The method of regulation of three-phase voltage

 

The invention relates to the field of electrical engineering and can be used for usadapter regulation or stabilization of the three-phase voltage. The technical result is to improve the quality of the output voltage and improve performance without additional losses. In the method of regulation of three-phase voltage injected four additional mode phase booster transformer, providing four additional levels of adjustable voltage located between the levels of the regulated voltage generated by the symmetric three-phase modes altadenablog current transformer and three-phase autotransformer. Switching different three-phase windings of the booster transformer is implemented with six times the mains frequency. 5 Il., table 2.

The invention relates to electrical engineering, in particular to the Converter equipment, and can be used for usadapter regulation or stabilization of the three-phase voltage with improved harmonic composition and performance.

There is a method of regulating a three-digit voltage (Transformer-key will perform noviny on the alternation of the symmetric modes of the three-phase booster transformer.

In this method, the mode of three-phase Takoradi" alternates in the first zone with the regime "three-phase bootstrap", and the second mode of "three-phase Valtournanche". Smooth control of three-phase voltage in both zones is due to a change in the relative duration of mode three-phase Takoradi" within the period of the high frequency switching of the secondary phase winding of the booster transformer enabling its primary winding in the load circuit.

The known method also provides for the division of each zone regulation of two sub-bands by introducing into the circuit switched secondary winding of the booster transformer an additional source of alternating voltage.

The disadvantages of this method of regulation of three-phase voltage should include limited opportunities for improving the harmonic content of the output voltage due to the complexity of the implementation of the separation of these zones regulation of sub-bands.

It also should include the contradictory requirements simultaneously improve performance and reduce switching losses due to the equality of the frequency modulation of the output voltage and switching keys.

For , snobunny on the alternation in each sub-band of the two modes of operation three-phase booster transformer for the formation of the corresponding two adjacent levels of the output voltage and the mutual change of the relative durations of these modes by switching the secondary phase windings of this transformer synchronously with the frequency of the network when you turn it phase primary windings between the network and the load.

Regulation involves three symmetric mode booster transformer with the corresponding levels of the output voltage UN. It is the modes of three-phase bootstrap", "three-phase Takoradi" and "three-phase Valtournanche", which correspond to the three levels of the output voltage: (1+CT)UWithUWith, (l-CT)UWithwhen supply of the secondary winding from the voltage UWithor levels Uc/(1-CT), UWithUWith/(1+CT) for supply of the secondary winding of the voltage load (CT ratio).

The disadvantages of the prototype method primarily include large distortion of the output voltage due to the large modulation depth (the difference between adjacent levels of the output voltage) for a given range regulated Luca the desire to improve performance and to improve the shape of the output voltage of the regulator by increasing the modulation frequency is constrained by the increase in switching losses.

The objective of the invention is to improve the quality of the output voltage and improve performance without additional losses.

The solution of the tasks achieved by improving the harmonic content of output voltage 2 times. This is due to the increase in the number of subranges regulation in 3 times in comparison with the method of the prototype and the increase in frequency modulation of the output three-phase voltage 6 times in relation to the switching frequency of the respective phase of the secondary winding of three-phase booster transformer.

Increasing the frequency modulation of the output voltage without increasing the switching frequency of the switches and, therefore, without additional switching losses can improve the performance regulation AC voltage three-phase network.

The technical result is achieved by the fact that introduced four additional mode phase booster transformer and relevant to them and their numbering four additional levels, which occupy an intermediate place between the levels of the regulated voltage generated by the symmetric modes of the three-phase current transformer and three-phase autotransformer, and Cosauti frequency network and represent the second mode switching phases single-phase Takoradi with two-phase valtozasaval" and the sixth mode switching phases single-phase Takoradi with two-phase voltotal", when accordingly when acquiescent and the opposite inclusion primary and secondary phase windings of three-phase booster transformer alternately each phase of the secondary winding two times short-circuited, while the other two are connected to DC voltage source and the respective phases of the AC voltage, and a third mode switching phases single-phase bootstrap with two-phase secretkey" and the fifth mode "of each phase switching phase Valtournanche with two-phase secretkey" when, respectively, when acquiescent and the opposite inclusion primary and secondary phase windings of three-phase booster transformer alternately each phase of the secondary winding two times connected to the constant voltage source or a corresponding phase source of alternating voltage, while the other two short-circuited, and the passage adjacent levels of the output voltage during soft sectiondating adjustment from the maximum to the minimum value occurs in the numbering of the above modes of operation three-phase booster transformer.

The essence of predlagaemy, illustrating the form of the output voltage in different sub-bands in accordance with the operations of the method the algorithm switching keys when the phase connection of the secondary winding of three-phase booster transformer to a source of alternating voltage, and Fig.3 and 4 are similar diagrams when connected to a DC voltage source.

The timing diagram (Fig.1-4) are presented for the case of output voltage regulation without the shift of the first harmonic relative to the mains voltage. In this embodiment, the method is intended for three phase voltage stabilizers.

The method also provides for the regulation of voltage-ahead or lagging the phase of the first harmonic. In these cases, while maintaining the same operations should shift algorithms switching keys respectively to the left or right relative to the mains voltage. This allows changes alternating modes of three-phase booster transformer to produce independent control of output voltage and input reactive power. In this embodiment, the method is intended for automatic compensation of deflection voltage and reactive power.

In Fig.5 presents CX is have two versions of the device, implementing the proposed method, which differ in the kind of current source feeding phase three-phase secondary winding of the booster transformer.

