Comparison between High Voltage SVG and SVC
1. Performance Comparison:
- Working Principle: SVG adjusts output voltage and current phase and amplitude to dynamically and continuously regulate reactive power, while SVC uses thyristor-switched capacitors or reactors for stepwise adjustments. SVG excels in precisely meeting power factor compensation requirements for wind farms connecting to the grid, ensuring a power factor range from 0.98 to 1.0 at any given moment.
- Output Capacity: SVC can only output either inductive or capacitive reactive power, whereas SVG offers continuous bi-directional adjustment from inductive to capacitive, better adapting to varying reactive power demands during full load and no-load conditions in wind farms.
- Response Time: SVG boasts a response time under 10 milliseconds, significantly faster than SVC's 2-3 cycles (40-60 milliseconds), which significantly enhances the voltage support capability of wind farms, thus more effectively meeting the grid's voltage stability requirements at wind farm connection points.
- Low Voltage Behavior: In the event of system voltage drops, SVC’s output reactive power decreases rapidly due to its impedance-like behavior, while SVG behaves like a current source, maintaining its output reactive current regardless of system voltage changes, providing more robust voltage support and improving low voltage ride-through capabilities for wind farms.
- Harmonic Characteristics: SVC is a harmonic source that requires additional filter circuits to mitigate its generated harmonics; conversely, SVG employs multi-level PWM control technology, offering superior harmonic suppression characteristics and built-in active filtering capabilities, thereby enhancing the power quality of wind farms by addressing issues such as harmonics, voltage fluctuations, and flicker.
- Losses: SVG has lower operating losses, consuming only 0.8% of its rated capacity compared to SVC's losses of over 1.5%. This considerable difference translates into significant energy savings.
- Resonance Issues: Due to its direct current control design, SVG does not experience resonance phenomena, greatly increasing safety by avoiding potential hazards caused by system parameter dependencies.
- Footprint: SVG has a smaller footprint compared to SVC, making it more suitable for installations with limited space.
- Operation and Maintenance: SVG utilizes cabinet structures and modular designs, making operation and maintenance easy and nearly maintenance-free. Its design also satisfies N-1 redundancy, ensuring high reliability and reducing field engineering efforts and subsequent maintenance costs.
2. Economic Analysis:
- SVG's lower operational losses lead to substantial economic advantages. Calculations show that using SVG instead of an equivalent-capacity SVC could save tens of thousands of yuan annually in electricity consumption just based on losses alone, assuming a full-year capacity utilization rate.
- Beyond lower losses, SVG's modular design and reduced maintenance requirements further contribute to overall economic benefits by minimizing on-site maintenance costs.
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