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This paper presents the modeling and characterization of the tower shadow effects using a wind turbine emulator in a laboratory environment. In particular, the downwind wind turbines are considered here as their tower shadow effects are more significant compared to the upwind counterpart. Simulation and experimental results have shown that the wind speed deficit due to this nonideal effect is significant. In addition, the tower shadow effects occur typically two to three times per revolution, depending on the number of blades. The modeling of the tower shadow profiles for tubular and four-leg tower configurations is presented. Typically, these towers are used in small wind turbine applications. The tower shadow profiles are emulated experimentally using a wind turbine emulator with its characteristics being explained. The limitations of emulating the tower shadow effects using a wind turbine emulator are demonstrated through the frequency response test performed in this study. In this study, the wind turbine emulator is connected to an isolated grid which is formed by three single-phase inverters. Finally, this paper concludes with a sensitivity analysis of the power oscillations for different widths and magnitudes of the tower shadow profile. [ABSTRACT FROM PUBLISHER]

This paper presents a methodology to control a two-staged ac/dc converter, which is a cascade combination of a three-phase ac–dc boost power factor correction (PFC) rectifier and a phase-shifted full-bridge (PSFB) dc/dc converter. This paper explains the issues of instability and losing unity power factor operation, i.e., high reactive power transfer with conventional PI compensator due to the sensitive variation of output impedance of the PFC stage at different loads. In this paper, this instability issue is resolved by the proposed state-feedback control methodology, which shows that there exists a load-insensitive range of controller parameters, providing unity PFC. As an additional benefit of this control, total number of sensors are reduced by three (an input phase current, a dc/dc primary current, and an output dc voltage), in comparison to the conventional PI-based control. This reduction is achieved by introducing two augmented state variables followed by their reduced state observer design. A 6-kW laboratory prototype of the integrated three-phase PFC and PSFB dc/dc is developed and designed to validate the proposed control algorithm. The experimental results show a conversion efficiency of 95.4% at full load, input total harmonic distortion of 4.1%, power factor of 0.998, and output voltage ripple of ±1%. [ABSTRACT FROM PUBLISHER]

High-voltage pulse-generators can be used effectively for bacterial decontamination in water treatment applications. Applying a pulsed electric field to the infected water sample guarantees killing of harmful germs and bacteria. In this paper, a modular high-voltage pulse-generator with sequential charging is proposed for water treatment via underwater pulsed streamer corona discharge. The proposed generator consists of series-connected modules similar to an arm of a modular multilevel converter. The modules’ capacitors are charged sequentially from a relatively low-voltage dc supply, then they are connected in series and discharged into the load. Two configurations are proposed in this paper, one for low repetitive pulse rate applications, and the other for high repetitive pulse rates. In the first topology, the equivalent resistance of the infected water sample is used as a charging resistance for the generator’s capacitors during the charging process. While in the second topology, the water resistance is bypassed during the charging process, and an external charging resistance with proper value is used instead. In this paper, detailed designs for the proposed pulse-generators are presented and validated by simulation results using MATLAB. A scaled down experimental setup has been built to show the viability of the proposed concept. [ABSTRACT FROM AUTHOR]

Mechatronic and robotic systems are increasingly used in the health care and medical industry in recent years. Once the surgery is shifted from operating room to clinic or surgeon's office by using an office-based surgical device, the patient cannot be administered general anesthesia and thus the patient's motion can affect the performance of such a surgical device and even the success of the surgery. For an office-based ear surgical device designed to insert a tube on the tympanic membrane, the patient's head motion will affect the success rate of tube insertion. To address this issue without adding any extra equipment, a head motion compensation system based on contact force control is developed in this paper. A model describing the displacement–force relationship of the soft membrane is built based on viscoelastic behavior and contact effect. Based on the model, a proportional-integral-derivative controller obtained via constrained linear-quadratic optimization algorithm and a disturbance observer are designed. Finally, several experiments for system performance validation are conducted on a mock-up system, whose results show that the optimal force controller can perform a good set-point tracking ability. Meanwhile, the proposed control scheme can compensate the motion and achieve an accurate and steady contact force control. [ABSTRACT FROM AUTHOR]

The time-varying operational conditions applied to wind turbines (WTs) not only challenge their operation but also make condition monitoring (CM) difficult. To achieve a reliable CM result, more advanced signal processing techniques, rather than the conventional spectral analyses, are urgently needed for interpreting the nonlinear and nonstationary (NNS) CM signals collected from the turbines. The work presented in this paper is an effort to meet such a requirement. Based on the proven capability of the spline-kernelled chirplet transform (SCT) in detecting the instantaneous frequencies within NNS monocomponent signals, this paper improves the SCT to enable it to detect the instantaneous amplitude of lengthy NNS multicomponent signals at a fault-related frequency of interest. The improved SCT is then applied for developing a new real-time CM technique dedicated to extracting fault-related features from WT CM signals. Experiment proves that the improved SCT has overcome existing SCT issues and is capable of correctly tracking the amplitude characteristics of NNS multicomponent signals at fault-related frequencies of interest. The new CM technique developed, based on this improved SCT, shows success in detecting both mechanical and electrical faults occurring in a WT drive train, despite the constantly varying operational conditions of the turbine. Moreover, its algorithm is efficient in computation, which not only enables it to deal with lengthy NNS CM signals but also makes it ideal for online use. [ABSTRACT FROM PUBLISHER]

