Microgrid Technologies

Microgrid Technologies

1. 1.Technical Requirements

2. 2. Platform Technologies

3. 3. Summary

Introduction

In the wake of Superstorm Sandy, a microgrid

kept the lights on for more than 60,000 residents of

Co-Op City in the northeastern section of New York City.

In addition to providing greater resilience than the

conventional powergrid, microgrids have also been recognized as a key strategy for improving energy efficiency, deferring or avoiding capital investments in new transmission

and distribution infrastructure and mitigating

cyber security risks. In the aggregate, these forces

are moving microgrids from the margins into the

mainstream of America’s energy economy. This is

the third eBrief in a three-part series on microgrids

describing the key regulatory, financial and technical

issues affecting microgrid projects. The first eBrief

described the regulatory issues likely to affect a

microgrid project, including the risk of violating

franchise laws and the possibility that the microgrid

will be subject to economic regulation under state

utility law. The second eBrief described several key

considerations for evaluating the potential economic

benefits and financial structures of a microgrid. This

eBrief focuses on critical technical issues involved

in pursuing microgrid projects using a system-level

approach that ensures a holistic approach to microgrid

planning. The first section of this eBrief considers

potential technical requirements of a microgrid

project. The second section surveys the three principal

types of components that comprise a microgrid.

These components are combined in the design

process to successfully achieve the project’s technical

requirements. n

Platform Technologies

A microgrid encompasses multiple interacting

components spread across a defined geographic

space. The components are connected and monitored

with advanced sensing, control and communications

technologies and can be configured to meet the

needs of a variety of dynamic load types and operate

under a range of grid conditions. At a minimum, these

components include: a transfer switch to separate

the microgrid from its adjoining utility and connect

to self-generation, a generator to supply power in

autonomous mode, interconnecting cables and an

end-user load. Microgrids must integrate several

technologies and components to achieve the required

platform functionalities within a set of infrastructure

constraints. Like the macrogrid, microgrids include

a wide array of power generating technologies,

distribution infrastructure components and control

systems. The components of a microgrid can be

broken down into three categories: infrastructure,

generation and controls

Infrastructure Components

Common infrastructure components include

automated relays, automated switchgears transformers,

inverters and uninterruptible power

supply systems. These components must be configured

to provide safe and adequate service based on the

requirements of the surrounding utility distribution

system, which are typically either network, radial or

loop distribution systems. Automated grid components

are key hardware components that execute the

Microgrid controller’s command to connect or

disconnect the microgrid from the main network

at times of grid disturbance. A microgrid’s ability to

“island” generation and loads simultaneously can

provide a higher level of reliability than that provided,

by the traditional electric grid. At the same time, the

infrastructure requirements of a microgrid capable of

islanding may be more complex and costly depending

on the type of surrounding utility distribution systems

Interconnection Technologies

Microgrids must meet certain specifications before they

can interconnect with the local utility’s distribution

grid, which are based on the previously described IEEE

1547 and 2030 standards. In addition to protecting

the distribution grid from potential power quality

and safety problems, interconnection technologies

are designed to capture the full spectrum of value

streams created by microgrids. Interconnection

technologies include network protectors, inverters and

similar devices. A network protector is a device that

automatically connects and disconnects its associated

network transformer from the secondary network.

An inverter is an electrical device that converts direct

current (DC) to alternating current (AC). Inverters

convert DC produced by generators to AC using a

system of switches that synthesize the DC waveform

into an AC waveform. Wind turbines and solar panels

commonly use inverters to interconnect with the (AC)

electric distribution system.

Monitoring and Controls Components

An integral piece of the microgrid is the intelligent,

automated control that connects the various Microgrid

systems together and optimizes their management.

A microgrid’s control system is critical for integrating

the system’s components – generation, power

distribution and loads – in the manner required to

achieve the project’s technical requirements and

optimize operation. Microgrid control solutions allow

Microgrid operators to intelligently manage and control

distributed energy resources for reliability, economics

and power quality while connected or disconnected

from the grid.

The control solution must be able to interface with

local utility systems, including Energy Management

Systems (EMS), Distribution Management Systems

(DMS) and Supervisory Control And Data Acquisition

(SCADA) systems, to ensure that the utility and

microgrid control systems interact efficiently and reliably.

The software will likely be deployed at

the control center or at a remote site and use

standard utility communication protocols like DNP to

communicate with any other grid components. The

software should follow industry standard advanced

cyber security requirements and meet NERC CIP

requirements for a control center deployment.

Solutions can be found that are “operator-free”

Which do not require traditional 24-7 monitoring.

A microgrid encompasses multiple

interacting components spread across a

defined geographic space. The components

are connected and monitored with advanced

sensing, control and communications

technologies and can be configured to meet

the needs of a variety of dynamic load types

and operate under a range of grid conditions

Microgrid operators can choose from a variety of

control solutions with varying levels of functionality

and design. A major design decision is required

between a centralized control solution that offers a

management system based on existing utility control

solutions or decentralized control solutions with more

reliance on distributed field devices. In addition, a

decision to invest in advanced functionality should

be made based on the microgrid operating plans and

economics. Standard microgrid control functionality

will include the following:

IEEE 1547 & 2030

The Institute of Electrical and Electronics Engineers

(IEEE) develops technical standards and establishes

best practices for the electronics, computing and

electric power industry. The IEEE is developing two

sets of standards that apply to microgrids. The IEEE

1547 set of standards establish technical requirements

for the interconnection of distributed resources

to electrical power systems. The IEEE 2030 set of

standards provide an interoperability reference model

and knowledge base for developing microgrids.

