Control Of Permanent Magnet Synchronous Machines Research Articles

Low-Complexity Deadbeat Model Predictive Current Control for Open-Winding PMSM Drive With Zero-Sequence Current Suppression

The application of model predictive current control (MPCC) on the open-winding permanent magnet synchronous machine (PMSM) drive system confronts the challenge of complexity due to the enumeration process and the multiobjective cost function evaluation. In this article, a new low-complexity MPCC is proposed to eliminate the online enumeration process and the cost function evaluation. In the proposed scheme, the reference voltage vector components are calculated based on the deadbeat principles. Then, the optimal voltage vector that matches the reference vector is selected from the control set based on predefined optimization criteria. These criteria are defined offline by solving the conventional current control cost function in the 3-D ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula> ), utilizing new 3-D analysis. The proposed control scheme is compared with the conventional finite control set (FCS)-MPCC and the existing 3-D-MPCC schemes using MATLAB simulation and hardware-in-the-loop (HIL) results. Compared with conventional FCS-MPCC and 3-D-MPCC schemes, the proposed control scheme presents the same salient features, such as fast dynamic response, low output current/torque ripple, and zero-sequence current suppression. The computational complexity of the proposed control scheme is much lower than the conventional FCS-MPCC.

Multiple reference frame-based current harmonic control for interior PMSMs considering motional EMF

For permanent magnet synchronous machines (PMSMs), current harmonics need to be controlled under two kinds of conditions. Under the first condition, the current harmonics caused by the non-sinusoidal back-electromotive force (EMF) and the dead time of inverters should be suppressed. Under the second condition, specific current harmonics should be injected to suppress the torque ripple of motors. Therefore, the accurate control of current harmonics is critical. It has been found that the original multiple reference frame (MRF)-based control algorithm cannot effectively achieve the control of current harmonics at high speeds. For the currents in MRFs, motional EMF was dominant rather than induced EMF at higher speeds. As a result, the original MRF-based control algorithm does not work at high speeds. To solve this problem, this paper proposed a novel MRF-based control algorithm that considers motional EMF. Furthermore, this paper achieved decoupling control of the current harmonics in MRFs for interior PMSMs. With the proposed control algorithm, the current harmonics of interior PMSMs can be controlled at both high and low speeds. Under the influence of non-sinusoidal back EMF and the dead time of the inverter, the effect of current harmonic control was verified on a laboratory test bench.

Compensation of Selective Current Harmonics for Switching-Table-Based Direct Torque Control of Dual Three-Phase PMSM Drives

Current harmonics are ubiquitous in dual three phase (DTP) permanent magnet synchronous machine (PMSM) drives. Due to back electromotive force (EMF) distortion, significant current harmonics are generated in the DTP-PMSM system. The influence of back EMF harmonics is investigated in this paper and a novel switching-table-based direct torque control method to compensate the selected current harmonics caused by the back EMF harmonics is proposed. It shows that by employing different optimal action time durations for voltage vectors in the z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> subspace and setting the synthetic voltage vectors to non-zero, the stator flux harmonics caused by the back EMF harmonics can be selectively compensated, as verified by experiments.

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.

Active Harmonic Suppression of Low-Reactance Multiphase Slotless Permanent Magnet Synchronous Machines

Harmonic suppression plays a key role in the current control of dual-three-phase (DTP) permanent magnet synchronous machines (PMSMs). Existing current control schemes are scarcely verified by designed DTP motor prototypes or consider the impact of inherent electromotive force (EMF) harmonics quantitatively. Also, few studies discuss the low-reactance case, which requires additional concerns for current prediction and modulation. Therefore, this article conceives and presents an improved deadbeat-based active current harmonic control scheme particularly for low-reactance PMSMs. From the aspect of motor design and finite-element analysis, the quantitative effect of EMF harmonics on control behaviors is analyzed. Based on the nonideal mathematical model (MMM) of the designed slotless PMSM with analyzed EMF harmonics, the proposed scheme is first introduced theoretically and verified by simulation. Subsequently, the slotless PMSM prototype fabrication and control experiments validate the proposed scheme and recognize the necessity of active harmonic suppression.

