Digital Real-Time Harmonic Estimator for Power Converters in Future Micro-Grids

One of the main challenges in future micro-grids is the presence of transients and fluctuations inevitably imposed by nonlinear loads. Therefore, real time identification of transients and fluctuations of the grid is essential for the future micro-grids. This identification can be used in different applications of “grid-connected” and “island” micro-grid such as grid synchronization, harmonic current injection for islanded mode micro-grids, etc. This paper focuses on developing a method to detect and monitor the disturbances and fluctuations in the utility grid. A novel real-time harmonic estimation technique is presented, which is able to quickly and precisely estimate dc component, and synchronous and asynchronous harmonic contents of the grid voltage despite of their unknown nature. The proposed technique can be used in the control system of power converters to potentially enhance the reliability and resiliency of future micro-grids. As a case study, the performance of the proposed harmonic estimator is evaluated in grid synchronization of the power converters. Simulation and experimental results from the case study show the ability of the converter to inject a smooth sinusoidal current in presence of disturbance and fluctuations in the grid voltage. These results verify the fast dynamic and accuracy of the proposed harmonic estimation technique.