Electric Objects

This section presents an in-depth description of all objects available in SAInt that are available to develop an electric network model. SAInt is written with an object-oriented programming language, and thus the presentation of available objects is approached with the object hierarchy. Figure 1 shows the hierarchy of the parent-child relationships of all electric objects. Table 1 gives concise descriptions of all electric objects.

The top-level base object in an electric network model is the "Electric Network" object ENET. An electric network may contain many other base objects, such as electric demands EDEM or electric lines LI. An electric branch EBR is the parent object, while an electric line LI or an electric transformer TRF are the child objects; this means that both the electric line and electric transformer share some base properties of the electric branch. Objects that are not a base class for any other objects can only be children. For instance, the electric line object LI is not a base class for any other objects, and thus it can only a child. See the schematic below for a visual representation of the complete hierarchical object structure for the electric network model in SAInt.

Relationship between objects in electric network. A child object is indicated by the head of a pointed arrow, while a parent is by the tail. Please, open the image in another window of your Internet browser to enlarge it.
Figure 1. Relationship between objects in electric network. A child object is indicated by the head of a pointed arrow, while a parent is by the tail. Please, open the image in another window of your Internet browser to enlarge it.
Table 1. Icons and descriptions of object types in electric network model.
Icon ObjType Display Name Description

enet

ENET

Electric Network

Models the characteristics and interactions of facilities and/or components of an electric network or market. Serves as a container for all objects in the electric network

esub

ESUB

Electric Sub

Models a subset of nodes, branches, and externals of an electric network. An electric sub is branch-oriented, i.e., only electric branches can be assigned to an electric sub, and every electric branch belongs to only one electric sub

ezn

EZN

Electric Zone

Models a subset of nodes, branches, and externals of an electric network. An electric zone is node-oriented, i.e., only electric nodes can be assigned to an electric zone, and every electric node belongs to only one electric zone

egrp

EGRP

Electric Group

Models a subset of different objects in an electric network. Except for the electric network, subs, and zones, any electric object can be added to an electric group. In contrast to electric subs and zones, electric groups do not follow any specific assignment rules. Thus, an electric object can be part of multiple electric groups

eno

ENO

Electric Node

Models a physical or virtual location in the electric network where electric power can be injected or extracted through externals (electric demand, generators, storages, etc.)

ebr

EBR

Electric Branch

Base object type for all electric branches. Models a directed connection between two electric nodes

li

LI

Electric Line

Models the transport of electric power between two distant locations

trf

TRF

Electric Transformer

Models a local increase (step-up) or decrease (step-down) of voltage between areas of different voltage levels in the electric network

ext

EXT

Electric External

Base object type for all electric externals. An electric external is a directed connection to a single node that allows the extraction and injection of electric power

edem

EDEM

Electric Demand

Models the extraction (consumption) of electric power at a node

xgen

XGEN

Generic Generator

Models a generator or an external network injecting electric power into the electric network

fgen

FGEN

Fuel Generator

Models the injection of electric power by a fuel generator that generates electricity by converting chemical energy stored in a fuel first into mechanical energy and then into electrical energy. A fuel generator requires a fuel object (oil, gas, coal, nuclear, etc.) for operation

hgen

HGEN

Hydro Generator

Models the injection of electric power from a hydro generator. The amount of electricity produced depends on the volumetric flow rate (TURB) driving the hydro turbines and a coefficient describing the active power generation per volumetric rate (PCOEFF). A hydro generator is always connected to a hydro power plant

wind

WIND

Wind Generator

Models the injection of electric power from a wind generator. The electric power generation profile for a wind generator can be generated from wind weather resource data and the characteristics of the wind generator (wind turbine power curve, hub height, etc.)

pv

PV

Solar Generator

Models the injection of electric power from a solar generator. The electric power generation profile for a solar generator can be generated from solar weather resource data and the characteristics of the solar generator (PanelType, Tilt Angle, etc.)

estr

ESTR

Electric Storage

Models the storage of electric energy in electric storage systems, such as battery, flywheel, or compressed air

sht

SHT

Electric Shunt

Models a shunt reactor or capacitor. Shunt reactors are placed locally to control the over-voltages at electric nodes under light load conditions (consume reactive power to reduce the nodal voltage), while shunt capacitors are used to boost the voltage in a stressed system (supply reactive power to increase the nodal voltage)

fuel

FUEL

Fuel

Models the consumption and emission of the fuel used by one or more fuel generators

hydp

HYDP

Hydro Plant

Models a hydro power plant consisting of one or more hydro generators. Water flows into the hydro power plant either from inflow (rain, etc.), water turbinated by another hydro power plant, or spillage from a hydro power plant. Hydro power plants have a maximum and minimum reservoir volume; the difference determines the volume that can be turbinated through a hydro generator. The hydro power plant has three outflow types, namely, outflow, turbination, and spilling

asvc

ASVC

Ancillary Service

Models the ability of generators and demands to provide reserve capacity (upward or downward reserve) to the electric network in case of an unexpected contingency

asvcx

ASVCX

Ancillary Service External

Models the facilities contributing to an ancillary service

ecnstr

ECNSTR

Electric Constraint

Models a user-defined linear equality or inequality constraint describing relations between the variables of different electric objects

evar

EVAR

Electric Variable

Models a variable of an electric object and its corresponding coefficient utilized in a user-defined constraint

