RU2734554C1 - Device for control of three-phase three-level active voltage rectifiers - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to the field of power conversion equipment and can be used for control of three-phase three-level active voltage rectifiers of voltage of high-voltage frequency converter as at rated mains voltage, and at short-term asymmetric failure of mains voltage. Device for control of three-phase three-level active voltage rectifiers is additionally equipped with fourth coordinate conversion unit (20), first (21) and second (22) low-pass filters, fifth coordinate conversion unit (23), inverting unit (24), in addition, unit of proportional-integral current controllers (13) includes first (25) and second (26) units of proportional-integral current controllers, second (27), third (28) and fourth (29) subtraction units, third adder unit (30), first (31) and second (32) crosstalk compensation units. Proposed control device improves operating reliability of active voltage rectifiers due to improved control system, which limits increase in phase currents of rectifiers during short-term asymmetric voltage failure of three-phase power supply source, and also limits swing of voltage fluctuation on capacitors of DC link of active rectifiers within allowable values. Besides, due to introduction of low-pass filters into control system efficiency of active rectifiers and reliability of operation of high-voltage frequency converter as a whole is increased.

EFFECT: technical result consists in creation of improved control system, which limits increase in phase currents of three-phase three-level active rectifier during short-term asymmetric voltage failure of three-phase power supply source, reduces number of false actuations of active rectifier switches due to introduction of low-pass filters into control system, and also limits swing of voltage fluctuation on capacitors of DC link of active rectifier within allowable values.

1 cl, 8 dwg

Description

The invention relates to the field of power converting equipment and can be used to control three-phase three-level active voltage rectifiers of a high-voltage frequency converter, both at the nominal mains voltage and with a short-term asymmetrical mains voltage dip.

Known high-voltage high-power frequency converter with active rectifiers, containing the first and second phase-shifting transformers, respectively at 0 and +30 degrees, the primary winding of the first phase-shifting transformer has six terminals and is connected in series with the primary winding of the second phase-shifting transformer, which is connected to a star, while the beginning the primary winding of the first phase-shifting transformer is connected to a power source, the secondary windings of these transformers are connected in a star and a delta and connected, respectively, to the first and second frequency converters, each of which consists of a three-level active rectifier, a three-level voltage inverter and a choke, with the same output phase terminals frequency converters are interconnected and connected to the AC motor, and the inputs of the DC link common for both frequency converters with a zero point are connected to the outputs of both ac rectifiers, the outputs of the specified link are connected to the inputs of both voltage inverters, a DC link voltage setting unit, a reactive power setting unit and a control system including a voltage sensor and a power supply current sensor, a DC link voltage sensor, a power supply voltage unbalance sensor, a unit correction of phase voltages of active rectifiers and the control unit, while the first and second inputs of the control unit are connected, respectively, to the DC link voltage setting unit and the reactive power setting unit, the third input of the control unit is connected to the output of the power supply voltage sensor, the input of the specified sensor is connected to the source power supply, the fourth input of the control unit is connected to the output of the current sensor of the power supply, the input of which is connected to the junction point of the primary windings of the first and second phase-shifting transformers, the fifth input of the control unit is connected to the output of the constant voltage sensor current, the inputs of which are connected to the outputs of the DC link with a zero point, and the output of the control unit is connected to the first input of the phase voltage correction unit of active rectifiers, the first and second outputs of which are connected to the control inputs of three-level active rectifiers, respectively, of the first and second frequency converters, when In this case, the second input of the phase voltage correction unit of active rectifiers is connected to the latter through the power supply voltage unbalance sensor (see. RF patent No. 157682, Н02M 5/458).

Let us note the peculiarity of the operation of an active voltage rectifier with a short-term asymmetrical voltage drop in the network. From the course of the theoretical foundations of electrical engineering, it is known that with asymmetric voltage dips, three-phase power supplies, in addition to the positive sequence voltage, also contain a negative sequence voltage. If, at the same time, there is no such negative sequence voltage from the side of the three-phase active rectifier, then this will lead to an increase in its individual phase currents twice or more. This is due to the fact that the values of these currents are limited only by the reactance of the reactors or the leakage reactance of the transformers, which are installed at the input of the active rectifier.

Thus, in case of short-term asymmetrical mains voltage dips, in order to increase the reliability of the operation of frequency converters with active voltage rectifiers, it is necessary to create an effective rectifier control system. The specified control system, when unbalance appears, must form a voltage of both direct and negative sequence at the input of the active rectifier. The latter will weaken the effect of the negative sequence voltage of the three-phase power supply, which will limit a significant increase in its individual phase currents.

In the known device, the control system uses the method of pulse-width modulation (PWM) with the removal of eight isolated voltage harmonics and nine switchings of the active rectifier keys for a quarter of the period of the mains voltage. From literary sources it is known that the specified modulation method is widely used in control systems of powerful electric drives of rolling mills (Khramshin TR, Krubtsov DS, Kornilov GP Methods of pulse-width modulation of powerful active rectifiers with voltage asymmetry. : online electronic scientific journal. 2014. Volume 2, No. 4. P. 7 - 13).

Let us note a distinctive feature of the PWM method with the removal of selected harmonics in the known device. First, this method makes it possible to exclude from the canonical series of a twelve-pulse rectification circuit eight harmonics of voltages - 11, 13, 23, 25, 35, 37, 47, 49 for a symmetrical mode of operation of the power supply, or eight harmonics - 3, 5, 7, 9 , 11, 13, 15, 17 for unbalanced operation of the power supply. This ensures, for the indicated operating modes, a correspondingly good and satisfactory electromagnetic compatibility of the active rectifier with the mains supply. Secondly, the PWM method with the removal of the allocated harmonics makes it possible to reduce the switching frequency of the switches of the active voltage rectifier, which reduces heat losses in these switches and in phase-shifting transformers, which means that it increases the efficiency of the device. Thus, the low switching frequency of the power switches provides an acceptable harmonic composition of the transformer currents and voltage at the point of common connection.

Note that the PWM method with the removal of the selected harmonics provides for preliminary calculations, the purpose of which is to create a database - the dependence of the switching angles on the modulation coefficient (Khramshin T.R., Krubtsov D.S., Kornilov G.P. Evaluation of pulse-width voltage modulation of active rectifiers of rolling mills. Mechanical engineering: network electronic scientific journal. 2013. No. 2. P. 48 - 52). For the known device, the dependences of nine switching angles on the modulation coefficient are calculated. To calculate the indicated angles in this PWM method, an objective function is set, which takes into account two conditions: maintaining the first harmonic at the level specified by the modulation coefficient; reducing the level of higher harmonics in the current to the desired value. In the known device, the phase voltage correction unit stores a database for nine switching angles depending on the value of the modulation factor for symmetrical and unbalanced operating modes of the power supply. Note that in the asymmetrical mode of operation of the power supply during the period of the mains voltage, the value of the modulation coefficient and the values of the switching angles change.

The disadvantage of the known device is its low reliability, since at the initial moment of the appearance of asymmetry, a surge of one of the phase currents of the active rectifier is observed, which can exceed the rated current by 2 times or more, which leads to the operation of the current protection of the device and its shutdown. In addition, a significant increase in the active rectifier current causes an increase in the voltage swing across the DC link capacitors above the maximum permissible value, which also leads to the operation of the protection of the known device for rectified voltage and its shutdown.

Let us explain why there is a surge of one of the phase currents of the active rectifier. In the known device, a power supply voltage unbalance sensor is installed, which switches the operating mode of the control system from the "symmetric" control mode to the "asymmetric" control mode. The principle of operation of this sensor is based on the detection of positive and negative sequence voltages in the mains voltage. If the unbalance sensor has not detected a negative sequence voltage, the control system maintains the "symmetrical" control mode. If the unbalance sensor detects negative sequence voltages as part of the mains voltage, the control system switches to "asymmetrical" control mode.

The process of decomposition of the mains voltage into direct and reverse sequences leads to a time delay in the formation of the control signal for the keys of the active rectifier. This time can be up to half a period or, at best, a quarter of the mains voltage period. The specified delay has a tangible effect when unbalance occurs, since it leads to a delay in switching the active rectifier control mode from "balanced" mode to "unbalanced" mode. In this case, in the phase with the greatest difference between the voltage of the power source and the first harmonic of the voltage of the active rectifier, a current surge is observed that significantly exceeds the rated current, which reduces the reliability of the known device.

