SU1757063A1 - Method of controlling converter with width-code regulation - Google Patents

Abstract

SUMMARY OF THE INVENTION The control method consists in periodically turning on and off with a mutual phase shift of 60 e hail of the main valves of the three phase bridge converter. The conduction and open-state zones of the valves are 180 el fad. Inside the extreme clock intervals of 60 degree durations of each control zone, modulating control stanels are formed, the number of which within each of the mentioned clock intervals at the initial output frequency E0 is equal to U In the range of the output frequency of the converter Fo-U / 2 F0 in the central part of the said clock intervals form additional modulating control signals with a duration of 12 e-hail Related regulation The frequency and magnitude of the voltage according to the economic law U / F-const is carried out at the expense of continuous stepwise variation of the durations of the extreme 24-degree sections of the main and modulating signals as a function of the current and initial output frequencies, the value of the control range and the amplitude of the supply voltage 4 silt (L S

Description

The invention relates to power electronics and can be used to control valve converters that power individual or group systems of a frequency-controlled asynchronous electric drive.

Algorithms for 120- and 150-degree control of three-phase bridge converters are known that provide a relatively good harmonic composition of the output signal curve, the shape of which, however, in these cases essentially depends on the nature and parameters of the load, which limits the widespread use of such control algorithms in electric drive converters.

A 180-degree three-phase bridge converter control method, invariant to load parameters, is also known, a characteristic feature of which is that modulating control signals, the number and duration of which determines the magnitude of the output voltage of the converter, are formed within the extreme clock intervals of 60-degree durations ( in the general case, at the initial frequency, it is reformed within the corresponding subintervals of n signals) included in the composition of the positive half-period about Qdim each gate and the negative half-cycle closed state

4 SL xj

O u)

However, with wide-range adjustment of the output frequency of the converter, a sequential change in the number of output pulses in the output voltage half-wave is carried out in a discrete way and leads to the appearance of undesirable current surges in the power circuits at the moments of transition from one control band to another.

The aim of the invention is to improve the quality of the converter control process due to the smooth unaccented variation of the output voltage shape during the associated frequency control F and the output voltage according to the law of constant ratio of the voltage to frequency in the output frequency range. Fo n e

GO 1G-

When controlled by the method in which the main valves of different phases and groups of the converter are periodically turned on and off with a mutual phase shift of 60 e. degrees in the sequence + A, -C, + B, -A, + C, -B, and for each valve they form positive conduction half-periods and negative half-periods of the closed state, each of which consists of three clock intervals of 60-degree durations, inside the extreme half-periods of clock intervals, they form modulating signals (pulses) of control, the duration of which determines the magnitude of the output voltage of the converter, and at the initial output frequency Fa the clock intervals are divided into even number in sub-intervals, in the frequency range

gn e fo

FO in the Centers of the indicated clock intervals form additional control signals with the corresponding half-period with a duration of 1 / 30F, the duration of the clock subintervals is defined as 0.8 / 6F0n, and the formation of the modulating control signals is carried out in the middle of the clock subintervals, the midpoints at the intervals of 24 to the degree plots are synchronized with the middle of the corresponding central on half of the clock interval of the clock subinterval (with an odd value of n / 2) or with the end and the beginning of the corresponding tstvuyuschih central on 24-degree sections of clock subintervals (with an even value of n /) with ttom on the frequency sub-bands F, T F c. inside the specified 24-degree parts. form by i modulating control signals with a length of 0

five

0 I 1 9 F

strength - (- p), on the frequency subranges at the edges of the 24-degree sections form control signals with duration

; i OJL MlLJLH -H) E + 0.8 Eo 24 F12 F0

and the duration of the remaining (i-2) and control signals is determined in accordance with the dependence

; -0.8 (1-1) E-0.8Eo

L6F0nE (l-1)

the values of the boundary frequencies, transitional from one, of the control sub-band to another (F i F i), are found as

0

P FonEQ-1

n-TGRGUP TE-

0

five

0

five

0

five

to the output frequency range converted E Fo n E FO

tel-tt-fi with g-. in clock centers

2 to 1, o Eo

intervals are synthesized on a single modulating control signal with a duration

, 1 1.6 ЕО Л Ш n E FO

where E and Еo are the current and minimum (nominal) amplitudes of the supply voltage converter, respectively

Fig. 1 is a diagram of the main power connections of the three-phase bridge converter, performed on the fully controlled valves of Fig. 2, time diagrams illustrating control signal generation algorithms and a linear output voltage curve; in fig. 3 is a functional diagram of a converter control system; Fig 4 shows timing diagrams illustrating its operation.

