Optimal SSSC-based power damping inter-area oscillations using firefly and harmony search algorithms

The static synchronous series compensator (SSSC) can add a series reactance to the transmission line, and when it is fed using auxiliary signals, it can participate in damping inter-area oscillations by changing the series reactance. In this paper, the effect of the SSSC on small-signal stability is investigated. The design of a controller for damping oscillations is designed and discussed. Moreover, using the firefly and the harmony search algorithms, the optimal parameters controlling SSSC are addressed. The effectiveness of these two algorithms and the rate of SSSC participation in damping inter-area oscillation are also discussed. MATLAB software was used to analyse the models and to perform simulations in the time domain. The simulation results on the sample system, in two areas, indicated the optimal accuracy and precision of the proposed controller

Three-dimensional potential and electric field distributions in HV cable insulation containing multiple cavities

Cross-linked polyethylene is widely used as electrical insulation because of its excellent electrical properties such as low dielectric constant, low dielectric loss and also due to its excellent chemical resistance and mechanical flexibility. Nevertheless, the most important reason for failure of high voltage equipment is due to its insulation failure. The electrical properties of an insulator are affected by the presence of cavities within the insulating material, in particular with regard to the electric field and potential distributions. In this paper, the electric field and potential distributions in high voltage cables containing single and multiple cavities are studied. Three different insulating media, namely PE, XLPE, and PVC was modeled. COMSOL software which utilises the finite element method (FEM) was used to carry out the simulation. An 11kV underground cable was modeled in3D for better observation and analyses of the generated voltage and field distributions. The results show that the electric field is affected by the presence of cavities in the insulation. Furthermore, the field strength and uniformity are also affected by whether cavities are radially or axially aligned, as well as the type of the insulating solid. The effect of insulator type due the presence of cavities was seen most prevalent in PVC followed by PE and then XLPE

Hierarchical control strategy for a three-phase 4-wire microgrid under unbalanced and nonlinear load conditions

This paper proposes an improved hierarchical control strategy consists of a primary and a secondary layer for a three-phase 4-wire microgrid under unbalanced and nonlinear load conditions. The primary layer is comprised of a multi-loop control strategy to provide balanced output voltages, a harmonic compensator to reduce the total harmonic distortion (THD), and a droop-based scheme to achieve an accurate power sharing. At the secondary control layer, a reactive power compensator and a frequency restoration loop are designed to improve the accuracy of reactive power sharing and to restore the frequency deviation, respectively. Simulation studies and practical performance are carried out using the DIgSILENT Power Factory software and laboratory testing, to verify the effectiveness of the control strategy in both islanded and grid-connected mode. Zero reactive power sharing error and zero frequency steady-state error have given this control strategy an edge over the conventional control scheme. Furthermore, the proposed scheme presented outstanding voltage control performance, such as fast transient response and low voltage THD. The superiority of the proposed control strategy over the conventional filter-based control scheme is confirmed by the 2 line cycles decrease in the transient response. Additionally, the voltage THDs in islanded mode are reduced from above 5.1% to lower than 2.7% with the proposed control strategy under nonlinear load conditions. The current THD is also reduced from above 21% to lower than 2.4% in the connection point of the microgrid with the offered control scheme in the grid-connected mode

Comparative evaluation of hybrid photovoltaic, wind, tidal and fuel cell clean system design for different regions with remote application considering cost

In this paper, a comparative evaluation to optimal, cost-effective, and reliable designing of hybrid renewable and clean energy systems consisting of photovoltaic (PV), wind turbine (WT), tidal, and fuel cell (FC) energy (PV/WT/tidal/FC) with hydrogen storage (HS) is proposed. The determination of optimal system configuration is provided for three regions of Iran: Gorgan, Urmia, and Yazd with suitable weather conditions because of assessing the potential of renewable energy in these regions. The evaluation is based on real data regarding radiation, wind speed and water speed, with the objective of minimising the hybrid system net present cost (HSNPC) and satisfying the reliability constraint, i.e. the load deficit probability (LDP). A whale optimisation algorithm (WOA) with high convergence and accuracy speed is considered to determine the optimal configuration of the hybrid system with the minimum HSNPC and cost of energy (COE) that satisfies the LDP for different regions. In this study, seven different design combinations of hybrid systems are implemented. The optimal combination is determined for any region in view of the lowest cost and best reliability, as well as the contributions from renewable energy sources and storage systems. It has been also confirmed that the WOA is superior to particle swarm optimisation (PSO) for hybrid system optimisation. The results showed that optimal combination for all regions comprises a hybrid PV/WT/tidal/FC based HS. The COE values for Gorgan, Urmia, and Yazd are found to be $0.7789,$1.0864, and $0.4477, and the LDPs for these regions are 0.0090, 0.0093, and 0.0090. Moreover, the results clarified the additional contribution of tidal energy for the Gorgan and Yazd regions, the additional PV contribution to the Urmia region, and the reduced contributions related to WT sources

Power Line Parameters.

<p>Power Line Parameters.</p

An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions - Fig 6

<p>System DG unit currents and NLL current waveforms with THD without any compensation: (a) system currents; (b) PV currents; (c) MT currents; (d) FC currents; (e) NLL 1 currents; (f) NLL 2 currents.</p

Block diagram of the power electronic interface configuration.

<p>Block diagram of the power electronic interface configuration.</p

Block diagram of the control system for the APF.

<p>Block diagram of the control system for the APF.</p