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Magnetically controlled reactors (MCRs) provide a flexible way of regulating reactive power. However, the stability of the MCR for reactive power compensation has not been researched deeply due to switching nonlinearity and ferromagnetic nonlinearity that are inherent in MCR. In this paper, a small-signal model of the MCR for reactive power compensation is established by means of a piecewise linearization method. Based on the derived small-signal model, the stability boundaries of some key parameters are analyzed. It is found that the most possibly unstable operating point corresponds to a specific saturation degree when the compensating reactive power changes. The analysis results in this paper will play an important role in designing MCR for reactive power compensation. Finally, simulations and experiments are performed to validate the stability analysis results.

Tunnels cause many traffic accidents in China every year, which is related to the inappropriate driving behaviors combined with less visual comfortability when driving across tunnels. The most common phenomenon when driving across the inlet and outlet sections of a tunnel is the abruptly varying visual brightness, causing a short-term blindness for a driver, known as the “ black hole ” and “ white hole ” effects, respectively. In this paper, we propose a tunnel brightness compensation model with spatial–temporal visual-content preservation. The highlights of this paper are twofold. 1) We analyze the visual brightness variation by introducing spatio-temporal orientation energy for a stable characterization of the visual comfortability of drivers in view of the distinguishable visual content caused by a sequential brightness variation. 2) We construct a tunnel brightness compensation model that preserves the spatial–temporal visual content by visual-content matching with multiple frames. Our method can manifestly improve the brightness quality and maintain the scene content simultaneously. Extensive visual brightness compensation experiments on 60 visual clips of inlet and outlet sections of tunnels demonstrate that the proposed method generates a state-of-the-art performance.

This paper studies the synchronization problem for linear complex dynamical networks (CDNs) on time scales. An intermittent dynamic time-interval pinning control strategy is designed to achieve synchronization for CDNs with the isolated node. Based on the Lyapunov approach and the theory of time scales, synchronization criteria are established for CDNs on general time scales. The main results in the paper show that, by controlling a proportion of the network nodes, the exponential synchronization can be achieved. Moreover, the infinitely fast switching of the pinning node set is avoided by means of the event-triggered strategy. According to our selection algorithm, the number of pinning nodes will be updated online at each pinning time. The modeling framework investigated in this paper is a unification and generalization of many existing continuous-time and discrete-time complex network models. Three numerical examples are given to illustrate the effectiveness and priority of the obtained results. Finally, the analytical results are applied to the distributed auxiliary control of microgrids and formation control of spacecraft.

The paper presents the application of delta-connected cascaded H-bridge multilevel static var generator (SVG) under unbalanced compensation currents or unbalanced supply voltages. Clustered balancing control for delta-connected SVG can be realized by injecting a zero-sequence current to the delta loop. But zero-sequence current injection may cause the high peak phase current which may break converter switches. The aim of this paper is to analyze the key factors that affect the maximum output current of the SVG with injecting zero-sequence current and acquire the quantitative relationship among unbalance compensation capability, the unbalance degree of the supply voltage, the initial phase of negative-sequence voltage, the unbalance degree of the compensation current, and the initial phase of negative-sequence current. On this foundation, the valid compensation range of delta-connected SVG under unbalanced conditions is obtained. Furthermore, the compensation characteristic of the negative-sequence current is deduced with the certain supply voltage, and the influence of supply voltage variation on the maximum output current for SVG is also considered with the certain compensation current. Finally, the correctness of the relevant theoretical analysis is verified by simulation and experiment.

Virtual space vector pulsewidth modulation (VSVPWM) for the neutral-point (NP)-clamped three-level inverter is briefly reviewed in this paper, as well as its carrier-based realization. The carrier-based VSVPWM (CB_VSVPWM) is featured with dual modulation waves and a single carrier. Although CB_VSVPWM can make NP voltage unfluctuating in theory, it does not have the NP voltage recovery ability. In practice, due to the effect of nonidea factor effects, NP voltage may shift. Thus, active NP voltage control (ANPVC) is necessary. To achieve that, three ANPVC approaches are proposed based on CB_VSVPWM in this paper. The NP voltage control ability of CB_VSVPWM with ANPVC is analyzed. Finally, comprehensive experiments are carried out to verify the feasibility of the proposed method.

Power hardware-in-the-loop (PHIL) is an attractive, real-time system testing and validation technique. Virtual models can be replaced with physical equipment to emulate system integration testing, and perform model validation without the cost and risk of a full scale power system. Power amplifiers are the principal components that facilitate the power interface between the physical and the virtual systems. This necessary interfacing introduces dynamics that do not exist in the real system and is the source of stability and accuracy issues affecting PHIL applications. This paper presents a stability analysis of a practical PHIL system based on the ideal transformer model interface algorithm that utilizes a voltage source converter for power amplification. A systematic approach to evaluate the expected stability characteristics of PHIL experiments is developed. The analysis in this paper shows that in a practical system, the power amplifier's filter, sampling, and measurement filtering are all shown to influence the stability in a counterintuitive way, leading to a nonmonotonic stability characteristic. An experimental PHIL platform based on a real-time digital simulator real-time computer has been used to validate the analysis and confirm the effects of the practical interface. Switching dead-time is also shown to have a significant stabilizing effect.

