Applied Mechanics and Materials Vols. 313-314

Abstract: Aiming at maximum wind power tracking control problem of wind power generation system below the rated wind speed, this paper presents an improved MPPT control strategy by using turbulent part of the wind speed as a search signal to find the maximum power point. By using the Matlab/Simulink simulation of the wind power generation system below the rated wind speed, this paper proves the effectiveness of this control strategy. The simulation results show that improved MPPT control strategy can well control the wind turbine speed to track the wind speed changes to maintain optimum tip speed ratio and the maximum power coefficient.

Abstract: This paper establishes the wind power system simulation model in Simulink/ Matlab environment. By adjusting the speed of variable speed wind turbine, the simulation model can keep running at the best operation condition, and then achieve maximum power transfer. In this process, this paper use PI controller to track and control the speed of wind turbine. Simulation results show that selecting the appropriate PI parameters can effectively track the speed and increase the efficiency of wind power generation system.

Abstract: The hierarchical decomposition and modeling method of large-scale power systems proposed previously is expanded to be suitable for AC/DC power systems in this paper. In the new model of AC/DC systems, DC systems will have the same position as AC systems. The components in AC/DC power systems are classified into three categories, namely conversion components, DC components and AC components. By analyzing the difference between DC interface and AC interface, the unified structural model suitable for any kind of component in AC/DC systems is built. Then, the hierarchical structural model is derived based on the hierarchical decomposition method. The main characteristics of the proposed AC/DC model are the same as that of previous AC model.

Abstract: Through the characteristic analysis of wind energy carried out, research and analysis on characteristic of Stand-alone Wind Energy Generation System and maths model of the PMSG. Advanced a control strategy with regulate power via adjusting the machine electromagnetic torque-rotate speed use in Stand-alone Wind Energy Generation System, and the wind energy generator automatically track power of load under the rate wind speed. A electronic power conditioner of generator output was designed based on a microchip using this control strategy. It effectively solves the problem of the unbalanced power in the system.

Abstract: A wind-solar hybrid DC power supply system for small wireless sensor devices is introduced in this paper. The environmental monitoring system is selected as the application platform, and ARM microprocessor is selected as the control core. With the use of the multi-stage constant current technology, the battery life and charge efficiency are optimized. With the design of LCD module and RS232 interface in the system, the difficulty of the system debugging and maintenance are reduced while the flexibility of the system is increased. The experimental result shows that the most use of wind and solar energy is realized in this system.

Abstract: Compared with other wave energy converters, point absorber wave energy converter (WEC)is more suitable for small wave conditions, and adapts to China’s coastal wavecharacteristics. Based on the linearregular wave theory, the power characteristic of point absorber WEC wasanalyzed in the paper. Using numerical calculation method based on linearpotential flow theory in frequency domain, we calculated the hydrodynamiccoefficients and response amplitude operator (RAO) of floater in wavecondition. And then the power of the point absorber WEC was calculated undergiven conditions. Based on the calculation, we studied the rule of influence of WEC’s major parameters to its output power. The research result offer importanttheory foundation for optimal design of point absorber WEC’s power characteristic.

Abstract: The ill-condition of the load-flow is caused by a variety of reasons. Among them, heavy load and a long line of radiation type slip(large r/x) are the two important reasons. In connection with the ill-conditon above, Newton-homotopy algorithm is introduced in this paper. The algorithm mixes the locally quadratic convergence of Newton-raphison with wide range convergence of homopoty algorithm, so it improves the ill-condition of Jacobian matrix in the process of load-flow calculating, and speeds the convergence. Finally, several examples show the efficiency of the algorithm.

Abstract: To promote the structure analysis efficiency of multi-section & variable taper wind turbine tower, a novel method is proposed. The effective factors are analyzed for the performances of wind turbine tower, and the main parameters of it are found out. Resolution on rapid structure analysis is presented according to standardized FEA flows. The parameterized modeling method of towers vertical section profiles and optimal FEM meshing method are described. Finally, a rapid structure analysis software is completed to check the method, and the SUT 77-1500 wind turbine is taken as the example to verify the feasibility of the method

Abstract: This study presented the DC bus instability in distributed power system driving by Photovoltaic (PV) source with constant power load (CPL). The aim of this study is to investigate the effect of PV source towards the performances of DC bus voltage stability using constant power load. The system first was tested using linear DC supply as voltage source and CPL was modeled and connected to the voltage source through LC filter network. A passive damping circuit was chosen to stabilize the DC bus instability. The system was repeated using PV source. PV array was modeled based on the parameters obtained from a commercial PV data sheet. A circuitry simulation was performed under the similar design excluding the DC source in order to investigate DC bus instability. Results showed that the stability of DC bus become unstable when using linear DC voltage supply and slightly affected when using PV source. The instability phenomenon due to the negative incremental impedance of a constant power load can be overcome by using damping technique. For linear DC voltage source, DC bus voltage system tends to oscillate. However, with PV source which is actually a current source input seems not much affecting the DC bus voltage stability.

Abstract: This paper is a contribution to improve the quality of the electrical energy, of which we study a new compensator that is a combination between a parallel active filter and an UPQC. The two FAP parts use a method of identification of the disruptive currents taking as a basis on calculates it of the reference currents from the components fundamental of the load current relative to the active and reactive continuous powers. that is based on the calculated reference currents from the fundamental components of the load current on the active and the reactive continuous power. That is metered to demonstrate the reliability and effectiveness of this compensator. We were compared it with the UPQC under the same operating conditions. The results of this work have shown that this new control method and highly efficient and super- compensator also gave satisfactory results compared to the UPQC in the case where the load is doubled.