This paper presents the design, modeling, implementation, and experimental results of an advanced current-sensorless control scheme for voltage source converter-power factor correction rectifiers. This proposal is aimed to reduce the complexity of the control while maintaining desirable features for ac/dc conversion, such as unity power factor, low total harmonic distortion in input current, continuous regulation of the dc voltage even facing ac voltage sags and dynamic load changes. Unlike other proposals, this scheme has a single feedback proportional-integral loop, uses few mathematical operations, and the dq0 reference frame is not included in the control scheme. These characteristics simplify the implementation of the proposed control thus improving its efficiency. The theoretical analysis and simulation validate the technical feasibility of the proposed control, and finally, various cases of study and experimental results obtained with a laboratory scale-down prototype are presented to confirm the viability and performance of the control.

In this paper, the active front-end (AFE) converter topology for the total harmonic distortion (THD) reduction in a wind energy system (WES) is used. A higher THD results in serious pulsations in the wind turbine (WT) output power and several power losses at the WES. The AFE converter topology improves the capability, efficiency, and reliability in the energy conversion devices; by modifying a conventional back-to-back converter, from using a single voltage source converter (VSC) to use pVSC connected in parallel, the AFE converter is generated. The THD reduction is achieved by applying a different phase shift angle at the carrier of digital sinusoidal pulse width modulation (DSPWM) switching signals of each VSC. To verify the functionality of the proposed methodology, the WES simulation in Matlab-Simulink^® (Matlab r2015b, Mathworks, Natick, MA, USA) is analyzed, and the experimental laboratory tests using the concept of rapid control prototyping (RCP) and the real-time simulator Opal-RT Technologies^® (Montreal, QC, Canada) is achieved. The obtained results show a type-4 WT with a total output power of 6 MVA, generating a THD reduction up to 5.5 times of the total WES current output by Fourier series expansion.

In this paper, the mathematical model of type-4 wind turbine topology is developed to represent its dynamic behavior. The main objective of a type-4 wind turbine is to deliver active power to the system, but to perform this action; it must absorb reactive power from the power network, causing disturbances and stress in the rest of the power system. Through the dynamic control system used in the back to back converter, the reactive power compensation at the PCC is achieved, making possible the energy exchange between the type-4 wind turbine and the rest of the power network.

The Active Front-End (AFE) converter topology is generated by modifying a conventional back-to-back converter, from using a single VSC to use pVCS connected in parallel. The AFE configuration improves the capability, efficiency and reliability of energy conversion devices connected to the power system. In this paper, a novel technique to reduce the total harmonic distortion (THD) in an AFE converter topology is proposed and analyzed. The THD reduction is achieved by applying a phase shift angle in the SPWM switching signals of each AFE converter VSC. To verify the functionality and robustness of the proposed methodology, the power system simulation in Matlab-Simulink is analyzed for a type-4 wind turbine converter with total power output of 9MW. The obtained simulation results show a THD reduction up to 2.5 for AFE connected to the power network.