Analysis of the Technical Differences between Static Var Generator (SVG) and Static Var Compensator (SVC)

In the field of dynamic reactive power compensation, static var generators (SVG) and static var compensators (SVC) represent two completely different technical approaches. However, it is often the case that users compare the two without considering their distinct technical differences. So, where do the technical differences between SVG and SVC lie?

Ⅰ. Differences in Core Technology Principles

The Static Var Generator (SVG) employs a voltage source inverter composed of fully controlled power electronic devices (IGBTs) to achieve reactive power regulation by generating controllable amplitude and phase of alternating current voltage. Its core advantage lies in:

1. Response speed is extremely fast (10ms);
2. Capable of simultaneously outputting reactive power of both capacitive and inductive types;
3. Operates independently without relying on grid voltage.

In contrast, SVC is essentially an impedance-type device. It changes the reactive power output by adjusting the equivalent impedance of thyristor-controlled reactor (TCR) or thyristor switching capacitor (TSC). Its working characteristics are significantly influenced by the grid voltage, and the response time is usually between 20 and 40 ms.

II. Comparison of Harmonic Characteristics

The Static Var Generator (SVG) employs PWM modulation technology, resulting in extremely low harmonic content in the output current (THD 3%). No additional filtering devices are required. In contrast, the TCR in traditional SVC devices generates a large amount of harmonics (with characteristic harmonics at 5th, 7th, 11th, and 13th), and multiple filtering circuits must be configured, which not only increases the but also introduces the risk of resonance.

III. Dynamic Performance Characteristics

In cases of impact loads, static var generators (SVGs) demonstrate significant advantages:

1. The total response time is 10ms (with SVC being 30-50ms).
2. Reactive power output can be continuously and smoothly adjusted (SVC undergoes stepwise changes);
3. Even under low voltage conditions, it can still output at full capacity (the output capacity of the SVC is proportional to the square of the voltage).