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Due to active power demand in the distributed power system, the large voltage deviation appears in the grid network. The battery energy storage system is optimal solution to support the active power when it is needed, which improves the voltage stability. To maintain the accuracy in the active power injection, the modified hysteresis current control of multilevel converter for grid connected battery storage system is proposed in this paper. It supplies accurate active power by estimating the exact reference current from the grid voltage at every sampling period. This novel control mechanism ensures that there will not be any mismatch in the active power requirement and supply; thereby it enhances the quality of grid under nay situation. The detailed control block diagram is addressed to generate the required PWM signals. And also, the detailed operating waveforms are discussed in this paper. The equivalent circuit of power transfer to grid is also reported in this paper. Mathematically it gives that the proposed approach can inject the actual active power needed by the system. To validate the proposed modified hysteresis current control scheme of multi-level converter, the entire simulation study has been developed and carried out in PSCAD/EMDTC software. The measured results observed and presented in this paper and also it confirms that the proposed has practical feasibilities to implement in the real system.

Intelligent reflecting surface (IRS) has received widespread attention because it can significantly improve the performance of wireless networks. The X-duplex is a more flexible duplex mode, which can decrease a small sum rate in exchange for a higher quality-of-service performance. In this article, an IRS transmission scheme based on X-duplex is investigated to enhance the flexibility and freedom of communication design. We present the X-duplex IRS with the simultaneous wireless information and power transfer, and establish a power consumption model based on real application scenarios. An alternating optimization algorithm is proposed to maximize the energy efficiency (EE) of a multi-input single-output (MIMO) network assisted by the X-duplex IRS. As for the X-duplex relay, we explore an algorithm based on the golden section to optimize the EE. Simulation results comprehensively evaluate the performance of the two auxiliary transmission methods. The X-duplex IRS has higher EE and weighted sum rate (WSR) than the X-duplex relay when sufficient transmission power is available. However, the IRS cannot entirely replace the traditional relay. The X-duplex relay with self-interference energy harvesting achieves a higher WSR and EE when the access point energy is limited or the transmission distance is short.

This paper describes an integrated voltage-boosting technique, which is essential to achieve compatibility between low-voltage PV panels and high voltage DC-links needed for the dc-to-ac conversion. To achieve the twin objectives of voltage-boosting and multilevel inversion, this paper proposes a transformerless T-type nine-level hybrid boost inverter. To improve the efficiency in the boosting stage of the proposed converter system, a significant portion of the PV energy is directly transferred from the PV source to the load, while the other part is processed through an interleaved converter, which is fused with the inverter. Thus, the proposed converter ensures a higher power density and reduces the power ratings of the semiconductor devices. This paper also introduces a modified zone-based PWM technique, which achieves a complete elimination of the switching frequency voltage transitions in the total common-mode voltage (TCMV). Thus, this technique mitigates the generation of leakage current while preserving the advantages of conventional multilevel inverters such as low dv/dt, inductive power capability. Besides that, a rigorous mathematical analysis for the common-mode equivalent circuit of the proposed configuration is also presented in this paper. Detailed simulation and experimental studies are carried out to validate the feasibility of the proposed configuration.

This paper proposes an improved hybrid parallel compen-sator (IHPC) for enhancing the power transfer capability of a photovoltaic (PV) grid-connected inverter. A thyristor switched capacitor (TSC) module is used in series with a conventional inductive-coupling voltage source inverter (IVSI) to reduce the DC-link voltage. Under a low DC-link voltage, the voltage across the insulated gate bipolar tran-sistor (IGBT) will also be low, which will reduce the voltage stress of the IGBT, thereby improving the reliability and reducing the loss of the VSI. First, the mechanism of reac-tive compensation for improving the PV inverter power transmission capability is analyzed. Then, the circuit con-figuration and operating principle of the IHPC are intro-duced. After that, an optimal control strategy for the IHPC is proposed to address the resonance problem caused by the TSC connected in series with the L filter and to improve the compensation performance of the IHPC. Finally, the effec-tiveness of the proposed IHPC and the control method is validated by the simulation and experiments. The results show that the IHPC with optimal control strategy can achieve continuous reactive power compensation under a low DC-link voltage, thereby enhance PV power transfer capability.