The device (Fig.5) contains the following elements: 1 - phase booster transformer, performed on the three magnetic core or in the form of a group of three single-phase transformers; 2 - network with clamps AC, BC and CC; 3 - connected in star without neutral wire load (winding AC motors, transformers, bridge converters) with clamps EN, VN and SN; 4 - switch containing four three-phase groups are completely managed by the nag two-way conductivity (Al, B1, C1), (A2, B2, C2), (A3, B3, C3) and (A4, B4, C4); 5 - DC voltage Ud; 6 - source AC voltage to terminals a, b, C, 0; 7 - phase jumper.

In the diagram (Fig.5) connect the phase of the secondary winding of the booster transformer 1 to the DC voltage source 5 shown in solid lines (source of alternating voltage 6 is off, the interfacial jumper 7 is closed) and to the source of alternating voltage 6 - dashed lines (the constant voltage source 5 is disabled, the interfacial jumper 7 open).

If connected the e key with double-sided conductivity can be used counter-parallel to the GTO and diode, and when connected to a source of alternating voltage 6 key represents, for example, two counter-parallel to a locked gate.

In table.1 shows the name and number of modes of operation of three-phase booster transformer, in which are formed the seven respective levels of the output voltage, and table.2 presents the number six subranges regulation of three-phase voltage when the rotation of the operating modes phase booster transformer in the specified variation limits fragile control.

In accordance with the table.1, 2 and Fig.1-4 operation method for controlling a three-phase voltage is as follows.

In the subrange regulation I alternated mode 1 (all phase secondary winding of the booster transformer is connected to a source of DC or AC voltage and turned on in accordance with the primary) mode 2 (two alternating phase secondary winding connected to a source of DC or AC voltage and turned on in accordance with the primary, while the third phase secondary winding short-circuited).

The alternation of these modes in each half-period output the secondary winding of the booster transformer quasisymmetric modulated volodarivka with frequency, six times the switching frequency of the switches.

The formation quasisymmetric modulated voltage in the other sub-bands is similar, with the only difference that they alternate in the following order of numbering of the modes (see table.2) and the output voltage adjustment is made between the following adjacent levels.

With the alternation of modes there is a change of names and the number of phase of the secondary winding of the booster transformer connected to the DC voltage source or to the respective phases of the AC source voltage.

Smooth control of three-phase voltage in all sub-bands is done by increasing the relative duration of one of these modes and a corresponding decrease in the relative duration of another mode. This is accomplished by changing the angle.

Analytical expressions of the dependency of the degree of regulationn=UN/IP of the current value of the output voltage and its first harmonicH1=UH1/Uc from the corner of regulationat each 30-degree interval (in each padeap the Directive.

a)=0-30and=180-150

b)=30-60and=150-120

in)=60-90and=120-90

g)=0-180

Option 2. The applied DC voltage source.

a)=0-30and=180-150

b)=30-60and=150-120

in)=60-90and=120-90

g)=0-180

In the above expressions, KT2=2KT1the coefficients of transformation of three-phase booster transformat the inclusion of its primary and secondary phase windings.

Claims

The method of regulation of three phase voltage, based on the alternation in each sub-band of the two modes of operation three-phase booster transformer for the formation of the corresponding two adjacent levels of the output voltage, and mutual change the duration of these modes within each half period of the mains voltage during the transition from one adjacent level to another by switching synchronously with a network of secondary phase windings of this transformer with phase included the primary windings between the network and connected in star without neutral wire load, the regulation involves three symmetric mode phase booster transformer and relevant to them and their numbering three levels, among them the fourth mode three-phase Takoradi”, similar to the operating mode of the three-phase current transformer, when all phase secondary winding short-circuited, and the first mode three-phase bootstrap” and the seventh mode three-phase Valtournanche”, respectively such operating modes raising and lowering of the three-phase autotransformer in which the phase of the secondary winding is enabled the voltage or to the respective phases of the AC voltage, moreover, in the case of the phase connection of the secondary winding of the booster transformer to a source of alternating voltage each key two-way conductivity is, for example, two opposite parallel included lockable thyristor, and when connected to a DC voltage source - counter-parallel to the GTO and diode, characterized in that it introduces four additional mode phase booster transformer and relevant to them and their numbering four additional levels, which, occupying an intermediate position between the levels of the regulated output voltage generated by the symmetric modes of the three-phase current transformer and three-phase autotransformer, formed by switching the phase of the secondary winding of three-phase booster transformer with six times the frequency of the network and represent the second mode switching phases single-phase Takoradi with two-phase valtozasaval” and the sixth mode switching phases single-phase Takoradi with two-phase voltotal” when accordingly when acquiescent and the opposite inclusion primary and secondary phase windings of three-phase is ocena, while the other two phases are connected to the DC voltage source and the respective phases of the AC voltage, and a third mode switching phases single-phase bootstrap with two-phase secretkey” and the fifth mode “of each phase switching phase waytoomany with two-phase secretkey” when accordingly when acquiescent and the opposite inclusion primary and secondary phase windings of three-phase booster transformer alternately each phase of the secondary winding two times connected to the constant voltage source or a corresponding phase source of alternating voltage, while the other two short-circuited, moreover, in each half-cycle of the output voltage alternation of the above modes occurs three times, forming as a result of this unbalanced enable phase of the secondary winding of the booster transformer quasisymmetric modulated volodarivka with a frequency of six times the switching frequency of the switches and, in addition, the passage of the levels of the output voltage during soft sectiondating adjustment from the maximum to the minimum value produced

 

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