Showing papers by "C.V. Nayar published in 2010"

Modeling of stand-alone variable speed diesel generator using doubly-fed induction generator

Abstract: Diesel generators are widely used to supply electric power to remote and isolated areas where grid extension is prohibitive due to financial and technical constrains. In order to maintain an acceptable efficiency and moderate operation condition, the conventional constant speed diesel generators are designed to run above a specific minimum load requirement, which is normally over 50% of rated power, even though the actual load power demand is low. This results in low fuel efficiency. Operating the diesel generator running under variable speed operation can avoid the defects of conventional constant speed diesel generator. This paper proposed a simulation analysis of a stand-alone variable speed diesel generator that the rotating shaft of diesel engine is directly coupled to a doubly-fed induction generator (DFIG) to obtain an output voltage with constant frequency and constant magnitude. Indirect stator flux orientation vector control strategy is adopted to control DFIG for stand-alone operation and the simulation results are presented and confirm the validity of the strategy.

Control of Photovoltaic-Variable Speed Diesel Generator battery-less hybrid energy system

Abstract: A predictive dispatch algorithm and control for a Photovoltaic-Variable Speed Diesel Generator battery-less hybrid energy system is proposed in this paper. The diesel generators are dispatched based on the predicted net load from the incorporated prediction models. The proposed algorithm is based on the one-hour ahead prediction models to forecast the renewable resource and the load demand. Besides, an adaptive dispatch which is based on one minute average data is also included to complement the predictive dispatch strategy. The adaptive dispatch reacts to the power flow imbalances occur during the intervals in between the prediction periods. This dual-dispatch algorithm is to ensure the on-line diesel capacity is always sufficient throughout the operation. Simulation of the system is performed using MATLAB/Simulink.

Solar Irradiance and Load Demand Forecasts in the Supervisory Control for Off-Grid Hybrid Energy System

Abstract: Efficient operation of a hybrid renewable energy system can be achieved if the power supply from the renewable energy generator and the load demand can be predicted. The forecasts of these parameters are essential for the supervisory control planning and decision making to ensure the generator capacity on the line is sufficient to meet the load demand at a given moment. Forecast models for predicting the solar resource and the load demand are proposed. The proposed models are applied to control an off-grid Photovoltaic-Variable Speed Diesel Generators Hybrid Energy System.

Simulation and components sizing of a stand-alone hybrid power system with variable speed generator

Abstract: Design and optimization of a hybrid power system is site specific. It depends mainly on the available of renewable sources and the load demand. Sizing of the components has significant influence on the system performance. Due to the weather dependant nature of renewable energy sources, a fossil fuel based constant-speed generator is an essential component in traditional hybrid power systems. However, the efficiency of this generator especially at light loads can be significantly improved by adopting a variable-speed operation. This paper presents a combined sizing and operation control programme that can be used with both traditional constant-speed generators as well as novel variable-speed generators. The programme uses the polynomial curve fitting for the fuel consumption characteristics of variable-speed generators. The accuracy of the calculations is verified by comparing with a well known renewable energy optimization package.

Optimum power control strategy for SEIG-based variable speed WECS

Abstract: Self-excited induction generators (SEIGs) have a significant potential for application in small scale wind energy generation systems due to their robustness, lower cost and lower maintenance requirements. This type of generator is often incorporated with variable speed wind turbines where maximum power extraction is possible. In such applications, SEIG is intensively used with full-sized converter configurations. Maximum power point tracking is a critical element of converter control to optimize power extraction from wind. In contrast to photovoltaic applications, many tracking algorithms in wind turbines face difficulty in handling rapid and high wind speed fluctuations. This paper presents an optimum control strategy for a SEIG based small-scale wind energy generator coupled to the grid through a buck-boost inverter. It combines two control strategies to minimize the time needed to reach the maximum power point of the generator under varying wind speeds. The computer simulation results confirm that the proposed controller outperforms traditional maximum power point controllers.