This paper proposes an effective test bed for a 380-V dc distribution system using isolated power converters. The proposed test-bed system is composed of a grid-interactive ac–dc converter for regulating the dc-bus voltage, a bidirectional converter for the battery power interface, a renewable energy simulator, dc home appliances modified from conventional ac components, a dc distribution panel board, and its monitoring system. This paper discusses three isolated power converters, i.e., a bidirectional ac–dc converter, a bidirectional dc–dc converter, and a unidirectional dc–dc converter for the effective power interface of a dc bus. These isolated power converters are designed using a dual-active-bridge converter and the resonant topologies of $CLLC$ and $LLC$. The proposed test-bed system was implemented using a 5-kW bidirectional ac–dc prototype converter, a 3-kW bidirectional dc–dc prototype converter, and a 3-kW unidirectional dc–dc prototype converter. Finally, the performance of the test-bed system has been verified using practical experiments of load variations and bidirectional power flow, employing the prototype converters. [ABSTRACT FROM PUBLISHER]

Bit stream (BS)-based feedback control systems often use a delta–sigma modulator ( $\Delta\Sigma$-M) as a two-level dynamic quantizer to encode and decode feedback signals. The stability and performance of such systems are critically dependent on the selection of the quantizer step size. This paper derives the stability condition of a BS-based control system in terms of the quantizer step size using sliding mode analysis. It is proved that the quantized system is equivalent to the original system on the sliding manifold under ideal sliding. However, the presence of the quantizer in a $\Delta\Sigma$-M introduces noise into the system that often degrades the performance of the overall system. This paper therefore determines the optimum quantizer gain, i.e., the upper and lower boundaries of the quantizer, which maintains the stability and reduces the quantization noise. BS-based proportional–integral–differential (BS-PID) controllers are designed using the proposed optimal dynamic quantizer and implemented using three different realizations. Simulation results show that the optimal quantizer significantly reduces the noise within the system bandwidth. The effectiveness of the BS-PID controller with the optimal quantizer is further demonstrated using the experimental prototype of a dc servomechanism by designing a BS-PID controller. The experimental results from a laboratory prototype illustrate that the BS-PID controller gives identical performance to a traditional PID controller and effectively controls the system while consuming less information rate (channel interfaces) and hardware resources. [ABSTRACT FROM PUBLISHER]

In dc microgrids, it is common that constant power loads (CPLs) exhibit negative incremental resistance. They degrade the stability margin of operation with their LC input filters and, thus, the whole system. In traditional active-damping methods, the extra stabilizing current is injected into CPLs to modify its input impedance to fulfill stability criteria. However, this injected current may cause undesirable performance of the loads, e.g., fluctuation in rotating speed of tightly regulated motors. There is always a compromise between stability margin and load performances. In order to overcome this drawback, this paper proposes a method that stabilizes the system from source-side converters, instead of from CPL themselves. In the proposed method, a virtual resistance is built in the source-side converter. This virtual resistor is effective around the resonant frequency of the LC input filter and thus can indirectly reduce its output impedance to fulfill Middlebrook's stability criterion. This paper also proves, both analytically and experimentally, that, in dc microgrids, resonant frequencies of LC filters of paralleled CPLs have to be different to maintain system stability. Simulation and experimental results are reported to verify the effectiveness of the proposed idea. [ABSTRACT FROM PUBLISHER]

Stereoscopic 3-D visualization (S3D) provides a user with higher comprehension of remote environments in teleoperation when compared to 2-D viewing. Studies in the literature have shown how stereo vision may contribute to improving perception of some depth cues, but it is hard to find work assessing stereoscopic 3-D viewing in telenavigation tasks involving medical flexible endoscopes. Nonetheless, the increased level of depth awareness provided by stereo viewing is remarkable, which facilitates endoscope teleguide, teleexploration, and teleintervention, leading to accurate navigation and faster decision-making. This paper assesses S3D in medical endoscopic teleoperation. We evaluate the usability of a flexible stereoscopic bronchoscope. Twenty test users are asked to teleguide a virtual endoscope, which operates in a realistically simulated bronchus environment under different viewing conditions and displays. The evaluation involves seven systems (from laptops to wall screen and head-mounted display), four approaches to stereo viewing (colored Anaglyph, polarized filters, shutter glasses, and separated displays), and five types of display technologies (digital light processing, cathode ray tube, liquid crystal display, light-emitting diode (LED), and organic LED). The results show a strong improvement in users' performance when the endoscope-camera view is (depth-) enhanced by stereo viewing. Users' performance and appreciation may vary in different systems, which is also commented in this paper. This study supports system designers in making informed decisions. [ABSTRACT FROM PUBLISHER]

Electric bicycles (EBs) are becoming increasingly popular in some regions such as China and Europe. However, wireless power transfer (WPT) for charging massive EBs poses a challenge related to the cost of WPT system (WPTS), especially in China, where EBs application is so sensitive to the product price. This paper presents an optimization method of the passive components for the S-LCC topology to decrease the cost of the overall system. With the novel method, the number of passive components can be optimized to the minimum and still with constant current and constant voltage outputs. A novel compensation method with an inductor array is also proposed to guarantee an inductive input impedance of WPTS, achieving soft switching and reducing the high switching losses of the high-frequency inverter (HFI). To demonstrate the validity of the proposed methods, an experimental setup is built. The performance of two WPTS indicates that massive EBs can be charged with only one HFI, and the cost of the overall system decreases accordingly. [ABSTRACT FROM PUBLISHER]

