179 results about "Three phase transformer" patented technology

The invention provides a three-phase transformer parameter estimation method and device, computer equipment and a medium, and belongs to the field of electrical control, and the method comprises the steps: obtaining synchronous phasor data of a target three-phase transformer; an improved LASSO algorithm is constructed; preprocessing the data through an improved LASSO algorithm; constructing a positive sequence component equivalent model of the target three-phase transformer; based on the positive sequence component equivalent model, determining a correlation among a plurality of circuit parameters of the target three-phase transformer, and determining the plurality of circuit parameters; and estimating structure parameters and magnetic circuit parameters of the target three-phase transformer based on the circuit parameters to obtain corresponding estimation results. Thus, complex specific experiments do not need to be carried out on the target three-phase transformer, on one hand, loss is low, the application range is wide, the parameters of the target three-phase transformer can be comprehensively estimated, on the other hand, better adaptability is achieved for complex conditions such as nonlinear characteristics of the transformer, and parameter evaluation is more accurate.

The invention relates to a flexible loop closing device and a flexible loop closing method. The flexible loop closing device is arranged between a first power distribution network and a second power distribution network, and comprises a three-phase full-bridge inverter and a three-phase transformer, the three-phase output end of the three-phase full-bridge inverter is connected with the primary side of the three-phase transformer. The secondary side of the three-phase transformer is connected with a control switch, and each control switch is connected in series between the first power distribution network and the second power distribution network; and the flexible loop closing device controls the control switch to be closed under the condition that the actual output voltage of the flexible loop closing device meets a preset condition, so that flexible loop closing of the first power distribution network and the second power distribution network is realized. By adopting the device, the switch can be controlled to be switched on under the condition that the actual output voltage of the flexible loop closing device meets the preset condition, at the moment, flexible loop closing of the first power distribution network and the second power distribution network is achieved, and large impact current generated by direct loop closing is restrained.

The invention discloses a power distribution network flexible interconnection topology adopting frequency mixing modulation and a control method, and belongs to the technical field of power generation, power transformation or power distribution. The topology comprises a full power module, a first three-phase transformer, an intermediate frequency converter, a power frequency converter, a series APF and a second three-phase transformer, wherein an alternating current port of the full power module and an alternating current port of the series APF are connected in series between a first alternating current system and a second alternating current system; a high-voltage side winding of the first three-phase transformer is connected with an alternating-current port of the full-power module, and a low-voltage side winding of the first three-phase transformer is connected with an alternating-current port of the intermediate-frequency converter; a high-voltage side winding of the second three-phase transformer is connected with the second alternating current system, and a low-voltage side winding is connected with an alternating current port of the power frequency converter; the direct current ports of the intermediate frequency converter and the power frequency converter are connected through a direct current bus with a bus capacitor. According to the control method, frequency mixing modulation is adopted, the functions of fault isolation, dynamic power flow adjustment and the like are achieved, and the size and the manufacturing cost are reduced.

The invention discloses a voltage regulating device and a control protection system and method thereof, and the device comprises a first transformer, a second transformer, a switching device, an AC contactor, an input circuit breaker, an output circuit breaker, a bypass circuit breaker, and a controller. The second transformer is a three-phase transformer with multiple secondary voltage classes, and the number of the selected switching devices depends on the number n of the secondary voltage classes of the second transformer. The controller is used for collecting current and voltage of a power grid system side, collecting current and voltage of secondary side loops of the two transformers, turning off contactors of the loops of all phases, turning on and turning off switching devices and turning off circuit breakers. According to the invention, the problems that the economical efficiency of large-scale application is low and the reliable operation cannot be ensured due to unreasonable transformer design parameters of an existing voltage regulating device under different load conditions at present are solved.

The invention discloses a true bipolar flexible low-frequency power transmission system. An existing flexible low-frequency power transmission system mainly adopts a three-phase power transmission structure which is the same as that of a power frequency power transmission system, and popularization of the flexible low-frequency power transmission system is restricted. The system comprises two frequency conversion stations, a low-frequency positive electrode line and a low-frequency negative electrode line, each frequency conversion station comprises an anode frequency converter and a cathode frequency converter; one side of the anode frequency converter is connected with a power frequency AC power grid through a three-phase transformer, and the other side is connected with a low-frequency transmission line through a single-phase three-winding transformer. One side of the cathode frequency converter is connected with the power frequency AC power grid through the three-phase transformer, and the other side is connected with the low-frequency transmission line through the single-phase three-winding transformer. The low-frequency positive electrode circuit and the low-frequency negative electrode circuit have the same voltage amplitude, the same frequency and a phase difference of 180 degrees. According to the invention, interconnection and mutual assistance among different three-phase alternating current systems are realized through a two-phase power transmission structure, a new system structure is expanded for low-frequency power transmission, and the line construction cost is reduced.

