GE DMC490 Software Configuration Manual

GE

Grid Solutions

TM

DMC490

Microgrid Controller

Software Configuration Guide

SWM0091

Version 1.00, Revision

GE

Information

3

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Security Notice

Many of the DMC490’s network services are unauthenticated and unencrypted (for example, DNP3/TCP Master). It
is the user’s responsibility to ensure these services are protected from unauthorized use.

Even though the DMC490 includes a host firewall, it is recommended that an external network firewall be placed
on the electronic security perimeter as an additional layer of protection.

Purpose

This guide provides detailed information on how to configure the software of the Multilin
DMC490 Microgrid Controller.

Intended Audience

This document is a resource for utility personnel and system engineers who are
implementing the DMC490 for a microgrid, and protection engineers who are controlling
network devices. It is intended for readers who have knowledge of substation automation
equipment and applications.

About this Document

Additional Documentation

For further information about the DMC490, refer to the following documents.

• D400 Substation Gateway Instruction Manual (994-0089)

• D400 Substation Gateway Software Configuration Guide (SWM0066 V5.2)

• D400 V5.20 online Help (includes D400 configuration tool online Help)

How to Use this Guide

For most operational features, refer to the documents listed above.

For information specific to the Microgrid Controller (MGC) feature, see the details provided in
this manual (SWM0091).

The DMC490 employs sophisticated applications that contain many advanced features and
capabilities. To successfully configure and operate the DMC490 for your environment, it is
highly recommended that you work through this entire guide and the D400 Substation
Gateway Software Configuration Guide (SWM0066 V5.2).

If you need assistance, contact General Electric Company GE Grid Solutions Technical
Support.

In configuration tables, “N/A” in the “Default” column indicates there is no default setting
provided, and “X” indicates the number is automatically incremented.

Document Conventions

This guide uses the Systeme International (SI) and the Microsoft® Manual of Style as a basis
for styles and conventions.

The following typographic conventions are used throughout this manual.

Bold face is used for:

– Names of software program menus, editors, and dialog boxes; also for the names of

menu commands, keyboard keys, icons and desktop shortcuts, and buttons and
fields in editors and dialog boxes

– Names of hardware components
– User input that must be typed exactly

Italic face is used for:

– Emphasis
– Cross-references to sections, figures and tables within this manual and for titles of

other documents

– File and directory names; examples of directory paths are generally given in the

Windows form

– Placeholders for user input that is specific to the user. May also include angle

brackets around the placeholder if the placeholder is already in italic text. For
example, c:\<product>\product.def

– References to a setting or field value shown

The software-related procedures in this guide are based on using a computer running

®

Windows

XP. Some steps and dialog boxes may vary slightly if you are using another version

of Windows.

Safety words and definitions

Before attempting to install or use the device, review all safety indicators in this document to
help prevent injury, equipment damage or downtime.

The following safety and equipment symbols are used in this document:

Indicates a hazardous situation which, if not avoided, will result in death

or serious injury.

Indicates a hazardous situation which, if not avoided, could result in death

or serious injury.

Indicates a hazardous situation which, if not avoided, could result in minor

or moderate injury.

Indicates practices that are not related to personal injury.

If you need help with any aspect of your GE Grid Solutions product, you can:

• Access the GE Grid Solutions Web site

• Search the GE Technical Support library

• Contact Technical Support

GE Grid Solutions Web Site

The GE Grid Solutions Web site provides fast access to technical information, such as
manuals, release notes and knowledge base topics.
Visit us on the Web at: http://www.gegridsolutions.com

GE Technical Support Library

Product Support

This site serves as a document repository for post-sales requests. To get access to the
Technical Support Web site, go to: http://sc.ge.com/*SASTechSupport

Contact Technical Support

The GE Grid Solutions Technical Support is open 24 hours a day, seven days a week for you to
talk directly to a GE representative.
In the U.S. and Canada, call toll-free: 1 800 547 8629
International customers, please call: [phone]
or email to [e-mail]

Have the following information ready to give to Technical Support:

• Ship to address (the address that the product is to be returned to)

• Bill to address (the address that the invoice is to be sent to)

• Contact name

• Contact phone number

• Contact fax number

• Contact e-mail address

• Product number / serial number

• Description of problem

Technical Support will provide you with a case number for your reference.

