Showing papers by "C.V. Nayar published in 2009"

Control and interfacing of a grid-connected small scale wind turbine generator

Abstract: An ac/dc/ac power converter is an important component to extract power from a variable speed permanent magnet wind generator and feed into the grid. This paper describes such a converter incorporating maximum power point tracking based on power fed to the grid at different wind speeds. Using the permanent magnet generator voltage, the grid current and the grid voltage samples, the proposed system achieves an enhanced dynamic behavior. This feature effectively prevents the grid from “boost” charging the dc side of the H bridge inverter at the beginning of operation. Since small wind turbines normally do not have expensive pitch control mechanisms, a thyristor based “dump-load circuit” is employed to protect the turbine from high wind speed operation when disconnected from the grid. The thyristor controller also protects the inverter from high dc voltage input from the wind generator at high wind speed. Preliminary results are included based on a laboratory 2kW prototype converter.

Design Considerations for a Distributed Generation System Using a Voltage-Controlled Voltage Source Inverter

Abstract: Voltage-controlled voltage source inverter (VCVSI) based distributed generation systems (DGS) using renewable energy sources (RES) is becoming increasingly popular as grid support systems in both remote isolated grids as well as end of rural distribution lines. In VCVSI based DGS for load voltage stabilization, the power angle between the VCVSI output voltage and the grid is an important design parameter because it affects not only the power flow and the power factor of the grid but also the capacity of the grid, the sizing of the decoupling inductor and the VCVSI. In this paper, the steady state modeling and analysis in terms of power flow and power demand of the each component in the system at the different values of maximum power angle is presented. System design considerations are examined for various load and grid conditions. Experimental results conducted on a 1 KVA VCVSI based DGS prove the analysis and simulation results.

Improved power transfer capability of SEIG in variable speed wind turbine generation system

Abstract: Self excited induction generator (SEIG) is well known for constant speed application such as micro-hydro generation due their low cost, reliability and simplicity in operation. Along with advanced power electronic converters SEIG is now also applied in variable speed operation such as wind turbine. Poor voltage regulation and over-sized machine are several drawbacks in variable speed operation using SEIG. In this paper a comprehensive sizing of shunt and shunt-series compensation capacitors for SEIG variable speed wind turbine driven are discussed. Steady state model of SEIG and power characteristic of wind turbine are the main discussion in this analysis. The results show a significant improvement in overall performance at which generation system is capable to operate at low wind speed regime. Also smaller power rating of induction machine could be used to provide same power transfer capability as in the over-sized machine.