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This paper presents research results of voltage gain number control methods of a power electronic resonant zero-current switching dc–dc switched-capacitor (SC) voltage multiplier (SCVM) in a topology with fault tolerance capability (FSCVM). The converters operated under the basic switching patterns are constant-voltage-gain dc–dc series-parallel resonant SC converters. However, this paper presents a method for the output voltage regulation by a special switching strategy. A variable voltage gain is made possible by selecting the number of active switching cells, using an appropriate control method. This creates a set of voltage ratio ranges. In addition, the proposed topology and method of control enable a fault-tolerant operation of the FSCVM under various failures of the device. The paper presents an analysis of the concept, simulation results and an experimental verification in a three-cell FSCVM dc–dc resonant boost converter operating at a 200-watt charge. Issues regarding the selection of components related to the problem of inrush currents that can occur during the voltage ratio increase are also analyzed in this paper, and the design for low inrush currents is demonstrated. [ABSTRACT FROM AUTHOR]

The efficiency of multiterminal dc (MTDC) grid simulation decreases with an expansion of its scale and the inclusion of accurate component models. Thus, the variable time-stepping scheme is proposed in this paper to expedite the electromagnetic transient computation. A number of criteria are proposed to evaluate the time-step and regulate it dynamically during simulation. Meanwhile, as the accuracy of results is heavily reliant on the switch model in the modular multilevel converter, the nonlinear behavioral model with a greater accuracy is proposed in addition to the classic ideal model, and their corresponding variable time-stepping schemes are analyzed. Circuit partitioning is effective in accelerating the MTDC grid simulation via fine-grained separation of nonlinearities. A subsequent large number of identical circuits enabled a massively parallel implementation on the graphics processing unit, which achieved a remarkable speedup over the CPU-based implementation. The inclusion of variable time-stepping schemes eventually makes the simulation of MTDC grid with highly detailed nonlinear switch models feasible. The results are validated by commercial device-level and system-level simulation tools. [ABSTRACT FROM AUTHOR]

The nonlinear state-space dynamical model of the drive train of large-scale wind turbine systems (WTSs) and its scaling for small-scale real-time WTS emulation in the laboratory are discussed in this paper. Shaft elasticity and the nonlinear, aerodynamical turbine torque are considered. To allow for a physically reasonable emulation of the dynamical behavior of multimegawatt wind turbine drive trains at a small-scale laboratory test bench, a general scaling method is presented, which is based on the ratios of physical SI-units. Furthermore, inertia emulation, elasticity emulation, and friction compensation are addressed and possible implementations are proposed. Simulation results of the full-scale WTS model and measurement results of the small-scale real-time WTS emulation are compared to illustrate the effectiveness of the proposed scaling. [ABSTRACT FROM AUTHOR]

In this paper, a new Lyapunov-based model predictive controller is proposed for a 7-level packed U-cell (PUC7) grid-connected inverter. A cost function of the proposed model predictive controller is designed from the system stability point of view, inspired by the Lyapunov control theory. The proposed controller eliminates the need for gains that are associated with cost function coefficients, as seen in classical model predictive control based controllers. Therefore, the control design problem is significantly simplified. In addition, the average switching frequency is also reduced, as shown in both simulation and experimental results, leading to a reduction in switching losses. Simulation and experimental tests, on a PUC7 lab prototype, demonstrate the excellent performance of the proposed control system, in terms of high disturbance rejection, robustness to parameter mismatches, and fast dynamic response. Such features qualify the proposed control strategy as a good candidate for grid-tied applications. [ABSTRACT FROM AUTHOR]

The lack of dc fault clearance capability is a major obstacle that restricts the development of high-voltage direct current (HVdc) systems. Employing an active mechanical dc circuit breaker (M-DCCB) is an effective method to handle the dc fault. However, the existing active M-DCCBs can interrupt the fault current once but have problems in making the second interruption instantly in case of reclosing a permanent dc fault. In this paper, a novel topology of the active M-DCCB is proposed by inserting a precharged capacitor into a bridge formed by four spark gap switches. The operating strategy for the proposed M-DCCB is discussed to handle the dc faults. Its parameters, including the oscillation inductor and the oscillation capacitor, are determined by inequations derived from the requirements of dc fault interruption. The selection standard for the spark gap switch is set based on its breakdown characteristics. Finally, simulations are conducted to investigate the performance of the proposed M-DCCB. Results show that the capacitor can accumulate a sufficiently large reverse charge voltage automatically charged by the fault current. The proposed active M-DCCB topology and the dc fault handling strategy can interrupt the dc fault in HVdc power systems consecutively. [ABSTRACT FROM AUTHOR]

