SU1339820A1 - Method of discrete frequency control and direct frequency converter - Google Patents

Abstract

The invention relates to a converter technique and m. used in variable frequency drives. The goal is to improve the quality of the output voltage over the entire range of control of its effective value, as well as to simplify the implementation with independence in terms of the phases of the formation of the output voltage. The device contains cathode-anodic thyristor rpynnri 4.5, the output of which are connected to the AC voltage regulators 8, 9. The order of alternating the connection W (L 20 g 22 23. 2H ZS

Description

each of the two forming voltages, is set alternately, which allows realizing sixfold of the input pulse frequency of the output voltage by two cathode-anodic thyristor groups. At the same time, the input to these groups

one

The invention relates to a converter technique and is intended for use in a frequency-controlled electric drive with discrete steps for changing the output frequency values below and at the input frequency of the converter, the shape of the output voltage curve can be close to sinusoidal, and its effective value is set to the desired adjustable value depending on the number of adjustable input voltage steps at the outputs of voltage regulators and frequency conversion can be carried out This is due to the natural commutation of the converter.

The purpose of the invention is to improve the quality of the output voltage of the converter over the entire range of control of its effective value, as well as to simplify implementation with the formation of the output voltage independent of the phases.

FIG. 1-6 show the timing diagrams that show how the converter works according to the proposed method; in fig. 7 is a power circuit of one independent output phase of the proposed converter; in fig. 8 is a block diagram of a converter control system according to the proposed method.

The diagrams shown in FIG. one

for the case of co2, co2 2-5 - for co

You have

"IO

Bh

on

Where

COD, cOgjj- output and input angular frequency of the converter. The converter is shown at - (j

™ 4tti ex

6 5

(Fig. 1 and 6), with I (Fig. 2),

the voltages of the opposite polarities, respectively, are fed through the regulators of the alternating voltage to their output terminals and summarize them in a common circuit with the load phase of the converter. 2 sec. f-ly, 8 ill., 2 tab.

12

7 (Fig. 3) and

 t

13

/.

(Fig. 4 and 5).

five

five

five

The simplification of the frequency converter and the combination of regulation of the output frequency and voltage of the converter according to the proposed method is implemented using the device (Fig. 7) as follows.

The two and, + and and, amplitudes of the input voltages of different phases and different polarities are summed up to form at each time the output voltage of the converter equal to the required reference output voltage and u, the sinusoidal form and given discrete frequency (Figs. 1 and 2 above) and with discrete approach of voltage regulation to the given one (below). According to the inventive method, two opposite polarities and those closest in phase to the input voltages are used to form the output voltage of the converter. For example, according to FIG. 1 voltage Ui, U (cOj, t -)

in the first half of the input voltage connection interval from tg to and according to fig. 2 input voltages and, V sinjU t, Uj (QB, t - -)

and,

from tjj to tg (tf, in Fig. 1-6, the time reference is taken). The alternation of cyclic connection of each of the two input J, Uj components U ,, of the voltages is carried out alternately through half

every interval of connection of the T th input voltage, for example, I see a cyclic connection U made at time t

about

and, - at the moment of time t (Kr. 1) and the moment of time t (Fig. 2). Thus, in the second half of the input voltage connection interval, i.e. after time t, u,

 V sinCa.t +

2Z ZL

and does not change

phase (fig. 1), and after time t

and and. does not change

and, (Dert phase (Fig. 2).

After each alternation of the connection, the newly connected input voltage U, or U is adjusted by the amplitude value according to the sinus dependence within the range of this trigonometric function from the zero value - at the time of connecting the input voltage to 0.866 in half of the connection interval of each input voltage. Further, the value of the trigonometric function with its switched phase decreases from a value of 0.866 to zero at the end of the connection interval. At the same time, the amplitude values of each of the two and, or Uj input voltages are controlled simultaneously for all three output phases of the converter according to the dependences Kj, -, ssin in

first half and Cr-h- sin (2iltu +

+) in the second half of each interval T connecting the input voltage, where Kp is the coefficient of regulation of the required reference effective value of the output voltage of the converter, 22 co and ex

the difference between the output and input angular frequencies of the converter, and t, varies within O t; "Each interval T connect the input voltage

Thus, according to the given control dependencies, the amplitude value of each of U, or u2 input voltages varies from zero at the beginning of the connection interval to the reference required amplitude value of the output voltage at half the connection interval and decreases according to a trigonometric relationship to zero at the end connection interval 20

input voltage, as can be seen from the curves U, or Uj (Fig. 1-6).

