LI J F, HAN A S. Research on inertia characteristics and lifting strategy of grid-connected inverter[J]. Journal of Henan Polytechnic University(Natural Science) , 2025, 44(1): 134-144.

doi: 10.16186/j.cnki.1673-9787.2023110056

Received: 2023/11/29

Revised: 2024/01/20

Published: 2025/01/02

Research on inertia characteristics and lifting strategy of grid-connected inverter

LI Jifang, HAN Aishan

School of Electrical Engineering， North China University of Water Resources and Electric Power， Zhengzhou 45000, Henan， China

Abstract: Objectives To address the problem of low inertia operation in the power system caused by the integration of a large-scale new energy source， Methods the inertia characteristics of grid-connected inverters were analyzed and methods of improving their inertia level were studied. Firstly， the essence of inertia in the power system was analyzed，and the relationship between the inertia level of grid-connected inverters and their device parameters was derived. The root locus method was used to plot the root locus of the DC-side voltage control loop with the DC-side capacitance as a variable. The value of the DC-side capacitance was optimized based on the root locus and the requirements for inverter inertia level under different grid conditions. Then， a frequency feedback loop was introduced into the DC-side voltage control loop of the grid-connected inverter， and an improved control strategy for the DC-side voltage and modulation strategy for the inverter were proposed to enhance the instantaneous inertia level of the grid-connected inverter. This allowed the DC-side capacitance to charge and discharge according to the fluctuation of the grid frequency， suppressing the instantaneous rate of change of the grid frequency. Results The proposed inertia enhancement strategy was validated using MATLAB/Simulink simulation platform. It was found that compared with  the proposed strategy not used， when the DC-side capacitance was set to 0.4 F and the virtual inertia time constant was 5 s，the maximum deviation of the system frequency drop was reduced by 0.11 Hz，and the average drop rate was reduced by 0.035 Hz/s. Conclusions The proposed strategy could effectively improve the inertia level of grid-connected inverters and suppress the instantaneous variation of the grid frequency.

Key words: power system; inverter; frequency stabilization; inertia; capacitor voltage; voltage control