With different structures and control strategies, inverter-interfaced renewable energy generators (IIREGs) have different fault characteristics from synchronous generators. This makes the conventional distance protection used in networks with synchronous generators not applicable for transmission lines emanating from IIREGs. Therefore, supported by the fault current analysis, operating performances of distance relays on both sides of the transmission line are unveiled. It reveals the problem that the conventional distance relay on the IIREG side has a high risk of malfunction or refusing to operate. To cope with this adaptability problem, an improved scheme based on time delay and zero-sequence impedance is proposed in this paper. To validate the operating performances of the scheme, a detailed IIREG model is built in a real-time digital simulator, and simulation tests are carried out. Apart from these, a field short-circuit test is performed in a real wind power plant to examine the practical feasibility of the proposed scheme. Both the simulation results and the field test confirm the problem of the conventional distance protection and verify the reliability of the improved scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach for the detection of stator faults in inverter-fed induction motor under closed-loop control. These faults, generally, start with interturn short circuit and can evolve to phase-to-phase or phase-to-ground faults, leading to stator currents unbalance. In the considered application, the stator windings are supplied by a static converter for the control of the speed and the rotor flux of the motor. The unbalance fault has been artificially created through additional resistance in series with one phase of the stator windings. The proposed diagnosis approach is based on the computation of the symmetrical components of the stator currents. The supply fundamental frequency and the three-phase phasors are estimated based on the maximum likelihood estimator. Then, the generalized likelihood ratio test is applied for unbalance fault detection. Simulation and experimental results on a 1.5-kW induction motor illustrate the effectiveness of the proposed approach, leading to an effective diagnosis procedure for stator faults in inverter-fed induction motor under steady state and closed-loop operation. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) has attracted extensive research in recent years. An appropriate model is necessary to analyze stability or to design MMC controllers. Several published MMC models have been derived in single-phase form to simplify the modeling mathematics. However, little attention is given to the zero-sequence voltage, which introduces coupling in the single-phase model and leads to significant error. In this paper, after revealing the mechanism behind the zero-sequence voltage, a more accurate generalized single-phase MMC model is proposed, which eliminates the zero-sequence voltage coupling effect and is linearized based on harmonic state space (HSS) theory to precisely characterize the internal harmonic features of MMC. A systematic HSS modeling process is presented for both open-loop and closed-loop conditions. And the proposed model is generalized as it can incorporate different control strategy by controller transfer function substitution. Hence it is valuable to analyze MMC stability and dynamics. Model effectiveness is verified by simulation results. [ABSTRACT FROM AUTHOR]

Cascaded H-bridge (CHB) is a promising topology for medium-voltage high-power applications. CHB consists of low-power H-bridge modules in each phase, and these modules are connected in a cascade manner to achieve multilevel operation. However, CHB requires a phase-shifting transformer with multiple secondary windings to generate an isolated dc source for each module, and this requirement increases the overall system cost. In this paper, a series connection of low-power modules is employed to realize a new power converter called a series-connected multilevel converter. Each phase of the proposed topology requires a single isolated dc source. Hence, the required number of secondary windings is considerably reduced. This approach also minimizes the complexity and cost of the overall system. The operation of the proposed topology is presented by using three-level neutral point clamped modules in each phase. Model predictive control (MPC) is employed to control the dc-bus capacitor voltage and output currents of the proposed topology. A discrete-time mathematical model of the proposed topology is also developed to predict the future behavior of control variables. The performance of the proposed topology with MPC is verified through MATLAB simulations and a scaled-down laboratory prototype. [ABSTRACT FROM AUTHOR]

A novel method for controlling direct voltage regulated active dc-link capacitance reduction circuits (ACRC) is proposed in this paper. Instead of forcing the dc-link voltage of the power conversion system to follow a constant reference, the ACRC imposes dc-bus voltage in proportion to the integral of its input current. Consequently, it resembles an adjustable value capacitor from the dc-link side. Therefore, as opposed to existing control strategies, the proposed method simultaneously allows the dc-link voltage to reflect the power balance of the system and the pulsating power component to be diverted into significantly reduced auxiliary capacitance via a bidirectional dc–dc converter. As a result, replacing bulk dc-link capacitance by the proposed circuitry does not require any modification of existing grid-connected power conversion system controllers, thus allowing plug-and-play operation. The proposed approach is validated by application to a commercial power factor correction front end by both simulations and experiments. [ABSTRACT FROM AUTHOR]

Model predictive control (MPC) has been widely advocated as a design strategy for many aspects of industrial electronics. The methodology has been strongly promoted by some researchers but has also attracted criticism from others. In this context, the purpose of this paper is twofold. First, we show that many existing and popular control strategies, including finite set MPC and linear controllers [proportional integral, proportional resonant (PR)], can be viewed as special cases of MPC. Second, we show that the predictive control framework allows one to embellish these classical control architectures with novel features and to design new and advanced control architectures to address various challenges posed by power electronics applications. The findings of the paper are supported by a practical example of designing of a novel form of PR controller with superior tracking performance and delay compensation, confirmed via simulation and experiments. [ABSTRACT FROM PUBLISHER]

