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Due to various operating conditions of power systems, bus voltages and load parameter values decrease. This causes the system to go into instability. Static Synchronous Compensator (STATCOM) is widely used to eliminate instability situations. Fuel cells can be used from energy storage systems to increase the efficiency of STATCOM in power systems. In this study, STATCOM and fuel cell are used together for steady and transient voltage stability in a 6-bus power system. In the voltage stability system, the relationship between the bus voltage-maximum load parameter in the steady-state operation is examined, while in the transient state study, the relationship between the bus voltage-maximum load parameter for the transient stability that occurs in the case of breaker opening-closing on the line in the system. In addition, the effects of the fuel cell at different power values are examined in detail. As a result of the study, it has been seen that the use of STATCOM and fuel cell together gives effective results in terms of voltage stability in continuous and transient situations. [ABSTRACT FROM AUTHOR]

Power systems are vulnerable to transients such as line contingency and short circuit. Various models are used to eliminate instability problems as soon as possible. In particular, the Power System Stabilizer (PSS), which is one of the synchronous generator controller models, is widely used. In this study, the transient stability of IEEE's 14 bus system was investigated in detail by using different PSS models together with secondary voltage control. In addition, it is considered to use the Automatic Voltage Regulator (AVR) together with the most suitable model for the coordinated operation of different PSS models and secondary voltage control. The pilot bus has been determined for the use of secondary voltage control consisting of central area control and cluster control, and it is aimed to provide coordination control of AVR and PSS models in the synchronous generator. This study was analyzed using the Power Systems Analysis Program (PSAT). By using different PSS models, synchronous generator angular speed changes, bus voltage profiles, and synchronous generator active-reactive power changes were investigated. As a result of the study, it was seen that the PSS 2 model provided system stability and reduced oscillations in a short time compared to other models. [ABSTRACT FROM AUTHOR]

Today, Flexible AC Transmission Systems (FACTS) devices provide local reactive power support in load centers and keep bus voltages within safe operating limits. In particular, the single use of parallel FACTS devices may not improve the safe operating conditions of the system depending on the load conditions. Therefore, avoiding parallel FACTS devices' high costs is crucial and determining their optimal places in the system. For this, Static Var Compensator (SVC), one of the parallel FACTS devices, is used. This study investigated the effects of multiple uses of SVC on different load buses on the maximum load parameter of the multi-machine system in a 3-machine 9-bus power system. Moreover, bus-voltage profiles and their changes in active-reactive power are studied in detail. In this study, three analysis methods were used. These are the no SVC, the single use of SVC, and the multiple uses of SVC. The Power Systems Analysis Program (PSAT) was preferred for this simulation study. As a result of the study, using multiple SVCs increases the maximum loading parameter value and improves the bus-voltage profiles and active-reactive power changes compared to others. [ABSTRACT FROM AUTHOR]

Stability analyzes are examined with the help of simulation programs in the continuous, economical and reliable operation of multi-machine power systems. The most common stability analysis in power systems is small signal stability. In this study, small signal stability analysis was investigated with different generator controller models in a 4-machine 2-field test system. Power System Stabilizer (PSS), Automatic Voltage Regulator (AVR) and Turbine Governor (TG) are used as different generator controller models. The simulation study was carried out in the Power Systems Analysis Program (PSAT). Comparisons were made between the situation where there are no controllers in the synchronous generator and the situations with PSS, AVR and TG models. Comparisons are given in figures and tables. In this study, it was observed that the use of PSS, AVR and TG models in a synchronous generator stabilized the system in a short time, the oscillations in the parameters were reduced and the system gave more effective results in terms of small signal stability. [ABSTRACT FROM AUTHOR]

The damping of small frequency oscillations is an important issue in terms of power system stability. These oscillations are damped by the power system stabilizer (PSS). In recent years, power electronics based Flexible AC Transmission System (FACTS) devices have been used efficiently in power system stability studies. In this study, different PSS models, the most advanced model of FACTS devices Unified Power Flow Control (UPFC) and Power Oscillation Damping (POD) were used to provide coordination controller. In addition to PSS models used in synchronous generators, Automatic Voltage Regulator (AVR) and Turbine Governor (TG) models were also used. Small signal stability analysis was carried out in a 2-field, 4-machine system. Power Systems Analysis Program (PSAT) was used for the simulation study. As a result of the study, angular velocity, voltage, active and reactive power comparisons were made in the use of different PSS models with UPFC-POD, and small signal stability analyzes were interpreted. [ABSTRACT FROM AUTHOR]

