Recent Advances in Electrical & Electronic Engineering - Volume 8, Issue 1, 2015

In this paper, a switching scheme based on minimization of total harmonic distortion (MTHD) of line voltage is studied. MTHD is suitable for some cases e.g. multilevel electrical drives and flexible AC transmission systems devices such as multilevel static var compensator, multilevel unified power quality conditioner and multilevel unified power flow controller, where DC link voltages are altering. By using MTHD the DC link values are set to the predefined values in order to optimize THD. In this paper the recently developed evolutionary optimization method named imperialist competitive algorithm (ICA) is used to solve MTHD problem. MTHD minimization is directly applied to line-to-line voltage waveform and the results compared with the case of a multilevel inverter with constant DC sources. The comparison of results validates the efficiency of MTHD in decreasing the THD value. Also, the obtained results compared with the results given in the recently published paper using GA, confirmed that ICA is more effective in this regard. Simulation and Experimental results are based on a seven-level multilevel inverter to verify the obtained results.

As the multimedia social network develops rapidly, protocols protecting the security of realtime multimedia are becoming very significant. The ZRTP protocol, one of Real-time Transport Protocols (RTPs) for real-time multimedia applications, has many advantages compared with others. Though the calculation cost is relatively high, the ZRTP protocol provides perfect forward secrecy and authentication against man-in-the-middle attack. As so many formal verification tools were proposed recently, formal method has become one of the main methods of security protocol analysis. However, the formal verification tools are rarely used for the Real-time Transport Protocols. In this paper, we innovatively utilize the formal verification tool Scyther- Compromise and Tamarin to analyse the ZRTP protocol. According to the results, we find that the ZRTP protocol is insecure under the eCK model though it provides the perfect forward secrecy property. The adversary can impersonate the endpoint when the shared secrets are revealed. Besides, the experiments of this paper show that the formal method can perform perfectly and play an important role in protocol analysis.

The main feature of existing delegation authorization models focuses on whether the delegatee could execute the delegated privileges, and delegator’s platform would be trusted or not. The paper proposed a delegation authorization security protocol based on remote attestation in multimedia social networks environment. Multimedia contents’ trusted delegation authorization can be guaranteed in the protocol. This protocol not only ensures delegator and the multimedia server trust in delegatee’s authentication and platform integrity, but also achieves the trusted access to the multimedia. Delegation verification, message interactions between entities are presented. The potential attacks are enumerated and analyzed, and the delegation authorization protocol based on remote attestation applied in Digital Rights Management implementing the trusted delegation and usage control functions compared by the other protocols available.

There are different kinematics and static stiffness characteristics for different structure parameters of the same type Parallel mechanism. So the reasonable design of the structure parameters becomes a key problem of parallel mechanism structure design. In this paper, the structure parameter optimization design method of 3-UPU parallel mechanism is proposed based on the comprehensive dexterity. First, the position mathematical model of Parallel mechanism is derived and the Jacobi matrix is established. By two methods (the condition number evaluation and the comprehensive dexterity evaluation), the structure parameters optimization design of 3-UPU parallel mechanism is proposed. Through analysis, the latter is superior to the former. The parallel mechanism structure parameters are optimized by the latter. The results show: In the known workspace and the considered mechanism structure, when the comprehensive dexterity is 1.26≤e≤1.28 , the optimized parameters meet the design requirements. And the data is beneficial for the error analysis of parallel mechanism.

In this paper, a bayesian framework for fault detection and isolation (FDI) based on kalman filtering is developed. Furthermore, in order to detect the faults affecting on the covariance matrix of the kalman filter, a real-time approach is presented. This proposed framework extracts the proper behavior of a mobile robot besides simultaneously localization and map building (SLAM). Actually the framework is a combination of the kalman filter and bayesian networks. Learning the model of the world is difficult. In particular when the system dynamics become nondeterministic, all aspects of the system cannot be directly observed and the sensors are subjected to noise. In many situations, learning a complete model is not possible. Therefore, only probabilistic models which are capable of taking uncertainty of sensors and environment can be employed. In this paper, we describe a framework as a composition between model-free and model-based systems. Model learning is perfectly based on bayesian network (BN) and fault detection is done by kalman filter. Experimental results show that the learned model outperforms the traditional BN. We demonstrate how the resulting algorithm can be used to detect faults in a complex system. Proposed method is not very sensitive to changing the map of robot. However, the Bayesian network and dynamic Bayesian network are very sensitive to changing the map and in the presence of the fault. The proposed method is tested in a real home environment with a mobile robot.

With the development of digital technology, more and more applications of current phase differential protection have been implemented in smart power grid and large power system, thereby reducing the dependency of wide area differential protection to accurate synchronous sampling. In this paper, the transmitted sample values are re-treated to promote implementation of WCPDP in the actual projects based on 0-1 quantitative principle. To enhance the WCPDP design and application, certain topics are concerned in the article respectively, such as segregated current starting algorithm, synchronization correction method and wide area protection scheme. The simulation results show that the WCPDP proposed by the paper has smaller amount of communication traffic, simpler principle, faster action and higher sensitivity which can accommodate the working conditions of high-resistance grounding fault, open-phase operation and evolving fault.

Aiming at the non-stationary characteristics of gas outburst time series, a novel gas outburst prediction model is presented in this paper. The proposed model is based on the extreme learning machine and empirical mode decomposition. First, the gas concentration time series is decomposed into a series of subsequence and residual quantity with EMD in order to reduce the calculation of local signal analysis for gas concentration in the scale and improve the accuracy of prediction. Then, each of the subsequence and residual quantity is predicted with ELM. Finally, the resultant prediction is obtained by combining the molecular sequences and residual quantity prediction. Considering the acquisition of gas concentration at mine working face as an example, the simulation results show that the EMD - ELM model is superior than ELM and LSSVM (Least Squares Support Vector Machine) model in prediction accuracy and the training speed.

The problem of modeling and D-stability analysis for discrete-time control systems in networked environments is researched. Firstly, a new modeling approach is proposed to describe the network behaviors into a unified framework such as random network-induced delays, packet dropout, and packet disorder etc. And the overall mathematic model of discrete-time networked control systems is derived with state feedback control strategy. Then with this model, the D-asymptotic stability condition, which is dependent on the upper bound of the equivalent network-induced delays, is presented in terms of spectra method. These can guarantee the performance in the presence of communication constraints. Finally, a simulation example is given to demonstrate the effectiveness and efficiency of the proposed theoretical results.

Reconfiguration methods of radiation pattern in bipolar-excited plasma antenna system are studied in this paper. The reconfiguration model of bipolar-excited plasma antenna is analyzed by using Boltzmann equation, BGK collision model and related theory of antenna, etc. The effects of plasma parameters on the radiation pattern are simulated by CST software. Through related experiments, the validity of reconfiguration model is testified. Results obtained indicate that the model has good precisions and can be used to calculate and analyze the bipolar-excited plasma antenna.