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Fault diagnosis and fault tolerant (FT) control of electric drive systems have been extensively studied by many researchers. Naturally, one would like to use fault diagnosis information to improve FT control to achieve good post-fault performance while it is safe to do so. In this paper, a novel FT control method is proposed for permanent magnet synchronous motor with inter-turn short circuit fault. Given fault severity, the proposed FT control can reduce torque ripple while keeping reasonable torque output. The theoretical derivation, simulation, and experimental validation are presented in this paper. [ABSTRACT FROM AUTHOR]

Partial shading condition drastically reduces the maximum power output of photovoltaic array. Partial shading occurs due to several factors, such as flying birds, trees, and passing clouds. Many ways can be mitigated partial shading problems in photovoltaic (PV) array. One among the way is reconfiguration techniques, namely reconfigure the location of PV modules in PV array based on irradiance levels in order to distribute shading effects and increasing maximum power. This paper proposed an optimal SuDoKu reconfiguration pattern for $9\times 9$ total-cross-tied (TCT) PV array to improve maximum power under partial shading conditions. In this approach, the physical location of PV modules in TCT array are rearranged based on optimal SuDoKu style without altering the electrical connections, so that the shading effects can distribute over the array. Further, the performance of proposed pattern investigated with existing SuDoKu pattern under different shading conditions by comparing the global maximum power point, mismatch losses, fill-factor, and efficiency using MATLAB-Simulink. Based on the results of this paper, it concluded that the proposed optimal SuDoKu reconfiguration arrangement is reducing the wiring arrangement and increasing the shading distribution over the array as compared to SuDoKu arrangement. [ABSTRACT FROM AUTHOR]

This paper proposes a novel simulation method to analyze the characteristics of the electromagnetic noise of claw pole alternators under stator winding interturn short circuit faults. For the two types of faults: short circuit between two wires of the same phase and short circuit between turns of the same wire, a general circuit model built in Matlab/Simulink was introduced to obtained the phase current and output current signals. The phase current was then used as current source and the claw pole alternator was simulated as an electric motor rather than a generator to analyze the magnetic force and electromagnetic noise by using 3-D finite element method and boundary-element method, respectively. A noise bench test was conducted to verify the simulation results. It is shown that under the stator winding interturn short circuit faults, the output current harmonics and electromagnetic noise of the three-phase 12-pole/36-slot claw pole alternator would increase greatly. The 12th order noise replaces the 36th order noise as the most dominant order noise at low speed. The method proposed in this paper can also be used to diagnose the stator winding interturn short circuit faults of claw pole alternators. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear analysis model for predicting the performance of eddy current recoil brakes (ECRB) is proposed by combining the magnetic equivalent circuit (MEC) model and the subdomain model. The subdomain model introduces the equivalent region to improve the inherent shortcomings of the equivalent current sheet (ECS) method. The outer tube is divided into a magnetic saturated region and an unsaturated region in the subdomain model to simulate the magnetic saturation of the outer tube during recoil. The MEC model is applied to calculate the air gap magnetic flux density and the relative permeability of the equivalent region. Leakage flux and magnetic saturation are considered in the MEC model. The eddy current resistance of ECRB is calculated by the subdomain model. The model is verified by the finite element model, and it is able to predict the performance of ECRB with different structural parameters. In addition, the prototype of the ECRB was manufactured. A test was carried out on a 155 mm artillery to verify the accuracy of the proposed nonlinear analysis model. [ABSTRACT FROM AUTHOR]

With the widespread application of lithium-ion battery packs, it calls for efficient balancing methods to improve the performance of these battery systems. The relevant research has focused on the design of equalization circuits and control strategies while neglecting quantitative analysis and comparison of battery active equalization structures from the systematic level. In this paper, we propose an improved system-theoretic modeling approach for active equalization structures that takes into account the battery's constraints, including equalization current rate and SOC operation range. Accordingly, the mathematical models of various active equalization structures are derived that can describe their equalization dynamic behavior. Then, the analytical algorithms are developed to estimate the balancing time of active equalization structures online. Finally, extensive numerical simulations are conducted to evaluate and compare the average performance of these equalization systems in term of equalization time. It then comes up with a comprehensive comparison among them. Consequently, the Multicell-to-Multicell (MC2MC) balancing structure benefits the fast balancing speed and the lowest sensitive to initial batteries’ SOCs. The global structure has the lowest implementation cost and the series structure benefits the simplest control. Moreover, the module-based structures have faster balancing speed when each module contains about 4–6 batteries. [ABSTRACT FROM AUTHOR]

Brushless doubly fed induction machine (BDFIM) which is able to operate in both induction mode and synchronous mode, has received increasing attention of researchers, in the last three decades. It could be considered as an emerging competitor for older structures, due to the substantial features such as brushless structure and requiring a fractionally rated frequency converter. The iron loss which constitutes a significant portion of total power losses is higher in BDFIM in contrast with standard induction machine. Even though it is essential to consider the iron loss effect on dynamic behavior of BDFIM, there is still no comprehensive study in the literature. The aim of this paper is to propose a dynamic model of BFIM in general reference frame in which the iron loss is taken into account. This model which is credible for all BDFIM operation modes including synchronous one, facilitates the performance analysis of BDFIM and implementation of the various control techniques. The supplementary simulations and experiments confirm that the proposed model is an appropriate candidate for BDFIM drives. Because of the complex structure of BDFIM, determination of the iron loss isn't straightforward. In this paper, a practical approach is introduced to calculate the iron loss of BDFIM in terms of frequency variations. The experimental data derived from a D132s prototype BDFIM is then compared with the calculated data from the finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