This paper proposes a novel active partial switching method for a boost power factor correction (PFC) converter, based on the predictive current mode control to achieve both current shaping capability and high power conversion efficiency. This method consists of a controller that maintains a switching stop angle near the peak voltage of the input voltage by means of output voltage control, and an adaptive current shaper that adjusts the switching stop period near the zero voltage of the input voltage based upon the load condition. The proposed method shows good PFC performance and high efficiency even under various disturbances such as input voltage and load fluctuations. Moreover, it has the advantage that it is possible to achieve high efficiency even under conditions of output voltage exceeding the peak value of the input voltage. For sequential explanation, this paper illustrates the design of the controller based on the frequency-domain response and provides theoretical analysis of the proposed method. Finally, to verify the effectiveness of the proposed method, experimental results are presented based upon a 2.4 kW boost PFC converter prototype.

In this paper, a high step-up coupled-inductor cascade boost dc–dc converter with lossless passive snubber is proposed. Although a conventional cascade boost converter has larger voltage gain compared to a boost converter, it is still not suitable for high step-up voltage conversion. In the proposed converter, a coupled inductor is adopted for the cascaded boost converter to further increase the voltage gain. However, a leakage inductance of the coupled inductor causes a high voltage spike at a main switch. A resistor–capacitor–diode snubber is commonly used to simply solve this problem, but it is also the cause of additional power loss. Therefore, the lossless passive snubber is suggested in this paper in order to prevent efficiency drop by a snubber circuit. In conclusion, the proposed converter has high voltage gain and improved power efficiency. Experimental results from an output 400-V 200-W prototype at a constant switching frequency of 50 kHz are presented to verify the performance of the proposed converter.

Disruptive innovations in electrical machine design optimization are observed in this paper, motivated by emerging trends. Improvements in mathematics and computer science enable more detailed optimization scenarios that cover evermore aspects of physics. In the past, electrical machine design was equivalent to investigating the electromagnetic performance. Nowadays, thermal, rotor dynamics, power electronics, and control aspects are included. The material and engineering science have introduced new dimensions on the optimization process and impact of manufacturing, and unavoidable tolerances should be considered. Consequently, multifaceted scenarios are analyzed and improvements in numerous fields take effect. This paper is a reference for both academics and practicing engineers regarding recent developments and future trends. It comprises the definition of optimization scenarios regarding geometry specification and goal setting. Moreover, a materials-based perspective and techniques for solving optimization problems are included. Finally, a collection of examples from the literature is presented and two particular scenarios are illustrated in detail.

In this paper, a robust energy management system is proposed for islanded microgrids, which at the same time considers static modeling of system frequency. The aim of this paper is to manage frequency excursions produced from load and renewable generation fluctuations. In microgrids, the use of inertialess and small-scale energy resources risks the frequency stability. In order to overcome this problem, first, the frequency-dependent behavior of the distributed energy resources is formulated precisely within the centralized hierarchical energy and reserve management context of a microgrid. Then, in order to handle microgrid uncertainties in a robust way, information gap decision theory (IGDT) technique is proposed. Furthermore, to address a robust hierarchical energy and frequency reserve management architecture, the problem is transmitted into a single-level mixed integer linear programming model and solved appropriately over a 24-h scheduling time horizon. Numerical simulation results obtained on a typical islanded smart microgrid are presented, including the demand response mechanism. The IGDT can help microgrid central controller (MGCC) to make operational decisions in front of major uncertainties. The obtained results verify that through the proposed IGDT-based energy management system, the MGCC can effectively stabilize the microgrid frequency along with its economic targets while considering severe uncertainties.

This paper proposes a new family of electric motors based on the concept of an airgapless device. In this type of device, the rotor is allowed to touch the stator at a contact point, which maximizes the internal flux and, therefore, the electromagnetic torque. A higher torque density motor is proposed in this paper due to a reduced reluctance caused by zero airgap situation. A comparison with other high-torque-density electric motors demonstrates the advantages of the proposed airgapless motors. The proposed motor will maximize the generated torque, allowing these types of motors to be competitive in applications where hydraulic motors are prevalent, i.e., low-speed and high-torque requirements. Hydraulic motor systems face two major problems with their braking system and with low efficiency due to a large number of energy conversion stages (i.e., a motor pump, hydraulic connections, and the hydraulic motor itself). The proposed electric motor, unlike hydraulic motors, converts electrical energy directly to mechanical energy with no extra braking system necessary and with higher efficiency. The modeling of this machine with a minimum number of poles is discussed before a generalization is presented. A proof-of-concept electric motor with nine magnetic bipoles is built to validate the theoretical assumptions proposed in this paper.

This paper presents a novel control strategy for nonlinear uncertain vehicle active suspension systems without using any function approximators [e.g., neural networks (NNs) or fuzzy logic systems (FLSs)]. Unlike previous results that neglect the effect of actuator dynamics, this paper incorporates the dynamics of a hydraulic actuator that is used to create the required active suspension forces into the controller design. To address the nonlinearities of this hydraulic system, an approximation-free control method is introduced. In this method, the widely used NNs and FLSs are not needed. This leads to reduced computational burden and complexity, and thus, it is more suited for practical applications. Moreover, by introducing a prescribed performance function and the associated error transform, the proposed controller can guarantee both the transient and steady-state suspension responses. The stability of the closed-loop system and the suspension performance requirements are rigorously proved. Finally, comparative simulations are conducted to validate the improved performance and robustness of the proposed method.

