Viboon Chunkag

Comparative Study of Fuel-Cell Vehicle Hybridization with Battery or Supercapacitor Storage Device

This paper studies the impact of fuel-cell (FC) performance and control strategies on the benefits of hybridization. One of the main weak points of the FC is slow dynamics dominated by a temperature and fuel-delivery system (pumps, valves, and, in some cases, a hydrogen reformer). As a result, fast load demand will cause a high voltage drop in a short time, which is recognized as a fuel-starvation phenomenon. Therefore, to employ an FC in vehicle applications, the electrical system must have at least an auxiliary power source to improve system performance when electrical loads demand high energy in a short time. The possibilities of using a supercapacitor or a battery bank as an auxiliary source with an FC main source are presented in detail. The studies of two hybrid power systems for vehicle applications, i.e., FC/battery and FC/supercapacitor hybrid power sources, are explained. Experimental results with small-scale devices (a polymer electrolyte membrane FC of 500 W, 40 A, and 13 V; a lead-acid battery module of 33 Ah and 48 V; and a supercapacitor module of 292 F, 500 A, and 30 V) in a laboratory authenticate that energy-storage devices can assist the FC to meet the vehicle power demand and help achieve better performance, as well as to substantiate the excellent control schemes during motor-drive cycles.

Analysis and Design of a Modular Three-Phase AC-to-DC Converter Using CUK Rectifier Module With Nearly Unity Power Factor and Fast Dynamic Response

In this paper, the analysis and design of a modular three-phase AC-to-DC converter using single-phase isolated Cuk rectifier modules is discussed based on power balance control technique. This paper analyzes the operation of a modular converter as continuous-conduction-mode power factor correction (CCM-PFC). Design equations, as well as an average small-signal model of the proposed system to aid the control loop design are derived. It is used to obtain the inductor current compensator, thus the output impedance and audio susceptibility become zero, and therefore, the output voltage of the converter presented in this paper is independent of the variations of the dc load current and the utility voltage. The control strategy consists of a single output voltage loop and three-inductor current calculator. The main objective of the proposed system is to reduce the number of stages and improve dynamic response of DC bus voltage for distributed power system. The proposed scheme offers simple control strategy, flexibility in three-phase delta or star-connected, simpler design, fast transient response, good inductor current sharing, and power factor closed to unity. Both simulation and experimental results are presented. They are in agreement with the theoretical analysis and experimental work.

Power balance control techniques applied to parallel AC to DC converters using single-phase SEPIC rectifier modules

Power balance control techniques applied to parallel AC to DC converters for single-phase SEPIC rectifier modules is presented. The analysis and simulation results of such system with nearly unity power factor using single voltage loop control and inductor current calculator for input current wave shaping and output voltage regulation have been shown. Each converter operates in continuous conduction mode and hysteresis current control with lockout switching-frequency at 100 kHz. The objective is to keep output voltage constant and current sharing in each converter equally, while keeping the power factor very close to unity. Analysis and simulation results indicate that such scheme is effective and parallel AC to DC converter has a high power density and fast transient response. The circuit is designed to operate at DC output voltage 48 V, output power 1,500 W.

Simulation and study of photovoltaic cell power output characteristics with buck converter load

This paper present the study of photovoltaic cell (PV Cells) output power characteristics by experimenting with the simulation of equivalent circuit and of output behavior of photovoltaic while connected to the buck converter, with adjustment of its duty ratio (D). Experimental result show that the maximum power point (MPP) is reduced 24 %, while connected to the buck converter load compared with the linear load (resistor). The simulation results from MATLAB / Simulink program have a good agreement with the experimental.

Unified Unbalanced Synchronous Reference Frame Current Control for Single-Phase Grid-Connected Voltage-Source Converters

This paper presents a unified structure of the unbalanced synchronous reference current control strategies for single-phase grid-tied voltage-source converters to obtain a zero steady-state error in the line current. An arbitrary waveform is used as the orthogonal current for the stationary to rotating frame axis transformation of the reference and measured grid currents. Various choices of such orthogonal signals lead to different control structures with the same performance characteristics. This causes a temporary unbalanced system, in which double-line frequency components appear in the control loops during the transient state. The proposed method with cross-axis decoupling, tuned at the control loop bandwidth by greater than eight times the grid frequency, has better performance than the existing virtual balanced synchronous reference frame scheme. Absence of the orthogonal signal generation guarantees the stability criterion of the control scheme. A zero steady-state error is still achieved under conditions of uncertainty in the converter parameters. Simulation and experimental results of a 1.5-kVA pulse width modulation rectifier validate the proposed methodology.

