Design, Analysis, and Verification of a Decoupled Dual-Output Wireless Power Transfer System with a Constant Voltage Output and a Constant Current Output

Abstract

Wireless power transfer (WPT) is extensively utilized because of its isolation and convenience. However, WPT systems require different types of outputs in specific applications. The existing dual-receiving WPT system has disadvantages such as redundant compensation components, unnecessary cross-coupling interference, complex control circuits, and low space utilization. To address these shortcomings, this paper proposes a dual-output WPT system capable of delivering both constant voltage (CV) and constant current (CC) outputs simultaneously. The WPT system utilizes a special coil structure design, in which the DD coil is used as the transmitter coil and the first receiver coil, and the Q coil is used as the relay coil and the second receiver coil. In addition, the DD coil and the Q coil can achieve natural decoupling under alignment conditions. Consequently, the impact of the unnecessary cross-coupling within the system can be eradicated. Initially, the natural decoupling properties of the magnetic coupler are analyzed from a theoretical perspective. Subsequently, a mathematical model for the proposed WPT system is constructed. Through theoretical deductions, it is demonstrated that under the zero-phase-angle (ZPA) conditions, the system is capable of attaining a CC output at the first receiving side and a CV output at the second receiving side. Finally, a verification experimental prototype with a constant voltage output of 72 V and a constant current output of 2.5 A was built. The experimental results verified the accuracy of the previous theoretical analysis.

1. Introduction

As a convenient and efficient way of energy transmission, wireless power transmission (WPT) technology has shown great application potential and development background in the fields of consumer electronics [1,2], implantable medical devices [3,4], and industrial automation [5,6]. WPT systems with a constant current (CC) output function are widely used in fields such as LED driving [7,8,9], and WPT systems with a constant voltage (CV) output function are extensively utilized in fields such as mobile device power supply [10,11,12]. However, it has been difficult for the traditional single-output WPT system to meet the energy supply needs in complex scenarios. WPT systems with CC and CV dual outputs have gradually become a research hotspot. Unnecessary cross-coupling will affect the stability of the system [13,14]. Therefore, reducing or eliminating unnecessary cross-coupling between systems is the key to building a stable dual-output WPT system.

To solve the above problems, in [15,16], researchers proposed placing multiple receivers at a distance from one another to reduce the impact of cross-coupling. However, these methods greatly reduce the utilization of system space; moreover, the coupling interference cannot be completely eliminated. To satisfy more practical requirements and improve system space utilization, authors adopted the method of magnetic shielding to suppress coupling interference by adding metal insulators around the coil [17,18], but these methods increased the overall volume and weight of the system. Regarding the above problems, the method of using decoupling reactance is proposed in [19,20]. By connecting the two receiving sides together using passive components, the effects of cross-coupling can be eliminated. But these methods make it difficult for the two receiving sides of the system to move. In order to improve the system’s freedom of movement, Zhong et al. in [21], Gong et al. in [22], and Qi et al. in [23] eliminated the interference of cross-coupling by changing the system’s resonant frequency. However, these methods cause frequency bifurcation in the system, thereby reducing system stability and reliability.

Therefore, specially designed magnetic couplers are being introduced into dual-output WPT systems. Through an appropriate design of the structure of the coils and positions, the influence of coupling interference can be eliminated. A bucking planar coil (BPC) is proposed in [24]. By changing the BPC direction, the magnetic flux is canceled, thus achieving decoupling. However, the number of turns of the BPC requires a special design, which greatly reduces the design freedom of the system. Based on the above issues, a dual-output system is proposed in [25]. As the magnetic flux flowing through the two mutually perpendicular solenoid coils tends to zero, it effectively eliminates the influence of cross-coupling. Moreover, the integration of the two solenoid coils onto the ferrite plate of the first receiving side greatly enhances the utilization of the system’s space.