In traditional networked control systems, wired communication networks are used for the transmission of information between the communicating systems. With the increasing demand for distributed systems and the growth in the scale of the applications, the use of wireless communication networks offers significant advantages over their wired counterparts. To facilitate the deployment of a fully automated closed-loop wireless networked control system (WNCS), this paper addresses several design considerations for a proposed topology for potential use as a closed-loop WNCS. The topology consists of a plant system having sensor and actuator nodes, a controller system having input and output nodes, an intermediate network system having interconnected nodes, and wireless communication links for the information transfer between the different nodes of the plant, controller, and network systems. More specifically, the design considerations addressed in the paper are: the condition requirements needed to facilitate the design of optimal controller and network systems, the joint design of optimal controller and network systems to control the plant system, and the structured model reduction of the closed-loop WNCS to reduce its scale. Finally, simulation examples are provided to demonstrate the applicability of discussed design considerations. [ABSTRACT FROM PUBLISHER]

This paper presents an active cross-connected modular multilevel converter (AC-MMC) based on series-connected half-bridge modules. It is intended for completely enhancing the performance of a medium-voltage motor drive system in the full speed range from standstill to rated speed under all load conditions. The proposed AC-MMC circuit is characterized by the cross connection of upper and lower arm middle taps through a branch of series-connected half-bridge converters, which have an identical voltage and current rating with the submodules in the upper and lower arms. This cross-connected branch provides a physical power transfer channel for the upper and lower arms. By properly controlling the amount of high-frequency current flowing through the cross-connected branch, the power balance between the upper and lower arms is achieved even at a zero/low motor speed under constant torque condition. Meanwhile, no common-mode voltage is introduced in the whole speed range. A control strategy with focus on submodule capacitor voltage control is also proposed in this paper to guarantee the normal converter operation. Simulation results obtained from a 4160-V, 1-MW model verify the feasibility of the proposal. Experiments on a downscaled prototype also confirm the validity of the novel circuit and the associated control strategy. [ABSTRACT FROM PUBLISHER]

Considering input constraints and parameter uncertainty of the nonholonomic wheeled mobile robots, a new control law has been designed in this paper to solve the tracking and stabilization control problems simultaneously. The asymptotic convergence of the stabilization or tracking errors is achieved by a smooth controller with time-varying feedback parameters subject to set conditions. A geometric-based parameter design strategy is employed to overcome the difficulties resulting from input constraints. With the parameter design strategy, the designed parameters satisfy the set conditions and the control inputs stay in the constrained domain. Experimental studies have been conducted to verify the effectiveness of the proposed control law. [ABSTRACT FROM AUTHOR]

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]

Process monitoring is an effective means to ensure process safety and improve product quality. On the one hand, it is possible that the fault will not affect process safety or product quality. On the other hand, not every fault affects both process safety and product quality simultaneously. To make process monitoring more purposeful and more accurate, a novel performance-indicator-oriented concurrent subspace (PIOCS) process monitoring method containing three subspaces with different degrees of importance is proposed in this paper. The first one is safety-related subspace, the second one is safety-unrelated quality-related subspace, and the third one is safety quality unrelated subspace. Through subspace division and construction, the fault can be categorized as safety-related fault, safety-unrelated quality-related fault, and safety quality unrelated fault. For mining safety and quality related information, both mechanism analysis and data analysis are used. In order to show the effectiveness and superiority, the proposed PIOCS method is tested under a number example and an industrial case study. Compared with traditional process monitoring methods, the proposed PIOCS method can obtain richer information, which is easy to show process operation condition clearly. [ABSTRACT FROM AUTHOR]

This paper proposes a novel finite-memory (FM) estimation method for vehicle roll and road bank angles. We consider a three-degree-of-freedom model based on bicycle and vehicle roll models, where there exist uncertainties in the model parameters. The existing estimation methods may show poor performance for the considered model with uncertainties. The accumulated errors, which might be caused by modeling uncertainties and numerical errors, may degrade the performance of existing methods because they use all past measurements. To overcome the weaknesses of the existing methods, a new FM estimation method is proposed and can prevent accumulated errors by using recent finite measurements. Both the simulation and experimental results show that the proposed estimation method ensures more reliable and accurate performance than the existing methods under various driving conditions. [ABSTRACT FROM AUTHOR]

To improve the interception performance in missile guidance applications, this paper proposes a novel control strategy for the integrated guidance and control design subject to input constraints. The system constraints are translated into a restriction in an invariant set, which is then enforced by manipulating the derivative of the applied reference. For the integrated system in the presence of disturbances and parametric uncertainties, disturbance observers are applied to estimate the lumped disturbances existing in each loop. The quadratic stability via dynamic surface control is guaranteed, and an ellipsoidal approximation of the invariant set is obtained, which can be enlarged to allow some degree of the input saturation. The effectiveness of the proposed scheme is illustrated using numerical simulations against a maneuvering target. [ABSTRACT FROM AUTHOR]

