Nearly optimal robust secret sharing

Abstract: We prove that a known approach to improve Shamir's celebrated secret sharing scheme; i.e., adding an information-theoretic authentication tag to the secret, can make it robust for n parties against any collusion of size δn, for any constant δ ∈ (0; 1/2). This result holds in the so-called “nonrushing” model in which the n shares are submitted simultaneously for reconstruction. We thus finally obtain a simple, fully explicit, and robust secret sharing scheme in this model that is essentially optimal in all parameters including the share size which is k(1+o(1))+O(κ), where k is the secret length and κ is the security parameter. Like Shamir's scheme, in this modified scheme any set of more than δn honest parties can efficiently recover the secret. Using algebraic geometry codes instead of Reed-Solomon codes, the share length can be decreased to a constant (only depending on δ) while the number of shares n can grow independently. In this case, when n is large enough, the scheme satisfies the “threshold” requirement in an approximate sense; i.e., any set of δn(1 + ρ) honest parties, for arbitrarily small ρ > 0, can efficiently reconstruct the secret

Single phase Unified Power Flow Controller (UPFC) : simulation and construction.

Unified Power Flow Controller (UPFC) is used to control the power flow in the transmission systems by controlling the impedance, voltage magnitude and phase angle. This controller offers advantages in terms of static and dynamic operation of the power system. It also brings in new challenges in power electronics and power system design. The basic structure of the UPFC consists of two voltage source inverter (VSI); where one converter is connected in parallel to the transmission line while the other is in series with the transmission line. The main scope of this paper involves the designing of a single phase UPFC using Matlab and Simulink software, and constructing a lab scale model of the UPFC. A microcontroller program has been developed to provide the required phase shift. The experimental result which has been obtained from a lab scale system showed a good agreement with the simulation result

Voltage regulation of uninterrupted power supplies

Uninterrupted Power Supply (UPS) systems are used as one solution of power quality problems and to provide ultimate protection for power disturbances such as power blackouts and brownouts. Many UPS systems suffer from poor output voltage regulation especially with heavy loads. This work is aimed to design and implement the UPS hardware system capable of producing continuous and constant 230Vac, 50 Hz output supply. A feedback loop has been implemented using microcontroller to adjust the dc level supplying the UPS inverter. At the end of the hardware implementation, tests have been carried out to determine the reliability and effectiveness of the designed system, and a good results have been obtained in improving the voltage regulation

Application of inverter based shunt device for voltage sag mitigation due to starting of an induction motor load

This paper shows a study of the static synchronous compensator (STATCOM) behaviors for voltage sag mitigation to an induction motor. The proposed of STATCOM stability model is justified based on the basic operation characteristics of phase control strategies. The simulation of 6 pulses STATCOM based on voltage source inverter (VSI) using Matlab Simulink is presented to show its good performance under balanced voltage sag condition due to the motor starting. Experimental testing has been made by using thyristor firing board control (FS36M). The STATCOM response of compensated reactive power to the system during voltage sag has been shown. Finally simulation results and experimental results have been described and compared once and good performance has been obtained

Effects of high power converter on power line carrier signal

Power line carrier (PLC) systems are used in transmission of signals for teleprotection, teletripping, telecontrol and speech communication. The signal to noise ratio (SNR) of the PLC is based on the noise level at the input of the carrier's receiver. The interference due to large power converter will be superimposed on the background noise at lower level. It has reduced the SNR to an unacceptable value. This paper deals with analysis of high frequency (HF) harmonics (higher than 20 kHz) produced from the converters, and the methods used to reduce the noise imposed on the PLC communication signal. The experimental and simulation results have been obtained for both processes

Construction of as prototype D-Statcom for voltage sag mitigation

This paper presents the design of a prototype distribution static compensator (D-STATCOM) for load compensation in an unbalanced distribution system. The DSTATCOM is intended to replace the widely used static Var compensator (SVC). The compensation scheme of the DSTATCOM is derived using the symmetrical component method.In this work, the 12-pulse D-STATCOM configuration with IGBT has been designed and the graphic based models of the DSTATCOM have been developed using the PSCAD/EMTDC electromagnetic transient simulation program. Accordingly,simulation is first carried out to illustrate the use of DSTATCOM in mitigating voltage sag in a distribution system. The D-STATCOM has been developed using DSP controller to achieve excellent overall performance. Simulation results prove that the D-STATCOM is capable of mitigating voltage sag by controlling PWM of the system using DSP board

Simulation of lightning surges on tower transmission using PSCAD/EMTDC: a comparative study

This paper describes the analytical and the experimental responses of the surges strike on the transmission line towers. A new method of calculating transmission tower surge response has been proposed. It has been found that the tower surge response calculated by the proposed method has a close agreement with the measured tower surge response obtained from scale model and field tests. Without the use of simulation program, this topic might be difficult to understand. PSCAD/EMTDC has been selected as the software used to generate the appropriate data needed to graphically demonstrate this phenomenon

Expert system-based approach to automate the design process of power electronics converters

The design of power electronics converters is still an ad-hoc process. Usually, this process is accomplished virtually using existing simulation packages before the real implementation. Despite, the use of these packages, the process is proved to be time consuming and bulky task. This paper describes an expert system approach to ease this cumbersome process by automating the design procedure. The present approach combines expert system techniques with object-oriented paradigm. The designer has firstly to choose the appropriate application of the converter. Then the system suggests the most appropriate (according to the user's specifications) topology that is formed in a schematic file accepted by the Pspice simulation package. The topology is displayed within the Schematic environment containing all the circuit parameters and components including the best (optimum) switching devices and control circuits, here the simulation is launched automatically in order to investigate the outputs. The topologies constitute the knowledge base of the system represented as objects. The switching devices are stored in database module accessed by the inference engine to select the optimum switch for a certain topology. This approach could be a kernel of a power electronics converters design aid tool, whereby the complexity of the design process can be reduced dramatically

Design of a prototype D-STATCOM using DSP controller for voltage sag mitigation

This paper presents the design of a prototype distribution static compensator (D-STATCOM) for load compensation in an unbalanced distribution system. The D-STATCOM is intended to replace the widely used static VAr compensator (SVC). The compensation scheme of the D-STATCOM is derived using the symmetrical component method. In this work, the 12-pulse D-STATCOM configuration with IGBT has been designed and the graphic based models of the D-STATCOM have been developed using the PSCAD/EMTDC electromagnetic transient simulation program. Accordingly, simulation is first carried out to illustrate the use of D-STATCOM in mitigating voltage sag in a distribution system. The D-STATCOM has been developed using DSP controller to achieve excellent overall performance. Simulation results prove that the D-STATCOM is capable of mitigating voltage sag by controlling PWM of the system using DSP board