To address the drawbacks of the aforesaid dual-output WPT system, including insufficient space utilization in [15,16]; metal insulators and excessive compensation components leading to increased system weight and cost in [17,18,25]; the system’s receiving side finding it difficult to move in [19,20]; the system having poor stability in [21,22,23]; and the complex design approach to the magnetic coupler in [24], this paper proposes a WPT system with CC and CV dual outputs. The transmitter coil and the first receiver coil are composed of two DD coils, and the relay coil and the second receiver coil are made up of two Q coils. Meanwhile, the first receiver coil and the relay coil are combined onto the ferrite plate on the first receiving side. The transmitting side utilizes the S compensation topology, the first receiving side utilizes the LCL compensation topology, and the second receiving side utilizes the S compensation topology. The proposed dual-output WPT system has the advantages of high space utilization, fewer compensation elements, an efficient transmission process, high system stability, and a simple magnetic coupler structure. At the same time, under ZPA conditions, the system is capable of achieving dual outputs of CC and CV that are independent of the load.

The structure of the manuscript is as follows. In Section 2, the proposed magnetic coupler is presented, and a detailed analysis of its decoupling characteristics is carried out. Section 3 presents an analysis and a complete theoretical derivation of the proposed dual-output WPT system. Section 4 describes an experimental prototype with an output current of 2.5 A on the first receiving side and an output voltage of 72 V on the second receiving side. The practicality and correctness of the proposed dual-output WPT system are proven by the experimental results. In the end, Section 5 concludes this paper.

2. Theoretical Analysis of Magnetic Coupler

Figure 1 shows the magnetic flux distribution of the Q coil and the DD coil. The DD coil is composed of two D coils with opposite directions connected in series. When the excitation current is increased, the current directions of the two D coil are opposite. Therefore, the directions in which the two D coils generate magnetic fluxes are opposite to each other. Further, in the magnetic field, the magnetic flux caused by one coil being excited and passing through the other coil can be expressed as follows:

$$\psi =\int \int \overrightarrow{B}·d\overrightarrow{S}$$

(1)

where B is the magnetic field strength of the DD coil, and S is the surface area of the DD coil perpendicular to the magnetic field direction. From the above analysis, it is noticeable that the two segments of the magnetic flux created by the DD coil, which are perpendicular to the X-Y plane upward and perpendicular to the X-Y plane downward, cancel each other out when flowing through the Q coil. Similarly, the magnetic fluxes from the Q coils also cancel each other when flowing through the DD coil. Furthermore, the correlation between the magnetic flux and the mutual inductance of the Q coil and the DD coil can be stated as follows:

$$M={\displaystyle \frac{\psi }{I}}$$

(2)

Therefore, the mutual induction between the DD coil and the Q coil is approximately zero, which means that the two coils are naturally decoupled.

In summary, to eliminate the unnecessary cross-coupling in the dual-output WPT system, a magnetic coupler is proposed in this paper with a special decoupling design, as shown in Figure 2. The transmitter coil ${\mathit{L}}_P$ and the first receiver coil ${\mathit{L}}_S$ are both composed of DD coils; the relay coil ${\mathit{L}}_1$ and the second receiver coil ${\mathit{L}}_2$ are both composed of Q coils; and the relay coil ${\mathit{L}}_1$ and the first receiver coil ${\mathit{L}}_S$ are combined on the first receiving ferrite plate. Figure 3 shows the coupling effects between the proposed magnetic couplers. ${\mathit{M}}_1$, ${\mathit{M}}_2$, ${\mathit{M}}_3$, ${\mathit{M}}_4$, ${\mathit{M}}_5$, and ${\mathit{M}}_6$ are the mutual inductances between ${\mathit{L}}_P$ and ${\mathit{L}}_S$, ${\mathit{L}}_1$ and ${\mathit{L}}_2$, ${\mathit{L}}_P$ and ${\mathit{L}}_2$, ${\mathit{L}}_P$ and ${\mathit{L}}_1$, ${\mathit{L}}_S$ and ${\mathit{L}}_2$, and ${\mathit{L}}_S$ and ${\mathit{L}}_1$, respectively. According to the above analysis, the value of the mutual inductance between the Q coil and the DD coil is approximately zero. It can be easily concluded that the mutual inductances ${\mathit{M}}_3$, ${\mathit{M}}_4$, ${\mathit{M}}_5$, and ${\mathit{M}}_6$ are all approximately zero. In other words, the magnetic coupler that has been proposed is capable of eliminating the effects of unnecessary cross-coupling.

