WO2006105693A1

WO2006105693A1 - Converter transformers with self-coupling compensation and harmonic shielding

Info

Publication number: WO2006105693A1
Application number: PCT/CN2005/000542
Authority: WO
Inventors: Fusheng Liu
Original assignee: Fusheng Liu
Priority date: 2005-04-05
Filing date: 2005-04-20
Publication date: 2006-10-12
Also published as: CN1665112A

Abstract

A converter transformer with self-coupling compensation and harmonic shielding is disclosed. A self-coupling tap is led out from the secondary winding in the supply transformer, this tap dividing the secondary winding into two stages: the analogous auto-transformer common winding and series winding. Both of them are coupled closely, the secondary windings of the two stages and the primary winding are arranged with one center on the iron core cylinder, wherein the common winding is arranged between the primary winding and the series winding, its equivalence impedance value being zero. The both ends of the common winding connect to the bypass of external filter capacitor inductance. The invention can take reactive compensation nearby for inductive current at user's power frequency, can utilize the induced current Ampere-turn balancing action of two windings divided by the tap at relevant harmonic frequency to neutralize the harmonic magnetic linkage, thereby leading the harmonic current to return to load nearby through the series winding and preventing the harmonic current from crossing the air gap into the primary power network, accordingly effecting a radical cure to the harmonic from the stump. It also prevents the harmonic current and the harmonic magnetic flux from damaging to the transformer when taking the harmonic shielding and isolating to the primary power network.

Description

Auto-coupling compensation and harmonic shielding converter transformer

Technical field

The present invention relates to the field of power transmission and power supply technologies, and more particularly to rectification, commutation and traction and electric arc furnace transformers and their compensation and filtering equipment.

Background technique

The number of non-linear electrical equipment used in modern urban power grids is increasing, including lighting in buildings and streets. Whether fluorescent or neon, most of them are formed by gas discharge in the tube, and the current between the poles is nonlinear. There are also many household appliances, including washing machines, refrigerators and air conditioners. Widely used in variable frequency speed regulation, as well as electric welding, which is widely used in construction and machining, forms a harmonic source that cannot be ignored, and a large amount of harmonic current. Injection into the power grid, causing distortion of the voltage waveform of the power grid, causing interference to adjacent communication signals, protection control and scientific research, and increasing the additional loss and heat of related electrical equipment, causing corresponding vibration and noise. Although the single-unit capacity of household electrical appliances is not large, it has entered thousands of households, and the number and distribution are wide, making it difficult to limit and suppress its harmonic interference. The power transformers used by these users are ordinary transformers, and the harmonics are unobstructed. With the economic development, the proportion and impact of such loads in the power grid is increasing. What methods are used to control and apply what kind of transformer power supply is worthy of attention.

The wide application of power electronics has promoted the production development of factory enterprises. The prominent problems in the power supply industry are high-power rectification, commutation and electric arc furnace loads, the latter including AC or DC steelmaking, no matter which steelmaking, The current is the same as the rectification power supply, and it is also the gap conduction and breaking, forcing the current waveform of the power supply network to be distorted. In addition to the power frequency fundamental wave, there are various high-order harmonic content, and the harmonic current is injected from the output side of the transformer. The harmonic current source is formed, and the winding of the power supply transformer flows to the side of the original power grid, which brings various adverse effects to the loop and adjacent equipment. The traditional method of harmonic control is passive filtering. The parallel branch of the CL component is commonly used as a tuner to shunt the injected nth harmonic current, such as the equivalent impedance of the filter branch Z^nX^ Xc/nO, that is, X^Xc/n ² , at the harmonic frequency, the inductive reactance is canceled by the capacitive reactance of the series, and the zero impedance of the parallel branch attracts the harmonic current to the shunt. Off, the filtering effect is best. However, in order to avoid resonance overvoltage and harmonic amplification, the actual selection of XL=K _s Xc/n ² , K _S is a safety factor greater than 1, the actual requirement of the coefficient should not be too small, thus significantly reducing the filtering effect. The active filter is a commutating device composed of power electronic components. The DC or stored inertial energy is provided with the load current waveform of the tracking detection and accompanied by the automatic control mode. The real-time inverter is equivalent to the distortion waveform but Compensation current in the opposite direction. This technology has long been used in industrialized countries, but its technology is more complicated, with more supporting equipment and high cost. It has not been widely used. The filter used by the enterprise department for the harmonic source can only filter up to about 50% of the harmonics, which should be actively explored and improved. Recently, China's Three Gorges construction, west power transmission to the east, the use of high-voltage direct current (HVDC) transmission for long-distance transmission and regional mainline, found that converter transformers imported from abroad, are placed between the converter and the filter, In this way, the harmonic current caused by the inverter and the reactive current required to supply the converter must pass through the winding of the converter transformer, not only occupying the considerable capacity of the winding, but also the original pair of the transformer. The square winding and its core cause additional loss and heat generation, increase vibration and noise, and increase the insulation difficulty of the winding, which is obviously unreasonable. Considering China's vast territory, long-distance transmission and large-area networking, after the cross-century HVDC should be more developed, we should actively explore the localization of converter transformers, improve filtering measures, and get rid of dependence on foreign technology.

