Variation Of Mutual Inductance Research Articles

A Decoupled Modulation Strategy for Constant Voltage/Current Wireless Charging System Under High Coils Misalignment

ABSTRACTOutput fluctuation and lower transmission efficiency under load and mutual inductance variation are hot concerned in the wireless charging system for power batteries. In this paper, a decoupled tracking strategy is proposed to realize constant voltage (CV) or current (CC) output and high transmission efficiency. The circuit model of series–series compensation network is built, and corresponding transmission characteristics can be derived. First, the load and mutual inductance value can be estimated by measuring the primary electrical information, including the inverter output voltage, current, and the phase error between them. Then load‐independent voltage or current output characteristics under coils misalignment can be maintained by tracking the optimal switching frequency of inverter part. In addition, the value of output voltage or current can be adjusted flexibly for different operation occasions by the employment of pulse‐width modulation. As a result, the load‐independent output characteristics realization and output adjustment can be decoupled. Based on only the primary measuring information, the CV/CC output can be maintained via the proposed hybrid control strategy when the coils misalignment and load variation happen, increasing the robustness of whole wireless power transfer (WPT) system. Furthermore, the soft switching of all power switches in the inverter part can be realized to reduce the switching loss. Compared with previous research, the proposed wireless charging system has a higher power density and a simplified control strategy. Finally, an experimental platform with 60‐V charging voltage and 3.6‐A charging current is built to verify the feasibility of the proposed sys‐tem and control method.

Coordinated Control of Constant Output Voltage and Maximum Efficiency in Wireless Power Transfer Systems

This article presents a coordinated control method used for wireless power transfer (WPT) systems. This method can improve WPT system transmission efficiency while maintaining the constant output voltage. First, the topology of the DC–DC converter is selected and the equivalent circuit model of the WPT system is established. Then, the WPT system characteristics are discussed and the mutual inductance estimation process is presented. Furthermore, the coordinated control method is proposed, where the constant voltage output is achieved by connecting the Buck–Boost converter after the diode rectifier. Meanwhile, the optimal phase shift angle is calculated and sent to the controller to achieve maximum transmission efficiency tracking control, according to the measured load voltage and current. Finally, simulations and experiments are adopted to verify the proposed coordinated control method. The experimental results indicate that the average system transmission efficiency is increased by 1.80% and the efficiency fluctuation is decreased by 2.67% when the system load resistance varies, while the average system transmission efficiency is increased by 1.80%, and the efficiency fluctuation is decreased by 3.14% when the mutual inductance changes. This means the proposed coordinated control method is effective under the conditions of the WPT load and mutual inductance variations.

Strong misalignment tolerance wireless power transfer with active adjustment of magnetic shielding

The variation of mutual-inductance is the essential reason for fluctuation of transmission power and efficiency during wireless power transfer (WPT) misalign. To maintain output power stability, current methods, such as primary regulation, secondary conversion, magnetic coupling mechanism (MCM) optimization, and compensation topology design, have not changed the characteristic of mutual-inductance changing with misalignment. A strong misalignment tolerance WPT system based on the influence of high permeability magnetic materials on equivalent electrical parameters of MCM is proposed. When the primary and secondary sides of MCM shift, the relative distance between magnetic shielding and coil (RDMSC) is adjusted to maintain the stability of mutual-inductance. The transmission efficiency and power are not affected by misalignment. Alternatively, RDMSC can be actively adjusted to meet the various needs of diverse loads at different times. Simulations and experiments are conducted. The effectiveness of the proposed scheme that RDMSC is actively adjusted to overcome misalignment is verified. This is a new method based on active adjustment of spatial electromagnetic coupling, which provides a new idea for WPT to overcome the influence of misalignment and maintain stable output.

Modeling and Control of WPT Systems in the Presence of Load and Mutual Inductance Variations

Modeling and Control of WPT Systems in the Presence of Load and Mutual Inductance Variations

Mutual Inductance and Load Identification of LCC-S IPT System Considering Equivalent Inductance of Rectifier Load

