Volume 17 Issue 4
Jan.  2020
Article Contents

Zhi-Hao Guo, Shi-Er Dong. Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems[J]. Journal of Electronic Science and Technology, 2019, 17(4): 291-299. doi: 10.1016/j.jnlest.2020.100009
Citation: Zhi-Hao Guo, Shi-Er Dong. Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems[J]. Journal of Electronic Science and Technology, 2019, 17(4): 291-299. doi: 10.1016/j.jnlest.2020.100009

Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems

doi: 10.1016/j.jnlest.2020.100009
Funds:  This work was supported by the National Natural Science Foundation of China under Grant No. 51574198 and Nanchong City 2018 Special Fund for City-School Cooperation under Grant No. 18SXHZ0021
More Information
  • Author Bio:

    Zhi-Hao Guo was born in Sichuan in 1993. In 2017, he received his B.S. degree in civil engineering from Southwest Petroleum University, Chengdu. He is currently pursuing his M.S. degree with the the School of Civil Engineering and Geomatics, Southwest Petroleum University. His main research interests are civil engineering housing design, steel structure design, and radio transmission

    Shi-Er Dong was born in Sichuan in 1963. He obtained his M.S. degree from Southwest Petroleum University in 1989. Now he is a professor with the School of Civil Engineering and Geomatics, Southwest Petroleum University. His research interests include structrural engineering and heating & gas supply, ventilating, and air conditioning engineering

  • Corresponding author: Z.-H. Guo and S.-E. Dong are with the School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu 610500 (e-mail: 2207522643@qq.com; ds_xyz@sina.com).
  • Received Date: 2018-11-20
  • Rev Recd Date: 2019-08-07
  • Publish Date: 2019-12-01

通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Figures(10)  / Tables(1)

Article Metrics

Article views(105) PDF downloads(26) Cited by()

Related
Proportional views

Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems

doi: 10.1016/j.jnlest.2020.100009
Funds:  This work was supported by the National Natural Science Foundation of China under Grant No. 51574198 and Nanchong City 2018 Special Fund for City-School Cooperation under Grant No. 18SXHZ0021
  • Author Bio:

  • Corresponding author: Z.-H. Guo and S.-E. Dong are with the School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu 610500 (e-mail: 2207522643@qq.com; ds_xyz@sina.com).

Abstract: As different power has its own receivers, this paper analyzes and designs a multiple-receiver wireless power transfer (WPT) system systematically. The equivalent circuit model of the system is established to analyze the key parameters including transmitter power, receiver power, transmission efficiency, and each receiver power allocation. A control circuit is proposed to achieve the maximum transmission efficiency and transmitter power control and arbitrary receiver power allocation ratios for different receivers. Through the proposed control circuit, receivers with different loads can allocate appropriate power according to its power demand, the transmitter power and system efficiency do not vary with the change of the number of receivers. Finally, this control circuit is validated using a 130-kHz WPT system with three receivers whose power received is 3:10:12, and the overall system efficiency can reach as high as 55.5%.

Zhi-Hao Guo, Shi-Er Dong. Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems[J]. Journal of Electronic Science and Technology, 2019, 17(4): 291-299. doi: 10.1016/j.jnlest.2020.100009
Citation: Zhi-Hao Guo, Shi-Er Dong. Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems[J]. Journal of Electronic Science and Technology, 2019, 17(4): 291-299. doi: 10.1016/j.jnlest.2020.100009
  • Wireless power transfer (WPT) has shown great advantages and convenience over the conventional charging method for industrial machines and consumer electronic devices[1]-[3]. In the construction project, the route layout is not only complex and needs to be repaired, but also faces the aging problem, which consumes huge financial and human resources, however, this situation can be easily solved by the form of wireless transmission. On the other hand, short-circuit lines, exposed sockets, and electrical equipment failure increase the possibility of fire, causing economic losses and casualties, so the employment of radio transmission in residential construction is extraordinary. Magnetic resonance coupling WPT is proposed for different power of different electrical appliances, which makes it possible to supply power from one receiver to several receivers. With a magnetic resonance coupling WPT system, many scholars have made significant contributions in different areas, such as high-efficiency power amplifiers and inverter design[4]-[6], coupled circuit model analysis[7]-[9], optimum load matching design[10]-[12], and high-efficiency rectifier regulator circuit design[13]. In a multiple-receiver system, some scholars always concern the system efficiency but ignore the power distribution to different receivers[14]-[16] which are usually in different charging positions and have different power requirements. If only blindly pursuing efficiency, the received power for receivers can not well matched their demand, and some electrical devices will be unstable, then the entire system will be in a terrible working condition. Therefore, the multiple-receiver WPT system still needs more extensive research.

