IET Power Electronics最新文献

While conventional control techniques for stabilizing power electronic converters with constant-power load (CPL) often rely on complete system state information, the associated challenges, including the cost and increased size due to the installation of multiple sensors, necessitate exploration of alternative methodologies. To address these concerns, a novel observer-based sliding-mode control approach is proposed. This approach aims to enhance cost-effectiveness and reliability in the context of a DC-DC buck converter supplying power to an unknown CPL. The core concept involves designing a state observer to estimate the system's current based on voltage measurements. A non-certainty equivalent adaptive update law is then introduced to estimate the unknown CPL, incorporating feedback from voltage measurements and current estimation. To guarantee stability in the face of uncertainties in system parameters, a thorough analysis utilizing the Lyapunov theorem is conducted on the closed-loop system. The efficacy and feasibility of the proposed control algorithm are substantiated through experimental results on the OPAL-RT platform, showcasing its promising performance.

The voltage reinjection strategy is an effective solution to improve the voltage quality of the voltage source inverters for high-power applications. In this article, the fundamentals of voltage reinjection strategy are analyzed to reduce voltage harmonics of the output voltage. Then, a novel voltage reinjection circuit is proposed which can generate a 5-level voltage to be injected on the voltages of the DC sources. The reinjected voltage can create a 60-pulse voltage waveform for a three-phase load. Turn ratio optimization of the reinjection transformer has a significant effect on the improvement of the harmonic situation of the output voltage. Furthermore, the proposed reinjection circuit provides ZVS conditions for the main switches to reduce switching losses considerably. The simulation results indicate that the proposed reinjection circuit can reduce the output voltage THD to 3.16% without any type of filter or modulation, and the load variation does not have a considerable effect on the voltage quality. The experimental results approve the analytical trend and simulation process and also confirm the reinjection circuit performance. According to the results, the proposed method has generated a semi-sinusoidal voltage waveform with $��T�H�D_V�=�3.78�\%�$ in the laboratory.

Torque ripple is an important factor affecting the smoothness of permanent magnet synchronous motor. However, for high saturation permanent magnet synchronous motor (HSPMSM), the flux linkage of permanent magnet is nonlinear, which leads to poor effect of traditional torque ripple suppression methods. Therefore, by systematically considering the amplitude and phase changes of the permanent magnet flux link-age for the first time, this paper analyzes the torque ripple mechanism of high saturation motors and establishes a corresponding mathematical model. To minimize the loss caused by harmonic currents, two torque ripple suppression methods are proposed: one based on the NSGA-II algorithm and the other based on an analytical method. Finally, the effectiveness of the two algorithms is verified by the experimental comparison. The experimental results show that compared with the traditional methods, the two algorithms can effectively suppress the torque ripple under the premise of considering the influence of the motor magnetic saturation on the flux linkage and inductance, and improve the output torque smoothness of HSPMSM.

A multi-input single-output converter that is based on the impedance network and the standard isolated converters is presented. The topology is named quasi Z-source full-bridge isolated converter (qZSFBIC). The proposed topology helps to integrate various renewable power generation systems with a common three-phase grid-connected inverter. It was also capable of providing isolation between the input and output circuits in addition to the boost function. The integration of multiple energy sources is achieved using fewer components than conventional converters. As a result, it achieves greater conversion efficiency and has improved circuit characteristics. It offers a larger voltage control range as compared to the conventional ZSC and enhances the input-output voltage transformation ratio. To determine whether or not the suggested converter is technically feasible, the circuit architecture, operating principle, control mechanism, and simulation results are presented. An improved proportional resonant-second order general integrator (IPR-SOGI) has been utilized to provide a gating signal for the voltage source inverter. The 1.5 kW, 400 V, 50 Hz model is designed to authenticate the proposed scheme with qZSFBIC. The results showed that the proposed converter offered double the time of boosting than the conventional ZSC converter and the conversion efficiency is around 89%.

A dc voltage restorer (dc-VR) with optimal droop control is developed to reduce the power loss and solve the dynamic current imbalance simultaneously of the zonal dc distribution system integrating multi-parallel energy storage. Firstly, the power loss model composed of line loss and converter loss is built and it is proved to be a strictly convex function with respect to droop coefficients, which indicates the power loss can be mitigated by optimizing the current distribution. Thus, an image-based droop optimization method is proposed to search for the optimal droop coefficients. Then, the economy of voltage compensation on power loss reduction is investigated and an ESS-combined dc-VR is designed, including an interleaved parallel architecture and a capacitor-integrated electric spring (C-ES). Unified virtual inertia is proposed for interleaved parallel bridge arms to make their dynamic performance consistent. And the newly introduced C-ES can keep the bus voltage at the rated level to reduce the system cost. Therefore, the problem of dynamic currents imbalance is addressed from the points of converter structure (dc-VR) and control system (unified inertia), and the power loss can be reduced by voltage recovery (C-ES) and optimizing the current reallocation which is achieved by updating sharing coefficients from the image-based droop optimization method. Finally, the simulation cases validate the effectiveness of the proposed optimal-droop dc-VR on dynamic current balance and power loss reduction, and hardware in the loop experiment results prove the consistent dynamic characteristics of the dc-VR's arms.

