Predictive Torque Control Algorithm Research Articles

An Improved Direct Predictive Torque Control for Torque Ripple and Copper Loss Reduction in SRM Drive

This paper introduces a direct predictive torque control (DPTC) method to minimize the torque ripple and copper loss of the switched reluctance motor (SRM). Generally, there is a problem with torque ripple during the SRM’s commutation. In this method, the commutation optimization is provided by a direct predictive torque control algorithm. Firstly, the reachable range of phase torques is predicted and the boundary of two continuous phases is modified. By dividing the torque range directly to determine the torque allocation set, the suppression of torque ripple becomes simple. Secondly, considering the optimization problem of copper loss during commutation, a cost function only related to the phase current is constructed. Further, the minimization of copper loss can be achieved by solving the cost function, and the work of setting weight parameters is not required. Finally, the proposed DPTC method is tested by simulation and experiment in a three-phase 12/8-pole SRM drive system and the results are compared with the existing predictive torque control methods. The results show that the proposed method has less torque ripple and copper loss, which effectively improves the torque control performance.

Enhanced Predictive Torque Control for Three-Level NPC Inverter-Fed PMSM Drives Based on Optimal Voltage Magnitude Control Method

The major drawback of conventional predictive torque control (PTC) is that it fixes the magnitude of the reference voltage vector (VV) to 70%. This limitation results in large torque and flux ripples and slow dynamic response, especially when the permanent magnet synchronous motor operates in low-speed regions. A promising approach for reducing torque and flux ripples is by replacing the two-level inverter with a three-level neutral-point-clamped (NPC) inverter. Nevertheless, because of the elimination of zero VV during torque decrement in a conventional PTC, a large torque ripple appears in the low-speed region. In addition, high-speed operation is not applicable unless more dc-link is injected. To solve these problems, an effective, creative, and low-complex PTC based on a reference voltage vector magnitude control method (RVVCM) is proposed in this article. The proposed PTC effectively minimizes torque and flux ripples by utilizing only the required magnitude of reference VV of the three-level NPC inverter based on the variable voltage control concept. Furthermore, the dynamic response of the torque is improved by applying the full magnitude of applied VV. Simulation and experimental results are presented to validate the effectiveness of the proposed RVVCM-based PTC algorithm.

Enhanced Weighting Factor Eliminated Predictive Torque Control of an Open End Winding Induction Motor Drive

Predictive torque control (PTC) of induction motor drives is one of the best suitable alternatives for direct torque control (DTC). In this article, the weighting factor eliminated PTC for four-level inversion fed open end winding induction motor drive (OEWIMD) has been introduced. The major limitations of classical PTC are as follows: assignment of weighting factor due to dissimilar control objectives, tuning of weighing factors and high computational burden. To circumvent these problems, this article introduces an effective weighting factor elimination-based PTC scheme to an OEWIMD. The proposed algorithm eliminates the complex tuning process of weighting factors by classifying the cost function. The proposed PTC algorithm is simple and provides less computational burden on the controller. In the proposed PTC, the cost function is segregated and ranked accordingly to reduce flux and torque ripples. Cost function-I is formulated to obtain optimum voltage vectors to reduce flux ripples. The same voltage vectors obtained from cost function-I are used in cost function-II to maintain minimum torque ripple. Therefore, the proposed PTC reduces torque and flux ripples with a limited number of voltage vectors and maintains minimum computational burden. The effectiveness of the proposed PTC is verified through MATLAB/SIMULINK and experimentation.

Indirect predictive torque control for switched reluctance motor in EV application

This paper presents a novel indirect predictive control method to reduce the torque ripple of switched reluctance motor drive in electric vehicle (EV) application. The proposed indirect predictive torque control algorithm includes two parts: torque inverse model and robust predictive current controller. The torque inverse model adopts the form of adding torque error compensator to the simple linear model to realize the accurate mapping from torque to current, which avoids the complex calculation of the traditional torque inverse model. Then the predictive current controller is designed to traverse all candidate switching states and use the switching state of minimizing the cost function as the optimal output. Further, the modeling error, parameter variations and sampling error are equivalent to a total disturbance, which are compensated by the developed disturbance observer to improve the robustness of the predictive control. The proposed predictive control scheme indirectly realizes the instantaneous torque control through the accurate tracking of current, which is easy to implement, and is suitable for driving electric vehicles. Simulation experiments are performed to verify the effectiveness of the proposed predictive control algorithm.

