SU836739A1 - Method of converting dc voltage into quasisinusoidal one - Google Patents

Description

The invention relates to electrical engineering and can be used to build secondary power supplies for electroautomatics devices and AC electric drives, operating on both alternating and constant loads in cases where coordination of voltage levels of the supply network and the consumer is required, as well as improved quality of the converted electric energy (in the sense of the harmonic coefficient of the output voltage) and acceptable overall dimensions. secondary source.

A large number of methods are known for converting a constant voltage to a quasi-sinusoidal one. The most rational methods of conversion are using inverters with a decrease in the number of higher voltage harmonics in the inverter itself, ie, before filtering [1] and [2].

The use of output filters for this purpose increases the mass, dimensions of the device and reduces its efficiency, especially at low frequencies. In addition, the use of filters is limited due to the possibility of resonance phenomena when powered by electric motor converters, and instability of the shape of the voltage curve in various modes.

, A combination of an inverter inverting the functions ^E and generating a voltage that is similar in shape to a sinusoid al s Nome allows izbezhat.otmechennyh drawbacks.

Closest to the invention ^and in technical essence is a method in which a constant voltage is converted into η rectangular shape-identical alternating voltages, these voltage variables 15 are shifted relative to each other by a fixed angle, and then summed [3].

However, the device for implementing this method has poor 20 weight and size indicators, since in order to obtain a voltage that is close in shape to sinusoidal, it is necessary to summarize a large number of rectangular transient voltage. In addition, this method performs geometric summation of stress vectors with large phase shifts between them. As a result, the installed power of the elements and components of the device and the mass of the device are increased in comparison with the method used when zooming in collinear vectors.

The purpose of the invention is the improvement of overall dimensions of the device that implements the method upon receipt of the output voltage of high quality.

This is achieved by the fact that according to the method of converting a constant voltage to a quasi-sinusoidal one by obtaining η identical alternating voltages in shape, shifted relative to each other by a fixed angle, and then adding them up, the constant voltage ^{15 is} converted to high-frequency with a frequency that is a multiple of the frequency of the indicated quasisinusoidal voltage then carry out its amplitude-pulse modulation and isolation of 20 by demodulating the voltage of a multi-stage form with uniform intervals quantization of erQ levels, and the phase angle between two adjacent multi-stage 25 voltages is chosen to be t ^ / n where t _u is the duration of the quantization intervals of the levels of multi-stage voltage.

Figure 1 shows a block diagram 20 of a Converter that implements the proposed method (option); figure 2 timing diagrams explaining the principle of operation of the Converter; in FIG. 3, a simplified modification of the pre-educator (option).

The principle of generating control signals of the keys of a single-phase inverter and switch when generating output voltage curves by the proposed method using 40 converters (Fig. 1) is illustrated by timing diagrams in Fig. 2, control signals supplied to the control 45 of the key inputs of a single-phase inverter;

U is the high-frequency voltage on the primary winding of the transformer;

-, Wig-- U _2o ~ control signals supplied to the control 55 inputs of the switch keys of the switch;

U _K -U _H - multistage output frequency voltages shifted relative to each other by an angle ij / 3?

ЦЦ, - converter output voltage, 65

The method is as follows.

The constant voltage is converted into a high-frequency voltage U-rp (Fig. 2b) with a frequency that is a multiple of the frequency of the output voltage of the converter U _w (Fig. 2d). Then, amplitude-pulse modulation of the high-frequency alternating voltage ϋγρ is carried out and, for example, three (n = 3) multi-stage voltages uj - и ^ - 'are selected (the number of steps for the example is also chosen to be three, see Fig. 2d) with equal-time quantization intervals (t _M ) of its levels. I w

By shifting the voltages U _m -Uh relative to each other by an angle t ^ = tn / 3 and summing these three voltages, a quasi-sinusoidal voltage U _{M is} formed at the output of the converter (Fig. 2e) with improved harmonic composition.

It should be noted that the magnitude of the phase shift between two adjacent multi-stage voltages is determined by the number η of the summed voltages and is equal to b <t = b _and / u. Increasing the operating frequency of the conversion i.e. the frequency of the voltage U _Tr (Fig), it is possible to significantly improve the overall dimensions of the device that implements the method.

