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This paper presents a robust nonlinear decentralized control scheme for islanded dc microgrids, where the main control objectives are to achieve the desired voltage at the common dc bus and to maintain the power balance. The proposed control scheme uses the partial feedback linearization scheme to simplify the dynamical models of different components in dc microgrids. In this paper, the dc microgrid includes a solar photovoltaic unit, a fuel cell system, and a battery energy storage system along with dc loads. The robustness of the proposed controller against parametric uncertainties is ensured by the parameter, appearing in the control inputs as unknown, which is then estimated through adaptation laws. The inherent noise decoupling capability of the feedback linearization scheme is used to provide robustness against external disturbances in dc microgrids. The performance of the proposed controller is evaluated on a dc microgrid through simulation and experimental studies in order to demonstrate the effectiveness and robustness under different operating conditions, while considering the effects of parametric uncertainties and external disturbances. Simulation results are also compared with an existing proportional-integral controller. [ABSTRACT FROM AUTHOR]

Nowadays, many applications are demanding more and more compact, cost effective, and robust electric drives. By using rare earth magnets, it is possible to achieve electrical machines with rather high torque volume ratio, accomplishing this way the compactness requirement. Nevertheless, rare earth permanent magnets are very sensitive to the temperature, so that the risk of being partially demagnetized arises as their working temperature increases. In addition, as it has been seen during the last years, the market of rare earth metals is quite volatile. The price of magnets could rise suddenly, leading to a significant impact on the cost, and so in the competitiveness of permanent magnet machines. Due to this fact, it is essential to reduce the dependency on rare earth market in order to accomplish cost-effective drive solutions. Some key points to face this problem can be to reduce the magnet volume, or to use magnets with worse thermal properties (magnets with less dysprosium). Nevertheless, in both cases, the adopted solution would lead to an increase in the risk of demagnetization, affecting to the robustness of the machine. In this paper, a methodology based on finite element analysis and experimental test is proposed to evaluate the demagnetization risk in permanent magnet machines. By applying this methodology, it is possible to accomplish competitive machine designs, achieving a good tradeoff between cost and robustness. The proposed methodology has been applied in a practical case, for the optimization of ten industrial motors, achieving good results. [ABSTRACT FROM AUTHOR]

A “condensate load” (condensate in \% of a totally full cylinder) over 1\% accumulated inside the dryer cylinders of a paper machine is likely to produce a drive overload, eventually increasing the acceleration time or even producing an overload trip. This paper proposes and evaluates a confident online condensate estimation algorithm that gives updated information at preset speeds and when the transition to the rimming stage is detected. The experimental evaluation performed on a 500-mm-diameter cylinder, with condensate load between 0.5 \% and 25\% , confirmed the ability of the algorithm to give accurate estimations within 0.5 \% intervals of condensate loads. The developed algorithm is a useful tool for the operators, allowing them to take the appropriate decisions according to the severity of the condensate accumulation detected. [ABSTRACT FROM PUBLISHER]

In the coming years, the electrification and the deployment of the electric motors in the urban transports will become a more and more widespread reality. The optimization stage of the electric motors usually does not consider in detail the real driving conditions of the car in which the motor is installed. It follows that the actual motor performance in operating points, particularly as regards the torque ripple and the efficiency, might be worse than expected. A robust solution is a required target. This paper deals with the design and optimization of a high-speed permanent-magnet-assisted synchronous reluctance motor for traction applications, taking into account both city and highway driving cycles. A procedure is employed in order to evaluate the most representative operating points, which have to be considered when a global optimization is required. An analysis of the solution robustness has been performed. Both results and advantages of the adopted methodology are highlighted. [ABSTRACT FROM PUBLISHER]

With increasing renewable distributed energy resources integrated into a microgrid (MG), it is difficult to realize its optimal operation due to various uncertainties, e.g., power outputs of wind turbines and photovoltaic cells. This paper presents a flexible scheduling model for the optimal operation of an MG in which the expectation of operational cost and the robustness of scheduling solutions are considered, simultaneously. To balance the tradeoff between minimizing the expectation of operational cost and enhancing robustness, the proposed flexible scheduling model of MG is formulated as a multiobjective optimization problem by introducing a robustness preference parameter. In this way, the relationship between the expected operational cost and the robustness of scheduling solution is investigated, and the fuzzy decision making method is used for selecting a suitable solution. Finally, a modified MG is used for case study, and simulation results verify the applicability and effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

The increasing penetration of distributed and renewable generation presents power systems with a challenge of accommodating multiple inverter-based generators. Distributed generators (DGs), capable of operating in the islanded mode, are often installed in microgrids. However, a control system for operating multiple DGs in the islanded mode using voltage-sourced converters is a real challenge under uncertainties in load parameters, unbalanced phase conditions, and transients. This paper proposes a novel approach to decentralized control of multiple DGs. This approach is based on a combination of a voltage controller using model predictive control and a fast current controller using a discrete-time sliding-mode controller for limiting the inverter currents under overload conditions. Performance of the proposed control system is compared with a robust servomechanism program controller. The proposed control strategy provides fast tracking, robustness, and fast transient recovery in voltage and current under: 1) short-circuit conditions; 2) load transients; and 3) unbalanced loads. Various scenarios including reference signal tracking and robustness against the load perturbations are considered. Results are presented and discussed. [ABSTRACT FROM PUBLISHER]

