Device switching scheme for direct torque control

This paper presents a Neuro-Fuzzy adaptive controller for speed control of a three phase direct torque controlled induction motor drive. The Direct Torque Control (DTC) scheme is one of the most advanced methods for controlling the flux and electromagnetic torque of machines. Control of electromagnetic torque/speed in these drives for high performance applications requires a highly robust and adaptive controller. Adaptive Neural-Fuzzy Inference System (ANFIS) is a hybrid between Artificial Neural Networks (ANN) and Fuzzy Logic Control (FLC) that enhances the execution of direct torque controlled drives and overcomes the difficulties in the physical implementation of high performance drives. MATLAB/SIMULINK implementation of 15 hp, 50 Hz, 4 pole squirrel cage induction motor controlled with the DTC scheme is presented in this paper. The PI controller used for speed control in conventional DTC drives is substituted by the ANFIS based controller. Simulation results show the use of ANFIS decreases the response time along with reduction in torque ripples.

This paper proposes 20-sector based direct torque control (DTC) scheme for dual inverter fed five phase induction motor drives with open-end stator windings powered by a single DC source. The proposed scheme utilizes 20 virtual voltage vectors that divide the space vector plane into 20 sectors, each sector spanning 18 degrees. The 20-sector based DTC scheme provides a smoother control over torque and flux compared to the conventional 10 sector-based DTC schemes for five phase induction motors. The switching scheme used in the proposed scheme eliminates the auxiliary plane harmonic voltages and provides higher DC bus utilization compared to two-level five phase voltage source inverter fed DTC schemes. The switching scheme for realization of these virtual voltage vectors does not generate any resultant common mode voltage across the stator windings and hence a single DC source is used to supply both the voltage source inverters. The proposed DTC scheme is validated by extensive simulation using MATLAB-Simulink software and experimentally verified on a laboratory prototype.

A virtual voltage vector based direct torque control (DTC) scheme with enhanced resolution for five-phase induction motor (IM) drives with open-end stator windings, fed by two inverters, is proposed in this article. In the proposed scheme, the voltage space vector plane is divided into 20 sectors, by using 40 virtual voltage vectors produced as resultants of the virtual voltage vectors of the individual inverters thereby substantially increasing the sector resolution compared to the 10-sector based conventional five-phase DTC schemes. This DTC scheme incorporates a five-level hysteresis comparator for torque control and the required voltage vectors of different magnitudes are produced by appropriately combining the vectors of the two inverters. The increased sector resolution along with five-level hysteresis torque controller facilitates finer flux and torque control. As the effective common mode voltage in the motor windings is made zero in every switching period, both inverters can be connected to a common dc supply without causing circulation of zero sequence current. The proposed scheme is validated by performing experiment on a five-phase IM drive.

Parameter sensitivity analysis of Direct Torque Control(DTC) scheme for dual inverter fed open end winding induction motor drive with single DC source is presented in this paper. The effect of stator resistance variation on the voltage vector selection in this DTC scheme is analysed using the voltage space structure of a dual inverter configuration with single DC source. Theoretical analysis is validated by simulation on a MATLAB Simulink platform. The results of the theoretical and simulation analyses are experimentally verified on an induction motor with open-end stator windings using TMS320F28335 digital signal processor.

A direct torque control (DTC) scheme for five phase induction motor drives with open-end stator winding configuration is presented in this paper. The DTC scheme proposed here make use of the non-adjacent line voltage vectors that are generated as resultants of the voltages produced in the two inverters. The method of generation of voltage vectors proposed in this paper does not produce common mode voltage across the motors windings. Both the inverters can be fed from a single DC source with a common DC link without any common mode current flow. Another important aspect of the proposed scheme is that it makes the average voltage produced in the non-torque producing plane (x-y plane) zero thereby preventing the flow of large harmonic currents through the windings. Also, this scheme can reduce DC voltage requirement by 47% when compared to that of a single–end inverter fed, star connected five phase induction motor drive for the same phase voltage. The proposed DTC scheme is verified experimentally using a laboratory prototype under both steady state and transient operating conditions.

