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This paper proposes an on/off control of boost power factor correction (PFC) converters to improve the light-load efficiency in paralleled power supply units (PSUs) for servers. The proposed scheme operates the PFC stages of two paralleled PSUs alternately during one cycle of a 60-Hz ac input only at light loads. This improves the light-load efficiency without deteriorating the heavy-load efficiency by reducing load-independent losses such as capacitive turn-on and core losses. In addition, the proposed scheme alleviates the harmonic distortion by reducing the discontinuous conduction mode region. Experimental results from 1.6-kW PFC boost converters are shown to verify the proposed work.

In this paper, a simple and low-cost open-circuit fault detection and identification method for a pulse-width modulated (PWM) voltage-source inverter (VSI) employing a permanent magnet synchronous motor is proposed. An open-circuit fault of a power switch in the PWM VSI changes the corresponding terminal voltage and introduces the voltage distortions to each phase voltage. The proposed open-circuit fault diagnosis method employs the model reference adaptive system techniques and requires no additional sensors or electrical devices to detect the fault condition and identify the faulty switch. The proposed method has the features of fast diagnosis time, simple structure, and being easily inserted to the existing control algorithms as a subroutine without major modifications. The simulations and experiments are carried out and the results show the effectiveness of the proposed method.

This paper proposes a simple position observer based on the instantaneous power and a tuning procedure for the proposed observer in driving the surface-mounted permanent magnet synchronous motor. In the instantaneous power of a three-phase system, the imaginary and real powers have the information related to the position and velocity. Using the instantaneous power, the difference between real rotor position and estimated rotor position is calculated. For easy design, gain parameters are described as a bandwidth of position observer. The proper bandwidth is expressed in terms of the desired load transient response, system inertia, and permitted acceleration range. Also, the sensitivity of phase resistance and inductance is analyzed. The described mathematical results show the necessity of accurate parameter information. Simulation and experimental results show the validity of the proposed design method and analysis.

A transformer magnetizing current offset for a phase-shift full-bridge (PSFB) converter is dealt with in this paper. A model of this current offset is derived and it is presented as a first-order system having a pole at a low frequency when the effects from the parasitic components and the switching transition are considered. A digital offset compensator eliminating this current offset is proposed and designed considering the interference in an output voltage regulation. The performances of the proposed compensator are verified by experiments with a 1.2-kW PSFB converter. The saturation of the transformer is prevented and the efficiency is improved by this compensator.

A novel method of the gate signal generation for the interleaved LLC converter is proposed, which is based on the relationship between the output signal of a toggle flip-flop having the double period of the input clock signal and the output gate signal of the LLC controller having almost half-duty cycle. The gate signals for the master and slave converters are generated using the rising and falling edge instants from the original control gate signal of the controller, respectively. Therefore, the required 90° phase difference between two signals can be always kept at any instant and at any output load condition. Copyright © 2010 John Wiley & Sons, Ltd.

A new double-ended type zero-voltage switching (ZVS) half-bridge zeta (HBZ) converter employing a double-ended rectifier (DER) is proposed. The proposed DER for the HBZ converter provides a bidirectional powering path in the rectifier. As a result, the improved voltage waveform of the rectifier reduces the output filter size and voltage stresses on rectifier components. Moreover, it offers a wide ZVS range. In addition, to minimize the secondary snubber loss, a simple lossless snubber is adopted. The operational principles and characteristics of the proposed converter are to be analyzed and verified experimentally.

A conventional phase-shift full-bridge (PSFB) converter has a serious voltage oscillation problem across the secondary rectifier diodes. To overcome this problem, a new voltage oscillation reduction technique (VORT), which effectively reduces the rectifier voltage oscillation by a simple nondissipative manner, is proposed. The concept of VORT is to utilize the operation of leading-leg transition, which does not cause severe rectifier voltage oscillation, to the lagging-leg transition. It is simply implemented by employing only a resonant capacitor in series with the transformer secondary and a small magnetizing inductance of the transformer without any lossy components. Moreover, the VORT can realize zero-voltage switching for all switches over a wide load range using the energy that is stored in the transformer magnetizing inductor and output filter inductor. The concept, operational principle, oscillation analysis, and design considerations of VORT are presented and verified experimentally.

