Search

In order to improve the integration and life time of ac voltage input wireless power transfer (WPT) system, a topology based on electrolytic-capacitor-less matrix converter with inductor-capacitor-capacitor-series (LCC-S) resonant network is proposed. The relationship between the conversion ratio of the output and input voltages and resonant parameters are analyzed. It reveals although the boost operation is achieved by the parameter design of LCC-S network, it makes the system sensitive to the parameter variations. In order to extend the voltage conversion range, the improved two-stage WPT system based on the single-stage one is proposed. The dual-side closed-loop control of the two-stage system without the wireless communication is further proposed. The corresponding small-signal model is built and the parameters of the closed-loop controllers are designed. The feasibility and practicability of the proposed system are verified by the experiments.

In this letter, an integrated wired/wireless charging topology is proposed to expand the adaptability of the electric vehicle charging stations and further improve the utilization of the charging facilities and venues. By reusing the common structures in the independent wired and wireless charging topologies, on the basis of achieving the wired and wireless charging functions, the integration of charging facilities is improved, and its cost is reduced. Based on the isolated converter in the wired mode, a frequency tuning strategy in the wireless mode is proposed to overcome the frequency detuning problem caused by the parameter fluctuations. The feasibility and practicability of the proposed topology and the frequency tuning strategy are verified by the experiments.

In the LCC-LCC wireless power transfer (WPT) system with the secondary buck converter, the overvoltage (OV), and overcurrent (OC) faults occur when the secondary buck converter is shut down suddenly. To ensure safety, this issue is analyzed at the transient level and the dual-side indirect closed-loop control strategy is proposed to achieve the closed-loop control of the terminal voltage and the secondary dc bus voltage. The secondary dc bus voltage is under the indirect control by the closed-loop control of the primary inverter current and this conclusion is proven in the transient level. Under the dual-side closed-loop control strategy, the two-stage WPT system forms a cascade system and there is the instability problem. The integrated design criteria of the dual-side controller parameters based on the cascade system stability theory are given. The feasibility and practicability of the proposed control strategy and parameter design method are verified by the experiments.

Inductive power transfer (IPT) systems are playing an increasingly important role in electric vehicles, rail transit, industrial production and daily life. In the above practical applications, the misalignment of coupling coils is a very common phenomenon. To achieve high efficiency and a stable output under coil misalignment, a novel hybrid IPT system with a four-coil coupler is presented in this paper. The presented IPT system only uses a single mode switch to satisfy the battery charging requirements. When compared with existing typical IPT systems, the presented IPT system has fewer compensation components, and does not need complex control, a communication link between the transmitter and the receiver, and frequency switching. Moreover, to ameliorate the misalignment tolerance of the system, a Double-D/Bipolar (DD/BP) four-coil coupler is applied to the presented IPT topology. A 680 W experimental prototype with a 94.7% peak efficiency is built to verify the feasibility of the proposed scheme. Experimental results indicate that the presented IPT system can cope with simultaneous variations of the load and coupling coefficient within a ± 150 mm misalignment in the Y-axis and a ± 15 mm in the X-axis.

The port harmonic features of the single-phase single-stage high-frequency isolated dc–ac converter is not analyzed so far and the corresponding theoretical basis for improving the current quality is still a research gap. In this article, a linear model in frequency domain of the single-stage high-frequency isolated dc–ac converter is originally derived based on the combined harmonic state-space and extended description function modeling technique. The systematic modeling process is analyzed and the accuracy of the modeling is verified by the simulation results. Combined with the model analysis, the harmonic coupling characteristics between the ac side and the dc side are clearly presented. On this basis, this article proposes a closed-loop control strategy to reduce the decrease of the dc-side and ac-side current quality caused by the harmonic coupling at the control level. Furthermore, this article constructs the compound controllers based on the p-type iterative learning to suppress the harmonic currents of the dc side and the ac side, respectively. The composite controller does not distinguish the harmonic frequency. Hence, the proposed controller achieves the effective suppression of the harmonic currents in real time. The effectiveness and feasibility of the proposed control strategy are verified by the experiments.

To significantly reduce switching loss of the high frequency inverter in battery wireless charger (BWC), improve the soft-switching stability and system reliability, a novel soft-switching BWC with low loss auxiliary network and reconfigurable rectifier is presented. The presented soft-switching BWC can implement the smooth switching between constant current mode and constant voltage mode without frequency switching and relays, which is beneficial to enhancing the system stability. With the help of a novel low energy consumption auxiliary circuit, the power switch tubes in the H-bridge inverter can implement zero-voltage soft switch-on and zero-current soft switch-off in the full range, completely eliminating switching loss of the inverter. The proposed scheme can enhance the system efficiency while refraining from the soft-switching range limitation and soft-switching failure caused by the system parameter perturbation. Finally, a 1-kW soft-switching BWC principle prototype is developed to validate the effectiveness and correctness of the proposed scheme.