Predictive Torque Control of Five-Phase Induction Motor Drive Using Successive Cost Functions for CMV Elimination

This article presents a predictive torque control (PTC) algorithm for a five-phase (distributed winding) induction motor fed by a three-level neutral-point-clamped inverter to remove the common-mode voltage (CMV). In this approach, a finite range of 31 voltage vectors (VVs) is chosen from the total available 243 VVs for the removal of the CMV. The xy-subspace current harmonic reduction is achieved with grouped VVs. The developed PTC algorithm has two successive cost functions: g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1h</sub> for stator flux and electromagnetic torque regulation and g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2h</sub> for xy-subspace current harmonic reduction. The purpose of these two successive cost functions is to reduce the complexity in determining the independent weighting factors. This algorithm retains the torque and flux responses similar to that of conventional PTC. The minimization in switching frequency is obtained in the presented PTC algorithm with the selected set of VVs. For evaluating and ascertaining the capabilities for CMV elimination and xy-subspace harmonic current reduction, the proposed algorithm is compared with the conventional PTC algorithm having a different set of VVs. Experimental outcomes show the significance of the discussed algorithm in the steady state and retain the transient operating conditions.

Grey Wolf Optimizer-Based Predictive Torque Control for Electric Buses Applications

This paper proposes an improved Predictive Torque Control (PTC) of a PMSM based on the Grey Wolf Optimizer (GWO) for smooth torque operation in Electric Bus applications (EBs). The embedded GWO is used to resolve the torque tracking tasks with minimal oscillations in running at the low speed of PMSM drives. The new PTC algorithm can successfully ensure the smooth time evolution of the torque and the speed. The design methodology is detailed and the provided experimental results show that the proposed PTC-GWO can be implemented in real-time on embedded hardware, offering high effectiveness in both steady and transient states of the PMSM drives, even at low-speed range.

Speed Sensor-Less Predictive Torque Control for Five-Phase Induction Motor Drive Using Synthetic Voltage Vectors

The predictive torque control (PTC) is researched extensively for control of electrical drives because of its fast-dynamic response and robust control. In multiphase motors, it is mandatory to design a multiobjective cost function with more than two terms for controlling xy-subspace current and common-mode voltage (CMV). However, selecting the weighting factor for multiple control variables is time penalizing and increases the computational burden. Using a noisy speed input from the speed sensor in the prediction model reduces the steady-state performance in terms of higher torque ripple, flux ripple, and phase current total harmonic distortion (THD), especially during low speeds. In this article, PTC for a five-phase induction motor (IM) drive without speed sensor [sensorless PTC (PTC-S)] is presented. The adaptive full observer is incorporated to estimate the stator flux, stator resistance, and rotor speed. The proposed algorithm is capable to eliminate CMV and xy-current harmonics having advantages over the conventional PTC (PTC-C) algorithm. The elimination of CMV is achieved by the selection of set of voltage vectors from available 243 voltage vectors. The proposed speed sensor-less control is implemented with a three-level neutral-point clamped (NPC) inverter using synthetic voltage vectors. The use of a synthetic voltage vector eliminates the xy-subspace current and reduces the computational burden. The PTC-S is implemented with a seven-level hysteresis torque comparator, which reduces the torque ripple significantly. To further improve the effectiveness of the control algorithm, two-step delay compensation is implemented. The discussed algorithms are tested on a laboratory prototype for experimental evaluation. The proposed study also highlights the effect of torque ripple reduction on the speed adaptive flux observer for sensor-less operation. The experimental results show the effectiveness and applicability by comparing the steady-state and dynamic performances of PTC.