The variation of mutual inductance and load parameters will affect the transmission power and efficiency of the inductive power transfer (IPT) system. The identification of mutual inductance and load parameters is an essential part of establishing a stable and reliable IPT system. This paper presents a joint identification method of load and mutual inductance for the LCC-S IPT system, which does not require the establishment of primary and secondary communication and related control. Firstly, the resistance-inductance characteristics of the equivalent load of the rectifier are analyzed by simulation, and then the rectifier and system load are equivalent to the circuit model of resistance and inductance in series. Secondly, the characteristics of the reflected impedance are analyzed, and the functional relationship between the transmitter impedance and the rectifier impedance is established by using the ratio of the real part to the imaginary part of the reflected impedance, which realizes the decoupling of the load and the mutual inductance. Thirdly, the functional relationship between the equivalent impedance of the rectifier and the load resistance of the system is obtained by data fitting. Then, the equations of the above two functional relationships are combined. By measuring the voltage of the parallel compensation capacitor at the transmitting side, the current of the transmitting coil and the phase difference between the two, the battery load can be solved first, and then the mutual inductance can be calculated, so that the high-precision identification of the load and mutual inductance can be realized. Finally, an experimental platform of the LCC-S IPT system is built for experimental verification. The experimental results show that the maximum identification errors of mutual inductance and load are 5.20% and 5.53%, respectively, which proves that the proposed identification method can achieve high precision identification.

Rotating-Coordinate-Based Mutual Inductance Estimation for Drone In-Flight Wireless Charging Systems

This article proposes a fast and real-time mutual inductance estimation method for drone in-flight wireless charging systems against the continuous varying of relative position between coupling coils. In previous studies, many efforts have been made to achieve accurate mutual inductance estimation when fixed misalignment occurs in coupling coils. However, the critical challenge for in-flight wireless charging systems is to track variations of mutual inductance caused by continuously changed misalignments between coupling coils, which is rarely explored in previous studies. Accordingly, this article proposes a rotating-coordinate-based mutual inductance estimation method to track the variation of the mutual inductance timely. By applying the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> dynamic model, the proposed estimation method is effectively enhanced in terms of rapidity and implemented simply as well as eliminating wireless communication links. With the salient features of accuracy, rapidity, and real time, it can be an ideal solution against the continuous disturbance of mutual inductance, especially for drone in-flight wireless charging systems. In this article, both simulated and experimental results are given to verify the validity of the proposed rotating-coordinate-based estimation method, wherein the relative error of the mutual inductance estimation is within 1%, and the estimation rapidity is less than 4 ms.

Variable Inductor Control for Misalignment Tolerance and Constant Current/Voltage Charging in Inductive Power Transfer System

In wireless power transfer system, not only the mutual inductance variation but also the self-inductance variation can be occurred under the misalignment condition. In light of the Unmanned Aerial Vehicles, the variation of the secondary self-inductance and mutual inductance are significantly under the misalignment condition. In order to stabilize the output voltage and current and achieve near-ZPA (near-zero phase angle) of the input impedance. A variable inductor control is presented in this paper, which regulate the inductance of the secondary side by adjusting the dc bias current under large <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> variation. The proposed control method does not need any auxiliary circuit, and constant current-constant voltage (CC-CV) charging can be achieved by controlling the duty cycle of the boost converter. To verify the proposed control method, a 500-W prototype was set up in the laboratory, and the variable inductor control method ensures a stable output voltage and current with horizontal and vertical offsets of 200 mm and 92 mm, respectively. Additionally, communication is not need between primary and secondary side, and the results show that the maximum efficiency is 92.9%, which is 2.3% higher than the conventional dc-dc regulation method.

Mathematical Model and Simulation Based on ANSYS Maxwell of the Magnetic Fluid Differential Transformer Inclination Sensor

A mathematical model of a mutual inductance magnetic fluid inclination sensor is established. The sensing element of the sensor is magnetic fluid. The composite magnetic core suspended in the magnetic fluid increases the permeability of the medium in the winding. The total magnetic induction intensity B in the winding is composed of two parts: the excitation magnetic induction intensity Bl and the additional magnetic induction intensity Ba generated by the magnetization of pure iron. The sensitivity S of the sensor and its influencing factors are derived. The output characteristics of the sensor are analyzed using ANSYS Maxwell simulation software. The results show that the variable resistance of the measuring circuit can eliminate the residual voltage at zero point, and the output voltage carrier after filtering and rectification is positive half cycle; The addition of pure iron to the magnetic core greatly increases the mutual inductance variation between the primary and secondary windings, and the inclination angle in a small range is linear with the mutual inductance variation; The recovery force of the composite core is proportional to the displacement.

