RU2566365C1 - Method of step-link control of output voltage for rectifier based on transformer with rotating magnetic field - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention may be used in control systems (B) based on transformers with rotating magnetic fields (TRMF). The suggested method of step-chord control is implemented due to vectorial addition of voltage values in separate sections of secondary circular TRMF winding by means of semiconductor switch (SS) switching branches of secondary circular n-section TRMF winding in compliance with new algorithm. Outputs of SS - multi-arm rectifying bridge are coupled to collecting bus bars supplying load of the rectifier. At each control step branches of circular TRMF winding are connected to collecting bus bars of the rectifier; the branches are divided by number of sections permanent for each section, in result value of rectified voltage is defined by vectorial sum of EMF for a group of sections placed between branches, connected by semiconductor switch to positive and negative collecting bus bars of the rectifier, and each next pair of branches connected to collecting bus bars of the rectifier has minimum phase shift in regard to the previous pair of branches.

EFFECT: improved energy characteristics.

1 tbl, 5 dwg

Description

Area of use

The method of step-chord regulation of the output voltage of the rectifier relates to the field of electrical engineering, in particular to semiconductor converters of electric energy parameters and can be used to control rectifiers built on the basis of transformers with rotating magnetic fields (TVMP).

State of the art

It is known that stepwise regulation of the output voltage is used to stabilize the output voltage of the rectifiers [B.C. Rudenko, V.I. Senko, I.M. Chizhenko, Fundamentals of converter technology, M., Higher School, 1980, 424 s], as well as for regulating AC voltage [Yu.S. Zabrodin. Industrial Electronics, M., Higher School, 1982, 496 s]. The method of stepwise regulation is implemented using pulsating magnetic field transformers containing primary or secondary windings with several sections, the taps of which are switched by semiconductor switches.

Closest to the claimed method of step-chord regulation is a method of step-by-step regulation of the output voltage of the rectifier by switching the taps of the secondary windings of the matching three-phase transformer with pulsating magnetic fields, with windings connected according to the star / star circuit (with taps) [B.C. Rudenko, V.I. Senko. THEM. Chizhenko, Fundamentals of transformative technology, M., Higher School, 1980, 424 pp.].

The purpose of applying the method of stepwise regulation of the rectified voltage by means of voltage boosting is to improve the energy performance of the rectifier, namely: shear coefficient and power factor.

The essence of the method of stepwise regulation of the output voltage of the rectifier is the arithmetic summation of the voltage of the voltage additives from the sections with higher voltages with the voltage of the main section with the rated voltage, due to which the value of the output voltage of the rectifier changes stepwise. A controlled rectifier (HC) that implements a stepwise regulation method contains two three-phase switches: uncontrolled, made according to a three-phase zero circuit on power diodes, which transfers the rated voltage to the load, and controlled, made according to a three-phase zero circuit on thyristors, which transfers an additional ( high) adjustable voltage.

The disadvantages of the analogue include:

1) the complexity of the design of the transformer due to the use of voltage boosts;

2) a significant ripple coefficient of the rectified voltage, since when regulating the voltage of the highest step of the voltage boost, first-order discontinuities occur in the curves of the rectified voltage;

3) an increase in the number of power switches in semiconductor switches;

4) deterioration in the quality of the supply voltage and current when regulating the voltage of the highest stage of voltage boost.

Object of the invention

The purpose of the invention is to improve the quality of the supply and rectified voltage based on the use of a new step-chord method of regulation, in which the rectified voltage is obtained by geometrically summing the voltages of individual sections of the secondary circular winding of a new type of transformer with a rotating magnetic field (TVMP). TVMP contains a primary three-phase and secondary circular n-sectional winding (KO), the taps of which are switched by a semiconductor switch in accordance with the new "chord" algorithm, which eliminates first-type discontinuities in the rectified voltage curve, which reduces the ripple voltage of the rectified voltage, reduces the shear coefficient between the first harmonics of the supply current and voltage, reduces the effect of HC from TVMP on the supply network and provides a high value of power factor at all stages of regulation Bani.