Summary of the invention

The technical problem to be solved by the present invention is to provide a novel filtering technology which can avoid the resonance overvoltage and harmonic amplification of the passive filter and achieve the similar effect of the active filter, without special compensation harmonic generation. The source, but the balance of the amperage of the coupling winding of the power supply transformer, through the auto-coupling induction relationship formed by the harmonics, constitutes a number of new technology integration products, in order to exploit the potential of the transformer, to achieve auto-coupling compensation and harmonics The combined effect of wave shielding.

The technical solution adopted by the invention is to introduce an auto-coupling tap in the middle of the secondary winding of the power transformer winding, and the tap divides the secondary winding into two common windings and series windings similar to the autotransformer, and the two are closely coupled, the two The segment winding and its original phase winding form a concentric arrangement of three windings on the core cylinder, and the windings arranged in the intermediate layer

'The two ends are connected in parallel with the capacitive reactance x _c and the inductive branch of the string, and the fundamental impedance X _{L is} much smaller than x _c , the middle layer winding is the shield winding, and its equivalent impedance is zero, the two ends of the secondary winding Connected to the power supply load.

The principle of the present invention: Let the number of harmonics filtered out be n, at the corresponding 11 times frequency, 'nX _L -X _c /n-0, the zero impedance branch attracts the nth harmonic current to the series winding, The series windings must pass through the common winding, ie the shield winding, due to the harmonic flux generated by the harmonics. The latter then induces the reverse current and takes the capacitive branch as the loop. The internal winding of the loop and the external branch The impedance is zero, the current is not depressurized, and thus does not need to be maintained by the corresponding potential. The opposite magnetic potentials of the two windings force the harmonic flux to cancel completely, so there is no in-phase original of the outer layer of the remaining harmonic flux. The winding realizes the decoupling of the harmonic shielding of the original winding, that is, the magnetic coupling, so that the harmonic current cannot cross the air gap to the original power grid.

The present invention has significant advantages over the prior art:

1. The invention is to grasp the harmonic source for treatment. At the valve side and the harmonic current inlet near the rectifier transformer, the capacitive CL branch connected by the secondary self-coupled tap I is low in harmonic frequency. The impedance action, the harmonic current is returned to the load near the series winding, and the harmonic flux generated by the series winding through the harmonic current is cancelled by the reverse magnetic flux induced by the shield winding, preventing the harmonic current from being transmitted to the original winding. . This is equivalent to setting up at the harmonic injection A barrier that intercepts harmonics from the source, but the fundamental current can pass as usual.

2. The present invention develops the potential of a transformer and utilizes the filtering effect of the transformer ampere balance. Although the CL component of the auto-coupled tap is similar to the passively filtered branch, the current and voltage of the circuit are constrained by the electromagnetic relationship of the coupled windings at both ends of the tap. There is no concern about resonant overvoltage and harmonic amplification, so it is optional. XfXc/n ² (equivalent to Ks=D without having to avoid the resonance point, to obtain the filtering effect that the passive filtering can not achieve. The invention also utilizes the condition that the equivalent impedance of the shield winding is zero, when the induced current passes through the loop No voltage drop, no need to maintain the potential generated by the harmonic flux, so that the harmonic flux generated by the series winding is completely offset by the reverse flux induced by the shield winding, which is similar to the harmonic compensation used by active filtering. It is realized by the auto-coupling induction of the coupled winding, which does not need the harmonic generation source and control system provided by the active filter, and achieves the same effect, and the technical difficulty and the cost are much lower.