1. Electric network (ENET)

An electric network object is the top parent object in any model of an electric system in SAInt (Figure 1). An electric network object is modeled as a directed graph consisting of sets of electric nodes, branches, and externals; branches connect two nodes, while externals are connected to only a single node. An electric network contains all of the geometric, topological, and relational information required to create the graph, as well as all network child objects and their static/physical properties that do not change during the execution of a simulation (e.g., the length of a transmission line).

The "nodes" of an electric network identify junctions in the network graph where branches and externals connect. among the network branches and the connection point for externals.

The "branches" of an electric network establish the connectivity of the network and can passively (e.g., electric lines) or actively (e.g., tap changing transformers) modify the state of the electricity that flows across them. Branches of an electric network are "lines" and "transformers".

The "externals" of an electric network represent objects supplying or withdrawing electrical power from the system. Externals of an electric network are generators, "demands", "shunts, and "storages. SAInt models a variety of different types of generators, such as "wind generators", "solar generators, "generic generators", "fuel generators, and "hydro generators",

An electric network can also contain other electric-specific objects such as "fuels", "ancillary services", "ancillary service externals", "electric variables", "electric constraints", and "hydropower plants".

Summaries for the properties and events of ENET.

By default, the event NOLASTHOR is set to False. If the sum of the TimeHorizon and TimeLookAhead of the last consecutive run exceeds the EndTime, the fraction of the TimeLookAhead that extends beyond the EndTime is truncated. For example, with a TimeWindow of 6 days, 2 days TimeHorizon, and 3 days TimeLookAhead, SAInt will execute 3 consecutive runs, where in the first run, the last TimeLookAhead is of 3 days, in the second run of 2 days, and in the last run is completely truncated rather than being of 2 days. In this example, if the event NOLASTHOR is set to True (not recommended), the last TimeLookAhead is completely neglected.

2. Electric network container

The child objects of a network can be grouped into the following subsets, also referred to as "containers": sub, zone, and group. These arrangements can be used to define relevant information for a network, or they can simply be used to conveniently aggregate outputs of a scenario.

2.1. Electric sub (ESUB)

A sub (also referred to as sub-network or sub-system) is a subset of nodes, branches, and externals of a network. A sub is branch-oriented, i.e., only branches can be assigned to a sub, and every branch belongs to only one sub. The FromNode and ToNode of a branch, as well as the externals connected to these two nodes, are implicitly added to the sub. Thus, nodes connecting branches of different subs and the externals connected to these nodes are always included in multiple subs. But all properties of a sub are determined by the branches belonging to it.

Summaries for the properties and events of ESUB.

2.2. Electric zone (EZN)

A zone is a subset of nodes, branches, and externals of an electricity network. In contrast to subs, zones are node-oriented, i.e., only nodes can be assigned to a zone, and every node belongs to one zone. Branches with a FromNode and ToNode belonging to the same zone ae implicitly added to the corresponding zone. In contrast, branches with a FromNode and ToNode belonging to two different zones do not belong to any zone. Externals are also implicitly added to the zone of the node they are connected to. But all properties of a zone are determined by the nodes belonging to it.

Summaries for the properties and events of EZN.

2.3. Electric group (EGRP)

A group is a sub of different child object types (e.g., nodes, branches, externals, fuels, ancillary services, hydro plants, constraints, etc.) of the whole network. In contrast to subs and zones, groups do not follow specific assignment rules. Thus, a child object can be assigned to multiple groups, and a group can have as many child objects assigned to it as there are child objects in the network.

Summaries for the properties and events of EGRP.

3. Electric node (ENO)

Nodes represent objects describing a junction among two or more electric branches, as well as a location in the electric network where power can be injected or extracted through externals (e.g., demand, supply, etc.).

Summaries for the properties and events of ENO.

4. Electric branch (EBR)

A branch is a directed connection between a pair of nodes. For each branch, one of the two nodes is referred to as FromNode and the other as ToNode. The flow along a branch is positive if the flow goes from the FromNode to the ToNode, and the flow is negative for the reversed direction.

An electric branch is used to model facilities that have an inlet, an outlet, and a flow direction, such as electric lines and electric transformers.

