M. Kenan Döşoğlu

Investigation of different load changes in wind farm by using FACTS devices

In this study, voltage, active power and reactive power variation of load bus were examined by Flexible AC Transmission Systems devices (FACTS) in grid-connected wind farm. In the system, FACTS devices, Static Synchronous Compensators (STATCOM), Static VAr Compensators (SVC), Static Synchronous Series Compensators (SSSC) and Thyristor Controlled Series Compensators (TCSC), were used. Also, dual feed induction generator (DFIG) was used as generator in the wind farm. This simulation study was done via Matlab/Simulink environment. According to different values of active and reactive loads at different times being attached to the system, shapes of load bus voltage, active power and reactive power variation were given, also the results were presented in tables. In the conclusion of this study, by means of FACTS devices that is used in the wind farm, instability was healed within a short time.

Symbiotic organisms search optimization algorithm for economic/ emission dispatch problem in power systems

This paper presents symbiotic organisms search (SOS) algorithm to solve economic emission load dispatch (EELD) problem for thermal generators in power systems. The basic objective of the EELD is to minimize both minimum operating costs and emission levels, while satisfying the load demand and all equality–inequality constraints. In other research direction, this multi-objective problem is converted into single-objective function by using price penalty factor approach in order to solve it with SOS. The proposed algorithm has been implemented on various test cases, with different constraints and various cost curve nature. In order to see the effectiveness of the proposed algorithm, its results are compared to those reported in the recent literature. The results of the algorithms indicate that SOS gives good results in both systems and very competitive with the state of the art for the solution of the EELD problems.

Symbiotic organisms search algorithm for dynamic economic dispatch with valve-point effects

Abstract In this study, symbiotic organisms search (SOS) algorithm is proposed to solve the dynamic economic dispatch with valve-point effects problem, which is one of the most important problems of the modern power system. Some practical constraints like valve-point effects, ramp rate limits and prohibited operating zones have been considered as solutions. Proposed algorithm was tested on five different test cases in 5 units, 10 units and 13 units systems. The obtained results have been compared with other well-known metaheuristic methods reported before. Results show that proposed algorithm has a good convergence and produces better results than other methods.

Enhancement of SDRU and RCC for low voltage ride through capability in DFIG based wind farm

Grid-integrated wind turbine may experience low voltages during transient events in grid. An increase observed in inrush current leads to low voltage. To control the increased current, an enhancement in a low voltage ride-through (LVRT) capability is required. This study examines the impact of an LVRT scheme on grid-integrated doubly fed induction generator (DFIG)-based wind turbines which are represented with new stator-damping resistor unit (SDRU) and rotor current control (RCC). Besides, both stator and rotor circuits of DFIG were enhanced with electro-motor force (emk). Designed as hybrid with SDRU and RCC, DFIG was examined to analyses symmetrical and asymmetrical faults in the grid. Electro-motor-force dynamic modeling of both stator and rotor was developed. The responses of wind turbine against low voltage are investigated in terms of bus voltages, angular speed, electrical torque, stator and rotor current, and d–q axes current. The results of the study show that the system became stable in a short time when the SDRU and RCC were incorporated with the stator and rotor electro-motor-force models.

Nonlinear dynamic modeling for fault ride-through capability of DFIG-based wind farm

Fault ride-through (FRT) is a control model enhanced to protect doubly fed induction generator (DFIG) during voltage dip occurring in grid. In this study, stator and rotor circuit dynamic modeling enhanced in terms of simulation performance and fast system responses during instability in DFIG-based wind farm, besides, a FRT capability strategy were enhanced for nonlinear supercapacitor modeling in DFIG-based wind farm. The transient stability analyses of the DFIG with and without supercapacitor as well as positive–negative-sequence dynamic modeling (PNSDM) were compared for three phases, two phases, two-phase-ground and a-phase-ground faults. Furthermore, variations such as DFIG output voltage, DFIG angular speed, DFIG electrical torque and DFIG d–q axis stator current variations were also evaluated. It was found that the DFIG-based wind farm became stable within a short time using the PNSDM and supercapacitor.

Application of Symbiotic Organisms Search Algorithm to solve various economic load dispatch problems

This paper proposes the application of Symbiotic Organisms Search (SOS) Algorithm to solve the various Economic Load Dispatch (ELD) problems. Both classical ELD problem which has smooth fuel cost function and nonconvex ELD problem which has nonconvex and discontinuous fuel cost function due to considering of some practical constraints like valve point effects, ramp rate limits and prohibited generating zones have been solved in the study. Three different test cases have been used to show the efficiency and reliability of the proposed algorithm. 38-unit test system has been used for classical ELD and 3-unit and 15-unit test systems have been used for nonconvex ELD problem. Results have been compared to various heuristic methods reported before in the literature and they show that proposed algorithm converges to the global optimum in early iterations and can produce superior results than others in the solution of ELD problems which have both smooth and nonconvex and discontinuous fuel cost function.

Analysis of Reduced Order Model based on doubly-fed induction generators during different fault times

In this study, three phase fault analysis of wind turbines consist of Doubly-Fed şnduction Generators (DFIGs) has been examined. The dynamic analysis of DFIG has been conducted by Reduced Order Model (ROM). Three Phase fault has been made in 34.5 kV bus, happended in three bus power systems. The three phase fault time has been choosen as 0.02 second, 0.05 second and 0.1 seconds. 154 kV bus voltage, 34.5 kV bus voltage, DFIG output voltage, DFIG angular speed, DFIG electrical torque and DFIG d-q axes stator and rotor current variations of system in different fault times has been examined. According to the results, it has been seen that three phase fault is especially effective upon 34.5 kV bus voltage and DFIG output voltage in different fault times analysis.

Control of DC link voltage unit with Fuzzy Logic Controller in the wind farm

In this study, the analysis of wind farm that has Double Feed Induction Generator (DFIG) with Fuzzy Logic Controller (FLC) in its operation connected to the grid is realized. In wind farm, DC voltage control is modeled with FLC. Bus voltages that are connected to grid, load bus voltage, DC link voltage, active and reactive power variations of wind farm are examined. Simulation results are demonstrated with figures by Fuzzy Logic Controller (FLC)-Proportion Integrate (PI) comparison. As a result of the studies, it is observed that FLC makes the system stable in a shorter time than PI.