Renata Rubeša, Tin Bobetko, Antun Andrić, Krešimir Mesić HOPS

Emil Cek, Matjaž Dolinar ELES

Lazar BizumicNeplan

The 15th International Workshop on Electric Power Control CentersReykjavik, Iceland, May 12-15, 2019

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ELES

SODO

HOPSHEP-ODS

The most promising appeared to be the establishment of international cooperation in setting up smart grids – and the idea of the SINCRO.GRID project was born.

In 2014, the transmission system operators (HOPS and ELES) and distribution system operators (HEP ODS and SODO) of Croatia and Slovenia began to search for joint solutions.

Croatia and Slovenia decided to present the project to the European Commission (EC) as a proposal for a Project of Common Interest (PCI) in the field of smart grids.

The increasing integration of decentralized renewable energy sources (RES) both in the regions of Slovenia and Croatia has led to a lack of flexibility resources needed to regulate the electricity system

The contract on co-financing of the project by EC was signed in Brussels on 22 May 2017.

Modernisation of telecommunication and IT infrastructure

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Deployment of 6 compensation devices to address at cross-border level overvoltage

Deployment of advanced dynamic thermal rating (DTR) systems in boththe Slovenian and Croatian transmission grids

Deployment of electricity storage systems. Batteries with a capacity of 10 MW will be installed in Slovenia to provide secondary regulation

Deployment of a virtual cross-border control centre (VCBCC) consisting of IT infrastructure and software to be used by TSOs for the coordinated optimization of voltage profile.

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GOAL: Voltage regulation and loss optimization in the power systems of Croatia and Slovenia. Maintain secure operation of the two control areas.

IDEA: Create a new joint application complementing the scope of the existing SCADA/EMS systems at both TSO sides aiming at additional business benefit through development of VCBCC, including:• Common optimization tool based on state

estimator’s and grid forecast input• Advanced visualization tools

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VVS (inter TSO Voltage-VAR Scheduler): tertiary voltage control, providing optimised coordination of regulating devices between multiple TSOs considering cross-border effects

VVC (intra TSO Voltage-VAR Control): secondary voltage controller performing real-time local voltage optimization considering constraints from the VVS with outcome in field-device control.

Local device control: primary voltage regulation performed by device controller (as automatic Q, U, tap or switch on/off control) at the grid connection point or on one of connecting nodes in case of transformer with OLTC.

How to design a system which will coordinate two neighbouring TSOs in voltage and reactivepower regulation but keep its independence in voltage control?

Field devices Field Devices

VVC (local SCADA/EMS)

• Optimization• Control• Set point to

devices

ELES

VVC(local SCADA/EMS)• Optimization• Control• Set point to

devices

HOPS

Voltage-Var Scheduler (VVS)• Optimization• Validation• Set point schedules

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VVS Optimization cycle

• Provide initial Voltage plan forecast for upcomingtimeframe (up to 24 h)

VVS Validation cycle

• Validate the initial result andprovide Final Voltageschedule for the next hour

VVC Implementation cycle

Implement the Final Voltage Scheduleonto the grid elements

JOINT ELES & HOPS APPLICATION = VCBCC INDIVIDUAL (TSO) SCADA SYSTEM

Voltage-Var scheduler (VVS) is envisioned as a commonapplication development aiming at providing global optimization results and consisting of the following two-step process: - Optimization cycle providing initial global results- Validation cycle providing validation check of the results

Voltage-Var Control (VVC) shall be designed as a individual TSO application, integrated in SCADA system and aiming at local devicecontrol

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VVS OPTIMIZATION CYCLE Main objective: solve the time-coupling optimization problem for upcoming N (i.e. 1 - 25) timestampson an hourly basis and set the foundation for later VVC process in terms of feasible Voltage plan forecast

Forecast grid models• Day-ahead (DACF)• Intra-day (IDCF)

