What is the difference between SVC and STATCOM?

STATCOM is a FACTS device of parallel reactive power compensation. It can emit or absorb reactive power, and its output can be changed to control specific parameters in power system. Static var compensator (SVC) rose in the 1970s and has developed into a very mature FACTS device. It is widely used in load compensation and transmission line compensation (voltage and reactive power compensation) of modern power system. In high-power power grid, SVC is used for voltage control or other benefits, such as improving system damping and stability. So, what is the difference between SVC and STATCOM?

The following is a list of contents

• What is STATCOM

• What is Static var compensator

• The difference between SVC and STATCOM

What is a STATCOM

STATCOM is a FACTS device of parallel reactive power compensation. It can emit or absorb reactive power, and its output can be changed to control specific parameters in power system. Generally, it is a solid-state switching converter. When its input end is connected with a power supply or energy storage device, its output end can independently send out or absorb controllable active and reactive power; It can improve the functions of power system in the following aspects: dynamic voltage control, power oscillation damping, transient stability, voltage flicker control and so on. Compared with traditional reactive power compensation devices, STATCOM has the advantages of continuous regulation, small harmonic, low loss, wide operation range, high reliability and fast regulation speed. Since its inception, STATCOM has received extensive attention and rapid development.

What is Static var compensator

Static synchronous var compensator is the most advanced reactive power compensation device. It no longer uses high-capacity capacitors and inductors to generate the required reactive power, but realizes the qualitative leap of reactive power compensation technology through the high-frequency switch of power electronic devices. It is especially suitable for dynamic reactive power compensation in medium and high voltage power system.

Static var compensator is a fast, smooth and controllable dynamic reactive power compensation device without rotating parts. It uses controllable reactors and power capacitors (fixed or group switching) in parallel. The capacitor can emit reactive power (capacitive), and the controllable reactor can absorb reactive power (inductive). By adjusting the reactor, the whole device can change smoothly from sending reactive power to absorbing reactive power (or reverse), and the response is fast.

The difference between SVC and STATCOM

Typical parallel FACTS devices are SVC and STATCOM, which represent two stages of the development of FACTS technology. SVC refers to the reactive power compensation system composed of fixed capacitor bank, thyristor controlled capacitor bank (TSC) and reactor Bank (TCR). By adjusting TCR and TSC, the reactive power output of the whole device changes continuously, the voltage is maintained within a certain range statically and dynamically, and the stability of the system is improved. However, due to the constant impedance characteristics of this equipment when the fluctuation of grid voltage exceeds a certain range, it can not give full play to its role when the fluctuation of grid voltage is large.

The main circuit of STATCOM is mainly composed of voltage source inverter and parallel DC capacitor composed of high-power power electronic devices. It is a reactive power compensation system completely different from the traditional SVC principle. This device breaks away from the constraints of the previous concept of reactive power. Instead of using conventional capacitors and reactors to realize reactive power compensation, it uses inverters to generate reactive power. The output three-phase AC voltage Vo is synchronized with the system voltage vs through the transformer, and the output of reactive power is adjusted by controlling v0. When VO > vs, capacitive reactive power is output; When VO < vs, inductive reactive power is output. Therefore, the magnitude of equipment reactive power is adjusted by its output current, and its output current is basically independent of the system voltage. These functions and principles are similar to synchronous condenser, but it is a complete static device. Therefore, STATCOM is also known as static tuner. Its dynamic performance is much better than synchronous condenser and starts no impact, Large continuous adjustment range, fast response speed and low loss. Due to the use of GTO, the commutation failure can be avoided. The capacitor on the DC side is only used to maintain the DC voltage, does not need a large capacity, and can be constructed with DC capacitor, so the device is small and economical.

Zhuhai Sinopak Electric Ltd. provides high-quality STATCOM. If you are interested in our products, please contact us:daniel.wu@sinopakelectric.com.