Toshihiko Noguchi

Voltage-Source PWM Rectifier–Inverter Based on Direct Power Control and Its Operation Characteristics

This paper describes a novel control strategy of direct power-control-based voltage-source pulsewidth modulation (PWM) rectifier-inverter. The key of this strategy is direct selection of a switching state of the PWM rectifier-inverter on basis of instantaneous power errors. A relationship between the instantaneous power and the switching state of the PWM rectifier-inverter is theoretically analyzed, which is essential to compose a switching-state table. Effectiveness of the proposed technique is examined through several experimental tests, using a 1.6-kW prototype. As a result, unity power factor operation is achieved by the proposed method, and the output currents are confirmed to be sinusoidal waveforms without large distortion under balanced and unbalanced power-source condition.

Direct yaw-moment control of electric vehicle based on cornering stiffness estimation

In this paper, novel direct yaw-moment control (DYC) with road condition estimation and anti-slip control is proposed for electric vehicles. An inner-loop observer controls the vehicle traction, and an outer-loop controller stabilizes the yawing motion. An immeasurable parameter known as cornering stiffness is estimated from the detected yaw-rate, steering angle, wheel speed and yaw-moment observer output in real time. Thus, the accurate control input can be generated with the estimated parameters. The proposed adaptive control is compared with a conventional robust control on dry and snowy terrain conditions. The experimental results show that the yaw-rate error is properly attenuated by the proposed control algorithm.

Multilevel Current Waveform Generation Using Inductor Cells and H-Bridge Current-Source Inverter

This paper presents a new circuit configuration of single-phase multilevel current-source inverter (CSI). In this new topology, a basic H-bridge CSI working as a main inverter generates a multilevel current waveform in cooperation with inductor cells connected in parallel as auxiliary circuits. Each inductor cell is composed by four unidirectional power switches with an inductor across the cell circuit. The inductor cells work by generating the intermediate level of the multilevel current waveform with no additional external dc-power sources. A simple proportional-integral controller is applied to control the intermediate-level currents of the multilevel output waveform. A five-level and a nine-level pulsewidth-modulation inverter configuration, with chopper-based dc-current sources, are verified through computer simulations. Furthermore, an experimental prototype of a five-level CSI is set up and is tested. The results show that the test circuit works properly to generate the multilevel output-current waveform with low output harmonics by using small size of inductors without any additional external dc-power sources, which proves feasibility of the proposed strategy.

Motion control of electric vehicle based on cornering stiffness estimation with yaw-moment observer

In this paper, two estimation methods of cornering stiffness are proposed based on yaw-moment observer (YMO). First, a simple method is developed under the assumption that cornering stiffness coefficients of front and rear wheels are identical. A novel direct yaw-moment control (DYC) with this estimation is proposed for electric vehicles with in-wheel motors. Second, a sophisticated method is introduced which can identify the front and rear cornering stiffness independently as well as it can estimate the side-slip angle of vehicle. Simulation and experiments are carried out to show the advantages of proposed methods on various road conditions

Mathematical model of novel wound-field synchronous motor self-excited by space harmonics

This paper describes mathematical modeling of a novel wound-field synchronous motor self-excited by space harmonics. The torque equation on the dq-reference frame is investigated to clarify the self-excitation mechanism of the proposed motor. It has been analytically explicated how the motor parameters give influences on the self-excited electromagnet torque. Furthermore, the current phase vs. torque characteristics are compared between the FEM based simulation result and the mathematical calculation result. Both of the results showed good agreement, which proves feasibility of the mathematical modeling discussed in the paper.

High-speed switching operation of MOSFETs using auxiliary circuit shorting load

This paper describes a high-speed switching technique of power MOSFETs applied to a chopper and a half-bridge inverter. The switching time must be shortened to operate power converters using the power MOSFETs at high-frequency, but parasitic output capacitance prevents the MOSFETs from turning off fast. In general, the turn-off time becomes longer as a load current is reduced because the reduced drain current takes a long time to charge the parasitic output capacitance. In the paper, a set of auxiliary switches and diodes in parallel with a load is proposed to reduce the turn-off time effectively. This additional auxiliary circuit makes a high-frequency drive of the power MOSFETs and switching-loss reduction of the power converter possible. It has been confirmed through experimental tests that the operational frequency range of the power converter expands to MHz-order and that the power conversion efficiency is effectively improved in a low-load range by employing the proposed technique.

A multilevel voltage-source inverter using H-bridge and two-level power modules with a single power source

This paper presents a different topology of multilevel voltage-source inverter obtained from the H-bridge inverter and two-level power modules with a single DC power source. In the proposed topology, a novel voltage balancing circuits is presented to keep stable DC capacitor voltages, and to reduce the capacitor size. A modular structure is also an important feature of the proposed topology instead of the minimum number of the power devices. The proposed topology is tested through computer simulation using PSIM software. Laboratory experimental tests were also conducted to verify the proposed multilevel inverter topology. The computer simulation and experimental test results showed that the proposed topology works properly to synthesize a multilevel voltage waveform with low harmonics distortion.

On-line parameter identification of IPM motor using instantaneous reactive power for robust maximum torque per ampere control

The reluctance torque of an IPM motor can be effectively utilized by applying the maximum torque per ampere (MTPA) control algorithm, which improves the efficiency and the power density of the motor. However, the motor is unable to operate accurately on the MTPA curve due to the parameter mismatch caused by magnetic saturation and/or temperature variation. This paper proposes the d-axis inductance, the q-axis inductance, and the magnetic flux linkage identification strategy by using the instantaneous reactive power of the IPM motor. The key feature of the technique is robustness against the winding resistance variation. Several experimental tests have been conducted to verify the feasibility of the proposed technique, and it has been confirmed that every parameter identification can be achieved within 5 % error.

Estimation of rotor current based on mathematical model of wound-field synchronous motor self-excited by space harmonics

This paper describes estimation of the rotor winding current based on a mathematical model of a self-excited wound-field synchronous motor where the space harmonics power is utilized for the field magnetization instead of the permanent magnets. The operation principle of the proposed motor is explicated by a voltage equation on the synchronous rotating reference frame. Furthermore, the rotor winding current is compared between the FEM based simulation and the mathematical calculation. Consequently, it has been confirmed that both operation characteristics in the steady state agree very well and indicate similar tendency.

Sensorless control of surface permanent-magnet motor based on model reference adaptive system

This paper describes a new method of rotor position and speed estimation of a surface permanent-magnet synchronous motor based on a model reference adaptive system (MRAS). The proposed method features the MRAS in a current control loop to estimate a rotor position and speed only with current sensors. A transient response of the estimated rotor position and speed in the MRAS determines transient behavior of the sensorless control. For this reason, the important point is to investigate a relationship between an actual and the estimated rotor speed. First, this paper proposes a structure of the sensorless control applied in the current control loop. Next, it proves the stability of the proposed method using hyperstability theory, and presents an optimal method of adjusting the transient behavior of the estimated rotor speed to that of the actual rotor speed with nonlinear compensation. Finally, several experimental results show the performance of the proposed method.