The closest analogue to the claimed invention is a control device for three-phase three-level active voltage rectifiers containing a high-voltage frequency converter, the input of which is connected to a three-phase power supply through a three-phase current sensor, the output of the specified frequency converter, which contains two active voltage rectifiers, a common DC link and two voltage inverter connected to the AC motor, the measuring outputs of the current sensor are connected to the first input of the active rectifier control system, the information outputs of the three-phase voltage sensor are connected to the second input of the control system, the inputs of which are connected to the junction point of the output of the three-phase current sensor and the input of the high-voltage frequency converter, the output of the DC link voltage sensor is connected to the third input of the control system, the inputs of which are connected to the information output of the high-voltage frequency converter, to The voltage regulator on the DC link capacitors of the frequency converter is connected to the fifth input of the control system, the regulator of the reactive component of the mains current is connected to the fifth input of the control system, the control output of the control system via the control bus is connected to the control input of the high-voltage frequency converter through the block of pulse-width modulators, while the control system for active voltage rectifiers contains the first coordinate transformation unit, a phase-locked loop, a proportional-integral current regulator, a proportional-integral rectified voltage regulator, a first subtraction unit, a second coordinate transformation unit, first and second adders, a third coordinate transformation unit, the first, second and third inputs of the first coordinate transformation block are connected to the first input of the control system, the fourth input of the said block is connected to the first output of the phase-locked loop, the first and second outputs of the first coordinate transformation unit are connected, respectively, to the first and second inputs of the proportional-integral current regulators, the second output of the phase-locked loop is connected to the third input of the current control unit, the first, second and third inputs of which are connected to the second input of the control system, the fourth input of the block of proportional-integral current regulators is connected to the fifth input of the control system, the fifth input of the block of current regulators is connected to the output of the block of proportional-integral regulator of rectified voltage, the input of which is connected to the output of the first subtraction block, the first and second inputs of which are connected respectively to the fourth and the third inputs of the control system, the first and second outputs of the block of proportional-integral current controllers are connected respectively to the first and second inputs of the second coordinate transformation block, the third input of which is connected to the first output of the phase-locked loop frequency, the first and second outputs of the second coordinate transformation unit are connected respectively to the first input of the first and to the first input of the second adders, the outputs of which are connected respectively to the first and second inputs of the third coordinate transformation unit, the third input of which is connected to the first output of the phase-locked loop, the outputs of the third coordinate transformation unit via the control bus are connected to the control output of the control system (see. RF patent No. 161102, Н02M 7/00).

The disadvantage of the known device, which is taken as a prototype, is low reliability, since at the initial moment of the appearance of asymmetry, a surge of one of the phase currents of a three-phase three-level active rectifier is observed, which can exceed the rated current by 2 times or more, which leads to the operation of the current protection of the device and turning it off. In addition, in the steady state, there may be an asymmetry of the phase currents of the active rectifier, as well as an increase in the swing of the voltage fluctuation on the DC link capacitors above the maximum permissible value, which also leads to the operation of the protection of the known device for the rectified voltage and its disconnection.

The inrush current and the asymmetry of the phase currents of the active rectifier are due to the fact that in the combined control method (by deviation and by perturbation) of the known control system, voltage control of the negative sequence of the mains voltage (perturbation control channel) is used. The disadvantage of this control channel is that the formation of the negative sequence voltage signal is carried out with a time delay of half a period, or at best, a quarter of a period relative to the mains voltage. The specified time delay leads to the fact that the control signals of the power switches of the active rectifier form the input phase voltages of the rectifier containing the negative sequence voltage, which also has a time delay of half a period, or at best, a quarter of a period relative to the negative sequence voltage of the mains voltage. Thus, the delayed negative sequence voltage of the active rectifier does not effectively suppress the negative sequence voltage of the mains voltage. In this case, as previously noted, at the initial moment of the appearance of asymmetry, a surge of one of the phase currents of the active rectifier is observed, and in the steady state, there may be an asymmetry of the phase currents of the active rectifier, as well as voltage fluctuations in the DC link, which leads to the shutdown of the rectifier. All of the above reduces the reliability of the rectifier.

The technical problem solved by the inventive control device is to increase the reliability of the three-phase three-level active voltage rectifier and increase its efficiency in the event of a short-term asymmetrical voltage dip of the three-phase power supply.

The technical result created by the invention consists in creating an improved control system that limits the increase in phase currents of a three-phase three-level active rectifier with a short-term asymmetrical voltage drop of a three-phase power supply, reduces the number of false alarms of the active rectifier keys, due to the introduction of low-pass filters into the control system, and limits the range of voltage fluctuations on the DC link capacitors of the active rectifier within the permissible values.

The problem is solved by the fact that the control device for three-phase three-level active voltage rectifiers containing a high-voltage frequency converter, the input of which is connected to a three-phase power supply through a three-phase current sensor, the output of the specified frequency converter, which contains two active voltage rectifiers, a common DC link and two inverters voltage is connected to the AC motor, the measuring outputs of the current sensor are connected to the first input of the active rectifier control system, the information outputs of the three-phase voltage sensor are connected to the second input of the control system, the inputs of which are connected to the junction point of the output of the three-phase current sensor and the input of the high-voltage frequency converter, to the third the input of the control system is connected to the output of the DC link voltage sensor, the inputs of which are connected to the information output of the high-voltage frequency converter, to the fourth input of the control system the voltage regulator on the DC link capacitors of the frequency converter is connected, the reactive component of the mains current is connected to the fifth input of the control system, the control output of the control system via the control bus is connected to the control input of the high-voltage frequency converter through the block of pulse-width modulators, while the control system is active voltage rectifiers contains a first coordinate transformation unit, a phase-locked loop, a block of proportional-integral current regulators, a proportional-integral regulator of a rectified voltage, a first subtraction unit, a second coordinate transformation unit, first and second adders, a third coordinate transformation unit, the first, second and the third inputs of the first coordinate transformation unit are connected to the first input of the control system, the fourth input of this unit is connected to the first output of the phase-locked loop, the first and second outputs are The first coordinate transformation unit is connected to the first and second inputs of the proportional-integral current controllers, respectively, the second output of the phase-locked loop is connected to the third input of the current control unit, the first, second and third inputs of which are connected to the second input of the control system, the fourth input of the unit is proportional to - integral current regulators is connected to the fifth input of the control system, the fifth input of the current regulator unit is connected to the output of the proportional-integral regulator of rectified voltage, the input of which is connected to the output of the first subtraction unit, the first and second inputs of which are connected respectively to the fourth and third inputs of the control system , the first and second outputs of the block of proportional-integral current controllers are connected respectively to the first and second inputs of the second coordinate transformation block, the third input of which is connected to the first output of the phase-locked loop, the first and the second outputs of the second coordinate transformation block are connected respectively to the first input of the first and to the first input of the second adders, the outputs of which are connected respectively to the first and second inputs of the third coordinate transformation block, the third input of which is connected to the first output of the phase-locked loop, the outputs of the third coordinate transformation block via the control bus are connected to the control system outputs of the control system, according to the invention, the control device is additionally equipped with a fourth coordinate transformation unit, first and second low-pass filters, a fifth coordinate transformation unit, an inverting unit, in addition, the unit of proportional-integral current regulators includes the first and the second blocks of proportional-integral current regulators, the second, third and fourth subtraction blocks, the third summation block, the first and second blocks of cross-link compensation, the first, second and third inputs of the fourth conversion block i coordinates are connected to the second input of the control system, the fourth input of the fourth block is connected to the output of the inverting unit, the input of which is connected to the first output of the phase-locked loop, the first and second outputs of the fourth coordinate transformation unit, respectively, through the first and second low-pass filters are connected to the first and the second inputs of the fifth coordinate transformation unit, the third input of the fifth unit is connected to the output of the inverting unit, the first and second outputs of the fifth coordinate transformation unit are connected respectively to the second input of the first and to the second input of the second adders, the first and second inputs of the second subtraction unit are connected to the fifth and to the first inputs of the block of proportional-integral current controllers, the output of the second block of subtraction is connected to the input of the first block of proportional-integral current controllers, the output of which is connected to the first input of the third block of summation, the first and second inputs of the third block are connected to Subtractions are connected respectively to the fourth and second inputs of the block of proportional-integral current controllers, the output of the third block of subtraction is connected to the input of the second block of proportional-integral current regulators, the output of which is connected to the first input of the fourth block of subtraction, the first input of the first and first input of the second blocks of compensation cross-links are connected respectively to the first and second inputs of the block of proportional-integral current regulators, the second inputs of the compensation blocks are connected to the third input of the block of proportional-integral current regulators, the output of the first block of cross-link compensation is connected to the second input of the fourth subtraction block, the output of which is connected to the second the output of the block of proportional-integral current regulators, the output of the second block of compensation of cross-links is connected to the second input of the third block of summing, the output of which is connected to the first output of the block of proportional-integral regulators current.

