Zero Phase Angle Research Articles

Resonance Capacitance Selection Method for Minimizing Leakage Magnetic Fields and Achieving Zero Phase Angles in Wireless Power Transfer Systems

This study proposes a novel approach for selecting the resonance capacitance of wireless power transfer systems, aiming to achieve a zero phase angle (ZPA) while simultaneously minimizing the leakage magnetic field. The performance of the method is validated across two key topologies: series–series (S–S or SS) and the double-sided inductor–capacitor–capacitor (LCC, LCC–LCC) topologies. By minimizing the vector phasor sum of the coil currents, the proposed approach effectively mitigates magnetic field leakage. The method is further validated through mathematical derivations, simulations, and experimental tests. The results reveal that using the proposed method to select resonance capacitances reduces the leakage magnetic field by up to 35.2% in the SS topology and by 42.0% in the double-sided LCC topology. Furthermore, the method improves the ZPA by more than 20° in both cases. These outcomes affirm the effectiveness of the proposed resonance tuning approach.

Analysis and design of a three‐coil IPT system with independent dual output ports

AbstractIndustrial applications tend to involve a substantial assemblage of electronic devices, and it is imperative to consider diverse charging requirements while charging these devices. This paper proposes a three‐coil single‐input‐and‐dual‐output (SIDO) inductive power transfer (IPT) system to meet the charging requirements of different devices. The system includes two independent output ports, providing constant voltage (CV) output and constant current (CC) output for different loads, respectively. In addition, the zero‐phase angle (ZPA) operation can be achieved, thus avoiding injection of reactive power and improving energy transfer efficiency. Unlike previous related studies, the receiver of the proposed SIDO IPT system only includes one receiving coil to pick up energy, eliminating unnecessary cross‐coupling and complex decoupling circuits in traditional IPT systems with multiple outputs. This study first analyzes the CC/CV output theory of the proposed SIDO IPT system in detail, and designs and optimizes the parameters by establishing an equivalent model. Then, the conditions for achieving zero‐voltage switching (ZVS) operation of the inverter are obtained by analyzing the sensitivity of CC/CV performance to the variation of the compensation capacitors. Finally, a verification experimental prototype with 2.5A CC output and 72 V CV output is established to verify the effectiveness of the proposed IPT system.

Energy injection adaptive technology for wireless power transmission based on parameter identification

AbstractThis paper presents an innovative adaptive strategy implemented in wireless power transmission (WPT) systems to overcome efficiency challenges due to coupling structure misalignment and load variability. A novel versatile transmitter, capable of alternating between single and dual voltage source states via two MOSFETs has been designed. Initially, the system operates in a single voltage source mode, mutual inductance and load characteristics are pinpointed using a particle swarm optimization algorithm. Subsequently, the system transitions to dual voltage source mode, where it fine‐tunes the auxiliary voltage source's amplitude and phase based on the determined mutual inductance and load values to realize zero phase angle for optimal impedance matching. The experimental results show that this method can obviously improve the output power of WPT system. This method stands out for its simplicity, adaptability and rapid response, suggesting its potential for practical use in dynamic charging applications.

A reconfigurable wireless power transfer system with constant exciting current for charging multiple batteries

At present, wireless power transfer (WPT) systems with constant current (CC) or constant voltage (CV) characteristics are typically achieved using a single transmitter and single pickup (STSP) configuration, which cannot transfer power to multiple battery loads simultaneously. In this paper, the LCC-LCC/S reconfigurable topology is proposed to realize the CC-to-CV transition for multiple battery loads. An LCC topology is designed on the primary side to achieve a constant current (0.362A) flowing through the transmitting coil to enable independent operation of power pickups. A reconfigurable LCC/S topology is designed on the secondary side to achieve the CC-to-CV transition of the battery loads. The received power from the pickups remains unaffected when pickups are moved in or out or are in different operating modes (CC or CV). The circuit can maintain zero phase angle (ZPA) operation, which greatly enhances the overall power density of the system. Additionally, detailed design process for the compensation parameters on both the primary and secondary sides are provided. Theoretical analysis proves that good system stability and robustness can be obtained in the case of variable quantity of pickups and quality factors of coils. The experimental prototype was built, with the CC value for the battery load designed at 0.7A and the CV value designed at 8 V. Experimental results demonstrate the smooth CC-to-CV transition of the proposed WPT system (with 3 pickups) at a power output of 15.4 W, and the system’s maximum efficiency can reach 75.5 %.

