Reactive power compensation devices enhance power systems by improving the power factor, boosting equipment efficiency, and reducing electricity costs. Strategically placing these devices along transmission lines increases system stability, and transmission capacity, and ensures voltage stability across the grid.
The SVC was a static reactive power compensation device. Its typical setup includes a Thyristor Controlled Reactor (TCR) and a Fixed Capacitor (FC) bank. You often need to connect these components in series with a specific number of reactors.
Engineers primarily use SVCs in medium and high-voltage power distribution systems. They are especially good for situations with heavy loads, serious harmonic problems, shock loads, and quick changes in load. This includes steel mills, the rubber industry, non-ferrous metallurgy, metal processing, and high-speed railways.
Power electronics have advanced, particularly with IGBT devices and improved control technology. As a result, a new type of reactive power equipment has emerged: the Static Var Generator (SVG).
Unlike traditional systems that use capacitors and reactors, the SVG creates reactive power with PWM (Pulse Width Modulation) control. It can either supply capacitive reactive power or absorb inductive reactive power.
Unlike SVCs, which use many capacitors, SVGs use multi-level bridge converter circuits or PWM technology. This eliminates the need to calculate system impedance during operation.
SVGs have several benefits compared to SVCs. They occupy less space and provide faster, smoother control of reactive power. They also allow for bidirectional compensation. This makes SVG exceptionally efficient for today’s power systems.
The SVC functions as a dynamic reactive power supply for power grids. It adjusts to the grid's demands by providing capacitive reactive power when needed and absorbing excess inductive reactive power. A capacitor bank connected to the grid provides reactive power. A shunt reactor absorbs any extra capacitive reactive power.
On the other hand, the Static Var Generator (SVG) operates using a high-power voltage inverter. The SVG can quickly absorb or release the needed reactive power.
It does this by changing the amplitude and phase of the inverter's output voltage. It can also control the amplitude and phase of the AC side current directly. This ability allows for quick changes in reactive power. This improves the stability and efficiency of the power grid.
The response speed of an SVC typically ranges from 20 to 40 milliseconds. In comparison, a Static Var Generator (SVG) reacts in under 5 milliseconds. This quick response helps it better control voltage changes and flicker. Under identical compensation capacities, SVGs offer superior performance in managing voltage instability and flicker.
SVGs function as current sources, meaning their output capacity is less influenced by bus voltage. This characteristic makes SVGs highly advantageous for voltage control. Even as system voltage decreases, SVGs maintain their reactive current output, operating as controllable constant current sources. This allows them to continue delivering rated reactive current even during voltage drops, showcasing strong overload capacity.
In contrast, bus voltage heavily affects SVCs' output capacity. As system voltage decreases, the reactive current output of an SVC drops proportionally, and they lack overload capacity. As a result, the reactive power compensation ability of SVG stays the same, no matter the system voltage. However, SVC performance drops steadily as the system voltage goes down.
The SVC uses silicon-controlled rectifiers to adjust reactance and relies on multiple capacitor banks for reactive power compensation. However, this setup is prone to resonance amplification, which can lead to safety issues.
Additionally, significant fluctuations in system voltage can adversely affect the compensation performance, resulting in higher operational losses.
In contrast, Static Var Generators (SVGs) do not require a filter bank and avoid resonance amplification. The SVG is an active compensation device.
It uses IGBT technology, which stands for Insulated Gate Bipolar Transistor. The SVG works as a current source. This design prevents resonance issues and significantly enhances operational safety.
SVC uses silicon-controlled rectifiers to change reactance. It also uses several groups of capacitors for reactive power compensation.
However, this method can lead to resonance amplification, which may cause safety accidents. When the system voltage changes a lot, the compensation effect will change. This will lead to higher operating losses.
The SVG matching capacitor does not require a filter bank. There is also no resonance amplification effect.
SVG is an active compensation device. A current source device made up of a shutdown device called IGBT is present. This design prevents resonance and greatly improves safety during operation.
A Static Var Generator (SVG) occupies less space than an SVC. For the same level of compensation, an SVG needs only half to two-thirds of the floor space that an SVC requires. This is because SVGs use significantly fewer reactors and capacitors than SVCs, resulting in a more compact design.
In contrast, the reactors in SVCs are larger. They also need enough space between them. This requirement increases the total floor area needed.
Conclusion
SVGs offer several advantages, including faster response times, lower harmonic content, and enhanced reactive power regulation. These features help SVGs greatly improve the power quality of electrical grids. This makes them the future of reactive power compensation technology.
YT Electric is the biggest OEM manufacturer of low-voltage AHF and SVG with more than 15 years' experience. All products hold certifications for ISO9001, CE, and CQC standards, and type test reports support them.
For more information on how our SVGs can help manage harmonics and improve power quality:
contact us at sales@ytelect.com.
Keywords: SVG and SVC, output reactive, compensation capacity SVG, point within the specified range
adjusting the amplitude, resonance phenomenon and greatly, dynamic reactive power regulation
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