Flexible topological converter applied to photovoltaic micro-inverter, and digital control device thereof

Abstract

The invention discloses a flexible topological converter applied to a photovoltaic micro-inverter. The flexible topological converter is used in a DC/DC link at a first stage of the micro-inverter, the micro-inverter operates in a full-bridge mode at high power and operates in a forward mode at lower power, design parameters of a transformer under the two situations are identical, the flexible topological converter can realize efficient conversion at high power and low power, and the high weighting efficiency of the micro-inverter is realized.

Description

technical field [0001] The invention relates to a flexible topology converter applied to a photovoltaic micro-inverter and a digital control device thereof, and belongs to the technical field of power electronic converters and control thereof. Background technique [0002] Micro-inverter is an important research direction of photovoltaic power generation. Compared with string power supply and centralized power supply, micro-inverter can ensure that photovoltaic cells work at the maximum power point, modular design, hot-swappable, redundant A series of advantages such as good performance, high reliability and convenient installation have attracted wide attention from all walks of life. [0003] The improvement of power conversion efficiency has always been an important research direction of photovoltaic micro-inverters. For this reason, researchers have proposed a variety of non-isolated micro-inverters and isolated micro-inverters. Since the output voltage of a single photo...

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Problems solved by technology

Since the output voltage of a single photovoltaic cell is low (25V-50V), to achieve grid connection, a two-stage circuit structure can be used, and then inverter is performed after boosting. It is difficult for the commonly used Boost converter to efficiently achieve a high boost ratio, so A high boost ratio converter with a specific structure is required. This type of converter generally uses the turn ratio of the coupled inductor to achieve a boost ratio of more than 10 times, but the high boost ratio converter also requires more diodes and passive components. However, micro-inverters that use high-frequency transformers to achieve electrical isolation can complete the inversion function with fewer power conversion stages. At present, flyback micro-inverters are more researched in isolated micro-inverters. In addition, forward, push-pull, full-bridge and Zeta micro-inverters have also been researched. The circuit structure of isolated full-bridge and Zeta micro-inverters is more complicated, which is not conducive to the improvement of circuit efficiency under low power conditions. Flyback and forward The circuit structure of the micro-inverter is relatively simple, but the secondary circuit diode of the forward micro-inverter commutates at the peak current, which causes parasitic oscillation and reverse recovery loss of the diode, and it is difficult to improve the efficiency; the flyback micro-inverter The power of the inverter is limited by the energy storage transfo

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