A finite-element analysis approach to determine the parasitic capacitances of high-frequency multiwinding transformers for photovoltaic inverters

Magnetic components such as transformers and inductors play a significant role in the efficiency and size/weight of inverter. They are also amongst the most difficult components to design, often requiring numerous design interactions and testing. Understanding and accurate prediction of parasitic winding capacitances of high-frequency multiwinding transformers in PV inverters is fundamental to improve performance, lower cost, and speed time to market. Parasitic capacitances are highly dependent on the winding geometry and the proximity of conducting surfaces. As the geometry of the components becomes more complicated, it is almost impossible to derive analytical equations that describe accurately the behavior of magnetic components. Currently, parasitic capacitances of the multiwinding transformers are only known with certainty once a prototype is built. Therefore a design-build-test cycle needs to be iterated, often at substantial cost and time. This paper presents a technique and method to quantitatively predict the parasitic capacitance of high-frequency multiwinding transformer by means of finite-element analysis (FEA). Comparison of the FEA results with a commercially constructed experimental prototype results shows good agreement.