Single-stage isolated three-phase bidirectional ac/dc converter and control method

Abstract

The invention discloses a single-stage isolation type three-phase bidirectional AC / DC converter and a control method. The converter comprises alternating-current side inductors, alternating-current side capacitors, a three-phase full bridge, bidirectional switches, transformer end potential bidirectional clamping switches, a single-phase full bridge, an isolation transformer a rectifier / inverter single-phase full bridge, a direct-current side filter inductor and a direct-current side filter capacitor. A combined control mode combining low-frequency sector switch selection and high-frequency full-bridge phase shifting is adopted. A current source type AC / DC structure is adopted, the rectification mode of the buck type is realized, and the starting impact problem of a conventional boost rectification mode is avoided; and meanwhile, electrical isolation is realized only by a single-stage power conversion circuit, only one full-bridge structure is arranged on the primary side and the secondary side of a high-frequency isolation transformer, and the power flow and the follow-current stage only needs to flow through two power tubes, so that the transmission loss is lowered.

Description

technical field [0001] The invention belongs to the technical field of DC microgrids, and in particular relates to a single-stage bidirectional AC / DC converter. Background technique [0002] As a new form of power supply, the research and application of DC microgrid with new energy as the core is still in the stage of rapid development, and there are still many problems to be solved. DC microgrid is the product of the integration of power electronics technology, information electronics technology and power system, involving multiple research fields such as converter devices, operation control, fault protection, power supply planning, system architecture and communication protocols. Among them, the interface AC / DC converter between the DC microgrid and the AC grid, as the link connecting the two networks, is responsible for regulating the energy balance of the entire microgrid, and is one of the focuses of DC microgrid research. In high-power occasions, a three-phase bidirec...

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Problems solved by technology

In addition, the rectification mode of the voltage source AC / DC converter is a boost (boost) type, which has the problem of start-up shock. It is necessary to add a start-up current limiting measure in the power transmission path, which affects the efficiency and power density of the converter. At the same time, the boost When the type circuit is working with no load or light load, the closed-loop control of the system is also difficult, and it is difficult to take into account the stability of the control and the fast dynamic response characteristics.

[0005] Isolated AC / DC converters usually require a two-stage structure. One is to add a power frequency isolation transformer in the front stage, which will lead to a large volume, weight and high cost of the converter; the other is to add a high frequency isolation transformer in the rear stage. Bidirectional DC / DC converter, but the two-stage power conversion has a great negative impact on system efficiency, and the existing high-frequency isolated bidirectional DC / DC converter has poor characteristics under the condition of wide voltage variation range, this conversion It is difficult for the converter to adapt to the application requirements of wide input and output voltage changes

[0006] In the Chinese patent application (publication number: CN108988676A), by adopting a single-stage isolated structure, the large-volume decoupling energy storage capacitor in the middle bus bar of the two-stage converter is omitted, which can improve the efficiency of the converter, but the soft-switching type The single-stage structure uses two phase-shifted full-bridge circuits connected in series, resulting in power transmission that needs to flow through the channels of four power devices, resulting in large transmission loss and affecting the further improvement of converter efficiency

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