Showing papers in "IEEE Transactions on Industrial Electronics in 2004"

Direct torque control of PWM inverter-fed AC motors - a survey

Abstract: This paper presents a review of recently used direct torque and flux control (DTC) techniques for voltage inverter-fed induction and permanent-magnet synchronous motors. A variety of techniques, different in concept, are described as follows: switching-table-based hysteresis DTC, direct self control, constant-switching-frequency DTC with space-vector modulation (DTC-SVM). Also, trends in the DTC-SVM techniques based on neuro-fuzzy logic controllers are presented. Some oscillograms that illustrate properties of the presented techniques are shown.

Power transfer capability and bifurcation phenomena of loosely coupled inductive power transfer systems

Abstract: Loosely coupled inductive power transfer (LCIPT) systems are designed to deliver power efficiently from a stationary primary source to one or more movable secondary loads over relatively large air gaps via magnetic coupling. In this paper, a general approach is presented to identify the power transfer capability and bifurcation phenomena (multiple operating modes) for such systems. This is achieved using a high order mathematical model consisting of both primary and secondary resonant circuits. The primary compensation is deliberately designed to make the primary zero phase angle frequency equal the secondary resonant frequency to achieve maximum power with minimum VA rating of the supply. A contactless electric vehicle battery charger was used to validate the theory by comparing the measured and calculated operational frequency and power transfer. For bifurcation-free operation, the power transfer capability and controllability are assured by following the proposed bifurcation criteria. Where controllable operation within the bifurcation region is achievable, a significant increase in power is possible.

Future vehicle driven by electricity and Control-research on four-wheel-motored "UOT electric march II"

Abstract: The electric vehicle (EV) is the most exciting object to apply "advanced motion control" technique. As an EV is driven by electric motors, it has the following three remarkable advantages: 1) motor torque generation is fast and accurate; 2) motors can be installed in two or four wheels; and 3) motor torque can be known precisely. These advantages enable us to easily realize: 1) high performance antilock braking system and traction control system with minor feedback control at each wheel; 2) chassis motion control like direct yaw control; and 3) estimation of road surface condition. "UOT Electric March II" is our novel experimental EV with four in-wheel motors. This EV is made for intensive study of advanced motion control of an EV.

Simple direct power control of three-phase PWM rectifier using space-vector modulation (DPC-SVM)

Abstract: This paper proposes a novel and simple direct power control of three-phase pulsewidth-modulated (PWM) rectifiers with constant switching frequency using space-vector modulation (DPC-SVM). The active and reactive powers are used as the pulse width modulated (PWM) control variables instead of the three-phase line currents being used. Moreover, line voltage sensors are replaced by a virtual flux estimator. The theoretical principle of this method is discussed. The steady-state and dynamic results of DPC-SVM that illustrate the operation and performance of the proposed system are presented. It is shown that DPC-SVM exhibits several features, such as a simple algorithm, good dynamic response, constant switching frequency, and particularly it provides sinusoidal line current when supply voltage is not ideal. Results have proven excellent performance and verify the validity of the proposed system.

An electrochemical-based fuel-cell model suitable for electrical engineering automation approach

Abstract: This paper presents a dynamic electrochemical model for representation, simulation, and evaluation of performance of small size generation systems emphasizing particularly proton exchange membrane fuel-cell (PEMFC) stacks. The results of the model are used to predict the output voltage, efficiency, and power of FCs as a function of the actual load current and of the constructive and operational parameters of the cells. Partial and total load insertion and rejection tests were accomplished to evaluate the dynamic response of the studied models. The results guarantee a better analytical performance of these models with respect to former ones with a consequent reduction in time and costs of projects using FCs as the primary source of energy. Additionally, this electrochemical model was tested for the SR-12 Modular PEM Generator, a stack rated at 500 W, manufactured by Avista Laboratories, for the Ballard Mark V FC and for the BCS 500-W stack.

Residual life predictions from vibration-based degradation signals: a neural network approach

Abstract: Maintenance of mechanical and rotational equipment often includes bearing inspection and/or replacement. Thus, it is important to identify current as well as future conditions of bearings to avoid unexpected failure. Most published research in this area is focused on diagnosing bearing faults. In contrast, this paper develops neural-network-based models for predicting bearing failures. An experimental setup is developed to perform accelerated bearing tests where vibration information is collected from a number of bearings that are run until failure. This information is then used to train neural network models on predicting bearing operating times. Vibration data from a set of validation bearings are then applied to these network models. Resulting predictions are then used to estimate the bearing failure time. These predictions are then compared with the actual lives of the validation bearings and errors are computed to evaluate the effectiveness of each model. For the best model, we find that 64% of predictions are within 10% of actual bearing life, while 92% of predictions are within 20% of the actual life.

