The growing demand for energy storage systems has highlighted the importance of accurate battery State-of-Charge (SOC) estimation, which directly affects energy availability and operational safety. Existing deep learning-based methods focus on single-cycle charge or discharge estimation, and their performance degrades when applied to continuous multi-cycle scenarios. To address this, a physics-gated neural network, named SocGate, is proposed for multi-cycle battery SOC estimation. The model incorporates physical knowledge through specially designed gate functions, which constrain the estimation within realistic physical boundaries while retaining the flexibility of data-driven modeling. Experiments conducted on a public lithium-ion battery dataset demonstrate that SocGate effectively estimates SOC across sequences involving three discharge cycles, two charge cycles, and two plateau periods. The model achieves a low mean absolute error of 0.46% and root mean squared error of 0.70%.

Accurately predicting the State of Health (SoH) of batteries has become increasingly important with the widespread adoption of lithium-ion batteries in electric vehicles (EVs). However, existing SoH prediction methods, such as equivalent circuit models and machine learning models, often neglect the integration of machine learning with signal processing. Therefore, the prediction accuracy of SoH on certain battery datasets can be further improved. In this paper, KUformer is proposed, integrating Kolmogorov–Arnold Networks (KAN) and Unscented Kalman Filter (UKF) within a Transformer framework. This model is designed for battery SoH data input characterized by long-term complex dependencies and smooth outputs, achieving high prediction accuracy. Experimental results on two battery datasets with different charging protocols demonstrate that KU-former achieves an average Root Mean Square Percentage Error (RMSPE) of 0.183%, representing at least 38% improvement over the current models, such as iTransformer and PINN.

In DC distribution system, load switching events and disturbances may cause significant overshoot in DC bus voltage under regular control strategies. To further enhance the dynamic performance of the system, a coordinated control strategy of real-time compensation utilizing EtherCAT communication is proposed in this paper. In this strategy, the state variation command is issued from the master controller to the AC-DC converter. Meanwhile, a compensation value is introduced to the DC-DC converter synchronously based on EtherCAT communication which owns the real-time and high-speed features. Theoretically, it can mitigate the transient process of DC bus voltage during master-regulated state variations. The proposed strategy is verified in a cascaded system of Dual Active Bridge (DAB) and a boost-inductorless single-phase bidirectional isolated AC-DC converter. In order to obtain the precise expression of the compensation, the small signal analysis upon both topology and control loop of the two converters is conducted. Finally, a 3.3kW cascaded experimental platform is built to verify the correctness and effectiveness of the proposed strategy.

This paper discusses the steady-state operation and the improved control strategy of the under-resonant dual-bridge-series-resonant converter (URDBSRC). To obtain more accurate results, time-domain analysis is adopted here to derive the expressions of inductor currents and the zero-voltage-switching (ZVS) conditions of all the switches. On this basis, this paper proposes a minimum current control (MCC) strategy combining extended-phase-shift modulation (EPSM) and variable-frequency modulation (VFM) to achieve minimum root-means-square (RMS) current while performing fully soft-switching over a wide voltage range and load variations. A 2kW URDBSRC prototype is designed to verify the effectiveness of the proposed control strategy.

The adoption of bipolar multi-port converters to integrate renewable energy/energy storage and bipolar bus in bipolar dc microgrid systems is considered as a promising solution, owing to its reliability and efficiency advantages. This paper presents a bidirectional bipolar multi-port dcdc converter with low voltage stress and high gain, that can achieve single-stage power conversion between the source and bipolar dc bus. High voltage gain and low port current ripple are achieved, which is very suitable as an interfacing converter for renewable energy and energy storage. Furthermore, the low voltage stress and soft switching performance of semiconductor devices can effectively improve the efficiency of the converter. In addition, the bidirectional power flow capability and the simple control method make the proposed structure a popular solution for bipolar dc microgrids. The operation principle, steady-state performance, and design considerations of the converter are discussed in detail. Meanwhile, a ±200V/2kW simulation model is constructed to verify the validity of the theoretical analysis.

