Energy and Power Engineering, 2013, 5, 906-913
doi:10.4236/epe.2013.54B174 Published Online July 2013 (http://www.scirp.org/journal/epe)
The Research of Three-phase Boost/Buck-boost
DC-AC Inverter
Xiangli Li, Zhaoyang Yan, Yanni Gao, Hanhong Qi
Key Lab of Power Electronics for Energy Conservation and Motor Drive of Hebei Province,
Yanshan University, Qinhuangdao, China
Email: lxl@ysu.edu.cn
Received March, 2013
ABSTRACT
This paper presents a new inverter based on three-phase Boost/Buck-boost single-stage inverter. The basic configura-
tion of the new topology and their fundamental principle are firstly introduced, the method of design double-loop con-
troller and sliding mode controller are clarified, an alyzed and compared in the following. Finally the valid ity and feasi-
bility of the new topology are tested by simulation. The results indicate that regulation of the voltage transfer ratio and
output frequency can be realized optionally by the new converter, furthermore the harmonic distortion of waveform is
low. So the inherent drawback of low voltage transfer ratio of traditio n al conv erter is effectiv ely settled. Th is study may
provide inspiration for further engineering application.
Keywords: Three-phase Boost Single-stage Inverter; Three-phase Buck-boost Single-stage inverter; Double-loop
Controller; Sliding Mode Controller
1. Introduction
As growing in the field of new energy development and
utilization, high power density, high reliability, pollu-
tion-free and high performance of a new generation of
high frequency transformation technology research has
important theoretical value and engineering value. Re-
cently, based on the new concept of novel topologies of
the DC-AC inverter has attracted more and more atten-
tion. Ramón O. Cáceres referred to a boost DC-AC in-
verter [1]. The new inverter generates an output voltage
larger than the dc input one depending on the instanta-
neous duty cycle. So this property is not found in the
traditional VSI, which produces an ac output instantane-
ous voltage always lower than the dc input. Through the
two groups of converter are cooperate, the load voltage
can be sine waveform. The topology can reduce the DC
source and the inverter needed DC-DC link. So it can
reduce the volume, reduce costs and improve efficiency.
The paper present three-phase Boost, Buck-boost sin-
gle-stage converter [2]. A control strategy for the three-
phase boost inverter which each Boost is controlled by
means of a double-loop regulation scheme that consists
of a new inductor current control inner loop and an also
new output voltage control outer loop is applied. A con-
trol strategy for the three-phase buck-boost inverter in
which each buck-boost is controlled by means of a slid-
ing mode controller is applied.
2. Introduction of the Three-phase
Boost/Buck-boost Single- stage Inverter
2.1. The Topology of Three-phase Boost
Single- Stage Inverter
The three-phase boost single-stage inverter is shown in
Figure 1. In this topology, three boost inverter which
driven by three 120°phase-shift DC-biased sinusoidal
reference make the output capacitor voltage changes over
the reference voltage to adjust the output voltage of the
boost and output voltage is an AC output voltage [3]. The
boost DC-AC inverter exhibits several advantages, the
most important of which is that it can naturally generate
an AC output voltag e from a lower DC input vo ltage in a
single-stage power stage.
1
V
in
V
1
D
2
D
3
D
4
D
5
D
6
D
Figure 1. The topology of three-phase Boost.
Copyright © 2013 SciRes. EPE
X. L. LI ET AL. 907
Control of the three-phase boost inverter can be achieved
by controlling each boost separately. So, analysis one
boost inverter can be an example to explain the principle
and working process. Using the average concepts, the
following voltage relationship for the continuous con-
duction mode is given by
1
1
1
1
in
V
Vd
(1)
where is the duty cycle.
1
d
As 101d where d
V is the capacitor voltage
of the DC-biased, where 01 is the capacitor voltage of
sinusoidal component, have 011 d. According to
[4], the single-stage-phase ac output voltage of the boost
converter can be compared with the dc inpu t voltag e gain
is:
VVV VVVV
11
1
2(1
2(1 )
om
in
VdGd
Vd

