Advanced Materials Research Vols. 614-615

Abstract: When single phase-to-ground fault happened in power network with arc suppression coil grounded, capacitor current through fault point is compensated and reduced by installing arc suppression coil. Zero-sequence current’s amplitude and phase of fault lines and sound lines are so similar that it increases the difficulty of selecting the fault line. But the resistance component of zero sequence current has no relationship with the arc extinguishing coil compensation, absolute value of resistance component to the fault lines show the maximum, and zero sequence current’s polarity of fault lines is contrary to sound lines. In this paper, because of the characteristic of resistance component, a method is put forward based on zero sequence energy to the line selection in distribution network, it import auto-reclosing techniques into the line selection. The principle is verified by MATLAB simulator. It has high accuracy to select the fault line with this method.

Abstract: Generation scheduling depended on accurate boundary conditions. Before the actual implementation, optimization result of day-ahead schedule was needed to be rolling corrected by two periods of intraday scheduling and real-time scheduling. It was key problem to establish optimization models which adapt to different dispatch period and coordinate different period generation scheduling for to achieving the best optimization results. This paper first discussed coordination mode of different period generation scheduling; Then, the mathematical models were established for day-ahead scheduling, intraday scheduling and real-time scheduling; Day-ahead scheduling and intraday scheduling including SCUC and SCED, intraday scheduling including SCED, and optimization goals were the minimum total cost of generation. In addition to boundary conditions, the difference between day-ahead scheduling and intraday scheduling model was that the optimal range from all units into AGC units; In real-time operation stage, the optimized objective was the minimum deviation between real-time schedule and intraday schedule for AGC units. Through practical application in a provincial, it proves that the proposed model is correct and effective.

Abstract: The paper proposed an application of intelligent AC-DC integrated power supply system in 500kV switching station. Firstly, this paper introduced current situation of AC-DC power supply system which is for home use and provided main components of this intelligent power supply system and its functions. And then, all cautions in operation and maintenance process is explained. Lastly, this paper summarized problems exposed in the system after running half year in 500kV switching station and put forward some aspects needed to be improved.

Abstract: With the injection of distributed generation (DG) into distribution network, complexity and uncertainty of power flow in distribution network follow. In order to calculate power flow more simply and accurately, considering the characteristics of distribution network with DG and the flexible applicability of RBF neural network, a special adaptive dynamic clustering RBFNN (DG-RBFNN) method, which clusters the input samples only according to the parameters associated with DG, has been used in this paper. Therefore, the results are more approximate to the real condition and the calculation process is simpler compared with conventional back/forward (B/F) method meanwhile the calculation scale is also relatively smaller compared with ordinary adaptive dynamic clustering RBFNN. Finally, according to a 21-bus 66 kV distribution network of Shenyang, Liaoning province simulation experiment, the availability of DG-RBFNN method is proved.

Abstract: The support vector machine (SVM) has been successfully applied in the short-term load forecasting area, but its learning and generalization ability depends on a proper setting of its parameters. In order to improve forecasting accuracy, aiming at the disadvantages like man-made blindness in the parameters selection of SVM, In this paper, the chaos theory was applied to the PSO (particles swarm optimization) algorithm in order to cope with the problems such as low search speed and local optimization. Finally, we used it to optimize the support vector machines of short-term load forecasting model. Through the analysis of the daily forecasting results, it is shown that the proposed method could reduce modeling error and forecasting error of SVM model effectively and has better performance than general methods.

Abstract: In view of the challenging issues in microgrid diesel modeling and connecting to the power grid, this paper presents the design and simulation of a diesel generation system which contains an internal combustion engine and a synchronous generator. Furthermore, droop control with PI regulator applies to the diesel generator model and the performance of the generation system has been tested under various operation conditions using the PSCAD/EMTDC simulation platform, the simulation demonstrates that synchronous diesel generation system can operate smoothly either in islanded mode or in the grid-connected mode. The transient response is analyzed and all the variables voltage/current/frequency are under IEEE 1547 standard.

Abstract: This paper studies the effect of the soft feedback in hydro-turbine and its governor system on power system transient stability. Low frequency oscillation phenomenon in which the hydraulic turbine sets participate occurred on power system many times this year, which with no mechanism discovered. In this paper, we first study the effect of mechanical load moment output of the prime mover system on the mechanism of low frequency oscillations, then by analysis of small-signal stability on hydro-turbine and its governor system and simulation experiments on an two-generator power system using PSASP, we come to the conclusion that: If the soft feedback output values of hydro-turbine governor systems are set small in the power system, it will come to the unstable oscillation condition.

Abstract: The objective of smart power consumption system is to make the large industrial user communicate actively with electric power operator by the means of smart measurement and control. The necessity of interactions between electric power corporation and large industrial users was analyzed. Then the interactive service architecture for large industrial user in smart power consumption and the relations among parts of the architecture were studied. The functions and key technologies of the interactive service architecture were also discussed. Further, by collecting the information such as internal power consumption information, device running information, laws of production, and development tend information et al., the electric power corporation can offer personalized, diversified, facilitated and interactive services for large industrial users. And the corporation can provide necessary information support for electric grid dispatching, power distribution planning, electric energy quality, line loss and power supply reliability.

Abstract: The inverter part is an important link of the voltage source STATCOM, and a key problem of inverter is how to generate PWM switch signals according to given parameter. The part of SPWM inverter in STATCOM was simulated in Matlab. The result shows that the inverter bridge was controlled by the three-phase pulse width modulation wave produced by the SPWM and the three-phase sine wave at the side of the inverter bridge is outputted. This method is suitable for studying of the STATCOM system.

Abstract: After a single-phase-to ground fault, fault voltage and current information should be sampled accurately for automatic equipments to detect the fault line. And zero sequence current is the very key element to detect the fault line after an earth fault happens. The widely used methods of getting zero sequence current are in details described. The common methods are by zoro sequence current transformers, by wye connections of three CTs, and by zero-sequence current transducer. A new method by magnetic field induction and the structure of magnetic induction device are introduced, as well as a new way by electronic current transformer and its application in digital substation.