Advanced Materials Research Vols. 732-733

Abstract: With the development of high voltage long distance transmission and expansion of the grid, continuous reactive power compensation devices become more and more important. This paper aims to analyze a novel hybrid adjustable reactor. Based on analysis of structure and theory, simulation model and prototype are done to verify the characteristics of this reactor. Results of simulation and test confirm that the variation range of reactive power capacity is 3.5%~84.0%, and work voltage and current are approximately sinusoidal, the harmonic content is quite little. In a word, this novel hybrid adjustable reactor will play an important role in reactive power compensation.

Abstract: Firstly, the operating mechanism in developing process of transformer internal latent fault and external accessory fault is analyzed. Then, dissolved gas analysis (DGA) outcome and average degree of polymerization (DP) are used as an indicator to classify transformers operating condition, the multi-state Markov process model based transformers operating condition is proposed to estimate the internal failure rate. According to the method of weather condition classification, the external accessory failure rate model is proposed by considering the influence of weather change. A time-varying transformer outage model for operational risk assessment is proposed by using the multi-state Markov process to estimate the time-varying failure probability. Finally, a numerical is presented.

Abstract: This paper discusses effect of shielding lines on reduction of electric field produced by overhead lines. Charge simulation method is used. Influences of height, space and number of shielding lines on electric field are calculated. Space between shielding lines has reverse roles on influencing area and maximal electric field. Number and space of shielding lines should be carefully selected to shielding a certain area. Analytical method is also used to express induced electric field by shielding lines. Result of comparison with charge simulation method shows that it is suitable for area outside of three phase lines.

Abstract: This paper proposes a cooperated control of the grid side converter (GSC) and rotor side converter (RSC) in doubly-fed induction generator (DFIG) wind power generation system under unbalanced grid condition. Mathematical model of doubly-fed induction generator (DFIG) and GSC under unbalanced grid voltage condition are investigated. Dual-dq current control strategies of the RSC and GSC under unbalanced grid condition are detailed studied. A cooperated control strategy of the GSC and RSC under unbalanced grid condition is proposed to provide enhance operation of DFIG system. The GSC is controlled to remove the total active power fluctuation of the system and RSC is controlled to eliminate the DFIG electromagnetic torque oscillation. Simulation based on Matlab/Simulink of a 1.5 MW DFIG prototype was carried out to validate the proposed cooperated control strategy.

Abstract: According to the characteristic of the shipboard power system, heuristic search for fast tracking shipboard power system network topology is introduced. Using for reference of the methods of fault diagnosis of the power systems, the Petri net technology is used to fault location and removal of uncertain and fault signals, which can modify the topology analysis results. Setting the topology analysis and remodel based on Petri net of the typical shipboard power system for example, the results is validated.

Abstract: Pulsed power load system releases large energy after short charging time,and has considerable influence on power quality of Isolated Power System (IPS). This paper builds two kinds of IPS models, pulsed power loads and energy storage module (ESM) in PSCAD^TM. The impact of pulsed power loads with different rated power on IPS is examined. It is also shown that the ESM and propulsion system can be used to further reduce the impact of pulsed power load on IPS.

Abstract: In this paper a distribution network reactive power planning mathematical model was established, taking the minimized sum of electrical energy loss at the different load operation modes and the investment for reactive power compensation equipments as objective function to solve the planning question respectively and taking the transformer tap as equality constraint. The evolution strategy is improved, The Euclidean distance is introduced into the formation of the initial population, and the initial population under the max load operation mode is based on the optimal solution of the min load condition. The Cauchy mutation and variation coefficient are introduced into the evolution strategy method. By means of improvement of fitness to ensure diversity of population in early and accuracy of the fitness value.

Abstract: The power system is a typical non-linear system, of which the influencing factors are complex. The existing power system stability analysis methods can only determine whether the system into chaos, and deem chaos unstable. The development of the science of chaos has opened up a new way for the power system stability analysis. First, chaotic time series based on the power system calculate the largest Lyapunov exponent of the power system time series by the use of C-C method in the chaos theory and reconstruction of phase space. Then it identifies Chaos according to the largest Lyapunov exponent. Finally, it determines whether the power system is the Lagrange stability according to the size of the index combined with systemic phase diagram. The analysis of actual power system simulation proved that it is feasible to use chaos theory to analyze the stability of the grid Lagrange.

Abstract: With energy saving and emission reduction paid more and more attention in electric power industry, long-term optimization dispatch in wind-integrated power system must take into consideration many inconsistent factors. In this paper on the basis of comprehensive consideration of coal consumption, emissions, openness and impartiality, a long-term multi-objective fuzzy optimization dispatch model is established. The model can optimize jointly generation maintenance scheduling, unit commitment and power output. After piecewise linearization of the objectives and the constraints, the optimization model is converted to a mixed integer linear programming (MILP) problem. An efficient optimization software CPLEX is employed to solve the problem. In order to analyze and compare different generation scheduling, a series of indices and fuzzy comprehensive evaluation method are utilized to evaluate the optimal results obtained. The proposed model is tested in IEEE 118-bus system incorporating three wind farms. The results show that the optimization model and the evaluation system built are effective and feasible.

Abstract: Transient stability assessment (TSA) is part of dynamic stability assessment of power systems, which involves the assessment of the systems ability to remain synchronism under credible disturbances. Recent research shows that transient stability status of a power system following a large disturbance such as a fault can be early predicted based on phase plane trajectories of generator variables. Based on this, a binary support vector machine (SVM) classifier with generator phase plane trajectory inputs was trained to predict the transient stability status. In order to find the best trajectory inputs, three different types of phase plane trajectories were designed. By investigating effectiveness of the three trajectories with New England 39-bus test system, classifiers with phase plane trajectories of electromagnetic power as inputs achieved better predictions than other two types of trajectories. The highest accuracy achieved by the classifier with inputs of electromagnetic power phase plane trajectories is 99.336% which can meet requirements of practical application.