Rectifier transformer with axial split filter winding

Abstract

The invention discloses a rectifier transformer with an axial split filter winding, and relates to rectifier transformers. A traditional rectifier transformer is difficult to meet the requirements of efficient filtering and reliable operation. A rectifier transformer with an axial split filter winding comprises a low-voltage winding, a filter winding and a high-voltage winding, the low-voltage winding, the filter winding and the high-voltage winding are sequentially arranged from inside to outside, and a first grounding electrostatic screen is arranged between the low-voltage winding and the filter winding; a second grounding electrostatic screen is arranged between the filtering winding and the high-voltage winding; the low-voltage winding comprises a first low-voltage winding and a second low-voltage winding which are axially split; the filter winding comprises a first filter winding and a second filter winding which are split axially; and the high-voltage winding comprises a first high-voltage winding and a second high-voltage winding which are axially split. According to the technical scheme, power loss and electromagnetic interference in the winding are effectively reduced, temperature rise and power consumption of equipment are reduced, the overall economical efficiency of the transformer is improved, and the service life of the equipment is prolonged.

Description

Technical Field

[0001] The invention relates to a rectifier transformer, in particular to a rectifier transformer with an axially split filter winding. Background Art

[0002] Rectifier transformers are important equipment used to convert AC into DC in power systems and are widely used in power grids, electrified railways, DC transmission, and renewable energy generation. In the rectification process, a large number of harmonics are usually generated. Harmonic currents not only affect the stability and power quality of the power system, but also have adverse effects on the rectifier equipment and other electrical equipment.

[0003] In the prior art, rectifier transformers usually use the following methods to reduce the impact of harmonics: first, by increasing the number of rectifier pulses, such as using 12 or more pulses for rectification, to reduce the amplitude of harmonics; second, by setting a capacitor screen between the grid-side winding and the valve-side winding to shield some high-order harmonics. However, these traditional technical means have limited effects in harmonic suppression, especially when facing high-order harmonics, it is difficult to completely eliminate the impact on the power grid and equipment.

[0004] In addition, during the actual operation of the rectifier transformer, the current distribution between the windings is uneven, especially when a fault or special operating conditions occur, which can easily lead to increased stray losses, reduce the operating efficiency of the equipment, and increase the thermal and mechanical stress of the equipment, affecting its short-circuit tolerance and long-term operating reliability.

[0005] With the development of renewable energy power generation (such as wind power, photovoltaic power generation, etc.), the power quality problem on the power generation side has become more prominent. Due to the instability of renewable energy power generation, the harmonic problem in the system is more serious, and traditional rectifier transformers are difficult to meet the requirements of efficient filtering and reliable operation. Therefore, the power system urgently needs a new type of rectifier transformer that can effectively filter out harmonics, improve current distribution, reduce stray losses, and improve the short-circuit resistance of the equipment. Summary of the invention

[0006] The technical problem to be solved and the technical task proposed by the present invention are to improve and perfect the existing technical solutions and provide a rectifier transformer with axially split filter windings to effectively filter out harmonics, improve current distribution, and reduce stray losses. To this end, the present invention adopts the following technical solutions.

[0007] A rectifier transformer with an axially split filter winding comprises a low voltage winding, a filter winding and a high voltage winding, wherein the low voltage winding, the filter winding and the high voltage winding are arranged in sequence from the inside to the outside, and is characterized in that: a first grounded electrostatic screen is arranged between the low voltage winding and the filter winding; a second grounded electrostatic screen is arranged between the filter winding and the high voltage winding; the low voltage winding comprises an axially split first low voltage winding and a second low voltage winding; the filter winding comprises an axially split first filter winding and a second filter winding; the high voltage winding comprises an axially split first high voltage winding and a second high voltage winding.

[0008] This technical solution uses axially split filter windings to provide a low-impedance channel for high-order harmonic currents, effectively suppressing the transmission of high-order harmonics between the primary winding (high-voltage side) and the secondary winding (low-voltage side). The introduction of a grounded electrostatic screen further blocks the interference of high-frequency harmonic currents, significantly improving the power quality of the rectifier system.

[0009] The axially split winding design makes the current distribution between the windings more reasonable, especially under special operating conditions (such as half-through operation or fault conditions), which can effectively balance the current distribution in the windings and reduce the stray losses of the windings, thereby improving the efficiency of the rectifier transformer.

[0010] The axial split structure helps to reduce the axial electromotive force of the winding under short-circuit condition by improving the current distribution inside the winding, thereby improving the short-circuit resistance of the rectifier transformer, enhancing the operating safety of the equipment, and reducing the damage caused by short-circuit faults.

[0011] The electrostatic screen not only effectively suppresses the interference of leakage magnetic field to the system, but also reduces the electromagnetic interference (EMI) in the system, improves the stability and electromagnetic compatibility (EMC) of the transformer, and provides guarantee for the stable operation of the power grid.

[0012] The combination of axial split design and electrostatic screen in this solution effectively reduces power loss and electromagnetic interference in the winding, reduces the temperature rise and power consumption of the equipment, improves the overall economy of the transformer, and extends the service life of the equipment.

[0013] As a preferred technical means: the first low-voltage winding is connected in a three-phase triangle and has a full-wave rectified 6-pulse output. The three-phase triangle connection can ensure the current balance of the three phases, effectively reducing the asymmetry and harmonic components of the current. It reduces the voltage fluctuation and current harmonics in the system and improves the quality and stability of the electric energy.

[0014] As a preferred technical means: the second low-voltage winding, three-phase star connection, full-wave rectified 6-pulse output. The three-phase star connection can provide better current balance and stability. The current phase difference between each phase is 120 degrees, which helps to reduce the asymmetry of the current, thereby reducing the harmonic current components in the system. The structural characteristics of the star connection enable the winding to better withstand unbalanced loads and instantaneous current shocks. When there are sudden load changes or nonlinear loads, the star connection design can better cope with these challenges and ensure the stability and reliability of the system. Through the full-wave rectified 6-pulse output, the harmonic components in the current can be better filtered out, reducing harmonic pollution in the power grid.

