SVG Vs SVC: Comparison of Static Var Generator And Static Var Compensator

Function of SVG

The SVG is an active compensation device based on power electronics technology, consisting of three core modules: detection, control & computation, and compensation output. It uses current transformers (CTs) to collect system current data, which is then processed by a control chip to analyze parameters such as power factor, apparent power, and reactive power. The system subsequently drives a self-commutated bridge inverter circuit composed of IGBTs to adjust the amplitude and phase of the output current. This enables the rapid absorption or injection of reactive power, achieving dynamic reactive power compensation. Additionally, the SVG can track and compensate for impact currents and harmonic currents.

Working Principle of SVC

The SVC is an impedance-type reactive power compensation device. It regulates reactive power by using thyristors to control the switching capacity of reactors and capacitors connected to the system, thereby altering the system's admittance. Common configurations include combinations of Thyristor-Controlled Reactors (TCR) paired with Fixed Capacitors (FC) or Mechanically Switched Capacitors (MSC).

 Reactive power compensation is essential for improving power factor, stabilizing voltage, and enhancing power quality in modern electrical systems. Two common devices used for this purpose are the Static Var Compensator (SVC) and the Static Var Generator (SVG, also known as STATCOM).

SVC typically consists of a Thyristor-Controlled Reactor (TCR) and Fixed or Switched Capacitors (FC/TSC). It regulates reactive power by varying the thyristor firing angle to change the effective impedance, offering stepwise compensation with a response time of 20–40 ms. In contrast, SVG uses an IGBT-based voltage-source inverter with PWM control to actively generate or absorb smooth reactive current. It responds within 5 ms, provides continuous compensation, and maintains full output even under low system voltage.

Key advantages of SVG over SVC include faster dynamic response, minimal harmonic generation (no extra filters required), better unbalanced load compensation per phase, no risk of LC resonance, compact footprint, and stronger low-voltage support. While SVC remains cost-effective for large-scale, slowly varying loads in transmission networks, SVG is increasingly preferred in industrial plants, renewable energy integration, and applications with fluctuating or impact loads due to its superior performance and flexibility.

In summary, SVG represents the modern direction of reactive power compensation technology, delivering faster, cleaner, and more reliable power quality improvement compared with conventional SVC solutions.