Solution for Power Quality - Detailed Explanation of Hybrid Reactive Power Compensation
The hybrid reactive power compensation scheme (SVG+intelligent capacitor) is an economical and efficient combination of "dynamic+steady-state" compensation. The core is to use intelligent capacitors to undertake most of the basic reactive power compensation, while allowing SVG to focus on handling the rapidly fluctuating parts, thereby achieving the best balance between performance and cost. The key to the stable operation of the system lies in coordinated control, which adopts a strategy of division of labor and cooperation: SVG serves as the host, and intelligent capacitors serve as the slave. During compensation, SVG is first put into operation, and after the intelligent capacitors are put into operation, SVG exits. SVG also serves as fine compensation to compensate for rapid changes or reactive power of small capacity loads; Simultaneously compensating for the capacitive reactive power of the load.
Core advantages and application scenarios
The most prominent advantage of this solution is that it significantly reduces the total investment cost while ensuring good compensation effect, because the expensive dynamic compensation device SVG only needs to be configured with a small capacity (usually 20% -40% of the total compensation capacity), and the rest is compensated by cost-effective smart capacitors.
- Typical applications:
- Automobile manufacturing: used for reactive power in welding workshops, compensating spot welding machines, and other fast impact loads.
- Metallurgical industry: used for loads such as rolling mills and electric arc furnaces, while compensating for reactive power and suppressing voltage fluctuations.
- Papermaking and chemical industry: Compensate for the reactive power impact caused by the start and stop of high-power motors such as internal mixers.
- Commercial buildings: Compensate for reactive power fluctuations caused by load changes such as elevators and central air conditioning to ensure power factor compliance.
Selection of Scheme and Key Design Points
- Capacity configuration: The key is to determine the capacity ratio between SVG and capacitors. This requires a detailed analysis of the load characteristics, such as reactive power change rate, harmonic content, etc.
- Control strategy: Excellent control can achieve "first input SVG, then input capacitor, and finally fine tune with SVG", and can intelligently avoid transient impact and resonance risks during capacitor switching.
- Harmonic environment: If the on-site harmonics are severe (total distortion rate THDi>10%), priority must be given to evaluation. Intelligent capacitors have limited anti harmonic capabilities, and can be equipped with anti harmonic capacitors or tuned reactors, or use APF to control harmonics.
- Layout method: It is recommended to use centralized compensation (installed on the main busbar of the distribution room) or local centralized compensation (installed at large impact load groups) to achieve optimal systematic management.
Important precautions
- Resonance risk: Capacitors and grid impedance may form parallel resonance, amplifying specific harmonics. Resonance point analysis must be conducted during design, and it is usually avoided by connecting reactors in series.
- Device selection: SVG should choose products with fast response speed (full response time<5ms); Intelligent capacitors should choose products with zero crossing switching and fault self exit functions.
- Professional evaluation: Before implementing the plan, a professional power quality test must be conducted, recording data such as reactive power variation curves and harmonic spectra as the basis for design.
In summary, SVG+smart capacitors are a highly flexible, economical, and practical advanced compensation solution, particularly suitable for industrial applications with severe reactive power fluctuations but cost sensitivity. Its success is highly dependent on precise measurements in the early stages and reasonable configuration in the design phase.