Misalignment between the magnetic coupled coils of inductive power transfer (IPT) system is inevitable, which significantly reduces the power transfer capability and system efficiency of IPT system. In this paper, an intermediate coil and dual decoupled receivers are employed to achieve high misalignment tolerance of IPT system. Besides, constant current (CC) output characteristic is obtained. Thanks to the intermediate coil, the inverter current can be limited when the receiver side moves out of the operating region (the mutual inductances are close to zero). With the proposed decoupled method, the design of the magnetic coupler is significantly simplified. In order to demonstrate the validity of the proposed method, a 3.2kW experimental prototype is designed and implemented. Experimental results show that the proposed IPT system can tolerate ±210mm x-axis and -20mm~60mm z-axis misalignment while the fluctuation of the output current is within ±5%. The maximum efficiency can reach 96.7% at full load.

This paper proposes a multi-port dc/dc/ac converter for residential systems integrating photovoltaics (PV), energy storage, dc bus and ac grid ports. The common ground structure of the proposed topology suppresses inverter leakage current generation. By multiplexing the power inductor of the battery port and corresponding switching devices, soft switching can be realized with relatively few devices. Based on the difference between photovoltaic power and load power, various modes of circuit operation and corresponding control strategies are analyzed. The soft switching range of the circuit under various working modes is given. A 1 kW laboratory prototype verifies the effectiveness of the proposed circuit. Related experimental results are presented.

A Parameter Design Method of CLLC resonant converter is introduced. Firstly, this paper analyzes the impact of the ratio (magnetizing inductance to resonant inductance, h) on the circuit characteristics, including the gain of CLLC resonant converter, the conditions at switching instants, the realization of soft switching and power losses. According to the analysis, a design method based on parameter optimization is demonstrated to achieve wide output voltage range with narrow frequency range. The proposed method is validated via experimental test on a 2-kW prototype, the efficiency is up to 98.3% within a certain frequency range.

This paper presents a new diagnosis method for open-switch faults in power converters based on Artificial Neural Network (ANN). The ANN inputs comprise both sampled signals and control signals. Only the signals of one switching period are used in the method. The combination of control signals and output signals enables the trained ANN to represent the internal characteristics of converter behaviors, which is crucial for fault diagnosis. Compared with other data-driven methods, the ANN approach is simpler, making it easier to be applied in microcontrollers. Besides, the ANN responds quickly to the fault due to the training with instant signals. Therefore, easy operation and fast diagnosis can be both achieved. Finally, the open-switch fault diagnosis in a two-level three-phase converter is studied for method validation. In this case, an ANN is trained with 9 input elements, 7 output elements, and 10 neurons in the hidden layer. Simulation results are given to demonstrate the good performance of the ANN method.

As it is known, dual-bridge series resonant converters (DBSRCs) can achieve a relatively high efficiency by reducing the switching losses. In order to further improve the performance of DBSRCs, it is significant to minimize the losses of MOSFET and wire losses in coil winding and PCB. Hence, reducing root-mean-square of current conducted in resonant tank deserves consideration. In this paper, time-domain analysis is applied to obtain the accurate root-mean-square of resonant tank current ( irms). From the perspective of control, phase shift modulation (PSM) and variable frequency modulation (VFM) are combined to realize the minimum irms under different output current and gain conditions. The possible influences caused by parameters of resonant tank, input voltage and transformer ratio are all taken into consideration, aiming at adapting different applications. For the purpose of simplifying the complexity of control, a fitted formula is produced, and with this method, high efficiency can be guaranteed when the output voltage varies in a wide range. The analysis and method are validated via experimental test on a 3.3kW DBSRC prototype, the efficiency can rise to 98% in a wide range, and the peak efficiency at rated operation point can reach up to 99%.

