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In this paper, a small-scale standalone wind energy conversion system composed of a squirrel-cage induction generator, a buck converter and a current-source inverter is proposed, as an attractive renewable energy solution for off-grid communities. Geared squirrel-cage induction generators are well-known for their robustness, simplicity, light weight and low cost. Current-source inverters, even though mainly used in medium-voltage, high power applications, and proposed for megawatt-level grid-connected wind energy conversion systems, offer potential benefits in small-scale off-grid wind energy conversion systems that are yet to be investigated and evaluated against those of commonly-used voltage-source inverters. In the proposed system, the generator's shaft speed is controlled by a buck converter to extract maximum available wind power in normal mode of operation, and the wind power is dumped when it is not possible to absorb maximum available power by the storage system and the load. A novel scheme for integration of a battery energy storage system is proposed and an effective power management algorithm is employed to maintain the supply-demand power balance through direct control of dc-link current. A systematic approach for the dc-link inductor design is presented. The feasibility of the proposed system and its performance under variable wind and load conditions are analyzed and demonstrated through simulation. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this paper is to provide an analytical review of wind turbine-generator systems for stand-alone applications. The review focuses on variable-speed wind turbines, as the future trend in wind energy conversion, in contrast with the traditional fixed-speed wind turbines. Indirect-drive and direct-drive turbines are comparatively evaluated. The concerns about long-term availability of permanent magnet materials and its impact on the future of permanent magnet synchronous generator are addressed. Having cost and efficiency in mind, viability of indirect-drive squirrel cage induction generator for stand-alone wind energy conversion systems is discussed. As an efficient induction machine design, permanent magnet induction generator is also examined. Finally, the potential of using switched reluctance machine, as a generator, in a direct-drive wind turbine system is investigated. [Copyright &y& Elsevier]

Abstract: Photovoltaic grid-connected inverters are distributed power generation devices that convert the dc power from solar panels to high-quality ac power at the utility grid interface. Adopting modular design in these systems improves expandability, serviceability, reliability and efficiency. In this paper, the phase-shifted carrier technique, which is normally used in high-power multiconverter schemes, is applied to a modular residential photovoltaic grid-connected inverter to improve the output power quality. First, it is shown, through analysis and simulation, that in the commonly-used grid-connected inverter topology based on the phase-shift modulated full-bridge converter, the well-known rule for the phase-shift between the carrier signals of the adjacent modules is not effective for both odd and even number of modules. Then, a new general rule for the phase-shift is systematically derived and its effectiveness in improving the output power quality for odd and even numbers of modules is verified through simulation. [Copyright &y& Elsevier]

Abstract: Unified power flow controller (UPFC) and interline power flow controller (IPFC) are FACTS devices that can control the power flow in transmission lines by injecting active and reactive voltage components in series with the lines, using power converter modules, based on an externally regulated dc-link voltage. One key issue, in this application, is to find a relationship between the injected voltage and the resulting power flow in the line. In this paper, this relationship is derived analytically, and used to design two power flow control schemes. The proposed control schemes are applicable to any series-connected FACTS controller with the capability of producing a controllable voltage. In this paper, the proposed power flow control schemes are applied to a voltage-sourced converter-based IPFC, and the resulting control performances are examined using PSCAD/EMTDC simulation package. The simulation results show the effectiveness of the proposed power flow control schemes. [Copyright &y& Elsevier]

Battery Energy Storage Systems (BESS) are important for applications related to both microgrids and electric vehicles. If BESS are used as the main energy source, then it is required to include adequate procedures for the estimation of critical variables such as the State of Charge (SoC) and the State of Health (SoH) in the design of Battery Management Systems (BMS). Furthermore, in applications where batteries are exposed to high charge and discharge rates it is also desirable to estimate the State of Maximum Power Available (SoMPA). In this regard, this paper presents a novel approach to the estimation of SoMPA in Lithium-Ion batteries. This method formulates an optimisation problem for the battery power based on a non-linear dynamic model, where the resulting solutions are functions of the SoC. In the battery model, the polarisation resistance is modelled using fuzzy rules that are function of both SoC and the discharge (charge) current. Particle filtering algorithms are used as an online estimation technique, mainly because these algorithms allow approximating the probability density functions of the SoC and SoMPA even in the case of non-Gaussian sources of uncertainty. The proposed method for SoMPA estimation is validated using the experimental data obtained from an experimental setup designed for charging and discharging the Lithium-Ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses a new technique for controlling SVCs (Fixed Capacitor–Thyristor Controlled Reactor) in power systems with the aim of canceling the reactive current component of the load. A complete model of the SVC with its control circuit is set up and simulated in the EMTDC program. The generated harmonics from the proposed SVC controller are considered to design simple tuned filters to cancel the undesirable harmonic components. The effect of these filters is considered as well in the SVC control design, so that the reactive current component absorbed by the combination of the load, SVC, and filters is eliminated. The proposed control technique is compared with respect to a standard PI-based SVC controller. [Copyright &y& Elsevier]