Disclosure of invention

The essence of the proposed method - step-chord regulation consists in geometric summation of the voltages of individual sections of the secondary circular winding of a new type of transformer with a rotating magnetic field. TVMP contains a primary three-phase and secondary circular n-section winding, the taps of which are switched by a semiconductor switch (PC). The direct order of the geometric summation of the instantaneous voltages of individual sections of the secondary circular winding is determined by the new "chord" algorithm for switching the taps of the n-section QO and is illustrated by the schemes shown in figure 1, when the QS contains a different number of sections.

If we assume that EMFs of the same amplitude are excited in each section of the CO, differing in spatial-phase shifts, and the EMF themselves are balanced by the corresponding drops in the sectional voltages, then the amplitude voltage on the CO section, when the HC is idling with TVMP, can be found as

where U _{ts_m} is the amplitude voltage at the ts section of the _{TBMP FET} (here t and s are the FB node numbers at the ends of one section); U _{l_m} is the amplitude voltage drop in the phase of the primary three-phase winding (TO) of the TVMP; w ₁ and w ₂ - the number of turns of the TO phase and one section of the TO, respectively; L ₁ and L ₂ are the inductances of the TO phase and one section of the TO, respectively.

To calculate the voltage between the nodes of the TO, you can use the topographic vector diagram based on the geometric interpretation of the design of the circular winding of the TVMP (figure 1). Then KO TVMP with 3 sections is represented as a triangle, with 4 sections - as a square, with 5 sections - as a pentagon, with 6 sections - as a hexagon, etc. (figure 1). In the case of a QA with 3 sections (figure 1, output 1.1), the voltage, for example, between nodes 1-2, 2-3, 3-1 is numerically equal to the length of the chord connecting the corresponding nodes (bends of the QoS):

For a KO with 4 sections (figure 1, output 1.2), the voltage between nodes 1 and 3 of the KO can be found as a value equal to the diagonal of the square, which is numerically equal to the sum of the projections of two sectional voltages U ′ ₁₂ and U ′ ₂₃ on the diagonal of the square:

With an odd number of sections KO N _SKL = 5, the switch of the taps of the KO sections forming the rectified voltage (U _d ) will alternately connect taps 1-3 and 1-4, 2-4 and 2-5, 3-5 and 3 to the load -1, 4-1 and 4-2, 5-2 and 5-3, etc. (figure 1, exit 1.3).

Therefore, with a five-section winding, the instantaneous value of the rectified voltage u _d (t) can be found, for example, as the voltage between nodes 1 and 3, which is expressed as the sum of the projections that differ in magnitude from the projections of the four-section KO (figure 1, output 1.3):

With an even number N _SKL = 6, the switch of the taps of the sections of the KO will alternately connect taps 1-4, 2-5, 3-6, 4-1, 5-2, 6-3, etc. to the load. (figure 1, output 1.4). Here u _d (t) can be found as the voltage between the diametrically located nodes 1 and 4, which consists of three projections:

From figure 1 it follows that with an even number N _SCR KO has 2n chords with a maximum voltage, and with an odd number N _SCR there are no such chords. Here, at each vertex (KO branch), there are two chords with the highest voltages, for example, chords 1-3 and 1-4 (1.3), from which u _d (t) is formed. The indicated geometric interpretation, which reflects the topology of the QoS, allows one to obtain a physical explanation of the reason for doubling the number of ripples in the curve of the rectified voltage of a shock wave with TVMP with an odd number of power switch pairs.

Similarly, you can calculate the maximum voltage between any two branches of the TO, for any number of sections of the TO or the number of pairs of power switches.

The voltage from the KO taps is fed to a semiconductor switch (PC), which is a multi-arm bridge rectification circuit, made on fully controllable semiconductor devices (PP), the role of which, depending on the voltage applied to the rectifier load, can be performed by two-operation (lockable) thyristors, field effect transistors or insulated gate bipolar transistors. The PC operates in accordance with the new algorithm, in which the switching of the power KO taps occurs without breaking its current circuits, which eliminates the appearance of first-order discontinuities (surges) in the output voltage. The outputs of the multi-arm bridge are connected to the busbars from which the rectifier load is supplied. As an example, we will consider a new regulation method for the case when the TVMP contains a nine-section KO and the rectifier switch is made up of 9 pairs of fully controllable power switches. Schematic diagram of HC with TVMP is presented in figure 2.

