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Simulating photovoltaic (PV) power systems becomes important when studying integration issues of the intermittent solar energy into electric grids. The accuracy of the maximum power point (MPP) in PV output model is a concern since it represents the capacity of power generation. This paper proposes a comprehensive approach to identify PV cell parameters and avoid model errors of the MPP based on standard and simplified equivalent circuits. The estimation accuracy has been improved while maintaining the computational simplicity. This paper begins with the definition of the performance index used to quantify the model accuracy at the MPP. Based on the availability of information from the manufacturer’s datasheets, the accuracy and complexity of different equivalent circuits are discussed and investigated. The proposed approach has been successfully tested for solar cells made of mono and multi crystalline material. [ABSTRACT FROM PUBLISHER]

The realm of hardware-in-the-loop simulation resorts to field-programmable gate arrays to achieve time steps below 1 \mu\s . Such low time steps are of importance for the aerospace and automotive industries, where power converters have their switching frequencies in the 10- to 200-kHz range. This paper proposes a network tearing technique that allows subsets of switches to be treated independently, alleviates embedded memory requirements, and reduces the computational burden. An iterative algorithm is used to determine the state of naturally commutated switches, thus offering a realistic model of the power converter, independently of its operation mode or topology. A Gauss-Jordan processing unit is implemented to solve interface voltages/currents from the torn circuit. Custom floating-point operators are used to ensure good accuracy, high-frequency operation, and low computational latency. A neutral-point-clamped converter case study is presented to demonstrate the effectiveness of the method. Simulation results are validated against a reference model at a 750-ns time step and a 30-kHz sine pulsewidth modulation switching frequency. [ABSTRACT FROM PUBLISHER]

This paper discusses the electrochemical modeling of a microphotosynthetic power cell (µ-PSC) in a similar way as the conventional fuel cell model while taking into consideration the electrochemical dynamics of the chemical contents of the cell. It also presents the development of an electrical equivalent circuit that represents the operation of the fabricated cell. The developed equivalent circuit is different from previous works in which they used the equivalent circuit of an ordinary solar cell. The proposed model predicts the performance of this type of power harvesting cell. The study includes the steady-state and transient responses when the cell is connected to an external load. In particular, the focus of this paper is related to the development of an electrical representation with a computationally efficient parameter model for real-time simulation and control. The performance of this model is simulated and results are evaluated and compared with experimental data. [ABSTRACT FROM AUTHOR]

Accurate estimation of power capacity is critical to ensure battery safety margins and optimize energy utilization. Power capacity estimators based on online identified equivalent circuit model have been widely investigated due to the high accuracy and affordable computing cost. However, the impact of noise corruption which is common in practice on such estimators has never been investigated. This paper scrutinizes the effect of noises on model identification, state of charge (SOC) and power capacity estimation. An online model identification method based on adaptive forgetting recursive total least squares (AF-RTLS) is proposed to compensate the noise effect and attenuate the identification bias of model parameters. A Luenberger observer is further used in combination with the AF-RTLS to estimate the SOC in real time. Leveraging the estimated model parameters and SOC, a multiconstraint analytical method is proposed to online estimate the power capacity. Simulation and experimental results verify that the proposed method is superior in terms of estimation accuracy and the robustness to noise corruption. [ABSTRACT FROM AUTHOR]

Large-scale circuit simulation poses a challenge to most simulation tools because of its high computational complexity. This paper presents an efficient method, which decouples the circuit topology and components’ characteristics in computation so as to make it suitable for large-scale circuit simulation. The proposed method is based on a circuit lemma, which indicates the relationship of branch voltages and currents. The proving process of this lemma is provided in this paper. The working principle of the proposed method is elaborated and its numerical stability is also analyzed. This method achieves nearly linear computational complexity and is very suitable for hierarchical and zonal computation. The proposed method is verified by real-time application on the more electric aircraft microgrid. Hardware-in-the-loop testing of this study case on Xilinx Virtex Ultrascale+ field programmable gate array (FPGA) board is achieved and the results are compared with PSCAD/EMTDC. The resulting waveforms from these two simulation tools show very good agreement on both normal and fault operation test scenarios, which demonstrates that the proposed method has very good performance on computational accuracy and efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a new average electrothermal model of the inductor dedicated to the computer analysis of dc–dc converters, such as a boost converter. The proposed model takes into account the influence of power losses in the ferromagnetic core on frequency and temperature. The considered model includes parameters, values of which are estimated on the basis of the catalog data of the inductor components—the core and the winding. To prove the usefulness of the average electrothermal model of the inductor, calculations of the characteristics of the boost converter are performed. The results of calculations are compared with the results of measurements and the good agreement between these results is achieved for two types of ferromagnetic cores made of powdered iron or ferrite. [ABSTRACT FROM AUTHOR]

