Deadbeat-direct Torque Research Articles

Novel deadbeat direct torque and flux control for interior permanent magnet synchronous motor

Novel deadbeat direct torque and flux control for interior permanent magnet synchronous motor

An Optimal Maximum Torque Per Active Flux and Field Weakening Operation for Deadbeat Direct Torque Control Based IPMSM Drive

An Optimal Maximum Torque Per Active Flux and Field Weakening Operation for Deadbeat Direct Torque Control Based IPMSM Drive

Deadbeat-Direct Torque and Flux Control of a Brushless Axial-Flux Magnetic-Geared Double-Rotor Machine for Power-Splitting HEVs

A deadbeat-direct torque and flux control (DB-DTFC) for brushless axial-flux magnetic-geared double-rotor machines (AMGDRMs) is presented in this paper. The AMGDRM is employed as a power-splitting component in hybrid electric vehicles (HEVs) to enable speed decoupling between the internal combustion engine (ICE) and load. Since the rigid connection between the ICE and the drive train is replaced by the AMGDRM, fast torque control of the AMGDRM is required for the ICE speed regulation. Furthermore, the ICE torque contains abundant harmonics, inevitable sinusoidal components are introduced to the modulating rotor torque for torque balance, and further to the PM rotor torque owing to the magnetic-gear effect. Since both the PM rotor of the AMGDRM and the traction motor contribute to the hybrid electric system total torque output (i.e., torque coupling), the cascaded traction motor should compensate the PM rotor torque ripple actively to guarantee smooth total output torque. However, proportional-integral (PI) regulator suffers from limited bandwidth and thus could not realize accurate torque decoupling. Therefore, DB-DTFC, where torque and flux linkage are decoupled and respectively achieve their reference commands within two sampling periods, i.e., deadbeat responses, is proposed to enable a faster and more robust ICE speed control and accurate torque decoupling. The DB-DTFC law is derived and discrete-time close-loop current and flux linkage observers of the AMGDRM are developed. The proposed scheme and its superiorities are experimentally validated on an AMGDRM prototype test bench.

Improved Deadbeat-Direct Torque and Flux Control for PMSM With Less Computation and Enhanced Robustness

Deadbeat-direct torque and flux control (DB-DTFC) significantly improves the torque response performance compared with the conventional direct torque control. However, the existing DB-DTFC algorithm suffers from a relatively heavy computational burden due to its intricate derivation. Thus, two simplified DB-DTFC algorithms for permanent magnet synchronous machines (PMSMs) are proposed in this article to relieve the burden. The first one is based on the stator flux differential, and the second one is based on the complex power of PMSM. Furthermore, the performance of DB-DTFC highly relies on the accuracy of machine parameters. Thus, modified stator flux observer and electromagnetic torque observer are designed to enhance parameter robustness based on disturbance observer theory. The theoretical derivation of the proposed methods is investigated in-depth. Finally, both simulation and experimental results verify that the proposed deadbeat methods can maintain the deadbeat performances with a reduced computational burden. Meanwhile, the modified observer can help the deadbeat algorithms work well when machine parameters change.

Computationally Efficient Deadbeat Direct Torque Control Considering Speed Dynamics for a Surface-Mounted PMSM Drive

In this article, a computationally efficient deadbeat (DB) direct torque and flux control is investigated for surface-mounted permanent magnet synchronous motor (SPMSM) drives. Unlike conventional DB direct torque control (DB-DTC), the proposed DB-DTC technique simultaneously manipulates the electromagnetic torque and stator flux along with rotor speed in a combined DB controller structure. Moreover, a simple and computationally efficient DB-DTC structure is achieved through a novel DB controller design in the stationary reference frame and it ensures an improved transient performance within finite time steps. The feedforward terms are properly designed to mitigate the effects of system uncertainties. The stability of the proposed DB-DTC has been proven and discussed in detail through Lyapunov theory and eigenvalue analysis. The designed DB-DTC strategy has been simulated via MATLAB/Simulink software and practically evaluated on a laboratory SPMSM drive with TI digital signal processor TMS320F28335. Extensive comparative evaluation with conventional proportional-integral (PI)-DTC and DB-DTC corroborate an improved control performance in speed/torque dynamic response (fast rise time) as well as reductions in torque and flux ripples under tough practical conditions (e.g., speed and torque step-changes, and speed reversal test cases) with significantly reduced computational complexity.

