Applied Mechanics and Materials Vols. 494-495

Abstract: This paper presents a grid-connected control strategy for single-phase photovoltaic (PV) system. Voltage source inverter (VSI) of a PV system is a core component which will produce some harmonics when the switch is operated between on and off continuously. To suppress harmonic distortion in the VSI output current, a fixed modulation index (MI) control loop based on PI controller is added to the traditional double closed-loop. The proposed method can fix the MI coefficient to be a large value in any conditions. The design of the controller and the stability of the grid-connected system are discussed in detail. Simulation and experiment results are presented to demonstrate the dynamic and precision performance of the controller for harmonic suppression when the proposed PV system is connected to the grid.

Abstract: One key issue for knowledge discovery is to build a model with simple structure, high performance and interpretability. Linear regression is simple and interpretable model comparing to other models such as neural network. This paper introduces linear regression into photovoltaic power forecasting. Experimental results on the data set collected by Zhongwei third photovoltaic power station of Ningxia Jinyang new energy Co., Ltd. show that, compared with neural network, linear regression performs better generated power forecasting.

Abstract: With the development of power technology and the improvement of reliability of power supply of power user requirement, small current grounding system become the main grounding mode of distribution network. Small current grounding power system fault line selection is always one of the puzzles in medium voltage distribution network relay protection technology, until now it has not been solved satisfactorily. In this paper, we summary and review the algorithms of small current fault line selection, review domestic and abroad extensive works and achievements in this field in recent years. Summarizing the fault line selection methods based on the steady state information and transient information and analyzing the advantages and disadvantages of various algorithms, at the same time, we study the difficulties of future research and the directions of research.

Abstract: The synchronization signals of the grid fundamental wave are applied to various fields, such as power protection system, power quality system, and large power grid interconnection. As new problems emerging during the development of the grid, the synchronization methods keep continuous improved. These methods appeared in accordance with the time sequence are zero crossing detection method, the maximum value algorithm, the Fourier transform method, filter method, and phase locked loop method. In this paper, the typical methods are studied and made analysis of their characteristics, which can be used as reference in the practical applications.

Abstract: A 220kV substation DC system ground fault detailed analysis and lookup scheme are proposed in this paper. The ground fault was mainly due to the cold weather as well as equipment wiring unreasonable wear the cable jacket rupture, causing 220kV main transformer cooler control box on the 2nd DC grounding occurred. In addition, through this ground fault finding, also found a DC system insulation monitoring device functional shortcomings and DC circuit loop back problems exist, the paper put forward DC circuit loop back detailed solutions, and the insulation monitoring device of the transformation proposal are proposed.

Abstract: This article briefly describes the modern power system of high-voltage reactive power compensation device development status, discusses the high voltage reactive power compensation device applications, with the traditional high-voltage reactive power compensation device matching, demonstration of a new generation SVC (Static Var Compensator) and SVG (STATCOM) advantages and application results. This paper focuses on the innovative technology in the new generation of high-voltage reactive power compensation device in the application, while a new generation of high voltage discussed reactive power compensation device application prospects.

Abstract: For the development of large wind turbines, the approach of trial and error is also not adequate for mass produced wind turbines, a reliability-concerned manufacturing must be involved for the future development. An approach which introduces probabilistic reliability assessment which incorporates reliability methods into wind turbine engineering is described. Fault Tree of wind turbine generators electrical components is firstly built. Then it is transformed to the Bayesian network and probabilistic distribution is preceded using Markov chain Monte Carlo inference. Finally a set of qualitative and quantitative reliability is given according to a specific probabilistic input.

Abstract: In this paper, the problem of the excessive generator tripping value of security and stability control after occurrence of the N-2 fault in the Shentou-Yantong transmission line of Shanxi DaTong Regional grid is studied. And the principle of security and stability control measures based on equal area criterion is analyzed. The reason leading to excessive generator-tripping value of security and stability control after the occurrence of the N-2 fault in Shentou-Yantong region is figured out, and it is that the steady-state stability limit of transmission section decreases and the accelerator power cannot be released. Finally, the results of theoretical analysis are verified by simulations. The simulation results indicate that too large generator-tripping value of security and stability control is mainly caused by decrease of the steady-state stability limit of the transmission section after occurrence of the fault in Datong. The conclusions in the paper have referential significance for the study on similar power concentrated send-out systems.

Abstract: On the basis of object oriented program (OOP) technology a method for developing transient calculation system for Gas Insulated Substation (GIS) is presented in this paper. The system is based on the graphical interfaces, and graphical component is designed according to electric main wiring diagram for primary system and is automatically converted to transient simulation model for satisfying the demand of field operating personnel.In this paper design principle and functions are described, and the calculation result is testified by the experiment at last.

Abstract: Because of the unsatisfied present situation of bidding evaluation in the field of electric power equipment, the LCC theory is introduced into the bidding evaluation method, which can be used to evaluate the total cost of electric power equipment. Combining with ADC method, the paper proposes a comprehensive procurement model and verifies it by a practical case.