Lithium (Li)-ion battery cells suffer from significant performance degradation at subzero temperatures. This paper presents a predictive control-based technique that exploits the increased internal resistance of Li-ion cells at subzero temperatures to increase the cell’s temperature until the desired power can be delivered. Specifically, the magnitude of a sequence of bidirectional currents is optimized such as to minimize total energy discharged. The magnitude of current is determined by solving an optimization problem that satisfies the battery manufacturer’s voltage and current constraints. Drawing bidirectional currents necessitates that a temporary energy reservoir for energy shuttling, such as an ultracapacitor or another battery, be available. When compared with the case when no penalty on energy withdrawn is imposed, simulations indicate that reductions of up to 20% in energy dispensed as heat in the battery as well as in the size of external storage elements can be achieved at the expense of longer warm-up operation time. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to present a six-phase induction machine (6PIM) model based on the so-called circuit-oriented approach suitable for simulation of electrical faults on both stator and rotor sides. This specific model has been developed by using only resistances, inductances, and controlled voltage sources. The coupling effects between both the stator and the rotor have been taken into account by the computation of stator–rotor mutual inductances. The model has been developed under the MATLAB/Simulink environment in order to have a universal tool that is easy to use with any control techniques. With this model, it is possible to simulate any type of electrical faults during the motion by closing or opening corresponding switches. The performances of the model have been validated by comparing simulation and experimental results of a 90-W 14-V 50-Hz two-pole 6PIM operating with different levels of load torque in healthy and faulty modes. Furthermore, this model has been associated to a fault-tolerant speed control method in phase opening occurrences in order to test the model accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes an improved hybrid method to compute the parameters of the two-diode model of photovoltaic (PV) module. Unlike previous methods, it attains the speed of the analytical approach by utilizing only datasheet information. Furthermore, its accuracy is not compromised as it does not require simplifications in its computation. Four parameters are determined analytically, while the remaining three are optimized by using an evolutionary algorithm, i.e., the differential evolution. The speed is improved because the parameters are optimized only once, i.e., at standard test condition, while the values at other conditions are computed analytically. Furthermore, a procedure to guide the initial conditions of the Newton–Raphson iteration is introduced. For validation, the algorithm is compared to other established computational methods for mono-, polycrystalline, and thin film modules. When evaluated against the experimental data, the mean absolute error is improved by one order of magnitude, while the speed is increased by approximately threefold. The standard deviation of the decision parameters over 100 independent runs is less than 0.1—which suggests that the optimization process is very consistent. Due to its speed and accuracy, the method is envisaged to be useful as a computational engine in PV simulator. [ABSTRACT FROM PUBLISHER]

The accuracy of power electronics simulation relies on the semiconductor switch model employed. Thus, in this paper where an ultrafast mechatronic circuit breaker (UFMCB) is implemented in real-time on the field programmable gate array, a detailed nonlinear thyristor model is proposed for extra device-level information regarding design evaluation. The cascaded thyristors impose a heavy computational burden on the UFMCB simulation, and node elimination is achieved following the proposal of a scalable thyristor model. For the convenience of the circuit breaker's integration into dc grid, a pair of coupled voltage–current sources is inserted as its interface, which achieves a reduction in the dimension of system admittance matrix, and the subsequent proposal of a relaxed scalar Newton–Raphson method further expedites the simulation by decomposing the nodal matrix equation. Meanwhile, the modular multilevel converter as a dc grid terminal adopts half-bridge and clamped double submodule topologies to test system performance in conjunction with the UFMCB. Real-time execution is achieved and the results are validated by ANSYS/Simplorer and PSCAD/EMTDC in device- and system-level, respectively. [ABSTRACT FROM AUTHOR]

