A Pure Integral-Type PLL with a Damping Branch to Enhance the Stability of Grid-Tied Inverter under Weak Grids

Kavli Affiliate: Yi Zhou

| First 5 Authors: Yi Zhou, Zhouchen Deng, Shi Chen, Yiwei Qiu, Tianlei Zang

| Summary:

In a phase-locked loop (PLL) synchronized inverter, due to the strong
nonlinear coupling between the PLL’s parame-ters and the operation power angle,
the equivalent damping coefficient will quickly deteriorate while the power
angle is close to 90{deg} under an ultra-weak grid, which causes the
synchronous instability. To address this issue, in this letter, a pure
integral-type phase-locked loop (IPLL) with a damping branch is proposed to
replace the traditional PI-type PLL. The equivalent damping coefficient of an
IPLL-synchronized inverter is decoupled with the steady-state power angle. As a
result, the IPLL-synchronized inverter can stably operate under an ultra-weak
grid when the equilibrium point exists. Finally, time-domain simulation results
verify the effectiveness and correctness of the proposed IPLL.

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