Contactless sliprings (CS) based on inductive power transfer (IPT) offer a safe and reliable power transfer solution for rotary applications. An accurate reluctance model for CS is presented in this paper along with the associated parameters identification, considering the partially linking effect of the magnetic flux. Aiming to obtain higher coupling coefficient and lighter weight, a design optimization for CS is also proposed by defining a new design parameter “ζ.” Both simulations and experimental measurements are presented to verify the effectiveness of the proposed modeling method. The maximum errors (between the identified results and the measured results) of the mutual inductance, the leakage inductance, and the coupling coefficient are 8.72%, 7.12%, and 5.98%, respectively, when the gap is less than the core window width. Comparative studies among different modeling methods are carried out, which testify that the proposed method has the highest accuracy. Finally, a 1.5 kW IPT system employing the designed CS is fabricated for verification. [ABSTRACT FROM AUTHOR]

In this paper, we designed and demonstrated a smartwatch strap wireless charging system for the first time. First, we designed a flexible printed circuit board (PCB) coil, shielding material, and receiver (Rx) circuit in a watchstrap. In the design process, we proposed a model for the flexible PCB coil with a bending radius of 40 mm and shielding materials. We used a flexible PCB coil that has 215  μm thickness with dimensions of 54.5 × 16 mm. In addition, ferrite core and sheet are applied on the transmitter (Tx) and Rx coils. We verified the proposed model through a three-dimensional (3-D) electromagnetic (EM) simulation and measurement in the frequency and time domains. The proposed flexible PCB coil inductance modeling results showed 7.5% and 3.4% errors when compared to the 3-D EM simulation and measurement results, respectively. Furthermore, we demonstrated the smartwatch strap wireless charging system using an LG Watch Urbane. A resonance frequency of 100 kHz with the series–series tuning topology is used in accordance with the Qi specifications. Finally, we achieved 30% dc–dc power transfer efficiency and exposed magnetic field of 270 mG, 1 cm away from the system through measurements. [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]

This paper investigates robust control strategies for wind energy conversion systems with variable-speed permanent magnet synchronous generators, which are integrated into the grid to provide reliable, secure, and efficient electrical power. A three-phase grid-side converter without a grid transformer is connected to the grid using an LCL filter with low resistive losses. In these working conditions, an instantaneous power proportional integral (PI) controller for the outer voltage-loop in the grid-side converter is used to regulate the DC-link voltage and generate the required currents for the inner current-loop in the grid-side converter. Two integral-type terminal sliding-mode controllers are proposed to control the active and reactive powers exchanged between the converter and the grid. The switching signals in the controllers are softened to attenuate chattering. The time-varying gains in the controllers are constructed to reduce control energy wastage and avoid overestimation of the boundaries of system uncertainties. Simulated and experimental results validate the proposed method. [ABSTRACT FROM AUTHOR]

Multilevel inverters are now-a-days being applied in electric vehicles (EV). Considering the dynamic operating conditions of an EV propelled by an induction motor, this paper proposes a flexible discontinuous modulation strategy for three-level neutral-point-clamped (NPC) inverter that can shift modulation pattern seamlessly from sinusoidal pulsewidth modulation (SPWM) to discontinuous PWM (DPWM). The modulation scheme is generalized at each degree of discontinuity to ensure minimum switching losses for variable load power factors. Additionally, a hybrid voltage balancing strategy, which comprises two sets of compensating offset signals with complementary features, has been introduced to mitigate voltage deviation problem at neutral point of the inverter. The unique feature of the proposed hybrid balancing approach is that it generates uniform compensating neutral current regardless of the level of discontinuity. This results in identical and predictable voltage balancing dynamics for the entire modulation transition covering SPWM and DPWM. It has been shown that the proposed hybrid balancing strategy does not lose its unbalance compensation strength even during transition from one modulation pattern to another. The effectiveness of the proposed scheme for wide variations in operating conditions is studied through extensive simulation, and validated in experimentation using a prototype NPC inverter with induction motor loads. [ABSTRACT FROM AUTHOR]

For the safe operation of redundant manipulators, physical constraints such as the joint angle, joint velocity, and joint acceleration limits should be taken into account when designing redundancy resolution schemes. Velocity-level redundancy resolution schemes are widely adopted in the kinematic control of redundant manipulators due to the existence of the well-tuned inner loop regarding the joint velocity control. However, it is difficult to deal with joint acceleration limits for velocity-level redundancy resolution methods. In this paper, a recurrent-neural-network-based velocity-level redundancy resolution method is proposed to deal with the problem, and theoretical results are given to guarantee its performance. By the proposed method, the end-effector position error is asymptotically convergent to zero, and all the joint limits are not violated. The effectiveness and superiority of the proposed scheme are validated via simulation results. [ABSTRACT FROM AUTHOR]