Generally, there exists a voltage distortion or nonlinear voltage gain between the reference and output voltages in a pulsewidth-modulation (PWM) voltage source inverter (VSI). Nonlinearity varies with operating conditions, such as the temperature, direct current (dc) bus voltage, and phase current level. Also, the nonlinearity affects the machine current distortion, torque pulsations, and degradation of control performance. In this paper, the nonlinearity in a PWM VSI is analyzed and a new online estimation method based on the model reference adaptive system is proposed to compensate the time varying voltage distortion, considering the parameter uncertainty caused by the temperature variation for a permanent magnet synchronous motor. The simulation and experimental results show the effectiveness of the proposed voltage difference estimator.

A new maximum power point tracker (MPPT) for a grid-connected photovoltaic system without solar array current sensor is proposed. The solar array current information is obtained from the sliding-mode observer and fed into the MPPT to generate the reference voltage. The parameter values such as capacitances can be changed up to 50% from their nominal values, and the linear observer cannot estimate the correct state values under the parameter variations and noisy environments. The structure of a sliding-mode observer is simple, but it shows the robust tracking property against modeling uncertainties and parameter variations. In this paper, the sliding-mode observer for the solar array current has been proposed to compensate for the parameter variations. The mathematical modeling and the experimental results verify the validity of the proposed method

A new online voltage distortion observation method against the motor parameter uncertainty of a permanent-magnet synchronous motor is proposed to estimate time-varying voltage distortion of a pulsewidth-modulation voltage-source inverter. This new estimation method is based on the model reference adaptive system.

A new improved robust variable structure controller is presented to provide an accurately prescribed tracking performance for brushless direct drive (BLDD) servo motors (SM) under uncertainties and load variations. A special integral sliding surface suggested for removing the reaching phase problems can define its ideal sliding mode and virtual ideal sliding trajectory from an initial position of SM. The tracking error caused by the nonzero value of the sliding surface is derived. A corresponding continuous control input with the disturbance observer is suggested to track a predetermined virtual ideal sliding trajectory within a prescribed value under all the uncertainties and load variations. The usefulness of the proposed algorithm is demonstrated through the comparative simulations for a BLDD SM under load variations.

This paper presents a new single-stage single-switched forward converter with magnetic coupled nondissipative snubber, which gives good power factor correction (PFC), low current harmonic distortion, and tight output voltage regulation. The proposed converter features low switch current and voltage stresses, essential for the design of a single-stage power factor correction converter. The prototype shows that the IEC1000-3-2 requirements are met satisfactorily with nearly unity power factor. This proposed converter with magnetic coupled nondissipative snubber is particularly suited for power supply applications with low power level.

An analysis and design of single-stage, single-switch bi-flyback ac/dc converter is presented. The main flyback stage controls the output power from the link capacitor voltage with Discontinuous Conduction Mode (DCM) or Continuous Conduction Mode (CCM) operation, while an auxiliary flyback stage supplies the power to the output directly from ac line input with DCM operation. This scheme can effectively reduce the voltage stress on the link capacitor and can achieve the power factor correction (PFC) without a dead band at line zero-crossings, which reduces the harmonic distortion in ac line current. Theoretical analysis of the converter is presented and design guidelines to select circuit components are given. The experimental results on a 60 W (15 V, 4 A), 100 kHz ac/dc converter show that maximum link voltage and maximum efficiency are around 415 V and 82%, respectively. The power factor is above 0.96 under universal line input and load conditions.

A new on-line dead-time compensation method for a permanent magnet (PM) synchronous motor drive is proposed. Using a simple disturbance observer without any additional circuit and off-line experimental measurement, disturbance voltages in the rotor reference dq frame caused by the dead time and nonideal switching characteristics of power devices are estimated in an on-line manner and fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Simulations and experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.

An improved stationary-frame-based current control scheme for a permanent-magnet synchronous motor (PMSM) is presented. To improve the current control performance in the stationary frame, the disturbance is estimated using the time-delay control. The proposed scheme is implemented on a PMSM using digital signal processor TMS320C31 and the effectiveness is verified through the comparative experiments.