Inductive power transfer (IPT) system for electric vehicle battery charging has many advantages over the traditional plug-in system. EV battery can be regarded as a wide range load according to the charging profile. The charging process requires constant current (CC) stage and constant voltage (CV) stage. The charging profile for IPT system is influenced by inductively coupled transformer, compensation structure and operating frequency. This paper proposes an IPT topology which naturally obtains CC and CV output functions simultaneously without increasing the complexity of control system. The system switches between the two charging modes in succession along with the change of load condition. It operates under the CC mode when the load resistance is small, which corresponds to the beginning of battery charging state. With the increase of load resistance, it switches to CV mode at a load turning point after which the battery is under the state of cutoff voltage. As the system is completely compensated, zero phase angle input is achieved during the entire charging process, which realizes soft switching for the entire load range. A fixed frequency control method is used to adjust the output accurately. The experimental IPT system is established to verify the theoretical analysis.

This paper presents an average model-based transistor open-circuit fault diagnosis method for grid-tied single-phase inverters which transfer power bi-directionally. It is easy to detect whereas tricky to identify the faulty transistor, for two different faults may show the same characteristics. In order to solve this problem, the inverter is changed to boost mode after fault is detected, so that the diagnosis variable can show distinguishable characteristics to locate the faulty transistor. The main advantage of this method is that the fault can be diagnosed fast without adding extra circuits. Additionally, it is featured with strong robustness against power change and sampling error. Finally, the effectiveness of the proposed method is verified by experiments.

This paper presents an average model-based diagnosis method for current sensor fault and IGBT open-circuit fault in grid-tied three-phase voltage-source inverters (VSIs). The diagnosis algorithm is based on observed inductor current sum deviation and bridge arm line voltage residuals with adaptive thresholds. The proposed method can guarantee fast diagnosis speed as well as strong robustness for both current sensor faults and IGBT faults, without extra hardware circuits. The fault diagnosis speed can be as fast as one switching period. No tuning effort is needed under different operating conditions since all the diagnosis calculation errors are covered in the thresholds. Finally, experiments are carried out to prove the effectiveness.

This paper presents the influence of switching frequency on the dual active bridge (DAB) dc-dc converter on the power transmission characteristics and the soft switching realization. Based on this, a switching frequency optimization of dual phase shift control is proposed to realize ZVS over the whole load range. It is an optimization of the PWM plus phase-shift control, which can reduce switching loss of power devices, and then improve whole efficiency of the DAB converter. A prototype is built and tested in the lab to verify the feasibility of the proposed solution. The experimental results show that the overall efficiency is improved and the range of soft switching is extended.

A novel load current sharing method is proposed for multi-module LLC resonant converters in high power application in this paper. The paralleled system is controlled by the maximum current sharing method to achieve load sharing automatically. Moreover, a series inductor is connected to each LLC output side to restrain the current ripple of double switching frequency. The maximum current sharing method is more stable than master-slave control and will not increase complexity. Theoretical analysis of the stability of individual module is based on the envelope model. And the stability of parallel operation is analyzed according to interface stability method. The analysis of the series inductor is given under first harmonic approximation assumption. Finally, an experimental prototype of a 4.8kW multi-module LLC converter system with 100V input voltage and 540V output voltage was built and tested to verify the proposed scheme.

A current soft-commutation Space Vector Modulation (SVM) scheme for three-phase current source converter (CSC) is proposed in this paper. With the presented SVM, the incoming switch has a positive collector-to-emitter voltage while the outgoing switch has a negative collector-to-emitter voltage during current commutations. That is, natural soft-commutations for switching transitions are achieved with accelerated current-commutating processes and lessened durations. As a result, distortion of the line currents can be reduced. Besides, due to the lessened overlapping time, the switching frequency is expected to reach as high as possible to reduce the ac filter and improve the line current quality. Especially, since the presented SVM is based on a closed-loop strategy, soft commutations can be reached in CSC with any power factor operation. The experiment verifies the proposition.

