Carlo Olivieri

Sensorless control of five-phase brushless DC motors

The present paper shows a rotor position estimation technique for a five-phase permanent magnet synchronous motor based on a back-EMF observer, focusing the attention on the design criteria that could be used to construct the sensorless strategy. Due to the polyphase structure of the machine this estimation method deals with a proper linear transformation which allows representing the five-phase motor through an equivalent two-phase model. After a short overview on the back-EMF model for the five-phase motor, the linear transformation and the observer-based estimation technique are presented. The analysis emphasizes on the choice of the observation dynamics through a proper design strategy of the related gain matrix and on some robustness criteria useful to enhance the sensorless strategy. Simulation and experimental results showing the response of the observer during transient and steady-state operation are presented.

Observer-based sensorless control of a five-phase brushless DC motor

This paper presents a rotor position estimation technique for a five-phase permanent magnet synchronous motor with independent phases, based on a back-EMF observer. The method involves the use of a proper linear transformation which allows representing the five-phase motor by an equivalent two-phase model. Due to its characteristics, the sensorless strategy can be used in multi-phase motors having non-sinusoidal back-EMF shape, such is the case of brushless DC motors used in fault-tolerant applications. After an overview of the back-EMF model for the five-phase motor, the linear transformation and the observer-based estimation technique are presented. Experimental results show the overall performance during transient and steady-state operation.

Analysis of phase-detection algorithms for back-EMF-based sensorless strategies through real-time simulations

The work developed in this paper presents a comparison between three different phase detection algorithms in order to study the benefits of using each of them when they are applied inside a sensorless rotor position estimation technique. In particular we will analyse the various aspects related to the use of each single algorithm when it is applied into a specific model-based sensorless strategy and when we also take into account the typical impairments affecting the implementation of the real setup, such as unwanted harmonic components and measurement offsets. As a first step a short overview on each phase-detection algorithm under consideration will be given and subsequently the proposed model-based estimation technique will be presented. As a second step the three algorithms are analyzed in detail highlighting their dynamical performances and their robustness properties against implementative knots, in particular through the use of software simulations and real-time simulations reproducing the specific test case of a five-phase motor.

EBG-Based Common-Mode Stripline Filters: Experimental Investigation on Interlayer Crosstalk

This paper deals with the filters based on EBG cavities employed for reducing common-mode currents along differential stripline traces. The crosstalk among differential interconnects routed in close proximity to EBG-based filters, and next to filtered pairs, is accurately quantified. The comparison between the experimental and simulation frequency-domain results validate the proposed filters effectiveness and make the simulation model reliable for investigating the complex multichannel crosstalk problem. This paper focuses on the stripline environment, where crosstalk occurs among traces routed on adjacent layers, with the EBG cavity acting as a coupling path. Multichannel time-domain simulations complete the characterization of the filter, showing the limited effects of the filter on the intentional differential signal, and the beneficial impact on reducing the potentially radiating common-mode harmonics. The quantification of the common-mode spectrum shows that the filtered harmonics are reduced by 10-15 dB; thus, minimizing the corresponding electromagnetic interference. Design guidelines are defined for the filter layout according to the relative position of unfiltered differential traces, when constraints force them to be placed in close proximity to EBG cavities and filtered pairs. In particular, the best layout for unfiltered traces on adjacent layers is orthogonal with respect to the filtered pair, whereas the parallel routing should be carefully used taking into account the signal bandwidth on the victim pairs.

Analysis of Near-Field Emissions From Common-Mode Filters Based on EBG Structures

This work studies the possible reduction of the direct near-field radiation from electromagnetic bandgap-based comm-on-mode filters on printed circuit boards by using lossy dielectric and magnetic materials. Different combinations of materials are considered and numerically simulated. The comparisons of their performances are reported and discussed.

Exploring Remote Monitoring of Degraded Compression and Bolted Joints in HV Power Transmission Lines

In this work preliminary yet comprehensive considerations are reported on the possibility for remote monitoring of degraded compression and bolted joints on high voltage overhead power lines. Measurements are performed on new, naturally aged, and artificially degraded joints to quantify the impedance discontinuity introduced along typical HV overhead lines. Numerical simulations, a preliminary time domain reflectometry (TDR) measurement campaign, and circuit simulations are performed on a real power line to study the TDR-based capabilities for the identification of the investigated joint impedances. This study sets the basic concepts to the development of a remote monitoring system for quantifying and locating degraded joints.

Detectability of Degraded Joint Discontinuities in HV Power Lines Through TDR-Like Remote Monitoring

The aim of this paper is to clarify some important aspects associated with the possibility to detect degraded compression and bolted joints in power transmission lines using a time-domain reflectometry (TDR)-based remote monitoring. The optimization of a TDR-based remote monitoring method is discussed, studying the effects of the source impedance, source-to-line connection, line characteristic impedance, and scope settings, providing useful guidelines for a future method and instrumentation refinement. The experimental results are presented consisting in the inclusion of lumped resistors of several values along a 130-kV power transmission line. The minimum detectable resistance is discussed based on the present available hardware. The TDR-based method is shown to be able to also identify the main features of the line layout such as phase transpositions and different heights of adjacent towers. This paper represents a preliminary base to keep developing the proposed method, with the aim to overcome the actual limitations (costs, reliability, etc.) in power line monitoring.

Reduction of EMI Due to Common-Mode Currents Using a Surface-Mount EBG-Based Filter

Common-mode (CM) noise on differential signals can be suppressed by planar electromagnetic bandgap (EBG) technologies. In this study, two new CM filter structures were designed, fabricated, and measured. The filters are based on a previously proposed geometry, a “sandwich-type” EBG structure that resonates at the desired filter frequency; however, the new filters are placed on the top of the PCB as a surface-mount component, instead of being implemented within the PCB stackup. Stripline and microstrip versions of the surface-mount filter are considered. The filters can be easily removed and substituted with another one that is designed to filter a different frequency but maintains the same footprint and external dimensions. In addition, the surface-mount filter allows us to incorporate dc blocking capacitors into the microstrip version of the filter, thus providing two functions in one package. The total radiated power (TRP) of the implemented filter is investigated and discussed. RF absorbing material and traditional shielding are considered to reduce the TRP.

Miniaturization approach for EBG-based common mode filter and interference analysis

This paper describes the effort to miniaturize common mode filters based on electromagnetic bandgap structures. It describes the proposed approach by means of a systematic analysis of different configurations. The typical 3-patch configuration proposed in the past is modified removing the central patch and the bridge dimensions are tuned for keeping the same target frequency. The analysis of the crosstalk is carried out for the relevant configurations in order to assess the possible implementation of these structures in high density printed circuit boards. The simulation results are discussed and compared to identify the best miniaturized geometry for a practical implementation.

A DSP-based real-time simulation equipment for fast motor control development

This work presents a rapid motor control prototyping technique based on the development of a real-time simulation environment structured on a DSP architecture. The considered case study refers to an Interior Permanent Magnet synchronous motor (IPM) drive arranging a field oriented speed control with the optimization of the torque-to-current ratio and the decoupling of the feeding voltages. The main topics of this work are related with the construction of the real-time simulation platform and with the implementation issues coming from the use of a hardware DSP-based setup. In particular it will be shown how such a kind of simulation architecture can model very closely the real behaviour of a controlled IPM drive and consequently how it can be used to properly tune the control algorithm without the needing of using the real motor drive saving this way a lot of deployment time.