Applied Mechanics and Materials Vols. 321-324

Abstract: Considering the complicated uncertainty of the occurrence of equipment failure and the serious level of its sequence due to voltage sags, this paper classifies the invalided samples into three categories. The corresponding uncertainty is measured by random entropy, fuzzy entropy and cross entropy respectively. A maximum hybrid entropy assessment model is proposed. Based on the quantitative assessments of equipment invalidation rates, the comprehensive assessment is carried out according to the corresponding weight. Compared with existing methods, the proposed method is able to overcome both over- and under-estimation problems, with the results in line with practice very well.

Abstract: Taking a series-parallel combined hybrid city bus as the prototype, the synergic electric power supply system (SEPS system) consisted of Ni-Mh battery pack and ultra-capacitor(UC)pack was designed to replace the original single electric power source which was battery pack. The element parameters were determined. By secondary development of ADVISOR, the simulation model and control strategy of the SEPS system and then the vehicle simulation model were built. Then the paper combined the ADVISOR with genetic algorithm to find the best capacity values of the battery pack and UC pack. The simulation results show that the vehicle with SEPS system can reduce the charge-discharge current of the battery pack, recapture more energy when braking which means better safety and fuel economy for the vehicle.

Abstract: A nonlinear model of proton exchange membrane fuel cell (PEMFC) based on an adaptive neuro-fuzzy inference system (ANFIS) is proposed to study different operational conditions effect on the dynamic response of Ballard 1.2kW Nexa power module. A hybrid learning algorithm combining back propagation (BP) and least squares estimate (LSE) is adopted to identify the parameters of input and output membership functions for the improvement of training efficiency in the ANFIS. The comparisons with the experimental data demonstrate that the obtained ANFIS model can efficiently approximate the dynamic output response of Nexa power module and is capable of predicting dynamic performance in terms of stack output voltage with a high accuracy.

Abstract: Modified Artificial Fish Swarm Algorithm (MAFSA) based on the global search characteristic of Artificial Fish Swarm Algorithm (AFSA), and combined with the local search of chao optimization algorithm(COA), can avoid trapping into local minimal value and decrease the iteration numbers, which was a swarm intelligence optimization algorithm applied to continuous space. MAFSA was proposed to optimize the reactive power optimization, which applied for optimal reactive power is evaluated on an IEEE 30-bus power system. The modeling of reactive power optimization is established taking the minimum network losses as the objective. The simulation results and the comparison results with various optimization algorithms demonstrated that the MAFSA converges to better solutions than other approaches and the algorithm can make effectively use in reactive power optimization. Simultaneously, the validity and superiority of MAFSA was proved.

Abstract: The oscillating buoy wave power device is more effective than other devices in energy conversion efficiency, and now it has been widely applied in development of marine wave energy. The oscillating buoy, which is an important component for the oscillating buoy wave power device, is closely related to energy conversion efficiency. In this paper, considering applying conditions in South China Sea, the dynamic characteristic for oscillating buoy is simulated using AQWA software. By analyzing and comparing dynamic characteristics of several different structure bodies, an optimal structure buoy is obtained and it has better energy conversion efficiency.

Abstract: For the purpose of studying the state of health of AOWEI 1.5V/80000F hybrid supercapacitor with aqueous electrolyte for the driving power system of supercapacitor city bus, an equivalent circuit model describing the electrical characteristic of hybrid supercapacitor is proposed according to its working principle. Then, the statistical method of correlation and regression analysis is presented to model the relationship of temperature and equivalent circuit model parameters based on experimental data. The goodness of fit and the test of statistical significance are fulfilled to verify the regression model and coefficients, and results show that the parameters of equivalent circuit model can describe temperature behavior of hybrid supercapacitor.

Abstract: The large expansion of electrical power systems usually results in problem of low frequency oscillations. Therefore, the conventional Power System Stabilizers (PSSs) used to solve this problem cannot provide an adequate damping of low frequency oscillations. Flexible AC Transmission System (FACTS) damping controllers are available for providing suitable damping for these oscillations. This paper, presents the simultaneous coordinated design of the multiple damping controllers between PSS and SVC-based stabilizer in a single machine infinite bus power system. The coordinated design problem of multiple damping controllers is formulated as an optimization problem. Particle swarm optimization algorithm is applied in order to search optimal controlling parameters by maximizing the objective function based on the eigenvalue. The simulation results for a wide range of operation condition show that the coordinated design able to provide better damping and stability performance.

Abstract: Because of the complex structure and the changeable parameters of the DFIG and the shortcomings of the traditional PI controller, a new nonlinear P+C (C for constant) controller is raised to achieve the active power and reactive power decoupling control. The simulation results show the validity, effectiveness and robustness of the method in this paper.

Abstract: The necessity of research on the vegetation-related failure and its inherent hidden timescale in the cascading failures is attached importance based on the facts of recent blackouts internationally. The dynamic behavior of line sag and the vegetation growth are modeled. The time of vegetation related failure after step increase of the line current due to other disconnect events is calculated considering specified physical circumstances, and it can help operators be aware of the necessary urgency of system crisis. Case studies are made on WSCC-9 and IEEE-24 test system respectively, and the results show the method proposed is able to identify collapse sequences due to vegetation-related failures and corresponding timescales, and make great contribution to the prediction and prevention of cascading failures.

Abstract: Smart grid need to transmit a large number of data through the Wireless Sensor Network (WSN). In the past, the core problem of WSN was to limit the energy consumptions of the node and prolong the life cycle. With the development of hardware technologies, and to improve the security and reliability of the transmit data, the core problem of WSN is changed to improve the connectivity and stability of WSN network. This paper summarized a new topology used in WSN network. Large area was divided into small grid as region. By calculate the weighted average values of each node in the region, we constructed a tree topology. The new topology improved the key technologies of WSN including data privacy, Qos, query algorithm and robustness. In the simulation experiments, the new topology can improve the stability and connectivity of the WSN remarkably.