The essence of the invention is illustrated by drawings, where:

- in Fig. 1 shows a functional diagram of a control device for three-phase three-level active voltage rectifiers of a high-voltage frequency converter;

- in Fig. 2 shows a functional diagram of a high-voltage frequency converter;

- in Fig. 3 shows a diagram of a three-phase three-level active voltage rectifier;

активного выпрямителя за четверть периода сетевого напряжения;- in Fig. 4, a shows the shape of the phase voltage at the input of a three-phase three-level active rectifier, and also indicates nine angles of switching keys

active rectifier for a quarter of the period of the mains voltage;

от коэффициента модуляции

;- in Fig. 4, b shows the dependences of nine switching angles of the keys of the active rectifier

on modulation index

;

- in Fig. 5 shows the shape of the phase voltage at the input of a three-phase three-level active rectifier, which contains false alarms;

и

, которые содержат высокочастотные составляющие;- in Fig. 6 shows oscillograms of the mains voltage components

and

that contain high frequency components;

- in Fig. 7, a shows the oscillograms of the phase currents of the active rectifier for the claimed control system;

- in Fig. 7, b shows an oscillogram of the voltage of a link of a constant high-voltage frequency converter for the claimed control system;

- in Fig. 7, c shows the dependence of the relative value of the modulation coefficient for the claimed control system;

- in Fig. 8 shows oscillograms of phase currents of an active rectifier for a known control system (for a prototype).

The claimed control device (Fig. 1) three-phase three-level active voltage rectifiers, contains a high-voltage frequency converter 1, the input of which through a three-phase current sensor 2 is connected to a three-phase power supply 3, and the output of the converter to an AC motor 4. The converter contains two active voltage rectifiers , a common DC link and two voltage inverters (to be shown later). The measuring outputs of the current sensor 2 are connected to the first input of the control system by 5 active rectifiers. The information outputs of the three-phase voltage sensor 6 are connected to the second input of the control system 5, the inputs of which are connected to the junction point of the output of the three-phase current sensor 2 and the input of the high-voltage frequency converter 1. To the third input of the control system 5, the output of the DC link voltage sensor 7 is connected, the inputs of which are connected to the information output of the high-voltage frequency converter 1. To the fourth input of the control system 5 is connected a voltage setter 8 on the capacitors of the direct current link of the frequency converter 1. To the fifth input of the control system 5 the setter of the reactive component of the mains current is connected 9. The control output of the control system 5 via the control bus through the block of pulse-width modulators 10 is connected to the control input of the high-voltage frequency converter 1. In this case, the control system 5 of active voltage rectifiers contains the first coordinate transformation block 11, the phase-locked loop 12, the block proportional-integral current regulators 13, a block of proportional-integral regulator of a rectified voltage 14, a first subtraction block 15, a second coordinate transformation block 16, the first 17 and second 18 adders, a third coordinate transformation block 19. The first, second and third inputs of the first coordinate transformation block 11 are connected to the first input of the control system 5. The fourth input of this unit is connected to the first output of the phase-locked loop 12. The first and second outputs of the first coordinate transformation unit 11 are connected, respectively, to the first and second inputs of the proportional-integral current regulators 13. To the third input the block of current regulators is connected to the second output of the phase-locked loop 12. The first, second and third inputs of which are connected to the second input of the control system 5. The fourth input of the block of proportional-integral current regulators 13 is connected to the fifth input of the control system 5. The fifth input of the block of regulators current is connected to the output of the proportional-integral regulator of rectified voltage 14, the input of which is connected to the output of the first subtraction block 15. The first and second inputs, which are connected respectively to the fourth and third inputs of the control system 5. The first and second outputs of the block of proportional-integral current regulators 13 are connected, respectively, to the first and second inputs of the second coordinate transformation unit 16. The third input, which is connected to the first output of the phase-locked loop 12. The first and second outputs of the second coordinate transformation unit 16 are connected, respectively, to the first input of the first 17 and to the first input of the second 18 adders, the outputs of which are connected, respectively, to the first and second inputs of the third coordinate transformation unit 19. The third input, which is connected to the first output of the phase-locked loop 12. The outputs of the third coordinate transformation unit 19 are connected via the control bus to the control output control systems 5.

The control device is additionally equipped with a fourth coordinate transformation unit 20, first 21 and second 22 low-pass filters, a fifth coordinate transformation unit 23, an inverting unit 24. In addition, the block of proportional-integral current regulators 13 includes the first 25 and second 26 blocks proportionally -integral current regulators, the second 27, the third 28 and the fourth 29 subtraction blocks, the third summation block 30, the first 31 and the second 32 blocks for the compensation of cross-links. The first, second and third inputs of the fourth coordinate conversion unit 20 are connected to the second input of the control system 5. The fourth input of the fourth unit 20 is connected to the output of the inverter 24, the input of which is connected to the first output of the phase-locked loop 12. The first and second outputs of the fourth conversion unit coordinates 20, respectively, through the first 21 and second 22 low-pass filters are connected to the first and second inputs of the fifth coordinate transformation unit 23. The third input of the fifth unit 23 is connected to the output of the inverting unit 24. The first and second outputs of the fifth coordinate transformation unit 23 are connected to the second input, respectively the first 17 and to the second input of the second 18 adders.

The first and second inputs of the second block of subtraction 27 are connected respectively to the fifth and to the first inputs of the block of proportional-integral current controllers 13. The output of the second block of subtraction 27 is connected to the input of the first block of proportional-integral current controllers 25, the output of which is connected to the first input of the third block of summation 30. The first and second inputs of the third block of subtraction 28 are connected respectively to the fourth and to the second inputs of the block of proportional-integral current controllers 13. The output of the third block of subtraction 28 is connected to the input of the second 26 block of proportional-integral current controllers, the output of which is connected to the first input of the fourth subtraction unit 29. The first input of the first 31 and the first input of the second 32 cross-link compensation units are connected respectively to the first and second inputs of the proportional-integral controller unit 13. The second inputs of the compensation units 31 and 32 are connected to the third input of the proportional-integral controller unit current tori 13. The output of the first 31 cross-link compensation unit is connected to the second input of the fourth 29 subtraction unit, the output of which is connected to the second output of the proportional-integral current regulators 13. The output of the second 32 cross-link compensation unit is connected to the second input of the third summation unit 30, whose output is connected to the first output of the block of proportional-integral current controllers 13.

The control system 5 (Fig. 1) three-phase three-level active voltage rectifiers can be made on the basis of a specialized microcontroller with peripheral devices, processor, RAM and ROM.

Let's give a brief description of the high-voltage frequency converter 1 (Fig. 2). It contains the first 33 and second 34 frequency converters, each of which, in turn, contains a three-level active voltage rectifier 35, a three-level voltage inverter 36 and a choke 37. current 4. The inputs of the DC link 38 common to both frequency converters with a zero point are connected to the outputs of both active rectifiers 35, and the outputs of the specified link 38 are connected to the inputs of both voltage inverters 36. In addition, the frequency converter 1 is equipped with the first 39 and the second 40 phase-shifting transformers, respectively, at 0 ^o and +30 ^o degrees. The primary winding of the first phase-shifting transformer 39 has six terminals and is connected in series with the primary winding of the second phase-shifting transformer 40, which is star-connected. In this case, the beginning of the primary winding of the first phase-shifting transformer is connected to a power source. The secondary windings of these transformers are star and delta connected and connected to the first 33 and the second 34 frequency converters, respectively. The described connections make it possible to obtain a twelve-pulse rectification circuit. Fully controlled thyristor switches are used in the power circuits of three-level active rectifiers 35 and voltage inverters 36.

A three-phase three-level active voltage rectifier 35 (Fig. 3) contains three phase racks 41, 42 and 43, the outputs of which are connected in parallel and connected to a DC link 38, which contains two series-connected capacitors 44 and 45. The first capacitor 44 creates a positive potential on phases of the inverter 36, and the second capacitor 45 is negative potential. The common point of the capacitors 46 is the neutral point of the three-phase three-level active rectifier 35 and creates a zero potential in its phases. Each of the phase struts 41, 42 and 43 contains four series-connected fully controlled thyristor switches 47, 48, 49 and 50. The cathode of the first diode 51 is connected to the connection point of the first 47 and second 48 controlled switches in each phase rack, the anode of which is connected to the neutral point 46 of the active rectifier. The connection point of the second 48 and third 49 controlled switches is the power input of the active rectifier 35 in each phase rack. The anode of the second diode 52 is connected to the junction point of the third 49 and the fourth 50 controlled switches in each phase rack, the cathode of which is connected to the neutral point 46 of the active rectifier. The power inputs of the first and second active rectifiers 35 (Fig. 2) are connected, respectively, to the secondary windings of the first 39 and second 40 phase-shifting transformers.

