Control method of solid-state transformer device with true bipolar low-voltage DC port

Abstract

The present invention provides a solid-state transformer device with a true bipolar low-voltage DC port and a control method thereof, including a plurality of isolated DC-DC converters, and the plurality of isolated DC-DC converters are serially input and output The output stages of the multiple isolated DC-DC converters are connected in parallel to realize DC flow increase to form a true bipolar low-voltage DC port for interconnection with a true bipolar DC micro-grid; based on the above-mentioned solid-state transformer structure, through DC Bias current control, realize the voltage balance of low-voltage DC positive and negative poles under asymmetrical load conditions, and share the DC bias current of each isolated DC-DC converter; With the design of the line mode, the DC components of the magnetic field formed by the DC bias current in the high-frequency transformer cancel each other, which solves the DC bias problem of the high-frequency transformer caused by the asymmetrical load.

Description

technical field [0001] The present invention relates to the fields of intelligent distribution network technology, power electronics technology, control technology and the like in power systems, and in particular relates to a solid-state transformer device with a true bipolar low-voltage DC port and a control method thereof. Background technique [0002] The massive access of distributed power sources and energy storage, and the rapid development of DC loads make DC microgrid technology have broad application prospects. Compared with the AC micro-grid, the DC micro-grid is better compatible with distributed power sources, energy storage and DC loads (electric vehicles, data centers, communication power stations, etc.), saving the cost of inverters required for equipment access, and improving Power transmission efficiency reduces the total loss of lines and converters, avoids problems such as reactive power, frequency, and phase synchronization, simplifies microgrid control, ...

AI Technical Summary

Problems solved by technology

[0004] The DC microgrid will be interconnected with the upper-level AC / DC distribution network through a power electronic converter. When a true bipolar structure is used, the converter is required to provide a true bipolar low-voltage DC port. After retrieval, Xunwei Yu et al. published in IEEETRANSACTIONS ON POWER ELECTRONICS In the paper "System Integration and Hierarchical Power Management Strategy for a Solid-State Transformer Interfaced MicrogridSystem" (2014) published on the Internet, a solid-state transformer topology is proposed, which can realize the interconnection of medium-voltage AC distribution network and low-voltage DC microgrid, but the solid-state transformer The transformer can only provide unipolar or pseudo-bipolar low-voltage DC ports. To realize a true bipolar DC microgrid, two sets of the same solid-state transformer device are required, and the total cost of the device is relatively high

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