According to Charles's Law, for an ideal gas at constant pressure, the volume is directly proportional to its absolute temperature ($V \propto T$).

1. Initial State: $V_1 = V$, $T_1 = 0^\circ\text{C} = 273 \text{ K}$.
2. Final State: The volume expands to $3V$. Since $V \propto T$, if the volume becomes 3 times the initial volume, the absolute temperature must also become 3 times the initial temperature. $T_2 = 3T_1 = 3 \times 273 = 819 \text{ K}$.
3. Calculate Increase: Change in temperature $\Delta T = T_2 - T_1 = 3T_1 - T_1 = 2T_1$.
4. Percentage Increase: $\% \text{ Increase} = \frac{\Delta T}{T_1} \times 100 = \frac{2T_1}{T_1} \times 100 = 200\%$.