This paper proposes a detailed equivalent model for electromagnetic transient simulation of a modular multilevel converter with embedded battery energy storage in its submodules. The model offers an accuracy identical to that of a detailed switching model (DSM), while it markedly reduces the computational complexity of simulations. This is achieved by modeling each multivalve as a Thevenin equivalent considering the full dynamics of each constituent submodule, which results in a significant reduction in the number of switchable nodes in the converter model and hence the dimensions of the system's admittance matrix. The paper presents the mathematical development of the model and validates it against detailed switching models through several case studies. Experimental results from a scaled-down laboratory setup are also presented for further verification. [ABSTRACT FROM AUTHOR]

This paper proposes a new equivalent magnetic network (EMN) model for vehicular dual-permanent-magnet vernier (DPMV) machines by applying a generalized modeling method. First, the magnetic circuit method and the meshing method are combined together to improve the modeling efficiency of the DPMV machine. The magnetic circuit method is used to generate conventional lumped parameter permeances to shorten time consumption, whereas the mesh method is utilized in disordered magnetic fields to obtain high precision. Second, a meshing solution for oblique region is proposed to enhance modeling flexibility. Moreover, the flux distributions in meshes are represented without magnetic field pre-delineation, which enables its utilization as a self-adaptive reluctance network model in design optimization. Finally, the proposed EMN model is used to predict the performance of the DPMV machine, considering leakage magnetic flux, local iron saturation, and magnetic field modulation effect simultaneously. Meanwhile, the effectiveness of the proposed EMN model is verified by comparison with finite-element analysis and experimental tests. [ABSTRACT FROM AUTHOR]

The brushless excitation structure characteristics of the aviation wound-rotor synchronous starter/generator (WRSSG) put forward the requirement on the brushless exciter (BE) model that both the stator and rotor windings can be interfaced with the external circuit directly. In this paper, a double-side variable-parameter voltage-behind-reactance (DS-VP-VBR) model of the BE considering magnetic saturation was established firstly to realize the direct connection between the stator and rotor windings with external circuits. Then, a double-side constant-parameter VBR (DS-CP-VBR) model with completely decoupled RL circuit was developed through the algebraic transformation and numerical approximation from the DS-VP-VBR model. In order to further improve the model accuracy, the leakage inductance variation of the stator and rotor windings were also considered. Computer studies under steady-state and transient operating conditions verified the validity and accuracy of the proposed BE DS-VBR models. [ABSTRACT FROM AUTHOR]

The paper focuses on the modeling of iron losses for synchronous electric machines. Specifically, the paper describes the inclusion of iron-loss resistance parallel to the main inductance of a dual-voltage alternator model. Integration of the iron loss resistance is implemented in two different models: a quadrature direct (QD) axis model and a voltage behind reactance (VBR) model. Simulations with both models are performed and compared against measurements with a machine prototype. The measurements show that the usually made assumption of constant iron loss resistance does not accurately represent the iron losses of a claw-pole alternator. Therefore, the parallel resistance is implemented also as lookup table (LUT) and derived from measurements. The presented models can be parametrized as conventional 2 $\times$ 3-phase synchronous machine with one-voltage level. [ABSTRACT FROM AUTHOR]

Since the linear induction motor commonly work with a laterally asymmetric secondary as it is applied to pull rail vehicles, this paper presents a complete equivalent circuit model considering the asymmetry to predict thrust, vertical and transversal forces. First, six correction factors are presented to quantify the variations in the air-gap magnetic flux and secondary induced current as the linear induction motor operating with a laterally asymmetric secondary. Second, it develops a circuit model based on the existing T-model for the rotary induction motor and two correction factors for the magnetizing branch, which is used to indicate the electromagnetic variations in the air-gap flux and secondary plate due to the asymmetry. Third, the mathematical expressions for the thrust, vertical and transversal forces are derived by applying the equivalent circuit model. Then, the six correction factors are calculated with a prototype motor, and the results of them are comprehensively analyzed. Finally, the characteristics in the prototype motor are calculated with the mathematical expressions in a range of rated speed, and validated by the experimental measurements carried out on a test rig and line for linear motors. [ABSTRACT FROM AUTHOR]

The hard switching operation of the insulated gate bipolar transistor (IGBT)-based multilevel converters (MLCs) in the transformer less direct integration of renewable power plants produces a considerable amount of switching and conduction power loss. This eventually causes higher junction temperature and lower thermal stability. The symmetrically designed MLC using third harmonic sixty-degree bus-clamped pulse width modulation (BCPWM) technique demonstrates reduced switching losses and better harmonic spectra. However, the development of analytical power loss model is a complex and challenging issue due to the discontinuous switching mode of IGBTs for the BCPWM in MLC. In this regard, an analytical model for calculating the average and the rms currents for the hard switching operation of IGBTs and antiparallel diodes (APDs) with BCPWM is proposed. Furthermore, to calculate the device turn-on and turn-off losses, a discrete form of equation is presented to evaluate the transition times of switching more precisely. The numerical power loss values of IGBTs and APDs found from the derived analytical equations for MLC are compared with the simulation and experimental results. The numerical results agree well with the simulated and the experimental outcomes, which validate the proposed analytical loss model. Moreover, an advanced three dimensional thermal impedance model with chip-wise interdependent multilayer thermal coupling effect is also considered in this paper to realize the critical thermal loading condition of the switching devices. [ABSTRACT FROM AUTHOR]