In this paper, an efficient algorithm strategy for synchronous rectification (SR) used in LLC resonant converters is proposed. The output voltage and the primary resonant inductor current of LLC converter are combined together to produce suitable drive signals for SR in the below resonance mode. In the other resonance modes, the drive signals for SR are synchronous with the drive signals of corresponding primary switches. In order to validate the feasibility of the proposed algorithm strategy, a 300W prototype with 100V input voltage, 25V output voltage is implemented using field-programmable gate array (FPGA). The measured maximum efficiency is 92.1% and the overall efficiency is higher than the one with conventional drive method for SR.

This paper presents a diagnosis method for open-transistor faults in voltage-source inverter (VSI) based on output phase voltages. When fault occurs, the faulty phase voltage will vanish during certain half periods, which can be utilized for diagnosing. In order to reduce calculation and improve noise resistance, the sliding-window counting method with first-in-first-out algorithm are introduced to detect the vanishment which indicates the faulty phase. Afterwards, the faulty transistor can be located by observing which half period the vanishment is in. Only output phase voltages are utilized and no complex algorithm is needed, thus this method can be easily embedded in existing voltage-loop or dual-loop controlled system without extra hardware circuits. Based on the time-domain characteristic of the faulty phase voltage, this method can achieve relative short detection time. Furthermore, it is capable of diagnosing simultaneous two-transistor faults. To validate the effectiveness of this method, experiments are carried out and discussed.

A control strategy combining a virtual oscillator control and multi-resonant control which is used in a parallel three-phase inverter system is proposed in the paper. The strategy retains the advantages of the virtual oscillator control and increases the quality of output voltage by introducing a P + multi-resonant based voltage regulator. The ability of eliminating the circulating current is also increased by a virtual impedance loop. The control structure is given and the selection of control parameters is explained in this paper. Finally, the effectiveness of proposed strategy is validated by simulation.

In this paper, an enhanced power sharing strategy employing adaptive virtual impedances for Q-ω and P-V droop-based islanded microgrids (MGs) is proposed. The proposed scheme improves the performance of dynamic response and system stability while accurate power sharing is obtained. The low-bandwidth communication is utilized to send the power commands. The adaptive virtual impedances consist of a resistor tuned by active power deviation and a complex impedance component tuned by reactive power deviation. And the former is to realize accurate active power sharing while the latter is to improve dynamic response and system stability. Meanwhile, the output current delay method to realize the virtual complex impedance is presented, avoiding the differential operation, which has high sensitivity to noises. Simulation results of a MG containing two distributed generation (DG) units with complex feeder impedance are presented to investigate the validity of the proposed strategy.

Based on magnetic induction, wireless power transfer have been proved to be promising in many applications, especially in EV charging systems. The coupling performance of loosely coupled transformers determines the overall feasibility of the whole systems. Considering volume, cost and coupling properties, a solenoid magnetic structure of 400mm*600mm with a 200mm air gap is utilized to transfer power in this study. By FEM simulation tools, the distance of wires and the coverage length are discussed to find the best coupling design. In addition, the position of the magnetic stripe cores is analyzed when taking account of the system cost. Moreover, additional shielding devices, which are made of aluminum, are designed to eliminate the back leakage magnetic flux. In order to improve the coupling performance, flux guiding ferrites are also added into the shielding devices to guide more leakage to flow to the secondary windings. Simulation results indicate the proposed design can increase the coupling coefficient k dramatically. Also, experimental results show great agreement with the simulation results.

Paralleled IGBTs have drawn much attention to increase current capability in high power applications. However, the current imbalance must be carefully concerned, which is caused by device characteristic difference and asymmetric circuit. In this paper, a current sharing model during turn-on period is proposed on the basis of parameterized IGBT model. The discrepancy of device parameters can lead to the difference of turn-on delay time, then, the influence of different device parameters on current sharing can be analyzed quantitatively according to the model. Moreover, the model can be used to predict the mismatch of current sharing, and the compensation of delay time can be obtained directly when active gate control method is applied. Finally, the model is verified by the experiments of two parallel connected IGBT modules (1200V, 300A) with a high accuracy. And the application of this model is also presented in the paper.