[0015] As a preferred technical means: the first low-voltage winding and the second low-voltage winding are provided with a control switch to realize the operation of the first low-voltage winding and / or the second low-voltage winding. When the first low-voltage winding 1 and the second low-voltage winding 2 are operated together, a full-wave rectified 12-pulse output is output. The control switch allows the first low-voltage winding and the second low-voltage winding to work independently or jointly, so that the rectifier transformer can select the operation mode according to actual needs and adapt to different grid conditions or load requirements. For example, when a higher current load capacity is required, the combined operation can be achieved to achieve a full-wave rectified 12-pulse output, thereby improving the power quality of the system. The full-wave rectified 12-pulse output can further reduce the harmonic components compared to the 6-pulse output. By controlling the switch to achieve 12-pulse output, the harmonic pollution in the power grid can be significantly reduced, the power quality of the power system can be improved, and the electromagnetic interference to the surrounding equipment can be reduced; the energy efficiency of the rectifier transformer can be improved, the energy loss can be reduced, and it is conducive to the stable operation of the system and the service life of the equipment can be extended.

[0016] When the connection methods of the first low-voltage winding and the second low-voltage winding are different, the first low-voltage winding adopts a three-phase triangle connection, while the second low-voltage winding adopts a three-phase star connection. The three-phase triangle connection makes the current of the load between the three phases basically equal, which is suitable for applications that require a relatively balanced current distribution and can effectively reduce the adverse effects of current imbalance. The three-phase star connection is more stable when the load is asymmetric, can effectively suppress current imbalance, provide better common-mode suppression capabilities, and can reduce common-mode noise and interference in the system. Using different connection methods can balance the harmonics and electromagnetic interference in the system to a certain extent, improve the stability and operating efficiency of the system, give full play to their respective advantages under different power environments and load requirements, and improve the performance and reliability of the rectifier transformer.

[0017] As a preferred technical means: the first filter winding is connected in parallel with the second filter winding to form a filter winding, and the three-phase delta connection is adopted. The first and second filter windings connected in parallel can jointly process the harmonics and high-frequency noise in the input power supply; through the three-phase delta connection, the harmonic components in the power supply can be effectively reduced, and the harmonic suppression capability of the rectifier transformer to the power grid can be improved. The self-balancing mechanism can effectively adjust the current distribution inside the axially split filter winding. When a part of the low-voltage winding is short-circuited, the unaffected part can bear more current load, thereby maintaining a balanced distribution of current between each winding pair.

[0018] The first filter winding and the second filter winding are relatively independent but interconnected structures, forming a self-balancing mechanism. When the axially split first low-voltage winding or the second low-voltage winding is in semi-through operation, the self-balancing mechanism of the axially split first filter winding and the second filter winding can effectively improve the current distribution between each winding pair, reduce the amplitude of the lateral leakage flux, reduce the stray loss of the transformer, and avoid the overheating problem of ferromagnetic structural parts.

[0019] As a preferred technical means: the first high-voltage winding is connected in parallel with the second high-voltage winding to form a high-voltage winding, and the three-phase triangle connection. The parallel connection can effectively increase the current carrying capacity of the high-voltage winding. By connecting the two high-voltage windings in parallel, the overall current can be distributed in the two windings, thereby reducing the current density of a single winding, reducing the heating and magnetic loss of the winding, and improving the power density and operating efficiency of the rectifier transformer. The use of a three-phase triangle connection can ensure the balance of the high-voltage winding in current distribution and mutual influence, making the interaction between the current and magnetic field between the phases more stable, helping to reduce the problems caused by electromagnetic interference and current imbalance, and improving the operating stability and reliability of the equipment. The three-phase triangle connection can produce a more uniform voltage waveform, which has a positive impact on the power output quality of the rectifier transformer. The stable voltage waveform can improve the efficiency and accuracy of the power supply equipment, which is beneficial to the normal operation of the power system and the stability of power conversion.

[0020] As a preferred technical means: the first low-voltage winding and the second low-voltage winding have the same capacity, equivalent impedance, inner diameter, outer diameter, height and winding direction. Since the two winding parameters are exactly the same, they will evenly share the current load during operation, which helps to reduce the current imbalance inside the winding, thereby reducing the concentrated generation of heat and improving the thermal stability and life of the rectifier transformer. The same capacity and equivalent impedance make the two windings basically consistent in electrical characteristics, and the current distribution is more uniform, which can reduce the additional loss of the conductor and the local heating caused by uneven current, and reduce the overall loss of the rectifier transformer. The consistency of winding parameters simplifies the manufacturing process. During maintenance and troubleshooting, the same parts can be more easily replaced and maintained, reducing maintenance costs and downtime. The same winding design can ensure the consistency of electrical characteristics such as inductance, resistance and capacitance, which is conducive to the rectifier transformer to maintain stable electrical performance under various working conditions and ensure the effective operation of the power system.

[0021] As a preferred technical means: the number of turns of the first low-voltage winding is √3 times the number of turns of the second low-voltage winding.

[0022] The first low-voltage winding is connected in a triangle, and the second low-voltage winding is connected in a star. The voltage relationship between the star connection and the triangle connection is a difference of √3 times. The number of turns of the first low-voltage winding is √3 times that of the second low-voltage winding, which can achieve the matching of the voltages of the two, thereby ensuring the voltage output balance of the rectifier transformer. Since the first and second low-voltage windings are connected in different ways and the number of turns is set accordingly, when they are operated in combination, they can more effectively offset certain harmonic components, especially reduce the influence of odd harmonics, which is important for improving the output power quality of the rectifier and reducing harmonic pollution to the power grid. This technical solution enables the first and second low-voltage windings to generate a 12-pulse rectifier system with a phase difference of 30° when they are operated in combination, effectively reducing the waveform distortion in the rectifier output and significantly reducing the pulsation of the DC output, thereby improving the efficiency and stability of the rectifier system.

[0023] As a preferred technical means: the first filter winding and the second filter winding have the same inner diameter, outer diameter, height, number of turns; and opposite winding directions.