Time-coupling optimizationfor upcoming timeframe

• Day-ahead Optimization processstarts at 21:00 and providesresults for period of 23:30 [D-1] to 23:30 [D]• Intraday Optimization process

continues on hourly basis duringthe business day

Initial Voltage schedule• Provide initial results for

the rest of the day

Inputs Process Outputs

Pre-Final Voltageschedule• Provide results for the

upcoming timestamp whichneed to be confirmed inValidation cycle

Other data• Constraints (generators,

nodes, branches)• Control variables• Cost function paramaters

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• minimize the overall cost of Voltage controlduring the day which consists of: − grid losses caused by power transmission and

operation of voltage control devices− cost of MVAr production in generating units as

auxilliary service

GOAL Objective function consistsof three components

• minimize the overall number, range and gradientof tap changes for VSRs and Trafos during day

• minimize the reactive power cross-borderexchange between HOPS and ELES during day

How

• Calculate the optimaloutputs on all voltagecontrol devices (Generator, SVC, VSR, Trafo) taking intoaccount muliple user-defined constraints usingNeplan Multi Period OPF (MPOPF) functionality

• Concept developed internally by HOPS & ELES

MPOPF

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0:35 1:35 2:35 3:35 4:35 5:35 6:35 7:35 8:35 9:35 10:35 11:35 12:35 13:35 14:35 15:35 16:35 17:35 18:35 19:35 20:35 21:35 22:35 23:350:301:302:303:304:305:306:307:308:309:30

10:3011:3012:3013:3014:3015:3016:3017:3018:3019:3020:3021:3022:3023:30

Not considered in Intraday VVS -> Pre-Final VS result is based on Day-ahead VVSNot considered in Intraday VVS for the respective run -> Pre-Final VS result is based on previous runIntraday VVS based on IDCF CGM model - Pre-Final VSIntraday VVS based on IDCF CGM model - Initial VSIntraday VVS based on DACF CGM model - Initial VS

Intraday VVS process start time

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Day-ahead VVS process start D-1 at 21:00

D-1 @ 23:300:301:302:303:304:305:306:307:308:309:30

10:3011:3012:3013:3014:3015:3016:3017:3018:3019:3020:3021:3022:3023:30

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VVS VALIDATION CYCLE Main objective: Validate the optimization result [Pre-Final VS] based on the Snapshot grid models,

security check and N-1 analysis in order to define the feasible result - Final Voltage schedule

Pre-Final VS for theupcoming hour (TS)• Voltage set points &

Tap positions of controlvariables for TS [hh:30]

Validation process

• Apply the final result of optimizationupon the merged snapshot at hh:30• Run power flow calculation• Perform security check based on multiple

business rules• comparison of voltages, taps, PF

results, etc• Perform security check based on N-1

analysis for relevant CBCOs

Inputs Process Outputs

Feasibility check

• decide whether theIntermediate Voltageschedule (Pre-Final) isfeasible to proceed to implementation cycle(VVC) in form of Finalvoltage schedule

Other• Snapshot files from the

local State estimators

10. 4. 2017 1

0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 14:30 15:30 16:30 17:30 18:30 19:30 20:30 21:30 22:30 23:300:301:302:303:304:305:306:307:308:309:30

10:3011:3012:3013:3014:3015:3016:3017:3018:3019:3020:3021:3022:3023:30

VVS Validation cycle based on most recent Snaphsot grid modelNot considered in VVS Validation cycle

VVS Validation cycle start time

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- SN

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VVC IMPLEMENTATION CYCLE Main objective: Implement the Final Voltage Schedule onto the grid elements which were considered

the control variables of the optimization process

Final Voltageschedule

• Voltage set points & Tap positions of controlvariables for TS [hh:30]

Pre-implementation check

• wait for Operator confirmation of theInput

AND• Run local security check based on

• predefined rules (voltage/tapdifference, etc.)• Load-flow results on realtime

Snapshot

Inputs Process Outputs

Real-time operation

• Implement the Finalvoltage schedule in thegrid [ELES and HOPS] through local SCADA interface

OR• Cancel implementation

Other• Base-case solution from

the local State estimators

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How to design a system which will coordinate two neighbouring TSOs in voltage and reactive power regulation but keep its independence in control?

The solution should be:• Flexible, enabling both joint and autonomous operation in TSOs• Highly configurable and extendible• Highly automated• Based on modern and widely accepted standards

The concept design process should:• Include experts of many different fields (power system operation,

voltage regulation, SCADA/EMS, network modelling, IT infrastructure, communication protocols…)

• Be based on critical and open design-thinking to allow innovative ideas

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