In the renewable energy collection system, non-frequency transient over-voltages, which are generated during the AC short-circuit fault and its clearance, may lead to large-scale disconnection or even destruction of renewable energy devices. This has become a decisive factor in restricting the power transmission limit of the renewable energy collection system. This paper contrasts the magnitude of transient over-voltages during the fault cleaning process when the permanent magnet synchronous generators (PMSG) use grid-following control strategies and grid-forming control strategies, and analyzes the impact of grid-forming control strategies on the transient over-voltages during fault cleaning process. The analysis results indicate that the grid-forming control strategy, which is applied in PMSG, has a clear advantage in reducing the transient over-voltage during the cleaning process.