Search

A wide-range active and reactive power flow controller is designed to operate the inverter in pure leading, pure lagging, and the mix with active and reactive power conditions. The key to achieving lagging power flow control is to ensure sufficiently high enough dc bus voltage to avoid duty cycle saturation. The key to achieving precision power flow control for a wide range of power level is to adopt the quasi-proportional resonant controller for the current loop and the admittance compensator to cancel the grid-voltage-induced negative power flow. In this paper, the current loop transfer function has been systematically derived for the controller design purpose. Phasor analysis was adopted to explain the need of dc bus voltage requirement. A 5-kVA grid-tie fuel cell inverter was used as the platform to show current loop controller design and admittance compensation. The proposed controller has been simulated, and the same parameters have been used for a DSP-based controller. Both simulation and hardware experimental results agree well with the theoretical analysis. Index Terms--Admittance compensation, fuel cell power conditioning system, LCL filter, proportional-resonant compensator, reactive power control, single-phase grid-tie inverter.

In order to design a high-efficiency, cost-effective, high-power driver for supplying multiple light-emitting diode (LED) strings in parallel, a novel single-stage bridgeless, soft-switched integrated AC–DC converter is proposed. The proposed converter can be derived by integrating the totem-pole bridgeless boost power factor correction (PFC) circuit and half-bridge LLC resonant converter. Therefore, the number of semiconductors in the line-current path can be significantly minimized, and the power losses in the secondary rectifier diodes and the primary switches can be dramatically reduced. Moreover, the twin-bus concept can be adopted to achieve the quasi-single-stage power conversion of the total LED driver with multiple LED strings load. In addition, this circuit allows removing the bulky electrolytic capacitors with short lifetime by increasing the bus voltage ripple, and thus, the long lifetime is another advantage of the proposed LED driver. The detailed operation principles and design considerations for the proposed converter are analyzed and discussed. The feature of the proposed solution was demonstrated using a 100-W hardware prototype with six LED strings. The experimental results showed the converter achieves full-range ZVS for primary switches and the efficiency of 94.5% under the 120 V input voltage. [ABSTRACT FROM AUTHOR]

In this paper, a single-stage integrated bridgeless AC/DC converter is proposed. As compared to its counterpart that is composed of totem-pole boost power factor correction (PFC) cascade fly-back DC/DC converter, the studied circuit has less components number while overcoming the limits of the totem-pole type. Thus, it is suitable to the low-power LED lighting applications. Furthermore, when both PFC inductors Lb and magmatic inductance Lm of the transformer TR1 operate at discontinuous current mode, the bus voltage vCB can be used to decouple the ac input and constant dc output power. Thus, the approach of increasing bus voltage ripple is employed to eliminate electrolytic capacitors and obtain long operation lifetime. Additionally, it is able to be compatible with our studied twin-bus configuration for increasing the overall efficiency. A 50-W hardware prototype has been designed, fabricated, and tested in the laboratory to verify the proposed converter validity. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a zero-voltage-switching (ZVS) full-bridge dc–dc converter combing resonant and pulse-width-modulation (PWM) power conversions for electric vehicle battery chargers. In the proposed converter, a half-bridge LLC resonant circuit shares the lagging leg with a phase-shift full-bridge (PSFB) dc–dc circuit to guarantee ZVS of the lagging-leg switches from zero to full load. A secondary-side hybrid-switching circuit, which is formed by the leakage inductance, output inductor of the PSFB dc–dc circuit, a small additional resonant capacitor, and two additional diodes, is integrated at the secondary side of the PSFB dc–dc circuit. With the clamp path of a hybrid-switching circuit, the voltage overshoots that arise during the turn off of the rectifier diodes are eliminated and the voltage of bridge rectifier is clamped to the minimal achievable value, which is equal to secondary-reflected input voltage of the transformer. The sum of the output voltage of LLC resonant circuit and the resonant capacitor voltage of the hybrid-switching circuit is applied between the bridge rectifier and the output inductor of the PSFB dc–dc circuit during the freewheeling phases. As a result, the primary-side circulating current of the PSFB dc–dc circuit is instantly reset to zero, achieving minimized circulating losses. The effectiveness of the proposed converter was experimentally verified using a 4-kW prototype circuit. The experimental results show 98.6% peak efficiency and high efficiency over wide load and output voltage ranges. [ABSTRACT FROM AUTHOR]