The equality of the connected values of the input voltages V, Ugti and a half of the interval of their connection are visible (Figs. 3 and 4) at the instants of time t ,, tj, and, and, at the instants of time at

all three output phases at the same time, the same dependence of the control U on the zero value at the time points, and the values of U, at the time points t, | tj are also visible. The regulation of the effective value of the output voltage is made by varying the value of the coefficient K- depending on the control of the input voltages. The total interval from t connecting the input voltage Uj (Fig. 4) is shown in all three output phases by equally adjustable values

 2 n

input voltages (cjg, t +)

2 -Vn, sin ", t, (cOe, t - -)

respectively. The full interval from t to tj of the input voltage connection is shown in all three output phases of the converter by input voltage V sin (c3avt - -),

 ex

2T

35

(), V sinoe.t respectively

vetstvenno. The other intervals for connecting and regulating input voltages and, and, are similar in frequency conversion with the difference that in each successive interval, as connected U, or and there are alternately lagging input voltages at COgju -Wg and leading at COEJ ,,, YOU

In tab. Figure 1 shows the data characterizing the frequency conversion process for an example (Fig. 4 and 5), where the function of time t is represented as continuous.

The times tJ (Figs. 4 and 5) correspond to the same conversion processes, only 55 of Figs. 5 with respect to the input U ,,, voltages and.

,,

t, Ug

(co, t

- -) 3

Ur. (w ,, t

BA

21Gch

+ -g-) shows them the corresponding switching functions h of cyclic switching of input voltages, from h to h for U, i.e. positive polarity Ug ,, and from h, Q on and, i.e. negative polarity Ug. Here, the values from b, to hj and from h, o to h, 2 refer to the first output phase of the converter (fig. 4), from h. to hj, and from h, to hjj.- to the second output phase, from hj to h and from h, j to the third. Within each group of switching functions, for example, from h to h, the upper ones refer to id, medium to and. and lower to u-. FIG. 5 also

wasp

the amplitude control functions of sinZQt are shown,

 sin (2Qt - -) and and „with sin (2jlt of which only values between 0.866 and -0.866 are used. In this case, for adjusting and, using U values, shown by a thicker line above the zero line of function U, and for U are the values shown by the thick line below the zero line of the function U. The continuous thick lines U ,, or. correspond to positive values of the regulating function U, and the discontinuous thick lines to negative values, for example, from t to t, U The amplitude is controlled by the AND function.

 about.-

 sin (2s2t + T limits from

t, to t - function -,

about/

 sin (2at + -). Data in the form of the depicted curves, switching and amplitude regulating functions (figure 4 and 5), summarized in table. 1, give non-. Walkable information to implement the proposed conversion method. The full cycle of repetition (Fig. 5) covers the interval from t to t, after which its repetition begins.

The frequency of the amplitude regulating function 2 Q is CO, and the switching function of the input voltages is 3jl. Having data on the conversion process (Figs. 4, 5 and Table 1), easily

write expressions for the output voltage of the converter. For example, when with vv1ch vk - 4 and 5) the voltage of the first output phase of the converter in the time interval t - t is equal to

t, KpU, (u, u ,. and.i ,,)

and

 Kp.U | sincOg t-sin (2Qt + | -) + + -sin (+ -) j. (-sLn2Qt) l

 KpU j sincJg.t-sin (2s7t + -) +

27 + sin (0g, t + -). Sin2Q.t.

The expression U in the time interval t, ... t is equal to

and

2 G U.

Bb, x.,, Sin (Q ,, t + -)

25

-sin (-f | -) + -sin (Ua.t + | -)

xsin (27it - -).

Further, the expression U, q, over time intervals can be written, using the data in Table. one.

Similarly, the voltage of other output phases can be written, for example, in the time interval t - t,

2 / - sin (CO ,, t - -) x

 sin (2Qt -) - (-sippcov t)

27

-sin2at) j;

.g. (Q ,, t + f}

2 ii G2 1

sin (2nt - -) 4 -sin (- -) U

-sin2sit) j. - -J

Just as the participation of each of

input voltages are determined by its switching function h, the participation of the corresponding amplitude-regulating

function U can also be expressed by its switching function 1. In this case, the switching function 1 is determined separately for the amplitude-controlled function U, used for the value of the input voltage U (positive polarity, and separately 1 for the UMI used for input voltages i, k, and, are formed from the sign leHHft of the functions of both polarities (Fig. 5). Thus,

Vl. “Al. - imd1p + - and „, 1,5 - and“, 1 ,,;

UMZ, - U, clis - U; ,,.

Then the output voltage of the phase p can be represented as the sum of the effective combinations of multiplications of the input and amplitude-regulating functions separately for the input voltages of positive Ud, Ug, U. and negative -U, - Uc polarities UB ,,, p and „, Ip , (ID, +

 and, hp.

