A hybrid flyback LED driver with utility grid and renewable energy interface
In renewable energy sources, the objective is maximum extraction and utilization of the available power. In this paper a hybrid flyback converter with multi ports-an AC Grid, a PV and a DC LED ports — is proposed to be used as an LED driver. The converter has the capability to achieve two objectives: first to maintain a continuous supply to the LED lighting system either from the Photovoltaic (PV) panel or the grid, and second to achieve maximum utilization of the solar PV panel by tracking the maximum power point and exporting surplus power to the grid, or getting the power deficit from the grid. The topology of the converter, operating principle, modes of operation and control structure are presented in this work. The concept of the hybrid flyback converter is verified using Matlab Simulink®. An experimental prototype is developed and tested for a 120-watt system, with 35 VDC solar panels, 120 Vrms 60 Hz grid and 24 VDC LED lights.
Optimum Design of the Current-Source Flyback Inverter for Decentralized Grid-Connected Photovoltaic Systems
Two alternative modes of operation for the current-source flyback inverter are investigated in this paper. The discontinuous conduction mode (DCM), where a constant switching frequency (CSF) control method is applied, and the boundary between continuous and DCM (BCM) that is introduced for photovoltaic (PV) applications in this paper (where a variable switching frequency control method is applied). These two control methods are analytically studied and compared in order to establish their advantages as well as their suitability for the development of an inverter for decentralized grid-connected PV applications. An optimum design methodology is developed, aiming for an inverter with the smallest possible volume for the maximum power transfer to the public grid and wide PV energy exploitation. The main advantages of the current-source flyback inverter are very high-power density and high efficiency due to its simple structure, as well as high-power factor regulation. The design and control methodology are validated by personal computer simulation program with integrated circuit emphasis (PSPICE) simulation and experimental results, accomplished on a laboratory prototype.
Small data optimized radio access network signaling/control design
The fast adoption of smart phone triggers the migration of tremendous internet applications from desktop to mobile terminal, as well as various inherently mobile oriented applications. Among them, Instant Message (IM) represents a large portion of applications. Unlike over traditional wired network, IM brought a great trouble to the mobile network called “signaling storm” due to its small data dominated traffic profile. This paper conducts a comprehensive analysis on the signaling/control overhead of IM, compared with streaming oriented voice/video applications. It figures out that shift from connection oriented to connectionless can solve the problem. A new slim Radio Resource Control (RRC) state with corresponding slim signaling transfer procedures is proposed for the connectionless scheme. Numerical results show that great signaling/control saving can be achieved with our new design.