4.1. Line (LI)

A line is an object which models the transmission of electricity between two connected locations.

Summaries for the properties and events of LI.

4.2. Transformer (TRF)

A branch in an electric network that represents a transformer. Note that for a transformer, FromNode is defined to be on the high-voltage end of the transformer and ToNode is defined to be on the low-voltage end of the transformer.

Summaries for the properties and events of TRF.

BB and BBDEF should be negative. In contrast, those for the line should be positive.

5. Electric external (EXT)

A directed connection to a single electric node, which allows the extraction and injection of power at that node. An electric external is used to model demands, generators, and storage facilities in an electric network. An arbitrary number of electric externals can be assigned to an electric node.

5.1. Electric demand (EDEM)

An object for representing electricity demand at a particular node. It can be controlled by defining a power set-point.

Summaries for the properties and events of EDEM.

5.2. Electric storage (ESTR)

An object for representing electricity storage at a particular node. An electric storage can supply or absorb power from the network depending on its control mode and the network conditions. Typically, the rate at which power can be injected into or withdrawn from the electric storage depends on its properties (ramp rates, maximum discharge power, etc.). It can also contribute to an ancillary service (up and down reserves) depending on its state of charge.

Summaries for the properties and events of ESTR.

The initial state of charge (SOC) of an ESTR is 0 % in all scenarios, unless differently defined by the user. This statement is not true for a CEM scenario. The initial SOC in CEM is flexible, but there is a constraint that forces the initial and final step to have the same SOC level.

With the release 3.6 of SAInt, the property VMSETDEF has been removed for ESTR objects. Instead, the property QSETDEF has been added, making electric storages treated in a similar way to WIND and PV objects with a default QSET. The default value of QSETDEF is 0 MVAr.

When opening a model created with a version of SAInt prior to 3.6, users should create a VSET event for instances of the ESTR object in their model. Note that single phase ESTR objects are restricted from the VSET property, and only QSET events can be used.

5.3. Electric shunt (SHT)

An electric shunt models a shunt reactor or capacitor. Shunt reactors are placed locally to control the over-voltages at electric nodes under light load conditions (consume reactive power to reduce the nodal voltage), while shunt capacitors are used to boost the voltage in a stressed system (supply reactive power to increase the nodal voltage).

A positive BSET means the shunt is capacitive, otherwise it is inductive.

Summaries for the properties and events of SHT.

5.4. Electric prosumer (EPS)

The object models the injection and extraction of electricity from an external network or a device or facility that can generate and consume electricity without storage. For example an electric prosumer object can describe a pumped hydro storage, an external grid, or a generic storage in the electric network. It allows to set an active power discharge (negative P) or charge (positive P).

Summaries for the properties and events of EPS.

5.5. Pumped hydro storage (PHSTR)

The object models a storage facility that extracts electricity from a network for pumping water into a reservoir using an electric pump and injects electricity into a network by converting the potential energy stored in the reservoir to electric energy using a hydro generator. A pumped hydro storage is always connected to a hydro power plant.

Summaries for the properties and events of PHSTR.

5.6. Generic generator (XGEN)

An object for representing a generic electricity generator. For example, it can represent a solar generator, wind generator, bio fuel generator, etc. It can also contribute to an ancillary service (up and down reserves).

Summaries for the properties and events of XGEN.

5.7. Hydro generator (HGEN)

A hydro generator object requires a connection to a hydro plant object. Electricity generation for hydro generators is determined by the flow of water through a hydro turbine at the hydro plant. It can also contribute to an ancillary service (up and down reserves) depending upon the volume of the hydro plant.

Summaries for the properties and events of HGEN.

A model prepared in SAInt version 3.2.X opened in version 3.3 or later, SAInt converts the hydro generator HGEN objects into a pumped hydro storage PHSTR objects. Pumped hydro storage objects are two-sided externals. Therefore, the PMIN property of the HGEN will be converted to PGMIN property and the PMAX will be converted to PGMAX. The value of the VOMPrice will be copied to VOMGPrice and VOMDPrice properties of the PHSTR. Once a scenario is run, the corresponding events, if any, will also be mapped to the PHSTR object automatically.

5.8. Fuel generator (FGEN)

Fuel generators require a connection to a fuel object, and electricity generation from a fuel generator incurs costs and emissions associated with the fuel object. It can also contribute to an ancillary service (up and down reserves).

Summaries for the properties and events of FGEN.

The FuelConsumptionCurve has to be strictly convex. Non-convex curves (concave) can be managed clicking on the AdjustCurve option. By doing so, the input points are convexified. Please keep in mind that the first point is always P = 0, and not PMIN.

