CN205863871U - A kind of 500kV transformer station intensive style direct current ice melting system having SVG function concurrently - Google Patents

Abstract

The utility model discloses an intensive DC ice-melting system for a 500kV substation with SVG functions, which comprises an electric energy measurement and protection device, a transformer, an operation mode switcher, a DC ice-melting unit and a dynamic reactive power compensation unit. The primary side of the transformer is connected to the AC busbar of the substation through an electric energy measurement and protection device, and the secondary side of the transformer is respectively connected to a DC ice melting unit and a dynamic reactive power compensation unit through an operation mode switcher. The utility model can realize the recovery and utilization of the heat loss of the device itself, and is compatible with the dispatching AVC system of the substation, provides effective guidance for the research on the multifunctional topology of the ice melting device and the development of the device, and is widely applicable to 500kV substations.

Description

A kind of 500kV transformer station intensive style direct current ice melting system having SVG function concurrently

Technical field

This utility model relates to the deicing device of electrical engineering, is specifically related to a kind of 500kV transformer station having SVG function concurrently Intensive direct current ice melting system.

Background technology

The southern area ice disaster such as the Guizhou of China, Hunan, Hubei take place frequently, due to Climate Anomalies or even north in recent years The northern area such as capital, Liaoning also time have ice disaster to occur, easily cause the broken string of falling tower after powerline ice-covering, serious threat to electricity Net safe and stable operation and power supply reliability.In order to improve the ability of transmission line of electricity opposing ice damage, domestic many units have developed The DC de-icing device of Multiple Type, provides solid technical guarantee for electrical network Winter safety stable operation, but deicing device The line ice coating phase uses the most in the winter time, and utilization rate is relatively low, and the deicing device investment of 500kV transformer station is big, the idle resistance of overequipment The popularization and application of deicing device are hindered, to this end, home and abroad minority colleges and universities and R&D institution develop and be applicable to 500kV transformer station The DC de-icing device having SVG no-power compensation function concurrently, not only can to icing circuit implement DC ice melting, also by change Device internal structure realizes dynamic passive compensation.But, there is techniques below problem in such device: problem 1, harmonic wave is big, takes up an area Area is big: can produce a large amount of 5 times, 7 inferior harmonic currents, device self and filtering during plant running needs configuration to organize Large Copacity more Capacitor, reactor, cause that plant area area is big, construction cost is high；Problem 2, ice-melt and the reactive-load compensation same capacity configuration of palpus: Whole volume SVG to be taken into account and deicing device, voltage takes the high voltage of SVG, and electric current takes the big electric current of deicing device, causes entirety Capacity is very big, and cost is high；Problem 3, caloric value is big, must use water-cooled: which loss is big, and operating cost is high, it is necessary to use Water-cooling pattern, increases water-cooling system, and water quality requirement is high, need to carry out deionization process, to prevent from leaking simultaneously, need again winter to carry out Antifreeze process, maintenance workload is big, affects device reliability.Therefore, SVG no-power compensation function is had concurrently for 500kV transformer station The feature of DC de-icing device, grind in the urgent need to carrying out the novel intensive DC de-icing device topological structure of 500kV transformer station Studying carefully, in order to solve the problem that existing deicing device exists, the structure for device designs and final development provides and instructs.

Utility model content

The technical problems to be solved in the utility model: for the problems referred to above of prior art, it is provided that one is capable of dress Put self thermal losses to recycle, and AVC system compatible can be dispatched with transformer station, for the multi-functional Study on topology of deicing device And device development provides effective and instructs, it is widely portable to the 500kV transformer station collection having SVG function concurrently of 500kV transformer station About type direct current ice melting system.

In order to solve above-mentioned technical problem, the technical solution adopted in the utility model is:

A kind of 500kV transformer station intensive style direct current ice melting system having SVG function concurrently, including electric energy measurement metering and protection Device, transformator, operational mode switch, DC ice melting unit and dynamic passive compensation unit, the former limit of described transformator leads to Crossing electric energy measurement metering and protection device to be connected with the ac bus of transformer station, the secondary of described transformator is cut by operational mode Parallel operation is connected with DC ice melting unit, dynamic passive compensation unit respectively.

