Veronica Biagini

Low Carrier–Fundamental Frequency Ratio PWM for Multilevel Active Shunt Power Filters for Aerospace Applications

Active power filters create sideband harmonics over a wide frequency range around the multiple carrier-frequency harmonics, and these can encroach into the low frequency range. This issue is particularly critical when low carrier-fundamental frequency ratios are used such as in aerospace applications, where high fundamental frequencies exist. A three-phase multilevel active shunt filter with a low switching frequency is proposed to mitigate the lowest order carrier-frequency terms. However, low carrier frequencies lead to reference voltage phase delay and attenuation and can introduce significant baseband harmonics. These effects cannot be hidden by employing multiple modulator converters. In addressing these problems, an improved modulation approach is proposed in this work that allows duty cycle updating (N - 1) times per switching period for each H-bridge of one phase of the N -level converter [rather than only once or twice as in the regularly sampled pulse width modulation (PWM)]. The proposed modulation approach is then combined with predictive current control in order to enhance the system performance. The control loop performance compared to regularly sampled PWM is verified through simulations and experimentally by employing a three-phase five-level active shunt power filters in a 400-Hz power network.

Control and Modulation of a Multilevel Active Filtering Solution for Variable-Speed Constant-Frequency More-Electric Aircraft Grids

The increase of power electronic subsystems in more-electrical aircrafts (MEA) brings severe challenges to aircraft power distribution in terms of power quality on board. Active filtering is a viable solution to this problem; however, given the high supply frequency in AC-MEA power networks, effective harmonic compensation using standard converter structures, traditional digital control and reasonable devices switching frequency is a demanding task. A five-level active shunt filter with an enhanced deadbeat current controller is proposed in this paper for a fixed frequency 400 Hz aircraft power grid. The controller shows higher immunity to measurement noise compared with the conventional deadbeat current controller. In order to enhance the system performance when the voltage reference has a high rate of change, a modified pulse width modulation algorithm is proposed. The effective reference tracking of the proposed modulation combined with the employed current control approach is experimentally verified. The proposed controller features a high bandwidth of the current control loop, capable of high frequency harmonic compensation, using a reduced devices switching frequency.

Improved dead beat control of a shunt active filter for aircraft power systems

This paper investigates the application of an improved dead beat digital control strategy to a 3-phase shunt active filter used for compensation of load harmonics in aircraft power systems. Due to the high rated frequency (400 Hz) such applications result particularly demanding for both power and control devices. To compensate the inherent delay of digital control systems, a simple method for predicting the values of relevant variables is proposed and analyzed. The converter topology, its analytical modeling and its control are described. Significant results obtained by experimental tests are finally reported and commented, referring to a prototype system purposely implemented.

A low-complexity rotary-linear motor useable for actuation of active wheels

The combination of a rotary and linear motion along the same axis is used in several applications, including tooling machines, robotics, automation etc. It may be also used to conveniently manage pairs of basic functions of active wheels in electric and hybrid vehicles. In such cases, rotary-linear machines may represent an interesting alternative to the usual employ of a separated actuator per each basic motion. Anyway, such machines often rely on a structure that is either not suited to be conveniently realized using common materials and manufacturing techniques, or exhibits a complex behavior not permitting an effective decoupled control of force and torque. This paper presents some results concerning the structure, theoretical modeling, FEM analysis, magnetic circuit modeling and drive control for an isotropic brushless machine recently proposed.

