Salah Kamel

Modeling and Analysis of Voltage and Power Control Devices in Current Injections Load Flow Method

Abstract This article presents a developed method to improve the representation of a voltage-controlled bus in the current injection load flow method. This improvement is based on a hybrid current and power mismatches formulation, where the load bus equations are represented by current mismatches and voltage-controlled buses bus equations are based on power mismatches. In this method, the advantages of the Newton–Raphson method and current injection mismatches method are collected. The total number of equations is reduced, where only one equation is required for each voltage-controlled bus. This article also describes direct modeling of voltage/power control devices in the developed load flow method. The static synchronous compensator can be represented as a voltage-controlled bus node in terms of power mismatch. The static series synchronous compensator and unified power flow controller are modeled by series impedance and two current injections at the corresponding nodes. In the case of unified power flow controller, additional power injection is included at the sending-end node to represent the voltage-controlled node. This modeling reduces the complexities of the computer program codes and enhances the reusability by avoiding the modifications in the Jacobian matrix. The IEEE data as well as systems from literature are used to validate the developed method and flexible AC transmission systems models.

Enhancing security of power systems including SSSC using moth-flame optimization algorithm

This paper presents a developed optimization technique based on moth-flame algorithm to determine the optimal placement and parameter setting of Static Synchronous Series Compensator (SSSC) for enhancing power system security under single line contingencies. A contingency analysis is performed on power system to determine the most severe line outage contingencies using performance index which based on the number of thermal overloads and voltage levels violation. IEEE 30-bus test system is used to verify the effectiveness of the developed algorithm. The obtained results demonstrate that the efficiency of the developed technique moreover, installing of the SSSC in its optimal location can enhance the security of power system by reducing the overloading of transmission lines and violation of bus voltages.

Constraints Violation Handling of GUPFC in Newton-Raphson Power Flow

Abstract Generalized Unified Power Flow Controller (GUPFC) is one of the newest Flexible AC transmission system (FACTS) devices based on voltage source converters. This paper presents a developed model of GUPFC based on power injection approach. The series converters of GUPFC is represented by injected complex loads as function of the specified powers flow, while the shunt converter is represented as a synchronous condenser that provides the reactive power compensation to control the bus voltage magnitude. The main advantage of the developed model is that the original structure and symmetry of the admittance and Jacobian matrices can still be kept avoiding the changes of the original Jacobian matrix. Consequently, the complexities of the load flow are reduced. This model includes simple strategies for handling the operating constraints of GUPFC, including the injected series and shunt voltages magnitude, currents of the series and shunt converters, and the real powers exchanged in the converters. The strategies are based on decreasing one or more values of specified values or by modifying the specified values as a function of the required constraint limits. The developed model and proposed strategies for handling violation of GUPFC operating constraints are tested on IEEE test systems such as 57-bus and 118-bus systems.

Modeling of a Downdraft Gasifier Combined with Externally Fired Gas Turbine using rice straw for generating electricity in Egypt

Egyptian farms produce annually about 43.640 Mega ton of the agricultural. 16 Mega ton from these residues has been utilized and about 27.64 Mega ton (63.34%) of the total agricultural wastes would be remain as a type of contamination. Hence, there is an urgent need to exploit these wastes especially the rice straw as priceless residue for electrical generation using the biomass gasification process. This paper is focused on modelling of a small scale power plant consists of a Downdraft Gasifier Combined with Externally Fired Gas Turbine which will deliver power on scale down to 71 kw and thermal energy (259 kWth). The developed power plant is modelled using Cycle-Tempo software. The results of modelling of the developed power plant revealed that, the increase of gasification temperature would decrease the calorific value of the produced gas and the contrarily occurred with the volume flow and the air-biomass ratio then, a large amount of N2 is appeared and the H2 would be reduced. Consequentially, the suitable temperature of gasification is 773.65 °C. Regarding the G-EFGT, the system modelling indicate that, the electric efficiency for the fired turbine decreases when the hot side temperature difference (Ths) rises from 50 °C to 200 °C. Therefore at high Ths, and Turbine inlet temperature (TIT) not exceeds 850 °C, the system needs a reaction temperature of 1250 °C at external oven.

Modeling of STATCOM in Load Flow Formulation

This chapter presents an easy modeling of STATCOM into a recent Newton–Raphson (NR) load flow method. This load flow formulation is based on power and current injection mismatches. In this new load flow, the current mismatch equations are used to represent the PQ buses while the power mismatches are used for PV buses. This load flow formulation decreases the required number of equations, the computation time and improves the convergence performance especially in case of PV buses. The developed STATCOM model is considered as an application for the representation of PV buses in the new NR power and current injection mismatches load flow formulation. In this model, the connected buses with STATCOM are converted to PV buses with zero active power generation and the voltage magnitudes are fixed at the pre-request values. The controlled buses are incorporated in load flow algorithm as power injection mismatch equations. The parameters of STATCOM can be calculated during the iterative process using simple equations based on its configuration.

