An architecture of multiple-integrated converter modules sharing an unfolding full-bridge inverter with a pseudo DC-link (MIP) is proposed for grid-connected photovoltaic (PV) systems in this paper. The proposed configuration can improve the power conversion, the control circuit complexity and the cost competitiveness. The proposed MIP is composed of distributed flyback dc-dc converters (DFC) and an unfolding full bridge inverter with an ac filter. The DFCs can eliminate the shading effect by using the individual maximum power point tracking (MPPT). In conventional flyback-type single-phase utility interactive inverter, discontinuous conduction mode (DCM) and boundary conduction mode (BCM) are popular because of the inherent constant current-source characteristics more desirable for grid-connection and of the simple procedures for the controller design. However, the operating mode suffers from a large current stress of the circuit components, which leads to the low power efficiency. To avoid this, the DFCs operates under Continuous Conduction Mode (CCM) that allows reduced current stresses and increased power efficiency, as well as the low material cost. The current control loop of the converters employ primary-side regulation contributing to improvement of dynamics as well as the cost reduction significantly due to the elimination of high linearity photo-coupler device. Development of a new DC current loop that maintains the level of DC current injection into the grid within the levels stipulated by IEEE 1547 will be dealt as well. The performance validation of the proposed design is confirmed by experimental results of a 200W hardware prototype.
In this paper, an integrated maximum power point tracking (MPPT) controller system using a ZigBee wireless communication module is proposed for multimodal power converters as a concept of an intelligent photovoltaic (PV) module of PV power conditioning systems. The proposed scheme can integrate all information under a single host controller to realize low-cost manufacturing. It can also simplify the monitoring and supervision processes through machine-to-machine communications for the smart-grid. The voltage and current information for each module are periodically sampled and transferred to the central inverter (or another host server) through the ZigBee module. After the transmission process, the MPPT control algorithm derives each of the PV voltage reference parameters to return to each PV module accordingly. The technical benefits of the proposed approach is the configuration of a PV-controller system composed of a single digital-signal processor (DSP), low-cost analog controllers, and some mandatory communication peripherals used to monitor the distributed multimodules. Also, the method is quite desirable for supervision and monitoring of the overall system due to its centralized control structure. For the experimental validation of the proposed MPPT control, multiple ZigBee (XBee-PRO series) modules, as well as a DSP, dual-module solar simulators, and a couple of 50 W dc-dc power conversion hardware prototypes were utilized.Index Terms-Communication networks, machine-to-machine, maximum power point tracking (MPPT), photovoltaic (PV) systems, ZigBee.
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