This paper proposes a maximum torque per ampere (MTPA) control method for a permanent magnet reluctance hybrid rotor dual stator synchronous motor (PMRHRDSSM) based on a sliding mode speed controller, in response to the complex and special electromagnetic relationship of the motor. The paper focuses on the special electromagnetic relationship of PMRHRDSSM with stator winding series structure. Firstly, the trajectory equation of PMRHRDSSM MTPA stator current vector is derived, and based on the relationship between PMRHRDSSM torque and reluctance dq-axis current, a PMRHRDSSM current controller that meets MTPA constraints is designed. Afterwards, a PMRHRDSSM sliding mode speed controller was designed with input speed error and output reference torque. Finally, an experimental platform for the proposed control method was established, and the control method was experimentally validated.

This article presents an innovative approach for real-time allocation of weighting factor values in model predictive control of electrical drive systems. In the proposed dynamic weighting factor assignment method, the cost associated with a specific variable is determined based on its corresponding set of predictions. This approach can be employed to optimize weighting factor values for a given system or even enhance performance metrics in comparison to conventional approaches that employ fixed weighting factors. Furthermore, the method determines the optimal value of weighting factors in real-time with low added calculation complexity. The proposed method is able to provide reliable constant weighting factors for a given working point as well. The practical application of this method is demonstrated through a case study of an LC filter equipped PMSM drive; the system encompasses six independent variables that require regulation. Experimental results utilizing both two and three level voltage source inverters and using various transient and steady-state situations prove the feasibility of the proposed dynamic weighting factor assignment method.

This study investigates the low-frequency oscillations (LFOs) in MMC-MVDC systems with high photovoltaic (PV) penetration, considering the whole operating conditions of the grid-connected MMC, including both the inverter and rectifier modes. First, the multi-port impedance models of converters and networks are developed, upon which a stability criterion is defined. The mechanism of LFOs is then identified using bus participation analysis and parameter sensitivity analysis. In addition, the stable zones of the dominant parameters are identified, taking into account the whole operating conditions of the grid-connected MMC. Interestingly, a phase-locked loop may induce LFOs in two low-frequency ranges. Finally, the experimental results confirm the correctness of the theoretical analysis.

Marine current power is attracting more attention as a renewable energy option. Similar to wind power, marine current power often requires a maximum power point tracking (MPPT) method to optimize power extraction from the free-flowing water. Research into MPPT methods for marine current power remains limited. Therefore, this paper presents a comprehensive investigation of MPPT methods for marine current power, building upon similar research in wind power. Three methods, namely the optimal tip speed ratio (OTSR), optimal torque (OT), and two variants of the perturb and observe (P&O) method, are explored. Using a simulation model developed for a specific marine current energy converter, where hydrodynamic calculations are coupled with electrical simulations, the study demonstrates that the OTSR method achieves MPPT with a comparably fast convergence time. After a change in water speed, the OTSR method achieves optimal operation within two turbine rotations. Additionally, the P&O methods are shown to achieve MPPT, albeit with a significantly longer convergence time. However, the P&O methods can be more convenient since no model of the system is required, and no water speed measurements are necessary. The proposed implementation of the OT method underperforms but positions the system close to the optimal operational point.

This paper proposes an adaptive complex coefficient filtered (CCF) full order extended state observer (ESO) type three phase enhanced phase locked loop (EPLL), which is employed in matrix reactance frequency converter (MRFC) for rotating vectors measurement estimation. EPLL phase detector was analysed first to track not only the rad frequency and transient phase, but also the amplitude of the rotating vectors. Full order ESO can filter out more high frequency disturbance, so it can track frequency and phase more accurately than proportion and integration algorithm. CCF modules were analysed in theory to attenuate the disturbance within two times of the EPLL's cut-off frequency. The whole adaptive CCF-ESO-EPLL design, including stability and parameter tuning were then interpreted. The proposed CCF-ESO-EPLL adapts the estimated frequency with CCF to attenuate the MRFC switching non-linear disturbance as well as unknown disturbance by the full order ESO. The MRFC topology necessary measured vectors, as well as the input side reactive power adjustment capacity, were discussed. The theoretical conclusion has been verified on a MRFC prototype. The proposed CCF-ESO-EPLL has less parameter tuning, less computation resource requirement, better steady and dynamic performance, and outstanding disturbance robustness.