RU2025032C1 - Method of asynchronous pulse-duration-code control over semiconductor converter of electric motor drive - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: method of control lies in successive formation of controlling signals with 60 degrees shift and in their sending to valves of three-phase bridge circuit of converter. Modulating control signals are formed in this case in centers of control half-periods, within intervals of 60 degrees durations in centers of corresponding clock subintervals. Value of output voltage is controlled by change of their durations. Duration of clock subintervals varies in function of frequency over bigger part of range (over 4/5 of entire range) by piecewise function with two reference points specified by corresponding coefficients characterizing mode of control. Additional modulating control signals of twelve degree durations are formed in centers of clock intervals. In process of control continuous change of durations of main and modulating control signals which are formed by one of boundaries of each of two 24-degree sections of clock pulses is performed. EFFECT: increased precision and efficiency of control. 2 cl, 4 dwg

Description

 The invention relates to power electronics and can be used in the development of converters based on three-phase autonomous voltage inverters designed to power asynchronous frequency-controlled electric drive systems.

 Known methods for controlling three-phase converters for an electric drive, based on a phased change in the number of pulses in the half-wave of the output voltage, and the specified change in the number of pulses occurs discretely, which leads to undesirable inrush currents in the power circuits of the converter at the time of discrete switching [1 and 2].

 There is also known a method of flexible nonlinear control of wide-adjustable converters, in which, thanks to special nonlinear modulation of the durations of the main and modulating control signals generated at the clock points, a smooth, unshocked transition from one form of the output signal to another is provided [3]. In this case, the average switching frequency of the converter valves is constant; over the entire control range, the ratio of voltage to frequency is constant.

 However, in the output voltage spectrum of the converter over the entire control range, there is sometimes a significant fifth harmonic component in amplitude, which negatively affects the nature of the processes in the controlled electric drive system and, in particular, creates a braking torque that is significant in magnitude as an asynchronous short-circuited electric motor, which is part of such systems, which is especially undesirable in the zone of low frequencies, where the engine is most sensitive to the influence of such factors. It is also known that in order to increase the reliability of the start-up mode of a converter loaded on an induction motor, the control law in the short-term starting mode should differ from the basic control law with U / F = const.

The aim of the invention is to improve the entire control range of the harmonic composition of the output voltage of the converter, as well as the system speakers in the starting mode and in the range of low output frequencies, achieved by changing at the initial frequency F _about K times, and at a frequency LF _about M times clock sub-intervals and the corresponding increase in the number of pulses in the half-wave of the output curve, as well as improving the reliability of the start-up process of the converter loaded on asynchronous motors gatel.

в диапазоне выходных частот преобразователя LF_oN0,8NF_о продолжительность τ определяют как
τ =

в пусковом режиме работы, при 2F_о>F≥F_о, значения упомянутых граничных частот, переходных от одного поддиапазона управления к другому, определяют соответственно как

в этом режиме λ = τ _

, при F

≥ F > F

λ′= 1/15F-(i-1)τ _

, а в номинальном режиме работы преобразователя при LF_о≥F > 2F_о значения граничных частот F_i ^II и F_i ^I находят соответственно как

при 0,8NF_о≥F>LF_о значения частот F_i ^II и F_i ^I находят соответственно как

при этом на диапазоне номинального режима работы преобразователя до частоты 0,8NF_о при F_i ^I≥F>F _i ^II