SUMMARY The AC-DC power supply for LED lighting application requires a long lifetime while maintaining high-efficiency, high power factor and low cost. However, a typical design uses electrolytic capacitor as storage capacitor, which is not only bulky but also with short life span, thus hampering performance improvement of the entire LED lighting system. In this article, a SEPIC-derived power factor correction topology is proposed as the first stage for driving multiple lighting LED lamps. Along with a relatively large voltage ripple allowable in a two-stage design, the proposal of LED lamp driver is able to eliminate the electrolytic capacitor while maintaining high power factor and high efficiency. To further increase the efficiency of LED driver, we introduced and used the twin-bus buck converter as the second-stage current regulator with Pulse Width Modulation (PWM) dimming function. The basic operating principle and the deign consideration are discussed in detail. A 50-W prototype has been built and tested to verify the proposal. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Effective photovoltaic power conditioning requires efficient power conversion and accurate maximum power point tracking to counteract the effects of panel mismatch, shading, and general variance in power output during a daily cycle. In this paper, the authors propose an integrated boost resonant converter with low component count, galvanic isolation, simple control, as well as high efficiency across a wide input and load range. Provided is a discussion of the converter synthesis, key operational features, converter design procedure, and loss analysis, as well as experimental verification by way of a 250-W prototype with a California Energy Commission efficiency of 96.8%. [ABSTRACT FROM AUTHOR]

This paper presents a unique modulation method for extending the input range of pulse-width modulation (PWM)-integrated resonant converters, such as the isolated boost resonant converter, while maintaining high conversion efficiency. The technique includes primarily the hybridizing of constant-on, constant-off, and fixed-frequency control depending only on the required duty cycle. The modulation scheme reduces core loss and conduction loss dramatically by decreasing the applied volt-seconds at the transformer and improving the switching period utilization. With hybrid-frequency control, the circuit also maintains zero current switching for the output diodes, minimizes switching loss, and eliminates circulating energy at the transformer across the entire operating range. It also allows for a predictable voltage gain, dependent only on duty cycle and transformer turns ratio. A detailed loss analysis is provided and verified against a 180 W experimental prototype, with an input range of 12–48 V and a switching frequency range of 30–70 kHz. Implementation issues are also handled with a variety of solutions for realizing the modulation scheme. Experimental results show greater than 4% weighted efficiency improvement in the prototype using the proposed method. [ABSTRACT FROM AUTHOR]

A novel soft-switching converter combining resonant half-bridge and phase-shifted pulsewidth modulation (PWM) full-bridge configuration is proposed to ensure the switches in the leading-leg operating at zero-voltage switching from true zero-load to full-load, and the switches in the lagging leg working at zero-current switching with minimum duty cycle loss and circulating conduction loss by significantly reducing leakage or series inductance. Experimental results of a 3.4-kW hardware prototype show that the circuit achieves true full-range soft switching with 98% peak efficiency. The hybrid resonant and PWM converter is attractive for electrical vehicle battery charger application. [ABSTRACT FROM PUBLISHER]

Using a bidirectional dc-dc converter along with low-voltage energy storage for the high-voltage dc bus and traction motor drives has been a prominent option for hybrid electric and fuel cell vehicles. This paper will describe the significance of energy management power converters and their circuit topology options for efficiency, size, and cost considerations. Whether isolated or nonisolated, soft switching techniques have been widely used in high-power bidirectional dc-dc converters. Through some design examples, the component selection and circuit design optimization are discussed, and their efficiency evaluation results are also given. Major difficulties of developing a high-power bidirectional dc-dc converter are found in lack of high-power passive components and lack of multiphase de-de controllers. More development work needs to be done in these areas. [ABSTRACT FROM AUTHOR]

High power boost converter has become the essential part of the distributed power system that enables energy to be fully utilized in fuel cell powered electric vehicles and stationary power systems. This paper presents analysis and design of a high-power multileg interleaved boost converter with a digital signal processor (DSP) based controller. A 20-kW converter was designed with coupled inductors to allow core-loss reduction and designed with high frequency switching to minimize the component size and eliminate the switching losses under discontinuous conducting mode operation. A dual-loop average current mode current control method implemented in DSP is employed to achieve the fast transient response. It was found through circuit analysis, simulation and experiment that the boost inductor interacted with the device parasitic capacitor and created unnecessary oscillating current whenever it reached zero current. Two high-power devices were used in both simulation and experiment to verify the analysis and design for a wide load range. Simulation and experiment results of the 20-kW boost converter under startup condition and load transient condition are also presented. Different anti-windup schemes for a typical PI-controller are evaluated. The results show that this typical controller with proper anti-windup scheme achieves better transient performance than without anti-windup scheme. [ABSTRACT FROM AUTHOR]