Conventional zero-voltage and zero-current-switching (ZVZCS) full-bridge converters are widely used because they can realize zero-voltage switching (ZVS) for the leading leg and zero-current switching (ZCS) for the lagging leg. However, the large turn-off loss of the leading leg is still unacceptable in high-voltage high-power applications where insulated-gate bipolar transistors (IGBTs) with current tailing are employed. Hence, it is preferable to achieve ZCS for all IGBTs of full-bridge converters. This paper analyzes the ZCS conditions for pulsewidth modulated (PWM) full-bridge converters and proposes a general strategy for achieving ZCS for main switches, including the control strategy and design method of the topology. Based on this theory, a novel ZCS PWM full-bridge converter with simple auxiliary circuit is derived and tested. It can achieve ZCS not only for the main switches of full-bridge converter, but for the auxiliary switch as well, and obtain high efficiency. The operation principle of the proposed ZCS PWM full-bridge converter and the design procedure are presented. The experimental results of a 600 V/2.5 kW prototype are also included to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

Supporting a wide operating range for industrial-standard backward-compatible transmitters often results in energy inefficiency. This paper describes an energy-efficient voltage-mode-serializing transmitter with an operating range of up to 32 Gb/s. The proposed transmitter uses a programmable internal supply to set the voltage level for various data rates optimally, thus improving overall energy efficiency. Output swing and pre-emphasis levels are largely adjustable while the constant output impedance is maintained using a dedicated control loop. CMOS-logic-based circuits and quarter-rate clocking enhance the energy efficiency over the entire data rate range, while a P-over-N voltage-mode driver is used to achieve a high maximum output swing. Two supply regulators with replicas provide constant pull-up and pull-down impedances of the output driver. The variable output swing, pre-emphasis, and internal supply are realized by using segmented output drivers and replicas. The proposed transmitter, fabricated in a 65-nm CMOS process, occupies an active area of 0.173 mm2. The prototype chip achieves a wide output swing range of 0.4–1.3 Vppd and an energy efficiency of 2.10–3.45 pJ/bit, across a data rate of 5 –32 Gb/s. [ABSTRACT FROM PUBLISHER]

Wind farm contains a large number of wind turbines, each of which is required to deliver certain amount of power so that the combined power from the wind farm is able to meet the total power demand. For such typical power tracking control problem, it is quite challenging to develop a computationally inexpensive and structurally simple solution. The problem is further complicated if the demanded power is unknown a priori and there exist modeling uncertainties as well as external disturbances in the system. In this paper, a neuroadaptive feedback control is presented. The barrier Lyapunov function based design technique is utilized to guarantee that the neural network (NN) training inputs are confined within a compact set such that the NN unit can maintain its learning/approximating functionality during the entire process of system operation. To address the issue of unknown power trajectory, an analytical model is proposed to reconstruct the unknown desired power profile. Both theoretical analysis and numerical simulation validate the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper proposes a dc voltage incipient sensor fault isolation method for single-phase three-level rectifier devices in high-speed railway electrical traction systems. Different incipient fault modes characterizing locations and incipient fault types are parameterized nonlinearly by unknown fault parameters. A new incipient fault isolation method is developed by combining sliding mode technique with nonlinear parameterization adaptive estimation technique. A bank of particular adaptive sliding mode estimators is proposed, which facilitates to derive new isolation residuals and adaptive threshold intervals. The isolability is studied, and the isolable sufficient condition is derived using new functions. For the practical electrical traction system in China Railway High-Speed 2, simulation and experiment based on TDCS-FIB (a software) are presented to verify the effectiveness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a novel multivariable sliding-mode extremum-seeking controller (MVESC) is proposed and utilized for maximum power point tracking in an alternator-based energy conversion system. The design extends a scalar-based sliding-mode extremum-seeking controller to the multivariable case by introducing a sliding-manifold vector for multiparameter control. The behavior of the controller in terms of convergence characteristics is studied using a Lyapunov-like stability analysis. The proposed MVESC is applied to an alternator-based energy conversion system, which results in optimal power conversion at different speeds and output voltages. Furthermore, the performance of the proposed controller is compared with a multivariable gradient-based method through experimental studies. The results demonstrate that the proposed controller offers advantages in terms of speed, accuracy, and robust performance. [ABSTRACT FROM AUTHOR]

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

This paper presents techniques for testing fractional horsepower (FHP) induction and brushless dc motors. The procedures for segregation of losses in these motors are presented. The issues encountered in testing FHP motors are discussed, and guidelines are provided to avert the issues. This paper also provides insights into understanding the test procedures outlined in the IEEE 114 Standard. [ABSTRACT FROM PUBLISHER]

This paper proposes an automatic any-cells-to-any-cells battery equalizer, which merges the forward and flyback converters through a common multiwinding transformer. The windings of the transformer are divided into two groups, which have opposite polarities. The principles of the proposed equalizer are that the equalization in one group is achieved based on forward conversion and the balancing between the two different groups is based on flyback conversion, by which the magnetic energy stored in the transformer can be automatically reset without using additional demagnetizing circuits. Moreover, only one MOSFET and one primary winding are required for each cell, resulting in smaller size and lower cost. One pair of complementary control signals is employed for all MOSFETs, and energy can be automatically and directly delivered from any high-voltage cells to any low-voltage cells without the requirement of cell monitoring circuits, thereby leading to a high balancing efficiency and speed. The proposed topology can achieve the global equalization for a long battery string through connecting the secondary sides of transformers without the need of additional components for the equalization among modules, which also overcomes the mismatching problem of multiple windings. The validity of the proposed equalizer is verified through experiments, and the balancing efficiency can reach up to 89.4% over a wide range of conditions. [ABSTRACT FROM PUBLISHER]