This paper presents the five degree-of-freedom (5-DOF) control of an electrodynamic MAGLEV suspension with active control of the levitation coils. A sled with built-in permanent magnets moves past an array of fixed coils to generate Lorentz forces that provide lift and guidance. When active control of the levitation coil currents is implemented, multi-DOF trajectory control can be achieved, leading to stable electrodynamic levitation that can actively reject disturbances independently of sled speed. This paper shows successful control of the multi-DOF trajectory of a passive sled by active control of the coil currents, using both a sliding mode controller with nonlinear input mapping from coil currents to levitation forces, and a multi-DOF nonlinear observer. The paper also compares the use of look up tables versus analytical models of the magnetic field density used to estimate the magnetic forces and torques acting on the sled. The performance of the proposed approaches is demonstrated experimentally.

The asymmetrical six-phase induction machine represents the most common multiphase machine type used in many high-power industrial applications. While a body of research covering control of the machine under fault conditions has been published in the literature, corresponding studies to investigate the dc-link voltage design requirements under postfault operation in a simple and efficient manner have not met the same interest. To this end, this paper first introduces the machine steady-state equivalent circuit under one open-phase fault, which simplifies the estimation of different machine characteristic curves instead of using tedious mathematical techniques. As far as the machine parameters are concerned in this paper, a modified locked-rotor test based on the derived equivalent circuit is also proposed to fully estimate the parameters of different subspaces using a simple technique without the need for additional tests. The proposed steady-state circuit is also used to understand the effect of the secondary subspace impedance, neutral configuration, and the postfault control strategy on the maximum achievable torque for a limited dc-bus voltage. The minimum dc-link voltage magnitude to provide rated output under postfault operation is also given. The proposed concepts have been experimentally verified using a prototype asymmetrical six-phase machine. Scopus

This paper employs the recently developed nonlinear control tools to solve the engineering problem of stable current control of fused magnesium furnaces (FMFs). By fully taking into account the nonlinearity, uncertainty, and couplings in FMFs, this paper first develops a dynamic model for controller design. A mild assumption for controller design is verified by using experimental data. Based on the dynamic model, this paper proposes a class of stable control rules for the disturbance-free model. Then, the result is extended to handle both measurement errors and external disturbances. With the proposed control algorithm, it is proved that the closed-loop system is robustly stable, and the three-phase currents ultimately converge to neighborhoods of the setpoints. If the system is disturbance-free, then asymptotic stability can be guaranteed. It is shown that the proposed control algorithm can be readily implemented as rule-based control. The notion of input-to-state stability and the nonlinear small-gain theorem are employed as tools for the designs. An industrial application is demonstrated to show the validity of the proposed design in solving practical engineering problems.

This paper proposes a novel algorithm of predictive torque control (PTC) for induction motor based on discrete space vector modulation (DSVM). DSVM technique increases the number of voltage vectors, which must be evaluated in the PTC method. This new technique is called PTC-DSVM, which presents a low sampling frequency. However, the high number of virtual vectors increases computational burden significantly. To overcome this problem, in this paper, a novel algorithm that reduces the number of admissible voltage vectors, based on the well-known direct torque control switching table, is presented. Both simulation and experimental results demonstrate that proposed PTC-DSVM has the same behavior as conventional PTC at the same switching frequency while the sampling frequency is three times lower. The low sampling frequency of the proposed algorithm makes it suitable for industries to use low-cost hardware or perform a high computational analysis.

Traditionally, the vector operation technique has been used to control three-phase converters using one cycle control. In this paper, a three-phase active power filter large-signal model with vector operation technique in a new coordinate system is presented. By using the vector operation technique, only two phase-legs are switching at high frequency, thus reducing the switching losses. This paper not only covers the literature gap about the modeling of three-phase converters using vector operation, but also presents a sliding mode control for this converter. The con- trol scheme consists of a nonlinear matrix transformation in order to obtain the voltages and currents in a new two- dimensional frame, ¿¿-frame, a sliding mode controller de- signed in these coordinates, and a modulator to obtain the control signals in natural frame. The sliding mode control is designed with the help of the presented large signal model assuring sinusoidal grid currents in phase with the grid voltages. This controller, provides a fast transient response against sudden load changes with a good current tracking capability and a reduction of the switching losses. A stability analysis is performed in order to validate the control parameters. Experimental results are provided using a fully-digital control system in order to validate the performances of the proposed controller.

This paper aims to solve a closed-loop identification problem for the space-periodic force ripple in permanent-magnet linear synchronous motor (PMLSM) systems. Conventional identification schemes use the overall error signal to update estimates. However, the error caused by mechanical vibration and measurement noise could affect and even deteriorate the identification performance. In this paper, a novel iterative learning identification method that utilizes the partial but most pertinent information in the error signal is proposed to identify the force ripple. First, the effective error signal caused by the reference trajectory and the force ripple are extracted by projecting the overall error signal to a subspace. The subspace is spanned by some basis functions selected on the basis of the physical model of the PMLSM and the sinusoidal model of the force ripple. The time delay of the PMLSM system is compensated in these basis functions. Then, a norm-optimal approach is proposed to design the learning gain. The monotonic convergence of the iterative learning identification is further analyzed. Numerical simulation and experiments are provided to validate the proposed method and confirm its feasibility and effectiveness in force ripple identification, as well as its compensation.

Permanent magnet motors and induction motors are used in many electric vehicles (EVs) and synchronous reluctance motors have been used in some experimental EVs. However, none of them meet all the objectives of high efficiency, high power density, and low cost. In this paper, a dual-rotor motor (DRM) is proposed with potential application in EVs. The proposed motor is a proof of concept and is unique because it uses a synchronous and an asynchronous rotor. A conceptual analysis and mechanical configuration of this motor are presented in this paper, and the experimental demonstration of its working principle is also presented. The preliminary results, presented in this paper, show that a DRM with two different rotor types (synchronous and asynchronous) is feasible, and this opens a new direction in R&D of such motors.

