The DC link voltage depend on:

1. Which type of grid you want to connect? single phase, three phase?, and RMS of thems.

In case of single phase 220V , the DC- Link voltage 400 V or higher

In case of three phase 380V , the DC- link voltage 700 V or higher

2. Which type of Power converter you use?

Because the power have to  transfer in both side of convert through DC-Link. So the DC voltage is need to be higher than the  AC-DC direction of the converter and make sure the power can transfer to grid. 

I did not research so much about that but hope you have some keywords for searching more information

The higher the link voltage, the lower the electric current necessary to transfer the same amount of energy.

The lower the electric current, the lower are electrical losses (Ploss=I2*R). The dimensions of wires are smaller and the costs for overcurrent protection (e.g. short circuit protection) is lower.

I think the DC-link-system voltage ranges up to 1000V. These are the voltage levels I found on websites of producers of solar inverters (1000V being the typical US-voltage level). Will be the typical voltage level in europe, too, because your installing company needs higher training levels for higher voltage levels.

As already stated: the higher the voltage, the lower the current and thus the losses. Though this is only a coarse rule of thumb.

Currently I'd expect some limit for the DC link voltage at 1 kV. Exceeding this limit significantly would require another class of semiconductors. These are available in principle, but too expensive for PV applications.