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The employment of solar microconverter allows a more detailed monitoring of the photovoltaic (PV) output power at the single module level; thus, machine learning techniques are capable to track the peculiarities of modules in the PV plants, such as regular shadings. In this way, it is possible to compare in real time the day-ahead forecast power with the actual one in order to better evaluate faults or anomalous trends that might have occurred in the PV plant. This paper presents a method for an effective fault diagnosis; this method is based on the day-ahead forecast of the output power from an existing PV module, linked to a microconverter, and on the outcome of the neighbor PV modules. Finally, this paper also proposes the analysis of the most common error definitions with new mathematical formulations, by comparing their effectiveness and immediate comprehension, in view of increasing power forecasting accuracy and performing both real-time and offline analysis of PV modules performance and possible faults. [ABSTRACT FROM AUTHOR]

An interacting multiple model (IMM) filter is a recognized method for adaptive estimation of states that is often necessary to characterize the behavior of dynamic systems with a multiple-mode operation. The traditional IMM filter adopts the measurement set to update the information about the active models. However, when this approach is used for fault-prognostic applications, it can lead to misleading state estimation. To overcome this problem, this paper proposes a novel fault-prognostic technique based on a modified IMM filter with fuzzy systems. The main methodological contribution of this paper is to build an approach based on an IMM filter able to make long-term fault predictions without measurements. This is done by incorporating a fuzzy system into the proposed IMM filter with the objective of modeling the system's dynamics and updating the probabilities of the observed modes. Furthermore, the proposed method and the standard IMM filter are compared in a numerical example and a real experimental platform PRONOSTIA for validation. The results analysis indicates a better prediction performance than the conventional IMM filter considering the failure time predictions and a measurement model not properly adjusted. [ABSTRACT FROM AUTHOR]

This paper proposes a novel fuzzified mechanical sensorless speed estimation technique for permanent magnet direct current (PMDC) brushed motor operated with pulse width modulation (PWM) based terminal voltage. For replacement of conventional mechanical speed sensors, few mechanical sensorless speed estimation techniques have been reported recently in the field of PMDC brushed motor. In this paper, a novel technique is applied over a recently reported semianalytical dynamic time-domain PMDC brushed motor model incorporating space-domain effects, namely slotting effect and commutation phenomenon to simulate the proposed estimation process. Ripple and back electromotive force based standalone estimation approaches are hybridized in order to eliminate uncertainties in all regions of estimation. In this paper, a discrete fuzzified hybrid speed estimation model has been proposed with adequate dynamic simulation responses. Further the proposed discrete speed estimation model has been applied experimentally over a PWM-driven 24-V, 12-teeth, 100-W PMDC brushed motor and various dynamic real-time responses have been compared with conventionally captured speed samples to validate the proposed model. [ABSTRACT FROM PUBLISHER]

In order to effectively suppress surplus torque, realizing high precision loading, this paper applies proportional resonant (PR) control to the load torque control of electric load simulator (ELS), and analyzes and optimizes the stability and dynamic performance of ELS. The mathematical model of ELS is built in z-domain first in this paper, to establish foundation for designing and analyzing PR controller. The stability of the ELS with PR controller is analyzed through Nyquist diagrams, and optimized by reasonably designing the phase compensation angle of PR controller. The dynamic performance is analyzed through pole–zero plots, and the resonant gain of PR controller is designed based on the pole–zero plots to optimize the dynamic performance. Experimental results on ELS are provided, and the proposed method is compared with other typical methods, validating the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

The nine-switch converter is a multiport converter having two three-phase terminals and a dc-link, just like a 12-switch back-to-back (BTB) converter, but with 25% reduction of active switch count. However, the reduction from 12-switch to 9-switch may not always be an efficient choice considering losses in the switches. Only the load–source combination for the ac–ac common frequency mode and the source–source combination for the ac–dc different frequency (ac–dc DF) mode have been reported, so far, to yield relatively lower loss for the nine-switch converter. This paper shows that the nine-switch converter can have relatively lower loss even with a load–source combination, instead of only source–source combination in its ac–dc DF mode—when the upper terminal is connected to a dc load and the lower terminal is connected to an ac source. Mathematical proof is presented with derivation of the particular operating parameters for which the nine-switch converter will have comparatively lower losses. The analysis is validated with simulation and experimental results of a 1-kW system. Finally, the benchmark of the application criteria of the nine-switch converter for having lower conduction loss than the BTB converter is updated in this paper. [ABSTRACT FROM AUTHOR]

The reduced chip size and unipolar current conduction mechanism make silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) suitable for high-frequency power electronics applications. Modeling the switching process of the SiC power MOSFET with parasitic components is important for achieving higher efficiency and power density system design. Therefore, this paper proposes a new concise yet accurate switching loss model for SiC power MOSFETs. Addressing the limitations in experimental measurements, numerical simulations are conducted to validate the proposed model taking the output capacitance Coss discharge and charge into consideration. The role of the parasitic components in the second-order model is discussed in depth for switching losses. Furthermore, this paper also provides guidelines in designing the gate driver for ultrafast SiC power MOSFETs. [ABSTRACT FROM PUBLISHER]

SiC mosfet based converters are capable of high switching frequency operation. In this paper, the converter is operated with 50-kHz switching frequency for an active front-end rectifier application. Due to high switching frequency, the grid-side filter size is reduced, and the possibility of a high bandwidth current control loop is utilized in this paper. A current control loop with bandwidth of 5 kHz is designed using a proportional–integral controller in synchronously rotating dq-reference frame. In addition, the performance of the controller is tested under unbalanced input supply conditions. During this condition, new feed-forward signals, which are added to the controller output, are proposed. The gain of the feed-forward signal can be modified to achieve balanced sinusoidal grid currents, constant dc-link voltage, or a controlled negative-sequence input current, which are typical application-depending requirements. A closed-form formula to calculate the gain of the feed-forward signal to achieve the above-mentioned requirements is also proposed in this paper. To verify the proposed method, the simulation and experimental results are presented in this paper. [ABSTRACT FROM PUBLISHER]

