Levent U. Gokdere

Integrated magnetics for interleaved DC-DC boost converter for fuel cell powered vehicles

The conception, analysis and experimental demonstration of an integrated magnetics (IM) core structure for a 3-phase interleaved DC-DC boost converter for fuel cell powered vehicles are presented in this paper. The benefits of current interleaving in reducing inductor current switching ripple at low switching frequency and with low inductance are well known. The IM core structure enables volume and weight reduction of the magnetics over a discrete implementation while providing further ripple reduction of inductor currents and improved efficiency. The effect of magnetic coupling between the interleaving phases in the IM core is described. A novel composite IM core structure, which minimizes inductor current ripple, is introduced. Comparative analysis with a discrete implementation is presented. The advantages of matched duty cycles in reducing resistive power loss and simplifying the converter transfer functions are presented. The impact of parameter variation on the performance capabilities of the converter is described. Average and small signal models of the converter with the IM core are derived. Experimental results are presented to validate the operation and performance advantages of the proposed core structure.

A passivity-based method for induction motor control

The control of an induction motor is a difficult problem, since the dynamics of the induction motor are nonlinear, the rotor electrical state variables (i.e., rotor fluxes or currents) are usually unavailable for measurement, and the motor parameters can vary significantly from their nominal values. The main purpose of this paper is to develop a control algorithm that forces the induction motor to track time-varying speed, position, and flux trajectories without knowledge of the rotor electrical state variables. To achieve this, a passivity-based method is developed. The key point with this method is the identification of terms, known as workless forces, which appear in the dynamic equations of the induction motor but do not have any effect on the energy balance equation of the induction motor. These terms do not influence the stability properties of the induction motor and, hence, there is no need to cancel them with feedback control. This leads to a simpler control structure and enhances the robustness of the control system. Experimental results show that the passivity-based method provides close tracking of time-varying speed, position, and flux trajectories without knowledge of the rotor electrical state variables.

A virtual prototype for a hybrid electric vehicle

A virtual prototype of a hybrid electric vehicle (HEV) is created within the virtual test bed (VTB) environment, which has been developed for modeling, simulation, analysis and virtual prototyping of large-scale multi-technical dynamic systems. Attention is focused on the electric system, which is composed of (i) a fuel cell system as a prime power source, (ii) battery and super capacitor banks as energy storage devices for high and intense power demands, (iii) DC-to-DC power converters to control the flow of power, (iv) a three-phase inverter-fed permanent magnet synchronous motor as a drive, and (v) a common DC bus. The simulation of the proposed system is conducted using two types of driving cycles. These are: (i) rapid acceleration and deceleration, and (ii) Federal Urban Driving Schedule (FUDS). The parameter values chosen for the components and the numerical results obtained by simulation are consistent with the practical HEV applications.

Lifetime control of electromechanical actuators

Existing actuator controls are typically designed based on optimizing performance and robustness to system uncertainties, without considering the operational lifetime of the actuator. It is often desirable, and sometimes necessary, to trade off performance for extended actuator operational lifetime. This paper introduces the concept of incorporating the actuator lifetime as a controlled parameter. We describe preliminary methods for speed/position tracking control of an electromechanical actuator (EMA) while maintaining a desired minimum lifetime of the actuator motor

Adaptive control of actuator lifetime

The harder an actuator is pushed to its performance limits, the shorter its lifetime becomes. Existing actuator controllers are typically designed to optimize performance and robustness, without considering the operational lifetime of the actuator. However, it is often desirable to trade off performance for extended lifetime in order to reduce vehicle maintenance cost and improve vehicle safety and mission readiness. We present two adaptive control algorithms for managing the performance and lifetime of motors in electromechanical actuators. The first algorithm provides tracking control of a desired motor lifetime by adapting the motor performance level. The second algorithm provides adaptive trade-off between motor performance and lifetime based on vehicle mission needs. Simulation results are presented to show the effectiveness of these control algorithms

Stochastic Optimal Control of a Servo Motor with a Lifetime Constraint

We consider a linear quadratic optimal regulation problem of a servo motor in the presence of stochastic load disturbance subject to a constraint that establishes a desired motor winding lifetime. To satisfy the constraint, a family of LQR control designs is parameterized with a single scalar performance weight that establishes a trade-off between performance and control power. Power analysis approach is then used to find the optimal value of the parameter that provides maximum disturbance rejection control in the given LQR family subject to the desired motor lifetime constraint

Passivity-based control of saturated induction motors

A passivity-based controller, which takes into account saturation of the magnetic material in the main flux path of the induction motor, is developed to provide close tracking of time-varying speed and flux trajectories in the high magnetic saturation regions. The proposed passivity based controller is experimentally verified. Also, a comparison between the controllers based on the saturated and nonsaturated magnetics is presented to demonstrate the benefit of the controller based on the saturated magnetics.

A virtual test bed for power electronic circuits and electric drive systems

Applications of the virtual test bed (VTB) to a power electronic circuit and an electric drive system are described. The VTB is a software environment that has been developed for design, analysis and virtual prototyping of large-scale multi-technical systems. It has the capability of integrating models, which have been created in a variety of languages such as SPICE, ACSL and SABER, into one simulation environment. It also provides advanced visualization of simulation results including full-motion animation of mechanical components. These two important features of the VTB are utilized in the modeling and simulation of a power electronic circuit and an electric drive system.

Graphical and visual simulation of electric drive systems

This paper introduces a new software environment, the Virtual Test Bed (VTB), which has been particularly developed for graphical and visual simulation of large-scale electric power systems. A possible application of the VTB to analysis of an electric drive system is also described: the application of ACSL/GM (Advanced Continuous Simulation Language/Graphic Modeller) to a field-oriented controlled induction motor.

Hybrid electric vehicle with permanent magnet traction motor: a simulation model

A simulation model for a hybrid electric vehicle is developed. A permanent magnet synchronous motor is considered for the drive part of the hybrid electric vehicle which comprises three energy sources: (i) a fuel cell, (ii) a battery bank, and (iii) a supercapacitor. A rotor-oriented speed controller is designed, and also verified by simulation results, to achieve trajectory tracking requirements of the hybrid electric vehicle within the inverter voltage and current limits.