Robust Maximum Efficiency Tracking Control of Wirelessly Powered Directly Supplied Heart Pumps

In recent times, wireless power transfer systems have been identified as a reliable option to supply power to medical implants. Up to now, Wireless Power Transfer Systems (WPTS) have only been used to charge batteries of low-power medical implants. However, for medical implants requiring a relatively higher power, such as a ventricular assist device, which is an implanted blood pump in the patient’s abdominal cavity, an external power supply has been used. When WPTS is used for medical implants, it increases the number of required power converter stages and hardware complexity along with the volume, which tends to reduce the overall efficiency. In addition, the existence of uncertainties in WPTS-based medical implants, such as load and mutual inductance variations, can lead to system instability or poor performance. The focus of this paper is to design a WPTS to supply power to the pump motor directly through its inverter based on the requirements of the motor drive system (MDS) without resorting to an additional DC-to-DC converter stage. To this end, the constraints that the drive system imposes upon WPTS have been identified. In addition, to make a reliable closed-loop operation, a µ-synthesis robust controller is designed to make sure the system maintains its stability and performance with respect to the system’s existing uncertainties. A number of experimental results are provided to verify the effectiveness of the adopted WPTS design approach and the corresponding closed-loop controller for WPTS. Furthermore, the experimental findings for the maximum efficiency tracking (MET) approach (to minimize WPTS coil losses) and constant DC link voltage control approach are shown and compared. According to experimental results and system efficiency analysis, the former appears to perform better. The system dynamic performance analysis, on the other hand, demonstrates the latter’s advantage.

A Self-Tuning LCC/LCC System Based on Switch-Controlled Capacitors for Constant-Power Wireless Electric Vehicle Charging

In this article, a self-tuning <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC/LCC</i> wireless power transfer system based on switch-controlled capacitors is proposed to maintain a high power factor on the primary inverter side and fixed output power on the secondary side against self or mutual inductance variation of the magnetic coupler. The PI control on the primary side and the method of gradient descent on the secondary side are proposed based on the proposed normalized mistuned <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC/LCC</i> circuit model. Only two switch-controlled capacitors on each primary and secondary side are used to implement the control scheme without the Wi-Fi communication or parameter identification. A 3 kW experiment setup was built in the lab and two different magnetic shields, namely ferrite and nanocrystalline, were tested on the secondary pad. According to the experiment results, the proposed system is proven to be able to maintain a high power factor (>0.9) and the desired dc output power against 52% mutual inductance variation and 12% self-inductance variation of the secondary pad. The proposed system can be applied as a wireless charger for electric vehicles or a high-power wireless charger test bench.

Phenomenon of Standing Waves on Uniform Single Layer Coils - Revisited and Extended

Accurate knowledge of the natural frequencies and shapes of corresponding standing waves are essential for gaining deeper insight into the nature of response of coils to impulse excitations. Most of the previous analytical studies on coils assumed shape of standing waves as sinusoidal but numerical circuit analysis and measurements suggest otherwise. Hence, this paper revisits the classical standing wave phenomenon in coils to ascertain reasons for this discrepancy and thereafter extends it by analytically deriving the exact mode shape of standing waves for both neutral open/short conditions. For this, the coil is modeled as a distributed network of elemental inductances and capacitances while spatial variation of mutual inductance between turns is described by an exponential function. Initially, an elegant derivation of the governing partial differential equation for surge distribution is presented which is then analytically solved, perhaps for the first time, by the variable-separable method to find the complete solution (sum of time and spatial terms). Hyperbolic terms in spatial part of solution have always been neglected but are included here, thus, yielding the exact mode shapes. Voltage standing waves gotten from analytical solution are plotted and compared with simulation results on a 100-section ladder network. The same is measured on a large-sized single layer coil. So, it emerges that, even in single layer coils, shape of standing waves deviates considerably from being sinusoidal and this deviation depends on spatial variation of mutual inductance, capacitive coupling, and order of standing waves.

Research on Optimization of Horizontal Omnidirectional Misalignment Tolerance of WPT Based on Double D Coupler

DD (Double D) coils have been researched and utilized due to their excellent misalignment tolerance. Here, a compound DD coupler sets for stationary wireless power chargers, which has significantly better anti-misalignment performance than single DD coupler in all directions, is proposed. The transmitting coils are composed of two parts of DD coils wound in opposite directions. Moreover, to obtain the low-level variation of mutual inductance between compound transmitting coils and receiving coils when offset occurs, a parameter optimization strategy of compensation coils is also proposed. With the properly designed parameters, the mutual inductance between transmitting and receiving coils could remain basically constant when misalignment occurs, which means that the efficiency and power remain relatively constant when offset occurs. Finally, both single DD coils and compound DD coils experimental prototypes are built to compare anti-misalignment ability performance. The results show that the proposed system is basically more stable and has a higher output power and more stable efficiency than that of unoptimized coupler during migration. In particular, with the employment of the antiparallel winding, the efficiency fluctuates from 85.5% to 85% when the 0.1-m offset in the X-axis and Y-axis occurs simultaneously. Moreover, the higher and basically more stable output power is also achieved.