3. The invention not only controls the harmonics of the power grid, but also stops the transmission of harmonics in the transformer windings, so that the damage of the harmonic waves to the transformer is effectively controlled, thereby improving the overall efficiency of the rectification and commutation transformation. Under normal power frequency voltage, the capacitive reactance of the compensation branch is much more sensitive to X C and compensates for the load reactive power. Arranging the reactive power compensation on the low voltage side of the extraction tap, which not only reduces the voltage level of the compensation device and its switching device, but also reduces the current value through the transformer winding, and avoids the network side access compensation to prevent the capacitive circuit and the power grid. Inductive reactance may cause resonance problems. For example, when the secondary winding of the rectifier transformer has no intermediate tap lead reactive compensation and filtering equipment, passive or active filters should be installed on the original square side high voltage bus, regardless of the filtering effect. The reactive and harmonic components caused by the load current must enter the high voltage bus through the transformer, and additional loss heat and noise vibration are added to the winding and the core, resulting in an increase in materials and costs. The present invention excludes these. Harmful effects of undesirable ingredients. This is good for the safety of the grid and the safety of the compensation equipment.

4. In the multi-phase rectifier, the present invention compensates for the inadequacy of simply increasing the pulse number P. Increasing the pulse number P of the rectifier is one of the important methods to weaken the harmonics. As the P value increases, the harmonic order of the characteristic harmonics increases, and the relative value of the harmonic current content is inversely proportional to this. Small, in order to increase the number of inverters and the complexity of their control, it is necessary to adjust the wiring combination of the secondary side of the transformer and the displacement angle between its adjacent phases, which not only increases the material consumption and cost, but also is difficult. To achieve the full elimination of harmonic current effects, especially the existence of non-characteristic harmonics, can not be managed by increasing the P value. In comparison, the present invention has no such disadvantages, which not only improves the filtering effect, but also brings economical savings and is technically superior.

DRAWINGS

1 is a schematic wiring diagram of a single-phase converter transformer of the present invention;

2 is a schematic view showing the arrangement of a single-phase converter transformer winding according to the present invention; 3 is an equivalent circuit diagram of a single-phase converter transformer of the present invention;

Figure 4 is a schematic diagram of the principle of the three-phase converter transformer of the present invention;

Figure 5 is a schematic wiring diagram of a three-phase six-pulse rectifier transformer of the present invention;

Figure 6 is a voltage phasor diagram of the extension winding of the converter transformer of the present invention;

Figure 7 is a schematic wiring diagram of a six-phase twelve-pulse converter transformer of the present invention.

detailed description

The specific structure of the present invention will be further described below in conjunction with the embodiments of the present invention.

Example 1

As shown in FIG. 1-3, this embodiment is a single-phase auto-coupling compensation and harmonic shielding converter transformer, including a primary winding 1, a secondary winding, and a cylindrical core 4, and an auxiliary tap is taken in the middle of the secondary winding to connect the secondary winding. Divided into a common winding 2 and a series winding 3, the three windings are arranged together on a circular core column 4, the series winding 3 is arranged in an inner layer close to the cylindrical core 4, the primary winding 1 is arranged in the outermost layer, and the common winding 2 is arranged in series Between the winding 3 and the primary winding 1, the two ends of the common winding 2 are connected to the branch of the capacitive reactance X _C series inductance XL, and both ends of the primary winding 1 are connected to the grid power supply, and the power supply load 5 and the two pairs in series The winding common winding 2 and the series winding 3 are connected in parallel.

This embodiment can be used for single-phase rectification load or electric arc furnace load supply, or for single-phase traction transformer of electrified railway or two single-phase transformers combined with V-shaped traction transformer. The output side of the latter is not directly Connected to the inverter, but the load characteristics of the power supply are similar, and the tapping of the secondary winding can be used to improve the reactive power compensation and filtering. The short-circuit impedance measured by the short-circuit between the two windings is converted into the equivalent impedance z ₁₂ , z ₁₃ , Z _{23 of the} same voltage level, and the equivalent impedances in FIG. 3 can be obtained by the following formula -

Z corpse. . 5(Z, ₂ + Z, 3-Z ₂ 3)

Z ₂ =0. 5(Z, 2+Z ₂₃ -Z ₁₃ )

Z ₃ =0. 5(Z,3+Z ₂₃ -Z ₁₂ )

The short-circuit impedance between the two windings is proportional to the distance between the two lines, and z ₁₂ , Z, 3 and z ₂₃ are proportional to the amplitude distances between the subscript windings & ₁₂ , a ₂₃ and a ₁₃ , respectively. It can be seen that a ₁₂ + a ₂₃ = a ₁₃ , then the intermediate winding Z ₂ =0. 5 (Z ₁₂ +Z ₂₃ -Z ₁₃ ), which should be proportional to a ₁₂ + a ₂₃ -a ₁₃ according to the corresponding distance relationship Therefore, it is not difficult to know that Z ₂ =0, so the equivalent impedance of the intermediate windings of the three windings concentrically arranged must be zero. The intermediate layer winding between the outer layer and the inner layer is the shield winding.