Most of the direct and indirect torque control schemes proposed for switched reluctance motors (SRMs) consider equal rotor and stator pole arc. Leading to a linear non-saturating inductance profile. However, actually, in SRM, the rotor pole arc is kept higher than the stator pole arc. Leading to a non-linear saturating inductance profile. And not considering this in control leads to underutilization of the maximum torque producing capacity during the constant torque region. In the proposed novel direct torque control (DTC) scheme, firstly, the rotor pole arc and saturation effect are incorporated by considering it in the sector formation for every electrical cycle. Second, the flux control loop is removed, and sectors are classified based on the actual inductance profile, which is rotor position-dependent. Also, the voltage vector selection rule is modified for torque control. And the proposed voltage vector concerning the sector, allows multiple phases to conduct simultaneously. Wherein each phase conducts according to its actual inductance profile. This also ensures complete energization of incoming phase current while the outgoing phase is maintained at a constant current level. Leading to a reduction in torque ripples during commutation. The proposed DTC scheme incorporating the rotor pole arc and saturation effect improves the operating range for effectively reducing the torque ripples and facilitates a higher torque/ampere ratio.

This paper investigates the performance of a novel direct torque control (DTC) strategy dedicated to interior permanent magnet (IPM) brushless AC (BLAC) motor drives. The proposed strategy is based on a dual control approaches, consisting in: (i) a conventional DTC strategy where the control laws are inspired from the earlier Takahashi DTC strategy implemented in induction motor drives, and (ii) the bus-clamping (BC) strategy recently-introduced for the control of voltage source inverters, yielding the so-called “bus-clamping DTC” (BC-DTC). It consists in the synthesis of two vector selection tables depending on the rotation direction, in such a way to clamp each motor phase during 60°-interval in every half cycle of the reference stator flux vector. A simulationbased comparative study between the performance of the introduced BC-DTC and the conventional one, considering appropriate criteria, has highlighted the superiority of the proposed strategy which exhibits lower inverter switching losses, reduced harmonic distortion of the motor phase currents and damped torque ripple in a wide speed range.

A review of reliable and energy efficient direct torque controlled induction motor drives

The variable-flux memory machine (VFMM) exhibits high efficiency over a wide speed range because its airgap magnetic flux can easily be regulated by varying the magnetization state (MS) of the employed low coercivity force permanent magnets. This paper proposes a second-order sliding mode (SM)-based direct torque control (DTC) strategy for the VFMM, which features a relatively low computational complexity and less dependence on machine parameters. The operating principle and mathematical model of the VFMM are first described and established. On this basis, a novel control scheme combining the DTC strategy with MS manipulation is proposed, in which the machine is controlled by utilizing the DTC strategy incorporating the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$i_{\mathrm {d}} = 0$ </tex-math></inline-formula> condition, while the MS manipulation is implemented by energizing reference stator flux linkage pulses. A super-twisting second-order SM controller is subsequently developed to achieve strong robustness. The developed control structure avoids a complicated decoupling algorithm and is simpler than that of the conventional field-oriented control (FOC) method. Finally, the effectiveness of the proposed control scheme is validated by simulation and experimental results.

The paper is devoted to the synthesis and performance analysis of a direct torque control (DTC) strategy, based on the bus-clamping technique, dedicated to three level NPC inverter fed induction motor drives. The principle of the proposed strategy consists in keeping the voltage vector of each motor phase during 60° of the half of a cycle of the reference stator flux vector. The synthesis of the vector selection tables (one for clockwise rotation and the other for anti-clockwise rotation) is achieved on the basis that enables the fulfilment of the control combinations related to the variations of the stator flux and the electromagnetic torque, along with a reduction of their ripples. Simulation results highlight the torque high dynamic as well as reduced ripple, exhibited by the three level NPC inverter fed induction motor drive under the control of the proposed bus-clamping DTC strategy.

