Xu Aoran

Research on the reactive power control of distributed generation system

This paper presents a centralized reactive control scheme of grid-connected inverter of distributed generation system. The power electronics interface performs the optimal operation to extract the maximum active power, while it also plays a key role in reactive compensation systems. A reactive power optimization algorithm including DG sources based on genetic algorithm is proposed. The corresponding particular model is built which takes into the minimum network loss and node voltage constraint. Genetic algorithm is used in reactive power optimization. The simulation examples show that the validity and effectiveness of the proposed algorithm in reducing network losses and improving the voltage profiles.

Inrush current on transformer differential protection affect the analysis and discussion

In this paper,based on the characteristics of transformer inrush current waveform analysis of the protection of its reliability and its high-pressure differential between trial. Together with a large transformer (voltage rating of 500kV) of the differential protection analysis of actual cases, their first-hand data and field research and analysis of test waveforms and found that in order to avoid inrush current caused the error transformer differential protection movement, on-site technical staff conducting differential protection setting process, notonly the parameters used, the data comply with the relevant rules and standards, Shu Xi differential protection features, but also must understand the high-pressure test on the transformer inrush current characteristics effects, and even more fully to play the modern computer equipment recorded the role of wave devices to increase as much as possible the actual effect of transformer differential protection.

Evaluation of Abandoned Wind Power by Neural Network Method

Wind farm operation is characterized by large scale, fast and disorderly, the construction of grid structure is not complete, the fast adjustment of power supply in the power grid does not match to others, the objective laws of electric power system and uncontrollable and intermittent of wind power, and adjustable power supply capacity constraints in power grid, all of them cause the consumptive ability of wind power grid, which leads to more and more abandoned wind. This paper studies the tower neural network method, according to different height wind speed and wind direction data of historical wind tower measuring, combining with the fan power of historical observation data of wind farm, and building the neural network model, then the sample data will be input to the neural network model which has built to get theoretical power fan and abandoned wind power. By comparing the wind tower method, neural network method, model machine method with area integral method calculate abandoned wind power data, evaluate the effect that based on abandoned wind power tower evaluation model of neural network method in low wind speed has a good reference value, relatively close to the measured wind speed.

Research on feeder protection strategy of distribution network connected with micro-grid

Traditional power distributed network is transformed from single power supply radial network to more than one power supply loop network, direction of the power flow is changed, Therefore action of right protection cannot be completed in the micro-grid operating in the grid-connecting mode and two kinds of operation mode switching of interconnection and lonely island. The four standard of distribution system protection namely, selectivity, reliability, sensitivity and quick action cannot be effectively meet. In paper, influence on relay protection of the micro-grid is expounded in order to solve the problem of micro power grid relay protection, according to the load sensitivity of feeder circuit, current differential protection module and inverse time over-current protection module are established, the parallel operation protection strategy is designed, the simulation results with the typical micro-grid show that performance of the proposed protection module is more rationality and effectiveness.

The sensorless control technology based on rotor initial position detection

This paper studies on sensorless control technology applied in permanent magnet synchronous motor. With respect to the problems in existing test method for initial position, the paper starts with the technology to observe flux linkage and detect initial position used in sensorless control technology in direct-drive permanent magnet wind driven generator, and on this base, a theory of detecting rotor initial position by mixing two-phase with three-phase for breakover is put forward. After simulation analysis, the correctness is verified, then on-site experiments are conducted on direct-drive permanent magnet wind driven generator twin trawling experimental platform provided by some cooperative institutions, with the direct-drive permanent magnet wind driven generator set on a condition with slow-speed of revolution. It turns out that the method of mixing two-phase with three-phase for breakover could not onlydetect the rotor initial position quickly and effectively, but also possibly control the error within ±15° electrical angle. At the same time, it is applicable for the low cost, easy to implement, which is capable of meeting the requirements to start a direct-drive permanent magnet wind driven generator.

Application of Information Integration in Intelligent Substation

In this paper, the data of information in intelligent substation are classified, information flow in communication network is analyzed, based on IEC61850 standards, and there are four categories: control and protection unit, the centralized fault recording unit, the monitoring and five-prevention unit and the measuring, in the application systems of substation. And then, the information integration scheme applied to intelligent substation is proposed. The plan completes the information collect, processing, upload and display, and other functions, realizes real-time communication efficiently between each layer in the internal substation, and between substations and higher control center, based on the unified modeling of all objects within the substation, building information integrated platform in the station level. Information integration platform can not only ensure authenticity, integrity and consistency within the substation information data, but also maximize the information sharing and interoperability of the equipment among application systems in the substation.

Embedded control in variable-speed constant-frequency wind-power generation

Now many kinds of technologies applied to wind-power generation are in the ascendant, among which the technology of variable speed and constant frequency (VSCF) is getting increasing recognition for its characteristic of high-efficiency and practicability. In this paper, it brought forward the method of emulating wind turbine by squirrel-cage induction motor to solve the prime motor issue for the study of wind power generating system in lab. The reliable and integrated laboratory experimental platform of wind power generation system was constructed in this paper. The result of the experiments all validated the validity and feasibility of the model of VSCF wind power generation system platform in the lab.

Study on the safety index of distribution system containing distributed generation and example analysis

In this paper, the safety index of distribution system containing distributed generation is discussed,Based on the research of the power distribution system. According to the practical situation, distribution system containing distributed generation such as the wind power generation unit is considered as a random power,and introduced the concept of “Island formation probability”. Research and analysis of the safety evaluation index of the distribution systems containing distributed generation, from the two aspects of system failure probability and failure consequence. And through the actual example verifies that this set of safety evaluation index of practicality. The set of indicators to characterize the security level of grid connected wind power system for different regions of the network or the same area of the different planning schemes, all has important guiding significance.