This paper presents a novel power conditioning unit (PCU) for variable-speed micro wind turbine applications. It contains a simple generator-side rectifier, galvanic isolation with a simple dc–dc converter, and a single-phase full-bridge inverter at the grid side. Variable-speed micro wind turbines based on a permanent magnet synchronous generator (PMSG) are increasingly used in residential and small commercial buildings, despite their relatively low output voltage. Therefore, they can be used easily for battery charging, while their grid integration requires a PCU with galvanic isolation. Most of available PCUs provide no galvanic isolation, or use relatively complicated topologies or four stage energy conversion for that purpose. The dc–dc converter proposed allows reducing the complexity of the PCU. Steady-state analysis shows that the converter is capable of regulating voltage in a wide range suitable for micro wind turbines, which is supported by experimental results within the input voltage range of 40–400 V. The prototype built for integration of a 1.3-kW PMSG-based micro wind turbine shows good performance over the entire 1:5 range of the given wind turbine output voltage. A study of efficiency and power losses was conducted according to the wind turbine power profile. [ABSTRACT FROM PUBLISHER]

In this paper, a new hybrid stator developed from conventional open-slot and split-tooth stators is proposed for a fault-tolerant permanent-magnet (PM) vernier (FTPMV) machine to improve its performance. The design considerations of the new hybrid stator for FTPMV machines are presented. Afterward, on the basis of the designed hybrid stator, new FTPMV machines with surface-mounted and spoke-array PMs are proposed and analyzed, respectively. Comparative evaluation of the proposed FTPMV, conventional FTPMV, and the conventional PM machines are performed by using finite-element (FE) analysis. It is found that the proposed FTPMV machines with the new hybrid stator definitely offer the improved performances such as higher torque density, higher power factor, and lower iron core loss as compared to that of the conventional FTPMV machines. Finally, the experiments on the prototype machines are conducted, verifying the FE analysis results and effectiveness of the proposed hybrid stator design for FTPMV machines. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel outer-rotor flux-switching permanent-magnet (OR-FSPM) machine with specific wedge-shaped magnets for in-wheel light-weight traction applications. First, the geometric topology is introduced. Then, the combination principle of stator slots and rotor poles for OR-FSPM machines is investigated. Furthermore, to demonstrate the relationship between performance specifications (e.g., torque and speed) and key design parameters and dimensions (e.g., rotor outer diameter and stack length) of OR-FSPM machines at preliminary design stage, an analytical torque-sizing equation is proposed and verified by two-dimensional (2-D) finite-element analysis (FEA). Moreover, optimizations of key dimensions are conducted on an initially designed proof-of-principle three-phase 12-stator-slot/22-rotor-pole prototyped machine. Then, based on 2-D-FEA, a comprehensive comparison between a pair of OR-FSPM machines with rectangular- and wedge-shaped magnets and a surface-mounted permanent-magnet (SPM) machine is performed. The results indicate that the proposed OR-FSPM machine with wedge-shaped magnets exhibits better flux-weakening capability, higher efficiency, and wider speed range than the counterparts, especially for torque capability, where the proposed wedge-shaped magnets-based one could produce 40% and 61.5% more torque than the rectangular-shaped magnets-based machine and SPM machine, respectively, with the same rated current density (5 A/mm2). Finally, the predicted performance of the proposed OR-FSPM machine is verified by experiments on a prototyped machine. [ABSTRACT FROM PUBLISHER]

Even though many public parking lots are located underground and indoors, most existing automatic parking space detection and tracking methods have difficulty handling such scenarios due to severe illumination and complex obstacle conditions. To overcome this problem, this paper proposes a method that detects and tracks parking spaces in underground and indoor environments by fusing sensors already mounted on mass produced vehicles. The proposed detection method finds parking spaces based on a high-level fusion of two complementary approaches: parking slot marking-based and free space-based. Parking slots are detected by estimating parallel line pairs and free spaces are detected by recognizing the positions of parked vehicles as well as pillars. The proposed tracking method enhances the previous method by considering pillar information. Since pillars degrade parking slot tracking performance, this method estimates a pillar region and utilizes it to remove false edges and to estimate the amount of occlusion. [ABSTRACT FROM PUBLISHER]

This paper presents a design methodology for an electronic ballast applied to ultraviolet radiation (UV) lamps for a drinking water purifier, providing adjustable UV dose in order to ensure the inactivation of microorganisms’ reproduction, commonly found in untreated water, which can be harmful to human health. The design methodology is based on the multiple segment summation source model, used for defining the UV dose applied to penstock purifiers, considering immersed lamps on a water slide enclosure, which in combination with its hydraulic behavior, provide a good performance for the microorganisms UV absorption along the entire purifier structure ducts. Thus, the water purifier was designed using hydrostatic simulations, in order to ensure compliance with the NSF/ANSI Standard 55, for commercial and residential applications. Thereby, an electronic ballast that guarantees a controlled preheating process for the UV lamp electrodes before its ignition and sets the nominal power point on the steady state, was implemented in order to guarantee the designed UV dose. Furthermore, the ballast incorporates a power factor correction flyback input rectifier stage, in discontinuous conduction mode, with universal input voltage range (90 V \text{rms}–240 V \text{rms}), attending the limits imposed by IEC 61000-3-2 Standard, for class-C devices. [ABSTRACT FROM PUBLISHER]

In this paper, different analysis and design techniques are used to analyze the drive motor in the 2004 Prius hybrid vehicle and to examine alternative spoke-type magnet rotor (buried magnets with magnetization which is orthogonal to the radial direction) and induction motor arrangements. These machines are characterized by high transient torque requirement, compactness, and forced cooling. While rare-earth magnet machines are commonly used in these applications, there is an increasing interest in motors without magnets, hence the investigation of an induction motor. This paper illustrates that the machines operate under highly saturated conditions at high torque and that care should be taken when selecting the correct analysis technique. This is illustrated by divergent results when using I–Psi loops and dq techniques to calculate the torque. [ABSTRACT FROM PUBLISHER]

