Search Results (42)

Multiple three-phase machine drives are inherently fault-tolerant due to their multiphase structure; however, they remain susceptible to inverter-related faults. A common fault is the loss of gate signals in one inverter leg, resulting in an open-phase condition. Under such conditions, a reverse conduction path is established through the freewheeling diodes of the faulted leg, leading to uncontrolled freewheeling diode current generation. The resulting freewheeling diode current becomes particularly critical in the field-weakening region, when the back-EMF may exceed the DC-link voltage and a large reverse current can occur. This paper derives an analytical expression for real-time prediction of the freewheeling diode current in a triple three-phase surface-mounted permanent magnet synchronous machine drive. The method is applicable in both the constant-torque and field-weakening regions. The analytical prediction is validated through comparison with both experimentally measured and numerically simulated freewheeling diode current waveforms over a wide range of operating points, including no-load and loaded conditions. The results show that the proposed model accurately reproduces the envelope and conduction boundaries, while maintaining good agreement with simulations and measurements. The predicted current can be utilized in post-fault control, fault detection, and sensorless position estimation. Full article

This paper presents a robust fault-tolerant control (FTC) strategy for a multiphase PMSM-based propulsion system. The proposed approach combines an innovative super-twisting sliding mode controller (IST SMC) with a fault-tolerant model of the machine when an open-circuit fault occurs. The electrical propulsion system mainly has a two-line structure with a single DC source, a five-leg inverter and a Five-Phase Permanent Magnet Synchronous Motors (5-Φ PMSM), suitable for marine propulsion applications. Two main scenarios are investigated in this work. Firstly, if an open-phase fault occurs in one of the two 5-Φ PMSMs, a reconfiguration step of the machine control is applied in order to improve the performance of the propulsion system and to ensure the continuity of operation. Then, if the fault occurs in one of the two inverters, the faulty one is removed and the electrical series connection is made between the two machines, where they are powered by a single five-arm inverter, thus ensuring the continuity of operation of the system. Considering these two scenarios, a comparative analysis is made between the IST SMC and the classical PI controllers in terms of robustness to uncertainties, external disturbances and tracking accuracy for healthy and faulty operation modes, and during transient states. Full article

Ripple currents on the direct current (DC) bus in variable frequency drive (VFD) systems originate from motor load current fluctuations and the high-frequency switching of power devices. The resulting Joule heating within the DC-link capacitors is a primary driver of lifespan degradation. To address the lack of systematic models for multi-phase H-bridge inverters and the over-design caused by empirical methods, this paper proposes a novel analytical method that incorporates the 2kπ/N phase difference of parallel units for precise ripple current quantification. First, a dynamic DC-link capacitor model is established based on a single-phase H-bridge inverter, and the expressions for the instantaneous, average, and root mean square (RMS) input currents are derived. Furthermore, by introducing the 2kπ/N phase difference (where k = 0, 1, …, N − 1) among N parallel H-bridge units, a universal analytical expression for the RMS input current and its harmonic spectrum in a multi-phase system is obtained. The analysis reveals that ripple current harmonics concentrate at 2m × f_sw (where m is a positive integer and f_sw is switching frequency) and their sidebands (2m × f_sw ± f_o, f_o is output fundamental frequency), and the coupling influence of modulation index and power factor angle on ripple amplitude is quantitatively characterized. A 12 × 160 kW twelve-phase H-bridge inverter is taken as a case study, and MATLAB (v2023b) simulations and hardware experiments demonstrate that the theoretical calculations are in close agreement with the simulated and measured results, with the errors of input current harmonic amplitudes all below 5%. Compared with traditional empirical design, the proposed method reduces the capacitor volume and cost by approximately 15–20% while ensuring system reliability. This method is directly extensible to other multi-phase inverter topologies, providing a theoretical foundation for the accurate selection of DC-link capacitors. Full article

Predictive current control of variable speed drives by direct command of inverter states allows fast control. Its application to multiphase system constitutes a flexible solution that tackles several objectives by means of a cost function with several terms. Weighting factors are used to give relative importance of each term. They have a remarkable effect on figures of merit. In particular, secondary plane content and average switching frequency are usually considered as figures of merit. However, weighting factor effect on global energy efficiency has not been studied before because losses have different sources (commutations, Joule effect, etc.) that do not have a clear link with weighting factors and because trade-offs might appear. The present work uses an experimental setup with a five-phase induction machine connected to a mechanical load. By measuring the power balance, it is possible to show the effect of weighting factor tuning on losses. By tuning ${\lambda }_{xy}$, efficiency increases by up to 25%. In parallel, optimizing ${\lambda }_{nc}$ reduces the average switching frequency by 9% and 18% across the evaluated configurations. This enables the selection of the most adequate values of the weighting factors. The results show that for each speed and load combination, the drive exhibits improved efficiency for some tuning. Full article