Characteristics of the multiple-input DC-DC converter

Abstract: In the zero-emission electric power generation system, a multiple-input DC-DC converter is useful to obtain the regulated output voltage from several input power sources such as a solar array, wind generator, fuel cell, and so forth. A new multiple-input DC-DC converter is proposed and analyzed. As a result, the static and dynamic characteristics are clarified theoretically, and the results are confirmed by experiment.

Repetitive-based control for selective harmonic compensation in active power filters

Abstract: This paper proposes a repetitive-based controller for active power filters, which compensates selected current harmonics produced by distorting loads. The approach is based on the measurement of line currents and performs the compensation of selected harmonics using a closed-loop repetitive-based control scheme based on a finite-impulse response digital filter. Compared to conventional solutions based on stationary-frame current control, this approach allows full compensation of selected frequencies, even if the active filter has limited bandwidth. Compared to synchronous-frame harmonic regulations on line currents, the complexity of the proposed algorithm is independent of the number of compensated harmonics. Moreover, it is more appropriate for digital signal processor implementation and less sensitive to rounding and quantization errors when finite word length or fixed-point implementation is considered. Experimental results on a 5-kVA prototype confirm the theoretical expectations.

TP model transformation as a way to LMI-based controller design

Abstract: The main objective of this paper is to propose a numerical controller design methodology. This methodology has two steps. In the first step, tensor product (TP) model transformation is applied, which is capable of transforming a dynamic system model, given over a bounded domain, into TP model form, including polytopic or Takagi-Sugeno model forms. Then, in the second step, Lyapunov's controller design theorems are utilized in the form of linear matrix inequalities (LMIs). The main novelty of this paper is the development of the TP model transformation of the first step. It does not merely transform to TP model form, but it automatically prepares the transformed model to all the specific conditions required by the LMI design. The LMI design can, hence, be immediately executed on the result of the TP model transformation. The secondary objective of this paper is to discuss that representing a dynamic model in TP model form needs to consider the tradeoff between the modeling accuracy and computational complexity. Having a controller with low computational cost is highly desired in many cases of real implementations. The proposed TP model transformation is developed and specialized for finding a complexity minimized model according to a given modeling accuracy. Detailed control design examples are given.

Fault-tolerant voltage-fed PWM inverter AC motor drive systems

Abstract: This paper shows how to integrate fault compensation strategies into two different types of configurations of induction motor drive systems. The proposed strategies provide compensation for open-circuit and short-circuit failures occurring in the converter power devices. The fault compensation is achieved by reconfiguring the power converter topology with the help of isolating and connecting devices. These devices are used to redefine the post-fault converter topology. This allows for continuous free operation of the drive after isolation of the faulty power switches in the converter. Experimental results demonstrate the validity of the proposed systems.

Direct torque control of induction machines with constant switching frequency and reduced torque ripple

Abstract: Direct torque control (DTC) of induction machines is known to have a simple control structure with comparable performance to that of the field-oriented control technique. Two major problems that are usually associated with DTC drives are: switching frequency that varies with operating conditions and high torque ripple. To solve these problems, and at the same time retain the simple control structure of DTC, a constant switching frequency torque controller is proposed to replace the conventional hysteresis-based controller. In this paper, the modeling, averaging, and linearization of the torque loop containing the proposed controller followed by simulation and experimental results are presented. The proposed controller is shown to be capable of reducing the torque ripple and maintaining a constant switching frequency.

Predictive current control of voltage-source inverters

Abstract: A new predictive current controller for a voltage-source inverter is presented in this paper. Practical aspects of realizing the new controller in a system with a digital signal processor (DSP) are considered. Delays introduced by measurements are considered and an improved algorithm with one-period prediction of current is presented. The controller was realized in an experimental system with DSP and field-programmable gate array circuits. Results of the simulations and experiments are presented.

