Applied Mechanics and Materials Vols. 291-294

Abstract: This research presents the DSP - based islanding protection for photovoltaic grid connected inverter with under / over frequency and under / over voltage islanding protection methods. The design is based on the TMS320VC33PGE digital signal processor on the NI SPEEDY 33 board from National Instrument Inc. The prototype is monitor the grid frequency and grid voltage at the point of common coupling (PCC) between the photovoltaic grid connected inverter, the local load and the distribution. The results of study, the prototype can turn off relay between photovoltaic grid connected inverter and utility grid when the frequency is change under 48Hz or over 52Hz and the voltage is change under 200V or over 240V.

Abstract: There is a problem about high current and voltage spikes in Buck and Boost converters,it will damage main power devices .Therefore, a novel Buck/Boost bidirectional DC/DC converter based on soft change current (SCC) network was given, and Buck and Boost modes ware particularly analyzed.Groups parameters of L/C/D are selected and simulated with Saber software. The optimal combination of L/C/D was ascertainned by observing groups switch waveforms. Theoretical analysis and simulation results show that the voltage and current spike of the power switches is deeply descreased by SCC network.

Abstract: In order to carry an economic analysis of micro-grid project represented by photovoltaic power-generation, this paper proposed a cost recovery model for micro-grid project through case studies. Meanwhile, based on how micro-grid participates in market competition, we have designed the framework for gaining profits. Issues like basic profits, reasonable depreciation method and the project’s financial profitability are analyzed in detail.

Abstract: This paper presents a methodology for substation optimal planning considering DG for peak shaving. Utility can take effective demand-side management (DSM) to encourage customer-owned DG to participate in peak load shaving, and it can also construct utility DG to meet the peak load demand. In this paper, the impact of DG on peak load shaving is analyzed, and DG is taken as a complement to T&D system to meet load demand, which is considered in the substation planning. Substations sizing and location and new-built utility DG capacity is optimized using Particle Swarm Optimization (PSO), in which supply area of each substation is obtained by Voronoi diagram method. Case study shows that planning result considering DG for peak shaving can defer T&D system expansion so that considerable investment can be saved. Especially for those areas with high cost of T&D system construction, constructing DG to meet peak load demand would be a more economic way.

Abstract: In order to solve the problem of solar energy photovoltaic grid technology, a kind of photovoltaic grid-connected simulation device based on FPGA was designed. It consists of FPGA, auxiliary fly-back switch power, full-bridge DC/AC converter, LC filter and some protecting circuit etc. The device has high speed of MPPT adjustment and tracking of frequency and phase, with frequency ranging from 30Hz to 55Hz, deviation is below 0.4%, stability is above 99.6%, converting efficiency is up to about 80%.

Abstract: Networking power quality monitoring system (NPQMS) has become more and more popular, but high construction cost blocks its further extensive application. The construction scheme of communication network based on distribution line carrier communication (DLCC) technique is an effective problem-solving strategy. For demonstrating the feasibility of this scheme, configuration and communication requirement of the NPQMS are discussed. Then, according to an actual case of the NPQMS, the communication rate and quality performance are estimated in detailed. This research work provides related theoretical basis and feasibility analysis of the construction scheme of DLCC network for the NPQMS in Smart Distribution Grid.

Abstract: In the perspective of realizing the on-line monitoring of power cable insulation, to analyze the changes of the traveling wave when the cable fault, thus we can found the power cable failures in advance and deal with it timely in order to make sure the safety and stability of power cables. Owing to high reliability, small size, strong anti-interference ability and application to cruel industrial environments of PLC, on-line monitoring system based on PLC has good resistance to interference of electric and magnetic and good stability.

Abstract: This paper introduces some typical control methods for the grid-connected inverters in the distributed generation (DG) systems, the double-loop control strategy is focused on and analyzed in detail. The proposed outer-loop control strategies are summarized. Meanwhile, the inner-loop control method established on dq rotating frame is introduced. The simulation models of the inverters for DG in the DIgSILENT software are introduced, and the simulations for the proposed control strategies are realized.

Abstract: To promote the ease of use and reliability of IEC 61968 based Information Exchange Bus and fulfill the rapid establishment of inter-buses and adapters-bus communication channels, this article first analyzes the status quo of distribution automation integrity. Combined with the concept of universal PnP technology, the functions of IEC 61968 based adapters as well as buses are improved and more adapted. Considering characteristics of IEC 61968 standards, components like adapter identification information, topic-authorization table, and topic-authorization routing table are introduced and then a set of special mechanisms are built, including binding&unbinding procedures for inter-buses and adapters-buses, retransmission scheme, and mergence of topic authorization routing tables used to control information flow. By implementing this theory, the adapters-buses and inter-buses PnP functions are realized and the ease of use and reliability of smart grid information exchange buses are enhanced.

Abstract: The quick & exact anti-islanding is a mandatory feature for grid-connected distributed generation system. The conventional passivity detection method has the biggish blind section and lower reliability, especially when the grid-connected inverter export power and burthen power are balanceable; the islanding detection often is disabled. And that the initiative islanding detection method is considered an effective measure, but if the arithmetic & parameter choice irrelevantly, the islanding can not be detected easily; even injected harmonic to the grid and destroy power quality. An improved voltage shift technique islanding detection arithmetic is put forward in this paper, and the correlative mathematics model is established, and the project is analyzed and studied theoretically based on IEEE Std.2009-929 criterion. The result shows the method will not affect power quality, at the same time it can detect islanding phenomenon quickly& exactly, so it is feasible.