IET Power Electronics最新文献

The integrated energy-consuming MMC (IEC-MMC) plays a critical role in dissipating surplus power generated during the low-voltage ride-through process in offshore wind systems to achieve low-voltage fault ride-through. As the core equipment of the converter station, the converter valve must undergo a complete type test to ensure normal operation and successful fault crossing. However, existing research has primarily focused on theoretical analysis and simulation of the energy dissipation process in the IEC-MMC, with limited investigation into equivalent testing methods for evaluating its fault ride-through performance at the module level. To address this research gap, this paper proposes an equivalent assessment index covering the entire fault ride-through process, taking the integrated energy-consuming MMC valve as the research object, and resolves the problem of the lack of assessment index for the fault ride-through equivalent test. Furthermore, an equivalent test circuit with integrated energy dissipation and a corresponding test methodology are proposed, offering a practical approach for replicating the stress variations experienced by the valve during fault ride-through. At the same time, it also provides an important reference value for the type test of the converter valve.

In megawatt-level (MW-scale) off-grid hydrogen production systems powered by renewable energy sources (RESs), a high-power hydrogen converter is essential for interfacing the medium-voltage DC bus (MVDCB) with the electrolyser. However, most existing converter topologies fail to meet the stringent requirements of such systems. This paper proposes a novel hydrogen converter based on a two-stage Input-Series Output-Parallel (ISOP) architecture, offering several key advantages, including high voltage step-up capability, improved efficiency, reduced output current ripple, enhanced system reliability, and flexible power regulation capability. The operation principles, snubber circuit optimisation using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), efficiency evaluation, and power balancing control strategies are thoroughly discussed. Experimental results validate the effectiveness of the proposed design and control approach, confirming the converter's suitability for renewable-integrated hydrogen production systems.

This paper investigates the application of Finite Control Set Model Predictive Control (FCS-MPC) for high-performance speed regulation of Brushless DC (BLDC) motors under dynamic operating conditions. The study addresses the challenge of precise tracking for complex references, including sinusoidal, square, triangular, and sawtooth waveforms essential for advanced applications such as robotic and hydraulic actuator systems in aerospace applications. A key contribution is the analytical investigation of the predictive cost function, which elucidates the trade-off between inverter switching frequency and tracking accuracy. This analysis identifies an optimal weighting factor that enables a ∼55% reduction in switching frequency while maintaining dynamic tracking errors below 0.5 RPM. For experimental validation, a custom BLDC motor drive was designed and implemented using an ESP32 processor, incorporating a novel bidirectional torque-limiting strategy for operational safety. Both simulation and experimental results confirm that the proposed approach achieves accurate dynamic speed control for frequencies up to 0.3 Hz. Furthermore, a comparative study demonstrates the superiority of the method, showing an 85% reduction in amplitude error compared to a conventional PWM-ON strategy for a 0.3 Hz sinusoidal reference.

This paper presents a novel design approach for an LLC resonant DC-DC converter tailored for electric vehicle battery chargers. The design methodology considers the non-linear load, ensuring a narrow switching frequency range and zero-voltage-switching (ZVS) conditions for optimal soft-switching. A hybrid design procedure is proposed with a strong emphasis on high efficiency and power density. The resonance frequency and an accurate range for the magnetising inductor are calculated by time-domain analysis using the efficiency formula. The resonant capacitor, magnetising inductor and resonant inductor are then calculated by frequency-domain analysis, considering ZVS conditions and the non-linear load's profile. In the time-domain analysis, a 3D surface map of efficiency versus resonance frequency and magnetising inductor provides an accurate resonance frequency and the range for the magnetising inductor. Furthermore, by drawing a surface map of load considerations versus the calculated resonance frequency and the defined magnetising inductance range, based on the load's profile and ZVS conditions, the optimal design parameters are identified by applying the maximum switching frequency and inductance ratio. Finally, the step-by-step design methodology is validated through experiments on a prototype converting 400 V from the input to an output voltage range of 320 to 420 V at 3.3 kW with a peak efficiency of 97.9%.

Boost converters are one of the most commonly used converters in power electronics due to their advantages, such as simple structure and low-cost implementation. Due to these issues, many papers have been published about the control method of this topology. This paper proposes a reinforcement learning (RL) controller based on the soft actor-critic (SAC) algorithm for boost converters. This approach aims at decreasing the limitation of conventional controllers, such as long settling times, overshoot, undershoot and instability. It also removes the need for a system model, which is often necessary in traditional control methods. Furthermore, the proposed method addresses the challenges of control under dynamic conditions, which is a problem that has not been sufficiently explored in prior reinforcement learning (RL) based controllers. The proposed approach has demonstrated promising performance in both steady-state and dynamic regulation across a wide range of operational variations. Simulation and experimental results show the superiority of the SAC algorithm over the conventional ones without relying on the system model.

