Research On Root Of Photovoltaic Micro-Inverter System

In this paper, micro-inverter has been studied and the current micro-inverter topologies have conducted deeply. Each structure has its own advantages and disadvantages and the occasions which can be applied.The paper has researched the current micro-inverter. The flyback current micro-inverter is the base, so micro-inverter flyback has been detailed analyzed, and mainly studied the micro-inverter flyback topology and the distribution of loss, researched and simulation analyzed the network control and maximum power point tracking technology, designed the main circuit of the device and system hardware circuit. The research for the photovoltaic grid-connected micro-inverter has a significant reference value.Firstly, the article has discussed the classification of photovoltaic grid structure, then the concept of micro-inverter and its advantages and disadvantages and its key technologies of micro-inverter has been introduced.Characteristics of the grid-connected micro-inverter topology has been discussed, and the advantages, disadvantages, characteristics and applied surrounding of the typical structure of voltage and current micro-inverter have been studied.Secondly, the photovoltaic grid structure’s working principle of the current micro-inverter has been mainly discussed in this paper, then the voltage and current stress of the switch circuit has been calculated in order to provide a basis for the choice of components and the switching loss calculation and transformer in the main circuit. The primary side switch and the switch of the secondary tubes, diodes and transformer losses have analyzed and calculated, and the map of the circuit loss has been drawed. To some conclusions, the main factors related to the loss and the changed factor that can decline the loss have been obtained, which has an important guiding significance for the design of the current type of micro-inverter.Thirdly, the tracking the maximum power of the photovoltaic grid-connected systems’s control problems have been studied through comparative analyzing several methods of the maximum power point tracking to find the maximum power for this design. Then the maximum power tracking control strategy has been studied, and analyzed the control strategy of multi-stage and single stage and multi-level control before class and after class control loop. The difference in the single-level control and dual-loop control is analyzed theoretically, while the maximum power point tracking algorithms and the effects have been simulation analyzed. Fixed switching frequency control method has been reseached in detail to establish a small-signal model of the flyback-type micro-inverters, inverter transfer function, and then the network voltage feed-forward network access current has been analyzed, the current loop PI controller hes been designed and the net current control algorithm and the effect has been simulation analyzed.Finally, the flyback current micro-inverter main circuit devices and hardware circuit have been designed. According to the previous theoretical analysis, a relatively low loss high frequency transformer, switch and diode have been designed, and the detection circuit and power management circuits have been designed, the overall design of the software to instructions have alse been designed, and finally a load independent experiments has been made.