Doubly fed induction generator (DFIG) is significantly affected by various faults occurring in the grid as they are directly connected to the grid. In order to realize the low voltage ride through (LVRT) capability, the DFIG must remain connected to the system for a certain period of time according to the grid code requirement. In order to achieve this, the high rotor current must be reduced in DFIG against faults occurring on the grid side. In this study, a decoupled feed-forward control model was developed for the LVRT capability. Positive, negative, natural, and forced methods were used for the decoupled feed-forward control (FFC) model. In addition to this developed model, while the stator electromotive force (EMF) model was developed for simulation study performance and ease of calculation, the rotor EMF model was also developed to predict the transient rotor current quickly. The developed models and the conventional model were used and compared in detail. According to the results obtained, it was observed that the system became stable owing to the developed model, while the oscillations formed as a result of the transient stability were damped. [ABSTRACT FROM AUTHOR]

One of the chief methods used to overcome voltage dip problems in doubly fed induction generator (DFIG)-based wind turbines is low voltage ride through (LVRT) capability. In order to solve such voltage dip problems during symmetrical and asymmetrical grid faults, this study presents a novel enhanced dynamic modeling approach for LVRT in DFIG. Positive and negative sequence models, along with natural and forcing flux models were used to enhance the proposed LVRT capability strategy for a DFIG. In addition, electro-motor-force (EMF) was applied for the enhancement of the stator and rotor circuit model. The novel statorrotor dynamic modeling was also used in boosting the transient stability operation against three phase and two phase faults. When the proposed dynamic modeling was applied, the system was stabilized within a short amount of time and the oscillations ceased. [ABSTRACT FROM AUTHOR]

Low-voltage ride-through is important for the operation stability of the system in balanced- and unbalanced-grid-fault-connected doubly fed induction generator-based wind turbines. In this study, a new LVRT capability approach was developed using positive–negative sequences and natural and forcing components in DFIG. Besides, supercapacitor modeling is enhanced depending on the voltage–capacity relation. Rotor electro-motor force is developed to improve low-voltage ride-through capability against not only symmetrical but also asymmetrical faults of DFIG. The performances of the DFIG with and without the novel active–passive compensator–supercapacitor were compared. Novel active–passive compensator–supercapacitor modeling in DFIG was carried out in MATLAB/SIMULINK environment. A comparison of the system behaviors was made between three-phase faults, two-phase faults and a phase–ground fault with and without a novel active–passive compensator–supercapacitor modeling. Parameters for the DFIG including terminal voltage, angular speed, electrical torque variations and d–q axis rotor–stator current variations, in addition to a 34.5 kV bus voltage, were investigated. It was found that the system became stable in a short time and oscillations were damped using novel active–passive compensator–supercapacitor modeling and rotor EMF. [ABSTRACT FROM AUTHOR]

In this paper, the response of variable speeds with grid connected threephase squirrel cage asynchronous generator is investigated. The generator side and the grid side are connected to each other using back-to-back inverters In the generator side control (GSC), torque control was performed with the indirect vector control technique, in grid side control (GSC) with direct vector control technique were performed DC bus voltage and reactive power control. In terms of application simplicity and fast dynamic response, hysteresis band controlled modulation technique (HPWM) was used on the generator side converter. Another modulation technique, sinus pulse width modulation (SPWM) was preferred on the grid side converter. An LCL filter is also used on the grid side because it is difficult to transfer power to the grid without a filter. All these control strategies were obtained by performing MATLAB / Simulink environment. From the results obtained, it was observed that the dynamic response of the system to the variable wind speeds was fast and the steady-state behavior of the DC bus voltage was observed. [ABSTRACT FROM AUTHOR]

There are many conditions for determining the voltage-maximum loading relationship in multi-bus power systems. One of these is the line contingency in power systems. In this study, Effects on voltage stability of the line contingency occurred different points in IEEE 14 buses power system. Line contingency is considered as disabled for a certain period of time of the breakers situated in line. The effects of line contingency at 19 points on the voltage-loading parameter were observed. Besides, In this study, the effects of bus voltage profile changes were investigated. As a result of this study, it has been seen that line contingency decrease the system loading parameter value and operating limits in different transmission lines. In particular, the line contingency between the state transmission line 2-3, which brought the loading parameter value and the operating limits to the critical value. [ABSTRACT FROM AUTHOR]

The effects of nonlinear load models on the system are an important issue in terms of power quality. In this study, the effect of nonlinear load models in the grid-connected Doubly Fed Induction Generator (DFIG) based wind turbine was investigated. Exponential, constant impedance, constant current, constant active power (ZIP) and induction motor are used as nonlinear load model. Composite load modeling is consist of exponential-ZIP-induction motor. Composite load modeling is turn on and turns off system within different times. Analysis and stability analysis of the composite load modeling were examined. This simulation study was carried out in MATLAB / SIMULINK environment. 34.5 kV bus voltage, DFIG terminal voltage, DFIG electrical torque, DFIG d-q axis stator current variations and DFIG d-q axis rotor current variations in composite load model analysis are examined. As a result of, it has been seen that composite load modeling which is activated as short time is effective on the power system. [ABSTRACT FROM AUTHOR]

