DOI : 10.17577/IJERTV15IS043806
- Open Access
- Authors : Duc-Tuan Do, Van-Nghiep Dinh
- Paper ID : IJERTV15IS043806
- Volume & Issue : Volume 15, Issue 04 , April – 2026
- Published (First Online): 04-05-2026
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License:
This work is licensed under a Creative Commons Attribution 4.0 International License
Soft Switching Dual Active Bridge Converter for Charging System
Duc-Tuan Do
Dr, Department of Electrical Engineering Thainguyen University of Technology Thai Nguyen, Vietnam
Van-Nghiep Dinh
Dr, Department of Electrical Engineering Thainguyen University of Technology Thai Nguyen, Vietnam
AbstractThis paper presents a dual-active-bridge (DAB) structure enabling bidirectional power transmission. With its two-stage energy conversion, this converter offers several outstanding advantages for high-power applications, particularly its zero-voltage switching capability (ZVS). The research focuses on a detailed analysis of the converter structure, including its operating principle, soft switching characteristics, steady-state mode, output characteristics, and control strategy, with a focus on applications in electric vehicle charging infrastructure. Additionally, a simulation model of the DAB structure with a maximum power of 10 kW was built on the PSIM platform, and the obtained results are presented and analyzed comprehensively.
Keywords Soft Switching; Dual-active-bridge converter; Charging system; Constant voltage; Constant current.
-
INTRODUCTION
dual-active-bridge (DAB) converters are widely used in many applications [1]-[3], for example: battery and accumulator management systems [4], electric vehicles [5], semiconductor transformers [6]. The literature mainly analyzes the steady-state operating conditions as well as the mathematical description of the converter, but has not clearly analyzed the soft switching process (ZVS) as one of the factors contributing to improving the efficiency of the converter in the systems [7]-[10].
In [7], the low-order model of the DAB converter is presented with the advantage of very high large and small signal accuracy in common applications, simple, and easy to understand. However, this low-order model still has some
disadvantages, such as the accuracy may decrease under more complex operating conditions or modulation techniques.
between speed and overshoot, is more efficient than traditional PI controllers, and has strong noise immunity. However, this method still has some disadvantages, such as a more complex control strategy in design compared to traditional linear methods.
The DAB converter for fast-charging of battery electric vehicles is presented in [12]. However, the operating principle of the DAB converter is not discussed.
From the above analysis, to clarify the working process of the DAB converter for a charging system with different description methods, a clear analysis of the operating states is necessary, which provides the reader with a clearer understanding of the soft switching process of the switches in the converter.
-
OPERATION PRINCIPLE
-
Analysis of the operating states of the DAB converter
A dual-active-bridge converter for a charging system is shown in Fig.1. The operation principle of the DAB converter is eight states.
State 1 [t0-t1] at time t0 switches S1 and S4 start conducting, while switches S6 and S7 are conducting as shown in Fig 2(a). The output voltage of the primary transformer vT1 is positive, and the output voltage of the secondary transformer vT2 is negative, as shown in Fig 3. Therefore, a positive voltage is applied to the inductor L, the current through the inductor increases linearly and is given by (1).
The equivalent circuit model of the DAB converter is presented in document [8] with advantages such as: helping the reader to better understand the physical nature of the converter; convenient for analyzing all transfer functions; can accurately reproduce both the steady state and the large signal transient state of the original system. However, the inference of the model can be very complex, which is one of the disadvantages of this method.
In document [9]-[11], the energy-shaping-based model is presented with the advantages: it can resolve the conflict
i(1) V1 nV2
I1
I2
S1
S3
iT1
S5
S7
V1
vT1
L
vT2
V2
n:1
S2
S4
S6
S8
L
Ts i(t0 )
2
(1)
This research was financially supported by the Program of the Ministry of Education and Training of Vietnam under grant number B2024-TNA-17.
Fig. 1. Dual-active-bridge (DAB) converter for charging system.
I1
I2
S1
S3
iT1
S5
S7
V1
vT1
L
vT2
V2
n:1
S2
S4
S6
S8
I1
I2
S1
S3
iT1
S5
S7
V1
vT1
L
vT2
V2
n:1
S2
S4
S6
S8
I1
S1
C1
S3
Discharg iT1
vT1
Charg
C3
I2
S5
S7
Charg
V1
L
vT2
V2
S2
Discharg
n:1
S8
C2
S
4
S6
C4
(a)
(g)
(b)
(c)
(d)
(h)
I1
S1
S3
iT1
S5
V1
vT1
L
n:1
S2
S4
S6
S7 C5
Discharg
vT2 Charg
S8 C6
I2
C7
Charg
V2
Discharg
C8
I1
I2
S1
S3
iT1
S5
S7
V1
vT1
L
vT2
V2
n:1
S2
S4
S6
S8
Fig. 2. Equivalent circuit of the DAB converter: a) State 1, b) State 2, c) State 3, d) State 4, e) State 5, f) State 6, g) State 7, h) State 8.
