Advanced Materials Research Vols. 516-517

Abstract: Wind generator and distribution systems after interconnection would change the short circuit fault characteristics of the original system and may lead to protection relay malfunctions, and review of the protection coordination. It is necessary to research the impact of existing protection strategies for distribution systems after wind generator interconnection. Linear programming methods were adopted for this study to review the coordination problems among feeder circuit breaker, lateral circuit breaker, and power fuse after radial distribution systems and wind generator interconnections.

Abstract: According to applying feature of power supply and distribution system in aerospace experiment field, the intelligent monitoring system is designed by adopting hierarchical distributed network structure which includes field layer, network layer, management layer, and command center layer. The monitoring software based on configuration software realized such functions as unify electric force management, optimize electric force balance, economize electrical energy loss, extend lifetime of equipments, improve qualities of environment protection, promote efficiency and managing level. Applying result indicates: the system satisfies the requirement of aero experimenting task.

Abstract: The economic dispatch control of cascade hydropower plants is a large scale non-linear constrained optimization problem, which plays an important role in cascade reservoirs daily optimal. This paper proposes a chaotic univariate marginal distribution algorithm (CUMDA) to solve the economic dispatch problem of cascade hydropower plants. In the proposed method, a chaotic search is integrated with univariate marginal distribution algorithm (UMDA) to effectively avoid premature convergence, chaotic sequences combine with adaptive approach are applied to help algorithm escape from local optimal trap. The feasibility of the proposed method is demonstrated for economic dispatch control of a test cascade hydro system. The simulation results show that the proposed method can obtain higher quality solution.

Abstract: With the proportion of the installed capacity of wind farm in the grid increasing, the impact of wind farm on the power system security becomes obvious. The steady-state security analysis is one of the important measures to improve the power system security. Based on DC flow, considering the available transmission capability limit, the paper chooses the biggest security region volume as objective function with the upper and lower limits of security region multi-dimensional cuboid being as control variables, which transforms the maximum steady-state security region into nonlinear programming problem with linear constraints. This not only includes the biggest points for the safe operation, but also the order expansion problem doesn’t exist. Then Lagrange-Quasi-Newton is used to solve the equation, and the analysis of the example proves the feasibility of the proposed model and algorithm. Then we assume that wind speed distribution is weibull distribution, so we can assess the safe operation probability of wind power.

Abstract: In this paper, power transfer distribution factor based on AC load flow has been proposed for multi-transaction environment in the presence of FACTS devices viz. SVC and TCSC. The method can be implemented for any number of transactions occurring simultaneously between sellers and buyer buses with FACTS devices. The results have been determined for intact and line contingency cases. The results have also been obtained with DC method for comparison under intact and contingency cases. The proposed method have been applied for IEEE 24 bus RTS.

Abstract: With the expansion of the grid, continuous reactive power compensation is vital for efficient operation of long transmission power lines or cables. Yunnan Electric Power Grid is planning to development saturable reactors for 500 kV long distance AC transmission lines. As the first stage of the development plan, the appropriate saturable reactor structure should be presented and verified by experiment. In this paper, different ferromagnetic materials, core structures and winding arrangements of saturable reactors are analyzed. Then, appropriate saturable reactor structure is determined by simulating calculation. Based on that, a small-scale prototype is designed and fabricated. The experimental results show that it can obtain a continuous controllable reactive power output.

Abstract: The detailed description about the OMIS (One Machine-Infinite Bus) and the SLIS(Single Load -Infinite Bus)will be done in this paper and the detailed introduction of these two concepts(the coherent generators and the coherent buses) and their aggregation. Based on the new OMIS model, the new methods of identifying the coherent generators and aggregating the coherent generators will be advanced. Based on the coherent generators, the new algorithm for the reserving coefficient of the steady angular stability will comes into being. Based on the new SLIS model, the new methods of identifying the coherent buses and aggregating the coherent buses will be put forward. Based on the coherent buses, the new algorithm for the reserving coefficient of the steady voltage stability will be brought about. A real example is used to validate the idea in this paper. A discussion on the angular references between the online data and the offline data will be done when the phases from the WAMS are used. The steady stability of two generators model will be acquired.

Abstract: Grounding system analysis and design considerations for large hydroelectric power plant are analyzed and discussed in this paper. The main work that has been carried out includes: constructing adequate soil structures and analyzing the effects of the finite heterogeneous soil structure, the modeled river length and the water reservoir levels; conducting accurate fault current distribution calculations and studying the influence of circulating current on the touch and step voltages. The paper discusses the design of the grounding system and its safety performance while considering the impact of the circulating current and inductive coupling from cables and long parallel conductors inside the plant. Two practical examples have been provided in this paper. Furthermore, the paper demonstrates the effectiveness of using heterogeneous finite soil volumes to analyze large hydroelectric power stations and confirms that accurate grounding software packages are required to account for large circulating currents within the ground conductors and strong inductive coupling that exists between metallic elements within the substation. The results and discussions presented here can be used as a reference for engineers to analyze extensive grounding systems and to design appropriate grounding systems for large hydroelectric power plant.

Abstract: A design thought about power load control and management system is presented. This thought realized the bidirectional data transmission between master stations and acquisition terminals by GSM/GPRS, it saved investment, shorten the development cycle. The system’s structure and main functions were introduced. Discussed high precision and real-time measuring hardware and software design thought about electric parameters in acquisition terminal such as AC voltage, AC current, active power, reactive power and etc. Using equal interval sampling method and interrupt technology in hardware design, reduced synchronization error and improved real-time performance. Using DFT algorithm and several effective data processing methods in software design, enhanced filtering ability, reduced calculation workload and calculation error. This system obtained the national patent, passed the comprehensive test and practical application. This indicates that the design thought about power load control and management system is advanced and related technology is effective.

Abstract: Based on analyses of several evaluation schemes, difficulty coefficient subtraction method was presented. An automation determination of training score method used in DTS was given, and the implementation process was introduced in details. Furthermore, marking for trainees’ training was carried out on four aspects of dispatching operation, power supply reliability, grid security, and economy of power network operation. According to the difficulty level of teaching plan, the difficulty coefficient was determined, the relevant calculation method of trainees' training score was proposed, and the weighted score and evaluation report were presented finally. Its practical applications indicate that the marking method of trainees’ training score is reasonable, able to reflect the practice of dispatchers' operation, and easy to realize generalization, extension and maintenance through the separation between program and standard of evaluation score.