In Figure 3, Z _s represents the equivalent impedance of the system. The branch Z!+Z _s is connected in parallel with 3⁄4. Because Z ₂ =0, it is impossible for the original winding and the system grid to shunt the harmonic current, which further shows The importance of Z ₂ =0. The n value of the shielded harmonic is taken as 3 or 5.

Example 2: As shown in FIG. 4, this embodiment is a Ξ phase auto-coupling compensation and a harmonic shielding converter transformer. The original side can adopt a star or delta connection (not shown), and the secondary winding is separated by a center tap. The star-shaped wiring consisting of two windings connected in series, the three-phase output terminals u, v, w and the neutral point n, the bow I is connected to its power supply load 5, the middle tap &, b, c leads and the external capacitive CL branch 7 is connected, the winding between the three taps and n is a shield winding, the latter being concentrically arranged with the series winding 3 and the primary winding 1 in the core 4, wherein the common winding 2 is arranged in the middle layer of the concentric winding, and its equivalent impedance is Zero, can shield the harmonics. The power supply load 5 can be a three-phase load or a single-phase load. The core can be used in a three-column structure. If the capacity is large, the three-phase load is unbalanced, or the five-column core can be used to provide a path for the zero-sequence flux. The modern urban power grid is seriously polluted by harmonics. The three-phase voltage of the power grid is asymmetrical, and the voltage waveform is not sinusoidal. Therefore, when the enterprise manufacturers do product testing and scientific experiments, they cannot use the regional power grid as the power source. Otherwise, the results are difficult to be accurate, so they have to be in the dead of night. Carrying out or starting a dedicated generator for power supply indicates that harmonic control of the city network should not be negligent. The urban network is subject to harmonic pollution, which is largely related to the non-linear load of many household appliances. Considering the decentralization of household appliances, it is impossible to separately filter at each access point. For areas with concentrated nonlinear loads, such as large shopping malls, high-rise users and construction sites, it is recommended to use transformers with harmonic shielding to supply power. This can block the turbulence of harmonic currents in order to improve the power quality of the grid.

Example 3:

This embodiment is a three-phase rectification power supply transformer with auto-coupling compensation and harmonic shielding. The original winding can be a star or a triangle (not shown), and the auxiliary winding has an extended-edge triangle with an intermediate lead-out tap, as shown in FIG. It is shown that the end points _U , V, w of the Yanbian are respectively connected with the three-phase rectifier bridge 6 on the valve side, constitute a rectified output of six pulses and are connected with the power supply load 5; the three-phase terminals of the triangles ∑ 1, b, c are respectively compensated The capacitive LC elements are connected. The triangular phase winding is equivalent to the common winding 2 of the autotransformer, which plays a shielding role in the filtering. The extended side winding is equivalent to the series winding 3 of the autotransformer; the same side of the extended side winding, the angular winding and the original winding 1 are in the cylindrical core 4 on the concentric arrangement. The magnetic flux is generated by the harmonic current, which is similar to the single-phase and three-phase output converter transformer described above, and is offset by the reverse magnetic flux induced by the in-phase shield winding. Figure 6 shows the phasor relationship between the phase voltage U _e of the edging winding and the phase winding voltage U _d of the in-phase winding, the phase voltage U _{e of the} adjacent-phase winding and the output phase-to-phase voltage U ₂ , where 0 is the phase shift generated by the edging winding Angle, derived from the geometric relationship of phasors -

Ue/Sin Θ = (U _e +U _c |) /Sin (60° - θ ) =U ₂ /Sinl20°

U _e / U ₂ = 2 Sin 0 /V3"

The above equation represents the corresponding relationship between the phase voltage U _{e of the} extension winding and the combined voltage U ₂ and displacement angle 延 of the output of the extension, which can be used to coordinate the phase with the associated wiring. If the number of winding turns of the extended winding and the delta connection is equal, when harmonic current passes, the harmonic currents of the two windings U _e and U _d are equal and opposite directions, forcing the harmonic magnetic flux to cancel. There are three An angular closed loop provides access to the third harmonic of the excitation. The n value of the shielded harmonic can be chosen to be 5 or 7. This illustration can be used to power the rectification load of the enterprise department.