The stator winding structure of the main exciter of the brushless synchronous starter/generator (BSSG) is changed at high speed for flux weakening, leading to a sudden excitation decrease of the main generator (MG) of BSSG. Consequently, when proportional-integral (PI) current loop-based control strategies are applied, large current overshoots will occur due to the lack of fast current control ability. This paper adopts model predictive current control (MPCC) to replace PI current control for a better dynamic performance. Besides, a parameter estimation scheme, based on the recursive least square (RLS) algorithm, is proposed to provide MG parameters for MPCC. An effectiveness analysis of the RLS algorithm is performed and two rules are given. According to the two rules, rather than the parameter dynamic characteristics adopted by traditional methods, three MG parameters, dq-axes inductances, and excitation flux linkage are estimated with two decoupled RLS estimators. In addition, a method is proposed to adjust the forgetting factor to track fast changing parameters of MG when the excitation changes suddenly. With the estimated parameters, MPCC is conducted to start BSSG. Experimental results show that fast current control of MG is achieved and large current overshoots caused by the sudden excitation change are avoided. [ABSTRACT FROM AUTHOR]

Differential power processing (DPP) is a promising architecture to solve the issue caused by mismatches among photovoltaic (PV) submodules. To eliminate the mismatch power losses, this paper presents an optimized PV-to-bus DPP system with submodule-level individual maximum power point tracking (MPPT) and module-level minimum-power tracking (MPT) simultaneous implementation according to the built mathematical model of the power processed by DPP converters with respect to the string current. Furthermore, a flexible time-sharing algorithm is adopted to reduce the number of MPPT units. Compared with other solutions, such as PV optimizer, the proposed scheme can reduce the effects of mismatches to the minimum regardless of mismatch conditions. The system cost is reduced since only one adaptive MPPT controller is required. Besides, the system efficiency is improved due to the true MPPT implementation and MPT control. Both simulation and experimental tests are provided to validate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

A multilevel dodecagonal voltage space vector generation scheme for variable-speed drive applications with single-dc-link operation requires a large value of capacitance for cascaded H-bridge (CHB) filters, when operated at lower speeds. In existing schemes, the multilevel dodecagonal structure is obtained by cascading a flying capacitor inverter with a CHB. In this paper, a new scheme has been proposed to minimize the capacitance requirement for full speed operation by creating vector redundancies using modular and equal voltage CHBs. Also, an algorithm has been developed to optimize the selection of vector redundancies among the CHBs in order to minimize the voltage ripple of the floating capacitors. The proposed algorithm considers instantaneous capacitor voltages and phase currents for optimal selection of vector redundancies. A mathematical model for capacitor voltage deviation is presented, and the effectiveness of the proposed algorithm is verified in both the simulation and the experiment. [ABSTRACT FROM AUTHOR]

Two-stage single-phase inverter system has found many applications in distributed generators and grid-connected systems. However, the existence of double-line frequency ripple on the dc-bus voltage due to single-phase inverter's operation has given rise to some design and reliability issues. Some of these are the degradation in the quality of inverter's output voltage and shortening of dc-bus capacitor's lifetime. The problem is rooted in the controller design of the front-end dc–dc converter, which is often designed based on a simplified mathematical model of the dc–dc converter that fails to account for some complex phenomena, such as system's nonlinearities and circuit parameter variations due to temperature and aging effects. In this paper, a disturbance-observer-based control is proposed where these unmodeled effects are treated in the form of lumped disturbance and compensated for in a feed-forward manner. The major advantage of this control solution is that only minimal plant information is needed for controller design and that a decoupled composite controller can be realized, where the feedback compensator is designed to meet certain stability criteria while the disturbance-observer-based feed-forward compensator is designed to handle fast transient events. A prototype of a dual-active-bridge (DAB) dc–dc converter implemented with disturbance-observer-based control is constructed to verify its effectiveness. Experimental results show that the dynamic response of the DAB converter is significantly improved and the double-line frequency ripple on the dc-bus voltage is effectively suppressed by the proposed control solution. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for the conversion of an implicit current–voltage (I–V) expression of a double diode model (DDM) photovoltaic (PV) module to an explicit expression of current in terms of voltage. A new method is proposed for the estimation of maximum power point (MPP) of a DDM PV module using the explicit I–V expression of a PV module under uniform irradiance condition. Further, a new mathematical model of a partially shaded PV array is developed using the proposed explicit expression. Since the explicit I–V expression is used for the estimation of MPP of a DDM PV module under uniform and nonuniform irradiance conditions, the estimation of MPP is simple, accurate, and efficient. The accuracy of the explicit expression is verified considering three different PV modules. A comparison of MPP of a DDM PV module extracted using the proposed method with different existing methods under different environmental conditions (DECs) is presented. The results obtained using the proposed method are validated with the experimental results under DEC. Also, the accuracy of the estimated global MPP of a PV array under partial shading conditions is verified. [ABSTRACT FROM AUTHOR]