The accuracy of a power-hardware-in-loop (PHIL) simulation is influenced by factors such as dynamics of the power amplifier (PA) and discretization of the real-time simulated part of the system. An open-loop voltage-source inverter (VSI) without an output filter is demonstrated to be a good choice for power amplification in terms of cost, size, design effort, bandwidth, and accuracy when the load on the PA is significantly inductive. An open-loop-VSI-based PA is shown to be accurate in emulating a synchronous generator, including the fast transients in the excitation control system. The discretization effects of the real-time simulator are captured effectively by the discrete-time (DT) modeling approach proposed in this paper. The DT model is shown to replicate fast transients in the PHIL simulation better than the existing continuous-time-based model. Stability of the PHIL simulation of a benchmark circuit is analyzed using the proposed DT modeling approach. The stability analysis is validated through simulations and experiments. The stability limits derived based on the proposed analysis are capable of suggesting maximum and minimum values of certain circuit parameters, as required for stability. [ABSTRACT FROM AUTHOR]

Supercapacitors benefit from unique features including high power density, long cycle life, wide temperature operation range, durability in harsh environments, efficient cycling, and low maintenance cost. This paper presents a validated lumped and computationally efficient electrical and thermal model for a cylindrical supercapacitor cell. The electrical model is a two-state equivalent electric circuit model with three parameters that are identified using temporal experiments. The dependence of the parameters on the state of charge, current direction and magnitude (20–200 A), and temperatures ranging from -40 °C to 60 °C is incorporated in the model. The thermal model is a linear 1-D model with two states. The reversible heat generation which is significant in double-layer capacitors is included in the thermal model. The coupling of the two models enables tuning of the temperature-dependent parameters of the electrical model in real time. The coupled electrothermal model is validated using real-world duty cycles at subzero and room temperatures with root-mean-square errors of (82 mV–87 mV) and (0.17 °C–0.21 °C) for terminal voltage and temperature, respectively. This accurate model is implementable in real-time power applications and also thermal management studies of supercapacitor packs. [ABSTRACT FROM PUBLISHER]

A detailed power transformer electromagnetic transient model would help in accurately predicting transient stresses and formulating adequate protection strategies in power systems. This paper presents a real-time nonlinear high-resolution magnetic equivalent circuit (HR-MEC) based transformer model on the field-programmable gate array for hardware-in-the-loop simulation. This model is inspired by the mesh generated in finite-element method (FEM) tools to depict the major flux paths in the transformer. All of the major nonlinear phenomena such as saturation, hysteresis, and eddy currents are captured in the transformer hardware emulation whose modules were developed in a 32-b floating point precision VHDL. The developed HR-MEC model and nonlinear numerical solution have been fully parallelized in hardware to achieve the lowest latency in the real-time implementation. The hysteresis in the transformer core is modeled using Preisach theory, and eddy currents are incorporated using a frequency-dependent network. The real-time results are validated using 3-D FEM analysis in JMAG software. [ABSTRACT FROM PUBLISHER]

Piezoelectric actuators (PEAs) have been widely used in nanotechnology due to their characteristics of fast response, large mass ratio, and high stiffness. However, hysteresis, which is an inherent nonlinear property of PEAs, greatly deteriorates the control performance of PEAs. In this paper, a nonlinear model predictive control (NMPC) approach is proposed for the displacement tracking problem of PEAs. First, a “nonlinear autoregressive–moving-average with exogenous inputs” (NARMAX) model of PEAs is implemented by multilayer neural networks; second, the tracking control problem is converted into an optimization problem by the principle of NMPC, and then, it is solved by the Levenberg–Marquardt algorithm. The most distinguished feature of the proposed approach is that the inversion model of hysteresis is no longer a necessity, which avoids the inversion imprecision problem encountered in the widely used inversion-based control algorithms. To verify the effectiveness of the proposed modeling and control methods, experiments are made on a commercial PEA product (P-753.1CD, Physik Instrumente), and comparisons with some existing controllers and a commercial proportional–integral–derivative controller are conducted. Experimental results show that the proposed scheme has satisfactory modeling and control performance. [ABSTRACT FROM PUBLISHER]

