Janaina Goncalves de Oliveira

Prototype of electric driveline with magnetically levitated double wound motor

This paper presents the ongoing work of constructing a complete driveline for an electric road vehicle, using a flywheel as auxiliary energy storage. The flywheel energy storage system (FESS) is connected in series between the main energy storage (batteries) and the wheel motor of the vehicle, allowing the batteries to deliver power to the system in an optimized way, while at the same time making efficient use of regenerative braking. A double wound permanent magnet electric machine is used to electrically separate the two sides. In order to minimize losses, the machine has a double rotor configuration and is suspended with magnetic bearings. A bench test set-up is being constructed to investigate the properties of this system in detail. This set-up will achieve a level of power and energy close to that of a full scale system. This will allow measurements of complete drive cycles to be performed, improving the understanding of the constituting components and optimization of the complete system.

Losses in axial-flux permanent-magnet coreless flywheel energy storage systems

This paper analyzes the losses of axial-flux permanent-magnet (AFPM) motor/generators integrated in flywheel energy storage applications with a coreless winding. This configuration has several advantages over traditional slotted ones for some applications since the losses in a toothless design are at a lower level than in an equivalent iron slotted devices. It has lower idle losses and potentially higher overall efficiency than conventional machines. 3-D finite element method (FEM) is used to calculate flux density in the air gap and to simulate the electromotive force (back EMF) and eddy current losses in the windings. A small-scale three-phase machine has been designed and constructed. Spin down tests have been performed in atmospheric pressure and at low pressure and eddy current, bearing and drag losses are presented.

Power Balance Control in an AC/DC/AC Converter for Regenerative Braking in a Two-Voltage-Level Flywheel-Based Driveline

The integration of a flywheel as a power handling can increase the energy storage capacity and reduce the number of battery charge/discharge cycles. Furthermore, the ability of recovering energy of ...

Battery Discharging Power Control in a Double-Wound Flywheel System Applied to Electric Vehicles

Flywheel Energy Storage Systems (FESS) are a good alternative for power handling and energy storage in hybrid and electric vehicles. The combination of a FESS and a battery has several advantages, such as higher peak power capacity and reduced number of charging/discharging cycles in the battery. Nevertheless, batteries have a significant effect on the performance of the system and the control of the flywheel-battery link should be optimized in order to increase the system efficiency.The FESS investigated in this paper has its novelty in the use of a double wound flywheel machine which divides the system in two different voltage/power levels. High-Voltage/Power (HV) side connects the flywheel machine to the wheel motor and Low-Voltage/Power (LV) side connects the flywheel machine to the battery.The present paper focuses on the converter system and the control logic which regulates battery discharging process and the flywheel rotational speed. Emphasis has been given to the overall power/energy management of the system. Simulations and experimental results show that an ON/OFF battery control allows a highly efficient system, requiring a robust speed control and high energy density for the flywheel machine.

Power electronics and control of two-voltage-level flywheel based all-electric driveline

A novel all-electric driveline comprising a flywheel with a permanent magnet doubly wound synchronous motor/generator is presented. The flywheel machine with a double set of windings divides the system in two voltage levels: a low voltage/power level, which is connected to the main energy storage source (e.g. battery) and a high voltage/power level, which is connected to the traction machine. A DC/DC + DC/AC converter makes the connection between the battery and the flywheel low voltage windings. An AC/DC/AC converter connects the flywheel high voltage windings to the wheel machine. A complete simulation of the system has been made in Simulink. Vector control based speed regulators have been designed and successfully simulated. DC link voltage control has been achieved by using synchronous rectification. Power estimation has been used during regenerative braking in order to charge the flywheel with the power generated from the vehicle speed reduction. Simulations have verified the functionality of the proposed system.

A Double Wound Flywheel System under Standard Drive Cycles: Simulations and Experiments

Flywheel systems are attractive for use in electric vehicles, being able to efficiently handle the large power needed for acceleration and regenerative braking. A double wound flywheel machine, divided in two different voltage levels by the windings, acting like a rotating transformer, is studied.The flywheel stator windings have two sides: a low voltage side connected to the battery and a high voltage side connected to the wheel motor. The load variations on the high voltage side have minimal affect on the low voltage side of the system, in which the speed control of the machine is performed.In this paper the functionality of the system is investigated by means of simulations and experiments. Different standard drive cycles are applied on the high voltage side to assess the effect of load variations in the system as a whole and particularly in the speed control. The response of the speed control system is investigated with computer simulations and experimental verification. The energy storage in the flywheel allows a steady power supply from the battery via the inverter, proving the functionality of the system.

Tests with a hybrid bearing for a flywheel energy storage system

This paper describes the design and experimental test of a passive magnetic bearing system composed by a superconductor magnetic bearing (SMB) and a permanent magnet bearing (PMB). This bearing setup is part of a flywheel energy storage system. The advantage of using a passive bearing system is that it offers low friction without the need of a magnetic bearing controller, increasing the reliability and decreasing the energy consumption. The first set of tests were quasi-static radial and axial force measurements of the PMB operating alone and together with the SMB. As the PMB is intrinsically unstable in one degree of freedom, the operation of the SMB together with the PMB is necessary to stabilize the system. After that, dynamic measurements were made for the SMB operating alone and together with the PMB. The resonant speeds were identified and the bearing radial and axial forces were also measured for the SMB and SMB + PMB operation. These results indicate that the studied bearing set is technologically feasible to be used in flywheel energy storage systems.

Designing, simulations and experiments of a passive permanent magnet bearing

This paper presents simulations and experimental results for two types of Passive Permanent Magnet Bearings. The bearing system under investigation consists of two permanent magnet rings opposing to each other in two different config- urations. The influence of parameters, such as thickness and radius of permanent magnets, in the force is presented through FEM calculations. Two setups of passive magnetic bearings have been built. Static measurements of radial and axial forces are reported and results compared with simulations. Also, dynamic tests show the behavior of the bearing and the magnitudes of force in the foothold. The results are presented to show trends in the parameters, so the conclusions are applicable for other sizes and applications. As an example, the application as a top bearing for a 12 kW vertical axis wind turbine is considered.

Grid connected PV system with load power compensation capability using sliding mode control

This paper presents the modelling and design steps for a grid connected Photovoltaic System using a single-stage three-phase Voltage Sourced Converter. As the PV array is directly connected to the DC bus, a Maximum Power Point Tracking algorithm provides the reference voltage for an outer DC voltage control loop. The interface converter is controlled using a direct power sliding mode control without any synchronization circuit. This is possible because the converters control is done in the stationary reference frame. Besides the active power injection, this system is able to compensate the reactive and harmonics power consumed by the loads. For the pattern switching, space vector modulation is used to generate constant switching frequency. Simulation results are presented to validate the proposed system during the active power injection and load compensation.

Topology and control of a two-phase residential PV system with load compensation capability

This paper describes the topology and control scheme of a photovoltaic system for two-phase three-wire residential consumers. The system is composed basically of a photovoltaic array, dc-link and a grid-interface three-phase voltage sourced converter. The paper describes in detail how this system can work in an installation that uses two-phases and neutral derived from a three-phase distribution system. The incremental conductance technique is used to track the maximum power point. All generated power is used to feed the load or injected to the grid. Simultaneously to active power injection, the interface converter is also controlled to perform reactive power and current harmonics compensation. A single-phase instantaneous powers technique is used to obtain reference currents. A predictive controller used to generate converter switching signals is described as well. Simulation results are presented to confirm the suitability of the proposed topology and control scheme.