Preferably, described DC ice melting unit includes rectification part, induced voltage suppressor and the switching of three-phase DC ice-melting One input of device, the AC of described rectification part and operational mode switch is connected, the DC side of described rectification part Pass sequentially through induced voltage suppressor to be connected with three-phase DC ice-melting switch, and by the output of three-phase DC ice-melting switch End provides ice-melt output voltage.

Preferably, described dynamic passive compensation unit includes SVG type dynamic reactive compensator and Capacitor banks and reactor Group, described SVG type dynamic reactive compensator is connected with another input of operational mode switch, and described SVG type is dynamic Two secondary input ends of reactive-load compensator respectively with the secondary outfan of Capacitor banks and Reactor banks, the TT&C system of transformer station with And the scheduling AVC system of transformer station is connected, a secondary input end of described Capacitor banks and Reactor banks exchanges mother with transformer station Line is connected.

Preferably, described SVG type dynamic reactive compensator is also associated with thermal losses UTILIZATION OF VESIDUAL HEAT IN unit.

Preferably, described SVG type dynamic reactive compensator is installed in the power cabinet closing space, the top of described power cabinet Portion is provided with interconnective blower fan and ducting outlet.

Preferably, described thermal losses UTILIZATION OF VESIDUAL HEAT IN unit includes that radiator and source pump, described source pump include steaming Sending out device, condenser and compressor pump, described radiator includes separate wind passage and the first aquaporin, and described vaporizer includes The second separate aquaporin and first medium passage, described condenser includes separate second medium passage and waste heat Utilizing passage, the first aquaporin arrival end of described radiator connects with ducting outlet, the port of export connects with closing space, described By circulating pump circulation between first aquaporin, the second aquaporin, between described first medium passage, second medium passage By compressor pump circulation, described UTILIZATION OF VESIDUAL HEAT IN passage includes that hot water heats passage, and described hot water heats passage end and is provided with Cold water inlet, the other end are provided with hot water outlet pipe.

Preferably, described UTILIZATION OF VESIDUAL HEAT IN passage also includes air heat dissipation channel.

Preferably, the connection group of described transformator is Y/y0d11, and described transformator is that upper and lower winding concentricity is complete Consistent axial direction double bundle structure transformer, two windings of the secondary of described axial direction double bundle structure transformer share an iron core Magnetic circuit is that axial split is arranged.

This utility model has the 500kV transformer station intensive style direct current ice melting system of SVG function concurrently and has an advantage that

1, this utility model includes electric energy measurement metering and protection device, transformator, operational mode switch, DC ice melting Unit and dynamic passive compensation unit, the former limit of described transformator is measured by electric energy measurement and protection device and the friendship of transformer station Stream bus be connected, the secondary of described transformator by operational mode switch respectively with DC ice melting unit, dynamic passive compensation Unit is connected, it is possible to realizes ice-melt capacity with SVG capacity because being separately optimized configuration, reduces device volume and cost, meets and melt Ice high reliability and dynamic passive compensation requirement, and there is harmonic wave control function, optimize transformer station's dynamic reactive and static reactive Coordinate.

2, this utility model can collect every line voltage distribution, electric current, meritorious and nothing with Measurement-control System of Transformer Substation information exchange The information such as merit, it is achieved neighboring station voltage is estimated, with transformer station dispatch AVC system compatible, it is achieved our station dynamic electric voltage, steady state voltage and Neighboring station voltage Multiple Optimization is coordinated to control.

3, this utility model cooling system uses closed cycle air-cooled, and operation maintenance is simple, and without the risk of infiltration, and easily In the recycling realizing device self thermal losses.

4, this utility model can carry out the recovery of device self thermal losses, heat recovery plant running thermal losses produced After, heat cold water, cold water is converted into the domestic hot-water of about 55 DEG C, it is achieved the recycling of energy, reduce plant running and become This, solve existing dynamic reactive compensation device and mended the idle difficult problem damaged and gained merit, it is achieved large power power electronic appliance is real The energy-conserving and environment-protective of meaning run.

Accompanying drawing explanation

Fig. 1 is the structural principle schematic diagram of this utility model embodiment.

Fig. 2 is the winding block diagram of the transformator of this utility model embodiment.

Fig. 3 be the transformator of this utility model embodiment two windings of secondary in flux distribution.

Fig. 4 is the thermal losses UTILIZATION OF VESIDUAL HEAT IN cellular construction schematic diagram of this utility model embodiment.

Fig. 5 is the principle schematic that application this utility model embodiment carries out reactive requirement and allocation strategy.

