In this work, a near-unity power factor front-end rectifier employing two current control methods, Average Current Control and Hysteresis Current Control, is considered. This rectifier is interfaced with a fixed-pitch wind turbine driving a Permanent Magnet Synchronous Generator. A traditional diode bridge rectifier without any current control is used to compare the performance with the proposed converter. Two constant wind speed conditions and a varying wind speed profile are used to study the performance of this converter for a rated stand-alone load. The parameters under study are the input Power Factor and Total Harmonic Distortion of the input currents to the converter. The wind turbine generator-power electronic converter is modeled in PSIM and the simulation results verify the efficacy of the system in delivering satisfactory performance for the conditions discussed. The efficacy of the control techniques is validated with a 1.5kW laboratory prototype and the experimental results are presented.

This study explores the feasibility of an AC/DC/AC drive with near unity power factor front-end rectifier and five-level rear-end multilevel inverter topology with a focus on achieving lower voltage total harmonic distortion and higher energy efficiency. The unity PF front-end rectifier in this AC/DC/AC drive may cause unbalanced voltage in the DC bus capacitors leading to high voltage distortion on the output AC voltage of a rear-end multilevel inverter. Based on the analysis, modelling and experimental results, rear-end multilevel flying-capacitor inverter with unity PF front-end rectifier in an AC/DC/AC power drive is proposed which is able to provide better DC voltage balancing when compared to diode-clamped topology. Having no diode components being used in this multilevel inverter, the flying-capacitor topology produces lesser commutation losses. Furthermore, rear-end multilevel flying-capacitor topology offers better efficiency and good quality output voltage without any bulky and expensive LC filter and even without any additional DC voltage balancing circuitry. The analytical performance of the drive is verified on a 1.3 kW laboratory prototype.

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