A CV‐type WPT system based on CLC‐N compensation with compact receiver

AbstractThe demand for wireless power transfer (WPT) systems that can maintain a constant voltage (CV) output characteristic is gradually increasing in some practical application areas of WPT, such as industrial power supplies. However, existing CV‐type systems are often limited by the parameter design of the loosely coupled transformer (LCT), and the configuration of the receiver side is not compact enough. Therefore, this paper proposes a strongly coupled system with a CV output function composed of capacitor‐inductor‐capacitor‐none (CLC‐N) topology. The system's transmitter uses a CLC compensation, while the receiver conforms to a minimalist design without the need for compensation components such as capacitors and inductors. The initial segment of the paper pertains to the discussion of the conditions required to satisfy both the zero‐phase‐angle (ZPA) and CV output functionality of the suggested system. Subsequently, an in‐depth approach to parameter design is outlined, accentuating that the output voltage remains unrestricted by the LCT's parameters. Additionally, this paper examines the realization of zero‐voltage switching (ZVS) within the suggested system as well as the influence that variations in compensation components have on the CV output function. To underscore the benefits of the suggested CV‐type WPT system that employs CLC‐N compensation, the paper presents a comparison with a range of other CV‐type WPT systems. Ultimately, an experimental prototype is fabricated to test the theoretical framework, and the results from these experiments confirm the feasibility of the suggested CV‐type WPT system based on CLC‐N compensation.

Hybrid Topology with Reconfigurable Rectifier for Enable CC and CV Output Characteristics in Wireless Power Transfer Systems

To achieve simple and reliable conversion from constant current (CC) charging mode to constant voltage (CV) charging mode in wireless power transfer systems, this paper proposes a hybrid topology equipped with a reconfigurable rectifier. An AC switch is adapted to simultaneously realize the change from half-bridge rectification to full-bridge rectification and achieve the shift from a topology with capacitors in the series compensated primary and secondary sides to a topology with capacitors in the series compensated primary side and the inductor-capacitor-inductor (LCL) compensated secondary side. Notably, communication between the transmitter and receiver sides is not necessary in the proposed method. Furthermore, the zero phase angle characteristic is successfully maintained in both charging modes. The experimental results obtained using the 48 V/0.7 A experimental prototype, which was built to validate the relevant theoretical analysis, show that output current/voltage can be achieved in CC/CV charging mode independent of load resistance. Notably, the maximum power transfer efficiency of the system during the charging process reached 95.33%.

Effects of phase angle and sensor properties on on-orbit debris detection using commercial star trackers

The recent proliferation of resident space objects (RSOs) in low Earth orbit (LEO) threatens the sustainability of space as a resource and requires persistent monitoring to avoid collisions involving valuable space assets. State-of-the-art ground-based space surveillance techniques, due to their susceptibility to atmosphere, weather, and lighting conditions, tend to focus on RSOs with characteristic length greater than 10 cm or 1 dm. Consequently, millions of smaller LEO RSOs remain untracked by ground-based methods, which reduces overall space situational awareness. Onboard satellite sensors offer a space-based method for tracking RSOs. Prior research has investigated the feasibility of using commercial star trackers (CSTs) — optical sensors prevalent on most active spacecraft — to observe, detect, and estimate the position and velocity of RSOs larger than 10 cm. In a recent effort, we expanded on these feasibility studies by assessing the capabilities of CSTs to detect debris particles smaller than 10 cm in characteristic length. We modeled the particles as Lambertian spheres with zero phase angle and ten percent reflectivity and found that typical CSTs can detect properly illuminated debris of characteristic length between 1 cm and 10 cm even at distances of tens of kilometers. More sensitive CSTs can characterize decimeter-scale RSOs hundreds of kilometers away; alternatively, they can track centimeter-scale and smaller RSOs at closer distances. In this paper, we summarize these key results and extend our previous study by relaxing its zero-phase-angle assumption and characterizing the effect of Sun-RSO-CST phase angle on debris detection range. We identify a number of representative CSTs with publicly available optical characteristics and consider the effects of properties such as pixel pitch, focal length, aperture diameter, and field of view (FOV) on the capability of each CST to detect debris at a given distance and relative velocity (in the form of streak speed). We find that, for debris particles modeled as diffuse Lambertian spheres, Sun-RSO-CST phase angles as high as 57° result in no more than 20% reduction to the useful RSO-CST detection range. In addition, we find that pixel pitch and focal length, rather than aperture diameter, tend to determine the capability of a given CST to resolve two distinct RSOs. Furthermore, streak speed may serve as a stronger limiting factor for detection of smaller debris particles than for larger ones. Despite these limitations, the overall results indicate that CSTs have the potential to substantially enhance space-based debris detection capability.