Silicon carbide (SiC) power mosfets are promising alternatives to Si devices in high-voltage, high-frequency, and high-temperature applications. The rapid and widespread deployment of SiC devices raises long-term reliability concerns, particularly for mission and safety critical systems due to limited field data and potential uncertainties. Therefore, it is essential to investigate progressive degradations and parameter shifts in SiC devices to develop system integrated degradation monitoring tools for self-monitoring converters, which can recognize failure precursors at the earliest stage and prevent catastrophic failures. This paper presents a comprehensive long-term reliability analysis of commercially available SiC mosfets under high temperature operation and high temperature swing, degradation related key precursors, and possible causes behind them. For this purpose, discrete SiC devices are power cycled and all datasheet parameters are recorded at certain intervals with the aid of the curve tracer. Variation of electrical parameters throughout the tests is presented in order to assess their correlation with the aging/degradation state of the switch. Among them, gate oxide charge trapping related threshold voltage drift and corresponding on state resistance variation has been observed for all samples. For some samples, bond wire heel cracking is found to be the root cause of sudden on state resistance and body diode voltage increases. The discussions regarding aging precursors are supported by failure analysis obtained through the decapsulation of failed devices. Finally, the findings are evaluated in order to define the suitability of electrical parameters as an aging precursor parameter under the light of practical implementation related issues. [ABSTRACT FROM AUTHOR]

This paper presents a speed estimation based vector control architecture for doubly fed induction generator (DFIG). The main advantage of the proposed architecture is that with this methodology the generator can be operated without a speed sensor and position encoder. The method calculates the machine parameters online using a recursive least square (RLS) technique based on identifying the transfer function relating to rotor speed and position error. Minimum variance controller (MVC) ensures that the position error is minimum by proper estimation of the speed. For illustration, first, the small signal model of the machine and the regulator design is discussed. Then, a methodology is proposed, in which machine's mutual inductance is estimated online, so that the estimation approach is robust to changes in the machine parameters. Second, the control architecture with the speed estimation technique is discussed. The proposed approach is validated using a real-time simulation platform for a GE 1.5 MW wind turbine (both for steady-state operations and grid disturbance conditions) and with hardware in the loop (HIL) experimental setup for a 2-kW doubly fed induction machine (DFIM). Simulation results demonstrate desired steady-state and dynamic performance of this sensorless control approach for DFIG-based variable-speed wind turbines. [ABSTRACT FROM AUTHOR]

Power electronics for the utility interface of distributed energy resource (DER) offers many benefits in the electric grid operation through flexibility of the DER controls. Energy from various generation sources including renewables can be efficiently delivered to the consumers with high power quality and reliability. However, mixed source microgrids comprising both inverter- and synchronous generator-based DERs are susceptible to collapse, particularly when the system operates in the islanded mode. This paper presents robustness studies on microgrids from a qualitative point of view, borrowing features from ecological systems that are highly robust. The interrelationships between ecological species translate into the dynamic behavior of DERs, affected by their sizes and locations within the grid. The advantage of such qualitative analysis over traditional quantitative viewpoint is it explicitly identifies the nature of interactions and interconnections between the subsystems as beneficial or detrimental to stability. From the robustness studies, the best possible microgrid configurations are determined for IEEE 33-bus system having a mix of inverter-based DERs and synchronous generator-based DERs. Furthermore, all possible microgrid cluster formations are studied for finding the most robust microgrid islanding strategies. [ABSTRACT FROM AUTHOR]

This paper investigates the injecting power stabilization of nonlinear dc microgrids (MGs) with constant power loads (CPLs). By considering a centralized controller scheme, the limitations of the communication utilities are considered. Therefore, limited information is transferred through the nonideal noisy communication network. Consequently, a cubature Kalman filter (CKF) with a third degree is proposed to mitigate the effect of the noisy measurement and the noisy network on the system's information. Moreover, an estimation-based robust feedback controller is developed to design an optimal value for the injecting power. The considered CKF algorithm is robust against the system uncertainty and noisy environments and has a low computational time for high-order dc MGs with a high number of sources and CPLs. In addition, a systematic procedure to compute the feedback gain of the controller is presented, which can be numerically solved by linear matrix inequality techniques. Hardware-in-the-loop real-time simulation results verify the simplicity of the controller implementation, enhanced performance for the case of limited information, and better robustness against the noisy measurements compared to the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

This paper presents a novel grid current control of a grid-connected voltage source converter with an LCL filter. The proposed control method uses an $\mathcal {H}_\infty$ synthesis method to shape the input admittance of the converter, to track a given current reference, and/or to limit the controller actuation at different frequency ranges. The converter admittance is shaped, both in magnitude and phase, following a model reference defined by the designer in the frequency domain. By specifying a low admittance magnitude reference, the optimization algorithm will obtain a controller that actively damp the filter resonance and attenuate/reject the grid voltage oscillations, either in a wide frequency range or concentrated at the main harmonic frequencies. Additionally, the proposed controller design methodology takes advantage of its admittance phase shaping capability to improve the system robustness in front of grid uncertainties and minimizing converter impact over grid stability due to its positive-real nature. The synthesized controller only measures the grid current and voltage to achieve the aforementioned results, reducing the number of sensors (and their associated cost) required for its implementation. Experimental results illustrate the correct behavior of the closed-loop system with the designed controller in time and frequency domain. [ABSTRACT FROM AUTHOR]

This paper presents an improved control scheme for the operation of grid-tied inverters in order to attain the IEEE 1547.2-2008 harmonic limit standard even with a wide range of grid parameters. This control structure includes an active damping with a new current estimator and a proportional-resonant controller with harmonic compensation. In order to guarantees the inverter operation with a wide range of grid parameters, the damping and the controller gains are designed considering robustness characteristics. Moreover, it proposes a new estimator for the current filter capacitor for operation with a wide range filter resonance frequency. The grid synchronization mechanism uses the modified second-order general integrator frequency-locked loop technique. Experimental results are carried out and presented to validate the control structure design and the proposed current estimation. [ABSTRACT FROM AUTHOR]

