A position sensorless algorithm is developed for IPMSM, while reflecting the saliency in an extended EMF term. Active flux is converted into a new linear regression form, and a high-pass filter was applied. Then, the gradient algorithm is applied to derive an estimate of the active flux in the stationary frame. The proposed observer is an inherently sensorless type because it does not require the rotor speed or position information. It is practically attractive since it does not require the use of pure integrator which is marginally stable. In addition, the observer can be constructed without the PM flux linkage constant. It is basically a model-based method. However, it is easily extended to a signal injection method which is robust in the low-speed region. Ultimate boundedness is established using the persistency of excitation condition. Validity of the algorithm is demonstrated experimentally via torque and speed control with a full load in the low-speed range.

Bi-directional buck-boost DC/DC converter is normally utilized for high speed operation of motors for hybrid electric vehicles (HEV). In this work, a dual inverter strategy is proposed for HEV motor with the purpose of accommodating high speed operation without increasing battery voltage. By setting the secondary inverter to take care of only reactive voltage component, the secondary inverter do not carry voltage source other than capacitor bank. DC link voltage regulation is achieved through the control of active power flow

For high speed motors, smaller rotor diameters are required to make the surface speed less than 250 m/s. At the same time, dynamo motors for propulsion systems often require high torque. In such an environment, permanent magnet synchronous motors are more suitable than induction motors. In this work, a 270 kW dynamo motor is designed with a Halbach array using samarium-cobalt permanent magnets. It utilizes the rotor back iron and carbon fiber sleeve on the rotor surface. Two design goals are set when the rotor inner and outer radii are fixed preferentially: minimization of PM usage and maximization of airgap field. A magnetic equivalent circuit is utilized to identify the saturation level of the rotor back iron and airgap field density. The Levenberg-Marquardt algorithm is applied to find the optimal coverage of radial magnet in a pole pitch and the optimal PM height. It is also observed that the resulting Halbach array motor is superior to surface-mounted permanent magnet motor in torque performance when the same amount of PM is used. A prototype motor was built on a real scale, but with a reduced stack length.

An overmodulation (OVM) technique is proposed based on Fourier analysis. The OVM trajectory is a mixture of 6 arc segments of the inscribed circle and 6 vertices of the voltage hexagon. By adjusting the holding angle at each vertex, the modulation index is determined. The fundamental component is expressed as a function of the holding angle, and the linearity with the modulation index is obtained by the inverse relation. This algorithm guarantees seamless transitions from the space vector PWM (SVPWM) to OVM and finally to the six-step. Apart from the VVVF control, the proposed algorithm works well with the interior permanent magnet synchronous motor (IPMSM) current controller. By computer simulation and experimental evidences, the effectiveness is demonstrated.

A loss minimizing control law is developed for a fuel cell electric vehicle (FCEV) permanent magnet synchronous motor (PMSM) which reflects the effects of field saturation and cross coupling. Inductances are modelled as functions of q-axis current based on the flux data obtained experimentally. For a given torque and a given speed, the loss minimizing current sets are searched from the experimental power loss data which are obtained for various d-axis current. The loss minimizing current sets are made into a lookup table, and it is utilized in the torque control loop. This controller guarantees high efficiency in every possible torque-speed operating point.

Synchronous reluctance motors (SynRM) show nonlinear behavior in the high torque region due to core saturation, especially on the d-axis. In this study, the maximum torque per ampere (MTPA) solution is sought in the mathematical frame. Firstly, flux data are obtained from finite element method (FEM), and fitted as the plane functions of currents by the least square method. Thereafter, the inductances are derived as binomials in i_d and i_q. These analytic expressions of inductances are used in deriving a necessary condition for the MTPA, and constructing an on-line MTPA control method. The effectiveness is verified through simulation and experimental results.