For the PMAXDEF property of a fuel generator, a value of 'Infinity' cannot be used in combination with the fuel consumption curve. Please ensure that PMAXDEF is set to a finite value whenever a fuel consumption curves is involved.

5.9. Wind generator (WIND)

An object for representing the electricity generator from a wind power plant generator. The electricity generation depends on the weather data (wind speed, temperature, etc.), the wind turbine power curve, and the wind properties (hub height, losses, etc.)

Summaries for the properties and events of WIND.

5.10. Solar generator (PV)

An object for representing the electricity generator from a solar power plant generator. The electricity generation depends on the weather data (global horizontal irradiance, diffuse irradiance, etc.), and the solar plant properties (tilt angle, losses, etc.).

Summaries for the properties and events of PV.

6. Fuel (FUEL)

A fuel object requires a connection to a fuel generator. The same object can be connected to several fuel generators.

Summaries for the properties and events of FUEL.

7. Hydro plant (HYDP)

A hydropower plant consists of a water reservoir connected to one or more hydro generators. Water is modeled to flow in the hydropower plant object either from inflow (rain, etc.), water turbinated by another hydropower plant, water pumped by a hydro generator, or spillage from a hydropower plant. The water outflow is modeled as water turbinated to another hydropower plant, turbinated to generate electricity, spilled with (spill) and without penalties (outflow).

Summaries for the properties and events of HYDP.

8. Ancillary service (ASVC)

Ancillary services represent the precautionary measures taken to ensure reliability of an electric network in the event of a disturbance (e.g., transmission line outage, generator outage, etc.). The ancillary service object is valid only in a DCUCOPF scenario.

Summaries for the properties and events of ASVC.

8.1. Ancillary service external (ASVCX)

Ancillary service externals are defined as external objects that can contribute to a particular ancillary service. The same object can contribute to multiple ancillary services.

Summaries for the properties and events of ASVCX.

9. Electric constraint (ECNSTR)

An object describing customized constraints that a user can create. Such constraints must be "linear constraints". This object is available only in a DCUCOPF scenario.

Summaries for the properties and events of ECNSTR.

For each constraint, the bounds are defined by the constraint properties. The bounds are compared to the sum of all variables that are linked to that constraint. Written generally for a constraint with N variables and a scenario with a time horizon containing T timesteps, the bounds are defined as at each timestep t:

ECNSTR.Name.LowBound(t) ≤ ∑N(EVAR.Namen.Coeff(t) * EVAR.NetObjIDn.ObjVarName(t))

ECNSTR.Name.UpBound(t) ≥ ∑N(EVAR.Namen.Coeff(t) * EVAR.NetObjIDn.ObjVarName(t))

[∑T(ECNSTR.Name.AvgLowBound(t))] / T ≤ [∑T∑N(EVAR.Name.Coeff(t) * EVAR.NetObjIDn.ObjVarName(t))] / T

[∑T(ECNSTR.Name.AvgUpBound(t))] / T ≥ [∑T∑N(EVAR.Name.Coeff(t) * EVAR.NetObjIDn.ObjVarName(t))] / T

As with all default event values, the properties LowBoundDef, UpBoundDef, AvgLowBoundDef, AvgUpBoundDef, and CoeffDef can be overridden in a scenario using events.

9.1. Electric variable (EVAR)

An electric variable object defines the link between an electric variable of an object (e.g., P, etc.) and an electric constraint object.

Summaries for the properties and events of EVAR.

Variables of the electric network in DCUCOPF
ObjType VariableName Description UnitType

ENO

VA

Voltage angle

ANGLE

LI

P

Active power flow through branch

PPOW

TRF

P

Active power flow through branch

PPOW

EDEM

P

Active power demand

PPOW

EPS

P

Active power demand

PPOW

ESTR

PD

Active power charge of storage

PPOW

ESTR

PG

Active power discharge of storage

PPOW

ESTR

SOC

State of charge of storage

PC

WIND

P

Active power generation

PPOW

PV

P

Active power generation

PPOW

XGEN

P

Active power generation

PPOW

HYDP

SPILL

Spilled flow through hydroplant

HQVOL

HYDP

TURB

Turbinated flow through hydroplant

HQVOL

HYDP

VOL

Reservoir volume of hydroplant

VOL

HGEN

P

Active power generation

PPOW

PHSTR

PD

Active power charge of pumped hydro storage

PPOW

PHSTR

PG

Active power discharge of pumped hydro storage

PPOW

FUEL

F

Fuel consumption rate

NO

FGEN

P

Active power generation

PPOW

FGEN

SHUTDOWN

Shutdown of fuel generator

ND

FGEN

STARTUP

Startup of fuel generator

ND

FGEN

UP

Commitment of fuel generator

ND

ASVCX

VAL

Contribution of external to ancillary service

NO