DC microgrids have been quite popular in recent times. The operational challenges like control and energy management of the renewable-driven standalone DC microgrids have been an interest of research. This paper presents a bidirectional quasi Z-source DC-DC converter (BQZSDC). This converter topology has been developed based on a conventional buck-boost type bidirectional converter, and it interfaces the storage system and the common DC bus. The challenge, however, lies in effectively managing the uncertain renewable energy sources and the storage system and catering for the loads simultaneously. An effective control strategy is needed for that energy management and to achieve various microgrid objectives. This paper deals with one such effective control strategy implemented for BQZSDC. That is, the fixed-frequency double-integral sliding mode control (FF-DISMC) controls the converter to regulate the DC bus voltage and battery current. A detailed analysis of the controller is conducted, and its performance is evaluated for both charging (buck) and discharging (boost) modes. Simulations have been performed in MATLAB, showing that the controller performs satisfactorily in achieving the objectives of voltage regulation and battery current regulation. Finally, the performance of the proposed controller is validated with the hardware setup.
This article proposes a bidirectional quasi-Z-source DC-DC converter (BQZSDC) to integrate distributed energy storage system with a stand-alone photovoltaic (PV)-connected system. The operational challenges like control and energy management of the renewable-driven stand-alone systems have been an interest of research. However, the challenge is managing the renewable energy source and the distributed energy storage system and simultaneously catering to the loads. This article analyzes the performance of a BQZSDC with a Lyapunov function-based controller for regulating DC link voltage (load voltage) and battery current. A duty-ratio feedforward control unit and a Lyapunov function-based feedback control unit are used to develop the controller. The duty-ratio feedforward control unit is used to reduce the burden on the feedback controller. The closed-loop system is exponentially stable with the feedback controller, offering excellent transient responsiveness even under large disturbances. Simulations in MATLAB/Simulink show that the controller functions satisfactorily in achieving regulation objectives. Finally, experimental results validate the performance of the proposed controller.
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