The magnetic resonant wireless power transfer (WPT) system with a class E inverter has wide application in mid-range power transmission, especially for several megahertz scenario. However, it is cumbersome for the existing modeling and analysis methods to obtain the analytical solution to the system variables, which limits the evaluation of system characteristic. This paper proposes a nonlinear mathematical model for the WPT system with a class E inverter. The equivalent small parameter method (ESPM) is first adopted to solve the proposed six-order nonlinear model, and symbolic-form steady-state periodic solutions are yielded. During the whole solving process, only three iteration steps are needed for the proposed method. Compared with other existing modeling and analysis methods, the symbolic periodic results acquired by the ESPM exhibit sufficient accuracy by virtue of the combination of more higher harmonics. Meanwhile, the calculation complexity is simplified remarkably. Simulation and available experiments validate the effectiveness and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive interval type-2 fuzzy logic control scheme is proposed for high-performance permanent magnet synchronous machine drives. This strategy combines the power of type-2 fuzzy logic systems with the adaptive control theory to achieve accurate tracking and robustness to higher uncertainties. Unlike other controllers, the proposed strategy does not require electrical transducers and hence, no explicit currents loop regulation is needed, which yields a simplified control scheme. But, this limits the machine's operation range since it results in a higher energy consumption. Therefore, a modified reference frame is also proposed in this paper to decrease the machine's consumption. To better assess the performance of the new reference frame, comparison against its original counterpart is carried-out under the same conditions. Moreover, the stability of the closed-loop control scheme is guaranteed by a Lyapunov theorem. Simulation and experimental results for numerous situations highlight the effectiveness of the proposed controller in standstill, transient, and steady-state conditions. [ABSTRACT FROM PUBLISHER]

This paper investigates the optimal consensus control problem for discrete-time multi-agent systems with completely unknown dynamics by utilizing a data-driven reinforcement learning method. It is known that the optimal consensus control for multi-agent systems relies on the solution of the coupled Hamilton–Jacobi–Bellman equation, which is generally impossible to be solved analytically. Even worse, most real-world systems are too complicated to obtain accurate mathematical models. To overcome these deficiencies, a data-based adaptive dynamic programming method is presented using the current and past system data rather than the accurate system models also instead of the traditional identification scheme which would cause the approximation residual errors. First, we establish a discounted performance index and formulate the optimal consensus problem via Bellman optimality principle. Then, we introduce the policy iteration algorithm which motivates this paper. To implement the proposed online action-dependent heuristic dynamic programming method, two neural networks (NNs), 1) critic NN and 2) actor NN, are employed to approximate the iterative performance index functions and control policies, respectively, in real time. Finally, two simulation examples are provided to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper focuses on the fault-tolerant control problem for an Internet-based three-tank system in the presence of possible sensor bias faults. The Internet-based three-tank system is an experimental setup that can be regarded as a typical networked system for evaluating networked fault-diagnosis and fault-tolerant control methods. Packet dropout phenomenon in the sensor-to-controller link is considered in this paper, and the fault type we deal with is chosen as the sensor bias fault. Fault-diagnosis unit is designed toward an auxiliary system. Sensor bias faults can be detected by comparing the residual signal generated by the fault detection filter and a prescribed threshold. After that, the fault can be isolated by using the residual analysis approach. Once the fault is isolated, it can be estimated iteratively in the least-squares sense. A fault accommodation method is proposed, and a fault-tolerant control strategy is achieved based on the fault information provided by the fault-diagnosis unit. The approach brought forward in this paper is demonstrated via an experimental study on the practical Internet-based three-tank system. Results show the effectiveness and the applicability of the proposed techniques. [ABSTRACT FROM PUBLISHER]

This paper presents an improved analytical method for predicting the magnetic field and forces in linear permanent-magnet synchronous machines (LPMSMs) accounting for both the primary end effect and secondary end effect. So far, the magnetic field calculation of LPMSM in most studies is conducted in Cartesian coordinate, whereas the end effect is neglected by applying periodic boundary. In this paper, to implement the analytical model, a polar presentation of the machine geometry is proposed and the subdomain method is applied to calculate the magnetic field. Then, according to the developed model, the tangential thrust and normal forces are calculated based on the Maxwell stress theory. Numerical results are subsequently obtained by finite-element method and employed to validate the analytical model. Finally, an LPMSM prototype is manufactured and experiments are conducted. The results show that the developed analytical model has high accuracy for predicting the magnetic field and forces. [ABSTRACT FROM AUTHOR]

This paper presents two continuous finite-time convergent control algorithms driving an output (the highest relative degree state) of an $n$-dimensional integrator to zero for a finite time using a scalar input in the presence of both matched and unmatched unbounded disturbances. No knowledge of all system states is required: only the output should be available for the control design. No knowledge or reconstruction of individual disturbances is assumed as well. This paper concludes with a case study of controlling an industrial benchmark DC motor, whose third-order mathematical model is perturbed by matched and unmatched disturbances. [ABSTRACT FROM PUBLISHER]

This paper presents both an event- and a self-triggered sampling and regulation scheme for continuous time linear dynamic systems by using zero-sum game formulation. A novel performance index is defined wherein the control policy is treated as the first player and the threshold for control input error due to aperiodic dynamic feedback is treated as the second player. The optimal control policy and sampling intervals are generated using the saddle point or Nash equilibrium solution, which is obtained from the corresponding game algebraic Riccati equation. To determine the optimal event-based sampling scheme, an event-triggering condition is derived by utilizing the worst case control input error as the threshold. To avoid the additional hardware for the event-triggering mechanism, a near optimal self-triggering condition is derived to determine the future sampling instants given the current state vector. To guarantee Zeno-free behavior in both the event- and self-triggered closed-loop systems, the minimum intersample times are shown to be lower bounded by a nonzero positive number. Asymptotic stability of the closed-loop system is ensured using Lyapunov stability analysis. Finally, simulation examples are provided to substantiate the analytical claims. [ABSTRACT FROM AUTHOR]