Table of Contents

DMC490 Overview ..................................................................................................................................................................... 8 Chapter 1 -

Application Overview ............................................................................................................................................................................................. 8

Microgrid Overview................................................................................................................................................................................................. 9

Microgrid Controller Setup ............................................................................................................................................................................... 16

DMC490 Configuration ......................................................................................................................................................... 17 Chapter 2 -

DMC490 Operation Modes .............................................................................................................................................................................. 17

Configuration Overview .................................................................................................................................................................................... 18

Configure Electrical Assets .............................................................................................................................................................................. 20

Configure Thermal Assets ................................................................................................................................................................................ 34

Configure System Settings .............................................................................................................................................................................. 40

Health Status and Monitoring .......................................................................................................................................... 45 Chapter 3 -

Forecasts ..................................................................................................................................................................................... 46 Chapter 4 -

Common Forecast Settings ............................................................................................................................................................................. 46

Forecasts for Renewables ............................................................................................................................................................................... 47

Forecasts for Electrical Load .......................................................................................................................................................................... 47

Forecasts for Grid Buy Price ........................................................................................................................................................................... 48

Forecasts for Grid Sell Price ............................................................................................................................................................................ 48

Forecasts for Heat Load ................................................................................................................................................................................... 48

Forecast Value Update Procedure .............................................................................................................................................................. 48

vii

DMC490 Overview Chapter 1 -

The DMC490 Microgrid Controller:

• Controls and monitors a microgrid

• Optimizes the dispatch of electrical generation, thermal generation, and energy storage to minimize

operating cost

Application Overview

The Microgrid Controller optimizes the dispatch of electrical generation, thermal generation, and energy
storage to minimize operating cost. It operates in a supervisory mode, issuing on/off and dispatch commands
every few minutes. The MGC works in a grid-connected or standalone microgrid.

Up to 32 electrical and heating resources are supported, including the following:

• Renewable, such as wind turbines, hydro, solar panels

• Dispatchable generators, such as diesel generators

• Combined heat and power (CHP) generation, or cogeneration

• Heating elements, such as boilers

• Storage, specifically hydrogen-based and batteries

• Utility grid connections

The block diagram of Figure 1 shows the microgrid approach. When the resources include Modbus server
functionality, the UR controllers are unnecessary. For example, when a wind turbine is added to the microgrid
and it has Modbus server capability, a UR controller is not needed for it.

Figure 1 Microgrid approach – Block Diagram

The storage can be short or long-term:

• Short-term storage functions of the MGC help in step-load changes resulting from load-generation

variations or in transferring to an islanded microgrid.

• Long-term storage from tens of minutes to several hours helps during peak demand periods and in

shifting power generation to environmentally-friendly renewable sources.

8

DMC490 Overview

Microgrid Overview

The Microgrid Controller controls microgrid generation and storage assets to optimize operation for the lowest
cost based on load and renewable forecasts.

A microgrid is a distribution network that operates with local (distributed) generation or islanded (grid
connection open). Both types can include renewable sources, such as wind, photovoltaics, and hydro. Because
the output from renewable sources can be intermittent and variable, and energy from these resources is not
always available when needed, renewable sources can be better utilized when there is storage in the
microgrid, such as an electrolyzer/fuel cell system or conventional battery storage.

Figure 2 shows a typical Microgrid where DG represents a Diesel Generator.

Figure 2 Typical microgrid

Islanded Power System Operation

Within any power system, the generated power must match the demand. The loading in the system is variable.
Consider the single-generator power system shown in Figure 3.

Figure 3 Single-generator power system

and Pm result from multiplying the torque with the angular velocity (speed).

P

e

Where:

is the electrical power

P

e

is the mechanical power

P

m

The basic torque balance equation for the generator is:

Eq. 1

9

DMC490 Microgrid Controller Software Configuration Guide

Where:

T

is the mechanical torque provided by the prime mover

m

is the electrical torque exerted by the loading of the power system

T

e

J is the inertia constant of the machine, and

ω is the rotational speed.

Solving for dω/dt, the result is:

Eq. 2

Multiplying by the top and bottom of this equation by rated speed, ω0, the result is:

Eq. 3

Speed is constant (dω/dt = 0) whenever mechanical power matches electrical power. This fact allows us to
control a generator to supply the required load by regulating the speed of the generator at a fixed value. This
method is known as isochronous control and is shown in Figure 4.

Figure 4 Isochronous control

Assume that electrical and mechanical power are initially equal and speed is equal to the reference speed.
When the loading of the system increases, then P

becomes greater than Pm. As seen in the previous equation,

e

the machine speed drops. The governor takes a measurement of machine speed and compares it with a
reference speed (nominal speed). The difference is an error signal that is applied to a transfer function (typically
a proportional/integral regulator). The output of the governor drives an actuator (for instance a valve in the
case of a steam turbine). This acts to increase the flow of steam to the turbine, increasing the mechanical
power to balance the electrical power.

The operating characteristic of an isochronous generator is shown in the plot of frequency (proportional to
mechanical speed) and power; see Figure 5.

10

DMC490 Overview

Figure 5 Isochronous operating characteristic

An isochronous machine maintains a constant frequency for any value of power up to its maximum rating.

