Controller Design for Autonomous Direct Current Microgrid Operation

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Abstract
In the last three decades, the development of new electricity-generation strategies based on renewable energy has been promoted, which has made it possible to offset the increase in electricity consumption, reduce production costs, and positively impact climate change. These new-generation strategies are based on distributed generation (DG) at different points of the electrical power system, which has economic, social, and environmental impacts by reducing greenhouse gas emissions. The new concept of an electric microgrid, which is an integrated energy generation and management system with autonomous capacity, allows efficient production and consumption, with alternating current (AC) and direct current (DC) microgrids being available. This work presents a topology of direct current microgrids for island mode operation, which aims to supply electricity to variable and constant power loads (CPLs), as well as for the autonomous charging and discharging of batteries. To achieve this objective, a microgrid model is developed, current and voltage control loop controllers are designed, and their performance in different types of operation is analyzed. As a contribution to this work, the parasitic elements in the microgrid model are considered, and the design of the controller in the voltage loop is presented for the power supply to the local linear and non-linear loads, in addition to managing the energy coming from CPLs and controls the charge and discharge of the battery. To validate the performance of the controllers, three microgrid operation tests are carried out, which are presented in the Simulations section. In these tests, it is observed that with the PI controller in the voltage loop, the DC_Link signal presents transients with an amplitude of 5 V below and above the 200 V reference, which shows the poor performance of the controller. However, in all three tests with the modified PI-P controller, the DC_Link voltage remains constant at 200 V, with a negligible transient amplitude of almost 0 V, showing better performance.
Funding Information
  • Secretaria de Investigación y Posgrado del Instituto Politécnico Nacional (IPN (2199)

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