In this paper, the simulation and stability of multi-port DC-DC converter will be presented. Traditional DC-DC converter topologies interface two power terminals: a source and a load. The construction of diverse and flexible power management and distribution systems with such topologies is governed by a tight compromise between converter count, efficiency, and control complexity. The DC-DC converter may be considered as an advanced environment-friendly electronic conversion system, since it is a greenhouse emission eliminator. By utilizing the advancement of these renewable energy sources, we minimize the use of fossil fuel and thus contribute to a cleaner and pollution-free environment. Finally, comparison between the averaged model and the actual switching converter model is been studied

Ahmad Harb

Issa Batarseh

Samir Al Sharif

Zhijun Qian

Journal of Measurements in Engineering

English

 72 JOURNAL OF MEASUREMENTS IN ENGINEERING. JUNE 2014, VOLUME 2, ISSUE 2  
44. Simulation and stability of multi-port DC-DC 
converter 
Samir Al Sharif1, Zhijun Qian2, Ahmad Harb3, Issa Batarseh4 
1Electrical Engineering Department at Taibah University, Madinah, KSA 
2, 4Electrical Engineering and Computer Science Dept. at University of Central Florida, Orlando, FL, USA 
3Energy Engineering Department at German Jordanian University, Amman, Jordan 
3Corresponding author 
E-mail: 3aharb48@gmail.com 
(Received 3 December 2013; received in revised form 15 April 2014; accepted 27 April 2014) 
Abstract. In this paper, the simulation and stability of multi-port DC-DC converter will be 
presented. Traditional DC-DC converter topologies interface two power terminals: a source and a 
load. The construction of diverse and flexible power management and distribution systems with 
such topologies is governed by a tight compromise between converter count, efficiency, and 
control complexity. The DC-DC converter may be considered as an advanced 
environment-friendly electronic conversion system, since it is a greenhouse emission eliminator. 
By utilizing the advancement of these renewable energy sources, we minimize the use of fossil 
fuel and thus contribute to a cleaner and pollution-free environment. Finally, comparison between 
the averaged model and the actual switching converter model is been studied. 
Keywords: multi-port DC-DC converter, simulation. 
1. Introduction 
Integrated power electronic converters are important for systems that are capable of harvesting 
power from solar sources, fuel cells, and mechanical vibrations used in applications such as 
communication repeater stations, sensor networks, hybrid electric vehicles and laptops. 
Furthermore, multi-terminal interface is important since such systems require mass energy storage 
to compensate for the mismatch between the sourcing and loading power patterns over a regular 
operational cycle. For example, a solar system, consisting of a regulated load interfaced to a solar 
array, requires storage batteries for storing excess power and re-supplying it to the load when 
needed. Limited research activities on multi-terminal converter topologies have been reported in 
open literature, with very few commercially installed systems in industry. Interesting ideas for 
multi-sourced converters with multiple control variables have been introduced based on the 
flyback (buck-boost) converter topology. As shown in Fig. 1, a three-port dc-dc converter has 
been proposed in [20] to have bidirectional and also ZVS capabilities. It is based on full bridge 
cells that allow bidirectional power flow in each port. Such a configuration facilitates the matching 
of different voltage levels in the overall system by the multi-winding transformer. The transformer 
design was optimally performed in order to incorporate the leakage inductances as required by the 
topology to affect the phase shift control. Furthermore, for the three-port converter, a dual-PI-loop 
based control strategy is proposed to achieve constant output voltage and power flow management. 
This topology has been verified through a hybrid fuel cell and super-capacitor system to improve 
the slow transient response of a fuel cell stack. 
As shown in Fig. 2, a half-bridge version of this multi-port converter has been proposed in [12] 
for a fuel cell and super-capacitor generation system. The topology comprises a high-frequency 
three-winding transformer and three half-bridge cells, one of which is a boost half-bridge. The 
converter is controlled by phase shift, which achieves the primary power flow control, in 
combination with pulse width modulation (PWM). With the PWM control it is possible to reduce 
the rms loss and to extend the zero-voltage switching operating range to the entire phase shift 
region. A control scheme based on multiple PI regulators manages the power flow, regulates the 
output, and adjusts the duty cycle in response to the varying voltage on the port. Compared with 
full-bridge based topology, it applies half input voltage to the transformer and adopts fewer 
44. SIMULATION AND STABILITY OF MULTI-PORT DC-DC CONVERTER.  
SAMIR AL SHARIF, ZHIJUN QIAN, AHMAD HARB, ISSA BATARSEH 
 © JVE INTERNATIONAL LTD. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 73 
switches to process the power. For this reason, the half-bridge based multi-port topology is more 
suitable for low to medium power applications.  
 
