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mart Power Solutions by Rockwill – Engineered for Reliability & Efficiency

Rockwill delivers integrated electrical solutions for smart grids, urban infrastructure, renewable integration, and industrial applications. From medium-voltage automation to EV charging networks and prefabricated substations, our systems ensure stable, efficient, and future-ready power distribution. Customized. Connected. Reliable.

Harmonic Mitigation Solution for New Energy Power Stations: Comprehensive Management of High-Frequency Harmonics in Photovoltaic Power Plants


Ⅰ. Problem Scenario
High-frequency harmonic injection from PV plant inverter clusters
During operation of large-scale centralized PV power plants, multiple inverters operating in parallel generate wide-band harmonics in the 150-2500Hz range (primarily the 23rd to 49th harmonics), leading to the following grid-side issues:

  • Current Total Harmonic Distortion (THDi) reaching 12.3%, significantly exceeding IEEE 519-2014 standard limits.
  • Causing capacitor bank overload, overheating, and protective device maloperation.
  • Increased Electromagnetic Interference (EMI) affecting nearby sensitive equipment.

II. Core Solution
Adoption of an LC passive filter topology, constructing efficient harmonic absorption circuits using customized reactors + capacitor banks.

  1. Key Equipment Selection

Equipment Type

Model/Specification

Core Function

Dry-Type Iron-Core Series Reactor

CKSC Type (Custom Design)

Provides precise inductive reactance, suppressing high-frequency harmonics.

Filter Capacitor Bank

BSMJ Type (Matched Selection)

Resonates with reactors to absorb specific harmonic bands.

  1. Technical Parameter Design
    Reactor Inductance: 0.5mH ±5% (@50Hz fundamental frequency)
    Quality Factor (Q): >50 (Ensures low-loss high-frequency filtering)
    Insulation Class: Class H (Long-term withstand temperature 180°C)
    Reactance Ratio Configuration: 5.5% (Optimized for 23rd-49th high-frequency band)
    Topology Structure: Delta (Δ) Connection (Enhances high-order harmonic shunting capability)
  2. Filter System Design Key Points
    Resonant Frequency Calculation:
    f_res = 1/(2π√(L·C)) = 2110Hz
    Accurately covers the target frequency band (150-2500Hz), achieving local absorption of high-frequency harmonics.

III. EMC Mitigation Effectiveness Validation

Indicator

Before Mitigation

After Mitigation

Standard Limit

THDi

12.3%

3.8%

≤5% (IEEE 519)

Individual Harmonic Distortion

Up to 8.2%

≤1.5%

Compliant with GB/T 14549

Capacitor Temperature Rise

75K

45K

Compliant with IEC 60831

IV. Engineering Implementation Advantages

  1. High-Efficiency Filtering:
    The 5.5% reactance ratio design specifically suppresses harmonics above the 23rd order, providing a 40% improvement in high-frequency response compared to traditional 7% schemes.
  2. Safety and Reliability:
    The Class H temperature rise insulation system ensures stable equipment operation in outdoor environments ranging from -40°C to +65°C.
  3. Cost Optimization:
    The low-loss design (Q > 50) results in additional system power consumption of < 0.3% of output power.

V. Deployment Recommendations

  1. Installation Location:​ Low-voltage side busbar of the 35kV collection substation.
  2. Configuration:​ Each 2Mvar capacitor bank series-connected with 10 CKSC reactors (Group-based automatic switching).
  3. Monitoring Requirement:​ Install an online harmonic analyzer to track THDi changes in real-time.

Solution Value:​ Effectively resolves high-frequency harmonic pollution in new energy power stations, extends capacitor lifespan by over 37%, and avoids PV output curtailment due to harmonic violation penalties.

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