Applied Mechanics and Materials Vols. 341-342

Abstract: According to the practical requirements of setting up large scale power quality monitoring systems and monitoring power quality in digital substations, an embedded power quality online monitoring device based on PowerPC and DSP is realized. The device structure, the overall hardware design, the PowerPC and the DSP systems are introduced. The design scheme based on PowerPC and DSP can take full advantages of the fast data calculation speed of DSP and the strong network processing ability of PowerPC. The test result of the measurement accuracy shows that the device can meet the power quality indicators measuring requirements of national standards.

Abstract: Active distribution network can realize the grid-connected operation of the large-scale intermittent power, and thus ensure the profits of the DG operators. It can also help to defer the investment for the power grid construction, reduce the standby power capacity, and improve the power supply reliability rate. Active distribution network planning should not only consider the content of the traditional distribution network planning, but also consider the influence of distributed generation output and demand side response regulation. Based on these prerequisites we establish a bi-level optimization model of active distribution network planning in this paper. From the perspective of saving investment for the electric power company, we use a function to minimize the total cost of the planning scheme, including both the plan and operation cost, with the consideration of a series of constraints such as DG and DSR. Hence we establish a bi-level optimization planning process of the active distribution network based on genetic algorithm.

Abstract: A method is provided to make natural frequency method be applied to single terminal traveling wave fault location in the paper. A group of fault distance suspected is calculated by single terminal method of traveling wave fault location method firstly, then deal with current travelling wave of fault by FFT to get the natural frequency reflecting fault location so that a fault distance can be calculated by it. Contrast the fault distance from natural frequency method and everyone of the group of fault distance suspected from single terminal method of traveling wave fault location method to determine the suspected fault distance closed to it is the calculation results we want. Numerical simulation shows the method can improve effectively the reliability of single terminal traveling wave fault location.

Abstract: In the present paper, the coupling numerical analysis of 3D flow field and temperature field inside a marine generator was analyzed based on coupling field analysis method. The overall flow-temperature field models consist of the marine generator stator and rotor and flow passage and the air gap. Numerical analysis of flow-temperature field of marine generator were simulated by the finite volume method. The velocity and pressure distribution of fluid inside flow passage and the temperature field distribution of stator and rotor of marine generator were obtained. The present results showed that, the coupling field analysis method of overall flow-temperature field with air gap, stator and rotor can reflect the complexity of the air flow more clearly, and the value of flow and temperature field were more reliable. The results also contribute theoretical basis on optimization of ventilation struture of generator.

Abstract: A method of parameter estimation of induction motor based on optimization using a chaotic swarm algorithm is presented. The parameter estimation methodology describes a method for estimating the steady-state equivalent circuit parameters from the motor performance characteristic, which is normally available from manufacturer data or from tests. The optimization problem is formulated as multi-objective function to minimize the error between the estimated and the manufacturer data. Chaotic ant swarm algorithm is a novel optimization method, which has the ability of global optimum search. A numerical simulation on the test motor is conducted. Simulation results show that the proposed method is effective in parameter estimation of the induction motor.

Abstract: Biodiesel as a renewable and environmentally friendly alternative fuel derived from natural fats or vegetable oils has better lubricating properties and much higher cetane ratings than today's lower sulfur diesel fuels. It is considered as an attractive alternative to replace diesel fuels. In order to investigate application of biodiesel on vehicle diesel engines, the power and fuel economies performances of a diesel fueled soybean biodiesel with different blending ratios were tested under different engine loads and speeds. Experimental results show that, compared with diesel fuel, with increase in the biodiesel in the blends, the brake power and torque, and the brake specific energy consumption increase but the fuel consumption per hour and brake specific fuel consumption decrease.

Abstract: Transformer inrush current generated has been plagued by engineering and technical personnel, is also a hot topic in the industry. Electro slag furnace is a common metallurgical industry furnace, used in the metal crystal more closely requirements, performance requirements and a variety of high quality roll alloys, high temperature alloys, nonferrous alloys. Electro slag furnace transformer is the core component, have a great no-load closing inrush current protection trip often makes itself affect the product quality and production efficiency or to expand on a power trip protection range. In order to suppress inrush current, with the primary winding series resistance speed-load closing the attenuation of inrush current, inrush current generated from the theoretical reasons to be discussed and a simple series resistance deduce the resistance of this method. Theoretical basis for comparison with other methods are not subject to a number of objective factors sufficient interference, the results demonstrate the practical application of this method is simple and inrush current suppression effect is very significant. Thus, the series resistance ESR furnace transformer inrush current suppression is a method of high cost.

Abstract: According to the theory of complex network and risk assessment, a intelligent risk automatic warning system of catastrophic accident based on conditional risk function is presented. The warning system introduces electrical betweenness and conditional risk expectations to overcome the insignificance of traditional risk assessment which only considered the status of grid and N-1 accident. A risk index system of catastrophic accident is constructed which reflects the risk of grid when it is current and in the next level of fault and portrays the trend of spreading to the catastrophic. The simulation results prove that this method which the new system use can identify the risks effectively. Consequently it provide effective reference information for security assessment of power system.

Abstract: Shunt capacitor is a main measure to reactive power compensation of power system, which has the advantages of flexibility and economy. In order to guarantee the safety of shunt capacitor, the methods for protecting against over-voltage, under-voltage, over-current and unbalance in circuits according to the different operation modes are used. This paper in detail introduces unbalance protection ways under different connection modes of capacitor group. It is analyzed and calculated that the unbalanced current and voltage with the effects of fault capacitor units, components and fuses on capacitor bank as well through a case of unbalance computation of shunt capacitor banks (SCB) of ungrounded single star with external fuse. It is indicated by PSCAD simulation analysis that the result of theory calculation is the same as the simulation, which provides theory basis of setting the tripping point and alarm point of relay protection.

Abstract: This paper proposes a new formulation of the preventive security-constrained optimal power flow (PSCOPF) which considers the constraints limiting the number of beforehand control actions and provides an approach to convert the proposed model to a nonlinear programming (NLP) which is more tractable by implementing an interior point algorithm (IPA). The proposed model and approach are illustrated on two standard test systems of IEEE-30 and IEEE-118. The results clearly indicate the system operation state can be changed from a given operation point to a PSCOPF satisfied operation point by exerting beforehand control actions in specified number. Furthermore, a minimum number of control actions can be obtained through this new formulation.