,

,

(фиг. 1). Указанные сигналы формируются на выходе системы управления 5 и по шине данных подаются на вход блока широтно-импульсных модуляторов 10.Note that the keys 47, 48, 49 and 50 (Fig. 3) in the phase struts 41, 42 and 43, receiving control signals from the unit of pulse-width modulators 10 via the data bus, form a width-modulated phase voltage at the input of the active rectifier 35 ... In this case, the amplitude values of the fundamental harmonics of these voltages are set by voltage control signals

,

,

(Fig. 1). These signals are generated at the output of the control system 5 and are fed via the data bus to the input of the unit of pulse-width modulators 10.

градусов относительно сетевого напряжения. С учетом изложенного, благодаря сигналу управления

,

,

фазы основных гармоник напряжений, сформированные на входах обоих активных выпрямителей 35 должны иметь сдвиги

градусов относительно сетевого напряжения. Note that the three-phase three-level active voltage rectifiers 35 (Fig. 2) of the first 33 and second 34 frequency converters are identical. Earlier it was noted that their outputs are connected to the inputs of a common DC link 38 with a zero point, and the inputs of one and the other rectifiers 35 are connected, respectively, to the secondary windings of the first 39 and second 40 phase-shifting transformers on

degrees relative to the mains voltage. With this in mind, thanks to the control signal

,

,

the phases of the fundamental voltage harmonics formed at the inputs of both active rectifiers 35 should have shifts

degrees relative to the mains voltage.

, ориентированной по вектору напряжения сети

.We give a brief description of all blocks of the control system 5 (Fig. 1) and indicate their purpose. Note that the operation of the control system 5 is performed in a rotating orthogonal coordinate system

oriented along the voltage vector of the network

...

– сетевой ток;

– сетевое напряжение;

– текущее значение напряжения на конденсаторах звена постоянного тока 38 высоковольтного преобразователя частоты 1;

– заданное значение напряжения на конденсаторах звена постоянного тока;

– заданное значение реактивной составляющей сетевого тока

. Выходным сигналом системы управления 5 является сигнал

,

,

– управляющий сигнал напряжения для активных выпрямителей 35. The input signals for the control system 5 (Fig. 1, Fig. 2) are:

- mains current;

- mains voltage;

- the current value of the voltage across the capacitors of the DC link 38 of the high-voltage frequency converter 1;

- the set value of the voltage across the DC link capacitors;

- set value of the reactive component of the mains current

... The output signal of the control system 5 is the signal

,

,

- voltage control signal for active rectifiers 35.

из неподвижной системы координат

в активную

и реактивную

составляющие сетевого тока во вращающейся системе координат

на частоте

основной гармоники напряжения сети. Отметим, что сигналы

и

являются сигналами обратной связи для блока пропорционально-интегральных регуляторов 13.The first coordinate transformation unit 11 (Fig. 1) converts the instantaneous values of the mains current

from a fixed coordinate system

into active

and reactive

components of the line current in a rotating coordinate system

at frequency

fundamental harmonic of the mains voltage. Note that the signals

and

are feedback signals for the block of proportional-integral controllers 13.

и частоту ω для пространственного вектора основной гармоники напряжения питающей сети

. Фазовый угол

обеспечивает точную синхронизацию формируемых сигналов управления в блоках преобразования координат 11, 16 и 19 заявляемой системы управления 5. Частота ω обеспечивает работу блоков компенсации перекрестных связей 31 и 32 в блоке пропорционально-интегральных регуляторов 13.The phase-locked loop 12 (Fig. 1) forms a phase angle

and frequency ω for the space vector of the main harmonic of the supply voltage

... Phase angle

provides accurate synchronization of the generated control signals in the coordinate transformation units 11, 16 and 19 of the claimed control system 5. The frequency ω ensures the operation of the cross-link compensation units 31 and 32 in the proportional-integral control unit 13.

и

, формируемые соответственно блоком пропорционально-интегрального регулятора выпрямленного напряжения 14 и задатчиком реактивной составляющей сетевого тока 9.The driving signals for the block of current regulators 13 (Fig. 1) are signals

and

, formed, respectively, by the unit of the proportional-integral controller of the rectified voltage 14 and the reactive component of the mains current 9.

на конденсаторах звена постоянного тока 38 (фиг. 2), поддерживая его на уровне

. На вход указанного регулятора 14 поступает сигнал ошибки

с выхода первого блока вычитания 15. На входы последнего 15 подаются задающий сигнал

с задатчика напряжения 8 на конденсаторах звена постоянного тока и сигнал обратной связи

с датчика напряжения звена постоянного тока 7. The unit of the proportional-integral regulator of the rectified voltage 14 carries out astatic voltage regulation

on the capacitors of the DC link 38 (Fig. 2), keeping it at the level

... The input of the specified controller 14 receives an error signal

from the output of the first block of subtraction 15. At the inputs of the last 15, a setting signal is supplied

from the voltage setpoint 8 on the DC link capacitors and the feedback signal

from the DC link voltage sensor 7.

, который равен разности сигнала задания

и сигнала обратной связи

для составляющей d канала регулирования сетевого тока. Сигнал ошибки

подается на вход первого пропорционально-интегрального регулятора тока 25, который обеспечивает астатическое регулирование активной составляющей сетевого тока

. Выходной сигнал напряжения

регулятора 25 подается на первый вход третьего блока суммирования 30. На второй вход блока 30 подается сигнал

, который формирует второй блок компенсации перекрестных связей 32. Сигнал

устраняет взаимное влияние между d и q каналами регулирования в блоке пропорционально-интегральных регуляторов 13. Здесь

– индуктивность реактора или индуктивность рассеяния трансформаторов, которые установлены на входе активного выпрямителя 35 (фиг.2).In the block of proportional-integral current controllers 13, the second subtractor 27 (Fig. 1) generates an error signal

, which is equal to the difference of the reference signal

and feedback signal

for the component d of the mains current control channel. Error signal

fed to the input of the first proportional-integral current controller 25, which provides astatic regulation of the active component of the mains current

... Voltage output signal

regulator 25 is fed to the first input of the third summation block 30. The signal is supplied to the second input of block 30

which forms the second cross-link compensation block 32. Signal

eliminates the mutual influence between d and q control channels in the block of proportional-integral controllers 13. Here

- the inductance of the reactor or the leakage inductance of the transformers, which are installed at the input of the active rectifier 35 (figure 2).

существует перекрестное влияние реактивной составляющей тока

активного выпрямителя 35 на его активную составляющую тока

и наоборот (см. Шрейнер Р.Т. Математическое моделирование электроприводов переменного тока с полупроводниковыми преобразователями частоты. Екатеринбург. УРО РАН, 2000. 654 с.).It is known that in a rotating coordinate system

there is a cross-effect of the reactive component of the current

active rectifier 35 to its active current component

and vice versa (see Shreiner RT Mathematical modeling of alternating current electric drives with semiconductor frequency converters. Yekaterinburg. URO RAS, 2000. 654 p.).

третьего блока суммирования 30 подается на первый вход второго блока преобразования координат 16 активной

и реактивной

составляющих напряжений из вращающейся системы координат

в составляющие напряжений

и

неподвижной ортогональной системы координат

. Output voltage reference signal

the third summation block 30 is fed to the first input of the second coordinate transformation block 16 of the active

and reactive

stress components from a rotating coordinate system

in stress components

and

fixed orthogonal coordinate system

...

, который равен разности сигнала задания

и сигнала обратной связи

для составляющей

канала регулирования сетевого тока. Сигнал ошибки

подается на вход второго пропорционально-интегрального регулятора тока 26, который обеспечивает астатическое регулирование реактивной составляющей сетевого тока

. Выходной сигнал напряжения

регулятора 26 подается на первый вход четвертого блока вычитания 29. На второй вход блока 29 подается сигнал

, который формирует первый блок компенсации перекрестных связей 31. Сигнал

устраняет взаимное влияние между d и q каналами регулирования в блоке пропорционально-интегральных регуляторов 13. In the block of proportional-integral current controllers 13, the third subtraction block 28 (Fig. 1) generates an error signal

, which is equal to the difference of the reference signal

and feedback signal

for component

mains current regulation channel. Error signal

is fed to the input of the second proportional-integral current controller 26, which provides astatic regulation of the reactive component of the mains current

... Voltage output signal

regulator 26 is fed to the first input of the fourth block of subtraction 29. To the second input of block 29 the signal

which forms the first cross-link compensation block 31. Signal

eliminates the mutual influence between d and q control channels in the block of proportional-integral controllers 13.