Absolute magnetic encoders (AMEs) use two magnets: a ring multipolar magnet (MPM) generating high-resolution and improving the accuracy for the encoder, and a bipolar magnet in the center calculating the number cycle of MPM signals. The phase outputs of these AMEs are tracked from the sinusoidal signals of the MPM. However, these sine/cosine signals are disturbed by amplitude differences, offsets, phase-shift, harmonic components, and random noise. In order to solve this problem, this paper presents an adaptive linear neuron based on a third-order phase-locked loop (ALN-PLL) to improve the accuracy of AMEs. The proposed approach consists of two main parts: The first part is an ALN algorithm that uses the phase feedback of the third-order PLL in order to build the mathematical model of input signals, and then reject the disturbances. The second part is a third-order PLL that is designed based on a dominant pole approximation algorithm. The proposed PLL can reduce noise and eliminate dc-error during the phase step, frequency step, and frequency ramp. The simulation and experimental results demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Electric vehicle (EV) dynamical wireless charging is an emerging application area of wireless power transfer technologies. Compared with a classical static charging mode, there are two key challenges in a dynamical charging process. One is to determine charging area and corresponding excitation unit. The other is to provide large energy in a short time interval. Based on multiexcitation unit configuration for EV dynamical charging, this paper proposes a charging area determining method. The dynamical mutual inductance can be calculated based on dc current input and load detection. A charging area can be figured out based on output power requirement. And a switching mode method is given to control the charging process for multiexcitation unit configuration. On this basis, a power and efficiency enhancement method is proposed by utilizing a multiexcitation unit in the charging area. This method is beneficial for improving system power capacity without increasing the voltage and current stress. Finally, experimental results show that this method can realize accurate charging area determining and control. And the output power of dual excitation unit configuration can increase almost four times than that of a traditional single excitation unit configuration. [ABSTRACT FROM AUTHOR]

Boom crane systems with high practicality, the control problems of which are more complex than those of most other underactuated systems due to their strongly nonlinear dynamical coupling characteristics, are widely applied in various places. In addition to the basic control objectives of accurate boom positioning and payload swing suppression, another challenging aspect is how to improve the transient performance of the state variables while ensuring time (sub)optimality during transportation. In this paper, to address the two aforementioned issues, i.e., complicated nonlinear dynamics and ensuring transient performance, a new nonlinear time suboptimal trajectory planning approach, which does not require linearizing the original nonlinear dynamics, is proposed to achieve efficient control results for the boom crane system. After performing an in-depth analysis, we find a transformation relationship between four tip signals and the state variables. Then, by planning proper trajectories for the tip signals based on the original nonlinear boom crane dynamics, we obtain swing-free time suboptimal trajectories for the boom pitch and yaw movements; hence, the boom can reach its destination accurately, and the payload swing can be suppressed. Moreover, the state variables can be restricted within specified ranges as required. The presented trajectory planner can be considered as the first solution for generating trajectories for the boom crane system, respecting various state constraints without the need for any linearization operations. Finally, some hardware experiments are introduced to verify the effectiveness of the presented control strategy. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive backstepping control scheme is presented to solve the position control problem for a gear transmission servosystem with unknown asymmetric sandwiched dead-zone nonlinearity. All the parameters involved in both the system and dead-zone models are allowed to be totally unknown. In contrast to the previous results where the effects of symmetric dead zone can be treated as additive disturbances in a transformed system, most of the unknown parameters of the transformed system are now time varying and dependent on the real-time value of relative displacement between the driving and driven gears. To deal with the above issue, new compensating terms in the quadratic form are introduced in the design of the virtual control signal for each recursive step. With the adaptive laws modified correspondingly, we can still show that all the closed-loop signals are ensured to be bounded and the output regulation error will converge to a compact set. Simulation results are provided to show the effectiveness of the proposed adaptive control scheme. [ABSTRACT FROM AUTHOR]

Nowadays, high-dynamic-range (HDR) imaging represents a prevailing trend and attracts much attention from both academic and industrial scholars. Since HDR images cannot be properly produced on the mainstream low-dynamic-range (LDR) displays, various tone-mapping operators or postprocessing technologies have been designed to transform HDR images into LDR images for visualization on LDR displays. However, it inevitably induces artifacts and distortions due to dynamic range compression. Besides, existing tone-mapped (TM) technologies cannot effectively handle all kinds of images with diverse contents and structures, leaving to a very challenging and urgent image quality assessment (IQA) problem. To cope with this challenge, in this paper, an effective blind quality assessment approach for TM images is proposed through a comprehensive consideration of their characteristics. More specifically, to dig out sufficient information from TM images, multiple quality-sensitive features are captured to fully represent different attributes, including colorfulness, naturalness, and structure. The connection between feature space and associated subjective ratings is established via a regression model. Extensive experiments on a recently released TM image database prove that the proposed approach is superior to the state-of-the-art no-reference IQA approaches. [ABSTRACT FROM AUTHOR]

MR16 lighting system with a high-frequency step-down electronic transformer is widely used in commercial lighting. In this paper, a single-switch quadratic boost light emitting diode (LED) driver compatible with electronic transformers for the MR16 lighting system is proposed and analyzed. It combines a prestage boost power factor correction (PFC) converter and a second-stage boost dc–dc converter with a single switch. The effect of the dc link voltage ripple of the prestage boost PFC converter on the output of the second-stage boost dc–dc converter is eliminated by a fast voltage mode control loop of a second-stage circuit. Therefore, flicker-free low ripple LED current is achieved. With a small dc link voltage ripple of prestage, the turn-on time of the active switch is almost constant in a half-line cycle. Therefore, PFC can be achieved with inductor current of prestage operating in a discontinuous conduction mode. With small input capacitance, the proposed LED driver presents a good compatibility performance with different kinds of electronic transformers. Furthermore, the proposed LED driver needs only one active switch and one control loop, which makes circuit volume small and low cost. Finally, a 4 W LED driver for a small-size MR16 lighting system is provided to verify the studied results. [ABSTRACT FROM AUTHOR]

