Luca Solero

Study of bi-directional buck-boost converter topologies for application in electrical vehicle motor drives

The use of a bi-directional DC-DC converter in motor drives devoted to EVs allows a suitable control of both motoring and regenerative braking operations. In particular, during motoring operations of a battery-fed DC motor drive, a DC-DC converter is to be used to adjust the motor current in order to follow the torque reference signal. On the other hand, a bi-directional arrangement of the converter is needed for the reversal of the power flow, in order to recover the vehicle kinetic energy in the battery by means of motor drive regenerative braking operations. This paper deals with the study and comparison of two bi-directional buck-boost converter topologies. Each of them allows stepping the battery voltage level either up or down, according to motor drive modes of operation. For each converter topology computer simulations of modes of operation are presented together with experimental test results.

Nonconventional on-board charger for electric vehicle propulsion batteries

Electric vehicles (EVs) are needed in densely populated urban areas to reduce air pollution. Battery chargers are needed to supply DC voltage to charge the high-energy battery parks used in EVs. This paper deals with an on-board battery charger arrangement that is fully based on the use of the power components of the EV motor drive. Desired features for EV battery chargers such as minimum volume, low cost, high efficiency, and high reliability are fully matched by means of the proposed solution. The proposed on-board charger arrangement has been installed on an electric scooter prototype being developed for the Far East markets. Design analysis and experimental results of the on-board charger prototype are presented.

Multiple input DC-DC power converter for fuel-cell powered hybrid vehicles

Customer demands for greater acceleration, performance, and vehicle range in pure EVs plus mandated requirements to further reduce emissions in HEVs increase the appeal for combined on-board energy storage systems and generators. This paper deals with a multiple input DC-DC power converter devoted to combine the power flow of multi-source on-board energy systems. The proposed energy storage arrangement includes fuel cell generator, ultracapacitor tank, and battery system. Possibility of optimization of the output capacitors bank in relation to the RMS value of the current ripple is investigated.

Performance of a 10 kW power electronic interface for combined wind/PV isolated generating systems

The hoped exploitation of pollution-free, low cost, renewable energy resources has always stirred up interest and inventiveness. The double-input single-output DC/DC power converter discussed in this paper, developed for combined wind-photovoltaic generating systems, aims to mitigate the output power fluctuations due to the intermittent nature of both solar and wind energy. Digital control of the whole apparatus also contributes to optimise the converter modes of operation, running both the energy input circuits at their maximum power level. The paper reports an overall description of the power interface characteristics and experimental results recorded in extensive laboratory tests of a 10 kW rated prototype.

Experimental study on reducing cogging torque and no-load power loss in axial-flux permanent-magnet machines with slotted winding

The axial flux permanent magnet machine (AFPM) topology is suited for direct-drive applications, and due to their enhanced flux weakening capability AFPMs having slotted winding are the most promising candidate for use in wheel-motor drives. In consideration of that, this paper deals with an experimental study devoted to investigate a number of technical solutions to be used in AFPMs having a slotted winding in order to achieve substantial reduction of cogging torque and power loss in the stator core. To conduct such an experimental study, a laboratory machine was purposely built incorporating facilities that allow easy-to-achieve off-line modifications of the overall magnetic arrangement at the machine air gaps, such as magnet skewing, angular shifting between rotor discs and accommodation of either PVC or Somaloy wedges for closing the slot openings. The paper discusses experimental results and gives guidelines for the design of AFPMs with improved performance.

Control strategy for multiple input DC-DC power converters devoted to hybrid vehicle propulsion systems

Customer demands for greater acceleration, performance, and vehicle range in pure EVs plus mandated requirements to further reduce emissions in HEVs increase the appeal for combined on-board energy storage systems and generators. This paper deals with the control system of an original HEV propulsion system that includes fuel cell generator and storage energy system combining ultracapacitor tank and battery. The three on-board power sources supply the vehicle traction drive through a multi-input DC-to-DC power converter which provides the desired management of the power flows. In particular, in the proposed arrangement the ultracapacitor tank is used for leveling the battery load current during transients resulting from either acceleration or braking operation of the vehicle. The paper outlines the features of the control unit of the DC-to-DC power converter being used in the proposed propulsion system and describes the main characteristics of a 35 kW prototype developed to conduct laboratory experiments and validate the control strategy.

