The superiority of SVG to SVC
Jan 03,2020

Compared with SVC, SVG is superior to SVC in the following aspects:

SVG: Static Var Generator(also as know static synchronous compensator or Statcom)

SVC: Static Var Compensator

1. Advanced working principle

(1)Static Var Compensator can be seen as a dynamic source of reactive power. According to the requirements of accessing the grid, it can provide capacitive reactive power to networks, and can also absorb excess inductive reactive power of the networks. The capacitor bank is usually connected to networks by a filter bank, and can provide reactive power to networks.

Principle of static var compensator

When there is not much reactive power, these excess capacitive reactive power is absorbed by a parallel reactor. The reactor current is controlled by a thyristor valve group. By adjusting the phase angle of the thyristor, the current value of the current flowing through the reactor can be changed to ensure that the reactive power of the SVC at the networks access point just stabilizes the voltage of the point within the specified range, which acts as a reactive power compensation for the power newtorks.

(2) Static Var Generator takes IGBT as the core component, and real time absorbs or generates the required reactive power by adjusting the amplitude and phase of the inverter output voltage, or directly controlling the amplitude and phase of the AC-side current, to achieve the purpose of quickly and dynamically adjusting reactive power.

principle of static var generator svg statcom

2. Faster response

Generally, the response speed of SVC is 20-40ms;

The response speed of SVG is 5ms~10ms, which can better suppress voltage fluctuations and flicker. Under the same compensation capacity, SVG has the best compensation effect on powerr factor correction.

3. Better low voltage characteristics

Static var generator has the characteristics of a current source, and the output capacity is little affected by the bus voltage. This advantage makes SVG have great advantages when it is used for voltage control. The lower the system voltage, the more dynamic reactive voltage adjustment is needed. The low voltage characteristic of SVG is good. The reactive current of the output has nothing to do with the system voltage, which can be regarded as a controllable constant current source. When the system voltage is reduced, it can still output rated reactive current and has strong overload capability. While SVC is impedance type, the output capacity is greatly affected by the bus voltage, and the system voltage is lower, the ability to output reactive current is proportionally reduced and does not have overload capability. Therefore, the reactive power compensation capability of SVG is independent of the system voltage, and the reactive power compensation capability of SVC decreases linearly with the decrease of system voltage.

4. Increased operational safety performance

Static var compenstor uses thyristor-regulated reactance plus multi-group capacitor as the main means of reactive power compensation, which is prone to resonance amplification, resulting in safety accidents. When system voltage fluctuation is large, the compensation effect is greatly affected, and the running loss is large; SVG matching capacitor doesn’t need to set the filter bank, so there is no resonance amplification phenomenon, SVG is an active type compensation device, which is a current source device composed of IGBTs that can turn off the device, thereby avoiding the resonance phenomenon and greatly improving the operation safety performance.

5. Harmonic Mitigation

Static var compensator uses the equivalent fundamental impedance of the thyristor to control the reactor, which is not only affected by the system harmonics, but also generates a large number of harmonics itself. It must be matched with a filter bank to filter out the harmonic content generated by the SVC itself; SVG Adopts three-level single-phase bridge technology, single-phase can output 5-level voltage waveform, and adopts carrier phase-shifting pulse modulation method, which is not only affected by system harmonics, but also can suppress system harmonics. Compared with SVC, SVG uses measures such as multiplexing, multi-level or pulse width adjustment technology to greatly reduce the harmonic content in the compensation current.

6. Smaller Size

With the same capacity of compensation, the SVG size is reduced 1/2 to 2/3 compared to the SVC. Because SVG uses fewer reactors and capacitors than SVC, it greatly reduces the size and footprint of the devices. The reactors in SVC are not only large in size, but also take into account the installation interval between them, so that the overall area is large.

In summary, the SVG reactive power compensation unit can greatly improve the power quality of the networks due to its fast response, low harmonic content, and strong reactive power adjustment capability. It has become the development direction of reactive power compensation technology.

ZDDQ related products,

  • Static Var Compensator(SVC)
  1. LV. contactor switched capacitor banks
  2. LV. thyristor switched capacitor banis(TSC)
  3. MV. contactor switched capacitor banks
  • Static Var Generator(SVG)
  1. LV. static var generator modular
  2. LV. Static var generator panel
  3. MV. Statcom
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