Novel perturbation and observation algorithms for variable-speed wind turbine generator systems

In this paper, two novel perturbation and observation (P&O) algorithms for maximising the output power of variable-speed wind turbine generator (WTG) systems are proposed. The proposed P&O algorithms use adaptive perturbation step sizes and adaptive observation periods, which are automatically tuned with turbine coefficient errors and rotor speed errors, respectively. The purpose of adopting adaptive parameters is to decrease steady-state oscillations around optimal operating power points, increase the tracking speed and keep the perturbation tracking in the right direction with small rotor speed overshoots under rapid wind speed variations. The proposed P&O algorithms are employed for estimating reference rotor speeds and operating duty cycles without the knowledge of wind turbine and generator parameters. The proposed WTG system include (i) a horizontal-axis wind turbine (HAWT), which is emulated by an induction motor and an AC driver; (ii) a permanent magnet synchronous generator (PMSG); (iii) a diode rectifier; (iv) a DC-DC boost converter and (v) a variable resistive load. The stability and rapidity of the proposed P&O algorithms are validated under random wind speeds. The experimental results show that the tracking power losses using the proposed P&O algorithms are less than those using a classic P&O algorithm.