To solve the problems of output voltage and system efficiency sharply decreasing in the case of misalignment for the electric vehicle inductive power transfer (IPT) charging system, a universal hybrid coupler with high misalignment tolerance is proposed. The hybrid coupler consists of a four-coil bipolar (BP) coupler, the T-type network and a compensation capacitor, which effectively achieves high anti-misalignment for any compensation networks. The introduction of the T-type network makes the two overlapping coils in the same side of the BP coupler transmitter decouple effectively and simplifies the design. Although the two overlapping coils in the receiver side are still coupled with each other, the parameter design only needs to consider the cross-coupling to be small enough, which significantly reduces the design difficulty of the coupler without iteration and repetition. Finally, a 2-kW misalignment-tolerance hybrid IPT system is constructed based on the proposed hybrid IPT coupler. A configurable series-series (SS) and series/inductor-capacitor- capacitor(S/LCC) compensation topologies are used to implement constant current (CC) and constant voltage (CV) load-independent outputs in the face of conditions where the coupling coefficient and load change simultaneously. The experimental results validate the correctness of the theoretical analysis.

Power semiconductor is one of the most fragile components in the drive system of electric vehicles. In order to diagnose the failure timely, this paper proposes a diagnosis method of the open-circuit fault for open-end winding permanent magnet synchronous motor (OEW-PMSM) fed by dual inverter with a single dc source. The OEW- PMSM can improve the speed range and tolerance capacity of driving systems. However, the open-circuit fault diagnosis methods for Y-connected PMSMs cannot judge the faulty switch because of the symmetry of the dual inverter structure. The first step of the proposed method is to detect the faulty switch combinations by the error of normalized average value and average value of the zero-sequence reference voltage. The next step is to judge the faulty switch from a certain fault combination. The experimental results show that the open-circuit fault can be diagnosed accurately.

Five-phase open-end winding permanent magnet synchronous motor (OEW-PMSM) fed by a dual inverter has gained increasing focus because of its advantages in voltage utilization, torque density, and reliability. In this article, an optimized modulation method with the sliding clamped strategy is proposed for the five-phase OEW-PMSM drive with a common dc bus. The conventional clamped strategies have a reduced switching sequence. However, the clamped inverter generates the zero-sequence voltage and third harmonic voltage, which would affect the performance of the motor. To solve this problem, the reference voltages in the proposed method are distributed by limiting the reference voltage of the clamped inverter on a line. And the reference voltage slides on this line bidirectionally. Therefore, the clamped inverter in the proposed method will not introduce additional harmonic components. For experimental verifications, the test results are presented with the resistance-inductance load and five-phase OEW-PMSM.

In order to further improve the integration of the ac-grid-connected hybrid energy storage system, a novel three-phase single-stage three-port high-frequency isolated dc–ac converter is proposed in this article. This converter connects two dc ports and one ac port via a three-winding transformer, saving one ac-side port. The ac-side port uses the matrix converter and the dc-side ports use the interleaved parallel boost converter, which has the advantages of low dc-side current ripple and wide voltage range. The proposed converter achieves galvanic isolation and bidirectional power conversion with the single-stage structure to improve the integration of the converter. A hybrid pulse width modulation plus space vector phase-shift modulation is proposed to achieve the direct control of the ac side current synthesizing vector and, thus, ensures the sinusoidal three-phase currents. On this basis, the relationship between the control freedoms is constrained with the optimization objective of minimizing the root-mean-square value of the transformer resonant current; thus, the efficiency of the converter is improved. The correctness and the effectiveness of the proposed converter and the corresponding modulation are verified by the detailed experimental results.

In order to realize the controllable power decoupling and eliminate the influence of the parameter error of the resonant elements, a three-port dc–dc converter applied switch-controlled capacitor (SCC) is proposed. The operating principle and transmission power expression of the proposed three-port converter under triple-phase-shift control are analyzed. By adjusting the phase-shift angle of the SCC to adjust the resonant frequency of the resonant tanks, the topology-level power decoupling of the circuit at a constant frequency can be achieved. The addition of switch-controlled capacitors provides more freedom for power regulation between ports. Besides, according to the proposed converter, a design method for the parameters of the resonant tank is proposed to eliminate the adverse effects caused by the parameter error of the resonant elements. Then, an optimized triple-phase-shift modulation strategy is adopted to achieve the minimum rms value of the resonant converter. An experimental prototype was designed to verify the correctness of the proposed converter and modulation strategy.