A two-degrees-of-freedom (two-DOF) ultrasonic motor, which could output linear motions with two-DOF by using only one longitudinal–bending hybrid sandwich transducer, is proposed and tested in this paper. The motion in the horizontal (X) direction is achieved by the hybrid of the second longitudinal and fifth bending vibrations of the motor, while the motion in the vertical (Y) direction is gained by the composition of two orthogonal fifth bending vibrations. The proposed ultrasonic motor is designed and the principles for the two-DOF driving were analyzed. Then, the simulation analyses of the motor are accomplished to verify the described principles. Finally, a prototype is fabricated and its mechanical output characteristics are tested. The results indicate that the maximum no-load velocities of the motor in horizontal and vertical directions are 572 and 543 mm/s under the preload of 100 N and the voltage of 300 Vp-p, respectively. The maximum output forces in horizontal and vertical directions are 24 and 22 N when the preload is 200 N. The simulation and experiment results verify the feasibility of the proposed two-DOF ultrasonic motor. [ABSTRACT FROM AUTHOR]

Due to its low harmonic, high efficiency, and high power factor (PF), the multipulse autotransformer has been frequently used in the aviation sector. Many studies have been carried out on the theoretical calculation and simulation analysis of the autotransformer. However, the practical application of the multipulse rectifier in the practical engineering field is inevitable. This paper investigates an 18-pulse rectifier power supply of 11 kW being constructed using a multipulse autotransformer to suppress the harmonics of a radar power system, in which the parameters of the various parts are designed in detail, and test results are simulated using MATLAB/Simulink software. The actual test suggests that, at the rated condition, the PF of the rectifier is 0.99, the total harmonic distortion of the input current is below 6.7%, and the efficiency is more than 96%. The power supply is successfully applied to the radar power supply system of a large transport aircraft, and meets the requirements of an environmental test. Furthermore, the results also provide powerful application support for the power supplies and distribution systems in other fields. [ABSTRACT FROM AUTHOR]

This paper investigates a modular slotless tubular permanent magnet linear synchronous motor, which includes several sectional motors by setting flux barriers and rearranging windings. It focuses on the design method of the different combinations with small detent force. The detent force models of the sectional and whole modular motor are established analytically in terms of a Fourier expansion and verified by a prototype. Then the design principles of the sectional motors are analyzed. On the basis of the models, the schemes whose flux barriers’ widths equal to one-third of the pole pitch are selected, followed by the comparison of two kinds of different sectional combinations. Their detent-force characteristics are then described in detail. The conclusions about the different combinations are drawn. [ABSTRACT FROM AUTHOR]

This paper investigates the optimal resource management in a microgrid under various operating conditions. A two-level optimization system is proposed for the distributed optimal resource management based on a multi-agent system framework. The proposed strategy generates a reference of the optimal power output at the top level through local communication. This strategy only requires the information among neighboring participants without a central control coordination, and simultaneously accomplishes resource optimization in a finite time while maintaining the supply–demand balance. The bottom-level control is responsible for the reference tracking of each corresponding participant in a microgrid. The convergent rate of the proposed algorithm is compared with other consensus-based algorithms through simulation studies. Simulation results in the IEEE 14-bus system and an actual islanded system are also presented to demonstrate the overall effectiveness of the proposed strategy. [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]

The purpose of this paper is to comment on the reference voltage tracking ability of a recently proposed state observer based adaptive sliding mode control for boost converters. It is shown that the control in the cited paper cannot track the reference voltage. A modified control law that enables reference voltage tracking while preserving the other advantages of the commented paper is proposed and validated by simulation and experimentation on laboratory hardware. [ABSTRACT FROM PUBLISHER]

This paper proposes a space vector modulation (SVM) scheme for a three-to-seven-phase matrix converter (MC), feeding a variable-voltage variable-frequency multiphase drive. The main feature of the proposed technique is that it utilizes only 129 out of 2187 possible active space vectors for a successful ac–ac power conversion. Since the number of vectors is significantly reduced, the switching patterns are simplified, and the execution time of the algorithm is shortened. Despite the drastic reduction in the number of active vectors, it is found that there is no significant degradation in the performance of the MC. Furthermore, the SVM also produces balanced sinusoidal input currents with a unity power factor over a wide operational frequency range (1–110 Hz). In this paper, the theoretical analysis is supported by simulation and validated using a hardware prototype. The output voltage can reach up to 76.93% of the input voltage, which is the maximum physical limit of a three-to-seven-phase MC. In addition, it exhibits a better harmonic profile than the carrier-based modulation scheme; the total harmonic distortion for the output voltage waveform is measured to be below 5% over the entire operating frequency range. [ABSTRACT FROM PUBLISHER]

