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In this paper, firstly, a monopolar High Voltage Direct Current (HVDC) transmission system model has been formed. Series, parallel and series-parallel active direct current filter designs were carried out to suppress harmonics caused by the converters in this HVDC transmission system. Simulations of the designed HVDC transmission system using these filter were carried out in MATLAB Simulink. Waveforms and total harmonic distortion (THD) values of load current and voltage were obtained in this transmission system model for filtered and unfiltered conditions. Harmonics in the load voltage and current were suppressed to a large extent by active direct current filter used in the HVDC transmission system. Furthermore, THD values for current and voltage were obtained significantly below 5%. According to these results, designed active direct current filters which have simple structure and not complex controller offer significant advantages.

In this study, a comprehensive performance analysis of power factor correction control methods are presented for an interleaved single-phase rectifier operating under continuous conduction mode. The control of interleaved converter is achieved using proportional-integral control, average sliding control and predictive current control methods to obtain unity power factor and lower total harmonic distortion of input current. The interleaved power factor correction converters have many advantages in increasing power density, reducing input current ripple and RMS current of the boost capacitor, reducing filter volume, and cutting down the cost of materials. The analysis of the interleaved converter is presented and verified exactly by simulations and experimental carried out on 1 kW power and 50 kHz switching frequency. The performance of the current control methods for the interleaved converter is investigated by Matlab/Simulink program for different cases of operation such as change in input voltage and load. It is observed from the analysis that predictive current control method is more suitable than the others because it doesn't need sense current.

In this study, the steady state characteristic of a Double Output Induction Generator (DOIG) driven by wind turbine operating at variable speed (shaft speeds in the subsynchronous and supersynchronous regions), constant frequency and constant voltage is investigated. Mathematical model on time domain is obtained for wind turbine and double output induction generator separately. A fuzzy logic controller is designed to obtain maximum total output power from the generator considering the restrictions of the system and the speed of the wind which is not constant. Finally, the simulation results and experimental results carried out in the laboratory are compared. This study shows that using an appropriate control strategy, maximum output power can be obtained from the wind tribune connected to DOIG.