Using the Smart Grid Lab to Test a Power Oscillation Damping Controller for Modular Multilevel Converters

IEEE PES Smart Grid Seminar 2019

Abel A. Taese

Norwegian University of Science and Technology

May 8, 2019 Outline

1 Background

2 Power Hardware In the Loop Principle

3 Test Setup

4 Results

5 Conclusion

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 1 / 17 Outline

1 Background

2 Power Hardware In the Loop Principle

3 Test Setup

4 Results

5 Conclusion System operators are requiring more services from converters to increase their utilization.

The services include Power Oscillation Damping (POD), frequency support, ac voltage support, and black start.

Background Background

Existing HVDC Link Planned HVDC Link 2 The number of HVDC links is increasing in the Norway 11 power system. 15 10 1 17 5

14 16 North Sea Denmark 3

12 9 8 18 6 7

Great Britain Germany

Netherlands 4 13

Belguim

1. Skagerrak 1, 2, 3 & 4 10. Caithness Moray 2. Troll A (1, 2, 3 & 4) 11. Johan Sverdrup 3. NorNed 12. COBRA Cable 4. BritNed 13. NEMO Link 5. Valhall 14. NORD Link 6. BorWin 1, 2, 3 & 4 (3 & 4 not commissioned yet) 15. NorthConnect 7. DolWin 1, 2 & 3 (3 not commissioned yet) 16. Eastern Link 8. HelWin 1 & 2 17. North Sea Link (NSN) 9. SylWin 18. Viking Link HVDC in the North Sea

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 2 / 17 The services include Power Oscillation Damping (POD), frequency support, ac voltage support, and black start.

Background Background

Existing HVDC Link Planned HVDC Link 2 The number of HVDC links is increasing in the Norway 11 power system. 15 10 1 17 5

14 16 North Sea Denmark 3

System operators are requiring more services 12 9 8 from converters to increase their utilization. 18 6 7

Great Britain Germany

Netherlands 4 13

Belguim

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 2 / 17 Background Background

8.9.2016 EN Official Journal of the European Union L 241/17

6. Any necessary mitigating actions identified by the studies carried out in accordance with paragraphs 2 to 5 and reviewed by the relevant TSO shall be undertaken by the HVDC system owner as part of the connection of the new HVDC converter station.

7. The relevant TSO may specify transient levels of performance associated with events for the individual HVDC system or collectively across commonly impacted HVDC systems. This specification may be provided to protect the The number of HVDC links is increasing in the integrity of both TSO equipment and that of grid users in a manner consistent with its national code.

power system. Article 30 Power oscillation damping capability

The HVDC system shall be capable of contributing to the damping of power oscillations in connected AC networks. The control system of the HVDC system shall not reduce the damping of power oscillations. The relevant TSO shall specify a frequency range of oscillations that the control scheme shall positively damp and the network conditions when this occurs, at least accounting for any dynamic stability assessment studies undertaken by TSOs to identify the stability limits and potential stability problems in their transmission systems. The selection of the control parameter settings shall be agreed between the relevant TSO and the HVDC system owner. System operators are requiring more services The HVDC system shallArticle 31 be capable of from converters to increase their utilization. contributing toSubsynchronous the torsional damping interaction damping capability of power 1. With regard to subsynchronous torsional interaction (SSTI) damping control, the HVDC system shall be capable of contributing to electrical damping of torsional frequencies.

oscillations2. The relevant TSO in shall specify connected the necessary extent of SSTI studies and AC provide inputnetworks. parameters, to the extent available, related to the equipment and relevant system conditions in its network. The SSTI studies shall be provided by the HVDC system owner. The studies shall identify the conditions, if any, where SSTI exists and propose any necessary mitigation procedure. Member States may provide that the responsibility for undertaking the studies in accordance with this Article lies with the TSO. All parties shall be informed of the results of the studies.

The services include Power Oscillation Damping 3. All parties identified by the relevant TSO as relevant to each connection point, including the relevant TSO, shall contribute to the studies and shall provide all relevant data and models as reasonably required to meet the purposes of the studies. The relevant TSO shall collect this input and, where applicable, pass it on to the party responsible for the studies in accordance with Article 10.

(POD), frequency support, ac voltage support, 4. The relevant TSO shall assess the result of the SSTI studies. If necessary for the assessment, the relevant TSO may request that the HVDC system owner perform further SSTI studies in line with this same scope and extent.