Design and development of an LC compensated WPT system with multiple constant voltage outputs function

SummaryWith the increasing demand for the constant voltage (CV) charging of multiple loads, this article proposes an LC compensated wireless power transfer (WPT) system with multiple load‐independent CV outputs function. Each transmission channel consists of a compensation capacitor and a compensation inductor forming a resonant loop. By configuring different combinations of compensation inductor and capacitor for each transmission channel, different CV outputs can be achieved without affecting the output voltages of other transmission channels. In addition, the proposed system can achieve near zero phase angle (ZPA) and zero‐voltage switching (ZVS) operations, thereby improving system efficiency. Firstly, a detailed theoretical derivation of the proposed system with multiple load‐independent CV outputs and ZPA operation is performed, and the detailed parameter design process is provided. Secondly, the implementation method of ZVS operation is introduced and verified through simulation. Finally, an experimental prototype of two transmission channels is taken as an example to verify the correctness and rationality of the proposed system.

Self-Switching Wireless Power Transfer System Design with Constant Current/Constant Voltage Output Features Based on LCC-LCL/S Topology

To meet the demand for constant current and constant voltage charging of batteries and to increase the system output power, the LCC-LCL/S-type self-switching wireless power transfer system is proposed. The system does not require communication between the primary and secondary circuits, and its output mode is controlled by simply changing the status of two switches on the secondary side. Notably, the system satisfies the zero phase angle characteristic before and after mode switching. The parameter design method is proposed based on the circuit topology and the maximum safe current constraint. To make the output voltage fluctuation as small as possible, the optimum load switching point for the system has been designed, and its optimality has been validated by simulation. Furthermore, the switching control strategy is proposed, considering the effects of the system no-load and load short-circuit in real situations. Finally, an experimental platform was built to achieve the high efficiency output of the system with the maximum output voltage of 46.21 V, the maximum output power of 180 W, and the maximum efficiency of 93.4%, which verified the applicability of the proposed method.

A Novel Impedance Matching of Class DE Inverter for High Efficiency, Wide Impedance WPT System

In high-frequency wireless power transfer (WPT) applications, Class D, E, and F inverters are most widely used. Class DE inverters combine the respective advantages of Class D and Class E inverters. However, the Class DE inverter is sensitive to changes in impedance, which can easily lead to the loss of soft switching characteristics, thereby reducing efficiency. In this paper, an impedance-matching compensation design method is proposed to expand the high-efficiency region of the Class DE inverter by matching impedance and parameters. The effect of the method on the zero-voltage switching (ZVS) characteristic of Class DE inverters is analyzed in detail. The proposed WPT system maintains a constant voltage and zero phase angle by employing PS/PS compensation topology. Theoretical analysis shows that the impedance can be compressed for the design of resonant network impedance, and the method can expand the high-efficiency region with a reasonable choice of parameters to match the phase. Finally, a 500 kHz, 1 kW WPT prototype was constructed with a coupling factor of 0.25–0.4 and a load range of 30–80 Ω. The inverter’s efficiency exceeds 95%, with optimal efficiency reaching 97.3%. The system efficiency is greater than 87%.

