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Study Of Optimal Control Strategy For Composite Energy Storage System In Micro-Grid

Posted on:2017-05-25Degree:MasterType:Thesis
Country:ChinaCandidate:F WangFull Text:PDF
GTID:2272330488451864Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
Micro-Grid is the inevitable outcome of booming in wind power, photovoltaic and other distributed grid power. It has prominent advantages in promoting access of distributed power supply and renewable energy, improving power security and enhancing energy utilization efficiency,etc. Energy storage system is of great significance for improving the power quality, stability, and operational efficiency in Micro-Grid and achieving peak load shifting. It also has become an integral part of the Micro-Grid and crucial technical support.First of all, the single energy storage method cannot satisfy both energy density and power density requirements of Micro-Grid storage under the condition of current technology. This paper proposes a new type of multiple composite energy storage system solution which consist of compressed air energy storage, battery and super capacitor.Based on the analysis of the characteristics of the energy storage device and the energy conversion efficiency, also considering economy and energy management flexibility, the topological structure of composite energy storage system is determined.Micro-Gird’s working condition is complicated. Underlying system power fluctuations and work mode switching, whether storage device power converter can maintain bus voltage or not is the key for stable operation and coordination of power distribution. The DC/DC and AC/DC power converter in composite energy storage system are analyzed in this paper. Its mathematical model is established based on switching theory. The system optimal switch law is designed to control power switch, The optimal bottom control of energy storage device power converter is realized. Simulation and physical experiment results show that compared with the traditional modeling and control methods, the proposed method can effectively guarantee the stability of Micro-Grid bus voltage under working conditions such as large variation of power.To solve energy management problem, considering different working properties of energy storage device, this paper use low pass filter and empirical mode decomposition to allocate power. Using the low pass filter we can configure the energy storage unit’s power flexiblely by changing the filter time constants. But the changing range is not easy to be determined when economy is considered. Using the EMD method to decomposite composite energy storage power can reduce the charging or discharging depth of energy storage unit. Thus, the energy storage expenses is reduced. In order to achieve the real-time control of composite energy storage, the power instructions need to be forecasted. Based on EMD method combined with the ARMA, the power signal is predicted. We found that under the same model order, this method is more accurate than the single ARMA method.Finally, the micro composite energy storage system test platform that containing compressed air energy storage, battery, super-capacitor is established. It can be used for related algorithm validation and lay the foundation for engineering practice of this kind of composite energy storage system.
Keywords/Search Tags:Composite energy storage, Compressed air energy storage, Micro-Grid, Converter control, Energy management
PDF Full Text Request
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