challenges and opportunities of optimization in smart gird...challenges and opportunities of...

© 2016 Eaton. All Rights Reserved.

Challenges and Opportunities of Optimization for Smart Gird

Yigang Wang, Ph.D.

Corporate Research & Technology

2 © 2016 Eaton. All Rights Reserved.

To be a power management leader,

it helps to have a 100 year head start

• Founded in 1911 by J.O. Eaton 伊顿由 J. O. Eaton先生始创于1911年

• Headquarters in Cleveland, Ohio 伊顿公司全球总部设于美国俄亥俄州克里夫兰市

• Regional Headquarters in Shanghai; Morges, Switzerland; Mexico City

• Innovation Centers in the USA, China and India

• $13.7 billion revenue in 2010 2010年的全球销售额达137亿美元

• Customers in 150 countries 客户遍及全球150多个国家

• 70,000 employees worldwide 全球现有员工7万多名

• 55% of sales outside the U.S.


We have transformed our company …

Helping Customers Use Power Efficiently, Effectively and Safely

Eaton’s Past

A Vehicle Component

Manufacturer…

Eaton Today

A Leader in

Power Management!

Eaton’s Past

A Vehicle Component

Manufacturer…

Eaton Today

A Leader in

Power Management!


CRT: We are about …

People

Solutions

Technology

Global

Research

Technology

“Innovation excellence

with the right people in the

right place”

“Valuable customer

solutions enabling

Eaton’s & our customer’s

growth”

“Research and

technologies

with

cross-business impact”

… being “world class” at innovating

power management solutions globally


Controls, Systems and Solutions

CSS System Modeling & Controls

• Dynamical modeling

• Control & Automation

• Sensors & Actuators

Machine Learning & PHM

• Inferential Sensing

• Health Monitoring/Management

• Complex Data Analytics

Safety & Fault Tolerance

• Functional safety methodology

• Cyber Security Framework


Emerging Industrial Applications: Smart Grid and Micro-grid

• Our current electric grid was built in the 1890s and has slowly been improved upon as

technology advances through each decade. We are stretching the current grid to its

capacity and addressing new technologies in a patchwork and piecemeal manner.

• With the help of computerized equipment and communication, smart grid that can

automate and manage the increasing complexity and needs of electricity.

• Control related topics

• Large scale power and energy management -> power flow analysis

• Smart grid power system stability


Inflection Point Driving Changes in Distribution

• Decreasing by 30%/year • Driven by off-shore manufacturing (China)

• Initially driven by mandates and subsidies

Note: Data for solar only http://www.seco.cpa.state.tx.us/publications/renewenergy/

2020: 15%

2025: 25%

2020: 33%

2025: 25% 2020:

30%

2030: 40%

2015: 29%

ME - 2020: 30%

VT - 2025: 24.8%

NH - 2017: 20%

MA - 2020: 22.1%

RI - 2020: 16%

CT - 2020: 27%

NJ - 2021: 20.4%

DE - 2026: 25%

MD - 2022: 20%

2015: 15%

2015: 10%

2015: 10%

2020: 20% 2025:

20%

2025: 15% 2020:

20%

2015: 15%

2021: 15%

2021: 18%

105 MW

2015: 5880 MW

< 10%

10% - 20%

> 20%

Legislated Renewable Standards Policies and Goals IREC North Carolina Energy Center

“inflection point” • Economic / social benefits prevail (< $0.10/kWh) • Renewable penetration exceeds 5% (point of

stability problems)

PV Price & Penetration Texas Renewable Energy Resource Assessment

• Penetration of PV at inflection point

• Other intermittent sources and loads continue to drive complexity in distribution grid


Bi-Directional Power Flow by Renewables

IEEE 34-Bus Test Feeder with PV integration

Voltage rise

introduced by

reverse power

flow introduced

by PV integration


Intermittency of Renewables

• Intermittency is one of major challenges of renewables

Data source: NREL

PV Power Output “Ideal” Insulation


Impacts of Renewable Intermittency

PV Power

Voltage at PCC


Economic Dispatch and Power Flow Analysis

• Objective: minimize the cost of generation

• Constraints

• Equality constraint: load generation balance

• Inequality constraints: upper and lower limits on generating units output

• Generating units and loads are not all connected to the same bus

• The economic dispatch may result in unacceptable flows or voltages

in the network

A B C L

© 2011 D. Kirschen and the University of Washington


Optimal Power Flow (OPF) - Overview

• Optimization problem

• Classical objective function

• Minimize the cost of generation

• Equality constraints

• Power balance at each node - power flow

equations

• Inequality constraints

• Network operating limits (line flows, voltages)

• Limits on control variables

© 2011 D. Kirschen and the University of Washington


General Power Flow Solution Methods

• Newton-Raphson: ∆𝑉 = (𝜕𝑃/𝜕𝑉)−1∆𝑃 • Iterative linear approximation (Jacobian matrix)

• Main computational cost: (𝐽−1𝑝 = 𝑏)

• Quadratic convergence

• Small region of attraction

• Gauss-Seidel: 𝑉 = −𝑌𝐿𝐿−1𝑌𝐿𝐸𝐸 + 𝑌𝐿𝐿

−1(𝑆

𝑉)∗

• Fixed-point iteration (𝑥 = 𝑓(𝑥))

• Main computation cost:

Admittance matrix inversion

• Linear convergence

• Small region of convergence


PF Solution Method in Distribution Network

• Gauss-Seidel more popular • Ideal loading condition: light loading

• Operating condition within convergence region

• Ideal topological structure: Radial or weakly

meshed

• Admittance matrix inversion not needed

• Impedance matrix (𝑍𝐿𝐿 = (𝑌𝐿𝐿)−1) can be formed

analytically

• Variations of GS • Forward-backward sweeping

• DistFlow


Approximate Power Flow Solution (𝑉 = 𝐾𝐸 − 𝑍𝐼)

• Gauss-Seidel Iteration:

𝑉(𝑖) = −𝑌𝐿𝐿−1𝑌𝐿𝐸𝐸 + 𝑌𝐿𝐿

−1(

𝑆

𝑉(𝑖−1))∗

• DC approximation:

𝑉 = −𝑌𝐿𝐿−1𝑌𝐿𝐸𝐸 + 𝑌𝐿𝐿

−1(𝑆

𝐸)∗

• Can we combine the two to approximate PF

solution by performing only one iteration or

first-order approximation of it?


Optimization Challenges for OPF

• Power flow equations are quadratic and hence OPF

can be formulated as a quadratically constrained

quadratic program (QCQP). It is generally nonconvex

and hence NP-hard.

• Renewable Integration makes optimization even more

challenging: from “static” power flow to more

“dynamic” power flow

• Some researches working on convex relaxations with

reasonable assumptions, such as Steven Low from

Cal-tech.

• More work needs to be done before industries can

take it.

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