5. The relevant TSO may review or replicate the study. The HVDC system owner shall provide the relevant TSO all and black start. relevant data and models that allow such study to be performed.

6. Any necessary mitigating actions identified by the studies carried out in accordance with paragraphs 2 or 4, and reviewed by the relevant TSOs, shall be undertaken by the HVDC system owner as part of the connection of the new HVDC converter station.

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 ENTSOE Grid Code 2 / 17 Background POD

POD is a service that aims to improve damping of electromechanical oscillations in a power system.

Typical frequencies of inter-area oscillations are 0.2 2 Hz. −

POD using converters can be achieved by injecting active power into the ac grid in counter-phase to the oscillation.

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 3 / 17 Background Test Grid

B1 20 kV : 380 kV B2 B3 B4 B5 380 kV : 20 kV B6

530 MW G1* 25 km 25 km 70 km G6 -46 MVar

308 MW 1389 MW 700 MW B7 20 kV : 380 kV B8 179 MVar 397 MVar 152 MVar G2* AC Grid 1 776 MW Droop mode 10% 916 MW Sign convention: 308 MVar Area 1 522 MW

46 MVar km 119 MVar Conv3 Machines: Positive = Production 25 B9 20 kV : 380 kV B10 Loads: Positive = Consumption Converters: Positive = Into the ac side G3 AC Grid 2 B20 AC Grid 3 700 MW 100 MVar Constant P mode Constant P mode Conv2 Conv1 B11 B12 B14 B15 B19 B21 B16 B17 B18 20 kV : 380 kV ±320 kV dc 380 kV : 20 kV G5 150 km 10 km G4*

807 MW 340 MW 128 MVar

100 MVar Fault 260 MW -798 MW km 80 MVar 222 MVar Area 2 25 811 MW 80 MVar B13 * Reference machine 300 MW 50 MVar

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 4 / 17 Background Electromechanical Oscillation

B1 20 kV : 380 kV B2 B3 B4 B5 380 kV : 20 kV B6

530 MW G1* 25 km 25 km 70 km G6 -46 MVar

308 MW 1389 MW 700 MW B7 20 kV : 380 kV B8 179 MVar 397 MVar 152 MVar G2* AC Grid 1 776 MW Droop mode 10% 916 MW Sign convention: 308 MVar Area 1 522 MW

807 MW 340 MW 128 MVar

100 MVar Fault 260 MW -798 MW km 80 MVar 222 MVar Area 2 25 811 MW 80 MVar B13 * Reference machine 300 MW 50 MVar

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 4 / 17 Background POD Action

B1 20 kV : 380 kV B2 B3 B4 B5 380 kV : 20 kV B6

530 MW G1* 25 km 25 km 70 km G6 -46 MVar

308 MW 1389 MW 700 MW B7 20 kV : 380 kV B8 179 MVar 397 MVar 152 MVar G2* AC Grid 1 776 MW Droop mode 10% 916 MW Sign convention: 308 MVar Area 1 522 MW

807 MW 340 MW 128 MVar

100 MVar Fault 260 MW -798 MW km 80 MVar 222 MVar Area 2 25 811 MW 80 MVar B13 * Reference machine 300 MW 50 MVar

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 4 / 17 Background The Challenge

B1 20 kV : 380 kV B2 B3 B4 B5 380 kV : 20 kV B6

530 MW G1* 25 km 25 km 70 km G6 -46 MVar

308 MW 1389 MW 700 MW B7 20 kV : 380 kV B8 179 MVar 397 MVar 152 MVar G2* AC Grid 1 776 MW Droop mode 10% 916 MW Sign convention: 308 MVar Area 1 522 MW

807 MW 340 MW 128 MVar

100 MVar Fault 260 MW -798 MW km 80 MVar 222 MVar Area 2 25 811 MW 80 MVar B13 * Reference machine 300 MW 50 MVar

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 4 / 17 Background The Proposed Solution

B1 20 kV : 380 kV B2 B3 B4 B5 380 kV : 20 kV B6

530 MW G1* 25 km 25 km 70 km G6 -46 MVar

308 MW 1389 MW 700 MW B7 20 kV : 380 kV B8 179 MVar 397 MVar 152 MVar G2* AC Grid 1 776 MW Droop mode 10% 916 MW Sign convention: 308 MVar Area 1 522 MW

