SU612217A1 - Method of controlling self-sustained inverter output voltage - Google Patents

Description

(54) METHOD FOR REGULATING OUTPUT VOLTAGE OF AUTONOMOUS INVERTER

filtering-o-oborulo) an and leads to a deterioration of the technical and economic indicators of the converter plant.

The aim of the invention is to reduce distortion of the output voltage over the entire range of its regulation.

This is achieved by regulating by a known method, when a sinusoid of output voltage is formed from a sequence of square impulses with different amplitudes, the size of each of which is equal to the area of the corresponding section of the sinusoid being formed, and their duration is changed in accordance with the required output voltage over the entire adjustment range, compare the area of each section of the sinusoid being formed with the product of the maximum possible pulse duration and amplitude less than its neighboring level for pulse portion and, if comparability okazhets area smaller or equal to said product of it, at the site .formiruyut pulse amplitude equal to the amplitude of the lower level of the adjacent portion of the pulse.

FIG. Figure 1 shows the curve for the case when the output voltage of the inverter is formed from five pulses of amplitudes A, -AZ (the half-period of the output voltage is divided into five equal clock intervals); in fig. Figure 2 shows the power part of the converter that implements the proposed method, and the time diagrams that clarify its operation. The magnitude of the output voltage of the inverter is maximum when there are no pauses between the formation pulses (Fig. La). The amplitude of the output voltage pulses is calculated according to this mode so that the product of the amplitude of the pulse for the maximum possible duration equals the area of the corresponding plot of the sinusoid of construction.

In the subsequent regulation of the voltage down from the maximum value, the area of each section of the sine wave is continuously determined and, since these areas must be equal to the areas of the corresponding formation pulses, the required durations of each pulse are found at each time point by dividing the area value by the amplitude value .

Determining the area of a sinusoid can be done differently, in particular, if the inverter control system has a reference sinusoid with a frequency equal to the frequency of the output voltage, with the ability to smoothly adjust the amplitude from maximum to zero, the amplitude of the reference sinusoid at each time point in the corresponding the scale unambiguously determines the duration of each pulse of the output voltage, since with rigidly fixed borders of the sinusoidal sections the connection between the duration of the pulses cos n playground forming plural portions snnusoidy lnneyna.

At the same time, the area of each sinusoid section is compared with the product of the maximum possible pulse duration and the amplitude of the lower level pulse of the neighboring section. So far, the compared area is greater than the above-mentioned product, the regulation is made only by continuously changing the pulse duration without changing the amplitude of the pulses. FIG. 1 b shows one of the moments of this stage of regulation. Such a mode is actually identities of the moment of regulation by a known method.

With further regulation, at the moment when the area of any part of the building sine wave is equal to the maximum possible pulse duration per amplitude of the lower forming pulse of the next part, at the described plot of the construction sine wave, an impulse is generated with an amplitude equal to the smaller amplitude of the pulse at the next plot. So in FIG. I depicts the moment of equality of the area of the HI sinusoid plot to the construction of the product of the maximum possible pulse duration by the amplitude of the impulse of sections II and IV, at this moment the impulse of forming the section III is reduced in amplitude to the neighboring impulses with simultaneous expansion of the duration to the maximal pulse regulation.

Further adjustment is carried out similarly: find the area of each plot of the sinusoid plot, divide by the corresponding amplitude of the formation pulse, which unambiguously determines the pulse duration, and simultaneously pass through the same OPS.

On fng. Gg shows the moment of equality of the areas of the And and IV plots of the sine wave constructed by the product of the amplitude of the impulses of the plots of I and V for the maximum possible duration - the amplitudes of the pulses of the plots of II and IV are discretely decreasing with simultaneous increase in their duration.

FIG. 1 d. Shows the moment of equality of the area of the area III sinusoid built proiz. maintaining amplitude of impulses of sites. And and IV for the maximum possible duration. At this moment, the amplitudes of the impulses of all segments become the same. Further regularity conducts continuously, down to the zero value of the output voltage.