Reliable water access in remote and desert-like regions remains a challenge, particularly in areas with limited infrastructure. Solar-powered submersible pumps offer a promising solution; however, optimizing their performance under variable environmental conditions remains a challenging task. This research presents an Artificial Intelligence (AI)-driven digital twin framework for modeling and optimizing the performance of a solar-powered submersible pump system. The proposed system has three core components: (1) an AI model for predicting the inverter motor’s output frequency based on the current generated by the solar panels, (2) a predictive model for estimating the pump’s generated power based on the inverter motor’s output, and (3) a mathematical formulation for determining the volume of water lifted based on the system’s operational parameters. Moreover, a dataset comprising 6 months of environmental and system performance data was collected and utilized to train and evaluate multiple predictive models. Unlike previous works, this research integrates real-world data with a multi-phase AI modeling pipeline for real-time water output estimation. Performance assessments indicate that the Random Forest (RF) model outperformed alternative approaches, achieving the lowest error rates with a Mean Absolute Error (MAE) of 1.00 Hz for output frequency prediction and 1.39 kW for pump output power prediction. The framework successfully estimated annual water delivery of 166,132.77 m³, with peak monthly output of 18,276.96 m³ in July and minimum of 9784.20 m³ in January demonstrating practical applicability for agricultural water management planning in arid regions. Full article

This project presents the development of an open-source educational platform based on an automotive Electrically Excited Synchronous Machine (EESM) repurposed from a KIA Sportage mild-hybrid vehicle. The introduction provides an overview of hybrid drive systems and the primary configurations employed in automotive applications, including classifications based on power flow and the placement of electric motors. The focus is placed on the parallel hybrid configuration, where a belt-driven starter-generator assists the internal combustion engine (ICE). Due to the proprietary nature of the original control system, the unit was disassembled, and a custom control board was designed using a Texas Instruments C2000 Digital Signal Processor (DSP). The motor features a six-phase dual three-phase stator, offering improved torque smoothness, fault tolerance, and reduced current per phase. A compact Anisotropic Magneto Resistive (AMR) position sensor was implemented for position and speed measurements. Current sensing was achieved using both direct and magnetic field-based methods. The control algorithm was verified on a modified six-phase inverter under simulated vehicle conditions utilizing a dynamometer. Results confirmed reliable operation and validated the control approach. Future work will involve complete hardware testing with the new control board to finalize the platform as a flexible, open-source tool for research and education in hybrid drive technologies. Full article

The growing need for high-efficiency and reliable propulsion systems in naval applications, particularly within the evolving landscape of submarine warfare, has led to an increased interest in multiphase Permanent Magnet AC motors. This study presents a modelling and simulation approach for a 3MW, seventeen-phase Permanent Magnet AC motor designed for submarine propulsion, integrating an AI-based drive control system. Despite the advantages of multiphase motors, such as higher power density and enhanced fault tolerance, significant challenges remain in achieving precise torque and variable speed, especially for externally mounted motors operating under deep-sea conditions. Existing control strategies often struggle with the inherent nonlinearities, unmodelled dynamics, and extreme environmental variations (e.g., pressure, temperature affecting oil viscosity and motor parameters) characteristic of such demanding deep-sea applications, leading to suboptimal performance and compromised reliability. Addressing this gap, this research investigates advanced control methodologies to enhance the performance of such motors. A MATLAB/Simulink framework was developed to model the motor, whose drive system leverages an AI-optimised dual fuzzy-PID controller refined using the Harmony Search Algorithm. Additionally, a combination of Indirect Field-Oriented Control (IFOC) and Space Vector PWM strategies are implemented to optimise inverter switching sequences for precise output modulation. Simulation results demonstrate significant improvements in torque response and control accuracy, validating the efficacy of the proposed system. The results highlight the role of AI-based propulsion systems in revolutionising submarine manoeuvrability and energy efficiency. In particular, during a test case involving a speed transition from 75 RPM to 900 RPM, the proposed AI-based controller achieves a near-zero overshoot compared to an initial control scheme that exhibits 75.89% overshoot. Full article

