High Voltage Direct-Current (HVDC) systems based on Modular

Multilevel Converter technology

by I.E.P.G. Ph.D. Candidate: A. PerillaDelft University of Technology. 23 August, 2018.

Welcome to the High Voltage Direct-CurrentVoltage Source Converter (VSC-HVDC) world.

Agenda:

Voltage Source Converters

❑ Definition and relevance

❑ Classification:

• Two & Three level converters.• Modular Multilevel Converters.

❑ General operation’s principles of VSCs.• Space-time vector theory.

❑ Modelling & Control of MMC.

Voltage Source Converter(VSC) technology

“The VSC technology is a technology used in the electrical power networks for

transferring (convert) power from one energy system to another one”.

❑Definition and relevance

Voltage Source Converter(VSC) technology

Energy systems (some examples):

Solar Power Plants

Electricity Grid

Wind Farms

Electricity Grid

In this electrical circuit, What should be the VSC voltage value to obtain the Psystem expecified during steady-state operation?

(The Voltage Sources are DC Voltage sources).

What would happen if the Voltage sources would be nowAC Voltage sources?

?

Voltage Source Converter(VSC) technology

Two levels VSC systems:

❑Classification:

Voltage Source Converter(VSC) technology

Three levels VSC systems:

❑Classification:

Voltage Source Converter(VSC) technology

Modular Multilevel VSC systems

❑Classification:

Modular Multilevel Converter (MMC)

Voltage Source Converter(VSC) technology

“The VSC technology is a technology used in the electrical power networks for

transferring (convert) power from one energy system to another one”.

❑Definition and relevance

Voltage Source Converter(VSC) technology

❑ General operation’s principles of VSC systems.

Space-time “vector” theory.

1929 189719181943

1984

1893 1888

1918

N. TeslaA. Kennelly

C. SteinmetzC. FortescueR. ParkE. Clarke

H. Akagi

Space-Time “Vector”Theory

Active Power

ReactivePower

DCVoltage

Voltage Source Converter

STSTVT has two different perspectives which are based on different

mathematical tools developed by the astonishing world-class mathematicians:

Leonhard EulerJoseph-Louis Lagrange However, for simplicity in this master course

Space-Time “Vector”Theory Leonhard

Euler

𝑒𝑗∗ = cos + 𝑗 ∗ sin 1918C. Fortescue

= 𝑒𝑗∗2∗𝜋3 = cos

2 ∗ 𝜋

3+ 𝑗 ∗ sin

2 ∗ 𝜋

3

Fortescue defined the vector (positive sequence vector) :

1 2

Where

Space-Time “Vector”Theory Leonhard

Euler

The instantaneous-complex alpha-beta transformation (for three phase balanced systems) can be defined as :

1943E. Clarke

1984H. Akagi

𝑣(𝑡)= 1 2 *

𝑣𝑎(𝑡)𝑣𝑏(𝑡)𝑣𝑐(𝑡)

𝑣(𝑡)= Space-time voltage’s “vector”

Space-Time “Vector”Theory Leonhard

Euler

𝑆(𝑡) = 𝑣(𝑡) *conj(𝑖(𝑡))

Instantaneous apparent complex power :

Complex three phase power (Steinmetz-Phasor approach):

𝑆 = 3 𝑉𝑓𝑛 ∗ 𝑐𝑜𝑛𝑗(𝐼𝑙) = 𝑃 + 𝑗𝑄

Where are 𝑉𝑓𝑛 𝑎𝑛𝑑 𝐼𝑙 phasors quantities

Space-Time “Vector”Theory Leonhard

Euler

We can apply another mathematical transformation to our Space-time voltage’s “vector” to simplify our power analysis.

𝑅 𝜃 =cos 𝜃 −sin 𝜃sin 𝜃 cos 𝜃

Apply 2D Rotation transformation

1929R. Park

Hey buddy, Let’s apply a Rotation Transformation !

Space-Time “Vector”Theory Leonhard

Euler

𝑽𝑺𝑪 − 𝑯𝑽𝑫𝑪 𝑬𝒏𝒈𝒊𝒏𝒆𝒆𝒓𝑽𝑺𝑪 −𝑯𝑽𝑫𝑪 𝑬𝒏𝒈𝒊𝒏𝒆𝒆𝒓

𝑅 𝜃 =cos 𝜃 −sin 𝜃sin 𝜃 cos 𝜃

Question 1:

Who is ?

Question 2:

Should be 𝒗 𝒕 aligned

with one rotating axe?

Space-Time “Vector”Theory Leonhard

Euler

Iq

Id

Welcome to the High Voltage Direct-CurrentVoltage Source Converter (VSC-HVDC) world.

BREAK ???

QUESTIONS SO FAR ???

Space-Time “Vector”Theory Leonhard

Euler

Iq

Id

Active Power

ReactivePower

Voltage Source Converter

❑ General operation’s principles of VSC systems.

Space-Time “Vector”Theory Leonhard

Euler

Active Power

ReactivePower

DCVoltage

Voltage Source Converter

❑ General operation’s principles of VSC systems.

Let’s use the whiteboard to explain the last one

Modular Multilevel Converter (MMC)

For simplicity in this master

course

Modelling & Control of MMC

❑ Circulating current suppression control CCSC (modelling) approach.

❑ Internal Energy Balance Control (modelling) approach.

There are two main modelling approach to control and model the MMC:

❑ Modelling & Control of MMC (Cigre

Version)

25

To the AC network

DC Current

AC Currents

MMC internal Reactor (Larm)

Based on CIGRE B4-57 working group report

(2014).

26

To the AC network

DC Current

AC Currents

MMC internal Reactor (Larm)

Based on CIGRE B4-57 working group report

(2014).

❑ Modelling & Control of MMC (Cigre

Version)

In summaryCCSC Modelling approach means:

❑ Modelling & Control of MMC (Cigre

Version)

Power SystemsTheory

Power Electronic

DesignTechniques

Control Systems Theory

(VSC) technology

In Summary…

Delft University of Technology. 23 August, 2018.

Thanks for

your

attentionArcadio Perilla

a.perilla@tudelft.nl

Intelligent Electrical Power Grids Group