SU1642570A1 - Method of control over three-phase self-excited voltage inverter - Google Patents

Abstract

The invention relates to electrical engineering and can be used in the development of adjustable or stabilized converters. The aim of the invention is to improve the harmonic composition of the inverter output voltage. The method of mapping is based on an algorithm of 180-degree symmetric key management of a three-phase inverter, in which n main control signals of 1U duration are formed symmetrically relative to the centers of these zones within the control intervals of 60-degree durations to compensate for parasitic harmonics within the extreme 30-degree sections of the control zones form additional control signals, the locations of fronts closest to the boundaries of the control zones They are found by shifting by Ј60 electric grades closer to the middle of the zones and controlling the fronts of the corresponding main control signals of the same name, and the duration of the additional control signals is related to the duration of the main impulses of the output voltage curve by a linear relationship - Ty K. 5 Il. § oe y u

Description

The invention relates to electrical engineering and can be used in the development of regulated or stabilized stand-alone three-phase voltage inverters.

The aim of the invention is to reduce the weight and size parameters of the output filter by improving the harmonic composition of the output voltage of the inverter.

Fig. 1 shows a simplified structure of a power circuit of a three-phase bridge inverter made on fully controlled valves; Fig. 2 shows timing diagrams explaining the proposed control algorithm; Fig. 3 shows the dependence of the magnitude of the coefficient K on Hz in Fig. 4 shows the characteristics of the spectral composition of the output voltage of the adjustable inverter; Fig. 5 shows a functional diagram of the control system implementing the proposed method.

The power circuit of a three-phase bridge inverter (Fig. 1) contains a pole of fully controlled valves of phases A, B, C, each of which is shunted in the opposite direction by a diode. To the output terminals of the converter are connected the phases Z ZB Zc of the load connected in a star.

Figure 2 shows the timing diagram (cyclogram) of switching, valves of phases A and B of the cathode group.

bridge inverter, as well as the curve of the linear output voltage of the converter as applied to option n 4, when within the clock intervals of 60 degrees duration there are four main control signals (switching off the signal valves in the conduction band and switching on, the signal in the zone of the closed junction valves) with a duration of D. At the same time, within the extreme 30-degree sections of the conduction zones and the closed state of the valves, additional control signals are generated, two of each x sections, close to the boundaries of half-periods, the fronts of which are formed, as ps / shown in Fig. 2, by shifting by 60 e.h. vanishing or advancing the fronts closest to the middle of the half-periods of the corresponding corresponding (i.e., shut-off or closing valves) main control signals. The continuer

five

Yu

425704

The bone ft of these additional signals is in the following functional relationship with the number n and the duration of the main signals

A (- -) el .grad.,

where K is a dimensionless coefficient chosen, depending on the desired value of n, in accordance with the data shown in FIG. So, with, we have, 303, respectively

0.303 (T5-ft) el. In particular, at 0, which corresponds to the maximum value of the output voltage of the converter, $ 3,638 el.grad.

 As follows from FIG. 3, the numerical value of K, a certain outcome from the condition of maximal reduction of the amplitude (—tr of parasitic harmonics of the spectrum,

close to the main one, decreases sequentially with increasing n, asymptotic

20

0

five

0

five

ki approaching the boundary value. 5 equal to 0.268.

An analysis of the shape of the linear output voltage curve of the inverter shows that the generation of additional control signals described above leads to the appearance of additional pulses in the extreme parts of the output half-wave and to a corresponding decrease in the duration of the main output pulses. Thus, in a three-phase bridge inverter, the control law is implemented, which is close to the pulse-width modulation algorithms, which improves the spectral composition of the output curves. This is confirmed by the characteristics of the harmonic composition of the output voltage of an inverter controlled by the proposed method (solid curves) constructed in Fig. 4, compared with the similar characteristics of a converter controlled by the prototype method (dashed lines) for the variants and which clearly illustrate , down to zero values, a decrease in the amplitudes closest to the main fifth and seventh harmonic components of the spectrum of the output voltage curve.

Figure 5 shows a functional diagram of a control system that implements the described method as applied to variant P3. The system is made on the vertical principle

0

five

ten

51642570

contains a clock pulse generator 1 associated with the inputs of the four-bit register 2 and the sweep generator of the linearly varying voltage 3, the sources of the reference 4 and the control voltage 5, the adders 6-8, the summing amplifier 9 associated with the adder 10, comparators 11-14 with output formers of short unipolar pulses, disjunctor 15 and counting triggers 16 and 17, connected by outputs to the logical distributor of control pulses 18.