Solar-powered aircraft require electric drives for the main propulsion system. It is critical that these drives provide both very high efficiency and low mass. This paper discusses the relative merits of different machine topologies based upon maximizing efficiency, taking into account power-electronic losses, motor losses, mass, and size penalties. Laminated machines are usually limited in their efficiency at light load because of their iron losses. This paper shows how, by combining a high pole number with an ultralow loss lamination material, these machines can be more efficient than other more complex arrangements which have been adopted by others. A demonstrator machine has been built and predicted efficiencies have been validated by test. It has then been used to propel a solar plane to over 60 000 feet and extend the aircraft flight-endurance world record from 30 to 84 h. [ABSTRACT FROM AUTHOR]

In this paper, a well-known adaptive input-output feedback-linearization (AIOFL) technique is used for speed and torque-tracking control of synchronous reluctance motor drive. This controller is capable of estimating motor two-axis inductances (Ld, Lq) simultaneously. The overall stability of the proposed control and the persistency of excitation condition are proved based on Lyapunov theory. In addition, the maximum rate of change of torque control scheme is applied to generate the motor dand q-axis reference currents which are needed for AIOFL controllers. Another contribution of this paper is to estimate the rotor speed and position. For low-speed estimation, we have to eliminate the current and voltage sensors' dc offsets, detect the stator resistance, and take into account the voltage drop of the inverter power switches. We solve these problems by using a simple technique for eliminating the voltage sensors and a simple method for online estimation of the stator resistance and modeling the voltage drop of the inverter power switches. It is worthwhile to mention that the current sensors' dc offsets, seen on the measured currents, are negligible. Finally, the validity of the proposed method is verified by experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes the employment of the differential evolution (DE) to offline optimize the covariance matrices of a new reduced delayed-state Kalman-ifiter (DSKF)-based algorithm which estimates the stator-flux linkage components, in the stationary reference frame, to realize sensorless control of induction motors (IMs). The DSKF-based algorithm uses the derivatives of the stator-flux components as mathematical model and the stator-voltage equations as observation model so that only a vector of four variables has to be offline optimized. Numerical results, carried out using a low-speed training test, show that the proposed DE-based approach is very promising and clearly outperforms a classical local search and three popular metaheuristics in terms of quality of the final solution for the problem considered in this paper. A novel simple stator-flux-oriented sliding-mode (SFO-SM) control scheme is online used in conjunction with the optimized DSKF-based algorithm to improve the robustness of the sensorless IM drive at low speed. The SFO-SM control scheme has closed loops of torque and stator-flux linkage without proportional-plus-integral controllers so that a minimum number of gains has to be tuned. [ABSTRACT FROM AUTHOR]

This paper presents an electromyographic (EMG)-based continuous control scheme including simple classifier for an electric-powered wheelchair, ultimately for quadriplegics. The proposed scheme utilizes three EMG signals as inputs for the muscle–computer interface. Since zygomaticus major muscles and transversus menti muscle of human face are able to move independently as well as to adjust contractile forces voluntarily, the surface EMG signals on these muscles are utilized for the electric-powered wheelchair control system. To extract the envelopes of the signal waveforms and to reflect the moving average activities, the root-mean-squares (RMS) operation and normalization are subsequently employed as initial signal processing. Then, an activation vector containing three normalized RMS signals is obtained in real time. The activation vector is applied to the simple classifier for finding out the motion command. Both desired linear acceleration and angular velocity are yielded from the linear combinations of the classification result and the magnitude of activation vector. Finally, desired wheel velocities of the wheelchair control system are obtained by using the integration and differential inverse kinematics. The effectiveness of the proposed control scheme is verified through several experiments such as avoiding obstacle cones and navigating long distance by the users. [ABSTRACT FROM PUBLISHER]

Although, the proton exchange membrane fuel cell is a promising clean and efficient energy converter that can be used to power an entire building in electricity and heat in a combined manner, it suffers from a limited lifespan due to degradation mechanisms. As a consequence, in the past years, researches have been conducted to estimate the state of health and now the remaining useful life (RUL) in order to extend the life of such devices. However, the developed methods are unable to perform prognostics with an online uncertainty quantification due to the computational cost. This paper aims at tackling this issue by proposing an observer-based prognostic algorithm. An extended Kalman filter estimates the actual state of health and the dynamic of the degradation with the associated uncertainty. An inverse first-order reliability method is used to extrapolate the state of health until a threshold is reached, for which the RUL is given with a 90% confidence interval. The global method is validated using a simulation model built from degradation data. Finally, the algorithm is tested on a dataset coming from a long-term experimental test on an eight-cell fuel cell stack subjected to a variable power profile. [ABSTRACT FROM AUTHOR]

