A Synchronization Method for Grid Converters with Enhanced Small-Signal and Transient Dynamics

An increasing integration of voltage source based renewable energy systems into the power system is a global trend, that has led to requirements for converter control during low voltage and fault situations. To guarantee stable operation, grid synchronization is a key factor, which greatly influences the stability and ride-through performance of the converter. This paper proposes an improved grid synchronization technique, which enhances the transient performance of the converter under severe grid conditions, such as three phase faults and voltage phase jumps. This is achieved by combining a low bandwidth Synchronous Reference Frame Phase-Locked Loop (SRF-PLL) together with a feed-forward term. This combination effectively results in a synchronization unit including high noise immunity, e.g. enhanced small-signal performance and a fast dynamic response with a phase tracking capability below 5 ms. The proposed synchronization unit is tested during phase jumps and symmetrical three-phase faults to analyze its performance, which is validated through simulations and experimental results.