In this paper, a novel bias-reduction method is proposed to analytically express and reduce the bias arising in sensor network localization problems, thereby improving the localization accuracy. The proposed bias-reduction method mixes Taylor series and a maximum-likelihood estimate and leads to an easily calculated analytical bias expression in terms of a known maximum-likelihood cost function. In contrast to existing contributions, this paper considers a sensor network as a whole when the bias is investigated by introducing the geometric structure of the sensor network into the proposed bias-reduction method via the rigidity matrix, a concept drawn from graph theory. The maximum-likelihood cost function is related to the rigidity matrix resulting in the final analytical expression of localization bias in terms of the rigidity matrix. Another important contribution of this paper is that, in addition to the presented simulation results, experimental results obtained by using a wireless localization system, which is developed based on reconfigurable software-defined radios (SDRs), are also provided to verify the performance of the proposed bias-reduction method. Both the simulation and experimental results demonstrate that the proposed method can reduce the bias, thereby improving the localization accuracy in different scenarios. [ABSTRACT FROM PUBLISHER]

This paper presents a promising solution to the problem of the bad environmental impacts of the induction-motor-based water pumps. Due to the low wire-to-water efficiency of the current residential water heaters (around 30%), a high energy cost is paid by every household in North America and even worldwide. The contribution of this paper comes in twofolds. The first is the development of a mapping algorithm that relates the pressure head $H$ and the water flow rate $Q$ to a corresponding torque and speed under the chart of best efficiency point, which was programmed to the controller. The second is the development of a cost-effective brushless direct-current (BLDC) motor through an extensive numerical analysis technique. The proposed motor solution designs the BLDC with minimal pulsating torque by comparing two different designs. The new controller is based on a modified field-oriented control. The controller printed circuit board is of two layers to offer a cost-effective solution. The proposed pump eliminates the need of a battery for the controller as the control voltage is fed directly from the line together with the motor. The motor simulation model and the controller design procedure are presented with simulation results of two possible prototypes. An experimental prototype for a 150-W residential pump was built, and preliminary results are given to highlight the merits of the work. [ABSTRACT FROM PUBLISHER]

Accurate simulation is an essential task in designing of integrated power systems to predict their electrical behavior. Thus, a very good description of their wiring circuits is required, and the availability of accurate models of power semiconductor devices and associated design parameters is crucial. This paper focuses on a novel extraction approach of design parameters for a 1-D finite-element-method model of the thyristor. These design parameters are also essential for physics-based analytical models. This paper presents an extraction procedure of the main design parameters of an ultrafast thyristor: the effective area of the device, the ambipolar lifetime, the doping concentration and width of the low-doped base region, and the doping concentration and width of the gate region. The extraction procedure of the thyristor design parameter is based on a comparative computation between simulation and experimental results, taking into account the physics of the component. Measurements are carried out on a sophisticated test circuit, which must be modeled with a sufficient accuracy. This paper details the parameter extraction procedure. Various electrothermal simulation results about the thyristor under test, using the extracted values of design parameters, show good agreement with experiment and confirm the validity of the presented extraction procedure. [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]

This paper proposes a simple and cost-effective current measurement technique for four-phase switched reluctance motor (SRM) control, by splitting the dual bus line of the converter, without pulse injection and voltage penalty. Only two Hall-effect sensors are utilized, where one is installed in the upper bus to measure two phase currents, and the other is placed in the lower bus to measure other two phase currents. In order to realize independent current measurement in the whole turn-on region, switching functions are redesigned so that upper switches of two phases act as the choppers, while lower switches of the other two phases are employed as the choppers. Compared to traditional drives, the developed system requires only two Hall-effect sensors in the dual bus line, without a need for individual phase sensors or additional devices, which reduces the cost and volume for SRM drives. Furthermore, compared to the single-sensor based current measurement scheme, the proposed method has no need to implement pulse injection and will not cause any voltage penalty and current distortion, which also improve the current measurement accuracy and system performance. Simulation and experiments carried out on a 150-W four-phase 8/6 SRM confirm the effectiveness of the proposed technique. [ABSTRACT FROM PUBLISHER]

This paper presents a microgrid control strategy to unify the control topology for energy storage systems and renewable energy sources inverters in an ac microgrid and to protect the microgrid reliability from unintentional islanding instability using control loops, which use thedc link voltage as a feedback. This bounds the dc link voltage and provides reliable operation in the microgrid. Simulation validates the proposed control strategy, and experiment results extol the concept. [ABSTRACT FROM PUBLISHER]

Interleaved converter legs are typically modulated with individual carriers per leg and phase-shifted pulse width modulation (PS-PWM) as it facilitates current balancing amongst the legs. Phase-disposition PWM (PD-PWM), despite the better harmonic performance, cannot be directly used due to the resulting current imbalance that may damage the converter. This paper addresses the current sharing issue and proposes a sorting algorithm implementation that enables single-carrier PD-PWM technique for interleaved two-level converter legs. An extension of the proposed algorithm through a switching state feedback loop, limiting the average switching frequency, is also developed. In both cases, the output current is of high quality and shared amongst the phase-legs, while the deviation between the phase-leg currents is well regulated. Simulation results demonstrate the general function of method for multiple interleaved legs as well as its current sharing capabilities for high-power applications. Experimental results from a low-power laboratory prototype validate the operation of the proposed approach. [ABSTRACT FROM PUBLISHER]