This paper presents a topology for wideband piezoelectric wind energy harvesting and a design optimization method for capturing maximum available energy considering the wind speed distribution model. The proposed device is useful for powering of wireless sensor nodes in smart monitoring applications. The device includes a piezoelectric beam that vibrates due to the interactions between miniaturized permanent magnets (PMs) embedded in a small turbine and a magnet at the tip of the beam. The design method determines the resonance frequency of the beam with respect to the wind speed distribution model. Compared to the conventional wideband topologies that include multiple beams for resonating at different frequencies, the suggested topology uses a single beam and achieves the wideband feature via the arrangement of PMs within the turbine. This feature enhances the power density of the piezoelectric wind energy harvester. The wideband feature of the device is experimentally verified using a device prototype in which the beam resonance occurs at the fan rotational speeds of 155.0, 193.5, 257.9, and 387.0 rad/s. The maximum power density, maximum efficiency, and cut-in wind speed of the device are 0.59 mW/\textcm^3, 24%, and 2.1 m/s, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes an acceleration-based robust controller for the motion control problem, i.e., position and force control problems, of a novel series elastic actuator (SEA). A variable stiffness SEA is designed by using soft and hard springs in series so as to relax the fundamental performance limitation of conventional SEAs. Although the proposed SEA intrinsically has several superiorities in force control, its motion control problem, especially position control problem, is harder than conventional stiff and SEAs due to its special mechanical structure. It is shown that the performance of the novel SEA is limited when conventional motion control methods are used. The performance of the steady-state response is significantly improved by using disturbance observer (DOb), i.e., improving the robustness; however, it degrades the transient response by increasing the vibration at tip point. The vibration of the novel SEA and external disturbances are suppressed by using resonance ratio control (RRC) and arm DOb, respectively. The proposed method can be used in the motion control problem of conventional SEAs as well. The intrinsically safe mechanical structure and high-performance motion control system provide several benefits in industrial applications, e.g., robots can perform dexterous and versatile industrial tasks alongside people in a factory setting. The experimental results show viability of the proposals. [ABSTRACT FROM PUBLISHER]

For interleaved boost-type converters, both functions of voltage regulation and current balance are important. In this paper, the decoupled current-balancing control (DCBC) with two parallel loops is proposed. At first, the small-signal transfer functions of the voltage-regulation loop and the current balancing loop to the controller output are derived. The results show that the voltage-regulation loop and the proposed current-balancing loop are nominally decoupled. That is, two PI-type controllers can be designed independently and included to implement the proposed DCBC. Additionally, the single-sensor sampling-current strategy is proposed to obtain two average inductor currents by sensing only the sum of diode currents. All the controllers are implemented in field-programmable gate array (FPGA). The provided simulation and experimental results demonstrate the proposed DCBC. [ABSTRACT FROM PUBLISHER]

Distributed maximum power point tracking (MPPT) photovoltaic (PV) systems have drawn increased attention since the inhomogeneous irradiance on PV modules can significantly deteriorate the effectiveness of solar energy harvest. To address the issue, this paper focuses on developing a highly efficient submodule integrated converter (subMIC), which is connected across each submodule of a PV panel. Gallium nitride (GaN) field-effect transistors are utilized in the synchronous buck converter topology to achieve high conversion efficiency and reduced size. A converter prototype, which is digitally controlled using a microcontroller for MPPT, is developed and tested, considering various irradiation conditions. The peak efficiency of the proposed GaN-based subMIC is measured to be higher than 99% at 400-kHz switching frequency, whereas the accuracy of MPPT is above 99% considering low-power conditions. [ABSTRACT FROM PUBLISHER]

More and more wind turbine manufacturers turn to using the full-scale power electronic converter due to the stricter grid code requirements to thoroughly decouple the generator from the grid connection. However, a commonly used type of this generator is still unclear, where the selections of the low-speed (LS; direct-drive) and medium-speed (MS; one-stage) permanent-magnet synchronous generators (PMSGs) are both promising solutions. This paper will assess and compare the reliability metrics for the machine-side converter (MSC) for those two configurations. First, a translation from the mission profile of the turbine to the current and voltage loading of each power semiconductor is achieved based on synchronous generator modeling. Afterward, a simplified approach to calculate the loss profile and the thermal profile is used to determine the most stressed power semiconductors in the converter. Finally, according to the lifetime power cycles, the lifespan can be calculated when operating in various wind classes. It is concluded that, although the LS PMSG is able to eliminate the gearbox, the lifespan of its MSC is lower than the one-stage MS generator. [ABSTRACT FROM PUBLISHER]

This paper considers the control of a seven-leg back-to-back voltage source inverter arrangement, feeding a four-wire load from a three-phase permanent-magnet synchronous generator (PMSG) operating at variable speed. The PMSG is controlled using a sensorless model reference adaptive system to obtain the rotor position angle. The seven-leg converter is regulated using resonant controllers at the load side and self-tuning resonant controllers at the generator side. The control system is augmented by a feedforward compensation algorithm that improves the dynamic performance during transients. Experimental results, which are obtained from a prototype, are presented and discussed. [ABSTRACT FROM PUBLISHER]

While current-mode control of dc–dc converters provides numerous benefits over voltage-mode control, previous models of the control strategy have been limited to the form of classical control models. Through the use of a state-space averaged (SSA) model of current-mode control, both the open-loop and closed-loop circuit parameters of open-loop control-to-output frequency response, conducted susceptibility, input admittance, output impedance, and any other desired response can be easily obtained. In this paper, SSA models of current-mode-controlled converters are derived and presented for buck, boost, and flyback topologies operating in continuous conduction mode. The new model allows for simpler and more accurate modeling than possible with previous methods, facilitates the modeling of cascaded converters, and allows for the use of state-variable feedback and other modern control methods in applications that use current-mode control. [ABSTRACT FROM PUBLISHER]

A single-objective predictive control method that deals with four main control objectives applied to a multivariable single-phase three-level neutral-point-clamped converter operating as an active power filter is proposed in this paper. The four control objectives are to self-support the dc-bus voltage under load variations, to compensate the reactive power and the current harmonics, and to balance the dc capacitor voltages by using a predefined combination of the redundant switching states of the converter. The main contribution of the proposed method is that these objectives are accomplished without using weighting factors in the cost function, which eliminates problems such as multiobjective optimization or additional empirical procedures for determination of these factors. As a result, the method is easy to implement and rapidly selects the optimal voltage to improve the dynamic-state performance. Experimental results from a 2-kVA prototype are presented to prove that the method is valid for single-phase compensation. The well-known effect of model parameter errors' issue, which is inherent in predictive control methods, is also tested to confirm that the harmonic distortion in the grid current is below 5% even when the predictive model has a 25% error between actual and theoretically estimated grid impedance values. [ABSTRACT FROM PUBLISHER]

