SU1757064A1 - Method of controlling three-phase bridge converter with width-code regulation - Google Patents

Abstract

SUMMARY OF THE INVENTION The control method consists in periodic switching on with a mutual phase shift of 60 el. The gradient of the main valves of the three-phase bridge converter at the same time of the conduction band and the closed state of each valve is 180 e. hail. The output voltage is controlled by varying the duration of the modulating signals generated within the extreme 60-degree clock intervals of the said conduction zones i of the closed state of the valves. It is proposed to make continuous adjustment of the duration of the output frequency and the output voltage. of the main and modulating control signals generated at the boundaries of the said extreme contact intervals. Duration of clock subsync fishing, inside and in the middle are formed modulating control signals to control the entire range varies depending on nonlinear providing a rational number of output pulses per half-wave of the output curve at each frequency subband. 2 hp f-ly, 4 silt SP C

Description

The invention relates to electrical engineering (a subclass of power converter equipment and electric drive) and can be used to control converters for a variable frequency drive of alternating current based on autonomous voltage inverters.

Asymmetrical key management algorithms for three-phase bridge converters with 180-degree control are known, in which control modulating signals are generated at the extreme portions of the clock subintervals, into which the clock intervals of 60-degree extension of lostei are divided.

However, the spectral composition of the output voltage of the transducers with similar control laws is not very good and often needs special improvement.

A converter control method is also known, which provides an improved output voltage. A characteristic feature of which is the formation of modulating control signals within the extreme clock intervals of the conduction half-periods and the closed state of the valves.

However, the wide-range control of the output frequency of the transducers accompanied by a change in the number

but

vj o

 J

pulses in the output half-wave, when controlled by an algorithm, is carried out in a discrete way and causes current surges in the power circuits at the moments of transition from one control sub-band to another.

The aim of the invention is to improve the quality of the control process by smoothly changing the shape of the output voltage of the converter without a shock.

When controlled by a method that provides N-fold coupled frequency control and the output voltage of the converter according to the law of the ratio of the voltage to the frequency at which the main valves of different phases and groups of the converter periodically turn on and off with a mutual phase shift of 60 el . 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 lengths, within the extreme half-periods of the clock intervals, control modulating signals (pulses) are generated, the duration of which determines the magnitude of the output voltage of the converter; the formation of the specified control modulating signals throughout the whole range is regulated and, starting with the initial frequency F0, is carried out in the midpoints of the clock subintervals with the duration r f Fo

6 F (F0 N + Fo - F)

with the middle

the mentioned clock intervals are synchronized with the middle of the corresponding central clock of the clock subinterval (for odd N) or with the end and the beginning of the Corresponding central clock subintervals (for even N), while on the frequency sub-bands F i FF 1-1-2, as well as at

Fo n e

odd N, in the range F 3- -F--. inside

clock intervals form on I modulating control signals with

1 / 1Eo h

fr duration (p pg Ё N

on

I -

i G3

and i

P-rgkg RSG - T -o E N

frequency bands Fi F i at the extreme parts of the clock intervals form control signals with duration

1 T2T

j. „. Ј -.- gn and duration os1 i Go t (I - I) I M

tialo-2) -and.ign, controls determine

at

BUT

according to

Fo

dependency eo

5 F (Fo N + Fo - F) 6F0E (i-1) N the values of the cut-off frequencies F i and F i, which are transitional from one control subband to another, are found as

E0 ((i-0-J Ee () tEN (i-0 z-4E ", EN (; - i (

F.-F,

2E „

 М-ШИЫСЕ М-ЕМО-ОГ-Е (i-0 (i-N-0 Ж0

where, 4.6 ... N with even N and, 5, ... N with odd N, is minimal (basic) and the current amplitude of the DC supply voltage converter is designated as E0 and E.

FIG. Figure 1 shows a simplified diagram of the power circuits of a three-phase bridge converter, which is made completely with controlled valves; in fig. 2 are timing diagrams illustrating the control method; in fig. 3 - curves showing the change in the duration of the clock intervals and angles

25 control in the process of regulating converters; in fig. 4 is a functional diagram of a converter control system implementing the method.

In the upper timing diagram (FIG.

