Sensorless Vector Control Of Direct-driven Permanent Magnet Wind Power Generator Based On MRAS

With the shortage of electric power and the worsening of power supplycircumstance problems increasingly, it has great significance to replace traditionalenergy sources by using renewable energy source to alleviate the energy shortage. Inrecent years, wind power is developing rapidly, and becomes a mature technology andthe most development potential of renewable energy. In the wind power market,Directly Driven Wind Turbine with Permanent Synchronous Generator (D-PMSG)attracts more and more attention. Compared to other wind energy generator,it hasadvantages of simple structure, high efficiency, low maintenance costs and higherreliability. For low-speed and multi-level generator, location and speed of detection isvery important for high-performance vector control.Because of the huge volume ofpermanent magnet wind generator, the high cost of installation of speed sensor and thelow system reliability due to vulnerable to external environmental impacts, thesensorless vector control mode is to become the inevitable choice of D-PMSG.The paper firstly introduces the wind power generation technology and thesensorless technology. Starting from characteristics of wind, mathematical model ofwind energy is established. And the mechanical characteristics of the wind turbine arestudied, modeled and simulated. As the components of the direct-drive wind powersystem, the permanent magnet synchronous motor, the DC bus link and a PWMconverter are introduced in detail, which are the foundation of the PMSG withoutposition/speed sensor control for the future analysis.Second, it analyzes the vector control principles of permanent magnetsynchronous generator. The MRAS based on flux observer method is selected. Theformula deducing is given to the design principles of MRAS and adaptive rule. Toovercome initial value, drift problems and resistance varies which effect the precisionof flux estimate, this paper analysis several improved method. A volume of feedbackis used in voltage model of stator flux observation. The volume of feedback is theerror of the current model and voltage model. Then the error is corrected by PIregulator. The stability of MRAS is analyzed by small-signal model. Finally the itintroduces Phase-locked loop(PLL) technology and the detection of rotor position andspeed of PMSG based on PLL.At last, the sensorless vector control of direct-driven permanent magnet wind power generator based on MRAS is analyzed by simulation and the simulation resultsare discussed. Then it shows that the improved MRAS speed estimation method hasthe better recognition accuracy, dynamic characteristics, it can meet the requirementsof system. In addition, the simulation of PLL which is used to estimate the rotorposition before grid-connected is built. And the result indicates that the PLL canestimate of rotor position accurately. To further verify the correctness and thefeasibility of the MRAS algorithms, the experiments are studied on the laboratorysimulation platform. It shows that the improved MRAS speed estimation method isfeasible.