When adjusting the output voltage upward, the processes described are repeated in reverse order.

In general, the number of adjustment steps is equal to N (n - the number of levels

OUTPUT voltage) ..

Thus, for the number of pulses per

half period i 5 and 6 (n "3) N 3,

for i - 7 and 8 (p 4) N - 6; for i 9 n io (n - 5) N С 10, etc.

The described control step is realized by means of an appropriately executed inverter key control system. The function of the control system in this case is both parametric control of the output voltage pulse duration in accordance with the required output voltage value, as well as comparing the area of each section of the sinusoid being formed with the product of the maximum pulse duration by the amplitude of the next smaller section. The logical part of the control system is constructed in such a way that if the compared area is less than or equal to the product described, a command is given to form an impulse in this area with an amplitude equal to the smaller in amplitude of the next section. The system is easily implemented on both discrete and integral elements of a wide nomenclature.

One of the most simple and common. The main power circuits of the converters that implement the method are inverter circuits made on a transformer with taps. A simplified version of the secondary side of the SSH1.0VO part of such an investor () of the torus is shown in FIG. 2 a.

The primary side of the inverter generates bipolar pulses without pauses at a frequency five times higher than the output frequency of the inverter. The controlled keys 1, 2, 3 are command to obtain output pulses with amplitudes Ai, Ai, Aj, respectively. Compared with the traditional implementation, a bridge is added to the inverter circuit on the controlled keys 4-7 (the diagonal of which includes load 8), which reverses the load current 8 at the required moments. In FIG. 26-, d show the conductivity intervals of the formation circuits on the secondary side of the transformer 9 of the inverter, respectively. control ranges shown in FIG. 16-day sootvetstviio. The conductivity of all circuits (Fig. 2 a) is a two-sided, which can be realized, for example, by meeting parallel-connected thyristors. Switching on and B1 10 keys can be performed by commands of the control system at any necessary points in time.

FIG. 26 shows the adjustment time by a known method: the output voltage curve (form of Fig. Ib) is formed by sequential switching of the controlled keys 1-2-3-2-1 - I-2 ..., the output voltage value is determined by the switching points and to disable managed keys.

Pa figs. 2c shows the first step of adjustment according to the proposed method: at the moment of sampling, the algorithm for switching the shaping keys changes: 1-2-2-2- - I-2 ..., the sequence of switching the bridge keys changes simultaneously.

FIG. 2 g at the moment of the second step of adjustment the forming keys work in the sequence 1 - 1-2-I - I - 1 - I - I - 2 -..., respectively, the algorithm of operation and the keys of the bridge 4-5 and 6-7 are changed.

For FIG. 23 (the moment of the last switching) and further on all the period the output voltage is formed using the control key 1, since the amplitudes of the shaping pulses in all parts of the output voltage here must be the same and equal to A |.

The proposed control method allows to significantly reduce the distortion of the output voltage during its regulation and thereby reduce the installed power of the filters.

Claims (2)

Invention Formula The method of controlling the output voltage of an autonomous inverter that generates a sinusoid of the output voltage using a series of rectangular pulses with ioodiak amplitudes, the area of each of which is equal to the area of the corresponding portion of the sinusoid being formed by varying the duration of the pulses, depending on , in order to reduce the distortion of the output voltage in the entire range of its regulation, compare the area of each section of the form emoy sinusoid with the product of the maximum possible pulse width for a smaller amplitude level of the adjacent portion of the pulse and generating a pulse at the site amplitude equal to the amplitude of the smaller according to the level of the impulse of the neighboring area, if the size of the compared area does not exceed the specified product. Sources of information taken into account in the examination: 1 1. USSR inventor's certificate No. 512547, cl. H 02 M 7/537. 2.-Toikal V.E., Lnpkovsky K.A., Meliychuk L.P. "Basic methods of improvement forms of single-phase voltage of single-phase av. autonomous inverter. Sat "Increasing the efficiency of devices of converting equipment, Part 1 K.," Naukova Dumka, 1972. p. 41-60. V "wx  L | fi f) ja L