30 2a) shows the control signal Uy, arriving at the valve + A at the time interval 0-60 el. hail during the first clock interval of the positive half-period of the conduction state of the valve, at the initial (minimum) output frequency of the converter Fo. In the interval 120-180 e. hail control signals are formed in the same way, and on the half-closed state of the valve 180-360 el. hail is similar to 40 but inversely control signals are formed symmetrically. Below, the corresponding plot of the linear output voltage of the UAB converter is plotted. Built curves

45 correspond to variant five times, with a minimum supply voltage, the range of the associated frequency control and voltage value (). In this case, the clock interval 0-60 e. hail (and 120-180

50 email hail) at the initial frequency F0 is divided into 5 clock sub-intervals of the same duration G0, equal to 12 el. hail each, inside and in the middle of each of which are formed the modulating signals of the control, unlike with the corresponding half-period, having in general form duration of 1, “Eo

Lo

6n fo

(1 - p), where Eo and E are corresponding to N

In this case, it is characteristic minimal (nominal) and the current value of the supply voltage converter. In the case of

Lo - (1 -i -9.6 e. Deg. 5o

An increase in the output frequency of the converter is accompanied by a change in the duration of t clock intervals, which is carried out according to

The N-Fl bthtrOrnoy feature of the control algorithm in question is that in this case, with odd N, the entire control range of the middle of each clock interval (i.e., points with ordinates 30, 150, 210, 330 e. degrees) is synchronized with the middle corresponding central clock subintervals. In the case of an even value of N, the mid-clock intervals are synchronized with the end and the beginning of the corresponding two central clock sub-intervals.

The process of adjusting the frequency of the output voltage of the converter is accompanied by a constant alternating variation, as indicated by arrows (Fig. 2), of the durations of the main and modulating control signals formed along the edges of the clock intervals. At the same time, to maintain a constant ratio of the output voltage of the converter to the frequency on the control subbands, where the main control signals are formed along the edges of the clock intervals, the duration of the modulating control signals varies depending on the current values of the output frequency F and the number f generated inside the clock the intervals of the modulating control signals in accordance with the expression

ЈЈ)

Fo e n

Within the control subbands, where modulating control signals are synthesized along the edges of the clock intervals, they are (extreme at the clock intervals of the modulating signals)

the duration I is defined as; 1 g h. ) FQ i

LLP g-I I-m I g-g: J

J- 1 (1 (F

12 F Eo

Fo N + Fo is F i, and the length of the I-ostal 12 F0E (1-1) N (1-2) and modulating control signals is defined as

1 6F (F0N + Fo -F) 6FoE (i-1)

The values of the cutoff frequencies that are transient from one subband to another are, respectively,

5 F

 EfN iVFNl.-0 E0lNMl-EN ("- r-4fflEN (, - rtf, -N-0

 Well G all

0

five

0

five

, F0 (NMUEN ((MtEN (i-0 2-4EaEN (i-i (N-, + J) F, F.shch3

For all considered control options 0 on the first, starting from the FO frequency, the output control frequency range of the converter is up from the initial value, the control process is carried out by sequentially changing (decreasing, as shown by the arrows in Fig. 2a) the duration of the last control intervals The duration of the modulating signal I control on this sub-band at and varies, 1.1Eo h

c according to l - - (-g)

The duration, t, of clock subintervals, as shown in the curve of r (Fig. 3), on this subrange of control is sharply reduced with increasing frequency, thus increasing the number of output pulses in the half-wave and improving the harmonic composition of the output voltage.

The upper boundary of the noted first frequency subband is observed at frequency F 5 1.31 F0 calculated from the condition where the duration of the main control signals at the clock intervals has decreased to close to zero values.

On the next adjustment sub-band (Fig. 26), the modulating signals with the duration I are formed along the edges of the clock intervals, and the duration of the remaining modulating signals is equal to

R1, while R1 and R are determined from the 5 expressions by substituting the corresponding and. The upper limit of this subrange (for) is the frequency E 5 2.56E0, for each duration H decreases to close to zero values. 0Next Control Range

lies in the area of the output frequencies F 5 F F, 83F0 and is characterized by a reduced by two units number of modulating control signals within 5 clock intervals () (Fig. 2c). In this zone, as follows from the curves (Fig. 3), it is observed, starting from a frequency, a gradual increase in the absolute duration T of clock intervals. In the output frequency range of the converter 4.6F0 (with E-F-Q). which correspond to the timing diagrams of the linear output voltage (Fig. 2), two extreme modulating signals with duration A and one central with

duration A, and from the frequency of the relay and to the upper (nominal) frequency converted N F0E

signal output frequency gpheobrezovas F0 N E

tel lm duration takto

to maintain subintervals equal to t - here: Asking, in particular, the number of Fm

rum to the output curve of the harmonic component to be completely excluded from the spectrum, the value of y on the entire die (Fig. 2e) in the centers of the same regulation zone can be determined

as

intervals are formed over one modulating control signal with a duration of

1 1 / 1Eo h 1 1 / 1EO

I-b () i-b () for

case. In the case of an even value of the index N, the indicated value coincides with the limiting values of the frequencies F 2 and F 2 calculated by the indicated dependencies.