A voltage-balanced phase-shifted three-level DC/DC converter is proposed. Its switch voltage stress is ensured to be only one-half of the input voltage and its four-step operation can reduce considerably the output inductor current ripple. Moreover, it features a small filter, no voltage unbalance problem, static/dynamic sharing of the switch voltage, high-efficiency, and high-power density. It is very suitable for high power converters operating from a high-input voltage.

A new discontinuous modulation method based on space-vector control is proposed and analyzed. The proposed technique employs a pulse-dropping method and is designed in the time domain. It features a very wide modulation range while maintaining the required waveform qualities and switching numbers in the overmodulation region. Since the modulation method and modulation index equation are simple, the proposed technique can be easily implemented by software and is applicable to the overmodulation region in ac motor drives. The performance indexes are discussed and experiments have been performed.

In this work, an on-line dead-time compensation method based on a time delay control for a pulse-modulation (PM) synchronous motor drive is presented. Disturbance voltages caused by the dead time are estimated on-line without any additional circuits nor off-line experimental measurements. The estimated disturbance voltages are fed back to the voltage reference as compensation. The proposed method is applied to a PM synchronous motor drive system and implemented using a DSP TMS320C31. The experimental results show the effectiveness of the proposed method.

A very simple control approach using a neural network for the robust position control of a permanent magnet synchronous motor (PMSM) is presented. The linear quadratic controller plus feedforward neural network compensator is employed to obtain the robust PMSM system approximately linearized using a field-orientation method for an AC servo. The neural network is trained in on-line phases and a feedforward recall and error back-propagation training compose this neural network. Since the total number of nodes is only eight, this system is realized easily by the general microprocessor. During normal operation, the input–output response is sampled and the weighting value is trained multi-times by an error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. The state space analysis is also performed to obtain the state feedback gains systematically. In addition, the robustness is also obtained without affecting overall system response. A floati...

In this paper, a new predictive current controller for a permanent magnet synchronous motor (PMSM) considering delays is presented. In a full digital current control system for a PMSM, there are inevitable delays in calculating and applying the inverter output voltages to the motor terminals. A predictive current controller implemented in a full digital system has serious problems such as the oscillation and large overshoot. A discussion of compensation methods to cope with the nonlinearities of the real system is also presented. The proposed current controller has been analyzed, and the experimental results are shown to prove the feasibility and effectiveness of the proposed predictive current controller using a prototype 750 W PMSM servo drive system.

In this paper, a dead-beat type digital controller has been introduced to overcome the problems of a conventional direct torque controller. The proposed induction motor drive with a digital dead-beat controller shows good transient response and negligible steady-state error even at a low switching frequency, which is needed for high power machines used for transportation. Including the rotor dynamics, the stability condition and steady-state error of the proposed control system have been examined in the z-plane. In addition, the good performance has been verified through the simulation and experiment. The flux and torque controllers have been designed with only stator voltage equations in the stator flux reference frame in order to take advantages of the direct torque control. Therefore, the proposed flux and torque controllers have simple forms and can be easily designed and implemented.

A DSP-based high speed sensorless control for a brushless DC (BLDC) motor using a DC link voltage control scheme is presented. By operating the BLDC motor in a highspeed range, the drive system can have a small size and be light weight at the same output rating. In the existing sensorless control schemes, the PWM technique is generally used as a speed control. However, since the PWM and inverter commutation cannot be performed independently, a significant commutation delay may exist in a high-speed region. On the other hand, using the DC linkvoltage control scheme, the inverter is operatedwiththe squarewave of 120° conduction and the speed control is achieved by regulating the DC link input voltage of the inverter through the chopper. By using this technique, since the voltage control and commutation can be achieved independently, a commutating delay does not exist even in a high speed region. Also, the phase current can have a waveform similar to the rectangular wave and the terminal voltage is more effi...

