Optimization Application in Integrated Transmission and Distribution Operation: Co-Simulation Approach Seyed Masoud Mohseni-Bonab Hydro-Québec/IREQ Power Systems Simulation and Evolution Varennes, QC, Canada s.m.mohsenibonab@ieee.org Ali Hajebrahimi Hydro-Québec/IREQ Power Systems Simulation and Evolution Varennes, QC, Canada ali.hajebrahimi.1@ulaval.ca Ali Moeini Hydro-Québec/IREQ Power Systems Simulation and Evolution Varennes, QC, Canada Moeini.ali@ireq.ca Innocent Kamwa Hydro-Québec/IREQ Power Systems Simulation and Evolution Varennes, QC, Canada kamwa.innocent@ireq.ca Abstract—The load increment as the consequence of electrification of everything in the modern distribution networks, makes it imperative to analyze the interactions between electric power transmission and distribution (T&D) systems. Such a massive electrification may deteriorate voltage profiles and power exchanges, which results consequently in lower grid efficiency. As a low-cost and effective solution, the installed controllable devices for voltage in distribution networks such as under-load tap changer (ULTC) and capacitor banks can be optimized to overcome the aforementioned challenges. This paper proposes a new integrated transmission and distribution co-simulation platform where the aggregated loads in transmission system simulator (i.e. MATLAB) are replaced by a distribution network modeled in distribution system simulator (OpenDSS) through a Python interface. The overall T&D system efficiency is then optimized while maximizing loading margin (LM) and minimizing the total system power losses are contemplated as two objective functions. The proposed approach is applied on a constructed T&D grid with 68K nodes and the results demonstrate that the efficiency of the T&D grid can be improved by optimal setting of the control variables. Index Terms— Integrated transmission and distribution (T&D) systems, Co-simulation, Optimization, Tap changer, Capacitor, loading margin. Nomenclature / B j N N Set of buses. L N Set of branches (transmission lines). G N Set of generating units. D N Set of load buses. / i j Index of bus Number where 1, 2, , B i N = K . l Index of transmission lines. / / y g b l l l Admittance/conductance/ susceptance of l th line. ij ij ij Y G jB = + ij th element of system Y bus matrix. Gi P Active power production at bus i . min max / i i G G P P Minimum/maximum values for active power. i D P Real power of the i th bus . i D Q Reactive power of the i th bus. min max / i i G G Q Q Minimum/ Maximum values for reactive power of the i th bus. min max / i i V V Minimum/ Maximum value for voltage magnitude of the i th bus. max S l Maximum value of power flow of l th transmission line. x Vector of dependent variables (optimization variables). / j i V V Voltage magnitude of bus i/j . / j i θ θ Voltage angle at bus i/j . i C Q Reactive power compensation at bus i. i R Voltage regulator at bus i. S l Power flow of l th transmission line. λ Loading parameter of the system. i L K Rate of load change at bus i. i G K Rate of change in active power generation of unit i. / PL LM Real power loss / loading margin. I. INTRODUCTION The imperative energy transition to decarbonise the society of tomorrow will increase the penetration of distributed renewable energies, the emergence of energy systems incorporating advanced power electronics (smart inverters), e- mobility and smart cities revolving around active distribution networks. According to pivotal rule of power grid in this transition, it is required to develop new class of tools serving as a basis for the simulation and analysis of these systems in evolution in which the new energy mix has high granularity of the involved equipment and high complex business models. The integrated transmission and distribution (T&D) studies in power system can be broadly classified into two categories: A) co-simulation of integrated T&D and B) co- optimization of integrated T&D. Co-optimization aims to construct a union framework, sometimes as a package, for studying several levels of power systems simultaneously. In co-simulation studies different dedicated software, two or more, are used simultaneously to study the effects of different phenomena in power systems, such as failures among 978-1-7281-5508-1/20/$31.00 ©2020 IEEE Authorized licensed use limited to: BIBLIOTHEQUE DE L'UNIVERSITE LAVAL. Downloaded on May 08,2021 at 23:51:03 UTC from IEEE Xplore. Restrictions apply.