Simulation Research on Deadbeat Direct Torque and Flux Control of Permanent Magnet Synchronous Motor

Direct torque control (DTC) is widely used in a permanent-magnet synchronous motor (PMSM), but it has its own shortcomings caused by high torque ripple. Deadbeat-direct torque and flux control (DB-DTFC) is a new torque and flux method compared with DTC. However, the traditional DB-DTFC is often based on rotor-flux-oriented control. The reference voltage of the stator is computed in a rotor-flux-oriented coordinate system, and the solution involves solving quadratic equations, which will increase the burden of computational processing. To improve the computation of the reference voltages and the control performance, this paper proposes a new DB-DTFC algorithm and introduces its basic principles. First, the proposed DB-DTFC algorithm uses the forward Euler equation to solve the reference voltage in a stator-flux-oriented coordinate system. Second, the discrete mathematical model is used to predict the next control current to achieve deadbeat control. Third, the structural model of the proposed DB-DTFC is constructed. Finally, the simulation model of the proposed DB-DTFC algorithm is built with a MATLAB/Simulink platform. The simulation results prove that the proposed DB-DTFC algorithm can achieve better control performance in torque and flux control compared with the DTC algorithm and SVM-based direct torque and flux control (SVM-DTFC) algorithm. In particular, the torque index of DB-DTFC is reduced about 6% in a limited speed range in comparison with the DTC algorithm.

Antidisturbance Sliding Mode-Based Deadbeat Direct Torque Control for PMSM Speed Regulation System

Deadbeat direct torque control (DBDTC) calculates the voltage vector based on the motor mathematical model and tracks the torque and flux reference within only one sampling cycle. However, in the traditional DBDTC, the reference torque is generated by a speed PI controller, which presents a low dynamic and poor precision, particularly under external disturbances. To sort out this issue, this article proposes an improved DBDTC control method basing on the sliding mode strategy. First, an antidisturbance sliding mode controller (ASMC) is presented which is superior in offering a fast and accurate reference torque for DBDTC. Along the way, an extended sliding mode disturbance observer is introduced, which estimates total disturbances and compensates the sliding mode controller. To reduce the chattering of sliding mode control, a novel reaching law is proposed. This novel reaching law introduces a system-state variable in the exponential terms of power reaching law and, meanwhile, includes an adaptive exponential reaching action. By this means, it increases system convergence rate to the sliding mode surface while suppressing sliding mode chattering. Finally, both simulation and experimental results show that the proposed control method has a better performance in terms of torque ripple reduction and speed dynamic response.

Real-Time Loss Minimizing Control of Induction Machines for Dynamic Load Profiles Under Deadbeat-Direct Torque and Flux Control

This article develops a real-time loss minimizing control technique on induction machines for dynamic load profiles. Steady-state loss minimization has been well addressed. However, when the steady-state optimal control is applied to a highly dynamic load profile, more losses are induced during transients due to the slow rotor flux dynamics. Several heuristic methods have been developed for real-time loss reduction, but they are not designed for minimum losses. Loss-minimizing flux trajectories have been generated by dynamic programming but require prior information of load profiles. In this article, a real-time loss minimizing control technique is developed for applications without prior information of load profiles. It resembles the loss-minimizing stator flux trajectory generated by a modified dynamic programming method, which generates the best practical solution for unknown load profiles. Both simulation and experimental results demonstrate the energy saving capability of the proposed method. Significant energy savings have been demonstrated on traction applications.

Flux Observer-Based MTPF/MTPV-Operation With Low Parameter Sensitivity Applying Deadbeat-Direct Torque and Flux Control

Through a combination of flux and current observers, deadbeat-direct torque and flux control for interior permanent magnet synchronous machines has preferred features comparing to the existing current vector control (CVC). These include simpler flux weakening control, less parameter sensitivity with increasing speed due to the Gopinath-style flux observer and evading of anti-windup strategies at the inverter voltage limit. The operation throughout the entire torque-speed range can be accomplished with a single control law. For the second flux weakening region, the algorithm inherently achieves the maximum torque per flux (MTPF) operation by applying the square-root-condition (SRC). In contrast to CVC, no look-up-table nor solving the parameter-dependent MTPF equation is required. In this article, the equivalence of the SRC method to the conventional MTPF strategy is demonstrated analytically, graphically, in simulation, and through experimental results without any stability problems. A sensitivity analysis regarding the machine parameters and iron losses compares and evaluates both methods. Superior performance of the SRC algorithm compared to the conventional method is proven.

Model Predictive Torque Control for Dual Three-Phase PMSMs with Simplified Deadbeat Solution and Discrete Space-Vector Modulation

Unprecise voltage vectors applied in conventional model predictive control (MPC) would cause additional ripples in electromagnetic torque. To eliminate the problem, this article proposes an improved model predictive torque control (MPTC) based on deadbeat solution and discrete space-vector modulation (DSVM) for dual three-phase permanent magnet synchronous machines (PMSMs). First, deadbeat-direct torque and flux control (DB-DTFC) algorithm is applied and simplified, so that the computational burden can be reduced. Second, the virtual voltage vectors (VVVs) are adopted in dual three-phase voltage vector space to reduce voltage harmonics. Also, the DSVM is further proposed in this VVVs based vector space to generate more voltage vectors. After that, the simplified DB-DTFC and the DSVM scheme are artfully combined to select suitable voltage vector candidates for the MPTC, and the best one is then chosen to control the dual three-phase PMSMs. Finally, both simulation and experimental results are given to verify the effectiveness of the proposed method.

