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This paper proposes and evaluates two robust sheet tension estimation algorithms based on unwind and rewind variables, respectively. The proper sheet tension estimation is guaranteed by a continuous monitoring of the differences between the actual estimated values and the values predicted from the last calibration of the estimation parameters. The evaluation was performed with the aid of a developed winder emulator that allowed the offline testing in a real-time field environment, including the initial setting of the estimation constants, and evaluation of both four- and six-shipping-roll cycles. The sheet tension estimation results confirm the precise and stable operation of the proposed robust estimation algorithms, in tests conducted with signals from a winder model, and with tests involving actual field signals from an operational winder. [ABSTRACT FROM AUTHOR]

The presence of condensate inside the dryer cylinders produces a significant increase in the power requirements during starting, putting at risk the capacity of the drive to complete a successful start. In past papers, authors developed estimation algorithms for the detection of condensate during section starting. This paper proposes and evaluates a new strategy that will complement the previous algorithms. This strategy will detect the presence of condensate from the condensate collapsing during the section shutdown. The proposed correlations are derived through a complete experimental evaluation in two experimental cylinders covering rim thicknesses up to 55 mm. The estimation algorithms are split into a low-/moderate-condensate-load zone and a high-condensate-load zone. Results confirm the robustness and accuracy of the proposed algorithms. [ABSTRACT FROM PUBLISHER]

Synchronous reluctance (SyR) machines are a high-efficiency alternative to induction motors for variable-speed applications. To mitigate the well known downside of their lower power factor, permanent-magnet-assisted topologies, in which either rare-earth or ferrite magnets are inserted into the rotor in suitable quantities, are often adopted. The design and optimization procedures for PM-assisted topologies have been thoroughly discussed in the related literature. This paper compares SyR machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliency-based position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor and the same custom-designed SyR rotor laminations. Among the three prototypes, one is a pure SyR motor, and the other two have NdFeB and ferrite magnets, respectively; both are designed to give the same torque at rated current. Results from simulations and experiments are presented comparing the transient overload capability of the three machines, in terms of torque capability and de-magnetization limit. A dynamic thermal model of the machines was developed within this scope. Moreover, the feasibility of saliency-based sensorless methods was investigated and is presented here for the three machines, both at high- and low-current loads. The results of the paper suggest that the ferrite-assisted solution is the best candidate for replacing induction motors in variable-speed applications, for its optimal tradeoff between performance and cost. [ABSTRACT FROM AUTHOR]

The presence of condensate inside the dryer cylinders of a paper machine produces a significant increase in the power required to accelerate the section, risking a drive overload and/or section shutdown. In previous works, the authors developed a robust estimation algorithm for the condensate power and a generalized correlation for the estimation of condensate loads in industrial dryer cylinders up to 55 mm of condensate rim. This paper presents and evaluates a rule-based expert system (ES) capable of detecting the presence and amount of condensate in up to three groups of cylinders with different condensate loads. The ES can give an early warning message to the operators and determine the condensate load and number of cylinders within each group. Evaluation is done using a combined condensate load for a fictitious 1500-mm eight-cylinder dryer section. Results show the capacity of the developed ES to give an early warning as well as a correct estimation of the condensate loads and number of cylinders involved. [ABSTRACT FROM PUBLISHER]

The paper aims to provide a guideline for rotor design of permanent magnet (PM) assisted synchronous reluctance machine (PMa-SynRM). Unlike interior PM machines, the PMa-SynRM is essentially an SynRM with dominant reluctance torque. The PMa-SynRM is often designed by directly embedding magnets into an SynRM rotor to improve the performance. However, how the PMs can be arranged in the rotor to enhance motor performance has not been fully discussed. This paper investigates the influence of several key factors concerning the PM arrangements, including number of PM layers, inserted positions, and PM sizes. The torque, flux linkages, power factor, and motor performance are comprehensively evaluated. Based on the analysis, a brief guideline is suggested for PMa-SynRM rotor design. Finite element analysis is used for evaluation and experiments are conducted to validate the analysis. [ABSTRACT FROM AUTHOR]

Estimation of induction machine parameters, which are commonly used in efficiency evaluation and control methods, can be effectively achieved by utilizing genetic algorithms (GAs). One of the difficulties of using GAs for efficiency estimation is the determination of variable (parameter) constraints (ranges). This paper focuses on the range determination of the parameters (variables) for GA applications. A wide range of variables can cause unstable outcomes. Hence, it is essential to determine an acceptable range for each variable prior to a GA run to produce stable and repeatable results. In this paper, relationships based on the nameplate information and a large database of tested induction motors provided by Hydro-Québec are proposed to determine reasonable induction motor parameter ranges. The proposed method is applied to three different cases. The results of the three cases are compared to each other and also against the corresponding experimental results, which validate the effectiveness and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a surface inspection system for rails is proposed. There is a lack of commercial systems and publications about surface inspection of rails. Therefore, the quality control developed by rail manufacturers depends on their own developed systems or on the equipment provided by very few sellers. Commercial systems must be configured manually by experts of seller companies. The configuration process requires large sets of all types of manufactured rails along several periods of time and the active participation of the quality engineers of the manufacturer. This is a long, cumbersome, and very expensive process. In this paper, we propose a new system that can be configured using a systematic method that can be performed by the quality engineers of the manufacturer. The proposed inspection system uses differential images of the rail surfaces obtained with a technique called the spectral images differentiation procedure. These images are processed using a computer vision algorithm that looks for variations in the pixel values among the images. In order to offer more information, a neural network approach is used for classifying detected defects into six types. The proposed system is an open solution for the inspection of rail surface, easy to implement at an affordable cost, which can be systematically configured by the quality engineers of the manufacturing company. [ABSTRACT FROM AUTHOR]