The invention discloses a three-phase transformer winding top deformation diagnosis method based on high-voltage oscillation wave detection, and relates to the field of transformer safety guarantee and fault diagnosis. Firstly, a mechanical device for controlling deformation enables the top of a winding of a transformer to generate deformation of different degrees, and deformation of the winding of the transformer is simulated. And the high-voltage oscillatory wave test device is further used to obtain oscillatory wave test curves under different fault degrees. Finally, according to the diagnosis method based on the high-voltage oscillatory waves, normalization processing is carried out on transformer winding oscillatory wave time sequence signals through a normal cumulative distribution function, a time sequence is mapped to a discrete symbol sequence, then the entropy value of the symbol sequence is calculated through a fuzzy membership function, and the high-voltage oscillatory waves are obtained. The method can effectively reflect the irregularity and complexity of the signal. The deformation fault of the three-phase power transformer can be safely and efficiently detected and diagnosed, and a guarantee is provided for power transmission safety.

The invention discloses a power transformer optimization design method considering iron core service magnetic characteristics. The power transformer optimization design method comprises the following steps: carrying out magnetic characteristic measurement on silicon steel sheets at different temperatures by adopting an advanced magnetic characteristic measurement device; through high-precision experimental measurement, a silicon steel material loss characteristic database covering a wide temperature range, multiple frequency bands and different magnetic densities is established; compiling a calculation program of the three-phase transformer considering the service characteristics of the iron core by adopting a C language and integrating an electromagnetic calculation process; and an improved genetic algorithm is adopted, and according to the single-target optimization mathematical model, the silicon steel material loss characteristic database is combined, and the improved genetic algorithm is utilized twice to obtain an optimal design scheme with the minimum power transformer cost and the minimum total loss as targets. The influence of actual working conditions on loss factors is considered, an advanced heuristic algorithm is adopted to replace a traditional optimization mode, and the problems that a traditional design method cannot consider the actual working conditions, and a traditional optimization algorithm is low in calculation efficiency are solved.

The invention discloses high-power three-phase transformer air duct manufacturing equipment, and relates to the field of transformer equipment manufacturing, the high-power three-phase transformer air duct manufacturing equipment comprises a coil and an adjusting piece, the coil is provided with an adjusting device, the adjusting device linearly moves on the coil, a lifting groove is formed in the position, corresponding to the adjusting device, of the coil, and the adjusting piece is arranged in the lifting groove. The adjusting device is located in the lifting groove, an adjusting channel is formed in the side edge of the lifting groove, and the adjusting channel communicates with the lifting groove; the adjusting piece is assembled with the adjusting device through the adjusting channel, and the adjusting piece drives the adjusting device to ascend and descend in the lifting groove; the adjusting device adjusts the perimeter of the coil through the lifting effect so that the wire can be wound into the air duct through the coil, and the inner diameter of the air duct can be adjusted through adjustment of the adjusting piece.

The invention discloses a three-phase transformer single-phase grounding short circuit leakage magnetic field simulation analysis method based on a combination of three single-phase transformers, and aims to solve the problem that leakage magnetic field distribution and electromagnetic force conditions of a three-phase transformer formed by the combination of the three single-phase transformers cannot be accurately simulated when a single-phase grounding short circuit fault occurs in the prior art. Constructing a three-dimensional finite element geometric model of the single-phase transformer according to parameters such as the actual size of the transformer; then importing ansys Maxwell software, and adjusting the position to generate a three-dimensional calculation model; setting material attributes of each field domain, creating a winding, and constructing an external circuit matched with different working conditions; then setting a solution domain and boundary conditions, carrying out reasonable mesh generation, and selecting a transient field for simulation solution; and finally, checking simulation results such as short-circuit current and magnetic flux leakage nephograms. The method can accurately analyze the single-phase grounding short circuit fault of the transformer, accurately simulate the fault condition, find hidden dangers in advance, and provide reliable support for fault prevention and scientific design.

