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In the past two decades, much research and industry effort has been dedicated to transportation electrification. In particular, aerospace industry, with the more electric aircraft (MEA) revolution, is shifting toward the usage of electrical in place of mechanical energy on board to save fossil fuel and reduce polluting emissions. For this reason, phase-locked loops (PLLs) systems have been well developed for synchronizing different power sources and loads within the aircraft electrical grid. Since one of the proposed solutions for MEA power grids is to operate at variable frequency from 360 to 800 Hz, a third-order model-based steady-state linear Kalman filter PLL (SSLKF-PLL) has been proposed in the literature to achieve fast tracking performance during such grid frequency variations. To suppress the potential disturbances due to harmonics in the grid, sensor scaling errors/unbalances, and dc offsets while maintaining low computational burden, this article aims to enhance the disturbance rejection ability of SSLKF-PLL by adding a repetitive observer (RO). Simulation and experimental tests show that RO allows stable and effective suppression of disturbances from all the abovementioned sources during variable frequency operation. The execution time of the proposed PLL is only 4.23 μ s using a Xilinx Zynq-7000-based platform, where the added RO takes 2.664 μ s to execute, and the SSLKF-PLL alone takes 1.566 μ s.

A novel fault detection and ride-through method for the three-phase 4-Leg Inverter (3$\Phi$4L Inverter) used in off-grid applications is addressed in this paper. Open circuit and short circuit faults of the power devices located in the $3 \Phi 4 \mathrm{~L}$ Inverter have been theoretically analyzed. Hence, the fault detection and converter protection strategy has been implemented using a combination of a resonant controller in the $\alpha \beta$ frame and a repetitive observer. The proposed strategy has been at first validated by means of simulation results performed in MATLAB/Simulink environment. The fault detection and ride-through algorithm has been then implemented in FPGA using LabVIEW environment and full experimental verification are performed on the prototype of the three-phase 4-leg inverter.

This paper presents a novel cascaded multilevel converter topology with reconfigurable battery modules able to merge the power conversion and the battery management functionalities for electric powertrain application. In the proposed topology, each battery cell can be individually connected or bypassed according to the required voltage and current levels. Both the charging and discharging processes can be controlled to avoid voltage imbalances between the cells and to enhance fault tolerance, battery life, and safety. Converter switching and conduction losses are evaluated and used as key parameters for the optimization of the proposed architecture. Furthermore, an efficiency comparison between a conventional three-phase IGBT-based inverter and the proposed topology is carried out. The two topologies are evaluated according to the WLTP Class 3 driving cycles, showing their average efficiency in each cycle. The comparison results show that the performance achieved with the proposed topology is extremely promising to combine state-of-the-art functionalities with the new paradigm of battery management.

A speed control scheme is presented for a three-phase surface permanent magnet synchronous machine with an open-end stator winding fed by a three-phase inverter and a floating bridge inverter. The latter is used to compensate for the reactive power of the main inverter and to maximize the active power received by the motor, without exceeding the available stator current and dc-link voltage. To reduce the switching losses, the dc-link voltage of the floating inverter bridge varies depending on the operating condition of the motor and the controllability requirements of the system. The experimental results show that a significant improvement in the speed range at constant power is achievable, proportionally to the dc-link voltage of the floating bridge inverter.

This paper presents a current limitation technique for a multiphase bearingless machine featuring a combined winding system. This winding structure allows each machine phase to produce both suspension force and motoring torque. Compared to more conventional systems where two separate windings are adopted for the force and torque generation, the combined winding one leads to higher compactness and simpler manufacture. The main challenges with the combined winding configuration consist of decoupling the force and torque generation and designing a proper current limitation algorithm. The former topic has been already tackled and presented in previous publications, instead the latter will be addressed in this paper. In particular, the so called smart limitation technique will allow to prioritize either the suspension force or the torque generation. In this paper the priority is given to the rotor levitation, hence the suspension force rather than the torque is essential. The technique can be extended to give priority to the torque generation in further work and can be applied to any multiphase bearingless machine with similar winding structures. Finally, simulation results and experiment validation are provided.

© 1972-2012 IEEE. In this paper, a dual-fed (DF) common dc-link topology open-end winding permanent magnet synchronous motor for aircraft high-speed starter-generator application is considered. While on one hand the common dc bus configuration significantly simplifies and reduces the costs of the topology, on the other hand it allows the zero-sequence current (ZSC) to flow freely in the system. High-speed machines are characterized by low phase inductance, which implies low zero-sequence impedance. A small time constant of the zero-sequence circuit produces a high-frequency, high-intensity ZSC ripple with the risk of harming the switching devices. This paper presents a novel hybrid space vector pulsewidth modulation that allows to instantaneously eliminate the zero-sequence voltage (ZSV) produced by the two voltage source converters (VSCs) by square wave modulating one of the two VSCs. The non-sinusoidal machine back electromotive force (EMF) has been considered and the effect of the converters' dead time on the ZSV has been analyzed. The square-wave-modulated VSC uses insulated-gate bipolar transistor (IGBT) devices, whereas the other uses Silicon Carbide (SiC) technology. The proposed topology is tested through both simulations and experiments.

