Impact of Reactive Current and Phase-Locked Loop on Converters in Grid Faults

Abstract

The precise control of output power by grid-connected converters relies on the correct identification and tracking of a grid voltage’s phase at the converter terminal. During severe grid faults, large disturbances cause the converter’s operating point to move away from the stable equilibrium point during normal operation. This leads to oscillations of both the active and reactive power fed into the grid. Using large-signal modelling, this study investigated the converter’s dynamic processes during and after such fault situations. The investigation considered the influence of the converter’s phase-locked loop (PLL), responsible for phase tracking, as well as that of the DC link on the converter-grid system, which has a major influence on the active power exchange with the grid. On this basis, this study also focused on the reactive current reference’s influence during and after fault clearing. Furthermore, an easily implementable strategy for reactive current injection, leading to minimum power oscillations, was presented. The results and the optimized strategies were validated via controller hardware-in-the-loop tests.

Deployment of a full‐size converter utilised hydropower plant to enhance inter‐area oscillation damping

“…The PLL estimates the frequency 𝜔 pll and the voltage phase angle 𝜃 pll at PCC. It is well known, that PLL affects the stability behaviour of grid-connected converters during severe grid faults [53]. Thus to obtain expressive results in this simulation study, the PLL dynamics is taken into account.…”

Investigating the effects of current thresholds on phase jump limits and withstand capabilities in grid‐forming converters

“…Most existing studies on the transient stability of GFM converters have focused on scenarios involving voltage dips, thereby overlooking the system dynamics under rated voltage amplitude conditions. During voltage dips, the active power output of the converter decreases in tandem with the terminal voltage, leading to minor variations in active power and a negligible impact on the overall power balance of the power system [16]. Conversely, in conditions close to rated voltage amplitude, the converter's active power output increases with the terminal voltage.…”

Large-Signal Impedance Modeling and Stability Analysis of a Grid-Connected Inverter Considering the Influence of a Limiter in Different Control Links

“…Moreso, it ignores the nonlinear limiter in practical systems and fails to analyze the constant amplitude oscillations induced by the limiter. Transient stability analysis techniques are frequently utilized in large-signal disturbance and limiter analysis [17][18][19].…”