The interwinding parasitic capacitance of transformers and the parasitic capacitance between semiconductor switches and the ground are two major contributors to the common-mode (CM) noise currents in switched mode power converters. In this paper, a generalized CM current cancelation approach is proposed for the reduction of CM noise in isolated power converters. The approach is demonstrated in a forward converter. In this approach, the total effect of the two parasitic capacitances on CM noise is represented with an equivalent parasitic capacitance (EPC) at low frequencies. With this EPC, different CM current cancelation techniques can be efficiently organized to simultaneously cancel the low-frequency CM noise caused by these two parasitic capacitances. Furthermore, the EPC can be used to evaluate and quantify the performance of CM noise reduction techniques. Both theoretical analysis and experimental results show that the proposed approach is easy to implement and can significantly attenuate low frequency CM noise and therefore greatly reduce CM filter size and cost. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel vector control method for an LCL-filter-based grid-connected converter (LCL-GCC) by using a recurrent neural network (RNN). The RNN is trained by using the Levenberg–Marquardt (LM) algorithm. A forward accumulation through time (FATT) algorithm for LCL-GCCs is developed to calculate the Jacobian matrix required by the LM algorithm. The objective of the training is to implement optimal control of an LCL-GCC by using an RNN. With the RNN vector control technique, the decoupling of the LCL system is not needed. Simulation study demonstrates that the proposed RNN-based vector control method is a damping-free technique and can tolerate a wide range of system parameter changes. In both simulation- and hardware-based experiments, the RNN vector controller demonstrates much improved performance than that of conventional passive damping (PD) and active damping (AD) vector controllers for LCL-GCCs. In general, the proposed RNN vector controller provides a good solution to overcome the low-efficiency problem associated with conventional PD vector controllers and the problem of sensitivity to system parameter change associated with conventional AD vector controllers. Overall, the RNN vector controller shows strong ability to trace rapidly changing reference commands, tolerate system disturbances, and satisfy various LCL-GCC control needs. [ABSTRACT FROM PUBLISHER]

This paper presents a grid current control technique on the power converter level. The submitted analysis deals with a control method of positive and negative current sequences in a grid-connected converter during voltage sags. The control method should assure the proper exchange of active and reactive powers without power ripple, the mitigation of harmonic distortion of grid currents, and should also enable the control of grid current peaks. A simple expression is determined, which allows estimation of maximum active and reactive powers exchanged between the grid and the converter without exceeding the admissible converter current. Some simulation and experimental results are reported to validate the theoretically predicted performance of the control strategy. [ABSTRACT FROM PUBLISHER]

An ultrahigh-frequency RF identification system, consisting of a fully integrated tag and a special reader, has been developed for short-range and harsh size requirement applications. The system is fabricated in the standard 0.18- \mu\m CMOS process. The whole tag chip with an antenna, an analog front end, a baseband, and memory takes up an area of 0.36 \mm^2 , which is smaller than other reported tags with an on-chip antenna (OCA) using the standard CMOS process. A self-defined protocol is proposed to reduce the power consumption and minimize the size of the tag. A specialized system-on-a-chip reader system, consisting of RF transceiver, digital baseband, MCU, and host interface, supports both the self-defined and International Standards Organization 18000-6 C protocols. Its power consumption is about 500 mW, which is much lower than other reported readers considering the transmission power. Measurement results show that the system's reading range is 2 mm with a 20-dBm reader output power. In addition, it has been verified that the data stored in the OCA tag embedded in a pearl can be successfully read out. With an inductive antenna printed on a paper substrate around the OCA tag, the reading range can be extended from several centimeters to meters depending on the shape and size of the inductive antenna. [ABSTRACT FROM PUBLISHER]

This paper presents a voltage-balancing method for stacked multicell converters (SMCs) based on phase disposition pulsewidth modulation. A cost function is evaluated to select the optimum state from a pool of redundant possible ones at each voltage level. It is demonstrated that, if sawtooth carriers are used for modulation instead of standard triangular ones, significant reduction in the switching frequency and the associated power losses of the power devices can be achieved without affecting the voltage-balancing capability. Experimental results from a seven-level SMC laboratory prototype are provided to verify the proposed voltage-balancing method against linear and nonlinear loads, as well as under transient conditions. [ABSTRACT FROM PUBLISHER]

Model predictive direct power control (MPDPC) has been proposed as an effective alternative to conventional direct power control for pulsewidth-modulation (PWM) rectifiers. However, the sampling frequency of MPDPC still has to be high to achieve satisfactory performance. Furthermore, the grid currents of MPDPC would become highly distorted under unbalanced network conditions. To cope with the problems above, this paper proposes an improved MPDPC for PWM rectifiers, which is able to operate under both balanced and unbalanced grid voltages. By using a new definition of instantaneous reactive power in the predefined cost function, the proposed MPDPC can obtain sinusoidal grid currents and eliminate twice grid-frequency oscillation in both active power and the new reactive power. Neither complicated positive/negative-sequence extraction of grid voltage/current nor power compensation is required. Depending on the desired performance, two variants of the improved MPDPC are proposed and comparatively studied. At the same sampling frequency, the first approach achieves relatively low switching frequency, whereas the second approach obtains lower power ripples. Both simulation and experimental results are presented to confirm the effectiveness of the proposed methods. [ABSTRACT FROM PUBLISHER]

