Integration Profile "Send Control Information" (SCI)

Schlagwörter: SCI

The SCI profile bases on the standard series IEC 61850 to transmit control information from the VPPOP or DEUOP (central or local control center) to the DEUOP or DEUC (station or DER/load controller). The control information can be a complete schedule for the DEUC as well as a direct control signal to balance the grid, which are depicted as instances of logical nodes (LN). The transferred data has to be encrypted usingand transmitted according to the Manufacturing Messaging Specification (MMS) via TCP/IP.

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1 Description

The SCI profile bases on the standard series IEC 61850 to transmit control information from the VPPOP or DEUOP (central or local control center) to the DEUOP or DEUC (station or DER/load controller). The control information can be a complete schedule for the DEUC as well as a direct control signal to balance the grid, which are depicted as instances of logical nodes (LN). The transferred data has to be encrypted usingand transmitted according to the Manufacturing Messaging Specification (MMS) via TCP/IP.

 

2 Actors/Transactions

ProfileSCI.PNG

Figure 1: Actors/Transaction Diagram CSE

 

Actors

Transaction

Optionality

Section

DEUC

Send Measurements [SCI-03]

R1,2

 

Transfer Schedule [SCI-01]

R2

 

Send Control Signals [SCI-02]

R1

 

DEUOP

Transfer Schedule [SCI-01]

R2

 

Send Control Signals [SCI-02]

R1

 

Send Measurements [SCI-03]

R1,2

 

VPPOP

Transfer Schedule [SCI-01]

R2

 

Send Control Signals [SCI-02]

R1

 

1) Not required for the profile coordinated VPP archetype where DEUs do not provide ancillary services nor secondary control energy.

2) Not required for the loosely cooperating VPP archetype (Demand Response system) where DEUs do not follow a predefined schedule but respond to change requests only.

 

2.1 Actor Descriptions and Actor Profile Requirements

General requirements for the Business Use Case are listed within the UCMR (ucmr-ies.offis.de). Further requirements, which affect the data exchange, are explained within the transaction description in detail. This section documents any additional requirements on the profile’s actors.

 

DEU

The Distributed Energy Unit (DEU) produces (or consumes) energy. Normatively this summarizes all the electrically connected physical parts of a VPP that can be managed and thus have an addressable control interface (DEUC). The DEU can be a DER, an adjustable load or an energy storage device. DEUs at the same premises may be grouped and controlled by a single control unit (DEUOP). Logically, the DEU data object comprises various logical nodes (according to IEC 61850-7-420) to store all the assets’ actual configurations.

 

DEUC

The Distributed Energy Unit Controller (DEUC) controls a specific DEU. Depending on the controlled DEU the DEUC includes DER, load or storage controllers from the SGAM perspective.

 

DEUOP

The Distributed Energy Unit Operator (DEUOP) controls a local group of DEUs and represents a station controller in SGAM. This actor handles both, the communication with the VPPOP and the joint control of several DEUs. It transforms schedules and control signals from the VPPOP into schedules and control signals that alter the behavior of the individual DEUs managed. A DEUOP can represent the entire group of DEUs it manages as a single asset.

VPPOP

The Virtual Power Plant Operator (VPPOP) creates aggregated forecasts to trade energy on the energy market, and calculates individual schedules per DEU to control the energy production (and load) that the VPP inserts (drains). In case “ancillary services” are legible and negotiated, the system operator (SO) can send grid requirements to the VPPOP, which in return creates direct DEU control signals forwarded to the relevant DEUC in order to initiate close to instantaneous DEU response helping the SO to balance the power grid the DEU is connected to, e.g. to start or stop single assets.

 

Notes

  1. Actors are logical entities, several may be located within the same physical unit. Not every physical unit required for the VPP operation also comprises an actor of the Use Case.
  2. Communication within a VPP shall be performed in accordance to the standard series IEC 61850, which defines data models and communication paths to transfer schedules, measurements and control signals between an operator and single assets. (Other standards exist but are here not considered.)
  3. A ‘router’ that relays messages received from a VPPOP to the addressed DEUCs and vice versa without altering the message is neither a DEUC nor a DEUOP. It is a lower layer component invisible to the VPP operation alike Ethernet switches are invisible to IP routing.
  4. Different DEUC instances may be integrated in a single physical box and may be executed in parallel on a single processor. Logically these are individual entities, and thus, such a box is not a DEUOP, it is a set of DEUCs that just happens to be in the same location.
  5. If the individual DEUs that a DEUOP manages comprise no individual DEUCs, the DEUOP includes DER, load and storage controllers from the SGAM perspective, and thus provides logically all the individual DEUCs of the managed DEUs. From an operational perspective, all the individual DEUs have their own logical DEUCs and all transactions between that DEUOP and these logical DEUCs occur internal.

 

2.2 Transactions

Within this part, a brief overview of the involved transactions within the Integration Profile “Send Control Information” is given.

