Operation analysis of high efficiency grid connected bi-directional power conversion system for various storage battery systems with bi-directional switch circuit topology
In recent years, there is an increasing demand for various types of storage battery systems, such as home battery systems, V2H(Vehicle-to-Home)/V2G(Vehicle-to-Grid) systems, and UPS systems. Performance requirements for the power conversion system within these storage battery systems are small size, light weight and high efficiency. We propose a new power conversion system so called the GAP-D3 converter that is a bi-directional power control system, comprising of a bi-directional switch circuit topology with natural commutation switching mode. This paper describes the features of GAP-D3 converter including this new current compensation control with simulation and experimental results.
Operation analysis of quasi-resonant high-frequency transformer link DC-AC converter applied for phase-shift PWM control in secondary side
In recent years, the soft-switching techniques have attracted attention for its peculiar advantages such as low swtching loss, high-power density, EMI/RFI noise reduction and so on. Authors have already reported before about quasiresonant DC-DC converter using new phase-shift PWM control scheme. By using proposed control scheme, circulating current is elimineted and ZVS (Zero Voltage Switchig) is achieved with small commutating current. As a result, the conduction losses caused by their currents are substantially reduced.In this paper, authors apply a proposed control scheme to a quasi-resonant high-frequency transformer link DC-AC converter. As a result, all switching devices in this DC-AC converter can achieve soft-switching with small commutating current irrespectively of inverter mode and rectifier mode. Its operating principle and unique features are described as compared with the symmetrical control scheme of DC-ACconverter. Operating performance of this DC-AC converter in steady-state are illutrated by means of simulating results.
A Critical Assessment on Functional Attributes and Degradation Mechanism of Membrane Electrode Assembly Components in Direct Methanol Fuel Cells
Direct methanol fuel cells (DMFC) are typically a subset of polymer electrolyte membrane fuel cells (PEMFC) that possess benefits such as fuel flexibility, reduction in plant balance, and benign operation. Due to their benefits, DMFCs could play a substantial role in the future, specifically in replacing Li-ion batteries for portable and military applications. However, the critical concern with DMFCs is the degradation and inadequate reliability that affect the overall value chain and can potentially impede the commercialization of DMFCs. As a consequence, a reliability assessment can provide more insight into a DMFC component’s attributes. The membrane electrode assembly (MEA) is the integral component of the DMFC stack. A comprehensive understanding of its functional attributes and degradation mechanism plays a significant role in its commercialization. The methanol crossover through the membrane, carbon monoxide poisoning, high anode polarization by methanol oxidation, and operating parameters such as temperature, humidity, and others are significant contributions to MEA degradation. In addition, inadequate reliability of the MEA impacts the failure mechanism of DMFC, resulting in poor efficiency. Consequently, this paper provides a comprehensive assessment of several factors leading to the MEA degradation mechanism in order to develop a holistic understanding.