Vehicle to Vehicle (V2V) energy sharing is emerging as an alternate solution to range anxiety and limited charging infrastructure challenges associated with electric vehicles (EVs). The existing off-board DC fast charging options for V2V ap- plication found in the literature are not effective due to the additional weight, size and cost of the external charger or interface. In this paper, a new V2V interface is proposed in which both EVs motor winding neutrals and negative rails of on-board drivetrains are directly connected to each other. This further helps in forming an integrated dual bidirectional DC-DC converter to control the direction of power flow. The proposed approach does not require reconfiguration of motor winding or mechanical clutch to arrest the motor from rotating and/or the reconfiguration of drivetrain inverter connections. The major hardware requirement for the proposed approach is, access to the already existing neutral connection of the EV motor phase windings. Furthermore, Finite Element Analysis is presented for 150 kW EV motor model and its performance validation with the high frequency DC current flowing in the motor windings during the V2V operation. A scaled lab prototype is developed to demonstrate the energy sharing between two Lithium-ion battery banks through proposed direct V2V power transfer concept.

In the inductive charging scenario of an electric vehicle (EV), the charger should have the capability to flexibly regulate the output power regardless of the misalignment and EV battery voltage. This paper proposes a hybrid voltage and frequency tuning strategy for a series-series (SS) inductive power transfer (IPT) system to regulate power through 0 to 3.3kW at any battery voltages and misalignment conditions without using additional converters. A voltage tuning is used to achieve full-power of 3.3kW and partly contribute to reducing the power. When the input voltage achieves the lower limit, a frequency tuning is used to further decrease the power to 0W, achieving the regulation through 0 to full power. The practical charging region is specified by 110mm airgap, 100mm misalignment in both x and y directions, and 180V-240V battery voltage range. Experiments are carried out at various conditions, and it shows that with an input voltage range of 180V-380V and a frequency of 82.5kHz~87.9kHz, the charging power can be regulated between 100W and 3.3kW at any case in the specified working region. In addition, a peak dc-dc efficiency of 95.7% is achieved at 3.29 kW.

In this paper, a new method is introduced for operation of three-phase symmetric cascaded H-bridge (CHB) multilevel inverter (MLI) after failure of power switches. When a switch fails, the faulty leg of the H-bridge is bypassed and the remaining leg is kept in use. Even with multiple faults in different H-bridge cells, the CHB is optimally reconfigured to continue its operation with its maximum healthy capacity. Based on the remaining operational part of the converter, a fault tolerant control scheme with zero-sequence voltage injection (ZSVI) is proposed to synthesize a balanced line-to-line voltage. Using this method, the post-fault line-to-line voltage of CHB is maximized with the minimum common mode voltage (CMV). Reduction of CMV is of importance in motor drive application. Also, fundamental component of CMV affects the real power of CHB phase legs. Through reducing the fundamental CMV, unidirectional power transfer from the dc side to the ac load is achieved in a wide operation region. The performance of the presented fault tolerant technique is verified in MATLAB/SIMULINK environment and validated on a three-phase 5-level hardware prototype

In this article, we consider the millimeter-wave simultaneous wireless information and power transfer nonorthogonal multiple access (NOMA) relay networks in the presence of multiple passive eavesdroppers, where the near and far Internet of Things (IoT) devices with different communication requirements are served by one source with the help of the relays, and stochastic geometry is used to characterize the distribution of multiple nodes. First, a NOMA pairing and relay selection scheme is designed. Then, the closed-form expressions for the energy-information coverage probability (EICP) and the effective secrecy throughput of the near IoT devices are derived. Finally, the EICPs of the far IoT device under random relay selection and opportunistic relay selection schemes are obtained. Moreover, the asymptotic expressions of the EICP for both the near and far IoT devices are derived, which show that the asymptotic EICP when the number of antennas at the source or relay tends to infinity is only dependent on the location distribution of nodes and blockage environment. The simulation results show that NOMA can outperform orthogonal multiple access, and the advantage of the opportunistic relay selection scheme over the random relay selection scheme is more obvious when the density of the relay is relatively large.

In this article, a two-hop simultaneous wireless information and power transfer relay network using a decode-and-forward strategy is considered. In order to improve the spectral efficiency, the relay node performs in full-duplex (FD) mode, and each node is equipped with multiple antennas. First, the end-to-end achievable rate is formulated for FD and half-duplex (HD) modes under imperfect channel state information (ICSI). Then, the optimal closed-form expressions for power allocation at the source and relay, as well as the energy harvesting ratios, are derived for primal variables associated with the dual variables through analytical solutions. We propose an iterative primal-dual algorithm based on the ellipsoid method so as to obtain final answers. Numerical results demonstrate the FD achievable rate superiority over the HD mode under proper self-interference cancellation (SIC). According to the existing results, there is an immense discrepancy between the achievable rates in perfect CSI and ICSI cases. Also, the impact of the relay distance from the source node, the number of antennas, and different SIC modes are investigated on the end-to-end achievable rate.

