Sobhy S. Dessouky

Control scheme of PMSG based wind turbine for utility network connection

With the growing of electrical energy demand, wind energy gains higher potential and plays a vital role in energy sectors. Direct driven permanent magnet synchronous generator (PMSG) with a full size back-to-back converter set is one of the promising technologies employed with wind power generation. This paper focuses on developing a control scheme of PMSG-based wind turbines to obtain maximum wind power extraction and meet network code requirements. Comprehensive models of wind speed, wind turbine, PMSG and power electronic converters along with their control schemes are implemented in MATLAB/SIMULINK environment. Simulation results show the feasibility and robustness of the proposed control schemes for PMSG based wind turbines.

Grounding resistance, step and touch voltages for a driven vertical rod into two layer model soil

This paper presents a new technique to calculate the grounding resistance (Rg), the touch and step voltages due to discharging current into a vertical rod in two layer soil. The technique is used the current simulation method (CSM). The study of grounding resistance and earth surface potential (ESP) are the outcome of mathematical manipulations of current simulation method, image theory, resistance and capacitance duality concept. The results are in a good agreement with the other techniques.

Modification of Duval Triangle for Diagnostic Transformer Fault through a Procedure of Dissolved Gases Analysis

Dissolved gas-in-oil analysis (DGA) is a sensitive and reliable technique for the detection of incipient fault condition within oil-immersed transformers. When the mineral oil is subjected to high thermal or/and electrical stresses, it decomposes and, as a result, gases are generated. This paper presents modification of Duval triangle DGA diagnostic graph to numerical method that is easy to use for diagnosing and the possibility to use for a Matlab program. The evaluation is carried out on DGA data obtained from three different groups of transformers. A Matlab program was developed to automate the evaluation of Duval Triangle graph to numerical modification, Also the fault gases can be generated due to oil decomposing effected by transformer over excitation which increasing the transformer exciting current lead to rising the temperature inside transformer core beside the other causes.

Performance improvement of a PV-powered induction-motor-driven water pumping system

This paper presents a modified control strategy to improve the performance of a 3-phase induction motor drive system fed by a standalone PV power source. The main functions of the proposed control strategy are: 1) ensuring successful motor starting, 2) matching the on-site induction-motor pumping load with the available PV power, and 3) forcing the PV system to operate at the maximum power point. The maximum power point tracking (MPPT) is based on perturb and observe (P&O) algorithm. The system consists of a DC/DC boost converter, DC link capacitor, 3-phase inverter, 3-phase induction motor and PV power panels. The PV panel structure is designed to maintain the system operating point at the PV maximum output power at variable solar irradiations. Simulation results demonstrate the operation of the unified system with and without controller under constant and variable solar irradiations. The main control objective is to run system as close as possible to the maximum power point operation under constant and variable solar irradiations. Simulation results using boost converter along with the P&O algorithm show an accurate MPPT at rapid-change of solar radiation and the ability of the system to approach for MPP.

Factors affecting offshore wind power integration to grid through VSC-HVDC

In this paper, the offshore wind power integration to the main ac grid through the voltage-source converter (VSC) high-voltage dc (HVDC) transmission is investigated. Vector control is used for the control of both offshore and onshore converter stations. The proposed model was implemented and simulated using Matlab/Simulink to investigate the factors affecting the wind power integration. The paper showed that at lower short-circuit ratio (SCR) values the maximum power transfer capability is reduced as well as the total harmonic distortion (THD) is increased greatly. An interesting result is that the maximum power transfer capability at lower SCRs is increased with lower grid angles while the current THD is decreased.