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This paper proposes a new sensorless vector control method for salient-pole permanent-magnet synchronous motors. With regard to phase estimation, the sensorless vector control method is featured by a new high-frequency voltage injection method (i.e., carrier modulation method), which is distinguished from the conventional ones by a unique ellipse shape of spatially rotating high-frequency voltage, and by a new phase-locked-loop method as a demodulation method whose input is a high-frequency current component multiplied signal. The new vector control method established by two innovative technologies for modulation/ demodulation can have the following high-performance and attractive characteristics. 1) It can allow 250% rated torque at standstill. 2) It can operate from zero to the rated speed under the rated motoring or regenerating load. 3) It accepts instant injection of the rated load even for zero-speed control. 4) Phase estimation is robust against inverter dead time, and proper phase estimate can be obtained even under circumstances where stator current crosses the zero at high frequency. 5) Computational load for estimating rotor phase is very small. Usefulness of the proposed new vector control method is verified through extensive experiments. Index Terms--Current component multiplied signal, high-frequency voltage injection, phase-locked loop (PLL), sensorless, synchronous motor.

Phase, frequency, and amplitude of single-phase voltages are the most important and basic information required for single-phase grid-connected applications. This paper proposes a method for instantly and robustly estimating the phase, frequency, and amplitude of frequency-varying single-phase signals for such applications, which is a phase-locked loop (PLL) method based on a structure. The proposed method has the following attractive features: 1) the estimation system results in a nonlinear system, but it can be stabilized; 2) all subsystems constructing the system can be easily designed; 3) 'two-phase signal generator' can autotune a single system parameter in response to varying frequency of the injected signal; 4) high-order 'PLL-Controllers' allowing fast tracking can be stably used; and 5) even in hostile envelopments, favorable instant estimates can be obtained. This paper proposes the estimation method and verifies its usefulness by extensive numerical experiments. Index Terms--Frequency estimation, phase estimation, phase-locked loop (PLL), single phase.

This paper proposes new practical optimal current control methods for a newly emerging class of synchronous motors with hybrid rotor fields by both permanent magnet and winding. In a practical situation with limited voltage, the extensively used permanent-magnet synchronous motor hardly achieves an ideal performance in an energy-efficient manner due to its constant magnet field, which simultaneously allows both low-speed high-torque and wide speed-range operations. The hybrid-field synchronous motors (HFSMs) are potential candidates that can achieve the ideal performance as practical motors with controllable hybrid rotor field. HFSMs can dynamically control the rotor flux according to the operation requirements by the low-speed, high-torque, and wide speed-range operations, etc. For the HFSMs, the same torque can be produced by a variety of stator and rotor currents due to the nonlinearity between the torque and the currents. Produced losses and required voltages depend upon the associated currents. Consequently, in the situation that current control systems are well constructed, appropriate determination of a set of stator and rotor current commands plays a key role to achieve the ideal performance in an energy-efficient manner. The proposed methods determine the current commands corresponding to a given torque command such that the total winding copper losses due to the stator and rotor currents can be minimized if the exact currents associated with the torque command exist; the best approximate torque can be produced if no exact associated currents exist, which is, of course, under the circumstance of a voltage limitation. The determined current commands are optimal in the sense of energy efficiency or degree of approximation under voltage limitation. New recursive algorithms searching the optimal current solution in real-time are also given as parts of the methods. The proposed methods are analytical but practical, whose usefulness is verified through experiments. Index Terms--Current command, efficient operation, hybrid field, synchronous motor, wide speed-range operation.

