SOME INVESTIGATIONS ON MULTI-PHASE INDUCTION GENERATOR FOR WIND ENERGY APPLICATION

Abstract

NS ON MULTI-PHASE INDUCTION GENERATOR FOR WIND ENERGY APPLICATION ABSTRACT With the depletion of the reserves of coal and fossil fuels, renewable sources viz. solar, wind, tidal waves, geothermal etc. are finding great attention for energy generation. The share of Wind energy is rapidly increasing due to their robust structure and direct connectivity to the grid. Latest research and development in the generator and power converter topology has led to remediation of generation constraint. New topologies of generators including multiphase induction generators with dual stator winding sets are represented as leading prominent contenders recently. The variable reactive power demanded by induction generators often pose a major issue which magnifies multifold when operated in a wind farm. Various researches are reported that minimize the contribution of reactive power from the grid along with interaction of generators on account of reactive power. Research is due for understanding the behavior of multiphase induction generator during low voltage on the grid end. This demand for analysis of air gap flux for transient operations and development of model to explore the potential of multiphase induction generators for application to three port energy device for distribution of generated energy along with capability of power transfer across the winding sets. The work carried out in this thesis is focused on the transient and steady state analysis of Asymmetrical Dual Stator Induction Generator (ADSIG) and comparing it with Squirrel Cage Induction Generator (SCIG) and Symmetrical Dual Stator Induction Generator (SDSIG) for various operating conditions. For doing so, a new decoupled equivalent circuit model of ADSIG is developed in d-q frame by transferring the rotor side winding v

leakage inductance to both the stators side circuit and the magnetization branch. The developed model of ADSIG is developed in MATLAB SIMULINK environment for observing the response in generation mode. A finite element model of the machine is also developed in INFOLYTICA MOTORSOLVE software to estimate its performance. Based on the model and design a hardware prototype of ADSIG is developed in laboratory to study the behavior of ADSIG. A detailed comparison of SDSIG and ADSIG is done with special emphasis on the air-gap flux when these generators are subjected to different types of loading conditions. A comparison is also been drawn for reactive power demanded by ADSIG, SDSIG and SCIG in respect of peak inrush currents. The analytical study is then validated both through simulations and experimentation in grid coupled mode. Three applications of ADSIG are also explored dually supported with study, simulation and experimental results namely soft coupling of two distribution feeder, dispatachable power transfer to grid, rural electrification. Application 1: The application of ADSIG as a three port network for routing power two different AC feeders under conditions of with and without wind energy inception is evaluated. ADSIG here in acts as a soft coupler routing of power between the feeders depending upon the loading on the respective feeder in absence of wind, and distributing the generated energy to the loaded feeder side automatically. The analysis is duly validated through simulation and experimentation results. Application 2: The problem of intermittent power generation is often not acceptable to weak AC grids in presence of variable wind conditions. An energy storage system (ESS) for curbing the intermittency and providing dispatchable study to such generation is often a requisite. A study of connection of ESS at one end and connection of grid at the other vi

end of ADSIG is made through analysis where in duly substantiated through analytical and experimental study. Application 3: Further a cost effective method for rural electrification is also proposed by using multiple ADSIGs to harvest the generated energy and provides power to the rural loads. The analysis and experimentation is done using both low wind speed (transformer action of ADSIG) and sufficient wind speed conditions (generator action of ADSIG) for reducing the effective loading on the rural feeder. All the analytical, simulated and hardware results are coherent and support for the candidacy of ADSIG to such applications.