Transient Response Improvement for Interconnected Linear Systems: Low-Dimensional Controller Retrofit Approach
For control engineers dealing with interconnected systems, this provides a systematic way to add low-dimensional controllers to improve transient response, though the approach is incremental over existing retrofit control methods.
The paper proposes a low-dimensional retrofit controller for interconnected linear systems to improve transient responses from local faults. The method uses hierarchical state-space expansion to design controllers specialized to specific subsystems, with performance demonstrated on a power system example showing trade-off between controller dimension and performance.
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.