Research On Machine Side Three-level Converter Of Direct-driven Wind Power Based On Sensorless Algorithm

With the advantages of simplicity, high efficiency and reliability, permanent magnet synchronous generator(PMSG) was increasingly applied to the industry. Compared to doubly-fed wind energy system, direct-drive wind energy system is superior in maximum power point tracking(MPPT), grid control and low voltage ride through(LVRT). As the conventional direct-drive wind energy system, the two-level PWM converter was usually applied, but the future of which are high voltage and high capacity, and three-level will be a good choice. Accurate rotor position angle detection was essential for the vector control of PMSG, and the solution usually was installing a position sensor in shaft, which not only increases the cost, also reduces the reliability by the environment as well. Fortunately, the sensorless technique can solve the problem and improve the reliability.Firstly, this paper applied a three-level(VIENNA) to the direct-drive wind energy system. Mathematical model of PMSG & VIENNA were built, and the equivalent circuit as well. Then the vector control based on zero d shaft current control of PMSG was introduced, and parameter design of the controller was displayed. The imbalance of VIENNA was analyzed, and the neutral voltage balance control equation was reduced.Secondly, sensorless algorithm of PMSG was discussed emphatically, from the flux estimation and back electromotive force(EMF) estimation. The sensorless based on closed loop of the stator flux estimation was further researched, the use of PI and sliding mode controller as a regulator of back EMF estimation of the sensorless algorithm was compared. And then the improved sensorless algorithm of sliding mode control type based on the second order generalized integrator(SOGI) was proposed, which can more accurately estimate the rotor position angle and has strong robustness.Finally, the simulation model and experimental platform were set up to verify the theory analysis. The accuracy and reliability of the above mentioned three sensorless algorithms and the improved algorithm were verified by MATLAB/Simulink model. The experiment platform based on DSP chip(TMS320F2812) and a 10 k W direct-drive system simulation platform was set up, the program of vector control algorithm and the sensorless algorithm was designed, which verified the sensorless algorithm.