1
)
(2)
where is maximum voltage gain (
m
Gop
in
V
V), is the
output volta ge peak - peak of singl e-stage boost conve rt er.
op
V
According to equation (2), the topology of the ac out-
put can be higher or below the intermediate dc voltage.
Three-phase boost single-stage inverter output current
of inverter side is positive and negative alternating. The
current bidirectional boost dc-dc converter is shown in
Figure 2.
The fundamental principle is: 1 and 2 are driven
by two Complementary signal differ 180°phase-shifted,
1 and 2 are the diode parallel. If 1 on, 2 off,
the inductor current direction is positive, the current will
be flow through the 1; If the inductor current is nega-
tive, the current will be flow throu gh the 1. If 1 off,
2 on, the inductor current direction is positiv e, the cur-
rent will be flow through the ; otherwise the current
will be flow through the .
S
2
S
S
D
D
S
D S
S
S
D
2
S
1
S
1
D
2
S
2
D
1
C
R
in
V
Figure 2. The current bidirectional boost dc–dc converter.
2
A three-phase buck-bilar to a three-phase boost
.2. The Topology of Three-phase Buck-Boost
Single-stage Inverter
oost is sim
single-stage inverter. A three-phase buck- boost single-
stage inverter is shown in Figure 3. Each of three-phase
buck-boost single-stage inverter ac output voltage of the
boost converter can be compared with the dc input volt-
age gain is:
11 1
1
2(1
(1 )
om
in
VdGd
Vd

)
(3)
where the is maximum voltage gain (
m
G op
in
V
V), is
the output voltage peak-peak of single-stage buck-boost
ase buck-boost single-stage inverter output
cu
inciple is: and are driven
by
op
V
converter.
Three-ph
rrent of inverter side is positive and negative alternat-
ing. The current bidirectional buck-boost dc-dc converter
is shown in Figure 4.
The fundamental pr1
S
er 2
S
ph
th
two Complementary signal diff 180°ase-shifted,
1
D and 2
D are the diode parallel. If 1
S on, 2
S off,
inductor current direction is positive, e curre will
be flow through the 1
S; If the inductor current is nega-
tive, the current will bflow through the 1
D. If 1
S off,
the nt
e
1
D
2
D
3
D
4
5
D
6
D
Figure 3. The topology of three-phase buck-boost.
2
S
1
D
1
S
2
D
1
C
R
in
V
1
L
Figure 4. The current bidirectional buck-boost dc–dc con-
verter.
Copyright © 2013 SciRes. EPE
X. L. LI ET AL.
Copyright © 2013 SciRes. EPE
908
he inductor current direction is positive, the cur-
2.3. The Compare of the Two Topology
logy and
3.1he Three
A doub control method [5-8] for the three-phase
ied. The mode
eq
2
S on tobtained, in which internal resistance have been ne-
glected: rent will be flow through the2
D; otherwise the current
will be flow through the 2
S. 1
1
1111
() Vo
L
inL o
tt
d
di
VLi iC
dd

(8)
The equation (8) shows that boost converter has nonlinear
relationship between different variables. So designing
consistency to the requirements of the boost inverter ac-
curate, stable and suitab le for various complex cond itio ns
of the controller is very difficult. A control strategy for
the three-phase boost inverter in which each boost is
controlled by means of a double-loop regulation scheme
is shown Figure 5.
Although the two converter have different topo
fundamental principle, but from the practical analysis is
similar: 1) Three-phase boost and buck-boost single-
stage inverter have same number of switches, the com-
plexity of the circuit is similar; 2) Under the condition of
the same input voltage, these topology can be throu gh the
duty ratios to adjusted the output voltage, to achieve the
goal of change the voltage transfer ratio; 3) For the sin-
gle-stage boost and buck-boost converter, the voltage
stress depends on the maximum gain and output voltage
and current stress depends on the required current.
The current control loop is defined by equation (4) and
equation (6). If choosing the duty cycle to the controller
output, the controller is variable and the plant seen by the
controller would exhibit a variable gain caused by the
variable output voltage 01 . Therefore, the control strat-
egy of the inductor current feedback value compared
with the reference value to control can replace equation
(6) with PI controller. The duty cycle 1 is then ob-
tained by means of the following expression, in which
V
d
L
ref
V is the controller output
3. The Control Scheme and Compared of the
Three-phase Boost/Buck-Boost
. Double-loop Control Scheme for t
Boost
le- loop
101
1in Lref
VV
dV
 (9)
boost is introduced. For simplify the system analysis,
only for a boost converter to introduce.
Firstly, the current inner loop is studThe cancellation of the input voltage influence acts as
a feed-forward control. This cancellation would not be
required if the current loop bandwidth is much faster than
the input voltage.
uations particularized for the boost converter are de-
scribed as follows:
11
1
in Lo
VV dV
1
(4)
Concerning the output voltage loop which is intro-
duced in Figure 6, is now defined by equation (5) equa-
tion (7). The design of the control structure for the output
voltage is based on the same philosophy as the current
loop. If the control variable are now the current reference
(
L
ref
i) for the inner loop, the plant seen by the controller
would show again a variable gain caused by the
term 1
1d
. Therefore, the capacitor current (c
i) is now
proposed to be the control variable, replace equation
(7)with PI controller from the equation (5), the calcula-
tion of the current reference from the use of duty cycle
(1
d),which appears inside the term 1 as shown in
equation (5), However, the calculation of duty cycle (1)
is provided by the inner current loop, and its use in the
current reference calculation would cause a coupling
between both inner and outer control loops that could
1dd
11 1
1
co L
ii di
1
(5)
where and are the capacitor voltage and current,
01
V1c
i
1
L
V an1
d
L
i are e inductor voltage and current, 1o
i is
outputrrent, and 1
d is the duty cycle.
The inductor and capacitor different equation
th
the cus are:
1
1111
L
LLL t
di
VriL
d
 (6)
11
111 1
c
iVo
cc t
dd
irC C
d

