In this paper, a robust DC-link voltage control scheme is proposed to improve the tolerance of photovoltaic (PV) grid-connected inverter to disturbances. The sensitive characteristic of the DC-link voltage complicates the dynamics of the inverter control system and limits its overall performance, especially when uncertain disturbances are considered. To cope with this issue, a voltage controller based on the linear active disturbance rejection control (LADRC) is designed. By exploring the principle of deviation regulation, an improved linear extended state observer (LESO) is established to ensure that the total disturbance can be estimated in a relatively timely manner. The linear state error feedback (LSEF) control law is generated to compensate for the total disturbance, which reduces the plant to approximate the canonical cascaded double integrator. The stability and disturbance rejection capability of the improved LADRC are further analyzed in frequency domain. Finally, theoretical analysis and experimental results con_rm the feasibility of the proposed control scheme.
- Photovoltaic (PV) grid-connected inverter
- DC-link voltage
- Linear active disturbance rejection control (LADRC)
- Deviation regulation
- Total disturbance
Figure 1. Schematic Of Two-Stage Pv Grid-Connected System Structure.
EXPECTED SIMULATION RESULTS:
Figure 2. Bode Plots For Estimating The Total Disturbance.
Figure 3. Time-Domain Curve For Estimating Internal Disturbance.
Figure 4. Bode Plots For Comparing Disturbance Term.
Figure 5. Bode Plots Of Disturbance Term With Different Bandwidths.
(A) !C D 30(Rad=S) (B) !O D 30(Rad=S).
In the PV grid-connected system, the robust control of DC-link voltage is crucial for energy transmission, which directly affects the power quality. Therefore, a DC-link voltage control strategy based on improved LADRC was proposed for grid-connected inverter in this paper. By describing the stability problem and power relationship of the DC-link, the voltage outer loop is modeled. Both theoretical analysis and experimental results prove that the proposed voltage control scheme achieves better control performance, either during the start-up process or operating conditions variation. The reason is that the D-LESO established according to the principle of deviation regulation can estimate the total disturbance in a relatively timely and accurate manner, which lays a foundation for disturbance compensation. At present, an increasing number of scholars are focusing their research on the combination of LADRC and intelligent algorithms, such as neural networks and fuzzy control. This paper is expected to provide these scholars with more ideas in order to apply LADRC more widely in the industrial field.
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