The paper deals with a newly developed sequential model predictive control strategy for the high-performance control of electric drives. The sequential nature of cost function evaluation allows to eliminate weighting factors whose tuning is not straightforward. In the first cost function evaluation, torque (or flux) error is minimized and, the second evaluation minimizes the flux (or torque) error. The first optimization generates two optimal voltage vectors that give minimum error for the controlled variable and the second optimization tests only the selected two vectors to find the global optimal. In this paper, a detailed analysis of the sequential MPC is carried out with a focus on the inversion of sequence of optimization with respect to the original algorithm. The paper also analyses the effect of selecting more than two vectors from the first evaluation and explains to the reader why some numbers of selected vectors produce flux and torque distortions while others do not control flux and torque at all

This paper presents the development and validation of a fast, accurate, and high dimensional Multiphysics analytical model for the optimization-based design of fractional-slot surface permanent magnet (PM) machines. The approach is non-iterative and high dimensional, i.e. considers a high number of input parameters. The resulting model takes an average of 0.03 seconds to run on a standard PC, and its accuracy is verified by both Finite Element (FE) analysis and experimental tests. Due to its accuracy and speed, the model can be easily integrated within a design optimization environment.

In a common dc-link dual-fed open-end winding permanent magnet synchronous motor (OEW-PMSM) topology, it is well known how the additional flow of a zero-sequence current (ZSC) is permitted. The low zero-sequence impedance characteristic of high-speed machines leads to high-intensity and high-frequency ripple of the ZSC. Therefore, there is a necessity to eliminate the zero-sequence-voltage (ZSV) produced by the two voltage source converters that feed the machine. Furthermore, the non-sinusoidal back electromagnetic force (back EMF) causes the circulation of a third harmonic ZSC. An OEW-PMSM high-speed starter-generator fed by a dual-inverter with a single dc-link is considered. Part I of this paper proposes a modulation for the considered topology able to eliminate instantaneously the ZSV produced. In this paper, a detailed analysis of the deadtime (DT) effect on the ZSV has been carried out and a novel hysteresis control for the ZSC using the DT as a control action is presented. The DT produces a ZSV distortion on the zero-axis that can be used to control the third harmonic ZSC flowing due to the non-sinusoidal machine back EMF.

This paper deals with the real time implementation of an Implicit Model Predictive Control strategy applied to a 3-phase Voltage Source Inverter (VSI) in stand-alone applications. Solving the optimization problem online with a sufficiently short sampling time allows to directly control the output voltage while respecting the desired constraints. Due to the resulting complex calculations and the related time-constraints, the implementation has been carried out on an industrial-grade FPGA to take advantage of the true parallel execution capabilities.

A model predictive control scheme for multiphase induction machines, configured as multi-three-phase structures, is proposed in this paper. The predictive algorithm uses a direct flux vector control scheme based on a multi-three-phase approach, where each three-phase winding set is independently controlled. In this way, the fault-tolerant behavior of the drive system is improved. The proposed solution has been tested with a multimodular power converter feeding a six-phase asymmetrical induction machine (10 kW, 6000 r/min). Complete details about the predictive control scheme and adopted flux observer are included. The experimental validation in both generation and motoring modes is reported, including open-winding postfault operations. The experimental results demonstrate full drive controllability, including deep flux-weakening operation.

Two different approaches to characterize the torque and radial force production in a Bearingless Multi-Sector Permanent Magnet (BMSPM) machine are presented in this work. The first method consists of modelling the motor in terms of torque and force production as a function of the stationary reference frame α-β currents. The current control reference signals are then evaluated adopting the Joule losses minimization as constrain by means of the pseudo inverse matrix. The second method is based on the control of the magnetic field harmonics in the airgap through the current Space Vector (SV) technique. Once the magnetic field harmonics involved in the torque and force production are determined, the SV transformation can be defined to obtain the reference current space vectors. The methods are validated by numerical simulations, Finite Element Analysis (FEA) and experimental tests. The differences in terms of two Degrees of Freedom (DOF) levitation performance and efficiency are highlighted in order to give the reader an in-depth comparison of the two methods.

with the increasing demand of low-cost, high-efficiency, high performance for AC motor drive system, the permanent-magnet synchronous motor (PMSM) with binary Hall sensors begins to be adopted in many fields. Compared with sensorless control, the usage of binary Hall sensors is a guarantee for the drive to achieve moderate control performance, and it is in smaller volume and more cost-effective compared with other types of position sensors. In this paper, a solution is provided to realize fully-closed loop control with low-resolution position sensors, by treating the position and speed estimators as separate systems. Results reveal that the model-based methods can take advantage of model information and model-free methods can smoothly process the quantized Hall position signal. Extensive experiment results are provided demonstrating the position control performance and basic servo performance for a PMSM drive using 3 bit-per-pole-pair sensing system.