A Dual-Band Coil Array With Novel High-Order Circuit Compensation for Shielding Design in EV Wireless Charging System

For the wireless power transfer (WPT) system in electric vehicle (EV) applications, a serious concern lies in the leakage electromagnetic field (EMF) emission. In order to address this issue, this article presents a dual-band coil array (DB-CA) with novel high-order circuit (HOC) compensation. The most attractive feature of DB-CA is that both the first and third harmonics of leakage EMF can be reduced simultaneously, while the system still resonates at the same frequency. A detailed mathematical model is established to intuitively reveal the relevance between impedance design and shielding performance, as well as the constraints to achieve resonance. In addition, the novel HOC compensation is employed to decouple the shielding design at each harmonic. Both simulated and experimental results verify the effectiveness of DB-CA, and a 1-kW WPT prototype operating at 85 kHz is established. By applying DB-CA, the leakage EMF can be reduced by 3.88 dB at 85 kHz and 1.84 dB at 255 kHz, respectively. Meanwhile, the system resonant frequency still locates at 85 kHz, and the achieved zero phase angle condition is independent with load condition. It can provide significant guidance to the design of shielding configurations in EV Wireless Charging System.

Decoupling Control of Double-Side Frequency Tuning for LCC/S WPT System

The parameter fluctuations will lead to the frequency detuning problem of the wireless power transfer (WPT) system, thus affecting the transmission efficiency and output stability. The traditional primary-side frequency tuning method cannot realize the full compensation of the secondary-side resonance parameters, and the double-side frequency tuning method with data communication still exists a coupling problem. Therefore, this paper proposes a decoupling control of double-side frequency tuning for LCC/S wireless power transfer (LCC/S WPT) system, which has the advantages of avoiding information exchange and circuit simplicity. Firstly, based on the circuit model, the influence mechanism of frequency detuning on the transmission efficiency and voltage gain are deeply studied. On this basis, a zero phase angle (ZPA) control method based on optimal efficiency tracking and a two-step perturb and observe method with maximum current search are proposed to adjust the primary and secondary resonance parameters respectively. Finally, a 200W experimental prototype was built to verify the effectiveness of the proposed frequency tuning strategy. It is strong robustness to the parameter fluctuations, and double-side can well maintain the resonance state, which can improve the transmission efficiency and stability of the LCC/S WPT system.

An Inductive Power Transfer System With Multiple Receivers Utilizing Diverted Magnetic Field and Two Transmitters for IoT-Level Automatic Catering Vehicles

Automatic catering vehicles (ACVs) are increasingly adopted in restaurants to save expensive human resources. Especially in special situations such as a pandemic, ACV offers a wise choice to keep social distance. In this paper, a wireless power transfer (WPT) system is proposed to charge four ACVs at the same time. With the help of ferrite cores, the flux can be guided through all four receivers while the leakage magnetic field can be reduced simultaneously. Two transmitters are utilized to confine the flux path further. Both areas #A and #B can charge UAVs with the consideration of the mechanical structure of the food preparation area and charging standby area (Areas #A and #B). The presented system can also realize zero phase angle (ZPA) to degrade the volt-ampere (VA) rating. Finally, an experimental setup is constructed, and the overall dc-dc efficiency is 87.6% when delivering 120 W to four loads.

Self- and Mutual-Inductance Cross-Validation of Multi-Turn, Multi-Layer Square Coils for Dynamic Wireless Charging of Electric Vehicles