Small-scale magnetically suspended control moment gyros with flat shaped rotor tilting by axial forces are easier to reduce size and weight than by radial forces. This paper presents a novel three-degree-of-freedom hybrid axial magnetic bearing without subsidiary air gaps. This new structure is more efficient because the loss on extra air gaps can be avoided. An order scheduling cross-feedback control strategy with order number adjusting with the rotor speed is also presented to compensate the gyroscopic effect. The damping ratios of nutation and precession are compared for cross-feedback controllers with different orders using generalized root locus with gain related to the speed of revolution. Simulation results show that, when increasing the order of the cross-feedback controller, the nutation stability rises, but precession drops. In experiment, high-order cross-feedback leads to high maximum stable speed, but collision at low speed. The solution is using first-order cross-feedback when the speed is below 6200 r/min, second order during 6200–9000 r/min, and third order above 9000 r/min. The digital control system implementing the presented control strategies on a field programmable gate array can keep the rotor in stable suspension from 0 to 12 000 r/min. [ABSTRACT FROM PUBLISHER]

This paper evaluates the benefits of using a high-level synthesis (HLS) tool to develop field-programmable gate array (FPGA)-based real-time simulators for power electronics systems. The investigated workflow generates a synthesizable hardware description from a system level C-code along with a set of directives that specify performance criteria such as area utilization and timing closure requirements. The performance of the HLS approach is evaluated for different circuit sizes and target clock frequencies. Results show that HLS can be used for hardware-in-the-loop (HIL) applications when the circuit to be simulated is small and the target clock frequency is not too high (up to 100 MHz). For larger circuits and higher clock frequencies, HLS will either require a simulation time-step that is too large for real-time simulation purposes, or will tend to use almost all of the FPGA resources. [ABSTRACT FROM PUBLISHER]

This paper extends a recent result on sliding mode control for general nth order systems with mismatched uncertainties. In this paper, a control is proposed to handle a larger class of mismatched uncertainties by extending the disturbance observer and modifying and generalizing the sliding surface. The practical stability of the overall system is proved and the results are verified by simulation of an illustrative example. [ABSTRACT FROM PUBLISHER]

This paper presents analytical expressions for steady-state waveforms, output power, and power conversion efficiency for the class-E inverter outside the class-E zero-voltage switching and zero-derivative switching conditions. The analytical expressions in this paper include the MOSFET-body-diode effect. By carrying out PSpice simulations and circuit experiments, it is shown that the analytical predictions agree with the simulated and experimental results quantitatively, which indicates the validity of the analytical expressions. Additionally, the switching-pattern distribution maps are also given by using the analytical waveform equations. [ABSTRACT FROM PUBLISHER]

With the increasing attention to the concept of microgrids, it has become important to identify the requirements that enable an electric distribution network to operate as a microgrid. This paper studies a realistic distribution network to accomplish the following: 1) determine the conditions under which the network can operate as a microgrid and 2) present the control scenarios that allow the islanded operation of the network. In particular, the employment of electronically coupled distributed energy resources with the fault-ride-through and synchronization capabilities is investigated. Another objective of this paper is to propose practical protection strategies that are effective in both operational modes of a microgrid (i.e., the grid-connected mode and the islanded mode), considering the system constraints; the protection strategies provide the microgrid with acceptable reliability against different fault scenarios. The effectiveness of the control and protection strategies is demonstrated and discussed through a comprehensive set of simulation studies conducted in the PSCAD/EMTDC software environment. [ABSTRACT FROM PUBLISHER]

Due to the significance of extracting the grid voltage information, the grid synchronization system plays an important role in the control of grid-connected power converters, and various grid voltage synchronization schemes have been proposed. This paper adopts the complex-vector-filter method (CVFM) to analyze the grid synchronization systems. With this method, the pairs of scalar signals, for example, the \alpha- and \beta-axis components in the stationary \alpha - \beta frame, are combined into one complex vector. As a consequence, the grid synchronization systems can be described with the complex transfer functions, which is very convenient to evaluate the steady-state performance, for example, the fundamental and harmonic sequence decoupling/cancellation, and dynamic performance of these systems. Moreover, the CVFM also provides a more generalized perspective to understand and develop the grid synchronization systems. Therefore, some of the representative systems are reanalyzed with the CVFM in this paper. A generalized second-order complex-vector filter and a third-order complex-vector filter are proposed with the CVFM to achieve better dynamic performance or higher harmonic attenuation. Moreover, a brief comparison of the complex-vector filters analyzed in this paper is presented. The effectiveness of the CVFM and the proposed two complex-vector filters are verified by the simulation and experimental results. [ABSTRACT FROM PUBLISHER]