The timing diagram (Fig. 2e) shows the shape of the control signal Uy synthesized during the positive conduction half-period of valve + A at the initial output frequency F0. Below, the corresponding curve of the linear output voltage of the UAB converter is plotted. In accordance with the algorithm for generating control signals according to the proposed method for each valve, the entire control range has a positive conduction half-life and a negative half-period of the closed state divided into three equal clock intervals of 60 hp each. In this case, the formation of the modulating control signals, opposite to the corresponding half-cycle of control, the duration of which determines the output voltage of the converter, is carried out (Fig. 2) within the extreme clock intervals of each half-period e.

A specific feature of the control method is the presence over most of the control range in the middle of the clock intervals additional 12-degree control signals, which are opposite to the corresponding half-period. The remaining 48-degree section within each clock interval, consisting of two symmetrical parts, is broken up at the initial frequency F0 into π segment (subintervals) with a duration of 48 / n el. hail (Fig. 2, the curves correspond to the variant). In the middle of each of the clock subintervals marked below by arcs, modulating control signals are formed, the number of which at the initial frequency within each half of the clock interval is equal to n / 2.

The overall range of the associated control of the magnitude and frequency of the output voltage of the converter according to the economical law with the constant ratio of the magnitude of the voltage to the frequency for the method, taking into account the fluctuation of the supply voltage, is

P fo n e

h ° 1.610

where E and Eo are the current and minimum (base) amplitudes of the supply voltage, respectively.

At the same time in the frequency range FO n E FO-md-p-regulation of the output frequency

Ј. With

This is accomplished due to the continuous stepwise variation of the durations of the main and modulating control signals formed along the edges of each 24-degree segment of the corresponding clock intervals. The adjustment process takes place in two stages according to two main reference algorithms, with the boundary values of the frequencies transitioning from one control subband to another, defined as

..tsFO n E (i -1)

F | TTTFTTM and

iFonE (l-l)

Fl 2 (1Т1) (and F, F i is the number of modulating control signals generated inside the specified sections. At the same time, the midpoints of the 24-degree sections are synchronized with

the middle of the corresponding central clock sub-slot (for an odd N) or with the end and the beginning of the corresponding central clock

podintervzpov (at an even value of N)

On control subbands, on which F i F F 4-2, the duration of the modulating control signals is defined as

, 0.8, 1 2Ео, Ш (F ГТТГЁ} (similar to the subranges correspond to the curves constructed in Fig. 2a, c). Within the subranges of regulation,

corresponding to the output frequencies F i F: F i, modulating control signals with a variable duration are formed along the edges of the 24-degree sections

j -PA M Cl rJLlLiii 2) E + Q.8 EO

24 F12 F0n E (V)

and the duration I of the remaining (-2) -i modulating signals is (Fig. 26)

i - ° -8 СЬ1) Ео А SFonETi TJ 1

8 high output frequency range

0

0

five

0

five

converter

n E FO n E FO

T6Е7 wp ° ces2E0

As the frequency rises, the duration of the additional modulating control signal central to the clock interval begins to decrease smoothly.

5 which at f

- Equivalent

(12

2t- | gaog171 /, “lWD og. Isols

email hail) .v

The specified change is made

, 1 1.6 Ео /. n% according to I tg-s-e-g (Fig. 2d),

O G P t Go

the value of I decreases to zero at the upper output frequency Fm ls.-0 (for and

I, D to

at), at which the value of the output voltage takes the maximum value.

The formation in the midpoints of the clock intervals over most of the control range of the signals of 12-degree durations provides in these modes complete elimination of the output voltage of the fifth harmonic component from the spectrum, which significantly improves the harmonic composition of the output curve. The said principle of forming control signals, the essential feature of which is the continuous identification (coding) of the durations of the extreme inside the sections of the main and modulating control signals.

 WITH

signals with the main pulse array, due to which a smooth, unstressed transition from one control subband to another is accomplished, can therefore be defined as a code-width,

In relation to the variant (,) analyzed (Fig. 2), the calculated values of the boundary frequencies take the following values:

for FVl, 09F0; FV1.71F0;

for F 2 F 2-4F0.

The durations of the modulating signals A for the frequency subbands F0 F and F 2 F F 4, as well as the durations I and I on the subband F F F F 4 are determined by substituting the corresponding values of i into the corresponding expressions indicated.