This paper presents a technique based on the novel bat algorithm (NBA) for the design of the parameters of power system stabilizers and the generalized Unified power flow controller-power oscillation damping in a multimachine power system. The objective is to ensure minimal damping rates to low-frequency electromechanical oscillation modes. Simulations were carried out on the New England system to compare the performance of the NBA with three other techniques: particle swarm optimization, bacterial foraging optimization oriented by particle swarm optimization, and the bat algorithm. For the cases analyzed in this paper, the NBA produced results superior to other techniques. Moreover, the proposed methodology was able to obtain solutions with high damping levels, which showed to be robust when a wide range of loading conditions of the power system were considered. [ABSTRACT FROM AUTHOR]

Critical process loads need to be safeguarded against power system disturbances and erroneous operations caused by human factors. During such events, a fast synchronism-supervised transfer scheme is required to ensure continuous operation. This paper discusses the implementation of a fast motor bus transfer scheme using existing protective relays. The scheme is designed to respond to local and remote (upstream) events in the substation. This makes possible an attempt to initiate a fast transfer for events that are remote to the motor bus. On a failure to achieve a fast transfer, the scheme resorts to an in-phase transfer and, if that fails, finally a residual transfer. Real-time dynamic modeling was performed to simulate motor bus decay and reacceleration. This paper provides the results of the simulations and the response of the transfer scheme. [ABSTRACT FROM AUTHOR]

Replacing the batteries of wearable medical devices is an inconvenience to the user. Wireless power transfer (WPT) could be a solution for this problem. However, the structure should be compact to satisfy the wearable device requirements and the power efficiency should be as high as possible for prolonging the user experience. Besides, as algorithms embedded in these devices become more complex, the device power consumption also increases. Fulfilling these specifications in a compact structure with better efficiency is the aim of this research paper. This paper proposes a power processing module for WPT applications. This module is embedded within the WPT path to convert receiving end ac power to dc power, and to simultaneously provide multiple dc–dc power conversion for wearable medical devices. The ac–dc circuit is specifically designed using a compact topology to convert wireless ac power to stable dc power. The dc power is further regulated by different mode controls either to perform battery charging or to provide independent voltage supplies to dc loads. The integrated circuit occupies an area of 1.9 × 2.3 mm when implemented on a 0.25 μm high voltage CMOS process. [ABSTRACT FROM AUTHOR]

Online sensing of sheet modulus of elasticity in the dry-end spans of printing grade paper machines (PMs) will permit the machine operators to control the mechanical properties of the produced paper. This paper develops an integrated sensorless tension control and sheet modulus of elasticity estimation algorithm, which is tested using field-recorded signals from a production PM and using a full model of the dry-end sections of this machine. Results show the ability of the proposed estimation algorithm to predict the sheet tension (tensile force) and sheet modulus of elasticity even in the presence of rapid changes in the speed and/or in other process operating conditions. The developed algorithms offer the papermaker new insights into the papermaking process. The ability to understand how modulus changes in real time provides a pathway to optimizing the operation of the PM drive system. [ABSTRACT FROM PUBLISHER]

This paper proposes a real-time visual interactive transient stability screening and remedial action tool that uses an approach based on Lyapunov functions to enable the selection of appropriate remedial actions that stabilize power systems due to large disturbances and cascading failures. At present, there is no effective tool that enables making a well-informed choice from amongst a profusion of remedial action alternatives. Conventionally, transient stability analysis of power system is performed offline to assess the capability of the power system to withstand specific disturbances and to investigate the dynamic response of the power system as the network is restored to normal operation. In this paper, postfault stable and controlling unstable equilibrium points are determined using a homotopy-based approach. Subsequently, stability assessment of the system and the corresponding potential remedial actions are determined from the equilibrium points of the system dynamical model. The real-time transient stability analysis and remedial action algorithm are incorporated with the visualization tool to facilitate interactive decision making in real time. The transient stability analysis and remedial action algorithm, and the visualization tool are demonstrated on several test systems including the equivalent Western Electricity Coordinating Council system and the simplified New England 39 bus test system. [ABSTRACT FROM AUTHOR]

This paper presents an optimal battery management algorithm for photovoltaic (PV) stations capacity firming using dynamic programming-based optimization and control architecture. The objective is to manage the output of battery energy storage system (BESS) so that PV station output swings are reduced significantly. First, BESS and PV station located in a medium-voltage distribution network on a North American power grid is modeled along with the reduced-order feeder model. Then, the proposed algorithm is designed and implemented on the power grid distribution feeder based on the feeder data streamed through utility communication infrastructure to the research laboratory. The theoretical formulation, simulation, and implementation results are discussed in detail in this paper. [ABSTRACT FROM AUTHOR]

The instantaneous power for a three-phase rectifier can be calculated directly in the orthogonal coordinate system via coordinate transformation. However, it is difficult to calculate the instantaneous power directly for a single-phase rectifier due to the lack of another phase. Therefore, an orthogonal signal generator (OSG) is required to create an orthogonal coordinate system. Currently, conventional OSG algorithms suffer from long response time. To remedy this problem, in this paper, an arbitrary phase-delay OSG algorithm is developed and applied to the direct power control (DPC) system in the single-phase rectifiers. First, the instantaneous power theory and DPC are presented. Then, the principle of the arbitrary phase-delay OSG method is introduced and the anti-interference ability of the proposed method is analyzed. Through the dynamic response analysis, the developed algorithm brings faster response, easier implementation, and less computational burden compared with other common OSG algorithms. Finally, the validity and advancement of the proposed algorithm are verified by simulations and hardware-in-the-loop experimental tests. A comparison with conventional OSG algorithms also proves the advantages of the developed method. [ABSTRACT FROM AUTHOR]