To improve the harmonic composition of the output voltage of the converter, it is advisable to modify the control algorithm so that an additional sequence of output pulses, the harmonic components of which are harmonized, is formed in the output curve over the entire control range, as shown by the dotted line (Fig. 2). antiphase with the harmonics of the main array of output pulses, would thereby contribute to the elimination (reduction) of the amplitudes of the most unwanted parasitic harmonics of the resultant guide curve

For this, the duration of the modulating control signals generated in the near half-bounds of the corresponding half periods of the half clock intervals must be appropriately changed. At the same time, inside the positive conduction half-periods, the duration of the modulating signals should be increased by a certain value of V0, and inside the negative half-periods of the closed state, the duration

modulating signals should be reduced by the same amount. The process of changing the duration of the modulating control signals in this case is carried out in this case by a corresponding shift of the fronts of the modulating control signals that are far from the edges of the half-periods of the modulating control signals.

To ensure full amplitude compensation of the parasitic harmonics in the upper amaponeon, it is advisable to adjust the frequency from (N-1) Fo to maximum 15

thirty

35

40

45

50

55

v 2 „rptn A-VA2-4C (B + C)

y - to arctg2 G - ±

Where

-smk (f-A),

gk lg l

C - cos - sin - o

for frequency subbands F i F F i +, as well as for F, (N-1) F0:

r-aj. kri -t, sin -j-,

for odd N and even N.

The nature of the change in the relative, expressed in e, hail, y values for a particular mode being analyzed () for (solid lines) and, 2E0 (dashed lines) is shown in FIG. 3

The generalized functional diagram of the converter control system is made according to the vertical principle and implements the control method (Fig. 4). At the output of the frequency setting unit 1, a signal Ui is generated, directly proportional to the output frequency of the converter, which is fed to the inputs of the clock generator 2 and the functional M-channel output of the converter 3. The pulse frequency of the generator 2 determines the frequency of the output signal of the scanning unit (generator) sawtooth voltage 4, which in this case is 6 times higher than the output frequency of the converter over the entire control range.

The signal of the generator 4 is continuously matched in the control pulse shaping unit 5 with the output signals U of the functional converter 3, the magnitude of which is proportional to the current

signal output frequency gpheobrezovas F0 N E

tel lm duration takto

to maintain subintervals equal to t - here: Asking, in particular, number 15

v 2 „rptn A-VA2-4C (B + C)

y - to arctg2 G - ±

Where

-smk (f-A),

0

five

0

five

0

five

gk lg l

C - cos - sin - o

for frequency subbands F i F F i +, as well as for F, (N-1) F0:

r-aj. kri -t, sin -j-,

for odd N and even N.

The nature of the change in the relative, expressed in e, hail, y values for a particular mode being analyzed () for (solid lines) and, 2E0 (dashed lines) is shown in FIG. 3

The generalized functional diagram of the converter control system is made according to the vertical principle and implements the control method (Fig. 4). At the output of the frequency setting unit 1, a signal Ui is generated, directly proportional to the output frequency of the converter, which is fed to the inputs of the clock generator 2 and the functional M-channel output of the converter 3. The pulse frequency of the generator 2 determines the frequency of the output signal of the scanning unit (generator) sawtooth voltage 4, which in this case is 6 times higher than the output frequency of the converter over the entire control range.

The signal of the generator 4 is continuously matched in the control pulse shaping unit 5 with the output signals U of the functional converter 3, the magnitude of which is proportional to the current

the values of the positions of the fronts of the output pulses a. inside the clock intervals (FIG. 2a). In this case, the operation of block 4 and the three-phase register 6 is synchronized by the initial setpoint so that zero (minimum) values of the 1M signal correspond to the midpoints of the clock intervals.

The values of the control angles a are predetermined by calculation from the indicated ratios characterizing the mode of control method implementation, relative, expressed in el. degrees, angles a 1 - 5 for the variant with (solid lines) and, 2E0 (dashed lines) are plotted in fig. 3 In the moments of equality of the current values of the signals of blocks 3 and 4, block 5 produces commands to form the fronts of the control (and output) impulses that are distributed to the corresponding valves using the logical distributor 7 control pulses Given the state of the outputs Oz Q2 SI register 6 on the period of the output frequency as 100, 001, 000, 101, 110, 111, 100, logical equations, implemented by the distributor 7 and arriving in the form of control The signals on the valves of the corresponding phases of the converter are as follows.