The static exciter is dominating among large grid-connected generators due to the weak dynamic performance of conventional brushless exciters. In this contribution, a six-phase double-star outer pole permanent magnet rotating brushless exciter is evaluated with different active rectification topologies. Both thyristor-based and chopper-based topologies are considered. A high speed response brushless excitation system is obtained by replacing the conventional rotating diode bridge rectifier with the proposed active rectification topologies on the shaft. The given two-stage system generates its own excitation power directly from the shaft, contrary to static exciters. The selection of an appropriate rectification topology could minimize the rotor armature phase currents for a given generator field current. The objective is a high-power factor and a high utilization of the exciter machine. An optimal rectification topology makes higher ceiling currents was possible, improving the transient behavior of the synchronous generator. In this paper, we show that six-phase topologies add complexity, but improve exciter redundancy, increase the available ceiling voltage, and reduce the steady-state torque ripple. Experimental results are given for validating the models implemented for the analysis. [ABSTRACT FROM AUTHOR]

This paper deals with a dynamic model for three-phase induction machines equipped with closed rotor slots and deep rotor bars. The thin bridges closing the rotor slots saturate highly as a function of the rotor current. The impedance of the rotor bars also varies much as a function of the rotor current frequency. An extended dynamic model, which takes into account the slot-bridge saturation and the deep-bar effect, is developed. The model extensions can be plugged into a standard machine model and parametrized easily. The proposed model can be applied to time-domain simulations, real-time control, and identification. The model is validated by means of finite-element analysis and experiments using a four-pole 5.6-kW induction machine. The results show that the accuracy of the proposed model is superior to the standard model, particularly under transient excitation typically used in standstill self-commissioning tests of induction motor drives. [ABSTRACT FROM AUTHOR]

This paper proposes a dynamic model with iron saturation to obtain better dynamic performance and more accurately steady-state performance than the dynamic model without iron saturation for the dual-stator brushless doubly-fed induction generator. Based on the proposed dynamic model, the MATLAB/SIMULINK model is established. The key to the simulation model considering iron saturation is that the magnetizing inductance can be updated for each simulation cycle. The magnetizing inductance used in the simulation is experimentally measured to guarantee the simulation accuracy. Dynamic simulations including the current, voltage, flux linkage, active power, and torque are performed, showing that the dynamic model considering iron saturation contributes to the merits of reducing the setting time and the oscillation amplitudes of the torque and the power in starting stage. Experimental assessment is carried out to verify the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a novel admittance model for the stability analysis of grid-connected voltage-source converters (VSCs) which features a symmetric structure. On this basis, the grid-connected VSC system can be represented by a reciprocal two-port circuit to explore the oscillation mechanism of the system. Furthermore, the grid-connected VSC system can be modelled as a single-input single-output (SISO) system rather than a multi-input multi-output (MIMO) system. We analytically evaluate the influences of the VSC control parameters and the power factor on the stability of the grid-connected VSC by employing the Nyquist criterion and the stability margin. In addition, we demonstrate that the VSC's current output is in inverse proportion to the system's gain margin. Further, an analytical expression of the current limit constrained by small-signal stability is derived in closed form so as to calculate the admissible current output. All of analysis results are verified by simulations based on Simulink and hardware-in-the-loop (HIL) platform. [ABSTRACT FROM AUTHOR]

Electro-mechanical-actuator (EMA) is the key component to convert electrical power into mechanical power for flight control in next-generation aircrafts. Multi-domain simulation of EMA can benefit its on-going evolution process. This paper presents the real-time multi-domain modeling and simulation of an EMA as elevator for flight control by utilization of a unified solver. Several key issues concerning the computational efficiency and successful implementation of this solver are provided and its relationship with state-variable model is also elaborated. Analysis shows that this solver could be a competitive candidate for multi-domain simulation because of its high computational efficiency and relatively less modeling effort. Electrical, mechanical, and thermal parts of the EMA are modeled and simulated interactively based on the proposed solver. The multi-domain model is implemented on FPGA board and executes in real time. Simulation results from FPGA board and commercial softwares under several test scenarios coincide with each other in very high degree, which showcases the efficacy of the proposed solver with respect to computational efficiency and ability to accommodate multi-domain models. The proposed model and solver are useful for hardware-in-the-loop design and testing of EMA. [ABSTRACT FROM AUTHOR]

High-frequency electromagnetic linear machine is one major component for linear eletro-hydraulic actuator that in turn is extrimely important for the flight control of more-electrical or all-electrical aircrafts. The employment of high-frequency linear machine helps to achieve high reliability and dynamic performance of the actuators. However, the capability of heat dissipation of the linear machine unavoidably constrains the input current, which in turn depresses its output performance. Therefore, this paper proposes a novel electromagnetic linear machine based on the self-powered direct oil-cooling windings. Specifically, the windings are immersed into the oil directly, which helps to decrease the temperature of the linear machine significantly and thus increase its output performance. In addition, the oil is pushed by the motion of the mover itself. No additional pump is required any more. Thus, the system can be simplified greatly. The design concept of high-frequency electromagnetic linear machine along with its operating principle is presented. A high-precision three-dimensional (3D) piecewise modeling method is proposed to simultaneously consider axial, radial and circumferential equivalent thermal circuits. Numerical simulation is conduced to validated the analytical model. A research prototype of the linear oscillating machine based on direct oil-cooling windings is developed and empolyed for experimental study, and the experimental result verifies the mathematical model of the thermal field well. [ABSTRACT FROM AUTHOR]

Modular multilevel converters have become the technology of choice in high voltage direct current systems. They are composed of a large number of submodules, which poses significant computational challenges to electromagnetic transient simulations. To address this issue, scholars proposed several approaches that are a trade-off between simulation accuracy and computational burden, which mainly achieve numerical efficiency by adopting reduced and simplified models of the converter arm submodules. This paper proposes a different simulation paradigm based on sub-circuit isomorphism. It is suited for the analysis of intrinsically modular electronic circuits, as it exploits the common behavior of structurally identical submodules by clustering them together. This method does not require any simplification of the submodule electrical model and minimizes the number of equations to be solved at each time step of the time domain analysis, thereby significantly reducing the computational effort. Thus, this method is suitable for thorough simulations of ac/dc networks, which may require the implementation of detailed transistor-level representations of the converter submodules. [ABSTRACT FROM AUTHOR]