This paper presents a novel oversampling deadbeat current control approach for permanent magnet synchronous motor drives capable of operating at a controller sampling frequency multiple of the power converter switching frequency. Model-based controllers suffer from heavy computational demand and performance degradation due to parameter uncertainties. The proposed controller concurrently with field-programmable gate array implementation permits to achieve a constant switching frequency and an optimal current ripple along with a high current-loop bandwidth and robust behavior to parameter variation. A disturbance observer has been added to the proposed controller in order to compensate for the converter voltage distortions. The proposed control strategy is tested through both simulations and experiments. [ABSTRACT FROM AUTHOR]

In this paper, a unified controller for switched reluctance motors is proposed for wide speed operations. The proposed controller achieves minimum output torque ripple at low and medium speeds and operates in a single-pulse mode at high speeds. Overlapping regions between the phases are controlled such that direct instantaneous torque control (DITC) and current control (CC) can be implemented simultaneously on different phases. This simplifies the torque sharing during commutation and minimizes torque ripple due to imperfect current tracking and mutual torque. A demagnetization curve concept to demagnetize the phase currents at an optimum angle is introduced to ensure high torque per ampere and single-pulse mode operation. This results in extending low ripple operation to medium speed ranges. The seamless combination of DITC, CC, and the demagnetization curves leads to torque ripple minimization, automatic excitation angle control, and smooth operation over a wide speed range. The effectiveness of the proposed unified controller is verified through simulation and experimental studies. [ABSTRACT FROM AUTHOR]

When the selected harmonic elimination pulsewidth modulation (SHEPWM) is adopted to three-level neutral-point-clamped converters to reduce the switching frequency, the neutral-point potential (NPP) problem becomes more severe compared with other modulations. It is because there is no degree of freedom for SHEPWM to control the NPP. SHEPWM realizes a better harmonic performance by calculating the switching angles offline based on harmonic requirements. Since it is harsh to solve the angles online, we cannot change the angles to control the NPP. Aiming at the low-frequency NPP fluctuation minimum, a novel current harmonic minimum method based on the optimal third-order/ninth-order harmonic is proposed in this paper. The optimal third-order/ninth-order harmonic is derived based on the relationships among the third-order/ninth-order harmonic and the NPP. They can be utilized to realize the low-frequency NPP fluctuation minimum without changing any switching angle online. Moreover, some comparisons, such as the solution ranges, weighted total harmonic distortion, the initial value of iteration calculation, show that the proposed method has a good output performance. Finally, the experimental results are given to verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear active disturbance rejection control (ADRC) scheme is designed to control the pneumatic muscle actuator system. To reflect the impact of the sampling period, a continuous-discrete extended state observer (CDESO) is employed to estimate the so-called total disturbance, which describes the unmodeled complexities. Then, a nonlinear composite controller is used, where the estimates provided by the CDESO act as the feedforward term. The sufficient conditions to guarantee the stability of the CDESO and the overall controlled system are provided, respectively. Finally, a number of practical experiments are conducted on a pneumatic motion platform in order to verify the applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Demand response (DR) has been recognized as a powerful tool to help mitigate power imbalances in a future smart energy system. This paper takes the point of view of a grid operator (GO) to establish an intraday resource trading framework, over which DR resources from different sectors (large industrial consumers and small- or middle-sized customers) are brought to the system level and are assessed by the GO along with the generators, with the aim of procuring the required system resources at minimal cost. Considering the distinct behaviors of the involved entities, Stackelberg game theory was adopted to analyze the coordination among the various decision makers. A unique Stackelberg equilibrium was identified that yields the optimal outcome for the resource trading game between the GO and demand-side participators. Simulation results demonstrated that the total procurement cost was minimized by applying the proposed approach. [ABSTRACT FROM AUTHOR]

The current lithium-ion battery remaining useful life (RUL) prediction techniques are mainly developed dependent on offline training data. The loaded current, temperature, and state of charge of lithium-ion batteries used for electric vehicles (EVs) change dramatically under the working conditions. Therefore, it is difficult to design acceleration aging tests of lithium-ion batteries under similar working conditions as those for EVs and to collect effective offline training data. To address this problem, this paper developed an RUL prediction method based on the Box–Cox transformation (BCT) and Monte Carlo (MC) simulation. This method can be implemented independent of offline training data. In the method, the BCT was used to transform the available capacity data and to construct a linear model between the transformed capacities and cycles. The constructed linear model using the BCT was extrapolated to predict the battery RUL, and the RUL prediction uncertainties were generated using the MC simulation. Experimental results showed that accurate and precise RULs were predicted with errors and standard deviations within, respectively, [-20, 10] cycles and [1.8, 7] cycles. If some offline training data are available, the method can reduce the required online training data and, thus, the acceleration aging test time of lithium-ion batteries. Experimental results showed that the acceleration time of the tested cells can be reduced by 70%–85% based on the developed method, which saved one to three months’ acceleration test time compared to the particle filter method. [ABSTRACT FROM AUTHOR]

