Applied Mechanics and Materials Vols. 668-669

Abstract: First based on the analysis of dynamic characteristics of wind power generators, the uniform extended flow model for transmission-distribution joint with wind power generators is derived. The master-slave decomposition and coordination solving methods is proposed. Master-slave system joint calculation, considering the affect between each other, realized the joint integration calculation of power system and improved the verisimilitude of results. And, the dynamic characteristics of dynamic element of the master-slave system are considered, and it makes the results more practical. Finally, through 94-node example system analysis, the effectiveness and necessity of the proposed model and method is verified.

Abstract: Distributed generation (DG) has an important influence on the voltage of active distribution networks. A unidirectional power distribution network will be transformed into a bidirectional, multiple power supply distribution network after DGs access to the distribution network and the direction of power flow is also changed. Considering the traditional forward and backward substitution algorithm can only deal with the equilibrium node and PQ nodes, so the other types of DGs should be transformed into PQ nodes, then its impact on active distribution network can be analyzed via the forward and backward substitution algorithm. In this paper, the characteristics of active distribution networks are analyzed firstly and a novel approach is proposed to convert PI nodes into PQ nodes. Finally, a novel forward and backward substitution algorithm is adopted to calculate the power flow of the active distribution network with DGs. Extensive validation of IEEE 18 and 33 nodes distribution system indicates that this method is feasible. Numerical results show that when DG is accessed to the appropriate location with proper capacity, it has a significant capability to support the voltages level of distribution system.

Abstract: This paper proposes a scheme of the looped network applied to low-voltage distribution network and introduces the control strategy for looped network in the normal event of a distribution network failure. Besides, the paper shows the superiority of the looped network in reducing the outage time and improving the power distribution reliability.

Abstract: With analyzing the cause and characteristics of security problems in the current power State Grid Unified Application Platform, this paper proposes a Role-Based Services Certification Model, RBSCM, to solve the security problems in electric power information system and designs a generalized and effective mechanism of security management. The paper provides a set of constraint specifications. These constraint specifications of RBSCM are organized to form a construction, and an enact process is proposed to make it scalable and flexible to meet the need of diversified service application systems.

Abstract: This paper introduces a design of different-frequency grounding resistance meter using MCU 80C196KB as the core. This instrument generates a current with a different frequency at about 120Hz to be injected into the ground grid. By adopting current-voltage method, the design enables an accurate measurement of the grounding resistance of large-scale ground grid, such as, power systems, architectural buildings, military facilities, and airports. The instrument controls the output of different-frequency electrical source by using MCU and DDS techniques. Moreover, the utilization of RMS-DC devices simplifies its data acquisition and data processing. In addition, the application of hardware and software filtering technology reduces the measurement error which may be caused by frequency interference, measuring disturbing between lead wires.

Abstract: This paper discusses effect of transmission tower on electric field under overhead lines. Charge simulation method is used. Transmission tower is taken into account by using a simplified frame. Segments of tower frame are represented by finite straight line charges. Overhead lines with conductor sag determined by catenary equation are also represented by finite straight line charges. Calculation results show that transmission tower has shielding effect on closed region and distortion effect nearby tower leg.

Abstract: There are multiple key management centers in power system due to historical and other aspects, and most key management centers are dispersed and serve different information security systems. It has not been implemented that key management centers are centralized management. And it is necessary to establish trust-based network system based on cryptographic techniques and achieve a safe and reliable access, transfer and application in network. We should build the infrastructure covering key management according to the requirements of the network, facilities and standardization to provide key support services for the certificate system, multiple key devices and key applications. Centralized key management is conducive to the protection of the business systems and reduces of duplication construction. This paper makes a structural design of key management infrastructure according to existing problems and actual demand of power business systems to provide support services for the currently running certificate system and key applications.

Abstract: For energy-saving and consumption-reducing, new energy-saving transformer becomes more and more important. Via an economic evaluation methodology called Total Owning Cost (TOC), this article compares energy-saving transformer with high-energy transformer for examples in the angle of transformer loss and picks up the optimum energy-efficient transformer which can be expected to gain more benefit during transformer life cycle. This article also analyses cost of silicon steel sheet used in the transformer core and benefit in Total Owning Cost (TOC) of upgrading silicon steel sheet which primarily reduces no-load loss. Based on calculated results of Total Owning Cost (TOC) and payback period, the new energy-efficient transformer replacement plan, economic discussion and promotion proposal are brought up.

Abstract: A design of encryption cards controlling multiple cipher chips’ high-rate parallel operation based on FPGA is proposed in this paper. According to the design method, we can achieve that multiple encryption card operates encryption in parallel way, which can improve the encryption and decryption rate of the encryption card without enhancing the performance of encryption chip, moreover, increase the key generation rate and management level of the key management system.

Abstract: A high efficiency rectifying antenna (rectenna) is designed at 5.8 GHz by using defected ground structure (DGS) filters for low-power energy transfer. A slot-coupled patch antenna is used as a receiving antenna with a high gain of 8.2dB. A DGS low-pass filter at the input port of the rectifying circuit is used to suppress the high order harmonics by 20dB. A DGS dc-pass filter is designed to block the AC signal from transmitting to the load. Both of the antenna and the filters are simulated by the full wave EM analysis software of HFSS. The RF-DC conversion efficiency of 51.8% is obtained when the received power is as low as 3mW.