Somdev, whose ranking has plummeted to 551, defeated Phau, who is ranked 78, 6-3 6-2 6-3 in close to a two-hour match here.
The 27-year-old Indian will next take on the winner of another first round match between Simone Bolelli of Italy and Polish Jerzy Janowicz.
Somdev converted two of the three break point chances that came his way and also hit a couple of aces to comfortably move ahead in the opening set which lasted for 31 minutes.
In the second set, which lasted for 44 minutes, Somdev double faulted once but won two of the four break point chances.
Somdev took another 35 minutes to wrap up the match as he broke the German twice and also had a better second serve winning percentage then Phau in the third set.