Combining Proportional-Integral, Deadbeat, and Repetitive Current Controllers in Energy-Storage-Equipped STATCOM Application

Energy-storage-equipped static synchronous compensators (E-STATCOM) are crucial devices in a modern power grid for regulating both the active and reactive power, thereby improving the efficiency and power quality. Current controllers commonly used with E-STATCOM devices include proportional-integral (PI), repetitive, and deadbeat controllers. However, each has application-dependent restrictions and therefore lack the ability to achieve optimal operation. This paper presents a novel hybrid current controller that combines the strengths of the PI, deadbeat, and repetitive controllers. The proposed current controller mitigates cross-coupling effects and provides a wide control bandwidth, thereby ensuring quick, precise, and robust response to system parameter variations. Moreover, the proposed controller provides an efficient disturbance rejection, presenting a holistic solution for enhanced performance of the E-STATCOM. The proposed controller not only overcomes the limitations of individual controllers, but also provides improved current regulation. A comparative analysis of the proposed hybrid controller and a conventional repetitive controller clearly shows the efficiency of the proposed technique. Experimental findings based on a three-phase E-STATCOM demonstrate that the proposed controller significantly minimizes cross-coupling effects and provides approximately
$150~\%$
higher bandwidth compared to the conventional controller. In addition, applying the proposed controller shows
$3~\%$
and
$6~\%$
of total harmonic distortions (THD) during normal system operation and during periodic disturbances, respectively, which is approximately
$38~\%$
lower than the THD observed with the conventional controller.