Grid Power Leveling using Ultra Capacitor, Battery and an Optimal Control Strategy for Reactive Power in DFIG based WECS
Diptoshi Roy1, Chandasree Das2

1Diptoshi Roy, M.Tech Student, Department of Power Electronics, VTU, BMSCE, Bangalore (Karnataka), India.
2Dr. Chandasree Das, Department of EEE, VTU, BMSCE, Bangalore (Karnataka), India.
Manuscript received on 10 September 2014 | Revised Manuscript received on 20 September 2014 | Manuscript Published on 30 September 2014 | PP: 38-43 | Volume-4 Issue-4, September 2014 | Retrieval Number: D1793094414/14©BEIESP
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Abstract: To harness the wind power efficiently the most reliable system in the Wind Energy Conversion system (WECS) is grid connected doubly fed induction generator (DFIG). Inconstancy in the output power and consequently voltage of the system is the result of random wind speed and turmoil of blade rotational speed. Battery energy storage system (BESS) is one, which helps to reduce the power fluctuations on the grid caused due to the varying and unpredictable nature of wind. This paper presents a comparative study between BESS and ultra- capacitor and the combination of both in a DFIG based WECS to reduce the power fluctuation on the grid. The performance analysis of the following cases (a) battery alone in dc-link (b) ultra- capacitor in dc-link (c) battery and ultra-capacitor in dc-link , have shown that the response with ultra-capacitor is best among all these cases. The analysis is done for all three modes of speed i.e. sub synchronous, synchronous and super synchronous and in all three modes, the power fed to the grid is kept constant. As the doubly fed induction generators used in grid interfaced wind energy systems are being called upon increasingly to address voltage regulation and provide adequate reactive power support; a reactive power control strategy is also studied and is included in this paper with grid and rotor side converters for voltage regulation and reactive power support respectively. The validity of this new approach has been tested in 16 bus IEEE power distribution system. The results obtained shows considerable reduction in losses by reactive power compensation. The modeling of battery, ultra-capacitor including model of rotor side converter for reactive power analysis are simulated in MATLAB-SIMULINK which helps to predict the behavior of the system in various aspects. An effort is made in this paper to study few issues like energy storage by ultra-capacitors, long term storage, reactive power control and a case study using 16-bus distribution system for grid connected DFIG based WECS.
Keywords: DFIG, Ultra Capacitor, Grid Power Leveling, 16 Bus Distribution System.

Scope of the Article: Smart Grid Communications