The integrated-gate commutated thyristor (IGCT), known for its low conduction losses and high reliability, is increasingly favoured in high-voltage and high-power applications. The junction temperature is a critical determinant of reliability, making the rapid and precise analysis of the transient temperature field indispensable. An analytical-numerical hybrid solution for the transient thermal analysis of the outer gate IGCT considering electrical-thermal coupling is proposed. Validation against FEA confirms the accuracy of the proposed analytical solution, while its computation time is reduced by 94.9%, which underscores its superiority in computational efficiency. Based on this, the proposed analytical-numerical hybrid solution is integrated into the VSC-HVDC simulation model, utilising the calculated maximum junction temperature feedback to optimise the switching frequency of VSC. Simulation results demonstrate that controlling the switching frequency based on the maximum temperature calculated can reduce the device's maximum junction temperature during VSC overload conditions, thereby enhancing the overload capacity of the converter. The analytical-numerical hybrid solution proposed in this article can be used for system simulation and has the potential to be applied to active thermal management of converters.

Current source inverters (CSIs) offer an alternative to voltage source inverters (VSIs) for electric motor applications. CSIs have some advantageous characteristics, such as the ability to inherently boost voltage, the absence of electrolytic capacitors, and reduced voltage stress on the machine. However, the increased component count and the need for a pre-stage to control the inductor current have limited the adoption of CSIs. For applications that must operate above a base speed, such as more electric aircraft (MEA), single-stage CSI converters are a promising solution. The ability to directly measure the terminal voltages allows for a simple and robust sensorless control approach to be used with this power converter. This approach based on a phase-locked loop (PLL) directly connected to the voltages with a feedforward compensation that depends on voltage drops on Rs and L0 is compared against a back-EMF (BEMF) observer. If a machine with an anisotropic rotor is used and the impedance is small, the feedforward compensation can be neglected leading to the classical PLL. Experimental results on a CSI7 converter driving a permanent magnet synchronous machine (PMSM) report that this kind of sensorless control can be a suitable alternative in motor drive applications.

An LLC resonant converter employing a novel reconfigurable rectifier (RR) for applications requiring a wide output voltage range is proposed in this paper. By integrating multiple rectifier structures—such as centre-tapped, full-bridge, and voltage-doubler rectifiers—into a single reconfigurable unit, the proposed RR can dynamically switch among different operating modes according to the output voltage requirement. As a result, the output voltage range is extended by a factor of 2 to 4 compared to conventional LLC resonant converters. Consequently, the normalised voltage gain range of the resonant tank is significantly narrowed, leading to reduced conduction and switching losses and improved overall conversion efficiency. The operational principles and mode-switching control strategy of the converter are analysed in detail. A 500 W prototype was built and tested to verify the effectiveness and feasibility of the proposed method.

Permanent magnet synchronous motor (PMSM) is prone to irreversible demagnetisation faults in complex operating conditions, threatening system reliability. To address this, a novel fault-tolerant control strategy is proposed, with its key contributions being: First, the introduction of a nonsingular fast terminal super-twisting sliding mode observer (NFTSTSMO) for high-fidelity, real-time flux linkage observation and demagnetisation fault reconstruction; Second, the development of a dual-vector finite control set model predictive fault-tolerant control (DV-FCS-MPFTC) scheme that explicitly incorporates the observed flux linkage to compensate for prediction errors. Experimental results confirm that the proposed method significantly enhances the fault tolerance and robustness of PMSMs under demagnetisation conditions, outperforming conventional approaches.

Permanent magnet synchronous motor (PMSM) is prone to irreversible demagnetisation faults in complex operating conditions, threatening system reliability. To address this, a novel fault-tolerant control strategy is proposed, with its key contributions being: First, the introduction of a nonsingular fast terminal super-twisting sliding mode observer (NFTSTSMO) for high-fidelity, real-time flux linkage observation and demagnetisation fault reconstruction; Second, the development of a dual-vector finite control set model predictive fault-tolerant control (DV-FCS-MPFTC) scheme that explicitly incorporates the observed flux linkage to compensate for prediction errors. Experimental results confirm that the proposed method significantly enhances the fault tolerance and robustness of PMSMs under demagnetisation conditions, outperforming conventional approaches.