A nonlinear speed control for a permanent-magnet (PM) synchronous motor using a simple disturbance estimation technique is presented. By using a feedback linearization scheme, the nonlinear motor model can be linearized in the Brunovski canonical form, and the speed controller can be easily designed based on the linearized model. This technique, however, gives an undesirable output performance under the mismatch of the system parameters and load conditions. An adaptive linearization technique and a sliding-mode control technique have been reported. Although good performance can be obtained, the controller designs are quite complex. To overcome this drawback, the controller parameters are estimated by using a disturbance observer theory where the disturbance torque and flux linkage are estimated. Since only the two reduced-order observers are used for the parameter estimation, the observer designs are considerably simple and the computational load of the controller for parameter estimation is negligibly small. The nonlinear disturbances caused by the incomplete linearization can be effectively compensated by using this control scheme. Thus, a desired dynamic performance and a zero steady-state error can be obtained. The proposed control scheme is implemented on a PM synchronous motor using a digital signal processor (TMS320C31) and the effectiveness is verified through the comparative simulations and experiments.

A single-stage power-factor-correction AC/DC converter with a simple link voltage suppressing circuit (LVSC) for the universal line application is proposed. A portion of the energy charged in a boost inductor is directly transferred to a load via LVSC without passing the link capacitor. Using simple circuitry, a low link voltage can be realized without input current deadbands at line zero crossings. The proposed converter is analyzed and design guidelines for the proper operation of a converter are given. A universal input (90-265-V/sub rms/) prototype converter with 5-V 12-A output is implemented to verify performance. The experimental results show that the maximum link voltage stress and efficiency are about 447 V and 81%, respectively. The power factor is above 0.96 under the universal line condition when the load is higher than 30%.

A simple and robust digital current control technique of a permanent magnet (PM) synchronous motor using a time delay control approach is presented. Among the various current control schemes for a voltage source inverter-fed PM synchronous motor drive, the predictive control is known to give a superior performance. This control technique, however, requires the full knowledge of machine parameters and operating conditions, and gives an unsatisfactory response under the parameter mismatch between the motor and controller. To overcome such a limitation, the disturbances caused by the parameter variations are estimated by using a time delay control approach and used for the computation of the reference voltages by a simple feedforward control. Thus, the steady-state control performance can be significantly improved in an extremely simple manner, while retaining the good characteristics of the predictive control such as the good transient response and stable inverter operation. The proposed control scheme is implemented on a PM synchronous motor using the software of DSP TMS320C30 and the effectiveness is verified through the comparative simulations and experiments.

The single-current sensor technique obtaining three phase currents from only a DC-link current sensor has been applied to reduce the cost and increase the reliability for various voltage-fed PWM inverters; however, in this technique there are some practical problems, such as unreliable detection of phase currents andphase shift. A new method that overcomes these problems by employing the estimation scheme with identified system parameters is proposed. The Space Vector PWM (SVPWM) strategy is modified to generate the switching pattern adequate for the proposed method. To obtain a good detection in spite of parameter uncertainties, system parameters used in the estimation method are identified using a recursive least square method (RLSM). Experimental results show that the proposed scheme not only provides a very good detection method for three phase currents without current sensors, but also identifies system parameters very well. This proposed method is very simple, has a small detection error, and gives ...

An integrated zero current switching (ZCS) quasiresonant converter (QRC) for the power factor correction with a single switch is presented in this paper. The power factor correction can be achieved by the discontinuous conduction mode (DCM) operation of an input current. The proposed converter offers good power factor, low level line current harmonics, and tight output regulation. The design equations are suggested and a prototype converter has been designed based on these equations and experimentally investigated. The input current waveform of the prototype shows less than 15% of total harmonic distortion. Also, the efficiency and power factor of about 84% and 0.977, respectively, can be obtained under the rated condition.

A digital signal processor (DSP)-based robust nonlinear speed control of a permanent magnet synchronous motor (PMSM) is presented. A quasi-linearized and decoupled model including the influence of parameter variations and speed measurement error on the input-output feedback linearization of a PMSM is derived. Based on this model, a boundary layer integral sliding mode controller is designed and compared to a feedback linearization-based controller that uses proportional plus derivative (PD) controller in the outer loop. To show the validity of the proposed control scheme, DSP-based experimental works are carried out and compared with the conventional control scheme.

A simple source voltage-clamped resonant link (SVCRL) inverter is proposed to clamp the DC-link voltage to the input source voltage and reduce the current rating of a resonant inductor. The current control of a permanent magnet synchronous motor (PMSM) employing a predictive current control technique (PCCT) for the SVCRL, inverter is also investigated to overcome the disadvantage of the current-regulated delta modulation (CRDM) control technique. By employing the PCCT based on the discrete model of a PMSM and estimation of back electromotive force (EMF), the minimized current ripple with a small number of switchings can be obtained. Finally, the comparative computer simulation and experimental results are given to show the usefulness of the proposed technique.

