Ding M.,Hefei University of Technology |
Wang B.,Hefei University of Technology |
Zhao B.,Zhejiang Electrical Power Test and Research Institute |
Chen Z.,Anhui Electrical Power Research Institute
Dianwang Jishu/Power System Technology | Year: 2013
Standalone PV-wind-diesel-battery hybrid microgrid supplies power to local loads by power sources within the microgrid, and the primary target is to enhance the accouplement between the generated power and the load maximally. To improve the economy of whole microgrid while the power supply reliability is ensured, it is necessary to perform optimal design of capacity configuration of the microgrid according to existing conditions in whether and resources and to choose optimal source capacity combination. Mathematical models for different kinds of power sources within the standalone PV-wind-diesel-battery hybrid microgrid are established respectively, and two economic models of investment cost and different expenses are built too. Based on the dispatching strategy and constraints of this hybrid system, the numbers of different power sources are taken as variables and the minimum composite cost and expenses as optimization objective, and then the optimal capacity configurations of different power sources in the system are solved by genetic algorithm. The reasonableness of the proposed models is verified by case study results.
Wang X.,Hubei University |
Zhang X.,Anhui Electrical Power Research Institute |
Zhan L.,Hubei University |
Ren Y.,Hubei University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012
The microstructure evolutions, including changes of substructure, precipitates, and the effect of microstructure degradation on the high temperature stress rupture limit and hardness of T91 steel were investigated using the specimens taken from the thermal aging materials and exploded superheater tubes. Results show that during long-term exposure the tempered martensite transforms to an equiaxed sub-grain structure with low dislocation density and coarsen M23C6 carbides through recover and recrystalization, and the Z-phase forms at final aging state. It is found that the microstructure and stress rupture limit of T91 steel are very stable after equivalent ageing at 600°C for 100000 h. M23C6 carbide coarsening and lath microstructure degradation to equiaxed sub-grain structure before the formation of Z-phase lead to the significantly breakdown of stress rupture limit, which is the main cause for the tube bursting. The lowing stress rupture limit and hardness of T91 is caused by microstructure degradation. © 2012 China. Soc. for Elec. Eng.
Xie Y.,Anhui Electrical Power Research Institute |
Chiang H.,Cornell University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011
As a novel effective approach to nonlinear optimization problems, the Trust-Tech method is applied to solving the optimal power flow (OPF) problem. The proposed method consists of two phases: Phase I locates the feasible solutions for OPF problem by searching the stable equilibrium point of the quotient gradient system corresponding to the constraints set, and the idea of active set is employed to deal with the inequality constraints so that the computational requirement can be reduced; Phase II reduces the feasible region by adding the extra inequality constraints with respect to the upper limit of the objective function into the original OPF problem. By alternating between the two phases, the proposed method can locate the optimal solution for OPF problem by gradually decreasing the upper limit of the objective. Numerical results of a number of test systems are given to demonstrate the effectiveness of the method. © 2011 State Grid Electric Power Research Institute Press.
Anhui Electrical Power Research Institute, State Grid Corporation of China and SUZHOU HD Electrical CO. | Date: 2011-09-22
A power frequency parameter simulation system for a power transmission line and a control method thereof, the system comprises a simulation main circuit (1), an interference power supply (2) and a procedure controller (3). In the system, a power frequency parameter of a 10 to 100 kilometers of 500 kV power transmission line is simulated in a parameter integration manner; and the control method comprises the following steps of: a step to detect the automatically zeroing during starting up, a step to control the reduction of the length of a simulation line and a step to control a simulation interference voltage. A long-distance power transmission line is realized to be moved into a room and be tested by means of the power frequency parameter test system, so the various inconveniences of on-site measurement are avoided. The system realizes intelligent control over the simulation power line according to acquisition and analysis of the procedure controller to a signal, secure and reliable test and experiment performed on the power frequency parameter of the line in a laboratory can be realized, reliable training equipment is provided for learners, the anti-interference capability of a tester can be checked, and the whole system is applicable to line parameter testers produced by most of the conventional factories in China.
Ding M.,Hefei University of Technology |
Wu X.,Hefei University of Technology |
Lu W.,Anhui Electrical Power Research Institute |
Zhang Z.,Anhui Electrical Power Research Institute
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012
A method of three-phase probabilistic power flow for distribution systems with single-phase and three-phase grid-connected photovoltaic (PV) systems is introduced using sequential Monte Carlo techniques. The hourly output power of PV system is simulated considering solar irradiance, random change of weather, efficiency and effective sunlight area of PV arrays, efficiency of maximum power point tracking (MPPT) and inverter, and the reliability of overall PV system. The time-varying load model with randomness is incorporated in the probabilistic power flow and a program is developed. Case studies verify the feasibility and applicability of the method. ©2012 State Grid Electric Power Research Institute Press.