λ′=1/15F-(i-1)τ-1/12(2i-1)F_oN , при
F

≥ F > F

λ =

-

а когда NF_о>F≥0,8NF_о λ =1/6-1/6F_оN.This goal is achieved by the fact that when controlling according to the specified method, providing N-fold, starting from frequency F _о , the associated regulation of the output frequency and voltage of the converter, which consists in the fact that the main valves of different phases and groups of the converter periodically turn on and off with mutual phase a shift of 60 email. hail. in the sequence + A, -C, + B, -A, + C, -B, and for each valve within one half-period from 0 to 180 electric degrees. form the interval of the conductivity of the valve, during another half-cycle from 180 to 360 el. degrees form the interval of the closed state of the valve, on the central clock cycles within the half-periods from 60 to 120 and from 240 to 300 el. they form modulating control signals, which are opposite to the corresponding control half-cycle, the number of which decreases successively with increasing output frequency of the converter F, and the generated modulating signals are generated in the middle of the clock subintervals of duration τ, the formation of each i-th one, counting from the reference points inside the clock intervals and to clock points, the modulating control signal is carried out when changing the output frequency of the Converter from F _about to the cutoff frequency F _i ^I , while m in the nominal operating mode on the sub-ranges of the output frequencies at which F _i ^ll ≥F> F _{i + 1} ^l (F _i ^l > F _i ^ll > F _{i + 1} ^l ), the duration λ of all modulating control signals is equal to each other, and on the frequency subbands on which F _i ^l ≥ F> F _i ^ll , along with the main array of modulating control signals with a duration of λ, a clock modulating signal with a duration of λ ′ is formed in the marked clock points in the output frequency range F _о N0.8NF _о в the centers of the indicated clock intervals form the central modulating control signals with For a duration equal to 1/30 F (12 electric degrees), as the indicated reference points, we choose symmetrical to each other with respect to the midpoints of the clock intervals the borders of the lateral 24-degree segments, and as the clock points, other borders of the segments, synchronize the mentioned reference points with the corresponding boundaries of the corresponding clock sub-intervals, in the output frequency range of the converter F _about NLF _{about the} duration τ of the clock sub-intervals is taken equal
τ =

in the output frequency range of the Converter LF _o N0.8NF _{about the} duration τ is determined as
τ =

in the starting operation mode, at 2F _о > F≥F _о , the values of the mentioned boundary frequencies transient from one control sub-band to another are determined respectively as

in this mode, λ = τ _

at F

≥ F> F

λ ′ = 1 / 15F- (i-1) τ _

, and in the nominal operating mode of the converter with LF _о ≥F> 2F _{о the} values of the boundary frequencies F _i ^II and F _i ^{I are} found respectively as

at 0.8 NF _о ≥F> LF _о , the frequencies F _i ^II and F _i ^{I are} found respectively as

while on the range of the nominal operating mode of the converter to a frequency of 0.8NF _about for F _i ^I ≥F> F _i ^II

λ ′ = 1 / 15F- (i-1) τ-1/12 (2i-1) F _o N, at
F

≥ F> F

λ =

-

and when NF _о > F≥0.8NF _о λ = 1 / 6-1 / 6F _о N.

 Figure 1 shows a diagram of the main connections of the power circuits of a thyristor voltage converter, made on the basis of fully controllable thyristors, loaded on an asynchronous electric motor (HELL); figure 2 - adjustment characteristic of the Converter and the curve of the change in the relative duration of the clock sub-intervals; figure 3 is a timing diagram illustrating the reference options for the formation of control signals to the inverter valves; figure 4 is a block diagram of a control system of the Converter.

а в диапазоне выходных частот преобразователя LF_оN0,8NF_опродолжительность τ определяют как
τ =

(см. построенные на фиг.2 кривые зависимости изменения относительной продолжительности τ^*=τ/τ_m от частоты F применительно к величине диапазона регулирования N=10 и значениям упомянутых коэффициентов К= 0,5, L=5 и М=0,25). При этом на частоте 0,8 NFо конечная величина продолжительности τ определяется для всех режимов (при любом N) как τ= 0,4/6NF_о, соответственно для анализируемого режима на начальной частоте F_о τ= 0,5/6NF_о, а на частоте LF_о (5F_о) τ=0,25/6NF_о(продолжительность тактовых подинтервалов при рассматриваемом способе управления изменяется по двум линейным зависимостям (фиг. 2), границей перехода от одной зависимости к другой при этом является частота LF_о).The timing diagrams constructed in Fig. 3 illustrate three basic algorithms for generating control signals to the converter valves during regulation, as well as the corresponding curves of the linear output voltage U _AB . The control signals U _y shown here are applied to the gate + A of the cathode group of the three-phase bridge converter circuit located in the positive conducting half-cycle of control, and the positive value U _y (main control signal) corresponds to the conducting state of the valve, and the zero value U _y (modulating control signal) - closed state (remember that the valves are fully controllable). The formation of control signals opposite to the corresponding control half-cycle with durations λ and λ ′ that specify the value of the converter output voltage over the entire control range F _о NNF _{о is} carried out in this case within the clock cycle intervals average at half-periods (60-120 and 240-300 electric degrees). in the centers of the clock sub-intervals shown in Fig. 3 by thin arcs from below, having a duration τ, which depends _on the values of the output frequency F within the frequency range F _о N0.8NF _о and is determined in the output frequency range frequency converter F _about NLF _about how
τ =

