Ying-Yu Tzou

High-performance programmable AC power source with low harmonic distortion using DSP-based repetitive control technique

This paper proposes a new control scheme based on a two-layer control structure to improve both the transient and steady-state responses of a closed-loop regulated pulse-width-modulated (PWM) inverter for high-quality sinusoidal AC voltage regulation. The proposed two-layer controller consists of a tracking controller and a repetitive controller. Pole assignment with state feedback has been employed in designing the tracking controller for transient response improvement, and a repetitive control scheme was developed in synthesizing the repetitive controller for steady-state response improvement. A design procedure is given for synthesizing the repetitive controller for PWM inverters to minimize periodic errors induced by rectifier-type nonlinear loads. The proposed control scheme has been realized using a single-chip digital signal processor (DSP) TMS320C14 from Texas Instruments. A 2-kVA PWM inverter has been constructed to verify the proposed control scheme. Total harmonic distortion (THD) below 1.4% for a 60-Hz output voltage under a bridge-rectifier RC load with a current crest factor of 3 has been obtained. Simulation and experimental results show that the DSP-based fully digital-controlled PWM inverter can achieve both good dynamic response and low harmonics distortion.

Adaptive repetitive control of PWM inverters for very low THD AC-voltage regulation with unknown loads

An adaptive repetitive control scheme is proposed and applied to the control of a pulsewidth-modulated (PWM) inverter used in a high-performance AC power supply. The proposed control scheme can adaptively eliminate periodic distortions caused by unknown periodic load disturbances in an AC power supply. The proposed adaptive repetitive controller consists of a voltage regulator using state feedback control, a repetitive controller with tuning parameters and an adaptive controller with a recursive least-squares estimator (LSE). This adaptive repetitive controller designed for AC voltage regulation has been realized using a single-chip digital signal processor (DSP) TMS320C14 from Texas Instruments. Experimental verification has been carried out on a 2 kVA PWM inverter. Simulation and experimental results show that the DSP-based adaptive repetitive controller can achieve both good dynamic response and low total harmonic distortion (THD) under large-load disturbances and uncertainties.

Design and implementation of an FPGA-based control IC for AC-voltage regulation

This paper presents a field-programmable gate army (FPGA)-based control integrated circuit (IC) for controlling the pulsewidth modulation (PWM) inverters used in power conditioning systems for AC-voltage regulation. We also propose a multiple-loop control scheme for this PWM inverter control IC to achieve sinusoidal voltage regulation under large load variations. The control scheme is simple in architecture and thus facilitates realization of the proposed digital controller for the PWM inverter using the FPGA-based circuit design approach. Bit-length effect of the digital PWM inverter controller has also been examined in this paper. The designed PWM inverter control IC has been realized using a single FPGA XC4005 from Xilinx Inc., which can be used as a coprocessor with a general-purpose microprocessor in application of AC-voltage regulation. Owing to the high-speed nature of FPGA, the sampling frequency of the constructed IC can be raised up to the range that cannot be reached using a conventional digital controller based merely on microcontrollers or a digital signal processor (DSP). Experimental results show the designed PWM inverter control IC using the proposed control scheme can achieve good voltage regulation against large load variations.

DSP-based multiple-loop control strategy for single-phase inverters used in AC power sources

This paper presents a fully digital multiple-loop control scheme for the regulation of the PWM inverters used in AC power sources. The proposed digital control scheme incorporates an inner current loop with an outer voltage loop to regulate the output voltage of the PWM inverter. The digital controller is designed through deadbeat theory so that the inverter can achieve fast dynamic response. To enhance the robustness of the PWM inverter concerned, an output voltage decoupling mechanism is added to improve the performance of the inner current loop. Besides, a load disturbance compensation scheme is also developed to remedy the voltage distortion caused by load variation. Both the frequency-domain and time-domain behavior of the proposed control scheme have been examined in this paper. A PWM inverter control system based on DSP TMS320C14 was constructed to verify the control law. The results show that the output voltage of the controlled PWM inverter has little distortion even under rough load conditions.

Design of a sensorless commutation IC for BLDC motors

This paper presents the design and realization of a sensorless commutation integrated circuit (IC) for brushless DC motors (BLDCMs) by using mixed-mode IC design methodology. The developed IC can generate accurate commutation signals for BLDCMs by using a modified back-EMF sensing scheme instead of using Hall-effect sensors. This IC can be also easily interfaced with a microcontroller or a digital signal processor (DSP) to complete the closed-loop control of a BLDCM. The developed sensorless commutation IC consists of an analog back-EMF processing circuit and a programmable digital commutation control circuit. Since the commutation control is very critical for BLDCM control, the proposed sensorless commutation IC provides a phase compensation circuit to compensate phase error due to low-pass filtering, noise, and nonideal effects of back-EMFs. By using mixed-mode IC design methodology, this IC solution requires less analog compensation circuits compared to other commercially available motor control ICs. Therefore, high maintainability and flexibility can be both achieved. The proposed sensorless commutation IC is integrated in a standard 0.35-/spl mu/m single-poly four-metal CMOS process, and the realization technique of this mixed-mode IC has been given. The proposed control scheme and developed realization techniques provide illustrative engineering procedures for the system-on-a-chip solution for advanced digital motor control. Simulation and experimental results have been carried out in verification of the proposed control scheme.

