A micro inverter or solar microinverter, is a device used in photovoltaics that converts direct current (DC)generated by single solar module to alternating current (AC). The output fromthe several micro inverters are combined and often fed to the electrical grid. Micro inverters with conventional string and central solarinverters, which are connected to multi polesolar modules or panels of the PV system 1.
Micro inverters have several advantages. The main advantage is that smallamounts of shading, debris or snow lines on any one solar module, or even acomplete model failure do notdisproportionately reduce the out put of the entire array. Each micro inverterharvests optimum power by performingmaximum power point tracking (MPPT) forits connected module 2.
Simplicity in design, lower amperage wires,simplified stock management, and added safety are other factors introduced withmicro inverter solution. For grid connection of a single PV module, it isnecessary to boost its voltage around 20% over the peak grid voltage to workproperly 3. The conventional micro invertercomposed of two stages: a step-up dc-dc stage is used to boost the dc-linkvoltage above the grid peak voltage, and a second stage is step-up inverterconnected to the grid as shown in general block diagram Fig. 1.a. The highfrequency transformer is used in dc-dc stage to achieve the required voltagestep-up ratio 4-8.
Here two converters are used, one of them with a highfrequency isolation transformer, results in lower efficiencies compared tostring based inverters 9. Recently, some single-stage step-updc-ac configuration have been proposed shown in Fig. 1.
b. The single stagestep-up have to full fill two functions with a single converter to elevate PVmodule voltage and realize dc-dc conversion 10-14. Then two stage microinverter composed of two stages: a step-up converter for dc-dc conversion shownin Fig. 1.c. This is similar to conventional model but the high frequencytransformer is eliminated here. And dc-ac conversion is to elevate the outputvoltage and here two boost converters are connected in differential mode. Itgreatly reduces the switching losses 16.