In this paper, a novel distributed iterative adaptive dynamic programming (ADP) method is developed to solve the multibattery optimal coordination control problems for home energy management systems. According to system transformations, the multi-input optimal control problem is transformed into a single-input optimal control problem, where all the batteries are implemented at their worst performance. Next, based on the worst-performance optimal control law, an effective distributed iterative ADP algorithm is developed, where, in each iteration, only a single-input optimization problem is implemented. Convergence properties of the distributed iterative ADP algorithm are developed to show that the iterative performance index function converges to the optimum. Finally, numerical analysis is given to illustrate the performance of the developed algorithm. [ABSTRACT FROM PUBLISHER]

Interior permanent-magnet (IPM) machines exhibit relatively large spatial harmonics in phase voltages and high nonlinearity in torque production due to both the presence of reluctance torque and the magnetic saturation in stator and rotor cores. To simulate the real electromagnetic behavior of IPM machines, this paper proposes a high-fidelity and computationally efficient machine model considering the magnetic saturation, the spatial harmonics, and the iron loss effect based on the inverse solution of the flux linkages extracted via finite-element analysis (FEA). Neither FEA nor a derivative computation is involved in the time-stepping simulation; thereby, the proposed model is computationally efficient and numerically robust. The high fidelity of the proposed machine model is validated by both the FEA and the experimental results. [ABSTRACT FROM PUBLISHER]

The modular multilevel converter (MMC) becomes attractive for medium- or high-power applications because of the advantages of high modularity, availability, and power quality. One of the technical challenges associated with an MMC is the balancing of the capacitors' voltages. In this paper, a voltage-balancing control method is proposed for the MMC under phase-shifted carrier-based pulsewidth modulation. The proposed voltage-balancing method uses the linearization method for pulse sorting without arm current measurement, which can control the capacitor charge transfer to balance the capacitor voltage in the MMC. In the proposed method, the voltagebalancing algorithm is implemented in each carrier wave period, which reduces the computational intensity and burden. In addition, the arm current can also be improved with the proposed method. The simulation studies with the professional tool PSCAD/EMTDC are conducted, and a downscale MMC prototype is also tested with the proposed method. The study results show the effectiveness of the proposed voltage-balancing method. [ABSTRACT FROM PUBLISHER]

Parameter mismatches seriously impact the stability and the rotor-speed accuracy in sensorless induction motor drives, particularly in low speed. To deal with the parameter sensitivity of the drive system with an adaptive full-order observer (AFO), this paper proposes a new unified parameter-sensitive equation that could accurately show the estimated rotor-speed error caused by all four kinds of parameter mismatches—rotor resistance, stator resistance, mutual inductance, and leakage inductance—with arbitrary feedback gains. With the proposed equation, the parameter sensitivity in the full operating region can be directly calculated, avoiding lots of simulations or experiments usually used in traditional analysis. Thus, the equation contributes to select a suitable feedback gains for a robust AFO. Moreover, based on steady-state operating point analysis, a feasible condition is proposed for judging the drive system's stability when parameter mismatches exist. The validity of the proposed analysis will be confirmed by simulation study and experimental results. [ABSTRACT FROM PUBLISHER]

The extremely constrained resource has hindered the efforts to implement the elliptic curve cryptography (ECC) into a radio-frequency identification (RFID) tag chip. In this paper, an ECC-based RFID digital baseband controller (DBC), which is compatible with ISO/IEC 14443 and Schnorr authentication protocol, is presented. In order to achieve low resources consumption and fast ECC computation speed, some techniques, such as the register reuse, clock multiplexer, and asynchronous counter, are adopted in this design. In addition, a linear feedback shift register-based stream encryption scenario is proposed for the data security. According to the synthesis result, the gate area and power consumption of DBC are 25.7 K and 14.7 \mu\W, respectively, in UMC 0.13 \mu\m CMOS technology. All of those characteristics make the realization of ECC-based DBC for RFID tag chip promising. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel high-conversion-ratio high-efficiency isolated bidirectional dc–dc converter. The proposed converter is operated in the step-down stage. The dc-blocking capacitor in the high-voltage side is used to reduce the voltage on the transformer, and the current-doubler circuits are used in the low-voltage side to reduce the output current ripple. The energy stored in the leakage inductance is recycled to the dc-blocking capacitor. When the proposed converter is operated with a step-up function, dual current-fed circuits on the low-voltage side are used to reduce the current ripples and conduction losses of the switches in the low-voltage side. The voltage-doubler circuit in the high-voltage side increases the conversion ratio. The proposed converter can achieve high conversion with high efficiency. Experimental results based on a prototype implemented in the laboratory with a high voltage of 200 V, low voltage of 24 V, and output power of 200 W verify the performance of the proposed converter. The peak efficiency of the proposed converter in the high-step-down and high-step-up stages is 96.3% and 95.6%, respectively. [ABSTRACT FROM PUBLISHER]

This paper presents a digitally master–slave controlled parallel system of multiple LLC resonant converters with an inner resonant current control loop in each module. Theoretical analysis of the stability of individual modules and the system with an inner resonant current loop is proposed based on the envelop model, which reveals the principle of the performance improvement brought by the resonant current control loop. Moreover, the inner resonant current loop eliminates the differences in small-signal characteristics among different static operating points, thus facilitating the voltage loop design. The analysis of parallel operation and a complete control loop design guide for paralleled LLC resonant converters is presented based on a small-signal model rather than on software simulation. Finally, the stability analysis and design are elaborated and verified through a 16-kW experimental system of four modularized LLC resonant converters. [ABSTRACT FROM PUBLISHER]