Kahyun Lee

Design and analysis of high-voltage transformer for HID lamp igniter

In this paper, requirements for the HID lamp igniter transformer capable of hot strike are described. A small size high voltage (HV) transformer composed of a ferrite core and an outer wall is designed. The characteristics such as flux linkage, current density and inductance are simulated with finite element methodology. The design guideline of the HV transformer that produces an output voltage with a peak value of 25 kV and a pulse width of larger than 100 nS for a 35 W automotive HID ballast prototype is discussed as an illustrative example

Dynamic model and control of wound-rotor machine in single-phase grid system

This paper proposes a novel wound-rotor machine which has a single-phase stator winding and three-phase rotor windings. The machine is called Single-Phase Wound-rotor Machine (SPWM). The machine can be driven in motoring and generating modes in single-phase grid system. The dynamic model and control system of the machine are also designed. Typically, the double revolving field model is used for singlephase machines, but it includes only the steady-state characteristics. So, the double revolving voltage model was proposed for dynamic analysis. However, the model cannot be applied to the proposed machine since the model requires more than two stator windings. In the proposed model, the SPWM is reconstructed from a d-q equivalent circuit of the three-phase wound-rotor machine. It includes the dynamic characteristics of the machine. Besides, the vector control based on the model is considered by applying an isolated inverter to the rotor side. The speed and grid power factor can be simultaneously controlled through the inverter while the rotor power is regulated. Simulation and experimental results present the validity of the proposed model and control.

Dynamic decoupling control method for PMSM drive with cross-coupling inductances

This paper proposes a decoupling control method for high-performance drive of permanent magnet synchronous motors (PMSMs). The conventional decoupling schemes proposed for removing coupling effects on d-q current regulation have the limited performance because the cross-coupling inductances caused by asymmetric structure and saturation are not considered. Those inductances may degrade the decoupling performance and even make the current control unstable by inducing the additional coupling voltages. Therefore, in this paper, a new voltage model including the cross-coupling inductances is developed and the compensation voltages for decoupling based on the model are calculated. The performance of the proposed decoupling method is verified by experimental results.

Decoupled current control with novel anti-windup for PMSM drives

This paper proposes a new current controller with modified decoupling and anti-windup schemes for a permanent magnet synchronous motor (PMSM) drive. In designing the controller, an improved voltage model, which is different from existing models in that it reflects all the nonlinear characteristics of the motor, is considered. In an actual PMSM, unintentional distortion occurs in inductance and flux due to magnetic saturation and structural asymmetry. In this paper, the effects of such distortion on voltage ripple are analyzed and the effect of voltage distortion on current control is analyzed in detail. Based on the voltage model, a decoupling controller is developed to effectively separate the d-q current regulators. The controller produces compensation voltages using the current error of the other axis. In addition, an anti-windup controller is designed that takes into account not only the integrator output in PI controllers but also the integrator output in decoupling controllers. The proposed current controller aimed at compensating all nonlinearities of PMSM enables high-performance operation of the motor. The feasibility of the proposed current control scheme is verified by experimental results.

Single-Phase Inverter Drive for Interior Permanent Magnet Machines

This paper proposes a novel drive method for interior permanent magnet machines (IPMMs). In the proposed system, a two-phase IPMM is fed from a single-phase H-bridge inverter for low-cost applications. Its main winding in d -axis is connected to the inverter and the auxiliary winding in q-axis is inherently short circuited. This configuration enables the motor to operate in a wider speed range with higher energy efficiency than most other single-phase drive systems. Also, its torque capability in the high-speed range is as high as that of the three-phase IPMM drive despite the reduced power devices, drivers, and current sensors. Accordingly, the proposed system has benefits such as simple structure, low cost, high-power density, and improved efficiency. In this paper, the system is modeled with an equivalent three-phase machine. Based on the model, its torque characteristics and operating areas are analyzed and compared to those of the conventional IPMM drives. A speed control algorithm is also developed. It includes a maximum torque per ampere control to improve drive efficiency and a flux-weakening control to maximize the feasible inverter output voltage. The proposed system and control algorithm are verified by experimental results.