Example 4:

In this embodiment, an auto-coupling compensation and a harmonic shielded commutation transformer of 6-phase 12-pulse waves are composed of two sides of the adjoining triangle. As shown in Fig. 7, the two sets of three-phase outputs of the secondary winding are respectively connected to the respective three-phase rectifying devices 6, and the inverters composed of two rectifying devices 6 are composed of 12 thyristors, forming 12 veins. The wave phase, the phase difference between the phases is 30°, and the auto-coupling taps of the auto-coupling compensation and the shield filtering extracted from the two-sided triangular windings are connected to the additional compensation and filtering device 7, that is, the capacitive branch CL.

Determination of 12-pulse phase angle displacement :: The phase-to-phase potential difference of 12-pulse phase is 360° / 12=30°; for this reason, one of the extended-edge triangles of the secondary winding should be moved forward by 15 ° and the other by 15 °. According to the above relationship, taking Θ =15 °, then U _e / U ₂ =Sinl5 ° / Sinl20° =0.2988, U _d / U ₂ =0.5177, (U _e + U _d ) / U ₂ = Sin (60 ° -15 ° ) I Sinl20 ° =0.8165 , so the ratio of the turns of the extended side winding to the triangular winding is U _e / U _d =0.2988/0. 5177=0.5773, the phase shift θ =15 ° is inevitable. However, it is necessary to pay attention to the difference between the angle advance and the backward shift, so that the phase difference between the two is 30°, in order to obtain the same sequence of the 12-phase pulsation of the conventional DC transmission converter transformer with star and delta connections. Converter effect. The intermediate taps from the secondary windings are connected to the additional compensation equipment to facilitate the removal of additional losses caused by components such as reactive and harmonic components in the load current through the transformer and the grid system. The maximum characteristic harmonic order of the 12-pulse phase is calculated as P ± l, so the η value can be taken as 11 or 13.

The DC output of the 12-pulse phase can be used as the power supply for urban traffic light rail locomotives. Generally, the DC output voltage is not high and the current is large. The series connection of the rectifier device 6 in Fig. 7 can be changed to parallel. The original urban rail transit is usually powered by a 24-pulse rectifier transformer, and the latter is formed by combining a plurality of phase shifts of the original secondary windings of the two transformers, not only the converter, but also the thyristor is multiplied, and The number of transformers is also doubled, and the floor space needs to be increased. Compared with the new type of rectifier transformer composed of 12 pulses, it is economically obvious and economical, and harmonic shielding windings are added to suppress the technical performance of harmonics. On the top, it will not be worse than the old product that doubles the pulse wave. As for the DC voltage on the output side, the average value of the DC no-load voltage in U _d , U is the effective value of the AC no-load voltage. When P is changed from 12 to 24, the ratio of U _d /U changes from 1.4 to 1.41. The comparison of gains and losses is not economical, which promotes the innovation and technological progress of the corresponding products.

The 12-pulse phase is used for commutation of DC transmission (including rectification at the head end and inverter at the end). The transformer has a high long-distance transmission voltage, and the two inverters should be colluded according to Figure 7. If the transmission capacity of HVDC is large, it is difficult to make a three-phase transformer structure and it is not convenient to transport. Three single-phase transformer products can be combined into a three-phase transformer group. The secondary windings of two sets of three-phase transformers should also be pressed. Figure 7 shows a phase difference of 30° between adjacent phases, and the number of winding turns at both ends of the tap should also maintain a relationship of U _e /U _d =0.5773. In this way, the HVDC commutation according to the embodiment is changed. Pressure device, although the transformer product structure is different from the traditional converter transformer, but the 12 pulse waves completed are the same. The difference is that the filter connected to the high-voltage busbar on the grid side is moved to the secondary tap-out tap near the valve side. The capacitive sensing device of the branch is only close to the inverter and is directly connected to the inverter. The high-power extended-side winding of the transformer secondary is isolated, and the current and voltage of the tap-out branch are subject to the electromagnetic relationship of the extended-side winding and the delta-connected winding. There is no need to worry about the adverse effect of the external capacitive component on the inverter. This eliminates all the shortcomings of the conventional wiring described above and allows the reactive and harmonic currents entering the transformer winding to be immediately compensated and removed. In comparison, this not only achieves significant economic benefits, but also reduces the reactive and harmonic content through the transformer windings, reduces the voltage drop across the line, and helps to reduce the commutation overlap angle during commutation, improving the technical performance of commutation. There are also benefits.