This paper presents a uniform control strategy for the bidirectional ac/dc interlinking converter (BIC) in hierarchical controlled hybrid microgrid. The uniform control strategy unifies different control structures for multifunctional BIC in terms of power management, ac and dc voltage support. With the unified control structure, various triggering mechanisms for BIC mode-switch are not compulsory in response to the relevant scenario changes in the power network. Therefore, the negative consequences, such as unsmooth transition and system collapse due to the inaccurate or slower mode switch, can be avoided. Moreover, the uniform control strategy is also applicable for the hierarchical controlled hybrid microgrid, whose control architecture is typically comprised of the centralized and decentralized levels. This enables the communication fault ride-through capability and the impact from the communication failures can thus be mitigated. To sum up the above two features, the proposed control strategy is able to provide a smooth operation for the BIC without control mode switch in the event of unintentional scenario changes in power or communication network. To verify the validity of the proposed uniform control strategy, the controller hardware-in-the-loop experimental results have been provided in this paper. NRF (Natl Research Foundation, S’pore)

Aiming at effective power management in microgrids with high penetration of renewable energy sources (RESs), this paper proposes a simple power control for the so-called second-generation, single-phase electric springs (ES-2), which overcomes the shortcomings of the existing ES control methods. By the proposed control, the unpredictable power generated from RESs is divided into two parts, i.e., the one absorbed by the ES-2 that still varies and the other injected into the grid that is controllable by a simple and accurate signal manipulation that works both at steady-state and during RES transients. It is believed that such a control is suitable for the distributed power generation, especially at domestic homes. In this paper, the proposed control is supported by a theoretical background. Its effectiveness is at first validated by simulations and then by experiments. To this purpose, a typical RES application is considered, and an experimental setup is arranged, built up around an ES-2 implementing the proposed control. Testing of the setup is carried out in three steps and proves not only the smooth operation of the ES-2 itself, but also its capability in running the application properly.

This paper proposes a novel control method for an asymmetrical-cascaded-multilevel-converter-based hybrid energy storage system (HESS), which includes one battery and several electrical double-layer capacitors (EDLCs). Traditionally, it is challenging to control the power distribution between different cascaded H-bridges by using different energy storage components as dc sources. In this paper, a feedforward space-vector-modulation (FFSVM) technique is used to distribute the active power between the battery and EDLCs. With the proposed voltage feedforward mechanism, the HESS can flexibly operate in the normal operation mode, the high-power output mode, and the reverse power absorption mode. The principle and effectiveness of the improved FFSVM technique are analyzed. Meanwhile, the state-of-charge-balancing mechanisms are introduced. The simulation results obtained in MATLAB/Simulink as well as the experimental results of a hybrid energy storage test bed based on the proposed system are presented to verify its performance.

Essential imbalance and fluctuation of the mobile train load draw some problems, e.g., three-phase unbalance, reactive power, voltage and load fluctuation, harmonics, etc. in both public and train supply networks (TSNs). Railway power flow controller (RPFC)'s good performance on dealing with those problems has been convinced in practice these years. However, as the primary task in commercialization, how to qualitatively determine RPFC's design capacity with high cost efficiency and how to comprehensively assess its performance in the design stage have perplexed engineers for many years. To solve those problems in both planning and real-time executing processes, this paper focuses on an RPFC design capacity optimization strategy for grid-connection compatibility and operating performance improvement in terms of both the utility and the TSN. The strategy not only makes a railway substation satisfy the grid-connection standards with high calculating efficiency, but also renders the RPFC to have the minimum design capacity, the excellent feeder voltage control ability, the good fixed capacitor installing prospect, and the high operating efficiency on the targets of reducing the investment and enhancing the transportation ability. The generic models, the industry-oriented design and the quantitative analysis, discussed in this paper give an insight for those concerned based on a balance transformer. Future RPFC projects on serviced railway power systems will benefit from the proposed methodology.

In this paper, the model predictive current control is introduced in the semicontrolled open-winding permanent magnet synchronous motor (OW-PMSM) generation system with a common dc bus to suppress the zero-sequence current for the first time. Particularly, the basic voltage vectors of the semicontrolled OW-PMSM, which are synthesized by the three-phase full-controlled converter and the three-phase uncontrollable diode bridge, is analyzed and their influences on the zero-sequence current are investigated for the first time in this paper. Then the current-error-based cost function that includes dq -axis current error and zero-sequence current error is designed to evaluate all the voltage vectors. Moreover, to further improve the steady-state control performance of the whole generation system, a zero-sequence current suppression method based on the uncontrollable side voltage vector adjustment, which has the advantage of low computation burden, is developed. In this method, two voltage vectors of the controllable converter are applied during one control period. Based on the distribution character of the basic voltage vector in the semicontrollable OW-PMSM generation system, the first voltage vector is selected according to the three-phase current direction to adjust equivalent vector of the uncontrollable diode bridge, whereas for the second voltage vector, the selection method based deadbeat voltage vector sector is designed to reduce the range of the candidate voltage vector. In addition, the vector durations are also computed. Finally, simulation and experiment are carried out to validate the proposed control approaches.