The efficiency of multiterminal dc (MTDC) grid simulation decreases with an expansion of its scale and the inclusion of accurate component models. Thus, the variable time-stepping scheme is proposed in this paper to expedite the electromagnetic transient computation. A number of criteria are proposed to evaluate the time-step and regulate it dynamically during simulation. Meanwhile, as the accuracy of results is heavily reliant on the switch model in the modular multilevel converter, the nonlinear behavioral model with a greater accuracy is proposed in addition to the classic ideal model, and their corresponding variable time-stepping schemes are analyzed. Circuit partitioning is effective in accelerating the MTDC grid simulation via fine-grained separation of nonlinearities. A subsequent large number of identical circuits enabled a massively parallel implementation on the graphics processing unit, which achieved a remarkable speedup over the CPU-based implementation. The inclusion of variable time-stepping schemes eventually makes the simulation of MTDC grid with highly detailed nonlinear switch models feasible. The results are validated by commercial device-level and system-level simulation tools. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) has attracted extensive research in recent years. An appropriate model is necessary to analyze stability or to design MMC controllers. Several published MMC models have been derived in single-phase form to simplify the modeling mathematics. However, little attention is given to the zero-sequence voltage, which introduces coupling in the single-phase model and leads to significant error. In this paper, after revealing the mechanism behind the zero-sequence voltage, a more accurate generalized single-phase MMC model is proposed, which eliminates the zero-sequence voltage coupling effect and is linearized based on harmonic state space (HSS) theory to precisely characterize the internal harmonic features of MMC. A systematic HSS modeling process is presented for both open-loop and closed-loop conditions. And the proposed model is generalized as it can incorporate different control strategy by controller transfer function substitution. Hence it is valuable to analyze MMC stability and dynamics. Model effectiveness is verified by simulation results. [ABSTRACT FROM AUTHOR]

Detailed high-order models of the insulated-gate bipolar transistor (IGBT) and the diode are rarely included in power converters for large-scale system-level electromagnetic transient (EMT) simulation on the CPU, due to the nonlinear characteristics albeit they are more accurate. The massively parallel architecture of the graphics processing unit (GPU) enables a lower computational burden by avoiding the computation of complex devices repetitively in a sequential manner and thus is utilized in this paper to simulate the wind farm-integrated multiterminal dc (MTdc) grid based on the modular multilevel converter (MMC). Fine-grained circuit partitioning is proposed so that the nonlinear switching elements are physically separated with the smallest circuit unit. By implementing these subsystems with the same attributes as a GPU program and computing it in a massively parallel manner, it is demonstrated that the GPU is able to achieve a significant speedup over multicore CPUs and its computation time incremental is much smaller when the MMC level scales up. The improved insight and accuracy of the proposed modeling methodology and the designed GPU program are validated at the system- and device-level by off-line commercial simulation tools. [ABSTRACT FROM AUTHOR]

Accurate stator turn fault (STF) modeling technique is of paramount importance to assess the machine fault behavior and develop fault detection and mitigation strategies for a fault-tolerant machine drive system. In this paper, an STF model is proposed for a triple redundant 3 × 3-phase permanent-magnet-assisted synchronous reluctance machine. The effect of turn fault current is represented by equivalent inputs to a general flux linkage model for each three-phase set. Subsequently, the flux linkage of the fault turns is derived according to the coil location and slot position of the fault. The complete model is obtained by combining the flux linkage model with the governing voltage equations. The effectiveness and flexibility of the proposed model have been validated by extensive finite element simulations and experimental tests in various operation conditions. It is demonstrated that the model can predict the machine behavior with and without the mitigation action in the form of terminal short circuit. [ABSTRACT FROM AUTHOR]

This paper proposes a novel FPGA-based matrix-inversion technique that is specifically tailored and optimized for real-time electromagnetic transients simulation of power electronic converters with high switching frequency. This is the first reported solution that is capable of solving the real-time equations related to using ideal switch model and the associated circuitry in very small time-steps (e.g., an average of 36 ns in a three-phase back-to-back converter case study), without requiring large amount of memory, being limited to small number of switches, adding parasitic elements, or depending on a priori knowledge of the circuit operation or switching strategy. The accuracy of the proposed real-time simulator is verified against the results from experimental measurements. [ABSTRACT FROM AUTHOR]