The functional diagram of the control system (FIG. 3) implements the control mode according to the method for the variant, FIG. 4 shows the timing diagram of its work. In this system, the output signal Ui of the frequency setting unit 1 is fed to the generator input 2 clock pulses, which form a sequence of pulses, the frequency of which throughout the control range is 12 times higher than the output frequency of the converter. These signals arrive at the input of the generator 3 of a linearly varying voltage, synchronizing its operation, so that at the output of the generator 3 a voltage Uz of sixfold frequency, symmetrical in both directions, is formed (Fig. 4) compared to the output signal of the converter, the amplitude of which decreases in proportion to the increase in the output frequency and is constantly recorded by the sensor 4 amplitude

From the output of sensor 4, a signal proportional to the amplitude of the voltage Uz is fed through amplifiers 5 and 6 to the inputs of comparators 7 and 8, in which they are associated respectively with the output voltages Uz of generator 3 and Us of integrator 9, to the accumulator element 10 which included a two-position key 11, controlled by the output signal of the comparator 7 The transmission factors of amplifiers 5 and b are 0.8 and 0.4, respectively. The output of the integrator 9 includes a threshold node 12 fixing the minimum (zero) voltage Ug, which is connected via input OR 13 to the input of the counting trigger 14 connected to the output 15 of the polarity of the integrator 9, and The tg / s of the integrator 9 and the amplitude of the output wave signals of the unit 15 are adjusted so that the steepness of the signals Us and Ug is identical. In this case, the initial setting of the output states of the indicated elements should ensure the maximum amplitude of the signal Ye, with the minimum voltage Uz.

For a period of time when the signal value Uz exceeds the voltage level at the output of the amplifier 5, the comparator 7 issues a command to switch the key 11, after which the capacitor 10 opens and the signal Ub is connected to the output of block 9. Due to the given connection scheme of the nodes 5-15 at the output of the integrator 9 (Fig. 4), a symmetrical sawtooth voltage Woo is formed with repeated intervals of a constant level equal to the amplitude H with a duration of 12 el. hail, in the central parts of the clock intervals.

The specified signal Ud. being the main sweep voltage in the system, it is fed to the inputs of the compres- sioning nodes 16-18, at the outputs of which the circuits form short unipolar pulses. Signals from the outputs of adders 13 and 20 and amplifier 21 with a transfer ratio of 0.5 are fed to the other inputs of the comparing nodes 16-18, the inputs of which receive signals from the source 22 of the reference voltage and the integrator 23. At the time the signals at the inputs are equal nodes 16-18 the system synthesizes commands (short pulses) on the formation of the fronts of the output pulses, which through the OR 24 element arrive at the input of the counting trigger 25, which is connected by its output to the information input of the logical distributor of control pulses on the gates Azovatel 26.

The output of the trigger 25 is also connected to the capacitor 27, which allocates a constant component of the sequence of pulse signals from the output of the trigger 25. The voltage of the capacitor 27 goes further to the healer 28, in which it is divided by the analog frequency signal Ui, resulting in At the output of the divider 28, a voltage is formed at an appropriate scale proportional to the total duration of the output pulses over a half period. This signal goes further to the negative input of the integrator, which is connected to the second positive input with the source 22 of the reference voltage, the amplitude of which is U25 -1-. Where

Uzt - maximum amplitude of the signal generator 3 observed at the initial output frequency of the converter Thanks to the above switching on, the amplitude of the signal at the output of the integrator 23 is proportional to the value (i-A) of the duration of the main output pulses The output voltage curve and the signal at the output of the summing amplifier 21 is proportional to the half duration A of the modulating signals management

In the process of coupled adjustment of the frequency and voltage of the converter, the internal feedback loop of the system, including the nodes and blocks 23, 25. 27 and 28, provides for the adjustment range from the initial frequency F0 to

FQ P

F2; -continuous implementation

according to the astatic principle, the formation of a correction signal arriving at the inputs of adders 19 and 20 and directly to the comparator 18 and automatically maintaining a constant volt-second total area of favorable pulses in the half-period during the change of the output frequency

At the same time, on the specified range, the implementation of the presented functional dependences between the duration of the signals controlling their temporal position and the current values of the output frequency of the converter as well as the automatic transition from one control subband to another, observed at the specified boundary frequencies F, and F i, is performed automatically.

