International Journal of Circuit Theory and Applications最新文献

To meet the stringent charging requirements of electric vehicles, wireless power transfer (WPT) systems must inherently possess both constant current (CC) and constant voltage (CV) output characteristics. However, most existing systems typically maintain CC and CV outputs only under fixed mutual inductance (MI) conditions, requiring parameter reconfiguration when MI varies, thereby limiting practical applicability. To address these limitations, this paper proposes a novel LCLC-LCC compensated WPT system that maintains both CC and CV outputs across varying MI conditions while ensuring zero phase angle (ZPA) operation in two modes. The comprehensive analysis of equivalent circuits for two operating modes and detailed derivation of topology parameters are given. Extensive simulation results validate the ZPA operation in two output modes. Finally, experimental verification is conducted. Experimental results demonstrate that the LCLC-LCC compensation system successfully achieves CC and CV outputs while maintaining ZPA input under varying MIs. When the coupling coefficient is 0.25, the maximum DC-DC efficiency in the two output modes is 93.28% and 94.35%, respectively.

Wireless power transfer (WPT) technology has been widely studied and applied due to its ability to transfer energy without physical contact. Compared to single-phase WPT systems, three-phase WPT systems offer advantages in power density and magnetic field distribution. However, changes in the distance between coupling coils can alter transmission power. The parity-time (PT) symmetry principle has been proven to enable stable power transmission in single-phase WPT systems. To enhance power transmission stability in three-phase WPT systems, this paper proposes a three-phase WPT system based on the PT symmetry principle. Two major challenges must be addressed for three-phase systems to operate in PT symmetric state: the design of circuit structures and parameter conditions that satisfy the PT symmetry and the complex circuit equations due to interphase mutual inductance. Firstly, a theoretical analysis is conducted to establish the conditions required for the three-phase WPT system to operate in a PT symmetric state. The circuit equations are then simplified based on the characteristics of three-phase symmetric systems. Following that, the transmission characteristics of the system are obtained using circuit theory. Finally, an experimental prototype is designed and built to validate the feasibility and effectiveness of the proposed three-phase PT-based WPT system.

The dual-channel permanent magnet synchronous motor (PMSM) combines high torque density, low torque ripple, and strong fault tolerance, making it ideal for applications in electric vehicles, aerospace, and wind turbine generators. However, the specific existence of unbalanced power supplies leads to current harmonics and current unbalance, which increases system losses and significantly affects control performance. In this paper, an improved current control scheme is proposed to solve these problems. First of all, the proposed approach introduces a transformation matrix that reformulates two odd harmonics into one even harmonic component, reducing the number of controllers. Meanwhile, the PI controller paralleled with multiple resonant controllers is developed, considering compensation in both the d–q and x–y subspaces, so that the major harmonics are suppressed. Even under substantial voltage differences, the system achieves a marked reduction in harmonics compared to traditional unbalanced supply systems. Finally, the experimental results demonstrate that the proposed control strategy can effectively improve performance.

The traditional phase-segregated arc suppression (AS) methods often neglect the influence of line voltage drop (LVD), resulting in the problem of large residual current when single-line-to-ground (SLG) faults occur at the end of heavily loaded lines, making reliable AS difficult. To effectively suppress fault currents during medium and low impedance SLG faults at the end of heavily loaded lines, the phase-segregated AS method considering LVD is proposed in this paper. Additionally, the phase-segregated AS method, which is based on sliding mode control using an exponential convergence rate, is utilized to reduce the total harmonics distortion of fault current and neutral point voltage after current injection. The simulation results validate the effectiveness of the proposed method under the case of the medium or low impedance ground fault occurring at the end of heavily loaded lines.

In three-level neutral-point-clamped (NPC) inverter, dead-time elimination PWM has advantages such as high voltage utilization, reduced switching loss, and avoid the dead-time effect (DTE). However, this modulation method has the issue of narrow pulses, which may affect the switching states and potentially lead to a short circuit in the inverter. To address this issue, this paper first analyzes two mechanisms and ranges of narrow pulse generation in a single-phase NPC inverter. Then, a novel narrow-pulses elimination strategy is proposed. The proposed strategy predicts the narrow pulses in advance and adjusts switching period to eliminate them. Additionally, the SOGI-PLL is used to predict the current phase angle to solve the narrow pulses and distortion in the current zero-crossing. Compared to existing narrow-pulse elimination methods, the proposed strategy can completely eliminate narrow pulses, ensuring reliable circuit operation while maintaining high-quality output waveform. Finally, the effectiveness of the proposed strategy is validated through simulations and experiments.

