This paper presents a simple overmodulation method employed in direct torque control (DTC) constant switching frequency (CSF) controller of induction machines. The proposed overmodulation method is ...utilized to extend a constant torque region and hence produce high torque capability in field-weakening region with six-step operation. It will be shown that the overmodulation operation using the DTC-CSF scheme can be established by controlling the stator flux locus from circular to the hexagonal shape. This is achieved by modifying the flux error status produced from the flux hysteresis controller before it is fed to the lookup table. The main benefit of the proposed method is its simplicity since it requires only a minor modification to the conventional DTC hysteresis-based structure and does not require a space-vector modulator.
Direct Torque Control (DTC) of Induction Motors (IMs) is popular in motor drive applications because of its robust and simple control structure. The IM winding can be controlled on both sides using ...dual inverter technique which more effective for Electric Vehicle (EV) with a greater number of voltage vectors. However, the battery performance of the dual inverter will deteriorate unevenly on both sides, resulting in fluctuating voltages for the EV system. This will lead to the generation of distorted stator currents and a significant droop in the stator flux, which in turn can increase the total harmonic distortion (THD) in the system. Additionally, the performance of torque may not be able to regulate effectively. This paper examines the effect of unstable voltage on voltage vector mapping performance with tilted angles and proposes new sector definitions based on voltage ratio conditions. Moreover, the proposed sector for each predefined voltage ratio is tested under three-speed conditions. The proposed technique effectiveness is validated through hardware experiments using a dSPACE 1104 controller and retuning the stator current for proper waveform. This approach improves the stator current waveform, improves stator flux droop, enhances torque regulation and minimizes the THD in the DTC system.
High-performance induction motor (IM) drives require fast dynamic responses, robust to parameter variations, withstand load disturbance, stable control systems, and support easy hardware/software ...implementation. Fuzzy logic control (FLC) for speed controllers is garnering attention from researchers, since it is proven to produce better results compared with the conventional PI speed controllers. However, fixed parameter FLC experiences performance degradation when the system operates away from the design point or is affected by parameter variations or load disturbances. The purpose of this paper is to design and implement a simple self-tuning fuzzy logic controller (ST-FLC) for IM drives application. The proposed self-tuning mechanism is able to adjust the output scaling factor of the main FLC speed controller by improving the accuracy of the crisp output. The IM drive employed an indirect field-oriented control (IFOC) method fed by a hysteresis current controller (HCC). The fixed parameter FLC for the main speed controller comprises nine rules that are tuned to achieve the best performance. Then, a simple self-tuning mechanism is applied to the main fuzzy logic speed controller. All simulation work was done using Simulink and fuzzy tools in the MATLAB software. The effectiveness of the proposed controller was investigated by conducting a comparative analysis between fixed parameter FLC and ST-FLC in forward and reverse speed operations, with and without load disturbances. Finally, the experimental testing was carried out to validate the simulation results with the aid of a digital signal controller board, dSPACE DS1104, with an induction motor drive system. Based on the results, the ST-FLC showed superior performance in transient and steady-state conditions in terms of various performance measures, such as overshoot, rise time, settling time, and recovery time.
PLTH Bayu Baru is one of the hybrid power plants (HPP) located in Baru beach, Pandansimo, Bantul, Yogyakarta, Indonesia. It generates electrical energy from two sources, wind and solar energy. ...However, a problem is encountered regarding wind turbine mechanics due to using a manual switch for braking during periods of excessive wind speed. This study proposes an automatic wind turbine braking system through a utilized fuzzy logic controller (FLC) for the PLTH Bayu Baru application. The Mamdani type FLC without complex mathematical models is applied to the Arduino Uno development board to realize the proposed systems. The error (Error_V) and delta error (dError_V) values from the generator voltage sensor become the input of the proposed systems, while the pulse width modulation (PWM) becomes the output for controlling the on/off period of the MOSFET as switching devices. The proposed systems have been tested on a micro-scale wind turbine with PMSG 12V/400W type. From the testing results, the proposed system successfully braked automatically at the point wherein the generator voltage exceeds the setpoint value. Also, the proposed system keeps the generator voltage less than 13.8V, so the problem caused by excessive speed can be resolved.