3. Theoretical Analysis of the Proposed Dual-Output WPT System

Shown in Figure 4 is the circuit architecture of the proposed WPT system with dual outputs. The direct current (DC) input voltage source is denoted as $U_D$. The high-frequency inverter (HFI) is composed of four MOSFETs (${\mathit{Q}}_1$–${\mathit{Q}}_4$). ${\mathit{C}}_1$, ${\mathit{C}}_2$, and ${\mathit{C}}_3$ are the compensation capacitors of the circuit. The parasitic resistances of every coil are represented by ${\mathit{R}}_P$, ${\mathit{R}}_S$, ${\mathit{R}}_1$, and ${\mathit{R}}_2$. ${\mathit{C}}_{f1}$ and ${\mathit{C}}_{f2}$ are the filter capacitors of the two receiving sides. The two battery loads are represented by ${\mathit{R}}_{B1}$ and ${\mathit{R}}_{B2}$. ${\mathit{U}}_{O1}$ and ${\mathit{U}}_{O2}$ are the two rectifier circuit input voltage phasors. ${\mathit{I}}_P$, ${\mathit{I}}_S$, ${\mathit{I}}_{O1}$, and ${\mathit{I}}_{O2}$ are the current phasors of each branch. The diodes (${\mathit{D}}_1$–${\mathit{D}}_4$) and (${\mathit{D}}_5$–${\mathit{D}}_8$) form two full-bridge rectifier circuits, the purpose of which is to convert the AC current phasors ${\mathit{I}}_{O1}$ and ${\mathit{I}}_{O2}$ into DC output currents ${\mathit{I}}_{B1}$ and ${\mathit{I}}_{B2}$, respectively. The relationship between the system DC input voltage ${\mathit{U}}_D$ and the root mean square (RMS) value of the AC output voltage phasors ${\mathit{U}}_{in}$ of the HFI can be expressed as follows [26]:

$$U_{in}={\displaystyle \frac{2\sqrt{2}}{\pi }}{U}_D$$

(3)

In the rectifier circuit, the connection between the RMS value of the current phasor ${\mathit{I}}_{O1}$ (voltage phasor ${\mathit{U}}_{O2}$) and the battery charging current $I_{B1}$ (charging voltage $U_{B2}$) can be expressed as follows [26]:

$${I_O}_1={\displaystyle \frac{\pi }{2\sqrt{2}}}{I}_{B1},{U_O}_2={\displaystyle \frac{2\sqrt{2}}{\pi }}{U_B}_2$$

(4)

To simplify the calculation, ${\mathit{Z}}_1$, ${\mathit{Z}}_2$, ${\mathit{Z}}_3$, ${\mathit{Z}}_4$, and ${\mathit{Z}}_5$ are the impedances of the passive components in each loop, respectively, defined as follows:

$$\left\{\begin{array}{ccc}{Z}_1=j\omega L_P+{\displaystyle \frac{1}{j\omega C_1}}& Z_2=j\omega L_S& Z_3={\displaystyle \frac{1}{j\omega C_2}}\\ Z_4=j\omega L_1& Z_5=j\omega L_2+{\displaystyle \frac{1}{j\omega C_3}}& \end{array}\right.$$

(5)

