Coordination optimization control of DC component and harmonics for grid-connected PV inverters

Area of Science:

• Electrical Engineering
• Power Systems
• Renewable Energy Integration

Background:

• Grid-connected inverters (GCIs) are crucial for distributed renewable energy systems.
• DC components and harmonics in grid current degrade power quality and violate standards like IEEE 1547-2003.
• These issues arise from factors like asymmetrical gate-driving signals, semiconductor imperfections, unbalanced grid voltage, and nonlinear loads.

Purpose of the Study:

• To develop a control strategy for mitigating both DC components and harmonics in grid-connected inverters.
• To enhance the power quality of grid currents in distributed renewable energy systems.
• To propose a coordinated control scheme that addresses the coexistence of DC components and harmonics.

Main Methods:

• A repetitive controller (RC) was developed for DC component compensation.
• A Discrete Fourier Transform-Repetitive Controller (DFT-RC) was presented for harmonic elimination.
• A coordination optimization control scheme using the Weight Factor Distribution Optimization Method (WFDOM) was introduced to adaptively allocate control effort between DC suppression and harmonic elimination.

Main Results:

• Simulation and experimental results validated the proposed method's feasibility and correctness.
• The WFDOM effectively allocated weight factors for DC suppression and harmonic elimination controllers based on relative deviations.
• The coordinated control scheme successfully addressed the coexistence of DC components and harmonics.

Conclusions:

• The proposed coordinated control scheme effectively improves grid current power quality in GCIs.
• The adaptive weight factor allocation ensures optimal performance when both DC components and harmonics are present.
• This method is applicable to high power quality photovoltaic (PV) power generation systems.