    This paper is based on a one-receiver WPT system to analyze the load how to affect the system efficiency, point out there is an optimal load on the system to maximize the efficiency, and propose a match method that allows any load to work at an optimal efficiency condition. And then this paper extends the circuit-model-based analysis and theory from a one-receiver system to a one-transmitter multiple-receiver system. The variation of transmitter power and system efficiency at different numbers of receivers and the power allocation at each receiver are studied. This paper proposes a method which can achieve any power allocation ratio at the receivers, and also the transmitter power and WPT system efficiency can remain unchanged as the number of receivers increases. Finally, an experiment working at 130 kHz is implemented. The result shows that the proposed control circuit for the transmitter and receivers can indeed effectively control the transmitter power, receiver power allocation, and transmission efficiency.

  • The circuit model and equivalent circuit model for the one-receiver WPT system are respectively shown in Figs. 1 (a) and (b). There is one transmitter (TX) and one receiver (RX). RX is coupled to TX with mutual inductance M. The coupling coefficient ${K_{i,j}}$ between two coils is

    Figure 1.  One-receiver WPT system: (a) circuit model and (b) equivalent circuit model.

    In Fig. 1 (a), Lt (or L1) and Ct (or C1) represent the corresponding inductance and capacitance of TX (or RX), respectively. Rt and R1 represent the parasitic resistances of the corresponding coil. Rs is the source resistance and RL is the equivalent load resistance.

    Establishing the Kirchhoff’s voltage law (KVL) equation of Fig. 1 (a), the following equations can be obtained:

    where Zt,t=Rs+Rt+jXt and Z1,1=RL+R1+jX1 represent the self-impedance of the transmitter circuit and receiver circuit, respectively. It is the current of the transmitter. I1 is the current of the receiver. $\omega $ is the operating angular frequency. ${M_{t,1}}$ is the mutual inductance between the transmitter and receiver. Vs is the power supply voltage of the transmitter. Xt is the equivalent reactance of the transmitter. X1 is the equivalent reactance of the receiver.

    Solving (1), the obtained results are as

    where Zt,1 and Zf,1 are the reflected impedance in the transmitter circuit and receiver circuit, respectively, due to the mutual inductance M. ${R_{t,1}}$ and ${R_{f,1}}$ are the real parts of Zt,1 and Zf,1 respectively, representing the reflected resistance. ${X_{t,1}}$ and ${X_{f,1}}$ are the imaginary parts of Zt,1 and Zf,1, representing the reflected reactance.

    Equation (8) is the input impedance in the source. When the WPT system is resonant, ${\rm{j}}\omega {L_t} - {1 / {{\rm{j}}\omega {C_t}}} = {X_t} = 0$ and ${\rm{j}}\omega {L_1} - {1 / {{\rm{j}}\omega {C_1}}} = {X_1} = 0$.

    The relationships between various parameters can be known from (9) to (13), and there is an optimal load RL-opt, which can make the WPT system maximize efficiency. And in (13a), ${k_{t,1}}$ is the coupling coefficient between the transmitter and receiver.

    Fig. 2 (a) shows a multiple-receiver (n-receiver) WPT system and Fig. 2 (b) is the equivalent circuit. The analysis is similar to that of one receiver. An n-order KVL equation can be applied to get the relationships of the n receivers and the transmitter. In the actual operating condition, the distance between the receivers is always adequately large. Therefore the cross coupling between the receivers can be neglected, ${M_{i,j}} = 0{\rm{ }}\left( {i\! \ne\! j \!\in\! n} \right)$.

    Figure 2.  Multiple-receiver WPT system: (a) circuit model and (b) equivalent circuit model.

