Parameter Design Oriented Analysis of the Current Control Stability of the Weak-Grid-Tied VSC

This paper studies the dynamic behaviors of weak-grid-tied VSCs with simplified transfer functions, which provides an accurate stability analysis and useful indications for tuning system parameters. A reduced-order multi-input multi-output (MIMO) function that contains four single-input single-output (SISO) functions VSC is first presented. It found SISO share same equivalent open-loop function, i.e., conclusion. The Bode plots show inner current loop behaves as a band-pass filter whose maximum gain approximately at frequency PLL's bandwidth. By criterion, harmonic amplification instability occur when its exceeds 0 dB caused by high bandwidth, large grid impedance or active power. also target less stable it works inverter than rectifier, due to risk local positive feedback in mode. An effective criterion further proposed guide selection proper bandwidth ensure system. Simulation results validate correctness efficacy criterion.