An improved digital current control technique of a permanent magnet (PM) synchronous motor with a simple feedforward disturbance compensation scheme is presented. Among the various current control schemes for an inverter-fed PM synchronous motor drive, the predictive control is known to give a superior performance. This scheme, however, requires the full knowledge of machine parameters and operating conditions, and cannot give a satisfactory response under the parameter mismatch. To overcome such a limitation, the disturbances caused by the parameter variations are estimated by using a disturbance observer theory and used for the computation of the reference voltages by a feedforward control. Thus, the steady state control performance can be significantly improved with a relatively simple control algorithm, while retaining the good characteristics of the predictive control. The proposed control scheme is implemented on a PM synchronous motor using the software of DSP TMS320C30 and the effectiveness is verified through the comparative simulations and experiments.

A new current control technique is presented for three-phase PWM inverterfed AC drives. The features of several existing approaches are analyzed and an integral variable structure control (IVSC) is proposed as an effective way of realizing the high-performance current control. The characteristics of the proposed IVSC are investigated and the design method is presented for the AC drives associated with a voltage-fed PWM inverter. By employing the proposed control, a robust control performance against the parameter uncertainties is obtained in both transient and steady states. The proposed control is applied to the three-phase induction motor drives and the performance improvement is well demonstrated through the simulations and experiments.

A DSP-based nonlinear speed control of a permanent magnet synchronous motor (PMSM), which is robust to unknown parameter variations and speed measurement error, is presented. The model reference adaptive system (MRAS)based adaptation mechanisms for the estimation of slowly varying parameters are derived using the MIT rule. For the disturbances or quickly varying parameters, a quasi-linearized and decoupled model including the influence of parameter variations and speed measurement error on the nonlinear speed control of a PMSM is derived. Based on this model, a boundary layer integral sliding mode controller to improve the robustness and performance of a PMSM drive is designed and compared with the conventional controller. To show the validity of the proposed control scheme, simulations and experimental works are carried out and compared with the conventional control scheme.

A current control technique for a permanent magnet synchronous motor (PMSM) with a simple disturbance estimation scheme is proposed. Among the various current control schemes for a PMSM drive, predictive control is known to give a superior performance. This scheme, however, requires the full knowledge of motor parameters. To overcome such a limitation, the disturbances caused by the parameter variations will be estimated by using disturbance observer theory and used for the calculation of the reference voltages by feedforward control. Thus, the control performance can be significantly improved with a relatively simple control algorithm. The proposed control scheme is implemented on a PMSM using DSP TMS320C30 and the effectiveness is verified through the comparative experiments.

A novel isolated zero voltage switching (ZVS) PWM power factor correction circuit is proposed. This circuit provides the input power factor correction and direct conversion from AC line to 48VDC bu...

A combined buck and boost push-pull quantum series resonant rectifier (PPQSRR) is newly proposed to achieve power factor correction without start-up inrush current. With the proposed control method and circuitry, a high power factor and wide range of output voltage without an inrush current can be obtained.

A predictive current control technique for a permanent magnet synchronous motor (PMSM) employing a resonant DC link inverter is proposed to overcome the disadvantage of the current regulated delta modulation (CRDM) control technique. Also, the discrete model of a PM synchronous motor and estimation of back EMF are investigated. Based on this discrete model and estimated back EMF, a predictive current control technique is newly developed. Using the proposed control technique, the minimized current ripple with a small number of switchings can be obtained. Finally, the comparative computer simulation and experimental results are given to show the usefulness of the proposed technique.

A new instantaneous torque-control strategy is presented for high-performance control of a permanent magnet (PM) synchronous motor. In order to deal with the torque pulsating problem of a PM synchronous motor in a low-speed region, new torque estimation and control techniques are proposed. The linkage flux of a PM synchronous motor is estimated using a model reference adaptive system technique, and the developed torque is instantaneously controlled by the proposed torque controller combining a variable structure control (VSC) with a space-vector pulse-width modulation (PWM). The proposed control provides the advantage of reducing the torque pulsation caused by the nonsinusoidal flux distribution. This control strategy is applied to the high-torque PM synchronous motor drive system for direct-drive applications and implemented by using a software of the digital signal processor (DSP) TMS320C30. The simulations and experiments are carried out for this system, and the results demonstrate the effectiveness of the proposed control.