Aiming at the problems of large switching loss and large output power fluctuation in the existing omnidirectional wireless power transfer (OWPT) system, a novel OWPT system with zero-switching-loss inverter and cylindrical transmitter coil is proposed. By introducing an auxiliary resonant network with simple structure and low-loss on each phase arm of the three-phase inverter, zero-voltage switching turn-on and zero-current switching turn-off within the full power range can be acquired. The switching loss in the main circuit of inverter is reliably eliminated. The transmitter coil is a cylindrical coil composed of the three curved rectangular coils, whose excitation current amplitude is equal and the phase difference is 120°. It can arise a spatial rotating magnetic field around the transmitter coil and provide an omnidirectional energy transmission channel. The operating principle of soft-switching is analyzed in detail, and the design rules of soft-switching in full power range and the parameter design method of coupler to reduce the fluctuation of output power are given. Ultimately, an experimental prototype is used to verify the feasibility of the proposed OWPT system. The experimental results indicate that the system output power is retained at 93.4–104.7 W and transfer efficiency is retained at 71.2%–78.1% under arbitrary angular misalignment of receiver.

The single-stage high-frequency (HF) isolated ac–dc converter has the advantages of high-power density, long life, and high efficiency. It has a broad application prospect in distributed power generation, ac microgrid, and energy storage system. In this article, its topologies are classified according to the energy storage components. The structure and operating principle of various topologies are introduced. Furthermore, the development of extended multiport single-stage HF isolated ac–dc converter is introduced. On this basis, the advantages and disadvantages, typical characteristics, cost, and power loss of various topologies are analyzed and summarized. Finally, the key issues that need to be solved are pointed out and the development trends are explored. This article aims to provide a reference for the subsequent research on single-stage HF isolated ac–dc converters and the advancement of their practicability.

With the purpose of improving the reliability of inductive power transfer (IPT) system, a three-coil hybrid IPT topology with improved tolerance to coupling variation and load-independent output is presented, which can ensure constant output of the system under the condition of load and coupling coefficient changing simultaneously. The topology adds two mode switches and an auxiliary compensation capacitor to the receiver side of the system to switch the series–series (SS) topology with constant current output feature and the series-inductor–capacitor–capacitor (S-LCC) topology with constant voltage output feature. Moreover, the transmitting coil adopts two coils in reverse series to improve the misalignment tolerance. The topology retains the merits of SS and S-LCC topology, such as soft-switching operation, decoupling between output and load, zero phase angle input, and the output features, that do not depend on the coupler parameters. Meanwhile, there is no need to build wireless communication between the receiver and the transmitter, which can simplify the control method. This article systematically describes the operating principle of the presented hybrid IPT charger, and the design ideas of compensation network parameters and coupler are also given. A 460-W experimental prototype is built to test the performance of the presented hybrid IPT charger.

In this article, the steady-state and transient models of the LCC-S compensated wireless power transfer system (LCC-S WPT) are built. From the steady-state model, the secondary charging voltage and current are, respectively, proportional to the primary inverter current and coil current. Then the indirect control strategy of the secondary charging voltage and current based on the dual primary current closed-loop control is proposed. From the transient model, the controller parameters design criteria are given. The transient characteristics of the both side variables of the indirect control strategy are originally analyzed. It is proven that a good secondary transient performance is ensured under the indirect way. Furthermore, the feedforward control of the input voltage is proposed to eliminate its transient effect. The feasibility and practicability of the proposed control strategy are verified by the experiments.

The bidirectional buck–boost current-fed isolated dc–dc converter suffers from the instability when feeding the constant power load (CPL). The mathematical models of buck and boost subsystems of the converter with CPL are derived. It is proven that CPL leads to the instability of the both subsystems and the system cannot be stabilized by the single output voltage closed-loop control. The active damping method is introduced to ensure the closed-loop stability of the converter. An optimal design method of the active damping feedforward coefficient is proposed to keep the open-loop stability of the two subsystems and ensure a good dynamic response. An input voltage feedforward is used to overcome the influence of nonminimum-phase characteristics between dynamic response and the stability of the boost mode. The unified design method of the closed-loop controller parameters based on Hurwitz criterion and frequency response is proposed to keep the closed-loop stability of the two subsystems. The correctness and feasibility of the parameter design method are verified by detailed experimental results.

In this article, the actions of the dual active bridge (DAB)-based three-phase single-stage ac–dc converter under the nonideal grid conditions and corresponding solution are researched for the first time. The average state-space model of the converter is built first. Then the effect of grid harmonics and unbalance on the three-phase grid current are analyzed and it reals the grid current harmonics, and unbalance is caused by the distorted grid. In order to solve this problem, a proportional-resonant (PR) + reduced parallel repetitive control closed-loop controller of grid current in the two-phase stationary frame is proposed. The parameter constraint and frequency-domain characteristics of the proposed compound controller are analyzed in detail. The detailed experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed closed-loop controller.