Fig. 1. Three-port full-bridge DC-DC converter 
 
Fig. 2. Three-port half-bridge DC-DC converter 
As shown in Fig. 3, a similar topology has been used in [18] to interface hybrid energy storage 
as the battery and ultra-capacitor to achieve high overall performance. It can interface current 
source input, and can achieve ZVS for all six main switches by the phase shift control. This paper 
also discusses the power topology operation and the control aspects of dynamic characteristics 
analysis and the control strategy. 
The above-mentioned topologies adopt a multi-winding transformer to couple different power 
ports. Therefore, all ports are fully isolated with each other. However, some applications do not 
require all ports to be fully isolated, and the share of some grounds may allow less component and 
fewer transformer windings. As shown in Fig. 4, a topology in [10] is intended for future hybrid 
and fuel cell vehicles which may have three voltage nets: 14 V, 42 V and high voltage (> 200 V) 
buses. A soft-switched DC-DC converter using four switches has been proposed to interconnect 
these three nets. Its power flow management is based on a combined duty ratio and phase shift 
control, but soft-switching range is limited when the phase shifts between two very different 
voltage levels to have large current swing. 
44. SIMULATION AND STABILITY OF MULTI-PORT DC-DC CONVERTER.  
SAMIR AL SHARIF, ZHIJUN QIAN, AHMAD HARB, ISSA BATARSEH 
74 JOURNAL OF MEASUREMENTS IN ENGINEERING. JUNE 2014, VOLUME 2, ISSUE 2  
 
Fig. 3. Triple-half-bridge bidirectional DC-DC converter 
 
Fig. 4. Reduced part, triple-half-bridge bidirectional DC-DC converter 
To sum up, these multi-port topologies can be classified into two categories: non-isolated 
topologies [1-10] and isolated topologies [10-23]. Non-isolated multi-port converters usually take 
the form of buck, boost, buck-boost, etc, featuring compact design and high power density; 
isolated multi-port converters using bridge topologies have the advantages of flexible voltage 
levels and high efficiency since high frequency transformer and soft-switching techniques are used. 
Also, isolation may be required for certain critical applications. 
 
Fig. 5. Three-port proposed DC-DC converter topology 
2. Analysis, modeling and control of multi-port DC-DC converter proposed topology 
In this paper, the three-port DC-DC Converter, shown in Fig. 5, is proposed. It is a modified 
version of the PWM half bridge converter that includes three basic circuit stages within a 
constant-frequency switching cycle to provide two independent control variables. The switching 
44. SIMULATION AND STABILITY OF MULTI-PORT DC-DC CONVERTER.  
SAMIR AL SHARIF, ZHIJUN QIAN, AHMAD HARB, ISSA BATARSEH 
 © JVE INTERNATIONAL LTD. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 75 
sequence shown in the figure ensures a clamping path for the energy of the leakage inductance of 
the transformer at all times. This energy is further utilized to achieve zero-voltage switching (ZVS) 
for all primary switches for a wide range of source and load conditions. 
2.1. Analysis of DC-DC multi-port converter 
Full-bridge converters are more suitable for higher power applications, typically above 1 kW. 
Applying the same concept of dual use of the phase legs, a three-terminal topology can be derived 
from the full-bridge circuit. The bidirectional terminal of this topology is controlled by changing 
the duty cycle of the phase legs to achieve the target voltage ratio. The two phase legs need to 
maintain equal duty cycles. The load terminal is controlled by phase shifting the driving 
waveforms of these two phase legs relative to each other, just like the mother ZVT full-bridge 
topology. 
The steady-state voltage relationships, assuming CCM operation of the load filter inductor, are 
given by: 
௕ܸ௜ = ܦ ௜ܸ௡,				
଴ܸ = 2݊߶ ௜ܸ௡, 
given that 0 ൑ ߶ ൑ min	ሺܦ, 1 − ܦሻ, where: ܦ is the duty cycle of each phase leg, ߶ is the phase 
shift between the two phase leg waveforms. 
 
a) 
 
