In long range optical fiber communication, dispersion is a major technological challenge that causes broadening of optical pulses when transmitted through the fiber. As a result, it limits the maximum transmission distance and the bit rate. Many efforts have been drawn to the development of dispersion compensating techniques to mitigate the effect of pulse broadening. In this thesis, modeling and analysis of broadband dispersion compensating photonic crystal fibers (DC-PCFs) for dispersion compensation of standard single mode fibers (SMFs) have been carried out. Three different PCF models such as circular photonic crystal fiber (C-PCF), modified circular photonic crystal fiber (M-CPCF) and modified octagonal photonic crystal fiber (M-OPCF) have been designed and their guiding properties have been analyzed using finite element method (FEM). A perfectly matched layer (PML) circular boundary is has been used to calculate the confinement loss. The proposed C-PCF exhibits a high negative dispersion coefficient of about -248.65 to -1069 ps/(nm.km) over the wavelength ranging from 1340 to 1640 nm. It is also demonstrated that the proposed C-PCF shows an effective dispersion of about ± 0.8 ps/(nm.km) over the band from 1400 nm to 1610 nm and. However, birefringence of C-PCF is not found so high and particularly in the order of about 7×10-4 at 1550 nm wavelength. On the other hand, M-CPCF shows a high negative dispersion coefficient of -203.8 to -835.14 ps/(nm.km) over 1340 to 1640 nm wavelength with a high birefringence of 2.2×10-2 at 1550 nm wavelength. In addition, the effective dispersion is found less than ± 0.8 ps/(nm.km) over the band from 1400 to 1640 nm. Finally, M-OPCF achieves negative dispersion coefficient of about -276.27 to -889.21 ps/(nm.km) over 1340 nm to 1640 nm with a high birefringence of 2.53×10-2 at 1550 nm wavelength. Moreover, the effective dispersion is less than ± 0.8 ps/(nm.km) over the band from 1430 to 1610 nm wavelength. Furthermore, the dispersion slope of the proposed DC-PCFs have been determined and found negative over the band of interest and residual dispersion slope (RDS) of the proposed DC –PCFs is achieved equal to that of conventional SMFs of about 0.0036 nm-1 at 1550 nm wavelength. In addition to these, effective area, confinement losses, and dispersion behavior for fiber’s global diameter variations and fiber’s structural parameters variation have been investigated. It has been found that the structural parameters and also global diameter variations do not affect the dispersion accuracy of the proposed DC-PCFs.

The penetration level of PV power in the low voltage (LV) distribution networks is rapidly increasing. The European Photovoltaic Industry Association reported that the cumulative installed PV capacity in the world was 24 GW at the end of 2009 and exceeded 100 GW in 2013. The Australian Clean Energy Regulator has published a report showing the total installed capacity of PV in Australia has exceeded 3 GW in 2014. Impacts of high PV penetration in LV residential distribution networks include voltage rise, voltage unbalance, and reverse power flow which may limit the level of photovoltaic penetration within the LV distribution networks. A LV distribution level four-wire unified power flow controller (UPFC) has been proposed for voltage regulation and phase current balancing. This voltage regulation device is shown capable of regulating the positive, negative and zero sequence voltage in LV distribution networks under high PV penetrations. At same time, this voltage regulator is capable of power factor correction, zero sequence or neutral current compensation, harmonics compensation and a degree of negative sequence current compensation. Instantaneous reactive power theory shows that DC-bus capacitor power will fluctuate at twice mains frequency during any unbalanced operation of the regulator. Real and instantaneous power balance of UPFC can be maintained by allowing the input shunt converter to draw a small positive and negative sequence current respectively. Instantaneous power balance with negative sequence current makes it possible to reduce the DC bus capacitance which allows long life ceramic or polypropylene capacitors to replace electrolytic capacitors.