+ A -QiQ3 + QiQ2U5 + QiQ3U5;

+ B QiQ2Q3 + QiQ3l 1 + ChQ2U-i + QiQ2U5 + + QiQ3Us:

+ C QiQ2 + QiQ3U5 + Q 1621) 5

To form an additional sequence of pulses, if the harmonic composition of the output voltage needs to be improved, the number of output channels of the functional converter 3 increases accordingly, register 6 should be four-bit with a corresponding modification of the logic functions performed by the distributor 7. - the existing patterns as the instrumental basis of the considered functional scheme of the control system should yt use digital microelectronics.

Thus, the control method allows to significantly improve the quality of the process of connected wide-range control of the magnitude and frequency of the output voltage of the converters for the electric drive by eliminating current surges in the power circuits of the converter and the load occurring at the moments of a change in the number of pulses in a half-wave output curve

The harmonic composition of the output voltage at the same time in the range of low and medium output frequencies is quite satisfactory due to the increased number of signals in the output half-wave, provided by a special non-linear modulation of the duration of clock subintervals. The advantages noted make it promising to use the method for controlling converters that supply systems of both general industrial, high-voltage and precision frequency-controlled electric AC drives.

Claims (3)

Claim 1 The control method of a three-phase bridge converter with a tacho-code regulation, which means that 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-hail in the sequence fA. -С В, -А, + С, -В, while for each valve they form positive conduction half-cycles and negative half-periods of the closed state, each of which consists of three clock intervals of degree durations, within the extreme time intervals on the clock intervals form modulating control signals characterized in that, in order to improve the quality of the control process due to the smooth unaccented change in the shape of the output voltage of the converter during the N-fold associated control of the frequency F and the value of direct voltage by law persistence ratio of the amount of voltage to frequency, said Forming a modulating control signals to control the entire range, starting with an initial frequency FO, is performed at the midpoints of clock sub intervalovsdlitelnostyu Fo T - moreover, the mid-F (FO N + Fo-F) of these said clock intervals are synchronized with the middle of the corresponding central clock sub-slot for odd N or with the end and the beginning of the corresponding central clock subintervals for even N, while on the frequency sub-bands F, F, F, +2 inside the clock intervals form on the i modulating control signals of duration 1.1 B5 BUT Ftf on the frequency subbands F i G F i n the extreme parts of the finished intervals form the control signals duration 1 g, Q-2) Fo, J-o FO N f r o F J Fo E (1 -1) R 5 and the duration of the remaining (1-2) -and CHI control fields is determined and correlated with X ---- p 1 Fo Yer  (Fo N 4-Fo Fl 6 Fo E (i-1) N the values of the cut-off frequencies F i and F i, which are transitional from one control band to another, are determined by F g. - b-JCE N-O-ENd- Nti-Oty- Q ЁО F .F.) - G0G "i) em (; - ozg-4e0Em {; - 1) (M .; , Oh jfЈ --- where 1 is 2,4,6 ... N with even N and K3.5 ... N with odd, E0 and E is minimal (basic) and the current amplitude of the supply voltage of the converter is constant. 2. The method according to claim 1, characterized in that in the output frequency range of the converter (N-1) F0 NF0 -c-longto nosity clock intervals are determined by 1 respectively as 3. Method of pop 2. characterized in that, in order to improve the harmonic composition of the output voltage of the converter, the entire control range is changed by the value of the duration of the half modulated near the edges of the half-periods 0 five clock intervals of the modulating / controlling signals, moreover, the duration of said control signals in conduction half-periods is increased and the indicated duration at closed-state half-periods is reduced by a corresponding shift far to the said half-period borders of the corresponding modulating control signals, and the value of y is determined according to the functional dependence v 2 yyyy A- y to arctg + cp- where k is the number of parasitic harmonics to be excluded from the spectrum of the output voltage A 2 sin k (If -№ (5l-A0) -) S) A 3 0 4 --v (2 liters of frequency sub-bands F i F. C - cos fsin 6 I sin 2 sin 2)  i / l ill i -smk (p -A), 0 for frequency subbands F i F Ј-F1 + 2, as well as for F (N-1) F0 C - cos k. k (r-A). krl - with In sin   ILOKI / - , for odd N, for even N. Fig.} -G - ngk what about g th gALJIJ) vo Oi 1 Fs and,