The magnetic potential drop in nonlinear iron can be replaced by equivalent current sheets on linear iron edges. Based on this principle, this paper proposes a nonlinear subdomain and magnet circuit hybrid model (SMCHM) for open-circuit field prediction in surface-mounted permanent-magnet machines. The values of current sheets are calculated from a magnetic circuit and used as boundary conditions in the subdomain model. The finite element (FE) validation is performed, which shows the SMCHM can accurately predict the magnetic field distribution and electromagnetic performance as nonlinear FE method does. The accuracy of SMCHM is significantly higher than the conventional subdomain model neglecting a nonlinearity effect, and the computation speed of SMCHM is dramatically faster than the FE model. [ABSTRACT FROM AUTHOR]

This paper details the design, construction, and test of a lightweight, low energy usage Thomson Coil actuator for the operation of a commercial medium-voltage vacuum switch. A novel latching design, directly linked to the actuator armature, helps to keep the actuator mass at minimum. Experimental results show that 125 J of electric energy is sufficient for operation of a commercial 27 kV vacuum interrupter in times suitable for medium-voltage dc protection applications. The use of high conductor density coils is shown to play a key role on the observed actuator performance. Finite element simulations are used to demonstrate that shorter operation times are feasible, without augmenting the consumed electrical energy, by further increasing coil conductor density. [ABSTRACT FROM AUTHOR]

Accurate modeling is the first step in developing a model-based diagnostics tool for different types of failures in electric motors. In this paper, a mathematical model for an interior-mount line start permanent magnet synchronous motor (LSPMSM) under the stator inter-turn fault is developed based on the principles of magnetic coupled circuit theory, electromechanical energy conversion and reference frame theory. The developed mathematical model is simulated using MATLAB and experimentally validated using a 1-hp, 4-pole, 400-V LSPMSM. To investigate the performance of the motor under the stator inter-turn fault at different loading levels, experimental and simulation results are compared and analyzed for both transient and steady-state responses of the current and speed. The simulation and experimental results are in very good agreement and show that under the stator inter-turn fault, the current magnitude and time response of the phase that contains the inter-turn are highly affected. In addition, due to asymmetry in the stator windings under this fault, the speed experiences some oscillations at steady state. Hence, the developed model can be used to detect the possibility and location of the stator inter-turn fault in an LSPMSM. [ABSTRACT FROM AUTHOR]

Doubly fed induction machine (DFIM) has been widely used in variable speed constant frequency electricity generation systems due to its small power converter capacity. Then another machine—brushless doubly fed machine (BDFM)—is widely concerned because of its similar characteristics but better reliability than DFIM. In fact, according to common features of DFIM and BDFM, these two machines can be collectively called doubly fed machine (DFM). Theoretical study on characteristics of these two machines has not formed concise, practical, and all-sided theoretical analysis system. Proceeding from basic theory of DFIM, this paper derived the physical model and established a novel synchronous–asynchronous series equivalent circuit model of DFIM at first. Based on the analysis method of DFIM, a novel equivalent circuit model of BDFM was established. These two models illustrated that the characteristic of DFM is the superposition of synchronous characteristic and asynchronous characteristic. Based on these circuit models, the characteristic under different operation mode was analyzed and corresponding analytical curves were drawn, which revealed the operation mechanism of DFM clearly. To verify the theoretical analysis of two novel equivalent circuit models, simulation models of DFIM and BDFM were established in Simulink and finite element analysis (FEA) software. Corresponding characteristic curves were drawn to compare with that obtained by circuit models. At last, combined with these characteristic curves, practical significance that circuit models and theoretical analysis bring to machine design and control theory was analyzed. [ABSTRACT FROM AUTHOR]

The maximum energy that can be harvested from a photovoltaic (PV) system at any instant depends on the effectiveness and response time of the maximum power point tracking (MPPT) algorithm used and related controllers. To facilitate proper controller design, a precise mathematical model of the system is required. This paper presents a comprehensive small signal model capable of describing the dynamics of the power stage and controllers. The power stage consists of a PV system and a dc–dc boost converter including the parasitic elements operating in inverse-buck mode. The MPPT and PV voltage controller constitute the control system. The steady state and transient responses of the system are evaluated by controller-hardware-in-the-loop approach where the power stage is simulated in a real time digital simulator and the control operations are performed in a digital signal processor. The frequency response is experimentally determined using a Gain-Phase analyzer. This unique approach allows control system designers to test and validate a control system design before implementing it with a laboratory scale hardware or any real-life application. This method adds an extra layer of design authentication on top of conventional offline simulations. [ABSTRACT FROM AUTHOR]

This paper proposes an evaluation method for equivalent circuit model of lithium polymer battery (LiPB), which is widely used in the hybrid electric vehicle (HEV), applying the Bode plot and the numerical method. The accurate circuit parameters are determined by numerical analysis and transfer function that is evaluated from the frequency response of LiPB. Generally, the inductive component of battery has an unexpected influence. However, this method takes account of the effect of increased inductive reactance by the high switching frequency. Moreover, the numerical analysis makes the inductive and capacitive components independent of each other, which results in the more accurate circuit parameters of LiPB. The propriety of the evaluation method proposed in this paper is verified by comparison between the voltage–current profiles of battery equipped in the real HEV and that of simulation result using the circuit parameters with respect to the state of charge (SOC) and frequency. [ABSTRACT FROM PUBLISHER]

