Comparative Analysis in Properties of all Types of Z-Source
Inverters
(Full text in English)
Hongsheng SU1, Hongjian LIN1
1
School of Automation & Electrical Engineering, Lanzhou Jiaotong University, China
Abstract
The traditional Z-source inverter and its other improved topologies are proposed in this paper. With boost and
buck capacity, traditional Z-source inverter has advantages of current and voltage inverters that both the
current source and the voltage source inverters can be connected with its DC bus and then inductive and
capactive loads can be used as its AC loads. In addition, the dead time is unnecessarily added to prevent upper
and lower switching devices of each phase leg in three-phase inverter bridge from conducting simultaneously.
Aiming at the shortcomings of the traditional Z-source inverter, two kinds of improved Z –source inverters,
quasi Z-source inverters and other enhanced Z-source inverters are analysed in this paper. They overcome the
shortcomings of traditional Z-source inverter, but they achieve the boost by inserting shoot-through zero
vectors into traditional zero vectors, this will reduce quality of AC output voltage in SVPWM. Finally, two kinds
of isolated shoot-through Z source inverters are introduced in this paper, they utilize controlled devices to
achieve the separation between shoot-through zero vectors and traditional zero vectors ,so that they make
sure higher quality of output voltage. Based on the comparative analysis on each Z-source inverter, using
MATLAB to verify the correctness of theoretical analysis in the end.
Keywords: Z-source inverters, traditional zero vector, shoot-through zero vector, comparative analysis,
simulation
1. Introduction
Conventional inverter has either voltage
source inverter or current source inverter.
The former has buck property, its AC side
load is an inductive load. The latter has
boost property; its AC side load is a
capacitive load [1]. For output voltage of the
inverter AC side being lower than the DC
voltage and a wide range variation of input
voltage, DC / DC chopper circuit often needs
to be added, which increases the complexity
of the control system and reduces the
efficiency of the system. What’s more, in
order to prevent the upper and lower devices
of each phase leg break-over at the same
time and thus damage the devices, the dead
time should be added to the switching signal
of devices, but this results in the waveform
distortion of AC output voltage instead [2].
To overcome the shortcomings of the
inverter mentioned above, Professor Peng
Fangzheng proposed Z-source inverter in
2003[3]. The inverter make the shootthrough phenomenon of the upper and lower
devices of each phase leg become a normal
state by using its unique impedance
networks while conducting its work [4] and
also avoids the distortion of output voltage
waveform because of insertion of the dead
time insertion as well as simplify the
circuit[5].
However, traditional Z-source inverter
also remains many deficiencies [6-8]: inrush
current, which is easy to damage the devices
of leg at startup. High capacitance voltage
on impedance network during steady state,
therefore large volume of capacitors are
required and then the cost increases for this
inverter. In addition, due to the shootthrough zero vectors replace part of
traditional zero vectors, so the circle
synthetic by SVPWM is not so smooth and
generating the effect of output AC
waveform.
So aiming at the deficiencies of
traditional Z-source inverter, other Z-source
inverter topologies are analysed and
advantages and disadvantages as well as
application of them are summarized.
2. Circuit characteristics analysis of all
kinds of Z-source inverters
Z-source inverter consist of passive
network and three-phase inverter. Z-source
inverter works in nine states of switch
including six effective vector states, two
traditional zero vector states and one shootthrough zero vector state. When the Zsource inverter works in six effective vector
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
34
states, inverter leg is equivalent to a current
source. When the Z-source inverter works in
traditional zero vector state, inverter leg is
regarded as the current source whose
current value is zero. When the Z-source
inverter works in shoot-through zero state,
inverter leg is short-circuited.
SVPWM modulation strategy is used in this
paper to make the upper and lower devices
of inverter leg turn-on and turn-off.
Compared to SPWM modulation strategy, it
has the advantages of high DC voltage
utilization, fast dynamic response, less
harmonic and fluctuation [9].
The following Z-source inverter topologies are understood to be ideal ones. T1 is
a shoot through interval in a switching cycle,
T 2 is a non-shoot-through interval in a
switching cycle i.e. the switching cycle
T = T 1 + T 2.
2.1 Traditional Z-source inverter
Traditional Z-source inverter is shown in
Figure 1 [10].
