Flexible power quality dispatch in smart micro grids

The interest on using renewable energy sources in power electrical systems has been increased in recent years, resulting in spreading of these sources especially in low voltage microgrids. On the other hand, the increasing number of non-linear loads in these microgrids leads to severe power quality problems such as harmonic pollution. In this thesis, a flexible method is presented to solve the power quality issues of the grid-connected microgrid based on multi-objective model predictive control implemented to several DGs with coordination between them, introducing flexibility in a multi-objective and robust method in the real-time changing condition of microgrid operation. The optimization cost function includes several terms which are concentrated on different objectives, such as compensating harmonics, fundamental and harmonic power sharing between several DGs and reducing switching losses in the interfacing converters. These objectives are prioritized based on the defined weighting factors. All of these objectives plus dynamic response of controller to reference changes have been studied. In order to verify the functionality of the proposed control method, it is applied to a microgrid prototype. The experimental results demonstrate the feasibility of the proposed approach.
The advantages of this proposed control method are, dealing with multi-objectives with different priorities, proposing a control method which is able to connect the parallel DGs to grid with the THD of 1.4%, controlling the switching frequency while having good dynamic response to changes. All of over mentioned characteristics are proved by performing several experimental tests based on different scenarios, such as fundamental and harmonic power sharing, harmonic current compensation, switching frequency reduction and dynamic response improvement.