Steel rails used in the transport sector and in industry are designed and manufactured to support high stress levels generated by high-speed and heavy-loaded modern trains. In the rail manufacturing process, one of the key stages is rolling, where fast, accurate, and repeatable rail profile measurement is a major challenge. In this paper, a rail profile measurement system (PMS) for rail rolling mills based on four conventional, inexpensive laser range finders is proposed. The range finders are calibrated using a common reference to properly express the point clouds generated by each range finder in the world coordinate system (WCS). The alignment of the point clouds to the rail model is performed by means of an efficient and robust registration method. Experiments carried out in a rail rolling mill demonstrate the accuracy and repeatability of the system; the maximum error is below 0.12%. All parallelizable tasks were designed and developed to be executed concurrently, achieving an acquisition rate of up to 210 fps. [ABSTRACT FROM AUTHOR]

The main advantage of the LCL filter in grid-tied converters is its ability to achieve a better harmonic mitigation in comparison with L filter. A proportional–integral (PI) regulator can be considered as a good candidate for controlling the LCL-filter system, as it is more convenient for real-time implementation. However, PI controller is not capable of stabilizing the grid-tied LCL -filter system when the resonance frequency of the LCL network is below a certain value that mainly depends on the sampling frequency. Such a problem can be overcome by adding an active damping (AD) to the PI controller. This paper presents the design, implementation, and performance testing of a stable PI current controller for a grid-tied inverter using LCL filter. The design process is based on combining feedback linearization (FBL) technique with a disturbance-observer-based control (DOBC). It turns out that the composite controller, consisting of FBL and DOBC, reduces to a PI current controller associated with a linear state-feedback control that plays the role of an AD. In addition, an antiwindup compensator arises naturally into the controller when considering the limits on the control input. An important feature of the proposed PI current controller is its ability to retain the nominal transient response achieved with state-feedback control even in the presence of model uncertainty and external disturbances. The proposed controller was verified through simulation and experimental tests. The results demonstrated the ability of the controller to provide good transient and steady-state performances. [ABSTRACT FROM AUTHOR]

In this paper, new model-based sensorless control methods are proposed that include independent estimations of position and speed errors, and compatible position and speed estimators. Using the proposed position estimator, a unity transfer function can be achieved from the actual position to the estimated position, eliminating the effects of load disturbances. This implies that the position error would ideally be zero, even in a transient state. In addition, the effects of parameter and voltage synthesis errors on the steady-state position error are analyzed. Experimental results verify both the analysis and the effectiveness of the proposed methods under severe load disturbances such as speed transient (20 000 r/min/s) and load torque transient (10 p.u./s). With the proposed methods, position estimation errors are significantly reduced by more than 50% during speed and load torque transients at identical dominant-pole placements, verifying the enhanced tracking capability and robustness of the proposed methods against external load disturbances. [ABSTRACT FROM AUTHOR]

This paper deals with a novel robust current control scheme for permanent magnet synchronous machine drives that improves the conventional cascade structure. The main idea is to substitute the commonly used decoupling network, which requires the precise knowledge of the system parameters in any working condition, with a more flexible and robust observer scheme. In particular, the traditional configuration is improved by means of two proportional-integral observers that allow the preservation of the desired drive performances even in the presence of disturbances and uncertainties. The increased robustness is achieved by maintaining the reliable basic scheme with a pure proportional controller in the forward path with advantages in terms of design and tuning. A genetic algorithm is used to optimize the controller and observer parameters. This multiobjective optimization leads to good stability and an overall enhanced performance of the drive above the operative range. The choice of the optimal solution is based on a novel fitness function that takes into account both dynamical features and disturbance rejection capabilities of the system. The effectiveness of the proposed control scheme compared with a standard proportional-integral control is verified by means of numerical simulations and experiments as well. [ABSTRACT FROM AUTHOR]

Induction cap sealers are actively controlled passive component dominant industrial power control equipment. In series resonant inverter-fed air-cooled induction sap sealer, the major part of power loss takes place in high-current passive tank circuit. To enable power transfer to mobile aluminum foil as and when needed, the tank circuit remains energized at rated current. Efficient power delivery to load needs minimum power loss in them. Litz-wire-based air-cooled system, to a large extent, meets this criterion. Further improved performance depends on optimal choice of passive components in the tank circuit. In addition to that, the quality and reliability of the controller depend on electrical and thermal stresses in each of them. At no load, the poor damping factor of litz-wire-based tank circuit tends to generate oscillatory current envelope resulting in increased power loss in tank circuit, as well as in increase e in voltage stress in resonant capacitor. Robust second-order sliding mode control is able to eliminate those problems. This paper further elaborates that the robust power control feature of second-order sliding mode control could uniquely be used to qualitatively differentiate among possible alternates of each constituent member of tank circuit. [ABSTRACT FROM AUTHOR]

In this paper, a robust voltage control is designed for a floating interleaved boost converter with high voltage gain. The proposed controller has an inner loop based on super-twisting sliding mode algorithm, which has continuous control signal and the sliding surface is defined for the inductor current. The reference current value is generated by active disturbance rejection control (ADRC) algorithm in the outer loop, based on the output voltage error. The stability of the sliding mode inner loop and the ADRC outer loop are proven using Lyapunov stability theorem and Routh–Hurwitz criteria, respectively. The robustness of the proposed controller is analyzed in depth, and validated by the simulations and experimental results obtained with a 100 W prototype converter. [ABSTRACT FROM PUBLISHER]