Model-based MTPA control of permanent magnet synchronous machine drives under one-phase open-circuit fault

This paper proposes a fault-tolerant MTPA control method for permanent magnet synchronous machine (PMSM) drives under one-phase open-circuit fault. The proposed method isolates the open-circuit faulted phase after the fault and the motor starts to operate as a two-phase machine fed by an H-bridge inverter. Neither an additional inverter leg nor a neutral-point access to stator or DC link is used for the speed control. This post-fault configuration enables the motor to operate in a wider range of speed even than the healthy system, despite the reduced power devices, drivers and current sensors. The behavior of the faulted system is analyzed with a modified d-q model. Based on the analytic results, a speed control algorithm is developed. The strategy includes a maximum torque per ampere (MTPA) control to improve the drive efficiency and a flux-weakening control to maximize the feasible inverter output voltage within the limit. The proposed control method is verified by experimental results.

Analysis and comparison of single inverter driven series hybrid system

This paper proposes and analyzes the novel single inverter driven series hybrid system. Conventional series hybrid power transfer system features the high-efficiency thanks to the variable torque and speed operation of the internal combustion engine. The increment in cost is, however, still remained as a hurdle. The proposed single inverter driven series hybrid structure reduces two high power inverters into one with low current rating. It also does not require rigid power transferring parts such as axles and enables flexible configuration. This paper presents the comparison of the proposed system with conventional parallel and series hybrid system. The characteristics of the electric system which uses single inverter are also analyzed. The feasibility and operation of the proposed structure are verified through the simulation.

Analytical approach for determining inductance matrix, harmonic voltage and torque ripple of slotted PM motors

This paper proposes a novel approach for calculating position-dependent inductance matrix of slotted permanent magnet synchronous motors (PMSMs) and advanced analytical models for machine voltage and torque. In a real PM machine, the slotted structure of the stator and rotor causes unintended variations in air-gap permeance and magneto-motive force (MMF). The proposed approach analyzes the effects of these variations on air-gap flux and winding inductances. The calculated d-q inductance matrix contains harmonic and coupling components. In this paper, both voltage and torque models are modified to reflect the changes in inductance matrix. Some nonlinear terms due to structural saliency are additionally considered. The results of simulation with finite-element method (FEM) are presented to verify the validity of the proposed inductance, voltage and torque models.

Single-phase stator control of interior permanent magnet machines with MTPA operation

This paper proposes a new interior permanent magnet machine (IPMM) drive system with low cost and simple configuration. The proposed system consists of a two-phase IPMM, a single-phase H-bridge inverter, and dc link. Between two-phase stator windings, a main winding is supplied by the H-bridge inverter for adjustable speed drives while an auxiliary winding is short-circuited. This structure makes the system operate in a wider range of speed than most single-phase drive systems. Furthermore, the system uses relatively fewer windings and semiconductor devices than a balanced three-phase IPMM system, yet its torque capability in high speed range has not reduced. This paper proves that the single-phase inverter is advantageous over the three-phase one for producing larger fundamental machine phase voltage in the overmodulation range. A square-wave mode voltage modulation scheme is applied to maximize the fundamental component. With an equivalent model of the proposed IPMM, its torque characteristics, operating range, and performance are analyzed and compared to those of conventional IPMM drive systems. In addition, a speed control algorithm aimed at minimizing the copper losses is proposed for higher motor efficiency. The feasibility of the proposed system and control method is verified by experiments under various operating conditions.

Wound Rotor Machine With Single-Phase Stator and Three-Phase Rotor Windings Controlled by Isolated Three-Phase Inverter

This paper proposes a single-phase grid-connected wound rotor machine that has the single-phase stator and three-phase rotor windings. The machine has no auxiliary winding or capacitor unlike conventional single-phase machines. Nevertheless, it can operate in all four quadrants of the torque-speed plane with a three-phase inverter. For adjustable speed drives, an isolated three-phase inverter is applied to the rotor windings while the stator winding is directly connected to a single-phase source. The grid filter and rectifier of the conventional system are eliminated and the rotor-side slip rings can be also removed by the inverter integration. So the overall structure of the proposed drive system is simple and cost effective. In this paper, the proposed machine is modeled into a modified d-q model considering the absence of q-axis stator coil. Its characteristics are analyzed and vector control methods of the grid power factor, dc-link voltage, and speed are proposed. For more efficient control, the optimal rotor current set is calculated from the minimum copper loss condition. The system has wider operating areas than other single-phase drive systems. The feasibility of the proposed system is verified by experiments.