Advanced Materials Research Vols. 1049-1050

Abstract: The design of a high efficiency, silicon controlled dimming and power factor correction (PFC) LED drive power supply is proposed.The LED driver power supply uses isolated flyback topology,with high efficiency and power factor,and also has a no-load protection,short circuit protection and overvoltage protection.The power controller chip LYT4326E and working principle of the circuit are analyzed.Experimental results verify that the full load efficiency of the power supply circuit is over 86%,with a high power factor and can run stably and reliably.

Abstract: This smart car control system by MC9S12G128 controller as the core, the use of a row of 18 laser tubes and 6 receiving tube as the path recognition sensor, through MC9S12G128 I / 0 interface for sensor signal, and use the feature extraction method to extract the track type, realization of the starting line, cross line recognition. According to road information, the design adopts fuzzy control algorithm of output PWM wave to control the gear steering, complete control of the direction of the car, the car speed extracted with the use of photoelectric encoder, comparing with the current set point to get speed deviation, and output PWM pulse is obtained by using the PID algorithm to control the motor to adjust the car speed, complete the closed-loop control of the car movement speed. Through the experiment, the system is designed to achieve the desired effect.

Abstract: This paper studies the power transformer fault quality diagnosis using rough sets theory and neural network. It is rough sets reduction as the pre-unit of neural network based on reduction algorithm with the attribute significance. The paper describes the reduction algorithm and implementation method detailed. Through the training and testing results with practical data, it is proved that the reduction algorithm with the attribute significance can make the number of input samples shorter, the training speed faster and the diagnostic accuracy higher. The algorithm is feasible and effective for applying to the fault diagnosis system of power transformer.

Abstract: Because the line impedance of low-voltage microgrids is mainly resistive and the transfer impedance of microgrid inverters is usually mismatched, a virtual reactance is usually added to the control loop of each microgrid inverter. It is found that the existing two virtual reactance implementation methods introduce harmonic components into the voltage control units of microgrid inverters in the condition of nonlinear loads after the theory and simulation analyses. To solve the problem, a second-order general-integrator (SOGI) virtual impedance implementation method of droop-controlled three-phase microgrid inverters is proposed. Simulation results are provided to show the feasibility of the proposed method.

Abstract: According to the characteristics of ultrasonic guided wave inspection, An exciting power, used for exciting ultrasonic guided waves in pipeline is designed based on DDS and FPGA. The excitation source consists of FPGA, D/A conversion circuit, a low-pass filter circuit and power amplifier circuit. Constructing DDS based on FPGA as the controller and signal generator. Filter circuit and power amplifier circuit are designed in this paper. The experiment results show that the excitation source can have high voltage and high frequency output capability, and can generate desired signal type with a good accuracy to fit the requirements in practice. It can be conveniently used for pipeline ultrasonic guided wave detection.

Abstract: This paper designed an analog control circuit which can automatically track the sun for PV bracket system to improve the solar cell photo-electricity conversion efficiency. The sunlight intensity can be real-time detected by sampling the short-circuit current of solar cell. The PV bracket system can be automatically adjusted to achieve a final horizontal angle and pitch angle by using the hysteresis comparator and dedicated motor driver chip, which always makes photovoltaic modules toward the sun's position. At the same time, the PV bracket system can be automatically reset by the hall switch when the sun reaches the sunset and the light intensity is less than the reference value. The experimental prototype is used to testify the correctness and reliability of the control system, which has better practicability and value to extend.

Abstract: In this paper, a wideband variable-gain amplifier (VGA) in CMOS for ultra wideband (UWB) system is designed. The operation frequency of the VGA is 4.2-4.8GHz, and the gain is continuously adjustable between 0 and 30dB. Cascaded Cherry-Hooper with two stages is adopted as the core unit of the VGA, and a temperature compensation circuit is used to reduce the effect of temperature on the performance of the system. The simulation shows that the temperature compensation circuit can compensate the effect of the temperature very well, and the noise figure of the wideband VGA can meet the requirements of the system.

Abstract: High speed encoder is the key element of high speed analog-to-digital converter (ADC). Therefor the type of encoder, the type of code, bubble error suppression and bit synchronization must be taken into careful consideration especially for folding and interpolating ADC. To reduce the bubble error which may resulted from the circuit niose, comparator metastability and other interference, the output of quantizer is first encoded with gray code and then converted to binary code. This high speed encoder is verified in the whole time-interleaved ADC with 0.18 Bi-CMOS technology, the whole ADC can achieve a SNR of 45 dB at the sampling rate of 5GHz and input frequency of 495MHz, meanwhile a bit error rate (BER) of less than 10^-16 is ensured by this design.

Abstract: The capacitive device is a important equipment in the power system. Its working state is usually monitored by charged detection. However, the traditional detection method needs a lot of cable wiring for each test, which makes a big security hidden danger. In order to solve the problem, a new wireless measurement method based on 2.4G wireless and Bluetooth technology is proposed in this paper, which not only achieves wireless synchronous measurement of current and voltage, but also meets the requirements of capacitive equipment charged detection.

Abstract: In smart substation, transmission line longitudinal protection debugging cannot take place, before the line communication channels construction, that cause it often occur that not fully debug, choose a suitable time for debugging in advance. In this paper, based on the analysis of the longitudinal protection debugging process, combining with the computer technology, and 3G/4G communication technology, design a set of intelligent substation EHV-line longitudinal protection device of temporary channels. Ensure, in intelligent substation, carry out advanced debugging, select the appropriate time debugging, debugging completely, before the longitudinal channel built, and establish a reliable foundation for the normal operation of the longitudinal protection equipment.