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Considering the diversity of battery data under dynamic test conditions, the stability of battery working data is affected due to the diversity of charge and discharge rates, variability of operating temperature, and randomness of the current state of charge, and the data types are multi-sourced, which increases the difficulty of estimating battery SOH based on data-driven methods. In this paper, a lithium-ion battery state of health estimation method with sample transfer learning under dynamic test conditions is proposed. Through the Tradaboost.R2 method, the weight of the source domain sample data is adjusted to complete the update of the sample data distribution. At the same time, considering the division methods of the six auxiliary and the source domain data set, aging features from different state of charge ranges are selected. It is verified that while the aging feature dimension and the demand for target domain label data are reduced, the estimation accuracy of the lithium-ion battery state of health is not affected by the initial value of the state of charge. By considering the mean absolute error, mean square error and root mean square error, the estimated error results do not exceed 1.2% on the experiment battery data, which highlights the advantages of the proposed methods. [ABSTRACT FROM AUTHOR]

Summary: The application of modular multilevel converters (MMC) in medium voltage static synchronous compensators (STATCOMs) has been investigated in recent years. A huge challenge for MMC‐STATCOM is to compute the gain of the controllers. Therefore, the contribution of this paper is the proposal of a control tuning methodology for MMC‐STATCOM. For this purpose, the control and tuning strategies are presented. Since MMC‐STATCOM can employ different modulation strategies, two distinct modulation strategies are considered: nearest‐level control, with variable switching frequency; and phase‐shifted carrier pulse‐width modulation, with fixed switching frequency. Moreover, the proposal was validated through simulation and an experimental platform. The results indicate that the power response follows the reference, besides supplying the internal losses of the converter. The 10% ripple tolerance of the submodule voltages is respected in steady state for both modulation strategies. Moreover, the 5% total demand distortion (TDD) limit recommended by the Institute of Electrical and Electronics Engineers (IEEE) standard is attended. These results demonstrate the effectiveness of the controls employed. [ABSTRACT FROM AUTHOR]

The worldwide energy revolution has accelerated the utilization of demand-side manageable energy systems such as wind turbines, photovoltaic panels, electric vehicles, and energy storage systems in order to deal with the growing energy crisis and greenhouse emissions. The control system of renewable energy units and energy storage systems has a high effect on their performance and absolutely on the efficiency of the total power network. Classical controllers are based on integer-order differentiation and integration, while the fractional-order controller has tremendous potential to change the order for better modeling and controlling the system. This paper presents a comprehensive review of the energy system of renewable energy units and energy storage devices. Various papers are evaluated, and their methods and results are presented. Moreover, the mathematical fundamentals of the fractional-order method are mentioned, and the various studies are categorized based on different parameters. Various definitions for fractional-order calculus are also explained using their mathematical formula. Different studies and numerical evaluations present appropriate efficiency and accuracy of the fractional-order techniques for estimating, controlling, and improving the performance of energy systems in various operational conditions so that the average error of the fractional-order methods is considerably lower than other ones. [ABSTRACT FROM AUTHOR]

Modern wind turbines with increasing power levels are continuously emerging. These power levels are reaching a point where excessively high currents are obtained if the traditional low-voltage wind-turbine structure is adopted. High currents lead to excessively high losses and the need for bulky and heavy conductors to carry them. A medium-voltage structure should be a more competitive alternative to be adopted in high-power wind turbines. In this article, a new converter solution with a modular multilevel structure suitable for driving modern/future high-power medium-voltage wind turbines is proposed. This converter topology has desirable features common to modular multilevel converters, such as the improved reliability at high voltage levels, and the possibility to synthesize high-power-quality staircase-shape voltages, which leads to low requirements for harmonic and ${dv}/{dt}$ filters. Furthermore, the proposed converter presents reduced capacitance and inductance requirements compared with other well-established modular multilevel converter topologies, which should result in a lighter and more compact solution. The proposed solution could potentially allow for the reduction of the overall costs of the supporting structure required to withstand the weight of the wind turbine. Simulation and experimental results are presented in this article to validate the proposed topology. [ABSTRACT FROM AUTHOR]