Figure 5 shows the equivalent circuit diagram of the system. For the purpose of facilitating further analysis, the internal resistance in the system is disregarded [27]. Based on Kirchhoff’s voltage law, the voltage expressions between different loops can be obtained as follows:

$$\left\{\begin{array}{c}{\mathit{U}}_{in}=Z_1{\mathit{I}}_P-j\omega M_1{\mathit{I}}_S\hfill \\ 0=-j\omega M_1{\mathit{I}}_P+\left(Z_2+Z_3\right){\mathit{I}}_S-Z_3{\mathit{I}}_{O1}\hfill \\ 0=-Z_3{\mathit{I}}_S+(Z_3+Z_4+R_{O1}){\mathit{I}}_{O1}-j\omega M_2{\mathit{I}}_{O2}\hfill \\ 0=-j\omega M_2{\mathit{I}}_{O1}+(R_{O2}+Z_5){\mathit{I}}_{O2}\hfill \end{array}\right.$$

(6)

The current phasors ${\mathit{I}}_P$, ${\mathit{I}}_{O1}$ and the voltage phasor ${\mathit{U}}_{O2}$ can be calculated as follows:

$$\left\{\begin{array}{c}{\mathit{I}}_P={\displaystyle \frac{{M_2}^2{\omega }^2{Z}_2+{M_2}^2{\omega }^2{Z}_3+R_{O1}{R}_{O2}{Z}_2+R_{O1}{R}_{O2}{Z}_3+R_{O2}{Z}_2{Z}_3+R_{O2}{Z}_2{Z}_4+R_{O2}{Z}_3{Z}_4}{A+B}}{\mathit{U}}_{in}\hfill \\ {\mathit{I}}_{O1}={\displaystyle \frac{j{M}_1\omega Z_3(Z_5+R_{O2})}{A+B}}{\mathit{U}}_{in}\hfill \\ {\mathit{U}}_{O2}=-{\displaystyle \frac{M_1{M}_2{\omega }^2{Z}_3}{A+B}}{\mathit{U}}_{in}\hfill \end{array}\right.$$

(7)

where $\mathit{A}$ and $\mathit{B}$ are expressed as follows:

$$\left\{\begin{array}{c}A={M_1}^2{M_2}^2{\omega }^4+{M_1}^2{\omega }^2{Z}_5(Z_3+Z_4)+Z_1{Z}_3{Z}_5(Z_3+Z_4)+{M_2}^2{\omega }^2{Z}_1{Z}_3\hfill \\ +Z_1{Z}_2{Z}_5(Z_3+Z_4)-Z_1{Z_3}^2{Z}_5+{M_2}^2{\omega }^2{Z}_1{Z}_2\hfill \\ B=R_{O1}{R}_{O2}({M_1}^2{\omega }^2+Z_1{Z}_2+Z_1{Z}_3)+R_{O1}(Z_1{Z}_2{Z}_5+{M_1}^2{\omega }^2{Z}_5+Z_1{Z}_3{Z}_5)\hfill \\ +R_{O2}({M_1}^2{\omega }^2{Z}_3+{M_1}^2{\omega }^2{Z}_4+Z_1{Z}_2{Z}_3+Z_1{Z}_2{Z}_4+Z_1{Z}_3{Z}_4)\hfill \end{array}\right.$$

(8)

Based on (5), (7), and (8), to ensure that ${\mathit{I}}_{O1}$ and ${\mathit{U}}_{O2}$ are independent of ${\mathit{R}}_{L1}$ and ${\mathit{R}}_{L2}$, A should be set to zero, that is,

$$\left\{\begin{array}{c}{M_1}^2{\omega }^2+Z_1{Z}_2+Z_1{Z}_3=0\hfill \\ Z_5=0\hfill \end{array}\right.$$

(9)