Modified water cycle algorithm for optimal direction overcurrent relays coordination

Abstract The optimization model of Directional Over Current Relays (DOCRs) coordination is considered non-linear optimization problem with a large number of operating constraints. This paper proposes a modified version for Water Cycle Algorithm (WCA), referred to as MWCA to effectively solve the optimal coordination problem of DOCRs. The main goal is to minimize the summation of operating times of all relays when they act as primary protective devices. The operating time of a relay depends on time dial setting and pickup current setting or plug setting, which they are considered as decision variables. In the proposed technique, the search space has been reduced by increasing the C-value of traditional WCA, which effects on the balance between explorative and exploitative phases, gradually during the iterative process in order to find the global minimum. The performance of proposed algorithm is assessed using standard test systems; 8-bus, 9-bus, 15-bus, and 30-bus. The obtained results by the proposed algorithm are compared with those obtained by other well-known optimization techniques. In addition, the proposed algorithm has been validated using benchmark DIgSILENT PowerFactory. The results show the effectiveness and superiority of the proposed algorithm to solve DOCRs coordination problem, compared with traditional WCA and other optimization techniques.

Stability of Distribution Networks with Wind Turbines

This chapter presents modeling of generators that are used in wind farms such as squirrel cage induction generators (SCIG), doubly fed induction generators (DFIG) and, permanent magnet synchronous generator (PMSG). Installing wind farms must fulfill some rules or requirements. These requirements are developed by transmission system operator in order to guarantee the continuity and stability of the interconnected grid. This chapter presents the stability of two different types of combined wind farms. The first type is based on a combination of SCIG and DFIG wind turbines and known as combined wind farm (CWF). CWF collects the benefits of SCIG and DFIG where SCIG is cheaper compared with DFIG and PMSG. Despite DFIG is expensive, DFIG is more stable than SCIG. CWF is more suitable for developing countries. The second type is based on a combination of modern generators DFIG and PMSG and known as modern combined wind farm (MCWF). MCWF collects the benefits of DFIG and PMSG where DFIG features by its ability to control the active power independently of reactive power while PMSG can operate used for small and medium powers. This chapter discusses the impact of CWF and MCWF on the stability of interconnected electric distribution networks during single line to ground and double lines fault as examples of unsymmetrical and during three phase fault and three phase open circuit fault as examples for symmetrical. Also, this chapter discusses the impact of CWF and MCWF on the stability of interconnected electric distribution networks during different types of operation conditions of electric distribution networks such as voltage sage and over voltage.

Optimal Allocation of Compensators

Electric distribution networks mainly deliver the electric power from the high-voltage transmission system to the consumers. In these networks, the R/X ratio is significantly high compared to transmission systems hence power loss is high (about 10–13% of the generated power). Moreover, poor quality of power including the voltage profile and voltage stability issues may arise. The inclusion of shunt capacitors and distributed Flexible ac transmission system (D-FACTS) devices can significantly enhance the performance of distribution networks by providing the required reactive power. D-FACTS include different members such as; distributed static compensator (DSTATCOM), Distribution Static Var Compensator (D-SVC) and unified power quality conditioner (UPQC). Optimal allocation of these controllers in the distribution networks is an important task for researchers for power loss minimizing, voltage profile improvement, voltage stability enhancement, reducing the overall system costs and maximizing the system load ability and reliability. Several analytical and optimization methods have been presented to find the optimal siting and sizing of capacitors and shunt compensators in electric distribution networks. This chapter presents a survey of new optimization techniques which are used to find the optimal sizes and locations of such devices. This chapter also presents an application of new optimization technique called Grasshopper Optimization Algorithm (GOA) to determine the optimal locations and sizes of capacitor banks and DSTATCOMs. The obtained results are compared with different algorithms such as; Grey Wolf Optimizer (GWO), Sine Cosine Algorithm (SCA).

Optimal Power Flow Using Recent Optimization Techniques

Abstract Optimal power flow solution gives the best secure operating point according to certain objective functions and satisfying the operation constraints of the system. Different objective functions in power systems can be optimizely achieved. These objectives can be; the total losses of transmission lines, total generation cost, FACTS cost, voltage deviations, total of power transfer capability, voltage stability, emission of generation units, etc. The control variables of the system can be adjusted during the optimization process. These control variables including the generated active powers, the voltage of generation buses, transformer tap settings. Several classical and modern optimization techniques have been proposed to solve the optimal power flow problem. Most of classical techniques are based on the sensitivity analysis and gradient-based methods. However, different metaheuristic optimization techniques have been proposed to avoid the trapping in local optimum which can be done in the classical technique. In this chapter, a comprehensive survey about the modern optimization techniques used to solve optimal power flow problems is presented. Different optimization techniques are considered as: nature-swarm-inspired methods, human-inspired algorithms, evolutionary-inspired algorithms, physics-inspired algorithms and ANN.

Desarrollo de parques eólicos eficientes basados en generadores de inducción de jaula de ardilla y generadores de inducción de doble alimentación con Compensador Estático de Energía Reactiva (SVR)

Squirrel Cage Induction Generators (SCIG) and Dual Power Induction Generators (DFIG) are the main types of generators used in wind farms. The impact of a grid disturbance on wind farms differs according to the type of generator used in the wind farm. The high reactive power requirement can lead to the disconnection of the SCIG generators from the grid during grid disturbances. DFIG wind turbines are considered to be of the modern type, but they are more expensive than SCIG wind turbines. DFIG wind turbines can provide voltage support to the grid during faults, but they suffer a reduction to zero in their output power without disconnecting the wind farm from the grid. With the progress of FACTS technology, the performance of wind farms using these devices has been improved.