To implement step-chord regulation according to the new algorithm for the operation of power keys (SCR), it is necessary to introduce a certain numbering procedure for SCR, which will formalize the description of the algorithm of the control device. Initially, one of the KO taps is taken as the base and is assigned the number “1”, and any branch can be taken as the base. The KO tap having a minimum negative phase shift relative to the “1” tap is given the number “2”. The KO branch having the minimum negative phase shift relative to the branch "2" receives the number "3", etc. Cathode SCR receive numbers in accordance with the expression (6)

where N _KK is the number of the current cathode key; N _KO is the number of the current tap of the circular winding, and the anode SCR receive numbers in accordance with the expression (7)

where N _KA is the number of the current anode key.

As a result, the SCR numbers of the cathode group take odd values (1, 3, 5, etc.), and the numbers of the power keys of the anode group take even values (2, 4, 6, etc.). A schematic diagram of the power part of the device with the proposed numbering of taps and power valves is shown in figure 2.

The voltage removed by the switch from a pair of KO taps and supplied to the HC busbars depends on the number of sections connected in series between the switched KO taps and is determined by the geometric sum of the EMF of the series-connected sections. So for HC with nine sections of KO (figure 2) you can get four levels of rectified voltage without gaps of the first kind (figure 3):

1) voltage U ₄ , determined by the geometric sum of the EMF of the four series-connected sections, when the switch connects to the busbars of the HC, taps 1 and 6 KO;

2) voltage U ₃ , determined by the geometrical sum of the EMF of three series-connected sections, when the switch connects taps 2 and 5 to the busbars U V;

3) voltage U ₂ , determined by the geometric sum of the EMF of two series-connected sections, when the switch connects taps 9 and 7 to the busbars U V;

4) the voltage U ₁ determined by the EMF section, when the switch connects to the busbars U In taps 3 and 4 KO.

The figure 4 presents a vector diagram, which is a set of all voltage vectors KO TVMP for all four levels of the output voltage of the Converter (figure 2), which allows you to create the proposed control algorithm PP, which consists in the fact that when working at any stage of regulation, the leads are connected in series to the load KO, divided by a constant for each step the number of sections KO. Each next pair of taps has a minimum negative phase shift in voltage relative to the previous pair of taps.

So for the converter (figure 2) according to figure 4 in the first stage, if we take for the reference point the moment of natural switching of the diametrical pair of power switches 1 and 2 (figure 2), according to the vector diagram (figure 4), at the first moment of time it should close SCR 5 and 16, while the 3rd KO tap is connected to the positive rectifier bus of the 5th SCR, and the 4th KO tap with the 16th key is connected to the negative rectifier bus.

After a time equal to π / N, from the moment the previous SCR pair is turned on, the next adjacent pair should be turned on, connected to the terminals of the SC having the minimum negative phase shift (SCR 17 and 6). At the same time, the previous SCR pair is switched off with a short time delay, which eliminates the breaks in the power circuits of the inductive coils that make up the KO sections, and thereby ensures high quality of the rectified voltage. Further, the switching process is repeated in a similar manner for subsequent pairs of power switches.

In the second stage, according to the vector diagram (figure 4), at the first moment of time, SCR 17 and 4 should be closed, while the 9th branch of the KO is connected to the positive rectifier bus with the 17th SCR, and the 7th branch of the KO with the 4th SCR connects to the negative bus of the rectifier.

After a time equal to π / N, from the moment the previous SCR pair is turned on, the next adjacent pair should turn on, connecting the KO terminals having the minimum negative phase shift (SCR 5 and 18). At the same time, the previous SCR pair is switched off with a short time delay, which eliminates the breaks in the power circuits of the inductive coils that make up the KO sections, and thereby ensures high quality of the rectified voltage. Further, the switching process is repeated in a similar manner for subsequent pairs of power switches.

In the third stage, according to the vector diagram (figure 4), at the first moment of time, SCR 3 and 18 should be closed, while the 2nd KO tap is connected to the positive rectifier bus with the 3rd SCR, and the 5th KO tap with the 4th SCR connects to the negative bus of the rectifier.

After a time equal to π / N, from the moment the previous SCR pair is turned on, the next adjacent pair should be connected, connected to the terminals of the QO having a minimum negative phase shift (SCR 1 and SCR 4). At the same time, the previous SCR pair is turned off with a short time delay, which eliminates the breaks in the power circuits of the inductive coils that make up the KO sections, thereby ensuring high quality of the rectified voltage. Further, the switching process is repeated in a similar manner for subsequent pairs of power switches.

