Modeling and Investigation Performance of Small-Scale PMSG based HAWT with FOC

This paper focused on modeling and simulation of small-scale horizontal axis wind turbine (HAWT) based on permanent magnetic synchronous generator (PMSG) with filed oriented control (FOC) circuit connected to 3-phase full bridge rectifier by MATLAB software. FOC system developed for generator side converter to regulate mechanical speed and electromagnetic torque at variable wind speed. Space vector pulse width modulation (SVPWM) had been implanted in FOC system to turn on six-IGBT switches and validate pure and steady-state of output voltage. Results showed optimum performance coefficient was 0.48 and tip speed ratio 8.1 at zero pitch angle, also when pitch angle increase by 5°coefficient performance decreased to 0.35. The simulated waveforms of the mechanical speed, and electromagnetic torque were contained two case, before and after applied FOC. With FOC, the results shown faster and smooth response to the faster change in wind speed.


Introduction
Variable speed wind turbine system has many features as compared with fixed speed wind turbine system such as low cost, small size, high efficiency, high power production, high power quality and, maximum power can be extracted at variable wind speed. There are many types of generators use in wind turbine systems. Permanent Magnet Synchronous Generator (PMSG) its common applied in modern wind turbines because of low weight, small size, high pole number, gear-less, less maintenance and, compact structure. Therefore it is an excellent applicant for this purpose. Power delivered to grid by variable speed wind turbines depend on wind speed and rotor speed of generator [1]. In the generating side, there are many control strategies used to regulate speed and extract maximum power of variable speed wind turbines. Felid oriented control (FOC) is a popular and modern control method because archive optimal utilization of wind energy [2]. A literature review represent ideas and researchers efforts in dealing with theoretical (simulation) and experimental of wind energy conversion system based on PMSG. P. Thayumanavan et al. [3] presented maximum power point tracking (MPPT) method based on sensor-less FOC to control speed and torque of PMSG. Electromagnetic torque had been control by set ݅ ௗ to zero and control by ݅ . B. Lahfaoui et al. [4] modeling and simulation of MPPT based on PMSG. MPPT connected DC boost convertor. Perturb and observe algorithm used in MPPT. B. Jain et al. [5] reviewed control methods of PMSG based wind energy conversion system connected to grid. Control methods included direct and vector methods. Direct torque and field oriented control method used to control speed and torque in machine side, while direct power control and voltage oriented control used in grid side. This paper focused as follows, section 2 presents modeling aerodynamic HAWT. In section 3, presents modeling of PMSG, MPPT based FOC and, VOC.

Aerodynamic Modeling of HAWT
The kinetic energy available from wind energy for x distance [6]: Wind power is derivative of kinetic energy: Air density ߩ equal 1.225 kg/m ଷ at stander conditions (101.3kPa, 288K).
Betz coefficient ‫ܥ(‬ ) is factor prove that ideal turbine can't extract more than 0.593 from the wind power.

Electrical Modeling
3.1. PMSG modeling PMSG rotor contained poles of permanent magnet (PM) generate magnetic field. Figure 2 shows equivalent circuit of 3-phase PMSG has 2-poles with abc-axis of stator. Current induced by rotor divide into two quadrature, q-axis and d-axis. Rotor position angle ‫ݎߠ‬ is angle made angle between d-axis and aaxis [7]. Following basic equations of PMSG modeling: Active power ܲ ௗ and reactive power ܳ ௗ in dq-frame Electromagnetic torque:

Modeling of flied oriented control
Because of fluctuation of wind speed that effect on speed of generator and power production field oriented control (FOC) use in generator side. By set ݅ ௗ௦ * = 0, maximum electromagnetic torque can be achieve. By quadrature current (݅ ௦ * ) can be controlled by electromagnetic torque [8].  Figure 4: FOC simulation.

Results and Discussions
Wind turbine based on PMSG system was simulated by MATLAB/Simulink 2017b. Figure 5 shows the coefficient performance with tip speed ratio, optimum performance coefficient was 0.48 at tip speed ratio 8.1 while pitch angle was 0 . It is clear from the figure when pitch angle increase by 5 coefficient performance decreased to 0.35 at tip speed ratio 9.3. Mechanical torque effected mainly by pitch angle, when pitch angle fixed at 0 maximum torque was 3.85N.m at mechanical speed 600r.p.m. When pitch angle increased by 5 mechanical torque drop to 2.64N.m at mechanical speed 320.3r.p.m.

Conclusions
This paper presented modeling and simulation of HAWT based on PMSG with filed oriented control system had been simulated by MATLAB/Simulation. Wind turbine system has rated 220W. To achieve stable operation of PMSG at variable wind speed the flied oriented control system was applied. Maximum mechanical torque and optimum performance coefficient were obtained at fixed pitch angle (0 ). Steadystate of electromagnetic torque and mechanical speed had been achieved under variable wind speed when used field oriented control. Machine stator flux linkages in dq-frame Wb