Advanced Materials Research Vols. 614-615

Abstract: In large-scale power system, low frequency power oscillation is becoming a serious threat to the power system operation. Analysis of low frequency oscillation includes model-based method and ambient-excitation-based method. Based on the investigation of the related recently-published papers, this paper presents a survey of ambient-excitation-based method. Firstly, the fundamental principle and underlying theory of ambient-excitation-based method are summarized. Furthermore, several ambient-excitation-based methods are categorized and their characteristics are introduced.

Abstract: This paper established the comprehensive optimal objective function considering the construction cost, operation cost and the peak regulation capacity limitation to optimize capacity allocation of wind and coal power ,according to the peak regulation capacity limitation. Based on construction cost and the limitation of peak regulation capacity, the objective function reflects the essence of the transportation of wind and coal power thoroughly. A quantum particle swarm optimization (QPSO) algorithm was put forward to solve the objective function. The algorithm takes advantage of its probability expression and superposition state, which potentially improves the searching ability. Besides, mutation operation of QPSO helps maintain population diversity. The analysis of result proves scientificity and feasibility of proposed model and algorithm in this paper.

Abstract: Aiming at a kind of multi-energy complementary isolated power system in Tibet ali area, which consists of photovoltaic (PV) station with storage device, hydro generator, and diesel generator, a new control strategy was presented. According to the power system characteristics, analyzed the new control strategy, it can realize the grid power output with zero steady-state error. In the DIgSILENT/PowerFactory simulation environment, building the multi-energy complementary isolated power system model and simulation based on the control strategy, the system can track the fast variation of the PV array output power or other output power. Two studied cases verify the control strategy.

Abstract: With the completion of Three Gorges Project, the power system in China is forming a huge AC/DC network. In the hybrid AC/DC parallel transmission system, a line fault will cause fluctuations even crash of the system. The HVDC transmission system based on the emergency DC power support (EDCPS) can provide a fast emergency power support for the interconnected AC power grid flexibly and improve the stability of AC power. A model of AC/DC hybrid transmission system is established in the PSCAD/EMTDC simulation environment. An improved PID controller is firstly introduced to the hybrid AC/DC transmission system. The simulation result shows the EDCPS has an obvious effect on keeping the voltage stability of the system.

Abstract: A kind of Static Var Compensator(SVC) subsection control strategy for transient process of dynamic load is presented in this paper. The strategy can determine SVC's action according to the condition of system and load so as to output different compensation capacity in different stage to make dynamic load stable and make sure the voltage is qualified; SVC will be shut when it's noneffective in this strategy so that other regulate way can be used timely. The validity and accuracy of the strategy is verified in tow-bus equivalent system.

Abstract: With the development of computer technology and power grid, integrated dispatching automation system has been gradually applied and used, for it has made considerable progress in technological advance and functional reliability. A method of real-time data acquisition and exchange that adapts to integrated dispatching automation system is proposed, which follows the principle of distributed collection and centralized use. It makes full use of dispatching data network and service bus, to achieve the integration of point multi-source data processing, data forwarding and data remote access, under the situation of normal operation or network failure.

Abstract: With regard to the slow-convergence disadvantage in the latter generations of GA, ACO is combined with GA in this paper to solve the optimal load allocation problem among thermal power plant units. By comparison with GA method, results show that GA-ACO has faster convergence than the GA method.

Abstract: Both PSD-BPA and PSASP are all important power system analysis tools. The aim in this paper is the models’ contrast and studing the difference between PSD-BPA and PSASP. First by the models contrast, the experience will be summed up. The method of model contrast is to deduce the transfer functions in order to find the differences of transfer functions between PSD-BPA and PSASP, so as to analyze the difference. After the research work, the discussion and study on the common problems will be taken and the rational advice will be put forward in the power flow calculation. The common problems in the transient calculation will be expounded, and the result will be tabled in order that these contents are obvious at a glance. At last the conclusion will be brought forward and some pieces of advice will be summed up.

Abstract: Reliable and accurate microgrid protection is significant for micro-grid operation.traditional proection methods can not meet the requirements of microgrid.this paper discusses the problems of the existing micro-grid protection methods. Then proposed a new microgrid protection scheme which uses integrated protection as the main protection of microgrid. this protection scheme is based on bi-directional blocking principle,which will send blocking signal if there is no fault .thus protects microgrid. The proposed method is proved to be an effective method for microgrid.

Abstract: To meet power customers’ satisfaction is the essential responsibilities of utilities. Considering the property of customer’s satisfaction degree, an analytical interval assessment method of voltage sag is proposed. The customer satisfaction degree is presented by interval number corresponding to the voltage tolerance for the tested equipment installed at the customer side. Based on the determination function derived from the relationship between the voltage magnitude and the length of fault line in the power system, critical fault positions are determined through analytical iterative algorithm. By the variation of satisfaction degree within a given interval, the interval sag frequency is calculated. Moreover, the quantitative sag frequency is determined by the help of the interval sag frequency. The proposed method is applied to a five-bus system and IEEE 30-bus testing system. The simulation results comparing with existing methods have shown that this method is credible and suitable for the practical engineering application.