Luca Peretti

• Doctor of Philosophy
• Professor (Associate) at KTH Royal Institute of Technology

This paper proposes an improved nonlinear extended state observer-based model-free predictive current control with an extended control set. First, the nonsmoothness problem of conventional nonlinear extended state observer model-free solutions is explained. By constructing a high-smoothness polynomial series at the transition points of the piecewis...

A multiphase induction machine model using vector space decomposition provides insights into many space harmonics through decoupled reference frames. In order to utilize this potential of the multiphase machine, the parameters of each vector space must be identified. These parameters are usually identified using the no-load and locked rotor test of...

Conventional model predictive current control of permanent magnet synchronous machines (PMSMs) relies heavily on a precise mathematical model, which may be challenging to obtain in certain cases. To address this issue, this paper proposes a model-free predictive current controller for PMSMs. Specifically, the dynamic model of the motor currents is...

Variable phase-pole machines possess the capability to expand their operational range by employing magnetic pole change while adhering to the same electrical voltage and current limits. This paper proposes a strategy to achieve a pole change with constant torque while simultaneously optimizing current distributions for stator copper loss minimizati...

This article develops a scalable analytical model that builds a relationship between any surface-mounted permanent magnet (SPM) motor and a general motor with variable slot-opening and air-gap length, considering both the saturation effect and slotting effect. It can not only give the performance of the single SPM motor but also show internal conne...

This paper proposed a hybrid analytical model for predicting the magnetic field distribution of slotted surface-mounted permanent magnet linear motor considering both iron saturation and end effect. In the proposed model, the segmented conformal mapping is developed to reduce the computation time while keeping same accuracy, especially when the end...

Automotive applications are revisiting the use of induction machines as magnet-free propulsive solutions due to their intrinsic robustness and reliability. Special multiphase configurations are under investigation to reduce the losses further and fulfill the stringent energy-efficiency and compactness requirements of the automotive industry. One of...

Presents corrections to the paper, (Validation of FEM-Based Parameter Estimation for Variable Phase-Pole Induction Machines).

In this article, an observer-based prescribed performance speed control method is proposed for permanent magnet synchronous motors. A transformed speed error is introduced and a suitable controller is designed to make it converge to zero, while guaranteeing the original speed error evolves strictly within a prescribed region. The controller is desi...

Multiphase electrical machines are inherently fault tolerant due to the higher number of phases. An important step in achieving a fault tolerant control is the ability to detect and identify the fault. In variable phase-pole drives, which are a class of multiphase machines that change the number of pole pairs during real-time operation, there are f...

Magnet-free variable phase-pole machines are competitive alternatives in electric vehicles where torque-speed operating region, reliability, cost, and energy efficiency are key metrics. However, their modeling and control have so far relied on existing fixed-phase and pole-symmetrical models, limiting their drive capabilities especially when switch...

The active short-circuit is a standard safety measure for permanent-magnet synchronous machine drives in electric vehicles, but it can lead to harmful torque and current transients. This paper introduces a mathematical and graphical method to determine the safe operating area of pre-fault current conditions, complying with user-defined torque bound...

DC-link current harmonics and common mode voltage (CMV) are key design challenges for inverter-based power electronic systems. Addressing them collectively without additional hardware and/or complexity has promising advantages. This article investigates the interleaved utilization of modified space vector PWM schemes for parallel-inverter systems,...

Induction machine-based multiphase electrical machines combine the robustness and reliability of well-known induction machines with the benefits of additional degrees of freedom, such as potential higher torque density and true fault tolerance. The subcategory of variable phase-pole machines allows extending the operational torque and speed range w...

Multiphase induction machines are investigated as competitive magnet-free candidates for high torque-density, overload-capable, and wide torque-speed range applications. These benefits are enabled by torque-enhancing harmonic injection and phase-pole changes. However, such operational modes may subject the different harmonic planes to cross-saturat...

This paper proposes a simplified discrete space vector modulation-based model predictive direct speed control with an improved load disturbance observer for permanent magnet synchronous motor drives. Firstly, a simplified discrete space vector modulation method is used to improve the steady-state performance of model predictive direct speed control...

In multiphase electric machines, high-performance control strategies require suitable electrical parameter estimation. This aspect is particularly true for the class of multiphase machines known as variable phase-pole induction machines. This work analyzes, calculates, and experimentally validates different parameter estimation methods for a wound...

Variable phase-pole machines are envisioned in applications requiring a large torque-speed operating area. The control of these machines relies on accurate models and parameters but research on their parameter identification is scarce. This paper presents an offline parameter-identification method for variable phase-pole machines adopting a harmoni...

