Wide Range High Efficiency Research Articles

A Control Strategy Based on Intermediate Bus Voltage Information for Wide-Range High-Efficiency Step-Up DC–DC Converters

A Control Strategy Based on Intermediate Bus Voltage Information for Wide-Range High-Efficiency Step-Up DC–DC Converters

A Multistructure Multimode Three-Phase Dual-Active-Bridge Converter Targeting Wide-Range High-Efficiency Performance

A three-phase dual-active-bridge (3p-DAB) converter is an attractive topology for bidirectional power conversion in high-power applications. However, conduction and switching losses are two main loss mechanisms that severely affect its efficiency performance, and adoption of any single modulation scheme or topology cannot minimize these losses over a wide operating range. For this purpose, a reconfigurable topology of the 3p-DAB converter is proposed in this article that utilizes a reconfigurable and tunable resonant network to offer multiple degrees of freedom in minimizing conduction and switching losses over a wide range of operating conditions. The converter is designed such that for 40-100% of the rated output power, it operates as a tunable 3p-DAB resonant immittance converter with its output power controlled by varying switching frequency and tuning the resonant frequency of a resonant immittance network to track the switching frequency. Below 40% of the rated output power, the converter transforms to a tunable 3p-DAB series-resonant converter with its output power controlled by varying the impedance of a series-resonant network while keeping the switching frequency and phase shift constant. The combination of both operation modes jointly leads to wide-range zero circulating current and soft switching of all the switches and, hence, a wide-range high-efficiency performance, as validated by the experimental results.

A Three-Phase Dual-Active-Bridge DC–DC Converter With Reconfigurable Resonant Network for Efficient Wide Voltage Range Operation

All power converters, including dual-active-bridge (DAB) dc–dc converter, cannot sustain a consistently high-efficiency performance over a wide range of operating conditions, and reconfiguration of operation mode represents a viable solution to this fundamental problem. To meet this challenge, a resonant-type three-phase DAB (3p-DAB) converter incorporating a three-phase reconfigurable resonant network has been proposed in this article. The proposed converter can operate either as a 3p-DAB resonant immittance converter (3p-DABRIC) or a 3p-DAB series resonant converter (3p-DABSRC) to enhance its efficiency performance over a wide range of voltage conversion ratio and output power levels. In addition, the proposed converter offers the flexibility to operate with unity power factor, full-range zero-voltage switching, and enhanced light-load efficiency under varying operating conditions by appropriate selection of the converter's operation mode. Based on a careful loss analysis and verification of the loss model by experimental measurements, it has been found that under wide range variations in voltage conversion ratio and output power levels, 3p-DABSRC delivers a more superior efficiency performance at low to medium power levels, whereas 3p-DABRIC generally achieves a higher efficiency at high power levels, and thus combination of both operation modes leads to an overall wide range high-efficiency performance.

Optimal Modulation for a Fifth-Order Dual-Active-Bridge Resonant Immittance DC–DC Converter

This paper proposes a fifth-order resonant immittance network based dual-active-bridge (DAB) converter and an optimal modulation method that will ensure high-efficiency operation of the converter under wide-range variations in voltage ratio and output power level. The proposed modulation method is based on the concept of total power loss minimization, where a loss model is developed and an optimization algorithm is formulated to compute the optimal set of internal and external phase shift parameters that will lead to the maximum efficiency for a given set of operating parameters including voltage ratio and output power level. It is found that to maintain high-efficiency operation under wide-range variations in voltage ratio and output power level, the DAB converter is required to switch between different operation modes and neither soft-switching operation nor unity-power-factor operation is able to achieve wide-range high efficiency performance when used alone. The importance of $reconfigurability$ of operation mode for achieving wide-range high efficiency performance is clearly illustrated in this paper.

Optimal design of axial hydro turbine for micro hydropower plants

In our country we have enormous low head potation flows in agricultures and aquacultures with almost fix flow rates that can be used as micro hydro power plants for producing energy. But the main problem is the high capital price per kW. Therefore there is needed to design a simple machine with a good runner for covering the various potential flows. In this paper an axial hydro turbine has designed for some low heads micro potential flow with flow rates ranged from 50 lit/sec to 150 lit/sec and heads ranged from 1 m to 5 m. The initial runner designed using classical methods and then the runner geometry has been optimized by evolutionary optimization algorithms. The final design has been simulated by a commercial flow solver in a various blade positions. The results showed a wide range characteristic curve with a wide range high efficiency.