This paper investigates the impact of tolerances related to permanent magnets on the cogging torque performance of Permanent magnet synchronous machines (PMSMs). These machines usually show a considerable sensitivity regarding tolerances for geometric dimensions and material characteristics. A consistent approach is presented in order to minimize the computational effort for evaluating the sensitivity, robustness, or reliability. Thereby, design of experiments is used to minimize the required number of finite element simulations. In this work, a Box–Behnken-based approach is considered. Subsequently, a surrogate modeling technique based on a second-order equation is applied. As a consequence, a reduction of the computational cost by 96% is achieved. The obtained results are compared with outcomes solely derived by means of finite element computations and very good agreement is observed. This is illustrated by providing the probability distribution of the cogging torque for the considered machine design. In addition, the cumulative distribution is presented, which usually is applied for analyzing the reliability. Considering the analysis of the impact of tolerances as part of optimization scenarios increases the number of designs to be analyzed by at least one degree of magnitude. The obtained results look promising for achieving this at feasible computational cost. [ABSTRACT FROM AUTHOR]

This paper proposes an automatic and intelligent stator fault diagnosis system for permanent magnet synchronous generators. The system is based on the use of a feedforward multilayer perception artificial neural network (ANN) performed by the back-propagation training algorithm. From a thorough study and analysis of the behavior of the negative-sequence voltage of the machine under different stator faults and different operating conditions, two new robust indicators of faults are selected as the ANN inputs. The two fault indicators are the phase angle of the negative sequence voltage and the frequency of the machine voltages. After successfully training and testing the ANN with specific and meaningful databases, the ANN behavior is validated by using an experimental database acquired from a real machine. The accurate results provided by the ANN prove the reliability of the proposed system to automatically diagnose different stator faults under variable speed, variable fault current, and variable load conditions overcoming different disturbances, such as the noisy signals and the harmonics in the machine. [ABSTRACT FROM PUBLISHER]

Permanent magnet synchronous motors (PMSMs) drives using three-phase voltage-source inverters (VSIs) are currently used in many industrial applications. The reliability of VSIs is one of the most important factors to improve the reliability and availability levels of the drive. Accordingly, this paper presents a robust fault diagnostic method for multiple insulated gate bipolar transistors (IGBTs) open-circuit faults and current sensor faults in three-phase PMSM drives. The proposed observer-based algorithm relies on an adaptive threshold for fault diagnosis. Current sensor and open-circuit faults can be distinguished and the faulty sensors and/or power semiconductors are effectively isolated. The proposed technique is robust to machine parameters and load variations. Several simulation and experimental results using a vector-controlled PMSM drive are presented, showing the diagnostic algorithm robustness against false alarms and its effectiveness in both IGBTs and current sensors fault diagnosis. [ABSTRACT FROM PUBLISHER]

A considerable amount of papers has been published in recent years proposing supervised classifiers to diagnose the health of a machine. The usual procedure with these classifiers is to train them using data acquired through controlled experiments, expecting them to perform well on new data, classifying correctly the condition of a motor. But, obviously, the new motor to be diagnosed cannot be the same that has been used during the training process; it may be a motor with different characteristics and fed from a completely different source. These different conditions between the training process and the testing one can deeply influence the diagnosis. To avoid these drawbacks, in this paper, a new method is proposed, which is based on robust statistical techniques applied in quality control applications. The proposed method is based on the online diagnosis of the operating motor and can detect deviations from the normal operational conditions. A robust approach has been implemented using high-breakdown statistical techniques, which can reliably detect anomalous data that often cause an unexpected overestimation of the data variability, reducing the ability of standard procedures to detect faulty conditions in earlier stages. A case study is presented to prove the validity of the proposed approach. Motors of different characteristics, fed from the power line and several different inverters, are tested. Three different fault conditions are provoked: a broken bar, a faulty bearing, and mixed eccentricity. Experimental results prove that the proposed approach can detect incipient faults. [ABSTRACT FROM PUBLISHER]

This paper develops a modeling method for robust stability analysis of nonlinear electrical power systems over a range of operating points and under parameter uncertainties. Standard methods can guarantee stability under nominal conditions, but do not take into account any uncertainties of the model. In this study, stability is assessed by using structured singular value (SSV) analysis, also known as $\mu$ analysis. This method provides a measure of stability robustness of linear systems against all considered sources of structured uncertainties. The aim of this study is to apply the SSV method for robust small-signal analysis of nonlinear systems over a range of operating points and parameter variations. To that end, a modeling methodology is developed to represent any such system with an equivalent linear model that contains all system variability, in addition to being suitable for $\mu$ analysis. The method employs symbolic linearization around an arbitrary operating point. Furthermore, in order to reduce conservativeness in the stability assessment of the nonlinear system, the approach takes into account dependences of operating points on parameter variations. The methodology is verified through $\mu$ analysis of the equivalent linear model of a 4-kW permanent magnet machine drive, which successfully predicts the destabilizing torque over a range of different operating points and under parameter variations. Further, the predictions from $\mu$ analysis are validated against experimental results. [ABSTRACT FROM PUBLISHER]

High-speed regimes allow an increase in the power density of electrical drives, which is a necessary characteristic in aeronautical applications. In such a context, together with the typical nonlinearities of low-speed drives, i.e., core saturation, phenomena related to high fundamental to sampling frequency ratios appear increasingly significant. This paper applies methodologies based on modern robust control to high-speed synchronous reluctance machines. The proposed method is based on a reformulation of the motor model as a linear parameter varying system. This allows transforming the current controller design in a multivariable optimization problem, which is solved with efficient numeric tools. The mathematical formulation of a robust digital controller directly designed in the discrete time domain is proposed. The controller performance are experimentally compared to of its counterpart designed in the continuous-time domain, and subsequently, discretized, as proposed in a previous work by the same authors, to have agreement a more standard decoupled current control using proportional-integral regulators. Results demonstrate the effectiveness of the proposed controller structure in current regulation, especially at high-speed regimes. [ABSTRACT FROM PUBLISHER]