At the fourth stage of regulation, at the first moment of time, keys 1 and 2 should be closed, while the 1st KO tap is connected to the positive rectifier bus with the 1st key, and the 6th KO tap with the 2nd key is connected to the negative rectifier bus.

After a time equal to π / N, from the moment the SCR pair 1 and 2 are turned on, the next adjacent pair (SCR 3 and SCR 4) should be connected, connected to the KO terminals with a minimum negative phase shift. At the same time, the previous SCR pair is turned off with a short time delay, which eliminates the breaks in the power circuits of the inductive coils that make up the KO sections, thereby ensuring high quality of the rectified voltage. Further, the switching process is repeated in a similar manner for subsequent pairs of power switches.

The procedure for enabling SCR for all stages of regulation is given in table 1.

Graphs of the values of the stages of the output voltage in fractions of the voltage section for the Converter (figure 2) are presented in figure 5.

The number of regulation steps N _{STUP of the} rectified voltage in the general case depends on n - the number of phases of the TVMP flux, and can be determined from expression (8.1) for even n and (8.2) for odd n.

So, for example, with n = 15, the number of steps for regulating the rectified voltage will be seven, for n = 19 the number of steps for regulating the rectified voltage will be nine, etc.

The advantage of this method of regulating the rectified voltage is that there are no first-order discontinuities in the rectified voltage curve, and also that here the ratio of the amplitude of the main ripple of the rectified voltage to the average value of the rectified voltage remains almost constant in value, which follows from the time diagrams (figure 5) and expressions for the ripple coefficient:

here the sequence number of the harmonic of the main ripple of the rectified voltage is numerically equal to the doubled number of phases (2n) of the TBMP.

Brief Description of the Drawings

The invention is illustrated by drawings in an amount of 5 (five) pieces. The figure 1 shows the geometric interpretation of circular windings with a different number of sections and voltage diagrams between nodes 1.2 KO with 3 sections (1.1), between nodes 1.3 KO with 4 sections (1.2), between nodes 1.3 CF with 5 sections (1.3) and voltage between nodes 1.3 CF with 6 sections (1.4). The figure 2 shows a schematic diagram of a device that implements a new method of step-chord regulation. The figure 3 shows the TVMP, where the KO diagram shows the maximum voltage values at the four stages of regulation in the form of vectors between the taps of the circular winding. The figure 4 presents a vector diagram, which is a set of all the voltage vectors removed from the taps KO for all four levels of the output voltage of the rectifier (figure 2), which allows you to create a new control algorithm. The figure 5 shows the curves of the rectified stresses for the four stages of regulation, obtained in accordance with the new method of step-chord regulation.

The implementation of the method

The proposed method of step-chord regulation is implemented by geometric summation of the voltages of individual sections of the secondary circular winding of a transformer with a rotating magnetic field using a semiconductor switch (PC), switching the taps of the secondary circular n-section winding of TVMP in accordance with the new algorithm. The outputs of the PC - the multi-arm rectifier bridge - are connected to the busbars from which the rectifier load is fed. At any regulation stage, rectifier busbars of the TVMP are connected to the rectifier busbars, separated by a constant number of sections for each stage, as a result of which the rectified voltage is determined by the geometric sum of the EMF of the group of sections located between the branches of the circular winding, which are connected to the plus and minus by the semiconductor switch busbar rectifier, and each subsequent pair of taps connected to the busbar rectifier has a minimum negative phase sd wig voltage relative to the previous pair of taps.

Claims (1)

The method of step-chord regulation of the output voltage of a controlled rectifier consists in the fact that at any stage of regulation on the busbars of the rectifier are connected the terminals of the circular winding of the TVMP, separated for each stage by a constant number of sections of the circular winding, characterized in that the value of the rectified voltage is determined by the geometric sum of the EMF of the group sections located between the taps of the circular winding, which are connected by a semiconductor switch to the positive and negative busbars straight of Tell, and each successive pair of taps connected to the assembly of the rectifier tire has a minimum negative voltage phase shift relative to the previous pair of taps.

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