Advanced Control Strategies for Inverter-Based Microgrids

Mehrdad Yazdanian

The utilization of renewable energy resources in the smart grid is distinct by its distributed nature as opposed to the large centralized power plants in the existing grid. The concept of microgrid is proposed as a solution for interconnection and proper control of a collection of distributed generation (DG) units. Microgrid has a hierarchical control structure with typically four levels each dedicated to a control task: 1) zero-level control consists of inner current and outer voltage control loops and is responsible for output current and voltage regulation of a DG unit; 2) primary control provides set points for the zero-level control and is responsible for power sharing and voltage and frequency stabilization; 3) secondary control deals with the restoration of voltage and frequency deviations caused by the primary control; and 4) tertiary control is responsible for the optimal operation of the microgrid and power management between the microgrid and the host grid. In the context of zero-level control, the use of PI-based controllers dominates the control practice in inverter-based microgrids. PI-based controllers are extensively used and studied in the literature. This dissertation proposes internal model control (IMC)-based voltage and current regulators. The proposed IMC-based approach has superior transient performance compared with conventional PI-based controllers. In the context of primary level control, the use of droop-based approaches dominates the control practice in inverter-based microgrids. However, droop-based approaches cause steady-state frequency and voltage deviations subsequent to generation and load changes. Usually, secondary control restores the voltage and frequency deviations utilizing low-bandwidth communication links. In this dissertation, a power sharing approach based on washout filters is proposed. This approach regulate the steady-state voltage and frequency to their nominal values without the use of communication links. Therefore, it eliminates the need for secondary control or outer control loops for voltage and frequency restoration and in turn reduces the complexity of the system. In addition to the control practice in microgrid, a nonmodel control approach is developed to improve the set point tracking capability of the electric drive system. The proposed approach reduces the overshoot without compromising the speed of the system.

Advanced Control Strategies for Inverter-Based Microgrids

Files and links (1)

Abstract

Metrics

Details