Low voltage ride through (LVRT) is one of the most popular methods to protect doubly fed induction generator (DFIG) against balanced and unbalanced voltage dips. In this study, a novel LVRT capability strategy is enhanced using forcing demagnetization controller (FDC) in DFIG-based wind farm. Moreover, not only stator circuit but also rotor circuit were developed by electromotor force (EMF) for LVRT in DFIG-based wind farm. The transient stability performances of the DFIG with and without the FDC and EMF were compared for three- and two-phase faults. In addition to variations such as 34.5 kV bus voltage and terminal voltage of DFIG, speed of DFIG, electrical torque of DFIG and d-q axis rotor-stator current variations of DFIG were also evaluated. It was seen that the system became stable within a short time using the FDC and EMF. [ABSTRACT FROM AUTHOR]

• Decoupled power-based sliding mode control modeling strategy was developed for uncertain parameters and chattering problems in DFIG. • The rotor electromotive force model was developed to provide dynamic stability in DFIG. • The stator electromotive force model was developed to improve the performance of the simulation study. • The developed models were examined via balanced and unbalanced fault analyses. Low-voltage ride through (LVRT) capability is the principal method used to counteract voltage dips and over-current, which are caused by various balanced and unbalanced faults. However, in providing LVRT capability during faults, oscillations that occur in parameter changes should be damped for a short time. In this study, a decoupled power-based sliding mode control (SMC) in doubly-fed induction generator (DFIG)-based wind turbines was developed in order to eliminate the oscillation problems that may occur during balanced and unbalanced faults. Besides, while the stator electromotive force model in DFIG is developed with the aim of improving simulation performance and enabling ease of calculation, the rotor electromotive force model is developed to dynamic stability in the system during various faults. The results obviously indicated that the proposed decoupled power-based SMC and stator-rotor electromotive force models enhanced the LVRT capability of the grid-code requirement and quickly restored dynamic stability to the system. [Display omitted] [ABSTRACT FROM AUTHOR]

The optimal design of Power System Stabilizer (PSS) parameters is a significant optimization problem in power systems. Metaheuristic search (MHS) algorithms are among the most commonly used methods for optimizing PSS parameters. The preferred MHS algorithm must have strong exploration capability and an effective exploitation-exploration balance. The Fitness-Distance Balance (FDB) is a novel method for MHS algorithms, and it is featured by balanced search and effective diversity capabilities. In this paper, the exploration and balanced search capabilities of the Social Network Search (SNS) have been developed by using the FDB method. The FDB method guides the search process in the SNS and enables a more efficient selection of solution candidates in the search space. The performance of FDB-based SNS (FDBSNS) has been tested in the CEC-2014 and CEC-2017 benchmark test suits, and its superiority against SNS has been verified. Moreover, the effect of the FDBSNS was investigated in WSCC 3-machine 9-bus and 10-machine 39-bus New England test systems in the optimal PSS design problem. The obtained results and statistical analyses demonstrated that FDBSNS is a robust MHS algorithm compared to the algorithms in the literature for solving the CEC benchmark suits and optimal PSS design problem. [ABSTRACT FROM AUTHOR]

Grid-connected doubly-fed induction generator (DFIG)-based wind turbines are very sensitive to voltage dip problems that occur in grid side. Therefore, different low-voltage ride-through (LVRT) capability methods are used to decrease the voltage dip problems. In this study, it is aimed to present a hybrid control approach to provide LVRT capability in DFIG. Moreover, it is aimed to develop electromotive-force (emf) models in a stator-rotor circuit. The rotor emf model is used to compensate for the voltage dip and reduce the oscillations while using the stator emf model to ensure the ease of calculation and accuracy of the simulation study. In the results, this paper is reporting that the hybrid control approach proposed in this study has given yield effective and better results in comparison with those of the conventional DFIG model. [ABSTRACT FROM AUTHOR]

• A new rotor resistance unit was developed for low voltage ride through capability in a doubly fed induction generator. • Stator and rotor dynamic modeling were developed against symmetrical and symmetrical faults. • Electromotive force models are developed in stator and rotor circuits. • A comparison was made of symmetrical and symmetrical faults with and without proposed model. It is very important to obtain smooth power and limit over-currents in grid-connected doubly fed induction generator (DFIG)-based wind turbines. Therefore, the rotor resistance unit can be used for power and over-currents control in DFIG. However, it may be insufficient to reduce oscillations in large power systems. This study aims to develop a new rotor resistance unit for low voltage ride through (LVRT) capability in DFIG. Moreover, electromotive-force (emf) models have been also developed in the stator and rotor circuit. The stator emf model of the simulation study was developed in the DFIG for accuracy and speed, while the rotor emf model was developed for over-current occurring in transient situations. In using the new rotor resistance unit and the stator-rotor emf, it was observed that the system stabilized in a short time, and the oscillations formed by the balanced and unbalanced faults on the grid side were damped. [ABSTRACT FROM AUTHOR]