807 MW 340 MW 128 MVar

100 MVar Fault 260 MW -798 MW km 80 MVar 222 MVar Area 2 25 811 MW 80 MVar B13 * Reference machine 300 MW 50 MVar

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 4 / 17 Background How the MMC can be used

idc

vc1 SM

Modular structure N vu = nuvcu vcu = vci vci SM Xi=1 Distributed Energy storage (Upper arm voltage)

vcN SM Larm No direct coupling of the capacitors into either iac

vdc C ac or dc side dc ic vg v Special energy control virtual capacitance c1 SM Larm support N vcl = vcj vcj SM vl = nlvcl jX=1 (Lower arm voltage)

vcN SM

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 5 / 17 Test option Cost Risk/safety Flexibility Time-to-test Accuracy1 Purely simulation ++ ++ ++ ++- Purely experimental ---- ++ PHIL +++++

PHIL gives a good compromise between simulation and experimental tests.

Background Why PHIL?

Goal To test the control algorithm under realistic conditions.

1Accuracy in representing a physical system Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 6 / 17 Background Why PHIL?

Goal To test the control algorithm under realistic conditions.

Test option Cost Risk/safety Flexibility Time-to-test Accuracy1 Purely simulation ++ ++ ++ ++- Purely experimental ---- ++ PHIL +++++

PHIL gives a good compromise between simulation and experimental tests.

1Accuracy in representing a physical system Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 6 / 17 Outline

1 Background

2 Power Hardware In the Loop Principle

3 Test Setup

4 Results

5 Conclusion When A and B are connected:

VA = VB (1) IA = IB The following connection has the same eect because (1) is satised.

A B IB + VA −

Power Hardware In the Loop Principle Introduction

A B

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 7 / 17 The following connection has the same eect because (1) is satised.

A B IB + VA −

Power Hardware In the Loop Principle Introduction

A B

When A and B are connected:

VA = VB (1) IA = IB

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 7 / 17 Power Hardware In the Loop Principle Introduction

A B

When A and B are connected:

VA = VB (1) IA = IB The following connection has the same eect because (1) is satised.

A B IB + VA −

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 7 / 17 The main challenge is time delays/lag introduced by: Measurement and communication system Power amplier bandwidth Simulation solver time step The consequences include simulation instability and deviation from actual dynamics

Power Hardware In the Loop Principle Introduction

If A is replaced by simulation = PHIL ⇒ Grid Emulator A Sim B IB + VA −

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 8 / 17 The consequences include simulation instability and deviation from actual dynamics

Power Hardware In the Loop Principle Introduction

If A is replaced by simulation = PHIL ⇒ Grid Emulator A Sim B IB + VA −

The main challenge is time delays/lag introduced by: Measurement and communication system Power amplier bandwidth Simulation solver time step

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 8 / 17 Power Hardware In the Loop Principle Introduction

If A is replaced by simulation = PHIL ⇒ Grid Emulator A Sim B IB + VA −

The main challenge is time delays/lag introduced by: Measurement and communication system Power amplier bandwidth Simulation solver time step The consequences include simulation instability and deviation from actual dynamics

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 8 / 17 Outline

1 Background

2 Power Hardware In the Loop Principle

3 Test Setup

4 Results

5 Conclusion Real-time Simulator B15 B19 To AC Grid 2 To DC Grid (Fig. 3) V V (Fig. 3) (dq) dc meas ac meas V V (dq) ac meas dc meas I I

Grid Emulator Interface dc V (abc) (abc) ac meas

Conv2P ac meas V dc meas I I AC A A Grid Emulator DC (Power Ampliﬁer)

Test Setup From Simulation to PHIL

B1 20 kV : 380 kV B2 B3 B4 B5 380 kV : 20 kV B6

530 MW G1* 25 km 25 km 70 km G6 -46 MVar

308 MW 1389 MW 700 MW B7 20 kV : 380 kV B8 179 MVar 397 MVar 152 MVar G2* AC Grid 1 776 MW Droop mode 10% 916 MW Sign convention: 308 MVar Area 1 522 MW

807 MW 340 MW 128 MVar

100 MVar Fault 260 MW -798 MW km 80 MVar 222 MVar Area 2 25 811 MW 80 MVar B13 * Reference machine 300 MW 50 MVar

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 9 / 17 Test Setup From Simulation to PHIL

Real-time Simulator B1 20 kV : 380 kV B2 B3 B15B4 B5 380 kV : 20 kV B6 B19 To AC Grid 2 To DC Grid 530 MW G1* 25 km 25 km(Fig. 3) 70V km V G6 (Fig. 3) -46 MVar

