The Development Of Interleaved Flyback Micro-inverter

With the advent of the world energy crisis, photovoltaic(PV) grid inverter ushered in the unprecedented opportunity. Traditional centralized photovoltaic grid inverter is mainly used in large scale solar farms. This form of inverter cannot guarantee that PV cells work well at the maximum power point due to various factors in the reality. Micro-inverter, also known as AC module, emerges as the times require. With its high efficiency of maximum power point tracking technology, convenience of installation, low cost of management and safety, micro-inverter has become a research hotspot in recent years.Interleaved flyback micro-inverter as a typical micro-inverter topology structure, is the main content of this article research. Through the analysis of interleaved flyback micro-inverter’s working principle, structure and features, the interleaved flyback micro-inverter is studied by the following aspects: contrast of the working mode of flyback, establishment of loss model, selection of important device, optimization of control strategy. Eventually, a corresponding experimental platform is set up and a rated power of 200 w experimental prototype is made for validation.In terms of structural principles, interleaved flyback micro-inverter working at the discontinuous conduction mode is mainly analyzed in this paper. Specifically, the working principle of each part of micro-inverter is also expatiated. the three working modes of flyback is compared, and thus the loss model of DCM mode is established, which provides a theoretical basis for the efficiency optimization.In the aspect of control strategy, this paper by theoretically compares the efficiency difference between 1 phase DCM operation and 2 phase DCM operation respectively under different output power. Eventually the hybrid control strategy based on instantaneous power output is adopted, and the related experiment is verified, the effect is proved well. The maximum power point tracking algorithm is realized by using variable step tracking under the peak current mode. Islanding detection is achieved by passive way. Grid control, through the establishment of flyback ac small signal model of non-ideal state, is compensated with the current PI loop, feedforward voltage and current equalization. Simulation model is also established under Matlab, and the grid current is verified.In terms of software and hardware design, this paper has carried on the detailed elaboration. Hardware, this paper introduces the main control chip TMS320F2812 referring to resource configuration, detection circuit, drive circuit, auxiliary power supply; Software, this paper introduces the interrupt control, state machine control, phase-locked loop control process. On this basis, efficiency experiments are conducted with the development of prototype, the test waveforms are given accordingly.