An Active Low-Frequency Ripple Control Method Based on the Virtual Capacitor Concept for BIPV Systems

This paper proposes an active low-frequency ripple control device (ALFRCD) based on virtual capacitor concept for building-integrated photovoltaic (BIPV) systems. With this method, the power quality of the BIPV system can be enhanced, and the lifetime and reliability are superior by reducing electrolytic capacitors. The low-frequency ripple current caused by the single-phase inverter can be compensated promptly by introducing a current integrator instead of unit feedback in the control strategy of the ALFRCD. With this current integrator, the device is unable to output dc current, which is similar to the function of a capacitor. Compared with the conventional method with high-pass filter, the presented method can achieve better compensation efficiency at most of the low frequencies and the response speed is superior as well. In addition, only one more integrator is needed in the control loop, which indicates the conciseness of the method. The performance is analyzed and the design algorithm is introduced in detail. Simulations and experimental results verified the proposed method´s reliability and superiority in comparison with the method with high-pass filter and a proportional-integral controller.