Multi-cell battery systems have been pervasively adopted as power supplies in industrial, commercial, and residential applications. Traditionally, battery systems consist of a large number of single cells interconnected by fixed topology to fulfill the requirements on voltage, current, capacity, and power. However, various cell unbalances introduced in manufacture and operational processes make battery systems suffer several major system-level deficiencies, including low energy efficiency, safety, second-use, and reliability issues. Therefore, dynamically reconfigurable battery (DRB) systems have gained popularity in recent years to achieve a higher energy efficiency and to prolong cycle life of battery systems by overcoming the adverse effects caused by cell unbalances. Unfortunately, current research on DRB systems mainly focuses on topology design with traditional management methods, lacking a theoretical foundation to study the performance optimization. In this paper, we propose a theoretical framework to optimize the DRB system performance by holistically considering various system design trade-offs on dynamical reconfiguration of the cell topology. Extensive numerical and experimental studies indicate the effectiveness and efficiency of the proposed optimization framework. Furthermore, the proposed framework can characterize the DRB system behaviors in a quantitative fashion, which provides design insights for such systems. A real-world case study has been provided to gain in-depth understanding of the proposed DRB systems. [ABSTRACT FROM AUTHOR]

An axial-flux permanent-magnet (PM)-assisted claw-pole generator (APCG) is designed based on an equivalent magnetic circuit model (EMCM). It is designed for generating power in vehicle with the merits of high power density, no brush, and wide airgap flux density modulation range. This paper mainly focuses on establishing the EMCM of the APCG and designing a set of optimal structure parameters. First, the topology and operation principle of the APCG are introduced in detail, including material, fabrication, and magnetic flux distribution. Second, the magnetic circuits in claw poles are simplified and the relationships among the key parameters are discussed. Finally, based on the simplified model and the relationships among the key parameters, the EMCMs of current and PM excitation are established, respectively. According to the EMCM, a scheme of a 4 kW APCG is carried out. Comprehensive investigations demonstrate that the EMCM is time-saving and relatively accurate when compared with a finite element method. [ABSTRACT FROM AUTHOR]

Since single-sided linear induction motors working with a lateral asymmetric cap secondary is a frequent operating condition, this paper develops an equivalent circuit model considering the asymmetric condition. First, an analysis model, which takes the longitudinal end effect and skin effect into consideration, is proposed. Second, a transversal analysis model considering the laterally asymmetric cap secondary is developed to derive its correction factors. Then, the influence of lamination eddy current on the effective air gap to transversely directed flux is contrastively analyzed. Third, the traction characteristics of a prototype motor with symmetric and asymmetric cap secondary are calculated by the equivalent circuit. Finally, these calculated results are verified by measurements carried out by a test rig of the linear motor. [ABSTRACT FROM AUTHOR]

Frequency response analysis (FRA) is a popular tool to detect transformer winding deformation faults. It has been recently used to diagnose the winding inter-turn short circuit fault of the electric machine. The application of FRA is based on the fact that the winding can be equivalent to an electrical circuit consisting of resistance, inductance, and capacitance. Therefore, to obtain an accurate broadband equivalent circuit model of synchronous machine and perform the fault analysis and diagnosis, this paper introduces the gray box model technique based on the state space and genetic algorithm. The electrical circuit of a form-wound coil of a 4 kW machine with known electrical parameters is used to verify the proposed method primarily. Besides, the equivalent circuit modeling is carried out and experimentally verified on an actual 5 kW synchronous machine. Finally, the fault simulation analyses of winding inter-turn short circuits are performed based on the proposed equivalent electrical circuit. The verification result shows that the circuit parameters identified by the proposed method are accurate. Moreover, the fault simulation results indicate that the inter-turn short circuit faults can cause apparent variations in the frequency response curves. It is feasible to detect the winding fault of the synchronous machine by the FRA method. [ABSTRACT FROM AUTHOR]

Switched reluctance motors (SRMs) have attracted much attention in industry due to the advantages of low cost, robust structure, high fault tolerance and high torque density. However, several disadvantages like high torque ripples and coil temperatures hinder their industrialization for some applications requiring high dynamic performance, like electric vehicles (EVs). In this paper, a multiobjective and multiphysics design optimization method considering both thermal and electromagnetic performance is presented for a 12/10 SRM. First, the topology of the SRM is introduced and the optimal parameters are defined. Then, the electromagnetic finite element model (FEM) is introduced and the 3D transient lumped-parameter thermal model (TLPTM), considering both axial and radial heat transfer for the SRM, is proposed. Second, the objectives and constraints of the optimization are determined. To improve the optimization efficiency, the sequential subspace optimization strategy is employed to find the optimal solution of this high-dimensional design optimization problem. Finally, to validate the effectiveness of the proposed method, both simulation and experimental results are given and discussed. Compared with the initial design, the optimal solution exhibits lower temperature, higher torque, lower torque ripple and less loss. [ABSTRACT FROM AUTHOR]

Impedance modeling of a permanent magnet synchronous generator (PMSG)-based wind energy conversion system (WECS) usually ignores the machine-side dynamics, instead, the machine-side system is simplified as a constant power source, while merely keeping the detailed grid-side converter model. This simplification is mainly based upon the intuition that the dc-bus capacitor is large enough so that the machine- and grid-side dynamics can be decoupled. However, the simplification probably does not hold in practice since there is always a tendency to minimize the capacitor size to achieve a smaller package for installation. Therefore, the machine-side system should not be ignored, otherwise maybe leading to error for stability analysis. To address this issue, this paper developed a complete ac-side impedance model of the PMSG-based WECS. Then, impact factors about the coupling characteristics between machine- and grid-side systems of the PMSG-based WECS are discussed. Finally, a case study of sub/super synchronous oscillation is carried out on a practical offshore wind farm integrated with a modular multilevel converter based high-voltage dc (MMC-HVDC) transmission system in China. The results show that ignoring the machine-side system would lead to an optimistic stability judgement, which confirms the necessity of the complete model of PMSG-based WECS. Furthermore, the system can be stabilized by either changing the couplings between machine- and grid-side systems of PMSG-based WECS or implementing active damping in the wind farm side MMC. [ABSTRACT FROM AUTHOR]

