Shih-Liang Jung

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.

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.

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>>

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>>

Design and implementation of a real-time lossless dynamic electronic load simulator

In this paper, the construction of a new power electronics instrument, dynamic electronic load simulator (DELS), is presented. A high-performance full-bridge power amplifier with two-stage output filter and 50 kHz switching frequency is designed for high bandwidth current loop requirement. The control of the proposed DELS mainly consists of an inner current controller and an outer load-model controller (LMC). Through the simulation and experiments, it is verified that the proposed DELS can replace a lot of RLC power components, exhibit the load behavior approximately and save a large amount of energy during burn-in test.

Design and implementation of an FPGA-based control IC for the single-phase PWM inverter used in an UPS

This paper presents an FPGA-based multiple-loop control scheme for the regulation of the PWM inverters used in UPS. The proposed control scheme incorporates an inner current loop with an outer voltage loop to regulate the output voltage of the PWM inverter, which is expected to be sinusoidal. The corresponding control gains are designed through deadbeat theory so that the inverter can achieve fast dynamic response. An output voltage decoupling mechanism and a load disturbance compensation scheme have been proposed to improve the stiffness of the controlled PWM inverter. The developed digital controller has been realized by a RAM-based FPGA XC4010 to verify its effectiveness. The simulation and experimental results show that the output voltage of the controlled PWM inverter has good transient response and little distortion under rough load conditions.

DSP-based digital control of a PWM inverter for sine wave tracking by optimal state feedback technique

This paper proposes a fully digital control scheme for the closed-loop regulation of a single-phase PWM inverter used to synthesize a sinusoidal waveform even under large load variation. An accurate sampled-data model of the PWM inverter considering the sensor dynamics has been derived. The optimal state feedback gains of the proposed digital controller are determined by fitting a specified step response through the steepest descent method. The gating signals of the switching devices are computed at every sampling instant by instantaneous feedback of the inductor current and output voltage. The design procedure of the proposed digital controller and its software realization have been described in detail. Moreover, a DSP-based (TMS320C14) fully digitally controlled PWM inverter has been constructed to verify the proposed control scheme. The simulation and experimental results show that satisfactory results can still be obtained even at low sampling frequency.<<ETX>>

A three-phase PWM AC-DC converter with low switching frequency and high power factor using DSP-based repetitive control technique

This paper presents a novel digital control scheme for PWM AC-DC converters with low switching frequency used in high-power applications. The proposed scheme incorporates an inner current loop with an outer voltage loop to improve input power factor and regulate the output DC-link voltage. The inner current loop consists of a predictive controller and a repetitive controller. The outer voltage loop is composed of a digital PI controller and a load current compensator. A PWM AC-DC converter employing DSP control has been constructed to verify the proposed control scheme. A nearly unit input power factor can be achieved even with a low switching frequency. Experimental results confirm the feasibility and features of the proposed repetitive control scheme for unit power factor regulation.

Self-tuning discrete sliding mode control of a closed-loop regulated PWM inverter with optimal sliding surface

This paper presents a self-tuning discrete sliding mode control scheme with feedforward compensation for the closed-loop regulation of PWM inverters used in uninterruptible power supplies (UPS). A self-tuning scheme is proposed to adjust the parameters of both the feedforward and sliding mode controllers. In designing the sliding mode controller, the authors have taken the effect of load disturbance into consideration to enhance the robustness of the controlled system. The sliding surface of the sliding mode controller is designed such that the behavior of the controlled PWM inverter system is optimal, subject to the defined cost function. Simulation and experimental results are given to show the superiority of the proposed control scheme.