Jang-Mok Kim

Speed control of interior permanent magnet synchronous motor drive for the flux weakening operation

A novel flux-weakening scheme for the interior permanent magnet synchronous motor (IPMSM) is proposed. This is implemented based on the output of the synchronous PI current regulator-reference voltage to the PWM inverter. The onset of flux weakening and the flux level are adjusted inherently by the outer voltage regulation loop to prevent saturation of the current regulator. Attractive features of this flux weakening scheme include no dependency on the machine parameters. The guarantee of current regulation at any operating condition, and smooth and fast transition into and out of the flux weakening mode. Experimental results at various operating conditions including the case of detuned parameters are presented to verify the feasibility of the proposed control scheme.

A new robust SPMSM control to parameter variations in flux weakening region

A new implementation strategy for the flux weakening control of a surface mounted permanent magnet synchronous motor (SPMSM) is proposed. It is implemented based on the output of the synchronous PI current regulator-reference voltage to PWM inverter. The onset of flux weakening and the level of the d-axis current are adjusted by the outer voltage regulation loop to prevent the saturation of the current regulator. The characteristics of this flux weakening scheme include no dependency on the machine parameters, the guarantee of current regulation on any operating condition, and fast transition into and out of the flux weakening mode. Experimental results at various operating conditions including 4-quadrant operation are presented to verify the feasibility of the proposed control scheme.

The State and Parameter Estimation of an Li-Ion Battery Using a New OCV-SOC Concept

The open circuit voltage (OCV) is widely used to estimate the state of charge (SOC) in many SOC estimation algorithms. But the relationship between the OCV and SOC can not be exactly same for all batteries. Because the conventional OCV-SOC differs between batteries, there is a problem in that the OCV-SOC data should be measured to accurately estimate the SOC in different batteries. Therefore, the conventional OCV- SOC should be modified. In this paper, a new OCV-SOC that is independent of the battery conditions is proposed. Thus, problems resulting from the defects of the EKF can be avoided by preventing the OCV-SOC data from varying. In this paper, the SOC and battery capacity are estimated using the dual EKF with the proposed OCV-SOC.

Position sensorless control of synchronous reluctance motor using high frequency current injection

This paper presents a position sensorless control scheme for synchronous reluctance motors using high frequency current injection. The rotor has inherent rotor saliency and its angle is estimated from d and q stator current injection and the appropriate signal demodulation. This scheme gives robust and dynamic estimation of the rotor angle independent of the operating condition including standstill and light and heavy loading. Experimental results of closed loop speed control of a 3.75 kW axially laminated synchronous reluctance motor are given to verify the proposed scheme.

Torque Maximization Control of 3-Phase BLDC Motors in the High Speed Region

This paper proposes a new torque control algorithm for BLDC motors to get the maximum torque in the high speed region. The delay of the phase currents is severe due to the stator reactance. The torque fluctuations of BLDC motors increase and the average torque is decreases due to a slow rise in the phase current when compared to the back EMF. In this paper, the phase current of BLDC motors under the high speed condition is analyzed and a torque maximization control is developed on the basis of using numerical analysis. Computer simulations and experimental results show the usefulness of the proposed control algorithm.

A Dead Time Compensation Algorithm of Independent Multi-Phase PMSM with Three-Dimensional Space Vector Control

This paper proposes a new dead time compensation method of independent six-phase permanent magnet synchronous motors (IS-PMSM). The current of the independent phase machines contains odd-numbered harmonics because of the dead time and the nonlinear characteristics of the switching devices. By using the d-q-n three-dimensional vector analysis, these harmonics can be extracted at the n-axis current. Thus, the current distortion can be compensated by controlling the n-axis current of the IS-PMSM to zero. The proposed method is simple and can be easily implemented without additional hardware setup. The validity of the proposed compensation method is verified with simulations and several experiments.

Signal Compensation for Analog Rotor Position Errors due to Nonideal Sinusoidal Encoder Signals

This paper proposes a compensation algorithm for the analog rotor position errors caused by nonideal sinusoidal encoder output signals including offset and gain errors. In order to achieve a much higher resolution, position sensors such as resolvers or incremental encoders can be replaced by sinusoidal encoders. In practice, however, the periodic ripples related to the analog rotor position are generated by the offset and gain errors between the sine and cosine output signals of sinusoidal encoders. In this paper, the effects of offset and gain errors are easily analyzed by applying the concept of a rotating coordinate system based on the dq transformation method. The synchronous d-axis signal component is used directly to detect the amplitude of the offset and gain errors for the proposed compensator. As a result, the offset and gain errors can be well corrected by three integrators located on the synchronous d-axis component. In addition, the proposed algorithm does not require any additional hardware and can be easily implemented by a simple integral operation. The effectiveness of the proposed algorithm is verified through several experimental results.

An Optimal Current Distribution Method of Dual-Rotor BLDC Machines

This paper proposes an optimal current distribution method of dual-rotor brushless DC machines (DR-BLDCMs) which have inner and outer surface-mounted permanent-magnet rotors. The DR-BLDCM has high power density and high torque density compare to the conventional single rotor BLDCM. To drive the DR-BLDCM, dual 3-phase PWM inverters are required to excite the currents of a dual stator of the DR-BLDCM and an optimal current distribution algorithm is also needed to enhance the system efficiency. In this paper, the copper loss and the switching loss of a DR-BLDCM drive system are analyzed according to the motor parameters and the switching frequency. Moreover, the optimal current distribution method is proposed to minimize the total electrical loss. The validity of the proposed method was verified through several experiments.

Vector control of interior permanent magnet synchronous motor without a shaft sensor

This paper describes the two control techniques to perform the sensorless vector control of interior permanent magnet synchronous motors (IPMSM) by injecting the high frequency voltage to the stator terminal. The first technique is the estimation algorithm of the rotor initial position including the identification of the rotor magnet N-S polarity at standstill. IPMSM possess the saliency which produces the ellipse of the stator current when the high frequency voltage is injected to the motor terminal. The major axis angle of the current ellipse gives rotor position information at standstill. The center of the current ellipse shifts because of the magnetic saturation effect from the origin, which makes it possible to identify the rotor magnet N-S polarity. The averaging method of the multi-cycles stator current is utilized to identify the rotor magnet N-S polarity. This averaging method increases the accuracy of the position estimation and solves the current ripple problem. The second control technique is a sensorless control algorithm that injects the high frequency current to the stator terminal in order to estimate the rotor position and speed. The rotor position and speed for sensorless vector control is achieved by appropriate signal processing to extract the position information from the stator current even in the low speed range. Experimental results are presented to verify the feasibility of the proposed control schemes.

Improved dynamic performance of interior permanent magnet synchronous motor drive in flux-weakening operation

A new flux-weakening scheme for an interior permanent magnet synchronous motor (IPMSM) is proposed. This control scheme enables the maximum torque operation for the fast acceleration in the constant power region according to the current and voltage limit condition. Especially the dynamic performance of the braking in the flux-weakening region is improved with the compensation of the stator resistance. Also since the onset of the flux weakening operation is automatically adjusted according to the load conditions, the machine parameters, and whether motoring or braking region, the stable and precise transition operation into or out of the flux weakening region can be achieved. The effectiveness of the proposed scheme is verified through experiments with an IPMSM drive system.