IET Power Electronics最新文献

Accurate estimation of the state of charge (SOC) and state of health (SOH) is critical for ensuring the safety and reliability of lithium-ion batteries, especially under varying temperature conditions. Temperature significantly impacts battery performance, introducing non-linear effects that complicate state estimation. This paper proposes a novel multi-scale co-estimation strategy that integrates a temperature-dependent fractional-order model (FOM) with a dual fractional-order adaptive unscented Kalman filter (DFOAUKF). The FOM is developed based on electrochemical impedance spectroscopy and the temperature-dependent open-circuit voltage, capturing intrinsic electrochemical characteristics of the battery. Parameters are identified using a combined offline and online method. The DFOAUKF algorithm leverages the time-scale differences between SOC and SOH, enabling micro-time SOC estimation in seconds and macro-time SOH estimation over test cycles, while adaptively updating noise covariance matrices. Experimental validation under dynamic stress test (DST) and urban dynamometer driving schedule conditions at 10$��{}^{\circ }�C�$, 25$��{}^{\circ }�C�$ and 40$��{}^{\circ }�C�$ demonstrates the robustness and accuracy of the proposed method. Results show that the root mean square errors of terminal voltage remains within 0.039 V, while SOC and SOH estimation errors are less than 1.25% and 0.64%, respectively, across all temperature levels and aging degrees. The findings highlight the effectiveness of the proposed co-estimation strategy in improving battery state monitoring and lifespan.

The central focus of this study is the integration of a high-performance six-phase permanent magnet synchronous generator (HPSG) with a three-phase grid, aiming to eliminate passive components such as capacitors and enhance power injection. The proposed solution uses an indirect matrix converter (IMC) based on space vector modulation (SVM) and compares three control strategies: the classical sliding mode controller with hyperbolic functions (SMC), the second-order PI controller (2nd-PI), and the integrator-based linear quadratic regulator (IB-LQR). The evaluation is performed under dynamic conditions using real-time simulation. A high voltage transfer ratio (VTR) of up to 96.6% is achieved. System performance and stability are validated through closed-loop simulations on a 1.35 MW inductive load. Results show that the SMC controller offers superior convergence and tracking (IAE, ISE, ITAE, ITSE) under three-phase short-circuit and dip voltage tests, compared to IB-LQR and 2nd-PI. However, SMC suffers from chattering and overshoot in the $�q$-axis. IB-LQR demonstrates consistent robustness under disturbance, while 2nd-PI offers a simpler and effective solution in steady-state operation. Furthermore, total harmonic distortion (THD) analysis at the point of common coupling (PCC) confirms that SMC provides the best harmonic mitigation among the three controllers.

With the recent rise in carbon neutrality policies, interest in renewable energy systems has surged, and the use of power electronic devices in these systems has led to the emergence of supraharmonic emission issues within the 2–150 kHz low-frequency range. Current standards define the frequency range of the artificial mains network (AMN) starting at a minimum of 9 kHz, leaving a gap in the standards for measuring supraharmonics in the 2–9 kHz range. This paper addresses the measurement challenges associated with supraharmonics caused by the expansion of renewable energy systems and proposes an AMN with enhanced low-frequency parameters. Specifically, we present an AMN optimised for input impedance, insertion loss (IL), isolation factor (IF), and voltage division factor (VDF) within the 2–9 kHz range. The optimisation of each stage was carried out using the particle two-swarm optimisation (P2SO) algorithm, culminating in the adoption of a 4–stage AMN. The optimised 4–stage AMN was implemented, and its performance was measured, with results aligning with the optimisation predictions. Conducted emission (CE) measurement was performed on a grid-tied PV inverter, revealing higher noise levels in the 2–9 kHz range compared with the present standard AMN.

A novel fully soft-switching interleaved high step-up converter is introduced in this paper. The suggested converter achieves high voltage gain using coupled inductors (CI) and a voltage multiplier cell (VMC). The main advantage of this design is its high efficiency, primarily achieved by eliminating switching losses and reducing conduction losses. An auxiliary circuit is employed to ensure zero voltage switching (ZVS) for the main switches, while the auxiliary switch itself operates under zero current switching (ZCS), addressing its switching loss. Regarding conduction losses, the low voltage stress on the switches allows for the use of switches with low on-resistance. Additionally, the interleaved technique reduces current stress on the switches, further improving conduction losses. Experimental results of the proposed converter, evaluated for a 30 V to 400 V conversion at 200 W output, are presented alongside theoretical analysis to validate its performance.

