I tried to put labels beside the second figure, its not a subfigure. In the document i used the command \topinset but in beamer I can't use this.
I am currently creating a third new small column width, but does not give good results, like this.
\begin{frame}
\frametitle{Estado estacionario del convertidor H-NPC}
\vspace{-1.2cm}
\begin{columns}
\column{0.5\textwidth}
\begin{figure}
\centering
\[\includegraphics[width=1\linewidth]{figs_ch4/ig.eps}\]
\caption{ \justifying .}
\end{figure}
\column{0.5\textwidth}
\begin{figure}
\centering
\[\includegraphics[width=1\linewidth]{figs_ch4/todos2.eps}\]
\caption{ \justifying .}
\end{figure}
\column{0.05\textwidth}
\begin{scriptsize}
\vspace{-85pt}
a)
b)
\vspace{40pt}
c)
\end{scriptsize}
\end{columns}
\end{frame}

