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| Predictive Control of LCL-Type Grid-Connected Inverter Based on Optimized Resonance Damping under Weak Grid Conditions |
| Wang Fengxiang1, Tang Xiaoxue1,2, Yu Xinhong1, Ke Dongliang1, Zhang Zhenbin3 |
1. National and Local Joint Engineering Research Center for Electrical Drives and Power Electronics Quanzhou Institute of Equipment Manufacturing Haixi Institute Chinese Academy of Science Jinjiang 362216 China;
2. College of Mechanical and Electrical Engineering Fujian Agriculture and Forestry University Fuzhou 350100 China;
3. School of Control Science and Engineering Shandong University Jinan 250061 China |
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Abstract As the global energy structure accelerates its transition to green and low-carbon, the penetration rate of distributed new energy generation in the power system has increased significantly. However, due to the geographical dispersion and power output volatility of distributed energy sources such as photovoltaic and wind power, they were usually required to be connected to the primary grid through long-distance transmission lines. The significant inductive impedance characteristics formed by the line distribution parameters and transformer leakage inductance make the grid-connected coupling point exhibit weak grid characteristics. In such a weak grid condition, the increase in the equivalent grid impedance causes the resonance peak of the LCL-type grid-connected inverter to shift, thereby affecting the system stability and power transmission capacity. As the key energy interface between the new energy power generation system and the grid, ensuring the safe and stable operation of the grid-connected inverter is crucial.
A resonant-damping optimization predictive control strategy based on capacitor voltage estimation was proposed. Firstly, according to the linear equivalence principle, a capacitor voltage estimation method was designed. The capacitor voltage was estimated, and the traditional capacitor voltage sensor was replaced. This method ensured measurement accuracy, significantly reduced hardware costs, and simplified the system structure. Secondly, a negative first-order high-pass filter was designed to dynamically reconstruct the super-local model of the inverter. The filter extracted the high-frequency oscillation components near the resonance frequency and provided real-time feedback signals for active damping control. Hence, the active damping characteristics at the resonance frequency were optimized, and the adverse effects caused by resonance peak shift were suppressed. Additionally, a two-step predictive current control strategy was designed to enhance the dynamic response performance of the system. Through the accurate prediction and advanced adjustment of the current at future moments, the system can quickly respond to load changes and grid disturbances, reducing current overshoot and adjustment time during the dynamic process. Meanwhile, by drawing Bode plots, the frequency characteristics of the proposed control strategy and the traditional control strategy were analyzed.
Experimental results show that the strategy effectively suppresses the low-order harmonic distortion of the inverter itself under weak grid conditions by optimizing the resonance damping of the LCL filter, thereby significantly reducing the harmonic distortion rate of the grid-connected current and enhancing system stability. Even in extremely weak grid scenarios, the system can still maintain stable operation while improving the power transmission capacity. The proposed method significantly enhances the system’s robustness and adaptability to weak grid conditions.
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Received: 13 May 2025
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2026, Vol. 41 