This paper presents a robust nonlinear control technique for a wide-speed-range operation of interior permanent magnet synchronous motor (IPMSM) based on the use of maximum torque per ampere (MTPA) and flux-weakening (FW) controls. The global asymptotic stability of the drive is demonstrated by Lyapunov stability criterion in conjuncture with Barbalat's lemma. For the proposed nonlinear controller, the MTPA and FW schemes are used to control the d-axis stator current below and above the rated speed, respectively. Control laws are developed based on an adaptive backstepping technique to ensure robust system stability. The system nonlinearities are also accommodated through the online estimation of critical parameters. The control and adaptive backstepping laws have been successfully implemented in a MATLAB/Simulink simulation environment. Simulation results indicate excellent speed response and parametric variation insensitivity. The complete drive system is implemented using the peripheral component interconnect (PCI)-based DS1104 digital signal processor (DSP) board for a 3.7-kW laboratory IPMSM. Both experimental and simulation results have demonstrated excellent drive performance, with an extended-speed-range operation and rejection of load disturbance. [ABSTRACT FROM PUBLISHER]

This paper deals with the evaluation of robustness of high-power press-pack insulated-gate bipolar transistor modules under short-circuit conditions. The severity of the tests is usually related to the achievement of the real failure mode which drives the device to withstand a big amount of energy. The most well-known methods to evaluate the robustness of the devices have been analyzed and improved in order to operate with the highest achievable di/dt and to consequently emulate the real circuit setup and failure mode. Experimental tests will be shown and evaluated under different voltage and temperature conditions. The tests described in this paper have been targeted to evaluate the capability of the device to withstand extremely severe conditions when they are used in a high-power converter. A driving protection feature dealing with the target of improving the functionality of protection against failure will be also described. [ABSTRACT FROM PUBLISHER]

Robustness and capability are critical issues for the industrial application of any novel electrostatic process. The aim of this paper is double: show how an experimental design methodology can contribute to assessing the robustness of a given tribo-aerodynamic charging process and validate a procedure for evaluating the capability of two tribo-aerodynamic chargers with respect to the specific requirements of electrostatic separation applications. The results of three fractional factorial experimental designs performed on starch and flour powders, in two devices similar to the triboguns employed for electrostatic powder coating, demonstrate that the tribo-aerodynamic charging is robust with respect to the three main control variables of the process: the injection and vortex pressures of the air in the pneumatic circuit and the material feed rate. The capability indexes computed for both the straight- and spiral-type tribocharges were satisfactory. [ABSTRACT FROM PUBLISHER]

Fault detection and fault accommodation, as well as fault tolerance, are important issues in closed-loop controlled three-phase converters. For such systems, power semiconductors and sensors are the most affected components by the occurrence of failures. Therefore, fault diagnosis and remedial operating strategies involving such components are highly required. In this paper, a new reliable approach is proposed, which aims to diagnose current sensor faults and power semiconductor open-circuit faults in permanent magnet synchronous motor drives. The proposed fault diagnosis scheme uses only the measured currents, which makes it suitable for real-time implementation. The performance of the proposed technique is analyzed through experiments. [ABSTRACT FROM AUTHOR]

In the traditional adaptive full-order observer (AFO) for speed-sensorless induction motor drives, the estimated rotor flux error is neglected in the speed estimation algorithm. In this paper, the estimated rotor flux error and an error coefficient are adopted in the speed estimation algorithm to improve the robustness of speed estimation. Based on the proposed speed estimation algorithm, the design of AFO is divided into two types: 1) designing the error coefficient with existed feedback gains for the stability of speed estimation and 2) designing feedback gains with constant error coefficient for the stability of speed estimation. With both proposed methods, the estimated rotor speed error caused by motor parameter deviation can be reduced especially at low-speed regenerating range. The feasibility of proposed methods is verified by experiments. [ABSTRACT FROM PUBLISHER]

From a traction application point of view, proper operation of the synchronous reluctance motor over a wide speed range and mechanical robustness is desired. This paper presents new methods to improve the rotor mechanical integrity and the flux weakening capability at high speed using geometrical and variable ampere-turns concepts. The results from computer-aided analysis and experiment are compared to evaluate the methods. It is shown that, to achieve a proper design at high speed, the magnetic and mechanical performances need to be simultaneously analyzed due to their mutual effect. [ABSTRACT FROM PUBLISHER]

This paper presents a novel model predictive torque control with discrete duty ratio optimization for a six-phase PMSM machine with high robustness against weighting factor variation. First, a two-step lookup table is developed to initially select the optimal voltage vector, which is to regulate the torque and flux in the energy conversion related subspace, as well as suppress the harmonic currents in the x–y subspace. Then, a null vector is inserted along with the selected optimal voltage vector to adjust the duty ratio with a set of value to avoid the complicated derivation. Subsequently, the optimal duty ratio is determined by a cost function to minimize the torque and flux error. So by using the proposed method, the torque ripple is reduced and even applying an improper weighting factor will not deteriorate the machine performance severely. Finally, experimentations are carried out to verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

This paper deals with a robust input–output feedback linearization control technique for induction motors. Indeed, classic feedback linearization presents two main disadvantages: 1) the accuracy of the dynamic model; and 2) the corresponding correct knowledge of the model parameters. To address this issue, the linear controller has been substituted with a suitably controller designed to be robust to the variations of the main parameters of the induction motor, like stator and rotor resistances, and the three-phase magnetizing inductance. The proposed controller has been tested both in numerical simulation and experimentally on a suitably designed test setup. Moreover, it has been compared with the classical feedback linearization based on linear controllers, highlighting the improvements in terms of dynamic performance, when parameter variations occur. Results confirm a significant increase of the robustness of the controller against parameter variations. [ABSTRACT FROM AUTHOR]

