Fault-Tolerant Cascaded H-Bridge based Enhanced-STATCOM in a Power Electronics Dominated Grid

Providing inertial power support from cascaded H-bridge (CHB)-based static synchronous compensators (STAT-COMs) significantly minimizes grid frequency deviation in a high-power electronics-based resources (PEBRs) network. However, power device faults in STATCOMS lead to frequency instability due to loss of energy. This study presents a novel approach to enhance the grid frequency characteristics even with multiple multi-phase device faults in CHB-STATCOM. This paper proposes an enhanced CHB-STATCOM (E-STATCOM) topology that aims to achieve balanced line voltages during switch faults and effectively handle large-frequency events. In this topology, a three-phase, battery-operated voltage source inverter (BOVSI) is connected in series with a three-phase CHB STATCOM. During post-fault conditions, the modulating signals of the enhanced converter are adjusted to achieve balanced line voltages. The BOVSI is calibrated to maintain the pre-fault line voltage and provide sufficient inertial power support to minimise frequency deviation during various frequency events. However, providing inertial power by BOVSI needs to measure the rate of change of frequency deviation. Obtaining this term by directly differentiating the frequency change sensed from the phase-locked loop (PLL) generates noise. This study uses frequency-locked loops (FLL) to generate a time-derivative term of frequency change, considerably reducing noise.