Difficulty stabilizing a system using sisotool on Matlab
Well, if you want a second order controller without overshoot. The equation for the second order system should be on the mold of,
$$H(s) =\frac{H_0}{\left(\dfrac{s}{\omega_0}\right)^2 +2 \dfrac{\zeta}{\omega_0} s + 1} = \frac{V_{in_{max}}}{LCs^2+\dfrac{L}{R}s+1},$$
Where, \$\omega_0 = \frac{1}{\sqrt{LC}}\$ and \$\zeta=\frac{\sqrt{L}}{2R\sqrt{C}}\$.

By looking at the overshoot formula for second order systems you will see that you want it to have 
$$\zeta = 0.$$

But, to have it as such you would have to have \$L=0\$, which you cannot for the system to work. Now, to get within the 20% overshoot that you want you can use the formula (on the wikipedia link) and figure out how big \$\zeta\$ can be.

With the following system/controller:

feedback(series(pid(1,0.001,0.000005),plant),1)








simulate this circuit &ndash; Schematic created using CircuitLab

I got the following result,