Commercial photovoltaic (PV) modules are made of different PV cell technologies such as monocrystalline, multicrystalline, amorphous silicon, and copper indium diselenide. Usually, a single- or a double-diode PV model is used to model the output characteristic. However, it is unclear which PV model is optimal for each PV cell technology as the modeling accuracy is dependent on the PV model used. To fill up this research gap, a generalized multidimension $(n \times m)$ diode PV model is proposed in this paper to determine the optimal PV model. The proposed PV model allows the diode network to be configured to better fit the output characteristics of different PV cell technologies. Both simulation and experimental results are presented to illustrate the advantages of the proposed model. From the results, the optimal PV model that matches each of the cell technology is established. They can be used as a reference PV model for future works. [ABSTRACT FROM PUBLISHER]

This paper analyzes short circuits in high-speed permanent-magnet (PM) machines. Analytical models are used to estimate the consequences of single-strand, parallel-strand, and phase-to-phase turn-to-turn short circuits, as well as open-circuit faults. The parameters for the analytical models are obtained from 3-D finite-element simulations and consider the actual position of each strand inside the slot. It is shown that parallel-strand short circuits are less severe than single-strand short circuits, both before and after fault mitigation actions. The potential for large fault current densities in high-speed PM machines is also demonstrated, with measured rms current densities up to 450 \A/mm^2 . A simple fault detector based on the synchronous detection of the machine and inverter neutral voltage difference is proposed, which is suitable for hardware implementation and can function as an independent observer of a drive system. The dependence of the detectability on the short circuit location and the effects of natural imbalances on the detector output are investigated. Experiments are performed to demonstrate the concept, showing that faults of at least 0.4% can be detected. [ABSTRACT FROM PUBLISHER]

Modeling partially shaded photovoltaic (PV) systems for online applications such as model-based MPPTs requires a PV circuit model with low computational time to simulate the large number of connected PV units within a reasonable amount of time. Unfortunately, the accurate PV models available in the literature are complex and suffer from high computational time due to their dependence on a transcendental implicit equation. This paper proposes a photovoltaic circuit model featuring lower computational time and comparable accuracy. The model utilizes the accuracy of the practical PV model and reduces the computational time by replacing the model series resistance with a third-degree-polynomial voltage-dependent source. The proposed model mimics the accurate characteristics of the practical model without being dependent on a transcendental implicit equation, thus providing low computational time. The model also introduces a new parameter to enhance the model's accuracy at low irradiance. The effectiveness of the model is shown by comparing the computational time and accuracy of the proposed model with those of the available models. A case study of partially shaded PV systems shows that the percentage of reduction in computational time improves with increases in the number of PV units in a simulated PV system, providing a clear advantage when simulating large PV systems. [ABSTRACT FROM PUBLISHER]

In this paper, we review relevant problems in the modeling of dc–dc converters with switched capacitors. We study several approaches that overcome the exposed modeling difficulties, addressing ideal and nonideal cases and using dynamic equations that are valid in a large-signal domain. [ABSTRACT FROM PUBLISHER]

Computational intelligence techniques are used to approximate the nonlinear operation of \LiFePO4 batteries using rule-based systems. In this paper, rule-based systems are not directly fitted to data, but comprise constructive blocks in a differential-equation-based dynamical model that is numerically integrated to infer battery voltage, charge, and temperature. The design methodology has been validated with three different \ \hspace*-1.8ptLiFePO4 batteries, and the results were found to be more accurate than those of a selection of statistical models and state-of-the-art artificial intelligence techniques. [ABSTRACT FROM PUBLISHER]