A new state-observer-based current balancing method for Modular Multilevel Converters with Interleaved half-bridge Sub-Modules (ISM-MMC) is presented in this article. The developed observer allows estimating currents through interleaved half-bridge legs in each submodule of ISM-MMC based only on arm current and submodule's capacitor voltage measurements. Then, the interleaved current balancing control uses the estimated currents to reduce the interleaved currents imbalance caused by upstream control actions. This technique minimizes the number of required current sensors in ISM-MMC, thereby reducing the converter's cost, weight, and volume. Capabilities of the proposed sensorless interleaved currents balancing control have been tested against standard parameter tolerances of the composing passive elements. In addition to that, a novel capacitor voltage balancing strategy for MMCs is developed. The new algorithm contains the main advantages of the classical sorting-based capacitor voltage balancing methods while providing an opportunity to decouple two balancing tasks of ISM-MMC, namely capacitor voltage and interleaved legs current balancing. The feasibility of the proposed methods is verified by extensive simulation and experimental tests on a laboratory prototype by the corresponding system response under the output characteristics variation and interleaved current control perturbation. [ABSTRACT FROM AUTHOR]

This article proposes a decoupled control scheme for the modular multilevel converter (MMC) to reduce the total harmonic distortion (THD) and eliminate one specific harmonic. First, to realize the decoupled control between the ac and dc paths of the MMC, an improved nearest level control (INLC) method is proposed. It applies the round function to generate the ac output voltage levels, instead of the arm output voltage levels. Thus, a staircase wave is generated by the INLC method. Then, by adding an additional pulse to each quarter of the staircase wave, one specific harmonic can be eliminated without optimizing each conduction angle. Furthermore, a decoupled circulating current fuzzy control method is proposed to suppress the second-order harmonic and balance the arm energy. By this decoupled control structure, the output voltage and the circulating current can be controlled independently. Taking the fifth-order harmonic as an example, simulation and experimental results validate that the proposed scheme can simultaneously realize THD reduction and one specific harmonic elimination in the MMC output voltage. [ABSTRACT FROM AUTHOR]

The open-circuit fault detection and localization (FDL) technique can improve the reliability of the modular multilevel converter (MMC). However, the conventional software-based FDL methods usually have a heavy computation burden or a limited localization speed. This article proposes a simplified and fast software-based FDL approach for the grid-connected MMC. First, the errors between the measured state variables (the output current and the circulating current) and their estimated values are calculated. By comparing these errors with their threshold values, the switch fault can not only be detected but also be localized to the specific arm. Then, the capacitor voltages in this faulty arm are collected, and the submodule (SM) with the highest capacitor voltage is selected. To confirm the switch fault in this SM, a modified Pauta criterion is presented to check the abnormal voltage data. As a result, the computation burden of the proposed software-based FDL approach is significantly reduced, and the faulty SM can be localized in a short period. Simulation and experimental results verify that the proposed approach can effectively detect and localize different open-circuit faults, and it is immune to the step of power references. [ABSTRACT FROM AUTHOR]

A new Modular Multilevel Converter with Interleaved half-bridge Sub-Modules (ISM-MMC) is proposed in this article. The ISM-MMC exhibits higher modularity and scalability in terms of current ratings with respect to a conventional MMC while preserving the typical voltage-level adaptiveness. The ISM-MMC brings the known advantages of classical MMC to low-voltage, high-current applications making it a novel candidate for the sector of ultrafast chargers for all types of electric vehicles (EVs). This advanced topology makes it possible to easily reach the charging power of the EV charging system up to 4.5 MW and beyond with a low-voltage supply. To operate the new converter, a hybrid modulation scheme that helps to exploit the advantages of the interleaving scheme is implemented and explained in this article. It has been verified that the typical MMC control methods are still applicable for ISM-MMC. A comparative study between classical MMC and ISM-MMC configurations in terms of output characteristics and efficiency is also given. Furthermore, it has been demonstrated that the number of ac voltage levels is synthetically multiplied by the number of interleaved half-bridge legs in submodules. Simulations, hardware in the loop, and experimental tests are carried out to demonstrate the feasibility of the proposed topology and the implemented modulation scheme. [ABSTRACT FROM AUTHOR]

Applications of lithium-ion batteries are widespread, ranging from electric vehicles to energy storage systems. In spite of nearly meeting the target in terms of energy density and cost, enhanced safety, lifetime, and second-life applications, there remain challenges. As a result of the difference between the electric characteristics of the cells, the degradation process is accelerated for battery packs containing many cells. The development of new generation battery solutions for transportation and grid storage with improved performance is the goal of this paper, which introduces the novel concept of Smart Battery that brings together batteries with advanced power electronics and artificial intelligence (AI). The key feature is a bypass device attached to each cell that can insert relaxation time to individual cell operation with minimal effect on the load. An advanced AI-based performance optimizer is trained to recognize early signs of accelerated degradation modes and to decide upon the optimal insertion of relaxation time. The resulting pulsed current operation has been proven to extend lifetime by up to 80% in laboratory aging conditions. The Smart Battery unique architecture uses a digital twin to accelerate the training of performance optimizers and predict failures. The Smart Battery technology is a new technology currently at the proof-of-concept stage. [ABSTRACT FROM AUTHOR]

