Hybrid energy storage DC transformer and its control method

Abstract

The invention discloses a hybrid energy-saving DC transformer and a control method thereof. The transformer comprises an AC reactor, a plurality of output rectification unit, a multi-winding high-frequency transformer and an energy-storage modular multilevel converter, wherein a power-type energy storage and an energy-type energy storage are respectively connected to two phase sub-modules of the energy-storage modular multilevel converter, the function of hybrid energy storage is achieved by controlling a low-frequency component and a high-frequency component in a high-voltage DC current to berespectively provided by the energy-type energy storage and the power-type energy storage, each secondary side of the multi-winding high-frequency transformer is subjected to diode rectification or controllable rectification and then a multi-path low-voltage DC output is obtained. The transformer is simultaneously compatible with functions of the DC transformer and energy storage, is flexible tocontrol, is high in integration and is suitable for occasions of a DC microgrid, a distribution network, a ship medium-voltage DC comprehensive power system and the like.

Description

technical field [0001] The invention relates to the technical field of DC power distribution, in particular to a hybrid energy storage DC transformer and a control method thereof. Background technique [0002] With the rapid development of power electronics technology, DC power distribution has received more and more attention and applications due to its advantages in power density and power quality, such as regional power distribution networks, microgrids, and ship integrated power systems. In order to meet the voltage conversion requirements in the DC power distribution network, it is necessary to study the DC transformer with the power electronic converter as the core. The most common DC transformer structure is as follows: figure 1 As shown, the primary side of the dual active full bridge circuit is connected in series and the secondary side is connected in parallel to realize the conversion from high voltage DC to low voltage DC. Its disadvantage is that the number of ...

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Problems solved by technology

Conventional large-scale energy storage requires a large number of battery cells connected in series and parallel, which not only has low efficiency and poor reliability, but also requires an additional energy management system for SOC (State of Charge, state of charge) balance control

On the other hand, it is difficult for an energy storage system composed of a single type of energy storage element to simultaneously meet the demands of the DC distribution network for instantaneous large power fluctuations and long-term continuous power supply. It is necessary to develop a hybrid energy storage system that uses different characteristics reasonably Energy storage components meet different needs of the grid

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