ENGN8527
Smart Grids 1

Paul Scott

Outline

Smart Grid

An electricity network that uses ICT to make automated decisions on the production, consumption and distribution of electricity

Spectrum of Network "Intelligence"

Advantages

  • Enable distributed generation
  • New markets for participants
  • Lower infrastructure costs
  • Cheaper to operate and maintain
  • Improved reliability

Sensors - Smarts - Actuators

Sensing

  • Meters
  • Voltage and current transformers

Meters



Electromechanical meters

  • Cumulative consumption

Smart meters

  • Interval readings
  • Peak consumption
  • Reactive power
  • Sophisticated pricing
  • Remote readings

Voltage/Current Transformers

  • Measure AC voltage and current
  • Can be used to activate protective equipment
  • When used together can calculate \(p\) and \(q\)

Actuation

  • Generator governor and exciter
  • Transformer tap ratios
  • Switchgear
  • Demand response
  • Synchronous condenser
  • FACTS devices

Generators

  • Governor set point for real power
  • Exciter DC voltage to adjust reactive power

Transformers

  • Tap ratio to maintain voltage
  • On-load automatic or off-load manual tap changing
  • Phase shifting transformers to control flows

Switchgear

  • Breakers, reclosers, sectionalisers
  • Interrupt and isolate faults
  • De-energise sections
  • Reconfigure
  • Not all rated to interrupt fault currents
  • Automatic, remote or locally activated

Demand Response

  • Special contracts with large loads
  • Network operator sends request to defer load

Synchronous Condensers

  • Synchronous motor with no load connected
  • Exciter for reactive power control

FACTS Devices

  • Source/sink reactive power
  • Power electronics with capacitors/inductors
  • Mechanically switched capacitors

Management/Automation

  • Dispatch engine
  • DMS

Dispatch Engine

  • Decides how the wholesale market is cleared
  • Used alongside contingency simulation,
  • and FCAS markets

Dispatch Engine

Dispatch Engine

Distribution Management System

  • SCADA
  • State estimation
  • Load flow studies

New Technologies

  • Distributed generation
  • Batteries
  • Electric vehicles
  • Inverters
  • EMS
  • Cheap networked sensing
  • Synchrophasors

Distributed Generation

  • Power supplied close to loads
  • Less control
  • Greater uncertainty

Batteries/Electric Vehicles

  • Smooth out consumption and PV generation
  • Electric vechicles to increase loads

Inverters

  • Convert DC to AC for PV and batteries
  • Power factor control

Energy Management Systems

  • Communicate with smart devices
  • Coordinates devices to reduce costs for house
  • Responds to price signals or requests from network

Cheap Sensing

  • Current
  • Temperatures
  • Sag

Synchrophasors

  • Enable phase angle measurements
  • Can identify frequency changes
  • Used for network monitoring and analysis

Communication

  • Power-line communication
  • Mobile phone network
  • Fibre optics (bundled with conductors)
  • Wireless (ZigBee and WiFi)

Communication

  • Reliability
  • Delay
  • Security

Dynamic Line Ratings

Can we push more power on our networks by safely operating closer to the network limits?

DLR: Motivation

  • Better utilisation of infrastructure
  • Reduce need to invest in upgrades

DLR: Description

  • High flows heat lines and which sag
  • Wind, ambient temp, radiation have large impact
  • Significant dynamics
  • Idea: Real-time line rating based on a combination of direct measurements and modelling

DLR: Characteristics

(Yang et al. 2009)

DLR: Usage

  • Dynamic trip currents for circuit breakers
  • Dynamic warnings for DMS system
  • DMS to take preventative action

Self-Healing Grid

What if the grid could automatically reconfigure itself to isolate a fault and resupply power?

SHG: Motivation

Utilities pay the regulator huge fines for downtime, and blackouts have huge opportunity costs for those affected

SHG: Description

  • Power supply restoration is the central problem
  • Take corrective action in under a minute
  • Remotely operable switches make this possible
  • Crews still go out and physically fix equipment

SHG: Overview

SHG: Overview

SHG: Overview

SHG: Automation

We can turn this into an optimisation problem:

  • Maximise number of loads served
  • By switching lines and redispatching generation
  • Subject to network constraints

SHG: Demo

SHG: Prediction

  • Machine learning to predict impending failures
  • Corrective action to prevent the situation escalating

References

  1. Yi Yang; Harley, R.G.; Divan, D.; Habetler, T.G., "Thermal modeling and real time overload capacity prediction of overhead power lines," Diagnostics for Electric Machines, Power Electronics and Drives, 2009. SDEMPED 2009. IEEE International Symposium on , vol., no., pp.1,7, Aug. 31 20096-Sept. 3 2009