Dynamic Wireless Power Transfer (DWPT) has high potential to overcome electric vehicles’ battery issues of size and range and to achieve fully autonomous driving. Accurately extracting the self- and mutual-inductance of the coils is essential for controlling and optimizing the overall performance of the DWPT system under real driving conditions. Due to the limited space for coil installation at the bottom of the vehicles, multi-turn, multi-layer square coils are proposed to maximize the space utilization of the DWPT system. For the first time, this paper presents a theoretical model for calculating the self- and mutual-inductance and the coupling coefficients of multi-turn, multi-layer square coils. Taking a four-turn, four-layer square coil as an example, the model is cross-validated by 3D coil modelling and simulation, as well as practical measurements. A theoretical–experimental verification is further conducted to indirectly corroborate the cross-validated coupling coefficients of the two coils. On average, the normalized root mean square errors of the resultant self-inductance and coupling coefficients of two identical coils are 1.04% and 4.29%, respectively. Specifically, for the selected case, normalized root mean square errors of the zero-phase angle frequencies of the system under different misalignment situations average out at 1.32%.

Balanced Dual-Side LCC Compensation in IPT Systems Implementing Unity Power Factor for Wide Load Range and Misalignment Tolerance

Misalignment tolerance and wide load range capability are necessary for a practical inductive power transfer (IPT) system. In pursuit of high-performance, input unity power factor and high efficiency are expected. In this paper, a balanced design method of dual-side LCC compensation is proposed to achieve input unity power factor over wide misalignment and load ranges. With the proposed method, dual-side LCC compensation is in a balanced state where zero phase angle frequencies coincide with designed voltage gain frequencies under coupling and load variations. Unity power factor can be implemented while maintaining voltage gain with frequency control. Possible output power versus frequency characteristics of this balanced dual-side LCC compensation are categorized and fully analyzed. One of them, with strong power regulation capability and high misalignment adaptability, is selected as the design target. Coil currents are optimized using a surplus degree of design freedom while selecting parameters. Unity power factor and coil current optimization ensure low losses in devices and coils, which benefits system efficiency. Thus, a wide load range, high misalignment tolerance, nearly zero reactive power, and high efficiency can be simultaneously implemented. The proposed method is verified on a 2.1kW prototype. The coil size of both primary and secondary sides is 600mm <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">×</i> 600mm, and the air gap is 150mm. Load power varies from 10% to 100% within the coupling range from 0.15 to 0.35. Nearly unity power factor is realized under various working conditions. The maximum dc-dc efficiency reaches 96.4%.

Analysis and Design of an S/S/P-Compensated Three-Coil Structure WPT System With Constant Current and Constant Voltage Output

Wireless power transfer (WPT) is a promising energy transfer method for its security, reliability and convenience, and has been applied in various scenarios. In practical applications, in order to prolong the battery lifecycles, the WPT system preferably has the load-independent constant current (CC) and constant voltage (CV) charging characteristics and zero phase angle (ZPA) operation for high power transfer efficiency. However, since the equivalent resistance of the battery significantly changes over the entire charging process, it is difficult to design a WPT system with the above functions. This manuscript proposes a S/S/P-compensated three-coil structure WPT system and its corresponding parameter tuning method to achieve CC and CV charging modes at two different ZPA operating frequencies. For the proposed three-coil structure WPT system, since only one compensation capacitor is required on the receiver, the compactness and portability of the receiver of the WPT system are guaranteed. Firstly, the comprehensive theoretical analysis for the CC and CV charging modes and ZPA operation is presented, and the detailed parameter design method of the proposed system is provided. Secondly, the sensitivity of variations in system parameters to CC and CV characteristics is analyzed, and the implementation of ZVS operation for further improving efficiency is introduced. Thirdly, a confirmatory experimental prototype with charging current of 4.6A and charging voltage of 56V is fabricated, and the experimental results are basically consistent with the theoretical analysis. Finally, a comprehensive comparison with previous WPT systems of the same type is carried out to highlight the superiority of the proposed three-coil structure WPT system.