Substituting (8) and (9) into (7), the input current phasor ${\mathit{I}}_P$, output current phasor ${\mathit{I}}_{O1}$, and output voltage phasor ${\mathit{U}}_{O2}$ can be expressed as follows:

$$\left\{\begin{array}{c}{\mathit{I}}_P={\displaystyle \frac{{M_2}^2{\omega }^2{Z}_2+{M_2}^2{\omega }^2{Z}_3+R_{O1}{R}_{O2}{Z}_2+R_{O1}{R}_{O2}{Z}_3+R_{O2}{Z}_2{Z}_3+R_{O2}{Z}_2{Z}_4+R_{O2}{Z}_3{Z}_4}{Z_3{R}_{O2}({M_1}^2{\omega }^2+Z_1{Z}_2)}}{\mathit{U}}_{in}\hfill \\ {\mathit{I}}_{O1}={\displaystyle \frac{j{M}_1\omega }{{M_1}^2{\omega }^2+Z_1{Z}_2}}{\mathit{U}}_{in}\hfill \\ {\mathit{U}}_{O2}=-{\displaystyle \frac{M_1{M}_2{\omega }^2}{{M_1}^2{\omega }^2+Z_1{Z}_2}}{\mathit{U}}_{in}\hfill \end{array}\right.$$

(10)

In addition, in order to prevent the losses arising from the reactive circulating current, the system should implement a ZPA operation, that is, the imaginary part of the input impedance ${\mathit{Z}}_{in}$(=${\mathit{U}}_{in}$/${\mathit{I}}_P$) should be zero. From (10), the constraint condition for the system to implement a ZPA operation can be expressed as follows:

$$Z_2{Z}_3+Z_2{Z}_4+Z_3{Z}_4=0$$

(11)

Therefore, ${\mathit{Z}}_{in}$ can be expressed as follows:

$$Z_{in}={\displaystyle \frac{Z_3{R}_{O2}({M_1}^2{\omega }^2+Z_1{Z}_2)}{{M_2}^2{\omega }^2{Z}_2+{M_2}^2{\omega }^2{Z}_3+R_{O1}{R}_{O2}{Z}_2+R_{O1}{R}_{O2}{Z}_3}}$$

(12)

According to (5), (9), and (11), the value of the compensation capacitor ${\mathit{C}}_1$, ${\mathit{C}}_2$, and ${\mathit{C}}_3$ can be calculated as follows:

$$\left\{\begin{array}{c}{C}_1={\displaystyle \frac{-{L_S}^2}{{\omega }^2{M_1}^2\left(L_S+L_1\right)-{\omega }^2{L}_P{L_S}^2}}\hfill \\ C_2={\displaystyle \frac{L_S+L_1}{{\omega }^2{L}_1{L}_S}}\hfill \\ C_3={\displaystyle \frac{1}{{\omega }^2{L}_2}}\hfill \end{array}\right.$$

(13)

From (10) and (12), it can be seen that the output current ${\mathit{I}}_{O1}$ and the output voltage ${\mathit{U}}_{O2}$ are independent of the loads. Furthermore, ${\mathit{Z}}_{in}$ is purely resistive, which means that the system can achieve a ZPA operation.

4. Parameter Design and Simulation Verification

4.1. Parameter Design of the Proposed WPT System

During the practical design phase, several iteration procedures are required to finalize the circuit parameters for the dual-output WPT system. The flowchart for the parameter design of the proposed WPT system is illustrated in Figure 6.

Due to the parameter design approach mentioned above, the theoretical parameters of the proposed dual-output WPT system are presented in

Table 1. Theoretical parameters of the proposed dual-output WPT system.

Parameters	Value	Parameters	Value
f	85 kHz	E	60 V
$L_{\mathrm{P}}$	101.93 μH	$C_1$	48.02 $\mathrm{n}\mathrm{F}$
$L_{\mathrm{S}}$	101.32 μH	$C_2$	72.31 $\mathrm{n}\mathrm{F}$
$L_1$	92.97 μH	$C_3$	37.64 $\mathrm{n}\mathrm{F}$
$L_2$	93.15 μH	$M_1$	39.07 μH
$M_2$	44.51 μH	-	-

.