[0024] Since the first and second filter windings have the same number of turns and opposite winding directions, when they are operated in parallel, the magnetic fields generated in the windings can cancel each other out. This design can significantly reduce the electromagnetic interference caused by the winding leakage flux, effectively suppress high-order harmonics, and reduce the impact on the transformer and its surrounding electrical equipment. The opposite winding design helps to reduce the axial leakage flux, thereby reducing the stray loss between the windings, avoiding the overheating problem of ferromagnetic structural parts, and improving the operating efficiency and reliability of the equipment. Under short circuit or other extreme working conditions, the windings of the transformer will be subjected to a large electromotive force, especially the axial force. By adopting the opposite winding design, the first and second filter windings can balance the electromotive force generated by each other, reduce the mechanical stress borne by the windings, help reduce the damage to the windings during short circuit, and improve the short circuit tolerance and mechanical stability of the transformer. Since the parameters of the first and second filter windings are exactly the same (inner diameter, outer diameter, height, number of turns), they can achieve symmetrical distribution of current. Combined with the opposite winding design, this structure helps to achieve self-balancing of current, especially when the filter winding works in conjunction with other windings, it can better control the current distribution, avoid current concentration in a certain winding, and further reduce the heating and energy consumption of the equipment. The symmetrical design of the filter winding combined with the structure of the same number of turns and opposite winding directions helps to provide a more effective zero-impedance channel, so that the harmonic current is better filtered in the winding, improving the filtering effect of the rectifier transformer and ensuring the power quality of the power grid and power equipment.

[0025] As a preferred technical means: the first high-voltage winding and the second high-voltage winding have the same inner diameter, outer diameter, height, number of turns; and opposite winding directions.

[0026] Since the first high-voltage winding and the second high-voltage winding have the same number of turns and opposite winding directions, the magnetic fields they generate during operation can offset each other, thereby effectively reducing the leakage flux between the windings, reducing the propagation of high-order harmonics in the transformer, and improving the power quality of the power grid. The design of opposite winding directions helps to weaken the leakage flux between the windings, thereby reducing the stray loss of the transformer and improving the energy efficiency of the equipment. When a short-circuit accident occurs in the transformer, the winding will be subjected to huge electric forces, especially axial forces. Through the opposite winding direction design, the electric forces generated by the first high-voltage winding and the second high-voltage winding partially offset each other, reducing the damage to the winding caused by the axial force, improving the short-circuit bearing capacity of the transformer, and extending the service life of the equipment. Since the first high-voltage winding and the second high-voltage winding have the same parameters and opposite winding directions, they can achieve self-balancing of current when running in parallel. The self-balancing mechanism can evenly distribute the current between the windings, avoid current concentration in a certain winding, reduce local heating and stress, and improve the operating stability of the transformer. The same number of turns and opposite winding directions enable the high-voltage winding to transmit power more efficiently.

[0027] Beneficial effects: The combination of axial split design and electrostatic screen in this solution effectively reduces power loss and electromagnetic interference in the winding, reduces the temperature rise and power consumption of the equipment, improves the overall economy of the transformer, and extends the service life of the equipment.

[0028] 1. This technical solution uses an axially split filter winding to provide a low-impedance channel for high-order harmonic currents, effectively suppressing the transmission of high-order harmonics between the primary winding (high-voltage side) and the secondary winding (low-voltage side). The introduction of a grounded electrostatic screen further blocks the interference of high-frequency harmonic currents, significantly improving the power quality of the rectifier system.

[0029] 2. The axially split winding design makes the current distribution between the windings more reasonable, especially under special operating conditions (such as half-through operation or fault conditions), it can effectively balance the current distribution in the windings, reduce the stray losses of the windings, and thus improve the efficiency of the rectifier transformer.

[0030] 3. The axial split structure helps to reduce the axial electromotive force of the winding under short-circuit condition by improving the current distribution inside the winding, thereby improving the short-circuit resistance of the rectifier transformer, improving the operating safety of the equipment, and reducing the damage caused by short-circuit faults.

[0031] 4. The electrostatic screen not only effectively suppresses the interference of leakage magnetic field to the system, but also reduces the electromagnetic interference (EMI) in the system, improves the stability and electromagnetic compatibility (EMC) of the transformer, and provides guarantee for the stable operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the winding arrangement of a 12-pulse rectifier transformer.

[0033] Figure 2 This is the second 12-pulse rectifier transformer winding arrangement diagram

[0034] Figure 3 Schematic diagram of winding arrangement of the present invention

[0035] Figure 4 This is the product model diagram of the present invention

[0036] Figure 5 This is a magnetic flux density distribution diagram of the first low-voltage winding and the high-voltage winding of the present invention when they are in semi-transit operation.

[0037] Figure 6 It is a cloud diagram of the amplitude short-circuit force of the windings when the first low-voltage winding and the high-voltage winding of the present invention are in semi-through operation.

[0038] Figure 7 It is a cloud diagram of the axial short-circuit force of the windings when the first low-voltage winding and the high-voltage winding of the present invention are in semi-through operation.

[0039] Figure 8 It is the radial force curve of the first low-voltage winding and the high-voltage winding of the present invention when they are in semi-transit operation.

[0040] Fig. 9 This is the axial force curve of the first low-voltage winding and the high-voltage winding during semi-transit operation of the present invention.

[0041] Fig.10 It is a schematic diagram of the high voltage winding connection principle of the present invention.

[0042] Fig.11 It is the wiring principle diagram of the filter winding of the present invention.

[0043] Fig.12 This is the wiring schematic diagram of the second low-voltage winding of the present invention.

[0044] Fig.13 This is the first low-voltage winding connection principle diagram of the present invention.

[0045] Fig.14 It is a star equivalent schematic diagram of the present invention.

[0046] In the figure: 1. first low-voltage winding; 2. second low-voltage winding; 3. first high-voltage winding; 4. second high-voltage winding; 5. first filter winding; 6. second filter winding; 7. first grounded electrostatic screen; 8. second grounded electrostatic screen; 9. core column. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0048] Embodiment 1

[0049] like Figure 3 As shown, the present invention includes a low-voltage winding, a filter winding and a high-voltage winding. The low-voltage winding, the filter winding and the high-voltage winding are arranged in sequence from the inside to the outside. A first grounded electrostatic screen 7 is arranged between the low-voltage winding and the filter winding; a second grounded electrostatic screen 8 is arranged between the filter winding and the high-voltage winding; the low-voltage winding includes an axially split first low-voltage winding 1 and a second low-voltage winding 2; the filter winding includes an axially split first filter winding 5 and a second filter winding 6; the high-voltage winding includes an axially split first high-voltage winding 3 and a second high-voltage winding 4.

