Stability of LCL grid-connected inverter under weak current network

¹ School of Electrical and Automation, Nantong University, 226004 Nantong, China
² School of Electrical Engineering and Automation, Anhui University, 230601 Hefei, China

^* Corresponding author: tisabel@usf.edu

Abstract

With the development of energy generation technology, In today’s weak grid environment, the research on the stability of gridconnected inverters is becoming more and more important, whose main task is to improve grid-connected current. The paper concludes the widely-used control strategy of LCL grid-connected inverter, including adjusting inverter parameters, introducing a filter, voltage source admittance control strategy, and passive/active damping method. This paper compares the different effects of upgrading strategies of LCL inverters and recognizes their advantages and limits. For example, the passive/active damping method not only can effectively suppress resonance peak, but can also preserve amplitude-frequency characteristics of low and high-frequency bands. However, the gain in low frequency or the harmonic in high frequency may be reduced. Then, the paper discusses future development trends and technical challenges faced by LCL grid-connected inverters. In principle, effective suppression of high-frequency resonance is the key to improving system stability. From the perspective of control strategy, improving system stability is as important as adopting advanced algorithms. Finally, the paper raises practical advice about increasing Inverter efficiency.