Iron Loss Minimization Strategy for Predictive Torque Control of Induction Motor

Today’s modern control strategies of an induction motor (IM) drive require a power source with an adjustable output voltage frequency and amplitude. The most commonly used converter topology is a two-level voltage-source inverter (VSI). However, the utilization of a VSI introduces additional voltage and current distortion, which leads to additional power losses in the machine’s magnetic circuit. Both the transistor switching frequency and the type of the inverter control determine the total harmonic distortion (THD) of the motor’s phase currents. In this paper, the influence of the inverter DC-link voltage on the iron losses of an IM controlled by a predictive torque control (PTC) is presented. It is shown that if the IM drive operates below the rated speed, it is possible to modify the PTC algorithm to reduce the additional iron losses caused by the non-harmonic inverter output voltage. The control of the DC-link voltage is achieved by using a silicon-controlled rectifier. Experiments were conducted on a 5.5 kW IM controlled by PTC, and the results are compared against a sinusoidal voltage supply created by a synchronous generator.

Enhanced predictive torque control of multi-level inverter fed open-end winding induction motor drive based on predictive angle control

ABSTRACT In this article, predictive torque control (PTC) of multi-level inversion (MLI) fed open-end winding induction motor (OEWIM) drive has been developed with predictive angle control technique. The classical PTC of induction motor drive involves direct control of torque and flux. The combination of direct torque control (DTC) with model predictive control (MPC) offers all the features of classical DTC and in addition it is easily implementable for MLI fed induction motor drives. This article introduces predictive angle control strategy for MLI fed OEWIM drive to reduce torque ripple, where as the classical PTC algorithm uses magnitudes of torque and flux. The proposed algorithm is developed by controlling the angle between stator flux and stator current, the voltage space vectors of MLI fed OEWIM drive are classified according to operating frequency range. The proposed PTC algorithm requires same computational time as that of classical PTC. The proposed algorithms are verified through simulation and experimental studies.

Simplified Predictive Torque Control for Surface-Mounted PMSM Based on Equivalent Transformation and Partition Method

Predictive torque control (PTC) is one of the most widely discussed strategies for high performance permanent magnet synchronous motor (PMSM) drive system because of its fast dynamic response and good stability. However, the complex prediction and optimization process requires a large amount of computation. Until now, few studies have carried out any systematic research on the simplification of the PTC. In this paper, a stepwise simplification method for the PTC strategy is proposed. Firstly, by using the equivalent transformation, the prediction process is simplified without affecting the control performance of the PTC. On this basis, the cost function is further simplified with additional presuppositions, and the optimization process is replaced by honeycomb-structured space partitioning for optimal voltage vector searching. Therefore, the computation burden caused by the multiple calculations in traditional PTC is greatly reduced. In addition, this paper provides the implementation details of the proposed control strategy. Moreover, the comparison between the traditional PTC and two simplified PTC is carried out in the evaluation of the transient performance, steady-state errors, control characteristics, computation burden, and compatibility with additional constraints. The experimental results prove the feasibility and effectiveness of the simplified algorithms, and this is beneficial to the future application of PTC strategy in the low-cost motor drive system. Moreover, the simplified PTC algorithm can achieve higher switching frequency, thereby improving the performance of torque and stator flux in the motor drive system with the application of new generation SiC power device.

Predictive Torque Control With Simple Duty-Ratio Regulator of PMSM for Minimizing Torque and Flux Ripples

In this paper, a new method for reducing the ripples of torque and flux is proposed for the predictive torque control (PTC) of permanent magnet synchronous motors. The conventional PTC uses equations to analyze the relationship between the electrical torque and voltage with a fixed magnitude of reference voltage. Consequently, flux and torque ripples increase significantly at low-speed operation. This paper proposes an improved PTC algorithm using a simple duty-ratio regulator. The proposed method will minimize the torque error by calculating an appropriate torque minimization function to mitigate the induced torque and flux ripple at low speed operation. This torque minimization function is synthesized into the space vector pulse-width modulation block to reduce the torque ripple induced owing to the fixed time duration. The proposed scheme considerably reduces the torque and flux ripples and establishes a fast-dynamic response of the torque in the transient state. Simulation and experimental results show that the proposed method achieves a more efficient steady-state performance and a faster step response compared with the conventional PTC.

