An Integral Battery Charger with Power Factor Correction for Electric Scooter

This paper presents an integral battery charger for an electric scooter with high voltage batteries and interior-permanent-magnet motor traction drive. The battery charger is derived from the power hardware of the scooter, with the ac motor drive that operates as three-phase boost rectifier with power factor correction capability. The control of the charger is also integrated into the scooter control firmware that is implemented on a fixed-point DSP controller. Current-controlled or voltage-controlled charge modes are actuated according to the requirements of the battery management system, that is embedded into the battery pack. With respect to previous integrated chargers, the ac current is absorbed at unitary power factor with no harmonic distortion. Moreover, no additional filtering is needed since the pulsewidth modulation ripple is minimized by means of phase interleaving. The feasibility of the integral charger with different ac motors (induction motor, surface-mounted phase modulation motor) is also discussed, by means of a general model purposely developed for three-phase ac machines. The effectiveness of the proposed battery charger is experimentally demonstrated on a prototype electric scooter, equipped with two Li-ion battery packs rated 260 V, 20 A

Direct Flux Field Oriented Control of IPM Drives with Variable DC-Link in the Field-Weakening Region

This paper presents the direct flux control of an interior permanent-magnet (IPM) motor drive in the field-weakening region. The output torque is regulated by the coordinated control of the stator flux amplitude and the current component in quadrature with the flux, and it is implemented in the stator flux reference frame. The control system guarantees maximum torque production taking into account voltage and current limits, in particular in case of large dc-link variations. The field-oriented control does not necessarily require an accurate magnetic model of the IPM motor, and it is able to exploit the full inverter voltage at different dc-link levels with no additional voltage control loop. The feasibility of the proposed control method is investigated in discrete-time simulation, then tested on a laboratory rig, and finally implemented on board of an electric scooter prototype. The motor under test is an IPM permanent-magnet-assisted synchronous reluctance machine, with high-saliency and limited permanent-magnet flu

A SyR and IPM machine design methodology assisted by optimization algorithms

The design optimization of synchronous reluctance (SyR) machine and its extension to internal permanent magnet (IPM) motors for wide speed ranges is considered in this paper by means of a Finite Element Analysis-based multi-objective genetic algorithm (MOGA). The paper is focused on the rotor design, that is controversial key aspect of the design of high saliency SyR and IPM machines, due to the difficult modeling dominated by magnetic saturation. A three step procedure is presented, to obtain a starting SyR design with the optimal torque versus torque ripple compromise and then properly include PMs into the SyR geometry, given the desired constant power speed range of the final IPM machine. The designed rotors have been extensively analyzed by computer simulations and two SyR prototypes have been realized to demonstrate the feasibility of the design procedur

Self-Commissioning of Inverter Nonlinear Effects in AC Drives

The paper presents a novel technique for an accurate identification of the inverter nonlinear effects, such as the dead-time and on-state voltage drops. The proposed technique is very simple and it is based only on a current control scheme. If the inverter load is an AC motor, the inverter effects can be identified at drive startup using as measured quantities the motor currents and the inverter DC link voltage. The identified inverter error is stored in a Look-Up Table (LUT) that can be subsequently used by the vector control algorithm. The proposed method has been tested on a 1 kVA inverter prototype and the obtained results demonstrate the feasibility of the proposed solutio

Self-Commissioning Algorithm for Inverter Non-Linearity Compensation in Sensorless Induction Motor Drives

In many sensorless field-oriented control schemes for induction motor (IM) drives, flux is estimated by means of measured motor currents and control reference voltages. In most cases, flux estimation is based on the integral of back-electromotive-force (EMF) voltages. Inverter nonlinear errors (dead-time and on-state voltage drops) introduce a distortion in the estimated voltage that reduces the accuracy of the flux estimation, particularly at low speed. In the literature, most of the compensation techniques of such errors require the offline identification of the inverter model and offline postprocessing. This paper presents a simple and accurate method for the identification of inverter parameters at the drive startup. The method is integrated into the control code of the IM drive, and it is based on the information contained in the feedback signal of the flux observer. The procedure applies, more in general, to all those sensorless ac drives where the flux is estimated using the back-EMF integration, not only for IM drives but also for permanent-magnet synchronous motor drives (surface-mounted permanent magnet and interior permanent magnet). A self-commissioning algorithm is presented and tested for the sensorless control of an IM drive, implemented on a fixed-point DSP. The feasibility and effectiveness of the method are demonstrated by experimental result

Direct Flux Vector Control of Synchronous Motor Drives: Accurate Decoupled Control with Online Adaptive MTPA and MTPV Evaluation

Direct flux vector control (DFVC) has an unique advantage in facilitating flux-weakening operation due to the choice of controlled variables: stator flux linkage magnitude and torque producing current. However, the dynamics in stator flux oriented reference frame is heavily affected by the nonlinear cross-coupling between the two axes. This paper presents a nonlinear transformation method to decouple the axes for a uniform bandwidth at all operating points. Respect to the literature, the proposed transformation takes magnetic saturation into account without approximation. Furthermore, the auxiliary-flux and auxiliary-current vectors are introduced to design a new adaptive evaluation of maximum torque per ampere (MTPA) and maximum torque per volt (MTPV) control laws, enabling to track the optimal control laws without the need for pre-processed look-up-tables (LUTs). The proposed scheme is experimentally validated on a 1.1 kW synchronous reluctance (SyR) machine test bench

Permanent Magnet minimization in PM-Assisted Synchronous Reluctance motors for wide speed range

This paper presents a technique to modify the rotor lamination of a permanent-magnet-assisted synchronous reluctance motor, in order to reduce the magnet volume with no side effect on performance. A closed-form analysis, which is based on a lumped parameter model, points out that the magnet quantity can be minimized with a significant saving of material volume and cost. At a second stage, the risk of demagnetization is evaluated since the minimized magnets are thinner than the starting ones and work on lower load lines in their respective B-H planes. A feasible drawing is analytically defined, which is robust against demagnetization at overload, showing that the saving of magnet quantity depends on the maximum current overload and can be significant. The theoretical formulation is validated with finite-element analysis and experiments on a prototype machin