Design of Decentralized Adaptive Sliding Mode Controller for the Islanded AC Microgrid With Ring Topology

Sliding mode control can restrain the perturbations generated from the intermittence of the renewable energy generation and the randomness of local loads when microgrids are operating in islanded mode. However, the microgrid consists of several subsystems and the interactions among them will cause the chattering problems under the overall sliding mode control. In this paper, the chattering restraint issues for voltage control of the islanded microgrid with a ring topology structure are investigated based on the decentralized adaptive sliding mode control strategies. Firstly, we construct a tracking error system with interconnections considering the power transmission among subsystems and nominal values of system states. Secondly, we design linear matrix inequalities (LMIs) according to the H∞ attenuation performance of the system external disturbances. Then, the tracking error performance and the control precision are guaranteed via the asymptotic stabilities of integral sliding mode surfaces. Adaptive laws are utilized to address the chattering problems of the sliding mode control. Finally, simulation results verify the effectiveness of the proposed decentralized control methods.

Design of captive portal LAN with redundancy connections

Captive portal networks are in great demand because users have privileged authentication in the form of usernames and passwords to enter the LAN network without having to share with other users. However, the captive portal network is difficult to implement redundant connection because it must be in the form of a ring topology and the application of a bridge network. Captive portal is a web page for the authentication process to enter the network where the authentication back end can use radius, kerberos, ldap with the AAA framework. Meanwhile, fault tolerance is a redundant connection mechanism as an alternative path provider if the main path is broken. Here there is a tiered mechanism so that fault tolerance can be implemented into the captive portal network. This study describes the process of designing a captive portal network starting from analyzing, conceptualizing and finally designing the network itself. The final result of this research is 2 pieces of redundancy connection network design to the captive portal framework.

Single-Line Bidirectional Optical Add/Drop Multiplexer for Ring Topology Optical Fiber Networks

A new type of passive single-line bidirectional optical add/drop multiplexer (SBOADM) is proposed and experimentally demonstrated. When the proposed SBOADM is placed as a node of a ring topology optical fiber network, the special routing function of the SBOADM can always drop down the desired downstream signals whether the signals are injected into the SBOADM in either the clockwise (CW) or counterclockwise (CCW) direction and can upload and send back the upstream signals via the reversed optical pathway of the downstream signals. Once fiber link failure occurs in the optical network, the blocked network connections can be recovered immediately by sending out the downstream signals in both the CW and CCW directions of the fiber ring. As in all passive devices, the SBOADM needs no power supply or complicated network management to achieve the bidirectional function. Thus, the proposed device is an optimal solution to enhance the stability and reliability of rapidly developed optical fiber networks.