Lagrangian modeling and passivity-based control of three-phase AC/DC voltage-source converters

Abstract: In this paper, we investigate the dc-bus voltage regulation problem for a three-phase boost-type pulsewidth-modulated (PWM) ac/dc converter using passivity-based control theory of Euler-Lagrange (EL) systems. The three-phase PWM ac/dc converters modeled in the a-b-c reference frame are first shown to be EL systems whose EL parameters are explicitly identified. The energy-dissipative properties of this model are fully retained under the d-q-axis transformation. Based on the transformed d-q EL model, passivity-based controllers are then synthesized using the techniques of energy shaping and damping injection. Two possible passivity-based feedback designs are discussed, leading to a feasible dynamic current-loop controller. Motivated from the usual power electronics control schemes and the study of Lee, the internal dc-bus voltage dynamics are regulated via an outer loop proportional plus integral (PI) controller cascaded to the d-axis current loop. Nonlinear PI control results of Desoer and Lin are applied to theoretically validate the proposed outer loop control scheme. The PWM ac/dc converter controlled by the proposed passivity-based current control scheme with outer loop PI compensation has the features of enhanced robustness under model uncertainties, decoupled current-loop dynamics, guaranteed zero steady-state error, and asymptotic rejection of constant load disturbance. Experimental results on a 1.5-kVA PC-based controlled prototype provide verification of these salient features. The experimental responses of a classical linear PI scheme are also included for comparative study.

An amplitude Modulation detector for fault diagnosis in rolling element bearings

Abstract: The purpose of this research is to identify single-point defects in rolling element bearings. These defects produce characteristic fault frequencies that appear in the machine vibration and tend to modulate the machine's frequencies of mechanical resonance. An amplitude modulation (AM) detector is developed to identify these interactions and detect the bearing fault while it is still in an incipient stage of development (i.e., to detect the instances of AM when the magnitude of the characteristic fault frequency itself is not significant). Use of this detector only requires machine vibration from one sensor and knowledge of the bearing characteristic fault frequencies. Computer simulations as well as machine vibration data from bearings containing outer race faults are used to confirm the proficiency of this proposed technique.

Design and implementation of low-profile contactless battery charger using planar printed circuit board windings as energy transfer device

Abstract: This paper paper presents the practical details involved in the design and implementation of a contactless battery charger that employs a pair of neighboring printed circuit board (PCB) windings as a contactless energy transfer device. A prototype contactless battery charger developed for application with cellular phones is used as an example to address the design considerations for the PCB windings and energy transfer circuit, plus demonstrates the performance of the contactless charger adapted to a practical application system.

The generalized discontinuous PWM scheme for three-phase voltage source inverters

Abstract: This paper presents analytical techniques for the determination of the expressions for the modulation signals used in the carrier-based sinusoidal and generalized discontinuous pulse-width modulation schemes for two-level, three-phase voltage source inverters. The proposed modulation schemes are applicable to inverters generating balanced or unbalanced phase voltages. Some results presented in this paper analytically generalize the several expressions for the modulation signals already reported in the literature and new ones are set forth for generating unbalanced three-phase voltages. Confirmatory experimental and simulation results are provided to illustrate the analyses.

A modular control scheme for PMSM speed control with pulsating torque minimization

Abstract: In this paper, a modular control approach is applied to a permanent-magnet synchronous motor (PMSM) speed control. Based on the functioning of the individual module, the modular approach enables the powerfully intelligent and robust control modules to easily replace any existing module which does not perform well, meanwhile retaining other existing modules which are still effective. Property analysis is first conducted for the existing function modules in a conventional PMSM control system: proportional-integral (PI) speed control module, reference current-generating module, and PI current control module. Next, it is shown that the conventional PMSM controller is not able to reject the torque pulsation which is the main hurdle when PMSM is used as a high-performance servo. By virtue of the internal model, to nullify the torque pulsation it is imperative to incorporate an internal model in the feed-through path. This is achieved by replacing the reference current-generating module with an iterative learning control (ILC) module. The ILC module records the cyclic torque and reference current signals over one entire cycle, and then uses those signals to update the reference current for the next cycle. As a consequence, the torque pulsation can be reduced significantly. In order to estimate the torque ripples which may exceed certain bandwidth of a torque transducer, a novel torque estimation module using a gain-shaped sliding-mode observer is further developed to facilitate the implementation of torque learning control. The proposed control system is evaluated through real-time implementation and experimental results validate the effectiveness.

A magnitude/phase-locked loop system based on estimation of frequency and in-phase/quadrature-phase amplitudes

Abstract: This paper introduces a new phase-locked loop (PLL) system. The proposed system provides the dominant frequency component of the input signal and estimates its frequency. The mechanism of the proposed PLL is based on estimating in-phase and quadrature-phase amplitudes of the desired signal and, hence, has application advantages for communication systems which employ quadrature modulation techniques. The studies demonstrate that the proposed PLL also provides a superior performance for power system applications. Derivation of the mathematical model and theoretical stability analysis of the proposed PLL are carried out using dynamical systems theory. Advantages of the proposed PLL over the conventional PLLs are its capability of providing the fundamental component of the input signal which is not only locked in phase but also in amplitude to the actual signal while providing an estimate of its frequency. Computer simulation is used to evaluate its performance. Evaluations confirm structural robustness of the proposed PLL with respect to noise and distortions.

