Fully actuated system modeling and control of LCL grid-connected inverter

The LCL filter is widely used in new energy grid-connected systems because of its good high-frequency filtering characteristics, but it is a third-order system, and the design of the controller is relatively complicated. By using the inherent fully actuated characteristics of the system, the mathematical model of the system can be transformed into a fully actuated model, which can greatly simplify the design of the controller. In this paper, the fully actuated mathematical model of the LCL grid-connected inverter is established, and its control strategy is derived. At last, the stability of the control strategy is verified by the simulations.

1 Introduction

For the new energy grid-connected systems, the power electronic converters and inverters are necessary for the electric power transform. But the high-frequency switching devices will inherently inject harmonics into the grid, which directly influence the power quality of the grid and will a decrease the system stability. Therefore, in order to attenuate high-frequency harmonics effectively, an LCL filter is usually used at the output of the inverter. The LCL filter has the advantages of low cost, small size, and good filtering effect, but its structure is a third-order resonant circuit with two resonance points, which makes the system control and design complicated.