V
C1
L1
D
C1
U dc
C2
VT6
VT4
i1 c
VT2
L2
Figure 1. The topological structure of the traditional
z-source inverter
Assuming capacitors C1 and C2 and
inductors L1 and L2 are identical, because of
symmetry Z-source network, we have:
C1 = C 2 = C
L1 = L 2 = L
(1)
Then we can can write:
VC1 =VC2 =VC
(2)
V L1 = V L 2 = V L
The equivalent circuits of traditional Zsource inverter, which operates in shootthrough zero vector state and non shootthrough state are as shown in Figure 2.
V L1
VC 2
i1 b
uc
VL1
C2
i1 a
ub
Vi
L1
VC1
VT5
ua
L1
dc
VT3
VT1
V
Vi
C1
C2
VC1
VC 2
Vi = 0
dc
VL 2
VL2
L2
L2
(a) equivalent circuit of non-shoot-through state
(b) equivalent circuit of shoot-through state
Figure 2. State equivalent circuit diagrams of the traditional Z-source inverter
By analysing the state figures of the above
equivalent
circuit, Z-source
inverter
operates in non-shoot-through state and
diode is turn-on, there are:
according to equation (2) to (4), we have:
Vdc=VL+VC
Vi = VC − V L =
，V = V
i
C
− VL = 2VC − Vdc
(3)
When the traditional Z-source inverter
operates in through state, the diode is turnoff, there are:
VC=VL
， V =0
(4)
i
In steady state, based on the inductor
voltage volt-second theorem, the average
value of inductor voltage in a switching cycle
is equal to zero. Therefore, we can write:
−
VL =
T1V C + T 2 (V dc − V C )
= 0
T
Assuming
T1
= D1
T
,
T2
= (1 − D 1 )
T
(5)
, and
VC =
T2
1 − D1
V dc =
V dc
T2 − T1
1 − 2 D1
∧
1
Vdc = BVdc
1 − 2 D1
(6)
(7)
where, D1 is shoot-through duty cycle, Vdcis
∧
input DC voltage, V i is the peak DC voltage
across the inverter, B is boost factor.
The dotted line in Figure 1 is the circuit
of inrush circuit flowing when traditional Zsource starts working. This moment,
capacitance of the capacitors in the Z-source
network are about zero and inductive
reactance is large enough, so the inrush
circuit at startup is very large and easy to
damage the devices. What’s more,
resonance happens through the interaction
between the captance and inductive
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
reactance, and thus make the system
unstable. In addition, due to the energy
storage elements does not connect directly
with DC input voltage, so the current flowing
into
the
three-phase
inverter
is
discontinuous.
Analysis of the following Z-source
inverters are the same as the traditional Z-
source inverter. All will be analysed during
their shoot-through state and non-shootthrough state.
2.2 Quasi-Z-source inverters
As shown in Figure 3[11], there are quasi
Z-source inverters that are symmetric and
asymmetric inverters.
C1
C1
L2
V dc
D
C2
35
D
L2
L1
V dc
Vi
(a) asymmetric quasi Z-source inverter topology
L1
C2
Vi
(b) symmetric quasi-Z-source inverter topology
Figure 3. The topological structure of two kinds of quasi Z-source inverters
For the asymmetric quasi Z source
inverter, due to the energy storage element
L being in series with input DC voltage, so
current flowing into the three-phase inverter
bridge is continuous. Contrary to the
asymmetric Z-source inverter, current is
interrupted for symmetric Z-source inverter.
Aiming at asymmetric quasi-Z-source
inverter, as shown in Figure 3(a), according
to volt-second theorem, during the steady
state, we have:
VC1 =
T1
D1
V dc =
V dc
T1 − T 2
1 − 2 D1
(8)
VC 2 =
1 − D1
T2
Vdc =
Vdc
T2 − T1
1 − 2 D1
(9)
Peak DC voltage across the inverter of the
asymmetric quasi Z-source inverter can be
written as:
∧
D
1− D1
1
Vi = VC1 +VC2 = ( 1 +
)Vdc =
Vdc = BVdc
1− 2D1 1− 2D1
1− 2D1
(10)
As to symmetric quasi-Z-source inverter,
consider Figure 3(b), we can write:
VC1 = VC 2 =
T1
D1
Vdc =
Vdc
T1 − T2
1 − 2 D1
∧
Vi = 2VC −Vdc =
T
1
Vdc =
Vdc = BVdc
T2 −T1
1−2D1
(11)
(12)
As can be seen from above analysis,
impulse current can be amortized and
suppressed for quasi Z-source inverters
owing to their energy storage inductor,
which is in series with their Z-source passive
impendence networks. However, they still
give rise to the inductor current and
capacitor voltage exceed the steady state
value after startup of quasi Z-source
inverter. Starting impulse current the start
flowing inductor current and voltage across
the capacitor exceeds the steady state value
and resonance oscillation may take place for
inductor and capacitor in the Z-source
impendence network, then affect the
stability of the system.
