A Switched Capacitor Based 13L6x Boost Inverter for Grid-Tied Transformerless PV Application

Transformerless grid-connected PV (photovoltaic) inverters are not suited for low-voltage PV applications because they have serious leakage current, low output voltage, and large filter sizes. In this paper, a new thirteen-level inverter based on the switched capacitor (SC) with an optional ac decoupling circuit is proposed, which offers a gain of input voltage that is six times higher while using fewer switches. Therefore, for low-voltage PV applications, this inverter is preferred without any boost dc/dc converter stages. Three SC cells are used to increase the input PV voltage and enable thirteen steps in the output voltage. The inverter's ac decoupling unit structure serves in keeping CMV (common mode voltage) constant during zero voltage generation operation, which significantly lowers leakage current. The active and reactive grid power are regulated by a proportional resonant (PR) controller. The proposed modulation method assists in balancing the voltages of switched capacitors at their base voltage with the allowed ripple. Details of the inverter circuit as well as the PWM scheme and control technique are also discussed. The proposed inverter's correctness is proven by the results of a Matlab simulation.