THREE LEVEL VOLTAGE SOURCE CONVERTERSVM IMPLEMENTATION

Presented By FA13-R09-005 Muqadsa Iftikhar

FA13-R09-013 Zunaib Ali FA13-R09-024 Madiha Naeem

Three Level VSC

Three Level VSC

Three Level VSC

The 27 switching states of the three-level inverter correspond to 19 space vectors. Based on their magnitude, these space vectors can be divided into four groups: zero vector, small vectors, medium vectors, and large vectors. Zero vector has three

There are three kinds of switching states P, O, and N in each bridge, so there exist 27 kinds of switching states in three-phase three-level inverter

Three Level VSC

• The Zero vector has three switching states,

• Each small vector has two switching states, and

• Each medium and large vector only has one switching states.

• In the small vectors,

• the vector containing switching state P is called P-type small

vector,

• the vector containing switching state N is called N-type small

vector. These vectors have different effect on neutral point

voltage deviation.

Three Level VSC

• Small vectors have a dominant effect on neutral point voltage,

• The P-type small vectors make NP voltage rise, while the N-type small

vectors make NP voltage decline.

• The medium vectors also affect NP voltage, but the direction of the voltage deviation is undefined. Zero vector and large vectors do not affect the NP voltage.

Space vector diagram of Three Level Inverter

Space vector diagram of Three Level Inverter

To calculate the dwell time of space vectors, the space vector diagram can be divided into six triangle sectors ( - Ⅰ Ⅵ)

Each sector is divided into four triangles (1-4)`

In the three-level NPC inverter, the reference vector 𝑉𝑟𝑒𝑓ሬሬሬሬሬሬሬሬԦ can be synthesized by the nearest three space vectors based on the volt-second balancing principle

If 𝑉𝑟𝑒𝑓ሬሬሬሬሬሬሬሬԦ falls into region 3 of sector I as shown in Fig. The three nearest vectors are 𝑉1ሬሬሬԦ,𝑉2ሬሬሬԦ 𝑎𝑛𝑑 𝑉7ሬሬሬԦ . The following expressions can be gotten based on the volt-second balancing.

Space vector and dewell time

Space vector and dewell time

Space vector and dewell time

Space vector and dwell time

The dwell times can be calculated as above when reference vector is in other sectors.

DETERMINATION OF TRIANGLE LOCATION

The location of the triangles is easy to get by the sector s and triangle M. 𝐾= ሺ𝑆− 1ሻ× 4+ 𝑀 S=1- 6 M=1- 4

Space vector and dwell time

Space vector and dwell time

Consideration for switching sequence

The neutral point voltage varies with the switching states of the NPC inverter, so the switching sequencing should be taken into account to control the neutral point voltage.

When the reference vector falls into different regions, there are two cases for the selected three vectors.

One is that there are two small vectors among the three vectors, such as in region 1, 3;

the other is that there is only one small vector, such as in region 2, 4. The switching sequencing is different for these two cases.

Consideration for switching sequence

In region 1, switching sequence 𝑉1𝑁ሬሬሬሬሬሬԦ− 𝑉2𝑁ሬሬሬሬሬሬԦ− 𝑉0ሬሬሬԦ− 𝑉1𝑃ሬሬሬሬሬሬԦ− 𝑉0ሬሬሬԦ− 𝑉2𝑁ሬሬሬሬሬሬԦ− 𝑉1𝑁ሬሬሬሬሬሬԦ In region 2, switching sequence 𝑉1𝑁ሬሬሬሬሬሬԦ− 𝑉13ሬሬሬሬሬሬԦ− 𝑉7ሬሬሬԦ− 𝑉1𝑃ሬሬሬሬሬሬԦ− 𝑉7ሬሬሬԦ− 𝑉13ሬሬሬሬሬሬԦ− 𝑉1𝑁ሬሬሬሬሬሬԦ