This paper proposes a method for estimating two inductances and capacitance of an LCL filter, connected between a converter and a grid. Only the dc-bus voltage and converter phase currents need to be measured. An excitation signal is fed into the converter voltage reference. The fundamental and selected harmonic components are removed from the stored identification data to prevent biases in the parameter estimates. The parameters of the hold-equivalent discrete-time model are estimated recursively. The inductance and capacitance estimates are calculated from the estimated discrete-time parameters using the corresponding closed-form model. The proposed method can be added to the existing converter control algorithms. It can provide the parameter estimates for the converter control. Further, it can be run occasionally during the normal operation in order to obtain an updated grid inductance estimate. Experimental results show that the proposed method yields very good parameter estimates and that it can also detect the changes in the grid inductance. [ABSTRACT FROM PUBLISHER]

This paper proposes a new estimator design algorithm for state-of-charge (SoC) indication of lithium-ion batteries. A fractional-order model-based nonlinear estimator is first framed including a Luenberger term and a sliding mode term. The estimator gains are designed by Lyapunov's direct method, providing a guarantee for stability and robustness of the error system under certain assumptions. This generic estimation algorithm is then applied to lithium-ion batteries. A fractional-order circuit model is adopted to predict battery dynamic behaviours. Assumptions based on which the estimation algorithm is developed are justified and remarked. Experiments corresponding to electric vehicle applications are conducted to parameterize the battery model and demonstrate the estimation performance. It shows that the proposed approach is able to estimate SoC with errors less than 0.03 in the presence of initial deviation and persistent noise. Furthermore, the benefits of using the proposed estimator relative to other estimators are calculated over different cycles and conditions. [ABSTRACT FROM PUBLISHER]

Electromagnetic transient (EMT) simulation of nonlinear elements in power systems is a particular challenge due to the requirements of an accurate representation and an efficient solution. The existing real-time simulators utilize a piecewise linear representation along with a fixed time step for the solution of nonlinear elements. This paper proposes the detailed methodologies for applying variable time stepping to real-time EMT simulation to improve the simulation accuracy and efficiency. The challenges, the feasible solutions, and corresponding restrictions of applying various variable time-stepping schemes along with nonlinear element solution methods in real time are discussed. The offline simulation and the real-time hardware emulation of two case studies, a full-bridge diode circuit and a power transmission system, are presented. The case studies were implemented on the field-programmable gate array device (Xilinx Virtex-7 XC7VX485T) in real time using high-level synthesis tool to achieve a parallelized and pipelined hardware design with minimum coding effort. The real-time emulation results captured by an oscilloscope are validated against the offline simulation on Saber and PSCAD/EMTDC software tools. [ABSTRACT FROM PUBLISHER]

The behavior of a photovoltaic (PV) module may be captured via its current–voltage ( $I$–$V$ ) characteristic. The single-diode model is able to adequately fit this characteristic while featuring limited parameterization difficulty, and is thus widely adopted to represent the performance of a PV module. However, the identification of the model's parameters is a complex task due to the nonconvex nature of the underlying optimization problem. In this paper, an efficient method for the parameter extraction of the single-diode PV model from experimental $I$ –$V$ curves is developed. This method features two advantages with respect to the existing procedures. On the one hand, it is able to find high-quality solutions at a reduced computational complexity. On the other hand, it does not rely on any preliminary data selection and it can thus be fully automated without user intervention. Numerical results obtained for case studies common in the literature and a large-scale repository show its performance. A computer program implementing the proposed methodology is available upon request via an e-mail to all interested researchers. [ABSTRACT FROM AUTHOR]

The modular power electronic transformer (PET) faces difficulty carrying out microsecond-level electromagnetic transient simulations. This article provides a high-speed and high-precision simulation method capable of eliminating the internal nodes and reducing the order of the nodal admittance matrix. Meanwhile, the parallel computing is integrated into the whole solution process, which achieves a significant simulation speedup. A physical prototype is established to prove that the detailed model (DM) is sufficient to reflect the dynamics of physical devices. Moreover, simulations in PSCAD/EMTDC are carried out to compare the proposed method with the DM in terms of accuracy and time efficiency. Simulation results show that the proposed method is accurate to simulate the external and internal dynamics of PET with hundreds of times simulation speed acceleration. [ABSTRACT FROM AUTHOR]