четвертого блока вычитания 29 подается на второй вход второго блока преобразования координат 16 активной

и реактивной

составляющих напряжений из вращающейся системы координат

в составляющие напряжений

и

неподвижной ортогональной системы координат

. Output voltage reference signal

the fourth subtraction block 29 is fed to the second input of the second coordinate transformation block 16 active

and reactive

stress components from a rotating coordinate system

in stress components

and

fixed orthogonal coordinate system

...

и

второго блока преобразования координат 16 подаются соответственно на первый вход первого 17 и на первой вход второго 18 сумматоров. Output voltage reference signals

and

the second block of transformation of coordinates 16 are supplied, respectively, to the first input of the first 17 and to the first input of the second 18 adders.

Note that a distinctive feature of the claimed invention is that it is equipped with five new blocks: the fourth coordinate transformation block 20, the first 21 and second 22 low-pass filters, the fifth coordinate transformation block 23 and the inverter 24.

,

,

дополнительный сигнал – сигнал сетевого напряжения. Сформированные широтно-модулированные фазные напряжения на входе активного выпрямителя будут содержать напряжение обратной последовательности, которое существенно ослабит действие напряжения обратной последовательности со стороны источника питания. Следовательно, в момент появления несимметрии броска тока в фазах активного выпрямителя не будет, что существенно повысит надежность работы трехфазного активного выпрямителя напряжения. Поясним назначение вновь вводимых блоков в систему управления активными выпрямителями.These blocks allow you to enter almost instantly, i.e. without significant delay, as part of the control signal of active rectifiers

,

,

additional signal - mains voltage signal. The generated PWM phase voltages at the input of the active rectifier will contain a negative sequence voltage, which will significantly weaken the negative sequence voltage from the power supply side. Therefore, at the moment of the appearance of asymmetry, there will be no inrush current in the phases of the active rectifier, which will significantly increase the reliability of the three-phase active voltage rectifier. Let us explain the purpose of the newly introduced blocks in the control system of active rectifiers.

на фазовый угол

. В дальнейшем фазовый угол

, под действием которого пространственный вектор напряжения вращается в противоположную сторону по отношению к напряжению сети, будет использован блоками 20 и 23 для преобразования координат из одной системы в другую систему. The inverting unit 24 changes the sign of the phase angle

phase angle

... Further, the phase angle

, under the influence of which the spatial voltage vector rotates in the opposite direction with respect to the mains voltage, will be used by blocks 20 and 23 to transform coordinates from one system to another system.

из неподвижной системы координат

в ортогональные составляющие

и

сетевого напряжения во вращающейся системе координат

обратной последовательности.The fourth coordinate transformation unit 20 (Fig. 1) converts the instantaneous values of the mains voltage

from a fixed coordinate system

to orthogonal components

and

line voltage in a rotating coordinate system

reverse sequence.

и

содержат составляющие первых гармоник напряжения обратной последовательности

и

, значения которых во введенной вращающейся системе координат

представляют собой постоянные уровни. Кроме того, сигналы напряжения

и

содержат составляющие первых гармоник напряжения прямой последовательности

и

, значения которых во введенной вращающейся системе координат

изменяются с удвоенной частотой питающей сети

. Note that voltage signals

and

contain the components of the first harmonics of the negative sequence voltage

and

whose values in the introduced rotating coordinate system

represent constant levels. In addition, voltage signals

and

contain the components of the first harmonics of the positive sequence voltage

and

whose values in the introduced rotating coordinate system

change with twice the frequency of the supply network

...

и

также содержат высокочастотные составляющие

. Поясним, почему указанные составляющие

присутствуют в составе напряжений

и

, а также, почему высокочастотные составляющие

не должны попасть в сигналы задания по напряжению системы управления 5. In addition, voltage signals

and

also contain high frequency components

... Let us explain why the indicated components

present in the composition of stresses

and

and also why the high-frequency components

must not be included in the voltage reference signals of the control system 5.

активного выпрямителя 35 от коэффициента модуляции

для указанного метода ШИМ, обеспечивающего заданное значение первой гармоники напряжения активного выпрямителя 35. Earlier it was proved that the claimed device uses the PWM method with the removal of eight isolated voltage harmonics and nine switches of the active rectifier keys for a quarter of the period of the mains voltage. For this PWM method in FIG. 4, a shows the ideal form of the phase voltage at the input of a three-phase three-level active rectifier 35 (FIG. 3) with respect to the neutral point 46 of the DC link 38. In FIG. 4, b shows the dependences of the angles of switching keys

active rectifier 35 from modulation factor

for the specified PWM method, providing the specified value of the first harmonic of the voltage of the active rectifier 35.

For the known device, the dependences of nine switching angles on the modulation coefficient are calculated. To calculate the indicated angles in this PWM method, an objective function is set, which takes into account two conditions: maintaining the first harmonic at the level specified by the modulation coefficient; reducing the level of higher harmonics in the current to the desired value. In the known device, the phase voltage correction unit stores a database for nine switching angles depending on the value of the modulation factor for symmetrical and unbalanced operating modes of the power supply.

, то на входе активного выпрямителя 35 (фиг. 3) мы будем иметь осциллограммы фазного напряжения, которые изображены на фиг. 5. Это напряжение было получено относительно нейтральной точки 46 (фиг. 3) активного выпрямителя в результате моделирования заявляемой системы управления в программной среде Matlab Simulink. Здесь вместо 9 переключений за четверть периода сетевого напряжения мы наблюдаем множественные ложные срабатывания широтно-импульсного модулятора 10 (фиг. 2). Такие переключения весьма нежелательны и недопустимы, так как в реальном активном выпрямителе 35 это может привести к перегреву тиристоров, срабатыванию защиты, что снижает надежность работы активного выпрямителя и системы управления в целом.If the claimed device has not taken measures to eliminate high-frequency components

, then at the input of the active rectifier 35 (Fig. 3) we will have phase voltage oscillograms, which are shown in Fig. 5. This voltage was obtained relative to the neutral point 46 (Fig. 3) of the active rectifier as a result of modeling the proposed control system in the Matlab Simulink software environment. Here, instead of 9 switchings in a quarter of the period of the mains voltage, we observe multiple false alarms of the pulse-width modulator 10 (Fig. 2). Such switching is highly undesirable and unacceptable, since in a real active rectifier 35 this can lead to overheating of thyristors, triggering of protection, which reduces the reliability of the active rectifier and the control system as a whole.

The reason for the multiple false alarms of the pulse-width modulator 10 is that a signal containing high-frequency voltage components that cause false alarms is supplied to the mains voltage control channel of the control system 5 from the three-phase voltage sensor 6 (Fig. 1).

This is due to the fact that the three-phase voltage sensor 6 is connected to the midpoint of the voltage divider, which from the side of the active rectifier 35 (Fig. 2) is represented by the inductive reactance of the reactor or the leakage inductive reactance of the transformer 39 (40), and from the side of the three-phase power supply 3 - its internal inductive reactance. In this case, in the ideal case, a pulse-width modulated voltage is applied to the specified voltage divider from the side of the active rectifier, as in FIG. 4, a, and from the side of the three-phase power supply 3, in the ideal case, a sinusoidal voltage is applied. Note that a three-phase power supply 3 in real operating conditions, due to the influence of other consumers, may also contain high-frequency voltage components. Taking into account the above, it can be argued that the voltage at the connection point of the three-phase voltage sensor 6 contains both a sinusoidal component of the mains voltage and high-frequency voltage components.

и

в неподвижной ортогональной системе координат

, полученные из фазных сетевых напряжений

, которые содержат высокочастотные составляющие. На осциллограммах (фиг. 6) видны высокочастотные составляющие, попадание которых в канал регулирования по сетевому напряжению системы управления 5 приведут к ложным срабатываниям широтно-импульсного модулятора 10 (фиг. 2), а также ложным срабатываниям активного выпрямителя 35 (фиг. 5). Последнее, как ранее отмечалось, недопустимо, так как это снижает надежность заявляемой системы управления. FIG. 6 shows the results of modeling in the Matlab Simulink software environment as an example. Here are the components of the mains voltage

and

in a fixed orthogonal coordinate system

obtained from phase mains voltages

that contain high frequency components. The oscillograms (Fig. 6) show high-frequency components, the entry of which into the mains voltage control channel of the control system 5 will lead to false alarms of the pulse-width modulator 10 (Fig. 2), as well as false alarms of the active rectifier 35 (Fig. 5). The latter, as noted earlier, is unacceptable, since it reduces the reliability of the claimed control system.

