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The development of a revolutionary design for transmission lines was recently introduced by shifting phase configurations and sub-conductors into “unconventional” arrangements that were geometrically optimized to maximize natural power. The objective of this paper is to study the electromagnetic transients that result from the simultaneous and sequential line energization and re-energization of the previously developed unconventional high surge impedance loading (HSIL) lines. Statistical switching overvoltage (SSOV) studies are performed using a frequency domain method based on the inverse numerical Laplace transform. Compared to a conventional line, all unconventional HSIL line designs studied in this paper lead to very similar surges for long line lengths (400 km) and similar values for short line lengths (100 km), indicating additional advantages of these lines. The use of a frequency domain method for SSOV studies offers enhanced accuracy, simulation flexibility, and substantially lower computational burden compared with traditional time-domain methods. [ABSTRACT FROM AUTHOR]

This paper proposes a light, flexible, and yet reliable multiparametric estimation algorithm for grid-connected voltage-source-converter-based systems. This approach combines the nonlinear least squares (NLSQ) fitting algorithm and the steady-state extended harmonic domain (EHD) model to take into account the harmonic effects. The EHD model is used to take advantage of the harmonic content of the electrical signals to provide robustness and improved performance to the NLSQ estimation methodology. In addition, this harmonic formulation reduces the necessity of synchronized measurements. Details of the implementation are provided by an experimental case study, in which the grid equivalent (Thevenin voltage, inductance, and resistance), the ac-side filter (inductance and resistance), and the converter switching and conduction loss resistance are accurately estimated for three different operating conditions. [ABSTRACT FROM AUTHOR]

The use of new generation devices based on renewable energy is a subject that increasingly becoming more important for the development of new distributed generation systems; one device developed for this purpose is the permanent magnet linear generator (PMLG). This work deals with the performance and power quality assessment of the PMLG under 2 different generation scenarios of microgeneration: the wave energy converter and the free piston engine linear generator. The performance of the PMLG is evaluated using the finite element method and experimental results under steady state condition of a 100-W prototype are presented to test and validate the proposed process design. The actuator displacement inside the PMLG was obtained from the equation that governs the movement of the 2 systems under study; this displacement was the excitation function used to conduct the simulation and the laboratory experiments. This work contributes to the design and development of power components devoted to microgeneration and creates the need for the modelling and development of power electronic converters for helping in control and power quality. [ABSTRACT FROM AUTHOR]

The undesirable harmonic distortion produced by distributed generation units (DGUs) based on power-electronic inverters presents operating and power-quality challenges in electric systems. The level of distortion depends on the internal elements of the DGUs as well as on the characteristics of the grid, loads, and controls, among others. This paper presents a comprehensive method, focused on power-quality indexes and efficiency for the design of microgrids with multiple DGUs interconnected to the ac grid through three-phase multi-Megawatt medium-voltage pulsewidth-modulated-voltage-source inverters (PWM-VSI). The proposed design method is based on a least square solution using the harmonic domain modeling approach to effectively consider explicitly the harmonic characteristics of the DGUs and their direct and cross-coupling interaction with the grid, loads, and the other DGUs. Extensive simulations and analyses against PSCAD are presented in order to show the outstanding performance of the proposed design approach. [ABSTRACT FROM PUBLISHER]

Integrating power electronics to the grid has introduced new small signal–signal stability challenges, which are commonly studied with average time-invariant models and, more recently, with harmonic state–space models. In both approaches, it is common to obtain the models by following an analytical formulation, which can be tedious and impractical in systems with different controllers and topologies, just to mention a few examples. This paper proposes a numerical approach based on shooting methods and the recursive evaluation of the time-variant Jacobian along the steady-state orbits to construct automatically a periodic linear time-variant model and its respective linear time-invariant model using the extended harmonic domain; these models include explicitly the harmonic components. The proposed modeling approach can be applied to systems with different converter topologies, controllers, and modulation techniques. A nonlinear periodic switched system (grid-connected parallel inverter-based microgrid) is used to validate the proposed linearization approach. • Applicable to periodic switched nonlinear systems. • Shooting methods compute the steady state directly. • Convergence to stable and unstable periodic steady-state solution. • Jacobian is computed numerically as a by-product of the shooting method. • The small-signal model considers the effects of any modulation pattern. [ABSTRACT FROM AUTHOR]