Brushless doubly fed induction machine (BDFIM) with apparent cost advantage and high potential in reliability is regarded as a viable alternative to the commonly applied doubly fed induction machine in modern energy conversion systems. Design and analysis of the current controller, which are key points for effective control of BDFIM, are for the first time intensively studied in this paper. The complete model of control winding current loop is developed in form of complex transfer function, and its differences from the conventional simplified model are clearly revealed. An improved feedforward current control method is proposed based on the complete model, offering simple and compact control structure with only few parameters involved. Stability and transient performance analysis is carried out on both conventional and improved current controllers, which theoretically proves stability improvement and faster dynamic performance of the improved current controller. The effectiveness and superiority of the proposed current controller, as well as the consistence between theoretical analysis and actual performance, are validated by experimental results performed on a prototype BDFIM system. [ABSTRACT FROM AUTHOR]

This paper presents a new approach for the small-signal modeling of the dc–dc LLC resonant converter aimed to supply high-power light-emitting diodes (LEDs). This small-signal modeling procedure is based on the extended describing function method, where for a reliable small-signal model of the LLC LED driver, the equivalent piece-wise linear circuit of the LED has to be considered under some conditions throughout the model development. Otherwise, the obtained model does not reflect the real dynamic behavior of the converter. Furthermore, a numerical analysis is presented showing the conditions where the proposed model better describes the real dynamic behavior of the converter in relation to the traditional approach where the LED is modeled by an equivalent resistance. From the obtained model, the feedback compensator is designed and implemented in order to track the average current reference and avoid output current ripple, consequently sidestepping output light modulation (flicker). Experimental results show the feasibility of the proposed small-signal model and the active ripple compensation through a dimmable digitally controlled LLC LED driver under closed-loop operation. [ABSTRACT FROM AUTHOR]

Linear ramp slope compensation (LRC) and quadratic slope compensation (QSC) are commonly implemented in peak-current-mode-controlled dc–dc converters in order to minimize subharmonic and chaotic oscillations. Both compensating schemes rely on the linearized state-space averaged model (LSSA) of the converter. The LSSA ignores the impact that switching actions have on the stability of converters. In order to include switching events, the nonlinear analysis method based on the Monodromy matrix was introduced to describe a complete-cycle stability. Analyses on analog-controlled dc–dc converters applying this method show that system stability is strongly dependent on the change of the derivative of the slope at the time of switching instant. However, in a mixed-signal-controlled system, the digitalization effect contributes differently to system stability. This paper shows a full complete-cycle stability analysis using this nonlinear analysis method, which is applied to a mixed-signal-controlled converter. Through this analysis, a generalized equation is derived that reveals for the first time the real boundary stability limits for LRC and QSC. Furthermore, this generalized equation allows the design of a new compensating scheme, which is able to increase system stability. The proposed scheme is called polynomial curve slope compensation (PCSC) and it is demonstrated that PCSC increases the stable margin by 30% compared to LRC and 20% to QSC. This outcome is proved experimentally by using an interleaved dc–dc converter that is built for this work. [ABSTRACT FROM AUTHOR]

In this paper, a small-scale experimental method for the study of the dynamic performance of an electromagnetic railgun is proposed. A silicon-based microbeam under electrostatic force was used to simulate the electromagnetic railgun. An experimental model was developed for a set of railgun parameters. On the basis of similarity theory, the natural frequency similarity ratio between the railgun and the experimental model was determined. The excitation and detection circuits of the experimental model were designed and fabricated. Using the experimental model, the natural frequency for the railgun was obtained and compared with the real full-scale one. Results revealed that the small-scale experimental results agreed well with the experimental result of the full-scale railgun. The proposed method can be used to predict the dynamic performance of the full-scale railgun system. [ABSTRACT FROM AUTHOR]

Three-phase interior permanent magnet synchronous motor (IPMSM) drive systems have gotten widely used recently in various applications due to their speed regulation characteristics and high power density. Compared with classical field-oriented control (FOC) and flux-weakening control, model predictive control (MPC) technique is more efficient and effective in achieving excellent performance without complicated controller tuning, but with explicit constraints. Yet, the optimum application of the MPC algorithm in a machine control system is still in the exploratory stage. In order to lower the current and torque ripples, this paper retains a modulator, but replaces all the proportional integrate control loops, which are contained in the conventional FOC systems with a single MPC controller. Moreover, we adopt a brand-new linearization approach to tackle the strong coupled nonlinear IPMSM mathematical model, obtaining an improved linear plant model, which is suitable for the motor with constant load torque. When it comes to flux-weakening control, the required d-axis current is calculated, after which it is used as the input of the proposed MPC controller, abandoning the previous natural field weakening method. Finally, for the purpose of lowering the dynamic speed and current overshoot, a further constraint in the change rate of manipulated variables is discussed. The improved control algorithm has been verified in both simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper presents real-time diagnosis for open-circuited (O-C) and unbalance faults in power electronic converters (PECs) connected to residential small wind systems grid-tied. The spectrum analysis along with the dc components of the voltage and current measurements available in the converter is utilized for the O-C fault detection, classification and localization of the power switching devices in the PEC, as well as the identification of the unbalance input voltage to the converter. The proposed methodologies in this paper require much fewer inputs compared to the previous researches; therefore, they avoid any additional sensors or hardware which include further costs and expenses on such systems. The experimental evaluations for the proposed algorithms are provided and demonstrate the effectiveness and the robustness of the proposed diagnostic algorithms in this paper. The PEC under study consists of three main subsystems: uncontrolled three-phase rectifier, boost chopper, and single-phase inverter. [ABSTRACT FROM PUBLISHER]