    Then the characteristic parameters can be expressed in the following equation in an n-receiver WPT system:

    It is supposed that the receiver power allocation ratio is Δ for receiver i and receiver j.

    From the above analysis, the relationship is very clear. When the number of receivers increases, Rin increases, while Pin and Pout decrease. However, as a magnetic resonance coupling WPT system, it is expected that the transmitter could supply more receivers. In addition, the original transfer status can not be destroyed with a new receiver access system, which means the transmitter power and transfer efficiency of the original transfer condition keep stable when the number of receivers increases or decreases. Besides, the power requirement and the equivalent load resistance ${R_{{L_i}}}$ of each receiver are definite but different. The receiver power is related to ${R_{{L_i}}}$, Ri, and Mi. Ri is the parasitic resistance of the coil of receiver i that is usually unchanged determined by its characteristics.

  • From the foregoing analysis, there is an optimal load in the WPT system that allows the system to operate at optimal efficiency. However, in practical applications, the load of each receiver is generally not equal to the optimal load, which limits the best transfer condition of the WPT system. Hence, the actual load needs to be changed to the optimal value. In Fig. 3, there are three types of circuit configurations that can implement the impedance match function, which are L-type LC network, T-type LC network, and π-type LC network, respectively.

    Figure 3.  Three types of circuit configurations for impedance match: (a) L-type LC network, (b) T-type LC network, and (c) π-type LC network.

    To control the power distribution of multiple receivers, from (16) and (17) it can be seen that the reflected impedance of each receiver to the transmitter plays a decisive role. When the transmitter and receivers of the WPT system are all resonant, Xi=0. The reflected impedance (${Z_{{t_1}}}$ to ${Z_{{t_n}}}$) of each receiver is pure resistance (${R_{{t_1}}}$ to ${R_{{t_n}}}$) and they are in series in the transmitter circuit. The resistance value of the receiver determines how much their respective received power. A part of power is consumed by the parasitic resistances of receivers (R1 to Rn) and transmitter (Rt), which must be considered in the calculation of efficiency and power. This means that any equivalent resistance value of the receiver circuit can be obtained through impedance match networks so that the power distribution can be precisely controlled. Therefore, it can be understood the role of the impedance match network at the receiver as follows.

    Firstly, the actual non-optimal load value can be converted to the optimal load value of the system.

    Secondly, as for multiple receivers, each transformed load is reflected to the transmitter and the sum value of the reflected resistances is equal to the best load value when the WPT system has only one receiver, and the ratio of each reflected resistance represents the power allocation.

    However, there is a problem. The problem of the power distribution at each receiver has been solved. But it can be known that if the transmitter circuit does not have any control circuit, then as the number of receivers increases, the sum of impedance reflected to the transmitter will increase unrestrictedly and the transmitter power is bound to decrease. Then even if the power distribution is achieved, each receiver can not receive enough power to make it work normally. Therefore, the power control at the transmitter is particularly important. In fact, when the WPT system has been working at the best efficiency state, it is impossible to achieve the increase of the transmitter power and the efficiency of the system at the same time as the number of receivers increases. These two situations are contradictory. As the efficiency increases, the power decreases, and vice versa.

    Therefore, the target of this paper is to ensure the best work condition of the system: The efficiency is unchanged with the increase of the amount of receivers, and the control of the transmitter circuit can be performed to ensure that the transmitter power does not change.

    In the multiple-receiver WPT system in Fig. 4, the L-type LC network is also applied to the transmitter, which is used to transform the sum of the reflected resistance to the optimal reflected resistance. Moreover, the sum of the reflected resistance must be greater than the optimal reflected resistance, so the L-type LC network is the most straightforward and simplest circuit configuration, whose loss is minimal.

    Figure 4.  Proposed multiple-receiver scheme for the MCR-WPT system.

  • Simulations were performed for the 1×4 coil array of the proposed system. The schematic of the proposed multiple-receiver magnetic coupling resonance wireless power transfer (MCR-WPT) system is shown in Fig. 4. There are four receivers, and the medium between the transmitter and receivers is a concrete wall.