Recurrent catastrophic inverter failures significantly undermine the reliability and economic viability of utility-scale photovoltaic (PV) power plants. This paper presents a comprehensive investigation of severe inverter destruction incidents at the Kopli Solar Power Plant, Estonia, by integrating controlled laboratory simulations with extensive field monitoring. Initially, detailed laboratory experiments were conducted to replicate critical DC-side short-circuit scenarios, particularly focusing on negative DC input terminal faults. The results consistently showed these faults rapidly escalating into multi-phase short-circuits and sustained ground-fault arcs due to inadequate internal protection mechanisms, semiconductor breakdown, and delayed relay response. Subsequently, extensive field-based waveform analyses of multiple inverter failure events captured identical fault signatures, thereby conclusively validating laboratory-identified failure mechanisms. Critical vulnerabilities were explicitly identified, including insufficient isolation relay responsiveness, inadequate semiconductor transient ratings, and ineffective internal insulation leading to prolonged arc conditions. Based on the validated findings, the paper proposes targeted inverter design enhancements—particularly advanced DC-side protective schemes, rapid fault-isolation mechanisms, and improved internal insulation practices. Additionally, robust operational and monitoring guidelines are recommended for industry-wide adoption to proactively mitigate future inverter failures. The presented integrated methodological framework and actionable recommendations significantly contribute toward enhancing inverter reliability standards and operational stability within grid-connected photovoltaic installations. Full article

Distributed temperature sensing (DTS) has been widely used in downhole dynamic monitoring. How to analyze its data and accurately interpret the flow profile using DTS data are still great challenges. Quantitative interpretation of downhole temperature measurements requires the development of an integrated flow and thermal model capable of handling multi-phase flow. The model must strike a balance between computational efficiency and achieving the highest possible accuracy. The finite difference method can solve the relevant problems well. The flow model and thermal model of reservoirs and wellbores are established. Combined with the single-phase flow theory, the coupling prediction model of wellbore and reservoir temperature is established through appropriate boundary and constraint conditions. The problem was solved iteratively using the finite difference method, and the coupled temperature prediction model’s reliability was confirmed through comparison with numerical simulation results. Based on the forward model, the sensitivity analysis of the influencing factors is carried out in this study which provides a theoretical basis for the inversion model. Taking the flow rate as the inversion parameter, the injection profile interpretation model based on DTS logging data is constructed. Four optimization methods are used in the inversion model which can balance the computational efficiency and model accuracy. The DTS data are preprocessed by the Kalman filter, and the inversion and interpretation evaluation of X injection well is carried out by the LSO-MCMC combined optimization algorithm. The results show that the method has high reliability in the interpretation accuracy of injection profile, and the inverted flow profile meets practical application requirements, confirming the method’s accuracy and effectiveness. Full article

The present paper deals with a review on bearing currents in electrical machines, with major emphasis on mechanisms, impacts, and mitigation strategies. High-frequency common-mode voltages from the inverter-driven system have been found to be the main reason for bearing current leading to motor bearing degradation and eventual failure. This paper deals with bearing currents—electrical discharge machining (EDM) currents, circulating bearing currents, and rotor-to-ground bearing currents—and the various methods of their generation and effects that are harmful to the bearings and lubricants of a motor. Mitigation techniques, among which the following have been taken into account, are studied in this context: the optimization of PWM modulation, and the use of shaft grounding brushes, insulated bearings, and passive or active filters. Finally, advantages, limitations, and implementation challenges are discussed. A review comparing three-phase and dual three-phase inverters showed that, due to the increased degree of freedom in modulation strategies, it is possible to eliminate common-mode voltages through active modulation techniques. Such added flexibility will reduce the risk of bearing currents effectively. It also highlights future research directions in bearing current suppression, including the development of multi-phase motor systems, real-time monitoring technologies with artificial intelligence, and the use of new insulation materials for the enhancement of bearing reliability. The results obtained should guide future research and engineering practices in suppressing bearing currents to improve motor durability with high performance. Full article

The growing demand for higher reliability and efficiency in modern electric drives, coupled with the increasing adoption of multi-phase machines, has necessitated advancements in fault-tolerant control strategies. This paper presents a fault tolerance analysis for a six-phase permanent magnet synchronous machine (PMSM) connected to a five-level cascaded H-bridge converter, employing a level-shift pulse width modulation (LSPWM) technique. Unlike existing strategies, this work integrates a unique combination of three key innovations: first, a fault detection mechanism capable of identifying faults in both machine phases and inverter legs with high precision; second, an open-circuit fault compensation strategy that dynamically reconfigures the faulty inverter phase leg into a two-level topology to reduce losses and preserve healthy switches; and third, a modified closed-loop control method designed specifically to mitigate the adverse effects of short-circuit faults while maintaining system stability. The proposed approach is validated through rigorous simulations in Simulink and Hardware-in-the-Loop (HIL) tests, demonstrating its robustness and applicability in high-reliability applications. Full article

