3@1s Pfc Converter

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1-4244-0449-5/06/$20.00 2006 IEEE IPEMC 2006

Simulated Study of Three-Phase Single-Switch

PFC Converter with Harmonic Injected

PWM by MATLABZhanlong Li and Yupeng Tang

School of Electrical Engineering; Beijing Jiaotong University; China

AbstractThis paper describes the operation and

simulation of a three-phase single-switch PFC converter

with a sixth-order harmonic-injection PWM. The PFC

converter operates in a discontinuous current mode (DCM).

In proposed method, the sixth-order harmonic is injected in

PWM so that the harmonic content of the input current

meet IEC555-2(A) requirement. The theoretical analysis ofthe harmonic-injection is discussed. Furthermore, the

model and simulation of PFC converter are made via

MATLAB/SIMULINK software. Finally the simulated

waveforms of the input current are also showed. And the

performance of the PFC converter with harmonic injected

PWM is verified on a simulation model, and a good

consistency is achieved.

Keywordpower factor correction (PFC); harmonic injection;discontinuous conduction mode (DCM); continuous

conduction mode (CCM); total harmonic distortion (THD)

I.

INTRODUCTIONRecently, three phase PFC converter have gained

considerable attention due to the increasing demand to

power quality. Based on the number of switches

controlled, all 3-phase PFC converters can be divided

into two groups: single switch PFC converters and

multiple switches PFC converters. Though the

multiswitch PFC converters are high-power high-

performance application, the increased number of

switches and the complexity of their control make them

too expensive in medium power levels.

So the single-switch three-phase DCM boost converter

is an attractive topology because of its simplicity, low

cost and high efficiency. However, there are somedisadvantages and advantages in this kind of topology.

For example, the DCM operation is associated with a

higher voltage or current stress. Several solutions to this

problem have been presented in Ref. [7] and Ref. [8].The

main switch has a reduced loss due to its zero current

switching .Also the boost diode has no the reverse

recovery problem for the same reason.

In DCM operation with constant frequency PWM, the

single-switch three-phase PFC converters have a larger

current distortion, so its not suitable to high power level.

According to IEC555-2(A) standard, the power level of

converter cant be increased in order to meet the

maximum permissible harmonic current. However, if in

order to meet the IEC555-2(A) specifications, the output

voltage of three phase rectifier must be boosted to 900V.

Such designs increase the voltage stress of switch.To reduce the harmonic current distortion, some

methods have been proposed. One of the methods is to

operate the converter on boundary between CCM and

DCM. Namely, when the current in the boost inductors

falls to zero, the main switch is turned on immediately.

With variable switching frequency, this method has

disadvantages like high switching losses resulted from

the increased switching frequency, and have difficulty in

designing the converter and the EMI filter.

Fig.1 The main circuit

This paper analyzes the performance of a single-

switch 3-phase PFC converter (Fig.1) that uses harmonic

injected PWM by MATLAB/SIMULINK software. In

section , the operation of converter is simply

introduced. In section , the method for reducingharmonic content is analyzed. Finally, in section the

waveforms of the input current by simulation are

showed.

II. OPERATION OF CONVERTERThe operation of the three-phase single-switch PFC

converter with a constant switching frequency is

analyzed in this section. The waveform of input current

in a period is showed in Fig.2. To simplify the analysis


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of the converter system, the following assumptions are

made.

zThe 3 inductors operate in DCM.zThe system components are ideal, such as: resistors,

inductors, capacitors.

zFor the switching frequency is much higher than theline frequency, the input voltages are considered to

constant within a switching period.

Fig.2 The waveform of input current in a period

According to Fig.2, the shape of the input current is

triangular pulse, and a switching period consists of four

time internals. When the switch is on, the input

inductors are fed by the input voltage and the energy is

accumulated in them. The peak of current is proportional

to the input voltage. When the switch is off, the current

start discharging until all of the phase currents falls zero.

In this internal (Toff), there are three different states

depending on the corresponding phase voltage. The first

internal (Toff1), all the phases conduct until one of the

phase currents falls to zero. The second internal (Toff2)is characterized by the two diodes. In the third internal

(Toff3), there is no current in the inductors. Actually, as

the input current is proportional to the input voltage,

there exist no low frequency harmonics in the input

currents. However, during the switch off interval, the

phase currents fall to zero at different moments.

Therefore, the phase currents are nonlinear functions of

their phase voltages, then it contains several low

frequency harmonics (Ref. [1] and Ref. [5]).

III. ANALYSIS OF HARMONIC REDUCTION WITHHARMONIC INJECTED PWM

Suppose 3-phase input voltage is equal in magnitude,purely sinusoidal, and with120D mutual phase.

sin( )

2sin( )

3

4sin( )

3

a m

b m

c m

U U t

U U t

U U t

=

=

=

(1)

Where Um is the peak voltage and =2 Lf , Lf is the

line frequency. According to Ref. [2], the average input

currents within a switching period are given by the

following equations.

2

2

2

sin( )(0 )

2 63 3sin( )

1 2sin( ) sin(2 )2 322

[ 3 3sin( )][ sin( )]3 6

( )6 3

sin( ) sin(2 )3

22[ 3 3sin( )][ sin( )]

3 6

( )3 2

oa

s

oa

s

oa

s

U D ti t

Lf M t

M t tU D

iLf

M t M t

t

M t tU D

iLf

M t M t

t

=

+

=

+ +

+ +

=

+ + +

(2)

Where Uo is the output voltage, D is the duty ratio, L is

the value of the input inductor, fs is the switching

frequency, andMis the ratio ofUo and 3 mU .