The design of electric machines for electric traction applications is always very demanding, due to the high-torque requirements at low-speed and high-speed requirements at comparatively low torques. In this context, designs that can stretch the torque-speed map of the machine without compromising other key factors is of great interest. This is why...

A multiphase machine control implementing vector space decomposition or harmonic plane decomposition for modeling purposes can reconfigure the stator's current distribution to generate magnetomotive force waves with different pole pair numbers simultaneously. The pole pair numbers are an integer multiple of the pole pairs generated by the physical...

This paper proposes the field separation theory for predicting the magnetic field of a quasi-Halbach array permanent-magnet motor considering the magnetization pattern and iron saturation. According to the proposed method, the air-gap field consists of a permanent-magnet field, winding current field, and equivalent saturation field. The equivalent...

Induction machines are the working horses in a lot of industries. Inter‐turn short‐circuit (ITSC) fault is one of the most common failure modes taking place in them. It can generate large fault currents that lead to a local temperature rise in the faulty stator slot, which deteriorates the working performance of the machine or even cascades to a co...

This paper presents a comprehensive method to predict the electromagnetic losses in surface-mounted permanent-magnet motors based on a hybrid analytical model. Hybrid analytical model will significantly improve the calculation speed compared with finite-element method while keeping great accuracy, making it a competitive alternative for the analysi...

A multiphase induction machine model using vector space decomposition provides insights into many space harmonics through decoupled reference frames. These decoupled reference frames host specific space vectors related to particular space harmonics. Based on the physical winding configuration, these vector spaces can be excited independently and si...

Condition monitoring of the insulation health of electric machines is usually performed with offline tests. In recent years, online condition monitoring methods for the groundwall insulation have been introduced. The majority of these works are based on leakage current measurements, requiring additional equipment compared to the standard one in con...

Online methods for stator insulation monitoring have been investigated with increasing interest in the last 15 years. These methods rely on the high-frequency behavior of the electric machine. In converter-fed machines, the high-frequency behavior is visible through the current ringings occurring during the switching commutations of the power elect...

An interturn short-circuit in the stator windings can lead to the breakdown of electrical machines. In the case of induction machines, several fault detection methods and faulted models have been developed in the recent decades. These models differ mainly in how the leakage inductances of the faulted winding are modeled. This work provides a genera...

Variable phase-pole machines have the potential to extend the operational range to higher speeds through magnetic pole changes. The state-of-the-art vectorspace decomposition cannot model the transient behavior of the pole change for any possible phase-pole configuration as it creates a discontinuity. The proposed harmonicplane decomposition theory...

With the increasing interest for zero-emission vehicles, electric boats represent a growing area. Weight is a limiting factor for battery-powered boats, therefore, the use of fuel cell/battery systems is investigated. The present study examines the power requirements, the energy-storage solutions and the sustainability assessment of a light and fas...

This paper deals with standstill identification of an induction motor drive for sensorless self-commissioning purposes. The proposed identification method is based on an advanced model of a squirrel-cage induction motor. The model includes the deep-bar effect and the magnetic saturation characteristics. The excitation signals are fed to the stator...

This paper deals with the non-linear modelling of synchronous machines by using the flux linkage as a state variable. The model is inferred from a conventional set of measurements where the relation between the currents and the flux linkages in the rotating reference frame (also known as dq reference frame) are known by measurements or estimated th...

This study proposes a model-based control strategy for flux weakening operation of a synchronous reluctance machine, with a methodology that is extendible to any synchronous machine. The strategy leverages in the presence of digital non-linear models that describe the relation between currents and flux linkages in the machine. Such models are usual...

This work presents a method for the robust detection, classification and possible compensation of harmonics in electric drives during real-time operation, with the aim of providing a framework for monitoring and diagnostic without the need of additional hardware. The detection is performed with a sparse fast Fourier transform algorithm, for its low...

This paper investigates the implementation and the use of the sparse fast Fourier transform algorithm in the converter control of a variable speed drive. The algorithm is proposed due to the reduction in computational complexity compared to the conventional fast Fourier transform for the special case of sparse signals. After discussing the theory a...

The present disclosure relates to a method for determining an undesired condition in an electrical drive system comprising an electrical machine and an electrical drive, wherein the method comprises a) obtaining a measured signal of an electrical or mechanical parameter concerning the electrical drive system, b) obtaining a frequency spectrum of th...