Sliding mode control of a closed-loop regulated PWM inverter under large load variations

A discrete sliding mode control scheme is presented for the closed-loop regulation of a pulse-width-modulated (PWM) inverter in application of high-performance uninterruptible power supply (UPS) systems. Based on the dynamic model of the PWM inverter, the sliding condition of the concerned system can be obtained and the PWM pattern is determined at every sampling instant by the proposed sliding mode control algorithm. Time response behavior of the digitally controlled PWM inverter by using a sliding mode control scheme under large load variations has been analyzed and a systematic design procedure is also suggested. A digital signal processor (DSP)-based (TMS 320C25) PWM inverter controller with a sampling rate of 10 kHz is implemented to verify the proposed control scheme. The constructed DSP-based digitally controlled PWM inverter system has fast dynamic response and low total harmonic distortion (THD) for AC phase-controlled nonlinear load.<<ETX>>

Fuzzy optimization techniques applied to the design of a digital PMSM servo drive

This paper presents a novel design approach by applying gradient optimization with fuzzy step-sizing techniques to the design of a digital permanent magnet synchronous motor (PMSM) servo drive. The servo specifications and design variables are specified and analyzed to formulate a controller optimization problem. The servo responses are then fed back to evaluate the overall system performances, which can be expressed as objective functions with respect to the servo control parameters. According to the objective functions and design specifications, the servo control parameters can be properly tuned toward their optimal values by using the proposed optimization techniques. In order to improve the convergent rate of the optimization process, a fuzzy-logic based step-size tuning strategy is presented. Because of the nonlinear property of the digital servo drives, the tuned servo control parameters may be only optimal for a particular operating point, therefore, once the optimum design is achieved, the proposed fuzzy optimizing controller can perform as an intelligent tuner for on-line gain adaptation under different loading conditions. The proposed fuzzy optimization servo tuner has been realized under a PC-MATLAB-based environment with an on-line controlled digital PMSM servo drive. Simulation and experimental results indicate that the control parameters of a digital PMSM servo drive can be optimized for its dynamic responses under various load conditions.

Design and implementation of all FPGA-based motor control IC for permanent magnet AC servo motors

This paper presents the design and implementation of a motor control IC for permanent magnet AC (PMAC) servo motors using the field programmable gate array (FPGA). This paper develops a hardware architecture for the digital control of PMAC servo motors. The proposed control structure has also been realized using FPGAs from Xilinx Inc. All the control functions, including the PWM waveform generation, current control, vector control, velocity control, and position control have been realized using FPGA based programmable logic gates. The constructed PMAC control IC includes 25000 logic gates and is realized using 8-bit integer arithmetic. Experimental results are given to verify the implemented PMAC control IC.

Discrete feedforward sliding mode control of a PWM inverter for sinusoidal output waveform synthesis

This paper presents a new discrete feedforward sliding mode control scheme for closed-loop regulation of PWM inverters in applications of high-performance uninterruptible power supply (UPS) systems. Owing to the existence of the feedforward path, discretization of the reference signal with large step size is not required. Moreover, only the output voltage needs to be measured as feedback in the proposed control scheme. A DSP-based digital-controlled PWM inverter has been implemented to examine the actual response of the designed controller. Simulation and experimental results show that the constructed digital PWM inverter control system has fast dynamic response and low total harmonic distortion (THD) under the proposed discrete feedforward sliding mode control scheme.<<ETX>>

A New Sensorless Starting Method for Brushless DC Motors without Reversing Rotation

This paper presents a new sensorless starting method for brushless DC motors without reversing rotation for unidirectional applications. The method can detect the rotor position at standstill and a specific start-up method is then used to accelerate the motor up to a middle-speed where conventional sensorless control algorithms based on the back- EMF can work properly. The proposed scheme employs only one current sensor at DC-link side of the inverter, and can be applied to a motor without knowing its parameters and additional position sensors. As compared with previous approaches, the presented technique can simplify the sensorless position detection procedure and lower the cost. The proposed initial rotor position detection technique has a resolution of 30 electrical degrees, and does not cause any rotor vibration during the detection process. The sensorless starting scheme has been implemented on a single-chip DSP controller (TMS320LF2407A) and experimental results reveal that the starting procedure can work smoothly without temporarily reversing rotation.