The aim of this work is to analyze a typical configuration of a Wind Turbine Generator System (WTGS) equipped with a Variable Speed Generator. Nowadays, doublyfed induction generators are being widely used on WTGS, although synchronous generators are being extensively utilized too. There are different types of synchronous generators, but the multi-pole Permanent Magnet Synchronous Generator (PMSG) is chosen in order to obtain its model. It offers better performance due to higher efficiency and less maintenance since it does not have rotor current and can be used without a gearbox, which also implies a reduction of the weight of the nacelle and a reduction of costs. Apart from the generator, the analyzed WTGS consists of another three parts: wind speed, wind turbine and drive train. These elements have been modeled and the equations that explain their behavior have been introduced. What is more, the whole WTGS has been implemented in MATLAB/Simulink interface. Moreover, the concept of the Maximum Power Point Tracking (MPPT) has been presented in terms of the adjustment of the generator rotor speed according to instantaneous wind speed.

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In this paper, a novel scheme for obtaining the fundamental-frequency positive-sequence grid voltage is proposed. The method is based on four simple mathematical transformations; two of them are in the stationary reference frame, which are able to eliminate odd harmonics from the original signals. The other two transformations are implemented in a synchronously rotating reference frame in order to eliminate even harmonics. The output of the last transformation block is the input to a synchronous reference-frame phase-locked loop for detecting the frequency and position of the positive-sequence voltage vector. The proposed algorithm was verified through simulations and experiments by applying distorted and unbalanced signals, containing positive and negative-sequence components. The results are in agreement with those theoretically predicted and indicate that the proposed scheme has a great potential for use in grid-connected converter synchronization algorithms.Index Terms-Converters, interconnected power systems, power quality.

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Integration of distributed generation (DG) such as photovoltaics (PV) represents a challenge for the traditional operation of distribution power systems. As the installed power of DGs grows, grid codes are being modified to involve DGs in the provision of ancillary services. This includes the ability to ride-through large disturbances. In this paper, the behavior of a single-stage PV system under unbalanced voltage conditions is studied, and a fault ride-through control scheme is proposed which is able to support the grid through the injection of reactive power. Furthermore, adjustable power quality is enabled as a trade-off between power ripple and current harmonics. The control scheme makes use of a current controller based on the space vector Fourier transform concept. No rotational transformation is required, and zero steady-state error is ensured when tracking distorted current references. The controller was tested in detailed PSCAD/EMTDC computer simulations, and implemented in a real grid-connected PV system to demonstrate its performance under unbalanced voltage conditions.

Master-Slave configuration is a suitable alternative\ud to droop control method used in microgrids. In this configuration,\ud only one inverter is the master, while the others are slaves. The\ud slave inverters are always current controlled whereas the master\ud inverter should have two selectable operation modes: current\ud controlled, when the microgrid is connected to the grid; and\ud voltage controlled, when it is operating in island mode. In gridconnected\ud mode, the master needs a synchronization system to\ud perform the accurate control of its delivered power, and, in\ud island mode, it needs a voltage reference oscillator that serves\ud as a reference to the slave inverters. Based on the master-slave\ud concept, this paper proposes a single system that perform both\ud functions, i.e., it can act as a synchronization system or as\ud a voltage reference oscillator depending on an input selector.\ud Moreover, the system ensures a smoothly transition between\ud the two operation modes, guaranteeing the safety operation of\ud the microgrid. Experimental results are provided to confirm the\ud effectiveness of the proposed system.Peer ReviewedPostprint (published version