Active Disturbance Rejection Control Strategy for Grid-Connected Photovoltaic Inverter Based on Virtual Synchronous Generator

In order to solve the problem of insufficient control performance of various traditional control strategies in the complex environment of grid-connected inverters, the active disturbance rejection control (ADRC) strategy based on the virtual synchronous generator (VSG) is proposed. The mathematical model of a grid-connected photovoltaic inverter based on the VSG is built. The proposed control strategy provides the inverter with more disturbance attenuation and provides rotational inertia. The control strategy estimates and compensates the total disturbance and generates the reference active power and reactive power by ADRC. The control strategy converts the three-phase voltage and current outputs into positive and negative sequences on the dq reference frame. The VSG control module generates a reference voltage command and outputs it to the dual closed loop PI feedforward decoupling control. The PWM signal is finally obtained by the PI feedforward decoupling control. The ADRC strategy based on the VSG does not change the original control characteristics of the VSG; it retains the characteristics of the synchronous generator, and it also provides inertia and damping for the power grid. The simulation shows that the ADRC strategy based on the VSG applied to the inverter can attenuate disturbances. Under the unfavorable conditions of the unstable reference power, such as the unbalanced three-phase voltage and the random disturbance, the output power matches the international electricity standard.