Why do I get high DC current in grid tied inverter output?
Basically, a voltage inverter is a voltage source. And the grid is also a voltage source.

So, in a grid-tied voltage inverter, you connect two voltage sources with only a (small) inductor in between.

The current in the inductor is given by:

$$ i(t) = \frac{1}{L} \int {(v_I(t) - v_G(t)) dt } $$

where \$ v_I(t) \$ and \$v_G(t)\$ are the inverter and grid voltages respectively.

The DC offset you observe certainly depends on the value of the integral from the beginning of the simulation to the time you begin to plot your current. If you change (slightly) the time offset between inverter command and grid voltage, the offset will change.

Real grid-tied inverters, cannot operate without a current loop which measures the current in the inductor and drives the inverter in order to obtain a given (usually sinusoïdal) current reference.

If you do not put this control loop, any small difference between the inverter command (and thus voltage \$v_I(t)\$) and the grid will make the current diverge.