+ U, hp) - U, lp, (, - H

- + in general, the output voltage in the natural form is Uft ,,, H (t) .U ,,. L (t) -U, where H (t), L (t) are the corresponding switching functions of the input and amplitude regulating voltage of both polarities

In the converter (Fig. 7), in one of its output phases, phase terminals 1-3 of the input voltage are connected to the input terminals of two cathode-anodic thyristor groups 4 and 5, the corresponding output terminals 6 and 7 of which are connected to the first 8 and second 9 controllers alternating voltage In this case, pin 6 is connected to the beginning of the primary winding of the first controller 8, and the end of this winding is connected to the common terminal of 10 phases of the input voltage of the converter. Output 7, the second cathode-anodic thyristor group is connected to the end of the primary winding of the second controller, and its beginning is connected to the common input terminal 10 of the converter. The output terminals 11 and 12 of the first and 12 and 13 second voltage regulators are connected in series with the terminals 11 and 13 of the converter load phase. Thyristors from 14 to 19 and from 20 to 25 form, respectively, the first 4 and second 5 cathode-anodic thyristor groups, and the thyristors from 26 to 33 and 34 to 41, respectively.

339820

but the keys of the variable output voltage of the regulators 8 and 9,

The converter works as follows f. shimm way.

The cathode-anodic thyristor group 4 together with the voltage regulator 8 forms the component U of the output voltage of the converter,

1Q and the group of 5 thyristors together with the regulator 9 - the voltage Uj, At the same time, both the cathode-anode groups and the voltage regulators each individually (Fig. 7) provide

15 conduction current in both directions, which is necessary when implementing direct frequency converters. The summation of the output voltages of the regulators 8 and 9 impulse 2Q is connected in series with their output terminals 1.1, 1 2 and 12, 13 in a series circuit with terminals 11 and 13 of the load phase.

In tab. 2 shows the intervals for shaping the output curve for example. 6

KIA at h included thyristors of the converter,

At time t | switching on the thyristor 14 voltage from the first

30 of the input phase is supplied to the voltage regulator 8, where from the secondary of its circuit with the included thyristor 28 it supplies voltage to the series load circuit. Wherein

35 includes the second step of voltage regulation U, with its value of 0.7 relative to the nominal value of the output value (U

bull 9

on

fig, 1). At this moment in time t, the switching on of the thyristor 21 supplies the voltage from the second input phase to the voltage regulator 9, where it supplies voltage from the secondary circuit using the switched on thyristor 35. into a serial load circuit. This includes the first step of voltage regulation U- with its value of 0.35 relative to U.

 W | X 9

The converter works similarly at other points in time and at other levels of the output voltage (Fig. 6) and at different output frequencies (Fig. 2-6).

The proposed converter allows two cathode-anodic thyristor groups (a total of 12 thyristors) to form, at the output, a six-fold input pulsation frequency in the output voltage of the converter, using the summed two voltages from the voltage regulators. Compared with the known method, where each of the input voltages U, or is formed using each of the 16 thyristors bridge circuits, the application of the proposed method reduces the number of thyristors and realizes the operation of the converter in the output phases. Independent operation of the output phases allows realizing a single-phase converter of this type, as well as independently choosing the switching points of the output phase thyristors, which in turn improves the quality of the output voltage of the converter.

The control system of the proposed method and the converter should, at the required time points, supply control pulses and distribute them to certain thyristors. These points in time and the included thyristors are set by the program, for example, similar to that given in table. 1 and 2, depicting a conversion process according to the proposed method (Figs. 1-6). For example, the full cycle of the conversion process is shown in FIG. 5 time intervals from

to "°

And At each of the indicated times from t to tg, control pulses are required to be generated via corresponding control channels (for example, according to Table 2 and the converter circuit, Fig. 7), which is specified by the program of control thyristor control pulses. The control system must synchronize the required sequence of the control pulses (program) with a certain phase of the input voltage converter system (for example, the time t in Figs. 1-6) so that the frequency conversion according to the pulse supply program is realized in a situation similar to at which the program is made.

For this purpose, one or several comparators are used, which reveal the times of zero values of the corresponding input voltages. When such time points are detected, zero values, for example, phase linear and intermediate values of them, can be obtained in sum

33982010

the sequence of control pulses, which (with sufficient precision in the selection of discrete points in time) can be used to select (decrypt) the control pulses specified by the program. Further, from this sequence of pulses, those that are necessary to realize

1Q of the compiled program, and distributed to the corresponding thyristors. Control programs are composed for each output frequency used from discrete values.

