Magdi M. El-Saadawi

Impact of wind farms on contingent power system voltage stability

With the global trend towards deregulation in the power system industry, the volume and the complexity of the contingency analysis results in the daily operation and system studies have been increasing. This paper discusses the impact of wind turbine generating units (WTGUs) on power system voltage stability. A probabilistic voltage stability algorithm is developed via power flow analysis where these units are modeled as P-Q bus(es) by detecting the collapse point on the Q-V curves. The developed algorithm also facilitates the computation of both the real and reactive power output of the fixed speed pitch regulated wind turbine at a specific site, wind turbine characteristics, wind speed and terminal voltage. The probabilistic nature of wind is considered by introducing the expected voltage stability margin as an index that combines both of the voltage stability and the wind distribution in one index. The proposed algorithm is implemented and applied on the IEEE 26-bus, voltage stability margin (VSM), and expected voltage stability margin (EVSM) are calculated at each wind speed. The accumulation of the EVSM over a specific period can be considered as the system voltage stability margin which is a single value that can be compared with the voltage stability margin of the all-conventional power system. Finally a contingency analysis for wind power through severe outage cases relevant to conventional power system is investigated.

A proposed reactive power controller for DG grid connected systems

Most of currently grid connected Decentralized Generation (DG) systems are power electronics interfaced, and only manage their active power production. With industrial inductive loads, the utility grid has not only to supply their reactive power needs, but also to supply extra reactive power to compensate for the expected power factor deterioration caused by DG active power injection. Among various DG options, Fuel cell technology makes a clean, highly controllable and economically viable DG option. Local reactive power compensation is a particular feature of fuel cell systems, as they will always be very close to the point of usage of electricity. With smart control algorithm of the grid coupling inverter, it is possible to enable reactive power management of the fuel cell DG system. This paper presents a smart control algorithm of the fuel cell DG grid coupling inverter, which provides active/reactive power management capability for the DG unit. The controller modeling and performance validation is performed at a test system, for a proposed operation scenario using Matlab/Simulink and Simpower system blocks. This validation proves the capability of using the proposed controller for power factor improvement.

A proposed dynamic model of Photovoltaic-DG system

Dynamic modeling is important to predict the energy production of Photovoltaic (PV) systems. It is needed to make informed technical and economical decisions. The simulation models of PV systems in literature are good enough for steady state analysis, but they are not suitable for dynamic analysis of grid operating and control conditions. This paper proposes a dynamic PV model suitable for Decentralized Generation (DG) applications. The proposed model relates the electrical output of the PV system to various input environmental parameters. The model is developed in Matlab-Simulink environment, and it is validated comparing the developed PV performance characteristic curves with those of the manufacturers data sheet and those developed by a commercial software package for a Solarex-MSX 60W PV type.

Influence of Distributed Generation on Distribution Networks During Faults

Abstract Distributed generation is playing an increasingly important and positive role in decreasing network losses, reducing electricity prices, maintaining environmental and economical benefits, reducing the investment in generation capacity, and delaying the upgrade of the transmission system. Therefore, researchers have become interested with distributed generation and its connection with the main power network. But before connecting these resources with the main grid on the low-voltage level, the worst-case scenario that could occur must be analyzed first. This article introduces a procedure to study the effect of the distributed generation units on distribution systems during short-circuit periods. This effect is measured in terms of fault current, transient time, voltage total harmonic distortion, voltage sag, and voltage swell. The main objective of this study is to study the influence of distributed generation on distribution systems so the maximum distributed generation penetration that can be adopted in a distribution system without degrading the system performance is determined. A general purpose alternative transients program version of the electromagnetic transient program is used to accomplish the above goals. The proposed method is tested on IEEE 13-node test feeder distribution system to demonstrate its performance.

A proposed framework for dynamic modelling of photovoltaic systems for DG applications

Dynamic modelling and simulation is essential to predict the overall electrical performance of photovoltaic (PV) systems. PV simulation models in the literature are not suitable for dynamic analysis with decentralised generation (DG) applications. This article proposes a framework for PV system dynamic modelling and simulation process. This framework presents the steps required to model the process of solar power generation, reflecting the environmental variables affecting the generation process. Based on the framework steps, a computer simulation model is developed in MATLAB-Simulink of the PV generator, and validated by comparing the developed PV electrical performance characteristic curves with those of the manufacturers data sheet and the ones developed by commercial software. The last step of the proposed framework is dedicated for testing the developed PV model for grid-connected operation. The proposed framework resulted in a simulation photovoltaic decentralised generation model which constitutes a computer-aided design tool that is helpful for real-world solar energy engineering.

Modeling and optimization of a hybrid power system supplying RO water desalination plant considering CO2 emissions

AbstractSeawater desalination is an attractive choice especially for remote areas where freshwater is rare. Egypt is moving toward the desalination of water as an alternative solution to the decrease in freshwater. The main objective of this study was to design an optimal, economic, and efficient hybrid system that feeds the electric needs of a small-scale brackish reverse osmosis desalination unit and a tourism motel located in Hurghada, Egypt. The optimization problem of sizing different components of hybrid system is a complicated one; it needs a special tool capable of solving it rapidly and effectively. Three different hybrid system scenarios are discussed to select the most optimum combination of them. These scenarios are the following: wind/PV/battery, wind/PV/diesel, and wind/PV/battery/diesel. In this study, a modified particle swarm optimization technique is applied for optimum sizing of the proposed hybrid system scenarios. The optimization problem is solved to minimize the annual total investm...

Rooftop PV systems with distributed batteries for voltage unbalance mitigation in low voltage radial feeders

This paper discusses the alleviation of voltage unbalance (VU) in low voltage four-wire ungrounded distribution networks. Unbalanced allocation of distributed rooftop Photovoltaic (PV) ratings and loads creates considerable neutral current in the neutral line. Because of the size limitation or non-connection of distributed batteries, this paper proposes three strategies for using the available distributed energy storage to reduce VU and neutral potential under a high penetration of distributed rooftop PVs. VU mitigation algorithms are presented and implemented in the MATLAB/software environment.