This paper proposes an online parameter estimation method based on a discrete-time dynamic model for the interior permanent-magnet synchronous motors (IPMSMs). The proposed estimation technique, which takes advantage of the difference in dynamics of motor parameters, consists of two affine projection algorithms. The first one is designed to accurately estimate the stator inductances, whereas the second one is designed to precisely estimate the stator resistance, rotor flux linkage, and load torque. In this paper, the adaptive decoupling proportional–integral (PI) controllers with the maximum torque per ampere operation, which utilize the previously identified parameters in real time, are chosen to verify the effectiveness of the proposed parameter estimation scheme. The simulation results via MATLAB/Simulink and the experimental results via a prototype IPMSM drive system with a TI TMS320F28335 DSP are presented under various conditions. A comparative study with the conventional decoupling PI control method is carried out to demonstrate the better performances (i.e., faster dynamic response, less steady-state error, more robustness, etc.) of the adaptive decoupling PI control scheme based on the proposed online parameter estimation technique. [ABSTRACT FROM PUBLISHER]

This paper presents the steady-state mathematical model of a five-phase induction machine with a combined star/pentagon connection. The connection splits the stator winding into two five-phase windings displaced in space by $\pi$/10 and connected in a combined star/pentagon configuration. Recent work limited to an experimental investigation demonstrated that the connection possesses improved fault tolerance when compared to a conventional star-connected stator, as well as avoids the pentagon connection problems. Although the machine has five-phase terminals, it is intrinsically an asymmetrical ten-phase machine, which introduces additional subspaces in the machine's mathematical model. In order to theoretically investigate and thoroughly assess this connection against conventional connections, this paper introduces the steady-state mathematical model based on vector space decomposition and symmetrical component theory. Finite-element analysis is first used to investigate the different harmonic current components induced in the cage rotor circuit, upon which the effect of different subspaces can be clarified and the required transformation matrix from phase variables to their sequence components can be derived. The model is verified using a 1-kW prototype five-phase induction machine. [ABSTRACT FROM PUBLISHER]

In this paper, a mathematical model of a 12-phase flux-switching permanent magnet (FSPM) machine designed for high-power wind power generation is established and investigated. First, the winding inductances in both the stator reference frame and the $dq$-axes reference frame are analyzed. It should be noted that the characteristics of the 12-phase winding inductances are different from those of its three-phase counterpart. The largest mutual inductance is much smaller than half of the self-inductance, and most mutual inductances are negligible, which brings the benefit of improved magnetic isolation between phases and causes the 12th-order inductance matrix to be sparse. Thereafter, an accurate inductance model is established, taking account of the magnetic coupling between adjacent three-phase winding sets. Finally, a flux-linkage equation, a voltage equation, a power equation, and a torque equation are derived in sequence. The effectiveness of the proposed mathematical model is verified by comparing the theoretical results with 2-D finite-element-analysis-based predictions. The work in this paper lays an important foundation for the control strategy of the 12-phase FSPM machine. [ABSTRACT FROM AUTHOR]

The main objective of this two-part state-of-the-art paper called “Recent Advances in the Design, Modeling, and Control of Multiphase Machines” is to present latest contributions in the multiphase machines' field. The first part of this paper focuses on the recent progress in the design, modeling, and control, whereas the drive is in healthy operation. This second part presents relevant contributions in two not analyzed fields. The first is in relation with the use of the additional degrees of freedom of multiphase machines and the exploitation of their fault-tolerant capabilities without adding extra hardware. The second one analyzes multiphase generation, particularly in grid-connected wind energy conversion systems and stand-alone applications. Recent progresses are shown and open challenges and future research directions are discussed. [ABSTRACT FROM AUTHOR]

In this paper, a novel analytical-based kinematic and dynamic modeling and control approach is developed for reference speed tracking of a multijoint robotic fish. The kinematic model is improved by the introduction of input signal for controlling body undulation amplitude without distorting the model structure. Next, the dynamic model is developed in the discrete-time domain primarily because fish swimming pattern generates oscillating continuous thrust where the effect of thrust over one cycle of undulation can be calculated through averaging. Hence, the dynamics can be discretized according to the undulation rate. The novelty in developing the discrete-time dynamical model is three fold. First, the thrust gradient is derived with assistance of Lighthill's large amplitude elongated body theory. More importantly, affine-in-control dynamical model form, essential for designing a real-time model-based control algorithm, is derived by inclusion of the updated kinematic model. Second, the thrust delay is studied via pulse input response of the motion system, and incorporated in the dynamical model. Third, drag force coefficient calculation is also proposed by comparing the thrust model and empirically recorded steady-state speeds of the robotic fish. Finally, discrete-time model-based sliding-mode control (SMC) is designed for speed tracking. Experimental results verify that SMC based on the proposed dynamical model, can significantly improve speed tracking performance of a multilink robotic fish. [ABSTRACT FROM PUBLISHER]

This paper studies the trajectory tracking control problem of an autonomous underwater vehicle (AUV). We develop a novel Lyapunov-based model predictive control (LMPC) framework for the AUV to utilize computational resource (online optimization) to improve the trajectory tracking performance. Within the LMPC framework, the practical constraints, such as actuator saturation, can be explicitly considered. Also, the thrust allocation subproblem can be addressed simultaneously with the LMPC controller design. Taking advantage of a nonlinear backstepping tracking control law, we construct the contraction constraint in the formulated LMPC problem so that the closed-loop stability is theoretically guaranteed. Sufficient conditions that ensure the recursive feasibility, and hence the closed-loop stability, are provided analytically. A guaranteed region of attraction is explicitly characterized. In the meantime, the robustness of the tracking control can be improved by the receding horizon implementation that is adopted in the LMPC control algorithm. Simulation results on the Saab SeaEye Falcon model AUV demonstrate the significantly enhance trajectory tracking control performance via the proposed LMPC method. [ABSTRACT FROM PUBLISHER]

