In this paper, an advanced control strategy for grid-tied photovoltaic (PV) cascaded H-bridge (CHB) inverter is proposed. The circuit topology consists of a proper number of power cells (H-bridge configuration) connected in series and supplied by individual PV modules. The adopted control method is a mixed staircase-PWM technique performed by means of a sorting algorithm to determine cells' switching state. The cells' state is related to the need of charging or discharging a particular cell much more than the others by calculating the voltage error at each dc-link (e.g., by considering the difference between the maximum power point tracking (MPPT) reference and the measured quantity). A dedicated P&O MPPT permits to control independently the voltage of each dc-link; thus, increasing the power extraction even in mismatched conditions. In order to prove the effectiveness and feasibility of the proposed approach, a set of experiments are performed on a laboratory prototype of a single-phase five-level PV CHB. The control section is implemented on FPGA by using a dSPACE real-time hardware platform; thus, obtaining fully dedicated digital circuits. Experimental results show good performance in terms of MPPT efficiency, total harmonic distortion, and power factor in both normal operation and mismatch conditions.

In this paper a power converter based on a modular multilevel topology integrated with energy storage devices for directly supplying of traction motors is discussed. The Modular Multilevel Converter (MMC) is one of the emerging technology for high- or medium- voltage transformerless power conversion. The possibility to directly control the traction motors by means of a dc/ac MMC topology, using also integrated energy storage systems (ESS) for recovering the kinetic energy, is exploited. Furthermore, a simplified mathematical model of the MMC with integrated ESS has been developed in order to evaluate the behavior of the traction unit during a typical load-cycle. The control law of the traction motor, integrated with energy storage flow management, has been introduced. The numerical results reported in the paper permit to confirm the feasibility of the proposed design and control strategy for light travel vehicle.

Residual lifetime estimation has gained a key point among the techniques that improve the reliability and the efficiency of power converters. The main cause of failures are the junction temperature cycles exhibited by switching devices during their normal operation; therefore, reliable power converter lifetime estimation requires the knowledge of the junction temperature time profile. Since on-line dynamic temperature measurements are extremely difficult, in this work an innovative real-time monitoring strategy is proposed, which is capable of estimating the junction temperature profile from the measurement of the dissipated powers through an accurate and compact thermal model of the whole power module. The equations of this model can be easily implemented inside a FPGA, exploiting the control architecture already present in modern power converters. Experimental results on an IGBT power module demonstrate the reliability of the proposed method.

In this paper the design and the control of an individual PV (Photovoltaic) panel dc-ac converter based on a double coupled-inductors boost topology are discussed. The operation principle of the proposed circuit is analyzed. A proper calibration of the PV panel simulation model is performed. An optimization procedure is proposed for choosing the fundamental parameters of both converter and control law based upon sliding control technique. Furthermore, a Maximum Power Point Tracking (MPPT) approach based on a Perturb & Observe (P&O) algorithm is used to track the actual maximum power point through successive approximations. Finally, the proposed inverter is employed as a grid inverter in a single PV panel application. The numerical results reported in the paper permit to confirm the feasibility of the proposed design and control strategy.

In this paper the design and the control of a PV (Photovoltaic) AC-module based on a double coupled-inductors boost topology are discussed. This circuital configuration allows obtaining of the high voltage amplification needed in individual panel applications. The operation principle of the proposed circuit is analyzed and a proper calibration of the PV panel simulation model is performed. The adopted control strategy is based upon sliding control technique in order to exploit its well-known properties of robustness. Furthermore, a Maximum Power Point Tracking (MPPT) approach based on a Incremental Conductance (IC) algorithm is used to track the actual maximum power point. Finally, the numerical results reported in the paper permit to confirm the feasibility of the proposed design and control strategy.