Marginal data: 1, electric energy measurement metering and protection device；2, transformator；3, operational mode switch；4, direct current melts Ice unit；41, rectification part；42, induced voltage suppressor；43, three-phase DC ice-melting switch；5, dynamic passive compensation list Unit；51, SVG type dynamic reactive compensator；510, space is closed；511, power cabinet；512, blower fan；513 and ducting outlet；52、 Capacitor banks and Reactor banks；6, thermal losses UTILIZATION OF VESIDUAL HEAT IN unit；61, radiator；62, source pump；621, vaporizer；622、 Condenser；623, compressor pump；624, cold water inlet；625, hot water outlet pipe.

Detailed description of the invention

As it is shown in figure 1, the 500kV transformer station intensive style direct current ice melting system that the present embodiment has SVG function concurrently includes electric energy Measuring and protection device 1, transformator 2, operational mode switch 3, DC ice melting unit 4 and dynamic passive compensation unit 5, The former limit of transformator 2 is measured by electric energy measurement and protection device 1 is connected with the 35kV ac bus of transformer station, transformator 2 Secondary is connected with DC ice melting unit 4, dynamic passive compensation unit 5 respectively by operational mode switch 3.In the present embodiment, Transformator 2 is by the input of output termination operational mode switch 3, the output of operational mode switch 3 after 35kV high pressure blood pressure lowering End input with DC ice melting unit 4 and dynamic passive compensation unit 5 respectively is connected, and operational mode switch 3 exports specified Voltage is 22.5kV, and rated capacity is that the DC voltage of 120MW treats each other DC ice-melting to three；Dynamic passive compensation unit 5 exports Rated voltage 20kV, rated capacity is ± perception of 100Mvar or capacitive reactive power.

In the present embodiment, electric energy measurement metering and protection device 1 use commercially available DNCLBH-35kV type electric energy measurement, metering With protection device.

In the present embodiment, transformator 2 uses from BYQ-350kV-20kV type 12 pulse wave transformer ground, this 12 pulse wave transformation The connection group of device is Y/y0d11, and transformator 2 is upper and lower winding concentricity on all four axial direction double bundle structure transformer, It is that axial split is arranged that two windings of the secondary of axial direction double bundle structure transformer share an iron circuit, passes through said structure Be capable of ice-melt rectification 5 times, 7 subharmonic automotive resistances, it is ensured that SVG harmonic compensation enters electrical network and benefit by transformator The rapidity repaid.In the present embodiment, transformator 2 is the unsaturation three-winding transformer of Low ESR, wide-voltage-regulation rectification, it is possible to achieve Many gears voltage export, transformator 2 uses Low ESR, wide-voltage-regulation method for designing simultaneously, by the preferred arrangement of aforementioned winding with Electric Field Calculation, makes transformer regulating wide ranges reach 80% (20%～100%), and the short-circuit impedance difference of each gear is less, can Use diode rectification ice-melt, meet ice-melt high reliability request.

As in figure 2 it is shown, transformator 2 be upper and lower winding concentricity on all four axial direction double bundle structure transformer i.e.: former Each phase of limit D winding, each phase of secondary y11 winding, each phase one_to_one corresponding of secondary d0 winding and concentricity complete Cause in axial direction double bundle structure；As it is shown on figure 3, Φ₁、Φ₂It is respectively the magnetic flux by two winding A phases of secondary, Φ₁-Φ₂For Magnetic flux by two winding B phases of secondary.Due to each phase of former limit D winding, each phase of secondary y11 winding, secondary d0 around Each phase one_to_one corresponding and the concentricity of group are completely the same in axial direction double bundle structure, therefore can meet formula:

F_{A (5,7 times)}=F_{Ay (5,7 times)}+F_{Ad (5,7 times)}=0

F_{B (5,7 times)}=F_{By (5,7 times)}+F_{Bd (5,7 times)}=0

F_{C (5,7 times)}=F_{Cy (5,7 times)}+F_{Cd (5,7 times)}=0

Wherein, F_{A (5,7 times)}Represent the harmonic wave of former limit A phase, F_{Ay (5,7 times)}Represent the harmonic wave of secondary y11 winding A phase, F_{Ad (5,7 times)}Table Show the harmonic wave of secondary d0 winding A phase, F_{B (5,7 times)}Represent the harmonic wave of former limit B phase, F_{By (5,7 times)}Represent the humorous of secondary y11 winding B phase Ripple, F_{Bd (5,7 times)}Represent the harmonic wave of secondary d0 winding B phase, F_{C (5,7 times)}Represent the harmonic wave of former limit C phase, F_{Cy (5,7 times)}Represent secondary y11 around The harmonic wave of group C phase, F_{Cd (5,7 times)}Represent the harmonic wave of secondary d0 winding C phase.Therefore, it is possible to realize ice-melt rectification 5 times, 7 subharmonic from Dynamic counteracting, it is ensured that SVG harmonic compensation enters electrical network and the rapidity of compensation by transformator.

In the present embodiment, operational mode switch 3 uses commercially available YXMS-20kV type operational mode switch.

As it is shown in figure 1, DC ice melting unit 4 includes rectification part 41, induced voltage suppressor 42 and three-phase DC ice-melting One input of switch 43, the AC of rectification part 41 and operational mode switch 3 is connected, the direct current of rectification part 41 Side passes sequentially through induced voltage suppressor 42 and is connected with three-phase DC ice-melting switch 43, and by three-phase DC ice-melting switch The outfan of 43 provides ice-melt output voltage.In the present embodiment, rectification part 41 uses the ZLQ-20kV of diode uncontrollable rectifier Type 12 pulse wave diode rectifier, is made up of two three phase rectifier full-bridges, can realize 12 pulse wave direct voltage outputs；Induced voltage Suppressor 42 uses the DYYZ-20kV type induced voltage suppressor of independent development；Three-phase DC ice-melting switch 43 uses commercially available RBQH-20kV type DC ice-melting switch.

As it is shown in figure 1, dynamic passive compensation unit 5 includes SVG type dynamic reactive compensator 51 and Capacitor banks and reactance Device group 52, SVG type dynamic reactive compensator 51 is connected with another input of operational mode switch 3, and the dynamic nothing of SVG type Two secondary input ends of merit compensator 51 respectively with secondary outfan, the TT&C system of transformer station of Capacitor banks and Reactor banks 52 (in the present embodiment, being specially transformer station's existing CKXT-12 type measure and control device) and scheduling AVC system (this enforcement of transformer station Example is specially transformer station's existing AVC-8 type system) it is connected, Capacitor banks and a secondary input end of Reactor banks 52 and change The ac bus in power station is connected.In the present embodiment, SVG type dynamic reactive compensator 51 uses DTWGBC-20kV type dynamic reactive Compensator, Capacitor banks and Reactor banks 52 are the existing capacitor of transformer station and Reactor banks.

As it is shown in figure 1, SVG type dynamic reactive compensator 51 is also associated with thermal losses UTILIZATION OF VESIDUAL HEAT IN unit 6, thermal losses waste heat Range site 6 can effectively solve that SVG type dynamic reactive compensator 51 caloric value is big, self thermal losses big, must use water-cooled, runs High in cost of production problem, it is achieved super-current power unit high efficiency and heat radiation, realizes self thermal losses simultaneously and recycles.

As shown in Figure 4, SVG type dynamic reactive compensator 51 is installed in the power cabinet 511 closing space 510, power cabinet The top of 511 is provided with interconnective blower fan 512 and ducting outlet 513, uses the room air closing space 510 to close and follows Ring, then avoid dust entrance indoor with the sealed type air cooling way of outdoor heat exchange, it is ensured that SVG type dynamic reactive compensator Stablizing and reliable of 51 working environments.