From formula (9), it can be seen that at
the same shoot-through duty ratio, the
capacitance of capacitor voltage is less than
the traditional Z source inverter during the
steady state, and thus the side and weight of
the capacitors can be reduced for this
topology. Because reverse blocking effect of
the diode, there is no in rush current at
startup start and the stability and reliability
of the system can be improved.
Two kinds of quasi Z-source inverters have
the same boost capacity as traditional Zsource inverter. In addition, traditional zero
vector is inserted into through zero vector to
realize boost for two quasi Z-source
inverters, so two zero vector are coupled
with each other and the waveform of output
voltage is affected with modulation strategy
in SVPWM.
2.3 Improved Z-source inverters
Two kinds of modified Z-source inverters
are shown in Figure 4[12].
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
36
V dc
L1
V
dc
Vi
C1
C2
D
V
i
L2
(a) Improved Z-source inverter 1
(b)Improved Z-source inverter 2
Figure 4. The topological structure of two kinds of improved z-source inverters
The position of their Z-source impedance
networks relative to three-phase inverter
bridge is different from the traditional one.
Consider Figure 4 based on inductor voltage
volt-second theorem, the capacitor voltage
and peak DC voltage across the inverter are
expressed as:
VC =
∧
Vi =
D1
V dc
1 − 2 D1
(13)
1
V dc = BV dc
1 − 2 D1
(14)
of output voltage is affected
modulation strategy SVPWM.
with
2.4 Enhanced Z-source inverters
Enhanced Z-source inverters are divided
into two types including improving boost
capacity and reducing capacitor voltage ones
in steady state. In order to improve boost
capacity of Z-source inverter and further
reduce its capacitor voltage during steady
state. Several enhanced Z-source inverters
were proposed. They were added impedance
network and passive switching devices to
form enhanced Z-source topologies. All of
them are listed as follow.
As can be seen from above formulas, the
capacitor voltage and peak DC voltage across
the inverter are the same as symmetric quasi
Z-source inverter. What’s more, The method
of boost for improved Z-source inverter is
similar to the symmetric quasi Z-source
inverter, so it still remains the same
shortcoming that two zero vector are
coupled with each other and the waveform
2.4.1 Enhanced Z-source inverter of
improving boost capacity
Enhanced Z-source inverters of improving
boost capacity [13] are presented in
Figure 5.
D2
C2
C1
L3 D 3
V dc
C3
D
L2
L3 D 3
L1
V dc
C2
C3
C1
D
L2
C4
Vi
(a) Enhanced Z-source inverter with auxiliary diodes
D4
D12
D5
L3
L1
D1
C1
Vi
(b) Enhanced Z-source inverter with auxiliary capacitors
L2
D3
D2
C2
D
V dc
L1
Vi
D6
L4
D
D8
7
L5
D11\
D9
D 10 \
L6
(c) Enhanced Z-source inverter with switching inductors
Figure 5. Enhanced z-source inverters of improving boost capacity
As shown in Figure 5(a), this topology,
called diode auxiliary enhanced Z-source
inverter, is added diodes D2 D3, inductor L3
and capacitor C3. Over the symmetric quasi
Z-source inverter to form boost chopper
circuit. It is in series with three-phase
inverter bridge to improve boost capacity
and make sure continuous input current into
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
three-phase inverter bridge. Diode D2 of the
topology in Figure 5 (a) is eliminated and
added capacitor C2 instead, so we can get
capacitor auxiliary enhanced Z-source
inverter, which is shown in Figure 5(b). Due
to the increase of energy storage element C2,
boost capacity of this topology is better than
that of the topology in Figure 5 (a) and
current inputting into three-phase inverter
bridge of this topology is continuous else.
As shown in Figure 5 (c), the switching
inductive Z-source inverter technology is
added several switching inductive energy
storage elements to further reinforce its
boost capacity, but due to the absence of the
energy storage element in series with input
DC voltage, so input current is discontinuous.
It is worth mentioning that three
enhanced Z-source inverters mentioned
above have extensibility features and then
corresponding impedance networks and
diodes can be aggrandized to increase their
boost capacity. Besides, impulse currents at
startup for them does not exist.
