Ageing Mitigation and Loss Control Through Ripple Management in Dynamically Reconfigurable Batteries

Dynamically reconfigurable batteries merge battery management with output formation in ac and dc batteries, increasing the available charge, power, and life time. However, the combined ripple generated by the load and the internal reconfiguration can degrade the battery. This paper introduces that the frequency range of the ripple matters for degradation and loss. It presents a novel control method that reduces the low-frequency ripple of dynamically reconfigurable battery technology to reduce cell ageing and loss. It furthermore shifts the residual ripple to higher frequencies where the lower impedance reduces heating and the dielectric capacitance of electrodes and electrolyte shunt the current around the electrochemical reactions.Comment: 8 pages, 8 figure

A proposed single-phase five-level PFC rectifier for smart grid applications: an experimental evaluation

The use of PFC rectifiers has assumed an increasingly preponderance, contributing in a decisive way to improve the power quality indices, since they allow to operate with sinusoidal current on the ac side and with controlled voltage on the dc side. In this paper is proposed a novel PFC rectifier that allows five levels of voltage. As noted in the paper, it presents a number of interesting advantages when compared to the conventional five level PFC rectifier, mainly because it requires less passive and active semiconductors to produce the different voltage levels and requires less hardware resources to implement the gate driver circuits. The proposed five level PFC (5L PFC) rectifier operates in boost mode and has a single dc link (although with a midpoint to achieve the various levels), being an important feature for applications in smart grids (e.g., smart electrical appliances and electric mobility chargers). The key topics of the 5L PFC rectifier are addressed and discussed based on the analysis of the principle of operation. As current control strategy it was adopted the model predictive control. Experimental results in steady and transient state were considered for an effective validation of the 5L PFC rectifier, verifying the operation with: sinusoidal current on the ac side; multi level operation with five levels; controlled dc link voltage.FCT - Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2019. This work has been supported by FCT Project newERA4GRIDs PTDC/EEI-EEE/30283/2017 and by ERDF - European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT, within project. Mr. Tanta was supported by FCT PhD grant with a reference PD/BD/127815/2016

Compensated State-Space Model of Diode-Clamped MMCs for Sensorless Voltage Estimation

Modular multilevel converters are well known in the energy sector. Generally, their stable operation is at the expense of numerous sensors, communication burden, and computationally expensive balancing strategies that challenge their expansion to cost-driven applications. Hence, introducing a sensorless voltage-balancing strategy with a simple controller is an attractive objective. Diode-clamped modular multilevel converters (MMCs) offer a simple and effective solution by providing a unidirectional balancing path between two modules through a diode. Ideally, the modulation technique should compensate for the lack of bidirectional energy transfer; hence open-loop operation is possible. Although the sensorless operation is desirable to reduce costs, good knowledge of the modules' voltages for system monitoring, and protection functions still improves operation in some applications or is mandatory in others. However, information should not be at the cost of additional sensors and communication bandwidth. This article develops a compensated state-space model for diode-clamped MMCs to estimate module voltages using an optimal estimator without any direct measurement at module levels. The model considers the effect of the diode-clamped branches and their balancing effect, resulting in 30%-50% reduction in estimation error compared to the conventional models using similar estimators. Simulations and experiments further confirm the provided analysis, where the estimator achieves &gt;97.5% accuracy.</p

General Decoupling and Sampling Technique for Reduced-Sensor Battery Management Systems in Modular Reconfigurable Batteries

The capacity and voltage rating of battery packs for electric vehicles or stationary energy storages are increasing, which challenge battery management and monitoring. Breaking the larger pack into smaller modules and using power electronics to achieve dynamic reconfiguration can be a solution. Reconfigurable batteries come with their own set of problems, including many sensors and complex monitoring systems, high-bandwidth communication interfaces, and additional costs. Online parameter estimation methods can simplify or omit many of these problems and reduce the cost and footprint of the system. However, most methods require many sensors or can only estimate a subset of the elements in the module’s equivalent circuit model (ECM). This paper proposes a simple decoupling technique to derive individual modules’ voltage and current profiles from the output measurements without direct measurement at the modules. The determined profiles can achieve a high sampling rate with minimum communication between the battery management system (BMS) and the modules. With accurate profiles, an estimation technique can easily determine the parameters of the modules. Provided simulations and experiments confirm this claim by estimating the parameters of a first-order ECM with a parallel capacitor. The proposed technique reduces the number of sensors from 2N + 2 to only two at the pack’s output terminals