Evaluation of modulation schemes for three-phase to three-phase matrix converters

Abstract: This paper presents a method for evaluating different modulation schemes employed with three-phase to three-phase matrix converters. The evaluation method addresses three important modulator characteristics: the output waveform quality, the input waveform quality and the switching losses associated with the modulation schemes. The method is used to evaluate four different modulation strategies, all based on the direct space-vector modulation approach. Further, regarding the switching losses, the paper proposes a new space-vector approach by which the switching losses can be reduced by 15%-35%, depending on the output load angle. This new modulation approach is applicable whenever the output voltage reference is below half the input voltage and the output voltage quality is then superior to that of the conventional space vector modulation scheme. The functionality of the new modulation scheme is validated by both simulations and experimental results and compared to waveforms obtained by using exiting space vector modulation schemes. The output voltage of the proposed scheme turns out to be comparable to the best of the conventional schemes while the input current is more distorted.

Active voltage clamp in flyback converters operating in CCM mode under wide load variation

Abstract: Active clamp topologies of low power dissipation have become a very attractive solution in order to limit overvoltages in flyback converters. Although many suitable topologies have been introduced for the case of discontinuous conduction mode (DCM), where the duty cycle value depends on the load level, in continuous conduction mode (CCM) it is more difficult to appropriately design such topologies so as to "sense" load changes-due to the small duty cycle divergence under wide load variation. Taking for granted that in order to achieve high power-factor correction in these converters, CCM is a more attractive mode of operation, a drastic solution for this case that will manage to eliminate voltage stresses under wide load changes has become very essential. For this purpose, this paper presents an active clamp topology with small power dissipation, suitable for flyback converters operating in CCM mode. Its main idea is the use of a load-dependent current source, consisting of an auxiliary converter operating in DCM mode. Experimental results highlight the effectiveness of the proposed topology under wide load changes, establishing it as an appropriate solution in order to develop flyback converters, even at the power range of 500 W.

Gain scheduler middleware: a methodology to enable existing controllers for networked control and teleoperation - part I: networked control

Abstract: Conventionally, in order to control an application over a data network, a specific networked control or teleoperation algorithm to compensate network delay effects is usually required for controller design. Therefore, an existing controller has to be redesigned or replaced by a new controller system. This replacement process is usually costly, inconvenient, and time consuming. In this paper, a novel methodology to enable existing controllers for networked control and teleoperation by middleware is introduced. The proposed methodology uses middleware to modify the output of an existing controller based on a gain scheduling algorithm with respect to the current network traffic conditions. Since the existing controller can still be utilized, this approach could save much time and investment cost. Two examples of the middleware applied for networked control and teleoperation with IP network delays are given in these two companion papers. Part I of these two companion papers introduces the concept of the proposed middleware approach. Formulation, delay modeling, and optimal gain finding based on a cost function for a case study on DC motor speed control with a proportional-integral (PI) controller are also described. Simulation results of the PI controller shows that, with the existence of IP network delays, the middleware can effectively maintain the networked control system performance and stabilize the system. Part II of this paper will cover the use of the proposed middleware concept for a mobile robot teleoperation.

Human-following mobile robot in a distributed intelligent sensor network

Abstract: The robots that will be needed in the near future are human-friendly robots that are able to coexist with humans and support humans effectively. To realize this, humans and robots need to be in close proximity to each other as much as possible. Moreover, it is necessary for their interactions to occur naturally. It is desirable for a robot to carry out human following, as one of the human-affinitive movements. The human-following robot requires several techniques: the recognition of the target human, the recognition of the environment around the robot, and the control strategy for following a human stably. In this research, an intelligent environment is used in order to achieve these goals. An intelligent environment is a space in which many sensors and intelligent devices are distributed. Mobile robots exist in this space as physical agents providing humans with services. A mobile robot is controlled to follow a walking human using distributed intelligent sensors as stably and precisely as possible. The control law based on the virtual spring model is proposed to mitigate the difference of movement between the human and the mobile robot. The proposed control law is applied to the intelligent environment and its performance is verified by the computer simulation and the experiment.

Unified analysis of switched-capacitor resonant converters

Abstract: A family of switched-capacitor resonant circuits using only two transistors is presented. The circuit operates under zero-current switching and, therefore, the switching loss is zero. It also offers a wide choice of voltage conversions including fractional as well as multiple and inverted voltage conversion ratios.