and in the output frequency range of the converter LF _about N0.8NF _{about the} duration τ is determined as
τ =

(see the curves of the dependence of the change in the relative duration τ ^* = τ / τ _m on the frequency F constructed in Fig. 2 as applied to the size of the control range N = 10 and the values of the mentioned coefficients K = 0.5, L = 5, and M = 0.25 ) Moreover, at a frequency of 0.8 NFо, the final value of the duration τ is determined for all modes (for any N) as τ = 0.4 / 6NF _о , respectively, for the analyzed mode at the initial frequency F _о τ = 0.5 / 6NF _о , and at the frequency LF _о (5F _о ) τ = 0.25 / 6NF _о (the duration of the clock sub-intervals _{for the} control method under consideration varies according to two linear dependencies (Fig. 2), the border of the transition from one dependence to the other is the frequency LF _о ).

An important feature of the considered algorithm for generating control signals to the converter valves is the fact that a central modulating signal is generated in the middle of each of the mentioned 60-degree intervals over the entire control range, and over most of the control range, in the zone F _о N0.8NF _о , the duration this signal is found as 1 / 30F (12 electric degrees), and in the increased frequency zone 0.8NF _о NNF _{о the} indicated value is found as λ = 1 / 6F-1 / 6NF _о . In this case, the formation of the main array of modulating control signals is performed inside the 24-degree duration extreme segments at the clock intervals. Moreover, inside the clock intervals in the zone F _о -0.8NF _о on each half of the clock interval, as shown in Fig. 3, the corresponding boundaries of the extremes inside the lateral 24-degree segments of the clock intervals are synchronized with the corresponding boundaries (in this case, with the nearest to the middle time intervals by borders) of the indicated segments. Another completely similar control option is also possible, in which the boundaries of the clock sub-intervals are synchronized with other, distant from the centers of the clock intervals, the boundaries of the indicated segments, while all relations characterizing the mode of formation of control signals are fully preserved.

The values of the preset expressions mentioned above in the expressions for determining the duration of the clock intervals of the coefficients K and M, taking values from zero to unity, as well as the values of the coefficient L (0.8N>L> 1), are very important parameters of the control mode under consideration. So, the value of the coefficient K characterizes the degree of change in the duration of the clock sub-intervals at the initial output frequency of the converter F _о compared with the duration of the clock interval 1 / 6F = 60 electric degrees observed at the upper point of the frequency range, at the frequency NF _o , at which the half-wave output voltage is formed from a single pulse. Moreover, the smaller the absolute value of the coefficient K, the shorter the duration of the clock sub-intervals at the initial output frequency and the greater the number of modulating signals within the clock intervals, the more pulses a half-wave of the converter output voltage is generated at the initial output frequency. The total initial number of modulating signals (without a central one) inside the clock intervals is determined from the expression 0.8N / K, i.e., for example, at N = 10 and K = 0.5, sixteen will be formed at the initial frequency inside the clock intervals modulating control signals. In the case where the specified quotient is a fractional value, the initial number of modulating control signals is rounded up. The specific value of the parameter K should be set, proceeding primarily from the requirements for the dynamic properties of the converter system and the harmonic composition of its output voltage in the region of the starting output frequencies, guided by the rule that a larger number of pulses in the output half-wave at the initial frequency (lower K) contributes to improving the harmonic composition of the output voltage and the dynamic properties of the system.

