SU1206913A1 - Device for synchronizing system for controlling inverter of frequency converter - Google Patents

Description

one

The invention relates to electrical engineering and electrical engineering, in particular, to devices for synchronizing the inverter control system of frequency converters for frequency starting speed control and synchronizing with a network of powerful synchronous machines, for example, motor generators of hydro accumulating stations and synchronous drives of compressors, with the possibility of switching these synchronous machines in the AC network, in particular in the network supplying the converter,

The PisBecTHo device for synchronizing an inverter control system of a frequency converter incorporating a controlled rectifier supplied from an AC network, the output of which through a shut-down reactor is connected to the inverter's input machines, contains a control system of a rectifier, a current sensor in the converter's power circuit, the first the adder, the output of which is connected to the input of the rectifier control system, the reference frequency source, the second adder and phase to the phase-frequency discriminators, with one input of the phase-frequency discriminator Inator is connected to the converter output, the other is to the output of the reference frequency source, the output is connected to one of the inputs of the second adder, the other input of which is connected to the inverter input, the output of the second adder is connected to the input of the inverter control system, one input of the first adder is connected to the sensor input current, and the other input of the first adder is connected to the output of the current setter in the power supply circuit of the converter, one input of the phase discriminator is connected to the output of the converter, the other to the AC network, and the code of the ene with a control input of the reference frequency source l, I

In this device, the beating of the signals at the output of the phase and phase-pass discriminators leads to a change in the power supplied to the synchronous machine 5 which is the load of the inverter, so that the cdc changes with the frequency of the beats to the angle of the inverter control, and the delay of the synchronization process.

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Reducing the time for synchronization can be obtained by increasing the angle of control of the inverter while simultaneously increasing

5 current in the power circuit of the converter, which leads to an increase in the power of the converter.

The closest in technical essence to the invention is

10 a device for synchronizing an inverter control system of a frequency converter comprising a control master oscillator comprising a phase-frequency discriminator,

5 consisting of a phase-shifting unit, an output connected to the distribution of pulses and the first and second switches, the inputs of the first switch are intended to be connected to the mains, the output is connected to the first input of the phase-shifting unit, the inputs of the second switch are connected to the output of the inverter, output - to connect

25 to the input of the controlled master oscillator, the control inputs of the switches are connected to the corresponding outputs of the distributor 2. In a known device, the phase voltage comparison at the output of the inverter loaded to the synchronous machine and the supply voltage of the alternating current network, to which it switches It is implemented by a special phase discriminator whose output signal beats delay the synchronization process. Reducing the beat of the output signal and increasing the fastness of the phase discriminator is achieved due to its considerable complication and reduction in the processability of production, since this requires the use of special multiwinding transformers and a large number of radio radio elements.

35

40

45

The purpose of the invention is to simplify the device and improve its speed.

This goal is achieved by the fact that a device for synchronizing an inverter control system of a frequency converter, including a controlled master oscillator, containing a phase-frequency discriminator consisting of a phase-shifting unit, an output connecting 3

the first and second switches, the inputs of the first switch are designed to be connected to the mains, the output is connected to the first input of the phase-shifting unit, the inputs of the second switch are intended to be connected to the output of the inverter, the output is to be connected to the input of the controlled switch. master oscillator, the control inputs of the switches are connected to the corresponding outputs of the distributor, equipped with an integrator with bipolar inputs and a potentiometer for setting the phase-shift control signal The first input of the integrator is connected to the output of the first switch. The second input of the integrator is connected to the output of the second switch. The output of the integrator is connected via a potentiometer for setting the control signal of the phase-shifting unit to the second input of the phase-shifting unit.

Fig. 1 is a schematic electrical block diagram of the device; Fig. 2 shows one possible embodiment of the phase-shifting unit; FIG. 3 is a diagram of the operation of the main components of the device.

