Unified Power Flow Controller (UPFC)

Unified Power Flow Controller (UPFC) is the most advanced FACTS solution which provides independent active power and reactive power control of the transmission system. The UPFC is a combination of static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC) coupled via a common DC voltage link.

Due to the dynamic and flexible control in both active and reactive power UPFC can bring a bunch of benefits to power transmission system:

  • Flexible power flow control
  • Dynamic voltage regulation
  • Improved system stability
  • Power oscillation damping
  • Regulation of loop current in meshed network to achieve optimal load flow
  • Increase of transmission capacity of existing network and avoid installation of new lines

UPFC solution from NR is based on state-of-art MMC converter. Through connection of sub-modules in series power regulation at various high voltage levels is achieved according to system requirement.

Unified Power Flow Controller (UPFC)


  • MMC converter with high flexibility
  • Redundant sub-modules to ensure high availability
  • Low converter losses
  • No filters required
  • Easy scalability

Case Study

UPFC for Nanjing Western Ring Grid

Nanjing Western-Ring Grid powers many important loads through complex meshed network. With the rapid increase of electricity demands, the UPFC solution is chosen to optimize power flow and improve flexibility and controllability of the grid. [View More...]


The first MMC based UPFC in the world was successfully put into service in 220 kV grid of Nanjing city on Dec.11th, 2015 by NR Electric. NR Electric is responsible for the total solution covering system study, basic design and detailed design, manufacturing and procurement, installation, commissioning. The successful operation of UPFC marks that NR Electric has completely owned the capability of designing, supplying, manufacturing and commissioning of UPFC as a turnkey solution provider.
  • Consulting and System Planning
  • Project Management
  • Conceptual & Detailed Design
  • Manufacturing & Testing
  • Engineering & Procurement
  • Site construction, installation
  • Onsite Testing & Commissioning
  • Operation and maintenance services