V Duy T K&TH 3 K55
V Duy T K&TH 3 K55
MC LCBi tp 1 : Thit k b bin i Buck vi cc thng s :3Chng 1.M hnh
ha b bin i Buck ch dng lin tc41.1. Phng php trung bnh khng gian
trng thi41.2. Phng php trung bnh ha mch ng ct8Chng 2.Tnh ton thng
s,thit k mch vng102.1. Tnh ton T C-rc102.2. Tnh ton cun cm
L-rL112.3. Mch vng iu chnh in p122.4. Mch vng dng in16Chng 3.M phng
b bin i Buck bng matlab vi thng s c th213.1. Mch vng in p213.2. Mch
vng dng in23Bi tp 2 : Thit k h truyn ng ng c mt chiu c tham s ch ra
trong bng s dng chnh lu cu 3pha iu khin hon ton s dng
Tiristor.24Chng 1.Tnh chn van mch lc25Chng 2.Nguyn l mch iu
khin.272.1. Khi ng pha ly im m t nhin ca tiristor272.2. Khu to in p
ta.272.1.1Phng php iu khin xung kp vi rng xung T =
20e-5.272.1.2Phng php iu khin xung chm vi tn s f = 10 KHz.29Chng 3.
iu khin vng kn31
Bi tp 1 : Thit k b bin i Buck vi cc thng s :in p uin=28(V),
uo=15(V)
in cm L=50
T in C=500,rC= 0,1
Tn s pht xung : =100KH
Ti : R=3
M hnh ha b bin i Buck ch dng lin tcPhng php trung bnh khng gian
trng thi
Hnh 1.1.S mch in b bin i Buck (a)S bin i b bin i Buck trong trng
thi 1 (b)S mch bin i Buck trong trng thi 2(c)
S dng nh lut Kirchoff ta c h phng trnh m t s mch in trng thi 1
:
(1.1)
H phng trnh khng gian trng thi :
A1 ;B1; C2=;D1=0
S dng nh lut Kirchoff ta c h phng trnh m t s mch in trng thi 2
:
(1.2)
H phng trnh khng gian trng thi :
A2=;B2; C2=;D2=0M hnh trung bnh m t mt b biens i DC/DC vi s tham
chiu ca h s iu ch d c vit li nh sau :
(1.3)
Suy ra :
A ;B; C=;D=0
B bin i Buck c m t trn min khng gian trng thi :
(1.4)
im lm vic cn bng ca b bin i Buck :
(1.5)
Hm truyn in p u ra v h s iu ch :
(1.6)
im lm vic cn bng ca b bin i Buck :
(1.7)
Suy ra IL= 5(A).Hm truyn gia dng in chy qua cun cm v h s iu ch
:
(1.8)
Ta thay s:
L=50rL=0
C=500
rC= 0,1
R=3D=uo/uin=15/28=0.536
Nhn xt : Hm truyn t gia in p u ra v h s iu ch cho thy c 1 im
zero nm bn tri mt phng phc nn h c m t bi hm truyn (1.6) l h pha cc
tiu.
Hnh 1.2. th Bode hm truyn in p u ra v in p u voH n nh, tuy nhin
gc phase ti tn s ct gn -1800 nn h rt d mt n nh khi c cc tc ng bn
ngoi. Do ,cn phi thit k 1 b b tng d tr phase s c ni phn sau.Phng
php trung bnh ha mch ng ct
Hnh 1.3. B bin i Buck vi tn hiu nh.Coi m hnh nh 1 mng 2 ca. Ta c
cng thc sau :
(1.9)
Hm truyn gia h s iu ch v in p u ra di min laplace:
(1.10)
Ta tm c cc hm truyn khc :
(1.11)
Trong : Tr khng song song gia mch t lc C v ti
Tr khng mch in cm Hm truyn gia h s iu ch vi in p u ra :
(1.12)
Hm truyn gia in p u ra v in p u vo :
(1.13)
Nhn xt : Hm truyn xut hin im Zero m nm bn tri mt phng phc nn h c
m t bi hm truyn (1.11)c cng l h pha cc tiu.Hai phng php u cho kt qu
hm truyn c tnh cht ging nhau,l h pha cc tiu v cn xy dng 1 b b cho h
thng.
Tnh ton thng s,thit k mch vng Tnh ton T C-rcT lc C phi ln m bo p
mch ip p u ra v s st p khi ng ti trong phm vi cho chp. p mch gm 2
thnh phn : do in tr ni tip t C gy ra, v do t lc cc xung in p t u ra
b bin i. p mch :
(2.1)
Hnh 2.1. p mch in p raThnh phn p mch do t C :
(2.2)
Suy ra gi tr t C p ng c yu cu :
(2.3)
i vi cc mch ngun DC-DC, p mch khng nn vt qu 1% Vo.Tnh ton cun cm
L-rL
Hnh 2.2. th dng in qua cun cm LDng in trung bnh chy qua cun cm
:
(2.4)
Dng in nh nht qua cun cm :
(2.5)
Khi cho 0,ta c gi tr in cm L nh nht :
(2.6)
Vi gi l tn s Switching,thng c chn l 20kHz hoc cao hn.Ta c :
(2.7)
Suy ra gi tr ca in cm l :
(2.8)
p mch dng in nm trong khong t 10% 30%
Mch vng iu chnh in pCu trc iu khin trc tip vng in p :
Hnh 2.3.Cu trc iu khin mch vng in p b bin i BuckHm truyn in p
gia in p u ra v h s iu ch di dng :
(2.9)
Trong := Vin = 28V
= = = 9.5
Hnh 2.4. th Bode ca hm truyn GvdH n nh,tn s ct l 5,24kHz v d tr
phase l PM=59.30,nh vy d tr pha tha mn.Tuy nhin, cn thit k 1 b b m
bo h thng n nh tt hn vi tn s ct bng 10kHz v trit tiu sai lch
tnh.
Ta xy dng b b PI : Ta thm 1 im khng nghch o vo h s khuch i vng
lp tn s . khng thay i d tr pha mong mun tn s ct( to ra nh thnh phn
PD) th .Chn = 2kHz.
(2.10)
Ti tn s ct :
(2.11)
Ta c :
Gcu_o= 2,152.Vy:
(2.12)
Hm truyn h :
(2.13)
Hnh 2.5. th Bode hm truyn h hNhn xt : H n nh,tn s ct l 10,9kHz v
d tr phase l PM=49,30 nh vy c tn s ct v d tr pha u tha mn.Hm truyn
kn :
(2.14)
p ng bc nhy ca hm Gk :
Hnh 2.6.p ng bc nhyTnh ton thng s b PI :
(2.15)
Mch vng dng in
Hnh 2.7.Cu trc iu khin mch vng dng in Hm truyn gia dng in qua
cun cm v h s iu ch (rc