The present invention discloses an AC voltage stabilization system with reactive power compensation, which mainly solves the problems of poor power quality of existing power grids and slow response speed of existing power grid voltage stabilizers. The AC voltage stabilization system includes a three-phase power input terminal and a three-phase power output terminal, a three-phase transformer with one end of the primary winding connected to the three-phase power input terminal, a three-phase rectifier circuit connected to the three-phase power input terminal, and a dual-core total control unit, an AC voltage stabilization unit connected to both the dual-core total control unit and the three-phase rectifier circuit, and a reactive power compensation unit connected to the dual-core total control unit and the three-phase power input terminal. Through the above design, the system can effectively stabilize the grid voltage and realize dynamic reactive power compensation of the grid at the same time, and has fast response speed, low cost, and convenient maintenance, and can effectively improve the actual output capacity and power quality of the grid. Therefore, it is suitable for promotion and application.

A three-phase transformer configured to transform a three-phase voltage. The transformer includes first, second, and third toroidal transformers. The first toroidal transformer is configured to transform a first phase of the three-phase voltage. The second toroidal transformer is electrically connected to the first toroidal transformer. The second toroidal transformer is configured to transform a second phase of the three-phase voltage. The third toroidal transformer is electrically connected to the first toroidal transformer and the second toroidal transformer. The third toroidal transformer is configured to transform a third phase of the three-phase voltage.

The application discloses a three-phase resonant converter, which comprises a three-phase transformer, a three-phase inverter circuit and a two-phase resonant branch, wherein the three-phase transformer comprises first to third primary windings and first to third secondary windings; the three-phase inverter circuit comprises first to third bridge arms, and each bridge arm is connected between a first input end and a second input end; the connection point of two switch tubes of the second bridge arm is connected with one end of the second primary winding; the two-phase resonant branch comprises first and second resonant branches, and each resonant branch is connected between the connection point of two switch tubes of the first bridge arm and one end of the first primary winding or between the connection point of two switch tubes of the third bridge arm and one end of the third primary winding; and the three-phase resonant converter further comprises a secondary rectifier circuit; wherein one end of the first, second and third primary windings and one end of the first, second and third secondary windings are homonymous ends; and the other end of the first, second and third primary windings and the other end of the first, second and third secondary windings are heteronymous ends. The three-phase resonant converter adopts the two-phase resonant branch, thereby reducing the complexity of the topology, reducing resonant components and lowering the design cost.

A bidirectional DC-DC conversion apparatus and a charging pile. The bidirectional DC-DC conversion apparatus includes a first power conversion circuit, a second power conversion circuit, a three-phase transformer, three phase resonant circuits, a resonant switching switch circuit, and an inductor circuit. Each phase of resonant circuit includes a first capacitor and a first inductor that are connected in series. One end of each phase of resonant circuit is connected to the first power conversion circuit, and the other end of each phase of resonant circuit is connected to the second power conversion circuit via the three-phase transformer. The resonant switching switch circuit is configured to connect a circuit between either of two ends of each phase of resonant circuit and the inductor circuit to enable each phase of resonant circuit and the inductor circuit to form an LLC resonant circuit.

The present invention discloses a method for reducing the order of a transformer temperature field model based on the Krylov subspace, belonging to the technical field of temperature field simulation of oil-immersed three-phase transformers. The present invention includes: Step 1. According to the actual physical dimensions of the transformer, construct a simulation model of the oil-immersed three-phase transformer and appropriately simplify the model. Step 2. Establish an electromagnetic field simulation model, use an eddy current solver, and simulate to obtain the transformer loss distribution. Step 3. Take the obtained transformer loss distribution as the excitation source of the fluid field, establish a fluid field simulation model, realize the coupled analysis of the electromagnetic field and the fluid field, and obtain the temperature field distribution characteristics of the oil-immersed three-phase transformer. Step 4. Build a reduced-order model for the transformer temperature field based on the Krylov subspace method. The present invention realizes the rapid simulation calculation of the physical field, reduces the simulation time, and further constructs a digital twin model of the transformer.

The application provides a residual magnetism estimation method and device for a three-phase transformer and electronic equipment. The estimation method comprises: for any single-phase transformer in the three-phase transformer, obtaining the voltage amplitude U m , the angular frequency ω of the power supply and the primary-side coil turn number N1; calculating the residual magnetism amplitude Φ m according to the voltage amplitude U m and the angular frequency ω of the power supply in combination with formula (1); obtaining the voltage closing angle α, the opening-starting time t open and the opening-ending time t open + Δt of the single-phase transformer at no-load opening; and calculating the residual magnetism Φ r of the single-phase transformer after opening according to the residual magnetism amplitude Φ m , the voltage closing angle α, the opening-starting time t open and the opening-ending time t open + Δt in combination with formula (2). The application calculates the residual magnetism Φ r of the single-phase transformer after opening in combination with formula (2), thereby replacing the complex integral term containing U C , reducing the calculation difficulty, and optimizing the accuracy of the residual magnetism estimation method for the transformer.

