STATCOM (Static Synchronous Compensator) is a power electronics-based device used in electrical power systems to provide fast-acting reactive power compensation, voltage regulation, and stability enhancement. It is a member of the Flexible AC Transmission System (FACTS) family and is widely used in modern power grids to improve power quality and system efficiency.

• A STATCOM consists of a Voltage-Source Converter (VSC), a DC capacitor, and a coupling transformer.
• The VSC generates an AC voltage in phase with the grid but with adjustable magnitude.
  • If the output voltage is higher than the grid voltage, it injects capacitive reactive power (leading).
  • If the output voltage is lower, it absorbs inductive reactive power (lagging).
• The DC capacitor provides the necessary energy storage for the converter.

Key Features of STATCOM:

1. Reactive Power Compensation
   • Generates or absorbs reactive power (VARs) dynamically to maintain voltage stability.
   • Unlike traditional SVCs (Static VAR Compensators), STATCOMs use voltage-source converters (VSCs) for smoother and faster response.
2. Voltage Regulation
   • Maintains bus voltage at a desired level by injecting or absorbing reactive power.
   • Helps mitigate voltage sags, swells, and flicker.
3. Dynamic Performance
   • Faster response compared to mechanical switches and thyristor-based compensators (response time in milliseconds).
   • Effective in damping power oscillations and improving transient stability.
4. No Need for Large Capacitors/Reactors
   • Uses DC capacitors and power electronics (IGBTs/GTOs) instead of bulky passive components.
5. Black Start Capability
   • Some STATCOMs can help restore power in case of a blackout by providing reactive power support.