A new simple control for the robust position control of a brushless direct drive (BLDD) motor using fuzzy logic controller (FLC) is presented. The integral-proportional (IP) position controller plus fuzzy logic speed controller is employed to obtain the robust BLDD motor system, which is approximately linearized using the field-orientation method for an AC servo. The speed FLC for a BLDD motor has the two rule tables. One is the coarse control rule table for the transient state and another is the fine control rule table for the steady state. The possibility of applying the FLC with simple structure to the AC servo system is investigated in detail. The overall system is controlled by using the microprocessor and the robustness is also obtained without affecting the overall system response. The experimental results show the performance of each control algorithm for the BLDD machine.

In this paper, a high frequency and soft-switched AC/DC rectifier employing a series-type resonant circuit is proposed to obtain the sinusoidal AC line current. Using the proposed rectifier, the high power factor and low harmonic currents are obtained in the AC line. Furthermore, several advantages such as the high power density and wide output voltage range can also be available. To regulate the output voltage of the proposed circuit, the digital proportional-integral (PI) controller is used whose sampling time corresponds to the zero-crossing point of the AC line voltage. Including this controller, the model for the closed-loop system is developed in order to examine the stability and dynamic characteristics. With this model, the gain of the PI-controller is determined by the pole assignment technique and the closed-loop dynamics is investigated by the root locus plots. A good agreement is made between the simulated and experimental results.

An overcurrent protection control technique of a zero current switched (ZCS) series resonant rectifier (SRR) is proposed. With the proposed control technique, the rectifier can be operated safely, and optimum rating devices can be used. By employing a zero current switching operation for all switches, the series resonant rectifier can be operated at high switching frequencies and high power levels. Based on the dynamic model of this rectifier, the characteristics of an internal operation are explored. With the proposed control technique, the unity power factor without an overcurrent and a wide range of output voltage can be obtained.

A new output voltage control technique is proposed to obtain the improved buck-boost operation of the quantum series resonant power converter (QSRC). The new nonlinear dynamic model of QSRC is first derived and the cross-coupled nonlinear term existing in the output voltage dynamics is decoupled by using control methods such as the periodic control of the boosting switch (PCBS) and the resonant current control (RCC). By applying the state-space averaging concept to the decoupled dynamics, two linear large signal averaged models are obtained for PCBS and RCC schemes. Using the proposed technique, the flux imbalance problem of the isolation transformer and the robustness of the output voltage response can be easily considered. This technique can also be widely applicable to the cascade buck-boost power converter, which can be implemented by inserting a boosting switch between the output filter inductor and the ripple capacitor of the forward power converter. The validity of the proposed scheme is confirmed by the computer simulations and the experiments.

To obtain a stable output voltage from a recently-developed rectification circuit called a quantum boost series resonant rectifier (QBSRR), two control schemes, digital PI (proportional-integral) control and deadbeat control, are derived for a computer-based system. Since the output voltage regulation loop has a sampling time corresponding to the zero crossing point of the AC line voltage, the output voltage can be controlled regardless of the 120 Hz ripple component. By deriving a simple and exact model for the current program loop (open loop) of a QBSRR and using the pole-assignmenl technique, the controller gains can be systematically designed in the digital PI control scheme. The deadbeat control scheme is also developed to maintain fast dynamic performance in the presence of any load variations. In this control scheme, the controller gain is adjusted in accordance with the load information using a load estimation method. Simulation and experimental results are presented to verify the usefuln...

A quantum series resonant inverter (QSRI)is utilized as a DC motor drive. A sampled-data dynamic model including both a QSRI and a DC motor is proposed to obtain an effective analytical tool. Based on this model, an optimal predictive resonant current (OPRC) control technique that minimizes the current error is developed and compared with other types of current control techniques. In respect of the current ripple and offset current, near optimum operational mode patterns can be obtained using the proposed OPRC control technique. The usefulness of an OPRC-controlled QSRI for a DC motor drive with four-quadrant operation is verified by employing motor current and speed controllers in simulation and experiment.

