A novel control strategy of circulating currents in paralleled single-phase boost converters for micro-grid applications

Modular multilevel converter (MMC) based STATCOM with vector control and virtual impedance voltage compensations

“…The transient was good, however, the practical implementation of repetitive controller requires complicated stability and design in choosing the appropriate low pass filters or comb filters needed to stabilize the controller. Liao et al in [22] have improved the balancing control but the issue of circulating current ripples and voltage ripples remain. Lives et al [23] and Tu et al [24] have studied the circulating current that could be employed to achieve capacitors voltage balancing, and suppress the circulating current by increasing the inductance of the arm of the MMC.…”

“…, the d-q voltage drop which contribute to the small variations between the STATCOM ) could be subtracted in form of compensation to mitigate the variations, and speed up the current response during the transients. The voltage compensation is derived as from (26) and (27), the corresponding desired STATCOM currents would have small deviations from their corresponding output currents, these variation are defined as Assume the resistance in(22) to be zero, and the total interfacing inductance T L in(22) which also contributes to the STATCOM variations is modified due to high-switching[31] and considered as 2 To reduce the variation assuming it happens during the transient time (i.e. t  ), in order to speed up the response of the PI-controller and reduce the current error in (28) and (29), an additional transient voltage could be derived from (21) as ) can be considered as non-transient terms, whose variations can be adequately controlled by the PI controllers; thus, ignored.…”