No abstract

No abstract

This study proposes a control design for the grid output current and for reducing the neutral-point voltage oscillation through the small-signal modeling of the three-phase grid connected with a three-level neutral-point-clamped (NPC) inverter with LCL filter. The three-level NPC inverter presents an inherent problem: the neutral-point voltage fluctuation caused by the neutral-point current flowing in or out from the neutral point. The small signal modeling consists of averaging, dq0 transformation, perturbing, and linearizing steps performed on a three-phase grid connected to a three-level NPC inverter with LCL filter. The proposed method controls both the grid output and neutral-point currents at every switching period and reduces the neutral-point voltage oscillation. The validity of the proposed method is verified through simulation and experiment.

No abstract

In this paper, a low cost and high reliability control scheme is proposed for 400Hz UPS system operated in parallel.The proposed control scheme is consisted of two parts which are synchronization and load sharing control. The synchronization control is achieved by discrete logic ICs and analog circuit. The load sharing control is realized by current transformers (CTs) without any controller.Therefore, this proposed control scheme is rather simple and the cost may be decreased, compared with control scheme using expensive controller such as DSP and CAN.The practical feasibility of the proposed control scheme is proved by simulation.. connecting AC power units in parallel will be described.The principle of sharing current and synchronization are adapted using sub-signal and CTs.Finally, simulations show the feasibility and performance of the proposed 400Hz UPS system operated in parallel I.