t
d
(7)
where 1
L, 1
C, 1
L
r
tan and are the values for the in-
(4)-(7), the following expression can be
1c
r
ucductanccacice, indtor and capacitor equivalent
series resistance.
From equation
e, pa
1c
V
r
L
s
1
L
i
Lref
V
in
V
1c
V
1
1d
L
V
in
V
PI
Lref
i
1
1
c
V
Figure 5. Proposed current control loop.
X. L. LI ET AL. 909
sC
1
PI
1
cref
U
c
U
cref
i
1o
i
1
L
i
in
V
1
1d
01
i
1c
i
c
V
c
V
c
in
V
V
Figure 6. Proposed output voltage control loop.
ake the system unstable. Using the average mode, m
boost converter is
101
1in
V
dV
 (10)
Therefore, the proposed output voltage control loop
can also be seen as the result of compensating the plant
variable gain (defined by ) with
1
1d
1
in
o
V instead, the
V
current reference is then given by the following expression
101 101
101
()
1
cin
Lref c
ii V
iii
dV

(11)
3.2. Sliding Mode Controller Analysis
e the sliding
ck-boost inverter
dy
ee-phase buck-boost single-stage in-
ve
ter output
vo
As for the three-phase buck-boost to introduc
control method. For simplify the analysis, only for a
buck-boost converter to introduce [9].
For the purpose of optimizing the bu
namics, while ensuring correct operation in any work-
ing condition, a sliding mode control [10, 11] is more
feasible approach.
Control of the thr
rter by controlling each boost converter. The funda-
mental principle is shown in Figure 7.
The sliding mode con troller make the conver
ltage track the reference signal as precisely as possible.
For the current bidirectional dc-dc converter, the state-
space molding of the equivalent circuit with state vari-
ables 1
L
i and 1
V is given by
11
111
1
111
11
100
1
11 0
L
Lin
di V
Li
dt LV
V
dV CL
RC C
dt

 


  




 


 

  


(12)
where and are the inductor and capacitance;
1
L
d; 1
C R
is a loa
is t status of the switches, defined
1 SS
on off
he
12
12
0 SS
off on (13)
When good transient response of the output voltage is
needed, a sliding surface equation in the state space, ex-
pressed by a linear combination of the feedback current
error, and is the feedback voltage error, can be given
11 1121
()()0
LLLref ref
SiVKiiKVV
(,)= (14)
1
K
and 2
K
where coefficients are proper gai
choice mutence condition of sliding
(15)
Sliding mode control is obtained by means of the fol-
lowing feedback control strategy, which relates to the
st
(16)
Compared the equation (12)-equatio
ns, the
st satisfy the exis
mode
()<0 if ()0
()>0 if ()0
Sx Sx
Sx Sx
atus of the switches with the value of ()Sx:
0 ()0
1 ()0
Sx
Sx
for
for
n (16), obtained
12
()()0
Lref refref
Ri vv
KK
 