I1
S1
V1
C1
S3
Charg iT1
vT1
Discharg
C3
I2
S5
S7
L
vT2
V2
S2
C2
S4
n:1 Charg S6 C4
S8
State 2 [t1-t2] at time t1 switches S6 and S7 begin to lock, while switches S1 and S4 are conducting as shown in Fig. 2(b). The energy accumulated in inductance L at time t1 charges capacitors C6 and C7, and capacitors C5 and C8 discharge. The output voltage on the secondary side of the transformer vT2 increases from -nV2 to +nV2 as shown in Fig. 3. If the energy accumulated in inductance L is sufficient to complete the charging and discharging process of the capacitors, then soft switching will be achieved when S5 and S8 begin to conduct at time t2. No energy is transferred from the primary to the secondary during this time.
I1
I2
S1
S3
iT1
S5
S7
V1
vT1
L
vT2
V2
n:1
S2
S4
S6
S8
State 3 [t2-t3] at time t2 switches S5 and S8 start conducting, while S1 and S4 are conducting as shown in Fig. 2(c). The output voltage on the primary side of the transformer vT1 is positive, and the output voltage on the secondary side of the transformer vT2 is also positive. If voltage V1 is greater than or equal to the voltage value of V2 applied back to the primary side of the transformer, then the current through inductor L increases linearly as shown in Fig. 3(a). Conversely, the current through inductor L decreases linearly as hown in Fig. 3(b). The current through inductor L is given by (2).
V1 nV2 1
(2)
i(2)
I1
S1
S3
iT1
S5
V1
vT1
L
n:1
S2
S4
S6
S7 C5
Charg vT2
Discharg
S8
C6
I2
C7
Discharg
V2
Charg
C8
L
2 Ts i(t2 )
(e)
(f)
State 4 [t3-t4] at time t3 switches S1 and S4 begin to lock at the most positive value of the current through the inductor, while switches S5 and S8 are conducting as shown in Fig. 2(d). The energy accumulated in inductor L at time t3 charges capacitors C1 and C4, and capacitors C2 and C3 discharge. The primary voltage of the transformer vT1 decreases from +V1 to – V1 as shown in Fig. 3. If the energy accumulated in inductor L is sufficient to complete the charging and discharging process of the capacitors, soft switching will be achieved when S2 and S3 begin to conduct at time t4. No energy is transferred from primary to secondary during this time.
t
t
2
t
t
t
t
i(1) i(2)
t
i(3) i(4)
t
t
t0 t1 t2 t3 t4 t5 t6 t7 t8
-nV2
nV2
2
-V1
S6 S7
S6 S7
V1
S5 S8
S2 S3
V1
2
S1 S4
State 5 [t4-t5] at time t4 while switches S5 and S8 are conducting, switches S2 and S3 start conducting, the equivalent circuit diagram is shown in Fig. 2(e). The output voltage on the primary side of the transformer vT1 is negative, the output voltage on the secondary side of the transformer vT2 is positive, as shown in Fig. 3. Therefore, the voltage applied to the inductor L is negative, the current through the inductor L decreases linearly and is given by (3).
vT1
i(3) V1 nV2
L
Ts i(t4 ) 2
(3)
n.vT2
iL
State 6 [t5-t6] at time t5 switches S5 and S8 begin to lock, while switches S2 and S3 are conducting as shown in Fig. 2(f). The energy accumulated in inductance L at time t5 charges capacitors C5 and C8, and capacitors C6 và C7 discharge. The output voltage on the secondary side of the transformer vT2 decreases from +nV2 to -nV2 as shown in Fig. 3. If the energy accumulated in inductance L is sufficient to complete the charging and discharging of the capacitors, then soft switching (ZVS) will be achieved when S6 and S7 begin to conduct at time t6. No energy is transferred from the primary to the secondary during this time.
i1 State 7 [t -t ] at time t switches S and S
are given control
6 7 6 6 7
i2
(a)
signals to open while switches S2 and S3 are conducting, the equivalent circuit diagram is shown in Fig. 2(g). The output voltage on the primary side of the transformer vT1 is negative, the output voltage on the secondary side of the transformer vT2 is also negative as shown in Fig. 3. If voltage V1 is greater than or equal to the voltage value of V2 applied back to the primary side of the transformer, then the current through inductor L decreases linearly as shown in Fig. 3(a). Conversely, the current through inductor L increases linearly as shown in Fig.