Having more than one generator operating in isochronous control creates a challenge. Measurement error
results in each machine having a slightly different idea of the actual system frequency, and each machine tries
to bring this value to the nominal frequency. To resolve this potential conflict, one machine is typically operated
in isochronous mode and the remaining generators are operated in droop control, resulting with the machine
receiving an additional power signal that it compares to a power reference.

Figure 6 Droop control used for two or more sources of power

At nominal frequency, the level of power output is determined by the power reference command because the
speed error signal is zero. When there is a drop in frequency, the generator increases output power according
to its droop setting. For example, a generator with a droop setting of 5% produces a 100% change in output
power for a 5% change in frequency.

Taken together the power and speed signals produce a sloped operating characteristic as shown in Figure 7.

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DMC490 Microgrid Controller Software Configuration Guide

Figure 7 Droop control operating characteristic

In grid-connected microgrids, the grid compensates for any imbalance between load and generation in the
microgrid, behaving like an isochronous machine for the microgrid. However, for islanded microgrids, there is a
need for an isochronous machine to maintain load-generation balance, and stabilize the frequency around the
nominal value in response to instantaneous load and renewable generation variations above or below the
forecasted values. Such an isochronous machine provides reserve margins in both positive and negative
directions to address the deficit or surplus of power, respectively. These margins are defined as a percent of the
total load in the microgrid.

Isochronous/non-isochronous operation of a generator impacts the behavior of the MGC in the process of
optimally dispatching the generation/storage devices in the microgrid. Thus, generating power of a
dispatchable generator (genset) operating in non-isochronous mode can pick any value between its lower and
upper bounds; however, for an isochronous dispatchable genset, lower and upper bounds of generating power
need to be changed in the optimization problem solved by the MGC so that the reserve margins are respected.
These concepts are demonstrated in Figure 8 and Figure 9, where the highlighted regions specify the intervals
that the generating power (P

) is allowed to change. PD

D

and PD

min

represent the lower and upper bounds of

max

dispatchable generating power.

Figure 8 Demonstration of non-isochronous operation of a dispatchable generator

Figure 9 Demonstration of the isochronous operation of a dispatchable generator

A diesel or a CHP unit can usually operate in isochronous mode due to the non-variable nature of their fuel
source, while highly-intermittent renewable power sources such as wind or solar cannot fulfill the requirements
of an isochronous machine. However, the MGC supports the isochronous operation of renewable power
generation units that are relatively less intermittent, such as run-of-the-river hydro units with reservoirs. In
order to support such a feature, a parameter entitled Renewable Capability is defined in the setup program.

12

DMC490 Overview

This is a parameter between 0 and 1, multiplied by the upper bound of renewable power generation unit, and
decided by the operator based on meteorological observation data.

Optimal Dispatch

The primary function of the MGC is optimal dispatch, which is the process of allocating the required load
demand among the available resources such that the cost of operation is minimized. The MGC minimizes cost
of electricity and/or heat in a microgrid, for example daily, and the prediction horizon can extend up to 48
hours.

Within a microgrid, resources include conventional generators and storage devices. The cost of operation is
typically defined by fuel cost but can include maintenance and other costs.

An optimal dispatch algorithm is used to minimize the total operational cost of the microgrid. This cost is the
sum of the fuel cost required to run the non-renewable generators, cost of electricity, which needs to be
bought from a grid when one exists, and the operational cost of renewable and storage devices. Other factors
include maintenance, start-up/shut-down costs, cost/revenue components associated with
importing/exporting power to the grid, minimum energy/power requirements for various generation assets and
minimum up/down times for some of the assets. The power bought from the grid plus the power generated
internally must equal the total load and the power exported to the grid at any instant of time. The algorithm
does not treat loads as dispatchable except to avoid situations of grid instability associated with imbalance
between supply and demand. In other words, the microgrid always supplies enough power to satisfy its loads
provided that this is physically possible given the power limits on the generators.

The optimal dispatch algorithm uses a technique known as model predictive control. It makes use of historical
data as follows: daily, weekly, and annual load profiles; hydro, wind, and solar forecasts; and fuel or electricity
market pricing information (when a bulk grid connection exists). Given this information, the algorithm
determines the cost of operation for a fixed period in the future, typically 24 hours. It then solves the
optimization problem with the objective to minimize the total costs and to determine the required control
actions. These control actions include selecting the best machines to be operated at any given time, by issuing
start/stop commands and sending proper isochronous or non-isochronous commands to dispatchable or
renewable power generation units. It determines when energy is stored and when it is supplied to the system.
Finally, it determines the best power reference point for each droop (non-isochronous) machine and for each
storage device. Figure 10 shows data flow between the MGC and the different component devices within the
microgrid.