This paper presents the design and experimental validation of a finite-state direct predictive control (DPC) for synchronous reluctance motor (SynRM) drives. The main features are the hierarchical selection policy of the optimal voltage vector and the dynamic scaling of the voltage amplitude, which keeps the current ripple limited even in the prese...

As the number of cells in multi-level converters increase, issues related to the high number of subsystems enter the power electronics area. Within this frame, this study presents a carrier-less approach to the voltage synthesis across the series of several voltage-source cells in multi-level converter topologies. The key idea is the exploitation o...

This paper proposes a model-based current/torque control strategy for synchronous machines, where the magnetic model mismatches are compensated in real time and the flux weakening operation is obtained without the need of an external voltage regulation loop. Starting from an initial (and potentially wrong) knowledge of the non-linear current-to-flu...

Like the damage that can be caused by soldiers marching in step across a bridge or the effects of the wind on the ill-fated Tacoma Narrows Bridge, resonance effects, if left undamped, can prove harmful to electric drives too: Pulses in the driving torque can be amplified by resonance with one of the driveline eigenfrequencies - leading to torsional...

This study presents a self-commissioning procedure for the estimation of the flux linkage curves of synchronous reluctance machines. The procedure exploits a quasi-standstill condition obtained by imposing fast torque oscillations. The flux linkage is calculated by means of a pure integration of the voltages and currents. With respect to the existi...

This work discusses an online stator resistance estimation method for synchronous machines. Multiple improvements are provided with respect to a similar method already been used for induction machines. The method is based on the temporary injection of a DC voltage in the machine phases during normal operation. The stator resistance estimation is ob...

The paper analyses a combined current model-voltage model estimator for flux linkages in permanent magnet synchronous machines, with the capability of converging to exact flux estimation even in presence of mismatches because of magnetic saturation. As a trend in next-generation electric drives, the whole algorithm, including both the flux estimato...

The digital implementation of the integral operator is a delicate part in electrical drives. Many solutions are available in the literature, which avoid the well-known output drift of ideal digital integrators when a spurious DC offset is present at their input. Such solutions try to extend the integration accuracy toward the zero frequency as well...

The aim of the research is the development of a finite-state predictive speed and current control algorithm for a permanent magnet synchronous motor (PMSM). The high computational requirement is one of the main limitations in the calculation and application of the switching states to the inverter, but an alternative control strategy is here propose...

This paper presents a torque harmonic compensation algorithm for wind turbine applications, where the presence of a converter managing the energy conversion can be also exploited for active compensation purposes. A general scenario is described first. The algorithm is then described with its mathematical background. A modification of the algorithm...

The paper presents - with experimental evidence - a highly fault tolerant, cost-effective and carrierless solution to synthesize voltages (or currents) across the series (or parallel) connection of several voltage-source (or current-source) cells. Hundreds of voltage-source cells already characterize modern multilevel HVDC converters and structures...

A method for finding an operating point of an electric motor which includes the steps of generating a perturbation signal, combining the perturbation signal with a current magnitude related to a drive system of the motor or combining the perturbation signal with a power magnitude related to the motor, yielding a combined signal, and sending, based...

The paper describes an emulator for wind turbines which aims to be a base for the development of control algorithms for wind turbine generators. The emulator is physically composed by two servomotors in a back-to-back configuration, each of them controlled by a 4-kW power electronics converter. A FPGA-based control board is employed to model the ef...

The emulation of mechanical systems by means of electrical systems is an application of electrical machines and drives which have received increased attention in the recent years. As power electronics-controlled machines are dynamically faster than conventional mechanical systems, it is widely recognised that the behaviour of the latter can be emul...

The study presents a self-commissioning procedure for the automatic parameter estimation of three-phase induction motor drives. The procedure consists of a step-by-step approach with different test signals to obtain the parameter values while maintaining the motor at standstill. The actual implementation is capable of mapping both inverter and moto...

A flux linkage estimator for synchronous machines which combines a voltage and a current model is analysed, based on an original scheme with some modifications. The proposed schemes assure convergence at steady-state and better transient performances. Simulation and experimental results were performed for different combinations of control schemes a...

10 years from now, we anticipate that there are good practical experiences of larger wind turbine generators, WTG, with ratings >10 MW, i.e., more than 100 m blade lengths. Due to logistics, these turbines are only offshore, maybe in deserts, but likely later than 2025. "Windy Spot" on land is judged to have mainly 2 to 7 MW WTGs depending on site-...

Communication networks have been traditionally employed in motion control applications, especially within factory automation systems. While in the past they were merely used to exchange non time critical data (e.g. parameters and configuration data) nowadays they allow for much more powerful performance. In particular, the recently introduced Real-...

