부산대학교 도서관

With the increasing connection of Inverter Based Resources (IBR) to power systems, further requirements are being placed on converters to both improve system reliability and IBR fault ride through performance. Most existing control strategies for six-pulse bridge inverters employ a balanced positive sequence control that injects positive phase sequence current only and suppresses negative phase sequence current delivery. This results in two major challenges for the converter and for the grid during network faults: (1) high second harmonic ripple on the dc bus voltage, resulting in significant stress on the converter and control performance; and, (2) exposure of the network to excessive voltage rise on the healthy phase(s), resulting in temporary over-voltage and equipment stress or disconnection. This paper presents a control strategy of Flexible Positive and Negative Sequence Control (FPNSC) and demonstrates the benefits of such an approach for both grid and converter. By describing a set of criteria that can be used to ensure equitable performance that benefits both power system and converter, and demonstrating that these criteria can all be satisfactorily met, this paper highlights the role of FPNSC in future grid code requirements.