Abstract
In this paper, a DC–single-phase AC power converter with an LLC resonant converter is presented for a photovoltaic (PV) micro-inverter application. This application requires the leakage current suppression capability. Therefore, an isolated power converter is usually combined for DC/AC systems. The LLC resonant converter is the one of the isolated power converter topologies, and it has good performance for conversion efficiency with easy control. On the other hand, a double-line frequency power ripple has to be compensated for in order to improve the performance of the maximum power point tracking (MPPT). Therefore, a bulky electrolytic capacitor is usually necessary for the power converter. However, the electrolytic capacitor may limit the lifetime of the micro-inverter. This paper introduces the PV micro-inverter with a LLC resonant converter. In addition, the active power decoupling circuit is applied in order to compensate the double-line frequency power ripple by the small capacitor in order to eliminate the electrolytic capacitor. Finally, the transformer design is considered in order to reduce the transformer losses. As a result, the conversion efficiency of the LLC converter is improved by 1% when the litz wire has many strands.
Highlights
Photovoltaic systems (PVs) are actively researched as a sustainable power solution due to their attractive characteristics such as flexibility, high system efficiency, and low manufacturing cost.In order to enhance the utilization of photovoltaic systems (PVs), the generative power optimization by maximum power point tracking (MPPT) is necessary.the decrease of the generative power due to the shade is a problem for PVs with the typical centralized power conversion system (PCS)
In order to enhance the utilization of PVs, the generative power optimization by MPPT is necessary
The decrease of the generative power due to the shade is a problem for PVs with the typical centralized power conversion system (PCS)
Summary
Photovoltaic systems (PVs) are actively researched as a sustainable power solution due to their attractive characteristics such as flexibility, high system efficiency, and low manufacturing cost. Note that the micro-inverters consist of the DC/AC converter and the isolated DC/DC converter because the leakage current due to the stray capacitance of the PV panel should be avoided for safety reasons and for easy installation In this case, a flyback converter or push-pull converter is often chosen because these circuits have some advantages, e.g., a low number of components. The active power decoupling circuit based on the boost converter is combined with the micro-inverter in order to eliminate the bulky electrolytic capacitor in order to improve the reliability. The conversion efficiency of the LLC resonant converter is evaluated using two type litz wire in order to reduce the skin effect due to the high switching frequency operation. A lot of papers have only considered the transformer loss or the inductor loss [12], and the relationship between the number of strands and the conversion efficiency is not clarified
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