Accurately calculating the mutual inductance between coils is crucial for achieving an efficient and reliable wireless power transmission system. However, when a double-sided magnetic medium coil undergoes any positional change, it typically relies on simulation software to obtain the mutual inductance value, lacking a straightforward calculation method. To address this, this paper proposes a unilateral mirror current equivalent method to derive the mutual inductance formula for coils with double-sided magnetic medium at arbitrary positions. This method replaces the magnetic medium on the receiving side with a mirror current coil, equating the mutual inductance to the sum of the mutual inductance when only the transmitting side magnetic medium is present and the mutual inductance when the mirror current is acting without magnetic media. By analyzing the variation of the mirror current coefficient, a formula for the mutual inductance between coils with double-sided magnetic medium during positional changes is derived. An experimental setup with the same parameters as the simulation model was built using acrylic plates, copper wires, and other materials. The mutual inductance experimental values were measured using an impedance analyzer. Simulation and experimental results indicate that the calculated mutual inductance values have an error of no more than 5.30% compared to experimental values. This method remains applicable even when the parameters of the coils and magnetic media change, and it is 70 times faster than simulation, thereby validating the effectiveness and speed of the calculation method.

The dynamic performance of power electronic interface power supplies is enhanced by the virtual synchronous generator (VSG) through the emulation of synchronous generator (SG) characteristics. In voltage source converter-based multiterminal high-voltage direct current (VSC-MTDC) systems, DC voltage regulation is achieved through the coordinated participation of converter stations, where the power reference of the VSG is influenced by DC voltage control. The droop coefficient of the VSG's DC voltage loop is found to significantly affect both the dynamic convergence of port power output and the steady-state distribution of port power. In this study, the impact of DC voltage droop control on system performance is analyzed, the influence of the droop coefficient on steady-state power distribution is assessed, and an optimization strategy is proposed to enhance the dynamic output characteristics of VSC-MTDC systems. Through simulations, it is demonstrated that the optimized droop coefficient improves system stability, accelerates dynamic response, and effectively balances power and frequency regulation. These findings provide valuable insights for the practical implementation of VSG-based control strategies in VSC-MTDC networks.

This paper presents a novel DC–DC boost converter topology that works similarly to a conventional PWM DC–DC boost converter, but with remarkable improvements. When the filter capacitor voltage in the conventional converter matches the output voltage, the proposed converter lowers the filter capacitor's rated voltage by an amount equivalent to the input voltage. As a result, compared to conventional boost converters, the proposed converter achieves 6% higher power density and 6.3% cost reduction due to the filter capacitance with the lower rated voltage. In addition, the proposed converter enables direct power transfer (DPT) by transferring part of the input energy to the output stage when the switch is in the on-state. This feature not only simplifies the structure of the converter but also increases its efficiency and lowers the cost, making it more practical for various applications. Comprehensive theoretical analyses of the converter are provided, supported by implementing of a 50-kHz, 100-W laboratory prototype. The experimental results validate the theoretical analyses, demonstrating an overall efficiency of 95.1% at the nominal output power rating.

To address the issue of output power fluctuation during dynamic wireless charging, this paper presents an optimized dynamic wireless power transfer (DWPT) system transmitting end for electric vehicles (EVs). The system realizes a load-independent constant-voltage output by selecting a multitransmitter LCC-S network topology. This paper gives an analysis of a dual-transmitter LCC-S network considering cross-coupling, as well as a multitransmitter LCC-S network eliminating cross-coupling. The conclusions are generalizable. This paper develops a generalized analytical model for the mutual inductance of rectangular coils. By partially overlapping the transmitter coils, the cross-coupling is eliminated, and an optimized design of the transmitter coils system is achieved. The optimization parameter is applicable to any conventional rectangular transmitter coils system. The system is designed to be simple and easy to apply, achieving automatic current distribution on the inverter side without control modules. A 2-kW DWPT prototype, using 85-kHz operation frequency, is constructed according to the designed magnetic coupler and circuit parameters. The experimental results show that the system can maintain a high average efficiency (80%) and 1.89kW average DC output power in the dynamic charging process. The changes in the load do not affect the output voltage. The transmitting end of the DWPT system can provide a constant-voltage output with only ±3% fluctuation, the output power fluctuates less than ±6% from the average, and the transmission efficiency fluctuates less than ±2% from the average.

This paper presents the design of a battery-free energy harvesting system that operates in intermittent mode (i.e., burst mode). This paper aims at keeping the step-up converter and load together in idle state without consuming any power during a large fraction of time in order to store energy at the supercapacitor. Once accumulated enough energy, the converter and load receive energy in a small time duration. The system deploys a feedback circuit to prevent energy waste by keeping the output voltage in the acceptable range of 3.3–4.2 V. Implemented with discrete components, the measurement result demonstrates that the system achieves a load dynamic range of 20,000 (i.e., 1 $�\mu$W to 20 mW) with a peak end-to-end efficiency of 60.85%. By means of the feedback circuit, the system improves the efficiency by up to 35.5%.