Jong-Joo Moon

Novel phase advance method of BLDC motors for wide range speed operations

This paper proposes a novel phase advance method of brushless DC motors (BLDCMs) for wide range speed operations. In order to extend the speed of BLDCMs, it is necessary to control phase currents to lead the phase back EMF by a phase advance method. Many phase advance methods have been studied for the speed expansion of the BLDCM during the last 20 years. However, these conventional methods increase the torque ripple even if it widens the range of speed for the BLDCM. As compared with the conventional method, the proposed method takes definite advantages. it can obtain wider range speed and lower torque ripple. A key of this method is to broaden conduction area of phase currents by using an advance angle. The usefulness of the proposed phase advance method is verified through simulation results.

Phase current estimation of BLDC motor drive system by using source side current of DC-link

This paper proposes an estimation algorithm of phase currents of inverter systems with the planar bus bars for brushless DC motors (BLDCM). In these inverters, a DC-link single current sensor measures the sum of a smooth capacitor current and phase currents of BLDCM. It is essential to extract phase currents from the measured single current to control BLDCM. Therefore, in this paper, the phase current is estimated by analyzing equivalent circuits of BLDCM in ON and OFF periods of switching elements. The usefulness of the proposed algorithm is verified through simulation and experimental results.

Classification and compensation of amplitude imbalance and imperfect quadrature in resolver signals

This paper proposes a detection and compensation algorithm of two non-ideal output signals of a resolver to reduce position error. Practically, a resolver generates position errors because of the amplitude imbalance and imperfect quadrature between the two output signals of the resolver. In this paper, a digital signal processor (DSP) based resolver-to-digital converter (RDC) is used to reconstruct the two output signals of the resolver. The proposed algorithm does not need any additional hardware. Furthermore, this algorithm can be applied to both the steady and transient states. The simulation results verify the effectiveness of the proposed algorithm.

Fault tolerant control strategy of 3-phase AC-DC PWM converter under multiple open-switch faults conditions

3-phase AC-DC PWM (Pulse Width Modulation) converter has a possibility of open-switch faults due to some trouble of the switching devices and gate drivers. In this case, the converter causes imbalance of the AC input currents and the pulsation of DC-link voltage. This paper proposes fault tolerant control strategy of 3-phase AC-DC PWM converter under multiple open-switch fault conditions. So a detection method of the open-switch faults and fault tolerance methods are suggested according to fault cases. In this paper, two or more switches fault cases are dealt with. Both computer simulation and experimental results verify the usefulness of the proposed fault-tolerant control algorithm.

Classification and Compensation of DC Offset Error and Scale Error in Resolver Signals

This study proposes a classification and compensation algorithm of two non-ideal output signals of a resolver to reduce position errors. Practically, a resolver generates position errors because of amplitude imbalance and quadrature imperfection between the two output signals of the resolver. In this study, a digital signal processor system based on a resolver-to-digital converter is used to reconstruct the two output signals of the resolver. The two output signals, “sin” and “cos,” can be represented by a unit circle on the xy-plot. The classification and compensation of the errors can be obtained by using the radius and area of the circle made by the resolver signals. The method computes the integration of the areas made by the two resolver output signals to classify and compensate the error. This system cannot be applied during transient response given that the area integration during the transient state causes an error in the proposed method. The proposed method does not need any additional hardware. The experimental results verify the effectiveness of the proposed algorithm.

Fault tolerant control method of seven-phase BLDC motor in asymmetric fault condition due to open phase

Open-switch faults of seven-phase BLDC (brushless DC) motor drive system cause torque ripple. This torque ripple makes unwanted noise and vibrations in the drive system. In particular, open-switch fault case of one-switch or two-switches in the same phase among fourteen switches of PWM inverter is analyzed. This paper proposes two fault tolerant control (FTC) methods for seven-phase BLDC motor in asymmetric fault condition due to open switch fault. One can reduce the torque ripple to similar level under the healthy condition. The other can partially compensate the output torque. The proposed method changes the conductive angle of the healthy phase current. The usefulness of this paper is verified through simulation results.

