Abstract
Traditional hierarchical control of the microgrid does not consider the energy storage status of a distributed hybrid energy storage system. This leads to the inconsistency of the remaining capacity of the energy storage system in the process of system operation, which is not conducive to the safe and stable operation of the system. In this paper, an improved hierarchical control strategy is proposed: the first allocation layer completes the allocation between the distribution energy storage systems considering the state of hybrid energy storage systems, and the second allocation layer realizes the allocation within the hybrid energy storage systems based on variable time constant low-pass filtering. Considering the extreme conditions of energy storage systems, the transfer current is introduced in the second allocation process. The SOC (stage of charge) of the supercapacitor is between 40% and 60%, which ensures that the supercapacitor has enough margin to respond to the power demand. An example of a 300 MW photovoltaic microgrid system in a certain area is analyzed. Compared with the traditional hierarchical control, the proposed control strategy can reduce the SOC change of a hybrid energy storage system by 9% under the same conditions, and make the supercapacitor active after power stabilization, which is helpful to the stable operation of the microgrid.
Highlights
With the continuous maturation of photovoltaic and other renewable energy power generation technologies, the installed capacity is getting larger and larger, and the megawatt-scale photovoltaic microgrid is gradually put into operation [1]
In order to solve the above problems, this paper proposes a power distribution strategy based on improved hierarchical control for microgrid hybrid energy storage system
After the supercapacitor completes the allocated power target, the lithium-ion battery is used to adjust the SOC of the supercapacitor to make it stay at 40%–60%, and the continuous schedulability of the hybrid energy storage system is improved, which contribute to the stable operation of the photovoltaic microgrid
Summary
With the continuous maturation of photovoltaic and other renewable energy power generation technologies, the installed capacity is getting larger and larger, and the megawatt-scale photovoltaic microgrid is gradually put into operation [1]. In reference [8], a hybrid microgrid hybrid energy storage control strategy based on droop control is proposed to realize the power allocation between energy storage units. In reference [13], this paper studies the islanded AC (alternating current) microgrid with hybrid energy storage system, and proposes a power sharing virtual impedance control strategy to stabilize the AC bus voltage while preventing overcharge and discharge of the battery, but it does not consider the working state of the supercapacitor and discuss in-depth. In order to solve the above problems, this paper proposes a power distribution strategy based on improved hierarchical control for microgrid hybrid energy storage system. 40%–60%, ensuring that thethe supercapacitor the stability of the photovoltaic micro-grid
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