 

2.2.1 SCI-01: Transfer Schedule

A VPPOP initiates the “Transfer Schedule” transaction. Each schedule in this transaction is created by the VPPOP, based on: the information gathered upon the individual DEUs, the schedule sold on the energy market, the requirements and limits of the relevant SO. The VPPOP is responsible to create and transmit a correct schedule to the DEUC. A correct schedule comprises the values of the LN FSCH (IEC 61850: Schedule). Based on the received data the LN DRCS (IEC 61850: DER controller status) and DRCC (IEC 61850: DER supervisory control) are defined. Via the transaction “SCI-03: Send signals”, these data objects are forwarded to the DEU where they define the LN DSCC and DSCH, which implementing the execution of the schedule. [Note: the logical resources of a DEU may physically be included in the DEUC; for example where the actual control signal is a simple analogous actuation voltage/current that for example operates a switch.]

 

The actual transmission process incorporates two general purpose subactors specified in the Transactions SCI-01 and SCI-02. For a better understanding the chain of actions is sketched. This applies similarly to all transactions using TCP/IP as transport means and MMS for compliant data transmission security.

 

Prior the actual transmission the data of the VPPOP LN are mapped into a payload data unit (PDU) according to the Manufacturing Message Specification (MMS) according to the IEC 61850-8-1 by the VPPOP’s encoder subactor (see Transaction SCI-01). The transmission of the created PDU via TCP/IP to the DEUC is initiated and handled by the VPPOP’s Transmission Initiator subactor. The PDU is received by the DEUC’s Transmission Receiver subactor, and decoded by its Decoder subactor, which creates the DEUC LNs.

 

2.2.2 SCI-02:

Similar to the first transaction “SCI-01: Transfer Schedule”, the transaction “SCI-02: Send Control Signals” is initiated and executed by the VPPOP. At this point, the schedule further contains the FSCH.ValASG, FSCH.EvTrg and FSCH.InSyn to react on grid requirements from the SO as an external event, i.e. the current schedule is interrupted by a new one (higher priority in the data object: FSCH.SchdPrio).

 IEC 61850 FSCH.png

Figure 2: Screenshot from the IEC 61850 FSCH

After the duration of the new schedule, the old schedule has to be to continue with the regular schedule. The VPPOP is responsible to create and to transmit the schedule to the DEUC by providing the values of the LN FSCH (Schedule). Based on this data the LN DRCS (DER controller status) and DRCC (DER supervisory control) are filled. Within the transaction “SCI-03: Send signals”, these data are provided for the LN DSCC and DSCH of the DEU for implementing the schedule. 

The data from the LN are mapped to the Manufacturing Message Specification by the Encoder of the VPPOP for transmitting the data via TCP/IP to the DEUC who decodes the data and stores the data in form of the DEUC LN.

 

2.2.3 SCI-03: Send Command

The transaction “SCI-03: Send Command” follows the transactions “SCI-01” and “SCI-02”. After receiving a schedule, the DEUC converts the information to single commands for the DEUs. Therefore, the data from the LN DRCS and DRCC of the DEUC are transferred to the LN DSCC and DSCH of the DEU which include the information for single assets to fulfill their part of the schedule.

The data from the LN are mapped to the Manufacturing Message Specification by the Encoder of the DEUC for transmitting the data via TCP/IP to the DEU who decodes the data and stores the data in form of the DEU LN.

 

 

3 Actor Options

Options that may be selected for each actor in this profile, if any, are listed in Table 1. Afterwards, the options are described and dependencies between options when applicable are specified.

 

Table 1: Actor Options

Actor

Option

Vol. & Section

VPPOP

Market participant

3.1

Plant Operator

3.2

DEUOP

Plant Operator

3.2

Producer

3.3

Consumer

3.4

DEUC

Producer

3.3

Consumer

3.4

 

3.1 Market participant

The VPPOP can interact as market participant for trading energy at the energy market in use of the standard series IEC 62325. The VPP is called commercial VPP (cVPP)[1].

 

3.2 Plant Operator

A VPPOP or DEUOP manages several small assets, which are outward represented as one large asset. Thus, the SO needs to communicate with the VPPOP or DEUOP when adjustments are needed to balance the power grid. Based on the agreed measures, the VPPOP or DEUOP adapts its schedule and notifies the DEUs to execute the change. in use of the standard series IEC 61850. The VPP is called technical VPP (tVPP)1.

 

3.3 Producer

DER and storages as well as combinations thereof managed by a DEUOP can occur as energy producer inserting an unknown schedule if not managed, or intending to fulfill a planned schedule when participating in a VPP.

 

3.4 Consumer

Loads and storages as well as combinations thereof managed by a DEUOP can occur as energy consumer causing an unknown load schedule if not managed, or intending to fulfill a planned schedule when participating in a VPP.

 

4 Integration Profile Process Flow

The data exchange for the VPP control information goes through a sequence of single transactions between the VPPOP, DEUC and DEU. Thereby, the sequence can start from two different viewpoints: the normal transmission of schedules or the control by direct control signals. Both transactions are followed by the transaction “SCI-03”, which sends executable commands to the DEU. The sequence of transactions is shown in Figure 4.

Additionally, the sequences show which LNs are required to represent the VPP schedule for providing the data needed by the DEUC and DEU to fulfill the schedule. In the following description of the transactions (see e.g. Transaction SCI-01: “Transfer Schedule”), the detailed description of the LNs is given through an overview of needed data objects and their common data classes. 

send-control-signal-sq_diagram_NEW.png

Figure 3: Sequence Diagram "Send Control Information"

 

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sobia
28. Mai 2017, 10:54
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