Jong-Lick Lin

Robustness analysis of uncertain linear singular systems with output feedback control

The robustness analysis for a linear singular system with uncertain parameters and static output feedback control is considered. The problem is transformed into a robust nonsingularity problem. Based on the linear fractional transformation (LFT) approach, the robustness bounds to preserve regularity, impulse immunity, and stability are found in terms of the structured singular value /spl mu/ with respect to parametric uncertainties. The LFT approach provides a unified framework for robustness analysis of both uncertain linear continuous/discrete-time singular systems.

A new approach of dead-time compensation for PWM voltage inverters

It is essential to insert a switching delay time in sinusoidal pulsewidth modulation (PWM) voltage-fed inverters to prevent a short circuit in the dc link. This causes the well known dead-time effect which is detrimental to the performance of the output voltage. Many compensation schemes were proposed to overcome the drawbacks. In this paper, based on a systematic approach, a new approach to accurately compensate the dead-time effect is presented. The system analysis and compensation synthesis are straightforward without averaging the output voltage deviation. The model of the PWM voltage inverter with a time delay circuit leads us to a systematic approach of compensation. The simulation responses and experimental results show the validity of the analysis and verify the effectiveness of the proposed compensation method.

Analysis and Design for a Novel Single-Stage High Power Factor Correction Diagonal Half-Bridge Forward AC–DC Converter

By means of components placement, the buck-boost and diagonal half-bridge forward converters are combined to create a novel single-stage high power factor correction (HPFC) diagonal half-bridge forward converter. When both the PFC cell and dc-dc cell operate in DCM, the proposed converter can achieve HPFC and lower voltage stress of the bulk capacitor. The circuit analysis of the proposed converter operating in DCM+DCM mode is presented. In order to design controllers for the output voltage regulation, the ac small-signal model of the proposed converter is derived by the averaging method. Based on the derived model, the proportional integral (PI) controller and minor-loop controller are then designed. The simulation and experimental results show that the proposed converter with the minor-loop controller has faster output voltage regulation than that with the PI controller despite the variations of line voltage and load. Finally, a 100-W prototype of the proposed ac-dc converter is implemented and the theoretical result is experimentally verified

Synthesis and analysis for a novel single-stage isolated high power factor correction converter

A novel single-stage isolated high power factor correction (HPFC) converter operating in the discontinuous conduction mode is proposed in this paper. It is an integration of a buck-boost converter with a flyback converter by means of components placement and synchronous switching technology. It can achieve HPFC, tight output voltage regulation and lower voltage stress of the bulk capacitor, which is independent of the loads. The small-signal mathematical model for the proposed converter is derived separately by the averaging method and the current injected equivalent circuit approach. The IsSpice simulations and experimental results successfully verify the dynamics and performances of the proposed converter.

Robust controller design for a series resonant converter via duty-cycle control

Robust controller design for a series resonant power converter is presented when load variation and unregulated input line voltage perturbation are taken into consideration. The perturbation of unregulated line voltage is treated as an exogenous disturbance and the load variation as a structured uncertainty of the converter. An averaged model, including disturbance and model uncertainty, is then derived. Two kinds of /spl mu/ synthesis-D-K and /spl mu/-K iteration schemes-are applied to design robust controllers to diminish the susceptibility of the regulated voltage to perturbations of load variation and unregulated line voltage. In addition, a classical controller is also designed for performance comparison. Finally, simulations and experimental results are presented to verify the feasibility of the robust control theory.

A novel ZCZVT forward converter with synchronous rectification

A novel zero-current-zero-voltage transition (ZCZVT) forward converter with synchronous rectification (SR) is presented in this paper. The proposed converter is operating at 300 kHz and processes the features of both zero-voltage transition (ZVT) at turn on and zero-current transition (ZCT) at turn off for the main switch. The auxiliary switch also achieves zero-current switching (ZCS). The flux of transformer can be reset without tertiary winding. The steady-state analysis and design considerations are investigated in detail in this work. Moreover, a self-driven synchronous rectification is also added to the ZCZVT forward converter to reduce the conduction losses of the output rectifier. For 48-V input and 12-V 100-W output, a prototype of the proposed converter for 300-kHz switching is built to verify the theoretical analysis. Finally, the power losses are well estimated. The overall efficiency of the proposed converter is achieved at 89% at full load.

Analysis and /spl mu/-based controller design for an electromagnetic suspension system

A SISO electromagnetic suspension system including an electromagnet, an iron ball, a position detector, and a current amplifier is built at the laboratory. It is inherently nonlinear and unstable. In this paper a controller is designed for the suspension system to regulate the position of the suspended ball around an equilibrium point. It is also required that the number of the suspended balls can be increased from one (0.533 kg) to three (1.6 kg). For mathematical modeling, the change of mass of the iron ball and the equilibrium points can be treated as structured uncertainties of the controlled plant. Then, a /spl mu/-synthesis algorithm is applied for a robust controller design to achieve the requirement of robust stability and robust performance. In addition, a classical phase-lead controller and a quadratic optimal controller are also designed for performance comparison.

Maximal stability bounds of singularly perturbed systems

Abstract The maximal stability bound e ∗ of a linear time-invariant singularly perturbed system is derived in an explicit and closed form, such that the stability of the systems is guaranteed for 0⩽e ∗ . Two new approaches including time- and frequency-domain methods are employed to solve this problem. The former leads to a generalized eigenvalue problem of a matrix pair. The latter is based on plotting the eigenvalue loci of a real rational function matrix derived by an LFT description system. The results obtained are coincident. Two illustrative examples are given to show the feasibility of the proposed techniques.

Small-signal modeling and control of ZVT-PWM boost converters

A small-signal model for zero-voltage-transition pulse width modulation (ZVT-PWM) boost converters is derived in this paper. The accuracy of the developed model is verified by experimental measurement. It shows that the ZVT-PWM boost converters exhibit better dynamical behavior than the conventional PWM boost converters. To achieve output voltage regulation and line voltage disturbance rejection of ZVT-PWM boost converters, a classical controller and a modified integral variable structure controller are designed. The output voltage regulation in the presence of line voltage and load variations for both controllers are compared by experimental results.

Dynamics analysis and controller synthesis for zero-voltage-transition PWM power converters

A small signal model for zero-voltage-transition pulse width modulation (ZVT-PWM) buck converters is proposed in this paper. It shows that the ZVT-PWM buck converter exhibits better dynamical behavior than the conventional PWM buck converter. Based on the derived model consisting of line voltage disturbances and load variations, /spl mu/-synthesis is applied for a robust controller design to achieve performance requirement. In addition, a classical controller and a sliding mode controller with modified integral variable structure are also designed for performance comparisons. Finally, simulation and experimental results are presented to verify the requirement for robust performance of ZVT-PWM converters.