(17
CR L)
12
()()
ref in
vV
KK
CR L

0 (18)
1
S
1
D
2
S
2
D
1
C
R
in
V
1
K
2
K
1
H
1
L
i
L
ref
i
1
11
(,)
L
Siv
2
S
1
S
2
1
V
ref
V
2
V
Figure 7. Sliding mode controller scheme.
Copyright © 2013 SciRes. EPE
X. L. LI ET AL.
910
If the sliding mode exists, the system behavior is com-
pletely determined by coefficients 1
K
and 2
K
. It is
determines the system respon
The sliding mode function is applied to a hys-
teresis comparator
se, stability and robustness.
()Sx
(1
H
), proby the switch control
signal (duced
) in the power switch and . By adjusted
1
S2
S
1
L
i and make so as to realize the ac-
curate tracg of ohrence signal.
In addition, the inductor current is related to the load, the
reference value is difficult to determine. Therefore, in
practical applications, the inductor current feedback by a
high-pass filter, take its high-frequency component to
replace the inductor current error, so only need to control
the high frequency component of the inductor current.
4. The Analysis of Simulation
4.1. Th
ide
nd 2 i
1
kin
Vthe
utp ()Sx
ut vo0,
ltage of te refe
e Result of Simulation
The simulation results are given assuming the three-
phase input voltage source, power switch, elements such
as inductance and capacitanceal. The prototype in-
verter parameters a specification are: input voltage
48
in
VV, switching frequency 0KHz,nductor 1
L
.13mH , three-phase load 123
RRR
32, capacitance 123
54CCC uF , the output
frequency is 50Hz, sliding mode controller coefficients
10.25K, 20.54K; double-loop control scheme for
each Boost are a current loop bandwidth close to 2KHz
and a voltage lo op bandwidth of about 800Hz, both phase
margins of 50°.
The contrast analysis diagrams are the three-phase boo
23
0LL
st
double-loop control and three-phase buck-boost sliding
phase boost double-
ol of load FFT:
nt:
distortion of the output voltage waveform
ve is low; 3)
-loop control,
w
mode control of load voltage:
The contrast analyses are three-
loop control and sliding mode contr
The contrast analyses are the three-phase boost dou-
ble- loop control and three-phase buck-boost sliding
mode control of capacitance voltage:
The contrast analyses are the three-phase Boost dou-
ble-loop control and three-phase buck-boost sliding
mode control of inductor curre
Three-phase buck-boost sliding surface of the sliding
mode control:
Three-phase boost single-stage inverter load sharp re-
duction in 0.05s, the simulation waveform graph is
shown below:
4.2. The Simulation Results Analysis
1) Three-phase boost/buck-boost single-stage inverter
indicates that regulation of the voltage transfer ratio can
be realized optionally and the output voltage can be ac-
curately tracked according to the reference given by the
change; 2) As can be seen from the Figure 8 and Figure
9 the harmonic
for three-phase symmetrical sinusoidal wa
From Figure 8 can be seen that the double
ithout overshoot system into a steady state quickly.
From Figure 9 can be seen sliding mode control of the
load voltage startup performance is poorer, before into
the sliding mode surface ,the system has overshoot, there
is a lot of impulse voltage, and power is not enough; 4)
The double-loop control is the direct control of the cur-
rent and it has strong robustness to external interference.
The buck-boost inverter capacitor voltage stress is lower
than the boost inverter, so the switching loss of the for-
mer is smaller than the latter, which adopts the double-
loop control of output harmonic is smaller than using
sliding mode control of output harmonic, as shown in
Figure 10 the harmonic is 0.6%, and in Figure 11, the
harmonic is 2.05%; 5) Compared with double-loop con-
trol, sliding mode control has better tracking. Sliding
mode control of the feedback voltage is almost consistent
and a given voltage (155.5 V) for 155.4 V, and the feed-
back voltage is 156 V in the double-loop con trol; 6) Fig-
ure 12 and Figure 13 shows the output capacitor voltage
has dc-biased.
00.050.1 0. 15
-
300
-
250
-
200
-
150
-
100
-50
0
50
100
150
200
t/s
载电负 压
Figure 8. Three-phase boost double-loop control of the load.
Copyright © 2013 SciRes. EPE
X. L. LI ET AL. 911
00.05 0.1 0.15
-300
-200
-100
0
100
200
300
400
t/s
负载电压
Figrue 9. Three-phase buck-boost sliding mode control of the load voltage.
Figure 10. Three-phase boost double-loop control of the
load FFT. Figure 11. Three-phase buck-boost sliding mode control of
the load FFT.
00.05 0.1 0.15
0
100
200
300
400
500
600
t/s
电容电压
Figure 12. Three-phase boost double-
loop control of the capacitance voltage.