The present invention discloses a three-phase calculation method, device and storage medium for a transformer based on matrix dimensionality reduction. Among them, the method includes: calculating the resistance value and reactance value of a three-phase transformer according to the nameplate information of the three-phase transformer; calculating the first turns ratio on the primary side of the three-phase transformer and the second turns ratio on the secondary side of the three-phase transformer according to the tap position and rated voltage of the three-phase transformer; determining the full matrix of the three-phase transformer based on the resistance value, reactance value, first turns ratio and second turns ratio of the three-phase transformer; performing dimensionality reduction processing on the full matrix of the three-phase transformer according to a preset matrix dimensionality reduction rule to obtain a dimensionality reduction matrix of the three-phase transformer; and superimposing the dimensionality reduction matrix of the three-phase transformer into the system matrix for three-phase calculation to perform three-phase power flow calculation and determine the three-phase power flow result of the three-phase transformer. The present invention can retain the physical meaning of transformer variables during the process of order reduction, which is beneficial to calculating various variables of the transformer, and at the same time reduces the amount of calculation.

Electronic component (15), comprising: - a magnetic circuit (22), - two electrical conductors (31, 32) each having a portion (27) arranged around the same part of the magnetic circuit, each of said portions forming between a first and a second end a winding, these two windings being in inductively coupled with each other via the magnetic circuit (22), and - a support (30) of the two electrical windings (31, 32), arranged between said electrical conductors and said portion (27) of the magnetic circuit, this support (30) comprising: - a wall (90) around which the electrical windings are arranged, and - three flanges (92, 93, 94) offset along the longitudinal axis of the support (30), so that one of the electrical windings is arranged between the first (92) and the second (93) flange and the other of the electrical windings is arranged between the second (93) and the third (94) ledge,characterized in that at least one step (95) is provided in the height of the first rim (92), so as to locally reduce the height of the first rim (92).,

The invention relates to an electronic component (15) comprising: - a magnetic circuit (22); - two electrical conductors (31, 32) each having a portion (27) that is arranged around the same part of the magnetic circuit, each of the portions, between a first end and a second end, forming a winding, these two windings being inductively coupled to one another via the magnetic circuit (22); and - a support (30) for the two electrical windings (31, 32), the support being arranged between the electrical conductors and the portion (27) of the magnetic circuit, characterized in that the support (30) comprises: - a wall (90) around which the electrical windings are arranged, and - three flanges (92, 93, 94) offset along the longitudinal axis of the support (30), such that one of the electrical windings is arranged between the first flange (92) and the second flange (93) and that the other of the electrical windings is arranged between the second flange (93) and the third flange (94), characterized in that the wall comprises at least one opening formed axially between the first flange (92) and the third flange (94).

The invention provides a method for measuring low-voltage direct-current resistance of a three-phase transformer bank, and belongs to the technical field of transformer measurement. The invention provides a method for measuring low-voltage direct-current resistance of a three-phase transformer bank. The method comprises the following steps of: connecting all phases of windings on a high-voltage side together; connecting the high-voltage side three-phase winding with the low-voltage side three-phase winding; direct current is introduced into the high-voltage side three-phase winding; measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured and the current of the corresponding high-voltage side winding or the corresponding low-voltage side winding; and calculating the direct current resistance of the to-be-measured phase according to the measured voltage and current. The three-phase transformer bank low-voltage direct-current resistance measuring method provided by the invention has the advantages that during measurement, direct current is introduced into the high-voltage side three-phase windings, so that the current in the three high-voltage side windings forms a loop, the number of excitation ampere turns of the three-phase iron core columns is increased, the three iron core columns are magnetically saturated, the inductance of coils is reduced, and the measurement accuracy is improved. And the test time is shortened.