This paper investigates a back-electromotive force (EMF) harmonic compensation strategy for six-phase permanent-magnet synchronous motors (PMSMs) to reduce current harmonics and improve system performance. Ideally, the back-EMF waveform should be perfectly sinusoidal. However, manufacturing imperfections such as suboptimal magnetic circuit design, uneven winding distribution, and mechanical eccentricity introduce low-order spatial harmonics, particularly the 5th, 7th, 11th, and 13th orders, which distort the back-EMF, increase current harmonics, complicate control, and reduce efficiency. To address these issues, this study proposes a compensation strategy utilizing common-mode and differential-mode current control. By injecting the 6th and 12th harmonics into the decoupled voltage commands along the d-axis and q-axis, the strategy significantly reduces current harmonic distortion. Experimental validation was conducted using a TMS320F28386D microcontroller, which controlled dual inverters via PWM signals and processed real-time current feedback. Rotor position feedback was provided by a resolver to ensure precise and responsive motor control. At a rotational speed of 900 rpm, with a peak phase current $I_m$ of 200 A and an IGBT switching frequency of 10 kHz, the phase-a current total harmonic distortion (THD) was reduced from 11.86% (without compensation) to 6.83% (with compensation). This study focused on mitigating harmonics below the 14th order. The experimental results demonstrate that the proposed back-EMF harmonic compensation strategy effectively minimizes current THD, highlighting its potential for improving the performance and efficiency of multi-phase motor systems. Full article

The paper presents the practical design and implementation of a three-level neutral point clamped (TNPC) six-phase inverter rated at 100 kVA. The study initiates with prior work review, whereby most research work done earlier was mainly simulation-based. Based on the simulation results, this paper focuses on the practical aspects of inverter design, such as the development of a power board on an Insulated Metal Substrate, a gate driver board, an interconnect board, and the main control board. An inverter physical prototype has been built and tested at 500 V and 20 kW of output power. The SiC semiconductor technology is the base of the inverter, which represents the main merit of the work. Finally, high power density, compact design, and high efficiency are shown, which are major contributions of the paper. Tests performed proved that the designed converter was operating reliably and efficiently. While a simple Sinusoidal Pulse Width Modulation (SPWM) control algorithm has been implemented, the overall performance of the inverter showed great promise for higher-power applications. Compact and high-efficiency TNPC converters are developed for meeting increasing demands of advanced energy, automotive, and industrial applications. Full article

This paper contains research on the development of a fault-tolerant six-phase synchronous reluctance motor (SynRM) based on the stator adopted from a general-purpose three-phase induction motor. In the design and calculation process, an extended Clarke transformation was developed for a six-phase asymmetrical system. To verify the proposed design approach, a field–circuit model of electromagnetic phenomena in the studied motor was developed and used to study the motor performance. The increased torque value and reduction in torque ripples were confirmed by comparison to the classical three-phase SynRM design. To illustrate fault tolerance capabilities, the operation of the studied three- and six-phase synchronous reluctance motors under inverter-fault conditions was examined. The conducted analysis shows, among other things, that from the electromagnetic performance point of view, only the proposed six-phase machine is able to properly operate under inverter-fault conditions. The results of the winding design calculations, the performed simulations of six-phase motor operation, and the preliminary tests of the prototype motor are presented and discussed. Full article

In the five-phase-inverter adjustable speed system, a five-phase two-level inverter usually adopts the nearest-two vector SVPWM (NTV-SVPWM) or the nearest-four vector SVPWM (NFV-SVPWM). The former one has a high-output-current harmonic, which increases the power losses, while the latter one has a low harmonic, but its sinusoidal voltage transfer ratio (VTR) is 0.812, which decreases load capacity. To improve the loading capacity and decrease the power losses of the five-phase-inverter adjustable speed system, a new space vector over-modulation method based on multi-vector weighting is proposed in this paper, and harmonic characteristics of the proposed over-modulation method are analyzed. The simulation results indicate that the proposed over-modulation method has a lower output voltage error than that with the traditional NFV-SVPWM and has a lower output current THD than that with the traditional NTV-SVPWM. The experimental results verify that the proposed method is correct and feasible. Full article