Research On Stand-Alone Wind Power Generation System Based On Hybrid Excitation Synchronous Generator

Fossil fuels are considered to be one of the major factors for environment pollution and globalwarming. Nowadays, the development of renewable energy sources has become the most importantstrategies in China. Because of relatively low cost and maintenance simplicity, stand-alone windpower system with battery is very suitable for providing energy for remote area. In this paper, thedesign of the variable-speed fixed-pitch wind turbine and the control strategies are deeply studied.Firstly, a5kW hybrid excitation synchronous generator for wind turbine is designed. It has themerit of high power density as permanent magnetic synchronous generator (PMSG) and goodcapability of air-gap magnetic field adjustment. In this paper, the configuration and operationprinciple of T/R-HESG are introduced. The winding distribution and structural parameters ofT/R-HESG are designed. The magnetic field distribution and static characteristics are obtained byfinite element method (FEM) by virtue of Ansoft Maxwell2D. In order to improve the reliability ofoperation, the brushless excitation is realized by the scheme of two-stage brushless excitation.Meanwhile, the exciter is the core part of brushless excitation system of exciter is designed to meetthe requirement of T/R-HESG. The characteristics of exciter and brushless excitation system aregained by simulation. The result of the simulation demonstrates that the scheme can satisfy therequirement of main generator.Then, the stand-alone wind power generation system is proposed. The aerodynamic characteristicsof wind turbine and mathematical model of two-stage brushless generator are analyzed. The Simulinkmodel of stand-alone wind power generation is built. The methods of maximum power point tracking(MPPT) are studied. Combining the charging characteristics of battery, the full range power controlstrategies are proposed to handle the power of the wind turbine during the variation of wind velocity.The results of the analysis are proved by the simulation in Simulink.Finally, the hardware and software of excitation current controller and power supply are designed.The experiments are done. The design of excitation current controller contains the main circuit,sample circuit, control circuit, speed measurement circuit and so on. Also, the relative experiments arefinished. To guarantee the operation of controller, half-bridge LLC resonant converter has been widelystudied for wide input voltage application. The battery can provide energy for excitation currentcontroller. The extra power supply can be eliminated, which can improve the reliability of system.