Research On Hybrid Energy Storage Optimal Capacity Configuration And Control Technology In Microgrid

As a solution of allowing high penetration distributed generations to connect grid, microgrid has been widely concerned. As significant parts of energy buffering, energy storage devices play an important role in microgrid. Hybrid energy storage technology, which is put forward recently, shows a lot of asvantages when compared to the single energy storage technology, and has been gradually researched and applied in the microgrid. The capacity configuration of energy storage devices affects the power supply reliability of microgrids and is directly related to its economic operations. At the same time, whether the control strategies of the hybrid energy storage are good or not will affect the popularization and application of hybrid energy storage. Hence, this article studies on optimal capacity confuration of a hybrid energy storage system (HESS) composed of batteries and ultra-capacitors, and does some researches on control technologies of a microgrid which contains HESS, renewable energy resources, and typical loads.According to the characteristics of wind turbine systems, photovoltaic power generations and charge-discharge characteristics of energy storage systems, this paper establishes their output mathematical models firstly. Also, a rational energy scheduling strategy based on the respective power compensation capabilities of ultra-capacitors and batteries, is proposed, which uses the principle of low pass filtering. Considering the rated power and state of charge of each energy storage type, we correct the respective compensation power. Additionally, we derive a mathemati-cal model that minimizes the daily cost of the HESS on the condition that the normal operation of HESS and microgrid is to be guaranteed. This paper proposes to ues a quantum-behaved particle swarm optimization (QPSO) algorithm to optimize the HESS capacity. We used a case of an isolated microgrid in north China to verify the proposed method. Comparisons between QPSO and traditional particle swarm optimization demonstrated that QPSO found the optimal solution faster and reduced the daily cost of the HESS.To show the power allocations of the HESS and energy schedulings of micore sources in the processes of HESS optimal capacity configuration, and to keep stability of microgrid when the opearation conditions change, studies on control technologies of a microgrid which contains hybrid energy storage are necessary. Because each micro source is mostly connected to the microgrid system buses through inventers, droop control and PQ control is designed respectively, which are commonly used in inventer control. Simulation results and analysises verify the validity of the control models, which provide foundations for construct of the whole microgrid simulation models.This article applies the designs of inveter control to an isolated microgrid which has has typical loads, a HESS (composed of batteries and ultra-capacitors), and renewable energy resources (wind energy and solar energy). In order to take full advantage of the outputs generated by wind turbines and photovoltaic devices, PQ control mode is chosen as the both interface inverters control method. Meanwhile, to correspond to the energy dispatch pcinciple, batteries are arranged to compensate for the gentle fluctuations and provide stable voltage and frequency of microgrid because of their high energy density. Droop control is chosen as the control method of batteries. Ultra-capacitors are arranged to compensate frequent fluctuations in the imbalance of power, because of their high power densities and fast response speeds. PQ control is chosen as the control method of ultra-capacitors and the access of power reference is described in detail. Then, dynamic simulations of an isolated microgrid verify the rationality of the simulation models and control methods. Simulation comparisons between HESS and single batteries storage furtherly verify that HESS is superior to single energy storage in the acpect of keeping voltage and frequency stable when the high power imbanlance occurs due to the power variation of loads and micro sources.