A vector control system is proposed for sensorless permanent magnet synchronous motor (PMSM) drives. In order to realize a simple and low-cost control system, the position sensor and current sensor are eliminated, and the motor current is detected from the direct current using the A/D converter of a microcomputer. When the direct current cannot be detected, the motor current is reversely converted from the current value of the dq axis. Finally, the effectiveness of the proposed control is verified by experiments using a salient pole PMSM.
This paper discusses a new power flow controller consisting of six cascaded converters. Each cascaded converter is composed of four series-connected H-bridge converters, and connected between one phase of the three-phase terminals at the sending end and another phase terminal at the receiving end. Each converter controls its current to be orthogonal to its voltage, and injects a reactive power into the grid. Then the average voltage across the dc capacitor can be kept at a constant level, because no active power is drawn from the grid to the converter. The new power flow controller can adjust not only the reactive power flow but also the active power flow by controlling only the reactive power through the six cascaded converters, because the converter voltage is shifted by ±30° from the phase voltages at the sending and receiving ends. Experimental results obtained from a 400-V, 10-kVA downscaled setup using twenty four H-bridge converters show the capability of controlling both active and reactive power flows as well as regulating the dc capacitor voltage.
This paper presents a new sensorless vector control method for permanent-magnet synchronous motors (PMSMs) that employs pulsating high frequency voltage injection. The frequency range of the injected voltage is almost the same as that of the PWM carrier. This allows high-speed phase estimation and a high performance drive, and possibly low acoustic noise due to the injected voltage. The proposed method injects a pulsating high-frequency voltage for current modulation in the quasi-synchronous reference frame, demodulates the modulated current, and produces a phase estimate in the same reference frame. The demodulation and phase estimation are characterized by a small current sampling period, filter-less extraction of the modulated current, new polarity processing of the current difference, and a new function that improves the positive correlation region. In addition, no further phase compensation is required. The usefulness of the proposed method is verified through extensive simulations.
This paper presents a new sensorless vector control method for permanent-magnet synchronous motors (PMSMs) by injecting a rotating high-frequency voltage. The frequency range of the injected voltage is almost the same as that of the PWM carrier. This allows high-speed phase estimation and a high performance drive, and possibly low acoustic noise due to the injected voltage. The proposed method injects a rotating high-frequency voltage for current modulation in the quasi-synchronous reference frame, demodulates the modulated current, and produces a phase estimate in the same reference frame. The demodulation and phase estimation are characterized by a small current sampling period, filter-less extraction of the modulated current, achievement of the maximum positive correlation region. In addition, no further phase compensation is required. The usefulness of the proposed method is verified via extensive simulations.
Contact loss measurement based on arc light detection makes it possible to estimate the current-collecting performance from catenary lines in electric railways before commercial operation, or after the installation, of new overhead contact systems and new pantographs. This measurement system consists mainly of a photo acceptor, a photo detector and a plastic optical fiber for connecting them. However, the system performance is affected by sunlight because the system detects only visible rays. Therefore, the authors develop a conversion system that can change a broad range of wavelengths—from ultraviolet to visible rays—emitted by the arc light to a voltage signal. The developed measurement system equipped with the wavelength converter can detect ultraviolet rays indirectly. This paper describes the operating principles of the wavelength converter and presents experimental results obtained with the measurement system.
An optimal design for a simultaneous wireless power transfer system is difficult to achieve, as the effect of multiple coils on the total efficiency is unclear. The power loss increases with the number of coils when they are arranged in a straight line. On the other hand, simultaneous wireless power transfer to multiple receiving coils surrounded by a large transmitting coil has not been studied. In this paper, the simultaneous wireless power transfer system is represented by an equivalent circuit, and a detailed study of the total efficiency and optimal load is carried out. The number of coils is increased, and an analysis is performed for both the equal coupling coefficient case and the unequal coupling coefficient case. From the theoretical analysis and experimental results, the total efficiency improves when more coils are added. Nevertheless, the final efficiency is bounded by the internal resistance and the load values at the receiving coils. The proposed equivalent circuit model also demonstrates that the maximum efficiency is achievable by using the optimal resistance for wireless power transfer containing a specific number of coils.
In this paper, a novel AC motor termed the flux-modulating synchronous machine (FMSM) is presented. The FMSM employs a doubly salient structure, and the armature and field windings are centrally wound around individual stator teeth. The rotor has neither permanent magnets nor windings. A 1.5-kW prototype machine with an outer-rotor configuration is newly designed and built to investigate the characteristics of the FMSM in a motor mode. The torque-generating mechanism is analyzed using a mathematical model of the FMSM, and experiments are conducted with a vector control system to confirm the validity of the theoretical analysis. The results show that the torque of the FMSM can be controlled by adjusting the armature and field currents, as in the DC motors.
This paper discusses a design approach for an ultra-high-speed permanent magnet (PM) motor whose specific application is an electrically operated supercharger for automotive engines. The motor is fed by a three-phase inverter with a 12-V battery power supply for automotive applications. The investigated motor has a rated output power of 1.5kW and a maximum rotation speed of 150,000r/min, and is designed to maximize both the efficiency and the power density. In order to achieve this goal, various technical problems must be overcome, e.g., the synchronous impedance must be greatly reduced, the iron and copper losses must be minimized, the power density must be improved, and mechanical stabilization in the high-speed operation range must be achieved. An electromagnetic field analysis on the basis of a finite element method (FEM) is conducted to fine-tune the detailed motor dimensions and to maximize the efficiency and power density at the same time. Consequently, the efficiency has been improved to over 97% (excluding mechanical losses), and the power density has been increased to approximately 13W/cm3 at the rated output power in the prototype motor design. The feasibility of the design is confirmed through experimental tests, using a prototype motor.