Commissioned by grid operator Amprion, Siemens built two reactive power compensation systems for the important Kriftel, Germany power grid node: a mechanically switched capacitor with damping network (MSCDN) and a power-electronic static synchronous compensator (STATCOM).
The systems have been running successfully in test operation since December 2018. They’re able to dynamically, rapidly, and flexibly increase or decrease the grid voltage on demand, which is necessary to keep the grid stable despite the increase in fluctuating power supplies from renewable and distributed energy sources.
At the same time, the system will help prevent gaps in supply due to large power plant shutdowns. The Kriftel substation between Frankfurt and Wiesbaden controls power distribution for the Greater Frankfurt Area and its almost six million inhabitants.
Siemens also built its first advanced power modules in Kriftel. These IGBT power transistor modules can supply more power than predecessor modules, which means that fewer modules are required for the specified control range than it was formerly the case.
The core of SVC PLUS, an advanced STATCOM, is its multilevel converter technology. By contrast with other self-commutated converter topologies, the voltage waveshape produced by SVC PLUS is practically sinusoidal due to the multilevel technology. This makes the low-frequency harmonic filters often used in earlier solutions superfluous and substantially reduces the space requirements for the overall unit. The average availability of a Siemens SVC PLUS system far exceeds 99 percent.
Alternating-current electricity transmission requires reactive power, which is typically provided primarily by large power plants. Due to the energy transition, many of these plants in Germany have been shut down – which is why grid operators like Amprion are responding by installing reactive power compensation systems. Reactive power supports grid voltage during long-distance large-scale power transmission. These large electricity transports are necessary when wind power from northern Germany is needed in its industrial south. By using reactive power, the grid voltage can be increased or decreased, and electricity can be efficiently transmitted.