Alberto Gaeta

Sensorless Vector Control of PM Synchronous Motors During Single-Phase Open-Circuit Faulted Conditions

This paper deals with the study and development of new control solutions of permanent-magnet synchronous motor (PMSM) drives specifically aimed to operate under sensorless vector control even during fault conditions. The phase imbalance produced by an open-phase fault leads to the failure of several sensorless estimation algorithms based on either machine models or high-frequency signal injection. Exploiting a recently proposed machine model for three-phase faulted PMSM drives, the practical implementation of sensorless vector controls for such drives under asymmetric conditions due to a single-phase open-circuit fault is performed. The effects of the magnetic/geometrical asymmetries during the fault are studied, and the techniques able to mitigate such effects on the rotor position information are provided. The rotor position estimation is achieved in a wide operating range during the fault as it is confirmed by experimental tests.

Optimization of transient operations in sensorless control techniques based on carrier signal injection

Rotor position estimation techniques based on signal injection represent the only way to develop sensorless vector control schemes for permanent magnet synchronous motors able to operate at low and zero speed. Unfortunately an unwanted interaction between transient current components and signal produced by the injection makes necessary to inject a quite strong signal to accomplish a correct estimation. The injection of a strong signal causes extra power losses, while resulting in a poor exploitation of the DC bus voltage. The paper first analyzes the mechanisms that generate such a phenomenon. A new approach is then proposed to overcome any interaction that has been positively evaluated by experimental tests.

Model Predictive Control for Shunt Active Filters With Fixed Switching Frequency

This paper presents a modification to the classical Model Predictive Control (MPC) algorithm and its application to active power filters. The proposed control is able to retain all the advantages of a finite control set MPC while improving the generated waveforms harmonic spectrum. In fact, a modulation algorithm, based on the cost function ratio for different output vectors, is inherently included in the MPC. The cost function-based modulator is introduced and its effectiveness on reducing the current ripple is demonstrated. The presented solution provides an effective and straightforward single loop controller, maintaining an excellent dynamic performance despite the modulated output and it is self-synchronizing with the grid. This promising method is applied to the control of a shunt active filter for harmonic content reduction through a reactive power compensation methodology. Significant results obtained by experimental testing are reported and commented, showing that MPC is a viable control solution for active filtering systems.

Sensorless Finite-Control Set Model Predictive Control for IPMSM Drives

This paper investigates the feasibility of a sensorless field-oriented control combined with a finite-control set model predictive current control (FCS-MPC) for an interior permanent-magnet synchronous motor. The use of an FCS-MPC makes the implementation of most of the existing sensorless techniques difficult due to the lack of a modulator. The proposed sensorless algorithm exploits the saliency of the motor and the intrinsic higher current ripple of the FCS-MPC to extract position and speed information using a model-based approach. This method does not require the injection of additional voltage vectors or the periodic interruption of the control algorithm and consequently it has no impact on the performance of the current control. The proposed algorithm has been tested in simulation and validated on an experimental setup, showing promising results.

HF injection-based sensorless technique for fault-tolerant IPMSM drives

High Frequency (HF) injection sensorless techniques potentially cover an important segment of the sensorless drives market, allowing rotor flux position estimation at low and zero speeds where standard sensorless methods fails. This paper proposes an innovative HF injection-based sensorless technique able to increase the robustness to open-phase faults, simply changing the HF signals processing method after fault detection and with no modifications on the additional signals generation at the inverter level. Experimental results performed on an IPMSM drive confirm the consistence of the proposed approach.

Modeling and control of three-phase PMSMs under open-phase fault

This paper deals with modeling and control of three-phase permanent-magnet synchronous motors (PMSMs) under open-phase fault conditions. Suitable reference frame transformations are introduced in order to obtain a q-d axis model similar to that normally used for machines working in healthy conditions. Adoption of such a model also allows implementing vector control strategies for PMSM drives under open-phase fault conditions in a wide operating range. Simulations and experimental tests confirm the validity of the theoretical analysis.

A Distributed Model Predictive Control Strategy for Back-to-Back Converters

In recent years, model predictive control (MPC) has been successfully used for the control of power electronics converters with different topologies and for different applications. MPC offers many advantages over more traditional control techniques such as the ability to avoid cascaded control loops, easy inclusion of constraint, and fast transient response. On the other hand, the controller computational burden increases exponentially with the system complexity and may result in an unfeasible realization on modern digital control boards. This paper proposes a novel distributed MPC (DMPC), which is able to achieve the same performance of the classical MPC while reducing the computational requirements of its implementation. The proposed control approach is tested on a ac/ac converter in a back-to-back configuration used for power flow management. Simulation results are provided and validated through experimental testing in several operating conditions.

Converter topologies comparison for more electric aircrafts high speed Starter/Generator application

This paper deals with the performance assessment of different permanent magnet motor drives topologies for Starter/Generator in More Electric Aircraft systems. The comparison is focused on the power electronics part of the system, assuming the possibility to adapt the machine structure to better fit the specific configuration. Simulations performed with Matlab/Simulink and Plexim Plecs will be used to evaluate some relevant key points such as efficiency, losses and motor current harmonic distortion. For all the topologies taken into account, simulations will be carried out considering both 2-Levels and 3-Levels converter structures, and different machine arrangements. All power electronics related data used for simulations are obtained from the datasheets of off-the-shelf power modules, both Silicon and Silicon Carbide technology based. The topology showing the best compromise between efficiency and current THD is then selected and a prototype built and tested to validate the models used for simulations.

A fault-tolerant power conversion topology for PMSG based Wind Power Systems

This work aims to investigate a novel fault tolerant topology for Permanent Magnet Synchronous Generator (PMSG) based Wind Power Systems (WPS), where the static power converter consists of two three-phase inverters connected in back to back configuration. The first inverter is used to control the PMSG while the other one is used to deliver power to the grid through an output filter and a line frequency transformer. Essentially, the fault tolerance is achieved by performing a cooperative control strategy when a faulty condition occurs in one of the two drives. Whenever a fault occurs in one of these two parts, the faulty elements are isolated, the faulty part is controlled in open phase mode and the resulting current flowing out the neutral point is redirected to the healthy part which is so exploited as a feedback current path. The proposed Fault Tolerant WPS (FTWPS) requires very limited modifications to the vector control performed in the PMSG as well as to the active and reactive power control implemented in the grid side, by keeping similar performance with respect to the healthy system. The theoretical analysis is supported by experimental tests, validating the effectiveness of the system configuration.

Finite states modulated model predictive control for active power filtering systems

This paper investigates the application of an improved Modulated Model Predictive Control strategy to active power compensators. The proposed control is able to retain all the advantages of a Finite Control Set Model Predictive Control whilst improving the waveform harmonic spectrum. In fact a modulation algorithm, based on the cost function ratio for different output vectors, is inherently included in the predictive control algorithm. In particular the case of a Shunt Active Filter is investigated and the converter topology, its analytical modeling and its control implementation are described in details. The cost function-based modulator is introduced and its effectiveness on reducing the current ripple is demonstrated. The proposed approach provides a straightforward and effective single loop control solution, maintaining an excellent dynamic performance despite the modulated output and it is self-synchronizing with the grid. Significant results obtained by experimental testing are reported and commented.