[0050] like Figure 4As shown, the present invention includes three core columns 9, on which axially split low-voltage windings, filter windings and high-voltage windings are respectively and sequentially coated; wherein the first low-voltage winding 1 is an upper low-voltage winding, the second low-voltage winding 2 is a lower low-voltage winding, and the upper low-voltage winding is located above the lower low-voltage winding; the first filter winding 5 is an upper filter winding, the second filter winding 6 is a lower filter winding, and the upper filter winding is located above the lower filter winding; the first high-voltage winding 3 is an upper high-voltage winding, the second high-voltage winding 4 is a lower high-voltage winding, and the upper high-voltage winding is located above the lower high-voltage winding.

[0051] This technical solution uses axially split filter windings to provide a low-impedance channel for high-order harmonic currents, effectively suppressing the transmission of high-order harmonics between the primary winding (high-voltage side) and the secondary winding (low-voltage side). The introduction of a grounded electrostatic screen further blocks the interference of high-frequency harmonic currents, significantly improving the power quality of the rectifier system.

[0052] The axially split winding design makes the current distribution between the windings more reasonable, especially under special operating conditions (such as half-through operation or fault conditions), which can effectively balance the current distribution in the windings and reduce the stray losses of the windings, thereby improving the efficiency of the rectifier transformer.

[0053] The axial split structure helps to reduce the axial electromotive force of the winding under short-circuit condition by improving the current distribution inside the winding, thereby improving the short-circuit resistance of the rectifier transformer, enhancing the operating safety of the equipment, and reducing the damage caused by short-circuit faults.

[0054] The electrostatic screen not only effectively suppresses the interference of leakage magnetic field to the system, but also reduces the electromagnetic interference (EMI) in the system, improves the stability and electromagnetic compatibility (EMC) of the transformer, and provides guarantee for the stable operation of the power grid.

[0055] The combination of axial split design and electrostatic screen in this solution effectively reduces power loss and electromagnetic interference in the winding, reduces the temperature rise and power consumption of the equipment, improves the overall economy of the transformer, and extends the service life of the equipment.

[0056] In this embodiment, the first filter winding 5 is connected in parallel with the second filter winding 6, and the first high-voltage winding 3 is connected in parallel with the second high-voltage winding 4; the first low-voltage winding 1 and the second low-voltage winding 2 respectively realize full-wave rectification 6-pulse output, and when the two are operated together, full-wave rectification 12-pulse output can be realized.

[0057] The first low-voltage winding 1 operates in half-through mode with respect to the high-voltage winding, which is equivalent to the operation of the first low-voltage winding 1 and the open circuit of the second low-voltage winding 2. Because the filter winding is a parallel structure, it actually participates in the operation of the product and can be regarded as a five-winding transformer operating in conjunction. There is no mature calculation model and theoretical basis to support the impedance calculation of this mode. The following is an analysis based on the applicant's experience:

[0058] Since the distribution ratio of the high-voltage winding current between the first high-voltage winding 3 and the second high-voltage winding 4 connected in parallel cannot be determined initially, assuming that the current per unit value of the first high-voltage winding 3 is a, the current per unit value of the second high-voltage winding 4 is 1-a.

[0059] Since the distribution ratio of the filter current between the first filter winding 5 and the second filter winding 6 connected in parallel cannot be determined initially, assuming that the current per unit value of the first filter winding 5 is b, the current per unit value of the second filter winding 6 is -b.

[0060] The semi-transmission impedance formula is as follows:

[0061] Z134=a*Z13+(1-a)*Z14+b*Z15-b*Z16-a*(1-a)*Z34+b*b*Z56-a*b*Z35+(1-a)*b*Z46+a*b*Z36-b*(1-a)*Z45

[0062] make get

[0063] Z13-Z14-Z34+2a*Z34-b*Z35-b*Z46+b*Z36+b*Z45=0

[0064] make get

[0065] Z15-Z16+2b*Z56-a*Z35+(1-a)*Z46+a*Z36-(1-a)*Z45=0

[0066] Among them: Z35 = Z46; Z36 = Z45 (structural symmetry), after merging, we get:

[0067] 2a*Z34+2b*(Z36-Z35)=Z14+Z34-Z13

[0068] 2a*(Z36-Z35)+2b*Z56=Z16+Z36-Z15-Z35

[0069] According to the equation, the specific data of a and b can be solved respectively, and the specific value of Z134 can be finally obtained by substituting it into the semi-transmission impedance formula;

[0070] Z3456 (high voltage winding to filter impedance) can be simply calculated by concentric formula, which will not be elaborated here;

[0071] Based on the above theoretical model, the product calculation plan was completed, and the impedance data was calculated as follows:

[0072] Key impedance indicators that must be guaranteed:

[0073] Z134=15.93% High voltage winding - inner low voltage winding 1 half through impedance

[0074] Z234=15.89% High voltage winding-external low voltage winding 2 half through impedance

[0075] Z3456=8.09% High voltage winding - filter winding impedance

[0076] To meet the performance requirements of the product, the recommended impedance indicators are:

[0077] Z1234=24.12% High voltage winding-low voltage winding full through impedance

[0078] Z156=7.86% Filter-internal low voltage winding 1 half through impedance

[0079] Z256=7.83% Filter-external low voltage winding 2 half-through impedance

[0080] The equivalent impedance of each winding is calculated as follows:

[0081]

[0082] The above data fully meets the relevant requirements, the impedance deviation is within the allowable range, and the electronic calculation scheme is initially successful:

[0083] Since the establishment of the theoretical model did not have the support of mature technologies in the early stage, a lot of leakage magnetic field finite element simulation work was carried out later. For specific figures, please refer to the attached Figure 5-Figure 9 As shown in Figure 3, the simulation results verify the correctness of the theoretical model.

[0084] Embodiment 2

[0085] The same points as in the first embodiment are not described in detail, except that:

[0086] like Fig.13 As shown, the first low-voltage winding 1 is connected in a three-phase triangle and has a full-wave rectified 6-pulse output. The three-phase triangle connection can ensure the current balance of the three phases, effectively reducing the asymmetry and harmonic components of the current. It reduces the voltage fluctuation and current harmonics in the system and improves the quality and stability of the electric energy.