Non‐linear deadbeat direct torque and flux control for switched reluctance motor

Non‐linear deadbeat direct torque and flux control for switched reluctance motor

Digital Implementation of Deadbeat-Direct Torque and Flux Control for Permanent Magnet Synchronous Machines in the M–T Reference Frame

In the traditional deadbeat-direct torque and flux control in the M-T reference frame (DB-DTFC-MT) scheme, the stator flux is calculated with the current model, and one-step delay in the digital system is neglected, which results in poor robustness to parameter variations and a serious oscillation in both the stator flux and torque, especially in the low-speed range. In this article, the digital implementation of DB-DTFC-MT is studied. First, the DB-DTFC-MT scheme considering the one-step delay in the digital system is deduced. Second, digital stator flux observer and current observer are developed to predict the stator flux and current in the next sampling instant. By using the predicted stator flux and torque, the oscillation caused by the one-step delay is eliminated and real deadbeat control is realized. Moreover, the robustness of the system to parameter variations is qualitatively evaluated. Although the system shows some sensitivity to the permanent magnet flux, it has strong robustness to the stator resistance and inductances, especially the d-axis inductance. Hence, a larger estimated d-axis inductance can be used in the system for reducing the pulsation in the d-axis current when tracking sinusoidal torque. All the proposed control designs are validated on a real-time control platform based on dSPACE DS1103.

Accurate Discrete-Time Modeling for Improved Torque Control Accuracy for Induction Machine Drives at Very Low Sampling-to-Fundamental Frequency Ratios

Operations at low sampling-to-fundamental frequency (S2F) ratios of induction machines are required for high-power or high-speed applications. The traditional indirect field-oriented control is open-loop control on torque, which is sensitive to machine parameters and degrades at low S2F ratios. Deadbeat-direct torque and flux control (DB-DTFC) is closed-loop control on torque but also degrades at low S2F ratios with inaccurate discrete-time approximations. This article presents a methodology of accurate discrete-time modeling for the flux and current observer and the deadbeat controller used in DB-DTFC. The current, flux, and torque estimations are improved with the proposed observer model at very low S2F ratios. The torque control is enhanced and insensitive to machine parameters under high-speed low-S2F-ratio conditions. The increased computational time of the proposed model is insignificant for real-time implementations.

Self-Sensing via Flux Injection With Rapid Servo Dynamics Including a Smooth Transition to Back-EMF Tracking Self-Sensing

Self-sensing control at zero and low speed has been widely implemented and studied by many researchers. This technique is based on injecting a high-frequency voltage or current into the motor to estimate the motor position and speed from the measured motor quantities like current or voltage. Tracking the motor back-EMF or flux signal has been used to control motors during medium- and high-speed operations. This article proposes a high-frequency flux injection (HFFI) based self-sensing using deadbeat-direct torque and flux control to control permanent magnet servo motor at zero and low speed with ideally zero torque ripple, unlike the standard current or voltage injection techniques. The HFFI is combined with a back EMF self-sensing technique to control the motor during medium- and high-speed operations. This article also proposes a method for a smooth transition between these two methods. The proposed controller is used to control different types of slightly salient servo motors during dynamic servo operations.

Deadbeat Direct Torque and Flux Control for Permanent Magnet Synchronous Motor Based on Stator Flux Oriented

Direct torque control (DTC) has become a widely acceptable alternative to field-oriented control in permanent magnet synchronous motor (PMSM) drives. Deadbeat direct torque and flux control (DB-DTFC) is a significant improvement over the classical DTC. However, there are some aspects that can be improved, such as insufficiently small electromagnetic torque ripple, unsmooth dynamic response, heavy computation burden, and relatively weak robustness to motor parameters variation. To improve the operation performance, an advanced DB-DTFC strategy is proposed in this article. First, the algorithm model based on stator flux oriented coordinate system is deduced. On this basis, the basic principle of proposed DB-DTFC is presented. Second, a novel graphical analysis method is proposed to help illustrate the proposed strategy. Third, a general solution method is proposed to solve the reference stator voltage, which is a key variable for the DB-DTFC. Finally, the stability of system is analyzed. Theoretical and experimental comparisons between the proposed DB-DTFC and the conventional DB-DTFC are done. The results show that the performance in the aspects of electromagnetic torque and stator current ripples reduction, dynamic response, computation burden, and robustness to motor parameters variation are all improved in the proposed DB-DTFC.