3(b). The current through inductor L is given by (4).
t
t
2
t
t
t
t
i(1)
i(2)
i(4)
t
i(3)
t
t
t0 t1 t2 t3 t4 t5 t6 t7 t8
-nV2
nV2
2
-V1
S6 S7
S6 S7
V1
S5 S8
S2 S3
V1
2
S1 S4
V nV 1
i(4) 1 2 Ts i(t6 )
(4)
L 2
vT1
n.vT2
iL
i1
i2
(b)
State 8 [t7-t8] at time t7 switches S2 and S3 begin to lock at the most negative value of the current through the inductor, while switches S6 and S7 are conducting as shown in Fig. 2(h). The energy accumulated in the inductor L at time t7 charges capacitors C2 and C3, and capacitors C1 and C4 discharge. The primary voltage of the transformer vT1 increases from -V1 to
+V1 as shown in Fig. 3. If the energy accumulated in the inductor L is sufficient to complete the charging and discharging process of the capacitors, soft switching will be achieved when S1 and S2 begin to conduct at time t8. No energy is transferred from the primary to the secondary during this time.
-
PI controller design
Although the performance of a PI controller depends on the algebraic selection system, it is still widely used in industry as a typical form of linear control. This is because PI controllers can achieve high accuracy standards, operate stably in noisy environments, and possess a simple structure that is easy to develop and implement. The PI controller is characterized by a pole at the origin along with a zero point, and can be represented as follows:
Fig. 3. Primary and secondary voltage waveforms of the transformer: a) when V1 nV2 and b) when V1 < nV2
(a)
(b)
Fig. 4. Bode plot of PI controller: a) Drawing using MATLAB software, b) Drawing using PSIM software.
TABLE I. Parameters of the Elements in the DAB Converter
V
1
f
1
L
V
2
I
2
P
o
R
load
n
750 V
100
kHz
58.6 µH
250 V
20A
5 kW
12.5
10/6
750 V
100
kHz
58.6 µH
500 V
20 A
10 kW
25
10/6
iLp
iLs
vT1
vT2
i2
i1
Fig. 5. Simulation results when V1 nV2
iLp
iLs
vT1
vT2
i1
i2
1 s
GPI (S) KPI PI ,z
s
(5)
In this case, PI,z is the angular frequency of the unique zero, and kPI is the DC gain.
Fig. 4 presents the Bode plot of the PI controller, constructed on the derived transfer function in (5), where the phase margin (PM) amplitude reaches 66° in the high-frequency region, the fc = 100 Hz (628 rad/s), Kpi =13.65, pi,z = 300 rad/s.
-
-
Simulation Results
To verify the working principle analysis, the authors used PSIM software to simulate the system. The simulation was
Fig. 6. Simulation results when V1 < nV2
performed in two cases: when V1 nV2 and when V1 < nV2. The circuit parameters are given in Table 1.
The primary and secondary currents in the transformer are shown at the top of Figs 5 and 6. Meanwhile, the primary and secondary voltages in the transformer are shown in the middle of Figs. 5 and 6. The top of Figs 5 and 6 presents the input and output current of the DAB converter.
v2
v2
i2
iload
iLp
iLs
D1
Fig. 7 shows the simulation results of CV mode when the load changes 25-50. Fig. 8 presents the simulation results of the CV mode when the input source changes from 800 to 700V. Fig. 9 depicts the simulation results of the CC mode when the load changes 16-14. Fig. 10 shows the simulation results of the CC mode when the input source changes from 800 to 700V
v2
i2
iload i
Lp
D1
iLs
Fig. 7. Simulation results of CV mode when the load changes 25-50
v2
iload
iLp
iLs
D1
Fig. 8. Simulation results of CV mode when the input source canges 800-700V.
v2
iload
iLp
iLs
D1
Fig. 9. Simulation results of CC mode when the load changes 16-14
Fig. 10. Simulation results of CC mode when the input source changes from 800 to 700V
-
CONCLUSIONS
This paper analyzes the working principle of a DAB converter applied to charging systems, specifically highlighting the soft switching range of switches. A simulation model of the converter was built and operated using PSIM software. The advantage of soft switching capability increases the converter's efficiency, thereby expanding its application range in fields such as energy storage systems, renewable energy systems like solar and wind power, and charging systems for electric vehicles, contributing to the gradual replacement of fossil fuel-powered vehicles with electric vehicles.
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