Applied Mechanics and Materials Vols. 719-720

Abstract: The protection is very important to detect abnormal motor running conditions such as over current, over voltage, overload, over temperature, and so on. When a failure is sensed by the protection system, a time delay should be specified to trip the motor. In the classical systems, motors are stopped with the time delay, which is adjusted constantly without considering the fault level. This paper presents a fuzzy logic-based protection system covering six different fault parameters for induction motors. The paper focuses on a new time-delay calculation for stopping induction motor and improves the overall detection performance. The time delay is computed by fuzzy logic method according to various fault parameters when one of the failures occurs on the motor. This system is successfully tested in real-time faults on the motor, and it shows that it provides sensitive protection by fuzzy rules.

Abstract: The concept of smart substations has been widely used in power systems. Since the variation in interfaces and communication manner, the operating& maintenance methods for smart stations have changed a lot compared with the traditional substations. In this paper , a training system based on virtual substation primary equipment combined with real secondary devices is developed for accident management and operating work in smart substations. The training system is also used to test the relay protection algorithms、Ethernet switch functions、fault recorder actions ,and so on.

Abstract: The application of virtual instrument technology to design solar irradiance acquisition system, an ideal combination of software and hardware, is aimed at collecting, storing and analyzing data of external temperature and solar irradiance.The data proves helpful in assessing whether the solar energy resource deserves to be developded economically.The system is reliable and has been verified by simulation software proteus.

Abstract: This essay is about the application of a diode-capacitor network on conventional non-isolated DC–DC converter. The study will focus on obtaining high step-up voltage gain, low switch voltage stress, simple control, and high conversion efficiency. Three single-switch step-up converters with high step-up ratio based on the diode-capacitor network are proposed. The principle of operation and theoretical analysis of every single-switch step-up converter is evaluated for both continuous and discontinuous conduction modes. Given the mirror-symmetrical characteristic of the diode-capacitor network, cascade single-switch step-up converters based on the single-switch positive-output step-up converter are achieved when several diode-capacitor networks are arranged in series. Simulation analysis and experimental results obtained from the implemented prototypes operating at 40 kHz are provided to verify the performances of the proposed step-up converters.

Abstract: The successive approximation analog-to-digital converter (ADC) has been widely used in electronic devices due to the corresponding characteristics which are low cost, low power consumption, high accuracy and so on. This paper expounds a design of successive approximation A / D converter to show how to use TCL5615 which is a dual-channel serial 10-bit D/A converter (DAC) to make the conversion accuracy to reach 14-bit.

Abstract: In the last several decades, a couple of fuzzy power flow algorithms were presented to deal with the uncertainties in power grid. But there is no a functional simulation tool introduced to simplify the calculation. This paper presents a simulation tool, Matpower, under one of the algorithms to do the fuzzy power flow calculation. The algorithm gives the user the possibility to specify fuzzy numbers to represent the possible behavior of loads and generations and outputs fuzzy membership functions for voltage magnitudes and phases, active and reactive power flows and generations. Matpower, as a simulation tool, was modified to handle fuzzy numbers and show fuzzy results. In a final section, we present results obtained with a case study based on a real power system to illustrate and highlight details of the proposed algorithm. Suggestions for future implementation of the fuzzy Matpower are also summarized.

Abstract: The harmonic current detection is an essential part for an active power filter (APF). A random harmonic current detection method for single-phase active power filter without the phase locked loop (PLL) is proposed. The detection errors caused by low pass filters are analyzed, and an improved method has been proposed which can increase the detection accuracy and response speed. This method can detect the single order harmonic current and decompose it. Theoretical analysis and simulation results show the validity of the proposed method.

Abstract: It is difficult to detect and judge a weak electric shock signals in the leakage current accurate in the low-voltage power grid .A novel chaotic detection of the electric shock current and Lyapunov exponent is introduced in this paper .Electric shock current component is extracted according to the characteristics that chaotic system’s bifurcation action from chaotic state is sensitive to the weak signals and immune to noise .The largest Lyapunov exponent is proposed as the judgment criterion of phase transition of chaotic system. It can automatically recognize the critical state before and after electric shock.

Abstract: Based on the digital serial communication, E1 and Ethernet port circuits connecting the electronic equipment on ships, characterizations of the digital signals transmitted through the circuits are analyzed. The situations when the EMI generated by the digital systems causing pollution to the grounding system and the grounding voltages coupled to the signal-transmitting circuits are simulated. Furthermore, the influence of the equivalent impedance of the main and branch grounding cables on the grounding performance are analyzed quantitatively. Therefore, the grounding demand is obtained. Finally, some anti-interference measures so as to improve the grounding performance are proposed.

Abstract: This document presents a high efficient method for interleaved active clamp flyback used in microinverter. The flyback converter was selected as a single stage topology that can boost the low PV panel voltages to a rectified AC output. How to handle the leakage energy for high efficiency and protecting the MOSFET ,how to calculate the parameter and choose the compenent also be showed in this document.