Detailed Modelling of MMC-HVDC Links · • Demand for VSC-HVDC systems is growing worldwide. •...

Power Conversion Group

School of Electrical and Electronic Engineering

The University of Manchester, UK

DeepWind’2015

Trondheim

4-6th February 2015

Antony Beddard

Detailed Modelling of MMC-HVDC

Links




DeepWind’2015

Trondheim

4-6th February 2015

• Demand for VSC-HVDC systems is growing worldwide.

• Modular Multi-level Converters (MMC) is the VSC topology

of choice.

• Focus is on the DC components

VSC-HVDC

XT=15%

Yg/D

MMC2

Vs2(abc)

220kV 370kV

D/Yg

MMC1

Is1(abc)

PCC1XT=15%

370kV 410kV

Vs1(abc)

Idc1

Is2(abc)

AC voltage magnitude and

frequency control

1000MW

Windfarm1

Active and reactive power

control

Rbrak

Vdc2

PCC2

Vn

SCR=3.5

Zn

XT=15%

Yg/D

MMC3

Vs3(abc)

220kV 370kV

D/Yg

MMC4

Is4(abc)

PCC4XT=15%

370kV 410kV

Vs4(abc)

Idc4

Is3(abc)


frequency control

1000MW

Windfarm2


control

Rbrak

Vdc3

125km DC cable

PCC3

Vn

SCR=3.5

Zn

130km DC cable

200km DC cableIdc2

Idc3




DeepWind’2015

Trondheim

4-6th February 2015

MMC

SM1

Arm

Single IGBT

Sub-module

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

Larm

+Vd/2

-Vd/2

Va

0V

Iua

Ila

Vua

Vla

• Types of MMC

• Half-bridge

• Full-bridge

• Alternate arm converter

• Selecting MMC Parameters

• Number of voltage levels

• SM capacitance

• Arm reactance




DeepWind’2015

Trondheim

4-6th February 2015

MMC Modelling Techniques

• Type 1 – Full physics based model

• Type 2 – Full detailed model

• Type 3 – Traditional detailed model (TDM)

• Type 3.5 – Accelerated model (AM)

• Type 4 – Detailed equivalent model (DEM)

• Type 5/6 – Average value model (AVM)

• Type 7 – Phasor domain model

• Type 8 – Power flow model

SM1

Arm

Single IGBT

Sub-module

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

SM1

SM2

SMn

Larm

+Vd/2

-Vd/2

Va

0V

Iua

Ila

Vua

Vla




DeepWind’2015

Trondheim

4-6th February 2015

Comparison of TDM(3), AM(3.5) and DEM(4)

DC line-to-line Fault

DC Fault

Signal DEM error (%) AM error (%)

Id 0.41 2.29

Va 0.22 1.12

Iua 0.51 1.83

Vc 0.07 0.07

TDM DEM AM

4.45 4.6 4.75 4.45 4.6 4.75 4.45 4.6 4.75

Time (s) Time (s) Time (s)

2

Id(k

A)

Va

(kV

)

300

-300

Iua

(kA

)

4

-8

Vc

(kV

)

21

18

-18

1

10

100

1000

10000

16 31 61

Sim

ula

tio

n d

ura

tio

n (

s)Number of MMC levels

TDM

DEM

AM




DeepWind’2015

Trondheim

4-6th February 2015

HVDC Cable Modelling

Types of HVDC Cable Model:-

• Lumped Parameter Model

• Bergeron Model

• Frequency Dependent Mode Model (FDMM)

• Frequency Dependent Phase Model (FDPM)

Layer Material

Radial Thickness

(mm)

Resistivity

(Ω/m)

Relative

Permittivity

Relative

Permeability

Conductor Stranded Copper 24.9 2.2x10-8* 1 1

Conductor screen Semi-conductive polymer 1 - - -

Insulation XLPE 18 - 2.5 1

Insulator screen Semi-conductive polymer 1 - - -

Sheath Lead 3 2.2x10-7 1 1

Inner Jacket Polyethylene 5 - 2.3 1

Armour Steel 5 1.8x10-7 1 10

Outer cover Polypropylene 4 - 1.5 1

Sea-return Sea water/air - 1 - -

*Copper resistivity is typically given as 1.68*10-8Ω/m. It has been increased for the cable model in PSCAD due to the stranded

nature of the cable which cannot be taken into account directly in PSCAD.