2.4.2 Enhanced Z-source inverter of
reducing capacitor voltage during
steady state
Enhanced Z-source inverters of reducing
capacitor voltage during steady state are
listed as follow[14]:
The following enhanced topologies
further reduces capacitor voltage stress
during steady state.
As can be seen in Figure 6(a), the
enhanced Z-source inverter topology in the
traditional Z-source inverter based on the DC
input voltage is dived into two that are
respective in series with the inductor
branches in the impedance network.
Vdc / 2
C1
L1
C1
D
L2
C2
L1
C2
V dc
Vi
Vi
D
37
C3
D1
L3
L4
Vdc / 2
C4
(a) Enhanced Z-source inverter with embedded DC power
(b) Enhanced Z-source inverter with tandem quasi-z network
C1
D
L2
L1
C2
V dc
Vi
C3
L3
D1
L4
C4
(c) Enhanced Z-source inverter with coupled quasi-z network
Figure 6. Enhanced z-source inverters of reducing capacitor voltage stress
It keeps symmetric for Z-source inverter
and decreases ripple current flowing through
DC power source as well as the capacitor
voltage stress during steady state by a factor
of two. Due to no adding energy storage
element, boost capacity is unchanged for
this topology. Enhanced Z-source inverters,
which are respectively added symmetric and
asymmetric quasi Z-source inverters are
shown in Figure 6(b) and (c). The topologies
both have continuous input currents and
lower capacitor voltage stress during steady
state, so small-sized, light-weighted and
low-cost capacitors can be used in the two
topologies.
Since there is no increase of energy
storage elements in the impedance network,
boost capacity of three inverters mentioned
above are remain unchanged. Because boost
capacity of all enhanced Z-source inverters
is increased by putting their shoot-through
zero vector replace partial even all
traditional zero vectors and two kinds of
zero vectors are coupled ,quality of output
voltage can be affected in SVPWM.
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
38
Figure 7(a) and (b) show Two kinds of
IST(Isolated
Shoot-Through)
Z-source
inverters.
2.5 Isolated shoot-through Z-source
inverters
Vi
Vi
(a)Isolated shoot-through Z-source inverter 1
(b) Isolated shoot-through Z-source inverter 2
Figure 7. Topological structure of shoot-through inverters
Based on improved Z-source inverter, two
topologies are added controlled device IGBT
to control the insertion of shoot-through
zero vector solely, and thus effectively solve
the coupling between shoot-through zero
vector and traditional zero vector. In
addition, a large capacitor Cu is used to
suppress the fluctuation of DC bus and supply
sudden large amounts of current. In order to
inhibit discharging of the large capacitor
through IGBT, diode VDS is needed.
Due to solving the coupling between
shoot-through zero vector and traditional
zero vector, IST Z-source inverter has higher
quality output AC voltage[15].
Summarizing boost factors and capacitor
voltages during steady state of all Z-source
inverters and enumerating them in the table
below:
Table 1. Comparison in properties of 13 kinds of Z-source inverter in properties
Enhanced Z-source inverters
Enhanced one with auxiliary diodes
boost factor
capacitor voltage during steady state/V
1/[(1− D1)(1− 2D1)]
Vdc /[2(1 − 2D1 )(1 − D1 )]
Enhanced one of auxiliary capacitors
1 /(1 − 3D1 )
Vdc /[3(1 − 3D1 )]
Enhanced one with switching inductors
(1+2D1)/(1−4D1)
Vdc (1 − D1 ) /(1 − 4 D1 )
Enhanced one with embedded DC power
1 /(1 − 2D1 )
Vdc (1 − D1 ) /[2(1 − 2D1 )]
Enhanced one with tandem quasi-z network
1 /(1 − 2D1 )
Vdc (1 − D1 ) /[2(1 − 2D1 )]
Enhanced one with coupled quasi-z network
1 /(1 − 2D1 )
Vdc (1 − D1 ) /[2(1 − 2D1 )]
Isolated shoot-through one
1 /(1 − 2D1 )
Vdc /(1 − 2 D1 )
3 MATLAB
Using MATLAB software for all Z-source
inverters mentioned above to conduct
simulations. Shoot-through duty ratio D1 is
taken as independent variable on the
horizontal axis, ratio of capacitor voltage
during steady state and DC power voltage
V C / V dc is used as dependent variable.
Besides, boost factor B is also regards as
dependent variable on the vertical axis.
