Advanced power electronics provide near-instantaneous response to changes in the system voltage. These systems also offer greater capacity and are more reliable and cost effective when compared to other dynamic compensation schemes, including synchronous condensers or mechanically switched systems.
SVC’s with Light Triggered Technology
Mitsubishi Electric further advances the standard SVC by offering Direct Light Triggered Thyristor (LTT) technology. Since its introduction, more than 65 SVCs using LTTs have been installed around the world.
The thyristor valve is the most critical component of an SVC and the thyristor itself is of particular importance. Though earlier SVC and High Voltage DC (HVDC) systems used Electrically-Triggered Thyristors (ETT), Mitsubishi Electric pioneered the application of Direct Light-Triggered Thyristors (LTT) for HVDCs in 1983 and SVCs in 1984.
With this technology, firing pulses, independent of the AC system voltage, eliminate the need for auxiliary energy within the valve itself. Compared to traditional ETT devices, these thyristors are fired directly through optical fibers requiring less complicated circuitry and no high-voltage insulation.
LTTs also provide a voltage divider with simple standard components instead of specialized circuits. The result is an optimized wiring module with less risk of accidental damage, quick and easy maintenance, and a reduced need for mandatory spare parts. LTT technology substantially reduces the number of electrical components in the valves, providing higher reliability by eliminating the possibility of electromagnetic interference (EMI).
LTT valves contain 90 percent fewer components when compared to similar ETT devices. Over a 30-year period that includes more than 100 large scale installations, Mitsubishi Electric has documented a 70 percent reduction in inspection time, 85 percent reduction in maintenance costs, and a thyristor valve forced outage availability rating of more than 99.9 percent.
STATCOM Systems Using MMC
Mitsubishi has developed, manufactured and commissioned many STATCOMs; including the world’s first utility STATCOM (+/- 80 MVAr) in 1991 and the world largest STATCOM (+/- 450 MVAr) in 2012. Today, Mitsubishi has developed the next generation STATCOM using the latest Modular Multilevel Converter (MMC) topology that applies Mitsubishi’s own reliable and proven Insulated-Gate Bipolar Transistors (IGBT) in many FACTS, HVDC, and other heavy industrial/utility applications today.