Research On Passive Self-adaptive MPPT Off-grid Wind Power Generator System

Off-grid wind power generator systems(OWPGS) have advantages of cheap, flexible for use, and little maintenance, so they have been applied in pastoral areas, forest areas, communication base stations, weather stations, islands, border posts etc. However, the characteristics of the generator systems in conventional OWPGS do not coincide with those of wind turbines, so conventional OWPGS cannot achieve maximum power point tracking(MPPT) automatically, leading to a low utilization of wind energy. Therefore, achieving MPPT at different wind speeds for OWPGS is an ongoing research goal. Conventional MPPT solutions relay on electrical control devices, but the electronic components contained in the electrical control device are likely to break down when exposed to extreme weathers, thereby resulting in the low reliability of OWPGS for outdoor use. Therefore, it is necessary for OWPGS industry to develop new MPPT technologies with high reliability.Based on an analysis of conventional MPPT technologies, this paper sought a novel MPPT solution, named passive self-adaptive MPPT method, from special designs of generator bodies and system circuit topologies. The new MPPT solution allows OWPGS to realize MPPT automatically without the need for any electrical control devices. Due to elimination of the electric control device, the new MPPT method reduces the use of electronic components, which improves the reliability of the system for outdoor use. Research work in this paper mainly includes the following parts:Based on an analysis of conventional MPPT technologies, the principle of the passive self-adaptive MPPT method is analyzed by using a graphic method and a mathematical method respectively. On this basis, a novel generator system, which employs high leakage inductance values to realize passive self-adaptive MPPT, is proposed, so it is named high-main-inductance generator system, i.e. HLIG; another novel generator system, which employs high main inductance values to realize passive self-adaptive MPPT, is also proposed, so it is named high-main-inductance generator system, i.e. HMIG. They have significantly high reliabilities due to the elimination of electrical control devices.The formula for calculating inductances of HLIG and HMIG are derived based on the double three phase voltage equation, and the mathematical models of HLIG system and HMIG system are established respectively. In addition, in the process in establishment of mathematical model, the quantitative relationship of electromagnetic coupling between two sets of windings of the HLIG system is proposed. These studies provide a theoretical basis to the design of the novel generator systemsDetailed design procedures of HLIG and HMIG are established respectively based on an iterative method. Methods for determining the double-winding-turn-number-ratio, the double-winding-power-distribution-ratio, and the pole/slot combination rules of the HLIG system and HMIG system are studied respectively; method for determining the double-winding-slot-distribution-ratio of HMIG system is studied. Thus, the relationships between design requirements and turn-number-ratio, power-distribution-ratio, slot-distribution-ratio, respectively, are obtained, providing theoretical support for the design methods. These studies provide a theoretical basis to the actual design and manufacture of the novel generator systemsBased on theoretical analyses and finite element analyses(FEA), the input power characteristics, output power characteristics, copper loss characteristics, iron loss characteristics and efficiency characteristics of the HLIG system and HMIG system are compared respectively, providing theoretical support for future technical improvements. Based on the experimental results, the static MPPT and dynamic MPPT performances of the HLIG system and HMIG system are discussed, and the results are compared with a generator system using the hill-climbing search method. The results indicate that the MPPT performance of the novel generator systems is superior to that of the system using hill-climbing search method.The proposed systems based on the passive self-adaptive MPPT method eliminate hundreds of electronic control components, being remarkably conducive to high reliability. The theoretical analysis and experimental results indicate that the proposed systems can realize the passive self-adaptive MPPT successfully and rapidly. Hence, the proposed systems are effective solutions to the MPPT problem for OWPGS.