This paper proposes a new fast chargingstrategy for lithium-ion (Li-ion) batteries. The approach relies on an experimentally validated high-fidelity model describing battery electrochemical and thermal dynamics that determine the fast charging capability. Such a high-dimensional nonlinear dynamic model can be intractable to compute in real-time if it is fused with the extended Kalman filter or the unscented Kalman filter that is commonly used in the community of battery management. To significantly save computational efforts and achieve rapid convergence, the ensemble transform Kalman filter (ETKF) is selected and tailored to estimate the nonuniform Li-ion battery states. Then, a health- and safety-aware charging protocol is proposed based on successively applied proportional-integral (PI) control actions. The controller regulates charging rates using online battery state information and the imposed constraints, in which each PI control action automatically comes into play when its corresponding constraint is triggered. The proposed physical constraint-triggered PI charging control strategy with the ETKF is evaluated and compared with several prevalent alternatives. It shows that the derived controller can achieve close to the optimal solution in terms of charging time and trajectory, as determined by a nonlinear model predictive controller, but at a drastically reduced computational cost. [ABSTRACT FROM AUTHOR]

A dynamic model of a battery is required for the appropriate real-time control during charging/discharging process. Present paper considers the development of nonlinear Dynamic Equivalent Electric Circuit Model (DEECM) of a Valve Regulated Lead-Acid (VRLA) battery based on the data obtained through the experimentation and the available datasheet information. Cases of charging, discharging, and the self-discharging are considered for 12V, 26Ah VRLA battery at room temperature. Accordingly, experimental ${\boldsymbol{v}} - {\boldsymbol{i}}$ characteristics of the battery are used to express the nonlinear model parameters as a function of measurable battery current and estimated open-circuit voltage as a part of parameter estimation. Further model is validated through voltage response test with maximum error of 0.4% during discharging and 0.7% during charging under different current levels. [ABSTRACT FROM AUTHOR]

This paper develops a magnetic equivalent circuit model suitable to the design and optimization of the synchronous ac homopolar machine. The ac homopolar machine is of particular interest in the application of grid-based flywheel energy storage, where it has the potential to significantly reduce self-discharge associated with magnetic losses. The ac homopolar machine features both axial and radial magnetizing flux paths, which requires finite element analysis to be conducted in 3-D. The computation time associated with 3-D finite element modeling is highly prohibitive in the design process. The magnetic equivalent circuit model developed in this paper is shown to be a viable alternative for calculating several design performance parameters and has a computation time which is orders of magnitude less than that of 3-D finite element analysis. Results obtained from the developed model are shown to be in good agreement with finite element and experimental results for varying levels of saturation. [ABSTRACT FROM AUTHOR]

The design of squirrel-cage induction motors (IMs) entails the capability to predict the motor efficiency map with high accuracy over an operating range. In particular, modeling harmonic rotor bar currents becomes important for loss analysis. In theory, it is possible to analyze an induction motor using time-stepping finite element analysis (TS-FEA); however, this is not viable due to computational limitations. To bridge this gap, we set forth a computationally efficient method that couples magnetostatic FEA with a qd-circuit model of the cage. The proposed IM model includes the effects of saturation, winding and slot harmonics, as well as nonuniform current density distribution in the rotor bars. The model is presented in two parts. Part I focuses on the formulation of a qd cage circuit model with segmented bars. Part II is a companion paper that proposes an FEA-based parameter estimation and a solution method. [ABSTRACT FROM AUTHOR]

This is Part II of a paper that sets forth a computationally efficient method to estimate harmonic rotor bar currents in induction motors for accurate loss analysis. The method couples magnetostatic finite element analysis (FEA) and an extended-qd cage circuit model. In Part I, we formulated two subproblems for determining separate components of the induced rotor currents. Part II begins with details regarding the subproblem solution methods. Second, we set forth an FEA-based parameter estimation for the subproblems. Finally, the proposed model is validated by comparing the estimated cage loss and computational effort against a 2-D nonlinear time-stepping FEA. [ABSTRACT FROM AUTHOR]

Cascaded connection of power converters is a dominant connection form in DC microgrids. In such systems, despite the possible instability caused by the impedance interactions between the individually designed converters, tightly regulated load converters acting as constant power loads (CPLs) tend to destabilize the system owing to their negative resistance characteristics. Hence, this paper proposes a new virtual series RC damper in parallel with the source-side converter's capacitor without compromising the load's dynamic performance. Using this design-oriented active damping method, which utilizes a simple control structure with a more straightforward tuning of the control parameter, the stability and performance of the system are guaranteed. The feasibility and robustness of the suggested active stabilization idea against unanticipated variations in input voltage amplitude, and CPL power rating (load changes) as well as step changes in output voltage reference, are also authenticated. The control and operation principles, as well as the circuit physical meaning realized by the presented technique for three cascaded systems comprising the basic DC/DC converters feeding CPLs, are theoretically analyzed. Simulation and experimental results are provided to validate the effectiveness of the proposed active stabilizer. [ABSTRACT FROM AUTHOR]

This paper proposes a new simplified model of a doubly fed induction generator (DFIG) that is integrated with a rotor-side converter for studies of large-scale transient stability. This model accurately considers the rotor field dynamics of an induction generator to yield simulation results that are more accurate in terms of voltage stability, as well as angle stability. The purpose of this paper is to provide a simple but effective DFIG model for the study of large-scale transient stability, and to examine the important aspects of rotor voltage and rotor slip power. This new simplified DFIG model with an electric/turbine control system was tested against a six-machine and 23-bus system, and the responses obtained in case studies of transient stability were compared with those of a PSS/E program. Finally, the proposed DFIG model was also validated by comparing the simulation results for a single-machine and infinite-bus system with those of PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

