voltage transformer and current transformer, synchronizing pulse unit, pulse-phase control unit, the load is connected to the 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 synchronizing pulse unit, the output of the pulse-phase unit Control is connected to the reactive power source thyristors, four multipliers, three integrators, a square root calculator and a comparison element are additionally introduced into it, wherein the first output of the network mode sensor is connected to the first and second inputs of the first multiplier and the first input of the third multiplier, Mode of the network is connected to the first and second inputs of the second multiplier and the second input of the third multiplier, the outputs of the first to third multipliers are connected to the first integrator inputs, the outputs of the first and second integrators are connected to the corresponding inputs of the fourth multiplier, whose output through the square root calculator is connected to the first input The output of which is connected to the input of the pulse-phase control unit, the output of the pulse synchronization unit is connected to the second inputs of the integrators, the output of the third integrator is connected to the second input of the comparison element.

The introduction into the device of a set of new elements (four multipliers, three integrators, a square root calculation device and a comparison element) and their interrelations allows to reliably measure the power factor K m of an electric locomotive at non-sinusoidal current and voltage, and various operating modes, which leads to an increase in the power factor K m , while the consumption of reactive power is reduced to a minimum.

This is due to the fact that the set of characteristics of the device for automatic control of reactive power makes it possible to determine the active and full power consumed by the electric locomotive during the network voltage period. With a nonsinusoidal voltage and current form, the power factor K m of an electric locomotive calculated over a single mains voltage period is determined by the ratio of the active P to the total S power. The total power is defined in the device as the product of the actual values ​​of the voltage U and the current I for one period of the mains voltage:

K m = P / S = P / U · I, (1)

Where P = U · i · dt,

U, I - effective values ​​of voltage and current, determined by the formulas (2):



When calculating by the formula (1), the higher harmonic components, characteristic for non-sinusoidal currents and voltages, are taken into account.

The ratio K m = P / S and is valid for sinusoidal current and voltage. In this case, the active power is determined by the relation P = U · I · cos , Therefore according to (1) K m = cos , Where - phase shift between voltage and current of the network, i.e. In this case, the power factor can be defined as the cosine of the angle of shear between current and voltage.

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. The appearance of reactive power is caused by the phase shift of the current consumed relative to the supply voltage. Therefore, in order to reduce the reactive power, it is necessary to approximate the shape of the current consumed to the form of the mains voltage.

In addition, the use of controlled thyristors in the reactive power compensator makes it possible to compensate the reactive power in all operating modes of the electric locomotive. With the change in the operating mode, the inductive component of the load current is changed, which has a reactive character. The device by changing the thyristor opening phase changes the capacitive current of the reactive power compensator, which ensures compensation of the inductive load current. The change in the load current automatically causes a change in the current of the reactive power compensator, ensuring compensation of reactive power in all modes of operation of the electric locomotive.

Based on the values ​​of the mains voltage u and current i, the device calculates the active P and the total power S consumed by the electric locomotive during the mains voltage period (formulas 1, 2). The difference in the calculated values ​​forms the opening angle of the thyristors of the reactive power compensator, causing the capacitive current to flow through it. The direction of this current is opposite to the inductive component of the load current, so when these currents are added, the total reactive load current decreases. Due to this, the form of the current consumed by the electric locomotive approaches the supply voltage, causing a decrease in the reactive power consumed and an increase in the power factor of the locomotive. In this case, the opening angle of the thyristors of the reactive power compensator is regulated in such a way as to ensure maximum compensation of reactive power and increase the power factor of the electric locomotive.

Thus, the device compensates for reactive power and increases the power factor of an electric locomotive under various operating conditions, as well as with any form of supply voltage and current consumption.

In addition, due to the approach of the current consumption curve i to the form of the mains voltage u, the switching of the consumed current i (changing the current direction to the opposite one) occurs at lower instantaneous values ​​of the mains voltage u. This contributes to a decrease in the ripple of the current i consumed, which is estimated by the current ripple coefficient K n . It is known [7] that a decrease in K n of less than 0.4-0.5 causes an increase in cos And the power factor K m of the locomotive. At the indicated values ​​of K n, the power factor K m of the electric locomotive reaches a stably high level, considerably exceeding this value for values ​​of K n greater than 0.4-0.5.

Thus, the increase in the power factor K m of the locomotive is carried out both by approximating the shape of the consumed current i and the mains voltage u, and by decreasing the ripple factor K n of the consumed current i.

The figure shows the circuit of the device for automatic control of reactive power.

DEVICE FOR AUTOMATIC REGULATION OF REACTIVE POWER

The device for automatic control of reactive power contains a load 1, a reactive power source 2, a network mode sensor 3, a synchronizing pulse unit 4, a pulse-phase control unit 5, four multipliers 6-9, three integrators 10-12, a square root calculator 13 and A comparison element 14. The reactive power source 2 consists of the series-connected inductance 15, capacitance 16 and two counter-parallelly connected thyristors 17, 18. The network mode sensor 3 includes a voltage transformer 19 and a current transformer 20.