The protection characteristics used for the detection of power systems’ oscillations are adjusted according to the recommendations of the equipment manuals and validated through transient stability studies. Once the characteristics are adjusted, the parameters do not change when topological changes occur in the system, which opens up the possibility of malfunction of the protection equipment, either by not considering special cases of failure during the study or by errors in the system. This paper describes the modeling and implementation of a virtual out-of-step protection algorithm based on traditional, unconventional methods. The proposed framework allows the user to implement a customized out-of-step protection algorithm and analyze a real fault event recorded in a COMTRADE file. Furthermore, the programming advantages include the possibility to import COMTRADE files from specific simulations and assess the adequate settings of the protective relay. The result brings a computational tool compatible with different simulation programs capable of reproducing stable and unstable power swing events through playback techniques. By assessing critical cases in which the omission of the tripping is reflected in a generator slip condition, this study proposes an alternative with the instantaneous power theory to analyze the oscillation conditions in the definite time frame. [ABSTRACT FROM AUTHOR]

A synchronous reluctance motor drive exhibits an inherent unlimited speed range capability; in fact, the maximum speed of this kind of machine is bounded only by mechanical limits. In order to exploit this peculiar characteristic of the drive while assuring the lowest power losses, a proper control algorithm has to be used. In particular, while the working speed is increasing, the control must be able to command the reluctance motor under the maximum torque per ampere condition at first, into the flux-weakening region, and then on the maximum torque per voltage trajectory. To this purpose, a novel voltage control loop is presented in this paper. It is combined with a field-oriented current control and profitably exploits a polar coordinate representation of the current reference to operate the reluctance machine in compliance with current and voltage rating constraints in all the different operating conditions. Additional merits of the proposed scheme are the ease of implementation and the simple design. The stability of the proposed control algorithm is proved through a small signal analysis and simulations and experimental tests confirm its effectiveness. [ABSTRACT FROM AUTHOR]

In a distribution system when fault occurs, prior operation of any other relay which is not designated as the primary relay causes undesired shedding of a healthy line. This phenomena of unwanted relay operation is termed as sympathetic tripping. For appropriate relay operation, issue of sympathetic tripping is required to be considered while addressing relay coordination problem. This paper proposes a phase fault protection scheme, which mitigates the issue of sympathetic tripping in the meshed network. The undesired relay operation in the network is restricted by imposing some additional constraints on the conventional relay coordination problem. The proposed nonlinear optimization problem is solved by using Shannon–Wiener differential evolution algorithm. Procured optimal relay settings will provide efficient protection against each phase fault without causing sympathetic tripping. The efficacy of the proposed algorithm is examined on modified IEEE-8-bus system, IEEE-14-bus system, and IEEE-30-bus system. The obtained results are verified by using GE Mutilin, model-750/760 overcurrent relay in ETAP (industrial simulation software). [ABSTRACT FROM AUTHOR]

With the wind power energy largely interconnected with power grid, it is necessary to develop a robust dynamic equivalent model of the wind farm for the system stability analysis and control. In this paper, a detailed wind farm model with doubly fed induction generators is established according to Western Electricity Coordinating Council benchmark test system. Then, the parameters identification process based on aggregation technique consisting of a hybrid algorithm combined improved-particle swarm optimization with improved-genetic algorithm is proposed for dynamic equivalent model development by using the measurement data from phasor measurement unit at the point of interconnection. Additionally, the robustness of the developed equivalent model is analyzed. The simulation results of the benchmark test system and IEEE-9 bus system demonstrate the effectiveness and robustness of the proposed equivalent modeling and identification methodology. [ABSTRACT FROM AUTHOR]

This paper deals with a novel reduced sensor strategy, for two-stage single-phase grid connected solar photovoltaic system with a battery, where the dc-link voltage sensor is not required. Moreover, for maximum power point tracking (MPPT), a new “normal harmonic search” (NHS) algorithm is used, and for voltage source converter (VSC) control, a novel “power normalized kernel least mean square” (PNKLMS) algorithm is proposed. The PNKLMS algorithm is used for active load component extraction from the load current, even when the load current is characterized by linear or nonlinear behavior. Moreover, PNKLMS algorithm is used for reference grid current generation. The NHS algorithm is an improved version of the harmony search, which is inspired to the music composition technique and its searching ability is improved by using the normal probability distribution factor. Therefore, NHS reaches the global maximum power point very quickly and is suitable for online searching on hardware. Moreover, the extracted power is fed into the grid. For control of VSC, the proposed PNKLMS control technique is used, which maintains the power quality. The performances of NHS-based MPPT and PNKLMS-based control technique with reduced sensor approach are tested on a developed prototype. The satisfactory steady-state and dynamic performances of the NHS algorithm are demonstrated under variable irradiance and temperature during partial shaded conditions. Moreover, the performances of the PNKLMS algorithm, without using dc-link voltage sensor are demonstrated during overvoltage, undervoltage, harmonics distortion, and load nonlinearity condition, results of which have satisfied the objective of the proposed system and the IEEE-519 standard. [ABSTRACT FROM AUTHOR]