As shown in Figure 4, thermal losses UTILIZATION OF VESIDUAL HEAT IN unit 6 includes radiator 61 and source pump 62, and source pump 62 includes Vaporizer 621, condenser 622 and compressor pump 623, radiator 61 includes separate wind passage and the first aquaporin, evaporation Device 621 includes the second separate aquaporin and first medium passage, and condenser 622 includes that separate second medium leads to Road and UTILIZATION OF VESIDUAL HEAT IN passage, the first aquaporin arrival end of radiator 61 connects with ducting outlet 513, the port of export and closing space 510 connections, by circulating pump circulation between the first aquaporin, the second aquaporin, first medium passage, second medium passage Between by compressor pump 623 circulation, UTILIZATION OF VESIDUAL HEAT IN passage includes that hot water heats passage, and hot water heats passage end and is provided with cold Water water inlet pipe 624 (connecing tap water), the other end are provided with hot water outlet pipe 625, the hot water of exportable about 55 DEG C.By above-mentioned knot Structure, it is possible to realize the air-cooled cooling to SVG type dynamic reactive compensator 51, and by SVG type dynamic reactive compensator 51 Interior Space Converting heat in gas becomes utilizable about 55 DEG C hot water output, it is achieved self heat waste of SVG type dynamic reactive compensator 51 The energy-conserving and environment-protective of consumption are reclaimed and utilize, and utilize source pump to make indoor cold wind temperature can be far below ambient temperature, thus Ensure that cooling system remains to reliability service under summer high temperature weather.In the present embodiment, radiator 61 uses RBLQ-60 type to dispel the heat Device, power device high efficiency and heat radiation technology based on complex superconducting flat-plate heat pipe, reduces power model heat generation density, simultaneously to wind Road is optimized design etc., thus improves the heat exchanger effectiveness of thermal losses UTILIZATION OF VESIDUAL HEAT IN unit 6.Source pump 62 uses commercially available RLJH-22 type condenser 62.The present embodiment uses power device high efficiency and heat radiation technology based on complex superconducting flat-plate heat pipe, drops Low power module heat generation density, is optimized design etc. simultaneously, thus improves the heat friendship of thermal losses UTILIZATION OF VESIDUAL HEAT IN unit 6 air channel Change efficiency.

In the present embodiment, UTILIZATION OF VESIDUAL HEAT IN passage also includes air heat dissipation channel, when hot water is dissolved nowhere when, it is possible to straight Connect and utilize air that medium is cooled down, thus improve the availability of source pump 62.

Due to the present embodiment SVG type dynamic reactive compensator 51 two secondary input ends respectively with Capacitor banks and Reactor banks The secondary outfan of 52, the TT&C system of transformer station (are specially transformer station's existing CKXT-12 type observing and controlling dress in the present embodiment Put) and the scheduling AVC system (in the present embodiment be specially transformer station's existing AVC-8 type system) of transformer station be connected, therefore Can coordinate to control in conjunction with the TT&C system of existing transformer station and scheduling AVC system feasible region voltage.In the present embodiment comprehensively Consider electrical network demand, propose Target Assignment such as our station dynamic electric voltage, steady state voltage, neighboring station voltage and reactive-load compensations different Regulation and control priority, while meeting high priority target, take into account the control target that priority is relatively low as far as possible, thus realize many Goal coordination controls, as shown in table 1.

Table 1: control target and priority list.

The TT&C system of transformer station can to SVG type dynamic reactive compensator 51 provide every, transformer station line voltage distribution, electric current, The information such as meritorious and idle, it is achieved neighboring station voltage prediction, according to the computational methods such as formula (1) of node voltage and power；

$U_s=\sqrt{{(U_0+\frac{PR+QX}{U_0})}^2+{\left(\frac{PX-QR}{U_0}\right)}^2}---\left(1\right)$

In formula (1), U_sFor neighboring station voltage to be predicted, U₀For our station voltage, take the meansigma methods of three-phase, R and X be our station with Impedance on this station interconnection, P and Q is our station and gaining merit and idle on this station interconnection, and P, with inflow our station for just, flows out Our station is negative, Q with flow into our station perception for just, the perception leaving our station is negative.The trend utilizing transmission line of electricity is joined with impedance Number, the busbar voltage of real-time estimation adjacent substations；Export idle when neighboring station voltage out-of-limit by control device, thus maintain Voltage stabilization in certain area.

As it is shown in figure 5, include in the step carrying out reactive requirement and distribution: 1, according to each phase in formula (1) estimation area The neighboring station voltage of adjacent transformer station；2, carry out reactive requirement analysis, first determine whether that our station transient voltage is the most stable, the most gradually increase Add output perception or capacitive reactive power Q* until our station Transient Voltage Stability；Judge that our station voltage is the most out-of-limit again, the most gradually increase Add and export perception or capacitive reactive power Q* until our station steady state voltage is stable, the most gradually realize neighboring station voltage and coordinate control, impact Property load dynamic compensation and dynamic reactive capacity Initiative Inventory Management；3, carry out without the distribution of work, when perception or capacitive reactive power Q* output, First realize the reactive-load compensation of certain capacity with self capacity of SVG type dynamic reactive compensator 51, at SVG type dynamic reactive compensator When 51 capacity can not meet actual reactive requirement, utilize SVG type dynamic reactive compensator 51 control transformer station's inner capacitor group and Capacitor or reactor in Reactor banks 52 realize reactive-load compensation, until meeting our station and neighboring station Reactive-power control demand.