 The important parameters of the control mode, characterizing the operation of the system in the middle part of the frequency range, are the coefficients M and L. Setting the required value of L selects the point (zone) of the control range at which it is necessary to provide the required switching frequency of the valves and the corresponding harmonic composition of the output voltage, which is set by the corresponding the value of the mentioned coefficient M. In this case, it is most expedient to select values of the coefficients L and M close to optimal for that part of the range it regulation, wherein with a frequency converter motor drive system as an executive authority functions most long lasting.

 The process of regulating the frequency of the converter output signal both in the starting and in the nominal operating modes is based in this case, as shown by the arrows in Fig. 3, a, b, on a constant stepwise variation of the durations of the main and modulating control signals generated at the clock points corresponding to the boundaries of 24-degree segments, opposite the boundaries of the segments in which synchronization with the boundaries of the corresponding clock sub-intervals is performed. The noted principle of generating control signals, an essential feature of which is the continuous identification (coding) of the durations of the main and modulating control signals generated at the clock points with the duration of the main signal array, due to which a smooth, unshocked transition from one control subband to another can be defined, can be defined as latitude code. Due to the fact that at the initial (starting) frequency, the choice of the duration of the clock sub-intervals specified by the value of the coefficient K can be arbitrary, and therefore, accordingly, the initial number of modulating signals and the number of output pulses in the half-wave of the output voltage can be arbitrary, the considered method of generating control signals to the valves a converter can be defined as asynchronous.

Inside the control sub-ranges, on which, as shown in Fig. 3, a, at the marked clock points, the main control signals are generated, the output voltage is regulated by changing the durations λ of the modulating signals according to certain dependencies. On the subbands on which, as shown in Fig. 3b, modulating control signals with a variable duration λ ′ are formed at the clock points, the duration λ of the remaining modulating signals is in accordance with other functional dependencies. The boundary values of the frequencies F _i ^I and F _i ^II , transitional from one control sub-band to another, are determined through the corresponding parameters of the control mode.

It is known that one of the most economical and often applied in nominal operation modes laws of control of converters for systems of a frequency-controlled asynchronous electric drive is control according to the law of constancy of the ratio of voltage to frequency at which, as shown in FIG. 2 for the frequency range of the nominal regulation 2F _о NNF _о = 10F _о , the voltage increases in direct proportion with the increase in the output frequency of the converter. It is also known that in a short-time starting mode of operation of a converter loaded on an induction motor, the relative voltage value should be significantly increased compared to the nominal mode, in this case it is advisable to maintain the voltage value increased and constant in the starting frequency range, and as the upper limit of the range starting frequencies take a frequency equal to twice the initial frequency F _about (see the range F _about N2F _about figure 2).

в этом режиме на всей зоне 2F_o≥ F > F_o λ = τ _

. при F

≥ F > F

:λ′= 1/15F-(i-1) τ -

В номинальном режиме работы прелбразователя при LF_о≥F>2F_о значения граничных частот F_i ^II и F_i ^I находят соответственно как

при 0,8NF_о≥F>LF_о значения частот F_i ^II и F_i ^I находят соответственно как

При этом на диапазоне номинального режима работы преобразователя до частоты 0,8NF_о при F_i ^I≥F>F_i ^II ,
λ = τ -

,
λ′=1/15F-(i-1)τ-1/12(2i-1)F_oN, при
F

≥ F > F

λ =

-

, а когда NF_о> F≥0,8NF_о λ=1/6F-1/6F_оN.Thus, in the starting mode of operation of the converter, in the frequency range F _о N2F _о , the mentioned values of the boundary frequencies and parameters of the control signals through which the required control law is realized should be defined as

in this mode, over the entire zone 2F _o ≥ F> F _o λ = τ _

. at F

≥ F> F

: λ ′ = 1 / 15F- (i-1) τ -

In the nominal operating mode of the freezer with LF _о ≥F> 2F _{о, the} values of the boundary frequencies F _i ^II and F _i ^{I are} found respectively as

at 0.8 NF _о ≥F> LF _о , the frequencies F _i ^II and F _i ^{I are} found respectively as

