Advanced Materials Research Vols. 383-390

Abstract: A FLC-PID controller is designed to solve parameter time changing and nor-linear problems of variable-pitch syetem. The FLC-PID control metod can improve the derivation responses of system. Control simulation are carried out to indicates that it is superior to the traditional PID and FLC controller.

Abstract: This study presents a novel bidirectional dc-dc buck-boost converter compatible with the flywheel energy storage system (FESS) and a robust control for bidirectional power flow, according to the single cycle average current control scheme and proportional-integral (PI) control theory. The proposed converter and its control are designed to adjust voltage to achieve current limiting start up and final speed keeping of the motor in charge mode and maintain a constant output voltage in the case that terminal voltage of the motor in the FESS drops continually in discharge mode. Simulation results demonstrate high performance of the converter in both steady-state and dynamic operations.

Abstract: The fuzzy control can react to the environment change quickly and keep the photovoltaic system work on its maximum power point all the time. However, the limitation in the fuzzy control itself and the characteristic of self-optimization lead to serious concussion of the system around the maximum power point. Whereas the PID control method is effective in the elimination of concussion and is easy to be realized. To tackle the problem, the fuzzy parameter self-tuning PID control method is adopted in the paper to achieve the MPPT control of PV system. The method can effectively eliminate the concussion around the maximum power point and improve the stability of the system; and achieve grid-connected operation with a high power factor in combination with the harmonic elimination PWM control of inverter. Simulation results show that the scheme has merits of simple structure, high power factor and reliable operation, etc. and is worthwhile to be popularized.

Abstract: Averaged 3D N-S equations and RNG k-ε equations were solved with parallel computing CFD code on the flow field of dual radial ventilation system without fan for a hydro-generator. The MRF(multiple implicit rotating frame) method was used to simulated the rotating motion of the generator and porous media model were used to simulate the pressure loss of air cooler. Rational tactics were selected to generate calculation grids to compromise with calculation CPU time and result accuracy and the grids of different parts were generated with ICEM-CFD. The flow characteristic of different parts was analyzed and flow flux of different section was obtained. The research indicated that the flow from leakage gap between poles and stators formed "air wall", which generated a recirculation zone and made the bar cooling bad. The local pressure loss of stator entrance is dominant. There are leeward and windward areas for the air flowing with circumferential velocity component. Rational design of stator ducts entrance with some diversion effect, can reduce the pressure loss of the stator ventilation and improve the cooling of leeward area in stator ducts.

Abstract: To explore the mechanism for saving energy and reducing consumption in pelletizing process, the pelletizing process is decomposed correlatively into two parts: the material flow process and energy flow process. On this basis, it is studied that the physical and chemical changes and the flow mechanism in ferrite flow and carbon flow respectively, by analyzing the changes and conversion of the ferrite and carbon flow in pelletizing process, variation of material and energy flow has been summarized, using the law to guide the production, minimizing consumption of energy and maximizing resource utilization will be achieved. It provides another path to reduce energy consumption for steel plant.

Abstract: Wind power is a clean and renewable energy, and its exploitation is developing rapidly across the world. The Variable Speed Constant Frequency (VSCF) wind power generation system requires the doubly-fed wind generator (DFIG) to have high response as well as good robustness. DFIG will be affected both by internal disturbance of parametic variations and external disturbance of the load torque oscillation. The dynamics of the current response of the present PI controlled rotor may be in bad condition. In addition, the above disturbances reduce efficiency and stability of the wind turbine. Internal model control (IMC) is a kind of control strategy based on mathematical model to design the controller, it has advantages such as simply to design, robustness, convenient to research. Compared with PI control, IMC has a faster response, and is insensitive to the parameter variation and disturbances, but the IMC highly depends on accurate model of the controlled object. To solve this problem, combine the neural networ and IMC to design the neural network internal model controller .The simulation indicates that the dynamic performance and the anti-interference ability of DFIG are improved.

Abstract: In this paper, a topology for a doubly-fed induction generator (DFIG) using a direct Two-stage Matrix Converter (TSMC), connected between the stator and the rotor, is presented. The input stage is connected to the grid and provides the required dc voltage for the output stages. Space vector modulation is used for the input stage producing the maximum dc voltage, with unity power factor operation at the TSMC grid-side input. Each of the output stage is connected to the rotor of a DFIG. The control of the generator rotor currents is carried out using standard vector control approach with a reference frame aligned with stator flux. The entire system is modeled and the results are presented to show the feasibility of the proposed scheme.

Abstract: In this paper, two chiller water units connected in parallel working using the predatory search strategy was observed. Predatory search strategy has been applied to solve the optimal load distribution strategy problem for the cooling system constituted by multiple chiller water units, which has the characteristic such as complexity, constraint, nonlinearity, modeling difficulty, etc. Compared with the conventional method,the results indicated that the predatory search strategy algorithms has much less power consumption and is very suitable for application in air condition system operation.

Abstract: In order to improve water quality retrievals of multi-spectral image accurately, this paper puts forward a method for water quality remote retrieva based on support vector regression with parameters optimized by genetic algorithm. The method uses SPOT-5A data and the water quality field data, chose four representative water quality parameters, support vector regression are trained and tested, the parameters of support vector regression are optimized by genetic algorithms. The result of experiment shows that the method has more accuracy than the routine method. It provides a new approach for remote sensing monitoring of environment.

Abstract: At present, there are two kinds of common generators in wind farms, which are induction generators (IG) and doubly-fed induction generators (DFIG). Based on the steady state mathematical models of these two kinds of generators, the processing methods of wind farms in power flow calculation are given. The core idea is to express active power of the generator by a function of wind speed and to express the reactive power by a function of active power, slip and terminal voltage, and then the Jacobian matrix will be corrected according to the relation between terminal voltage and reactive power in the wind farm node. Finally, the IEEE 14-bus test system including wind farm is applied for power flow calculation and analysis. The numerical results show that the mentioned methods are feasible and can satisfy the requirements of the engineering application, which can pave a foundation for further research.