The above is only preferred implementation of the present utility model, and protection domain of the present utility model is not limited merely to Above-described embodiment, all technical schemes belonged under this utility model thinking belong to protection domain of the present utility model.Should refer to Go out, for those skilled in the art, without departing from the some improvement under this utility model principle premise and Retouching, these improvements and modifications also should be regarded as protection domain of the present utility model.

Claims (8)

1. A 500kV substation intensive DC deicing system with SVG function, characterized in that it includes electric energy measurement and protection device (1), transformer (2), operation mode switcher (3), DC deicing unit (4) and the dynamic reactive power compensation unit (5), the primary side of the transformer (2) is connected to the AC busbar of the substation through the electric energy measurement and protection device (1), and the secondary side of the transformer (2) is connected by running The mode switcher (3) is respectively connected with the DC ice melting unit (4) and the dynamic reactive power compensation unit (5). 2. The 500kV substation intensive DC ice-melting system with SVG function according to claim 1, characterized in that: the DC ice-melting unit (4) includes a rectifying component (41), an induced voltage suppressor (42) and a three-phase ice-melting line switcher (43), the AC side of the rectification component (41) is connected to an input end of the operation mode switcher (3), and the DC side of the rectification component (41) is sequentially passed through the induced voltage The suppressor (42) is connected to the three-phase ice-melting circuit switcher (43), and provides an ice-melting output voltage through the output terminal of the three-phase ice-melting circuit switcher (43). 3. The 500kV substation intensive DC deicing system with SVG function according to claim 1, characterized in that: the dynamic reactive power compensation unit (5) includes an SVG type dynamic reactive power compensator (51) and a capacitor group and reactor group (52), the SVG type dynamic reactive power compensator (51) is connected to the other input end of the operating mode switcher (3), and the SVG type dynamic reactive power compensator (51) The secondary input terminals are respectively connected to the secondary output terminals of the capacitor bank and the reactor bank (52), the measurement and control system of the substation and the dispatching AVC system of the substation, and the primary input terminals of the capacitor bank and the reactor bank (52) are connected to the substation connected to the AC bus. 4. The 500kV substation intensive DC deicing system with SVG function according to claim 3, characterized in that: the SVG dynamic reactive power compensator (51) is also connected with a heat loss waste heat utilization unit (6) . 5. The 500kV substation intensive DC deicing system with SVG function according to claim 4, characterized in that: the SVG dynamic var compensator (51) is installed in the power cabinet of the closed space (510) (511), the top of the power cabinet (511) is provided with a fan (512) and an air duct outlet (513) connected to each other. 6. The 500kV substation intensive DC deicing system with SVG function according to claim 5, characterized in that: the heat loss waste heat utilization unit (6) includes a radiator (61) and a heat pump unit (62), The heat pump unit (62) includes an evaporator (621), a condenser (622) and a compression pump (623), the radiator (61) includes independent air passages and first water passages, and the evaporator ( 621) includes a second water channel and a first medium channel that are independent of each other, and the condenser (622) includes a second medium channel and a waste heat utilization channel that are independent of each other, and the inlet end of the first water channel of the radiator (61) It communicates with the outlet of the air duct (513), and the outlet end communicates with the closed space (510). The first water channel and the second water channel circulate through the circulating pump, and the first medium channel and the second medium channel communicate with each other. Circulating through the compression pump (623), the waste heat utilization channel includes a hot water heating channel, one end of the hot water heating channel is provided with a cold water inlet pipe (624), and the other end is provided with a hot water outlet pipe (625). 7. The 500kV substation intensive DC deicing system with SVG function according to claim 6, characterized in that: the waste heat utilization channel also includes an air cooling channel. 8. The 500kV substation intensive DC deicing system with SVG function according to any one of claims 1 to 7, characterized in that: the connection group of the transformer (2) is Y/y0d11, and the The transformer (2) is an axial double-split transformer with the same concentricity of the upper and lower windings, and the two secondary windings of the axial double-split transformer share one iron core magnetic circuit and are axially split.