Multiphase machines have several advantages when compared to three-phase machines. Reliability is one of the most important of those advantages, since the multiphase machine can operate with one or more phases open-circuited. However, the traditional models and control of a balanced induction machine can no longer be used under such open-phase conditions. This paper addresses important issues in the modeling and control of nine-phase induction machines operating under open-phase faults. The development of the proposed model is presented in detail, including an algorithm to guarantee the proper representation of isolated neutral motors. Simulation results illustrate the postfault behavior of the nine-phase motor due to an open phase, including the elimi-nation of torque ripple by applying the proper control methods. Experimental results from a laboratory test setup illustrating the operation of a nine-phase induction motor under one open-phase fault are presented and used to validate the proposed model. [ABSTRACT FROM AUTHOR]

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]

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 proposes a novel frequency-based predictive sequence estimator that allows for the isolation of voltages and currents harmonic components, needed for the control of grid-tied converters. The proposed method relays on an enhanced sliding Goertzel transformation ($\text{SGT}$) by adding a predictive estimator with a prediction horizon equal to the SGT processing window. The performance of the proposed method is compared with the well-established DSOGI alternative, proving a higher estimation bandwidth as well as improved immunity to changes in the magnitude, frequency, and phase of the tracked signals. Additionally, the closed-loop performance in a current-controlled grid-tied inverter using the proposed sequence extractor is analyzed. The presented results allow us to quantitatively measure the estimator impact over the power converter performance in a real application. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems exhibit multiple local and one global maximum power points (MPPs) in their P –V and I–V curves during partial shading conditions (PSC). Thus, to improve the efficiency of the system, a global maximum power point tracking (GMPPT) algorithm is necessary. This paper presents a hybrid GMPPT algorithm for constant voltage load applications using a single current sensor. The proposed method combines single current sensor hill climbing (SSHC) and artificial bee colony (ABC) algorithms to track the GMPP. The SSHC algorithm detects the event of PSC and tracks the MPP during uniform insolation conditions. The output current of the power electronic interface is measured effectively at selective duty cycles to identify the type of P–V curve pattern and, thus, initiate either SSHC or ABC. The search space for the ABC algorithm is reduced in the proposed technique to improve the convergence speed. The proposed GMPPT technique is simulated in MATLAB and validated through experimental prototypes for various PSCs. The proposed algorithm tracks the GMPP with excellent efficiency and fast speed. [ABSTRACT FROM AUTHOR]

This paper investigates the modeling methods for the structural design optimization of permanent magnet synchronous linear motors (PMSLMs), which are applied to linear motion machines. First, an initial PMSLM model is established by finite element analysis (FEA), and the data space is obtained for subsequent rapid regression modeling. Second, a powerful regression machine learning method, that is, distance-weighted K-nearest neighbor algorithm (DW-KNNA), is introduced to establish a calculation model by grasping the nonlinear relationships between input structural parameters and output motor performances. Model comparison experiments among analytical method, response surface method, K-nearest neighbor algorithm, and DW-KNNA demonstrate the superiority of the DW-KNNA. Finally, the differential evolution algorithm is used to determine the best combination of structural parameters and performances. The FEA and prototype motor experiments proved the validity and advantages of the proposed method. [ABSTRACT FROM AUTHOR]

A model predictive control scheme for multiphase induction machines, configured as multi-three-phase structures, is proposed in this paper. The predictive algorithm uses a direct flux vector control scheme based on a multi-three-phase approach, where each three-phase winding set is independently controlled. In this way, the fault-tolerant behavior of the drive system is improved. The proposed solution has been tested with a multimodular power converter feeding a six-phase asymmetrical induction machine (10 kW, 6000 r/min). Complete details about the predictive control scheme and adopted flux observer are included. The experimental validation in both generation and motoring modes is reported, including open-winding postfault operations. The experimental results demonstrate full drive controllability, including deep flux-weakening operation. [ABSTRACT FROM AUTHOR]

In order to enable voltage ride-through operation, fast and reliable voltage dips detection is necessary. It has been noticed by the analysis of a huge number of measurement results recorded in-field, in laboratory, and obtained by simulation that the voltage dips may be characterized by specific low-order voltage harmonics pattern, which appears at the beginning and at the end of the voltage dips. This feature is named harmonic footprint. This paper proposes a new method of voltage dips detection based on harmonic footprint as part of smart algorithm for detection and classification of power quality events. The aim is to achieve reliable smart voltage dips detection in 1 ms range. Several methods for harmonic estimation in real time were compared in order to choose the optimal one. The footprint is modeled by mathematical function and applied for voltage dips smart detection using recurrent neural network. The proposed method was tested for voltage dips detection analyzing signals from measurement in the real distribution grid (680 records), computer simulations using IEEE-13 bus test grid, and testing in the laboratory. The reliability (detection rate) and speed of voltage dips detection are tested and verified. Furthermore, the future research directions for presented method are outlined. [ABSTRACT FROM AUTHOR]

In this paper, binary Hall-effect sensor faults are investigated in rectangular-current-fed brushless dc (BLDC) drives and a very effective methodology for their detection, identification, and compensation is explored. It is shown that these faults cause erroneous commutation, generally leading to unstable operation. Using a fault detection and identification technique proposed by the authors in a recent paper on low-cost field-oriented drives, it is possible to pinpoint the faulty sensors. In this paper, it is demonstrated that the destabilizing effect of these faults on motion-state estimation can be compensated for in any position and speed estimation algorithm, as long as it is properly readapted. To this end, it is shown how to incorporate such fault-compensation in three state-of-the-art estimation algorithms: 1) the zeroth-order algorithm (ZOA); 2) the hybrid observer (HO); and 3) the vector-tracking observer (VTO). Comparative experimental tests are performed and it is verified that stable operation is achieved with three, two, or only a single Hall-effect sensor functioning correctly. These results show that the classical BLDC drive with three Hall-effect sensors has an inherent double redundancy to position-sensor faults. With the proposed method, this property can be exploited in systems that require very high reliability, such as in aerospace and automotive applications. Redundancy can be increased, using more than three Hall-effect sensors; reduced using two sensors; or eliminated using a single sensor, in ultra low-cost applications where redundancy is not a requirement. [ABSTRACT FROM AUTHOR]

