Abstract
With the rapid development of renewable energy generation, single-phase grid-connected inverters have been widely applied in modern power systems. Since the power output of the renewable sources is continuously changing, independent active/reactive power control and a rapid current tracking performance is supposed to be achieved in a single-phase grid-connected inverter. However, the poor orthogonal-axis-constructing strategy and the ineffective decoupling in some widely-used controllers have severely weakened the dynamic performance of the single-phase inverter. To deal with the challenges above, this study proposes a comprehensive control strategy for current control in a single-phase grid-connected inverter. In the proposed control strategy, a virtual closed-loop is constructed to improve the dynamic performance and realize independent power control under a synchronous frame. Then, complex vector theory is used to model the virtual closed-loop based single-phase inverter, and a novel digital controller is designed based on zero-pole cancellation and minimum beat control to completely decouple the active/reactive components and achieve a supreme current tracking performance. Experimental results are shown to validate the feasibility of the proposed current controller.
Highlights
With the raising demand of high-efficiency and environmental-friendly electric power supply, micro-grids have been widely applied as a new kind of distribution network structure, which significantly facilitates access for renewable distributed generation (DG) such as photo-voltaic plants and wind turbines [1,2,3,4,5,6,7]
In the past several decades, various control techniques have been proposed to improve the performance of the single-phase inverter, among which Proportional-Integral (PI) control is most widely applied in the single-phase inverter, due to its good steady and dynamic performance
This paper proposes a comprehensive control scheme for a single-phase grid-connected inverter
Summary
With the raising demand of high-efficiency and environmental-friendly electric power supply, micro-grids have been widely applied as a new kind of distribution network structure, which significantly facilitates access for renewable distributed generation (DG) such as photo-voltaic plants and wind turbines [1,2,3,4,5,6,7]. A one-step predicting scheme (PRE-ICSF) was proposed to deal with the coupling issue caused by the digital delay [18] In this method, the predicted current is used to generate the decoupling term. In order to enhance the dynamic active/reactive power tracking performance of the single-phase grid-connected inverter, a novel current control strategy is proposed to deal with shortcomings of the previous methods. An orthogonal axis constructing method, which has a rapid dynamic response to the disturbance in the system, is brought out to achieve independent active/reactive power control in a single-phase inverter. The coupling issue in the single-phase inverter is discussed and an improved complex-vector based controller, which is applied in the single-phase situation, is designed to realize precise decoupling of the system.
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