CN-119519365-B - Topological structure and method of single bridge arm power electronic transformer

CN119519365BCN 119519365 BCN119519365 BCN 119519365BCN-119519365-B

Abstract

The invention discloses an improved single-bridge arm power electronic transformer topological structure, which belongs to the field of power electronic converters and comprises a three-phase alternating current filter inductor L g , a phase main bridge arm circuit, a three-phase public half-bridge circuit, a high-frequency series inductor capacitor L 1 /C 1 , a high-frequency isolation transformer, a low-voltage side rectifier and a public isolation DC-DC converter. The topological structure belongs to a single-stage structure, only one string of bridge arms is needed for each phase, the mixed frequency conversion is directly adopted to realize the power transmission on the alternating current side and the direct current side, the number of devices of the power electronic transformer can be reduced, the cost is reduced, a three-phase common half-bridge circuit is introduced, the multi-frequency coupling degree of the bridge arms is reduced, the control is simplified, the number of sub-modules of the main bridge arms is optimized by combining reasonable circuit parameter design, and the efficiency can be improved. The topology is suitable for all applications requiring medium voltage ac to low voltage dc conversion.

Inventors

LIU JINJUN
DENG ZHIFENG
DU SIXING

Assignees

西安交通大学

Dates

Publication Date: 20260505
Application Date: 20241125

Claims (3)

1. The working method of the single-bridge arm power electronic transformer topological structure is based on the single-bridge arm power electronic transformer topological structure and is characterized by comprising a three-phase alternating current filter inductor L g , a phase main bridge arm circuit, a three-phase public half-bridge circuit, a high-frequency series inductor capacitor L 1 /C 1 , a high-frequency isolation transformer, a low-voltage side rectifier and a public isolation DC-DC converter; the three-phase alternating current filter inductor Lg is used for filtering high-frequency harmonic waves in three-phase alternating current; the phase main bridge arm circuit is used for converting three-phase alternating current into high-frequency alternating current by adopting mixed frequency conversion; the three-phase common half-bridge circuit is used for assisting the phase main bridge arm circuit to perform voltage and current transformation; The high-frequency series inductance capacitor L 1 /C 1 is used for filtering power frequency fundamental waves and high-frequency PWM harmonic waves generated by the phase main bridge arm circuit and the three-phase common half-bridge circuit; The high-frequency isolation transformer is used for realizing electric isolation and voltage conversion and transmitting high-frequency alternating current from a primary side to a secondary side; the low-voltage side rectifier is positioned at the secondary side of the high-frequency isolation transformer and is used for converting high-frequency alternating current into low-voltage direct current and transmitting most of power of the circuit; a common isolation DC-DC converter for supplementing the transmission of the remaining portion of power; the phase main bridge arm circuit is formed by connecting N sub-modules in series, wherein N is a positive integer greater than or equal to 1, the sub-modules are full-bridge circuits formed by four switching tubes and a direct-current side capacitor, the upper switching tube and the lower switching tube are conducted in a complementary mode, and the midpoint of each half-bridge is respectively led out of an external port Q1/Q2, wherein the Q2 port of one sub-module is connected with the Q1 port of the other sub-module, and the sub-modules are sequentially connected in series to form a phase main bridge arm; a. the a-phase main bridge arm leads out an upper port and a lower port Ma1/Ma2, the b-phase main bridge arm leads out an upper port and a lower port Mb1/Mb2, and the c-phase main bridge arm leads out an upper port and a lower port Mc1/Mc2; The upper port of the phase main bridge arm is connected with a three-phase medium-voltage alternating current power grid through a filter inductor, wherein for a phase a, a port Ma1 is connected with an a-phase power grid va through a filter inductor Lg, for a phase b, a port Mb1 is connected with a b-phase power grid vb through a filter inductor Lg, and for a phase c, a port Mc1 is connected with a c-phase power grid vc through a filter inductor Lg; The upper port of the phase main bridge arm is also connected with a high-frequency isolation transformer through a high-frequency series inductance capacitor, wherein for the a phase, the port M a1 is connected with a T a port of the high-frequency isolation transformer through a high-frequency series inductance capacitor L 1 /C 1 , for the b phase, the port M b1 is connected with a T b port of the high-frequency isolation transformer through a high-frequency series inductance capacitor L 1 /C 1 , and for the c phase, the port M c1 is connected with a T c port of the high-frequency isolation transformer through a high-frequency series inductance capacitor L 1 /C 1 ; The three-phase common half-bridge circuit comprises three half-bridges consisting of six switching tubes, wherein the three half-bridges are provided with common direct-current side ports, the midpoints of the three half-bridges are respectively connected with M a2 /M b2 /M c2 ports of a, b and c three-phase main bridge arms, and the common direct-current side ports of the three half-bridges are connected with an input port P com /N com of a common isolation DC-DC converter; the primary side of the high-frequency isolation transformer comprises ports Ta, tb, tc and Tcom, the secondary side comprises a port S 1 ~S i , and i is a positive integer larger than 1; the primary side Tcom port is a common port of the primary side three windings, and is connected with a direct current side Ncom port of the three-phase common half-bridge circuit; the low-voltage side rectifier structure can be provided with three full-bridge direct-current side parallel structures and Shan Quan bridge structures according to different numbers of secondary side ports of the high-frequency isolation transformer; The working method comprises the following steps: The three-phase alternating current power supply filters high-frequency harmonic current through a three-phase alternating current filter inductor Lg to enter a phase main bridge arm circuit, the phase main bridge arm circuit and a three-phase public half bridge circuit convert the three-phase alternating current into high-frequency alternating current through mixed frequency conversion control, and energy transmission is carried out through a resonant circuit formed by high-frequency series inductance capacitors L1/C1; The high-frequency alternating current is electrically isolated and transmitted through a high-frequency isolation transformer, and corresponding high-frequency alternating current is generated on the secondary side; the common isolation DC-DC converter is connected with the three-phase common half-bridge DC side and the low-voltage DC bus to transfer the rest small part of power and maintain the voltage stability at two ends.
2. The single leg power electronic transformer topology of claim 1, wherein said common isolated DC-DC converter is a DC-DC converter with isolation and bi-directional power flow functions; The common isolation DC-DC converter is selected from a double active bridge converter and a CLLC resonant converter.
3. The single leg power electronic transformer topology of claim 1, wherein the high frequency isolation transformer is selected from the group consisting of three mutually independent two winding transformers, three input three output six winding transformers, and three input single output four winding transformers.