In comparison with three-phase induction machines, modern single-phase induction machines normally have skewed rotors, but show an elliptic magnetic field during start-up. In order to properly model the start-up of such a machine, this three-dimensional (3-D) characteristic has to be accounted for. This leads to the application of the 3-D finite-element method. This paper will introduce a new approach to model and analyze the start-up of such a single-phase machine, with the aim of higher computational efficiency. Furthermore, this paper will discuss how symmetries, both in the circumferential direction and along the motor shaft, can be exploited despite the skewing. This is achieved through transforming (rotating) the cutting plane, doubling the skewing angle, and increasing the rotor conductor conductivity. The analysis is carried out on a small two-pole 100-W machine used for household appliances. The theoretical results are compared with experimental results for six rotors; each with a different skewing angle. [ABSTRACT FROM AUTHOR]

Many advanced energy conversion systems utilize multiphase (e.g., six or more phases) electrical machines that feed high-count-pulse (e.g., 12 or more pulses) rectifiers for supplying dc power. Efficient simulation of such power systems in commonly-used state-variable-based programs requires fast and accurate models of electrical machines and power electronic converters with compatible interfaces. As an alternative to the existing $qd$ and voltage-behind-reactance (VBR) machine models, this paper develops a constant-parameter VBR model for six-phase permanent magnet synchronous machines to offer computationally efficient interface. For system-level studies where the switching details of rectifiers can be neglected, a multiple-reference-frame parametric-average-value model is developed for the 12-pulse rectifiers that provides fast simulation and preserves the dominant ac harmonics of interest. The accuracy and numerical efficiency of the proposed machine-converter models are verified using the detailed and alternative existing models. [ABSTRACT FROM AUTHOR]

Magnetic gears offer a promising alternative to mechanical gears with the added benefit of contactless power transfer. However, quick and accurate analysis tools are required to optimize magnetic gear designs and commercialize the technology. Therefore, this paper proposes an extremely fast and accurate 2-D magnetic equivalent circuit (MEC) model of radial flux magnetic gears with surface mounted magnets. This MEC model's distinguishing characteristics include a heavily parameterized gear geometry and a parametrically adjustable systematic flux tube distribution which allow for accurate and efficient analysis of a wide array of designs. Furthermore, the model is fully linear which results in very quick simulation run times without sacrificing significant torque prediction accuracy for most practical designs. This is Part I of a two-part paper and focuses on the implementation of the MEC model. Part II validates the accuracy of the MEC model by comparing its torque and flux density predictions with those produced by nonlinear finite-element analysis. [ABSTRACT FROM AUTHOR]

A high-order model is required for an accurate simulation of the synchronous alternator spatial harmonic content. However, some hydro-generators have fractional slot per pole per phase windings, and carrying transient simulations of these machines with finite-element software often leads to unacceptable computation time. This paper details a large alternator modeling method that provides an excellent compromise between accuracy and speed. It is a combination of magnetostatic finite element method and coupled circuits model. The paper details the construction of this model and explains the procedures to identify several model parameters from experimental data as the standstill frequency response and open and short circuit tests. The effectiveness of this modeling method is validated by the study of a large 109-MVA hydrogenerator having an instrumented rotor pole. We compare transient and steady-state simulation waveforms of the damper bar currents during sudden two- and three-phase short-circuit to the experimental measures. [ABSTRACT FROM AUTHOR]

This paper presents analytical methods to calculate the equivalent circuit parameters for large-scale brushless doubly fed machines (BDFMs) with magnetic wedges utilized for closing stator open slots. The use of magnetic wedges reduces the magnetizing currents in the machine, reflected in the values of magnetizing inductances, but also increases leakage fluxes affecting the value of series inductances in the equivalent circuit. Though such effects can be modeled by numerical models, the proposed analytical methods are particularly helpful in optimizing machine design, inverter rating, reactive power management, and grid low-voltage ride-through performance. The conventional analytical methods cannot be readily applied to the BDFM due to its complex magnetic field distribution; this paper presents analytical methods to calculate the magnetizing and leakage inductances for the BDFM with magnetic wedges used in the stator slots. The proposed methods are assessed by experimentally verified finite-element models for a 250 kW BDFM. [ABSTRACT FROM PUBLISHER]

Partial shading of photovoltaic (PV) power generators causes typically multiple maximum power points (MPPs) on the electrical characteristics of the generators. In this paper, the effect of partial shading on the number of MPPs has been studied by using MATLAB Simulink simulation models of a real PV generator composed of 18 series-connected PV modules. In most cases, partial shading conditions lead to the occurrence of multiple MPPs, but also only one MPP can be present despite of the partial shading. Conditions, which lead to one or multiple MPPs in electrical characteristics of PV generators, have been studied systematically. It was found out that reasons for having one or more MPPs originated directly from physical properties of PV modules: the ratio of MPP current to short-circuit current, power losses in bypass diodes, and the value of the parasitic shunt resistance of PV cells. These phenomena are thoroughly explained in this paper. [ABSTRACT FROM PUBLISHER]

A precise simulation of the internal faults of synchronous generators is crucial for the design of the main protection scheme; therefore, an accurate model is necessary. In this paper, based on the circuit-coupled finite element method (CCFEM), an improved model of a synchronous generator with internal faults is proposed, wherein the localized model of each stator coil is built as per its actual structure. Using this model, the internal fault occurring inside the coil can be accurately simulated, better approximating the location of the actual fault point; thus, the fault currents can be calculated more accurately. The accuracy of the improved model is verified by a dynamic simulation experiment. Moreover, the electromagnetic magnitudes, such as the air gap flux density, fault currents, field current, and all the damper currents are investigated in detail, under fault conditions, thereby revealing the fault characteristics more clearly and providing a basis for designing protection schemes. [ABSTRACT FROM PUBLISHER]

