Renewable sources contribute an increasing share of the electrical power, and the concept of distributed generation (DG) is about to completely change the basic architecture of the electric power grid. The new structure includes the interconnections of microgrids that are composed of DG units, loads and energy storage systems. At the same time, vast advances in computational power and the ability to get high-bandwidth measurements thanks to Phasor Measurement Units (PMUs) open up many new possibilities to implement advanced control designs for control of microgrids.
Current control of distributed generation units in grid-connected mode
The connection of a DG unit to a weak power system is challenging due to stability issues resulted from dynamic interactions between the DG unit and the grid. LCL-based DG unit is a particularly challenging case due to the presence of a high resonant peak in its frequency response. This project proposes a robust control strategy to overcome the stability issues of an LCL-based DG unit connected to a weak grid. The main advantage of the proposed control strategy is that it guarantees stability and satisfactory transient performance against the variations of grid impedance. Moreover, it is able to decouple the d- and q channels of the control system which enables independent regulation of the real and reactive output power of the DG unit. Real-time simulations and experimental tests illustrate the effectiveness of the proposed controller in terms of improved transient performance, robust stability, and satisfactory controller set-point tracking.
Publications:
A Robust Active Damping Control Strategy for an LCL-based Grid-connected DG Unit, in IEEE Transactions on Industrial Electronics, 2017.
Decoupled dq-Current Control of Grid-Tied Voltage Source Converters Using Nonparametric Models, in IEEE Transactions on Industrial Electronics, vol. 60, num. 4, p. 1356 – 1366, 2013.
A Multivariable Design Methodology for Voltage Control of a Single-DG-Unit Microgrid, in IEEE Transactions on Industrial Informatics, vol. 9, num. 2, p. 589 – 599, 2013.
Voltage and Frequency Control of Islanded Microgrids
This project focuses on the problem of voltage control of islanded inverter-interfaced microgrids con- sisting of several distributed generation (DG) units with radial structure. The main objectives are to (i) design a decentralized/distributed voltage controller with minimum information exchange between DG units and their local controllers (ii) design a fixed-/low-order dynamic output feedback controller which ensures stability as well as desired performance of the microgrid system in spite of load parameter uncertainties.
Publications:
Sadabadi, Mahdieh S., Qobad Shafiee, and Alireza Karimi. “Plug-and-Play Voltage Stabilization in Inverter-Interfaced Microgrids via a Robust Control Strategy.” IEEE Transactions on Control Systems Technology 25.3 (2017): 781-791.