I have a table with an empty first column. All the other columns are filled with text or formulae. I want to write the words "DC grid" vertically over the whole first column except for the first two rows (which are already used) without changing the overall look of my table.
The problem is, I cannot simply use \multirow because I want to write over several cells (not just rows). I tried to do tables inside tables (nested tables) but I can't get rid of the additional space added by the nested table.
Here is my table (I want to write "DC grid" vertically in the empty first column):

\begin{table}[!htbp]%200pts de large
\centerline{\resizebox{0.90\linewidth}{!}{\begin{tabular}
{|>{\centering}p{15pt}|>{\centering}p{25pt}|>{\centering}p{55pt}|>{\centering}p{20pt}|>{\centering}p{23pt}|>{\centering}p{70pt}|}\hline %\pm
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\multicolumn{3}{|c|}{\multirow{2}{*}{\textbf{Eigenvalues}}} & \textbf{Freq. (Hz)} & \textbf{Damp. ratio} & \centering \multirow{2}{*}{\textbf{Dominant states}}\tabularnewline\hline
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& \multirow{1}{*}{$\lambda_{dc_{1,2}}$} & \multirow{1}{*}{$-56.7 \pm j2130$} & \multirow{1}{*}{$339$} & \multirow{1}{*}{$0.027$} & $X_{p_1}$, $X_{p_2}$, $X_{p_3}$, \tabularnewline\cline{2-5}
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& \multirow{1}{*}{$\lambda_{dc_{2,3}}$} & \multirow{1}{*}{$-56.7 - j2011$} & \multirow{1}{*}{$320$} & \multirow{1}{*}{$0.028$} & $\Delta u_{s_1}$, $\Delta u_{s_2}$, $\Delta u_{s_3}$ \tabularnewline\cline{2-5}
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& \multirow{1}{*}{$\lambda_{dc_{5,6}}$} & \multirow{1}{*}{$-60.0 \pm j1426$} & \multirow{1}{*}{$227$} & \multirow{1}{*}{$0.040$} & $\Delta u_{s_4}$, $\Delta u_{s_5}$\tabularnewline\cline{2-6}
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& \multirow{4}{*}{$\lambda_{dc_{7,8}}$} & \multirow{4}{*}{$-57 \pm j1223$} & \multirow{4}{*}{$195$} & \multirow{4}{*}{$0.047$} & $i_{l_{1_1}}$, $i_{l_{2_1}}$, $i_{l_{1_4}}$, $i_{l_{2_4}}$, $i_{l_{1_5}}$, $i_{l_{2_5}}$\vspace{0.4mm}, $\Delta u_{s_1}$, $\Delta u_{s_2}$, $\Delta u_{s_3}$, $\Delta u_{s_4}$, $\Delta u_{s_5}$\tabularnewline\cline{2-6}
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& \multirow{1}{*}{$\lambda_{dc_{9}}$} & \multirow{1}{*}{$-117.1$} & \multirow{1}{*}{ -- } & \multirow{1}{*}{ -- } & $i_{l_{1_1}}$, $i_{l_{2_1}}$, $i_{l_{1_2}}$,\tabularnewline\cline{2-5}
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& \multirow{1}{*}{$\lambda_{dc_{10}}$} & \multirow{1}{*}{$-4.497$} & \multirow{1}{*}{ -- } & \multirow{1}{*}{ -- } & $i_{l_{2_2}}$, $i_{l_{1_3}}$, $i_{l_{2_3}}$,\tabularnewline\cline{2-5}
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& \multirow{1}{*}{$\lambda_{dc_{11}}$} & \multirow{1}{*}{$-4.476$} & \multirow{1}{*}{ -- } & \multirow{1}{*}{ -- } & $i_{l_{1_4}}$, $i_{l_{2_4}}$, $i_{l_{1_5}}$,\tabularnewline\cline{2-5}
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& \multirow{1}{*}{$\lambda_{dc_{12}}$} & \multirow{1}{*}{$-0.604$} & \multirow{1}{*}{ -- } & \multirow{1}{*}{ -- } & $i_{l_{2_5}}$, $i_{l_{1_6}}$, $i_{l_{2_6}}$,\tabularnewline\cline{1-6}
%
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\end{tabular}}}\vspace{3mm}
\caption{Modal Analysis of the 5-Terminal HVDC Grid}\label{tab5}\end{table}%


