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One of the most important concerns in manufacturing industries and utilities over the utilization of voltage controlled voltage source inverters (VCVSIs) is to generate and maintain a steady sinusoidal output voltage to the critical load which has been the focus of considerable research in recent years. VCVSIs output voltage fluctuation may be caused by abrupt or periodic changes of the load current that are significant. The purpose of this paper is to keep the amplitude of the output voltage wave form at the reference level under these conditions. The proposed method presents a fast voltage variation detection technique using phase space mathematical method to improve voltage fluctuation. A controller that takes advantage of this detection method is applied to a full bridge inverter to keep the voltage level at the desired point. To investigate the efficiency and accuracy of the proposed controller, a system is modeled using Matlab/Simulink and the results is compared with open-loop and RMS controllers. The simulation results approve the capability of the proposed controller to provide a sinusoidal output voltage and mitigate voltage fluctuation to a considerable level by using phase space method.

This study presents the study of configuration, working, controller of the fundamentals of the STATCOM and significant function of each custom power devices. Flexible Ac Transmission Systems (FACTS) controller achieves fast control response time as well as providing better control than conventional control. However, Static Synchronous Compensator (STATCOM) could be seen as one of the key Flexible Ac Transmission Systems (FACTS) devices which are based on the Voltage Source Converter (VSC) technology. The capacitive and inductive compensation could be provided by the controller and could as well control output current over the rated maximum capacitive or inductive range without depending on the ac system voltage.

Distribution static synchronous compensator (D-STATCOM) has been developed and attained a great interest to compensate the power quality disturbances of distribution systems. In this paper, a novel single-phase control scheme for D-STATCOM is proposed to improve voltage profile at the Point of Common Coupling (PCC). The proposed voltage mode (VM) controller is based on the phase space algorithm, which is able to rapidly detect and mitigate any voltage deviations from reference voltage including voltage sags and voltage swells. To investigate the efficiency and accuracy of the proposed compensator, a system is modeled using Matlab/Simulink. The simulation results approve the capability of the proposed VM controller to provide a regulated and disturbance-free voltage for the connected loads at the PCC.

Sending the private data is always one of the fundamental problems in the communication systems. Therefore, information hiding was presented to protect the data. The evolutionary process has been continued until the watermarking as a new technique was generated to promote the copyright marking. Watermarking is trying to embed the private data such as text or numbers as a guest signal in the host signal with minimal effect on it. Audio watermarking was introduced as a one of watermarking techniques against the attackers and hackers that were raised on social networks.This paper presents an audio watermark algorithm with a blind detection which is based on a spread spectrum (SS) technique. A series of simulations were done on the proposed algorithm to estimate the Bit Error Rate (BER) for various values of signal-to-watermarking ratio (SWR) and bit rate. The simulationresults show that by decreasing the SWR ratio, the BER ratio is reduced to less than 10−3.

The Distribution Static Compensator (D-STATCOM) can be used as a parallel voltage sag mitigation device at distribution systems. The D-STATCOM is also able to regulate and balance the bus voltage by absorbing or generating the required reactive power at specific buses. This study presents an overview on D-STATCOM structure and its simplified model that can be used for voltage sag analysis. In addition, this study also investigates the effect of various load and network parameters on the nominal power requirement D-STATCOM and its ability to compensate voltage sag. The results illustrate the performance of D-STATCOM by using an injection current to various conditions for voltage sag mitigation. In addition, the result shows that the D-STATCOM is not economical and effective in high voltage networks with low inductance feeder.

Voltage sag is a common power system disruption, usually associated by power system failures. Therefore the accurate detection of voltage sag event is vital issue for mitigation and voltage sag analysis. This paper presents a new method based on phase-space technique for fast voltage fluctuation (sag/swell) detection. The control strategy is built on phase-space, which has the ability to track the amplitude of the voltage sag in actual time. The main objective of the proposed technique is to accurately detect the occurred voltage sag and force the compensating device to inject required voltage to improve the line voltage to the pre-fault level. Static compensator (STATCOM) as a compensating device has been proposed for network stability improvement and power quality. It is simply connected in parallel to the electric network and it has numerous advantages for electrical grids. The main aim of this study is to improve network stability; power factor, power transfer ranking and able to avoid some disturbances such as swells and sags. Another significant element for STATCOM effectiveness in voltage sag mitigation is the simulation results have demonstrated the superiority of the proposed controller and voltage sag detection technique and sag detection algorithm to be utilized in the STATCOM.

Nowadays, the protection of private information in a communication system has become an important issue. Watermarking is introduced as a new technique to information hiding. In order to hide data (such as text or numbers (guest signal)), video, image and audio are used as a host signal . This paper proposed an audio watermark algorithm with a blind detection which is based on spread spectrum (SS) technique. A series of simulation is done over the watermarking algorithm. Error probability has been investigated for various values of the bit rate (R). The simulation result shows that by increasing the bit rate the error probability is also increased.