Simulation results are as follows.
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
39
3
2
1.8
2.5
1.6
2
1.2
VC / Vdc
VC / Vdc
1.4
1.5
1
0.8
1
0.6
0.4
0.5
0.2
0
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0
0.05
0.1
0.15
(a)
0.25
0.3
(b)
15
10
10
B
B
15
5
0
0.2
D1
D1
5
0
0.05
0.1
0.15
0.2
0.25
0
0.3
0
0.05
0.1
0.15
D1
0.2
0.25
0.3
D1
(c)
(d)
Figure 9. Boost capacity and capacitor voltage during steady state of all kinds of Z-source inverters
From the above simulation results, we can
know switching inductive enhanced Z-source
inverter has the best boost capacity of all,
enhanced Z-source inverter of DC power
embedded, coupled network and trandem
type have the lowest capacitor voltage
during steady state.
4. Control strategy
There are several space vector pulse
width modulation techniques used for Zsource inverters to control the connection
and break of switch devices in three-phase
inverter bridge. The control strategies are
listed as follow [15-18]:
(1) Simple SVPWM Boost Control Strategy
(2) Maximum SVPWM Control Strategy
(3) Shoot-through State segmented
SVPWM Boost Control Strategy
For Simple SVPWM Boost Control Strategy
and Maximum SVPWM Control Strategy,
partial traditional zero vectors or all
traditional zero vectors are replaced by
shoot-through zero vectors to realize boost,
but switching frequency is increased and Zsource system’s efficiency is reduced. For
Shoot-through State segmented SVPWM
Boost Control Strategy, shoot-through zero
vectors which are distributed equally to each
phase leg to balance the loss of electrical
current are inserted during commutation, so
switching frequency of switching devices
remains unchanged and the system has
higher efficiency.
In conclusion, we choose it to control the
connection and break of the switching
devices of each phase leg.
Figure 10(a) and (b) shows the control
theory of SVPWM.
(T − T3 − T2 ) / 4 T2 / 2
T3 / 2
(T − T3 − T2 ) / 2
β
T3 / 2
T2 / 2
(T − T3 − T2 ) / 4
U 6 (110)
U 2 (010)
U ref
U 3 (011)
U1 (001)
U 4 (100)
α
U 0 (000)
U 7 (111)
U 5 (101)
T1 / 6
Figure 10. Control theory of SVPWM
Only analysing the first sectors in this
paper, other sectors have the same analytic
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
40
approach. U1~U6 are six active vectors,
U0 (000) and U7 (111) are traditional zero
vectors, Uref is a of reference voltage vector
of synthesized by two active vectors. By
controlling the connection and break, these
eight vectors are produced and they
approximate a flux linkage cycle. At last,
high output-quality voltage waveform in
inverter of inverter’s AC side is generated.
This vector is through the eight-leg
switches control to produce, and thus take
advantage of the eighth flux vector to
approximate the circle and then the output
waveform of the inverter’s AC side.
5. SIMULINK
All topologies are simulated in MATLAB
along with Simulink and SimPower Systems
Toolbox. According to the relationship
between modulation ratio m and shoot-
through duty ratio D1: D1 = T1 = 1 (2 − 3m)
T 2
[19-20].
Assuming m=0.8, we have D1 = 0.307 .
Other simulation parameters can be also
set: Vdc=200 V, the capacitance of capacitor
and inductance of inductor are decided by
inhibiting the ripple current of inductor and
ripple voltage of capacitor, different
topologies have different capacitances and
inductances.
Simulink based simulations are shown in
Appendix 1 (Figure) including output phase
voltages and output line voltages as well as
input currents of all kinds of Z-source
inverter mentioned above.
Summarizing the properties of all Zsource inverters and enumerating them in
the table below.
Table 2. AC output voltages conparison of 13 kinds of Z-source inverter in properties
Enhanced Z-source inverters
Traditional one
Asymmetric quasi one
Symmetric quasi one
Improved one
Enhanced one with auxiliary diodes
Enhanced one with auxiliary capacitors
Enhanced one with switching inductos
Enhanced one with embedded DC power
Enhanced one with tandem quasi-z network
Enhanced one with coupled quasi-z network
Isolated shoot-through one
Phase voltage/V
210
210
210
210
280
310
390
210
210
210
210
As can be seen from Table 1 and Figure 8,
traditional Z-source inverter has limited
boost capacity, larger and discontinuous
input current and higher capacitor voltage
during steady state. Aiming at overcome the
deficiencies of traditional Z-source inverter.