в канал регулирования по сетевому напряжению системы управления 5 (фиг. 1) их необходимо отфильтровать из сигналов

и

, которые сформированы на выходе блока 20. Эту задачу решают фильтры нижних частот 21 и 22.Thus, in order to avoid high frequency components

into the mains voltage regulation channel of the control system 5 (Fig. 1), they must be filtered from the signals

and

, which are formed at the output of block 20. This problem is solved by low-pass filters 21 and 22.

,

и прямой последовательности

,

, а также удаляют высокочастотные составляющие

. В качестве фильтров нижних частот в заявляемой системе управления используются фильтры с конечной импульсной характеристикой, работающие по принципу выделения скользящего среднего (с периодом усреднения 0,001 с). FIG. 1 filters 21 and 22 pass the components of the first harmonic of the mains voltage negative sequence

,

and direct sequence

,

and also remove high-frequency components

... Filters with finite impulse response are used as low-pass filters in the claimed control system, operating on the principle of separating a moving average (with an averaging period of 0.001 s).

,

и

,

из вращающейся системы координат

обратной последовательности в составляющие напряжений

и

неподвижной ортогональной системы координат

. Отметим, что сигналы

и

являются сигналами регулирования по сетевому напряжению

. Указанные сигналы

и

содержат составляющие напряжений как прямой последовательности, так и обратной последовательности сетевого напряжения, если в источнике питания 3 имеет место несимметрия. При этом сигналы

и

не содержат высокочастотные составляющие.The fifth coordinate transformation unit 23 converts signals

,

and

,

from a rotating coordinate system

reverse sequence to voltage components

and

fixed orthogonal coordinate system

... Note that the signals

and

are mains voltage regulation signals

... Specified signals

and

contain voltage components of both positive sequence and negative sequence of the mains voltage, if there is an unbalance in the power supply 3. In this case, the signals

and

do not contain high frequency components.

Note that in the mains voltage regulation channel, i.e. in blocks 20, 21, 22 and 23, there is practically no signal processing time delay. In the fourth 20 and fifth 23 coordinate transformation blocks, arithmetic and logical operations are performed without a time delay, and in the low-pass filters 21 and 22, which operate on the principle of separating a moving average (with an averaging period of 1/1000 s), the delay does not exceed 0.001 s.

The specified delay is 5 times less than a quarter of the mains voltage period. It was previously noted that a quarter-cycle delay of the mains voltage occurs in the voltage control channel of the prototype. In this case, with a short-term asymmetric voltage drop in one of the phases of the active rectifier, a significant current surge occurs, which reduces the reliability of the control system and the entire system as a whole (in the prototype).

и

пятого блока преобразования координат 23 (фиг.1) подаются соответственно на второй вход первого 17 и на второй вход второго 18 сумматоров. Выходные задающие сигналы

и

указанных сумматоров подаются соответственно на первый и второй входы третьего блока преобразования координат 19. Указанный блок осуществляет преобразование в неподвижной системе координат задающих управляющих напряжений

и

в управляющие напряжения

,

,

, которые подаются на блок широтно-импульсных модуляторов 10. Последний блок по шине данных управляет работой ключей 47, 48, 49 и 50 (фиг. 3) в соответствующих фазах активного выпрямителя 35, при этом на его входе формируется требуемое широтно-модулированное напряжение фиг. 4,а. Output voltage signals

and

the fifth block of coordinate transformation 23 (Fig. 1) are supplied, respectively, to the second input of the first 17 and to the second input of the second 18 adders. Output reference signals

and

of these adders are fed, respectively, to the first and second inputs of the third coordinate transformation block 19. The specified block transforms the master control voltages in a fixed coordinate system

and

into control voltages

,

,

, which are fed to the block of pulse-width modulators 10. The last block on the data bus controls the operation of switches 47, 48, 49 and 50 (Fig. 3) in the corresponding phases of the active rectifier 35, while at its input the required width-modulated voltage is generated in Fig. ... 4, a.

The control device for three-phase three-level active voltage rectifiers of the high-voltage frequency converter 1 operates as follows.

и сетевого напряжения

. На третий вход – сигнал текущего значения напряжения на конденсаторах звена постоянного тока

. На четвертый и пятый входы – задающие сигналы

и

.The first and second inputs of the control system 5 (Fig. 1) receive signals of instantaneous values of the mains current, respectively

and mains voltage

... The third input is a signal of the current value of the voltage across the DC link capacitors

... On the fourth and fifth inputs - setting signals

and

...

,

и сигналов обратной связи

,

формирует управляющие сигналы

и

. Ранее было подробно описано, как осуществляется процесс формирования указанных сигналов.It was previously noted that the control system 5 (Fig. 1) uses a combined control method for deviation and for disturbance. Deviation control channel, which includes blocks 11, 13, 14, 15 and 16 under the action of the setting signals

,

and feedback signals

,

generates control signals

and

... Previously, it was described in detail how the process of generating these signals is carried out.

формирует управляющие сигналы

и

. Ранее было подробно описано, как осуществляется процесс формирования этих сигналов.Disturbance control channel, which includes blocks 20, 21, 22, 23 and 24 under the action of a signal

generates control signals

and

... Previously, it was described in detail how the process of generating these signals is carried out.

,

и

,

на выходе системы управления 5 формируется сигнал

, который управляет работой блока широтно-импульсных модуляторов 10. Указанный блок 10 по шине данных управляет работой ключей 47, 48, 49 и 50 (фиг. 3) активного выпрямителя 35, при этом на его входе формируется требуемое широтно-модулированное напряжение, например, как на фиг. 4,а.Under the action of the specified control signals

,

and

,

a signal is generated at the output of the control system 5

, which controls the operation of the unit of pulse-width modulators 10. The specified unit 10 on the data bus controls the operation of switches 47, 48, 49 and 50 (Fig. 3) of the active rectifier 35, while the required width-modulated voltage is generated at its input, for example, as in FIG. 4, a.

Let us note the distinctive features of the disturbance control channel in the claimed invention.

Firstly, the blocks for transforming coordinates 20 and 23 do not create a time delay for signals in the process of their transformation, since arithmetic and logical operations are performed in these blocks.

обратной последовательности позволяет сохранить с максимальной достоверностью информацию о составляющих напряжения обратной последовательности

и

в составе сетевого напряжения при его несимметричном провале. Это позволяет пятому блоку преобразования координат 23 (фиг.1) сформировать сигналы

и

, которые содержат достоверную информацию об обратной последовательности сетевого напряжения. Ранее об этом было подробно описано.Second, the application of the coordinate system

reverse sequence allows you to save with maximum reliability information about the components of the negative sequence voltage

and

as part of the mains voltage in case of its asymmetrical failure. This allows the fifth coordinate transformation unit 23 (Fig. 1) to generate signals

and

which contain reliable information about the negative sequence of the mains voltage. This has been described in detail earlier.

Third, the use of low-pass filters 21 and 22, which operate on the principle of separating a moving average (with an averaging period of 1/1000 s), makes it possible to exclude false alarms of the switches of the active rectifier 35. This has been described in detail earlier.

и

не превышает 0,001 с, в то время как в прототипе задержка сигналов достигает 0,01 с, или в лучшем случае 0,005 с. Указанное достоинство позволяет при кратковременном несимметричном провале сетевого напряжения

сформировать на входе активного выпрямителя 35 напряжение подобное сетевому напряжению. При этом в фазах активного выпрямителя не будут иметь место броски токов. Ранее об этом было подробно описано.Fourth, the delay in the formation of control signals

and

does not exceed 0.001 s, while in the prototype the signal delay reaches 0.01 s, or at best 0.005 s. The indicated advantage allows for a short-term asymmetrical drop in the mains voltage

form at the input of the active rectifier 35 a voltage similar to the mains voltage. In this case, there will be no inrush currents in the phases of the active rectifier. This has been described in detail earlier.

Consider three modes of operation of the proposed control device for three-phase three-level active voltage rectifiers.

The first mode is the operation of the device in a steady state and symmetrical voltage of the power supply 3.