Online parameter identification is vital for boosting the accuracy of the battery equivalent circuit model (ECM) under dynamic profiles. However, traditional recursive least squares (RLS) method easily decays with the noise corruption from sensors or insufficient exciting signal in reality, which further limits the performance of ECM in battery modeling and states estimation. This article thus proposes a reliable online parameter identification method for battery ECM, which utilizes a well-designed information appraisal procedure based on the Fisher-information-based Cramer–Rao lower bound (CRLB). Without increasing much computing complexity, a comprehensive appraisal indicator, derived recursively from CRLB, enables a new mechanism for online parameter updating. Simulation and experimental results prove the validity of the proposed method under different driving cycles, temperatures, and aging conditions. The results show that the identification accuracy of the proposed method has been significantly improved comparing with a typical RLS and a multiple adaptive forgetting factors RLS method. [ABSTRACT FROM AUTHOR]

Fast charging is an enabling technique for the large-scale penetration of electric vehicles. This article proposes a knowledge-based, multiphysics-constrained fast charging strategy for lithium-ion battery (LIB), with a consciousness of the thermal safety and degradation. A universal algorithmic framework combining model-based state observer and a deep reinforcement learning (DRL)-based optimizer is proposed, for the first time, to provide a LIB fast charging solution. Within the DRL framework, a multiobjective optimization problem is formulated by penalizing the over-temperature and degradation. An improved environmental perceptive deep deterministic policy gradient (DDPG) algorithm with priority experience replay is exploited to tradeoff smartly the charging rapidity and the compliance of physical constraints. The proposed DDPG-DRL strategy is compared experimentally with the rule-based strategies and the state-of-the-art model predictive controller to validate its superiority in terms of charging rapidity, enforcement of LIB thermal safety and life extension, as well as the computational tractability. [ABSTRACT FROM AUTHOR]

In a medium voltage direct current (MVDC) multidrive system, several power electronics converters share a common MVDC bus. The contribution of this article relies on the systematic modeling approach of MVDC multidrive systems for the analysis of the MVDC bus power quality. Particularly, the interaction between the harmonics injected by the converters at the dc-link (due to the switching and modulation) with the natural resonances of the MVDC system (due to the line impedances and converters’ bus capacitors) is the key point for the proposed power quality analyses. For that purpose, the analytical modeling of both, the MVDC bus system and the current harmonics injected at the dc-link by the MV converters (3L NPC topology) is addressed in this article. The signal power quality study can be conducted entirely in the frequency domain through the proposed modeling approach at a low computational cost. This article demonstrates the applicability of the methodology for a real case study based on a high-power medium-voltage 5.1-kV MVDC multidrive system. [ABSTRACT FROM AUTHOR]

One of the main technological stumbling blocks in the field of environmentally friendly vehicles is related to the energy storage system. It is in this regard that car manufacturers are mobilizing to improve battery technologies and to accurately predict their behavior. The work proposed in this article deals with the advanced electrothermal modeling of a hybrid energy storage system integrating lithium-ion batteries and supercapacitors. The objective is to allow the aging aspects of the components of this system to be taken into account. The development of a model including the electrothermal behaviors makes it possible to evaluate the progressive degradation of the performance of the hybrid energy storage system. The characterization of both components constituting the hybrid system is carried out via a hybrid particle swarm–Nelder–Mead (PSO–NM) optimization algorithm using the experimental data of an urban electric vehicle. The obtained results show the good performance of the developed model and confirm the feasibility of our approach. The use of the PSO–NM optimization algorithm facilitated the identification of the parameters of the developed model with high efficiency, as the error observed is less than 3%. The advanced model associated with an adapted sizing method can be used in many cases to compare energy management strategies in electric vehicle applications. [ABSTRACT FROM AUTHOR]

This article concerns the estimation algorithms of battery's parameters and state of charge (SOC) and it is twofold. First, we present a simple variable length block wise least square estimation algorithm by considering locally linear SOC and open circuit voltage (OCV) relation on the run. The proposed algorithm can estimate accurately the parameters and follow the parameter changes. After estimating the battery parameters, SOC is directly computed from the combination of estimated parameters and SOC-OCV relation. This estimation scheme, which assumes hysteresis effect is negligible, is an online method. Second, if the hysteresis effect is considered in the model, we present an additional least square optimization problem to estimate SOC accurately. In this case, some parameters are tuned up in an offline way. Our approach compared with the extended Kalman filter based estimation method. The algorithms are validated by experiments with real data obtained from lab tests. [ABSTRACT FROM AUTHOR]