The bipolar pad is one of the most promising topologies in inductive power transfer systems for electric vehicles. However, there is scant literature on the analytical model of the bipolar pad. In this paper, a 3-D analytical model of the inductive power transfer system including a bipolar transmitter and a square receiver is developed based on the superposition of two 2-D subdomain analytical models. Ferrite and the aluminum shields with finite dimension are taken into account on the transmitter and receiver sides. An analytical calculation of the mutual inductance is then carried out with respect to the main parameters of the inductive power transfer system, namely the dimension of the coils, the conductivity and the permeability of the shield. Two study cases are demonstrated to highlight how the proposed method can accelerate speed up the pad design process. Calculation results of the proposed model are compared with both a finite element analysis model and experimental measurements, demonstrating that the proposed model is 9 times faster than the finite element analysis method. When comparing with the experimental results, computational error of the proposed model is less than 6% in most of the study cases

One of the challenges faced in the design of inductive power transfer (IPT) highway is the detection of electric vehicle (EV), to enable charging, as it travels along the highway. When a primary coil buried under the highway has sufficient coupling with the secondary coil mounted on the vehicle, it is energized to initiate IPT. In this paper, a tunneling magnetoresistance (TMR) sensor based EV detection method on an IPT highway is proposed. In the proposed scheme, a detection coil is wound around the outer boundary of the secondary coil and it is excited at 400 kHz. The TMR sensors are arranged close to the primary coil such that it senses the magnetic field generated by the detection coil. The TMR sensors are placed over the leading and trailing edges (in the direction of EV travel) of the primary coil. From the leading edge TMR sensor outputs, the energization point of that primary coil to begin IPT is decided. Similarly, from the trailing edge TMR sensor outputs, the de-energization point to stop IPT from that primary coil is decided. Also, the effective area of overlap between the coils due to lateral misalignment is estimated. This enables the driver in correcting the lateral misalignment so that efficient charging is possible from the subsequent primary pads. A laboratory scale prototype was built and was tested. The results obtained prove the usefulness of the scheme.

To ensure the effectiveness of the inductive power transfer (IPT) systems for high power applications, the multiple coils are being used. But the cross-couplings among the same side coils reduce the efficiency of the system. Thus, the decoupling coils are commonly used to mitigate the same side couplings in multiple transmitters and receivers system. The decoupling coils are either used outside of the main coils or concentric with the main coils. In both cases, these decoupling coils do not take part in the power transmission and have some adverse effects on the system performance. In this paper, a new IPT system with dual transmitters and dual receivers with integrated decoupling coils is introduced. Besides mitigating the mutual inductances of the same side coils, the proposed decoupling coils are also taking part in power transmission. In addition, the proposed coils also have good misalignment performance. A three-dimensional finite element analysis (FEA) tool ANSYS MAXWELL is used to investigate the proposed magnetic coupler. A scaled-down experimental setup is used to verify the feasibility of the proposed structure. The maximum dc-dc efficiency of this system is 93.14 % while delivering 700 W to the load with a 200 mm air gap.

In order to address the issue of wireless communication signal blocking in the traditional cavity resonance wireless power transfer (CR WPT), a wall-meshed cavity resonator constructed of the meshed metallic walls is proposed together with an analytical design method. This cavity resonator can not only generate and confine the electromagnetic waves of natural resonant modes inside the cavity resonator, but also support wireless communications with outside. The wall-meshed cavity resonator is analytically designed by the known theoretical equations without time-consuming optimizations and verified by electromagnetic simulations and experiments. The results show that the proposed CR WPT system can achieve simultaneous wireless power transfer in the cavity and wireless communications with outside. The maximum power transfer efficiency is higher than 85%. The power transfer efficiency exceeds 60% within about 70% areas inside the wall-meshed cavity. For wireless communication signals passing through the wall-meshed cavity, the attenuation at 2.1 GHz (4G), 2.45 GHz (Wi-Fi), and 3.5 GHz (5G) is about 6.0 dB, 5.1 dB, and 3.8 dB, respectively. Additionally, the safety performance of the proposed CR WPT system is numerically investigated by the specific absorption rate analysis of a human torso model.

