Composite control of single-phase inverter based on SRFPI and reduced-order LADRC

One of the development trends of inverters is toward higher performance. Periodic and non-periodic disturbances will result in excessive harmonic distortion in the output voltage and reduce the performance of single-phase inverters. The linear active disturbance rejection control (LADRC) method is used in inverter control because of its good anti-interference ability. When compared to a full-order LADRC, the reduced-order LADRC (RLADRC) algorithm efficiently reduces the system’s phase lag, simplifies the control structure by reducing the order and the control parameters, and exhibits comparable disturbance rejection capabilities. In this paper, a composite voltage control scheme based on the combination of RLADRC, and the synchronous reference frame proportional–integral​ (SRFPI) control is explored for single-phase off-grid inverters. The basic idea is that the non-periodic disturbances of system can be efficiently eliminated by RLADRC, while the periodic disturbances can be restrained by SRFPI. The design of RLADRC is given in detail. Moreover, the Thevenin equivalent model of the inverter control system is derived for stability and robustness analysis. Finally, compared with SRFPI-LADRC based method, the comparative experimental results demonstrate that the inverter realizes fast transient response, good load regulation and lower total harmonic distortion (THD) with the proposed SRFPI-RLADRC based composite control strategy.