In cases of obtaining increased output powers with limited capabilities of the element base, it may be rational to divide the converter into η parallel channels with a serial connection of their outputs (Fig. 1). The Converter (figure 1) contains three identical parallel channels. Each channel includes a single-phase bridge inverter 1 with four. keys 2-5, forming its two racks. The inverter 1 is loaded on the primary winding of the matching transformer 7. Its secondary winding is directly connected to one of its taps 8, and connected to the output terminals of the channel through the other taps 914 through the keys 15-20 of the switch 21.

The outputs of all three channels are connected in series. Due to the shift by the corresponding fixed phase angles of the output voltages of the channels, it is possible to obtain significantly less distortion of the resulting output voltage of the converter compared to distortions of the output voltage of any of the channels.

The block diagram (Fig. 1) also contains single-phase inverters 22 and 23, matching high-frequency transformers 24 and 25, switches 26 and 27, a phase-shifting device 28 and channel control systems 29-31.

The phase shifting device 28 provides a phase shift of the output voltages Uh “ ^and and ^Ш channels. Channel control systems 29-31 generate key management signals for single-phase inverters and switches.

The principle of forming the control signals of the Converter shown in figure 1, is illustrated by the example of the formation of voltage uj (Fig.2A).

Each quantization interval (t)) of the output voltage and * channel levels is divided, for example, into six 15 sub-intervals. On the subintervals t _o -, t ₂ -t ,, and t ₄ ~ t _F, release pulses are generated for the keys 2.5 of the single-phase inverter 1 and key 18 of the switch 21, and on the subintervals 20 t _d -t ₂ , t ^ -t ^ they generate gate pulses for the keys 3,4 of the single-phase inverter i and the key 18 of the switch 21. In this case, an alternating voltage is generated in the primary winding 6 of the transformer 7, and a sequence of rectangular pulses representing 'the first stage of the output voltage U * is formed at the channel output. channel ·. The formation of voltages U ^ r θ® ^{at the} output bto- '' ^{j of the} horn and third channels is carried out similarly.

The proposed method can be implemented by various devices having a different structure. For example, ’5 in the converter, the block diagram of which is shown in FIG. 3, the conversion of direct voltage to a high-frequency variable occurs in one channel, followed by modulation 40 and demodulation of this alternating voltage in η parallel channels.

The proposed method can significantly improve the overall dimensions of the device as a whole, primarily due to the increased conversion frequency. So, in the frequency range under consideration up to 10 kHz, the use of permaloy cores can reduce the transformer mass by three to four times. In this ^ee GVW device decreases by 30-40%.

The reduction in installed power also occurs due to the fact that according to the proposed method, geometrical summation of sectors with phase shifts between them is substantially smaller than in the known device [h].

Claims (3)