This paper details a technique in the time domain for the fast periodic steady-state solution of systems with unified power-flow controllers (UPFCs) incorporating three strategies for the practical representation of the UPFC commutation process. The computation of the periodic steady-state solution of power systems with UPFCs including the proposed UPFC control strategies is efficiently obtained by extrapolation to the limit cycle using a Newton method based on a numerical-differentiation procedure. The periodic steady-state solution is validated against the solution obtained with the electromagnetic transient program PSCAD/EMTDC and against an implementation with the power system blockset of SIMULINK. [ABSTRACT FROM AUTHOR]

• An optimal design method in the Extended Harmonic Domain of the LCL filters. • Quantitative and qualitative assessment of different LCL filter design methods. • A Review of Passive Power Filters. • A Matlab graphic user interface (GUI) for the design of LCL filters. This paper presents a design method based on the extended harmonic domain modeling for L and LCL passive filters of active-front-end PWM two-level voltage source converters for grid-connected renewable energy sources. The proposed design method is tested under several operating scenarios, such as high and low power levels and switching frequencies. Also, a dedicated graphical user interface (GUI) with five other design methods is provided to ease the evaluation of the proposed design method. The GUI also computes the power quality indexes and the steady-state waveforms for each design methodology. In addition to this, an in-depth overview of filtering technologies and applications is presented to identify the primary practical use of passive filtering and to justify the use of LCL filter in grid-connected systems. The obtained results show that the proposed design method leads to the smallest passive filter parameters, and it is the only method that fulfills all the imposed power quality requirements as well as power specifications. [ABSTRACT FROM AUTHOR]

This paper presents a control scheme of a wide-area controlled static VAr compensator (WAC-SVC) and its real-time implementation in a hardware-in-the-loop (HIL) simulation scheme with three control objectives: (1) to increase the critical clearing time, (2) to damp the power oscillations, and (3) to minimize the maximum line current. The proposed control scheme considers a correction strategy to compensate the delays up to 200 ms. In addition to this, a generator tripping scheme based on synchrophasor measurements to determine the proximity to the loss of synchronism is proposed. A delay compensation algorithm based on polynomial approximations is also developed. The proposed WAC-SVC is experimentally validated using a Real-Time Digital Simulator platform (RTDS), industrial communication protocols, a commercial device for PMU-based control implementations, and digital relays with PMU capability. The real-time simulation results confirm its effectiveness and feasibility in real industrial applications. Furthermore, practical guidelines to implement this kind of control schemes are provided. [ABSTRACT FROM AUTHOR]

It is well known that a low level of electrolytes in batteries produces a malfunction or even failure and irreversible damage. There are several kinds of sensors to detect the electrolyte level. Some of them are non-invasive, such as optical sensors of level, while some others are invasive; but both require one sensor per battery. This paper proposes a different approach to detect the low electrolyte level, which neither requires invasive sensors nor one sensor for each battery. The approach is based on the estimation of the internal resistance of an equivalent electrical circuit (EEC) model of the battery. To establish the detection criterion of the low level of electrolytes, a statistical analysis is proposed. To demonstrate the feasibility of this approach to be considered a valid method, multiple experiments were performed. The experiments consisted of determining how the internal resistance is affected at eight different levels of electrolyte at different aging levels of vented lead–acid (VLA) batteries. The results have demonstrated the feasibility of this approach. Hence, this approach has the potential to be used for the reducing of sensors and avoiding invasive methods to determine the low level of electrolytes. [ABSTRACT FROM AUTHOR]

This paper deals with a battery energy storage system (BESS) in only one of its multiple operating modes, that is when the BESS is charging the battery bank and with the focus on the control scheme design for the BESS input stage, which is a three-phase LCL-filter PWM rectifier. The rectifier's main requirements comprise output voltage regulation, power factor control, and low input current harmonic distortion, even in the presence of input voltage variations. Typically, these objectives are modeled by using a dq model with its corresponding two-loop controller architecture, including an outer voltage loop and a current internal loop. This paper outlines an alternative approach to tackle the problem by using not only an input–output map linearization controller, with the aim of a single-loop current control, but also by avoiding the dq modeling. In this case, the voltage is indirectly controlled by computing the current references based on the converter power balance. The mathematical model of the three-phase LCL-filter PWM rectifier is defined based on the delta connection of the filter, which accomplishes the requirements of a 100 kW BESS module. Extensive simulation results are included to confirm the performance of the proposed closed-loop control in practical applications. [ABSTRACT FROM AUTHOR]