Starting with frequency

with F ° n FT, the magnitude of the U20 signal exceeds the amplitude of the sawtooth voltage, and the half-period of the linear output voltage curve is synthesized with three pulses. The magnitude of the signal U21 at the output of amplifier 21 with a further increase in frequency decreases successively to zero at a frequency F of 0.8 Fm.

Half-wave of the output signal of the converter after this moment and up to the maximum FO n

Noise frequency Fm

sixteen

formed from three

pulses at half period

This moment is recorded by a logical node consisting of a comparator 29, one input of which receives a signal from the output of sensor 4 of amplitude and the second receives a constant voltage from the first output of source 30 defined as

llЛ

Uao (i) - --- According to the signal of the comparator

29, the key 31 closes, after which, in the compreshive node 32, the current value of the signal Uz is compared with the voltage taken from the second output of the source 30 and defined as

,,, 0 8 Ihm 2 from (-) - ---

0 To the input of a three-bit register 33 over the entire adjustment range, pulses are output from the generator 2 clock pulses Numerically expressed states of the output bits Oz Q2 Qi pe5 of the horn 33 at the period of the output frequency (Fig 4) are respectively recorded as 100, 001 000 101 110, 111. these signals arrive at the clock inputs of the logic distributor 26 Logic functions,

0 implemented by the valve 26 and received in the form of control signals to the corresponding valves, have the form

+ A-QiChH Qi 02112 5 + 01 Oz025

five

± QiQ2QT QiQ3U2 QiQ2U25 + QiQ2U25 + QiQ3

iC QiQ; t-QiOiU2r) -QiQ2Q25

Thus, the proposed method

0 allows for a smooth, non-impact

changing the shape of the output curve on everything

conversion control range .... n e fo

l, providing at the same time in the zone of gos, I, Oh to

5 a complete elimination of the most undesirable fifth harmonic component in the output voltage spectrum, and this is ensured in the simplest way without additional switching of the power circuit valves causing additional electric energy losses. This eliminates unwanted current surges in the power circuits of the converter and the load that is significantly

5 improves the quality of the electrical energy conversion process as well as the reliability of the operation of high-power converter systems and systems of frequency-controlled erectro drive as a whole

Claims (1)

Claims The method of controlling a converter with a width-code control, is that the main valves 5 different phases and groups of the converter are periodically turned on and off with a mutual phase shift of 60 e-hail per series ™ + A-C + B, -A, + C-B, and for each valve they form The positive conduction half-cycles and the negative half-periods of the closed state, each of which consists of three clock intervals of 60 degrees, form modulating control signals within the extreme half periods of the clock intervals, and at the initial output frequency F0 the clock intervals are divided into even n number of subintervals. characterized in that, in order to improve the quality of the process of wide-range adjustment of the converter due to smooth unaccented variation of the output voltage form during the associated control of the frequency F and the output voltage according to the law of the ratio of the voltage value to the frequency output frequencies F0-,. in diazzo, o to n e fo no frequency f0-gp-- at the centers indicated . to clock intervals form additional control signals which are opposite to each other with the corresponding half-period; by value - „« p clock intervals are determined by K e K F0 n The control signals are carried out in the midpoints of the clock sub-intervals, the midpoints of the 24-degree sections at the said intervals are synchronized with the middle of the corresponding central half-clock interval of the non-modulated duration 0 five 0 five Q five an even value of p / 2 or with the end and the beginning of the corresponding central on 24-degree sections of the clock subintervals with an even value of p / 2; 0.8 x 1 2 Eo, T21 7 7yyyy) on the frequency subbands F i FF 1 at the edges of the said 24-degree sections generate duration control signals Ji -M - 0.8Q -1) 0 2) E + 0.8Eo 24 F12 Fo n E (i - 1) and the durations of the remaining (i-2) -n control signals are determined in accordance with the dependence ; -0.8 (i-1) E-0.8Eo 6F0nE (l-1) the values of the boundary frequencies, transient from one ps, 1 control band to another (F i F i), are found as Fon Efi-G) 2 (i-1) (i-b27E + TEo: p | i FQ n E (1 - 1)  2 i - 2 Eo in the output frequency range of transformed E Fo n E F0 tel -ffc-- at clock centers / toI, D to intervals are synthesized on a single modulating control signal for a long time1 1 A Pstu I TGg: V s, where E and Eo OGPS Go respectively, the current and nominal (minimum) amplitudes of the supply voltage converter. F 1 About 30 ° Shg1 ABOUT FIG L