Voltage harmonic control of weak utility grid through distributed energy systems

This thesis proposes a closed loop control method to reduce the voltage harmonics of the weak utility grid through distributed energy systems (DES). It is desired to have uniform voltage and frequency around the grid. Because of the nonlinear behavior of the distributed loads and sources, the voltage of the utility gets distorted. It would be possible to correct the distorted utility grid locally where the DESs get connected. The proposed method imposes the extra responsibility on the DES of estimating the grid voltage harmonics and injecting additional current to rectify the pollution in the grid voltage. Recursive Least Squares Estimation (RLSE) technique has been implemented to estimate the grid voltage harmonics, this estimation technique works harmoniously with closed loop harmonic voltage controller. DES with the proposed control technique reduces the voltage harmonics and provides sustainable energy to the utility grid. The results are verified with simulation and experimental tests on a 5kW utility interactive energy conversion system.