Claims

Rights request

1. A converter transformer with auto-coupling compensation and harmonic shading, comprising a primary winding (1), a secondary winding, and a core (4), characterized in that: an auto-coupling tap is drawn in the middle of the secondary winding of the winding of the power supply transformer, The tap divides the secondary winding into two common windings (2) and series windings (3) similar to the autotransformer, the common winding (2) and the series winding (3) are tightly coupled, and the primary winding (1) in phase with it A concentric arrangement of three windings is formed on the cylindrical core (4), and the two ends of the common winding (2) arranged in the intermediate layer are connected in parallel with the branch (7) having the capacitive reactance X _c string with the inductive reactance X _L , and under the fundamental wave The impedance X _{c is} much larger than Χι^, the common winding (2) is the shield winding, its equivalent impedance is zero, the two ends of the original winding (1) are connected to the grid power supply, the power supply load (5) is connected to the common winding (2) and The windings (3) are connected in parallel.

2. The converter transformer of harmonic coupling and harmonic shielding according to claim 1, characterized in that: the series winding (3) is arranged in an inner layer close to the cylindrical core (4), and the original winding (1) is arranged at the most The outer layer, the common winding (2) is arranged between the series winding (3) and the primary winding (1).

3. The converter transformer for harmonic compensation and harmonic shielding according to claim 1, wherein: the primary winding (1) is a star or a triangle, and the secondary winding is connected in series by two windings separated by a center tap. The star connection is formed, the three-phase output terminals u, v, w are connected to the neutral point n and connected to the power supply load (5), and the intermediate taps &, b, c are connected to the external capacitive CL branch (7). The winding between the three-tap and the neutral point n is a shield winding, and the latter is tightly coupled with the series winding (3) to balance the harmonic current passing through, preventing the harmonics from flowing through the air gap to the original In the square power grid, the three-phase windings are arranged concentrically in the three-phase iron core, and the power supply load (5) may be a three-phase or single-phase non-linear load relative to the midpoint n. If the capacity is large and the three-phase load is unbalanced, The phase core can also be replaced with a five-column structure to provide access to the zero-sequence flux.

4. The converter transformer of the auto-coupling compensation and the harmonic shielding according to claim 1, wherein: the original winding (1) is a star or a triangle, and the auxiliary winding is an extended-edge triangle having an intermediate lead-out tap, and the extension three The phase terminals u, _v , and w are respectively connected to the three-phase rectifier device (6) on the valve side to form a rectified output of six pulses and connected to the power supply load (5); the three-phase terminals a, b, and 0 of the extended triangle are respectively It is connected with the external compensation capacitive CL branch (7); its triangular phase winding is equivalent to the common winding of the autotransformer (2), which shields the corresponding harmonics. The extended winding is equivalent to the series connection of the autotransformer. Winding (3); the same-side extension winding, the angular winding and the primary winding (1) are concentrically arranged on the cylindrical core (4). .

5. The auto-coupling compensation and harmonic shield converter transformer according to claim 4, wherein: the phase voltage of the extension winding, the phase voltage U _{2 of the} output of the extension winding, and the phase voltage of the triangular winding are U _d , The relationship is:

Ue/Sin Θ = (U _e +U _d ) /Sin (60° - θ ) = U _a /Sinl20° , ie U. / U ₂ = 2 Sin Θ / 7 , " θ " is the phase shift angle produced by the edging winding. ,

6. The converter transformer of the auto-coupling compensation and the harmonic shielding according to claim 4, wherein: the secondary side is two extended-edge triangles, respectively connected to the respective three-phase rectifying devices (6), and two rectifying devices (6) Inverter consisting of 12 sets of crystal tubes, which constitutes 12 pulse wave phases, the phase difference between them is 30°, and the angular vertices in the two delta delta connections respectively lead to auto-coupling of auto-coupling compensation and harmonic shielding. The tap is connected to the additional compensation and filtering capacitive CL branch (7).

7. The converter transformer of the auto-coupling compensation and the harmonic shielding according to claim 4 or 5 or 6, wherein: the edge of one of the secondary windings is shifted by 15°, and the other is shifted by 15°; The ratio of the phase voltage of the extension winding with a displacement of 15° to the three-phase output voltage is i U ₂ =0.2988, U _d / U ₂ = 0.57177 , (U _e + U _d ) / U ₂ = 0. 8165 .