[0087] like Fig.12As shown, the second low-voltage winding 2 is three-phase star-connected and has a full-wave rectified 6-pulse output. The three-phase star connection can provide better current balance and stability. The current phase difference between each phase is 120 degrees, which helps to reduce the asymmetry of the current and thus reduce the harmonic current components in the system. The structural characteristics of the star connection enable the winding to better withstand unbalanced loads and instantaneous current shocks. When there are sudden load changes or nonlinear loads, the star connection design can better cope with these challenges and ensure the stability and reliability of the system. Through the full-wave rectified 6-pulse output, the harmonic components in the current can be better filtered out and the harmonic pollution in the power grid can be reduced.

[0088] The first low-voltage winding 1 and the second low-voltage winding 2 are provided with a control switch to realize the operation of the first low-voltage winding 1 and / or the second low-voltage winding 2. When the first low-voltage winding 1 and the second low-voltage winding 2 are operated together, a full-wave rectified 12-pulse output is output. The control switch allows the first low-voltage winding 1 and the second low-voltage winding 2 to work independently or jointly, so that the rectifier transformer can select the operation mode according to actual needs and adapt to different grid conditions or load requirements. For example, when a higher current load capacity is required, the combined operation can be achieved to achieve a full-wave rectified 12-pulse output, thereby improving the power quality of the system. The full-wave rectified 12-pulse output can further reduce the harmonic components compared to the 6-pulse output. By controlling the switch to achieve 12-pulse output, the harmonic pollution in the power grid can be significantly reduced, the power quality of the power system can be improved, and the electromagnetic interference to the surrounding equipment can be reduced; the energy efficiency of the rectifier transformer can be improved, the energy loss can be reduced, and it is conducive to the stable operation of the system and the service life of the equipment can be extended.

[0089] The connection methods of the first low-voltage winding 1 and the second low-voltage winding 2 are different. The first low-voltage winding 1 adopts a three-phase triangle connection, while the second low-voltage winding 2 adopts a three-phase star connection. The three-phase triangle connection makes the current of the load between the three phases basically equal, which is suitable for applications that require a relatively balanced current distribution and can effectively reduce the adverse effects of current imbalance. The three-phase star connection is more stable when the load is asymmetric, can effectively suppress current imbalance, provide better common-mode suppression capabilities, and can reduce common-mode noise and interference in the system. Using different connection methods can balance the harmonics and electromagnetic interference in the system to a certain extent, improve the stability and operating efficiency of the system, give full play to their respective advantages under different power environments and load requirements, and improve the performance and reliability of the rectifier transformer.

[0090] like Fig.11As shown, the first filter winding 5 and the second filter winding 6 are connected in parallel to form a filter winding, and the three-phase delta connection is formed. The first and second filter windings 6 connected in parallel can jointly process the harmonics and high-frequency noise in the input power supply; through the three-phase delta connection, the harmonic components in the power supply can be effectively reduced, and the harmonic suppression capability of the rectifier transformer to the power grid can be improved. The self-balancing mechanism can effectively adjust the current distribution inside the axially split filter winding. When a part of the low-voltage winding is short-circuited, the unaffected part can bear more current load, thereby maintaining a balanced distribution of current between each winding pair.

[0091] The first filter winding 5 and the second filter winding 6 are relatively independent but interconnected structures, forming a self-balancing mechanism. When the axially split first low-voltage winding 1 or the second low-voltage winding 2 is in semi-through operation, the self-balancing mechanism of the axially split first filter winding 5 and the second filter winding 6 can effectively improve the distribution of current between each winding pair, reduce the amplitude of the lateral leakage flux, reduce the stray loss of the transformer, and avoid the overheating problem of the ferromagnetic structure.

[0092] like Fig.10 As shown, the first high-voltage winding 3 is connected in parallel with the second high-voltage winding 4 to form a high-voltage winding, and the three-phase triangle connection. The parallel connection can effectively increase the current carrying capacity of the high-voltage winding. By connecting the two high-voltage windings in parallel, the overall current can be distributed in the two windings, thereby reducing the current density of a single winding, reducing the heating and magnetic loss of the winding, and improving the power density and operating efficiency of the rectifier transformer. The use of a three-phase triangle connection can ensure the balance of the high-voltage winding in current distribution and mutual influence, making the interaction between the current and magnetic field between the phases more stable, helping to reduce the problems caused by electromagnetic interference and current imbalance, and improving the operating stability and reliability of the equipment. The three-phase triangle connection can produce a relatively uniform voltage waveform, which has a positive impact on the power output quality of the rectifier transformer. The stable voltage waveform can improve the efficiency and accuracy of the power supply equipment, which is conducive to the normal operation of the power system and the stability of power conversion.

[0093] In order to simplify the structure and improve the reliability and stability of the work, in this embodiment, the first low-voltage winding 1 and the second low-voltage winding 2 have the same capacity, equivalent impedance, inner diameter, outer diameter, height and winding direction. Since the two winding parameters are exactly the same, they will evenly share the current load during operation, which helps to reduce the current imbalance inside the winding, thereby reducing the concentrated generation of heat and improving the thermal stability and life of the rectifier transformer. The same capacity and equivalent impedance make the two windings basically consistent in electrical characteristics, and the current distribution is more uniform, which can reduce the additional loss of the conductor and the local heating caused by uneven current, and reduce the overall loss of the rectifier transformer. The consistency of winding parameters simplifies the manufacturing process. During maintenance and troubleshooting, the same parts can be more easily replaced and maintained, reducing maintenance costs and downtime. The same winding design can ensure the consistency of electrical characteristics such as inductance, resistance and capacitance, which is conducive to the rectifier transformer to maintain stable electrical performance under various working conditions and ensure the effective operation of the power system.

