Han-Woong Park

A new approach for minimum-torque-ripple maximum-efficiency control of BLDC motor

Torque-ripple control of the brushless DC motor has been the main issue of the servo drive systems in which the speed fluctuation, vibration, and acoustic noise should be minimized. Most methods for suppressing the torque ripples require Fourier series analysis and either iterative or least-mean-square minimization. In this paper, a novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms which include the case of three-phase unbalanced conditions. As a result, the proposed approach provides a simple way to obtain optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results.

A novel high-performance voltage regulator for single-phase AC sources

Regulation of load voltage in single-phase applications is becoming an important issue for critical loads. This paper presents a novel high-performance single-phase voltage regulator which has a common arm between the rectifier and inverter, and adopts an appropriate switching strategy. The proposed voltage regulator employs six switches and can be implemented by only one three-phase inverter module. The proposed voltage regulator has the capability of delivering sinusoidal input current with unity power factor, good output voltage regulation, and bidirectional power flow. For these purposes, a fully digital controller is designed and implemented using a TMS320F240 digital signal processor. In addition, a novel low-cost AC capacitor is also presented. This type of capacitor requires two DC capacitors and two diodes, enabling low-cost and compact manufacturing. Consequently, the complete voltage regulator system, which is mainly suitable for an uninterruptible power supply as well as reactive or nonlinear loads, can be constructed compactly and inexpensively. Experimental results are presented to verify the feasibility of the proposed voltage regulator system.

A robust control of permanent magnet synchronous motor using load torque estimation

Field-oriented control has made permanent magnet synchronous motor drives possible for the high performance applications. With a high-performance field oriented control system, the torque and flux producing components of the stator current are decoupled so that the independent torque and flux controls are possible as in DC motors. Thus, a high quality control of the stator current vector is essential for the successful implementation of the field-oriented control since the current controller has a direct influence on the drive performance. The current control schemes for a voltage source inverter-fed PMSM drive can be classified as hysteresis control, ramp comparison control, synchronous frame proportional-integral (PI) control, and predictive control. Among them, the predictive control is known to give a superior performance. However, this control scheme requires the information on the machine parameters and operation conditions with the sufficient accuracy, and cannot give a satisfactory response under parameter mismatch. To overcome such a limitation, the robust speed control of a PMSM using sliding mode control with load torque estimation is presented. The load disturbance is detected by the observer of an unknown and inaccessible input, and is compensated by the feedforward current. The proposed control schemes are applied to PMSM driven by a three-phase voltage-fed PWM inverter and the effectiveness is verified through the comparative simulations.

Reference frame approach for torque ripple minimization of BLDCM over wide speed range including cogging torque

Torque ripple control of brushless DC motor has been the main issue of servo drive systems in which the speed fluctuation, vibration and acoustic noise should be minimized. In this paper, the novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms including even the case of 3 phase unbalanced condition. As a result, the proposed approach provides a simple and clear way to obtain the optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results.

Development of a high performance single-phase voltage regulator composed of 3 arms bridge

Regulation of load voltage in single-phase application is becoming an important issue for critical loads. This paper presents a novel high performance single-phase voltage regulator which has a common arm between the AC/DC and DC/AC power converters and adopts an appropriate switching strategy. As a result, the proposed voltage regulator can reduce the number of switching devices and system loss, while maintaining the capabilities of power factor correction and good output voltage regulation. In addition, novel low-cost AC capacitor using two DC capacitors is also presented. Therefore, the whole voltage regulator system can be more compact, simpler and less expensive than conventional designs. The fully digital controller is designed using a high-speed DSP, and the proposed system is validated through experimental results.

A novel high performance position sensorless control of switched reluctance motor drives

In this paper, a sliding mode observer is applied to eliminate the shaft position encoder of a switched reluctance motor (SRM) drive. The sliding mode observer estimates rotor position and velocity to control the speed of the motor by means of controlling the current level. The position and speed estimations are derived from a sliding mode observer that requires terminal measurements of phase voltages and currents. The proposed sliding mode observer has an important feature that the observer along with PI controller are highly robust to the errors in position and speed or change in load torque. The results show that position and speed sensorless observers can be reliably used for control of an SRM. Experimental results using a four phase, 8/6 SRM and the fixed-point digital signal processor (DSP) are presented.

Position sensorless speed control scheme for permanent magnet synchronous motor drives

A sensorless control strategy for permanent magnet synchronous motors is presented in this paper. A speed control scheme based on the measurement and observation of stator current, voltage, and flux vector is proposed. Two phase voltages and two stator currents are measured and processed in discrete form in DSP. The rotor position and speed are estimated through the stator flux and its derivative estimation. Flux and its derivative are calculated in the stationary reference frame and used to estimate the speed and position. The rotor position angle is then used in a microcontroller to produce the appropriate stator current command signals for the hysteresis current controller of the inverter. The closed-loop speed control has been shown to be effective from standstill to rated speed. Moreover, a flux drift problem caused by the integration can be eliminated so that a stable sensorless starting and running operation can be achieved. Computer simulation and experimental results are presented to demonstrate the effectiveness of the proposed scheme.

A new approach for pulsating torque minimization of brushless PM motor

Torque ripple control of brushless DC motor has been the main issue of the servo drive systems in which the speed fluctuation, vibration and acoustic noise should be minimized. Most methods for suppressing the torque ripples require Fourier series analysis and either the iterative or least mean square minimization. In this paper, the novel approach to achieve the ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms including even the case of 3 phase unbalanced condition, and the motor winding currents are controlled to follow up the optimized current waveforms by delta modulation technique. As a result, the proposed approach provides a simple and clear way to obtain the optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results.

Microcontroller based single-phase SRM drive with high power factor

A novel high power factor drive of an single-phase switched reluctance motor (SRM) is presented. It achieves sinusoidal, near unity power factor input currents. The proposed SRM drive has no additional active switches. And a single-stage approach has a simple structure and low cost. A prototype to drive an SRM equipping a suitable encoder is designed to evaluate the proposed topology. The characteristics and validity of the proposed circuit is discussed with an experimental results.A novel high power factor drive of a single-phase switched reluctance motor (SRM) is researched. It achieves sinusoidal and near unity power factor input currents. The proposed SRM drive has one additional active switches. And a single-stage approach has a simple structure and low cost. A prototype to drive an SRM equipping a suitable encoder is designed to evaluate the proposed topology. The characteristics and validity of the proposed circuit is discussed with some simulations and experimental results.

A novel optimal excitation scheme of brushless DC motor

In this paper, the new vector control scheme of BLDCM producing loss-minimized ripple-free torque based on the d-q-0 reference frame is presented including 3 phase unbalanced condition. The optimized phase current waveforms that are obtained by the proposed method can be reference values that the motor winding currents are forced to track by a delta modulation technique. As a result, it can be shown that the proposed work provides a simple and clear way to obtain an optimal motor excitation current.