Executive Summary : | A Matrix Converter (MC) can be a good alternative to the back-to-back converter (BtoB-VSC) in the DFIG based WECS application due to its compact size, increased efficiency and longer life span compared to the former. However, while laboratory prototypes of such systems have been shown to offer similar performance as that of a BtoB-VSC fed DFIG when connected to a balanced three phase grid, no work has so far been reported on the control strategy of an MC fed DFIG connected to an unbalanced/harmonic distorted grid or during symmetrical/asymmetrical grid voltage dips. With the imposition of very strict ‘Grid Codes’ these systems will not gain commercial acceptability unless it performs at least as well as a BtoB-VSC fed DFIG under these operating conditions. This project aims to develop and experimentally validate the necessary modulation/control strategies for an MC fed DFIG based WECS under these abnormal grid conditions. To achieve these objectives a model of a MC fed DFIG based WECS will be developed first. “Co-Ordinated control” strategies, as reported in the literature, for BtoB-VSC fed DFIG based WECSs connected to unbalanced/harmonic distorted grids will be adapted to the MC fed DFIG while maintaining input output power balance of the MC. Also a new modulation strategy for the MC has to be developed so that it can generate ‘arbitrarily programmable’ input current waveform. For successful LVRT of the MC fed DFIG a novel reconfiguration strategy for the MC input filter is also being proposed so that the MC can control the grid side line currents utilizing the clamped rotor terminal voltages as the input as well as the reactive current drawn from the DFIG rotor. This way, it is expected, that the MC will be able to provide the reactive power support as required by the grid code. Once all these control strategies are formulated and verified by simulation a laboratory prototype of the MC fed DFIG based WECS will be developed. The control algorithms proposed so far will be implemented on a suitable real time controller platform and the performance of laboratory prototype using the proposed control algorithms will be verified first under static grid abnormality. A “regenerative grid simulator” unit will be utilized for creating programmable grid abnormalities. Next the model of the existing IIT Kharagpur campus distribution network will be implemented on the real time controller platform and the dynamic interaction of the proposed WECS control algorithm and the distribution network will be evaluated through HIL simulation. Once completed successfully, the research work carried out under this project will offer new insight in to the behavior of the MC fed DFIG based WECS when operating from unbalanced/harmonic distorted grid as well as during symmetrical/asymmetrical grid voltage dips. It will also help bring the MC fed DFIG based WECS a step closer to commercial acceptance and utilize the benefits an MC offers over the back to back VSC. |