The semi-dual-bridge resonant isolated dc–dc converter (SDBRC), as a class of emerging topologies, is suitable for the application situation that requires only the unidirectional power transfer while a wide buck–boost voltage conversion range. In this article, a three-level SDBRC is proposed. Its operation principle is analyzed, and the transfer power and voltage conversion ratio as the functions of the two phase shifts are derived. Furthermore, a coordinated control rule of the two phase shifts is proposed, which ensures the monotonicity between the phase shifts and the average output power over the entire power/voltage range. The voltage stress of the power devices of the proposed topology is reduced to half of the power supply voltage; therefore, the cost and ON-state loss of the power switches are effectively reduced. The detailed simulation and experimental results validate the correctness and feasibility of the proposed topology and its modulation strategy.

Since the dc side current of the single-stage isolated three-phase buck-type rectifier (1S-ITBR) is discontinuous, the conventional current space vector pulsewidth modulation presents a poor grid current characteristics. In this article, the expressions of the instantaneous grid current of 1S-ITBR and the amplitudes of various-order grid current harmonics are originally derived. These results reveal the essential reason for causing t low-order current harmonics. Then, the improved calculation method of dwell times of the effective current space vectors with the goal of eliminating the grid current distortion is proposed to improve the grid current quality. The correctness of the harmonics analysis and the feasibility and validity of the proposed improved method are experimentally verified.

High step-up Y-source coupled-inductor impedance network boost dc–dc converter with common ground and continuous input current is presented in this paper. The proposed converter has added auxiliary diodes and capacitors to three-winding Y-shaped coupled-inductor cells to constitute the current conduction path and realize the voltage-double function. Compared to other magnetically coupled boost converters, the proposed converter can produce the higher voltage gain with more degrees of freedom in winding match. The same output gain can be obtained by using different winding turn ratios. Also, the proposed converter has a common ground and realizes the continuous input current. The corresponding topologies and steady operation principles are analyzed. The experimental results in a 300-W prototype have verified the validity of the theoretical analysis.

The two-phase quadrature-coordinate enhanced phase-locked loop (QC-EPLL) possesses a better transient performance than the standard single-phase EPLL. In this paper, a virtual QC-EPLL (VQC-EPLL) based on signal delay method is proposed to realize using QC-EPLL to estimate the synchronization information of the single-phase grid. Furthermore, the effect of the input harmonics and DC offset on the VQC-EPLL is originally derived and it reveals these nonideal conditions causes the unexpected periodical ripple in the estimated amplitude, phase angle and frequency. Furthermore, the improved approach, including the DC offset estimator and finite impulse response filter is proposed to eliminate these effect. Detailed experimental results verify the correctness and feasibility of the theoretical analysis and proposed improved approach.

In the IGBT-based bidirectional isolated dual-active-bridge (DAB) dc–dc converter, it is not necessary that the IGBTs of the secondary-side H-bridge inverter (HB2) retain under on state because in this system, the function of synchronous rectification cannot be realized. This paper firstly analyzes the characteristics of the DAB converter with all of the IGBTs of HB2 keeping under OFF state. Its main drawback is that the flow back current in the primary dc side is caused and the current stress is increased. Furthermore, a hybrid modulation strategy is proposed and the control rule of the two inner phase shifts of the primary and secondary H-bridge inverters is determined to eliminate the flow back currents in the entire power range, enhance the maximum transfer power, and achieve a good inductor current characteristic. The experimental results verify the correctness of the theoretical analysis and the feasibility and practicability of the proposed hybrid modulation strategy.

This paper originally analyzes the effect of the harmonics, dc offsets, and unbalance on the three-phase enhanced phase-locked loop (3P-EPLL). It proves that 3P-EPLL is not able to accurately estimate the amplitude, phase angle, and frequency of the grid in such cases. In order to correctly estimate the grid synchronous information even under the nonideal grid conditions, an improved 3P-EPLL combined with the multiple delayed signal cancellation (DSC) filters is proposed. A DSC operator is set at the each input of 3P-EPLL to eliminate the input dc offsets and even-order harmonics. And the cascaded DSC (CDSC) module is plugged in both the frequency and amplitude loops to remove the effect of most of the odd-order harmonics and unbalance. The relationship between the delay constant of the DSC operator and the order of the harmonics hoping to eliminate is derived to design the structure of the CDSC module and determine the delay constant of each DSC operator in the CDSC module. Detailed experimental results of the standard 3P-EPLL and proposed one validate the theoretical analysis and the proposed phase-locked loop.