и

, которые содержат составляющие только прямой последовательности. Благодаря фильтрам нижних частот 21 22 управляющие сигналы

и

не содержат высокочастотные составляющие.The mains voltage regulation channel generates control signals

and

which contain only direct sequence components. Low-pass filters 21 22 control signals

and

do not contain high frequency components.

,

, которые обусловлены сигналами задания

,

и сигналами обратной связи

,

. Пропорционально-интегральные регуляторы тока 25, 26 и напряжения 14 обеспечивают астатическое регулирование контролируемых параметров

,

и

в канале регулирования по отклонению. The deviation control channel generates control signals

,

, which are due to task signals

,

and feedback signals

,

... Proportional-integral regulators of current 25, 26 and voltage 14 provide astatic regulation of controlled parameters

,

and

in the deviation control channel.

содержит информацию о значении коэффициента модуляции

, который обеспечивает заданное значение первой гармоники напряжения активного выпрямителя 35. В соответствии со значением коэффициента модуляции

в блоке широтно-импульсных модуляторов 10 из базы данных осуществляется выбор значений углов переключений ключей

(фиг. 4,б) активного выпрямителя 35. Signal generated by control system 5

contains information about the value of the modulation index

, which provides the set value of the first harmonic of the voltage of the active rectifier 35. In accordance with the value of the modulation coefficient

in the block of pulse-width modulators 10 from the database, the values of the switching angles of the keys are selected

(Fig. 4, b) active rectifier 35.

To confirm the performance of the proposed device in the Matlab Simulink software environment, it was simulated for symmetric and asymmetric modes of operation.

. На фиг. 7 описываемому первому режиму работы системы управления соответствует временной интервал от 0,15 с до 0,2 с. Сравнение осциллограмм на фиг. 6 и фиг. 7,а позволяет сделать вывод, что уровень высших гармоник на фиг. 7,а значительно меньше, чем на фиг. 6. Наличие незначительных высших гармоник в составе сетевого тока обусловлены широтно-модулированными входными напряжениями активного выпрямителя 35 (фиг. 4,а). Ложные срабатывания ключей активных выпрямителей как на фиг. 5 в заявляемом устройстве отсутствуют, благодаря работе фильтров нижних частот 21 и 22 (фиг. 1) в канале регулирования по сетевому напряжению.Simulation showed (Fig. 7, a) that for the considered mode of operation, the phase currents of the active rectifier 35 are almost sinusoidal and have the same amplitude

... FIG. 7, the described first mode of operation of the control system corresponds to a time interval from 0.15 s to 0.2 s. Comparison of the oscillograms in Fig. 6 and FIG. 7, a allows us to conclude that the level of higher harmonics in FIG. 7, but significantly less than in FIG. 6. The presence of insignificant higher harmonics in the composition of the mains current are due to the width-modulated input voltages of the active rectifier 35 (Fig. 4, a). False operations of switches of active rectifiers as in Fig. 5 in the claimed device are absent due to the operation of low-pass filters 21 and 22 (Fig. 1) in the mains voltage regulation channel.

на конденсаторах звена постоянного тока 38 (фиг.2, 3) высоковольтного преобразователя частоты 35. Ранее отмечалось, что напряжение

- это контролируемый параметр, поддержание которого на уровне

осуществляет канал регулирования по отклонению. Для первого режима работы заявляемого устройства отклонение напряжения

от заданного

менее 0,5%. Это хороший показатель.FIG. 7, b shows an oscillogram of changes in the current voltage value

on the capacitors of the DC link 38 (Fig. 2, 3) of the high-voltage frequency converter 35. It was previously noted that the voltage

is a controlled parameter, the maintenance of which at the level

implements a deviation control channel. For the first mode of operation of the claimed device, the voltage deviation

from given

less than 0.5%. This is a good indicator.

. FIG. 7, c shows the dependence of the relative value of the modulation factor for three modes of operation of the claimed system. If the reference signals of the control system 5 are unchanged, then for a symmetrical operating mode, the specified coefficient remains constant. In our case, its value is

...

The second mode is the operation of the device in a transient mode, i.e. from the moment of the voltage drop in the three-phase power supply 3 to the moment of the steady-state asymmetrical mode of operation of the active rectifier. FIG. 7, the second mode corresponds to the time interval from 0.2 s to 0.23 s, i.e. one and a half periods of mains voltage.

(фиг. 7) произошел двухфазный провал напряжений в фазе

на 20%, в фазе

на 45%. At a moment in time

(Fig. 7) there was a two-phase voltage dip in the phase

by 20%, in phase

by 45%.

и

(фиг. 1), которые содержат составляющие прямой и обратной последовательности и не содержат высокочастотные составляющие.The mains voltage regulation channel generates control signals

and

(Fig. 1), which contain components of the direct and negative sequence and do not contain high-frequency components.

,

, которые обусловлены сигналами задания

,

и сигналами обратной связи

,

. Пропорционально-интегральные регуляторы тока 25, 26 и напряжения 14 обеспечивают астатическое регулирование контролируемых параметров

,

и

в канале регулирования по отклонению.The deviation control channel generates control signals

,

, which are due to task signals

,

and feedback signals

,

... Proportional-integral regulators of current 25, 26 and voltage 14 provide astatic regulation of controlled parameters

,

and

in the deviation control channel.

осуществляет выбор значений углов переключения ключей

(фиг. 4,б) из базы данных блока широтно-импульсных модуляторов 10. As previously generated by the control system 5 signal

selects the values of the angles of switching keys

(Fig. 4, b) from the database of the block of pulse-width modulators 10.

до

в течение времени от

до

напряжение на входе активного выпрямителя 35 также быстро изменяется, практически без задержки. Ранее было отмечено, что система управления 5 должна сформировать такие сигналы управления

для активного выпрямителя, чтобы он, в свою очередь, сформировал на своем входе напряжение подобное сетевому напряжению, которое ограничит броски фазных токов выпрямителя.Simulation showed that in the claimed device, the control system 5 (Fig. 1) promptly fulfills the appearance of asymmetry, which is confirmed by the graph of a rapid decrease in the relative value of the modulation coefficient in Fig. 7, c. By reducing the modulation factor from

before

during the time from

before

the voltage at the input of the active rectifier 35 also changes rapidly, with practically no delay. It was previously noted that the control system 5 must generate such control signals

for an active rectifier, so that it, in turn, forms a voltage at its input similar to the mains voltage, which will limit the inrush of the rectifier phase currents.

в ортогональной системе координат

описывает кривую в виде овала за период сетевого напряжения. Это обусловлено наличием составляющей обратной последовательности напряжения в составе сетевого напряжения. Наличие обратной последовательности приводит к тому, что зависимость коэффициента модуляции

(фиг. 7,в) кроме постоянной составляющей содержит переменную составляющую. Частота колебания

равна удвоенной частоте сетевого напряжения, а ее амплитудное значение составляет

от уровня постоянной составляющей коэффициента модуляции

. Note that after a voltage drop, the space vector of the mains voltage

in the orthogonal coordinate system

describes a curve in the form of an oval for the period of the mains voltage. This is due to the presence of a negative voltage sequence component in the mains voltage. The presence of the negative sequence leads to the fact that the dependence of the modulation coefficient

(Fig. 7, c) in addition to the constant component contains an alternating component. Oscillation frequency

is equal to twice the frequency of the mains voltage, and its amplitude value is

on the level of the constant component of the modulation coefficient

...

, что можно считать допустимым значением

, так как задающие значения

для системы управления 5 остались неизменными, а система управления осуществляет их поддержание. Modeling has shown that phase currents inrush during the transient mode do not exceed

, which can be considered a valid value

, since the setting values

for control system 5 remained unchanged, and the control system maintains them.

To compare the claimed control system (Fig. 1) and the control system that was used in the prototype, it was simulated (prototype) in the Matlab Simulink software environment. Recall that in the prototype in the voltage regulation channel, a direct and negative sequence voltage isolation unit is used. It was previously noted that this block introduces a time delay of up to 0.01 s, or at best up to 0.005 s, in the generation of the control signal. At the same time, at the moment of the appearance of asymmetry, a surge of one of the phase currents of a three-phase three-level active rectifier is observed, which can exceed the rated current by 2 times or more, which leads to the operation of the current protection of the known device (prototype) and its shutdown. The asymmetry of the phase currents for the prototype, as well as an increase in the amplitude of the voltage fluctuation on the DC link capacitors above the maximum permissible value, leads to the operation of the protection of the known device for the rectified voltage and its shutdown. FIG. 8 shows oscillograms of the phase currents of the active rectifier for the prototype, confirming the above.