The device for synchronizing the inverter control system of the frequency converter of the voltage source, for example, from series-connected between the supply network 1 and the output 2 of the inverter 3 of the controlled downlight 4 and the DC link 5, contains the control system 6 of the inverter 3, the current regulator 7 and voltage 8 rectifier, controlled master oscillator 9 and phase-frequency discriminator 10. The phase-frequency discriminator consists of a distributor of 11 pulses, a phase-shifting unit 12 with a limiting unit 13, the first 14 and the second 15 switches, the first switch turns 16 are connected to the converter power supply 1, output 17 is connected to the first input 18 of the phase-shifting unit 12, the second switch input 19 is connected to the output 2 of the inverter 3 of the converter, output 20 is connected to the input 21 of the controlled master oscillator 9, and the first the input 22 of the limiting unit 13 controlling the 23 inputs of the switches 14

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and 15 are connected to the respective outputs 24 of the distributor.

In addition, the synchronization device is equipped with an integrator 25 with bipolar inputs, the first input 26 of the integrator 25 is connected to the output 17 of the first switch 14, the second input 27 of the integrator is connected to the output 20 of the second switch 15. The integrator 25 with different polarity inputs is made, for example , on the inverting 28 and integrating 29 amplifiers, the first input of the integrating amplifier is connected to the second 27 input of the integrator 25, the second input is connected to the output of the inverting amplifier 28, the input connected to the first input 26 of the integrator 25. You the course of the integration amplifier 29 is connected to the output of the integrator 25. The output of the integrator, via the entered potentiometer 30, of setting the control signal of the phase-shifting unit is connected to

25 to the second input 31 of the phase-shifting unit. In addition, the device includes a zener diode 32 connected in parallel with the potentiometer for setting the control signal of the phase-shifting unit. The controlled rectifier 4 is connected to the AC mains 1 through the switch 13, the inverter 3 is connected to the load to the synchronous machine 34 through the switch 35. Switching

 the synchronous machine 34 is powered by an AC network through a switch 36.

Switch 36 can be connected to both the AC mains supplying the converter and any AC mains. In this case, the inputs 16 of the first switch must be connected to the network 37.

45 The regulation of the excitation current of a synchronous machine is carried out by the excitation regulator 38, to the input of which a reference signal of the excitation current is supplied

5 strokes and a positive feedback signal on the stator current, as well as a differential voltage signal Uj. and voltage U at the output of the converter.

55 Phase-shifting unit 12 and blocks "kc f ALIN of the block 13 for limiting the phase of the distributor control pulses (Fig 2) can

40

From a series-connected integrator 39 with a shunting key 40 and a zero-body 41, the integrator's input is connected via resistors to the block inputs 42 and 43, the output of the zero-organ is connected to the output circuit 45 through a resistor and diode to output 45 control unit, and the control input 46 of the shunt key 40 is connected to the control input of the distributor.

The inputs 47 of blocks 12 and 13 are supplied with a voltage V, which determines the switching threshold of the null organ.

The distributor 11 includes a logic element 48 2H-2PUIH one-shot 49, a binary counter 50, a decoder 51.

The boundary phases f d ,,, and the phase of the frequency discriminator 10 are set by potentiometers 32 and 53, which are fed through a rectifier with filter 54 to the output voltage of the inverter. Communication with the supply network of the phase-shifting unit 12 and block 55 f, and 56, limiting unit 13 with the voltage at the output of the inverter can be made through phase set transformers 57 and 58, respectively.

The schematic diagrams of blocks 12, 55 and 56 can be completely identical (Fig. 2). In FIG. 3, the following notation is used:

-59 - output voltage 17

first switch 14j

-60 - voltage at high speed 20

the second switch 15;

-61 is the voltage at the output of the integrator 26;

-62 is the voltage at the output of the one-shot 49;

-63 - output voltage 45

block 56 block 13

restrictions;

-64 - output voltage 45

phase shifter 12j

-65 is the voltage at the output of the f-ff unit 55, c of the limiting unit 13,

The dashed lines in diagrams 59 and 60 show two bypass voltages, respectively, at the input and output of the converter. Device for synchronization of the frequency converter control system in the frequency start mode and synchronization of the synchronous machine with the network 10

15

0 5 0

five

0

five

0

Variable current works as follows.

