Grid connection low temperature waste heat power generating system and starting control method thereof

The invention discloses a grid connection low temperature waste heat power generating system and a starting control method of the grid connection low temperature waste heat power generating system. The grid connection low temperature waste heat power generating system mainly comprises an expansion machine, a permanent magnet synchronous power generator, a back-to-back converter, an organic working medium Rankin circulating heat exchanging system and a corresponding control device; when the system starts, the expansion machine is driven by electricity and reaches a rated rotating speed, the energy wasted due to the low rotating speed when organic working medium directly pushes a turbine is saved, the method can be used for starting the low temperature waste heat power generating system to conduct the grid connection power generation without satisfying the synchronous condition between the voltage of the power generator and the voltage of a grid, the impact on the system of the traditional starting method is reduced, friendly connection into the grid can be realized by the starting method, and the stable, reliable and efficient operation of the grid connection low temperature waste heat power generating system can be realized.