Advanced Materials Research Vols. 805-806

Abstract: Direct torque control (DTC) which replaces the conventional current loop with torque loop can directly control the electromagnetic torque in order to reduce the torque error within the hysteresis bandwidth, and it can attenuated commutation torque ripple and the torque ripple of brushless DC (BLDC) motor with un-ideal back electromotive force (EMF) waveforms. Further, the key issue of feedback torque calculation in torque loop is the estimation of back-EMF in sensorless DTC of BLDC motor. So a sliding mode observer (SMO) is employed to estimate the back-EMF in real time. The torque and rotor speed can be derived from the estimated back-EMF. Simulation results demonstrate the proposed method is valid and effective.

Abstract: Repetitive control (RC) has the ability to compensating periodical disturbance and it is an effective way to improve the output waveform of inverter loaded nonlinear load, but the dynamic response is slow. From the perspective of output impedance, state feedback control is used to configurate the pole of the system so that it can modify the ouput impedance characteristic of the system, increase the damp ratio and promote the dynamic performance of the system. The simulation results show that the proposed compound control strategy make the system has advantages of good output waveform and fast dynamic response.

Abstract: In this paper, a new method for induction motor fault diagnosis is presented. It is based on the so-called an auxiliary winding voltage and its Park components. The auxiliary winding is a small coil inserted between two of the stator phases. Expressions of the inserted winding voltage and its Park components are presented. After that, discrete Fourier transform analyzer is required for converting the signals from the time domain to the frequency domain. A Lissajous curve formed of the two Park components is associated to the spectrum. Simulation results curried out for non defected and defected motor show the effectiveness of the proposed method.

Abstract: Information and cyber security of Industrial Control Systems (ICS) faces severe challenges and has gained considerable importance. Information security assessment is an essential component of information security assurance infrastructure mechanisms. First, a hierarchical model of smart grid was abstracted. Based on the proposed model and the information security risks and information security protection demands of power control systems, an information security assessments framework for power control systems was proposed in dimensions of system layers and life cycle to guide the security assessment contents of power control systems. Finally, a test bed function design for power control system security assessment was proposed. The power control system security test bed may include four parts, such as power control system security assessment management platform, power control system simulation environment, security assessment tools, and security policy. The proposed security assessment framework and test bed functional design can be used to guide the electric power utilities in their power control system information security efforts.

Abstract: Radio interference (RI) of DC transmission lines due to the corona discharge has become a restraining factor of power grids design and operation, so the suppression of RI is very important. In this paper, a new idea for suppressing RI by mounting ferrite cores on the conductor is proposed. By measuring and comparing RI values of the test stranded wire with and without ferrite cores, test results show this approach to suppress RI is effective. Further research results also show inhibitory effects at negative voltage are better than positive voltage and the material of ferrite cores affects the inhibition effects.

Abstract: According to the characteristics of Wet Flue Gas Desulphurization (FGD), this paper brings forward the automatic control requirements and the control methods. The automatic control system is composed of a Programmable Logic Controller (PLC) and an industrial control computer (PC). The automatic control system can monitor the operating parameters of FGD system automatically and conduct automatic control and adjustment to FGD system. The PLC is responsible for the data collection and automatic control, while the PC is responsible for the surveillance of FGD system operation and the data processing through mutual communications between PC and PLC, which realizes the communication between human and machine and ensures the safe, stable and economic operation of the FGD system.

Abstract: The reliability test of the overload relay is an important way to find out weak parts and improve the reliability of products. So reliability test technology is of great significance. The reliability test method of overload relay is studied on. By use of reliability tester, the reliability test for the typical productsJRS1D-25 is carried out. According to the test result, the reliability analysis is developed from two aspects of product structure and material characteristics. The failure reasons of the overload relay are found out and the improvement measures are put forward.

Abstract: Stepper motor is a common electromagnetic device, the corresponding circuit of control and driver, effective algorithm of acceleration and deceleration play a very important role in improving overall performance. Many advantages were achieved using the control system based on ATMEGA128, such as higher simplicity, low cost, high reliability, high torque at low speeds, and high motion accuracy. At the same time, by using algorithm of acceleration and deceleration, the efficiency of stepper motor is further enhanced, and the actual effect of control of stepper motor is smooth and has good results.

Abstract: The paper aims to introduce the design which uses high integrated sensor to detect the humidity and temperature parameter and employs the CAN bus to makes it more compatible. The paper further illustrates the hardware schematic diagram and dwells on its principle along with the introduction of software programs. It finally reveals the running record of the system.

Abstract: If characteristic impedance along a transmission line mismatch on a printed circuit board, high-speed signal has serious signal integrity problems. When signal path of a differential pair jumps layers, mismatched impedance between differential via and differential line will affect the signal integrity. The models of a coupled transmission line and via are presented in this paper. Impedance matching of the coupled transmission line and differential via for differential signals is studied. The effects of differential via dimensions on differential signals is simulated and analyzed.