Direct Torque Control (DTC) scheme introduces a robust and simple control of electrical drive. However, its shortcomings such as broad torque ripple and variable switching frequency have offered ...several improvements like Space Vector Modulation (SVM) strategy, multilevel inverter (MLI) topology, etc. The conventional DTC which is fed by the two-level inverter has limited voltage vector, results in some difficulties to optimize the operation, especially at low operating speed. In contrast to MLI, the abundant of voltage vector has provided various amplitudes and angles that can overcome the problem of conventional DTC. Thus, this paper introduces the selected optimal voltage vector obtained from five-level Cascaded H-Bridge (CHB) inverter that employs in DTC hysteresis-based to achieve better optimization that similar to the DTC-SVM. Initially, the research work begins with an investigation on the performance comparison between a DTC hysteresis-based between two-level inverter (conventional method) and a five-level CHB inverter (proposed method). Here, a DC generator acted as a load is employed to control the operating speed instead of the speed controller (speed controller is negligible). Hence, the DTC method is optimized by minimizing the torque ripple as well as retaining the torque control capability at constant torque region on several operating speed. The selected optimal vector from the look-up table DTC of five-level CHB inverter must be dynamically appropriate to any change of torque (increased or decreased torque). For simplicity, this paper will only discuss the experimental results for both topologies of drive system. From the experimental results, it is verified that the torque ripples by the proposed method have achieved 10% and 50% reduction at high and low operating speed respectively. It is found that the DTC hysteresis-based result simpler control method than DTC-SVM while maintaining similar output performance.
•Five-level Cascaded H-Bridge (CHB) inverter is proposed in the DTC scheme.•Optimal voltage vector is selected to analyze the torque performance on the several operating speeds.•The torque performance on each operating speed is verified by using experimental test.
The first and the most important step in solving the environmental problems created by cars with internal combustion engines is research and development of electric vehicles. Selection of a proper ...drive and optimal control strategy of electric vehicles are the major factors to obtain optimal energy management in order to extend the running distance per battery charge. This paper presents a brief review of direct torque control (DTC) of induction motors (IM) as well as its implementation for electric vehicle (EV) applications. First, the basic DTC technique based on hysteresis controllers will be introduced, and then an overview of the major problems in a basic DTC scheme will be presented and explained, as well as some efforts for improving the technique. The main section presents a critical review of DTC for EV applications, taking into consideration the vehicle mechanics and aerodynamics of electric vehicles. The review is very important to provide guidelines and insights for future research and development on the DTC of IM drives for sustainable reliability and energy efficient EV applications.
Modern electric vehicles (EVs) that drive an induction motor (IM) fed by a traction inverter are fast gaining popularity due to their simple configuration and robustness. The direct torque control ...(DTC) technique is one of the best control methods to drive the IM, especially in open-end winding configurations, as it offers more voltage vectors. However, the existence of hysteresis controllers and improper switching technique causes larger torque ripples that leads to variable switching frequency. The study will be focused on the open-end winding induction motor where the direct current (DC) power is fed from both sides of the stator windings using the dual inverter configuration. To minimize the torque ripples, a simple switching technique using the duty cycle control method is proposed by injecting a high-frequency square wave into the default inverter switching status to form the new pattern of voltage vectors. The effectiveness of the proposed technique is tested through MATLAB/Simulink software and validated experimentally with a lab-scale setup using a dSPACE controller. The findings show that the proposed method reduces torque ripple by over 50% while keeping the DTC's simple structure.
This paper presents a novel direct torque control (DTC) approach for induction machines, based on an improved torque and stator flux estimator and its implementation using field-programmable gate ...arrays (FPGA). The DTC performance is significantly improved by the use of FPGA, which can execute the DTC algorithm at higher sampling frequency. This leads to the reduction of the torque ripple and improved flux and torque estimations. The main achievements are: 1) calculating a discrete integration operation of stator flux using backward Euler approach; 2) modifying a so called nonrestoring method in calculating the complicated square root operation in stator flux estimator; 3) introducing a new flux sector determination method; 4) increasing the sampling frequency to 200 kHz such that the digital computation will perform similar to that of the analog operation; and 5) using two's complement fixed-point format approach to minimize calculation errors and the hardware resource usage in all operations. The design was achieved in VHDL, based on a Matlab/Simulink simulation model. The Hardware-in-the-Loop method is used to verify the functionality of the FPGA estimator. The simulation results are validated experimentally. Thus, it is demonstrated that FPGA implementation of DTC drives can achieve excellent performance at high sampling frequency.
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