The utility model relates to the technical field of transformers, in particular to a multi-tap high-power three-phase transformer which comprises a first core column, a second core column and a third core column. A first primary winding and a first secondary winding are wound outside the first core column; a second primary winding and a second secondary winding are wound outside the second core column; and a third primary winding and a third secondary winding are wound outside the third core column. According to the utility model, the first transfer bar is connected to the first end connecting bar or the first middle connecting bar, the second transfer bar is connected to the second end connecting bar or the second middle connecting bar, and the third transfer bar is connected to the third end connecting bar or the third middle connecting bar, so that different loops on the primary side can be conducted; therefore, multi-tap input is achieved on the input side, connecting bars on the output end side are reduced, and the overall structure is neater and more reliable.

The application discloses a kind of traction network impedance simulation system and control method based on voltage source converter, and main substation is simulated by three-phase transformer, and traction substation is simulated by single-phase transformer.Three-phase transformer steps down power supply voltage, and the voltage on the high-voltage side of the single-phase transformer of the traction substation group comes from the same two-phase voltage of the three-phase transformer, which supplies the traction network after stepping down the voltage. Among them, for the impedance simulation of the traction network, the movement of the train is equivalent to the change of the line impedance, and the VSC is used to simulate the impedance of the traction network. The VSC is used to realize the change of the impedance of the traction network on both sides of the train during the train operation. The VSC device is used to simulate the impedance of the traction network on both sides of the train during the train operation, and relevant researchers can use the invention to carry out experimental verification of the related theory of the new type of substation group bilateral traction power supply system, and promote the development of the new type of substation group bilateral traction power supply technology.

A three-phase transformer configured to transform a three-phase voltage. The transformer includes first, second, and third toroidal transformers. The first toroidal transformer is configured to transform a first phase of the three-phase voltage. The second toroidal transformer is electrically connected to the first toroidal transformer. The second toroidal transformer is configured to transform a second phase of the three-phase voltage. The third toroidal transformer is electrically connected to the first toroidal transformer and the second toroidal transformer. The third toroidal transformer is configured to transform a third phase of the three-phase voltage.

The utility model discloses a transformer winding and three-phase transformer relates to transformer technical field, the transformer winding includes the two coil that distributes along the vertical direction, the opposite end face of two coil is both the meshing surface, each meshing surface protrudes towards the other meshing surface to form a plurality of protrusions, the multiple protrusions are distributed in the circumferential direction of the corresponding meshing face at intervals, a groove is formed between any two adjacent protrusions on each meshing face, the multiple protrusions of any meshing face and the multiple grooves of the other meshing face are consistent in number and correspond to each other in a one-to-one mode, and the correspondingly-arranged protrusions and the grooves are matched in shape. And the bulges on one meshing surface are inserted into the corresponding grooves on the other meshing surface, so that the two coils are meshed. According to the transformer winding, when the upper coil and the lower coil are in butt joint, the protrusions of the upper coil are inserted into the grooves of the lower coil, so that the upper coil and the lower coil are tightly attached, the upper coil and the lower coil can be effectively prevented from shaking relatively in the transportation process, and reliability is better.

The application provides a short-circuit protection method and device for a transformer. The short-circuit protection method comprises: obtaining output voltages of a plurality of output lines of at least one winding on a low-voltage side of the transformer; performing real-time calculation and short-circuit judgment according to the output voltages, and sending a protection signal when the short-circuit is judged. The short-circuit protection device comprises: a voltage obtaining unit for obtaining output voltages of a plurality of output lines of at least one winding on a low-voltage side of the transformer; a short-circuit judgment unit for performing real-time calculation and short-circuit judgment according to the output voltages, and sending a protection signal when the short-circuit is judged; and a controllable circuit breaker arranged on a high-voltage side of the transformer and connected with the short-circuit judgment unit, for cutting off the connection between the transformer and a power grid after receiving the protection signal. The application provides a short-circuit protection method and device based on voltage characteristics, realizes short-circuit protection of a three-phase transformer through line voltage detection, greatly reduces the protection cost, and improves the protection reliability.

Certain aspects of the present disclosure provide techniques for charging a plurality of electric assets. One embodiment of a system includes EVSE for charging an EV, the EVSE including a three-phase transformer for sending energy to the EV and an edge environment that is coupled to the EVSE. The edge environment may include logic that causes the system to receive configuration information associated with the EVSE, where the configuration information includes a phase assignment for the EVSE, determine whether the phase assignment is labeled as unknown, where the phase assignment of unknown was applied in response to a determination that a previous phase assignment was invalid or missing, and generate an optimization problem for the EVSE. In some embodiments, the logic may cause the system to solve the optimization problem to generate a trajectory for the three-phase transformer and cause implementation of the trajectory on the EVSE.

