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Speed-Sensorless DTC-SVM for Matrix Converter Drives With Simple Nonlinearity Compensation
Lee, Kyo-Beum,Blaabjerg, Frede,Yoon, Tae-Woong [Institute of Electrical and Electronic Engineers] 2007 IEEE transactions on industry applications Vol.43 No.6
<P> This paper presents a new method to improve the sensorless performance of matrix converter drives using a parameter estimation scheme. To improve low-speed sensorless performance, the nonlinearities of a matrix converter drive such as commutation delays, turn-on and turn-off times of switching devices, and <SMALL>ON</SMALL>-state switching device voltage drop is modeled using <B><I>p</I></B>–<B><I>q</I></B>– <B><I>r</I></B> transformation and compensated using a reference current control scheme. To eliminate the input current distortion due to the input voltage unbalance, a simple method using <B><I>p</I></B>–<B><I>q</I></B>– <B><I>r</I></B> transformation is also presented. The proposed compensation method is applied for high performance induction motor drives using a 3-kW matrix converter system without a speed sensor. Experimental results are shown to illustrate the feasibility of the proposed strategy. </P>
Kyo-Beum Lee,Frede Blaabjerg 대한전기학회 2006 International Journal of Control, Automation, and Vol.4 No.1
In this paper, an improved direct torque control CDTC) method for sensorless matrix converter drives is proposed which enables to minimize torque ripple, to obtain unity input power factor, and to achieve good sensorless speed-control performance in the low speed operation, while maintaining constant switching frequency and fast torque dynamics. It is possible to combine the advantages of matrix converters with the advantages of the DTC strategy using space vector modulation and a flux deadbeat controller. To overcome the phase current distortion by the non-linearity of a matrix converter drive, the simple non-linearity compensation method using PQR power theory are presented in the proposed scheme. Experimental results are shown to illustrate the feasibility of the proposed strategy.
Robust and Stable Disturbance Observer of Servo System for Low-Speed Operation
Lee, Kyo-Beum,Blaabjerg, Frede IEEE 2007 IEEE transactions on industry applications Vol.43 No.3
<P> A new scheme to estimate the moment of inertia in the servo motor drive system in very low speed is proposed in this paper. The speed estimation scheme in most servo drive systems for low-speed operation is sensitive to the variation of machine parameter, especially the moment of inertia. To estimate the motor inertia value, the observer using the Radial Basis Function Network (RBFN) is applied. A control law for stabilizing the system and adaptive laws for updating both of the weights in the RBFN and a bounding constant are established so that the whole closed-loop system is stable in the sense of <B><I>Lyapunov</I></B>. The effectiveness of the proposed inertia estimation is verified by simulations and experiments. </P>
Kyo-Beum Lee,Blaabjerg, F. IEEE 2008 IEEE transactions on industrial electronics Vol.55 No.2
<P>This paper presents a new direct torque controlled space vector modulated method to improve the sensorless performance of matrix converter drives using a parameter estimation scheme. The flux and torque error are geometrically combined in a new flux leakage vector to make a stator command voltage vector in a deadbeat manner. A new sensorless method of estimating the rotor speed, flux, stator resistance, and rotor resistance is derived and verified with experimental results. Common terms in the error dynamics are utilized to find a simpler error model involving some auxiliary variables. Using this error model, the state estimation problem is converted into a parameter estimation problem assuming the rotor speed is constant. The proposed adaptive schemes are determined so that the whole system is stable in the sense of Lyapunov. The effectiveness of the proposed algorithm is verified by experiments.</P>
Simple Power Control for Sensorless Induction Motor Drives Fed by a Matrix Converter
Kyo-Beum Lee,Blaabjerg, F. IEEE 2008 IEEE transactions on energy conversion Vol.23 No.3
<P>This paper presents a new and simple method for sensorless control of matrix converter drives using a power flowing to the motor. The proposed control algorithm is based on controlling the instantaneous real and imaginary powers into the induction motor. To improve low-speed sensorless performance, the nonlinearities of a matrix converter drive such as commutation delays, turn-ON and turn-OFF times of switching devices, and on-state switching device voltage drop are modeled using a PQ power transformation and compensated using a reference power control scheme. The proposed sensorless control method is applied for the induction motor drive using a 3 kW matrix converter system. Experimental results are shown to illustrate the feasibility of the proposed strategy.</P>
Kyo-Beum Lee,Blaabjerg, F. Institute of Electrical and Electronics Engineers 2007 IEEE transactions on industrial electronics Vol.54 No.6
<P>In this paper, an improved direct torque control (DTC) method for sensorless matrix converter drives is proposed, which is characterized by minimal torque ripple, unity input power factor, and good sensorless speed-control performance in the low-speed operation, while maintaining constant switching frequency and fast torque dynamics. It is possible to combine the advantages of matrix converters with the advantages of the DTC strategy using space-vector modulation and two PI controllers. To overcome the degrading of dynamic torque response compared with the basic DTC method and the phase-current distortion due to the nonlinearity of the matrix converter, an overmodulation strategy and a simple nonlinearity-compensation method using transformation are also presented. Experimental results are shown to illustrate the feasibility of the proposed strategy.</P>
A Fault Diagnosis Method in Cascaded H-bridge Multilevel Inverter Using Output Current Analysis
Lee, June-Hee,Lee, June-Seok,Lee, Kyo-Beum The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.6
Multilevel converter topologies are widely used in many applications. The cascaded H-bridge multilevel inverter (CHBMI), which is one of many multilevel converter topologies, has been introduced as a useful topology in high and medium power. However, it has a drawback to require a lot of switches. Therefore, the reliability of CHBMI is important factor for analyzing the performance. This paper presents a simple switch fault diagnosis method for single-phase CHBMI. There are two types of switch faults: open-fault and short-fault. In the open-fault, the body diode of faulty switch provides a freewheeling current path. However, when the short-fault occurs, the distortion of output current is different from that of the open-fault because it has an unavailable freewheeling current flow path due to a disconnection of fuse. The fault diagnosis method is based on the zero current time analysis according to zero-voltage switching states. Using the proposed method, it is possible to detect the location of faulty switch accurately. The PSIM simulation and experimental results show the effectiveness of proposed switch fault diagnosis method.
An Improved Control Method for a DFIG in a Wind Turbine under an Unbalanced Grid Voltage Condition
Lee, Sol-Bin,Lee, Kyo-Beum,Lee, Dong-Choon,Kim, Jang-Mok The Korean Institute of Electrical Engineers 2010 Journal of Electrical Engineering & Technology Vol.5 No.4
This paper presents a control method, which reduces the pulsating torque and DC voltage problems of a doubly fed induction generator (DFIG)-based wind turbine system. To reduce the torque and power ripple, a current control scheme consisting of a proportional integral (PI) controller is presented in a positive synchronously rotating reference frame, which is capable of providing precise current control for a rotor-side converter with separated positive and negative components. The power theory can reduce the oscillation of the DC-link voltage in the grid-side converter. In this paper, the generator model is examined, and simulation results are obtained with a 3 kW DFIG-based wind turbine system to verify the proposed control strategy.