Over the past few years, multiple types of modifications have been proposed onto the Direct Torque Control (DTC) scheme. Among others is the implementation of Space Vector Modulation (SVM). In this paper, two new control strategies are proposed onto an SVM-DTC. Instead of using PI torque and flux controllers, a fuzzy logic control method is implemented in the proposed modification to achieve a more constant switching frequency while minimizing the torque error. The fuzzy logic controller controls the voltages in direct and quadratic reference frame (Vd, Vq). This approach fully utilizes the switching capability of the inverter and thus improving the overall system performance. To overcome issues in open loop stator flux such as DC drift and saturation, a closed loop estimation method of stator flux is also proposed based on voltage model and low pass filter. The performance of the proposed control strategy is benchmarked with that of a conventional DTC–SVM. Simulations and experiments were carried out and the results show that the proposed method outperforms the conventional DTC-SVM in terms of DC-offset elimination and overall system robustness. &lt;p class="MsoNormal" style="text-align: justify; text-indent: 36.0pt;"&gt;&lt;span style="font-size: 9.0pt; font-family: 'Arial','sans-serif'; color: black;" lang="EN-US"&gt;Over the past few years, multiple types of modifications have been proposed onto the Direct Torque Control (DTC) scheme. Among others is the implementation of Space Vector Modulation (SVM). In this paper, two new control strategies are proposed onto an SVM-DTC. Instead of using PI torque and flux controllers, a fuzzy logic control method is implemented in the proposed modification to achieve a more constant switching frequency while minimizing the torque error. The fuzzy logic controller controls the voltages in direct and quadratic reference frame (V&lt;sub&gt;d&lt;/sub&gt;, V&lt;sub&gt;q&lt;/sub&gt;). This approach fully utilizes the switching capability of the inverter and thus improving the overall system performance. To overcome issues in open loop stator flux such as DC drift and saturation, a closed loop estimation method of stator flux is also proposed based on voltage model and low pass filter. The performance of the proposed control strategy is benchmarked with that of a conventional DTC–SVM. Simulations and experiments were carried out and the results show that the proposed method outperforms the conventional DTC-SVM in terms of DC-offset elimination and overall system robustness. &lt;/span&gt;&lt;/p&gt;

This paper presents a direct torque control (DTC) scheme for matrix converter driven induction motor. The proposed scheme uses the simplified carrier-based PWM scheme of matrix converter for generation of PWM voltages. The proposed DTC scheme is characterized by the advantages of simple structure, unity input power factor operation of matrix converter, minimum torque ripple, and uniform switching as with carrier based modulation. A speed sensorless closed loop speed control of the induction motor is implemented along-with the DTC scheme. The novel carrier based modulation method is used to generate the PWM voltages from the matrix converter

This paper presents a simplified self-tuned Sugeno type neuro fuzzy controller (NFC) based direct torque control (DTC) scheme for induction motor (IM) drive. A simple tuning algorithm is developed based on the reference and actual acceleration of the motor. The online tuning strategy adjusts the parameters of the consequent layer of the NFC in such a way to minimize the square of the error between actual and reference acceleration of the IM. In a conventional DTC scheme the band limits of flux and torque hysteresis controllers remain fixed and hence the torque and flux ripples are high. In order to optimize the torque ripples of the IM the hysteresis band limits are adjusted online for the torque hysteresis controller. In order to test the performance of the proposed NFC based DTC scheme for IM drive a complete simulation model is developed using MATLAB/Simulink. The proposed NFC based DTC scheme is implemented in real-time using DSP board DS1104 for a prototype 1hp squirrel cage IM. The performance of the proposed drive is tested at different operating conditions in both simulation and experiment.

Direct torque control (DTC) is one of the most widely used control strategy in induction motor drives. DTC drive utilizes the hysteresis band control which is one of the simplest and popular control scheme. The major problems in the conventional DTC scheme is large torque ripple, stator current distortion and variable switching frequency. This paper presents a DTC scheme for five phase induction motor drive to achieve constant switching frquency and minimum distortion in the stator current. The proposed DTC scheme is validated by extensive simulation on a Matlab-Simulink platform.

This paper proposes a novel direct torque control (DTC) scheme to reduce the torque and stator flux ripples for permanent-magnet synchronous motor (PMSM) drives using a relatively low sampling frequency. Unlike the conventional DTC in which the voltage vectors are determined by hysteresis controllers, the proposed DTC uses nonlinear saturation comparators and a duty ratio modulation scheme for switch selection and switching duration determination. Compared to the conventional DTC, the proposed DTC scheme significantly reduces the steady-state torque and flux ripples of PMSMs while preserving most of the intrinsic properties of the conventional DTC, e.g. fast dynamic, robust to disturbances, no coordinate transformation, etc. The effectiveness of the proposed DTC scheme is verified by simulation and experimental results on a 200W PMSM drive system.