The principle of operation of the system is explained by the dotted curves shown in the timing diagram (Fig. 2). The clock frequency of the generator 1 is 12 times the output frequency of the inverter. The frequency of the sweeping sawtooth symmetrical in both sides of the voltage Uj of the generator 3 is six times higher than the output frequency. The voltage of the source of the reference voltage 4 is n times smaller than the amplitude of the signal Uj. The magnitude of the voltage U of source 5 controls the value of the parameter D and, accordingly, 5 the value of the output voltage of the converter. The transfer coefficient of summing amplifier 9 is 2K, while the amplitude of the signal UQ at the output of amplifier 9 is proportional to the value of the parameter y. At the outputs of the comparators 11-14, signals are allocated to the formation of the fronts of the control signals, which through the disjunctor 15 and directly arrive at the inputs of the counting triggers 16 and 17 connected to the distributor 18. Digitally expressed states of the outputs of the register 2 for the output period frequencies are recorded as 1000, 1001, 0010, OOP, 0000, 0001, 1010, 1011, 1011, 1101, 1110, 1111. Logic functions implemented by the distributor 18 and received in the form

+ B Q4Q2q, u17 + (UQ2Q, + Q3Q2Q, + QsQzQtUi + Q + Q QjQzu 6 +

+, 7 - JUQgQz.Q,;

 Q3Q2Q "U 7 + Q3Q2Q, + +, + JUQiQiU, 7 +, b + + Q5u, 6 + Q4Q3Q, U17 + Q4Q2Q,.

Claims (1)

Invention Formula The method of controlling a three-phase autonomous voltage inverter, which consists in the fact that the main valves of different phases of the inverter are periodically turned on and off with a mutual phase-to-phase shift of 60 el.grad, with for each main valve during one half-period from 0 to 180 el.grad. form the conduction band, during the other half period of 20 from 180 to 360 el.grad. form the zones of the closed state, the clock interval of the conduction band from 60 to 120 al.h. and the clock interval of the closed state zone is from 240 to 300 25 al-degrees. are divided into n segments of 60 / n electr. lengths, in the middle of each of which, respectively, form the main signals for switching off and switching on valves with a duration of 30, which in order to reduce the mass and output indicators of the output filter by improving the harmonic the composition of the output, eg from the inverter, for each main valve within the intervals of 0-30,. 150-180, 180-210, and 330-360 el.grad. generate additional shut-off and turn-on signals, 40 close to the half-period limits the fronts of which are formed by shifting by ± 60 al. close to the middle of the half-periods of the fronts of the corresponding identical main signals 45 on and off (on - "- 60 el, .grad at intervals of 150-180 and 330- 360 el. degrees and -60 el. degrees at intervals of 0-30 and 180 -210 el.grad,). the duration of the additional control pulses on the corresponding control signals determine the inverter gates, have the following functional dependence: to (60 / n-) el.grad., where the numerical value of the coefficient K is defined-A Q4Q3QaQ (+ Q4Q.3QiQt + (U hQzQH + + + Q2Ut6 + Q3U16 + + + u57.  It is given in accordance with the dependence of 55-K on p shown in Fig. 3 of the description. 0 + B Q4Q2q, u17 + (UQ2Q, + Q3Q2Q, + + QsQzQtUi + Q + Q QjQzu 6 + +, 7 - JUQgQz.Q,;  Q3Q2Q "U 7 + Q3Q2Q, + +, + JUQiQiU, 7 +, b + + Q5u, 6 + Q4Q3Q, U17 + Q4Q2Q,. Invention Formula The method of controlling a three-phase autonomous voltage inverter, which consists in the fact that the main valves of different phases of the inverter are periodically turned on and off with a mutual phase-to-phase shift of 60 el. Degrees, while for each main valve during one half-period from 0 to 180 .hail. form the conduction band, during the other half period from 180 to 360 el.grad. form the zone of the closed state, the clock interval of the conduction band from 60 to 120 al. and the clock interval of the closed state zone is from 240 to 300 5 el.grad. are divided into n segments of 60 / n electr. lengths, in the middle of each of which form, respectively, the main turn off and turn on taps with a duration of 0, which is so as to reduce the mass and output indicators of the output filter by improving the harmonic the composition of the output napr - from the inverter, for each main valve within the intervals of 0-30,. 150-180, 180-210, and 330-360 el.grad. generate additional off and on signals for valves, 0 close to the half-time limits the fronts of which are formed by shifting by ± 60 al. the fronts close to the middle of the half-periods of the corresponding main signals of the same name 5 on and off (on - "- 60 el, .grad at intervals 150-180 and 330- 360 el. degrees and -60 el. degrees at 0-30 and 180 -210 el.grad,).  It is given in accordance with the dependence of 55-K on p shown in Fig. 3 of the description. + f + A five H -A ; - -with n 3 I g A 28 Zc FI.1 FIG.