A deregulated power system is considered to be a highly complex uncertain system due to the presence of multiple bilateral transactions. Load frequency control in such a system hence assumes significance because of the challenging nature of operation and therefore use of robust controllers is imperative. Conventional robust controller designs give higher order controllers and hence restricts its application in the industry. But the alternative is to use structured H-infinity controllers, which give sufficiently lower-order controllers and can be used in system with nonlinearities. In this paper, structured H-infinity controller has been designed for a deregulated power system considering the effect of nonlinearities like generation rate constraint, governor deadband, and time delay associated with communication network in the system from practical point of view. These physical constraints demand an electrical energy storage system. Hence, load frequency control is accomplished with a structured H-infinity controller supplemented with redox flow battery in each area of a two-area deregulated power system consisting of GENCOs of reheat thermal type. [ABSTRACT FROM AUTHOR]

The vibratory feeders had already been proven to be efficient devices for tribocharging granular plastics in view of their separation in high-intensity electric fields. In this paper, the vibratory feeder was used as a tribocharger operating with a free-fall electrostatic separator. There are two aims at embarking on the study: 1) formulate recommendations regarding the optimum values of three control variables of the separator; and 2) assess the robustness of the triboelectrostatic separation. The 50%-ABS–50%-HIPS mixture of 4-mm-size granules employed in the experiments is typical for the recycling of plastics from waste electrical and electronic equipment. The investigation was conducted according to a composite factorial experimental design, and it revealed that the separation efficiency significantly depends on the high-voltage applied to the electrode system and on the position of the splitters that define the geometry of the product collector, but is less affected by the material transport velocity on the tray of the vibratory feeder. Using Taguchi's methodology, it was possible to predict the most robust process design, with respect to the uncontrolled variation of granule size and ABS content. The former of these “noise” factors has a significant effect on the outcome of the process, whereas the latter has little influence on separation efficiency. [ABSTRACT FROM PUBLISHER]

This paper presents a new least-mean-square (LMS) algorithm based deadtime compensation method to suppress the current distortion in permanent-magnet synchronous motor (PMSM) field-oriented control (FOC) drives. Compared to conventional average value compensations, the proposed method is robust to switching device parameter variations thanks to the online adaptation capability of the LMS algorithm. Similarly, the disturbance observer compensators are also immune to switching device parameter variations; however, varying motor parameters degrade their compensation performance. Without prior knowledge of switching device or motor parameters, the proposed method can directly reduce the deadtime current harmonics by generating compensation voltage references. In addition, the proposed method is easy to implement since it does not require voltage errors estimation or current harmonics extraction, which are necessary for disturbance observer and adaptive filter based methods. The proposed method is tested on a 2.5-kW voltage-source inverter PMSM drive controlled by an FOC algorithm. Its effectiveness is validated by both experimental results and spectrum analysis. [ABSTRACT FROM AUTHOR]

In this paper, a fifth-order boost point-of-load converter is developed by cascading a modified fourth-order boost converter with a combination of L–C and diode. This topology has the following salient features: Single-switch topology, common ground between source and load, low-voltage stress across intermediate capacitors, and voltage gain same as other reported fifth-order boost converters with no common ground. Steady-state and dynamic analyses demonstrate the proposed converter's boosting feature and dynamic performance, respectively. A contoured robust Bode plot methodology is employed to design the robust voltage-mode controller to ensure load voltage regulation in the presence of uncertainties. The necessary and sufficient conditions under which the designed controller guarantees the load voltage regulation and robust stability are obtained. A step-by-step robust controller design procedure is outlined. The salient features of the proposed converter and its robust performance are studied analytically, using the MATLAB platform, and validated experimentally on a 60-W prototype module. [ABSTRACT FROM AUTHOR]

This paper presents a grid-side current controller for grid-tied inverters with LCL filter, including harmonic current elimination. The proposed controller only measures the grid current and voltage and it combines excellent dynamic characteristics with good robustness. Contrarily to previously proposed harmonic-current controllers, the presented solution offers a generalized method that gives a consistent (with minimal variation in the reference-tracking dynamics) and stable performance irrespectively of the number of current harmonics to be canceled and of the resonant frequency of the LCL filter (provided that it is lower than the Nyquist frequency). The response to reference commands is completely damped and fast. The response speed is set in accordance with the low-pass characteristic of the LCL filter so as to limit the control effort. Concerning the disturbance rejection, the controller offers an infinite impedance to any disturbances (such as grid voltage harmonics) at a set of arbitrarily specified frequencies. This allows the designer to eliminate all the undesired current harmonics with a simple design process. In addition, the performance of the presented controller is evaluated in terms of a fundamental tradeoff that exists between robustness to variations in the grid impedance and the number of frequency components rejected. Finally, simulation and experimental results that validate the proposal are presented. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive nonlinear disturbance observer (ANDO) for identification and control of a two-axis motion control system driven by two permanent-magnet linear synchronous motors servo drives. The proposed control scheme incorporates a feedback linearization controller (FLC), a new double-loop self-organizing recurrent wavelet neural network (DLSORWNN) controller, a robust controller, and an ${{\mathcal H}_\infty }$ controller. First, an FLC is designed to stabilize the XY table system. Then, a nonlinear disturbance observer (NDO) is designed to estimate the nonlinear lumped parameter uncertainties that include the external disturbances, cross-coupled interference, and frictional force. However, the XY table performance is degraded by the NDO error due to parameter uncertainties. To improve the robustness, the ANDO is designed to attain this purpose. In addition, the robust controller is designed to recover the approximation error of the DLSORWNN, while the ${{\mathcal H}_\infty }$ controller is specified such that the quadratic cost function is minimized and the worst-case effect of the NDO error must be attenuated below a desired attenuation level. The online adaptive control laws are derived using the Lyapunov stability analysis and ${{\mathcal H}_\infty }$ control theory, so that the stability of the ANDO can be guaranteed. The experimental results show the improvements in disturbance suppression and parameter uncertainties, which illustrate the superiority of the ANDO control scheme. [ABSTRACT FROM AUTHOR]