This paper presents an improved dc-link voltage balancing algorithm for a three-level neutral-point-clamped inverter by considering phase current direction. Detailed studies on the effects of change in load current direction on the dc-link capacitor voltages are presented. A maximum value of power factor is numerically derived, above which it affects the capacitor voltage balancing capability. Compared with the previously presented research work, the inputs to the space-vector pulsewidth-modulation block are the three phase currents and the difference between the two capacitor voltages. Depending on the states of the two dc-link capacitor voltages and phase current direction, redundant voltage vector sequences are selected. The selected vectors keep the capacitor voltage deviations within 5% of the total dc-link voltage. Two zero switching vectors (i.e., PPP and NNN) are also removed from all subsectors of the earlier proposed strategy, which one used to produce higher common-mode voltages. Detailed simulation and experimental results are presented in this paper for a 6.0-kW surface permanent-magnet synchronous machine. Both the simulation and experimental results show the required performance of the proposed system. [ABSTRACT FROM AUTHOR]

This paper deals with a modified technique for the recognition of single stage and multiple power quality (PQ) disturbances. An algorithm based on Stockwell's transform and artificial neural network-based classifier and a rule-based decision tree is proposed in this paper. The analysis and classification of single stage PQ disturbances consisting of both events and variations such as sag, swell, interruption, harmonics, transients, notch, spike, and flicker are presented. Moreover, the proposed algorithm is also applied on multiple PQ disturbances such as harmonics with sag, swell, flicker, and interruption. A database of these PQ disturbances based on IEEE-1159 standard is generated in MATLAB for simulation studies. The proposed algorithm extracts significant features of various PQ disturbances using S-transform, which are used as input to this hybrid classifier for the classification of PQ disturbances. Satisfactory results of effective recognition and classification of PQ disturbances are obtained with the proposed algorithm. Finally, the proposed method is also implemented on real-time PQ events acquired in a laboratory to confirm the validity of this algorithm in practical conditions. [ABSTRACT FROM PUBLISHER]

The operation of variable-speed ac drives with loss-minimizing flux strategies can produce important energy savings without the need of any investment. This paper proposes algorithms for the evaluation of loss motor components and the flux level that produces the minimum-loss operating condition, covering the whole constant-torque operating region. Both scalar and vector drives are considered, although it is found that the operation of scalar- and vector-controlled drives with optimum flux (or $d$ -axis current) gives very similar results for the same operating points. Evaluation is done using four induction motors of 4, 11, 55, and 110 kW. Results confirm that important savings can be achieved, especially in applications where motors operate with high speed and low to moderate load torque. Results will be used in a follow-up paper to evaluate the expected savings of the use of these strategies in a pulp mill and in a paper mill. [ABSTRACT FROM PUBLISHER]

Interconnected renewable energy sources (RES) require fast and accurate fault ride through (FRT) operation, in order to support the power grid, when faults occur. This paper proposes an adaptive phase-locked loop (adaptive d\alpha\beta\PLL) algorithm, which can be used for a faster and more accurate response of the grid-side converter (GSC) control of a RES, particularly under FRT operation. The adaptive d\alpha\beta\PLL is based on modifying the tuning parameters of the d\alpha\beta\PLL, according to the type and voltage characteristics of the grid fault, with the purpose of accelerating the performance of the PLL algorithm. The proposed adaptive tuning mechanism adjusts the PLL parameters in real time, according to the proposed fault classification unit, in order to accelerate the synchronization performance. The beneficial effect of the proposed adaptive tuning mechanism on the performance of d\alpha\beta\PLL is verified through simulation and experimental results. Furthermore, the benefits of using a faster synchronization method on the control of the GSC of RES are also demonstrated in this paper. Additionally, a new synchronization technique named frequency–phase decoupling (FPD)- d\alpha\beta\PLL is presented, which applies an FPD technique from the literature in the structure of d\alpha\beta\PLL, with the purpose of improving the performance of d\alpha\beta\PLL. Finally, the adaptive tuning mechanism proposed in this paper is combined with the FPD- d\alpha\beta\PLL in order to introduce the adaptive FPD- d\alpha\beta\PLL, which presents an even faster time performance and is an ideal solution for the synchronization of RES under grid faults. [ABSTRACT FROM PUBLISHER]

This paper concentrates on the LCL filter with damping resistance intended to connect the shunt active power filter of an active dc-traction substation to the point of common coupling with the transmission grid. In order to find design conditions and conceive a design algorithm, attention is directed to the transfer functions related to currents and the associated frequency response. The mathematical foundation of the design method is based on meeting the requirements related to the significant attenuation of the high-frequency switching current, concurrently with the unalterated flow of the current that needs to be compensated by active filtering. It is pointed out that there are practical limitations and a compromise must be made between the two requirements. To quantify the extent to which the harmonics to be compensated are influenced by imposing the magnitude response at both highest harmonic frequency to be compensated and switching frequency, a performance indicator is defined. As an additional design criterion, the damping power losses are taken into consideration. The validity and effectiveness of the proposed method are proved by simulation results and experimental tests on a laboratory test bench at small scale reproducing the specific conditions of a dc-traction substation with six-pulse diode rectifier. [ABSTRACT FROM AUTHOR]

