This document describes the simulation of a four port DC-DC converter. It includes an introduction, objectives, methodology, simulation models and results. The key modes of operation - SITO, SIDO, and DIDO - are modeled and simulated in Simulink. Simulation results show the converter maintains a constant output voltage despite varying loads and solar irradiance. Recommendations for future work include adding MPPT control and hardware implementation.

1. Project Member:
Rochak Silwal (070BEL334)
Sagar Bhatta (070BEL335)
Samar Baraiya (070BEL336)
Bimal Gyawali (070BEL349)
Simulation of a Four Port DC-DC
Converter
Date: August 11,2017
Project Supervisor:
Assoc. Prof. Dr. Netra Prasad Gyawali
Department of Electrical Engineering
IOE,PULCHOWK CAMPUS

2. Introduction
Scope
Objective
Methodology
Simulation Models and Results
Conclusion
Recommendations for future work
Reference
Table of Contents 2

3. Introduction
 A Four port DC-DC Converter consists of four ports, one port
connected to the input solar PV one port connected to the energy
storage system for charging and discharging and two ports for the
outputs.
 The converter utilizes the bidirectional port to charge and discharge
energy storing device (e.g.: Battery).
 The converter use the closed feedback control loop to make output
voltage constant.
3

4. Four Port DC-DC
Converter
DC
Output1
DC Output2
Vref
Vref
controller
controller
PWM
Generator
DETAIL BLOCK DIAGRAM 4

5. Scope
 Constant DC voltages are maintained at both output ports
irrespective of the change in solar irradiance and varying load
patterns.
Multiport converters can be used for relatively high-power
applications.
5

6. Objectives
 To simulate the different operational modes of four port
DC-DC converter in both open and closed loop system.
6

7. Methodology
Related Theory.
Simulink Modelling on MATLAB for three modes of DC-DC
converter : DIDO mode, SITO mode and SIDO mode.
Generation of gate signal for switches using open loop and closed
feedback loop on Simulink model.
Constant voltage output also during the Variation of Load pattern on
Resistance and solar irradiance.
Waveform Testing and Debugging.
Final Documentation.
7

8. 8
Circuit Configuration of the Proposed
Four-Port DC-DC converter
Switch S1 is used to boost the input voltage based on the operation of
boost converter.
Switches S2 and S3 are used to discharge and charge the battery
respectively.
Switch S4 is used to control the distribution of the total output power.

9. 1.SITO(Single Input Triple Output) Mode
Switch S2 is kept OFF in this operation mode.
Four different switching states in one switching period.
a. State I:
Operational Modes of Four-port
DC-DC converter
9

10.  Equations involved during this state:
b. State II:
 S3 is turned ON, and S1 and S4 are turned OFF.
 S1 is turned ON, and S3 and S4 are turned OFF. 10

11. Equations involved during this state:
c. State III:
 S1 and S3 are turned OFF, and S4 is turned ON.
 At the end of State I, S1 is turned OFF and the
operating state changes from State I to State II. 11

12. d. State IV:
 S1, S2, and S4 are turned OFF.
 The operating state is exactly the same as that in state IV
described during the DIDO mode.
 At the end of State II, S3 is turned OFF, and S4 is turned
ON.
12

13. 2. SIDO(single Input Double Output) Mode
a. State I:
 In this mode only battery supplies power to the loads.
 Switch S2 is kept ON and S3 is kept OFF in this operation mode.
 Three different switching states in one switching period.
13
 S1 is turned ON, and S4 is turned OFF.

14.  Equations involved during this state:
b. State II:
 At the end of State I, S1 is turned OFF and S4 is turned ON.
14

15.  Equations involved during this state:
c. State III:
 At the end of State II, S4 is turned OFF. and the operating
state changes from State II to State III.
 S1 and S4 are all turned OFF.
 Equations involved during this state:
15

16. 3.DIDO(Double Input Double Output) Mode
 Switch S3 is kept OFF during this operation mode.
 Four different states in one switching period.
a. State I:
 S1 and S2 are turned ON, and S4 is turned OFF.
 Equations involved during this state:
16

17. b. State II:
 At the end of State I, S2 is turned OFF and the operating
state changes from State I to State II.
S1 is still turned ON, and S4 is still turned OFF.
 Equations involved during this state:
17

18. c. State III:
 When S1 is turned OFF, and S4 is turned ON, the
operating state changes from State II to State III.
 Equations involved during this state:
18

19. d. State IV:
 At the end of State III, S4 is turned OFF and the operating
state changes from State III to State IV.
 S1, S2, and S4 are all turned OFF.
 Equations involved during this state:
19

