SU748790A1 - Device for control of inverter with pulse-width modulation - Google Patents

Description

: 54) DEVICE MANAGEMENT DEVICE WITH PULSE-IMPULSE MODULATION

The invention relates to electrical engineering and can be used in control devices for semiconductor frequency converters, which are intended for frequency control of an AC motor. A device for controlling an Inverter with Pulse Width Modulation (BUS) 1J is known. The known device has the disadvantage that in order to ensure the operability of the device, low-pass filters are installed at the output of the master oscillator unit, introducing a significant phase shift when the modulation frequency changes, in addition, the amplitude of the output voltage of the inverter is controlled over one channel. The closest in technical essence and effect achieved is a device containing two independent generators and a driver of control signals for the power gates of the inverter. The first generator consists of three frequency-controlled multivibrators, controlled by a multivibrator, to the input of which a signal is set to the frequency of the modulating voltage. The second oscillator. Includes a common under-adjustable multivibrator, a phase shifter and a phase-adjustable multivibrator. The input of the phase-shifting device is supplied with a signal for setting the amplitude of the modulating voltage. The outputs of the generators are connected to the inverter valve control signal shaper, which includes the output windings of each valve control, connected in parallel in two chains, one of which consists of, according to the included windings, frequency controlled multivibrator of this phase and phase adjustable multivibrator, and the other from The windings of the same frequency controlled multivibrator and a common unregulated multivibrator 2. The disadvantages of this device are the dependence of the phase shift of the fundamental harmonic of the output voltage of the inverter on the depth modulation and the sinusoidal law of modulation, which leads to uneven rotation of the motor at low frequencies.

the presence of one channel for controlling the inverter voltage. .

The purpose of the invention is to improve the output voltage spectrum of the inverter.

The goal is achieved by the fact that in the control unit of the inverter with PWM, consisting of two frequency generators and the signal generator of the inverter power valves control, the inverter control signal is formed by the inverter

in modulators, $ opNMpo ya; tSH1y signaling equipment: 5t% mi

iodulators, two integrators,

each of which is covered by a nonlinear feedback element, two zero-bodies, two elements AND the first trigger / ph and the first inputs of the jcsfO and fourth modulators to the outputs for connecting the input signal of the first component of the inverter output voltage, the first inputs of the second and the fifth module of the equalization signal of the second component of the main harmonic of the output signal. inverter voltages, the first inputs of the third and sixth modulator-constant offset signal, the second input of each modulator is connected to the corresponding output of the control signal of the modulators, the outputs of the modulators are connected to the inputs of the integrators in such a way that the outputs of the first TreX modulators are connected to the entrances ° o2nogyy11Tёgratora; a, the output of other modulators is to the inputs of the second injector, the output of each integrator is connected via the null-organ to the first input of the corresponding element I, the second input of the first element I is connected to the second input of the sixth modulator, the second input of the second element I is connected to the second the input of the third modulator, and the outputs of both elements And connected With the inputs of the trigger.

Fig. 1 is shown in detail in a block diagram of an inverter control device with pulse-width modulation; Figs. 2 and 3 are timing diagrams explaining pa6qTy devices,

The device contains modulators 1-6, generators 7 and 8, the outputs that are connected to the inputs of the imaging unit 9 Styles of control modulators 1-6. The modulators 1-3 are connected via the integrator 10, the null organ 11th element AND 12 are single: the input trigger 13, and the modulators 4-6 are connected via the integrator 14, null organ 15 and the element 16 And with another input trigger 13. The integrators 10 and 14 are covered through non-linear elements 17 and 18 by feedback. Second entrances; elements 12 and 16 And are connected to the outputs of the imaging unit 9 control signals modulators.

The output of the device are the outputs of the flip-flop 13, according to the signals carried out: hUTc switching elements of one phase of the inverter. The inverter operates in a pulse-width modulation mode with a carrier frequency equal to the frequency of the generator 8. The frequency of the fundamental harmonics of the output voltage of the converter is equal to the difference between the frequencies of the generators 7 and 8. The first and second components of the main harmonics are given by the input signals U and U of the first I at the first the inputs of the modulators are 1, 4 and 2, 5, respectively. The first inputs of the modulators 3 and 6 are given a constant bias signal U

The principle of operation of the device is as follows.

The generator 7 forms a system of pulse sequences with a constant angular frequency. The generator 8 forms a second system of pulse sequences with an angular frequency.

and;...,

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ff is the phase shift between the signal tdes of the oscillators 7 and 8.

I The signals from the outputs of the generators 7 and 8 are fed to the inputs of the driver 9, in which the control signals for the modulators 1-6 are formed.

