A wind turbine two level back-to-back converter power loss study

Wind power conversion systems are a widespread renewable energy source and, as such, have been studied intensely over the past two decades. Wind energy conversion system is connected to the electrical grid through a power converter, an LC filter and a step-up transformer. It is necessary to know the efficiency of the whole energy transfer system and to know the efficiencies of each individual part of that system, i.e. converter, filter and transformer efficiencies, in order to achieve a high-efficiency energy conversion system. This paper presents a simulation model used to determine the grid- and generator-side inverter losses, LC filter and step-up losses, total converter losses and converter efficiency, as well as grid voltage THD and grid and converter current THDs. This paper also decribes the method used to determine the maximum torque per amp (MTPA) algorithm parameters, used to control the generator-side inverter. Simulations were done at nominal operating conditions, as well as for varied DC link and grid voltages, ranging from zero to nominal converter power.