20. Key Equations & Waveforms
SITO MODE SIDO MODE DIDO MODE
20

21. Relationship between output
voltages, Resistance Ratio and
duty cycles
SITO MODE SIDO MODE DIDO MODE
21

22. System Parameters for Simulation
System Parameters Values
Inductance ( L ) 1mH
Capacitance ( Cin) 33 µF
C1 200 µF
C2 200 µF
Switching Frequency ( fs ) 50 kHz
Simulation Time (for open loop) 0.6 sec
Simulation Time (for closed loop) 1 sec
Kp 0.001
ki 0.3
Saturation limit 0-0.8
22

23. Simulation Models and Results
Complete Simulation Model for SITO Mode
Different Operational Modes in Open Loop
23

24. Simulink Model for PWM Generator 24

25. Variation of Load Pattern in R1 25

26. Current and voltage waveforms
AT R2=20 Ω & R1=15Ω AT R2=20 Ω & R1=20Ω AT R2=20 Ω & R1=10Ω
vo1>vo2 Vo1<vo2
26
Vo1=vo2

27. Complete Simulation Model for SIDO Mode 27

28. Simulink Model for PWM Generator 28

29. Current and voltage waveforms
AT R2=20 Ω & R1=20Ω AT R2=20 Ω & R1=15Ω AT R2=20 Ω & R1=10Ω
vo1>vo2 Vo1<vo2Vo1=vo2
29

30. Complete Simulation Model for DIDO Mode
30

31. 31

32. AT R2=20 Ω & R1=20Ω AT R2=20 Ω & R1=15Ω AT R2=20 Ω & R1=10Ω
vo1>vo2 Vo1<vo2Vo1=vo2
32

33. Different Operational Modes in
Closed Loop
Complete Simulation Model for SITO Mode
33

34. Feedback Control Loop 34

35. Gate Signals Generated by PWM Generator 35

36. Waveforms of SOC, Current for Battery
And Inductor Current 36

37. voltage waveforms
AT R2=20 Ω & R1=20Ω
AT R2=25 Ω & R1=15Ω
AT R2=40 Ω & R1=10Ω
37

38. Complete Simulation Model for DIDO Mode 38

39. 39Feedback Control Loop

40. Gate Signals Generated by PWM Generator
40

41. voltage waveforms
AT R2=25 Ω & R1=15Ω
AT R2=30 Ω & R1=15Ω
AT R2=10 Ω & R1=10Ω
41

42. Complete Simulation Model for SIDO Mode 42

43. 43Feedback Control Loop

44. Gate Signals Generated by PWM Generator
44

45. Waveforms of SOC, Current for Battery
And Inductor Current 45

46. voltage waveforms
AT R2=25 Ω & R1=15Ω
AT R2=25 Ω & R1=30Ω
AT R2=20 Ω & R1=20Ω
46

47. 47
=
PV Voltage
(36 V)
Final Result
Battery Voltage
Vo1
Vo2
=
=
=
(48 V)
(64 V)
(48 V)

48. Conclusion
Two different constant DC voltages are maintained at both
output ports irrespective of the change in solar irradiance and
varying load patterns.
The circuit configuration and mechanism of different operational
modes of four port DC-DC converter have been analyzed in
both open and closed loop system.
Thus, two different DC loads working at varying voltages can be
operated individually or simultaneously which provides flexibility
to the system.
48

49. Recommendations for future work
MPPT function can be enabled in case of high load demand.
Hardware Implementation of four port DC-DC converter.
A Four Port DC-DC Converter can be used to supply the grid and
local load demand using inverter.
49

50. Reference
H. Wu, K. S. Ding, and Y. Xing, ‘‘Topology derivation of nonisolated
three-port DC-DC converters from DIC and DOC,’’ IEEE Trans. Power
Electron., vol. 28, no. 7, pp. 3297-3307, Jul. 2013.
Z. Qian, O. Abdel-Rahman, H. Al-Atrash, and I. Batarseh, ‘‘Modelling and
control of three-port dc/dc converter interface for satellite applications,’’
IEEE Trans. Power Electron., vol. 25, no. 3, pp. 637-647, Mar. 2010.
H. Wu, R. Chen, J. Zhang, Y. Xing, H. Hu, and H. Ge, ‘‘A family of three-
port half-bridge converters for a stand-alone renewable power system,’’
IEEE Trans. Power Electron., vol. 26, no. 9, pp. 2697-2706, Sep. 2011.
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51. THANK YOU!!!
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52. 52Page Numbers
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