Static compensator (STATCOM)
Electrical loads both generate and absorb reactive power. Since the transmitted load often varies considerably from one hour to the next, the reactive power balance in a grid varies as well. This can result in unacceptable variations in voltage, including voltage depression or even voltage collapse.
Like a Static Var Compensator (SVC) but faster, STATCOM continuously provides variable reactive power in response to voltage variations, supporting the stability of the grid. STATCOM operates according to voltage source converter (VSC) principles, combining unique power semiconductor technology with millisecond switching. STATCOM functions with a very limited need for harmonic filters, contributing to a small physical footprint. If required, switched or fixed air core reactors and capacitors can be used with the VSC as additional reactive power elements to achieve any desired range.
Installing a STATCOM at one or more suitable points in a grid will increase power transfer capability by enhancing voltage stability and maintaining a smooth voltage profile under different network conditions. Its ability to perform active filtering is also very useful for improvements in power quality.
Hitachi Energy's offerings in the high power STATCOM field include SVC Light STATCOM as well as PCS 6000 STATCOM, where PCS 6000 STATCOM is applicable for unit ratings up to 40 Mvar and SVC Light STATCOM is applicable for ratings exceeding 40 Mvar.
SVC Light® STATCOM
SVC Light can be considered a voltage source behind a reactance. Physically, it is built as a Modular Multi-level Converter (MMC) operating with distributed DC link or operating at constant direct current (DC) voltage (depending on VSC topology). It generates and absorbs reactive power by electronically processing voltage and current waveforms in a voltage source converter. The grid views it as a synchronous machine without inertia. As a result, SVC Light® is capable of generating and absorbing reactive power, which enables a compact design and small footprint through the removal of capacitor banks and shunt reactors. The high overall effective switching frequency of the semiconductors provides extremely fast control and a smooth output voltage. It is particularly useful in applications such as mitigating the voltage flicker created by electric arc furnaces, voltage balancing, harmonic filtering and grid voltage recovery.
SVC Light is available for system voltages up to 69 kV and converter ratings over -/+ 400 Mvar. For higher voltages, a step-down transformer is used to connect SVC Light to the grid. SVC Light provides a symmetrical operating range. For asymmetrical operations and in order to optimize performance, thyristor-switched reactors and capacitors are operated in parallel to form hybrid solutions.
PCS 6000 STATCOM
PCS 6000 STATCOM is an efficient power system package specifically designed to be connected to demanding networks. The flexibility of the system allows it to be applied to a wide range of applications such as dynamic voltage stabilization, voltage balancing of asymmetrical loads, mitigating voltage flicker created by electric arc furnaces, and active harmonic filtering.
The PCS 6000 STATCOM is particularly competitive in terms of installation time and space requirements. Furthermore, the high efficiency and low maintenance lead to low operational costs. The PCS 6000 provides outstanding performance for both steady state and dynamic operation as a pure static device with no switched passive elements.
The PCS 6000 STATCOM solution is virtually maintenance free, due to the minimized number of moving mechanical parts. Outages for inspection can therefore be scheduled according to the customer’s needs and preferences. No rotating parts in the energy path result in extremely high reliability, availability and low operational costs combined with long life expectancy. The equipment is typically installed in a pre-assembled container. The STATCOM system including controls, power electronics and cooling unit are tailor made for fulfilling the customer specific requirements.