At the output of current regulator 7, a signal is generated that ensures such a mode of operation of the converter (for example, by changing the angle of the rectifier control), at which the current value in the stator windings of the synchronous machine, i.e. inverter output current converter. The frequency of the inverter output voltage is set by the control system 6 by any of the known methods, the magnitude of the inversion angle J (the angle between the first harmonics of the output current and the voltage of the inverter inverter) depends on the magnitude and sign of the voltage at the output of the frequency discriminator, since the signal is control for the inverter control system. Thus, for the current inverter, the output voltage can be generated from the counter-emf voltage of the inverter (Fig. 1), the range of changing the inversion angle / 3 being limited by the control system 6 due to its synchronization with the voltage of the synchronous machine. Usually, the inversion angle p varies in the range of 30–150 electr, hail, with angles greater than 90 el, hail, corresponds to the regenerative braking mode of the synchronous machine,

During the frequency start and during synchronization of the synchronous machine with the AC network, the distributor, pulses 11 alternately, with the frequency determined by blocks 12 and 13, generates control pulses by switches 14 and 15. At the output of switch 14, the corresponding sections of phase-generating voltages are connected mains supply, and the output of the switch 15 - corresponding to the corresponding sections of phase voltage at the inverter output of the converter. Voltage diagrams 59 and 60 generated at the switch output are shown in FIG. 3.

These voltages are essentially offset by some analogs of the voltages at the output of the mitels and the input of the inverter (when the synchronous machine turns synchronous with the AC network),

Up to the rotational speed of the synchronous machine, less synchronous, with the power supply network, the switching pulse frequency of the distributor 11 is determined by the operation of the block 56 of the limiting unit 13 which is synchronized with the voltage at the output of the switch 1 and the constant voltage proportional to the voltage at the inverter output of the converter. The output signal of the zero-organ 41 (diagram 63) of the block 56 together with the output signal of the zero-organ 41 of the main unit 12 is fed to the input of the logic element 48 so that if there are unit potentials at the output of the zero-organs 41 of these channels, 48 a signal is generated that triggers the one-shot 49, whose output pulse (figure 62) switches the pulse distributor 11 and sets the integrators 39 of all three blocks 12, 55 and 56 to the initial state.

At the same time, due to the large signal level at the output of the integrator with the bipolar inputs 25 (the phase difference of the supply voltage and voltage on the synchronous machine is large), the phase-shifting unit 12 synchronized with the AC supply network through the switch 14 generates an output signal corresponding to the logical unit, before block 56 of block 13 of limitation (Fig. 3, voltage 64 on the code of the null organ 41 of channel 12). Thus, before the rotational speed is less than synchronous, the switching of the distributor 11 of the phase-frequency discriminator 10 is carried out by the block 56 of the limiting unit 13, which operates at a frequency that is a multiple of the inverter inverter output voltage frequency (the multiplicity value is determined by the inverter inverter power circuit and for the three-phase bridge circuit is six). In this case, the integrator 39 of the block 56 operates in such a way that it stabilizes the volt-second area of the voltage difference received at its inputs 42 and 43 from the voltage sensor 54 at the output of the inverter 3 and the voltage at the output 20

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switch 15 (output phase discriminator). The level of these voltages is chosen so that the voltage at the output 20

5 is negative, therefore, the controlled master oscillator 9 operates in the mode of the minimum allowable inversion angle (30 electra grades), which increases the power supplied

 to the inverter load - a synchronous machine 34, which is proportional to the current value of the power circuit of the converter and the value of cos.

Thus, in the process of ch15

20

total start-up or speed control of a synchronous machine up to a synchronous one, the output voltage of the 20 phase-frequency discriminator is negative and close to the maximum possible level, and

The output 17 of the first switch 14 pulses with a frequency determined by the frequency difference between the supply voltage and the output voltage of the inverter inverter.

In this case, the average value at the inputs of the integrator 25 is always negative and equal to the average value of the voltage at the output 20 of the switch 15, therefore the voltage at the output of the integrator is always positive and close to the maximum possible level. The level of the ripple of this voltage is small and is determined by the constant of the integrator time, which can be chosen insignificant, since the average value of the input voltage of the integrator is constant in sign. Zener diode 32 provides an additional reduction of the voltage ripple at the output of the integrator 25, and, consequently, the minimum ripple of the control signal of the phase shifter 12, and as a result, the minimum angle of control jb by the inverter.