AC current regulation for low-pulse-ratio inverters is particularly challenging because the controller bandwidth is often comparable to the target fundamental frequency and this constrains the transient response. This paper presents an improved current regulation strategy to address this issue, using state feedback concepts to deterministically compensate for pulsewidth modulation (PWM) transport delay so that the controller gains can be significantly increased. Controller design principles are presented using discrete linear-quadratic-regulator theory, and an elegant strategy is applied to make the system more robust to PWM saturation. Experimental results for both 50-Hz and 400-Hz systems confirm the theoretical concepts and demonstrate the superior transient performance of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper presents an integrated environment for the rapid prototyping of a robust fuzzy proportional- integral-derivative (PID) controller that allows rapid realization of novel designs. Both the design of the fuzzy PID controller and its integration with the classical PID in a global control system are developed. The architecture of the fuzzy PID controller is basically composed of three parallel fuzzy subcontrollers. Then, the parallel subcontrollers are grouped together to form the overall fuzzy PID controller. The fuzzy proportional, integral, and derivative gains are direct output from the parallel fuzzy subcontrollers and are derived in the error domain. Thus, the proposed architecture presents an alternative to control schemes employed so far. The integrated controller is formulated and implemented in real time, using the speed control of a brushless drive system as a test bed. The design, analysis, and implementation stages are carried out entirely using a dSPACE DS1104 digital-signal-processor-based real-time data acquisition control system and MATLAB/Simulink environment. Experimental results show that the proposed hybrid fuzzy PID controller produces superior control performance than the conventional PID controllers, particularly in handling nonlinearities and external disturbances. [ABSTRACT FROM AUTHOR]

In this paper, the influence of measurement errors and inverter irregularities on the performance of sensorless control is studied. The control algorithm is based on the back-electromotive-force estimation whose robustness with respect to the machine parameter uncertainties has been already studied by supposing that the current measurements and the power stage are ideal. Here, these hypotheses are removed and it is shown, analytically and experimentally, that the control performances at low speeds are highly affected by the imperfection of the electronic components. Finally, the interest of online stator resistance estimation improving the sensorless control performances in spite of the above disturbances is presented. [ABSTRACT FROM AUTHOR]

In this paper, the local trajectory tracking control problems ascribed to two interacting plants, considered as agents, are formulated as adaptive control problems, which involve online interaction estimation and interaction elimination. This approach gives rise to a robust decentralized collaborative control with virtually no information on the part of the agents. It is shown that when the interconnection effects are viewed as exogenous unstructured disturbances, such disturbance can be actively estimated and canceled from each individual subsystem model dynamics. The case presented deals with two agents, two interconnected boost dc–dc power converters, powered each one by a nonidentical photovoltaic module that represents a time-varying power supply. Then, a backstepping-based control together with an extended state observer is developed by each agent. The mutual goals of agents are to maintain a desired behavior (time-varying current demand) of the entire system in order to maintain the desired output voltage value and an equitable current sharing in each converter in order to supply a dc motor. The proposed distributed control technique is implemented in two TMS320F28335 digital signal processor (each one per agent) and its performance is experimentally evaluated in real time. It is shown that the proposed scheme is robust with respect to interaction, unmodeled nonlinearities, and unmodeled dynamics. [ABSTRACT FROM AUTHOR]

In this paper, an intelligent adaptive tracking control system (IATCS) based on the mixed H2/ H\rm{\infty } approach for achieving high precision performance of a two-axis motion control system is proposed. The two-axis motion control system is an X-Y table driven by two permanent-magnet linear synchronous motors (PMLSMs) servo drives. The proposed control scheme incorporates a mixed H2/ H\rm{\infty } controller, a self-organizing recurrent fuzzy-wavelet-neural-network controller (SORFWNNC), and a robust controller. The SORFWNNC is used as the main tracking controller to adaptively estimate an unknown nonlinear dynamic function (UNDF) that includes the lumped parameter uncertainties, external disturbances, cross-coupled interference, and frictional force. Furthermore, a robust controller is designed to deal with the approximation error, optimal parameter vectors, and higher order terms in Taylor series. Besides, the mixed H2/ H\rm{\infty } controller is designed such that the quadratic cost function is minimized and the worst case effect of the UNDF on the tracking error must be attenuated below a desired attenuation level. The online adaptive control laws are derived based on Lyapunov theorem and the mixed H2/ H\rm{\infty } tracking performance so that the stability of the IATCS can be guaranteed. The experimental results confirm that the proposed IATCS grants robust performance and precise dynamic response to the reference contours regardless of external disturbances and parameter uncertainties. [ABSTRACT FROM AUTHOR]

A control concept is matured through its increased utility in the market place. Although traditional sliding-mode control (SMC) with its simple control function seems to have the ability to reject disturbances and generate parametric insensitivity features, proportional-plus-integral (PI) control is still regarded as the industry standard. Prolonged persistent research in SMC [such as its transition to second-order sliding mode (SOSM)] is always in place; however, comparatively, its market penetration in shaping up a complete established industrial product is far below expectation. The absence of a support system in the form of very large scale integration circuits to translate its control function for actuation increases the design cycle time that adds to inertia to its market penetration. Second, implementing SOSM is not simple either. Is there any other reason? This paper, using a purely practical approach operating on respective proven control functions, tries to figure out how PI dominates over SOSM ideas in shaping up a complete market-driven engineered product for a multiple-input multiple-mode complex and yet most popular arc welding (gas metal arc welding) process, where disturbances and parametric variations are thick and large. [ABSTRACT FROM AUTHOR]