SVM PMSM Drives with Low Resolution Hall-Effect Sensors

In this paper a back-EMF-based method is used in conjunction with three very low-cost integrated circuits based on the Hall-effect to estimate the rotor position of the direct-drive PMSMs to be used for traction purpose of an electric wheelchair. A speed estimator based on rotor frame machine model (SERF) has been implemented for the PMSM drives, and then the rotor position estimation is achieved by means of a discrete integration of the estimated speed. The three Hall effect sensors are used to detect the rotor initial position as well to reset the error on the rotor position estimation every 60 electrical degrees. In the specific application, SVM technique has been implemented together with the field oriented control. Simulations and experimental results are shown in the paper

Permanent-magnet, direct-drive, starter/alternator machine with weakened flux linkage for constant-power operation over extremely wide speed range

As consequence of the considerable increase of the electrical power demand in vehicles, the adoption of a combined direct-drive starter/alternator system is being seriously pursued and a new generation of vehicle alternators delivering power up to 6 kW over the entire range of the engine speed is soon expected for use with connection to a 42 V bus. The surface permanent magnet (SPM) machines offer many of the features sought for such future automotive power generation systems, and thereby a substantial improvement in the control of their output voltage would allow the full exploitation of their attractive characteristics in the direct-drive starter/alternator application without significant penalties otherwise resulting on the machine-fed power converter. Concerning that, this paper reports on the original solution adopted in a proof-of-concept axial-flux permanent magnet machine (AFPM) prototype to provide weakening of the flux linkage with speed and thereby achieve constant-power operation over a wide speed range. The principle being utilized is introduced and described, including design dimensions and experimental data taken from the proof-of-concept machine prototype.

Power balance control of multiple-input DC-DC power converter for hybrid vehicles

In this paper design of voltage and current conditioning system is proposed for a multiple input dc-dc power electronic converter (MIPEC) devoted to combine hybrid-electric vehicles (HEV) different on-board energy sources; the proposed arrangement for the propulsion system includes fuel cell (FC), ultra-capacitor (UC) tank, and battery unit system (BU). In terms of power sources, the proton exchange membrane fuel cells (FCs) are being increasingly accepted as the most appropriate supply for electric vehicles (EVs) because they offer clean and efficient energy without penalizing performance or driving range. The FC generator, that is the main energy source, has poor efficiency at light load thus the BU is devoted to supply the power at such situation in order to save total efficiency. The UC tank is used to satisfy acceleration and regenerative braking requirements accomplishing the system load transients and improving the on-board BU life time. The paper is mainly focused on modeling the converter for both steady-state and dynamic behavior. Regulators tuning is also carried out, as well complete control system implementation on DSP board is accomplished. Information on carried on experimental test campaign are provided. Achieved results show power balancing appropriate to characteristics of generation and storage units.

High-Speed Generator and Multilevel Converter for Energy Recovery in Automotive Systems

This paper deals with the design solution adopted for a high-speed axial-flux permanent-magnet generator devoted to supplementing power in automotive 42 V electrical systems through a low-voltage multilevel neutral-point-clamped converter. The axial-flux permanent-magnet generator is suitably designed to be directly coupled with a radial turbo-expander which provides recovery of kinetic energy available from the exhaust gases of an internal-combustion engine. The multilevel converter is properly sized for systems having low voltage and high first-order harmonic frequency. The paper describes the proposed 4-kW power rating generating system and discusses various issues resulting from electromagnetic, thermal, and mechanical design of the high-speed axial-flux permanent-magnet generator. As well, investigations on modulation strategy, total harmonic distortion, and power losses are presented for the low-voltage neutral-point-clamped power electronic converter.