Other Z-source inverters show them in
different ways.
For reducing the capacitor voltage during
steady state, Z-source inverters in
Appendix 1 (h), (i), (j) have the lowest
capacitor voltages of all during steady state,
but two of them,enhanced DC power
embedded and enhanced quasi trandem Zsource inverter, have the discontinuous
input currents. Besides, these three
topologies costs increases.
Aiming at boost capacity, Z-source
inverters in Appendix 1(e), (f), (g) have the
better boost capacity. Thereinto, switching
inductive Z-source inverter has the best
boost capacity of all, but its input current is
discontinuous and it still has the incrush
Line voltage/V
350
350
350
350
470
520
580
350
350
350
350
input current/A
205 (discontinuous)
310 (continuous)
340 (discontinuous)
430 (discontinuous)
410 (continuous)
270 (continuous)
520 (discontinuous)
260 (discontinuous)
280 (discontinuous)
220 (continuous)
310 (continuous)
current at startup. What’s more, costs for
these three Z-source inverters increases
much.
As to improved Z-source inverters, quasi
Z-source inverters and shoot-through Zsource inverters. Appendix 1(b), (c), (d), (k)
show their simulation results that they have
lower capacitor voltages than traditional Zsource inverters and incrush currents does
not exist in them. In addition, these three
topologies are more economic than other
topologies. Last but not the least,the quality
of output voltage including output phase
voltage and output line voltage for isolated
shoot-through Z-source inverter is the best
due to its shoot-through zero vectors
inserted solely by IST-IGBT.
Overall, isolated shoot-through Z-source
inverter has the best property of all.
6. Conclusions
Aiming at the disadvantages of traditional
Z-source inverter, analysis and research are
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
conducted for the structural principle of
other kinds of Z-source inverters in this
paper. By comparing with other Z-source
inverters in their properties including boost
capacitor,capacitor voltage during steady
state, input current of three-phase inverter
bridge, no incrush current at startup, the
overall performance of isolated shootthrough Z-source inverter is the most
excellent. According to the conclusion of this
paper, isolated shoot-through Z-source
inverter will be used in permanent-magnet
direct-driven wind power system next due to
its wide application and limited localization
a) A traditional one
41
with photovoltaic power generation,wind
power generation and fuel cell technology
pullulating.
7. Acknowledgements
This work is supported by the National Natural
Science Foundation of China (Grant No.61263004)
and Gansu Province Natural Science Foundation
(Grant No.1212RJZA071).
8. Appendix 1
AC Output voltage of all kinds of Z-source
inverters are presented as follows:
b) An asymmetric quasi one
(c) A symmetric quasi one
(d) An improved one
(e) An enhanced one with auxiliary
diodes
(f) An enhanced one with auxiliary
capacitors
(g) An enhanced one with switching
Inductors
(h) An enhanced one with embedded DC
power
(i) An enhanced one with tandem quasi-z
network
42
ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
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ELECTROTEHNICĂ, ELECTRONICĂ, AUTOMATICĂ, 63 (2015), nr. 3
10. Biography
Hongsheng SU was born in Jingyuan (China), on November 1969.
He graduated from Lanzhou
Jiaotong University, Electrical
Engineering and Automation in
Lanzhou (China), in 2001.
He received the PhD degree in Power Systems
and Automation from Southwest Jiaotong
University of Chengdu (China).
He is Professor at the Lanzhou Jiaotong
University, in Lanzhou (China). His research
interests concern: Automatic control and
reliability engineering, System Security and
Reliability, grid-connected wind power system
based on Z-source inverter and its gridconnected control, Power Systems and Its
Automation.
Correspondence address: School of Automation
and Electrical Engineering, Lanzhou Jiaotong
43
University, Anning West Road No.88, Anning
District, Lanzhou, Gansu, China, 730070, e-mail:
lhj41333696@163.com
Hongjian LIN was born in Hai nan
(China), on November 1990.
He graduated from Lanzhou
jiaotong University, Electrical
Engineering and Automation in
Lanzhou (China), in 2013.
He received the bachelor’s degree in electrical
engineering and the automatization specialty
from Lanzhou jiaotong University of Lanzhou
(China). He is a postgraduate in Lanzhou
jiaotong University, in Lanzhou (China).
His research interests concern: grid-connected
wind power system based on Z-source inverter
and its grid-connected Control as well as power
system and Automation.