b) 
Fig. 6. Simulation waveforms a) basic switching waveforms b) terminal voltages and currents 
This topology operates as boost-derived push-pull converter when supplying energy from the 
bidirectional terminal to the load. This topology is thus an attractive alternative for low voltage 
storage devices since it saves on the turns-ratio of the transformer and simplifies its design. The 
center-tapped transformer and the bidirectional terminal inductor assembly is suitable for being 
wound on a single core, in an integrated magnetic fashion. 
Simulation results are shown in Fig. 6. Again, control was adjusted at ݐ =	5 ms and at 10 ms 
to independently control the voltages of the load and bidirectional terminals. Converter ability to 
handle negative current in the bidirectional terminal was verified. 
3. Small signal average model 
The small signal model is tailored for deriving multi-port DC-DC converters under different 
44. SIMULATION AND STABILITY OF MULTI-PORT DC-DC CONVERTER.  
SAMIR AL SHARIF, ZHIJUN QIAN, AHMAD HARB, ISSA BATARSEH 
76 JOURNAL OF MEASUREMENTS IN ENGINEERING. JUNE 2014, VOLUME 2, ISSUE 2  
modes of operation. It would be difficult to define different modes since there are various modes 
of operation. After we define the model therefore, a competitive method is used to realize smooth 
and seamless mode transition. 
3.1. Analysis of multi-port DC-DC converter modeling  
In this section we derive small signal transfer functions of the proposed DC-DC converter 
based on the state equations for four energy storage elements during each circuit stage. The storage 
elements are battery capacitor ܥଵ , the transformer magnetizing inductance ܮ௠ , the output 
inductance ܮ௢, and the output capacitance ܥ௢. In Fig. 7 the three main circuit stages are shown. 
 
Fig. 7. Basic waveforms of the multi-port converter 
In stage I (ݐ଴ − ݐଵ), S1 is gated ON and the state equation is derived as follows: 
ە
ۖۖ
ۖ
۔
ۖۖ
ۖ
ۓܥଵ ⋅
݀ݒ஼ଵ
݀ݐ =
−ݒ஼ଵ
ܴ௕ + ݅௅௠ + ݊ ⋅ ݅௅௢,
ܮ௠ ⋅
݀݅௅௠
݀ݐ = −ݒ஼ଵ,
ܮ௢ ⋅
݀݅௅௢
݀ݐ = ݒ஼ଵ ⋅ ݊ − ݒ௢,
ܥ௢ ⋅
݀ݒ௢
݀ݐ = ݅௅௢ −
ݒ௢
ܴ .
	
While stage II (ݐଵ − ݐଶ), S2 is gated ON, the state equation is found to be as follows: 
ە
ۖۖ
ۖ
۔
ۖۖ
ۖ
ۓܥଵ ⋅
݀ݒ஼ଵ
݀ݐ =
−ݒ஼ଵ
ܴ௕ + ݅௅௠ + ݊ ⋅ ݅௅௢,
ܮ௠ ⋅
݀݅௅௠
݀ݐ = ݒ஼ଶ − ݒ஼ଵ,
ܮ௢ ⋅
݀݅௅௢
݀ݐ = ሺݒ஼ଶ − ݒ஼ଵሻ ⋅ ݊ − ݒ௢,
ܥ௢ ⋅
݀ݒ௢
݀ݐ = ݅௅௢ −
ݒ௢
ܴ .
	
44. SIMULATION AND STABILITY OF MULTI-PORT DC-DC CONVERTER.  
SAMIR AL SHARIF, ZHIJUN QIAN, AHMAD HARB, ISSA BATARSEH 
 © JVE INTERNATIONAL LTD. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 77 
In stage III (ݐଶ − ܶ + ݐ଴), S3 is gated ON, the state equation is derived as follows: 
ە
ۖۖ
ۖ
۔
ۖۖ
ۖ
ۓܥଵ ⋅
݀ݒ஼ଵ
݀ݐ =
−ݒ஼ଵ
ܴ௕ ,
ܮ௠ ⋅
݀݅௅௠
݀ݐ = 0,
ܮ௢ ⋅
݀݅௅௢
݀ݐ = −ݒ௢,
ܥ௢ ⋅
݀ݒ௢
݀ݐ = ݅௅௢ −
ݒ௢
ܴ .
	
Let us add small perturbation ݔො to state ܺ, one can found: 
ݔ = ܺ + ݔො,			݀ = ܦ + መ݀, ݒ = ܸ + ݒො,
where መ݀ ≪ ܦ, ݒො ≪ ܸ. 
Now, apply the averaging method to the three state equations and neglect second order terms, 
one obtains: 
ە
ۖۖ
ۖ
۔
ۖۖ
ۖ
ۓܥଵ ⋅
݀ݒො஼ଵ
݀ݐ =
−ݒො஼ଵ
ܴ௕ + ଓሶ
መ௅௠ሺܦଵ + ܦଶሻ + ݊ ⋅ ଓሶመ௅௢ሺܦଶ − ܦଵሻ + ܫ௅௠൫ መ݀ଵ + መ݀ଶ൯ +
݊ ∙ ଴ܸ ∙ ൫ መ݀ଶ + መ݀ଵ൯
ܴ ,
ܮ௠ ⋅
݀ଓሶመ௅௠
݀ݐ = −ݒො஼ଵሺܦଵ + ܦଶሻ −
൫ መ݀ଵ + መ݀ଶ൯ ∙ ܦଶ ∙ ௜ܸ௡
ሺܦଵ + ܦଶሻ +
መ݀ଶ ∙ ௜ܸ௡,
ܮ௢ ⋅
݀ଓሶመ௅௢
݀ݐ = ݒො஼ଵ ⋅ ݊ ∙ ሺܦଵ + ܦଶሻ − ݒො଴ +
൫ መ݀ଵ − መ݀ଶ൯ ∙ ݊ ∙ ܦଶ ∙ ௜ܸ௡
ሺܦଵ + ܦଶሻ +
መ݀ଶ ∙ ݊ ∙ ௜ܸ௡,
ܥ௢ ⋅
݀ݒො௢
݀ݐ = ଓሶመ௅௢ −
ݒො௢
ܴ .
 