This paper presents a resonant frequency tuning (RFT) Delta-Sigma (-) signal-transformed pulse density modulation (PDM) class-D converter for inductive power transfer (IPT) applications. The proposed power controller provides a load-adaptable pulse modulation by tracking a zero phase angle(ZPA) and peak-power frequency, i.e. resonant frequency in the primary-side high frequency inverter. The switching frequency is regulated in accordance with the variations of the load and coupling co-efficient between the transmitting(Tx) and receiving(Rx) coils. The output power is controlled by the RFT - PDM which is effective for reducing a low frequency oscillation (subharmonics), thereby the high efficiency power transmission can attain. The essential performances of the proposed IPT power controller are demonstrated in experiment of a 400W-500kHz of prototype, whereby the feasibility is clarified from a practical point of view.

In an inductive power transfer (IPT) system, the variations of passive parameters affect the system performance. This paper investigates the impact of the variation of resonant parameters on the system power and efficiency in a 5.7 kW LCC compensated IPT system for electric vehicle (EV) charging application. For the single-parameter variation, the sensitivity of power and efficiency to each parameter is investigated by LTspice simulation. For multi-parameter variations, exhaustive analysis and Monte-Carlo methods are applied to quantify the sensitivity issue. It indicates that with random multi-parameter variations within ±10%, the 5.7kW IPT system only has a 73.87% probability to satisfy a 10% power fluctuation of [5.13kW, 6.27kW] with efficiency above 92%. To mitigate the sensitivity issue, the cascade Monte-Carlo method is used to optimize the central values of parameters at the design stage, which can increase the yield rate in mass production from 73.87% to 82%. Furthermore, a frequency tuning method is proposed to regulate power and efficiency. Finally, a 5.7kW full-power prototype is implemented. Experiments are performed using three special parameter combinations, which validated the sensitivity concern and the feasibility of the proposed frequency tuning method.

Because a transmitter-side controller of an inductive power transfer (IPT) system cannot directly measure its load conditions, i.e. receiver-side output voltages and currents, wireless communications are commonly used in many IPT systems. However, the wireless communication can cause a devastating failure of the IPT system because of its tens of milliseconds delays and frequent data losses. The mismatch between the transmitted and the received power can destroy the receiver-side power converters. In this study, receiver-side load voltage and current observers for a seriesseries tuned IPT system are proposed using well-known disturbance observer theories. A load current observer that has a 10kHz estimation bandwidth and a load voltage observer that has a 200Hz bandwidth are proposed. Estimated load voltage and current have much faster dynamics than the wireless feedback signals without data loss. Therefore, the proposed observers can bring significant advances in reliability and performance of the IPT system. Design guidelines for the observers that have low steady state errors and fast dynamics are suggested. Theoretical performances of the proposed observers are evaluated by simulations and experiments. Estimated current followed its actual value in 0.1ms and the estimated voltage followed its measured value in 4ms as expected from the simulations.

This paper investigates the robust beamforming design in a secrecy multiple-input single-output (MISO) network aided by the intelligent reflecting surface (IRS) with simultaneous wireless information and power transfer (SWIPT). Specifically, by considering that the energy receivers (ERs) are potential eavesdroppers (Eves) and imperfect channel state information (CSI) of the direct and cascaded channels can be obtained, we investigate the max-min fairness robust secrecy design. The objective is to maximize the minimum robust information rate among the legitimate information receivers (IRs). To solve the formulated non-convex design problem in bounded and probabilistic CSI error models, we utilize the alternating optimization (AO) and successive convex approximation (SCA) methods to obtain an approximate problem. Then, an iteration-based algorithm framework was proposed, where the unit modulus constraint (UMC) of the IRS is handled by the penalty dual decomposition (PDD) method. Moreover, a stochastic SCA method is proposed to handle the outage constrained design with statistical CSI. Finally, simulation results validate the promising performance of the proposed design.

Inductive power transfer (IPT) systems are appropriate for electric vehicles charging applications because of the advantages of safety and convenience. However, due to the considerable influence of pad misalignment, improving misalignment tolerance is important for IPT systems. Besides, constant current (CC) and constant voltage (CV) output characteristics are usually required for electric vehicles battery charging. Therefore, to fulfill both features, a hybrid IPT system implementing high misalignment tolerance with inherent CC-CV output is proposed for electric vehicles charging applications in this paper. Two coils connected reversely in series are applied in transmitter side while two coils respectively compensated by a capacitor and an inductor-capacitor-capacitor are applied in receiver side. Hence, without extra DC-DC converter or complicated control strategy and corresponding circuits, CC-CV output can be naturally achieved with high misalignment tolerance which obviously increase the system reliability. Besides, zero-voltage switching and zero phase angle condition can be easily achieved. A 1kW experimental prototype is built. The experimental results show that the fluctuations of the constant charging current and the constant charging voltage are less than 5% when the proposed system operates within the predetermined misalignment range.

