Distributed energy control in electric energy systems

TL;DR

This paper introduces a unified approach to model and control instabilities in electric energy systems by generalizing interaction variables, enabling layered distributed control using reactive power concepts and stability conditions.

Contribution

It proposes a novel interaction variable framework for modeling and controlling energy system instabilities, integrating physical interpretation with layered control design.

Findings

The interaction variable captures system-wide effects and reactive power.

The layered control approach ensures stability using FBLC or SMC.

The method is demonstrated on a simplified RLC circuit model.

Abstract

The power interactions of any component in electric energy systems with the rest of the system happen naturally, as governed by the energy conservation principles. There may, however, occur instances when the rate at which power gets generated by one component through local energy conversion is not exactly the same as that absorbed by rest of the system. This is when instabilities get induced. To model and control such instabilities, this paper generalizes the notion of interaction variable used to characterize diverse system components in a unified manner. The same variable captures aggregate system-wide effects and sets reference points for multi-layered distributed output feedback control. It has a physical interpretation of instantaneous power and generalized reactive power. The higher layer design utilizes the interactive energy state-space model to derive intermediate reactive power control, which becomes a control command to the lower layer physical model. This command is implemented using either Feedback Linearizing Control (FBLC) or Sliding Mode Control (SMC), for which sufficient stability conditions are stated. This paper claims that the proposed design is fundamental to aligning dynamic interactions between components for stability and feasibility. Without loss of generality, we utilize a simple RLC circuit with a controllable voltage source for illustrations, which is a simplified representation of any controllable component in microgrids.