Abstract
This study designs a discrete-time backstepping sliding-mode control (DTBSMC) method for an LCL-type grid-connected inverter. Firstly, the dynamic model of a discrete-time three-order system is derived, and a discrete-time backstepping control method cascading with the sliding-mode control theory is designed via Lyapunov stability verification. Moreover, the system state equation is transformed into a special form by using a time-varying mapping for overcoming the difficulty of a non-causal problem. Besides, through the recursively subsystem design for the high-order LCL-type inverter, the asymptotic system stability can be ensured by step-by-step virtual control designs. In addition, the proposed method can combine both the advantages of the backstepping control method and sliding-mode control theory. Therefore, the inverter system can have strong robustness under the condition of a power grid with varied grid impedances. Finally, the effectiveness of the proposed DTBSMC method is verified by numerical simulations and experimental results in comparison with a traditional proportional-resonant (PR) method and a backstepping control method.
Highlights
With the increasing penetration of distributed generations (DGs), three-phase grid-connected inverters have been widely used as the interfaces between DGs and the power grid [1]
The research topic is motivated by the aforementioned discussion, and a discrete-time backstepping sliding-mode control (DTBSMC) strategy is proposed for an LCL-type grid-connected inverter in this study
EXPERIMENTAL RESULTS An experimental prototype has been constructed as shown in Fig. 8 to verify the effectiveness of the proposed discretetime backstepping sliding-mode control (DTBSMC) scheme
Summary
With the increasing penetration of distributed generations (DGs), three-phase grid-connected inverters have been widely used as the interfaces between DGs and the power grid [1]. Chen et al [19] adopted a secondorder high-pass filter on the feedback path of the capacitor current, and the improvement of the robustness against the grid impedance variation was achieved In these methods, the damping strategy still requires to be carefully designed or an elaborate compensation strategy is necessary for enhancing the system stability performance. The research topic is motivated by the aforementioned discussion, and a discrete-time backstepping sliding-mode control (DTBSMC) strategy is proposed for an LCL-type grid-connected inverter in this study. The major contributions of the proposed DTBSMC method can be emphasized as follows: 1) the dynamic model of a discrete-time three-order LCL-type grid-connected inverter system is derived, and the discrete-time backstepping control method cascading with the SMC theory is designed with the discrete-time Lyapunov stability theorem.
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