Difference between SVG and SVC

Different Working Principle

Static var compensator (SVC) working principle: SVC can be regarded as a dynamic reactive power supply. According to the demand of the power grid, it can not only provide capacitive reactive power to the power grid, but also absorb the redundant inductive reactive power in the power grid. Usually, the capacitor bank in the filter connected to the power grid can provide reactive power to the power grid. The reactive power of these excess capacitive reactive power is absorbed by a shunt reactor.

SVG working principle: SVG is based on a high-power voltage inverter. By adjusting the amplitude and phase of the output voltage of the inverter, or directly controlling the amplitude and phase of the AC side current, the required reactive power can be quickly absorbed or released, so as to achieve the purpose of fast and dynamic adjustment of the inverter. reactive power.

Response Speed

Generally, the response speed of static var compensator is 20-40ms; the response speed of SVG is not more than 5ms, which can better suppress voltage fluctuation and flicker. Under the same compensation capacity, SVG has the best compensation effect on voltage fluctuation and flicker.

Low Voltage Characteristic

SVG has the characteristics of the current source, and the output capacity is less affected by the bus voltage. The advantages make SVG have great advantages when used for voltage control. The lower the system voltage, the need for dynamic reactive power regulation voltage, the low voltage characteristics of SVG, the output of reactive current has nothing to do with the system voltage and can be used as a controllable constant current source, the system voltage drops, the rated reactive current can still be output, and it has a strong overload capacity;

The output capacity is greatly affected by the bus voltage. The lower the system voltage is, the reactive current output capacity will be proportionally reduced, and there is no overload capacity. Therefore, the reactive power compensation capability of SVG has nothing to do with the system voltage, while the reactive power compensation capability of SVC decreases linearly with the decrease of system voltage.

Improved Operation Safety Performance

SVC uses silicon-controlled rectifiers to adjust reactance and multiple groups of capacitors as the main means of reactive power compensation, which is prone to resonance amplification, resulting in safety accidents. When the system voltage fluctuates greatly, the compensation effect will be greatly affected, and the operating loss will be large.

The SVG matching capacitor does not need to set up a filter bank, and there is no resonance amplification phenomenon. SVG is an active compensation device, which is a current source device composed of a shutdown device IGBT, which avoids the resonance phenomenon and greatly improves the operational safety performance.

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