Moreover, in the range of the nominal operating mode of the converter to a frequency of 0.8NF _about for F _i ^I ≥F> F _i ^II ,
λ = τ -

,
λ ′ = 1 / 15F- (i-1) τ-1/12 (2i-1) F _o N, at
F

≥ F> F

λ =

-

and when NF _о > F≥0.8NF _о λ = 1 / 6F-1 / 6F _о N.

 In all the given dependences, the parameter i characterizes the number of modulating control signals generated inside the mentioned 24-degree segments.

At the first, starting from the starting frequency F _о , the control sub-range, the algorithm for generating control signals and the initial number of control modulating signals i inside the given segments should be determined as follows. First of all, the quotient of the 0.4N / K division characterizing the value of i is found, and in the case of a fractional value of 0.4 N / K, the resulting value is rounded up to the nearest whole number. Based on the obtained value of i, the values of the boundary frequencies F _i ^II and F _i ^I corresponding to these values of i, N, K, L and M are determined, and the determination of these values should be carried out according to the dependencies presented above, which describe the inverter start-up mode. In the case when the first value F _i ^I found in this way is less than the starting frequency F _o , the algorithm for generating control signals on the first control sub-band, in the zone F _i ^I > F≥F _о , must correspond to the control variant for F _i ^I ≥F> F _i (Fig. 3, b), otherwise, control modulating signals must be generated in the zone F _i ^II > F≥F _о according to the second of the mentioned algorithms (Fig. 3, a). It should be noted once again that in the starting frequency range of the converter F _о N2F _о, all parameters of the control mode must be determined in accordance with the relations that describe the starting mode of operation.

In accordance with the foregoing, with respect to the control mode selected as an example, with N = 10, K = 0.5; L = 5 and M = 0.25, the initial value of parameter i for the analyzed option is defined as i = 0.4N / K = 8, which in this particular case is an integer (in the case of a fractional value of the quotient from the division, the initial i is rounded to a large side). Since in the first control zone F _B ^II > F≥F _о , the initial formation algorithm corresponds to the form of control signals shown in Fig. 3, a, which after the frequency F ₈ ^II = 1,019F _о is replaced by the second reference algorithm (Fig. 3, b ), the boundary of which will be the frequency F ₈ = 1,144 F _о , after which the value of the index i decreases by one (i = 7). Further transition from one control sub-range to another in the starting mode is performed at frequencies F ₇ = 1.198F _о , F ₇ ^I = 1.371F _о , F ₆ ^II = 1.444F _о , F ₆ ^II = 1.718F _о , F ₅ ^II = 1.836 F _about . The value of the next in order boundary frequency F ₅ ^I lies above the upper boundary of the start-up mode (above the frequency 2F _о ), therefore, further determination of F _i ^II and F _i ^I should be made according to the other of the given dependencies that characterize the nominal control mode in relation to the frequency range, limited above the frequency of LF _about . Accordingly, according to other dependences, starting from a frequency of 2F _о , the durations of the modulating control signals λ and λ ′ should be determined. The similarly determined values of the following order of boundary frequencies in the nominal operating mode of the converter are respectively equal: F ₅ ^I = 2,317F _о , F ₄ ^II = 2,630F _о , F ₄ ^I = 3,874F _о. The next order value of the boundary frequency lies above the base value LF _о = 5F _о, therefore, starting from the marked frequency, the change in τ and determination of the values of the boundary frequencies in the upper frequency range should be carried out according to other dependencies given in the description text above. The corresponding values of the upper cutoff frequencies lying in this sub-range are F ₃ ^II = 5,648 F _about , F ₃ ^I = 6,039 F _about , F ₂ ^II = 7,982 F _about , F ₂ ^I = 7,928F _about . Starting from the last frequency and to a frequency of 0.8NF _о , one modulating control signal (i = 1) with a duration of λ = 1/12 (0.8 / F-1 / F _о N) = is formed inside each of the 24-degree segments. 1/12 (0.8 / F-1 / 10F _about ), decreasing to zero at a frequency of 0.8NF _about .