This paper develops a sliding-mode control (SMC) approach for systems with mismatched uncertainties via a nonlinear disturbance observer (DOB). By designing a novel sliding surface based on the disturbance estimation, a DOB-based SMC method is developed in this paper to counteract the mismatched disturbance. The newly proposed method exhibits the following two attractive features. First, the switching gain is only required to be designed greater than the bound of the disturbance estimation error rather than that of the disturbance; thus, the chattering problem is substantially alleviated. Second, the proposed method retains its nominal performance, which means the proposed method acts the same as the baseline sliding-mode controller in the absence of uncertainties. Simulation results of both the numerical and application examples show that the proposed method exhibits much better control performance than the baseline SMC and the integral SMC (I-SMC) methods, such as reduced chattering and nominal performance recovery. [ABSTRACT FROM PUBLISHER]

Bidirectional inductive power transfer (IPT) systems are attractive for applications such as electric vehicles and vehicle-to-grid systems which preferably require “contactless” and two-way power transfer. However, in contrast to unidirectional IPT systems, bidirectional IPT systems require more sophisticated control strategies to control the power flow. An indispensible component of such control strategies is the robust and accurate synchronization between the primary- and pickup-side converters, without which the transfer of real power in any direction cannot be guaranteed. This paper proposes a novel technique that synchronizes converters on both the primary and pickup sides of bidirectional IPT systems. The technique uses an auxiliary winding, located on the pickup side, to produce a synchronizing signal which, in turn, can be utilized to regulate the real power flow. This paper also presents a mathematical model for the proposed technique and investigates its sensitivity for component tolerances. The viability of the technique, which is applicable to both single- and multiple-pickup IPT systems, is demonstrated through both simulations and experimental results of a 1-kW prototype bidirectional IPT system. [ABSTRACT FROM PUBLISHER]

Reluctance network (RN) method is suitable for the modeling of complex magnetic field. In traditional RN models, the meshes cover the whole cross-sectional area of the electric machines, so much time is required. In order to improve the modeling efficiency, a new modular RN structure and two mesh generation methods are proposed in this paper. The size and shape of the mesh elements are identical and their permeance calculations are unified. These characteristics can greatly enhance the modeling flexibility of the RN. Then, the proposed methods and the simple magnetic circuit method are combined to analyze the performances of a linear permanent magnet vernier machine. Finally, finite-element analysis and experimental tests are carried out to evaluate the proposed method. Results show that the proposed method has high accuracy and high modeling speed. [ABSTRACT FROM PUBLISHER]

This paper analyzes the performance of a grid-tied, wide power range, transformerless, modified three-phase current-source inverter (CSI), named CSI7. The CSI7 topology is here analyzed along with a suitable space vector modulation strategy able to attenuate the excitation of the output CL filter. The theoretical analysis and simple analytic expressions highlighted the performance and limitations of the topology when employed as a single-stage photovoltaic (PV) inverter, with a particular emphasis on injected grid current distortion and ground leakage current values. The inverter wide input range allows interfacing PV strings of different module count with a simple closed-loop control. The principle of operation and control is described; the viability of the CSI7 topology was assessed with simulations and extensive experiments on a full-size laboratory prototype. [ABSTRACT FROM PUBLISHER]

In a dc microgrid (DC-MG), the dc bus voltage is vulnerable to power fluctuation derived from the intermittent distributed energy or local loads variation. In this paper, a virtual inertia control strategy for DC-MG through bidirectional grid-connected converters (BGCs) analogized with virtual synchronous machine (VSM) is proposed to enhance the inertia of the DC-MG, and to restrain the dc bus voltage fluctuation. The small-signal model of the BGC system is established, and the small-signal transfer function between the dc bus voltage and the dc output current of the BGC is deduced. The dynamic characteristic of the dc bus voltage with power fluctuation in the DC-MG is analyzed in detail. As a result, the dc output current of the BGC is equivalent to a disturbance, which affects the dynamic response of the dc bus voltage. For this reason, a dc output current feedforward disturbance suppressing method for the BGC is introduced to smooth the dynamic response of the dc bus voltage. By analyzing the control system stability, the appropriate virtual inertia control parameters are selected. Finally, simulations and experiments verified the validity of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

A traction drive control system (TDCS) plays an important role in safety running of high-speed trains. This paper presents a new fault-injection strategy for safety testing and fault diagnosis verification in the TDCS. First, the fault scenarios on the signal level of each faulty component are analyzed. Then, the fault-injection method based on signal conditioning is proposed, and the injected signal, reflecting the fault scenario at a fault point, is generated to simulate the fault scenarios. Subsequently, the injected signal benchmark is constructed for all faults in traction converters, traction motors, sensors, and traction control units. Finally, a fault-injection benchmark platform is developed to simulate various fault scenarios in the TDCS. The simulation and comparison results show that the presented strategy is effective and easy to implement. [ABSTRACT FROM PUBLISHER]