Generally, the modal degeneration problem existed in the design of ultrasonic motors using composite vibration modes can be overcome by adopting the same-order orthogonal-bending composite vibrations. The conventional excitation and the modified hybrid one of sandwich type orthogonal-bending composite vibrations with the same order are compared and analyzed in this paper. Compared with the conventional one, the modified hybrid excitation favors that two groups of ceramics exciting two orthogonal-bending modes are placed in the optimum excitation position. Moreover, the modified hybrid excitation can achieve larger vibration amplitude than the conventional one, while the amount of the ceramics adopted and the exciting voltages applied are the same. The first-order orthogonal-bending composite vibrations are chosen to analyze the advantage of the modified hybrid excitation. Finite-element method is adopted to compare the amplitudes of the models with the same sizes but different excitations. The prototypes corresponding to two excitations are fabricated and tested to verify the results of the theory and simulation. It is proved that the modified hybrid excitation can improve the performance of the sandwich type ultrasonic motors using bending composite vibrations. [ABSTRACT FROM PUBLISHER]

The electromagnetic and heat issue is the core of the key problems for large synchronous generators. This paper presents a new method to account for the rotary excitation field of a large synchronous generator using a new 3-D static frequency-domain finite element to solve the end magnetic field and electromagnetic losses via phase transformation. The solution time is significantly reduced. Both magnetic flux leakage and temperature testing of the end structures are conducted. There is good consistency between the theoretical simulation and the experimental results for both magnetic and thermal fields. The regularity of the magnetic and thermal field distributions is studied drawing on the electromagnetic and heat transfer theories. [ABSTRACT FROM PUBLISHER]

In this paper, the optimal output regulation problem is considered for the model-free 2-degree-of-freedom (2-DOF) helicopter. A multistep Q-learning (MsQL) method is developed with multistep policy evaluation. First, by introducing the Q-function, the optimal output regulation problem is converted to finding the optimal Q-function. Therefore, the MsQL algorithm is proposed and its convergence theory is established by showing that it generates a nonincreasing Q-function sequence that converges to the optimal Q-function. In the MsQL, the step-size of multistep policy evaluation can be different at each iteration and an adaptive tuning rule is proposed. The MsQL learns the optimal Q-function by using real system data rather than using a system model. Finally, the developed MsQL method is employed to solve the optimal output regulation problem of the model-free 2-DOF helicopter, and its effectiveness is verified. [ABSTRACT FROM PUBLISHER]

This paper proposes a new method for fast radial vibration computation in switched reluctance motors. Only a piecewise first-order linear function is used to calculate the total peak acceleration, which is rather fast. The overall radial vibration is the superposition of natural oscillation of each mode. Before that, several critical parameters need to be calculated or measured in advance, including weight factor, natural frequency and damping ratio of each mode, in order to obtain the respective analytical expression of natural oscillation of each mode. First, the total peak acceleration concerning the multiple of current and its slope is derived analytically from the perspective of abrupt change of radial force. Then, a simple method for calculating weight factors is presented for the distribution of peak acceleration of each mode from the total peak acceleration. Natural frequencies are measured and compared by three methods, including finite-element analysis, hammer impulse test, and dc pulse excitation. The calculation of damping ratio is improved since the traditional damping ratio calculation method cannot be used in a multiple degree-of-freedom system. Finally, both simulation and experiments are conducted to verify the effectiveness and accuracy of the proposed method. [ABSTRACT FROM PUBLISHER]

In this paper, two switched-capacitor quasi-switched boost inverters (qSBIs) are proposed. By adding one capacitor and one diode to the qSBIs, the proposed inverters achieve high voltage gain with low voltage stress on active switches, capacitors, and diodes. The proposed inverters can extend to n-cell for voltage gain improvement. The operating principle, steady-state analysis, and impedance parameter selections of the proposed inverter are presented. A full comparison between the proposed inverter and other impedance-source inverters is addressed. A 500-W prototype is built to verify the operating theory of the proposed inverter in both the standalone mode and the grid-connected mode. Simulation and experimental results validate the theoretical analysis. [ABSTRACT FROM PUBLISHER]

Since the hot metal silicon content simultaneously reflects the product quality and the thermal state of the blast furnace, its modeling is crucial and representative. In order to facilitate the realization of control, this paper proposes a Bayesian block structure sparse based Takagi–Sugeno (T–S) fuzzy modeling method, with which the main important fuzzy rules and the corresponding pivotal consequent parameters can be selected automatically to obtain a compact fuzzy model with good generalization performance. For being conjugate to the Gaussian likelihood that would lead to the associated Bayesian inference to be performed in closed form, a hierarchy of block structure sparse priori is adopted, and the variational Bayesian inference is used to solve it. The screening of model inputs and data processing appropriately consider the characteristics of the blast furnace process. The applicability and performance of the proposed method are demonstrated on no. 2 blast furnace of Liuzhou Steel in China. [ABSTRACT FROM PUBLISHER]

This paper proposes a multiloop framework for current control of grid-connected voltage source inverters (VSIs) with LCL output filter. The discrete-time model is of third-order with a nonminimum phase zero when controlling the grid side current. This poses some difficulties on the design of most types of controllers. Motivated by this problem, the inner loop is implemented by a discrete-time sliding mode control law to ensure the tracking of the converter side current. This can be achieved regardless the grid impedance and voltage, making the converter to behave like a current source inverter with a capacitive+inductive (CL) filter. Thus, the problem of current control falls from a third-order system to a second-order system. Several types of controllers can be designed to implement the outer loop based on the equivalent CL circuit. In this work, a resonant controller with a virtual resistor was applied. Simulations and experimental results are presented to validate the proposal. [ABSTRACT FROM PUBLISHER]