Abstract
This study presents a new active and reactive power control scheme for a single-stage three-phase grid-connected photovoltaic (PV) system during grid faults. The presented PV system utilizes a single-stage three-phase current-controlled voltage-source inverter to achieve the maximum power point tracking (MPPT) control of the PV panel with the function of low voltage ride through (LVRT). Moreover, a formula based on positive sequence voltage for evaluating the percentage of voltage sag is derived to determine the ratio of the injected reactive current to satisfy the LVRT regulations. To reduce the risk of overcurrent during LVRT operation, a current limit is predefined for the injection of reactive current. Furthermore, the control of active and reactive power is designed using a two-dimensional recurrent fuzzy cerebellar model articulation neural network (2D-RFCMANN). In addition, the online learning laws of 2D-RFCMANN are derived according to gradient descent method with varied learning-rate coefficients for network parameters to assure the convergence of the tracking error. Finally, some experimental tests are realized to validate the effectiveness of the proposed control scheme.
Highlights
The cerebellar model articulation neural network (CMANN) is a lookup-table based neural network which can be thought of as a learning mechanism that simulates mammalian cerebellum
Since the singlestage three-phase grid-connected PV system is a nonlinear system with uncertainties, the plant model is difficult to obtain by mathematical analysis or experimentation
This study has proposed an intelligent active and reactive power control scheme using 2D-recurrent fuzzy CMANN (RFCMANN) for single-stage three-phase grid-connected PV system operating during grid faults
Summary
The cerebellar model articulation neural network (CMANN) is a lookup-table based neural network which can be thought of as a learning mechanism that simulates mammalian cerebellum. A two-dimensional RFCMANN (2DRFCMANN) with Gaussian basis function control scheme is proposed for the active and reactive power control of the single-stage three-phase grid-connected photovoltaic (PV). The 2D-RFCMANN control scheme is proposed to control the output voltage of the PV panel via the maximum power point tracking (MPPT) in normal condition, and the reactive power based on LVRT requirement with considering the power balance between dc-link bus and ac grid during grid faults. The analysis of the instantaneous active/reactive output power of the three-phase GCI during grid faults is carried out by using symmetric component method.
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