In this paper, an optimal voltage vector based model predictive control strategy is investigated for the direct power control of a doubly fed induction machine. The model predictive control computes optimal voltage vector that minimizes the error in active and reactive power. The computed voltage vector, if within the linear regulation range, is passed onto a modulator to be applied in the next sampling instant. In the over-modulation range the voltage vector is linearly scaled down, before modulation, to maintain optimality. The paper also focuses on the saturation of main flux inside an induction machine and its impact on reactive power control when stator current sensors are not installed. The machine's saturation characteristic is fully utilized to realize full-state stator flux observer that is used to estimate stator currents which give accurate prediction of reactive power. Consequently, stator current sensors can be excluded. Simulations and experimental analyses are conducted on a test machine to verify fast dynamics of predictive control and the estimation accuracy of stator current.

A mathematical model enabling to predict the electromagnetic x-y forces and torque for a given input current in a Multi-Sector Permanent Magnet Synchronous (MSPMS) machine is presented. The rotor static eccentricity is also accounted and the analytical calculations are validated by means Finite Element Analysis (FEA). Furthermore, a novel force and torque control is proposed based on input current minimization and is applied to suppress the Unbalanced Magnetic Pull (UMP) caused by the rotor eccentricity. The effective operation of the force suppression technique is verified by means of FEA.

Finite State Model Predictive Control (MPC) has been recently applied to several converter topologies as it can provide many advantages over other MPC techniques. The advantages of MPC include fast dynamics, multi-target control capability and relatively easy implementation on digital control platforms. However, its inherent variable switching frequency and lower steady state waveform quality, with respect to standard control which includes an appropriate modulation technique, represent a limitation to its applicability. Modulated Model Predictive Control (M2PC) combines all the advantages of MPC with the fixed switching frequency characteristic of PWM algorithms. The work presented in this paper focuses on the Indirect Matrix Converter (IMC), where the tight coupling between rectifier stage and inverter stage has to be taken into account in the M2PC design. This paper proposes an M2PC solution, suitable for IMC, with a switching pattern which emulates the desired waveform quality features of Space Vector Modulation (SVM) for matrix converters. The switching sequences of the rectifier stage and inverter stage are rearranged in order to always achieve zero-current switching on the rectifier stage, thus simplifying the current commutation strategy.

This paper proposes a Predictive Control, formally Dead-Beat (DBC), for a four-leg inverter having an Active Split DC-bus on the fourth leg and LC filters on phase-to-neutral outputs. Such a configuration permits to reduce the voltage ripple on the neutral point connected to inverter grounding. As only few control techniques have been investigated for Active Split DC-bus, the paper proposes to investigate the performance of DBC, which has been widely used for other power electronics applications. The main advantage of DBC over the classical PI or Resonant controller is that no tuning is required for control loop, while obtaining very fast transient response as well it can handle general constrained nonlinear systems with multiple inputs and outputs in a unified and clear manner. These features are highly valuable in power electronic converters used to supply the electrical utility loads in micro-grids. However, one of the main drawback of the DBC is the limited capabilities on harmonics compensations required when supplying unbalanced and non-linear loads. The paper presents continuous-time and discrete-time models of DBC applied to a four-leg VSI with Active Split DC-bus, highlighting the performance through simulation results as well as experimental tests.

The paper presents an alternative radial force control technique for a Multi-Sector Permanent Magnet machine (MSPM). Radial force control has been widely investigated for a variety of bearingless machines and can be also applied to conventional PMSM aiming the reduction of the mechanical stress on the bearings as well as reduce the overall vibration. Traditional bearingless motors rely on two independent sets of windings dedicated to torque and suspension respectively. The work presented in this paper takes advantage of the spatial distribution of the winding sets within the stator structure towards achieving a controllable net radial force. In this paper the α-β axis model for the MSPM and the theoretical investigation of the force production principle is presented. A novel force control methodology based on the Single Value Decomposition (SVD) technique is described. The predicted performances of the MSPM have been validated using Finite Element simulations and benchmarked against state of the art control techniques.

In this paper, a finite control set Model Predictive Control (MPC) for grid-tie quasi-Z-Source (qZS) based multilevel inverter is proposed. The proposed Power Conditioning System (PCS) consists of a single-phase 2-cell Cascaded H-Bridge (CHB) inverter where each module is fed by a qZS network. The aim of the proposed control technique is to achieve grid-tie current injection, low Total Harmonic Distortion (THD) current, unity power factor, while balancing DC-link voltage for all qZS-CHB inverter modules. The feasibility of this strategy is validated by simulation using Matlab/Simulink environment. 2016 IEEE. Scopus

Model predictive control (MPC) has a number of desirable attributes which are difficult to achieve with classical converter control techniques. Unfortunately, the nature of power electronics imposes restriction to the method, as a result of the limited number of available converter states. This, combined with the spread spectrum nature of harmonics inherent with the strategy, complicates further design. This paper presents a method for removing this characteristic without compromising the desirable functionality of predictive control. The method, named modulated MPC, is applied to a two-level three-phase converter and compared with a number of similar approaches. Experimental results are used to support theoretical analysis and simulation studies.