Applied Mechanics and Materials Vols. 433-435

Abstract: This paper presents a wireless remote monitoring system of water quality parameters based on Android platform and GPRS communication technology. This system realizes the remote collection, storage and management of water quality parameters, and also realize the remote control of the control nodes. In acquisition part, sensors collect data which is sent to the remote server through GPRS module, and water quality parameters from the server is sent to the Android mobile phone. In the control part, the control commands from the android mobile phone is sent to the server, and the server again send it to the lower machine to control the control nodes. After practical testing to the system in Liyang, Jiangsu province, temperature measurement accuracy reaches 0.5°C, PH measurement accuracy reaches 0.3, water level control precision can be controlled within ± 3cm, dissolved oxygen control precision can be controlled within ±0.3 mg/L, all the indexes can meet the requirements.

Abstract: This paper analyzes the status and problems of domestic water quality monitoring, and presents a controlling system,that takes the PC as monitoring computer and Siemens S7-226 programmable logic controller (abbreviated PLC) as the terminal equipment, to realize wireless transmission of data and instructions via GPRS communication module. Also it elaborates water quality parameter monitoring systems hardware and software implementation. The result shows that the system is stable and reliable, and method is easy for operator to grasp. Through real-time monitoring and controlling, the result shows that its value is stable, achieves the intended purpose. It provides a practical way to improve china's water environment.

Abstract: With the rapid increase of the installed capacity of wind power, the output power fluctuations of wind park had a great influence on the stability of the grid. Energy storage system in the wind farm can smooth the fluctuations of wind power effectively, and improve grid ability to admit wind power. The model of energy storage system based on vanadium redox flow battery was builded according to the state of charge, voltage and current characteristics. A kind of power control strategy with low-pass filtering was designed based on the new system model. Simulation results show that this model is more closer to the actual vanadium flow battery characteristics, the control strategy based on low-pass filtering can stabilize the output fluctuations of the wind farm power.

Abstract: An implied defect in one of the elevator control software is analyzed and modified. This defect would cause the elevator keep running up and down unbreakably between the next layer and previous layer of the target layer. The modification of the control software without adding physical parts was proposed. Three software design patterns to improve the safety of the elevator control software were discussed. The methods are validated to be reliable and feasible.

Abstract: In allusion to the difficulty of achieving accurate mathematical model of active power filter (APF), the Takagi-Sugeno (TS) fuzzy control is led into DC voltage control of APF. To solve the problem of control system stability, the control approach based on Lyapunov stability theory is applied to the current control. Both methods can ensure the control accuracy and stability. By means of adaptive fuzzy neural system in Matlab/Simulink the parameters of TS fuzzy controller are optimized and experiments are performed. Results show that under the time-varying load and variation of power system parameters both robustness and control accuracy of the control system can be ensured by the proposed control method.

Abstract: The active power filter with LCL filter (LCL-APF) possesses the advantages of wide bandwidth of compensation and a small amount of switching ripples. A direct power control (DPC) method of LCL-APF without harmonic current detection technology is proposed. Not only the complex detection of load harmonic current and compensation harmonic current is omitted, but also the total rate of harmonic distortion of grid side is reduced from 27.7% to 1.12%. To overcome the disadvantages of resonance caused by three-order LCL filter, the power of active power damping is added in the power controller. Thus, the dynamic control performance of LCL-APF is improved, as stable waveforms of grid current and power after 0.04s proved. Meanwhile, a modified DPC control loop is formed. Simulation results prove that the proposed method is correct and feasible. In view of the fact that it is rapid and accurate, especially the power level of 150kW, so it is suitable for the distributed generation system.

Abstract: This paper presents a novel soft switching topology and its control method applied on three-phase current source inverter. The main switch transistors of the inverter can be achieved in soft switching on the current pass-through step, which can reduce switch stress and improve efficiency. The soft switching circuit consists of two auxiliary switch transistors and some passive devices, such as inductor, capacitor and diode. It has many advantages as follows, simple control, fewer devices, high reliability, and so on. This paper analyzes the principle of soft switching circuit, and simulate by using the current space vector control method with MATLAB. The simulation results demonstrate the feasibility of the method.

Abstract: The shipboard power system (SPS) supplies energy to sophisticated systems for weapons, communications, navigation and operation. It is critical for the system to be reconfigurable for the purpose of survivability and reliability. The present paper proposes a new variation of PSO model for restoration of shipboard power system. A new inertia weight of S-Curve Decreasing variation is introduced. Particle Swarm Optimization with S-Curve Decreasing Inertia Weight (SDW-PSO) approach can improve the speed of convergence as well as fine tune the search. The proposed Particle Swarm Optimization algorithm enables to find the optimal combination of loads that can be supplied after the occurrence of the fault, in which the priorities of the loads and the constraint of balance between the total load and total generation are considered.

Abstract: With the continuous construction of ultra high voltage (UHV) power grid, East China-Central China North China will be interconnected via UHV lines to be a UHV synchronous grid in the future. Further expansion of the grid scale, the existing active power and frequency control mode has been unable to adapt to the new features. Based on the future structure of North China-Central China-East China synchronized power grid, the article built the whole network of the AGC control model using PSD-FDS full dynamic simulation program. By the simulation of examples, the problems of AGC control mode for UHV synchronous power grid has been pointed out visually. Finally, the paper presented an ideal AGC control mode called centralized control mode to deal with the new challenge.

Abstract: According to the specific requirements of time domain airborne electromagnetic method detection system, a whole bridge high-power switching power supply is designed based on limited double pole control. Combined with the designed whole bridge topologies, its working process is discussed and the realization process of soft switch is analyzed. Through the specific experimental analysis, it can verify that the limited double pole control method can well realize zero voltage switch and zero current switch of the switch tubes, it can improve the work efficiency of the switching power supply. The power supply has been successfully applied to the scientific research project at present.