эл.град. эл.град.Timing diagrams illustrating the process of generating control signals on the upper part of the control range when 0.8 <NF _о ≅F <NF _о are shown in Fig. 3, c. In this case, at the centers of the clock intervals, one central modulating control signal is generated with a successively decreasing duration, defined as λ = 1 / 6F-1 / 6F _о N. In this operating mode, it is advisable to improve the harmonic composition of the output voltage (excluding the fifth harmonic from the spectrum component) by forming an additional sequence of modulating control signals (dotted line in figure 3, c). These additional signals are generated in this case at the extreme 30-degree sections of the control half-periods, inside the zones 0-30, 150-180, 180-210 and 3330-360 el. hail. In this case, the locations of the edges of the additional modulating control signals closest to the boundaries of the half-periods of the edges are determined respectively as 12 and 168 and as 192 and 348 el. Grad. The duration of these additional control signals is determined in accordance with the dependence
γ =

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 Sufficiently complex, mainly non-linear dependencies characterizing the mode of carrying out the techniques of the described control method, it is advisable to carry out using modern digital (microprocessor) controls. In FIG. 4 is a block diagram of a converter control system made according to a vertical principle, the base blocks of which are built on a digital basis. The following are characteristics of the composition of the system and the principle of its functioning.

Using the frequency setting unit 1, the required converter output frequency is set, the signal U ₁ is generated at its output, which is proportional to the value of the output frequency, which is fed to the inputs of the clock generator 2 and N / K channel at the output of the functional converter 3. The pulse frequency of the generator 2 scan unit 4 determines the output frequency (symmetric sawtooth generator 48 el.grad length. with pauses in between the voltage 12 ^on them), which on the whole control range in w there are times higher than the output frequency of the converter. The signal of block 4 is constantly compared in block 5 of the formation of control pulses with the output signals U _{3 of the} functional converter 3, the value of which is proportional to the current values of the fronts of the control signals and output pulses α ₁ Nα _2i inside the clock intervals (see time diagrams U _AB in Fig. 3 ) The indicated values are preliminarily determined by calculation from the ratios characterizing the mode of generating control signals for both the starting and nominal control ranges. It should be borne in mind that
α ₁ = 84 ^o - (τ-λ) / 2, α ₂ = α ₁ -λ,
α ₃ = α ₁ -τ, ... α ₂ i = α _2i-1 -λ. At moments of equality of the current values of the signals of blocks 3 and 4, as shown in the internal timing diagram in Fig. 4, block 5 generates commands for generating the edges of the control (and output) pulses, which are distributed among the corresponding valves of the converter in accordance with the accepted reference law 180- degree control using a logical distributor 6 control pulses connected by its clock inputs to the corresponding outputs of the three-digit register 7, the work of which over the entire range of regulation Bani synchronized clock generator 2.

 Thus, the described law of generating control signals to the valves of a three-phase bridge converter allows us to ensure that the most undesirable fifth parasitic harmonics are completely excluded from the output voltage spectrum over the entire control range, and for the most part of the control range, this effect is provided by the most economical phase-pulse method, without additional switching in power circuit. It is also achieved due to the increased number of control and output signals at a half-cycle in the zone of low and medium output frequencies that the dynamic properties of the system in these zones are improved. At the same time, a smooth, unstressed transition from one regulation sub-range to another is carried out over the entire control range. Due to the two-zone task of the duration of the clock sub-intervals, the described method has sufficient versatility, allowing to provide the required switching frequency of the valves and the spectral composition of the output signal in almost any desired control zones. The described modification of the nominal control law in the starting frequency zone makes it possible to increase the reliability of the implementation of a very important and complex starting mode of the converter loaded on an induction motor. The noted advantages can be used with effect when creating converters for both special and general industrial systems of a frequency-controlled electric drive, including high-voltage converter systems.

