Advanced Voltage Support and Active Power Flow Control in Grid-Connected Converters Under Unbalanced Conditions

Abstract

Large distributed generation units have recently become crucial requirements for supporting the grid and increasing its reliability. The presence of the zero-sequence voltage significantly affects the accuracy of traditional voltage support schemes (VSSs) during the majority of grid faults. Additionally, the traditional VSSs have only been utilized in STATCOM applications with zero active power. Zero-sequence compensated voltage support (ZCVS), an advanced VSS for converter-interfaced units, is proposed in this paper to precisely regulate the three-phase voltages at the connection point within pre-set safety limits. In addition to compensating for the zero-sequence component, the proposed plan takes active power injection into account. The proposed VSS, in contrast to the more conventional approaches, can be applied to resistive distribution systems. However, this paper's contribution is ternary. The addition of the limited active power oscillation (LAPO) to the ZCVS is proposed as the second contribution. Even under severe unbalanced faults, this feature supports the ac host grid and limits the oscillation to a predetermined value, providing an adjustable setting for the dc-link voltage oscillation. Thirdly, the ZCVS is included in the formula for the maximum active power delivery (MAPD) to the AC grid. Using selected simulation and experimental test cases, the successful outcomes of the proposed support scheme and complementary strategies are demonstrated