Advanced Materials Research Vols. 1070-1072

Abstract: The historical data of wide area measurement system (WAMS) contains the daily record of the number of oscillations. The phenomenon, which the number of these oscillations suddenly increases at a certain frequency, indicates that the risk of weak damping oscillation with this frequency will increase. In other words, the statistical characteristics of these oscillations can reflect the system stability level. In this paper, the formulation of the small signal analysis including power disturbance on the power grid is given firstly. Then the relationship between the oscillation probability and damping ratio is obtained theoretically. Finally, a case study is carried out based on a 10-machine 39-bus power system. Simulation results verify the validity of the expression of oscillation amplitude of tie-line active power and the relationship between the oscillation probability and damping ratio. These theoretical results can be used to guide the power operator to assess the damping level of the power grid based on the daily number of oscillations recored by WAMS.

Abstract: These are some questions during construction of distribution automation at switching station, such as long outage time, construction workload and other issues. In this paper, proposed three coping modes: General mode, no blackout mode, optimization mode. Meanwhile, combine the actual situation of each switching station to analysis three modes, and practical applications in distribution automation construction of A and B cities. It has a guiding role in actual projects.

Abstract: Senior applications based on PMU have to process a large amount of data. An effective method to solve the problem is need to find. Firstly, the characteristics of real-time data message of WAMS and the method for receiving and processing real-time data based on the message bus of the smart grid dispatching technical support system were analyzed, and then, the producer/consumer model which is commonly used in the data receiving and processing was introduced emphatically. The advantages and disadvantages of three different ways to realize the buffer were explained. Finally, the test results of practical application were given. The test results show the producer / consumer model using the ring buffer can effectively solve the problem of a large number of PMU data processing.

Abstract: Power system dynamic simulation is an effective way to fully grasp the power system dynamic response, and it is also the basis guiding power system planning, design and operation. The operation of the generator characteristics determines the dynamic characteristics of the power system to some extent, so enhancing the accuracy of generating set model parameters has great significance on improving the reliability of power system dynamic simulation. Due to the operation of the power system characteristics and special requirements on the safe and stable operation, we cannot understand its correctness of dynamic response by means of exerting disturbance test, which limits the simulation error evaluation work of the generating set. PMU data from effective disturbance scenarios is used in this paper to study the realization of the generator speed control system of hybrid simulation technology based on data measured by PMU. The corresponding hybrid simulation program is developed by using C++. The evaluation of speed regulation system error of the model parameters is realized on the basis of the simulation error index. The validity of speed control system model parameter error evaluation methods is proved by PMU data measured from disturbance scenarios of four Units in an area.

Abstract: Distributed generation system (DGs) is considered to be an advanced configuration of distributed generation through the effective organization of renewable energy power sources, loads and energy storage devices, which can operate either isolation or connected with grid. This paper studied the control of DGs which is constructed with DFIG (Double Fed Induction Generator) based Wind Farm, PV (Photovoltaic) generation farm and Storage Batteries. The paper studied the simulation model of the DGs and the control strategy.

Abstract: Power system stabilizer in a power system is a closed-loop controller. The conventional participation factor method just considers the effect of PSS input signal. When the system stress is heavier, it may give misleading results. Based on the participation factor of modal analysis, an integrative participation factor is proposed to determine the optimum PSS location. The integrative participation factor takes into account both the input and control effect of PSS controllers. The case studied in 2-area 4-generator power system power system confirms that the integrative participation factor is more reasonable and effective than the participation factor method.

Abstract: In daily operation process,the results of online short-circuit current calculation and fault wave recording is different, the differences between the two results affected the dispatcher’s decision. In-depth analysis of the calculation process and finding the possible causes of the differences should be done. The on-line PSASP short-circuit current calculation based on power flow and scheme was studied. The boundary conditions and calculation models of two methods were studied, the influence of the modeling scope and equivalent circuits to the short-circuit current was also studied. Fault wave recording calculated short-circuit current through forward calculation, the middle to both sides calculation and backward calculation, and the differences of the three calculation mode were also analyzed. Through the above analysis and comparison, online data equivalent to 220kV high voltage side of the transformer greatly impacts short-circuit current, but effective value calculation method of fault wave recording has a little impact on the short-circuit current, mainly in the following reasons, the first one is that non-dispatching power plant is equivalent to a load, the second one is that several different types of load is equivalent to a load using one load model, the third one is that all devices connecting to low voltage side of the 220kV transformers are equivalent to 220kV. Conclusions of the analysis can provide the basis for the practical work of online short-circuit current calculation.

Abstract: In this paper a blackout AC power flow model considering the probability of line stoppage in the process of power grid growth is given,and the self-organized critical state in the process of power grid growth is studied with the power grid upgrade rate is equal、greater or less than the load growth rate.Simulation results show that power grid upgrading rate must meet the system's load growth, or the probability of failure will be greatly increased with the grid exceed the critical state while the load growth faster than the grid upgrading in the long process of building the power grid. The model and simulation results presented in this paper provide a theoretical basis for the planning and construction of the power grid.

Abstract: To explore the self-excitation risks in weak interconnection power grid from the wind power flow, a vector control model of variable speed wind turbine based on doubly fed induction generator (DFIG) is established using electromagnetic transient simulation software PSCAD/ EMTDC. Start from the basic circuit model, the self-excitation phenomenon is analyzed with wind power integration. Simulation results show that the effect of wind power integration on the self-excitation risk is mainly determined by DFIG’s operation method, and wind power integration will affect self-excitation engineering judgment method at the same time. When DFIG works in phase late operation or has no reactive power exchange with the main power grid, cutting the wind turbine after broken thread quickly can restrain the worsening trend to a certain extent. However cutting the wind turbine after broken thread when DFIG works in phase advance operation may cause a voltage jump of the hydraulic synchronous generator in parallel with the wind turbine.

Abstract: In this paper, a novel method to determine the voltage stability margin of the wind power integrated system using PQ curve is proposed, in which the wind power turbine output characteristics and the load characteristics are both considered. The PQ curve under different wind power turbine output conditions can be constructed that also combines the mathematical model of different load characteristics. The geometric distance between the node power point and the border of the PQ curve and its corresponding probability are calculated and multiplied as margin. Thus the weakest bus can be determined. Finally, taking the operation mode data about the IEEE-30 power grid for calculation example, the proposed method is effectively validated by the results on the method of sensitivity analysis based on voltage stability margin.