Generation and Transmission of Electrical Energy in High-Altitude Wind Power Generating System

This paper presents a high-altitude wind power generating system supported by a light gas filled blimp/aerostat that extracts electrical energy from high-altitude streamlined wind. The optimal generation and transmission mechanisms that give suitable power-to-weight (P/W) ratio and efficiency of the overall system are investigated. The variations in weight and total losses of the permanent magnet synchronous generator with changes in generation voltage and pole-pair number (frequency) have been analyzed. The design of the tether that transmits electrical power to the ground-based station is also presented. AC and dc transmission mechanisms using aluminum/copper-based conductors are studied and compared to find optimal weight of the tether. It is found that aluminum conductor gives better P/W ratio than using copper conductor. From the detailed analysis of generation and transmission mechanisms, it is concluded that the optimal electrical power architecture is medium voltage (MV) ac generation as well as transmission. It exhibits better P/W ratio and efficiency in comparison with low-voltage ac generation and MV dc transmission. The selected optimal electrical architecture simplifies electric system by transferring the power electronic converter from the airborne unit to the ground-based station and thereby improves the overall P/W ratio by a factor of 7% approximately.