This paper proposes a novel low-cost control strategy of gearless traction permanent-magnet synchronous machines for direct-drive elevator applications. It can improve robustness of the weight-sensorless traction machine system installed with an ordinary incremental encoder. In order to improve the riding comfort for the passengers during brake releases, a novel starting torque compensation strategy without a weight transducer is presented. After analyzing the dynamic characteristics and the friction torque of the elevator traction system, two starting torque compensation methods based on the dichotomy and the staircase method are proposed for the weight-sensorless elevator applications. This way, electromagnetic torque can be generated to balance the load torque, and sliding can be prevented when the elevator brake releases during the starting operation. To achieve the current vector decoupling control for the traction machine installed with an incremental encoder, the initial rotor position estimation at standstill based on a hybrid signal injection method is adopted. First, a high-frequency oscillating sinusoidal voltage signal is injected to obtain the magnetic pole position. Then, two pulse voltage vectors are injected in the positive and negative directions to identify the magnet polarity. The experimental results demonstrate the feasibility of the proposed control strategy with an 11.7-kW traction machine. [ABSTRACT FROM PUBLISHER]

The goal of this paper is twofold. First, we aim at investigating the potentials of reset observers (ReOs) applied to process control. Second, we aim to overcome the existing performance limitations of the temperature control in domestic cookers. To this end, we present an adaptive simmering control for induction cookers, whose parameters are updated online, depending on the estimates provided by a multiple-model ReO (MMReO). This new observer results in extending the idea of multiple models to the state observer framework. The MMReO consists of a reinitialized ReO and of multiple fixed identification models. The resultant control scheme satisfies the user requirements such as quick heating up, accurate temperature control, and fast disturbance rejection, outperforming previous results. Moreover, the proposed control scheme reduces energy consumption, and consequently, it can increase the efficiency of the whole cooking process. Additionally, a fixed robust quantitative feedback theory (QFT)-based controller is designed, and it is also used for comparison purposes. Several verification tests are carried out in real induction hobs to emphasize the effectiveness of our proposal compared with the QFT-based controller. [ABSTRACT FROM AUTHOR]

In this article, a sliding mode control (SMC) is applied to regulate the delivered power of a symmetrical six-phase induction generator. For this, the SMC strategy associated to the field-oriented control strategy is used in order to adjust the inner current loops of a squirrel cage six-phase induction generator (SC6PIG). In this way, the control algorithm switches between positive and negative feedback according to the position of the operating point in the phase plane. This technique guarantees the robustness of the SC6PIG in case of the loss of one to three stator phases or machine converter legs. The switching line slope and the initial operating point have been set so that the system starts with a negative feedback, then it continuously switches back and forth to positive feedback in order to maintain the desired trajectory of the system. The simulation and experimental results demonstrate the effectiveness and the robustness of this technique since the delivered power of the SC6PIG presents the same dynamics in healthy or faulty modes with one to two phase losses. [ABSTRACT FROM AUTHOR]

High speed becomes an important development direction of flywheel energy storage system (FESS) for higher energy storage density. However, the high speed leads to a wide-range and rapid speed variation (tens of thousands of revolutions in seconds) and a limited frequency modulation index, both of which aggravate the current harmonics and deteriorate the robustness of the discharge control, and even lead to instability. To address this issue, this article proposes a robust and practical discharge control strategy for high-speed FESS with RLC filter, which realizes speed adaptation and harmonic suppression. In this scheme, the linear extended state observer and two-degree-of-freedom internal model control (TDOF-IMC) are applied to FESS in the framework of linear active disturbance rejection control (LADRC). Besides, considering that high-speed FESS usually require sensorless control due to magnetic bearings, a reduced-order Luenberger observer for the investigated FESS is proposed. The salient feature of this strategy is to introduce the TDOF-IMC containing FESS dynamic information into LADRC, so that the discharge control is both practical and robust. Experiments and simulations verify the effectiveness of the control strategy. [ABSTRACT FROM AUTHOR]

In this article, a detailed analysis of fast output sampling (FOS)-based multirate output feedback (MROF) technique is done in the context of discrete time sliding mode control (DTSMC) based on nonswitching reaching law. In addition, for better performance and improved robustness, the relative degree of the sliding variable is chosen as two instead of one. Quantitative analysis of robustness in terms of ultimate band for the relative degree two (RD2) approach is done and compared with that of relative degree one (RD1) approach. First, only RD1 and RD2 approaches are proposed for speed tracking of a dc motor under parametric uncertainty. Then the same task is done using MROF-based RD1 and RD2 approaches. The proposed work is validated experimentally and is used for tracking a reference speed of a dc motor. [ABSTRACT FROM AUTHOR]

High speed becomes an important development direction of permanent magnet synchronous machines (PMSM) for higher power density. However, with the reduction of the switching-to-fundamental frequency ratios (SFRs), the dynamic performance and robustness of the current controller deteriorate and even lead to instability. To address this issue, this article proposes a distinctive current controller designed directly in the discrete-time domain for PMSM, which combines two-degree-of-freedom internal model control (TDOF-IMC) with active damping. The salient feature of this controller is that from the point of directly assigning or optimizing the pole and zero coordinates, a distinctive current controller is designed. Specifically, the TDOF-IMC realizes the ability to arbitrarily arrange the pole–zero placement of the closed-loop transfer function, and, therefore, the current tracking response can be improved. The addition of active damping enhances the antidisturbance ability, and as a result, the dq-axis current oscillations effectively at low SFR are getting weakened. On this basis, current control can achieve better dynamic response and robustness at the same time. Finally, simulation and experimental results validate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]