Recent Advances in Electrical & Electronic Engineering - Volume 7, Issue 2, 2014

The traditional artificial potential field algorithm has the shortcomings of appearing trap area easily and shaking in front of obstacles. This paper, studying traditional artificial potential field deeply, optimizes the sensor data with the introduction of the BP network and the GA algorithm, unmanned vehicles achieving autonomous obstacle avoidance and prognoses in advance when passing the path with obstacles, and effectively eliminating system instability caused by shock and dead zone. Comparing with traditional artificial potential field algorithm, the improved algorithm makes a further improvement in the respects of system stability and efficiency.

This paper proposes a new method based on continuous wavelet transform circuits for the analysis of harmonics in real-time. To measure harmonics, the wavelet transform of harmonic signal is realized by analog CMOS VLSI composed of analog filter bank, whose impulse response is Morlet wavelet. Nonlinear least square method is employed to obtain the transfer function of the filter with CMOS log-domain integrators as main building blocks. By changing the values of the integrators bias currents, this circuit can realize various scales wavelet transform of harmonic signal. Simulation results report that the implementation of continuous wavelet transform by analog circuits provides accurate and fast harmonic analysis in power systems.

This paper presents a searching method for optimal frequency of variable frequency pulse charging. Based on the analysis of the characteristics of the battery impedance, we give charging frequency a positive and reverse disturbance to make it form a hysteresis loop. Variations of current were recorded before and after the two disturbances. According to the frequency disturbance rules based on the hysteresis loop, we determine whether it is the optimal frequency. Otherwise, we continue the new round of disturbances until the operating point frequency is fixed at the optimal frequency. This method can dynamically search for the optimal frequency in charging to improve the energy transfer efficiency, significantly shortening the battery charging time. Experiments show that under the same conditions, the charging rate is increased by 28% compared with the traditional way of charging with constant current and constant voltage, and increased by 15% compared with the fixed frequency charging mode.

Pumped-storage power plants are extensively used in power systems because of excellent performances in peak load, frequency regulation and emergency reserve. Generator-motor is an important part of pumped-storage power plant and plays a key role in the operation of the whole power plant, consequently the safety and stability of the power plant and even the power grid are directly influenced by the performance of generator-motor. This paper offers a 3-D eddy current field calculation on generator-motor of Guangzhou Pumped-storage Power Plant B using finite element method (FEM). A 3-D generator-motor model is presented in this paper and the distribution of current density and flux density are educed, as well as the radial air-gap flux density and the harmonic analysis. Through the calculation on 3-D eddy field of generator- motor, electromagnetic distribution, mechanical strength, magnetic flux density and winding current of motor are obtained, offering reference for the design, model selection and localized manufacturing of motor.

In non-sinusoidal and unbalanced systems, optimal sizing of the capacitor banks is not a straightforward task as in sinusoidal and balanced systems. In this paper, by means of qualitative and quantitative analysis, it is interpreted that the classical capacitor selection algorithm widely implemented in Reactive Power Control (RPC) relays does not achieve optimal power factor improvement in non-sinusoidal and unbalanced systems. Accordingly, a computationally efficient algorithm is proposed to find the optimal capacitor bank for smart RPC relays. It is further shown in a simulated unbalanced and non-sinusoidal test case by using Matlab software that the proposed algorithm provides better power factor improvement when compared with the classical algorithm. It is also figured out from the simulation results that both algorithms cause almost the same harmonic distortion and unbalance deterioration levels in the system.

Aiming at the problem that the three-dimensional (3D) node localization precision is affected by the model parameters of least squares support vector regression (LSSVR) node localization method for wireless sensor network, a localization method based on LSSVR optimized by differential evolution (DE) algorithm is proposed in this paper. Firstly, the 3D node localization model is built through LSSVR and the kernel function parameter and the regularization parameter are optimized by DE algorithm. Then, the fitness function of DE algorithm is constructed according to the mean square error of a number of virtual nodes from the predicted position and their actual position, and the global optimal parameters of LSSVR are acquired through limited modeling parameters iterative searching method. Finally, the LSSVR optimized by DE algorithm is used to realize the node localization. The simulation results show that the localization accuracy of the proposed method is superior to that of least square (LS) and LSSVR method.

Flexible mechanical characteristics of power lines and poor conditions induce difficulties for the precise trajectory tracking control of a de-icing robot with an n-link robot manipulator. A robust fuzzy control based on adaptive sliding mode technique for precise trajectory tracking of a deicing robot is presented in this paper. The global controller is composed of three terms. The fuzzy inference system is utilized to approximate the unknown system structure and parameters, and the adaptive sliding mode control term is adopted to counteract the perturbations of the de-icing robot system. Meanwhile, a compensation term is designed to compensate the modeling errors, the approximation errors and others. The online adaptive laws of the controller parameters are derived via Lyapunov function method to guarantee the system stability. Finally, the experimental apparatus is provided to verify the correctness and effectiveness of the proposed scheme. Experimental results show that this scheme has more fast dynamic response and higher tracking precision than traditional feedback linearization control, and removes the control chattering phenomenon which is a main disadvantage of conventional sliding mode control in terms of robustness.

Improving transmission efficiency, quality factor, channel spacing and crosstalk levels are the top priorities in designing optical demultiplexers, suitable for wavelength division multiplexing applications. In this paper we proposed a novel structure for designing optical demultiplexer based on photonic crystal ring resonator. For performing wavelength selection task, we used two ring resonators. The resonance wavelength of the ring resonators depends on the dimensions of the ring core, therefore we chose two different values for the lattice constant of the ring resonators core section. As a result, our proposed structure is capable of selecting two optical channels with central wavelength equal to 1552.2 nm and 1553.3 nm. The channel spacing is 1.1 nm. The transmission efficiency of both channels is more than 99% and the crosstalk level is better than -11 dB.

A novel ultra-wideband (UWB) radar system is showed in this paper. It contains a UWB picoseconds pulse transmitter, a balanced sampling receiver and antennas. The radar transmitter produces a couple of balanced pulses with very fast leading edges and high amplitude when the pulse repetition frequency (PRF) is up to 1MHz. The receiver downconverts the echo signals from the antenna. The transmitter and the receiver both take the balanced modes that they can integrate directly with antennas, and they all have wide bandwidths. Measurement results demonstrate that this radar system is well used for sensing objects without destruction. And it can achieve both fine range resolution and enough operating distance at the same time, which enhances the capacity for target detection and classification effectively.

Wide-area integrated impedance protection (WIIP) algorithm based on wide-area measurement system is proposed for the purpose of improving the reliability and sensibility of fault component identification of wide-area protection. Two commonly used methods nowadays in wide-area protection are the current differential protection (CDP) and the directional pilot protection (DPP). The CDP, though responsive to all types of system faults, is subject to the distributed capacitance and earth resistance of transmission line; the DPP, which is easy to implement and does not need much traffic, is subject to system oscillations, conversion failure, and two phases operation. Integrating the advantages of these two algorithms, WIIP is obtained by evaluating in virtue of the ratio of the average voltages to the sum of all incoming and outgoing currents at each protected objects. The advantages of WIIP are verified by the fault analysis of two-terminal system and multi-terminal system. The research results show that WIIP presented in this paper is more preferable than CDP in the aspect of the sensitivity and DPP in the aspect of the dependability. The simulation effects can be obtained by using WIIP method applied in the case of abnormal operations of relay protections, circuit breakers, measurement error scenarios and substation DC failure.