This paper presents an improved saliency-based position sensorless drive of an interior permanent-magnet synchronous machine (IPMSM) with a single current sensor, used for low cost applications. The phase current, reconstructed from a dc-link current, shows a reconstruction error resulted from the difference of the sampling point from that of a full current sensor drive. This reconstruction error results in degradation of the overall sensorless control performance. In this paper, we analyze the impact of the reconstruction error depending on the injection frequency for a high frequency voltage signal injection sensorless control. Based on this analysis, we propose an improved position sensorless drive that employs a new current reconstruction method. In order to minimize the reconstruction error, the proposed current reconstruction method predicts the dq -axis currents with the same sampling point as a full current sensor drive. Several experimental results are provided to verify the analysis of the reconstruction error and the proposed method's improved sensorless control performances.

Tap changers are commonly used to maintain the limits in medium-voltage lines. Initially based on electromechanical switches, efforts have been made since the 1990's to reduce maintenance expenses with thyristor-based versions. Among the methods to limit the short-circuiting current in commutating taps, the multiwinding coil has demonstrated, during decades of use in the low-voltage field, to be reliable and cheap. Two previous papers showed that multiwinding changers can be applied to medium-voltage lines up to 34.5 kV, 15 MVA with no parallel or series thyristor association. This paper proposes a new topology, based on a double array of tap switches per phase, allowing for step-up the power from 15 to 36 MVA and insertion in any point of the line with no connection to the head transformer. A comparative cost analysis gives technical and economical results for a typical 10 MVA, 34.5 kV stabilizer demonstrating the advantages of the proposed circuit over the electronic single array topology and the classic mechanical solutions.

An electrical signature analysis (ESA)-based method to detect bearing defects in electromechanical drivetrains (e.g., wind turbines) is proposed in this paper. The novelty of the proposed technique is justified by its capability to detect a defect that occurs in a drivetrain bearing, external to the machine. Unlike the traditional vibration-based method, the electrical measurements of the terminal machine are utilized in this case to perform the fault detection. The proposed ESA-based method is developed utilizing a new electrical signal model of bearing defect, proposed in this paper, based on the excitation of torsional resonances. The proposed ESA-based method and the signal model are validated through experimental tests. The proposed technique demonstrates excellent fault detection capability even at low operating speed, which is advantageous over the traditional vibration-based method in terms of sensor cost, installation complexity, and detection reliability.

This paper develops a novel voltage equalizer by combining wireless power transfer (WPT) and a voltage multiplier (VM) for series-connected energy storage cells. The physical isolation achieved by WPT can offer several unique benefits that traditional equalizers can hardly provide. In this paper, the characteristics of a multiple-output VM are analytically discussed and used to develop an equivalent one-output VM model. Based on this model, parameters of the WPT system are properly designed. The proposed design methodology can achieve a single-switch voltage equalizer without feedback control, which dramatically decreases the circuit complexity and cost. Moreover, this methodology can naturally ensure a robust system under small coil misalignment. In the experiment, the proposed system is built to balance four series-connected ultracapacitor modules. The system efficiency is 72.8% at a load power level of 10 W.

This paper proposes a magnet-frozen-permea-bility finite-element method and an experimental approach for inductance analysis of a variable-flux permanent magnet machine. The machine studied uses Alnico magnets, whose nonlinear magnetic properties deteriorate the inductance calculation accuracy. Besides the machine core permeability is frozen, the magnet-frozen-permeability approach freezes nonlinear B–H curves and nonlinear permeabilities of the magnets in the finite-element analysis. Because the soft magnets have low coercive force, conventional symmetric inductance measurement currents may demagnetize them. This paper presents a zero-start dc-biased current trajectory tracking approach. This approach uses positive current, which avoids demagnetization during the inductance measurement. Meanwhile, based on flux linkage-current curves, influences of resistance can be eliminated. Cross-magnetization effects are evaluated in the two proposed methods. Inductances of these two methods are compared and show good agreements.

This paper analyzes the combination in a cascaded H-bridge multilevel inverter (CHBI) based on transformers with the different turn ratios for increasing the voltage level and proposes the switching method for achieving the output voltage distribution among H-bridge cells (HBCs). The transformers used in this paper are connected to the output of the respective HBCs, and the secondary sides of all the transformers are connected in series for generating the final output voltage. Only one of the transformers, in particular, has a different turn ratio for increasing the output voltage level. In this paper, the possible turn ratio of the special transformer with a different turn ratio is discussed in detail, and a switching method based on the level-shifted switching method for the topology used in this paper is proposed. To verify the effectiveness of the proposed method, a three-phase 21-level CHBI is experimentally tested.

High-frequency components of acoustic noise radiated by the electric powertrain make the subjective perception of electric vehicles worse than expected under certain operating conditions. In order to investigate the influence of acoustic components on sound quality, a pulse width modulation (PWM)-fed electric powertrain is studied in this paper. First, the acoustic noise of the electric powertrain is collected in a semianechoic chamber. Then, two types of acoustic components of the electric powertrain, namely harmonic order noise and switching noise, are distinguished through the analyses of supplied current from the inverter and gear vibration. Furthermore, the relationship between subjective perception and spectral characteristics of the noise is discussed, based on which sensitivity is established. Subsequently, the contributions of acoustic components to psychoacoustical parameters are determined. After that, a sound quality model of the acoustic noise radiated by the electric powertrain is established. The comparison between jury test and prediction shows that the established model can be used for sound quality evaluation of the electric powertrain. Finally, the influences of harmonic order noise and switching noise on subjective perception are discussed. The main original contribution of this paper concerns the influences of harmonic order noise and switching noise radiated by PWM-fed electric powertrain on sound quality.

