Power conversion system for low power high altitude wind power generating system

Abstract

In high altitude wind power (HAWP) generating system, medium voltage AC (MV-AC) permanent magnet synchronous generator (PMSG) is used. The generated electrical power is transmitted to ground without any power conditioning in the air-borne unit. The ground based power conversion system (PCS) interfaces variable voltage and variable frequency medium voltage power into distribution level grid voltage. The proposed PCS consists of a three-level vienna rectifier for generation side control, a half bridge DC-DC converter for isolation and step-down purpose and a grid/load connected inverter for load side active power control. Three-level operation in the generation side converter reduces the switch/diode voltage stress to half and therefore allows to use low voltage rating power semiconductor devices. The vienna rectifier is controlled for sensorless maximum power-point tracking (MPPT) of the air-borne wind turbine. The phase lock loop (PLL) is used for speed and rotor position detection of the PMSG for optimal torque control of the airborne wind turbine (AWT). Simulation studies have been carried out using computer programs like PSIM and MATLAB. For the validation of the proposed methodology, scaled down laboratory based prototype is built and tested. The obtained experimental results confirm the performance of the PCS for interfacing HAWP generation system to the grid.