International Journal of Applied Power Engineering (IJAPE)
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Load Frequency Control of DFIG-isolated and Grid Connected Mode
Get PDFWind energy is one of the extraordinary promising sources of renewable energy due to its clean character, free availability and economic viability. A Doubly Fed Induction Generator (DFIG) feeds power from both the stator and the rotor windings at speeds above synchronous speed of the machine. This paper deals the load frequency control of doubly fed induction generator in isolated mode and grid connected mode. The wind turbine model is obtained using MATLAB/ SIMULINK which consists of DFIG, rotor side rectifier, grid side inverter and grid. This model is controlled by conventional controllerand proposed Load Frequency Control (LFC) method. The results are proven that frequency control gives better results in all the aspect
Dynamic Modeling of Autonomous Wind–diesel system with Fixed-speed Wind Turbine
Get PDFWind turbines have often connected to small power systems, operating in parallel to diesel generators, as is typically the case in autonomous wind–diesel installations or small island systems with high wind potential. Hence, the modeling and analysis of the dynamic behavior of wind–diesel power systems in presence of wind power will be important. In this paper, the system under study is modeled by a set of dynamic and algebraic equations (DAE). Dynamic behavior of a wind-diesel system is investigated by the proposed dynamic model. Wind-diesel system consists of wind turbines that are connected to synchronous diesel generator via short transmission line with local load. Dynamic stability of autonomous wind–diesel systems are discussed with emphasis on the eigenvalue analysis and the effective parameters on system stability. In this regards, saddle node bifurcation and hopf bifurcation are also investigated
Comparative Study on the Performance of A Coherency-based Simple Dynamic Equivalent with the New Inertial Aggregation
Get PDFEarlier, a simple dynamic equivalent for a power system external area containing a group of coherent generators was proposed in the literature. This equivalent is based on a new concept of decomposition of generators and a two-level generator aggregation. With the knowledge of only the passive network model of the external area and the total inertia constant of all the generators in this area, the parameters of this equivalent are determinable from a set of measurement data taken solely at a set of boundary buses which separates this area from the rest of the system. The proposed equivalent, therefore, does not require any measurement data at the external area generators. This is an important feature of this equivalent. In this paper, the results of a comparative study on the performance of this dynamic equivalent aggregation with the new inertial aggregation in terms of accuracy are presented. The three test systems that were considered in this comparative investigation are the New England 39-bus 10-generator system, the IEEE 162-bus 17-generator system and the IEEE 145-bus 50-generator system
Transmission Loss Allocation Based on Lines Current Flow
Get PDFIn this paper, the transmission loss allocation problem has been studied and a new method for loss allocation in pool electricity markets has been proposed. To do that, at first using a transmission line loss equations respect to bus injected currents, the share of each bus from the mentioned transmission line losses has been determined. Then, this method has been applied to the total network transmission lines and the share of each bus from the total losses has been acquired. The proposed method is based on the main network relations and no any simplifying suppose has been used. Finally, the proposed method is studied on a typical network
Design and Development of Power Electronic Controller for Grid-connected PV Array
Get PDFDesign and simulation of a simple power electronic interface for grid-connected PV array has been proposed using boost converter and line-commutated inverter with maximum power point tracking (MPPT) controller. The output of PV array varies with irradiation, and hence the duty cycle of the PI controller is adjusted automatically to supply a constant DC voltage to the inverter circuit, the output of which is directly connected to the grid. The MPPT controller extracts maximum power from the solar array and feeds it to the single-phase utility grid. The proposed scheme has been modeled in the MATLAB 7.1 software and the complete system has been simulated for open loop and closed loop configurations. The active power fed to the grid is taken for different firing angles in open loop mode and the firing angle for maximum power has been determined. This is compared with the firing angle obtained from the closed loop mode and found that both results agree with each other
Determination of Fault Location and Type in Distribution Systems using Clark Transformation and Neural Network
Get PDFIn this paper, an accurate method for determination of fault location and fault type in power distribution systems by neural network is proposed. This method uses neural network to classify and locate normal and composite types of faults as phase to earth, two phases to earth, phase to phase. Also this method can distinguish three phase short circuit from normal network position. In the presented method, neural network is trained by αβ space vector parameters. These parameters are obtained using clarke transformation. Simulation results are presented in the MATLAB software. Two neural networks (MLP and RBF) are investigated and their results are compared with each other. The accuracy and benefit of the proposed method for determination of fault type and location in distribution power systems has been shown in simulation results
Reduced Dielectric Losses for Underground Cable Distribution Systems
Get PDFThis paper describes the process to reduce dielectric losses for underground cable distribution system. As already known, that system is an alternative solution to energy distribution systems in urban areas. Influence of large capacitance is a separate issue that needs to be resolved. Large capacitance effect on Express Feeder of 10 miles long has resulted in power losses more than 100 MW per month. In the no-load condition, current dispatch has recorded 10 Amperes, and has increased the voltage at receiving end by 200-500 Volts, with leading power factors. Installation of the inductor to reduce cable loss dielectrics is done by changing the power factor (pf) to 0.85 lagging. After installation of the inductor, which is 5 mH/700 kVAR, dielectric losses is reduced to 3.57%, which is from 105,983 kW to 102,195 kWh per month. The capacitive leakage current has also been reduced from 249.61 Ampere to 245.17 Ampere
Investigation and Comparison of the Effect of Facts Devices, Capacitors and Lines Reactance Variations on Voltage Stability Improvement and Loadability Enhancement in Two Area Power System
Get PDFThis paper studies the important power system phenomenon and voltage stability by using continuation power flow method. Voltage collapse scenario is presented which can be a serious result of voltage instability and also the parameters that affected by voltage collapse are discussed. In analyzing power system voltage stability, continuation power flow method is utilized which consists of successive load flows. In this paper steady-state modeling of Static VAR Compensator (SVC) and Unified Power Flow Controller (UPFC) and effect of compensator and variation of line reactance on the voltage stability have been studied and Comparison between performance of UPFC and SVC and installation shunt capacitor and variation of line reactance for improve voltage stability has been done.Case studies are carried on 11 bus network in two areas. Simulation is done with PSAT in MATLAB. Continuation Power Flow was implemented using Newton Raphson method. Simulation results show the proper performance of UPFC, SVC, installation shunt capacitor and variation of line reactance to improve voltage control and significantly increase the loadability margin of power systems