A Self-Tuning LCC/SP System for Electric Vehicle Wireless Charging against Large Self- and Mutual Inductance Variations

An LCC/SP self-tuning wireless charging system is proposed herein for use in a wireless charging test bench. With different dislocations in addition to changes in the coil self-inductance and mutual inductance caused by different secondary magnetic shielding materials, the system can ensure that the high power factor of the primary side remains unchanged without changing the circuit topology. Based on this normalized detuning LCC/SP circuit model, a switch-controlled capacitor (SCC) self-tuning method based on PI control is proposed. The control scheme employs only two MOSFETs and capacitors, without WIFI communication or parameter identification. A 2 kW experimental device was set up in the laboratory, and experimental verification was carried out with large-scale dislocations and different secondary magnetic shielding materials. The experimental results confirm that the system can maintain a high power factor (&gt;0.9) under a system mutual inductance variation of 47.7% and secondary coil self-inductance variation of 12%, and that it can be applied in electric vehicle wireless chargers or high-power wireless charger test benches.

Wireless power transfer system based on LCC/LCL-S variable structure with constant output power

In magnetic coupling wireless power transfer system, the relative position of power transfer coils may change during the operating condition. In order to solve the mutual inductance variation caused by the movement of coils, increase the anti-offset capability of the system to achieve constant power output, a variable structure is proposed in this article. Build the mathematic models of LCC-S and LCL-S structures and analyze the expressions of output power and efficiency in two structures. Design the switching condition, the relationship between coupling coefficient at switching point and parameter setting of capacitor array is obtained with the same input voltage and constant output power. The coupling coefficient range is estimated by output open circuit voltage with a small-voltage input, and the controlling strategy is put forward. Analyze the efficiency of variable structure and build the loss model. It is proved that the switching and input harmonic loss can be reduced by using LCC/LCL-S structure, while the transfer efficiency can be improved through the structure switching between two structures. The simulation results show that the variable structure can effectively reduce the variation range of input voltage and decrease the total harmonic distortion (THD) of input voltage by 46.6%, and keep THD of input current small in a wide range of coupling coefficient.

Wireless Charging Constant Power Output System Based on LCC/S-S Self-Switching

Conventional wireless charging systems cause output power fluctuations during the offset process, and a single topology can cause power reduction or a large impact on the wireless charging network as the coupling mutual inductance changes. For this reason, in this paper, by combining LCC-S and S-S topologies, the high output characteristics of the S-S topology network in the low coupling state and the high output characteristics of the LCC-S topology network in the protection and high coupling in the very low coupling, the power output in the offset state is greatly maintained by combining with the voltage regulation circuit. In this paper, firstly, the theoretical derivation of the working principle of the designed topology is carried out, then the mutual inductance variation range generated by the offset state of the coil is found through finite element simulation, and the accuracy of the theoretical derivation is verified by building a constant power output model of the self-switching system using matlab, and finally, an experimental platform for wireless power transmission is built, and the experimental results confirm that the system power can be maintained within a certain offset range The output fluctuation is within 5%, which verifies the feasibility and realism of the design.

Design, Simulation, and Parameter Optimization of a MultiStage Induction Coilgun System

This article proposes a method to design a three-stage induction coilgun system using the finite-element method (FEM). The system is designed to launch a 21.5 kg projectile. The method which is used to calculate the mutual inductance and the mutual inductance gradient between the two coils is expressed. Furthermore, the variation of mutual inductance and its gradient with respect to the distance between the two coils is indicated. The system parameters (i.e., coil currents, mutual inductance, mutual inductance gradient, force, velocity, and magnetic field distribution) are calculated and analyzed utilizing ANSYS Maxwell software. To verify the performance of the initial design, its analytical model is developed and validated in MATLAB software. The results of the analytical model are compared with the results obtained from the FEM method, and it is shown that they are well-matched in all waveforms. Besides, the efficiency of the system is improved through optimization by applying a genetic algorithm (GA). In this way, the efficiency of the system is enhanced from 29% to 36.6% and also the muzzle velocity is increased from 128 to 143 m/s. This method can be used to design a large-scale multistage induction coilgun (MSIC) for launching massive projectiles and reach high velocities.