308 MW 1389 MW 700 MW B7 20 kV : 380 kV B8 179 MVar 397 MVar 152 MVar (dq) dc meas ac meas

G2* V AC Grid 1 V 776 MW Droop mode 10%

916 MW Sign(dq) convention:

308 MVar Area 1 522 MW km ac meas 46 MVar Conv3 dc meas I

119 MVar MachinesI : Positive = Production 25 B9 20 kV : 380 kV B10 Loads: Positive = Consumption Converters: Positive = Into the ac side G3 AC Grid 2 Grid Emulator Interface B20 AC Grid 3 700 MW 100 MVar Constant P mode Constant P mode

Conv2 Conv1 dc V B11 B12 B14 B15 B19 B21 B16(abc) B17 B18 20 kV : 380 kV (abc) ±320 kV dc ac meas 380 kV : 20 kV Conv2P ac meas V dc meas I I G5 150 km 10 km AC G4* A A DC Grid Emulator 807 MW 340 MW (Power Ampliﬁer) 128 MVar

100 MVar Fault 260 MW -798 MW km 80 MVar 222 MVar Area 2 25 811 MW 80 MVar B13 * Reference machine 300 MW 50 MVar

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 9 / 17 Test Setup Converter Rating

Parameter Simulated PHIL Rated Power 900 MW 60 kW DC Voltage 640 kV 600 V AC Voltage 380 kV 400 V SINTEF MMC Converter

There is a 1 : 1 ratio between simulated and physical power, voltage, and current in Per-unit.

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 10 / 17 Outline

1 Background

2 Power Hardware In the Loop Principle

3 Test Setup

4 Results

5 Conclusion Results Test Cases

No. Label Description 1 Base Base case both POD2and VCS3disabled 2 POD POD controller enabled 3 POD + VCS Both POD and VCS enabled

A fault at bus B14 is used to perturb the system at t = 10 s.

1Power Oscillation Damping 2Virtual Capacitance Support Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 11 / 17 Results Rotor angles

1.600 − Base POD POD + VCS

1.800 −

G5 Rotor angle in (rad) 2.000 − 0 5 10 15 20 25 30 35 40 45 50 Time in (s)

0.48 − Base POD POD + VCS 0.49 − 0.5 −

G6 Rotor angle in (rad) 0.51 − 0 5 10 15 20 25 30 35 40 45 50 Time in (s) Rotor angles of G5 and G6 (experimental).

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 12 / 17 Results Rotor speeds

1.004 Base POD POD + VCS 1.002

1.000

G5 Rotor speed in0 (pu) .998 0 5 10 15 20 25 30 35 40 45 50 Time in (s)

1.0001 Base POD POD + VCS

G6 Rotor speed in0 (pu) .9999 0 5 10 15 20 25 30 35 40 45 50 Time in (s) Rotor speeds of G5 and G6 (experimental).

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 13 / 17 Results Energy and Active Power

0.685 Base POD POD + VCS

0.680

Arm Energy in (pu) 0.675 0 5 10 15 20 25 30 35 40 45 50 Time in (s)

Base POD POD + VCS 0.01 0 0.01 − POD power in (pu) 0 5 10 15 20 25 30 35 40 45 50 Time in (s) Active power and energy measurements of Conv2 (experimental).

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 14 / 17 Results Impact of PHIL delay

1.600 − Sim PHIL Sim + Delay

1.800 − G5 Rotor angle in (rad)

2.000 − 0 5 10 15 20 25 30 35 40 45 50 Time in (s) Comparison of simulation and experimental results.

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 15 / 17 Outline

1 Background

2 Power Hardware In the Loop Principle

3 Test Setup

4 Results

5 Conclusion Conclusion Conclusion: Application

The test grid has a poorly damped inter-area oscillation

Damping of the oscillation was improved by using POD controller

The oscillation propagated to the healthy ac grid because of the POD Action

Virtual capacitance support diverts most of the oscillation into the MMC capacitors.

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 16 / 17 Conclusion Conclusion: Test Setup

The smart grid lab gives a robust and exible platform for testing complex applications

PHIL oers a good tradeo between simulation and experimental test options.

PHIL time delays can cause instability and deviation from actual dynamics

Further investigation and evaluation of other interfacing methods can be done to mitigate these problems.

Abel A. Taese (NTNU) IEEE PES Smart Grid Seminar 2019 17 / 17 Thank You!

Abel A. Taese [email protected] PhD Student Power Electronics Systems and Components Group Department of Electric Power Engineering Norwegian University of Science and Technology