(54) METHOD FOR CONVERSION OF CONSTANT VOLTAGE TO QUASI-SINOIDIDIC DEVICES AND UNITS AND DEVICES OF THE DEVICE, AND WEIGHT OF THE DEVICE, AS WELL. :; y: 4th the collinear vectors. The purpose of the invention is to improve the mass parameters of a device implementing a method in obtaining high quality output voltage. This is achieved by the fact that, according to the method of transforming a constant voltage into a quasi-sinusoidal by obtaining and identical in form of variable voltages, shifted relative to each other at a fixed angle, and their subsequent summation, the constant voltage is converted into high frequency with frequency, a multiple of the frequency of the indicated quasi-sinusoidal voltage, then its amplitude-pulse modulation and isolation by multi-step voltage demodulation with uniform mi-intervals It is designed to level 9, and the phase shift between two adjacent multistage voltages is chosen to be where the duration of the quantization intervals of the multistage voltage levels. Figure 1 shows the block diagram of the Converter that implements the proposed method (option); Fig. 2 are timing diagrams explaining the operation of the converter; FIG. 3 shows a simplified modification of the converter (option). The principle of forming the control signals of the single-phase keys of the inverter and switch when forming the output voltage curves of the proposed method by means of the converter (Fig. 1) is explained in the time diagrams in Fig. 3, where and -. control signals supplied to the control inputs of the keys of the single-phase inverter; and - high frequency voltage on the primary winding of the transformer; h . -Uj are control signals applied to the control inputs of the switch keys; many dull output voltage voltages shifted relative to each other by the angle V3; output transducer voltage. The method is carried out as follows. A constant voltage is converted into a high-frequency voltage U-fp (Fig. 26) at a frequency that is a multiple of the frequency of the output voltage of the Uf converter (Fig. 2d). Next, the pulse-amplitude modulation of the high-frequency alternating voltage U and the selection of, for example, three () multi-step voltages and (the number of steps is also chosen to be equal to three, see fig. 2d) with time-varying quantization intervals (t) its levels, i ш Shift voltage Uf, -U relative to each other at an angle, / 3 and sum these three voltages, form a quasi-sinusoidal voltage Ots (fig.2d) with an improved harmonic composition at the output of the converter. It should be noted that the magnitude of the phase shift between two adjacent multistep voltages is determined by the number n of summed voltages and is equal to t.tn/H. Increasing the conversion frequency, i.e. voltage frequency UTP (Fig, 26), it is possible to significantly improve the weight and dimensions of the device that implements the method. In cases of obtaining increased output powers with limited possibilities of the eccentric base, the rationing of the converter into π parallel channels with the series connection of their outputs can be rational (Fig. 1). The converter (FIG. 1) contains three identical parallel channels. Each channel includes a single-phase bridge inverter 1 with four. keys 2-5, forming its two racks. Inverter 1 is loaded onto the primary winding of matching transformer 7, ITS secondary winding of one of its spurs 8 directly, and by other taps 914 via switches 15-20 of switch 21 connected to output terminals of the channel. The outputs of all three channels are connected in series. Due to the shift to the corresponding fixed phase angles of the output voltages of the channels, it is possible to obtain significantly smaller distortions of the reactive output voltage of the converter compared to the distortions of the output voltage of any of the channels. The block diagram (Fig. 1) contains the same single-phase inverters 22 and 23, matching high-frequency transformers 24 and 25, switches 26 and 27, phase shifting device 28 and channel control systems 29-31. The phase shifter 28 provides the phase shift of the output voltages of the UH c channels. The channel control systems 29-31 generate key control signals for single-phase inverters and switchboards. The principle of forming the control signals of the converter shown in Fig. 1 is illustrated by the example of voltage formation uj (Fig. 2a c). Each quantization interval (the output voltage and channel levels are divided, for example, into six sub-intervals. At sub-intervals, tj-t, and t.-tg- Starting pulses are generated for 2.5 single-phase inverter 1 keys and switch 18 key 21 a on subintervals, tg.- form OTPI scattering pulses for keys 3,4 of single-phase inverter i and switch 18 key 18. At the same time, in the primary winding 6 of transformer 7, an alternating voltage U is formed, and a sequence of square impulses is formed at the channel output first step out The voltage of the channel Uj. The formation of voltages U and its output from the second and third channels is similar. The proposed method can be implemented by various devices having a different structure. For example, in a converter whose circuit diagram is shown Fig. 3, the conversion of a constant non-high frequency voltage to a high frequency variable occurs in one channel, followed by the modulation and demodulation of this alternating voltage in n parallel channels. The proposed method makes it possible to significantly improve the weight and dimensions of the device as a whole, primarily due to the increased conversion frequency. Thus, in the frequency range up to 10 kHz, the use of permallo cores reduces the weight of the transformer by three to four times. In addition, the total mass of the device is reduced by 30-40%. . The decrease in the installed power also occurs due to the fact that the proposed method performs geometric summation of sectors with phase shifts between them, which are significantly smaller than in the limestone device H. Claims: A method of converting a constant voltage into a quasi-sinusoidal by obtaining and identical in form of variable voltages shifted relative to each other by a fixed angle, and their subsequent summation, characterized in that, in order to improve the weight and size parameters of a device implementing the method, To obtain each of these alternating voltages, the DC voltage is converted to high frequency with a frequency that is a multiple of the frequency of the specified quasi-sinusoid voltage and then Its amplitude modulation and separation by demodulation of multi-stage voltage with equal-time quantization intervals of its levels are implemented, and the shift angle between two adjacent multi-stage voltages is chosen to be equal to, where the duration of multi-stage voltage quantization intervals . Sources of information taken into account in the examination 1. Konstantinov VG Multiphase transistors on transistors. M., Energie, 1972, p.96. 2. Chizhenko I.M. and others. Fundamentals of converting technology g N., Higher Stake, 1974, p. 430. 3. Rudenko B.C. et al., Development and study of a thyristor frequency converter with an improved output voltage form. -Sat. Current tasks of the conversion technology, part 4-Kiev: Naukova Dumka, 1975, pp.126-135. fo k b Vrp, V, 8 % % ViO Utf 836739