A new selective harmonic elimination method for wind farm using permanent magnet Synchronous generator, under wind speed change

Different types of generators are used in wind farms including Synchronous and Asynchronous generators and Double Fed Induction Generators (DFIG). In Synchronous generator case, a power electronic circuit called a cyclo-converter is used as an interface to connect the generator to network. This circuit uses a DC-AC inverter with controllable switches that implies the proper and fixed amplitude and frequency in the output. This paper proposes a new method to minimize the harmonics amplitude that contains the firing angles control and a three-phase coupling transformer. In this method, 11 firing angles are defined for every bridge in a quarter of cycle. Then all the harmonic amplitudes is calculated as a function of θ₁ to θ₁₁. Then an objective function is defined as a complex of unwanted harmonics (except the even harmonics, and triplen harmonics that are eliminated with the coupling three-phase transformer). This objective function is minimized with numerical methods, to find the optimized values of θ₁ to θ₁₁. All of this calculation are redone for some admissible amounts of V_dc in a bounded certain range, and some operating points are gained. A neural networked, trained by these operating points, will have the control of firing the switches after that.