Modeling and statistical analysis of distribution parameters of random cable bundles based on image recognition technology

In this paper, a modeling method of actual bending random bundled wire harness is proposed. Firstly, based on image recognition technology, the three-dimensional coordinates of bending wire harness axis are reconstructed by using two photos of actual wire harness in side view and top view; then the random bundled wire harness is realized based on random transfer path method. Based on this modeling method, this paper analyzes the statistical characteristics of distribution parameters of bending random wire harness by Monte Carlo simulation, and finds that the variation trend of self inductance, mutual inductance and mutual capacitance along the line is consistent with the variation trend of wire harness height, while the trend of self capacitance is opposite; the coefficient of variation of self capacitance, self inductance and mutual inductance has negative correlation with wire harness height; the bundling randomness is not obvious It will change the mean value of self inductance and self capacitance, but reduce the mean value of mutual capacitance and mutual inductance.

Measurement of Magnetic Plates at a Few Hertz With Two Concentric Coils and Thickness Estimation Using Mutual Inductance

We propose a low-frequency eddy current measurement methodology for the thickness of ferromagnetic materials. The instrumentation is built with two concentric coils passing with up to a few hertz alternating currents. The magnetic plate under examination is regarded as the core of the coils that accounts for the mutual inductance. The mutual inductance available by taking the difference between the reactance of the two coils connected in series, cumulatively and differentially coupled, respectively, is a quantity that almost does not vary with the material's electrical conductivity but the magnetic permeability and is not liable to change with frequency. The mutual inductance can be used to estimate a magnetic plate's thickness. Furthermore, we use a set of test pieces (TPs) of the same magnetic property to establish a relationship between the thickness variation and the mutual inductance variation. This relationship is ideally permeability-invariant and applicable to other sets of TPs. The amount of thickness variation can be estimated, despite the difference on permeability.

Model-Based Analysis and Quantification of Bearing Faults in Induction Machines

The detection of rolling-element bearing fault can be accomplished by monitoring and interpreting a variety of signals, including the vibration, the acoustic noise, and the stator current. The existence of a bearing fault as well as its specific fault type can be readily determined by performing frequency spectral analysis on the monitored signals with various signal processing techniques. However, this traditional approach, despite being simple and intuitive, is not able to identify the severity of a bearing fault in a quantitative manner. Moreover, it is often times tedious and time-consuming to apply this approach to electric machines with different power ratings, as the bearing fault threshold values need to be manually calibrated for each motor running at every possible speed and carrying any possible load. This article, thus, proposes a quantitative approach to estimate the bearing fault severity based on the airgap displacement profile, which is reconstructed from the mutual inductance variation profile estimated from a quantitative electrical model that takes the stator current as input. In addition, the accuracy of the developed electrical model and the estimated bearing fault severity are validated by the simulation and experimental results, and the explicit airgap variation profile is reconstructed with the superposition of multiple Fourier series terms estimated from the stator current via the proposed scheme. The proposed method offers a quantitative and universal bearing fault indicator for induction machines with any power ratings and operating under any speed and load conditions.

Design of Inductive Power Transfer System With a Behavior of Voltage Source in Open-Loop Considering Wide Mutual Inductance Variation

This article analyses the fundamental aspects of the principal resonant network topologies for inductive power transfer systems. From the analytical derivation, different features, such as the variation of the coupling factor or load changes, are studied. Based on this study, a resonant series–series topology is selected, which cancels the leakage inductance. Due to the specifications, the air gap distance and its tolerance ( $\pm \text{12}\%$ ) produce a wide variation of the coupling factor of the inductive link. Therefore, through fast three-dimensional simulations by finite elements, the inductive link is designed so that this variation is minimized. This maintains the resonance and the designed system, in turn, behaves like a voltage source regardless of power, and thus, evades the implementation of a control stage. A dc–dc converter is constructed where the distance between the primary and secondary side vary from 35 to 45 mm, and the power ranges from 0 to 5 kW. The output voltage range goes from 38 to 55 $V_{\text{DC}}$ . Experimental results for the dc–dc converter report an efficiency of over 94%.