Description

Topological structure and method of single bridge arm power electronic transformer Technical Field The invention belongs to the field of power electronic converters, and particularly relates to a topological structure and a method of a single-bridge arm power electronic transformer. Background "Intelligent", "clean", "power electronics" will be a necessary trend in future grid systems. The conventional power frequency transformer is insufficient to meet the requirements and challenges of the future power grid due to the inherent defects of fixed voltage frequency conversion, inflexible regulation method, huge volume and weight, poor disturbance resistance and harmonic performance and the like. The power electronic transformer is used as a novel power electronic device, has rich functions of adjustable voltage conversion, reactive power control, harmonic elimination, unbalanced operation and the like, can greatly reduce the volume and the weight, and is a powerful choice for replacing the traditional power frequency transformer. The power electronic transformer may be classified into an AC (alternating current) -AC (alternating current) conversion type, an AC (alternating current) -DC (direct current) conversion type, and a DC-DC conversion type according to the type of input/output port. The invention is focused on AC-DC type, the input AC port is connected with a medium-high voltage AC power grid, the output DC port is connected with a low-voltage DC bus, and the invention is suitable for occasions needing DC connection such as data center power supply, new energy grid connection, super charging station, AC-DC hybrid power distribution network and the like. The existing AC-DC type power electronic transformer topological structure is mainly divided into a two-stage structure and a single-stage structure. The two-stage structure usually adopts a series H-bridge type or modularized multi-level type structure, the topology is often more in conversion stage number, huge in module number (device number), and numerous in passive devices such as a capacitive-inductive high-frequency transformer, and the cost and the volume of the device are greatly increased. The single-stage topological structure can effectively reduce the number of devices by reducing the electric energy conversion links, but the efficiency of the device is often lost, and the control complexity and the implementation complexity are increased. Disclosure of Invention The invention provides a topological structure and a method of a single-bridge arm power electronic transformer, aiming at reducing the number of devices of the power electronic transformer, reducing the cost and simplifying the control by improving the topological structure of the existing power electronic transformer. And by combining proper circuit parameter design, the efficiency is improved. The topology is suitable for all applications requiring medium voltage ac to low voltage dc conversion. In order to achieve the above purpose, the present invention adopts the following technical means: The invention provides a topological structure of a single-bridge arm power electronic transformer, which comprises a three-phase alternating current filter inductor L g, a phase main bridge arm circuit, a three-phase common half-bridge circuit, a high-frequency series inductance capacitor L 1/C1, a high-frequency isolation transformer, a low-voltage side rectifier and a common isolation DC-DC converter; the three-phase alternating current filter inductor Lg is used for filtering high-frequency harmonic waves in three-phase alternating current; The phase main bridge arm circuit adopts mixed frequency conversion and is used for converting three-phase alternating current into high-frequency alternating current; the three-phase common half-bridge circuit is used for assisting the phase main bridge arm circuit to perform voltage and current transformation; The high-frequency series inductance capacitor L 1/C1 is used for filtering power frequency fundamental waves and high-frequency PWM harmonic waves generated by the phase main bridge arm circuit and the three-phase common half-bridge circuit; The high-frequency isolation transformer is used for realizing electric isolation and voltage conversion and transmitting high-frequency alternating current from a primary side to a secondary side; The low-voltage side rectifier is positioned at the secondary side of the high-frequency isolation transformer and is used for converting high-frequency alternating current into low-voltage direct current, transmitting most of power of the circuit and maintaining the stability of bus voltage; And the public isolation DC-DC converter is used for supplementing and transmitting the rest part of power and maintaining the voltage stability of the two ends. The phase main bridge arm circuit is further improved, the phase main bridge arm circuit is formed by connecting N sub-modules in series, N is a positive integer