When synchronous with the network, the frequency of rotation of the synchronous machine 34 establishes a certain phase shift between the supply voltage and the voltage at the output of the inverter, the value of which depends on the output current of the converter

and power load synchronous machine. At the same time, the synchronization of the pulse distributor 11 begins to occur by phase-shifting the blow,

com 12, and the sign of the voltage at the input of the integrator 25 is changed, tag; as the voltage at the output of the 20 phase clock. the total discriminator becomes positive,

The level of this voltage determines the control signal controlled by the master oscillator 9, and hence the inversion angle j, which is obtained so that in steady-state mode (synchronous speed with the network) power is supplied to the synchronous machine (i. -COS P) ), equal to the power load on its shaft.

When synchronous with the supply network or 37, the frequency of rotation of the synchronous machine, the voltage on the code of switches 14 and 15 coincide in frequency, and their average values are determined by the phase difference between those voltages on the phases of the specified network which are bypassed by switch 36,

Since the output voltages of the switches 14 and 15 are fed to the bipolar inputs 26 and 27 of the integrator 25 (the output voltage of the switch 14 is fed to the input of the integrating amplifier 29 through the inverting amplifier 28, and the output voltage of the switch 15 is received directly), they subtracted, and the magnitude of the difference signal is determined by the phase shift of these voltages. The initial level of the output signal of the potentiometer 30, which determines the control angle of the phase-frequency discriminator, is chosen so that with equal frequencies mains voltage and synchronous mask, the output signal of switch 2.0 was positive and more than the output signal of switch 14; in this case, the output voltage of the integrator 25 will begin to decrease, changing the phase of the switching pulses of the distributor 11 generated by the unit 12 so that the voltage difference across the inputs 26, 27 of the integrator becomes zero, which

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corresponds to zero phase shift between shunt voltages when switching a synchronous machine by switch 36 to power

5 from the mains.

At the same time, due to the small time constant of the integrator 25, the process of synchronization of the voltage phase of the power supply to the network and the synchronous machine

 Oh happens in a few seconds

(instead of several minutes in the base object), which significantly reduces the time spent on sequential start-up and synchronization with the network of several synchronous machines,

Equal stresses on the synchronous machine and the network are provided by the excitation controller at the expense of supplying one of its inputs with a signal for the difference in the network voltage U and the voltage U on the synchronous machine. Switching the synchronous machine to the mains supply is carried out by

25 command sensor ip, uCf, L which controls the coincidence of the amplitudes (li), phases (LSD) and frequencies (dR) of the first harmonics of shunt voltages. First, the shunt switch 36 is turned on, which ensures that the synchronous maogana is switched on to the network 37, without a jog, then the converter is switched off via the auxiliary contacts of the switch 36.

(or blocking control pulses

rectifier 4 and inverter 3 and the inverter remains in the hot standby mode for emergency braking of the synchronous machine)

Thus, the introduction of an integrator 25 with bipolar inputs allows phase alignment of the voltages of the network supplying the converter and the voltages to

converter output without the introduction of a special phase discriminator, which simplifies the device. Connecting the integrator to the switch outputs significantly reduces its time constant and

thereby reducing the time spent on synchronization of the synchronous machine, due to the high speed of the phase controller.

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Compiled by V. Bunakov Editor L. Zaitseva Tehred 3. Paliy Corrector A. Zimokos

Order 8731/57 Circulation 632 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Branch 111111 Patent, Uzhgorod, st. Project, 4

Claims (1)

A DEVICE FOR SYNCHRONIZATION OF THE INVERTER CONTROL SYSTEM OF THE FREQUENCY CONVERTER, including a controlled master oscillator, containing a phase-frequency discriminator consisting of a phase-shifting unit, an output connected to the pulse distributor and the first and second switches, with the inputs of the first switch intended for connection to the mains. the output is connected to the first input of the phase-shifting unit, the inputs of the second switch are for connecting to the output of the inverter, the output for connecting to the input of the controlled master oscillator, the control inputs of the switches are connected to the corresponding outputs of the distributor, characterized in that in order to simplify the device and increase its speed , it is equipped with an integrator with bipolar inputs and a potentiometer for setting the control signal of the Phase-shifting unit, the first integrator input is connected to the output of the first mmutatora, a second input connected to the output of the integrator of the second switch, the integrator output from the reference signal control potentiometer phase shifter unit is connected to the second input of the phase shifter unit. ABOUT* ίο & 1206913