Applied Mechanics and Materials Vols. 313-314

Abstract: The grid is one of the most important ways of distributed power generation.Micro-grid existence provides a new approach to solve the contradiction between the large power grids and distributed power.This paper studies the stability of Micro-grid contained DG. It establishes the simulation model of typical Micro-grid and studied the impact of transient stability in micro-grid by different fault types and different fault points. Look for the general rules of Micro-grid stability impact by different control mode and different disturbance. Dynamic response curve of Voltage and frequency in micro-grid is reached .Analysis of simulation results, this paper gets the general rule on the effect of stability of Micro-grid.

Abstract: This paper presents bees two-hive algorithm for solving the optimal power flow (OPF) problem with various constraints. The objective of the proposed technique is to improve the quality solution of the conventional bees algorithm that minimize the total fuel cost subject to operational and physical constraints i.e. energy balance, generation and transmission limits including security constraints. The proposed methodology is tested on the IEEE 30-bus test system. The results obtained using the proposed approach are compared to GA, PSO, BA and other conventional. The comparison of quality solution with other algorithms confirms performance of proposed technique. Simulation results demonstrate that bees two-hive algorithm provides better results than other heuristic techniques.

Abstract: Nonconventional energy sources are playing important role in meeting current power/energy demands. However these sources cannot provide High voltage/power. For power conditioning and voltage amplification solid state power converters are very much essential. One such approach to obtain high voltage was to use cascaded multilevel inverter but cascaded multilevel inverters require separate DC sources and they cannot be used for regenerative applications. To overcome these limitations, a novel configuration is using diode clamped multilevel inverter is proposed here. . The conditioned DC voltage from photovoltaic cells or fuel cells or batteries is boosted and inverted by means of multistage Multilevel Inverters (MLI). Three different configurations are presented in this paper. From the simulation results of all three configurations, the topology which is found to be better is implemented in the real time. A proto type is developed to boost 40 V input DC to 100 V AC and the experimental results for the same are presented.

Abstract: On-site experience suggests the possibility of condensation of the moisture in Current transformers (CTs) which is impossible theoretically if temperature distribution in the CT is uniform. In order to study the temperature distribution in a typical CT, finite element analysis software (COMSOL Multiphysics) is used to obtain the temperature distribution of the outer surface and inside of SF₆ in CT in different ambient temperatures (20 °C to-10 °C). Besides, experiments are conducted to obtain the temperature of different positions on the CT surface that correspond to conductor, shell, spacer and porcelain bushing that are inside the CT with different ambient temperature. Both simulation and experiments show that temperature distribution in the CT is non-uniform, and the closer the part is to the conductor, the higher the temperature. Furthermore, maximum temperature difference remains about 35 °C in both simulation and experiments with different ambient temperatures from 20 °C to-10 °C.

Abstract: To improve transformer longitudinal differential protections reliability, this paper deeply analyzes generation mechanism and characteristic of transformer inrush current, and uses PSCAD/EMTDC software to simulate 188 kinds of transformer operation states. They are including internal fault current, inrush current and no-load closing with internal fault. On the background of those simulations, it proposes a simple and accurate method to identify inrush current based on SVM. SVM selects Gaussion Kernel, and takes three-phase differential current, fundamental, secondary harmonic and third harmonic as characteristic quantities. Many cross-validation results verify that the training SVM has high accuracy. This method can identify inrush current and internal fault current (including no-load closing with internal fault current) rapidly and accurately. It takes less time, and is easy to perform.

Abstract: This paper presets comparisons of type of monitor in personal computer set on electrical energy saving and side effect on power quality. The 3 types of monitor in personal computer consists of cathode ray tube : CRT type inch, liquid crystal display : LCD type, and light emitting diode : LED type and side of each monitor is 19 inch. The experimental results as shown the power consumption and side effect on power quality such as power factor and %THDi each monitor types. The experiment results shown the best effectiveness is LED monitor type, it can be saving of energy up to 75.69 % of CRT monitor type and 45.30 % of PC. Set with CRT monitor type. However, the LED monitor type are generated of %THDi very high level and low level of power factor.

Abstract: Flexible AC Transmission System (FACTS) devices namely Unified Power Flow Controller (UPFC) will gives a basic control for transmission line real/reactive power flow and bus voltage/shunt reactive power. UPFC helps in regulating the power and mitigating the rotor speed instability and damping oscillations. UPFC placement was conducted at each line in the entire network system to obtain the most suitable optimum location for most effectiveness performance. The performance of the optimal UPFC location is checked by applying a fault across a transmission line to which UPFC is connected and the power flow in the line and stability of the system is determined. Available Transfer Capability values indicate allowable highest magnitude of active power (MW) that can be transferred from the source to the sink over and above the already committed uses (base case) of the whole network without exceeding any line thermal loading and bus voltage limits. Finally, simulations were carried out using PSAT software to validate the performance of the UPFC which connected to a transmission line. The effectiveness for UPFC is demonstrated on IEEE 9 bus and IEEE 24 bus system while for ATC is demonstrated on IEEE 6 bus system and all the results are compared.

Abstract: This paper presents cooperative object transportation using connected robots. Previous studies of object transportation mainly used pushing or grasping methods to manipulate objects. A pushing method, however, cannot control the object motion precisely and a grasping method requires complicated gripping action before the transportation. Therefore, we suggest a new object transportation method which uses a rope. The method consists of three phases according to the behavior: the approaching, enclosing and transportation phases. Robots and an object have different formation controllers in accordance with their phases. Real experiments are presented to prove the validity of the proposed method.

Abstract: Expansive-Spaces Trees (EST) is a single-query sampling-based path planner. When EST is applied to robot navigation in dynamic environments, EST confronts the risk of a collision with dynamic obstacles since it has generated a path without any consideration for dynamic obstacles. This paper proposes an efficient path replanning technique for EST-based robot navigation in dynamic environments. The proposed technique replans a collision-free and efficient path instead of the original EST path which may cause a collision with dynamic obstacles. Besides, the replanned path can be easily merged into the original EST path because it preserves the property of EST. Simulation results in various dynamic environments reveal that the proposed technique can successfully replan a collision-free and efficient path for EST-based navigation.

Abstract: The goal of the work is construction and testing of the mobile robot for waste rock exploring. It is descripted concept of mobile service device with ability to explore waste rock, detect toxic gases and monitors that area. The area of waste rock is dangerous for human, because surface of waste rock is inconsistent and it might be very unstable for human walking. Furthermore dangerous gases can occur in these places. Some of the gases are undetectable by human. Another problem is temperature on the surface. Due these properties on the whole is proper to use mobile robot to explore these places.