Analysis and improvement of the small-signal stable power limit of a grid-connectedinverter based on an impedance method
DOI：DOI: 10.19783/j.cnki.pspc.211570
Key Words:grid-connected inverter  small-signal stable power limit  impedance method  improved phase-locked loop
Author NameAffiliation
WANG Jinlong 1. School of Electrical Engineering, Shandong University, Jinan 250061, China
2. State Grid Xinjiang Electric Power Co., Ltd., Urumqi 830063, China 
ZHAO Haoran 1. School of Electrical Engineering, Shandong University, Jinan 250061, China
2. State Grid Xinjiang Electric Power Co., Ltd., Urumqi 830063, China 
WANG Peng 1. School of Electrical Engineering, Shandong University, Jinan 250061, China
2. State Grid Xinjiang Electric Power Co., Ltd., Urumqi 830063, China 
LUO Jia 1. School of Electrical Engineering, Shandong University, Jinan 250061, China
2. State Grid Xinjiang Electric Power Co., Ltd., Urumqi 830063, China 
SUN Kaining 1. School of Electrical Engineering, Shandong University, Jinan 250061, China
2. State Grid Xinjiang Electric Power Co., Ltd., Urumqi 830063, China 
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Abstract:As the proportion of renewable energy power generation in the grid continues to increase, the problem of power system small-signal stability caused by grid-connected inverters has become increasingly prominent. To clarify the power margin of the grid-connected inverter system and improve the small-signal stability of the system, the impedance method is used to study the small-signal stable power limit of the inverter. From the boundary conditions of the generalized Nyquist stability criterion, the small-signal stable power limit of the grid-connected inverter is quantitatively calculated. It is pointed out that the power limit is less than the static stability power limit, and decreases with the decrease of the grid short-circuit ratio, and decreases with the increase of the phase-locked loop bandwidth. An improved phase-locked loop structure is proposed to increase the grid short-circuit ratio from the control point of view, thereby improving the small-signal stable power limit of the grid-connected inverter. Finally, the effectiveness of the improved phase-locked loop in improving the small-signal stable power limit is verified by impedance analysis and system simulation. This work is supported by the National Natural Science Foundation of China (No. 51707106).
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