Virtual sensor: application to vehicle sideslip angle and transversal forces

Abstract: This paper compares four observers (virtual sensors) of vehicle sideslip angle and lateral forces. The first is linear and uses a linear vehicle model. The remaining observers use an extended nonlinear model. The three nonlinear observers are: extended Luenberger observer, extended Kalman filter and sliding-mode observer. Modeling, model simplification, and observers are described, and an observability analysis is performed for the entire vehicle trajectory. The paper also deals with three different sets of sensors to see the impact of observers results. Comparison is first done by simulation on a valid vehicle simulator, and then observers are used on experimental data. Our study shows that observers are more accurate than simple models as regards unmeasurable variables such as sideslip angle and transversal forces. It also shows that speed of center of gravity is not an indispensable variable here.

Induction machine fault detection using SOM-based RBF neural networks

Abstract: A radial-basis-function (RBF) neural-network-based fault detection system is developed for performing induction machine fault detection and analysis. Four feature vectors are extracted from power spectra of machine vibration signals. The extracted features are inputs of an RBF-type neural network for fault identification and classification. The optimal network architecture of the RBF network is determined automatically by our proposed cell-splitting grid algorithm. This facilitates the conventional laborious trial-and-error procedure in establishing an optimal architecture. In this paper, the proposed RBF machine fault diagnostic system has been intensively tested with unbalanced electrical faults and mechanical faults operating at different rotating speeds. The proposed system is not only able to detect electrical and mechanical faults, but the system is also able to estimate the extent of faults.

Modeling of power electronic loads in AC distribution systems using the generalized State-space averaging method

Abstract: Most of the loads in ac distribution systems have positive incremental impedance characteristic. However, power electronic loads, when tightly regulated, sink constant power from the system. Therefore, they have negative incremental impedance characteristic. This can cause negative impedance instability. Power electronic loads usually have a controlled or uncontrolled rectifier at the front end. In this paper, these loads are modeled using the generalized state-space averaging method. An assessment of their effects in ac distribution systems is also presented. Experimental results are presented to verify the proposed analysis.

A new modulation method to reduce common-mode voltages in multilevel inverters

Abstract: This paper proposes a new modulation strategy for multilevel inverters, which selects voltage vectors that generate zero common-mode voltage in the load, working at low switching frequency. Experimental results confirm that the method is highly effective and simple to implement in a modern microprocessor. The voltage distortion (total harmonic distortion), the number of commutations, and the linearity are also studied. Finally, it is concluded that the proposed strategy is highly suited for inverters with a high number of levels.

Dual-inverter control strategy for high-speed operation of EV induction motors

Abstract: An integrated starter/alternator (ISA) is normally designed to have high pole structure (10-14 poles) for high starting torque. However, its back electromotive force (EMF) at the peak revolutions per minute should be less than its battery voltage for the power flow control. For example, the back-EMF of a 12-pole ISA should be 42 V at 6000 r/min. These types of conflicting requirements lead to a nonclassical motor design that has extremely large field-weakening range (8:1/spl sim/10:1). In this paper, we are considering the use of an induction machine instead of a permanent synchronous machine. As an idea for solving the voltage limit problem, two inverters are utilized with an objective of sharing the required voltage. The secondary inverter only takes care of the reactive voltage component that grows very fast in high-speed operation. Therefore, an extra voltage source is not required for the secondary inverter. Only a capacitor bank suffices for the secondary inverter.

Problems associated with the direct torque control of an interior permanent-magnet synchronous motor drive and their remedies

Abstract: This paper investigates problems associated with the implementation of a direct torque control (DTC) strategy for an interior permanent-magnet synchronous motor drive. The DTC technique is increasingly drawing attention because of elimination of current controllers and, hence, their inherent delays, and elimination of the rotor position sensor. The latter advantage perhaps is the main impetus for considering this new approach of torque control. Problems associated with this controller, namely, the offset in the current measurements, the stator resistance variation, and the requirement of initial rotor position are addressed in this paper. Ways of mitigating of these problems are also investigated in this paper. These are evaluated with modeling and experimental studies, results of which are also presented.

Modeling and analysis of multiconverter DC power electronic systems using the generalized state-space averaging method

Abstract: This paper presents a modular approach for the modeling and simulation of multiconverter DC power electronic systems based on the generalized state-space averaging method. These systems may consist of many individual converters connected together to form large and complex systems. In addition to simplifying the analysis procedure, by using the proposed method, the time step for analysis of the system can be increased. Therefore, the required computation time and computer memory for complex systems can be reduced considerably. In this paper, after introducing the proposed approach, results of applying the method to a representative system are presented.