The three-phase four-leg inverter is widely used in microgrid recently. The control strategy is critical for the performance of nonlinear four-leg inverter system owing to the problems of coupling, disturbances of nonlinear/unbalanced loads, variable operating condition, etc. In view of the above problems, a nonlinear composite controller is proposed for four-leg inverter system under $dq0$ reference frame by integrating a higher-order sliding mode observer (HOSMO) and finite-time feedback control technique. The HOSMO can observe the uncertainties and disturbances by means of the soft sensing manner for feedforward compensation, which economises some sensors for their states being inconvenient to measure. In addition, it is a novel way for the HOSMO to realise the decoupling of the inverter system under $dq0$ frame. The finite-time feedback controller works in coordination with the HOSMO which provides more rapid convergence rate and further improves anti-disturbance capacity of the system. Finally, the simulation results with PI comparison illustrate the feasibility of the proposed method for stabilizing system.

三相四脚逆变器最近在微电网中得到广泛应用。由于耦合、非线性/不平衡负载的扰动、可变工况等问题，该控制策略对非线性四臂逆变器系统的性能至关重要。针对上述问题，提出了一种非线性复合控制器，用于四个-腿逆变器系统下$dq0$通过集成高阶滑模观测器 (HOSMO) 和有限时间反馈控制技术来参考框架。HOSMO可以通过软传感的方式进行前馈补偿来观察不确定性和扰动，从而节省了一些传感器状态不便测量的问题。此外，HOSMO实现逆变器系统解耦也是一种新颖的方式。$dq0$框架。有限时间反馈控制器与HOSMO协同工作，提供了更快的收敛速度，进一步提高了系统的抗干扰能力。最后，与PI比较的仿真结果说明了所提出的系统稳定方法的可行性。