(фиг. 7,а) и известной системы (прототип)

(фиг. 8,а) можно сделать вывод, что в переходном режиме от 0,2 с до 0,23 с броски тока в заявляемой системе управления существенно меньше и не превышают допустимые значения

, здесь

.Comparing the oscillograms of the inrush current of the rectifier of the claimed system

(Fig. 7, a) and the known system (prototype)

(Fig. 8, a) it can be concluded that in the transient mode from 0.2 s to 0.23 s, the inrush current in the claimed control system is significantly less and does not exceed the permissible values

, here

...

(снижение

) на конденсаторах звена постоянного тока 38 от заданного значения

Однако указанное отклонение не превышает 5% от

, что соответствует допустимому значению. В течение времени переходного процесса от

до

с можно считать, что происходит восстановление напряжения

до заданного значения

. Simulation showed (Fig. 7, b) that for the considered operating mode of the device, a voltage deviation is observed

(decrease

) on the capacitors of the DC link 38 from the set value

However, the indicated deviation does not exceed 5% of

, which corresponds to the valid value. During the transient time from

before

c we can assume that there is a voltage recovery

to the set value

...

(фиг. 3, фиг. 7) и напряжение звена постоянного тока

(фиг. 2, фиг. 7) в течение времени переходного процесса не превышают предельно-допустимых значений.Thus, thanks to the claimed control system (Fig. 1), the main parameters of the active rectifier 5 are input currents

(Fig. 3, Fig. 7) and DC link voltage

(Fig. 2, Fig. 7) during the time of the transient process do not exceed the maximum permissible values.

The third mode is the operation of the device in a steady state with an unbalanced voltage of the power supply 3.

The considered operating mode of the device is short-lived, since the voltage dip is short-term with a duration of no more than 0.5 s. However, this mode of operation of the device is also of interest.

FIG. 7 this mode of operation of the active rectifier corresponds to a time interval from 0.23 s to 0.25 s.

формирует на входе активного выпрямителя 35 напряжение требуемой формы, которое ограничивает броски его фазных токов.The previously described control channels for deviation and for mains voltage continue to work, as during the transient process, and the control signal

generates at the input of the active rectifier 35 a voltage of the required form, which limits the inrush of its phase currents.

(фиг. 7,в), а также зависимость

содержат переменные составляющие, которые обусловлены обратной последовательностью напряжения в составе сетевого напряжения. Амплитудное значение переменной составляющей

составляет

от уровня заданного значения

, что подтверждает высокие показатели качества регулирования и надежность заявляемой системы управления.For the considered mode of operation, as in the previous transient mode, the dependence of the modulation coefficient

(Fig. 7, c), as well as the dependence

contain variable components that are due to the reverse voltage sequence in the mains voltage. The amplitude value of the variable component

is

from the setpoint level

, which confirms the high quality of regulation and the reliability of the claimed control system.

,

и

. Simulation showed that with a constant load 4 (Fig. 1) of a high-voltage frequency converter 1 and keeping the control signals of the active rectifier (Fig. 3) at the same level, the amplitude values of its phase currents (Fig. 7, a) are increased and equal

,

and

...

несимметрия его фазных токов не превышает 2,5%, что также подтверждает высокие показатели качества регулирования и надежность заявляемой системы управления.At rated current of the active rectifier

the asymmetry of its phase currents does not exceed 2.5%, which also confirms the high performance of regulation and the reliability of the claimed control system.

Comparing the oscillograms of the rectifier current of the inventive system (Fig. 7, a) and the known system (prototype) (Fig. 8, b), we can conclude that in the transient and steady-state mode, the phase current asymmetry of the prototype reaches 40% or more, which confirms the low rates quality regulation and low reliability of the prototype control system.

Thus, the inventive control device increases the reliability of the operation of three-phase three-level active voltage rectifiers of a high-voltage frequency converter with a short-term asymmetrical voltage dip of a three-phase power supply. Thanks to the improved control system of active voltage rectifiers, the increase in the phase currents of the rectifiers during a short-term asymmetrical voltage drop of a three-phase power supply is limited, and the swing of the voltage fluctuations on the DC link capacitors of active rectifiers is limited within the permissible values. In addition, due to the introduction of low-pass filters into the control system, the efficiency of active rectifiers and the reliability of the operation of the high-voltage frequency converter as a whole are increased.

Claims (1)

A control device for three-phase three-level active voltage rectifiers containing a high-voltage frequency converter, the input of which is connected to a three-phase power supply through a three-phase current sensor, the output of the specified frequency converter, which contains two active voltage rectifiers, a common DC link and two voltage inverters are connected to an AC motor , the measuring outputs of the current sensor are connected to the first input of the control system of active rectifiers, the information outputs of the three-phase voltage sensor are connected to the second input of the control system, the inputs of which are connected to the junction point of the output of the three-phase current sensor and the input of the high-voltage frequency converter, the sensor output is connected to the third input of the control system DC link voltage, the inputs of which are connected to the information output of the high-voltage frequency converter, a voltage generator is connected to the fourth input of the control system I am on the capacitors of the DC link of the frequency converter, the reactive component of the mains current is connected to the fifth input of the control system, the control output of the control system via the control bus through the block of pulse-width modulators is connected to the control input of the high-voltage frequency converter, while the control system of active voltage rectifiers contains first coordinate transformation block, phase-locked loop, block of proportional-integral current regulators, block of proportional-integral rectified voltage regulator, first subtraction block, second coordinate transformation block, first and second adders, third coordinate transformation block, first, second and third inputs of the first coordinate transformation block are connected to the first input of the control system, the fourth input of the specified block is connected to the first output of the phase-locked loop, the first and second outputs of the first coordinate transformation block connected respectively to the first and second inputs of the block of proportional-integral current regulators, to the third input of the block of current regulators is connected to the second output of the phase-locked loop, the first, second and third inputs of which are connected to the second input of the control system, the fourth input of the block of proportional-integral current regulators connected to the fifth input of the control system, the fifth input of the current regulator unit is connected to the output of the proportional-integral regulator of the rectified voltage, the input of which is connected to the output of the first subtraction unit, the first and second inputs of which are connected respectively to the fourth and third inputs of the control system, the first and second the outputs of the block of proportional-integral current controllers are connected, respectively, to the first and second inputs of the second coordinate transformation block, the third input of which is connected to the first output of the phase-locked loop, the first and second outputs of the second conversion block coordinates are connected respectively to the first input of the first and to the first input of the second adders, the outputs of which are connected respectively to the first and second inputs of the third coordinate transformation unit, the third input of which is connected to the first output of the phase-locked loop, the outputs of the third coordinate transformation unit via the control bus are connected to the control system outputs of the control system, characterized in that the control device is additionally equipped with a fourth coordinate transformation unit, first and second low-pass filters, a fifth coordinate transformation unit, an inverting unit, in addition, the unit of proportional-integral current regulators includes the first and second units proportional-integral current regulators, the second, third and fourth subtraction blocks, the third summation block, the first and second cross-link compensation blocks, the first, second and third inputs of the fourth coordinate transformation block are connected to the second input du control system, the fourth input of the fourth block is connected to the output of the inverting unit, the input of which is connected to the first output of the phase-locked loop, the first and second outputs of the fourth coordinate transformation unit, respectively, through the first and second low-pass filters are connected to the first and second inputs of the fifth conversion unit coordinates, the third input of the fifth block is connected to the output of the inverting unit, the first and second outputs of the fifth coordinate transformation block are connected respectively to the second input of the first and to the second input of the second adders, the first and second inputs of the second subtractor are connected to the fifth and to the first inputs of the block in proportion - integral current regulators, the output of the second subtraction block is connected to the input of the first block of proportional-integral current controllers, the output of which is connected to the first input of the third summation block, the first and second inputs of the third subtraction block are connected to the fourth and second inputs of the block of proportional-integral current regulators, the output of the third block of subtraction is connected to the input of the second block of proportional-integral current regulators, the output of which is connected to the first input of the fourth block of subtraction, the first input of the first and first input of the second blocks of compensation of cross-links are connected respectively to the first and second inputs of the block of proportional-integral current regulators, the second inputs of the compensation blocks are connected to the third input of the block of proportional-integral current controllers, the output of the first block of cross-link compensation is connected to the second input of the fourth block of subtraction, the output of which is connected to the second output of the block of proportional integral current regulators, the output of the second block of cross-link compensation is connected to the second input of the third summation block, the output of which is connected to the first output of the block of proportional-integral current regulators.

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