ZETA CONVERTER APPLIED IN POWER. FACTOR CORRECTION. ADRIANO PÃRES. (Oral Presenter). DENIZAR CRUZ MARTINS. IVO BARBI. POWER ...
ZETA CONVERTER APPLIED IN POWER FACTOR CORRECTION
ADRIANO PÉRES (Oral Presenter)
DENIZAR CRUZ MARTINS IVO BARBI
POWER ELECTRONICS RESEARCH GROUP FEDERAL UNIVERSITY OF SANTA CATARINA FLORINÓPOLIS - SC BRAZIL
1 - INTRODUCTION
PRIMARY OBJECT:
ANALYSIS OF THE ZETA CONVERTER OPERATING IN DISCONTINUOUS CONDUCTION MODE FOR POWER FACTOR CORRECTION.
THE MAIN ATTRACTIVE OF ZETA CONVERTER IS THAT IT IS A NATURALLY ISOLATED STRUCTURE, WHICH ALLOW A REGULATED OUTPUT VOLTAGE WITH ONLY ONE POWER PROCESSING STAGE.
WITH THE EXCEPTION OF THE ZETA CONVERTER ALL OTHERS (BUCK, BOOST, BUCK-BOOST, CUK AND SEPIC ) HAVE BEEN EMPLOYED TO CORRECT THE POWER FACTOR OF POWER SUPPLIES. HOWEVER THEY HAVE THEIR INTRINSIC LIMITATIONS:
BOOST: IS NOT NATURALLY ISOLATED OPERATES ONLY AS A STEP-UP VOLTAGE IT IS NOT CAPABLE OF PROTECTING ITSELF AGAINST A LOAD OVERCURRENT OR SHORT-CIRCUIT
CUK AND SEPIC: ARE NATURALLY ISOLATED AND OPERATE AS STEP-DOWN AND STEP-UP VOLTAGE, HOWEVER: DO NOT PROTECT THEMSELVES AGAINST OVERLOAD AN ADDITIONAL CIRCUIT IS NEEDED TO LIMIT THE INRUSH CURRENT
BUCK: IS CAPABLE TO LIMIT THE INRUSH CURRENT AND PROTECTING AGAINST OVERLOAD, HOWEVER: FOR POWER FACTOR APPLICATION, THE DC OUTPUT VOLTAGE IS REFLECTED TO THE PRIMARY SIDE OF THE TRANSFORMER BLOCKING THE RECTIFIER DIODES HAS NO FUTURE IN POWER FACTOR CORRECTION APPLICATIONS.
BUCK-BOOST IT IS THE ONLY CONVERTER CAPABLE OF SATISFYING ALL THE MENTIONED SPECIFICATIONS SIMULTANEOUSLY.
ZETA HAS PROPERTIES SIMILAR TO THE FLYBACK CONVERTER IN SOME PARTICULAR APPLICATIONS IT IS MOST ADVANTAGEOUS OVER THE OTHER DC-DC CONVERTERS.
2 - PROPOSED CIRCUIT S1 D2
Vin
Lo
C1
D4
Co
D1 D3
N1
D5
Ro
N2
Fig. 1 - Proposed Circuit.
OPERATION STAGES
i S1
- VC1 + S1
iLo Lo
C1
+ Vin
iin
iLm
D1
Lm
Co
Ro
Vo -
a)First S tage (t0,t1)
S1
- VC1 +
i S1
iLo Lo
C1
+ Vin
iin
iLm
D1
Lm
Co
Ro
i D1
Vo -
b)S econd S tage (t1,t2)
S1
- Vc1 +
ilo Lo
i S1
C1 +
Vin
iin
iLm
Lm
D1
Co
Ro
Vo -
c)Third S tage (t2,t3)
Fig. 3 - Operation Stages.
THEORETICAL WAVEFORMS
Fig. 4 - The Main Waveforms for a switching period.
Vin Iin
IS1
VS1
VD1
iLm
iLo
Fig. 5 - The Main Waveforms for a line period.
3 - MATHEMATICAL ANALYSIS 3.1 - LINE CURRENT THE INPUT CURRENT INCREASES LINEARLY ACCORDING THE FOLLOWING EQUATION:
Vp sin( wt ) iin ( t ) t L
(4)
IF WE CONSIDER AN INPUT FILTER TO ELIMINATE THE HIGH FREQUENCY HARMONICS, THUS:
iin ( t )
Vp D sin( wt ) L fs
(5)
SO, THE INPUT CURRENT IS A SINUSOIDAL CURVE WITH UNITY POWER FACTOR.
3.3 - OUTPUT CHARACTERISTIC (G)
G
Vo D Vp 2
Ro L fs
(16)
Fig. 8 - Normalized output characteristic.