    Fig. 5 presents the magnetic field distribution obtained with the high-frequency structure simulator (HFSS). It can be seen from the magnetic field distribution that due to the strong coupling between the transmitter and receivers, the magnetic field can penetrate the concrete wall to make contactless WPT in receivers (electrical equipment) of the wall. In addition, we have realized multiple sets of different power allocation by adjusting the matching capacitors.

    Figure 5.  Magnetic field distributions obtained with HFSS.

    Fig. 6 shows the efficiency of the four receivers. By optimizing the values of the matching capacitors, the receiver power and transmission efficiency of the four receivers are 4:3:2:1, and the sum of efficiency reaches 80%.

    Figure 6.  Efficiency of the four receivers.

  • In order to prove the correctness of the power control method, a prototype of a one-to-three non-contact charging device was designed. It is mainly composed of a switching power supply, a source transmitting coil, three receiving coils, a rectifying voltage regulator circuit, and a load device (a lamp, a fan, and a camera) after each coil. Figs. 7 and 8 are the matching circuit structures of the transmitter and receiver, respectively. A cement board is used between the transceiver terminals instead of the wall in the actual use.

    Figure 7.  Matching circuit photograph for the transmitter.

    Figure 8.  Matching circuit photograph for the receiver.

    The input voltage of the switching power supply is 12 V. The digital signal source converts 50 Hz commercial power into 130 kHz high-frequency alternating current. The transmitting coil converts electric field energy into magnetic field energy. The transmitting and receiving coils are coupled, so the magnetic field can penetrate the wall and be coupled to the receiving end. It converts magnetic field energy into electric field energy. During the test, the load devices at each receiving end are different, and the coil size is also different. That is to say, the key parameters of the wireless energy transmission system have different load impedance and coupling coefficients, so that precise power control and power distribution are required. At the same time, the matching capacitors on both sides of the transceiver are optimized. Table 1 shows the performance parameters of each coil in the system.

    Transmitter coilLamp coilCamera coilFan coil
    Self-inductance (μH)178.0842.1924.7251.50
    Capacitor Cp1 (nF)4.7221.6037.4416.21
    Capacitor Cp2 (nF)11.2024.108.929.88
    Size (mm)470.0×340.0×2.5R40.0×1.2R70.0×2.0R70.0×2.0
    Coupling coefficient0.1200.1620.182
    Operating frequency (kHz)150

    Table 1.  Parameter of this system

    The rated power of the three receivers (lamp, camera, and fan) is 1.5 W, 5.0 W, and 6.0 W, respectively, and the working voltage under the rated power is 5 V, 5 V, and 12 V, respectively, which can be seen from Figs. 9 and 10. The input DC voltage of the transmitter is 20.5 V, the current is 1.1 A, the power is 22.55 W, and the three receivers are fully loaded. The total output power of the system is 12.5 W and the system’s working efficiency is 55%.

    Figure 9.  Photograph of the prototype and the test setup for three receivers.

    Figure 10.  Photograph of the prototype and the test setup for the transmitter.

  • In this paper, we analyzed the multiple-receiver magnetically coupled resonant WPT system. Firstly, based on the equivalent circuit model, the paper analyzed the power distribution ratio of different receivers, and with the increase of receivers, the power of the transmitter decreased. The proposed impedance matching circuit at the transmitter and receivers can realize arbitrary power allocation of multiple receivers, and the transmitter can maintain the transmitter power unchanged. In the experimental verification, the transmitter and receivers are separated by a concrete wall, and the magnetic field emitted from the transmitter can effectively penetrate the concrete to supply power for indoor electrical equipment (lamp, camera, and fan), and verify the theoretical correctness. Due to the limited experimental conditions, the experiment did not do high-power verification. Theoretically, it can be extended to high-power devices, such as air conditioners, refrigerators, televisions, washing machines, etc., all of which can be wirelessly powered. This technology has great reference significance for the intelligent building in development nowadays. In the construction project, there are widespread problems in the complicated indoor wiring process, high cost, troublesome maintenance, short circuit, exposed sockets, and fire caused by electrical equipment failure, etc. With the development of WPT, these problems will be well resolved in the future.

Reference (16)

Catalog

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return