Linear ADRC direct current control of gridconnected inverter with LCL filter for both active damping and grid voltage induced current distortion suppression

The conversion and utilisation of renewable energy generations often require grid-connected inverters. When applying LCL filter to remove power electronic chopping harmonics, the power quality faces two issues of resonance damping and grid voltage induced current distortion. Conventionally, two separate control algorithms are required to treat the two issues, requiring an additional current sensor, increasing control complexity and limiting performance. This study demonstrates that linear active disturbance rejection control (ADRC) is able to treat both resonance damping and grid voltage induced current distortion as overall disturbance at the same time through a single structure, while achieving higher power quality for dynamic, steady-state, small and large parameter setup, as well as parameter variations, as validated by experimental results. In principle, the ADRC can be configured with or without knowledge of the system model. This study also reveals that it is the measurement noise tolerance that makes the two configurations different in practice. By using model information in ADRC algorithm, the required bandwidth can be reduced, offering more tolerance to measurement noise. Moreover, the ADRC controller has only two parameters to tune for 'fast' or 'slow', which makes it easy for implementation.