Time filter

Source Type

Liu X.M.,Jiangxi Electrical Power Company | Pan L.,Hunan Institute of Science and Technology | Zheng H.,East China University of Science and Technology
Applied Mechanics and Materials | Year: 2013

This paper presents a time Petri net model with the optimizing mechanism based on ant colony systems that addresses the problem of schedule optimization. The choice rules and pheromone update rules of artificial ants are embedded into the evolution rules of a time Petri net, so the modeling and scheduling analysis of real systems can be integrated into the same model. Compared with the approaches based on the heuristic search and genetic algorithms, our method efficiently unifies the modeling and analysis of schedule problems based on a time Petri net. © (2013) Trans Tech Publications, Switzerland.

Cai X.,Tsinghua University | Guo J.,Tsinghua University | Hu T.,China Academy of Machinery Science and Technology | Zhang Z.,China Academy of Machinery Science and Technology | Chen S.,Jiangxi Electrical Power Company
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2014

Extremely low frequency (ELF) magnetic signal is usually used as the magnetic field source for tracking and location of mobile robots in oil and gas pipeline inspection, because the ELF signal is able to penetrate high permeability materials, such as metal pipeline, soil and rock. The diameter, thickness and buried depth of the pipelines vary with the circumstances in the tracking and locating engineering practice of inspection robots, which requires different types of ELF magnetic transmitters with different transmitting power. In this paper, the propagation rules of ELF magnetic signal and the engineering application of signal transmission and reception in the pipeline environment are combined together, and then a complete reverse optimal design method of the ELF magnetic transmitter is proposed. Firstly, according to the relationship between detection probability of the algorithm used in the ELF signal receiver and the corresponding peak SNR, the lowest peak SNR required by the receiver under a certain detection probability is derived, and then the minimal magnetic flux density at the front end of the receiver is determined. Secondly, the required minimal source magnetic flux density of the ELF magnetic transmitter in the pipeline is calculated reversely based on the minimal magnetic flux density at the front end of the receiver. Thirdly, the ferromagnetic core coil structure and circuit topology of the transmitter are designed under the constraints of the source magnetic flux density and the geometric dimension of the transmitter. The design result obtained with the proposed method not only meets the magnetic flux density requirement of the receiver, but also guarantees that the service life of the power supply for the transmitter greatly exceeds the required working duration in the pipelines. At the same time, even when the related parameters in practical circumstance change, the magnetic flux density at the front end of the receiver still meets the requirement of detecting ELF signal with high detection probability.

Fang J.-J.,Jiangxi Electrical Power Company
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2013

In the light of such problems as low load variation speed, large fluctuation of the main control parameters and excessively low temperature of the main reheat steam existing in a 660 MW ultrasupercritical unit of Jingdezhen Power Plant owned by China Electric Power Investment Corporation, presented was an advanced solution to modern large-sized ultrasupercritical units adopting AGC control by organically fusing the predictive control technology and neural network learning technology with the self-adaptive control technology. By utilizing a INFIT (a PLC-based advanced thermodynamic control and application platform) real-time optimization control system, the control scheme above-mentioned was successfully accomplished on the spot. The practical application in the units shows that to use INFIT platform to realize the advanced control technology can obviously improve the load regulation performance, operation stability and average main and reheat steam temperatures of the units, thus enhancing in a comprehensive way the safety and cost-effectiveness of the units as a whole.

Li Y.-S.,North China Electrical Power University | Guo S.-F.,Jiangxi Electrical Power Company | Ren G.-W.,Henan Xinyang Power Supply Company | Liu J.,North China Electrical Power University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

For analyzing doubly-fed wind power generation system and its operation characteristics in power grid accurately, its electromechanical transient models are developed. The mathematical model and pitch angle control model are established for components of doubly-fed wind power generation system including the wind turbine, mechanical device and doubly-fed induction generator. Based on its electrical-magnetic model, the models of converters control system of rotor and network sides are obtained, considering electromechanical operation characteristics. On this basis, the user defined (UD) models of doubly-fed wind power generation system in PSASP are constructed. The UD models are applied in the single machine infinite bus system for simulation. The results show that the models developed can reflect the transient characteristics of the system.

Wang H.,Jiangxi Electrical Power Company
Wuli Xuebao/Acta Physica Sinica | Year: 2012

Generation of triangular optical pulses in conventional normal dispersive (ND) fiber is experimentally realized using a passive nonlinear pulse shaping method based on a combination of pulse pre-chirping, group-velocity dispersion and self-phase modulation in a section of ND fiber. It is found that by optimizing the parameters of launching pulse power level and ND fiber length, high-quality triangular optical pulses with nearly constant gradients of leading and trailing edges and linear frequency chirp profiles can be obtained for a wide range of different pulse pre-chirping values. For different pulse pre-chirpings, high launch power is required for triangular optical pulse generation. The tolerance of triangular pulse formation to ND fiber length and launch power level is improved with the increase of pulse pre-chirping, which means that it is easy to obtain triangular pulses for higher pulse pre-chirping. © Chinese Physical Society.

Discover hidden collaborations