Claims (1)

1. METHOD OF ASYNCHRONOUS WIDTH-CODE CONTROL OF A SEMICONDUCTOR CONVERTER FOR ELECTRIC DRIVES with N-fold, starting from frequency F ₀ , the frequency and output voltage range, in which the main valves of different phases and groups of the converter periodically turn on and off with a phase shift of 60 phases electric city in the sequence + A, -C, + B, -A, + C, -B, and for each valve within one half-period from 0 to 180 electric degrees. form the interval of conductivity of the valve, for another half-period from 180 to 360 el.grad. form the interval of the closed state of the valve, on the central intervals inside the indicated half-periods of the 60-degree intervals from 60 to 120 and from 240 to 300 electric degrees. form modulating control signals, opposite to the corresponding half-period of control, the number of which decreases successively with increasing output frequency of the converter F, and the generation of these modulating signals is performed in the middle of the clock sub-intervals with a duration of τ, the formation of each i-th counting from the reference points inside the clock intervals and to clock points, the modulating control signal is carried out when changing the output frequency of the Converter from F ₀ to the cutoff frequency F _i ^′ , while m in the nominal mode of operation on the sub-bands of the output frequencies at which
F _i ^{′ ′} ≥ F> F _{i + 1} ^′ (F _i ^′ > F _i ^{′ ′} > F _{i + 1} ^′ )
the duration λ of all modulating control signals is equal to each other, and on the frequency subbands on which F _i ^′ ≥ F> F _i ^″ along with the main array of modulating control signals with a duration of λ, a clock modulating signal of duration λ ′ is formed at the marked clock points, different the fact that, in order to improve the entire range of regulation of the harmonic composition of the output voltage of the converter, in the starting mode and in the range of low and medium output frequencies, the dynamic characteristics of drive threads fed by the converter, is achieved by changing the initial frequency F ₀ in K times, and at a frequency LF ₀ in M time duration clock subintervals and corresponding to this increase the number of pulses in a half-wave output curve, as well as to improve the reliability of the process of starting a converter loaded on an induction motor in the range of output frequencies F ₀ ÷ 0,8NF ₀ , central modulating control signals with a duration of 1/30 F. clock sub-intervals, in the range of output frequencies of the converter F ₀ ÷ LF ₀ , the duration τ of clock sub-intervals is taken equal to τ =

, in the output frequency range of the converter LF ₀ + 0,8NF _{0, the} duration τ is determined as τ =

, in the starting operation mode, at 2F ₀ > F ≥ F _{0, the} values of the mentioned boundary frequencies transient from one control sub-band to another are determined respectively as

,

,
in this mode, λ = τ _

,
at F

≥ F> F

λ ′ = 1 / 15F- (i-1) τ _

,
and in the nominal operation mode of the converter with LF ₀ ≥ F> 2F _{0, the} values of the boundary frequencies F _i ^{′ ′} and F _i ^{′ are} found respectively as

at 0.8 NF ₀ ≥ F> LF ₀ , the frequencies F _i ^{′ ′} and F _i ^{′ are} found respectively as

in the range of the nominal operating mode of the converter to a frequency of 0.8 NF ₀ for F _i ^′ ≥ F> F _i ^{′ ′}

λ ′ = 1 / 15F- (i-1) τ - 1/12 (2i-1) F _o N,
at F

≥ F> F

λ =

-

,
and when NF _o > F ≥ 0.8NF _o
λ = (1/6) F-1/6 (F _o N)
2. The method according to claim 1, characterized in that on the control sub-range 0.8NF ₀ <F ≅ NF ₀ form inside the intervals 0 - 30, 150 - 180, 180 - 210 and 330 - 360 el. additional modulating control signals, while the locations of the edges closest to the boundaries of half-periods of the edges of additional modulating control signals are determined respectively as 12 and 168 and as 192 and 348 el. degrees, and the duration γ of the marked signals is found as
_{γ =}

electric city

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