To meet higher voltage output requirements, semiconductor switches are typically connected in series or stacked in multiple stages, which leads to a greater number of magnetically coupled isolators for gate drivers, as well as considerable requirements for isolation performance. In this study, we propose a diode-capacitor chain (DCC), which realizes an isolated power supply for switch drivers in each stage of the tail-cut pulsed modulator. The proposed DCC reduces the number of isolators required and makes the withstanding voltage consistent across each stage, decreasing it from thousands to hundreds of volts. After analysing the working principle and theoretical calculation of DCC, the study delves into the supplying performance and its influencing factors. Finally, an 8-stage prototype (7 kV, nanosecond scale) was designed to verify the reliability and compatibility of DCC. The result demonstrates that DCC reduces the withstanding voltage to less than 0.9 kV for each stage. The DCC consists purely of diodes and capacitors without interfering with load waveforms, which offers a different solution to an isolated power supply scheme for the tail-cut pulsed modulator at a nanosecond scale.

For the power oscillation problem of inverters in photovoltaic (PV) grid-connected systems under disturbances of grid frequency and active power reference value, a steady-state damping optimisation strategy based on active control feedback is proposed. Existing studies mainly focus on the analysis of the damping characteristics of inverters in virtual synchronous generators (VSG), while ignoring the damping characteristics of the traditional droop control with a low-pass filter (LPF) power calculation process. Based on the simplified structure of power control, this paper points out that the damping characteristics of traditional droop control are highly dependent on the power control coefficient and exhibit poor dynamic performance. On this basis, the proposed strategy introduces a synchronous reference frame phase-locked loop (SRF-PLL) into the power control loop, calculates the difference between the output angular frequency and the angular frequency of the active control output, and compensates for the angular frequency of the power control output; at the same time, a PI controller is introduced to weaken the dominant influence of the droop coefficient on the system dynamics, thereby effectively improving the damping characteristics of the system. Finally, the effectiveness of the proposed method is verified through simulation and experiment.

In an industrial context where high reliability is an increasingly important requirement, thermal modelling of power semiconductors becomes necessary for diagnostics and prognostics. This paper proposes a simulation-based methodology that can estimate junction temperatures in insulated gate bipolar transistors and diodes much faster than conventional methods with an improved accuracy. The approach is based on a combination of conventional steady state simulation techniques with a post-processing stage. The analysis is carried out by first calculating the conduction and switching losses and then obtaining the junction temperature by using the device thermal network. The obtained results (including both simulations and experiments) are compared to state-of-the-art methods, highlighting the accuracy of the proposed method.

A multilevel DC–DC converter is a promising solution to save cost and promote the power density of DC solid-state transformers. Among the multilevel DC–DC topologies, the stacked flying capacitor half-bridge five-level LLC resonant converter can withstand higher DC-bus voltage with fewer components. However, there is still no active capacitor voltage balancing strategy for this topology. To solve this problem, an extra voltage level is introduced to the conventional two-voltage level modulation of the converter and the switching states of the extra level are analysed in this paper. Based on the three-voltage-level modulation, an active capacitor voltage balancing strategy for the five-level LLC converter is proposed. The voltage balancing strategy is realised by adjusting the duration of specific switching states. And it can achieve simultaneous and decoupled balancing control for the DC-bus and flying capacitor voltages. A 1 kW prototype is built to verify the proposed balancing strategy in various conditions. The simulation and experimental results demonstrate the correctness of the analysis and the effectiveness of the proposed balancing strategy.

A novel multi-port converter topology is introduced for the synchronised integration of photovoltaic (PV) power and a hybrid energy storage system, addressing energy demands in net-zero carbon buildings. This topology, characterised by soft-switching operation and reduced component complexity, multiplexes the leading leg of a phase-shifted full-bridge to interface with both the battery and PV source, thus minimising power switch count by four and improving energy transfer efficiency. Furthermore, an integrated control scheme is developed to achieve adaptive switching between PV maximum power point tracking (MPPT) and battery voltage-limiting protection via voltage comparators. A high-frequency filter is also integrated to facilitate supercapacitor power management for hybrid energy storage. Experimental results from a prototype converter demonstrate high port efficiency, effective mitigation of shock loads and PV fluctuations on battery performance, and successful adaptive protection switching when the battery voltage limit is exceeded.

This paper proposes a novel LLC resonant converter featuring two completely identical resonant circuits. By adjusting the control strategy of primary-side switches, the two resonant circuits can operate independently or in series, allowing the entire resonant converter to function equivalently in half-bridge or full-bridge LLC resonant converters. The proposed converter exhibits three distinct operating modes, and all modes maintain identical resonant frequency while achieving a wide output voltage regulation range (0.5 to 4 times) within a narrow frequency variation range (70 to 130 kHz). Furthermore, zero voltage switching (ZVS) of primary side switches is consistently ensured across all operating modes. Compared with the conventional LLC resonant converter, the proposed topology extends the output voltage regulation range without requiring additional switches or complex control strategies. Experimental results validate the effectiveness and practicality of the proposed converter, demonstrating an operational efficiency of no less than 96% across various operating modes.