| Because the shortage of fossil fuels and the environmental pollution caused by burning fossil fuels is becoming increasingly serious, human pay ever more attention to the development and utilization of renewable energy resources. However, many renewable energy generations are subject to environmental constraint, and its output power will show a strong characteristic of randomness and volatility. When renewable energy access to the low voltage power distribution network, it will have a bad influence on power balance, reliability of power distribution and power quality of the AC side. Hybrid energy storage system, is considered to be one of the most important methods to solve the power fluctuation of renewable energy generation for its technical and economical advantages. This dissertation focuses on the new energy management strategy and control of a hybrid energy storage system.In this thesis, the equivalent circuits of the two storage devices are firstly analyzed, and then the main structure of hybrid energy storage system which is connected with renewable energy generation system at AC side is designed. Secondly, the detail circuit topology of this hybrid energy storage system is determined. Its modeling and control are carried out too. The storage device’s charge and discharge is controlled in a way of setting a constant compensating power, in which the subsequent energy management can be easily realized. The whole circuit model of Hybrid energy storage system is built in Matlab, and the results of simulation, which lays the foundation for the following energy management, prove that the control method of the circuit is effective.In order to improve the smoothing power fluctuation and the working condition of battery effect of this hybrid Energy Storage System, a control strategy for hybrid Energy Storage System is put forward on the basis of the traditional power allocation method using low pass filter(LPF). This strategy reallocate the power fluctuatuion between battery and supercapacitor according to the real time state of charge of supercapacitor by changing the time constant of LPF. In order to solve the problem that battery and supercapacitor may suffer over-charge and over-discharge during compensating the power fluctuation, an analysis is carried out and a method which can not only avoid over-charge and over-discharge of battery and supercapacitor but also increase the compensating rate of hybrid energy storage system is put forward. The results of Matlab/Simulink simulation shows the effectiveness of the proposed method in smoothing power fluctuation and the reduction of energy compensated by battery, and the cycle life of battery is prolonged too.Finally, a small scale hardware experimental platform of this hybrid energy storage system is built, and DSP 28335 is used to control the charge and discharge of storage device. The energy management is carried out between battery and supercapacitor, and the preliminarily relevant result of experiment proves the validity of the proposed energy management strategy. |
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