SVM ALGO

Determination of Sector Determination of Triangles

Calculation of Dewell Time

Arrangement of switching points

Determination of switching sequence

DETERMINATION OF SECTORS

Taking input and finding sector

DETERMINATION OF SECTORS

Vq

Vd

3theta1

2mag

1sector

ReIm

123456

AND

AND

AND

AND

AND

AND

6

5

4

3

2

1

-K-K*u

K*u

|u|u

< -60

>= -120

< -120

>= -180

< 180

>= 120

< 120

>= 60

< 0

>= -60

< 60

>= 0

u(1) + 60

6

u(1) + 120

5

u(1) + 180

4

u(1) - 120

3

u(1) - 60

2

u(1) - 0

1

3

c

2b

1

a

[2/3 -1/3 -1/3]

[0 1/sqrt(3) -1/sqrt(3)]

180/pi

DETERMINATION OF TRIANGLES

In each sector, there are four triangles defined as in Fig.

The calculation of the dwell times for the three nearest space vectors is

different. The determination of the triangles is judged by three rules.

TRIANGLES RULE 1 RULE 2 RULE 3

M

1 YES - -

2 NO YES -

3 NO NO YES

4 NO NO NO

DETERMINATION OF TRIANGLES

k2k1

V_beta_i

V_alfa_i

V_beta

V_alfa

k2

k1

3Vd0

2Vq0

1trngl

-K-

sqrt(3)/2

-K-

sqrt(3)

1

0.5

-C-11

1

u(1)*u(1) + 2*u(2)

k1*k1 + 2*k2

u(1)*sin(u(2)*pi/180)

V_beta

u(1)*cos(u(2)*pi/180)

V_alfaI n

S S/H >

1

2

rem

rem

-K-

2/sqrt(3)

-K-

1/sqrt(3)

0.5

0.53S/H pulse

2theta1

1mag

Trngl

Vq0

Vd0

Ts-pulse

s/w state selector

state selector

Discrete,Ts = 1e-005 s.

powergui

phase votage

phase current

0.55

m

mag

theta1

S/H pulse

trngl

Vq0

Vd0

local vector gen.

line voltage

sector

trngl

s/w state selector

gating signals

gating signal generator

gm

CE

ga9

gm

CE

ga8

gm

CE

ga7

gm

CE

ga6

gm

CE

ga5

gm

CE

ga4

gm

CE

ga3

gm

CE

ga2

gm

CE

ga12

gm

CE

ga11

gm

CE

ga10

gm

CE

ga1

abc

fourier

pi/2

delta

c phase

b phase

a

b

c

sector

mag

theta1

abc -> mag + local theta1

a phase

v+-

v+-

v+-

v+ -

v+ -

v+ -

f(u)

Vc_ref

f(u)

Vb_ref

f(u)

Va_ref

Scope3

Scope1

[gc2]

Goto9

[gc1]

Goto8

[gb4]

Goto7

[gb3]

Goto6

[gb2]

Goto5

[gb1]

Goto4

[ga4]

Goto3

[ga3]

Goto2

[gc4]

Goto11

[gc3]

Goto10

[ga2]

Goto1

[ga1]

Goto

2

[gc2]

[gc1]

[gb4]

[gb3]

[gb2]

[gb1]

[ga4]

[ga3]

[gc4]

[gc3]

[ga2]

[ga1]

ma

k

Db4

ma

k

Db3

ma

k

Db2

ma

k

Db1

ma

k

Da2

ma

k

Da1

i+ -

i+ -

i+ -

2 Constant<= 1e-005

100v2

100v1

-C-

0

-C-

-

[1x4]

+

Taking sector, Vref magnitude and angle, and finding triangle

DETERMINATION OF DWELL TIMEState Selector Block

DETERMINATION OF DWELL TIME

1

s/w state selector

Vq0

Vd0

Ta

Tb

T0

vector -> time calculator

Ta

Tb

T0

Ts-pulse

trngl 3

trngl 3timer

Ta

Tb

T0

Ts-pulse

trngl 1

trngl 1timer

Ta

Tb

T0

Ts-pulse

trngl 0

trngl 0timer

Ta

Tb

T0

Ts-pulse

trngl 2

trgnl 2timer

1

Scope2

Scope1

1

2

3

4

4Ts-pulse

3

Vd0

2Vq0

1Trngl

DETERMINATION OF state point

1trngl 1

>

<=

>

<=

>

<=

AND

AND

4

3

2

10.5

4

Ts-pulse

3T0

2Tb

1Ta

Switching point selector using dwell time

Switching Sequence

Switching point selector using dwell time

Gating signal using Triagnle, Sector and switching state

Trngl

Vq0

Vd0

Ts-pulse

s/w state selector

state selector

Discrete,Ts = 1e-005 s.