This paper presents an online procedure for the automatic search of the maximum-torque-per-ampere operating region for a synchronous reluctance motor. The algorithm is based on a signal-injection method with a random-based perturbation pattern applied to a common direct-torque-controlled drive. Among motor parameters, only the stator resistance is...

In the modern sensorless and self-commissioning drives scenario, the availability of precise phase voltage measurement represents an undoubted advantage. But the task is not trivial, and few viable solutions are available. The present paper proposes an up-to-date digital method for the measurement of the instantaneous phase voltages of a three-phas...

Speed and current closed loops control represent the heart of any advanced AC servo drive. These inner loops usually feature high-dynamic feedback control, with possible axes decoupling and a straight feedforward action of the back-electromotive force (back-EMF). More sophisticated techniques as single-rate or multi-rate control could be exploited...

This paper presents an auto-tuning technique for the speed controller in electrical drives. The method is based on the model reference approach, where a perturbation frequency is injected into the speed control loop and superimposed to the torque reference signal. The tuning is performed by a simple signal processing elaboration before and after th...

Several emerging applications require fast and precise torque control. Torque measurements are still expensive, bulky, and delicate. On the other hand, estimation techniques are all valid in principle, but their accuracy is largely affected by model identification and commissioning. This paper presents an accurate model for an effective torque esti...

The paper deals with a Model Predictive Control (MPC) algorithm applied to electrical drives. The main contribution is a comprehensive and detailed description of the controller design process that points out the most critical aspects and gives also some practical hints for implementation. As an example, the MPC is developed for a permanent magnet...

The paper presents a result of the system identification theory applied to an industrial machine. The case study was a labelling machine driven by a permanent magnet synchronous motor drive. The identified system model has been used to tune the closed-loop speed control of the drive. A brief recall of the basic principles of power spectral density...

This thesis is the result of a three-years work at the Department of Technique and Management of Industrial Systems of the University of Padova, located in Vicenza, Italy. The research concerns advanced control methodologies for electrical drives. In particular, the first part of the thesis deals with sensorless control of induction motors, in whic...

High-performance sensorless ac drives require the exact knowledge of the motor phase voltages in the whole speed range. The use of voltage sensors may be eschewed if the reference voltage signals, generated by the control algorithm, can be used instead. To this aim, an accurate compensation of most of inverter nonidealities is essential. This paper...

In the last decades, several schemes have been proposed for speed-sensorless control of induction motor drives. Promising approaches are closed-loop observers, as model reference adaptive systems (MRAS) and Kalman filters, and open-loop estimators, which have recently aroused lively interest because of their simplicity and low-cost profile. As know...

The paper presents a detailed sensitivity analysis comparison between two existing low-cost sensorless solutions for induction motor drives. The first solution is a V-type approach, in which the inverter voltage references are calculated from the machine equations instead of obtained as the output of PI current regulators. The scheme is obtained fr...

The paper deals with the model predictive control (MPC) algorithm applied to control a permanent magnet synchronous motor, which is, at present, among the motors with the highest power efficiency and then very attractive for energy-saving applications. Absolute novelty of the proposed MPC is its feature of inherently managing the flux weakening con...

Low and medium power full-digital AC generator sets are largely used in both industrial and civil fields. During the last years, more demanding applications for AC generators have emerged. They require more power combined with a cleaner voltage source. Consequently, particular care is requested for both the mechanical and electrical design of a new...

The paper deals with a voltage-fed (V-type) vector-controlled induction motor drive without speed or position sensors. At first, the drive algorithm is briefly described. Details are then given about the capability of the proposed drive to operate in the flux-weakening region with full inverter output voltage. The parameter sensitivity is also disc...

The electric power steering offer several advantages over traditional hydraulic power steering such as improved fuel economy, assist action, available with the engine off, reduced components, modular assembly, customized steering characteristics, and no need for hydraulic fluid. The steer-by-wire (SBW) system employ two motor drives, the first for...

Several emerging applications require fast and precise torque control. Torque measurements are still expensive, bulky and delicate. On the other hand, estimation techniques are all valid in principle, but their accuracy is largely affected by model identification and commissioning. This paper proposes an accurate model for the electromechanical con...

This paper deals with position control of a direct drive rope-based lift system at mechanical brake releasing. The electrical equipment includes a high-torque, low-speed permanent magnet synchronous motor with external rotor directly connected to the rope pulley. The drive uses only stator current sensors for torque control and an incremental encod...