4.2. Simulation Experiment Verification of the Proposed Dual-Output WPT System

According to the detailed theoretical parameters designed in Table 1, the frequency sweeping curves of the output current ${\mathit{I}}_{B1}$, output voltage ${\mathit{U}}_{B2}$, and input impedance angle under different load conditions were obtained through MATLAB2020b simulation, as shown in Figure 7. As can be clearly seen from Figure 7, at an operating frequency of 85 kHz, the first receiving side and the second receiving side can obtain a CC output and a CV output, respectively. In addition, the system can attain a ZPA operation. From the simulation results shown above, the feasibility of the basic working characteristics of the propose dual-output WPT system is proven.

5. Experimental Verification

5.1. Magnetic Coupler Size Design

Due to the limitation of the actual installation space, the magnetic coupler dimensions in the WPT system require a rational design. The size of the magnetic coupler for the proposed dual-output WPT system is shown in Figure 8. The DD coil serves as the transmitter coil and the first receiver coil, and the Q coil serves as the relay coil and the second receiver coil. Among them, the relay coil and the first receiver coil are combined onto the ferrite plate on the first receiving side.

Table 2. Detailed parameters of the proposed dual-output WPT system’s magnetic coupler.

Parameter	Specific Information
Litz wire	400 strands with a diameter of 3.2 mm
transmitter DD coil	Size of 212 mm × 212 mm, 14 turns
first receiver DD coil	Size of 212 mm × 212 mm, 14 turns
relay Q coil	Size of 212 mm × 212 mm, 14 turns
second receiver Q coil	Size of 212 mm × 212 mm, 14 turns
Air gap	50 mm
transmitting side ferrite plate	Size of 212 mm × 212 mm × 2.5 mm
first receiving side ferrite plate	Size of 212 mm × 212 mm × 2.5 mm
second receiving ferrite side plate	Size of 212 mm × 212 mm × 2.5 mm

reveals the size parameters of the suggested magnetic coupler.

5.2. Experimental Prototype

To prove the correctness and rationality of the theoretical analysis for the proposed dual-output WPT system, a prototype for verification experiments with a CV output of 72 V and a CC output of 2.5 A was built, as shown in Figure 9. On the left side of the experimental platform is the DC input power supply ${\mathit{U}}_D$, which provides a stable DC energy input for the entire system and is directly connected to the HFI. The high-frequency AC output of the HFI is connected to the transmitting side series compensation capacitor ${\mathit{C}}_1$, which, together with the transmitting coil ${\mathit{L}}_P$, constitutes the transmitting end circuit. The magnetic coupler, as the core component of the system, is in the middle position in the figure. The first receiving side’s parallel compensation capacitor ${\mathit{C}}_2$ is connected to the first receiving coil ${\mathit{L}}_S$ and is located on the side close to the magnetic coupler. The second receiving side’s series compensation capacitor ${\mathit{C}}_3$ is connected to the second receiving coil ${\mathit{L}}_2$ and is located on the other side of the experimental platform. The two full-bridge rectifier circuits are located at different positions of the experimental platform. The load resistors $R_{B1}$ and $R_{B2}$ simulate the load in actual applications and are connected to the output ends of the two full-bridge rectifier circuits, respectively. The oscilloscope is used to monitor the electrical signals of key nodes in the system and is connected to each test point through a probe, as shown in the figure.

Table 3. Detailed parameters of the proposed dual-output WPT system.

Parameters	Value	Parameters	Value
f	85 kHz	E	60 V
$L_{\mathrm{P}}$	100.21 μH	$C_1$	47.33 $\mathrm{n}\mathrm{F}$
$L_{\mathrm{S}}$	103.11 μH	$C_2$	71.25 $\mathrm{n}\mathrm{F}$
$L_1$	93.34 μH	$C_3$	36.58 $\mathrm{n}\mathrm{F}$
$L_2$	94.65 μH	$M_1$	40.22 μH
$M_2$	43.79 μH	-	-

provides the comprehensive parameters of the proposed dual-output WPT system.