In this paper, two structures are proposed for the switched-inductor quasi-Z-source inverter. In the proposed structures to extend the voltage gain of inverter, two new switched-inductor structures are used. In the proposed structures, voltage across the capacitors in the Z-source network and in the switched-inductor is symmetric and small. The other advantage of proposed inverters is known as achieving higher voltage gain per smaller duty cycle ratio (of shoot-through). Compared with a conventional continuous input current switched-inductor quasi-Z-source inverter at the same gain voltage, there is less of a ripple of input current in the proposed inverters. In this paper, at first the both the conventional and the proposed switched-inductor Z-source inventers are thoroughly investigated to find out their governing relations. Then, the proposed Z-source inverters are compared with the conventional ones by simulating them to assess their performance efficiency. Next, applying the simple boost pulse width modulation the simulation is carried out with PSCAD/EMTDC software. After that, to evaluate the obtained results, the prototypes of the proposed inverters with 48 Vdc input voltage are used.

Microinverters require high voltage gain capability for interfacing the low dc voltage output of photovoltaic (PV) module to single-phase ac grid. A two-stage nonisolated inverter is proposed in this paper, with a first boost stage and a second traditional pulse width modulated grid-tied inverter stage. The proposed boost stage consists of a coupled inductor added with a voltage multiplier to achieve the required high voltage gain at high efficiency and to operate over a wide input voltage range. Among the coupled inductor topologies, adding a clamp circuit is a common solution to limit the voltage spike caused by leakage inductance. In the proposed converter, the resonance between the coupled inductor and voltage multiplier is used to address the issue of voltage spike, thereby reducing both component count and device voltage stress. Detailed analysis and design procedure of the proposed converter is presented in this paper. Experimental results of a 250-W microinverter are presented to validate the proposed converter.

A comprehensive analysis for a family of two-level pulsewidth modulation plus phase-shift (PPS)-modulated-isolated-bidirectional dc–dc converters is presented in this paper. Compared with the traditional phase-shift control, the PPS control features reduced current stresses, reduced conduction losses, guaranteed zero-voltage switching (ZVS) operation, and wide conversion-ratio variation range. In this paper, all eight operation modes are revealed, and then the unified solution of the power transmission capability for each mode is proposed, applicable for any two-level PPS converters. Based on the unified solution, component stresses and ZVS operation are analyzed to assist component selection. Most importantly, the control maps for three different combinations of the two-level PPS converters are proposed, to assist converter operation and design in the low-circulating-current region. In the control map, a circuit parameter k is proposed and its upper limit is found, providing a design limit to select switching frequency, leakage inductance, turns ratio, and power level. A 29–67 V/380 V prototype—the combination of group C plus group A—rated at 100–1000 W was built. The analysis is verified by both simulation and experimental results.

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.

Due to the strong gyroscopic effects, the stable control for the nutation vibration of high-speed rotors is an important concern in magnetically suspended control moment gyros (MSCMGs). This paper addresses the two key challenges on the nutation mode control of AMB-rotor systems: using the complex coefficient representation method to obtain the accuracy nutation frequency, and proposing an adaptive tracking approach to ensure stable operations over the entire speed ranges. In order to improve the phase margin of the nutation mode, this paper proposes a nutation mode tracking compensation method based on the cross-feedback-control scheme. First, the analytical calculation for the nutation frequency of the high-speed rotor under the closed-loop condition is carried out. Then, the compensation control method using an adaptive tracking filter in the nutation control path is proposed to provide an adequate damping for the nutation mode. Simulation results show that the nutation mode tracking compensation provides a greater phase lead for the nutation mode compared to the conventional nutation mode filtering approach. Finally, the experimental results on a developed double-gimbal MSCMG prototype validate the effectiveness of the proposed method.

A new isolated single-stage soft-switching power-factor-correction (S4 PFC) driver for supplying light-emitting diodes (LEDs) is introduced in this paper. In the proposed LED driver, the switches voltage stress and also the dc-bus voltage is limited to the peak of the line voltage. Hence, low voltage rated mosfet s and diodes can be used. The efficiency is improved because the switches are turned on under zero current switching (ZCS) condition and turned off under zero voltage zero current switching (ZVZCS) condition. Also, no current feedback is required since the converter provides an output current independent of output voltage. In this paper, operating principle of the proposed LED driver is presented and design considerations are discussed. To verify the theoretical analysis, a laboratory prototype of the proposed converter for supplying a 50 W/70 V LED module from 220 Vrms/50 Hz ac mains is implemented, and the experimental results are presented. Since current feedback is not used, dimming property and operation for universal voltage range is not achievable.

In this paper, a complete mathematical model for a half-tracked vehicle with eight degrees of freedom is established. It is difficult to control a suspension system owing to complexity of system itself and irregular excitations from road surfaces. A road excitation model is analyzed in which a relationship between the vehicle body and the gun is taken into account. Active disturbance rejection controllers are proposed in all channels of six independent subsystems by decoupling the original system. With switch extended state observers, total disturbances are eliminated for the half-tracked vehicle. Simulation results are presented to illustrate effectiveness of the proposed method in this paper.