Multi-sampled carrier-based PWM for multilevel active shunt power filters for aerospace applications

Active power filters create sideband harmonics over a wide frequency range around the multiple carrier-frequency harmonics and these can encroach into the low frequency range. This issue is particularly critical when low carrier-fundamental frequency ratios are used such as in aerospace applications, where high fundamental frequencies exist. A multilevel Active Shunt Filter with a low switching frequency is proposed to mitigate the lowest order carrier frequency terms. However low carrier frequencies lead to reference voltage phase delay and attenuation and can introduce significant baseband harmonics. These effects cannot be hidden by employing multiple modulator converters. In order to overcome these problems, a multi-sampled modulation approach is proposed, which allows duty cycle updating (n−1) times per switching period for each H-bridge of one phase of the n-level converter (rather than only once or twice as in the regularly sampled PWM). The proposed modulation approach was combined with predictive current control in order to enhance the system performance. The control loop performance compared to regularly sampled PWM is experimentally verified by employing a five-level ASF in a 400Hz power network.

Multi-domain simulation and analysis of electromagnetically actuated reclosers

This paper deals with the analysis and simulation of an electromagnetic actuator for medium voltage reclosers. At first the actuator structure and its theoretical analytical model is shortly presented; a detailed finite element (FE) model is then reported and described. A mid-level simulation model based on co-energy approach is finally presented, allowing estimating the effect of different control strategies as well as different design parameters. Several simulation results provided by the models are reported and commented referring to different case studies. The results obtained by a purposely developed prototype are finally compared with the simulation results in order to verify the effectiveness of the proposed approaches.

Advanced Variable Structure PI controllers

With the advance of digital control hardware the simple but effective proportional-integral-derivative (PID) control technology is moving towards a higher level of performance and robustness. A more general class of Variable Structure (VS) PID has derived from original PIDs to improve their performances and capabilities. This paper revises the main properties of VS regulators and proposes a novel VS PI controller that combines the advantages of popular PIs with the more flexibility of VS controllers. The proposed regulator is compared with the classic PI over several examples taken from the literature, including first, second and fourth order dynamical systems. An experimental set-up is implemented on purpose using AVR® 32 Microcontrollers in a hardware in the loop approach to validate the simulation results in a more realistic environment.

Modeling and control of a rotary-linear drive using a novel isotropic brushless machine

Rotary-linear motors, able to provide both force and torque along the same axis, represent an interesting solution for managing combined linear and rotary motions along the same direction, as alternative to the usual employ of 2 separated normal motors. Anyway, rotary-linear machines are often either relatively expensive to manufacture or rather complicated to control. A novel type of brushless permanent magnet synchronous rotary-linear motor, designed to overcome the above problems, was recently proposed. Its structure and theoretical analytic model, as well as its FEM detailed modeling, are reported in companion papers. In this paper the simulation modeling of a complete drive using such machine and basing on its theoretical model is presented, also reporting some simulation results confirming the theoretical expectations. A mode retailed mid-level simulation model of the machine based on the equivalent magnetic circuit approach is then described, permitting to estimate the effects of the main non-ideal aspects of the machine structure. Some simulation results provided by the model are finally reported and commented.

Control of an unconventional converter for 3-phase extension of 1-phase mains supply

Due to historical reasons, the most diffused solution for electric energy transmission is via fixed voltage and frequency a.c. grids. A 3-phase symmetric supply results typically preferable; anyway, due to practical reasons 1-phase feeders are mostly used for low-power final distribution up to several kVA. This paper deals with a low-complexity converter that was recently proposed to provide a high power quality reversible interface between 1-phase supply and 3-phase loads. Some improvements in the control system are presented, reporting and commenting simulation results showing better performances under nonlinear, unbalanced and variable loads.

Multi-domain mechatronic approach for the design of a vacuum contactor actuation drive

This paper illustrates the development, up to prototype stage, of an electromechanical actuation system for a medium-voltage vacuum contactor. Such development is carried out using a multi-domain simulation-based mechatronic approach, i.e. developing coordinated sub-models for the mechanism linking the actuator to the movable parts of the interrupter, the rotational electromagnetic actuator, and the power and control electronic circuit supplying the actuator and governing the system via a digital control unit. After a preliminary analysis, the modeling, design and check of the parts via coordinated simulations is presented. A prototype of the system, manufactured to validate the design procedure is finally presented.