Transient Response Improvement for Interconnected Linear Systems: Low-Dimensional Controller Retrofit Approach

TL;DR

This paper introduces a systematic method for designing low-dimensional retrofit controllers for interconnected linear systems, enhancing transient response by local control actions through hierarchical state-space expansion.

Contribution

It presents a novel hierarchical state-space expansion technique for designing low-dimensional retrofit controllers tailored to local subsystems.

Findings

Improved transient response in power systems example

Trade-off between retrofit controller dimension and performance

Theoretical basis for performance enhancement via tuning

Abstract

In this paper, we propose a method of designing low-dimensional retrofit controllers for interconnected linear systems. In the proposed method, by retrofitting an additional low-dimensional controller to a preexisting control system, we aim at improving transient responses caused by spatially local state deflections, which can be regarded as a local fault occurring at a specific subsystem. It is found that a type of state-space expansion, called hierarchical state-space expansion, is the key to systematically designing a low-dimensional retrofit controller, whose action is specialized to controlling the corresponding subsystem. Furthermore, the state-space expansion enables theoretical clarification of the fact that the performance index of the transient response control is improved by appropriately tuning the retrofit controller. The efficiency of the proposed method is shown through a motivating example of power system control where we clarify the trade-off relation between the dimension of a retrofit controller and its control performance.