JST-NSF-RCN WS on Distributed EMS

Fundamental Theory for Scalable Power
Systems Control

Takayuki Ishizaki (Tokyo Institute of Technology)

Collaborative Works Overview
intelligent BAs
Sasahara

RetConNMR

Prof. Imura

Wind-Integrated
Power Systemvisit

Prof. Ilić

Interval Optimization

RetConRetrofit Control

ConAnMe

Network Model Reduction

Koike

Convex Analysis

Prof. Ramdani

Multiperiod Electricity
Market Design?

ConAn

Prof. Chakrabortty
visit
Sadamoto

Network Control Theory
IEEE TRANSACTION ON AUTOMATIC CONTROL, VOL. X, NO. X, ... 20XX

In addition to the preexistent controller, we suppose that aset of additional decentralized controllers is designed such thateach of them stabilizes the corresponding disjoint subsystem,
namely!
x̂˙ i = Ai x̂i + Bi u′iyi′ = Ci x̂i .

RetConNMR
Preexistent controller

connection

Profs. Johansson & Sandberg
In particular, we suppose that an additional dynamical map
K̂i (·) is designed such thatx̂˙ i = Ai x̂i + Bi K̂i (Ci x̂i )Compensators



(27)

is stable. In the following, we denote the index set of sub-Additional controllers

Large-Scale Power Systems Control
IEEJ EAST30 Model (stable system composed of 30 generators)
parameters?
parameters?
parameters?

retrofit

localdisturbanceNorth east area

Area of interest 

parameters?
parameters?

Complete global modeling is unrealistic!!

Tokyo area
Controller design by local model?
Stability? Better performance?
4/13

Problem Formulation: Retrofit Control
Subsystem of interest (model available)possibly large scale

Other subsystem(s) (model unavailable)

Assumption:(i)
are measurable(ii) the preexisting system without"Problem# Find a retrofit controller(a) the whole system is kept stable and (b)is stable
such thatis made small for any

Hierarchical State-Space Expansion
Coupled state equation ofand

astate-space expansion
to cascade realization

stable (assumption)

Hierarchical realization-dimstabilized bystable"Lemma# If
thendecoupled!

andandfor any
6/13

Localized Controller Design
Hierarchical realization"Lemma#model available!

Design a controller

such thatis stable andconstant

Then the closed-loop system is stable andGeneralization to dynamical controller design is straightforward

How to implement??
7/13

Controller Implementation
How to implement??

withwith"Theorem# The closed-loop system with the retrofit controller
Localizing
compensatoris internally stable and it satisfies

Demonstration by Swing Equation Modelretrofit

Global perf.

low gain LQR

Freq. deviation

Highhigh gain LQR
Local perf.

unstable!

: retrofit control: design based on infinite bus modelTime

Scalable development of large-scale stable network systems based on
distributed design and implementation of multiple retrofit controllers

Enhanced Damping of Wind Power Systems
by T. Sadamoto, A. Chakrabortty

20 MVA

40 MVA

Poorly damped as wind penetration level increasesretrofit
retrofit

relative gen.
angles (deg) Freq. diff. (Hz)relative gen.
angles (deg)

6 MVA

w/o controllerTime (s)w/ controllerTime (s)Retrofit control of wind power plant can enhance damping performance

Concluding Remarks
Retrofit control
Localization of controller design and implementation
Stability guarantee and control performance improvement

Hierarchical state-space expansion
Redundant realization with cascade structure
Systematic analysis for stability and control performance
General Theory: T. Ishizaki, T. Sadamoto, J. Imura, H. Sandberg, K. H. Johansson:
Retrofit Control: Localization of Controller Design and Implementation. arXiv

Power Systems Application: T. Sadamoto, A. Chakrabortty, T. Ishizaki, J. Imura:A Retrofitting-Based Supplementary Controller Design for Enhancing Damping
Performance of Wind Power Systems. ACC2017

Thank you for your attention!