powergui

phase votage

phase current

0.55

m

mag

theta1

S/H pulse

trngl

Vq0

Vd0

local vector gen.

line voltage

sector

trngl

s/w state selector

gating signals

gating signal generator

gm

CE

ga9

gm

CE

ga8

gm

CE

ga7

gm

CE

ga6

gm

CE

ga5

gm

CE

ga4

gm

CE

ga3

gm

CE

ga2

gm

CE

ga12

gm

CE

ga11

gm

CE

ga10

gm

CE

ga1

abc

fourier

pi/2

delta

c phase

b phase

a

b

c

sector

mag

theta1

abc -> mag + local theta1

a phase

v+-

v+-

v+-

v+ -

v+ -

v+ -

f(u)

Vc_ref

f(u)

Vb_ref

f(u)

Va_ref

Scope3

Scope1

[gc2]

Goto9

[gc1]

Goto8

[gb4]

Goto7

[gb3]

Goto6

[gb2]

Goto5

[gb1]

Goto4

[ga4]

Goto3

[ga3]

Goto2

[gc4]

Goto11

[gc3]

Goto10

[ga2]

Goto1

[ga1]

Goto

2

[gc2]

[gc1]

[gb4]

[gb3]

[gb2]

[gb1]

[ga4]

[ga3]

[gc4]

[gc3]

[ga2]

[ga1]

ma

k

Db4

ma

k

Db3

ma

k

Db2

ma

k

Db1

ma

k

Da2

ma

k

Da1

i+ -

i+ -

i+ -

2 Constant<= 1e-005

100v2

100v1

-C-

0

-C-

-

[1x4]

+

Gating signal using Triagnle, Sector and switching state

1gatingsignals

trngl

s/w state selectorsector 6

sector 6

trngl

s/w state selectorsector 5

sector 5

trngl

s/w state selectorsector 4

sector 4

trngl

s/w state selectorsector 3

sector 3

trngl

s/w state selectorsector 2

sector 2

trngl

s/w state selector

sector 1

sector 1

1

2

3

4

5

6

sector selector

3s/w stateselector

2trngl

1sector

Gating signal using Triagnle, Sector and switching state

1sector 1

s/w state selector trngl 3 data

trngl 3

s/w state selector trngl 2

trngl 2

s/w state selector trngl 1 data

trngl 1

s/w state selector trngl 0 data

trngl 0

1

2

3

4

trnglselector

1

2s/w stateselector

1trngl

Gating signal using Triagnle, Sector and switching state

1trngl 0 data

[1 0 0]

[-1 -1 -1]

[1 1 1]

[1 1 0]

[0 0 0]

[0 0 -1]

[0 -1 -1]

1

2

3

4

5

6

7

1s/w state selector

RESULTS

RESULTS

FOR 9-LEVEL

FOR 9-LEVEL

Space vectors in the Cartesian coordinate system (sector I).

FOR 9-LEVEL

To reduce the voltage harmonic distortion, the reference voltage Vref can be synthesized by the three nearest vectors. With V* lying in ∆𝐸𝐹𝐺, the reference voltage can be approximated by vectors

𝑉ሬԦ𝐸 = 72 + 𝑗ξ32 𝑉ሬԦ𝐹 = 3 + 𝑗ξ3 𝑉ሬԦ𝐺 = 4 + 𝑗ξ3

These vectors are converted to 𝛼𝛽− 𝑓𝑟𝑎𝑚𝑒.

FOR 9-LEVEL

Space vectors in the 600 coordinate system (sector I).

Each Sector has:

36 triangles

Total triangles

36*6=216

FOR 9-LEVEL

Switching sequence is difficult to determine.

Large, small Alternation methods as discussed previously becomes

complex in this case.