Predictive Torque Control Algorithm for a Five-Phase Induction Motor Drive for Reduced Torque Ripple With Switching Frequency Control

This article presents a progressive comparison of predictive torque control (PTC) algorithms for a five-phase induction motor fed with a two-level five-phase inverter. The extension of three-phase PTC to the five-phase motor, introduces current harmonics of the order 10n $\pm$ 3 (n = 0, 1, 2.. .), which are not responsible for torque/flux production. The inherent disadvantage of PTC is being a variable frequency algorithm, which adds complexity to the design of magnetic components. This disadvantage of PTC can be overcome by applying dwell time ( $t_{s}$ ) to the voltage vectors obtained through a minimum torque ripple condition, which is determined based on the ripple equation. In the proposed algorithm, a set of synthetic voltage vectors are generated and used for reducing flux and torque error through cost function. The use of synthetic voltage vector simplifies the cost function and further reduces the computation time. A two-step delay compensation is adopted to improve the precision of the control algorithm further. In each control cycle, an optimal switching time is calculated to reduce the torque ripple and to maintain the constant switching frequency. In this article, a modified PTC is proposed, which targets to achieve constant switching frequency, eliminate the xy-subspace current harmonics, reduce the torque ripple, and minimize the computational burden involved in the conventional predictive torque control algorithm. The experimental study is carried out on a laboratory prototype. The results show compliance with all the experimental study with different PTC algorithms with different sampling frequencies, and the modified cost function.

Improvised predictive torque control strategy for an open end winding induction motor drive fed with four‐level inversion using normalised weighted sum model

Open end winding induction motor (OEWIM) drives are better alternate for multi-level inverter fed induction motor drives. OEWIM drives can be used in industries and electric vehicles but they entail ripple-free torque. Predictive torque control (PTC) strategy offers high dynamic performance and lesser ripple in torque, flux when compared with direct torque control. Classical PTC involves high switching frequencies and empirical methods to select weighting factors. The selection and tuning of weighting factors are cumbersome. In this article, a new normalised weighted sum model (WSM) based PTC of four-level inverter fed OEWIM is introduced to curtail torque, flux ripples, switching frequency and enhance the selection of weighting factors. The proposed algorithm uses multi-objective cost function and the optimisation of cost function is performed by using normalised WSM. The normalisation of individual cost function simplifies the selection of weighting factors to select optimal voltage vector. As a result, the proposed PTC offers all the features of classical PTC and overcomes the difficulties involved in classical PTC. Simulation and experimental studies are performed on dual inverter fed OEWIM with four-level inversion. The effectiveness of proposed algorithm is verified by comparing proposed PTC algorithm with classical PTC algorithm.

Torque Ripple Minimization of Predictive Torque Control for PMSM With Extended Control Set

To reduce the steady-state torque ripples for permanent-magnet synchronous motor drives with predictive torque control (PTC), this paper proposes a modified PTC algorithm based on the extended control set (ECS-PTC). In the proposed algorithm, more candidate voltage vectors are extended to the control set, which forms the ECS, and then, the torque control precision could be improved and the torque ripples will be reduced. More attractive thing is that a new voltage vector synthesis method is deigned in ECS-PTC, and the corresponding predictive model and cascaded predictive algorithm are set up on the basis of this method. With the help of them, the optimal vector can be selected from ECS in a shorter control period of time, and its amplitude is also optimized at the same time to achieve high-precision control effects for torque and flux. In addition, the three-phase duty ratios of the output vector can be determined in ECS-PTC directly, without the help of space vector pulse width modulation. The experimental results show that ECS-PTC has excellent dynamic torque performance, and it also has more stable torque control performance and better execution efficiency at the same time.