Novel Phase Advance Method of a BLDC Motor for Wide Range Speed Operations

his paper proposed a novel phase advance method for brushless DC motors (BLDCMs) to extend the speed operating range, and obtain the maximum torque in the high speed operation region. The angle of the phase currents should be advanced about the back-EMF to increase the speed operating region and obtain maximum torque. Many advance methods have been studied for BLDCMspeed expansion. The conventional method could widen the speed range, but also increase the torque ripple. To resolve the issues with conventional methods, the proposed method broadens the conductive angle of the phase current including advancing the phase current angle to the back-EMF (Electro-Magnetic Force). The broad conductive angle is derived by analyzing the phase current and back-EMF. The usefulness of the proposed method is verified through mathematical analysis, computer simulation and experimental results.

Sensorless control method of 3-Phase BLDC motor through the real time compensation of back-EMF constant

This paper proposes the novel sensorless control algorithm for 3-Phase BLDC motors with trapezoidal back-EMF. The proposed algorithms include both the new back-EMF estimation method by using the DC current model and a compensator for the electric parameter errors of the BLDC motor to improve performance of sensorless control more exactly. The back-EMF can be easily calculated from the electrical voltage equation. However, it has some errors at the commutation period. This error can be reduced by using the proposed sensorless control algorithm which is derived by using the mechanical and electrical equation simultaneously for the accurate estimation of the back-EMF. In this case, the back-EMF estimation is affected by the electric parameters. If the motor parameters have errors, there will be some errors of the estimated back-EMF. Therefore, a new algorithm is needed for parameter error compensation. Among the motor parameters, stator resistor and back-EMF constant are mainly affected by the temperature. Therefore, this paper proposes the new sensorless control algorithm with the real time compensation of the motor parameter variation according to temperature. The main attractive features of the proposed algorithm have the robustness to the parameter variation and the transient state, and the less torque ripple by using the DC-current model. The usefulness of the proposed sensorless control method is verified through the simulation.

Maximum efficiency control method in 7-phase BLDC motor by changing the number of the excited phase windings

This paper proposes a maximum efficiency control method in 7-phase brushless DC motors (7-phase BLDCMs) used for the ship propulsion system. In the same load condition, the system loss of the 7-phase BLDCM is dependent on the number of the excited windings and the instantaneous phase currents. Thus, it is necessary to determine the excitation number of the phase windings according to the load condition. The 2- and 4-phase excitation methods are proposed for the maximum efficiency operation. The phase excitation method of the minimum system loss according to the load condition can be obtained from the loss analysis. In addition, by using the loss analysis, the optimal speed which is the changing point of the phase excitation to select the optimal excitation methods (2-, 4- and 6-phase excitation) can be calculated and derived. The proposed method can be easily implemented by controlling the conductive angle of the phase current at the suitable phase windings. The maximum efficiency operation can be achieved by using the proposed excitation method and 6-phase excitation method. The usefulness of the proposed control algorithm is verified through simulation results.

Capacitance Estimation Method of DC-Link Capacitors for BLDC Motor Drive Systems

This paper proposes a capacitance estimation method of the dc-link capacitor for brushless DC motor (BLDCM) drive systems. In order to estimate the dc-link capacitance, the BLDCM is operated in quadrant-II or -IV among four-quadrant operation. Quadrant-II and -IV are called reverse braking and forward braking, respectively. During the braking operation of the BLDCM, the capacitor is charged by the phase current and then the voltage is increased during the braking operation time. The capacitor current and voltage can be obtained by using the phase current sensor of BLDCM and the dc-link voltage sensor. The capacitance and be easily obtained by the voltage equation of the capacitor. The proposed method guarantees the reliable and simple calculation of the dc-link capacitance without additional hardware system except several the sensors already installed for the motor control system. The effectiveness of the proposed method is verified through both the simulation and experimental results.