In this paper, a three-phase grid interfaced solar photovoltaic (PV) system is controlled through a fixed forward prediction (FFP)-based algorithm, which extracts the fundamental current component of load connected at point of common coupling. This voltage-source converter with the FFP-based control algorithm feeds the PV power to the grid along with balancing of loads, reduction of harmonics, stabilization of the grid under voltage sag/swell, and voltage unbalance conditions. Moreover, the rate of convergence of this algorithm is very high. Simulated performance of this system is verified experimentally. The incremental conductance-based maximum power point tracking algorithm is applied on a PV array for the extraction of maximum power from it. The system is tested under different abnormal conditions such as load unbalance, solar PV array connection/disconnection, voltage sag, voltage swell, voltage unbalance, and variable solar insolation. The distortions levels of voltage/current are found to be within limits as defined in an IEEE-519 standard while feeding active power to a distribution network and connected loads. [ABSTRACT FROM AUTHOR]

In this paper, an optimal power dispatch framework for a battery integrated end-user-driven microgrid is proposed that is capable of working in grid-connected and islanded mode. The proposed framework integrates a rule-based dispatch algorithm for the islanded mode that can schedule the battery considering maximum end-user flexibility, with a receding horizon based optimal dispatch algorithm for the grid-connected mode that maximizes grid stability and minimizes grid exchange power to the microgrid. The main advantage of the proposed architecture is that it enables the end-user to operate the microgrid economically (minimizing power from the grid) and at the same time ensures flexibility and grid-level reliability. To demonstrate the applicability and scalability, the proposed architecture is evaluated on a modified IEEE 33 node and IEEE 123 node distribution feeder including three-phase and single-phase connected end-user microgrids suitable for real-time implementation. The test results show that the approach is scalable and the proposed architecture improves feeder reliability and end-user flexibility, keeping overall cost to a minimum. [ABSTRACT FROM AUTHOR]

It is essential to improve the resiliency of power distribution systems (PDS) given the increase in extreme weather events, number of malicious threats, and consumers’ need for higher reliability. This paper provides a formal approach to evaluate the operational resiliency of PDS and quantify the resiliency of a system using a code-based metric. A combination of steady state and dynamic simulation tools is used to determine the resiliency metric. Dynamic simulation tools help analyzing the impact of short-term events, which might affect operational resiliency in the long term. A dynamic optimization algorithm for changing operating criteria to increase the sustainability of the most critical loads has been proposed. The proposed theoretical approach is validated using a simple PDS model and simulation results demonstrate the ability to quantify the resiliency using the proposed code-based metric. The time-dependent quantification of resiliency has been demonstrated on a test system of two connected Consortium of Electric Reliability Technology Solutions (CERTS) microgrids. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid phased locked loop (HPLL) algorithm for high power master-slave configured (MSC) centralized inverters for large photovoltaic power plants. Proposed PLL technique is a combination of double second order general integral (DSOGI) PLL and enhanced PLL (EPLL) with a zero crossing detector, which enables faster synchronization of slave inverters and enables early export of power into the grid. ${{3}}{\hbox{-}}\phi $ PLL structures such as synchronous reference frame (SRF), double decoupled SRF (DDSRF), EPLL, DSOGI, and DSOGI with frequency locked loop (FLL) are discussed, and a comparative analysis with the proposed PLL technique is presented. The proposed PLL technique is superior as compared with existing PLL techniques in master-slave configurations where it can provide faster synchronization, dynamic interleaving of the hardware timers generating carrier waves for master-slave converters, and low voltage ride through (LVRT) capability. The proposed PLL technique along with the existing techniques is simulated and compared in MATLAB/SIMULINK and digitally implemented in TMS320F2812 based discrete signal controller. The performance of the proposed HPLL technique is experimentally validated with unbalanced and distorted grid signals. Experimental results of proposed HPLL show faster grid synchronization in MSC-based grid-connected inverter, LVRT capability, and dynamic interleaving of MSC inverters. [ABSTRACT FROM AUTHOR]

This paper presents a novel binary backtracking search algorithm (BBSA) for an optimal scheduling controller applied to the IEEE 14-bus test system for controlling distributed generators (DGs) in microgrids (MGs) in the form of virtual power plant (VPP) toward sustainable renewable energy sources integration. The VPP and MGs models are simulated and tested based on real parameters and loads data recorded in Perlis, Malaysia, employed on each bus of the system for 24 h. BBSA optimization algorithm provides the best binary fitness function, i.e., global minimum fitness for finding the best cell to generate the optimal schedule. The fitness function is generated based on real conditions such as solar irradiation and wind speed and preparation of battery charge/discharges, fuel states and demand of the specific hour. The obtained results show that the BBSA algorithm provides the best schedule to control DGs ON and OFF based on controller decision. Results obtained from the BBSA are compared with binary particle swarm optimization in terms of objective function and power saving to validate the developed controller. The developed BBSA optimization algorithm minimizes the power generation cost, reduces power losses, delivers reliable and high-quality power to the loads, and integrates priority-based sustainable MGs into the grid. Thus, VPP can enable efficient integration of DGs and MGs into the grid by balancing their variability. [ABSTRACT FROM PUBLISHER]