WHERE
x
Ro L fs
4 - SIMPLIFIED DESIGN PROCEDURE AND EXAMPLE 4.1 - SPECIFICATIONS
- Po = 200W - Vo = 72V - vin = 311.sin(w.t) 10% - fs = 100kHz 4.2 - CALCULATION
Io
Po 200 2 .78 A Vo 72
Vo a 3 . 89 Vo WHERE SIDE)
VO'=280V
(TURNS RATIO)
(OUTPUT VOLTAGE REFERRED TO THE PRIMARY
THE RELATION OF THE VOLTAGES ARE:
Vpmax 342V ; max
Vpmax 1 . 22 Vo
Vpnom 311V ; nom 1 . 11 Vpmin 280V ; min 1 .0
CRITICAL DUTY CYCLE AND CRITICAL ZETA INDUCTANCE
Dc
1 0 . 45 1 max
min Vpmin Dc 2 Lc 198 H 4 Io fs CHOOSING THE EQUIVALENT ZETA INDUCTANCE EQUAL TO 75% OF THE LC, LM=LO' AND KEEPING 2% OF RIPPLE IN THE OUTPUT VOLTAGE, WE OBTAIN:
Lm Lo 290 H Lo Lo 2 19 . 2 H a
Co 247 F
Co Co a 3800 F 2
5 - EXPERIMENTAL RESULTS
Lo D2
C1
D3
Cf1
M1
Dg
T1
Rgd
vi
Lf
D1
Cf2
Dgd
Co
Ro
Cgd D4
D5
Rg
Cg
Fig. 10 - Implemented converter.
320 Amplitude
Vin
240 160 Iin*200
80 0 -80 -160 -240 -320 0.0
4.0
8.0
12.0
Time (ms)
Fig. 11 - Line current and voltage.
16.0
20.0
100
100
Amplitude(%)
Amplitude(%)
80
80
TDH=3.52% (voltage)
60
TDH=5.94% (current) cos =0.9979 FP=0.9961
60
40
40
20
20
0
0
0
4
8
12
16
20
24
28 32 36 Harmonic (n)
40
0
4
8
12
16
20
24
28 32 36 Harmonic (n)
Fig. 12 - TDH of the input voltage and current.
(V) 72.8 VCo
72.0 71.2 (V) 72.8
VC1
72.0 71.2 70.4 0.0
8.0
16.0
24.0
32.0 40.0 Tempo (ms)
Fig. 13 - Ripple of the voltage in C1 and Co.
40
(V),(A) 943 786 VS1
629 IS1*100
472 314 157 0 -157 0.0
5.0
10.0 Tempo (ms)
15.0
20.0
Fig. 14 - Switch voltage and current. (A) 30
iD1
25 20 iS1*3
15 10 5 0 -5 0.0
5.0
10.0
15.0
20.0 Tempo(m s)
Fig. 15 - D1 and S1 current. 100
% 80 60 40 20 0
0
50
100
150
200Po
Fig. 16 - Efficiency curve. G 0,6 0,5 0,4 0,3 - - - Experimental
0,2 0,1 0,05
___ 0,1
0,15
0,2
0,25
Theoretical 0,3
D
Fig. 17 - Output characteristic.
5 - CONCLUSIONS BASED ON THE THEORETICAL AND EXPERIMENTAL RESULTS WE CAN DRAW THE CONCLUSIONS AS FOLLOWS: -IN DISCONTINUOUS CURRENT MODE, DRIVEN BY A STANDARD PWM INTEGRATED CIRCUIT, THE ZETA CONVERTER DRAWN A LINE CURRENT PROPORTIONAL TO THE INPUT VOLTAGE IN A MANNER SIMILAR TO THE FLYBACK CONVERTER, WITH NO HARMONIC CURRENT NEITHER PHASE DISPLACEMENT. -THE OPERATION IN THE CONTINUOUS CURRENT MODE IS ALSO POSSIBLE, PROVIDED THAT ACTIVE POWER FACTOR CORRECTION BE IMPLEMENTED. -AS THE FLYBACK CONVERTER, THE ZETA CONVERTER PROVIDES: ISOLATION, HIGH POWER FACTOR, OVERLOAD AND SHORT-CIRCUIT PROTECTION, LIMIT OF THE INRUSH CURRENT AND REGULATION OF THE OUTPUT VOLTAGE USING ONLY ONE ACTIVE SWITCH.
References 1. H. Endo, T. Yamashita and T. Sugiura "A High-Power-FactorBuck Converter", IEEE PESC Records, pp.1071 -1076 1993 2. N. Mohan, T. M. Undeland and R. J. Ferrara "Sinusoidal Line Rectification with a 100kHz B-SIT Step-up Converter", IEEE APEC Records, pp.92 -98 1984. 3. M. J. Kocher and R. L. Steigerwald "An AC to DC Converter With High Power Quality Input Waveforms", IEEE PESC Cnference Records, pp.63 -75 1982. 4. H Le-Huy , J. Ρ. Ferriewx and E. Toutain "An AC-DC Converter With Low-Harmonics Input Current", Second European Conference on Power Electronics and applications, pp.1201 -1207 1987. 5. C. A. Canesin and I. Barbi "A Unity Power Factor Multiple Isolated Outputs Switching Mode Power Suply Using a Simple Switch", IEEE APEC Records, pp.430 -436 1991.