[0094] The number of turns of the first low-voltage winding 1 is √3 times the number of turns of the second low-voltage winding 2. The first low-voltage winding 1 adopts a triangle connection, and the second low-voltage winding 2 adopts a star connection. The voltage relationship between the star connection and the triangle connection is a difference of √3 times. The number of turns of the first low-voltage winding 1 is √3 times that of the second low-voltage winding 2, which can achieve the matching of the voltages of the two, thereby ensuring the voltage output balance of the rectifier transformer. Since the first and second low-voltage windings 2 are connected in different ways and the number of turns is set accordingly, when they are operated in combination, they can more effectively offset certain harmonic components, especially reduce the influence of odd harmonics, which is important for improving the output power quality of the rectifier and reducing harmonic pollution to the power grid. This technical solution enables the first and second low-voltage windings 2 to generate a 12-pulse rectifier system with a phase difference of 30° when they are operated in combination, effectively reducing the waveform distortion in the rectifier output, and significantly reducing the pulsation of the DC output, thereby improving the efficiency and stability of the rectifier system.

[0095] The first filter winding 5 and the second filter winding 6 have the same inner diameter, outer diameter, height, number of turns, and opposite winding directions. Since the first and second filter windings 6 have the same number of turns and opposite winding directions, when they are operated in parallel, the magnetic fields generated in the windings can cancel each other out. This design can significantly reduce the electromagnetic interference caused by winding leakage flux, effectively suppress high-order harmonics, and reduce the impact on the transformer and its surrounding electrical equipment. The opposite winding direction design helps to reduce the axial leakage flux, thereby reducing the stray loss between the windings, avoiding the overheating problem of ferromagnetic structural parts, and improving the operating efficiency and reliability of the equipment. Under short circuit or other extreme working conditions, the windings of the transformer will be subjected to a large electromotive force, especially axial force. By adopting the opposite winding direction design, the first and second filter windings 6 can balance the electromotive force generated by each other, reduce the mechanical stress on the windings, help reduce the damage to the windings during short circuit, and improve the short circuit tolerance and mechanical stability of the transformer. Since the parameters of the first and second filter windings 6 are exactly the same (inner diameter, outer diameter, height, number of turns), they can achieve symmetrical distribution of current. Combined with the opposite winding design, this structure helps to achieve self-balancing of current, especially when the filter winding works in conjunction with other windings, it can better control the current distribution, avoid current concentration in a certain winding, and further reduce the heating and energy consumption of the equipment. The symmetrical design of the filter winding combined with the structure of the same number of turns and opposite winding helps to provide a more effective zero impedance channel, so that the harmonic current is better filtered in the winding, improve the filtering effect of the rectifier transformer, and ensure the power quality of the power grid and power equipment.

[0096] The first high-voltage winding 3 and the second high-voltage winding 4 have the same inner diameter, outer diameter, height, number of turns; opposite winding direction. Since the first high-voltage winding 3 and the second high-voltage winding 4 have the same number of turns and opposite winding direction, the magnetic fields generated by them during operation can offset each other, thereby effectively reducing the leakage flux between the windings, reducing the propagation of high-order harmonics in the transformer, and improving the power quality of the power grid. The design of opposite winding direction helps to weaken the leakage flux between the windings, thereby reducing the stray loss of the transformer and improving the energy efficiency of the equipment. When a short-circuit accident occurs in the transformer, the winding will be subjected to huge electric power, especially axial force. Through the opposite winding direction design, the electric power generated by the first high-voltage winding 3 and the second high-voltage winding 4 partially offset each other, reducing the damage of the axial force to the winding, improving the short-circuit bearing capacity of the transformer, and extending the service life of the equipment. Since the first high-voltage winding 3 and the second high-voltage winding 4 have the same parameters and opposite winding directions, they can achieve self-balancing of current when running in parallel. The self-balancing mechanism can evenly distribute the current between the windings, avoid the current from being concentrated in a certain winding, reduce local heating and stress, and improve the operating stability of the transformer. The same number of turns and opposite winding directions allow the high voltage winding to transfer power more efficiently.

[0097] like Fig.14The star equivalent schematic diagram of the product is shown. When the low voltage winding and the high voltage winding are in full-through operation, the full-through impedance Z1234 = 24%;

[0098] When the first low voltage winding 1 and the high voltage winding are in semi-transmission operation, the semi-transmission impedance Z134 = 16%;

[0099] When the second low voltage winding 2 and the high voltage winding are in semi-through operation, the semi-through impedance Z234 = 16%;

[0100] When the filter winding and the high-voltage winding are in operation, the impedance Z3456 = 8%;

[0101] When the first low voltage winding 1 and the filter winding are in semi-through operation, the semi-through impedance Z156 = 8%;

[0102] When the second low voltage winding 2 and the filter winding are in semi-through operation, the semi-through impedance Z256 = 8%;

[0103] When the first low-voltage winding 1 and the second low-voltage winding 2 are split and operated, the split impedance Z12 = 16%;

[0104] The first low voltage winding 1 equivalent impedance Z1 = Z1234 - Z234 = 8%;

[0105] The equivalent impedance of the second low voltage winding 2 is Z2=Z1234-Z134=8%;

[0106] High voltage winding equivalent impedance Z34 = Z134-Z1 = 8%;

[0107] Filter winding equivalent impedance Z56 = Z156 - Z1 = 0%;

[0108] The zero impedance characteristic of the filter winding provides a short-circuit channel for high-order harmonic currents. When the low-voltage winding and the high-voltage winding are in full-through operation, most of the harmonic currents generated by the 12-pulse rectification of the low-voltage winding flow through the filter winding, and have little effect on the current of the high-voltage winding. The specific data are as follows:

[0109] When the low voltage winding (valve side winding) is in 12-pulse rectification operation, the harmonic current content percentage (corresponding to the fundamental wave):

[0110] 3 5 7 11 13 17 19 23 25 29 31 35 37 41 43 47 49 1.0 21.0 13.8 8.3 6.8 4.7 4.0 2.9 2.4 1.7 1.4 0.9 0.7 0.5 0.4 0.4 0.4

[0111] When the low voltage winding (valve side winding) is in 12-pulse rectification operation, the harmonics generated by the valve side winding flow through the filter winding in percentage:

[0112] 3 5 7 11 13 17 19 23 25 29 31 35 37 41 43 47 49 76 99 99 95 95 98 98 91 90 97 97 90 90 97 97 90 90

[0113] When the low voltage winding (valve side winding) is in 12-pulse rectification operation, the harmonics generated by the valve side winding flow through the high voltage winding in %:

[0114] 3 5 7 11 13 17 19 23 25 29 31 35 37 41 43 47 49 24 1 1 5 5 2 2 9 10 3 3 10 10 3 3 10 10

[0115] When the low-voltage winding (valve-side winding) is in 12-pulse rectification operation, the sum of square harmonic currents generated by the valve-side winding is approximately 8% of the sum of square harmonic currents of the rated current, of which more than 99.5% flows through the filter winding, and less than 0.5% flows through the high-voltage winding, which can be basically ignored.