Accurate characterization of power semiconductors over wide operating ranges is a necessity to accomplish better electrical and thermal designs of power converters. Especially, switching losses of power devices are rarely given sufficiently detailed in their datasheets, since they also depend strongly on the driving circuitry and design of the power converter itself. A means to extract the switching losses are double pulse measurements where the desired operating points can be freely chosen. This paper introduces a temperature conditioning unit that allows the adjustment of the junction temperature between −40 °C and 200 °C using thermoelectric coolers (TECs). The unit is for an automated double pulse test bench with dc-link voltages of up to 1 kV and switching currents of up to 1 kA. Up to 1 kW of electrical power is required to power the TECs. The design of the power converter is shown as well as the control scheme. An algorithm, which automatically extracts the switching losses of the measured double pulse waveforms is presented. An exemplary characterization of an Infineon EconoDual power module is conducted and the results are presented. [ABSTRACT FROM PUBLISHER]

This paper presents an islanding detection method for a two-stage photovoltaic (PV) inverter. The novelty in this method is that it does not rely on instantaneous value of the grid voltage for identifying the islanded condition. Instead, the islanding condition is detected by the saturation of the proportional integral (PI) controller of the outer voltage control loop. This makes the proposed detection algorithm more reliable compared with other voltage-based detection algorithms, as it is immune to malfunctions caused by the sudden load changes or other transients. In addition, a simple but accurate implementation strategy for low-voltage ride through (LVRT) operation is also proposed and integrated with the anti-islanding operation. Both these methods are placed inside the overall control structure that can perform seamless transition between grid-connected and standalone modes of operation. The simulation results demonstrate the effectiveness of the proposed anti-islanding and LVRT techniques. Finally, hardware results on a 2 KW laboratory prototype are presented for experimental verification of the proposed anti-islanding and LVRT schemes. [ABSTRACT FROM PUBLISHER]

In a microgrid, the overcurrent relays see significant variation in the short-circuit currents during transition between grid-connected and islanded modes of operation. Further, with the disconnection of one or more distributed generators (DGs), the changes in the short-circuit currents are observed by the relays. As a consequence, the existing protection scheme may either delay the relay operation or fail to operate. This paper proposes an optimal and single protection scheme suitable for all operating modes of microgrid along with every type of phase faults in the system, i.e., three-phase symmetrical (3\text-\phi ), line-to-line, and double line-to-ground faults. The optimal setting of the directional overcurrent relays is obtained using a metaheuristic-based optimization algorithm. Moreover, the proposed scheme is validated using GE Multilin, model-750/760, overcurrent relay in ETAP (industrial simulation software) on the modified IEEE 9-bus 4-DG microgrid. [ABSTRACT FROM PUBLISHER]

This paper proposes a new method to determine the sizing and siting of diesel generators (DGs), photovoltaic (PV) solar panels, and batteries for off-grid systems. In this work, the objective is to reduce the total system cost while fulfilling the load demand and maintaining the power quality of the system, among other constraints. This is achieved by employing a two-stage particle swarm optimization algorithm; the first for siting and sizing of the system and the second for its scheduling. Three case studies, namely only DGs, DGs + PV, and DGs + PV + batteries systems, based on the energy requirement of an Indonesian island are presented. In addition, real solar irradiance and temperature data are utilized together with a measured load profile. The results reveal that a system that relies only on DGs is not able to keep the system voltage within the tolerable range (from 0.95 to 1.05 p.u.), while yielding a lifetime cost of 104 million USD. The DGs + PV system requires a lower lifetime cost, 67 million USD. Nevertheless, the voltage of the system reaches values lower than 0.95 p.u. for certain nodes during night-time as the PV are not able to provide power. Finally, the DGs + PV + batteries system yields the lowest cost, 64 million USD, and is able to keep the values of the voltage within the desired range, as batteries can provide power when PV are not operating. [ABSTRACT FROM PUBLISHER]

Space vector modulation (SVM) is a widely used method for multilevel inverters. Most of the SVM methods are nearest three vector (N3V) based schemes. Therefore, several researchers have proposed advanced implementation algorithms with reduced complexity for N3V methods. However, topologies like neutral point (NP) clamped inverter (NPCI) require some distinctive methods (called as non-N3V methods) to balance NP voltage for high modulation index and low power factor operations. Currently, the existing non-N3V methods exercise highly complex algorithms for duty ratio calculation and subtriangle identification. This paper presents a new approach, suitable for both N3V and non-N3V methods, with reduced implementation complexity. The proposed algorithm is based on an equivalent two-level space vector diagram and does not require any trigonometry, coordinate transformation, or volt-second balance solution. Unlike other carrier-based methods, it can change the switching sequence as well as the duration of redundant vectors. Moreover, the proposed approach does not require extra steps for implementing hybrid modulation and it can also be extended to multilevel topologies. One N3V, two non-N3V, and hybrid methods are developed using the proposed modulation algorithm, and are compared in detail. Simulation and experimentation on a three-level NPCI verify the validity of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

The modularization of process plants is regarded as a promising approach to cope with upcoming requirements in the process industry regarding flexibility. Within the Decentralized Intelligence for Modular Assets Project, a concept has been developed to overcome current deficiencies in implementing modular plants and especially their automation. On one hand, the approach considers a clear separation of engineering efforts into plant-independent module engineering and plant-specific integration engineering. On the other hand, the concept provides a method for the fast integration of a module's automation system into a higher level process control system. To do so, each module provides its process functionality in encapsulated services. The core of the integration method is a file-based description of the module including its services, operating screens, and communication variables. The so-called “module-type package” is currently under standardization by different organizations. This paper presents the general approach as well as current results of the standardization efforts. Furthermore, the results are executed on an application demonstrator to allow a practical assessment. Thus, module engineering and integration engineering, as well as corresponding software tools can be demonstrated. [ABSTRACT FROM AUTHOR]