The data transmission is always necessary for wireless power transfer system, however, the interference between power and data is the major problem for the full-duplex simultaneous wireless power and data transfer (SWPDT) system. To solve this problem, in this paper, a novel SWPDT system based on the double-side LCCL and dual-notch filter is proposed. In the power transfer channel, by the double-side LCCL topology the high impedance of power branches at the data carrier frequency reduces the power interference largely. In the data transfer channel, the dual-notch filter is utilized to separate the data carriers and realize the full-duplex communication, which could reduce the ipsilateral data interference and improve the signal-to-noise ratio (SNR). The transfer functions of data transmission is derived by the analysis on the impedance of each part. Since the interferences of power and ipsilateral data source are analyzed, the expression of SNR could be derived and the corresponding factors to improve the SNR are discussed. An optimization of data transfer channel to maximize the SNR is proposed by shifting the dual-notch filter and transformers. The experimental setup with 400W output power, 200kb/s data rate is conducted to verify the feasibility of proposed SWPDT system and the correctness of the design method.

The integration of unmanned aerial vehicles (UAVs) into future-generation wireless networks is a promising strategy for complementing terrestrial communication infrastructures that will lead to capacity and coverage improvements. Unfortunately, the energy limitations of the existing off-the-shelf small-size UAVs are significant challenges, especially during long missions. In this article, first, we investigate the communication model of a heterogeneous UAV-assisted wireless network that consists of multiple energy-constrained battery-powered small-size UAVs (a.k.a. follower UAVs) and a large-size UAV (a.k.a. dispatcher UAV) with solar energy harvesting capability. Subsequently, we propose an aerial energy sharing algorithm to improve the lifetime of the system by orchestrating energy balancing among follower UAVs. In particular, the dispatcher UAV having large energy capacity owing to its battery size and solar energy harvesting capability shares its energy with follower UAVs using radio-frequency-based power transfer through beamforming. The proposed energy sharing algorithm considers the placement, available battery capacity, and mission execution time of the follower UAVs to decide the energy sharing points with optimum efficiency. Extensive simulations show that our proposed algorithm outperforms existing algorithms in terms of charging efficiency and energy balancing among UAVs.

In this letter, a solution to achieve changeable inductance without any other auxiliary circuit based on PWM modulation for coupled inductor is proposed to reduce the circulating current at steady-state and limit the inrush current during start-up for input-serial-output-parallel (ISOP) dual-active-bridge (DAB) converter in solid-state-transformer (SST) applications. By modulating the PWM signals, the equivalent inductance of coupled inductor can be changed without any other auxiliary circuit. The smaller equivalent inductance is adopted in steady-state to reduce the circulating current and increase the power transfer capability. And the larger equivalent inductance is used to limit the inrush current during the start-up. The analysis based on the modulated coupled inductor for the steady-state and the start-up process is given. The design consideration for the coupling coefficient is introduced according to the optimization of leakage inductor root-mean-square (RMS) current, inrush current and the filter capacitance. Finally, the comparison of experimental results between the proposed solution and the conventional method from a 1600W/250kHz prototype verifies the effectiveness.

To design simple and efficient inductive power transfer (IPT) systems, minimum number of conversion stages and effective maximum efficiency tracking (MET) are the primary design criteria. The MET control uses a fast mutual inductance estimation (MIE) algorithm to achieve fast tracking of the maximum efficiency point especially when the variation of the gap distance and misalignment of the magnetic coupler are significant. The feedback control of the MET-MIE IPT system should be designed without a wireless communication channel to improve stability and robustness. In this paper, a novel MET-MIE control strategy is proposed for achieving simplicity and high efficiency in IPT systems. Verifications are provided by simulations and experiments. It is shown that maximum efficiency can be tracked with less than 4% error in MIE under significant variation of the gap distance and misalignment of the magnetic coupler.

Coil design and operating frequency are key factors impacting the efficiency of inductive power transfer system. This paper presents the modeling of PCB spiral coils, design optimization and analysis on coil geometry and operating frequency for medium voltage applications, such as auxiliary power supplies for medium voltage converters. Analytic model considering the geometric distribution of the magnetic field is proposed to calculate with high accuracy equivalent electrical parameters of coils. For a defined design space and constraints, a large number of coils are designed in order to determine their performances and select optimal coil geometries. Selected coil designs are prototyped and experimentally verified under design-specific conditions. In addition, further characterization is performed considering variations of several parameters that can be encountered in practice.