Severe voltage fluctuations at different points of the network are the main concerns of the widespread low-voltage electrical energy distribution networks. In particular, small industrial loads and rural consumers in remote geographical areas, which are fed by long lines, always experience great voltage drops. The use of common distribution transformers equipped with off-load tap changers has not been effective in solving this problem due to issues such as lack of access to all network points for operators, the need to de-energize the line during tap change, and the successive and unpredictable load changes. Therefore, the use of transformers with automatic voltage adjustment at different points of distribution networks has attracted much attention. The present research aimed to implement a simple solid-state voltage regulator (SSVR) in the low power range to automatically eliminate severe voltage fluctuations. In this research, a solid-state voltage regulator with a rated power of 5 KVA was designed and built to automatically compensate for the voltage of a small group of home customers (who have a severe voltage drop due to the distance from the distribution post). The results of the measurements showed that this equipment can limit the voltage changes to 220±3%, while it does not affect the power quality. In addition, various hardware and software protections were designed for the device built against network disturbances and abnormal consumer functions.

Voltage stability may be improved by various control functions. In this paper, it is shown that how High Side Voltage Control (HIVC) may be employed for this purpose. Two test systems, namely a 22- bus and IEEE U8-bus systems are used to demonstrate the proposed tuning strategy for HSVC control parameters.

In this paper, a model for distribution network expansion planning is presented, which is based on a bi-level model and can resolve the conflict between the medium and low voltage distribution networks in the size and optimal placement of transformers. In the proposed model, the upper and lower levels are medium and low voltage networks, respectively. The conflict between the two levels is that each network tends to determine the location and size of the transformers according to their wishes. Therefore, this paper has tried to solve this conflict, which is the size and location of transformers, by presenting a bi-level model, and to reach an optimal point that is in accordance with the desire of both levels. The objective function of the first level is the voltage stability criterion and the objective function of the second level is to reduce the operating and investment costs by considering distributed generations. Since the desired model is non-linear, it is solved using the tabu search by splitting the model into two sub-problems. To show the effectiveness of the proposed model, the problem is solved in three different scenarios and necessary comparisons have been made.

There are fewer problems encountered with optical voltage transducers in comparison with their inductive and capacitive counterparts. Although capacitive and inductive transformers are used vastly for the purpose of measurement and protection in the networks, they cause problems such as core saturation and improper transient responses which decrease the accuracy of measurement and efficiency of the protection schemes. As a result, optical voltage transducers are considered as proper candidates for replacing the conventional inductive and capacitive transformers. Lighter weight, smaller size, larger dynamic range, wider bandwidth, insensitivity to electromagnetic interference, stability over temperature change, absence of iron core saturation, low maintenance and replacement cost, etc. are some of the advantages of optical voltage transducers over inductive and capacitive transformers. In this paper, the Modified Adaptive Method is introduced in order to measure the integral of electric field with minimum number of sensors. Using this algorithm makes the effects of other fields minimum. One more advantage of this method is the possibility of improving the accuracy of the measurement by using a correction factor. The correction factor is determined by considering the level of accuracy, environmental conditions and the number of sensors. Simulation results show the great validity and effectiveness of this method over a wide range of variations.

Background: Epilepsy is a neurological disorder in which nerve cells of the brain from time to time release abnormal electrical impulses. These cause a temporary malfunction of the never cells of the brain. Materials and methods: In this experimental study, two electrode voltage and current clamp techniques were used to determine the efficacy of a new quinazolinone compound on PTZ induced epileptiform activity and underlying ionic conductance in D5 neuronal membrane of Helix aspersa. Results: The results demonstrated that the convulsant drug PTZ (25mM) changed the shape and increased the frequency of spontaneous action potentials. At holding potential of - 40 m V, PTZ led to a reduction in amplitude of inward and outward currents. Extracellular application of the new quinazolinone compound (0.1 mM) in epileptic model produced a hyperpolarization of the resting membrane potential and a decrease in frequency of action potentials. Under voltage clamp condition, tested new compound decreased the peak amplitude of the inward and increased the outward currents. Application of the new compound added PTZ, caused a reduction in frequency, amplitude and duration potential. Resting membrane, potential was affected and shifted towards more hyperpolarized voltage. At holding potential of - 40 m V, the new compound in the absence of PTZ depressed the total membrane conductance. Simultaneous application of quinazolinone and PTZ produced a remarkable reduction in membrane ionic currents. Conclusion: It may be concluded that new quinazolinone compound causes a reduction in cellular excitability and inhibition of PTZ induced epileptic activity via changing membrane ionic conductance.

This paper presents the low voltage Dynamic Voltage Restorer (DVR) based on application of Space Vector Pulse Width Modulation (SVPWM) for three phases Voltage Source Converter (VSC) and it is the standard PWM techniques to utilize the DC-AC power conversion. A control technique based on SVPWM is also proposed for dynamic voltage restorer. The DVR was a power electronics device that was able to compensate voltage sags on critical loads dynamically. By injecting an appropriate voltage, the DVR restores a voltage waveform and ensures constant load voltage. The compensating signals are determined dynamically based on the difference between desired and measured values. The DVR consists of VSC, injection transformers, passive filters and energy storage (lead acid battery). The efficiency of the DVR depends on the efficiency of the control technique involved in switching of the inverter. In this paper a novel structure for voltage sags mitigation and for power quality improvement are proposed. There was an increasing trend of using Space Vector PWM (SVPWM) because of their easier digital realization and better dc bus utilization. The proposed control algorithm is investigated through computer simulation by using PSCAD/EMTDC software and hardware implementation using DSP TMS320F2812. The results of the simulation and experimental show the performance of the proposed low voltage dynamic voltage restorer and prove the validity of the proposed topology. It was concluded that the proposed low voltage dynamic voltage restorer works well both in balance and unbalance conditions of voltages.

This paper presents a new approach for estimating and improving voltage stability margin from phase and magnitude profiles of bus voltages using sensitivity analysis of Voltage Stability Assessment Neural Network (VSANN). Bus voltage profile contains useful information about system stability margin including the effect of loadgeneration pattern, line outage and reactive power compensation, so it is adopted as input pattern of VSANN. In fact, VSANN establishes a functionality for VSM with respect to voltage profile. Sensitivity analysis of VSM with respect to voltage profile and reactive power compensation extracted from information stored in the weighting factor of VSANN is the most dominant feature of the proposed approach. Sensitivity of VSM helps one to select the most effective buses for reactive power compensation aimed enhancing VSM. The proposed approach has been applied to IEEE 39-bus test system which demonstrated applicability of the proposed approach.