Hybrid energy storage frequency division control method considering unbalanced current change rate of DC microgrid

Abstract

The invention discloses a hybrid energy storage frequency division control method considering the rate of change of the unbalanced current of the DC microgrid. The method is mainly based on the traditional frequency division control method, adding a link of limiting the rate of current change, and the hybrid energy storage system The total current to be balanced is decomposed into high-rate-of-change current components, low-rate-of-change instantaneous current components, and low-rate-of-change average current components; the sum of high-rate-of-change current components and low-rate-of-change instantaneous current components is used as the output reference current of the supercapacitor, low The average current component of the rate of change is used as the battery output reference current. The invention overcomes the defect that the battery cannot track the current with a high rate of change due to its own slow dynamic response characteristics, and at the same time reduces the current stress on the battery and prolongs its service life; the distribution of unbalanced current is more precise and accurate, and the DC bus is improved. The speed of voltage recovery reduces the overshoot of the bus voltage; only the DC bus voltage needs to be detected, and the power information of each unit is not required, which reduces the demand for communication.

Description

technical field [0001] The invention relates to the technical field of hybrid energy storage system control, in particular to a hybrid energy storage frequency division control method considering the unbalanced current change rate of a DC microgrid. Background technique [0002] The output power of the renewable energy power generation system has the characteristics of intermittent, fluctuating and random. Therefore, in the process of connecting to the grid or applying to the micro-grid, it is necessary to configure the energy storage system to smoothly control its output power. Batteries have high energy density but slow dynamic response and effective charge and discharge times. Supercapacitors have high power density and cycle life but low energy density. Therefore, these two energy storage elements are commonly used to form a hybrid energy storage system. The most common control method adopted for this hybrid energy storage system is the frequency division control strateg...

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Problems solved by technology

However, this decomposition method does not consider that due to the slow dynamic response speed of the battery, the power with a high rate of change cannot be compensated, resulting in a slow response speed of the entire hybrid energy storage system; at the same time, this method needs to rely on the communication device to collect the power information of each unit. Reduced reliability

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