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This study presents the design and experimental validation of feedback control along with a high‐gain observer to regulate the DC‐link voltage in dual‐stage grid‐tied photovoltaic (PV) system. In particular, the composite controller is designed to ensure accurate and fast control of the DC‐link voltage in response to abrupt changes in either the delivered active power or grid voltages. The high‐gain observer is employed to estimate the unknown disturbance, which is then cancelled by the feedback controller to ensure asymptotic regulation. Fast disturbance estimation is required to retain the nominal transient response specified under the feedback controller, which mandates using high‐observer gain. However, high‐observer gain magnifies the effect of the measurement noise, which results in poor steady‐state performances. This problem is addressed here by using a non‐linear gain to allow for on‐line adjustment of the observer gain. Specifically, a large observer gain is used during transients to ensure fast disturbance estimation, while a reduced observer gain is employed in the steady‐state regime to mitigate the effect of the measurement noise. Experimental results demonstrated the ability of the proposed controller to achieve accurate control, good transient response, fast disturbance rejection, and negligible sensitivity to the measurement noise. [ABSTRACT FROM AUTHOR]

This study proposes a novel decoupled proportional-integral (PI) current controller for grid-tied inverters. The proposed controller can be viewed as the modification of the existing decoupled PI current controller to include the reference jump in order to achieve nominal performance recovery in response to step changes in the current reference. The modified decoupled PI current controller is derived based on combining feedback-linearisation technique with a disturbance observerbased control approach that belongs to the high-gain observer technique. The key feature of the composite controller is its ability to retain the transient performance specified under the feedback-linearising control, particularly when the control does not saturate. Furthermore, by considering the control saturation in the observer design, an anti-windup scheme arises naturally into the controller, leading to an improved transient performance in the presence of saturation. The effectiveness of the proposed controller was verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

The design and the experimental validation of a continuous-time model predictive control (CTMPC) for a permanent magnet synchronous motor (PMSM) drive with disturbance decoupling is discussed. The CTMPC approach uses Taylor series expansion to derive a closed-form solution to the problem of model predictive control even though the system behaviour is described by a non-linear model. This type of controller requires an exact knowledge of the system model to guarantee an accurate prediction of the system behaviour, while the PMSM is usually subjected to model uncertainties and external disturbances such as the load torque. Moreover, in the proposed approach, the predicted speed tracking error is directly used to determine the required voltage command without the need for a cascaded control scheme. As a result, the load torque is seen as unmatched disturbance which makes exact disturbance decoupling more challenging. To overcome such a problem, a non-linear disturbance observer is designed and combined with the CTMPC method to enhance the prediction accuracy under parameter variation and unknown load torque. The feasibility of the proposed approach is experimentally investigated, and good transient and steadystate performances are obtained. [ABSTRACT FROM AUTHOR]

In this study, a state feedback control law is combined with a disturbance observer to enhance disturbance rejection capability of a grid-connected photovoltaic (PV) inverter. The control law is based on input-output feedback linearisation technique, while the existing disturbance observer is simplified and adopted for the system under investigation. The resulting control law has a proportional-integral (PI)/almost PI-derivative-like structure, which is convenient for real-time implementation. The objective of the proposed approach is to improve the DC-bus voltage regulation, while at the same time control the power exchange between the PV system and the grid. The stability of the closed-loop system under the composite controller is guaranteed by simple design parameters. Both simulation and experimental results show that the proposed method has significant abilities to initiate fast current control and accurate adjustment of the DC-bus voltage under model uncertainty and external disturbance. [ABSTRACT FROM AUTHOR]