Remaining Opportunities in Capacitive Power Transfer Based on Duality With Inductive Power Transfer

Wireless power transfer (WPT) has proven to be an effective solution for electric vehicle charging. As two mainstream near-field WPT technologies, inductive and capacitive power transfer (IPT and CPT) have many similarities. This paper aims to explore the remaining opportunities in CPT systems, not yet reported in existing literature, based on duality with the mature IPT technology. First, a generic modeling method based on two-port network theory is proposed, which contributes to unified modeling and analysis for both inductive and capacitive couplings. Then, power transfer mechanism of IPT and CPT couplers is compared, and unified transfer efficiency is derived, promoting CPT theory developments. Last, the duality between existing IPT and CPT circuits is demonstrated in two aspects: compensation circuit configuration and resonant relationship. 14 CPT topologies are derived based on duality with the existing 7 mainstream IPT circuits, of which 11 circuits do not exist in literature, offering future opportunities in CPT. Detailed comparison and evaluation of the derived 14 CPT circuits are conducted, and high-performance circuits are recommended. As a demonstration, a case study of a 2.1kW 3MHz CPT system is implemented in hardware based on the newly proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> - <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SS</i> topology. This example system achieves a peak efficiency of 93.19% with the predicted circuit properties of load-independent constant-voltage (CV) output and zero-phase-angle (ZPA) property.

Simple Enhancement of Series–Series-Compensated Inductive Wireless Power Transfer Links Operating With Load-Independent Voltage Output at Fixed Frequency to Attain Zero Inverter Phase Angle

It is well-known that series-series compensated resonant inductive wireless power transfer links (SS-IWPTL) may be designed to attain load independent voltage output (LIVO) for given operating frequency and coupling coefficient. Unfortunately, corresponding inverter output impedance is either highly-inductive or highly-capacitive (inductive region is typically preferred due to natural zero-voltage switching (ZVS) of inverter transistors), significantly increasing inverter volt-ampere (VA) rating. The letter demonstrates that designing the SS-IWPTL for operation in the capacitive region and then adding a shunt inductor across AC-side terminals of either inverter or rectifier while allows attaining inverter zero phase angle (ZPA) thus minimizing its VA rating.

An LCC‐S compensated wireless power transfer system using receiver‐side switched‐controlled capacitor combined semi‐active rectifier for constant voltage charging with misalignment tolerance

AbstractThe output characteristics of wireless power transfer systems are strongly susceptible to coupling and load variations. To achieve a constant voltage output under varying coupling and load, a voltage regulation method based on a combination of a semi‐active rectifier (SAR) and a switched‐controlled capacitor (SCC) is proposed for the LCC‐S topology. Adjusting the SAR can effectively regulate the voltage, and the introduction of SCC compensates the impedance brought by SAR, ensuring that the resonance condition is fully satisfied at the receiver side. Thus, the proposed wireless power transfer system can achieve zero phase angle over the entire load and coupling range, minimizing reactive power losses. This control method only needs to collect the signal from the receiver side, which enables single‐side control as well as avoids the wireless communication. The situation of coupler parameter drift due to misalignment is also considered. Even if the self‐inductance changes, the zero phase angle can be guaranteed on the receiving side by adjusting the SCC, and the zero voltage switching of the transmitter side can still be achieved. The principle prototype of 3 kW is constructed and the experimental results prove the effectiveness of the proposed method.

Compact Z-Impedance Compensation for Inductive Power Transfer and its Capacitance Tuning Method

This article proposes a Z-impedance compensation for inductive power transfer (IPT). There are three contributions. First, a Z-impedance-S compensated IPT topology is developed to achieve constant transmitting current, load-independent constant-voltage output, and zero-phase angle (ZPA) property, which is an alternative to the conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -S topology. Second, compared to an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> circuit, the Z-impedance compensation burdens much smaller current/voltage stress and shows lower sensitivity to compensation capacitance drift, contributing to high-power applications. Third, a capacitance tuning method is proposed to regulate power, which improves the misalignment tolerance. Two 5 kW Z impedance-S and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -S IPT prototypes are implemented. Experiments show that the Z-impedance-S IPT system achieves comparable power and efficiency with an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -S IPT system with smaller current/voltage stress and lower sensitivity. The proposed capacitance tuning method is effective to maintain a rated 3 kW output within a horizontal misalignment of [0 100 mm] with zero-voltage-switching and ZPA operation. Meantime, A peak dc-dc efficiency of 96.88% is realized in the Z impedance-S IPT system at 3.47 kW.