THREE LEVEL VOLTAGE SOURCE CONVERTER
SVM 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 𝑉𝑟𝑒𝑓 can be
synthesized by the nearest three space vectors based on the volt-second
balancing principle
If 𝑉𝑟𝑒𝑓 falls into region 3 of sector I as shown in Fig. The three nearest
vectors are 𝑉1, 𝑉2 𝑎𝑛𝑑 𝑉7 . 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 = 𝑆 − 1 × 4 + 𝑀
S=1- 6
M=1- 4

Space vector and dwell time

Space vector and dewell 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
𝑉1𝑁 − 𝑉2𝑁 − 𝑉0 − 𝑉1𝑃 − 𝑉0 − 𝑉2𝑁 − 𝑉1𝑁
In region 2, switching sequence
𝑉1𝑁 − 𝑉13 − 𝑉7 − 𝑉1𝑃 − 𝑉7 − 𝑉13 − 𝑉1𝑁

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
3
theta1
2
mag
1
sector
Re
Im
1
2
3
4
5
6
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
2
b
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
k2
k1
V_beta_i
V_alfa_i
V_beta
V_alfa
k2
k1
3
Vd0
2
Vq0
1
trngl
-K-
sqrt(3)/2
-K-
sqrt(3)
1
0.5
-C-
1
1
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_alfa
In
S
S/H >
1
2
rem
rem
-K-
2/sqrt(3)
-K-
1/sqrt(3)
0.5
0.53
S/H pulse
2
theta1
1
mag
Trngl
Vq0
Vd0
Ts-pulse
s/w state sele
state selector
mag
theta1
S/H pulse
trngl
Vq0
Vd0
local vector gen.
gm
CE
ga9
g
C
gm
CE
ga5
g
C
a
b
c
sector
mag
theta1
c -> mag + local theta1
[gc2]
[gc1]
[gb2]
m
k
Db3
<= 1e-005
Taking sector, Vref magnitude and angle, and finding triangle

DETERMINATION OF DWELL TIME
State 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 3
timer
Ta
Tb
T0
Ts-pulse
trngl 1
trngl 1
timer
Ta
Tb
T0
Ts-pulse
trngl 0
trngl 0
timer
Ta
Tb
T0
Ts-pulse
trngl 2
trgnl 2
timer
1
Scope2
Scope1
1
2
3
4
4
Ts-pulse
3
Vd0
2
Vq0
1
Trngl

DETERMINATION OF state point
1
trngl 1
>
<=
>
<=
>
<=
AND
AND
4
3
2
10.5
4
Ts-pulse
3
T0
2
Tb
1
Ta

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
mag
theta1
S/H pulse
trngl
Vq0
Vd0
local vector gen.
sector
trngl
s/w state selector
gating signals
gating
signal generator
gm
CE
ga9
gm
CE
ga6
gm
CE
ga5
gm
CE
2
gm
CE
ga10
gm
CE
1
a
b
c
sector
mag
theta1
abc -> mag + local theta1
f(u)
Vc_ref
f(u)
Vb_ref
f(u)
Va_ref
Scope1
[gc2]
[gc1]
[gb2]
[gb1]
m
a
k
Db3
m
a
k
Db1
<= 1e-005

Gating signal using Triagnle, Sector and switching
state
1
gating
signals
trngl
s/w state selector
sector 6
sector 6
trngl
s/w state selector
sector 5
sector 5
trngl
s/w state selector
sector 4
sector 4
trngl
s/w state selector
sector 3
sector 3
trngl
s/w state selector
sector 2
sector 2
trngl
s/w state selector
sector 1
sector 1
1
2
3
4
5
6
sector
selector
3
s/w state
selector
2
trngl
1
sector

Gating signal using Triagnle, Sector and switching
state
1
sector 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
trngl
selector
1
2
s/w state
selector
1
trngl

Gating signal using Triagnle, Sector and switching
state
1
trngl 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
1
s/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
𝑉𝐸 =
7
2
+ 𝑗
3
2
𝑉𝐹 = 3 + 𝑗 3
𝑉𝐺 = 4 + 𝑗 3
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.