In this paper, the effect of SSSC on voltage sag following transformer inrush current is investigated. Static synchronous Series Capacitor (SSSC) as a dynamic system, besides its capability in increasing power transfer in transmission lines, can be used to enhance different power system issues. Hence, voltage sag as one of the key components of the power quality is alleviated for the sensitive loads that are connected to the same bus which the power transformer is energized from.

This paper presents a new intelligent algorithm, named binary real genetic algorithm (BRGA) to design parameters of PSS and (STATCOM) controller simultaneously. The proposed algorithm has a strong search capability and high speed convergence to find the global optimum points. The objective function used in this paper to be minimized is the time integral absolute error (ITAE). The objective will be minimizing the deviations of rotor speed (Dw) and the voltage of the bus in which (STATCOM) has been installed. The simulations are carried out on a two-area four-machine power system to show the superior performance of the proposed method, when compared with GA and PSO algorithms.

In recent years, due to shortage of energy resources, use of new energies such as wind energy has been rising. Therefore, the study for the optimal use of these energy resources is very necessary. Nowadays, doubly fed induction generators (DFIGs) are used in modern wind power plants. Stability investigation of power system connected to DFIG is very essential. Static VAR compensator (SVC) and static synchronous compensator ((STATCOM)) are installed in parallel with transmission lines. The main applications of these compensators are fixing and adjusting of the voltage in a certain amount and stability improvement. Parameters tuning of these compensators is very important. In this research, at first, an appropriate way is suggested in order to choose the objective function for minimizing oscillations resulted from disturbances. Then optimal tuning of SVC and (STATCOM) control parameters will be done by genetic algorithm in the form of an optimization. Ultimately, efficiency of suggested methods will be considered in order to improve the stability of DFIG voltage, DFIG rotor speed, DFIG active power and the rotor speed of synchronous generators. This topic is evaluated and analyzed in a sample network with considering and comparison of results in the presence and absence of SVC and (STATCOM). All simulation and optimization steps are done by the MATLAB software.

Power grids are complex, interconnected and nonlinear systems, and this will be more severe when they are subjected to high wind resources penetration. Static synchronous compensators ((STATCOM)) are used to improve voltage regulation and to meet grid codes in power systems, including doubly fed induction generators (DFIG) based wind farms. Despite the nonlinear nature of (STATCOM), the conventional control method in them is based on linear PI controllers with constant gains, which they cannot guarantee the optimal performance for (STATCOM). In this paper, a comparison has been performed between two nonlinear control methods based on differential flatness theory for static synchronous compensators in the WSCC system includes DFIG based wind farms and simulation results demonstrate the effective performance of both methods in comparison with the conventional linear control method.

Unbalanced loads in the distribution grid can cause unbalanced supply voltage and reduce the power quality of the system. Besides, reactive power loads might create the voltage disturbances such as voltage sag/swell. In this paper, a four-wire distribution static synchronous compensator (D(STATCOM)) integrated with Yy-transformer to compensate both the unbalanced voltage and reactive power is proposed. A D(STATCOM) based on modular multilevel converter (MMC) connects to the group of taps in the primary windings of Yy-transformer to constitute an interconnected structure. The compensating currents flow through the taps. This structure is similar to an autotransformer. Compared to the conventional MMC-D(STATCOM), with proposed structure, The D(STATCOM) connection point voltage decreases and one can trade-off between the capability of the power device's rated voltage and current. Therefore, it can be decreased the primary investment costs, the voltage stresses and the size of compensation system. Furthermore, a control algorithm based on measuring the point of common coupling (PCC) instantaneous voltage and current is presented that it is able to compensate the zero and negative sequence voltage due to unbalanced laod and grid. To compensate these components, voltage and current loops are used to track accurately the reference voltages of MMC-D(STATCOM) by means of unbalanced algorithm. Simulation results verify the proposed method.

The development and use of FACTS devices for power transmission system has led to the application of these controllers to improve the stability of power systems. This paper discusses the optimal control of static compensator ((STATCOM)) to improve transient stability. To demonstrate the ability of the proposed control strategy, it has been applied on a single machine and multi machine power systems. Different modes of operation of compensator regarding the modulation of active and reactive power has been considered. In multi machine system, since the control signal based on the state variable is not available at the compensator bus, the derivative of an electric quantity derived from local measurement has been utilized.

With the rapid progress of semiconductors in the level of voltage and power of the power system as well as the progress of control systems, compensators with high flexibility and performance range have been designed and built to increase the flexibility of energy transmission systems. to be These compensators installed in power systems are called flexible ac transmission systems (FACTS). One of the most important advantages of FACTS devices in the transmission system is to increase the transient stability margin of the power system by controlling the active and reactive power of the line during the occurrence of a fault in the system. In this article, the effect of one FACTS device with parallel connection, i. e. static compensator, on transient stability is investigated. The studied system is a two-machine power system including a hydropower plant and a local power plant. The simulation results show the effect of the compensator on the damping of electric power angle fluctuations. Also, the simulation results show the lack of influence of the compensator on the transmission active power in the transmission line. The simulation results have been obtained using Simulink MATLAB software.

In this article the performance of a DI(STATCOM) as an efficient parallel compensator, for obtaining the power indexes has been considered, then, to improve the performance of DISTATVOM, each of its PI controller has been substituted by a non-liner fuzzy-neural controller, based on trial error and derivation of system error. The cause of detorioration of power quality and the method of their compensation, in a distribution network, has been analysed, using Matlab. The simulation results show that, by using the fuzzy-neuralcontroller in place of linear controller in DI(STATCOM) controller, the ability of compensation in the active and reactive power voltage sag, swell and fliker, and reduction of low current and voltage harmonics has been improved cansiderably.