الفهرس 
2.2. Grid connected PV systemOnly 14 pages are availabe for public view
 |  | from | 111 |  |  |
| | | from | 111 | | |
Abstract
Solar energy gained an enormous attention in the past few years, due to the introduction of the Fed-In Tariff policies in several countries around the globe. These policies encouraged the private sectors to invest in the PV grid-connected stations. As a result, the penetration level of PV systems, including centralized stations, increased rapidly especially in the Medium Voltage (MV) networks
Despite their benefits, the increase in the penetration level of centralized PV stations in the MV grid is accompanied with several drawbacks. The main drawback is the fluctuations in the output power of the PV stations which might deteriorate the quality of the supply at the point of common coupling (PCC). Consequently, some utilities set restrictions upon the fluctuations of the power injected from the PV stations to the grid. Moreover, in many cases the PV stations are operated at a unity power factor, regardless of their capability to inject reactive power and improve the voltage profile.
The objective of this thesis is to attempt solving the two aforementioned problems using energy storage systems (ESS). The first phase of the research, the planning stage, aims to determine the optimal size of the batteries and their corresponding inverters to maximize the overall gained net profit of the Photovoltaic Hybrid System (PVHS). The problem takes into considerations different technical constraints related to the system and the grid, including the power fluctuations restrictions imposed by the utility. The second phase, the operation stage, utilizes the batteries in managing the reactive power injected by the PVHS inverters to support the static and dynamic voltage stability at the PCC.
The first phase is performed by formulating a linear programming (LP) problem to determine to optimal rating of the batteries and their corresponding inverters. The optimization is solved using MINOS solver in GAMS software. In this phase, the pattern of the power injected from the PVHS to the grid is determined and satisfy the power fluctuation limitation imposed by the utility.
In the second phase, a supervisory reactive power management strategy is proposed to control and coordinate the reactive power injected from PV hybrid system (PVHS) inverters to support the grid voltage. The PVHS is implemented using a PSCAD/EMTDC software package to study the dynamics of control loops for active and reactive power. The results of the proposed control strategy are compared to the requirements of the German and the Spanish grid codes. The simulation results reveal accurate, fast and improved dynamic response of the proposed system.