A predictive power control for a four- switch three phase (FSTP) grid side converter (GSC) of doubly fed induction generators (DFIG) is presented. In this new method, three voltage vectors are employed to ensure that the proposed strategy maintains the switching frequency constant while the ripple of the active and reactive powers of the GSC is minimized. Moreover, a compensation power to eliminate the DC voltage deviation in the capacitors is presented, and it can be estimated without using any low pass filter. The proposed method can be implemented in a microcontroller very easily. Firstly, the proposed strategy has been evaluated in Matlab/Simulink environment and afterwards it was implemented in a laboratory prototype. The simulation and experimental results of the proposed predictive strategy show that it is capable to suppress the DC link voltage offset, featuring balanced currents and a fast dynamic response while the GSC current THD is low. Furthermore, the performance of the proposed method is compared to two other predictive controls. The results prove that the proposed method is well suitable for the FSTP GSC of a DFIG.

This paper presents a model predictive current control (MPCC) for three-phase four-switch converters (TPFSC) connected to surface permanent magnet synchronous generators (SPMSGs) in oscillating water column (OWC) wave energy plants, that brings some benefits over the existing control methods used in this type of plants. The proposed MPCC for TPFSC follows the current references with great accuracy whereas the switching frequency of the IGBTs is fixed and low. This method minimizes the current reference tracking error, and its fast response makes it suitable for the power take-off (PTO) systems present in wave energy converters (WECs). Furthermore, the system features a fast capacitor voltage offset suppression control. The dynamic performance and the voltage offset control of the proposed strategy for TPFSC feeding a SPMSG is evaluated in Simulink environment. Later, experimental studies are carried out on an 8.7 kW laboratory SPMSG prototype. Finally, the capability of the proposed method to harvest the maximum energy from irregular waves is assessed using an OWC power plant emulator.

The increasing penetration of Electric Vehicles (EVs) in LV distribution networks can potentially cause voltage quality issues such as voltage unbalance and under-voltage conditions. According to the EV charger characteristics, some strategies can be adopted to mitigate the aforementioned effects. Smart decentralized charging controls seem to be a more practical solution than centralized controls, since there is no need for communication because they rely only on local measurements. The four most relevant decentralized charging strategies, two for single-phase and two for three-phase EV chargers, have been implemented in a typical three-phase four-wire European LV distribution network. Simulations have been carried out for scenarios with single-phase EV chargers, three-phase EV chargers, and a combination of both. Single-phase controls are aimed at under-voltage regulation, while three-phase controls are focused on mitigating voltage unbalance. Results show that the implementation of a decentralized EV charging control is an adequate solution for Distribution System Operators (DSOs) since it improves the reliability and security of the network. Moreover, even though decentralized charging control does not use any communication, the combination of three-phase and single-phase controls is able to mitigate voltage unbalance while preventing the under-voltage condition.

This paper focuses on Hybrid Energy Storage Systems (HESS), consisting of a combination of batteries and Electric Double Layer Capacitors (EDLC), for electric urban busses. The aim of the paper is to develop a methodology to determine the hybridization percentage that allows the electric bus to work with the highest efficiency while reducing battery aging, depending on the chosen topology, control strategy, and driving cycle. Three power electronic topologies are qualitatively analyzed based on different criteria, with the topology selected as the favorite being analyzed in detail. The whole system under study is comprised of the following elements: a battery pack (LiFePO4 batteries), an EDLC pack, up to two DC-DC converters (depending on the topology), and an equivalent load, which behaves as an electric bus drive (including motion resistances and inertia). Mathematical models for the battery, EDLCs, DC-DC converter, and the vehicle itself are developed for this analysis. The methodology presented in this work, as the main scientific contribution, considers performance variation (energy efficiency and battery aging) and hybridization percentage (ratio between batteries and EDLCs, defined in terms of mass), using a power load profile based on standard driving cycles. The results state that there is a hybridization percentage that increases energy efficiency and reduces battery aging, maximizing the economic benefits of the vehicle, for every combination of topology, type of storage device, control strategy, and driving cycle.

Doubly fed induction machines typically work as a generator in wind turbine systems and as motor/generator in pump storage hydropower plants. Nowadays they have an important role in the integration of renewable energies in power systems. This paper presents a new technique for differential protection of doubly fed induction machines, including the rotor. The proposed protection, which is based on the comparison of the vector components Id-Iq of the rotor and stator currents, can protect the whole induction machine during the internal faults. This protection considers the dynamic variation of the rotor frequency and the extremely low rotor frequency along the different operation points of the DFIM. The proposed method is validated using simulations on a 2 MW DFIM and the experimental results are obtained in a laboratory setup. The results show that the proposed differential protection effectively protects the entire induction machine during internal faults and does not trip in case of external faults