15 An example of one of the possible solutions of the software control system is shown in FIG. 8. The half-period of one phase of the mains voltage is filled with a high-frequency pulse train, it is read out and at the required moments (according to the thyristor control pulse feeding program), control pulses are generated. Similar devices, containing a 1st null organ, are connected via an NAND gate to the first binary counter, the counting input of which is connected to the output of the pulse generator, and the overflow output

3Q with shaper are also known. Thyristor control devices are also known, which contain a synchronization unit, a clock pulse generator, a counter, a clock decoder20

25

owls, counter, decoder and pulse generator.

Synchronization pulse shaper 42 (FIG. 8) with mains voltage generates a short pulse

at the time of the transition voltage through zero. The synchronization unit 43 synchronizes the pulses of the high-frequency generator 44 with the pulses of the generator 42.

Impulse shaper 42 is

a resolution pulse for the passage of high frequency pulses from the generator 44 to the output of the block 43. The synchronization block 43 sets the number

pulse generator 44 — between two pulses of the generator 42. The pulses synchronized with the network voltage are fed to the input of a binary counter 45 pulses, which counts them. The decoder 46 generates repetition pulses of the counter 45 after the number of pulses of the generator from the synchronization unit 43, corresponding to

eleven

DURING the pulse control transducer pulse duration The output of the binary pulse counter 45 is connected to the decoders 47-49 pulses. The decoders decode the pulses following the output of the synchronization unit 43 and are counted by the binary counter 45, for example, the corresponding time from t to tg (Fig. 5). The decoded pulses arrive at the distributors 50-52 pulses through the thyristors. Pulse distributors are a trigger line. The blocks 53 amplify the control pulses. Blocks 54 and 55 are inserted to reduce the effect of interference and eliminate spurious impulses. Block 54 counts a predetermined number of input voltage periods, after which the decoder 55 of the reset pulse resets all previously recorded information.

13

8S

n

 ex

Claims (2)

1. A method of discrete frequency control, consisting in cyclic connection at certain time intervals of input voltages with forward or reverse order of their alternation to form the output voltage of the converter, in summing the voltages of different input phases, in adjusting the amplitude value of each of the two input voltages. voltages with a repetitive dependence of their change in each interval of connecting input voltages, in setting discrete values of frequencies of the output voltage of the converter but dependencies V  ™ CO.vHa-based pre the compiled program for the supply of pulse control thyristors of the converter, mdesOts | |, with gx the angular output and input frequency of the converter, m is the frequency of the ripple, k, n are integer numbers, about the fact that, in order to improve the quality of the output voltage of the converter, the output voltage transducer is formed by two opposite polarities, the closest in phase and adjustable ten y. 5 20 339820 2 by the amplitude value, the input voltages of different phases, the alternation order of which is connected alternately through half the connection interval of each input voltage, during which the amplitude values of each of the two input voltages are controlled according to dependencies Kp - jesin2f7t IJ in the first half and I and U + -; - in the second half-interval of connection of each input voltage of the converter. Kp-gsin (2Qt fault V - At b P and g outm the ratio required effective value of the output voltage of the converter to the nominal Nom, 2 Q within limits 6V Oh and the time SST met t, "Tj. each interval T connect the input voltages of the converter. 0 0 five 0 five 2. A direct frequency converter containing in each of its output phase two cathode and two anode thyristor groups, the inputs of each of which are connected to the terminals of the phases of the three-phase input voltage of the converter, and the outputs of the first and second cathode-anode thyristor groups are connected together , which also contains transformer – thyristor variable voltage regulators and voltage supply control units connected in series to the load phase circuits and software control implementation units, including a comparator, a counter pulses, decoders and pulse distributors, characterized in that, in order to simplify the frequency converter with the formation of output voltage, phase-independent, the output of the first cathode-anodic thyristor group is connected to the beginning of the input voltage of the primary winding of the first regulator, and the end of this winding - to the common output of the input voltage of the converter, the output of the second cathode-anodic thyristor group is connected to the end of the input output of the primary winding of the second regulator, and its beginning to the common input output reobrazovatel. (T) I s h to Rt n - M SE CN s & CN WITH with tD four Se , S4G4G4 : uh t cm CN f3 & P - with p p uh b with & CN  dT I I I I I I I I N S p IP SE at 4J I 1l U With a nominal value of U ,,, table 2  .  y x in A. / 7 K L-, 7  . / A /. 7 V: / v /. / Vy v  A 1 /% ± h . . w / o / L w / / / g / l // ;; r  / i „ ./A . , -r-yc- .. r ./- , -, Y  A . . w / / / g / l // ;; r  / i „, A /. , c- .. r ./- .3 . Ut H.ZH Twigs H 53 53 5J Editor N. Dumbass Compiled by G. LSCHYK Tehred M. Dvdyk Proofreader S. Shekmar Order 4241/52 Circulation 659Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4