Electronic component (15), comprising: - a magnetic circuit (22), - two electrical conductors (31, 32) each having a portion (27) arranged around the same part of the magnetic circuit, each of said portions forming between a first and a second end a winding, these two windings being in inductively coupled with each other via the magnetic circuit (22), and - a support (30) of the two electrical windings (31, 32), arranged between said electrical conductors and said portion (27) of the magnetic circuit, characterized in that the support (30) comprises: - a wall (90) around which the electrical windings are arranged, and - three rims (92, 93, 94) offset along the longitudinal axis of the support (30),such that one of the electrical windings is arranged between the first (92) and the second (93) rim and the other of the electrical windings is arranged between the second (93) and the third (94) rim, characterized in that the wall comprises at least one opening arranged axially between the first rim (92) and the third rim (94). Abstract figure: Fig.27,

The application discloses a high-power synchronous motor test system, which comprises a test motor M1, a test motor M2, an auxiliary test motor M3, a three-phase transformer, a first variable-frequency power supply, a second variable-frequency power supply and a voltage sensor. The test motor M1 is coaxially connected with the test motor M2, and the auxiliary test motor M3 is coaxially connected with the test motor M1. The first variable-frequency power supply is circuit-connected with the auxiliary test motor M3, so that the auxiliary test motor M3 drives the test motor M1 and the test motor M2 to synchronously rotate. The output end of the second variable-frequency power supply is circuit-connected with the primary side of the three-phase transformer. The alternating current end of the test motor M1 is circuit-connected with one end of the three open windings of the secondary side of the three-phase transformer. The other ends of the three open windings of the secondary side of the three-phase transformer are circuit-connected with the alternating current end of the test motor M2. The second variable-frequency power supply acquires the three-phase voltage signal of the alternating current end of the test motor M1 through the voltage sensor. The application reduces the test cost and reduces the harmonic influence.

The invention discloses a loss optimization method and system for an integrated three-phase transformer, and the method comprises the steps: building a transformer equivalent magnetic circuit model according to a magnetic core structure of the integrated three-phase transformer, and obtaining an equivalent magnetic circuit diagram; calculating the magnetic flux value of each part of the transformer magnetic core according to the equivalent magnetic circuit diagram; according to the magnetic flux value of each part, calculating to obtain a balanced three-phase inductance value; according to the three-phase inductance value and the magnetic flux distribution, a total magnetic core loss value is obtained through calculation by adopting a segmented integration mode through a Steinmez formula; under the given working condition and device parameters, the size of each part of the magnetic core is selected as an optimization variable, the three-phase inductance and magnetic flux balance and the side column and cover plate magnetic flux consistency serve as optimization constraints, optimization calculation is conducted according to the total magnetic core loss value, and the optimal magnetic core size parameter is obtained. According to the invention, the problems of non-uniform magnetic circuit distribution and asymmetric transformer parameters caused by unmatched magnetic core sizes can be solved, so that the performance and efficiency of the transformer are improved.

The application discloses a high-voltage direct-current converter topology and a control method thereof, and belongs to the technical field of power generation, power transformation or power distribution. The topology is composed of a high-voltage side filter inductor, a three-phase MMC inverter circuit, a three-phase leakage inductor, a three-phase transformer, a three-phase diode rectifier circuit, a medium-voltage side filter inductor and a medium-voltage side filter capacitor. The topology structure of the application can realize higher reliability, lower cost and smaller size by the relatively mature high-voltage side modular structure and the medium-voltage side diode series connection technology. By precisely controlling the three-phase current to be a positive-negative half-cycle symmetrical trapezoidal current, reliable commutation of the three-phase rectifier diode is realized, and meanwhile, smooth direct-current is synthesized on the high-voltage side and the medium-voltage side, so that the operation efficiency of the converter and the port power quality are significantly improved, and the filter size is reduced.

An electrically insulated connector holder for a three-phase transformer wherein the connector holder (40) is a separate body comprising six main electrical connectors (50) attached thereto, each comprising a main terminal (51, 52, 53, 54, 55, 56); and a primary connector (60) conductively embedded in three portions (41, 42, 43) thereof, in each portion comprising a primary terminal (61, 62, 63), the primary terminal being external to the connector holder; and wherein the connector holder (40) further comprises a secondary connector (70), which is electrically conductive and insulated from the primary connector (60), embedded in three portions (41, 42, 43), each portion comprising a secondary terminal (71, 72, 73), which is external to the connector holder (40), the secondary connector (70) interconnecting the three secondary windings.