Wind generation forecast approaches are typically based on fixed model structures, which might fit well with existing data but fall short in forecasting out-of-sample data. The reason lies in that predetermined models cannot always capture the actual dynamic features of wind farms, resulting in unavoidable model errors. In this paper, a novel ultra-short-term wind generation forecast approach based on multivariate empirical dynamic modeling is proposed. The time series of wind generation and the explanatory variables are applied for attractor reconstruction according to Takens’ theorem. By this means, the dynamics of the original wind generation system can be accurately captured by the trajectories of the state variables in the reconstructed space. Then, using a simplex projection approach, wind generation can be directly forecasted with the trajectories. A unique feature of the proposed approach is that its effectiveness depends solely on the potential context hidden in the sequences of the state variables rather than the correctness of the predetermined models. Consequently, this approach can faithfully depict the dynamics of wind farms and improve the forecast accuracy. Case studies illustrate that the proposed approach can obtain advanced forecast results comparing with the benchmark methods. [ABSTRACT FROM AUTHOR]

This paper deals with a single stage solar photovoltaic (SPV) array tied to a three phase grid using an improved second-order generalized integrator quadrature (ISOGI-Q) based control algorithm to improve the power quality of the grid. The maximum point power tracking (MPPT) is achieved by using an incremental conductance method. The incremental conductance MPPT method is effective to extract crest power from an SPV array, as well as to control the dc bus voltage. The ISOGI-Q based control serves multifunctionalities such as load balancing, power factor correction, and improved solar power penetration into a distribution network. Test results of the ISOGI-Q based control algorithm are found to be satisfactory for improved power quality in terms of load balancing, harmonics elimination, and very effective power factor correction under various dynamic conditions such as load unbalancing, variable solar insolation, distorted grid, and imbalanced grid voltage conditions. Distributed static compensator capabilities of a photo-voltaic based system are useful to supply the active power to the load and surplus power to the grid. The control algorithm is verified on a proposed topology and obtained responses are found satisfactory, and total harmonic distortions of source currents are observed within an IEEE-519 standard limit. [ABSTRACT FROM AUTHOR]

Correct estimation of harmonics and sequence components is essential to monitor the overall performance of three phase power systems. Least mean square (LMS) based adaptive models have simpler structures to estimate the required parameters for a given power quality (PQ) event. However, these models are not very much effective in case of time-varying and short duration disturbances. Least mean fourth (LMF) is comparatively a better approach than LMS to deal with different PQ problems, but high computational complexity limits the filter performance in case of practical applications. LMS/fourth (LMS/F) filter is a compromise between LMS and LMF to improve the error convergence properties. The proposed model explained in this paper is based on the concept of LMS/F with Volterra expansions of input samples. The proposed Volterrra LMS/F filter is tested in case of distorted power signals to estimate harmonics, decaying dc, and sequence components in presence of white Gaussian noise. The detail comparison results are presented using MATLAB simulations to verify the performance of the adaptive model. [ABSTRACT FROM AUTHOR]

This paper presents the design, control, and experimental investigation of an autonomous wind–solar hybrid energy system feeding 3-phase 4-wire loads. The wind energy block consisting of a double fed induction generator (DFIG) is equipped with maximum power point tracking (MPPT) algorithm. The control of DFIG consists of two converters, namely rotor side converter (RSC) and load side converter (LSC) connected back to back at dc link. The MPPT operation requires speed control, which is realized using field oriented control through RSC. The rotor position required for vector control is estimated with model reference and adaptive system algorithm. The voltage and frequency control is realized through LSC. The solar photovoltaic (PV) power is extracted using a dc–dc boost converter to the common dc link. The dc–dc converter is also equipped with MPPT algorithm to extract maximum power from the incident irradiance. The system is modeled in MATLAB and its performance is presented at conditions, e.g., unbalanced nonlinear load, varying wind speeds, and solar irradiation. Under all these conditions, currents flowing through stator windings of DFIG are balanced with low total harmonics distortion (THD). The THDs of load voltages under all operating conditions are also within requirement of IEEE 519 standard. Finally, simulated results are validated experimentally by developing a prototype of the system using a 5-kW solar array simulator and a 3.7-kW DFIG. [ABSTRACT FROM AUTHOR]

For special types of electric machines, it is essential and of utmost interest to develop a mathematical model, characterize a machine for performance evaluation, and test the machine for study and applications. A 2-D analytical method for the performance evaluation of axial flux permanent magnet (AFPM) machine has been presented in this paper. The method computes the electromagnetic torque, magnetic field distribution, cogging torque, and back-electromotive force of the machine using quasi-3-D modeling. Fourier Transform is used for the solution of Maxwell's equations in different regions of the AFPM machine. A surface mounted AFPM motor is designed and developed and tested. Experimental results are demonstrated and compared with the results computed from the analytical model to validate the effectiveness and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

With the popularity of electrical vehicles, the lithium-ion battery industry is developing rapidly. To ensure battery safe usage and to reduce its average lifecycle cost, accurate state of charge (SOC) tracking algorithms for real-time implementation are required for different applications. Many SOC estimation methods have been proposed in the literature. However, only a few of them consider the real-time applicability. This paper classifies the recently proposed online SOC estimation methods into five categories. Their principal features are illustrated, and the main pros and cons are provided. The SOC estimation methods are compared and discussed in terms of accuracy, robustness, and computation burden. Afterward, as the most popular type of model-based SOC estimation algorithms, seven nonlinear filters existing in literature are compared in terms of their accuracy and execution time as a reference for online implementation. [ABSTRACT FROM AUTHOR]