Applied Mechanics and Materials Vols. 373-375

Abstract: Space vector pulse width modulation (SVPWM) is a method to control the AC asynchronous motor. SVPWM technology applied in AC speed regulation system can not only improve the shortcoming of low voltage utilization in the pulse-width modulation (PWM) technology, but have little torque ripple and low noise advantages. In this paper, a SVPWM vector control AC asynchronous motor speed regulation system employing a core TMS320LF2407A-type DSP chip was presented, and simulated the speed regulation system by MATLAB SIMULINK. The obtained simulation results indicate that the proposed speed regulation system has excellent dynamic and static performance, thus SVPWM control technology of asynchronous motor based on DSP has been implemented.

Abstract: The doubly-fed wind power generation system containing crowbar protection circuit will change from reactive power source to reactive power load during the low voltage ride-through, which is likely to aggravate burdens to the fault system. Aiming at solving this problem, the paper will introduce the STATCOM compensation device, and put forward a comprehensive control strategy. Under the coordinated control strategy, the STATCOM will cooperate with the compensation capacity of the doubly-fed generator to support the reactive power. The voltage at point of common coupling will be raised and the ability of low voltage ride-through of the wind turbines will be improved. A simulative model of doubly-fed induction generator is established in MATLAB and the strategys rationality and effectiveness will be verified by the simulative results.

Abstract: Vegetable quality safety is the current hot issue that arose government, social concern and global attention. Now, Along with the continuous development of Agricultural Science and Technology, we have been completed the automatic control system, including vegetable quality safety of information and its monitoring, tracing, emergency management, monitoring, etc., and have formed the automated control system integration model and evaluation system of the vegetable quality and safety regulation based on the whole industry chain, which is the great significance on a sound specification of vegetable quality and safety information system and safeguard consumer interests.

Abstract: In order to prevent large scope blackouts, the paper has established a model of power system cascading failures from the perspective of risk .Taking both the load of branch and the power flow changes into account, the model defines the probability of branch outage which can reflect the real-time operating condition. The consequences severity of cascading failure is measured by bus low voltage, power line overload level and the amount of isolated loads. In the process of searching fault link, the paper uses the structure transmission importance of branch to determine the next breaking branch, which can speed the search of the cascading failure mode. The simulation of the IEEE 39-node system shows the effectiveness of the method.

Abstract: This paper deals with the setting calculation data center (SCDC), which is based on Common Information Model (CIM). The construction consists of data splicing and graphics stitching. The splicing method of the information related to setting calculation gains more attention, especially the operation mode. Further more, it brings up a method called dynamic partitioning to improve calculation efficiency. It gives a proper element range relying on the maximum and the minimum operating modes provided by the grid. We only need to consider the network elements in this range to involve in setting calculation. Out of this range we use a simplified equivalent model. At last, the effectiveness and accuracy of the algorithm are verified by the result of the practical example and it is reasonable and effective in its application in engineering.

Abstract: Study on the temperature controlling optimization problem of a novel microchip level PCR instrument, a compound control scheme based on Smith predictive and adaptive Fuzzy-PID is presented. Because the temperature control system of microchip level PCR instrument is a time-varying, non-linear and pure time delay complex system, to achieve the different temperature zones rapid switching and the temperature precision controlling is easy to be affected by time delay factor, it may encounter problems such as large overshoot, and even poor stability in the control of system with time delay. In this system, Smith predictable compensation control temperature algorithm should be adopted to decrease the overshooting and oscillating, adaptive Fuzzy-PID control temperature algorithm should be adopted to solve the problem of low precision and poor capability because of the fuzzy rules roughness. The simulation results show that the Smith predictive adaptive Fuzzy-PID temperature control algorithm has the fast response, high precision temperature controlling and strong robust properties, and it can provide a reference for the intelligent temperature control system design of microchip level PCR instrument. Keywords: Microchip level PCR instrument; Smith prediction; Adaptive Fuzzy-PID controlling algorithm; Temperature control system

Abstract: In this paper, output feedback controller is applied to solve robust fault-tolerant problem for singular bilinear system with Markovian jump. The aim of this problem is to design a output feedback controller that ensures stochastic stability of the closed-loop system and the -induced gain from the noise signal to the estimation signal remains bounded by a prescribed value, whether the actuators are normal or abnormal. The controller can be constructed by solving a set of linear matrix inequalities. An illustrative numerical example is given to demonstrate the applicability of the approach.

Abstract: Trapezoidal curve is selected as the hydraulic pumping unit load running speed curve. Designed a new hydraulic system of hydraulic pumping unit according to the electro hydraulic proportional control technology and then expounded its working principle, in which the electro-hydraulic proportional directional throttle valve have been used. The system is feasible on the theory by analyzing its mathematical model. It would meet the requirement of hydraulic pumping unit and realize the advantages of it via controlling the input current signal of the amplifier.

Abstract: Power plant relay protection setting value of the hidden harm causes of relay protection device is not correct, safe and stable operation of the power plant. In this paper, from the angle of the safe operation of power plant, the hidden danger to plant with the protection setting is studied and then the risk evaluation method of power plant relay protection setting values of hidden trouble is proposed. From the power plant relay protection setting value considering two aspects of probability and consequences of potential outbreak of different values, value potential risk is considered, and of a certain power plant in Hubei was made the risk assessment and analysis, in order to verify the theoretical rationality and accuracy.

Abstract: Based on the theory of risk, a new model is proposed for cascading failure in power system. According to fault factor of power line itself and the impact of real-time power flow, the branch outage probability model is established, and then the probability of cascading failure can be calculated. The severity function of cascading failure is defined by the analysis of fault consequences including the decrease of load margin, bus voltage offset and power line overload. The use of the set of danger lines which is judged by the amount of active power increase and load margin of power line can speed the search of fault mode. The simulation and analysis of IEEE 39-node proves the effectiveness of the method.