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In this paper, a control method is proposed that allows the extraction of maximum power from each individual photovoltaic string connected to the Modular Multilevel Converter (MMC) and inject balanced power to the AC grid. The MMC solution used does not need additional DC–DC converters for the maximum power point tracking. In the MMC, the photovoltaic strings are connected directly to the sub-modules. It is shown that the proposed inverter solution can provide balanced three-phase output power despite an unbalanced power generation. The maximum power of the photovoltaic string is effectively harnessed due to the increased granularity of the maximum power point tracking. An algorithm that tracks the sub-module capacitor voltages to their respective voltage references is proposed. A detailed modeling and control method for balanced operation of the proposed topology is discussed. The operation of the MMC under unbalanced power generation is discussed. Simulation results are provided that show the effectiveness of the proposed control under unequal irradiance.

Lithium-ion (Li-ion) batteries have been competitive in Electric Vehicles (EVs) due to their high energy density and long lifetime. However, there are still issues, which have to be solved, related to the fast-charging capability of EVs. The pulsed current charging technique is expected to improve the lifetime, charging speed, charging/discharging capacity, and the temperature rising of Li-ion batteries. However, the impact of the pulsed current parameters (i.e., frequency, duty cycle, and magnitude) on characteristics of Li-ion batteries has not been fully understood yet. This paper summarizes the existing pulsed current modes, which are positive Pulsed Current Mode (PPC) and its five extended modes, and Negative Pulsed Current (NPC) mode and its three extended modes. An overview of the impact of pulsed current techniques on the performance of Li-ion batteries is presented. Then the main impact factors of the PPC strategy and the NPC strategy are analyzed and discussed. The weight of these impact factors on lifetime, charging speed, charging/discharging capacity, and the temperature rising of batteries is presented, which provides guidance to design advanced charging/discharging strategies as well as to determine future research gaps.

This paper utilizes a Wireless Smart Battery Management System (WSBMS) to manage battery cells in Electric Vehicles (EVs). WSBMS is the cell-level Battery Management System (BMS) based on wireless communication. Compared with the conventional modularized BMS, the proposed system has the advantages of high fault tolerance and sufficient scalability. In addition, the proposed balancing algorithm based on the state-ofhealth (SOH) and the state-of-charge (SOC) can balance battery cells with any number, different aging states, and reasonable capacity deviation. A prototype is built, and the balancing algorithm is verified by simulation and experimental results considering four cases with different states of battery cells.

Modular Multilevel Converter (MMC) topology has emerged as an attractive solution for Photovoltaic (PV) applications. Such a structure due to its inherent modularity allows distributed architecture of utility scale PV plant. Moreover, converters scalability allows for direct connection to the medium voltage grid by avoiding the need for the step-up transformer. The isolation is provided at the interface between the PV array and the MMC by using an isolated DC-DC converter. In this work the MMC performance is evaluated and compared with the main central inverter configurations in terms of annual energy yield, efficiency and levelized cost of energy. Efficiency curve from no load to full load is obtained for the MMC through simulations using standard IGBT half-bridge modules. It is seen that the efficiency curve is flat for a wide range of loads resulting in a higher annual energy yield and lower Levelized Cost of Energy (LCOE).

Abstract-The modular structure and the many other advantages of the Modular Multilevel Converter makes it an attractive converter for Battery Energy Storage Systems, allowing the battery units to be distributed throughout the convert, connected in each submodule. However, such an arrangement results in large oscillating components in the battery current, which is harmful to battery performance and lifetime. In most literature this is solved using DC-DC converters as active interfaces between battery and submodule. This paper investigates a passive filter arrangement as an alternative solution to the DC-DC converters. Where the batteries are interfaced with the submodules using a passive filter that suppresses the fundamental component and control technique that injects circulating current to suppress second harmonic component. It is concluded that this passive technique could be an attractive solution especially where high reliability is of concern.