An Interface System for Microturbine Generators

Abstract

This thesis presents an interface system for a microturbine unit with a low voltage ride through capability. The proposed system is controlled for grid connected and islanding modes of operations. The interface system is based on a back to back converter to control the active and reactive power flow and regulate the PCC voltage during normal operation. Moreover, the proposed interface system is found capable of riding through the faults and supporting the grid with the maximum allowable reactive power. Furthermore, the proposed interface system keeps the rated voltage and frequency at the load terminals during the islanding mode of operation.

Different simulation test cases are carried out to evaluate the dynamic performance of the proposed control algorithm for various operation modes of the interface system using MATLAB/SIMULINK software package. A fast response, accurate tracking, and robustness of the proposed interface system are revealed from the simulation results.

During faults, the system is simulated in two different scenarios. The first is to supply the reactive power required by setting the reference of the quadrature current iqG* to the maximum and the other is to supply the reactive power by regulating the ac voltage at the PCC. The results show that it is preferable to set iqG* at its maximum value during the fault to meet any grid code requirements. Furthermore, The proposed system exhibits a seamless transfer between the grid connected mode and the islanding mode of operation.