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Alsofyani, Ibrahim Mohd,Idris, Nik Rumzi Nik,Lee, Kyo-Beum Institute of Electrical and Electronics Engineers 2018 IEEE transactions on power electronics Vol.33 No.9
<P>The magnitude of hysteresis torque band has a considerable effect on the performance of two-level direct torque control (DTC) of induction machines. The conventional DTC fails at low speed due to the poor flux regulation. In this paper, two dynamic hysteresis torque band (DHTB) strategies for the conventional DTC are proposed to solve this problem by dynamically altering the amplitude of hysteresis torque band based on a flux error range. In this way, the simplicity of DTC algorithm is retained since it only requires a minor modification on its structure. The paper also presents further analysis on flux degradation, particularly the droop in between the flux sectors. In addition, the switching frequency effect of reverse voltage vectors for both DHTB schemes is investigated on the performance of the speed-sensorless DTC drive. The effectiveness of the proposed schemes is confirmed by simulation and experimental validation. Results show a significant enhancement in the flux regulation and dynamic torque response from zero motor speed.</P>
Ibrahim Mohd Alsofyani,Nik Rumzi Nik Idris,이교범 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.1
It is well known that the selection of extended Kalman filter (EKF) covariance elements has a considerable bearing on the effectiveness of EKF performance. The observability at very low frequency is also an essential property for the selection of EKF elements. This paper investigates the optimization of the EKF covariance elements when zero frequency is included in the training profile for direct torque control (DTC) of induction motor. In addition, the paper studies the optimization of EKF by speed and torque fitness functions using a non-dominated sorting genetic algorithm-II at zero and high speeds under stable flux regulation. For this purpose, DTC with constant switching frequency controller which has the capability of establishing continuous flux rotation regardless of speed variation is used. The optimized results of EKF for both DTC motor drives and speed and torque cost functions are verified experimentally.
Ibrahim Mohd Alsofyani,Kyo-Beum Lee 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.1
In this study, discrete space vector modulation (DSVM) is used to achieve the flux and torque ripple reduction of finite set model predictive torque control (FS-MPTC) fed by a three-level neutral point clamped inverter (3L-NPCI). In the proposed DSVM, the synthesis of voltage vectors (VVs) can be controlled and implemented online, thereby eliminating the need for a VV lookup table. In addition, a simple and efficient preselection VV strategy is presented to reduce the number of candidate VVs in the prediction stage. The problem of capacitor voltage imbalance in 3L-NPCI is easily solved without including it as a control objective in the cost function. Thus, the complexity of tuning multiple weighting factors can be reduced. Hence, the proposed PTC-DSVM algorithm is simple and is capable of minimizing torque/flux ripples. It can also achieve a fast torque dynamic performance while maintaining balanced capacitor voltages. The effectiveness of the proposed method is verified through experimental results.
Halabi, Laith M.,Alsofyani, Ibrahim Mohd,Lee, Kyo-Beum The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.11
Recent developments in power electronics technologies have resulted in a need for fast responses and dynamic control. However, existing control schemes are still limited to the available digital signal processors (DSPs) and their associated high prices. The field-programmable gate array (FPGA) offers fast performance and high control flexibility by providing a reconfigurable computing speed. However, it has some implementation limitations in standalone systems. In this regard, this paper presents a hardware setup for a three-level hybrid active neutral point inverter (HANPC) using a FPGA and a DSP. A unique method using digital and analog modulation is designed in this study using Vivado software. The proposed method depends on receiving analog reference signals from the DSP and then performing all the required processes using the FPGA. Direct pulse width modulation is generated to control the HANPC without changing the hardware configuration of the main topology. The implemented hardware is based on a 15 kW HANPC topology that is mainly controlled by a Digilent Zybo-Z7-20 FPGA. The effectiveness of the proposed system was verified by experimental results.
Detection of Open-Circuit Faults in Multi-Level Hybrid Active Neutral Point Clamped Inverters
Halabi Laith M.,Alsofyani Ibrahim Mohd,Lee Kyo-Beum 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.4
In the fi eld of renewable energy, power converters serve an important role in power generation systems. However, they are vulnerable to faults of several types, among which open-circuit faults are the most common. In this context, this paper proposes an effi cient method to detect and identify faults in various components of power converters accurately. The distortion in the output voltage and current waveforms of the system induced by open-circuit faults are calculated and compared to pre-established threshold values to detect the faulty devices. In addition, an accurate look-up table is prepared to identify locations of faults in multi-level inverters. The proposed method is analyzed in detail and its eff ectiveness is verifi ed based on simulation and experimental results. The results demonstrate that the proposed method improves fault detection signifi cantly.