This study presents a wind energy conversion system based on a dual stator‐winding induction generator. The generator can work at variable wind speed and can also be connected to the grid. The proposed energy conversion system presents three operation zones that depend on the wind speed and are delimited by the power ratio assigned to each of the two stator windings. The generator design starts from a three‐phase squirrel‐cage induction machine and allows a simple assembling of the new windings, what results in an economical, robust and reliable machine. These features make the generator appropriate for wind energy conversion systems located in remote places or in developing areas with limited resources, as well as for distributed generation systems and microgrids. This report also includes experimental and simulation results of the generator operation in the three working areas.

This paper combines three different methods for the analysis of a self-oscillating bidirectional dc-dc converter under hysteresis control. First, the describing function method is used to predict the steady-state limit cycle, along with its oscillation amplitude and frequency. Second, the Tsypkin method is applied to provide more precise information on the dynamical behavior of the system. To complete the study, a sliding-mode approach is used to provide more insight into the system response in terms of its parameters. A comparative study among the results obtained from the different approaches in the frequency and time domain is given. Finally, an experimental prototype validates the theoretical and the numerical predictions.

Ferroresonance is one of the most destructive transient phenomena in power systems. This complex phenomenon involves the association of nonlinear magnetizing inductances and capacitances, and may be initiated in many different ways, which makes its characterization very difficult. This work links EMTP and MATLAB and presents some computer tools that have been developed for assessing ferroresonance behavior. These tools allow users to visualize 2-D and 3-D bifurcation diagrams which can be used for performing sensitivity analysis, predicting the phenomenon at different stages, and finding safety zones for power system parameter design.

This paper proposes a system, based on a self- excited induction generator with a shunt electronic converter, to feed isolated three-phase and single-phase linear or nonlinear loads. The electronic converter is composed by a three-phase four-wire voltage source inverter (VSI) and, connected to its dc side, two dc/dc converters. The VSI compensates the current harmonics, the reactive power and the load unbalances. The first of the dc/dc converters is a battery charger/discharger and the other converter dissipates the active power excess, through a chopper, so these dc/dc converters keep the active power balance of the complete system. The designed control architecture assures that, in steady state, the rms values of the voltages and the frequency remain at the their reference values. The simulated results show a good performance of the system under different loading conditions.

Load and supply parameters may be uncertain in microgrids (MGs) due for instance to the intermittent nature of renewable energy sources among others. Guaranteeing reliable and stable MGs despite parameter uncertainties is crucial for their correct operation. Their stability and dynamical features are directly related to the controllers’ parameters and power-sharing coefficients. Hence, to maintain power good quality within the desirable range of system parameters and to have a satisfactory response to sudden load changes, careful selection of the controllers and power-sharing coefficients are necessary. In this paper, a simple design approach for the optimal design of controllers’ parameters is presented in an islanded MG. To that aim, an optimization problem is formulated based on a small-signal state-space model and solved by three different optimization techniques including particle swarm optimization (PSO), genetic algorithm (GA), and a proposed approach based on the combination of both PSO and GA. The optimized coefficients are selected to guarantee desirable static and dynamic responses in a wide range of operations regardless of the number of inverters, system configuration, output impedance differences, and load types. Through the proposed design and tuning method, the performance of the MG is improved as compared to those obtained using state-of-art techniques. This fact is demonstrated by using numerical simulations performed on a detailed model implemented in PSIM^© software.

In this work, we present an electronic system that simplify the incorporation of additional sources to a previously existent small PV system. Particularly, we investigate how to proceed with a low voltage, high-current PEM fuel-cell. The proposed system is developed from the concept of loss-free resistor, and can be easily adapted to any type of energy source and storage elements. Among the advantages of the proposed system, the PV array keeps its maximum power point (MPP), with independence of the power delivered by the new source. In addition, the proposed system allows also a particular MPPT for the new source if required. Finally, as additional benefits, sources can the incorporated or extracted with hot-swapping, and the energy production profile can be smoothed, predictable, and even constant, as wanted by the utility grid regulators.