5.3. Experimental Results

In Figure 10, the output voltage and current of the HFI, the output current of the first receiving side, and the output voltage of the second receiving side are presented. In Figure 10a, the load resistance $R_{B1}$ of the first receiving side and the load resistance $R_{B2}$ of the second receiving side are 5 $\Omega$ and 30 $\Omega$, respectively. In Figure 10b, $R_{B1}$ and $R_{B2}$ are 10 $\Omega$ and 60 $\Omega$, respectively. It is evident that under different load conditions, the system is capable of attaining a CC output of 2.5 A and a CV output of 72 V. In addition, under different combinations of $R_{B1}$ and $R_{B2}$, the phase difference between ${\mathit{I}}_P$ and ${\mathit{U}}_{in}$ is always zero, which implies that the suggested system is capable of a ZPA operation.

When the load $R_{B1}$ changes from 5 $\Omega$ to 19 $\Omega$ in steps of 2 $\Omega$ and the load $R_{B2}$ changes from 30 $\Omega$ to 65 $\Omega$ in steps of 5 $\Omega$, 64 different combinations are measured, and the corresponding power distribution surface diagram is shown in Figure 11. It can be clearly seen that through a reasonable parameter design, the power distribution ratio of the first receiver and the second receiver can satisfy the complementary relationship and change evenly with the changes in the two loads.

The overall efficiency surface of the system under different load conditions is shown in Figure 12. The proposed dual-output WPT system achieved a maximum efficiency of 92.1% under the conditions of an $R_{B1}$ of 17 $\Omega$ and an $R_{B2}$ of 55 $\Omega$.

Same as the method in [28,29], the contribution of loss by each system’s component is obtained from the measured respective internal resistances and the measured resonant currents flowing through them. The resonant currents can be measured by an oscilloscope. The total power loss of the proposed system mainly includes the LCT loss, the compensation capacitors loss, the inverter loss, and the rectifier loss. Figure 13 shows that the losses generated by the two rectifiers and the magnetic coupler make up the vast majority of the total losses, with the rectifiers accounting for 32.59% and the magnetic coupler accounting for 45.28%. Using coils with high-quality factors can further cut down the losses of the magnetic coupler.

For the purpose of further illustrating the merits of the dual-output WPT system proposed in this paper, the results of this study in comparison with previous similar studies are shown in

Table 4. The results of this study in comparison with previous similar studies.

Proposed in	Ref. [15]	Ref. [19]	Ref. [20]	Ref. [21]	Ref. [22]	Ref. [23]	Ref. [25]	This Work
Space utilization	Low	Normal	Normal	Normal	Low	Low	High	High
Quantity of compensation components at the transmitting side	2	3	1	2	3	3	3	1
Quantity of compensation components at the receiving side	2	3	3	2	6	2	4	3
Complex control	Yes	No	Yes	Yes	Yes	Yes	No	No

and summarized as follows:

(1) In the dual-output WPT system proposed in this paper, the coupling interference is eliminated by rationally designing the magnetic coupler. Compared with [15,20,21,22,23], it does not require complex control strategies and is more suitable for practical applications.

(2) In this paper, a dual-output WPT system is proposed, characterized by its simple structure and fewer compensation components, which reduce the system’s weight and cost and provide greater benefits compared to [19,22,23,25].

(3) In the proposed system, the relay coil and the first receiver coil are combined onto the ferrite plate on the first receiving side. Compared with [15,19,20,21,22,23], it effectively improves the space utilization of the system and makes the system more compact.

6. Conclusions

In this paper, a dual-output WPT system with a special decoupling design is proposed. This system has the ability to realize CC and CV dual outputs that are not affected by a load under ZPA conditions. The proposed magnetic coupler can achieve natural decoupling between the DD coil and the Q coil, which can eliminate the influence of cross-coupling. At the same time, the relay coil and the first receiver coil are combined onto the ferrite plate on the first receiving side, which greatly enhances the space utilization of the system. Compared with the traditional dual-output system, the proposed system has the characteristics of fewer compensation components, a compact design, elimination of cross-coupling interference, and simple control. Therefore, the system can be suited for various practical scenarios including electric vehicles and medical devices.