Ray-Lee Lin

A classification and evaluation of paralleling methods for power supply modules

There is a fairly large number of methods for paralleling power converters. This paper classifies and examines these paralleling schemes, focusing on the active current-sharing approaches. Based on this classification, some new paralleling schemes can be achieved. Emphasis is placed on discussion and assessment of merits and limitations of these schemes. Finally, the prominent features of the dominant paralleling schemes are verified by simulation of a two-paralleled buck converter system.

Study and Implementation of a Current-Fed Full-Bridge Boost DC–DC Converter With Zero-Current Switching for High-Voltage Applications

This paper presents a comprehensive study of a current-fed full-bridge boost dc-dc converter with zero-current switching (ZCS), based on the constant on-time control for high-voltage applications. The current-fed full-bridge boost converter can achieve ZCS by utilizing the leakage inductance and parasitic capacitance as the resonant tank. In order to achieve ZCS under a wide load range and with various input voltages, the turn-on time of the boost converter is kept constant, and the output voltage is regulated via frequency modulation. The steady-state analysis and the ZCS operation conditions under various load and input-voltage conditions are discussed. Finally, a laboratory prototype converter with a 22-27-V input voltage and 1-kV/1-kW output is implemented to verify the performance. The experimental results show that the converter can achieve high output voltage gains, and the highest efficiency of the converter is 92% at full-load condition with an input voltage of 27 V.

Improved soft-switching ZVT converters with active snubber

A new family of improved soft-switching ZVT power converters with an active snubber is developed in order to improve the efficiency of conventional ZVT power converters using a feedback inductor. Besides the ZVT turn-on performance of the main switch, the improved ZVT soft-switching power converters have less turn-off switching loss of the main switch than do conventional ZVT converters using a feedback inductor. With this new technique, an improved single-phase CCM ZVT soft-switching PFC power converter prototype has been implemented to show higher efficiency improvement than the conventional ZVT converters using a feedback inductor.

Analysis, Design, and Control of Bidirectional Cascoded Configuration for a Fuel Cell Hybrid Power System

This paper presents a cascoded configuration combining a fuel cell (FC), a battery, and an ultracapacitor module (UCM) to create a hybrid power system. A cascoded configuration is constructed using a modified bidirectional flyback converter, which connects the battery and UCM in cascode to efficiently provide hybrid power. An active FC voltage control strategy is presented to manage the power flows of the proposed cascoded system. In this paper, the simulated hybrid power of the motion of an electric vehicle is illustrated in different situations. The experimental results show that the power flows using the proposed control strategy verify the theoretical analysis. In addition, the overall efficiency of the proposed hybrid power system at overload operation is much higher than the conventional one, and it can achieve 96%.

A Novel Constant Power Control Circuit for HID Electronic Ballast

This paper presents a constant power control circuit for a three-stage high intensity discharge (HID) electronic ballast. The three-stage electronic ballast is composed of a boost pre-regulator to achieve high power factor, a dc-dc buck converter to regulate lamp current with constant lamp power, and a full-bridge inverter to drive the HID lamp with a low frequency ac square wave current. The buck converter operating in current mode utilizes current sense level-shift technique to achieve constant power output. The proposed constant power control circuit is easily designed and implemented for the three-stage HID electronic ballast. Finally, a laboratory prototype of a 70-W HID electronic ballast is implemented. The measured results show that the proposed ballast can be applied for various HID lamps with low lamp power variation (less than 0.6%)

Equivalent Circuit Model of Light-Emitting-Diode for System Analyses of Lighting Drivers

This paper presents the equivalent circuit models of the light-emitting-diode, including the piece-wise linear model, DC model and small-signal model. In order to characterize the equivalent circuit model of the LEDs, a piece-wise linear model is built by adopting the superposition concept of the multi-branch equivalent circuit model. Furthermore, in order to perform the DC and small-signal analysis of the LEDs, the equivalent DC and small-signal resistance will be derived from the piece-wise linear model.

Optimization of an MRT train schedule: reducing maximum traction power by using genetic algorithms

Because of the traction power load characteristics of mass rapid transit (MRT) systems, a significant difference exists between the peak and valley of the traction power load curve. Furthermore, an extremely high traction power peak occurs if numerous trains are accelerating simultaneously. Careful train scheduling can avoid the simultaneous acceleration of too many trains, thus reducing maximum traction power. This paper employs genetic algorithms to optimize train scheduling and uses the Kaohsiung MRT system as an example. Simulation results show that the proposed method can significantly reduce the maximum traction power.

Multicascoded Sources for a High-Efficiency Fuel-Cell Hybrid Power System in High-Voltage Application

This paper presents a high-efficiency multicascoded hybrid power system for high-voltage application. For a cascoded configuration, the source is serially connected to the output terminal of a converter to increase the voltage conversion gain by one. In addition, parts of the energy from the sources are supplied directly to the output load with high-efficiency features. Based on these, a three-cascoded hybrid power system integrating the fuel cell (FC), battery, and ultracapacitor module is presented. A two-loop active FC control strategy is proposed to manage the power flows of the proposed system. The whole efficiency and hybrid power flows of the multicascoded system are discussed and demonstrated under different hybrid situations. Finally, the experimental results from a prototype circuit of the FC hybrid power system show that the hybrid system can provide 200 V of output voltage, 500 W of rated power, and about 1 kW/25 min long-term overload power. In addition, the whole efficiency of the proposed hybrid power system can achieve 93.6%.

Current-fed full-bridge boost converter with zero current switching for high voltage applications

This paper presents a current-fed full-bridge boost converter with zero current switching (ZCS) based on constant on-time control for high voltage applications. The proposed converter utilizes the leakage inductor and the winding parasitic capacitor resonant tank to achieve ZCS. In order to achieve ZCS under wide load range, the turn-on time of the full-bridge boost converter is kept constant and the output voltage is regulated via frequency modulation. Finally, a laboratory prototype converter with 1 kV/600 W is implemented to verify the ZCS performance of the proposed converter. The highest efficiency of the proposed converter is 92%.

Magnetizing inrush model of transformers based on structure parameters

This paper proposes a circuit model for the transient period of inrush current in a transformer. The magnetizing inrush model is developed from the structural parameters of the transformer. In the analysis of the magnetization curve, the relationship between the magnetic flux density and magnetic field intensity differs from the ordinary B-H curve; this paper interchanges the B and the H and characterizes the B-H of the magnetic core as a simple tangent function in the H-B planes. Furthermore, the concept of inrush equivalent inductance is also used in the magnetizing inrush model. Using the magnetizing inrush model, an inrush current value can be estimated before the transformer is manufactured. Moreover, in the future, this model can provide the power system with a more thorough transient analysis. During this research, the inrush currents are simulated using the circuit model from ICAP/4. Fourteen actual transformers, each with a different winding structure, are used for demonstration. Experiments and simulations are carried out to examine the proposed method.