This paper introduces a battery charging scheme from a solar photovoltaic (SPV) by using a single sensor-based maximum power point tracking (MPPT) strategy. Here, for quick and efficient tracking, a novel hybrid “Cauchy and Gaussian sine cosine optimization” (CGSCO) algorithm is proposed for MPPT, which is based on only a single current sensor. The main objective of the CGSCO algorithm is, maximum extraction of the power from SPV panel and efficiently charging the battery through maximizing the charging current of the battery. Due to the single sensor, the cost of the charging scheme is very low, as well as the algorithm complexity and computational burden are very less, so it can be easily implemented on the low-cost microcontroller. In this paper, a single current sensor-based battery charging scheme by CGSCO algorithm is tested on MATLAB simulator and verified on a developed hardware of the SPV system. The panel condition, with and without shaded as well as dynamic environmental condition (variable temperature and insolation), is considered during simulation as well as on hardware implementation. Moreover, the tracking ability is compared with the most recent state of the art techniques (Grey wolf optimization and Lagrange interpolation particle swarm optimization (LIPSO)) as well as compared with “CGSCO with the conventional dual (voltage and current) sensor-based MPPT scheme.” The efficient battery charging with quick MPPT by CGSCO algorithm w.r.t. all state of the art techniques as well as dual sensor-based MPPT scheme, in steady-state as well as in dynamic conditions meets the motive of the work. [ABSTRACT FROM PUBLISHER]

The paper describes a general model of a hybrid-excited synchronous machine with multiple voltage levels each generated by a 3-phase stator system in a voltage-behind-reactance formulation. The different voltage level of each 3-phase stator system is realized in the same machine design. The rotor is excited through an excitation winding and a permanent magnet. The model incorporates magnetic saturation of the main inductance, magnetic and electric coupling between all phases, and the field winding and a mechanical displacement angle. The cross coupling between q and d axes of the main inductances is included as a constant saliency factor $\alpha$ for all saturation levels. The turn ratio of each 3-phase stator winding system to another 3 -phase system is also modeled as a constant value. Each 3-phase system saturates the iron core with a different weighting represented by the number of turns relative to the reference stator system. The proposed model is included in a field-oriented control scheme. Simulations are carried out with requested \boldsymbol{I_{q,d}} and field winding currents to demonstrate model's dynamics, and the results are verified with measurements on a test bench. [ABSTRACT FROM PUBLISHER]

Transient simulation programs, either nodal analysis-based electromagnetic transient program (EMTP-like) or state-variable-based, are used very extensively for modeling and simulation of various power and energy systems with electrical machines. It has been shown in the literature that the method of interfacing machine models with the external electrical network plays an important role in numerical accuracy and computational performance of the overall simulation. This paper considers the state-variable-based simulation packages, and provides a constant-parameter decoupled RL-branch equivalent circuit for interfacing the ac induction and synchronous machine models with the external electrical network. The proposed interfacing circuit is based on the voltage-behind-reactance formulation which has been shown to have advantageous properties. For the synchronous machines, this paper describes both implicit and explicit (approximate) interfacing methods. The presented case studies demonstrate the advantages of using the proposed interfacing method over the traditional qd-models that are conventionally used in many simulation packages. [ABSTRACT FROM AUTHOR]

In this paper, a method is presented for removing the risk associated with the testing and development of novel drive system topologies, prototype electrical machines, advanced control system strategies, or a combination of the aforementioned without using any real motors/generators. The test platforms for low-power machines are relatively inexpensive and accessible; however, as power levels increase into the upper kilowatt and megawatt range, validation of prototype machines and drives becomes costly. The proposed induction machine emulator (IME) platform utilizes the power hardware-in-the-loop concept in conjunction with a high-fidelity machine model and load dynamics. The electrical machine and its load dynamics are simulated with a real-time digital simulator, which generates appropriate control commands to a power electronics-based voltage amplifier that interfaces to a variable speed drive (VSD). Specifically, the current draw is recreated by altering the phase and magnitude of a voltage amplifier connected to a VSD under test via a unique transformer-based LCL-type coupling network. Based on the proposed concept, the use of a multiwinding, tap-changing transformer establishes a truly versatile and universal test platform for a wide range of power levels. In addition, this paper presents a control strategy in the synchronously rotating reference frame in dq coordinates for the power electronic converters in IME operation. Experimental results at the 25-kVA power level validate the feasibility and highly dynamic performance of the proposed test platform. [ABSTRACT FROM AUTHOR]

In a recent work, the authors computed generator parameters from a load-rejection test based on what they called hybrid state model of the synchronous machine. The state matrices were presented in compact numerical form and may prove tedious to implement. Such a model is a complicated function of the unknown machine parameter vector to be computed which is not always easy to comprehend in an identification process for engineering applications. In this paper, therefore, the decoupled property of the so-called hybrid model along with the application of the complete well-known solution of the linear control systems theory is used to derive time-variant analytical waveforms of the phase voltages and the field current following a generator tripping (load rejection) and an open stator field short-circuit tests in terms of the generator parameters. In the cross-identification approach, the field short-circuit test is used to compute the generator d-axis parameters while the q-axis parameters are obtained from the load-rejection test q-axis data. The proposed identification technique is successfully applied for the parameter identification of a 4-pole 1.5-kVA, 208-V, and 60-Hz saturated laboratory synchronous generator. [ABSTRACT FROM PUBLISHER]