Aiming at the deficiency of common methods in inverter modeling, the modeling of three-phase three-wire inverter based on generalized state space averaging method is presented in this paper, which also takes the dead-time effect into consideration. By using the proposed method, the calculating fundamental components of voltages and currents are in accord with the simulation and experiment of actual devices considerably compared with conventional state-space averaging method. Besides, it provides effective means for precise closeloop controller design. The simulations by means of Matlab are well developed to describe the proposed theoretical model. In addition, an experimental platform based on three-phase three-wire inverters is built and shown to validate the effectiveness of the mathematical results.

In this paper, an improved active clamp coupled inductor and switched capacitor based converter is proposed for high step-up applications for photovoltaic power generation systems. The topology of the proposed circuit is based on coupled inductor technology, and two voltage double cells are added to extend the voltage gain and reduce the voltage stress of diodes. Then, the switch has an extremely low voltage stress compared with the output voltage, and an active clamp circuit is added to suppress the switch voltage stress. Therefore, low voltage rated and low on-resistance switches can be used to reduce the on-state losses. Furthermore, zero voltage switching turn-on is achieved to reduce the switching losses. Finally, a prototype is built to verify the theoretical analysis.

In this paper, a novel hysteresis loss calculation approach named the double-envelope method is proposed. The method can clearly separate the low-frequency loss and the high-frequency loss. By recording the points where the inductor current reaches minimum or maximum in every switching period, the envelopes of magnetic field H and flux density B in the time domain are acquired, and then the double envelopes on the B-H plane can be obtained. A dynamic minor loop of amorphous core is modeled to calculate the high-frequency loss. With this method hysteresis loss of the AC filter inductor in PWM inverters can be calculated accurately and rapidly. Moreover only the width of the minor loop is needed to measure in experiments, while other parameters can be acquired at the design stage. In order to verify the proposed method, the total loss of an AC filter inductor in a three-level NPC inverter is measured in different switching frequencies and load conditions. The changing trends of the low-frequency loss and the high-frequency loss with currents and switching frequencies are discussed.

A soft switching design of an isolated boost converter with coupled inductors is investigated in this paper. Compared with the former proposed converter, reverse-recovery problem of secondary diodes is removed within the whole operation range and ZVS ON of the main MOSFETs is obtained as well. Moreover, the restricted range of duty ratio is enlarged to achieve soft switching and an optimal operation point is obtained with minimal ripple of input current when duty ratio approaches 0.5. At last, a 150W prototype for vehicle inverter with 10V to 16V input voltage, 360V output voltage is implemented to verify the design.

In this paper, a sliding-mode control scheme for LLC resonant dc/dc converter is presented. The proposed controller operates at two fixed switching frequencies with sliding-mode control implementation. The large-signal dynamic model and steady-state characteristics are explored using the extended describing function method. The parameters design and the sliding motions are discussed on the phase plane. The proposed control scheme significantly improves the dynamic response against transient load changes while preserving the closed-loop stability and the attractive features of LLC resonant converter. The simulation and experimental results demonstrate the validity of the sliding-mode control strategy and the fast transient response compared with the conventional PI control.

In this paper, a simple networked control strategy of current-sharing for three-phase inverter parallel operation is proposed, which makes full use of network data to achieve relatively good performance without increasing complexity of system. Different with the master-slave mode, the communication architecture is built by autonomous mode and thus ensuring the inverters can share the power information between each inverters. The comparative description is embarked with the droop-only method and it shows that the superior performance of current-sharing for parallel operation can be realized. The experimental results demonstrate the validity of these schemes and the analysis.