Class-D Zero-Current-Switching Rectifier as Power-Factor Corrector for Lighting Applications

An analysis and design of a zero-current-switching (ZCS) Class-D current-source driven rectifier for the lighting applications is presented, which is one of the resonant rectifiers as a power-factor corrector to improve a poor power-factor and high line current harmonic of a single-stage converter. A high power-factor is achieved by the utilization of output characteristics of a Class-D ZCS rectifier, which is inserted between the front-end bridge rectifier and the bulk-filter capacitor. The conduction angle of the bridge rectifier diode current was increased and a low-line current harmonic and a power-factor near unity can be obtained. The design procedure is based on the principle of the Class-D ZCS rectifier, which also ensures more accurate results and the proposed scheme provides a high efficiency and a more systematic and feasible analysis methodology. The active switches can be operated under the soft-switching condition. The validity of this approach was confirmed by simulation and experimental results.

Redundant Operation of a Parallel AC to DC Converter via a Serial Communication Bus

The redundant operation of a parallel AC to DC converter via a serial communication bus is presented. The proposed system consists of three isolated CUK power factor correction modules. The controller for each converter is a dsPIC30F6010 microcontroller while a RS485 communication bus and the clock signal are used for synchronizing the data communication. The control strategy of the redundant operation relies on the communication of information among each of the modules, which communicate via a RS485 serial bus. This information is received from the communication checks of the converter module connected to the system to share the load current. Performance evaluations were conducted through experimentation on a threemodule parallel-connected prototype, with a 578W load and a -48V dc output voltage. The proposed system has achieved the following: the current sharing is quite good, both the transient response and the steady state. The converter modules can perform the current sharing immediately, when a fault is found in another converter module. In addition, the transient response occurs in the system, and the output voltages are at their minimum overshoot and undershoot. Finally, the proposed system has a relatively simple implementation for the redundant operation.

Improvement of self-oscillating electronic ballast with high power factor: A combination of charged-pump and valley-fill

This paper proposes a novel 36W / 220Vrms / 50Hz of half-bridge inverter self-oscillating electronic ballast for a fluorescent lamp with high power factor and low line input current harmonics. The system performance can be improved by combining together with a charged pump and valley fill circuit. Details of design and circuit operation are described. This ballast is developed to reduce a number of ICs controlling power electronic switches that are costly and sizeable. Instead of these ICs, This ballast employs self-oscillation method to control power electronic switches. The combination of a bridge rectifier, current source charge pump with valley fill circuit to improve power factor and Series - Resonant Parallel - Load Inverter (SRPLI) are main concept. This electronic ballast is designed and tested to find the proper frequency and signal to stimulate the operation of power electronic switches to trigger fluorescent lamp suitably. The experimental results show that the proper frequency of the prototype is around 40 kHz with input power factor of 0.988, THDi 4.7% at full load and efficiency of more than 90%.

Redundant three-phase AC to DC converter using single-phase CUK rectifier module with minimized DC bus capacitance

This paper presents a redundant three-phase ac to dc converter using single-phase CUK rectifier module with nearly power factor and minimized dc bus capacitance based on power balance control technique. The focus of the proposed control strategy is to reduce the dc bus capacitance value under condition step load change from 10% (75W) to 100% (750W). Using power balance control technique does minimized dc bus capacitance, inductor current sharing, redundant operation, high power factor and tight dc bus voltage works on the principle of modular three-phase rectifier with parallel single-phase CUK rectifier module. Simulation results are used to illustrate the operation and performance features of the modular three-phase rectifiers.

Class E ZVS inverter with matching resonant circuit and resonant gate drive

This paper presents the class E ZVS inverter with matching resonant circuit and resonant gate drive. The matching resonant circuit is used for wide range of load and resonant gate drive is used to reduce the gate drive loss. The proposed circuit was simulated at 5 MHz constant switching frequency, 150 W output power, and 200Omega full load resistance. The simulation results shown that the inverter can operate in zero voltage switching (ZVS) operation from full load to open circuit and the gate drive loss reduced significantly.