Conventional permanent magnet (PM) machine open-phase fault detection relies on the estimation of current harmonics using available phase current sensors. Because the magnitudes of current harmonic are proportional to the machine load condition, it is still a challenge to detect a phase fault at light load when fault-induced current harmonics are too small to estimate. This paper investigates the phase fault detection specifically for the conditions under low fault harmonic magnitudes. Both fault-induced harmonics in dq currents and neutral point (NP) voltage are analyzed to find a suited signal for the fault detection. By adding a voltage sensor to measure the NP voltage in a PM machine, a better fault detection performance is achieved because the fault harmonic in NP voltage results in the reduced effect on torque loads and sensor measurement errors. A 50-W PM machine is tested to verify the phase fault detection performance under low fault harmonic magnitudes. This paper includes the experimental evaluation on the detection limitation in terms of load capability using current and voltage fault signals.

This paper presents a new multilevel converter topology based on a variable or multilevel dc-link stage. This stage is shared by all inverter output phases, thus increasing the number of output voltage levels while reducing the overall number of active devices compared to traditional topologies; therefore, it is called a reduced multilevel converter (RMC). The converter is not capable of reducing the blocking voltage of the devices; hence, unlike other multilevel converters aimed at medium-voltage applications, this converter is interesting for low-voltage- and high-power-quality-demanding applications such as photovoltaic inverters, wind energy conversion systems, and uninterruptible power supplies. The main novelty behind the proposed concept is the basic dc cell used to generate the variable dc-link voltage, which includes a controlled path through the floating capacitors to provide the necessary degree of control to enable a shared multilevel dc link for all the output phases of the converter. The dc cells are connected in a multicell structure to increase the number of levels of the converter. A five-level version of the RMC topology is briefly compared to other five-level converters such as the five-level active neutral-point-clamped converter and the five-level flying capacitor converter. This paper presents the structure of the new topology with its operating principle, switching states, main characteristics, and experimental validation using finite-control-set model-predictive control.

Commutation error degrades the operating performance of a high-speed permanent magnet brushless dc motor (BLDC) sensorless drive significantly. It is caused by different kinds of nonideal factors such as low-pass filters (LPFs), digital control delay, and other units in a control loop. This paper analyzes the commutation error caused by different kinds of nonideal factors and points out that the total commutation error is substantially equivalent to the error of an internal power factor (IPF) angle of the BLDC motor. The purpose of the commutation correction in this paper is to regulate the IPF angle to zero. A novel phase-lock loop (PLL)-based commutation correction strategy is proposed and designed in detail in this paper. The proposed PLL consists of a novel PM flux linkage based phase discriminator to detect the IPF angle, an LPF, and an autophase regulator (APR). The function of the proposed PLL is to lock the IPF angle to a reference value. Compared to the conventional scheme, the greatest advantage of the proposed scheme is that the proposed PLL is robust to any kind of phase delay caused by nonideal factors in the control loop, and it is quite important for a high-speed motor drive. Both simulation and experimental results verify the effectiveness and superiority of the proposed correction strategy.

To improve light load efficiency, a three-phase photovoltaic (PV)-based microinverter may operate in single-phase, two-phase or three-phase mode depending on the available input power. Therefore, its dc-link capacitor may be subjected to large peak-to-peak voltage ripple when operating in phase skipping mode. This paper determines the minimum value of the dc-link capacitor by allowing the maximum acceptable voltage ripple on the dc link. This allows for the use of film capacitors instead of electrolytic capacitors in order to improve the microinverter reliability. Unfortunately, higher dc-link voltage ripple introduces harmonic distortion on the inverter output current waveform if it is not compensated for by the dc-link voltage controller. This paper proposes a simple synchronous control method to regulate the dc-link voltage with the presence of large voltage ripple. The dc-link voltage controller is synchronized with the phase-locked loop and samples the average value of dc-link voltage without introducing unwanted harmonics into the voltage sense path. Experimental results were obtained from a 300-W three-phase half-bridge microinverter prototype to verify the proposed dc-link voltage control performance. Inverter output current total harmonic distortion of 1.6% was achieved even though the dc-link peak-to-peak voltage ripple reached as high as 87 V with 219-V split dc-link voltage. Dynamic response is fast enough to easily track the most extreme ramp change in input PV power.

In applications that demand single-input dual-output (SIDO) or dual-input single-output (DISO) dc–dc converters, employing two separate single-input single-output (SISO) converters is a solution. However, the number of components is doubled, resulting in high overall cost. In order to reduce costs, this paper proposes a novel topology synthesis methodology, with which a variety of SIDO and DISO dc–dc converters with reduced components can be derived. The principle of topology synthesis states that integrated SIDO and DISO dc–dc converters can be easily developed from conventional SISO converters by replacing a diode with a basic cell inclusive of additional input/output port. The principle is effective for many SISO dc–dc converters, and as an example, topology synthesis based on buck, boost, buck–boost, Cuk, sepic, and zeta SISO converters is performed in this paper. In order to achieve better understanding of the proposed converters, the integrated SIDO Cuk converter is specifically analyzed and experimentally verified. In comparison with the conventional scheme of two separate SISO Cuk converters, good cross regulation is retained while the number of diodes, inductors, and capacitors is reduced in the proposed SIDO Cuk converter. In addition, zero-voltage-switching operation of one switch is achieved, contributing to lower switching losses. Finally, a prototype circuit with 48-V input and 156 V/1 A, 24 V/4 A outputs is built to validate the theoretical analysis.

