Research On Control Of Small Stand-alone Wind Turbine System

For the benefits of flexible, small initial investments, clean and safe, stand-alone wind power is suitable for power the remote areas and grid uncovered areas. In addition, we also have rich wind energy resources in the inland areas. For promoting the ecological construction and improving the energy structure, develop stand-alone wind energy will have a positive meaning. At present, two important problems need to be solved for developing the stand-alone wind energy, one is the research of efficient maximum wind energy capture technology, in order to improve the wind energy using efficiency and further reduce the cost of wind power. The other is how to reduce the output voltage’fluctuation, improve the quality of output power. Aiming to solve these problems, this paper designed a stand-alone off-grid wind power control system. on the one hand, improved the method of maximum wind energy capture strategy. on the other hand, researched the coordinated control method, realized the energy balance between supply and demand, thus reducing the output voltage’fluctuation.Firstly, based on analyzing the mathematical model of stand-alone wind energy system, a kind of control structure without measuring speed was deduced. Combined with fuzzy control’s adaptive for nonlinear system and PI control’s good stability, fast responsibility, we designed a hill climb search method based on fuzzy and PI theory. The method used fuzzy logic to determine the reference search step length, by using PI controller to regulate closed-loop voltage, to track the reference search step length, thus achieved the maximum wind energy. Using Lyapnov theory, analyzed the stability of the method. Simulink results show that the new method increased the efficiency by34.1%.Secondly, designed an energy coordination control strategy, which coordinated the wind turbines, energy storage, dump load and load, realized the energy balance of supply and demand, let the output voltage more stable. By analyzing the reason of output voltage fluctuation, we draw the conclusion that the energy balance of the system can be realized by maintaining the dc voltage. Wind turbines based on the state of load demand and energy storage, switched in three mode:the maximum power tracking, constant power, as well as limiting mode. An combined energy storage system using super capacitor and battery was proposed. This paper used battery to buffer low frequency fluctuations, super capacitor to buffer the high frequency fluctuations. In this way, not only improved the efficiency of energy utilization, but also reduced the number of battery charging and discharging, prolong the service life of the battery.Thirdly, the design process of stand-alone wind power generation system’s hardware which includes the design idea, design principle and parameter selection was elaborated throughly. The controller consist of the main circuit, detection circuit, and LED illumination load. Main circuit converted the fluctuating wind into power which the load can use directly. Detection circuit converted the analog such as voltage and current into digital signal, meeting DSP’s computation requirements. Under the circumstance where access of AC power or diesel generator, when wind power and battery power supply weakly, the cutting circuit will automatically connected the load to the AC power, ensure the load working stably. Thsi paper researched the LED drive technology previously,and designed a kind of LED driver with high efficiency and low temperature producing prototype. Based on this research, Thsi paper used the LED illumination as the load of controller, further carried out the follow-up research work.Fourthly, the whole control strategy was digitally implemented by using TMS320F2808DSP. In the process of software establishment, Thsi paper used the concept of modular design method. First of all, devided the control functional, featured the same unit as one module. Secondly, according to the module’function designed the software. Finally, designed a preemptive multitasking operating method to dispatch each function module.Fifthly, analyzed the problems met in the process of debug and proposed the solutions. The overall software and hardware was tested, results verified the feasibility of the whole design.