[0116] Compared with the prior art, this embodiment has at least the following advantages:

[0117] The present invention provides a 12-pulse rectifier transformer with an axially split filter winding, wherein the low-voltage winding is axially split for 12-pulse rectification, the filter winding is axially split for upper and lower parallel connection, the high-voltage winding is axially split for upper and lower parallel connection, a grounded electrostatic screen is provided between the low-voltage winding and the filter winding, and a grounded electrostatic screen is provided between the filter winding and the high-voltage winding; a traditional 12-pulse rectifier transformer, wherein the low-voltage winding is axially split for 12-pulse rectification, the high-voltage winding is axially split for upper and lower parallel connection, and a grounded electrostatic screen is provided between the low-voltage winding and the high-voltage winding;

[0118] When the low-voltage winding (valve side winding) is in 12-pulse rectification operation, the present invention provides a 12-pulse rectifier transformer with an axially split filter winding. In addition to the two shunt effects of the grounded electrostatic screen, the harmonic current mainly flows through the filter winding, and has little effect on the high-voltage winding current. In traditional 12-pulse rectifier transformers, the harmonic current flows through the shunt of the grounded electrostatic screen, and the rest flows into the high-voltage winding, which has a greater impact on the high-voltage winding current, and may seriously affect the safety of the power grid.

[0119] When the first low-voltage winding 1 or the second low-voltage winding 2 is in semi-through operation with respect to the high-voltage winding, the present invention provides a 12-pulse rectifier transformer with an axially split filter winding. The self-balancing mechanism of the upper and lower parallel filter windings can effectively improve the distribution of current between the winding pairs, greatly reduce the amplitude of the lateral leakage magnetic flux, and fundamentally ensure the short-circuit safety of the product. The traditional 12-pulse rectifier transformer has no means to improve the distribution of current between the axially parallel windings, and the short-circuit axial force generated by the lateral leakage magnetic flux has a great influence on the product, and the structural design requires special consideration.

[0120] When the first low-voltage winding 1 or the second low-voltage winding 2 is in semi-through operation with respect to the high-voltage winding, the present invention provides a 12-pulse rectifier transformer with an axially split filter winding. The self-balancing mechanism of the upper and lower parallel filter windings can effectively improve the distribution of current between the winding pairs, greatly reduce the amplitude of the transverse leakage flux, and avoid the overheating problem of ferromagnetic structural parts such as the core clamps and the oil tank from the root. The traditional 12-pulse rectifier transformer has no means to improve the distribution of current between the axially parallel windings, the amplitude of the transverse leakage flux is large, and the overheating problem of the clamps and the oil tank requires extra attention.

[0121] This embodiment has better performance than the following two 12-pulse rectifier transformer windings:

[0122] 1. If Figure 1 As shown, a 12-pulse rectifier transformer winding is formed, and the winding specifically includes a low-voltage winding (valve side winding), a filter winding, and a high-voltage winding (grid side winding). The filter winding is composed of an inner filter winding 5 and an outer filter winding 6 split in the radial direction, wherein the inner filter winding 5 is connected in parallel with the outer filter winding 6; the low-voltage winding is composed of an inner low-voltage winding 1 and an outer low-voltage winding 2 split in the radial direction; a grounded electrostatic screen is provided between the inner low-voltage winding 1 and the inner filter winding 5; a grounded electrostatic screen is provided between the inner filter winding 5 and the high-voltage winding 3; a grounded electrostatic screen is provided between the high-voltage winding 3 and the outer filter winding 6; and a grounded electrostatic screen is provided between the outer filter winding 6 and the outer low-voltage winding 2.

[0123] In order to meet the performance of the product, the key impedance indicators that need to be guaranteed are:

[0124] Z13=16% High voltage winding 3-internal low voltage winding 1 half-through impedance

[0125] Z23=16% High voltage winding 3-external low voltage winding 2 half-through impedance

[0126] Z356=8% High voltage winding 3-filter 5, 6 impedance

[0127] To meet the performance of the product, the impedance indicators for reference are:

[0128] Z123=24% High voltage winding 3- low voltage winding 1, 2 full through impedance

[0129] Z156=8% Filter 5, 6-Internal low voltage winding 1 half through impedance

[0130] Z256=8% Filter 5, 6-external low voltage winding 2 half-through impedance

[0131] The equivalent impedance of each winding is calculated as follows:

[0132]

[0133] The star equivalent schematic diagram of the product is as follows Fig.14 shown.

[0134] Basic formula for transformer winding impedance:

[0135]

[0136] Where: I (winding current); W (winding turns); ∑D (leakage magnetic group area); ρ (Rockwell coefficient); et (turn potential);

[0137] The calculation method of ∑D and ρ is related to the arrangement of the winding pair, which can be divided into two types: concentric and staggered. The impedance calculation method of the radial split winding is concentric.

[0138] According to the basic formula, the impedance value between each winding can be calculated and adjusted normally in the conventional way to meet the requirements of the above-mentioned key impedance indicators.

[0139] The above-mentioned radially split 12-pulse rectifier transformer with filter winding is a relatively mature and traditional product solution. The calculation method used is also based on evidence. Under the premise of meeting the key impedance indicators of the product, its advantages are that the ampere-turn balance between each winding pair is very perfect and the product safety factor is high. However, because the number of radially split windings is too large, the product has a large appearance, high cost, and low economy and market competitiveness.

[0140] 2. If Figure 2 As shown, another 12-pulse rectifier transformer winding has a structure of a low-voltage winding (valve side winding) axially split structure, a high-voltage winding (grid side winding) axially split structure, and an integrated filter winding structure.