The continuous, accurate, and robust sliding mode tracking controller based on a disturbance observer for a brushless direct drive servo motor (BLDDSM) is presented. Although the conventional sliding mode control (SMC) or variable structure control (VSC) can give the desired tracking performance, there exists an inevitable chattering problem in control which is undesirable for a direct drive system. With the proposed algorithm, not only are the chattering problems removed, but also the prescribed tracking performance can be obtained by using the efficient compensation of the disturbance observer. The design of the sliding mode tracking controller for the prescribed, accurate, and robust tracking performance without the chattering problem is given based on the results of the detailed stability analysis. The usefulness of the proposed algorithm is demonstrated through the computer simulations for a BLDDSM under load variations. >

This paper proposes the reduction technique of commutation torque ripple in brushless DC motor drive. The proposed method modulates the current slope of the incoming phase and the outgoing phase in commutation interval respectively. These slopes can be modulated by using specific duty ratio during commutation. Since the proposed method controls the commutation interval, it does not require additional control loop and sensing circuit to acquire the interval. Hence, motor drive system can be achieved at a low cost with the proposed scheme. The motor drive scheme with the proposed technique is implemented by digital controller employed digital signal processor. The experimental results verify that the proposed method is valid and useful in reduction of commutation torque ripple.

This paper proposes a simple position estimator based on instantaneous power and a tuning procedure for the proposed estimator in driving surface mounted permanent magnet synchronous motor. In the instantaneous power of three phase system, the imaginary and real power has the information related to the position and velocity. Using the instantaneous power, the difference between real rotor position and estimated rotor position is calculated. For easy design, gain parameters are described as bandwidth of position estimator. And, the proper bandwidth is expressed as the desired load transient response, system inertia and permitted acceleration range. Also, the sensitivity of phase resistance and inductance is analyzed. The described mathematical results show the necessity of accurate parameter information. Simulation and experimental results show the validity of the proposed design method and analysis.

A transformer magnetizing current offset for a phase-shift full-bridge (PSFB) converter is dealt in this paper. A model of this current offset is derived and it is presented as a first order system having a pole at a low frequency when the effects from the parasitic components and the switching transition are considered. A digital offset compensator eliminating this current offset is proposed and designed considering the interference in an output voltage regulation. The performances of the proposed compensator are verified by experiments with a 1.2kW PSFB converter. The saturation of the transformer is prevented by this compensator.

In general, a zero-voltage switching (ZVS) condition of boost-integrated DC-DC converters is load-dependent and lost at a light load due to an insufficient energy stored in a leakage inductor. To extend a ZVS load range without increasing an external leakage inductor at a light load condition, a frequency modulation (FM) control is proposed. By modulating a switching frequency adaptive to a load current at a desired load range, ZVS can be recovered through an energy stored in a boost inductor so that the switching losses can be significantly reduced. Thus, the conversion efficiency at a light load condition can be improved. A ZVS boost integrated flyback (BIF) converter with a voltage doubler rectifier (VDR) is presented to apply the proposed control method as an example. Experimental results from a digitally implemented prototype are shown to demonstrate the proposed work.

A discrete time domain modelling is presented for the pulse-width modulated series resonant converter (PWM-SRC) with a discontinuous current mode. This nonlinear system is linearized about its equilibrium state to obtain a linear discrete time model for the investigation of small signal performances such as the stability and transient response. The usefulness of this small signal model is verified by dynamic simulation.

A method for the robust position control of brushless DC (BLDC) motors is presented. The linear quadratic controller plus load torque observer is used to obtain an approximately linearized robust BLDC motor system for an AC servo, using the field-orientation method. The gains are obtained systematically from a discrete state space analysis. The robustness is obtained without affecting the overall system response. The load disturbance is detected by a zero-observer of the unknown and inaccessible input, and is feedforward compensated without requiring noisy current information. The overall system is controlled using a microprocessor, and the performance of each control algorithm is compared with both the simulation and the experimental results for two types of machines, a BLDC motor and a brushless direct drive (BLDD) motor. >