Grid Forming Control of PHC Based STATCOM

Voltage stability, power quality, and reactive power support are critical in modern power systems, particularly with increasing renewable energy integration and distributed generation. Static synchronous compensators (STATCOMs) are vital for addressing these challenges. Utilizing modular multilevel converters (MMCs) as STATCOMs enhances reactive power compensation and voltage management. Among various MMC-STATCOM topologies, the parallel hybrid converter (PHC) configuration is preferred because of its smaller capacitor size, reduced component count, and lower switching losses. Traditional PHC-STATCOMs operate in grid-following (GFL) mode, which is inadequate under weak grid or isolated operation due to dependency on grid for obtaining the phase angle. Grid-forming (GFM) control, emulating synchronous generators, provides autonomous voltage and frequency regulation, essential for grid stability with high renewable energy penetration. Implementing GFM control in MMC-based STATCOMs, particularly PHC-STATCOMs, poses challenges such as voltage modules (VMs) balance, stability during disturbances, and fast dynamic response. This paper explores GFM control implementation for PHC-STATCOM, addressing aforementioned challenges under different test case scenarios like balance/unbalance grid, unbalance load etc. Finally, a hardware prototype of 370 V/± 5 kVAR, 7-level 3-phase PHC-STATCOM has been developed to verify the proposed GFM control.