Wind energy is one of the most promising sources of renewable energy for the future. Although wind turbine technology is more mature than, for example, wave and tidal energy, there is still room for improvement. Small and medium-sized wind turbines in particular often have a disappointing energy yield. The research presented in this PhD aims to increase this energy yield. On the one hand, the efficiency of the generator and converter is jointly increased by the use of a non-conventional optimized current form. By better matching this waveform to the non-sinusoidal voltage waveform of the generator, losses can be reduced. On the other hand, the energy yield is also increased by taking into account the losses in the maximum power control. Classic power control maximizes turbine rotor power. The scheme proposed here takes into account a possible shift due to losses in the system. The PhD also provides advice to the wind turbine industry to avoid some common design mistakes.