[0141] The winding structure specifically includes low-voltage winding (valve side winding), filter winding, and high-voltage winding (grid side winding). The high-voltage winding consists of an axially split upper high-voltage winding 3 and a lower high-voltage winding 4 (3 and 4 are connected in parallel); the low-voltage winding consists of an axially split upper low-voltage winding 1 and a lower low-voltage winding 2; a grounded electrostatic screen is set between the low-voltage winding and the filter winding; a grounded electrostatic screen is set between the filter winding and the high-voltage winding;

[0142] The arrangement of winding pairs in this scheme includes concentric and staggered types. The impedance of the diagonal arrangement is difficult to calculate using conventional methods. Let's establish equations and analyze them one by one:

[0143] The upper low-voltage winding operates half-through the high-voltage winding, which is equivalent to the upper low-voltage winding operating and the lower low-voltage winding being open-circuited, and can be regarded as the operation of a three-winding transformer; because the distribution ratio of the high-voltage winding current in the upper and lower parallel high-voltage windings and the lower high-voltage windings cannot be determined initially, assuming that the current per-unit value of the upper high-voltage winding is a, the current per-unit value of the lower high-voltage winding is 1-a, and the half-through impedance formula is as follows:

[0144] Z134=a*Z13+(1-a)*Z14-a*(1-a)*Z34

[0145] make get

[0146]

[0147] Among them: Z34 is concentric; Z13 is staggered, which can be calculated according to the basic formula; Z14 is diagonal arrangement, which cannot be calculated according to the basic formula, and can be obtained by the following formula:

[0148]

[0149] The half-through impedance of low voltage winding 1 to high voltage windings 3 and 4

[0150] Z234=Z134 (structural symmetry) half-through impedance of low voltage winding 2 to high voltage windings 3 and 4

[0151] The total through impedance of low voltage windings 1 and 2 to high voltage windings 3 and 4

[0152] Z345 (calculated according to the basic formula) filter impedance to high voltage windings 3 and 4

[0153] According to the above formula, the calculated solution results are as follows:

[0154] When Z134=Z234=16%;Z345=8%

[0155] Z1234=17.5%(basically a fixed value)

[0156] The equivalent impedance of each winding is calculated as follows:

[0157] Z1=Z2=Z1234-Z234=1.5%

[0158] Z34=Z134-Z1=14.5%

[0159] Z5=Z345-Z34=-6.5%

[0160] From the above, we can see that the equivalent impedance of the filter winding is far from zero and cannot meet the key impedance index requirements.

[0161] The embodiments of the present invention can reasonably adjust the spatial positions between the first low-voltage winding and the second low-voltage winding; the low-voltage winding and the filter winding, and the filter winding and the high-voltage winding, so that the equivalent impedance of the filter winding is as close to zero as possible; the equivalent impedance of the high-voltage winding and the two low-voltage windings are each close to one-third of the high-low total impedance. Such an impedance distribution mode can greatly reduce the transmission of high-order harmonic currents between high and low voltage windings. Compared with conventional rectifier products, it has the characteristics of high impedance, low loss, low noise, strong short-circuit resistance, and excellent detuning effect. It can be applied to related industries such as new energy power generation, peak-shifting power generation, and compressed air energy storage.

[0162] The rectifier transformer with an axially split filter winding shown above is a specific embodiment of the present invention, which has embodied the substantial characteristics and progress of the present invention. According to actual use needs and under the guidance of the present invention, equivalent modifications in shape, structure, etc. can be made to it, which are all within the protection scope of this scheme.

Claims

1. A rectifier transformer with an axially split filter winding, comprising a low voltage winding, a filter winding and a high voltage winding, wherein the low voltage winding, the filter winding and the high voltage winding are arranged in sequence from the inside to the outside, characterized in that: A first grounded electrostatic screen (7) is arranged between the low-voltage winding and the filter winding; a second grounded electrostatic screen (8) is arranged between the filter winding and the high-voltage winding; the low-voltage winding comprises an axially split first low-voltage winding (1) and a second low-voltage winding (2); the filter winding comprises an axially split first filter winding (5) and a second filter winding (6); and the high-voltage winding comprises an axially split first high-voltage winding (3) and a second high-voltage winding (4).

2. A rectifier transformer with axially split filter winding according to claim 1, characterized in that: The first low-voltage winding (1) is connected in a three-phase triangle and has a full-wave rectified 6-pulse output.

3. A rectifier transformer with axially split filter winding according to claim 2, characterized in that: The second low-voltage winding (2) is three-phase star-connected and has a full-wave rectified 6-pulse output.

4. A rectifier transformer with axially split filter winding according to claim 3, characterized in that: The first low-voltage winding (1) and the second low-voltage winding (2) are provided with a control switch to realize the operation of the first low-voltage winding (1) and / or the second low-voltage winding (2); when the first low-voltage winding (1) and the second low-voltage winding (2) are operated together, a full-wave rectified 12-pulse output is produced.

5. A rectifier transformer with axially split filter winding according to claim 4, characterized in that: The first filter winding (5) and the second filter winding (6) are connected in parallel to form a filter winding, which is connected in a three-phase triangle.

6. A rectifier transformer with axially split filter winding according to claim 4, characterized in that: The first high-voltage winding (3) and the second high-voltage winding (4) are connected in parallel to form a high-voltage winding, which is connected in a three-phase triangle.

7. A rectifier transformer with axially split filter winding according to claim 4, characterized in that: The first low-voltage winding (1) and the second low-voltage winding (2) have the same capacity, equivalent impedance, inner diameter, outer diameter, height and winding direction.

8. The rectifier transformer with axially split filter winding according to claim 4, characterized in that: The number of turns of the first low-voltage winding (1) is √3 times the number of turns of the second low-voltage winding (2).

9. The rectifier transformer with axially split filter winding according to claim 4, characterized in that: The first filter winding (5) and the second filter winding (6) have the same inner diameter, outer diameter, height, number of turns, and opposite winding directions.

10. The rectifier transformer with axially split filter winding according to claim 4, characterized in that: The first high-voltage winding (3) and the second high-voltage winding (4) have the same inner diameter, outer diameter, height, number of turns, and opposite winding directions.

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