Evaluation of electromagnetic fields, which is caused by the lightning channel, is an appealing topic in order to consider the indirect effects of lightning on the power lines. In most computations ...of lightning electromagnetic fields, the return stroke channel is assumed to be a straight and a vertical channel. However, in reality, the lightning channel is most often inclined and has some tortuosity on scales. This paper provides general expressions for the electric field and the magnetic flux density, at any point, that are radiated from an inclined lightning channel. These general expressions are based on the Maxwell’s equations. The proposed equations can estimate the components of the electric field and the magnetic flux density directly at any observation point and for any kind of lightning channel (vertical or inclined). Also, by using the suggested general expressions, the electromagnetic fields can be computed in close, medium and far ranges. The proposed expressions support the notion of the vertical lightning channel by assuming the channel angle with respect to Z-axis equals zero. In this paper, the analysis of the suggested expressions for the electric field and the magnetic flux density that radiated from an inclined lightning channel as well as their verifications by comparing their results with the results of the others is achieved. Also, these suggested expressions are used to investigate the effect of channel geometry, number of the segments to which the channel is sub-divided, position of the observation point with respect to each segment of the channel, and each segment orientations (defined with the azimuth angle
ϕ
) and inclination angle
θ
on the electromagnetic field distributions.
The power system is nonlinear with frequent changes in operating regions. Analog proportional integral derivative PID controllers are widely used in excitation control of power systems. Fuzzy logic ...control is often viewed as a form of nonlinear PD, PI or PID control. This paper describes the design principle, tracking performance of a fuzzy proportional-integral PI plus derivative D controller. This controller is developed by first describing discrete time linear PID control law and then progressively deriving the steps necessary to incorporate a fuzzy logic control mechanism into the modifications of the PID structure. The bilinear transform (Tustin’s) is used to discretize the conventional PID controller. In this paper some performances criteria were utilized for comparison with other PID controllers, such as settling times, overshoots and the amount of positive damping. The proposed scheme is robust to variations in operating conditions to match the fluctuations of load demand in the power system.
This paper presents a Model Predictive Control (MPC) technique for frequency stabilization of renewable power systems with inherent nonlinearities. To prove the effectiveness of the proposed ...technique, the Egyptian Power System (EPS), which includes both conventional generation units (i.e., non-reheat, reheat and hydraulic power plants) and wind turbines is tested using Matlab/SIMULINK® software. Furthermore, the performance of the proposed MPC technique is compared with an optimal Proportional-Integral (PI) controller-based Particle Swarm Optimization (PSO) algorithm under different load profiles and system uncertainties. The simulation results emphasize the superior robustness of the proposed MPC-based LFC in comparison to the optimal PI controller.
The applications of shunt FACTS devices as Static Var Compensator SVC and Static Synchronous Compensator STATCOM controllers and series FACTS device as Static Synchronous Series Compensator SSSC ...controllers are thoroughly investigated in this paper to improve the transient stability performance of a power system. Separately and combination of SVC, STATCOM and SSSC controllers are proposed and compared. The effect of combined SVC and STATCOM controllers in enhancing power system transient stability has been examined. By combination among shunt FACTS and with series FACTS, the transient stability performance of the system has been significantly unproved than used each one independently. The proposed controllers are tested on a two-area multi-machine power system which is close to realistic interconnected power system model and subjected to a severe disturbance of three-phase fault at the mid-point of one tie line. The nonlinear simulation results are presented to show the effectiveness of the proposed controllers and its ability to provide efficient damping of the system oscillations.
This paper proposes a new topology for single-phase photovoltaic PV grid-tied applications. The whole system consists of a two-stage, high-frequency boost inverter cascaded by rectifier-inverter ...system. A single-phase high-frequency transformer is used to link both stages and provide galvanic isolation between the AC and DC sides. A single-stage high-frequency boost inverter (HFBI), in the first stage, boosts and converts the DC output voltage of the PV array to a high-frequency single-phase square waveform and achieves maximum power point tracking (MPPT). In the second stage, the rectifier-inverter system (RIS) interfaces HFBI to the grid. The proposed topology has many advantages such as increasing the inverter output voltage level, MPPT, high reliability, small size, and light weight. In addition, a proportional integral current control (PI) is used to inject a sinusoidal current into the grid at unity power factor. The proposed topology has been verified analytically using PSIM software and experimentally by using a laboratory prototype.
This paper proposes a new topology for a single-phase grid-tie DC-AC boost inverter for the application of PV systems that utilize high-frequency transformer for galvanic isolation. In the first ...stage, a new single-stage high-frequency boost inverter is proposed to boost and convert the DC output voltage of the PV modules to a high-frequency single-phase square waveform in addition to extracting maximum power point (MPP) from PV modules. The second stage is a direct single-phase AC-AC matrix converter that interfaces the system to the grid. Therefore, a single-phase high-frequency transformer is used to link both stages and provide isolation between the AC and DC sides. The proposed system has many advantages such as increasing the inverter output voltage level, maximum power point tracking (MPPT), high reliability, safety, small size and light weight. The proposed topology has been verified analytically by using PSIM software and experimentally by using a laboratory prototype.
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