In renewable energy based systems Grid-Connected Voltage Source Converters (GC-VSC) are used in many applications as grid-feeding converters, which transfer the power coming from the renewable energy sources to the grid. In some cases, the operation of GC-VSC may become unstable or uncontrollable due to, among others: a grid fault or an inappropriate current-power reference, that give rise to fast electrical transients or a saturation of the controller. In this paper, an improved control scheme is proposed to enhance the controllability of GC-VSC in all these situations. This solution consists of two parts, on the one hand a new Proportional-Resonant (PR) controller with anti-windup capability to be used as current controller, and secondly a new current/power reference modifier, which defines the suitable reactive current/power reference to keep the system stable. It is worth to mention that the proposed scheme does not need information about the grid parameters as it only uses the converter current, and the voltage at the capacitors of Inductor-Capacitor (LC) output filter.
A human hand is a very complex grasping tool which can handle object of different sizes and shapes. Many research works have been done to develop an artificial robot hands with similar capabilities to a human hand, such a robot hand is also called a multi finger gripper. Most parts of this research are dedicated to control of multi finger grippers with emphasis on the finger tips or finger joints. By controlling a multi finger gripper, we enable the gripper to handle an object; in another words, controlling a multi finger gripper can be viewed in terms of controlling an object's pose and the forces between the object and its environment. Hence, an object pose controller with feedback from an object pose sensor suits multi finger gripper control. Also due to the non-linear dynamic system behavior in the joints of most multi finger grippers, an effective, easily-adaptable joint controller is employed. The paper discusses the object pose controller with great detail in a new joint controller. Since the joint controller is based on microcontroller and we do not use an exact analytical model for this case.
This paper presents the application of compensating capacitors for optimal power flow in transmission system. The compensating capacitors are placed at suitable locations in the transmission system and the size of reactive power to be injected by the capacitors to the system is obtained using artificial immune system (AIS) optimization technique. AIS will find the best value of reactive power of the compensating capacitors so that the total system loss is minimum. It is found that applying the AIS optimization technique is prospective approach for finding optimal reactive power output of the installed compensating capacitors in controlling reactive power of transmission system.
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