DeepWind’2015

Trondheim

4-6th February 2015

0

100

200

300

400

500

600

700

2.490 2.494 2.498 2.502 2.506 2.510

Vo

ltag

e (

kV)

Time (s)

Vd2-CEPIM

Vd2-Bergeron

Vd2-FDMM

Vd2-FDPM

0

2

4

6

8

10

12

14

16

2.490 2.494 2.498 2.502 2.506 2.510

Cu

rre

nt

(kA

)

Time (s)

Idc2-CEPIM

Idc2-Bergeron

Idc2-FDMM

Idc2-FDPM

Comparison of Cable Models

• The choice of cable model can have a

significant impact on the simulation

results.

• Computational efficiency is

approximately the same for the

travelling wave models.

• The CEPIM was found to be the least

computationally efficient model.

• FDPM is therefore the default model of

choice for typical VSC-HVDC studies

in this work.




DeepWind’2015

Trondheim

4-6th February 2015

XT=15%

Yg/D

MMC2

Vs2(abc)

220kV 370kV

D/Yg

MMC1

Is1(abc)

PCC1XT=15%

370kV 410kV

Vs1(abc)

Idc

Is2(abc)


frequency control

1000MW

Windfarm


control

DC link voltage control and

AC voltage magnitude control

AC GridRbreak

Vd2

165km DC cablePCC2

Dynamic Braking System

• Typically employed for HVDC windfarm connections

• Normally located onshore

• Common models:

• Voltage dependent current source

• Power electronic switch with resistor

• Control – Two level switching, PWM etc.




DeepWind’2015

Trondheim

4-6th February 2015

HVDC Circuit Breaker

• Required for large HVDC grids

• Hybrid DC breakers are currently the preferred topology

• Modelling options – Cigre WG B4-57 technical brochure

SA

Ib

Is

Ls

Disconnector

Auxiliary DC Breaker

Main DC Breaker

Current

Limiting

Reactor

Residual

DC

Current

Breaker

Hybrid DC Breaker

BRKLs

SA

I Ib

Ic

Is

CL

Mechanical DC Breaker Solid-state Breaker




DeepWind’2015

Trondheim

4-6th February 2015

Control

• MMC Control

• Modulation - Nearest level control (NLC), selective harmonic elimination etc.

• Capacitor balancing controller (CBC)

• Circulating current suppressing controller (CCSC),

• Outer controllers similar to traditional VSCs. i.e. not specific to valve topology

Onshore

outer

controller

Current

controller

P*/V*dc/freq*

I* V*Q*/V*ac

Inner VSC

control

FSVSC

V

MTDC

controller

P*/V*dcOffshore

outer

controller

V*ac

freq*




DeepWind’2015

Trondheim

4-6th February 2015

MTDC Control Strategies

Control Method MMC1 control mode MMC4 control mode Comments

Centralised DC slack bus DC voltage & AC voltage

magnitude

Active power & reactive

power

P*=500MW

Voltage margin control DC voltage & AC voltage

magnitude

Voltage margin & reactive

power

Vd-High=620kV,

Vd-Low=580kV

Droop control Standard droop & AC

voltage magnitude

Standard droop & reactive

power

Droop gain =- 0.1

XT=15%

Yg/D

MMC2

Vs2(abc)

220kV 370kV

D/Yg

MMC1

Is1(abc)

PCC1XT=15%

370kV 410kV

Vs1(abc)

Idc1

Is2(abc)


frequency control

1000MW

Windfarm1


control

Rbrak

Vdc2

PCC2

Vn

SCR=3.5

Zn

XT=15%

Yg/D

MMC3

Vs3(abc)

220kV 370kV

D/Yg

MMC4

Is4(abc)

PCC4XT=15%

370kV 410kV

Vs4(abc)

Idc4

Is3(abc)


frequency control

1000MW

Windfarm2


control

Rbrak

Vdc3

125km DC cable

PCC3

Vn

SCR=3.5

Zn

130km DC cable

200km DC cableIdc2

Idc3




DeepWind’2015

Trondheim

4-6th February 2015

Example Simulation Results – MMC disconnection

Centralised DC slack bus Margin Control Droop control




DeepWind’2015

Trondheim

4-6th February 2015

Example Simulation Results – MMC1 AC fault

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

2.24 2.26 2.28 2.30 2.32 2.34 2.36 2.38 2.40 2.42 2.44Curr

ent

(kA

)

Time (s)

Droop

Margin

Slack




DeepWind’2015

Trondheim

4-6th February 2015

Thank you!




DeepWind’2015

Trondheim

4-6th February 2015

• Slide 1 – Picture courtesy of: Danish Energy Authority (left) CleanTechnica

(right)

• Slide 6 - Picture courtesy of ABB

References

Detailed Modelling of MMC-HVDC Links · • Demand for VSC-HVDC systems is growing worldwide. •...

Documents

Transcript of Detailed Modelling of MMC-HVDC Links · • Demand for VSC-HVDC systems is growing worldwide. •...