In Ref. [1] and Ref. [2], the reason for three-phase

single-switch PFC converter with the sixth-order

harmonic injected PWM has been discussed in detail.

There is no more analysis here. Only the theory of

harmonic injected PWM is showed

According to the frequency spectrum of input current,

the fifth-order harmonic and the seventh-order harmonic

are the dominant, if neglecting the higher order

harmonics, the three-phase input currents can beapproximated as:

)3

5sin()3

4sin(

)3

5sin()3

2sin(

)5sin()sin(

51

51

51

++=

+=

=

tItIi

tItIi

tItIi

c

b

a

(3)

Now the THD of the input current is the following

equation.

5

1

ITHD

I

= (4)

The idea of harmonic-injection is that the suitable

sixth-order harmonic is injected in PWM to modulate the

duty cycle, so that decrease the fifth order harmonic

content of the input current. The following (5) is the duty

cycle after modulated.

( ) ( )[1- cos(6 )]mD t D t m t= (5)

IfD(t) of (2) is substituted by Dm(t), it is not difficult

to understand the following equation.


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Fig.3 The simulated circuit model of PFC converter with harmonic injected PWM

2mod

2mod

2mod

)]6cos(1[

)]6cos(1[

)]6cos(1[

tmii

tmii

tmii

cc,

bb,

aa,

=

=

=

(6)

After simplifying the above equation, and ignoring the

presence ofm2 (m26) of the

voltage signal rectified by the 3-phase rectifier bridge.Then, the sixth order harmonic is gained, but is not the

injected signal. Finally, the amplitude and the polarity

are modulated by a multiplier and an adder itself

respectively. Therefore, the desired injection signal is

obtained.

Fig.3 with the following parameters has been

simulated via MATLAB/SIMULINK software. The

simulated results are also showed.

The main parameters of the simulated circuit:

The input phase voltage: UinP=220Vrms/ f=50Hz

The switch frequency: fs =10k Hz

The output: Uout

=800V/Pout

=6.4kW

The output capacitor: Co=220uF

The input inductor: L=0.21mH

The EMI filter: Lf=6mH, Cf=4uF

Fig.4 shows the amplified input current waveform of

one boost inductor. It can be seen that the input current

has fallen to zero at the end of period, so the converter

operates in DCM.

ref ref

v+

-

VM1

v+

-

VM

R

Signal(s)Pulses

PWM Generator

zeros(s)

s

PI

A

B

C

A

B

C

Lg

m

C

E

IGBT

K

Gain2

-K-Gain1

A

B

C

A

B

C

Filter

Dot Product

Diode

C

A

B

C

Source

InputOutput

Filter1

A

B

C

+

-

Bridge1

A

B

C

+

-

Bridge

A B C

a b cTransformer


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Fig.4 The amplified inputcurrent waveform without t he EMI filter

The following figures show the input current in the

case of with harmonic-injection and without harmonic-

injection. According to the figures, with the sixth-order

harmonic injected PWM, the fifth-order harmonic

content is attenuated by adjusting the amplitude of the

sixth-order harmonic, but the seventh-order harmoniccontent increases. However, the total current distortion is

improved evidently. Furthermore, with the optimized m,

the value of THD meets the IEC555-2(A)

requirement(THD


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V. CONCLUSIONIn this paper, the sixth-order harmonic-injection

method for a 3-phase single-switch PFC converter was

presented. Using this method, undesirable high voltage

transfer ratio can be avoided, without sacrificing the

excellent power factor. The whole simulated model of

the main circuit and the control circuit was made and

analyzed. Finally, the analysis with the determinedparameters is conformed by simulation using

MATLAB/SIMULINK software. The simulated results

are showed.

REFRENCES

[1]. Q. Huang and F. C. Lee, Harmonic Reduction In A Single-Switch, Three-phase Boost Rectifier With High Order Harmonic

Injected PWM in IEEE Power Electronics Specialists Conf.

(PESC) Rec., 1996, pp 1266-1271.

[2]. Yungtaek. Jang, and Milan.M Jovanovic, A Novel RobustHarmonic-injection with Method for Single Switch, Three-phase,

DCM Boost Rectifiers, IEEE Transactions on Power

Electronics, vol.28, No.1 March 2000,pp. 268-27.

[3]. Yungtaek. Jang, and Milan.M Jovanovic, A comparative Studyof Single-Switch Three-Phase High-Power-Factor Rectifier,

IEEE Transactions on Industry Application, vol.34, No.6

November/December 1998, pp. 1327-1334

[4]. J. Sun, N. Frohleke, and H. Grotstollen, Harmonic reductiontechniques forsingle-switch three-phase boost rectifiers. in conf.

Rec IEEE-IAS Annu . Meeting, 1996, pp. 1225-1232.

[5]. DaFeng Weng and S. Yuvarajan, AC-DC Converter usingsecond-harmonic-injected PWM in PESC95 Rec., pp. 1001-

1006,1995

[6]. Akiteru Ueda, Satoko Ando, Akihiro Torii, Study on LC FilterDesign Method for Boost Type Rectifier with Single Switching

Device, IPEC-Tokyo 2000, pp.820-825

[7]. E. Ismail, C.Oliveira, and R. Erickson, A low-distortion three-phase multi-resonant Boost rectifier with zero current switching ,

inProc. of IEEE APEC95, pp. 849-855,1995

[8]. K. Chen, A. Elasser, D. A. Torrey, A soft switching activesnubber optimized for IGBTs in single switch unity power factor

three-phase diode rectifiers, in Proc. of APEC94, pp. 280-286,

1994

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