In this paper, optimal phase advances under fault-tolerant control (FTC) of a five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) have been proposed under different fault conditions. Critical applications where the consistency and safety are the major concerns in automotive and aerospace industries require reliable control systems. The multiphase motor is considered a promising candidate for these applications as it has redundant phases primarily for fault-tolerant operation. However, advanced FTC for a PMa-SynRM with maximization of reluctance torque has been limitedly studied until now. In the conventional approach, to maintain constant magnetomotive force under fault conditions, phase currents of a motor need to increase significantly. However, this will easily saturate the PMa-SynRM resulting in significantly reduced reluctance torque. To overcome this issue, this paper proposes a novel phase current control method that maximizes the reluctance torque with minimum phase current. Here, a phase current control with a novel phase advance has been proposed under various fault conditions. Extensive theoretical and experimental analysis has been carried out to verify the effectiveness of the proposed idea with 5-hp dynamo system controlled by TI DSP F28335.

Precise positioning of a robot plays an very important role in advanced industrial applications, and this paper presents a new kinematic calibration method based on the extended Kalman filter (EKF) and particle filter (PF) algorithm that can significantly improves the positioning accuracy of the robot. Kinematic and its error models of a robot are established, and its kinematic parameters are identified by using the EKF algorithm first. But the EKF algorithm has a kind of linear truncation error and it is useful for the Gauss noise system in general, so its identified accuracy will be affected for the highly nonlinear robot kinematic system with a non-Gauss noise system. The PF algorithm can solve this with non-Gauss noise and a high nonlinear problem well, but its calibration accuracy and efficiency are affected by the prior distribution of the initial values. Therefore, this paper proposes to use the calibration value of the EKF algorithm as the prior value of the PF algorithm, and then, the PF algorithm is used further to calibrate the kinematic parameters of the robot. Enough experiments have been carried out, and the experimental results validated the viability of the proposed method with the robot positioning accuracy improved significantly.

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.

A fusion of inertial navigation system and global positioning system (GPS) has been proposed to implement a robust navigation system for a transporter. In several cases, the GPS signals are not reliable to localize a transporter. In order to overcome this difficulty, a fault detection and isolation (FDI) algorithm has been used to detect and isolate the contaminated satellite signals. When the FDI algorithm is used alone, and the number of reliable satellite signals becomes less than four owing to GPS signal errors, the receiver cannot estimate the position precisely. In this paper, a modified FDI algorithm has been proposed and applied for the navigation of a transporter on a flat yard in order to avoid losing its positioning while it passes through a structured area. In the modified FDI algorithm, signal-to-noise ratio, measurement of quality indicator, and Doppler shift data are incorporated. In order to verify the effectiveness of the proposed algorithm, the navigation experiments have been conducted on a campus using a mobile robot to simulate the transporter on a shipbuilding yard and the results are demonstrated in this paper.

This paper presents a practical discrete-time fractional order terminal sliding mode (DFOTSM) control strategy for high-precision tracking tasks based on a linear motor. In particular, the practical parametric uncertainties involving sliding friction, uncertain payload, and disturbance in tracking tasks are considered in this paper. Combining Grunwald–Letnikov fractional order definition and terminal sliding mode technique, the proposed method synthesizes a novel DFOTSM control law to drive the sliding mode dynamics into the stable region in finite steps theoretically, even though the system is suffering from uncertainties and disturbances, and the motion on the surface can guarantee higher tracking precision than the conventional discrete-time terminal sliding surface by selecting suitable controller parameters. The theoretical analyses give out the guideline of parameter selection, and experiments are carried out on the linear-motor-based test platform to demonstrate that the proposed controller is easily implemented and can achieve high-precision tracking, fast response, and considerable robustness to uncertainties.

Force estimation methods enable robots to interact with the environment or humans compliantly and safely without additional sensing device. In this paper, we present a novel method for estimating unknown contact forces exerted on a robot manipulator. The force estimation method is divided into two steps. The first step is to identify a robot dynamics model. A parametric model is derived first based on rigid-body dynamic (RBD) theory. To improve the model accuracy, a nonparametric compensator trained with multilayer perception (MLP) is added to compensate for errors of the RBD model. The result is a semiparametric model that provides better model accuracy than either the RBD model or the MLP model alone. The second step is to construct a force estimation observer. A novel estimation method called disturbance Kalman filter (DKF) is developed in this paper. The design of DKF based on a time-invariant composite system model is presented. DKF can take both manipulator's dynamics model and disturbance's dynamics model into account. As with Kalman filter, it can provide robust and accurate estimation against uncertainty. Simulation and experimental results, obtained using a six-degrees-of-freedom Kinova Jaco2 manipulator, demonstrate the effectiveness of the proposed method.

As a kind of direct-on-line motor, super premium efficiency (IE4) line-start synchronous reluctance motors (LS-SynRMs) were developed recently and are now used in many applications, including fans, pumps, and compressors. This paper presents an optimum design and comparative study of LS-SynRMs with additional losses and impact during the manufacturing process (electrical steel cutting/punching damage as well as squirrel-cage die-casting with bubble effects). The work results indicate that the LS-SynRM design with the “manufacturing process loss” effect should be considered and compensated for the design in order to achieve an IE4 class efficiency and ensure synchronization. Furthermore, the LS-SynRM rotor with multilayer flux barriers and rotor slots is investigated in detail. The influences of optimum design geometrical parameters (flux barriers thickness, segments thickness, length of rotor slots, etc.) on the performances of the basic model and optimum design model are evaluated with finite-element analysis (FEA) results. For more accurate results, the effects of saturation, saliency ratio, inductance difference, and the change in the B-H/B-P curve in damaged motor core edges are considered. Meanwhile, in the squirrel cage, the porosity rate distributions are considered. The copper loss, iron loss, starting torque, power factor, efficiency, and synchronization ability are investigated. The experimental results verify the accuracy of the process presented in this paper.