The load 1 is connected to the mains via a current transformer 20 and parallel to a circuit of inductively coupled inductors 15, capacitors 16 and back-to-back thyristors 17, 18. The voltage transformer 19 is connected in parallel to the network and its output is connected to the first and second input of the first multiplier 6, The first input of the third multiplier 8 and the input of the pulse synchronization unit 4. The output of the current transformer 20 is connected to the first and second input of the second multiplier 7 and the second input of the third multiplier 8. The outputs of the first to third multipliers 6-8 are connected to the first inputs of the integrators 10-12. The outputs of the first 10 and the second integrator 11 are connected to the corresponding inputs of the fourth multiplier 9 whose output through the square root device 13 is connected to the first input of the comparison element 14. The output of the comparison element 14 is connected to the input of the pulse-phase control unit 5. The output of the pulse synchronization unit 4 Is connected to the second inputs of the integrators 10-12, the output of the third integrator 12 is connected to the second input of the comparison element 14. The output of the pulse-phase control unit 5 is connected to the thyristors 17, 18 of the reactive power compensator 2.

As a multiplier the chip K525PSZ is used, the integrator is executed on the basis of operational amplifier K140UD7, the device of calculation of a square root is made on the basis of operational amplifiers and is described in [5]. The pulse synchronization unit is made according to the patent [6].

The device for automatic control of reactive power operates as follows.

At the output of voltage transformers 19 and current 20, a voltage proportional to the instantaneous values ​​of the supply voltage u and the consumed current i is formed. With the help of multipliers 6-8, these signals are converted. At the output of the multiplier 6, a signal proportional to u 2 is formed. The output signal of multiplier 7 is i 2 . The signal at the output of the multiplier 8 is proportional to the product u · i of the current consumed and the supply voltage. With the help of integrators 10-12, the signals coming to their inputs are integrated. At the end of each network voltage period, the signal at the output of the integrators 10-12 is, respectively: U 2 · dt, I 2 · dt and U · i · dt. The signal at the output of the third integrator 12 is proportional to the active power P consumed by the converter during the mains voltage period. The multiplier 9 and the square root calculator 13 are designed to calculate a signal proportional to the total power S consumed by the converter over the network voltage period. A signal proportional to the total S and active P power is applied to the first and second inputs of the comparison element 14, respectively, from the outputs of the square root calculator 13 and the third integrator 12. At the output of the comparison element 14, a voltage proportional to the difference of these signals is generated. The signal from the output of the comparison element 14 is fed to the input of the pulse-phase control unit 5 where the input signal is converted into a phase of the control pulses of the thyristors 17, 18 of the reactive power compensator 2. The adjustment is reduced to a decrease in the output voltage of the comparison element 14, which corresponds to the maximum reduction Reactive power consumed by the converter due to the creation of a capacitive component of the converter current by means of thyristors 17, 18. Synchronous operation of the integrators 10-12 is provided by the pulse synchronization unit 4.

Thus, using the principle of regulation in terms of the magnitude of the difference between the active and total input powers, it is possible to maximally compensate the reactive power of the load when operating with both sinusoidal and distorted forms of mains voltage and current.

The device for automatic control of reactive power was tested in the Belogorsk depot of the Trans-Baikal Railway on an electric locomotive VL65. The operation of the device allowed to increase the power factor of the locomotive to 0.9 - 0.92 in all modes of its operation, which, in turn, led to a 10-12% decrease in electric power consumption.

INFORMATION SOURCES

1. A.S. 1468791. A device for controlling a compensated rectifier-inverter converter of an electric rolling stock. The inventors VA Kuchumov, V.A. Tatarnikov, NN Shirochenko, ZG Bibineishvili. - Opubl. In the BI. N 12 1989, MKI B 60 L 9/12.

2. NN Shirochenko, VA Tatarnikov, ZG Bibineishvili. Improving the power of AC electric locomotives. - Railway transport, 1988, N 7. S.Z.Z.

3. A.S. 1674306. Device for automatic control of reactive power. The authors of the invention are AS Kopanev, BM Naumov, IK Yurchenko. - Opubl. In the BI. N 32 1991 MKI H 02 J 3/18.

4. LA Bessonov. Theoretical bases of electrical engineering. - Moscow: Higher School, 1984.

5. E.A. Colombet. Microelectronic means for processing analog signals. - M .: Radio and Communication, 1991.

6. Patent No. 2118038. Synchronizing pulse driver. The authors Yu. M. Kulinich and V. V. Kravchuk.

7. B.N.Tikhmenev. Electric locomotives of alternating current with static converters. M.: State Transport Railway Publishing House, 1958.

CLAIM

Device for automatic control of reactive power, containing a load, which uses a thyristor converter, a reactive power source consisting of series-connected inductance, capacitance and two counter-parallelly connected thyristors, a network mode sensor including a voltage transformer and a current transformer, a unit Synchronizing pulses, a pulse-phase control unit, the load being connected to the supply network via the current transformer and parallel to the reactive power source, and the output of the voltage transformer is connected to the input of the synchronizing pulse unit, the output of the pulse-phase control unit is connected to the reactive power source thyristors differing In that four multipliers, three integrators, a square root calculator and a comparison element are additionally introduced thereto, wherein the first output of the network mode sensor is connected to the first and second inputs of the first multiplier and the first input of the third multiplier, the second output of the network mode sensor is connected to the first And the second input of the second multiplier and the second input of the third multiplier, the outputs of the first, second and third multipliers are connected to the first integrator inputs, the outputs of the first and second integrators are connected to the corresponding inputs of the fourth multiplier, whose output through the square root calculator is connected to the first input of the comparison element, The output of which is connected to the input of the pulse-phase control unit, the output of the pulse synchronization unit is connected to the second inputs of the integrators, the output of the third integrator is connected to the second input of the comparison element.

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Published on February 15, 2007