This paper proposes a new sensorless vector control method that can be applied to both of salient-pole and non-salient-pole permanent-magnet synchronous motors (PMSMs). The proposed method estimates the phase of a rotor flux by a newly developed state observer in a stationary reference frame for sensorless vector controls of PMSMs. The flux state observer has the following attractive features: 1) it requires no steady-state conditions for the dynamic mathematical model of the motor; 2) its order is the minimum second; 3) a single observer gain is simply constant over a wide operating range and can be easily designed; 4) it utilizes motor parameters in a very simple manner; and 5) its structure is very simple and can be realized at a very low computational load. The proposed speed-estimation method, which exploits the inherent physical relation of integration/derivation between phase and speed, is very simple and can properly estimate rotor speed. The usefulness of the proposed method is examined and confirmed through extensive experiments. Index Terms--Flux state observer, integral-feedback speed estimation, minimum order, sensorless vector control, synchronous motor.

This paper proposes a new sensorless vector control method that can be applied to both salient-pole and nonsalient-pole permanent-magnet synchronous motors (PMSMs). The proposed method estimates phase of rotor flux by a newly developed flux-state observer for sensorless vector control of PMSMs, which is referred to as the 'D-state observer.' The D-state observer has the following attractive features: 1) it requires no additional steady-state condition for the motor mathematical model; 2) its order is the minimum second; 3) a single observer gain is simply constant over a wide operating range, and easily designed; 4) it utilizes motor parameters in a very simple manner; and 5) its structure is very simple and can be realized at a very low computational load. Usefulness of the proposed method is examined and confirmed through extensive experiments. Index Terms--D-state observer, flux-state observer, minimum order, phase-locked loop (PLL), sensorless vector control, synchronous motor.

This paper proposes a new sensorless vector control method for a salient-pole permanent-magnet synchronous motor (SP-PMSM). The proposed method is directly based on a new principle called 'mirror-phase characteristics' and has the following high-performance and attractive features: 1) it can allow 250% rated torque at standstill, under which strong flux saturation usually occurs; 2) it can allow ultralow-speed control (the observed minimum speed ratio to the rated speed under the rated motoring or regenerating load is 1/1800); 3) in spite of the ultralow-speed performance, it can operate up to the rated speed; 4) it accepts instant injection of the rated load even for zero-speed control; 5) it accommodates a load with huge moment of inertia.; 6) it is insensitive to all motor parameters; 7) it is also insensitive to saturation phenomena of stator flux; and 8) it is so simple that it can be implemented with no additional hardware. The high performance and usefulness of the new 'mirror-phase vector control' method are verified through experiments. Index Terms--D-module, high-frequency signal injection, mirror phase, phase-locked loop (PLL), salient pole, sensorless, synchronous motor, vector control.

This paper proposes a new nth order two-input/output filter in module for two-phase signal processing. The filter can make the distinction between positive and negative frequencies of two-phase signals and can allow for processing the signals based on frequency polarity. The filter can also change dynamically its filtering characteristics by simply injecting a shift signal to the filter. The filtering effects equivalent to ones by parallel-arranged filters with vector rotators can be obtained, but in a much simpler manner. Unified analyses about attractive general properties of the proposed filter are given for easy designs and realizations as well. Effectiveness of the analyses and usefulness of the filter are examined and confirmed through numerical experiments. The proposed two-input/output filter in module has potential usefulness in a variety of polyphase signal filtering applications, including three-phase power systems with active filtering function and sensorless vector controls of three-phase ac motors. Index Terms--D-module, filter, magnetic bearing, negative phase, positive phase, power system, sensorless vector control.

SUMMARY This paper proposes new three-phase current control methods for AC motor drives, which detects only a phase current from among three-phase currents. The first proposed method first detects a phase current, and then estimates the two-phase current in the stationary reference frame using the detected single phase current. The second proposed method first detects a phase current, then synthesizes the two-phase quasi-current in the dq rotating reference frame, and finally produces two-phase current estimates by extracting the positive-phase component from the quasi-current. The third proposed method produces two-phase current estimates by filtering out the negative-phase component from the quasi-current. This paper presents the principles and detailed characteristic analyses of the proposed methods and validates them on the basis of extensive experiments. [ABSTRACT FROM AUTHOR]