Photovoltaic (PV) grid-connected system requires the inverter possesses excellent dynamic and static characteristics. In view of the mathematical model of the inverter is nonlinear, we will adopt a kind of nonlinear control strategy called Passivity-Based Control (PBC) based on current model. First we establish the standard EulerLagrange (EL) current mode for inverter, then we also prove that this inverter is strictly passive. Based on passivity of inverter, we can redistribute the system energy, and adopt the approaches of injecting damping and decoupling to improve system performance. In this paper, we can make the power factor of inverter achieve one, and current of inverter output can fast track the grid voltage, we can also make the active power of system fast track the PV array maximum power point. Usually, we can use Single Chip Microcomputer or other kinds of computer with this algorithm for our design, this algorithm can be programmed with the computer language, such as C/C++ and assembly language, etc. Simulation results show that passivity-based control based on current model method can make the inverter possess better robustness and dynamic.
Key management plays fundamental role in research on security service in wireless sensor networks (WSNs). However, due to the resource constraints, establishing pairwise keys in WSNs is not a trivial tasks. Several exiting key management schemes have been proposed in literature to establish pairwise keys between sensor nodes, but they either can not offer strong resilience against node capture attacks or have overly large memory requirement to achieve high degree of connectivity. In this paper, we prose an efficient pairwise key management scheme. In the proposed scheme, the sensor nodes are given different security level and the compromised sensor nodes cannot disclose the key information in the sensor nodes which have higher security level The analysis indicates that compared with existing approaches, this proposed scheme offers a stronger resilience against node capture attack.
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