Direct Torque Control for Three-Phase Open-End Winding PMSM With Common DC Bus Based on Duty Ratio Modulation

This article introduces the classical direct torque control (DTC) to a three-phase open-end winding permanent magnet synchronous motor with common dc bus for the first time. The electromagnetic torque and the stator flux are controlled at the same time. However, the zero-sequence current is not suppressed, and the ripples of the electromagnetic torque and stator flux are large. To improve the operation performance of this drive system, a DTC based on a duty ratio modulation (DRM-DTC) is proposed. First, a deadbeat zero-sequence current controller is proposed in the DRM-DTC to suppress the zero-sequence current. Second, another strategy, which is based on a graphical analysis method and a simple deadbeat direct torque and flux controller, is proposed to optimize the duty ratio of the active voltage vector. Thus, the electromagnetic torque and stator flux ripples can be reduced. Finally, an optimized pulsewidth modulation implementation strategy is proposed in the DRM-DTC to further reduce the switching frequency of inverters. The classical DTC and the proposed DRM-DTC are compared through simulation and experiment, and the results verify the effectiveness of the proposed strategy.

Extending High-Speed Operating Range of Induction Machine Drives Using Deadbeat-Direct Torque and Flux Control With Precise Flux Weakening

Flux weakening techniques have been developed for field-oriented control (FOC) drives to achieve the maximum torque capability above the base speed. Deadbeat-direct torque and flux control (DB-DTFC) has the advantages of precise torque and flux control and reduced parameter sensitivity compared to FOC, thus it has the benefit of more consistently achieving the maximum torque capability in the flux weakening region more accurately. This paper introduces a flux weakening strategy for DB-DTFC. Considering voltage and current limits, a simple solution to the optimal trajectory for the stator flux magnitude is derived to achieve the maximum feasible torque over the entire operating range. Results show that the speed control is extended to a significantly higher range beyond the base speed. Torque control is less sensitive to machine parameters and has better dynamics in the flux weakening region compared with the traditional FOC drives. Self-sensing is also investigated in the flux weakening region. Challenges of self-sensing are addressed to significantly extend the high-speed operating range.

Torque Ripple Minimization in Six-Step PMSM Drives via Variable and Fast DC Bus Dynamics

Six-step modulated drive systems have been shown to have higher power density and lower switching loss than pulsewidth modulation drive systems. It has also been shown that by manipulating the dc bus voltage, six-step mode can drive permanent magnet synchronous machines (PMSMs) over a wide speed range, and maintain the machine operating point on the maximum torque per ampere curve below the base speed to reduce the machine copper loss. However, high torque ripple exists while in this type of six-step mode. This paper develops the control design methodologies to leverage the variable and fast dc bus manipulation, provided by two-step finite-settling-step dc-to-dc converter control, to minimize torque ripple in six-step PMSM drives. Two torque control algorithms: existing voltage angle based torque control and deadbeat-direct torque and flux control are used to evaluate torque ripple reduction capability and energy savings potential of six-step PMSM drive systems.

Deadbeat-Direct Torque and Flux Control of Wound Field Synchronous Machine at Low Sampling to Fundamental Frequency Ratios

Enhancements to the deadbeat-direct torque and flux control (DB-DTFC) of wound field synchronous machines (WFSMs) are proposed allowing for operation at low sampling frequency to fundamental frequency ratios. Discrete-time current and flux linkage observers, which properly model WFSM d-q and d-f cross-coupling are formed using a Taylor series approximated sampled Laplace approach. The effect of the Taylor series order on the discretization error and model accuracy is examined. The torque curve to determine the inverter voltage commands is derived from the flux linkage model coefficients. Experimental comparison of the WFSM torque response is made between the classical DB-DTFC with current and flux observers formed using a z-transform approach and the torque line derived from a forward Euler method and the newly proposed observers and torque curve.

Minimising torque ripple of SRM by applying DB‐DTFC

Since the traditional direct torque control (DTC) of switched reluctance motors (SRMs) has the shortcomings of large torque ripple and non-constant switching frequency, this study proposes the deadbeat-direct torque and flux-linkage control (DB-DTFC) method for SRM. By analysing the basic principles of SRM, a discrete-time model is established to predict the future states of the SRM drive system. With DB-DTFC, the stator flux and torque can be manipulated during each pulse-width modulation cycle to minimise torque ripple during operation. As a result, the proposed DB-DTFC can minimise the torque ripple as well as apply space-vector modulation with a constant switching frequency. Finally, to verify its effectiveness, DB-DTFC was applied to the 15 kW three-phase 12/8-pole SRM test bench in real time and the results are compared with conventional DTC.