00.05 0.10.15
-
100
0
100
200
300
400
500
600
700
t/s
电容电压
Figur . e 13. Three-phase buck-boost sliding mode contr ol of the ca pacitanc e voltage
Copyright © 2013 SciRes. EPE
X. L. LI ET AL.
912
0.05 0.1 0.150.2 0.25
-40
-20
0
20
40
60
80
100
t/s
电感电流
Figure 14. Three-phase Boost double-loop co ntr ol of the inductor c urrent.
0.05 0.1 0.15 0.2 0.25
-20
-10
0
10
20
30
40
50
60
t/s
电感电流
Figure 15. Three-phase Buck-boost sliding mode c ontrol of the inductor current.
00.05 0.1 0.15 0.2 0.250.3
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
S(x)
滑模面
Figure 16. Three-phase Buck-boost sliding mode control of sliding surface.
0.01 0.02 0.03 0.04 0.05 0.06 0.070.08 0.090.1
-
200
-
150
-
100
-50
0
50
100
150
200
t/s
Figure 17. Three-phase boost double-loop control of the load sharp reduction voltage.
Copyright © 2013 SciRes. EPE
X. L. LI ET AL.
Copyright © 2013 SciRes. EPE
913
5. Conclusions
The paper deals with the topology and comparison of
three-phase boost, buck-boost single-stage inverter. A
control strategy for the three-phase buck-boost inverter
has been proposed in this project in which buck-boost
converters of the buck-boost inverter are controlled by
means of a sliding mode control, while the three-phase
boost inverter in which each boost is controlled are by
means of a double-loop control scheme that consists of a
new inductor current control inner loop and a new output
voltage control outer loop. These loops include several
compensations that mak
e boost converters. In addition, some feed-forward reg-
ulations are also designed to make the system highly ro-
bust for both of input voltage and output current distur-
bances. The simulation result shows that regulation of the
voltage transfer ratio and output frequency can be real-
ized optionally by the new converter, furthermore the
harmonic distortions of waveform is low and have the
advantage, such as robustness, good tracking perform-
ance. These new inverter is intended to be used in unin-
terruptible power supply (UPS) and ac driver systems
design whenever an ac voltage larger than the dc link
voltage is needed, with no need of a second power con-
version stage.
ments
[2] Z. X. Yan, J. X. Li, W. Zhang, Q. Zhang, Y. N. Zheng
and W. Y. Wu, “Topology Family and the Simulation of
BOOK” Differential Single-stage Stage Inverter,”
IEEE, 2010. doi:10.1109/63.737601
e possible an accurate control of
th
6. Acknowledge
This work was supported by key programs of
NSFC(50837003), and by the Program of the Science
and Technology Foundation of Hebei province of China
(11213943),and also be supported by the Doctor Re-
search Fund of Yanshan University(No.B549).
REFERENCES
[1] R. O. Cáceres and I. Barbi, “A Boost DC–AC Converter:
Analysis, Design, and Experimentation,” IEEE, Transac-
tions on Power Electronics 19 99, Vol. 14, pp. 134-141.
[3] Z. Y. Yan, J. X. Li, Y. N. Zheng and W. Y. Wu, “Re-
search of Double-Boost Single-stage Stage DC/AC Con-
verter based on SPWM,” Vol. 47, No. 9, 2007, pp. 17-19.
[4] N. Vazquez, D. Cones, C. HemaIldez, et a1., “A New
Nonlinear Control Strategy for the Boost Inverter,” IEEE
International power Electronics Conference, Mexico,
2003.
[5] P. Sanchis, A. U. E. Gubía and L. Marroyo, “Boost
l Strategy,” IEEE Trans-
ol. 20, No. 02, 2005, pp.
343-353. doi:10.1109/TPEL.2004.843000
DC-AC Inverter: A New Contro
actions on Power Electronics, V
[6] B. Kalaivani, V. K. Chinniyan and J. Jerome, “A Novel
Control Strategy for the Boost DC-AC Inverter,” India
International Conference on Power Electronics, 2006, pp.
341-344.
[7] R. Cáceres, R. Rojas and O. Camacho, “Robust PID Con-
trol of a Buck-Boost DC-AC Converter,” IEEE, 1998, pp.
180-185.
[8] P. Sanchis, A. Ursua, E. Gubia and L. Marroyo, “Buck-
Boost DC-AC inverter: Proposal for a New Control
Strategy,” 35th Annual IEEE Power Electronics Special-
ists Conference, 2004, pp. 3994-3998.
[9] Z. Q. Cai, F. Hong and Wang, “Research on a Sin-
,” Power Supply
[11] J. Chen, “The Research of DC-AC Inverter Based on
Sliding Mode s, University,2003.
gle-stage-stage Buck/Boost Inverter
Technologies and Application, Vol. 11, No. 4, 2008, pp.
43-47.
[10] H. Ma, T. Zhang and S. L. han, “Analysis and Design of
Sliding Mode Control for Novel Buck Inverter,” Transac-
tions of China Electrotechnical Society, 2005, Vol. 20,
No. 7, pp. 50-56.
Control,” Master’s Thesi
[12] J. L. Zhu, Z. Yue, X. P. Zhang, S. S. Liu and S. W. Liu,
“A Study of BMC and BBMC with High Volt- age Trans-
fer Ratio. Proceedings of the CSEE,” 2007, Vol. 27, No.
16, pp. 85-91