This research investigated the effect of different environmental conditions including moisture, saline and alkaline conditions on the notch sensitivity of short and 2D plain woven glass fibers reinforced epoxy matrix composites fabricated by the hand lay-up technique with fiber volume content of 23.5 and 38.6 vol.%, respectively. The test was carried out through open hole tension test at constant ratio of (D/W = 0.2) and the notch sensitivity of these composites under different environments was evaluated by comparing the notched tensile strength and the characteristic distance (do) of these composites applying Whitney-Nuismer mathematical model. The results indicated that the environmental exposure has a pronounced negative effect on the notched tensile strength of all composites compared to the unconditioned state (virgin state). Moreover, the fracture zone of the composites under the alkaline environment is smooth and shows much less fiber pull out validated by SEM micrographs which distinguishes brittle failure.

Fault current calculations inside a grid-connected and isolated AC microgrid is one of the major challenges due to the fault current contributions of inverter-based distributed generators units, which are different in location and inverter control during the fault. Therefore, this paper is aimed at calculating fault current for grid-connected and isolated microgrids using two methods; virtual impedance and the proposed method. The proposed method is used to calculate the short circuit current contribution of DG is controlled to analyze the equivalent model of inverter-based DG. The inverter control limits its current to 2p.u of the inverter rating. The proposed algorithm is tested on a standard IEEE 33-bus distribution network with 5 DGs using MATLAB code programs. The results show that the impact of q DG on the fault current is significant especially when faults occur at busses near to the DG location. The fault current value, calculated using the proposed method, is less than its value calculating by the virtual impedance method by more than 30% for grid-connected microgrid and by approximately 50% for the isolated microgrid.

This paper is aimed at investigating MPPT of PV system controlled by SPWM which is generated by comparing sinusoidal wave with variable frequency sawtooth wave. Perturb and Observe (P&O) method is used for MPPT control of PV system. NPC three-phase three-level converter with LCL filter is designed to produce output voltage with minimum Total Harmonic Distortion (THD) and high efficiency. The simple and fast method to get MPP of PV system with variable irradiation is digital control where the maximum power point is obtained from look-up table for the values of optimum voltage that achieve the maximum power for each irradiance value is used for digital control signal in microcontroller. The output voltage harmonic of multi-level three-phase inverter is controlled using SPWM control. THD of output voltage of multi-level three-phase inverter is 22% of stand-alone and grid-connected PV system. Small rate LCL filter is used to limit voltage harmonics within medium and low voltage limits (5%). THD output voltage of LCL filter is 4.9% and 3.51% of stand-alone and grid-connected PV system respectively

This paper is aimed at investigating the steady state analysis of a grid connected PMSG wind turbine in fixed and variable speed using MATLAB/SIMULINK. The case studied is Zafarana, Egypt. The average values of wind speed of month and day of Zafarana region is obtained from NASA site. Zafarana region has the highest wind speed which is greater than 12 m/sec. The transient analysis is investigated of the grid connected PMSG wind turbine during three-phase-to-ground fault at terminal of grid in different fault time and islanding mode. PMSG wind turbine is based on low-voltage ride-through (LVRT). The time required for recovering pre-fault values of voltage and current is less than 0.1 sec. LVRT is used to protect wind turbine from high fault current as well as to compensate PMSG voltage. PMSG is loaded by converter and capacitor which work as STATCOM. The current protection device is used to limit the fault current where the tripping current of relay is calculated using IEC method. The PMSG wind turbine consists of three protection devices; over speed protection, LVRT and point connection circuit breaker CEI. There are three protection zones in terms of the fault of; the protection zone of the fault of wind turbine (Zone 1), the protection zone of the fault of wind farm (Zone 2), the protection zone of the fault of grid (Zone 3).

Due to the increasing penetration level of microgrids (MGs), it becomes a critical issue for MGs to help sustaining power system stability. Therefore, this paper is aimed at investigating comparison between transient analysis AC and DC Microgrid connected to the grid in case of using Superconducting Fault current limiter (SFCL) at the connection point of Microgrid and grid. When the three-phase-to-ground fault is applied at connection point of Microgrid and grid, the SFCL minimized the oscillating currents and the active and reactive power of AC and DC microgrid to range 20-30%. The transient analysis of AC microgrid is better than DC microgrid except the values currents and the active and reactive power are very high during the fault. The time required to recover pre-fault values of AC microgrid (0.1 sec) is less than those time of DC microgrid (3 sec).

This paper is aimed at investigating MPPT of PV system controlled by SPWM which is generated by comparing sinusoidal wave with variable frequency sawtooth wave. Perturb and Observe (P&O) method is used for MPPT control of PV system. The simple and fast method to get MPP of PV system with variable irradiation is digital control where the maximum power point is obtained from look-up table for the values of optimum voltage that achieve the maximum power for each irradiance value is used for digital control signal in microcontroller. The output voltage harmonic of multi-level three-phase inverter is controlled using SPWM control.

NULL

NULL

NULL

NULL