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DMC490 Microgrid Controller Software Configuration Guide

DMC490

Microgrid Controller

System

Loads

Renewable
generators

Power generated
Online status
Availability

Power consumed
Online status

Dispatchable

generators

Power generated
Online status
Availability

Storage

devices

Start/stop
Input preferences
Output preferences

Power generated
Power consumed
State of charge
Online status
Availability

Setup tool

Operational

parameters (settings)

Start/stop

Isochronous/droop

Output preferences

Figure 10 Data flow for a system with dispatchables, renewables, and storage

Model Predictive Control

Model predictive control (MPC) is used for optimal dispatch in the microgrid. In this method, a model of the
process to be controlled is used to evaluate the behavior of process outputs in response to control inputs. The
model response is evaluated for a finite period extending into the future, known as a prediction horizon. The
outputs are optimized over this period in order to arrive at the ideal values of outputs to be applied at the
current time.

Figure 11 Model predictive control

Applied to the dispatch challenge, inputs represent internal physical states of the process such as
offline/online, availability, isochronous operation, storage state of charge, and metered power of the devices.
Generators and storage devices are modeled by their power ratings and efficiency curves. Forecasts model the
loading of the power system, the contribution of renewable sources, and the price of grid power (if one exists).
Finally, outputs take the form of start/stop commands and power reference commands applied to generators
and storage devices.

Generation must match load in a stable power system. Dispatchable generation including the storage equals
the total load minus the total power supplied by renewable sources. These resources are assumed to have
local controllers that are designed to maximize the use of available renewable energy.

The problem to be solved by the MGC is a multi-interval optimization problem. As shown in Figure 12, an
assumed prediction horizon of 24 hours is divided into multiple time steps/intervals, such as 120 twelve-minute
or 240 six-minute time intervals.

14

DMC490 Overview

Figure 12 Prediction horizon

Different routines within the optimization framework are formulated and solved at each time step (for example,
12 minutes) over the prediction horizon (24 hours) based on load, renewable resources, and price forecasts. In
this framework, a variety of operational considerations are factored in. These include and are not limited to the
support of a hydro unit in isochronous mode, minimum up/down times required for storage charging,
interaction with the grid, and support of manual-start dispatchable generators.

The objective function of the optimization problem can, in general, include the following terms:

• Fuel/operation costs of all power generation devices in the microgrid

• Cost/incentive terms for storage device charging/discharging. These are more subjectively

determined, being driven by the requirement to prevent simultaneous charging and discharging and
the need to limit storage cycling.

• Penalty terms mainly related to those generation/storage devices allowed to have their limits on

minimum powers violated (that is, having soft constraints)

• Power importing/exporting costs/revenues when the microgrid is grid-connected

Also, the constraints of the optimization problem capture the following limitations for both electrical and
thermal systems:

• Minimum and maximum values of generated power with the consideration of their isochronous or

non-isochronous operation, and the microgrid reserve margin requirements

• Limits on importing/exporting powers considering the microgrid reserve power requirements (for grid-

connected microgrids)

• Power balance in the microgrid considering the contribution of power generation/storage devices,

load, and any grid

• Minimum, maximum, and initial values of storage devices state of charge

• Limits on storage input and output powers

• The energy balance equation of storage devices representing the storage state of charge in each time

step based on its value in the previous time step as well as charging and discharging powers with the
consideration of the related efficiencies and standby losses

When the prediction horizon is long enough, the algorithm can determine when to charge storage, because it
can anticipate times when the loads are large and when the stored power can be utilized. The optimal dispatch
algorithm implemented within the microgrid controller can be configured for up to 32 resources. Assuming a
worst-case scenario where all resources are committed, the optimization problem can have on the order of
20,000 variables and 40,000 constraints.

Incorporation of CHP Plants

Combined heat and power (CHP) is the generation of electricity and heat in a single process. Inclusion of CHP
plants in the microgrid significantly increases the overall efficiency of the system by using the hot exhaust
gases from the gas turbine to heat water. Recovered heat can also be used for district heating or covering the
heat demand requirement of the system. The incorporation of CHP plants introduces another energy source
(natural gas) and another energy carrier (heat) into the system.

A CHP plant can be modeled by constant conversion ratios. The conversion ratios indicate efficiency. For
example, a gas-to-electricity conversion ratio of 0.35 means that 35% of the energy content of natural gas is
converted to electricity and the remainder is in the form of heat. Two dimensionless conversion ratios for gas­to-electricity (rge) and gas-to-heat (rgh) are defined as shown in the following figure. Typical values of rge and
rgh are 0.35 and 0.45, respectively, considering a 20% parasitic loss.

15