Conversion of signals U, U and and is carried out on two identical channels. The signals from the output of the modules 1-3 are summed up and passed through the series-connected integrator 10, the null organ 11 and the circuit 12. Ovapadn-i, and the signals from the output of the modulators 4-6 - Through the integrator 14, the null organ 15 and the element 16 I. As a result of the conversion of input C ± mod by modulators 1–3, at their outputs we have alternating signs of rectangular-shaped form, the amplitude of which is determined by the corresponding input effects (UX, u, UCM). These signals are summed at the input of the integrator 10.

The integration of signals is carried out within the period of the frequency of the oscillator 8. At the same time, two integration intervals can be distinguished - measuring and working. The result of the integration on the measurement interval depends on KX, and Uy ,. In the working interval, only the bias signal is integrated. In the working interval of Fig. 2, zero integrator 11 is triggered by passing the X-RAY signal of the integrator 10 and the trigger 12 is switched through the element 12 and the non-linear element 17 provides zero initial conditions for the integrator for each subsequent and measuring interval. Element And 12 prevents switching of the trigger within the measuring interval for each channel with excessively large input influences U and U, since in this case the output signal of the integrator can pass through zero at the measuring interval.

The second channel, which includes modulators 4-6, integrator 14, null organ 15 and element 16I, is built on the same principles and differs only in that while the first interval has a measuring interval, in the second channel it is working and vice versa . This is achieved by appropriately generating control signals for modulators 1-3 and 4-6. As a result of the signal conversion on the second channel, the null body 15 is triggered and the trigger 13 switches to the opposite state. Further, the process is periodically repeated, i.e. the trigger 13 switches with the frequency of the generator COOP2

In case the input is -; Since Uj, O, and Uy O, the integration rate in the measurement interval of FIG. 2 is two times lower than in the working interval. Therefore, the zero-bodies 11 and 15 operate in the middle, corresponding to the working intervals (tj and 1), corresponds to the symmetric switching law of the trigger 13; (modulation depth is zero). If the input actions are not zero, then due to the integration of the signal, one of the null organs switches later, and the other - earlier by the value of At (see Fig. 4). as a result, the switching law of the trigger 13 becomes asymmetrical with respect to the duration of the half periods, and. As seen from FIG. 3, there is a symmetric double-sided modulation of the original (with both O and Uy 0) trigger signals 13. The control signals of the Modulators 1 and 2, as well as 4 and 5, are formed in such a way that the mean values of modulated The signals Xy and Uy in each of the mentioned channels are periodic functions of the phase difference between the generators 7 and 8 and are shifted between themselves by 180 electrical degrees. Therefore, when their O and Uy O signals are constant, the increments of n & f are periodic, close to harmonic, functions of the phase difference of the generators 7 and 8. As a result, when the frequencies are unequal, Wonj at the output of the device we have symmetric two-sided pulse-width modulation according to a harmonic law with a frequency equal to the frequency difference bJ jUJonj, and a modulation depth depending on U and ich /. ....

Introduction of the former 9, modulators 1-6., Integrators 10 and 14, non-linear elements 17 and 18, zero.

bodies 11 and 15, circuits 12 and 16 And the coincidence, as well as trigger 13, favorably distinguishes the proposed PWM inverter control device from the known one, since the use of syms metric two-sided modulation of the output signal of the device eliminates the dependence of the phase shift of the main harmonic of the output voltage of the inverter from depths and frequencies. modulation.

Claims (2)

1. An inverter controller with pulse-width modulation, consisting of two independent frequency generators connected to a driver of control signals for the inverter power valves, characterized in that, in order to improve the spectrum of the output voltage of the inverter, the driver of the IGNA-, 0 control of power inverter fans) is made in the form of six modulators, a driver for controlling these modulators, two integrators, two null-organs, 5 two elements K, and a trigger, with the first inputs of the first and fourth modulators connected to the terminals for connecting the input signal for setting the first Soast is the main 0 harmonics of the output voltage of the inverter, the first inputs of the second and fifth modulator-input signal of the second component of the main harmonic of the output voltage of the inverter, the first inputs of the third and the sixth modulator-constant bias signal, the second input of each modulator is connected to the corresponding output of the modulator control signal generator, the outputs of the first three modulators are connected to the inputs of the first integrator, the outputs of the second three modulators - to the inputs of the second integrator, the output of each integrator through the zero-organ is connected to the first 5 input of the corresponding element I, the second input of the first element I is connected to the second input of the sixth modulator, the second input of the second element I is connected to the second input p tego modulator, and the outputs of both AND gates are connected to trigger inputs. . . 2 .. The device according to n.l, about tl and - ch and e with the fact that one of Five independent frequency generators are six-phase, and the other two-phase, with an unregulated phase angle of the output signals. Sources of information, 0 taken into account in the examination 1. Sandler A.S. and Gustsky Yu.M. Thyristor inverters with a width-impu. Gsnyj modulation. M, 1968, p., 72-86, 2. USSR author's certificate 5 No. 197743, cl. H 02 R 13/18, 1967. W, ten W, y / e W, 8