Consolidated Easy-Use SCADA: complete SCADA

functionality for secure, reliable and efficient

operation. The user interface provides clear and easy-to-

operate user environment.

Forecast: utilizes historical load data as well as

seasonal weather conditions to forecast load profiles

within the microgrid over hourly and weekly intervals.

Interfaces to local building automation, metering

systems, SCADA systems and more provide the load

profile data to develop a complete load forecast.

Generation Forecast: optimization allows each

microgrid owner to determine at an aggregate level

whether to optimize generation dispatch based on

economics or emissions or a combination of the two.

A variety of robust weather forecasting systems aresupported

to forecast renewable generation production

in order to balance the generation to the load forecast.

Generation & Load Management: regulates the

real power output of the generating units within

the microgrid to maintain the desired frequency

and voltage when in island mode and to maintain

net interchange with the external grid when in grid

connected mode.

Load Shed: performs shedding or disconnecting of

loads when requested by an operator or automatically

during disturbance conditions (such as islanding)

to maintain system stability. The loads are virtually

ordered according to predetermined priority schemes.

Thus the sequence of events can be controlled and the

most important loads remain connected.

Data Archiving: a Historical Information System (HIS)

to provide a solid and reliable archive to store power

system historical data.

Optional, advanced features could include:

• Market Participation

• Fast Load Shed

• Control Center Redundancy

• Advanced Cyber Security

Advanced functionality in the microgrid control

solution can enable microgrid operators to participate

in energy markets by intelligently managing their own

power generation with visibility into the power needshourly increments up to day-ahead or seven day-ahead

horizons. This allows microgrid operators to achieve full

economic value from the microgrid while maintaining

their traditional base load needs.

Monitoring is also an important consideration for

microgrids. A microgrid operator may want to monitor

a wide range of potential parameters, including

voltage, frequency, real power, reactive power, current,

switch status points and relay status points. In many

scenarios, monitoring is required for control and/or

synchronization purposes. For example, voltages may

need to be measured at multiple locations to detect

when to disconnect the microgrid from the macrogrid

and determine when conditions on the macrogrid are

suitable for reconnecting.

A robust control architecture is needed for dynamic

optimal management, communications between

subsystems and demand management.

Generation Assets

Microgrids can use electricity generated from a wide

range of power technologies, using both renewable

and non-renewable energy resources as fuel. The

portfolio of generating technologies selected for a

specific microgrid, which might include renewableenergy

resources, combined heat and power, energy

storage systems or many other technologies, present

different cost-benefit scenarios. Some examples are

discussed below.

Solar Photovoltaics

Solar photovoltaic technologies convert solar radiation

electricity when required. There are several promising

energy storage technologies for microgrid applications

including advanced lead‐acid, lithium‐ion, flow and

sodium‐sulfur batteries. While battery prices are

expected to continue to drop in pricing, currently there

are limited regional applications where battery cost

justifies the investment.

Renewable Energy Technology

Typical module Capacity Sizes

Small hydro

1–100 MW

Micro hydro

25 kW–1 MW

Wind turbine

200 Watt–3 MW

Photovoltaic arrays

20 Watt–100 kW

Solar thermal, central receiver

1–10 MW

Solar thermal, Lutz system

10–80 MW

Biomass, e.g. based on

gasification

100 kW–20 MW

Fuel cells, phosphoric acid*

200 kW–2 MW

Fuel cells, molten carbonate*

250 kW–2 MW

Fuel cells, proton exchange*

1 kW–250 kW

Fuel cells, solid oxide*

250 kW–5 MW

Geothermal

5–100 MW

Ocean energy

100 kW–1 MW

Stirling engine

2–10 kW

Battery storage

500 kW–5 MW

Summary

Selecting the optimal technologies is critical to the

success of a microgrid project. In particular, a robust,

front-loaded design process that encompasses steady

state and dynamic state studies is vital to selecting

the optimal generating technologies and system

components for a microgrid.

When selecting a Microgrid vendor, be sure to evaluate

their skills at not only the overall Microgrid design

and system stability studies, but their capabilities

to successfully integrate the entire system – both

existing and new components regardless of technology

provider. This will ensure your system operates as

designed.

Lastly, it is extremely important to design the Microgrid

control system during the planning stage to ensure

the complex networks of power generating and

distribution components are designed to deliver the

expected benefits – both financially and operationally.

The controls system must maintain system stability,

optimally balance supply and demand and respond in

real-time to changes conditions on the central power

grid. Microgrids that operate during severe weather

events or in the wake of natural disasters should

also be designed with control capabilities needed to

mitigate any potential safety risks. Anyone considering

a microgrid must be careful to select project partners

with strong track records in the microgrid space and

proven abilities to integrate components from multiple

vendors.

Platform Technologies

Microgrid Technology

March 2016

About Ecofirma Power Systems Ltd

The Ecofirma Power Systems (EPS) Energy Management Division offers an end-to-end portfolio of products and solutions to develop intelligent energy

networks for forward-thinking utilities, municipalities, military bases, large industry, cities, and commercial customers. Ecofirma Power Systems’

turnkey Microgrid capabilities pull together financing, consulting, advanced grid technology, generation assets, O&M, and an

adapted supervisory control and data acquisition system sized for microgrid management, all within a comprehensive systems

integration package. The company offers a broad microgrid business model approach based on the concept of design, build,

operate, and maintain, with financing options supported by Ecofirma Power Systems Financial Services. For more information visit

www.ecofirmas.com/microgrid

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