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As wind penetration level into power systems increases, provision of frequency support from wind plant is anticipated to become a requirement in grid codes. In addition to the virtual inertial response, two different approaches to delivering droop response from wind plant are presented and compared in this paper. The combination of droop and inertial response from wind plant has been assessed for a frequency time series. Simulation results show that the proposed approaches to delivering combined droop and inertial response can provide superior performance to either inertial or droop response alone.

This study proposes a day-ahead optimal energy dispatch model for integrated energy system based on AC/DC interconnected infrastructure. In the infrastructure, micro-turbines turn high-frequency AC power into industrial-frequency AC power and incorporate it into the energy system's power system. Within the process, waste heat is sent into the waste heat boiler and lithium bromide chillier to interconnect with the heating and cooling systems. DC battery and photovoltaic generations connected with the energy system's power grid through the inverter are used as the flexible energy storage and power generation unit to build an autonomous integrated energy system based on AC/DC interconnection. In the optimisation model, the goal is set as system's lowest daily operation cost and lowest energy consumption. The constraints include system operation constraints and equipment constraints. Simulation results show that by performing the schedule made by the dispatch model, the operating efficiency of various types of AC/DC equipment in the energy system has been improved, energy waste scene has been reduced significantly and energy consumption in the energy system is reduced by 16% compared with other energy supply structure without AC/DC interconnected infrastructure under traditional schedule strategies.

This paper proposes a day-ahead optimal economic dispatch model for building Combined Cooling, Heat and Power (CCHP) system based on centralized energy storage infrastructure. In the model, the loads are met by the centralized energy storage equipment directly, and the storage equipment are charged by varieties of energy supply devices in the energy station of the building CCHP system. The model is solved by the interior point method with Hessian matrix iteration. Simulation results show that by performing the schedule made by the dispatch model, the storage status of the centralized energy storage fluctuates in large dynamic range by flexible charging and discharging and the daily operation cost of the building CCHP system decreases remarkably compared with other traditional schedule strategies. DOI: http://dx.doi.org/10.5755/j01.eie.24.4.21478

The application of electric power system transmission line protection based on traveling-waves or transient components suffers maloperation in case of single-phase earth fault. When single-phase earth fault happens, the system can still run for 1 or 2 hours because the phase voltage is still symmetry, and the ground current of fault phase is small. But single-phase earth fault will cause the increase of non-fault-phase's voltage. Long time of grounding operation will easily make fault expand to two points or more earth short circuit, and even lead serious interphase short circuit fault. Therefore, in order to prevent more serious fault caused by single-phase earth fault, it is necessary to find out the fault line and ground fault lines as soon as possible. The analysis result in this paper conforms well to the meteorological observations and zero-sequence current detection data of Empirical mode decomposition (EMD). And these results provide useful reference for the discriminant method of fault line work in power system. According to the differences, the paper proposes a method identifying single-phase earth fault based on Empirical mode decomposition. AutoCAD simulation results proved the method is feasible.

In order to improve levels of power loss and local voltage magnitudes of distribution network, the optimization allocation problem of distribution generations (DG) in active distribution network is developed. A multi-objective model consisting of the total construction and operation cost and power loss is built, and the algorithm based on glowworm adaptive step strategy is proposed to obtain some optimize allocation pareto sets of DG in distribution network. Then the best allocation set is selected from the above candidate pareto sets by the interactive fuzzy decision technique. The simulation and analysis of IEEE 33-bus system is carried out. Simulation results show the proposed model and algorithm feasible and effective.

Multiple power modes and energy storage devices is distributed in microgrid and use of wind and solar energy to bring volatility and intermittent, in order to provide a stable power, micro-grid energy storage device must be researched. In order to improve power quality, reduce storage configuration capacity, improve the economic system, We have a research on the optimization of variety of micro-grid energy configuration and economy operation. This paper analyzes their differences and characteristics of energy storage devices and can conclude that complex microgrid energy storage device is reasonable storage mode. Next, the paper have a description on mathematical models of economic and environmental benefits and restrictions to maintain the stability of the micogrid. Finally, our paper analyze their strengths and weaknesses as well as summary of the algorithms used to solve these models.

Electrical power equipment reliability is the basis of the stability operation of distribution network. Equipment reliability includes inherent reliability and operational reliability. Inherent reliability focus on familial defects. Operational reliability focus on meteorological, load rate and others. This paper evaluates power equipment reliability based on integration platform of Jiangsu province electric power company. The inherent reliability and operational reliability are researched separately. The quantitative relationship between fault and condition is researched based on data mining. Weighting coefficients is calculated to combine different factors. On this basis, the reliability evaluation model is constructed and develop the relative software. Operation shows that power equipment reliability evaluation system has engineer applicability and practicality.

A desired islanding detection method applied in microgrid not only can detect islanding correctly within acceptable duration as same as that in distributed generation system, but also ensures the smooth transition from grid-connected mode to islanded mode. In the paper an islanding detection method is presented, which considers the characteristics of system equivalent impedance that varies with the microgrid connecting main grid or not, with the help of the negative current injection into the point of common coupling (PCC), and then identifies the negative voltage variations near PCC. The method is able to avoid the negative impact on the operation stability of the microgrid. Through the Matlab/Simulink simulation, the rapidity and affectivity of these principles are verified.

In the analysis of power system small signal stability, the state-space equation which is based on the comprehensive consideration of synchronous generator, automatic excitation system, prime mover and its speed control system and power system stabilizer, is often of high dimension. This makes it difficult for researchers to analyze of all state variables in the dynamic process. The modal perturbation theory employed in the present study can not only reduce the order of the original model and the computational efforts but also obtain the dynamic changes of all state variables. Afterwards, the paper established a complete state-space equation of simple power system and the basic form of reduced-order model. A case study of a single machine was then conducted, in which satisfactory reduction effects were achieved when the original model was reduced to 4th, 3rd and 2nd order models.

Researching on interaction between wind farm and power system, it usually uses simple model to describe the wind farm. The wind turbines in a wind farm always suppose as a coherent generator group, every wind turbines have identical wind speed. As wind turbine locates in the different site in the wind farm, the wind speed at each wind turbines will not change simultaneously. Wake effect is another factor that should take into consideration. So, it needs to get wind speed equivalent model. The equivalent model of wind speed in the wind farm is based on output of power. Gust wind and ramp wind are discussed. Wind farm will change gust wind into step varying wind and make ramp wind into different type wind. The arrangement of wind turbines will also affect equivalent model of wind speed. The result show that the length of wind farm will smooth the power output. It explains why the power output fluctuation of wind farm is smaller than single wind turbine. The onshore wind farm located in Dongtai Jiangsu province is proposed as an example. The equivalent wind speed model and equivalent impedance connected to grid are calculated. The results illustrate the impact of wind speed model on wind farm output.