The pulsed current has been proposed as a promising battery charging technique to improve the charging performance and maximize the lifetime for lithium-ion (Li-ion) batteries. However, the effect of the pulsed current charging is inconclusive due to the changeable current mode and conditions. This article systematically investigates the effect of various pulsed current charging modes, i.e., positive pulsed current mode, pulsed current-constant current mode, negative pulsed current mode, alternating pulsed current mode, sinusoidal-ripple current mode, and alternating sinusoidal-ripple current mode on battery performance. Moreover, a comprehensive analysis of the frequency impact on the quality of the current mode is performed. The current modes in this work are evaluated considering the maximum rising temperature, discharging capacity, and charging speed according to experimental results. Furthermore, this work provides guidance for developing pulsed current charging strategies to satisfy future charging requirements. [ABSTRACT FROM AUTHOR]

Temperature monitoring is of paramount importance for guaranteeing the safety and proper operation of lithium-ion batteries. Traditional temperature sensors suffer from heat transfer delay, where internal battery temperature cannot be measured directly. Motivated by this, this letter proposes a novel sensorless temperature estimation method based on broadband impedance spectroscopy. In this letter, pseudorandom sequence (PRS) with finite signal levels is utilized for impedance measurements. The measured impedance information is merged into an impedance-temperature model, which cooperates with a specially designed least-square method for temperature estimation. The proposed framework is robust against interference, whereas simple enough for online implementation. Experimental results suggest excellent estimation accuracy of the proposed method under different circumstances. [ABSTRACT FROM AUTHOR]

To improve the prediction accuracy and prediction speed of battery remaining useful life (RUL), this paper proposes an improved light gradient boosting machine (LightGBM)-based framework. Firstly, the features from the electrochemical impedance spectroscopy (EIS) and incremental capacity-differential voltage (IC-DV) curve are extracted, and the open circuit voltage and temperature are measured; then, those are regarded as multi HIs to improve the prediction accuracy. Secondly, to adaptively adjust to multi HIs and improve prediction speed, the loss function of the LightGBM model is improved by the adaptive loss. The adaptive loss is utilized to adjust the loss function form and limit the saturation value for the first-order derivative of the loss function so that the improved LightGBM can achieve an adaptive adjustment to multiple HIs (ohmic resistance, charge transfer resistance, solid electrolyte interface (SEI) film resistance, Warburg resistance, loss of conductivity, loss of active material, loss of lithium ion, isobaric voltage drop time, and surface average temperature) and limit the impact of error on the gradient. The model parameters are optimized by the hyperparameter optimization method, which can avoid the lower training efficiency caused by manual parameter adjustment and obtain the optimal prediction performance. Finally, the proposed framework is validated by the database from the battery aging and performance testing experimental system. Compared with traditional prediction methods, GBDT (1.893%, 4.324 s), 1D-CNN (1.308%, 47.381 s), SVR (1.510%, 80.333 s), RF (1.476%, 852.075 s), and XGBoost (1.119%, 24.912 s), the RMSE and prediction time of the proposed framework are 1.078% and 15.728 s under the total HIs. The performance of the proposed framework under a different number of HIs is also analyzed. The experimental results show that the proposed framework can achieve the optimal prediction accuracy (98.978%) under the HIs of resistances, loss modes, and isobaric voltage drop time. [ABSTRACT FROM AUTHOR]

This paper presents a new solution for filtering current harmonics in three-phase four-wire networks. The original four-branch star (FBS) filter topology presented in this paper is characterized by a particular layout of single-phase inductances and capacitors, without using any transformer or special electromagnetic device. Via this layout, a power filter, with two different and simultaneous resonance frequencies and sequences, is achieved--one frequency for positive-/negative-sequence and another one for zero-sequence components. This filter topology can work either as a passive filter, when only passive components are employed, or as a hybrid filter, when its behavior is improved by integrating a power converter into the filter structure. The paper analyzes the proposed topology, and derives fundamental concepts about the control of the resulting hybrid power filter. From this analysis, a specific implementation of a three-phase four-wire hybrid power filter is presented as an illustrative application of the filtering topology. An extensive evaluation using simulation and experimental results from a DSP-based laboratory prototype is conducted in order to verify and validate the good performance achieved by the proposed FBS passive/hybrid power filter. Index Terms--Active power filters, hybrid power filters, passive power filters, power line filters, power system harmonics, reactive power control.