An Advanced Voltage Support Scheme Considering the Impact of Zero-Sequence Voltage Under Microgrid Faults Using Model Predictive Control

Negative sequence voltage affects the consequences of the presence of zero-sequence voltage in different ways under various grid fault conditions. The prime objective of the work presented in this article is to confine the point of common coupling (PCC) phase voltages within the stipulated limits during faults considering all the sequence voltages of a microgrid. Depending on the phase and amplitude of sequence voltages, the proposed scheme defines a control parameter to classify all possible faults into two categories. In the first category, the defined control parameter decides the positive and negative sequence grid currents to accommodate the zero-sequence voltage at the PCC within the stipulated limits. In the second category, the zero-sequence current is supplied along with the positive and negative sequence currents to achieve the objective. Accordingly, a four-leg inverter is employed to accomplish the voltage limit goals under various fault conditions. Resistive-inductive grid impedance of the microgrid is considered for the implementation of the proposed voltage support scheme. The LC-filter-based model predictive control is employed to control the four-leg three-level inverter for achieving three objectives, such as grid current control, active damping, and dc-link capacitor voltage balancing simultaneously. Analysis and experimental results are reported to support the concept.