Afterwards, the system can be represented in state-space matrix form: 
݀ܺ
݀ݐ = ܣ ∙ ܺ + ܤ ∙ ܷ,	 ܻ = ܫ ∙ ܺ,
where: ܺ represents the state variables ஼ܸଵ, ݅௅௠, ݅௅௢ and ௢ܸ, ܷ represents the control inputs ݀ଵ and 
݀ଶ, ܻ represents the system outputs, and ܫ stands for the identity matrix: 
ܣ =
ۏ
ێ
ێ
ێ
ێ
ێ
ێ
ێ
ۍ − 1ܴ௕ ∙ ܥଵ
ሺܦଵ + ܦଶሻ
ܥଵ
݊ ∙ ሺܦଵ + ܦଶሻ
ܥଵ 0
− ሺܦଵ + ܦଶሻܮ௠ 0 0 0
݊ ∙ ሺܦଵ − ܦଶሻ
ܮ௢ 0 0 −
1
ܮ௢
0 0 − 1ܥ௢ −
1
ܴ ∙ ܥ௢ے
ۑ
ۑ
ۑ
ۑ
ۑ
ۑ
ۑ
ې
,			ܺ = ൦
ݒො஼ଵ
ଓ௅̂௠
ଓ௅̂௢
ݒො௢
൪, 
44. SIMULATION AND STABILITY OF MULTI-PORT DC-DC CONVERTER.  
SAMIR AL SHARIF, ZHIJUN QIAN, AHMAD HARB, ISSA BATARSEH 
78 JOURNAL OF MEASUREMENTS IN ENGINEERING. JUNE 2014, VOLUME 2, ISSUE 2  
ܤ =
ۏ
ێ
ێ
ێ
ێ
ێ
ێ
ۍ ܫ௅௠ − ݊ ∙ ௢ܸ/ܴܥଵ
ܫ௅௠ + ݊ ∙ ௢ܸ/ܴ
ܥଵ
− ܦଶ ∙ ௜ܸ௡ሺܦଵ + ܦଶሻ ∙ ܮ௠
ܦଵ ∙ ௜ܸ௡
ሺܦଵ + ܦଶሻ ∙ ܮ௠
݊ ∙ ܦଶ ∙ ௜ܸ௡
ሺܦଵ + ܦଶሻ ∙ ܮ௢
݊ ∙ ܦଵ ∙ ௜ܸ௡
ሺܦଵ + ܦଶሻ ∙ ܮ௢
0 0 ے
ۑ
ۑ
ۑ
ۑ
ۑ
ۑ
ې
,			ܷ = ൤݀ଵ݀ଶ൨. 
We use MATLAB’s Simulink to compare the averaged model with the actual switching 
converter model as shown in Fig. 8. 
Step
x' = Ax+Bu
 y = Cx+Du
State-Space model
d1
d2
1
2
3
PWM block
s1
s2
s3
Vb
Io
Vo
PLECS
Circuit
Converter Model
D2
D1
v b
v o
v b
v o
io
io
 
a) 
 
b) 
Fig. 8. a) Model comparison due to duty cycle step,  
b) Averaged model and circuit model comparison for battery-regulation mode 
4. Conclusion 
The simulation and stability of a multi-port DC-DC convertor is being presented. The DC-DC 
converter is considered as an advanced The DC-DC converter may be considered as an advanced 
environment-friendly electronic conversion system, since it is a greenhouse emission eliminator. 
By utilizing the advancement of these renewable energy sources, we minimize the use of fossil 
fuel. At the end a cleaner, pollution free environment is achieved. So, a comparison between the 
averaged model and the actual switching converter model has been made. The study shows that 
44. SIMULATION AND STABILITY OF MULTI-PORT DC-DC CONVERTER.  
SAMIR AL SHARIF, ZHIJUN QIAN, AHMAD HARB, ISSA BATARSEH 
 © JVE INTERNATIONAL LTD. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 79 
the simulations, for both actual and averaged models, are nearly identical. 
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Simulation and stability of multi-port DC-DC converter

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Simulation and stability of multi-port DC-DC converter

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