The field-programmable gate array (FPGA) based hardware-in-the-loop (HiL) test, which minimizes the time-step of the real-time simulation below 500 ns, is an enabling technology for the development of the control unit of high-power electronic systems (HPE). In order to improve the time performance of FPGA-based HiL, this article proposes a novel parallel structure using the predictive behavior of the power electronic system. With this structure, we design an improved system-level solver applied to HPE. A piecewise insulated-gate bipolar transistor (IGBT) model is used to determine the state of the switch, offering a quasi-realistic model of the power converter. A parallel integration method is also implemented to solve the status of the circuit elements. Moreover, the proposed parallel structural can execute both the IGBT model and circuit element model at the same time, thus, reducing the simulation time-step significantly. The numerical accuracy of the solution, the architecture design, and the issue of the parallel computation are discussed in detail. An ac–dc–ac topology is presented as a case study. At last, a 25 ns time step in the National Instruments FlexRIO platform is achieved. Results comparison with the reference model is also identified and discussed. [ABSTRACT FROM AUTHOR]

Hysteresis in piezoelectric actuators (PEAs) causes significant position errors and limits the application of PEAs. Compensating hysteresis via inverse models is one of the most popular approaches to reduce its effects. However, the construction of an accurate model is very challenging since hysteresis is coupled with creep and high-order dynamics, and hysteresis properties are also affected by operating conditions and aging effects. To overcome these challenges, this article proposes an adaptive generalized Maxwell-slip (AGMS) algorithm to identify and compensate for hysteresis online. By evenly distributing the saturation deformations throughout the desired range, a linear relation between the output force and the spring stiffness is generated, which enables a low-computational-complexity algorithm, such as the recursive least-squares algorithm, to update the stiffness online. Since the GMS model is self-invertible, an inverse model can be further analytically constructed in real time and utilized to compensate for the hysteresis. Experimental and comparison studies are carried out. The results show that this approach relaxes the requirement on the precision of the model and is robust to the operating conditions due to the capability of updating model parameters online. The normalized root mean square tracking error is approximately 0.4%. [ABSTRACT FROM AUTHOR]

The state of charge (SOC) of lithium-ion batteries (LIBs) is an important evaluation index in battery management system of energy storage systems. However, it is always a challenging task to accurately estimate SOC of LIBs, because of the existence of nonlinear characteristics and significant temperature effects. To improve the SOC estimation accuracy and robustness, a model-based estimation approach for SOC and impedance of LIBs is proposed against uncertain loading profiles and ambient temperatures. First an auto regressive exogenous model for online model order determining and parameters identification is established to monitor parameters variations based on numerical subspace state space system identification method. Second, a sequential Monte Carlo filter is employed to overcome the nonlinear and non-Gaussian error distribution state estimation problems caused by complicated open-circuit voltage characteristics. Finally, evaluation of the adaptability and generality of the proposed method are verified by different LIBs under different operating conditions. Experimental results indicate that the proposed method shows great performance, whose estimation value converges to real SOC within an error of $\pm \text{3}\%$ , and the battery model can simulate battery dynamics robustly with high accuracy. [ABSTRACT FROM AUTHOR]

This work proposes to develop a novel real-time (RT) magnetic equivalent-circuit machine model, for providing accurate electromagnetic (EM) device characteristics in a time frame acceptable for RT applications. Utilizing this model with the Hardware-in-the-Loop (HIL) concept enables a wide variety of useful applications. HIL concept requires accurate, RT models to emulate the characteristics of the modeled system, thus the proposed method provides a larger range of observable dynamics for large-scale simulations, controller tests, or hardware emulations. The proposed model is implemented for a switched reluctance machine (SRM) on a field-programmable gate array (FPGA). Finite-element analysis (FEA), lumped parameter modeling, and an experimental test bed serve to benchmark the modeling accuracy and RT applicability under static, dynamic, and controlled test conditions. [ABSTRACT FROM PUBLISHER]