CCS-MPC for PMSM with Wide Speed Range based on Variable DC-Bus Voltage Control applied to the Flywheel Energy Storage System

In this paper, in order to verify the effect of variable DC-bus voltage control, CCS-MPC (Continuous-Control-Set MPC) control is used to research the control of PMSM (Permanent-Magnet Synchronous Machine) in a wide speed range. In order to maximize the speed of PMSM, the MTPA control, the field weakening control and the variable DC-bus voltage control are applied in the different speed range of PMSM. CCS-MPC can eliminate the control delay by controlling the predicted step size. When CCSMPC is applied to the PMSM control with a wide speed range, the advantages of strong adaptability of CCS-MPC can be exerted.

Harmonic-Separation-Based Direct Extraction and Compensation of Inverter Nonlinearity for State Observation Control of PMSM

Nonideal switching characteristics of voltage source inverter (VSI) will result in distortions in both phase currents and reference voltages of a permanent magnet synchronous machine (PMSM) drive system, which will also consequently introduce ripples into the output speed and shaft torque, and result in a performance deterioration in the state observation control. To solve this issue, a method of directly extracting and compensating the nonlinear voltage disturbance due to VSI nonlinearity employed in PMSM drives is proposed in this paper. Firstly, the distorted voltage due to VSI nonlinearity is directly extracted via a harmonic separation scheme, which can be easily compensated by a proportional integral controller afterwards. Since both 6th harmonic and DC terms of dq -axis distorted voltages due to VSI nonlinearity are well compensated, the proposed method shows sufficiently good performance under both $i_{d}=0$ and maximum torque per ampere controls ( $i_{d} ), as verified on two prototype PMSMs being salient pole and non-salient pole, respectively, both developed for a low-speed rotary actuator. In addition, the application of proposed method to state observation controls such as the model-based sensorless control and the deadbeat predictive current control, is finally investigated. Test results manifest that the proposed method can effectively improve the accuracy of observed rotor position/speed, and the ability of current tracking.

A Novel Matrix Transformation for Decoupled Control of Modular Multiphase PMSM Drives

When multiphase drives are used for specific applications, the modular solutions are preferred as they use consolidated power electronics technologies. The literature reports two modeling approaches for multiphase machines having a modular configuration of the stator winding. The first approach is the vector space decomposition (VSD) that models the energy conversion as for an equivalent three-phase machine. The main alternative to the VSD is the multistator (MS) modeling that emphasizes machine modularity in terms of torque production. Both approaches have advantages and disadvantages for multiphase machines with a modular structure. Therefore, this article aims to combine the VSD and MS approaches, defining a new matrix transformation and, hence, developing a new modeling approach for multiphase machines with a modular structure. The proposed transformation allows a decoupled and independent torque control of the sets composing the machine, preserving the torque regulation's modularity. Together with a new vector control scheme, it has been applied to a modular permanent magnet synchronous machine (PMSM) with a nonstandard spatial shift between windings. Experimental results are presented for a nine-phase PMSM prototype with a triple-three-phase stator winding configuration.

Model Predictive Control of PMSM Drives Based on General Discrete Space Vector Modulation

Apart from the basic voltage vectors of a inverter, virtual vectors can be generated by discrete space vector modulation (DSVM) technique. Thus, DSVM based-model predictive control (MPC) can achieve reduced torque ripples and current harmonics for a permanent magnet synchronous machine (PMSM) drive. However, the computational burden is also significantly increased due to a large number of candidate voltage vectors. In this article, a novel DSVM-based MPC is proposed, which can select the optimal voltage vector and calculate three-phase duty ratios in an efficient way without enumerating all the candidate voltage vectors, hence achieving good performance with low computational burden. The effectiveness of the proposed method is validated by the presented experimental results.

Fault-Tolerant Hybrid Current Control of Dual Three-Phase PMSM With One Phase Open

A fault-tolerant hybrid current control is proposed for dual three-phase permanent magnet synchronous machines (PMSMs) with one phase open in this article. The maximum torque control, minimum copper loss control, and single three-phase mode control are unified in the proposed method, which is a combination of single three-phase mode control and maximum torque control with different percentages. When the percentage of single three-phase mode control ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> ) varies from 0% to 100%, the hybrid current control transitions from maximum torque control ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k \,\,=0$ </tex-math></inline-formula> %) to minimum copper loss control ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k\,\,=50$ </tex-math></inline-formula> %) and then to single three-phase mode ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k =100$ </tex-math></inline-formula> %). Therefore, the hybrid current control can be switched among the aforementioned three control methods easily and smoothly. Meanwhile, it can be a mixed mode with a tradeoff between the maximum torque control and the minimum copper loss control, such as the minimum copper loss control for a given torque within the full torque range, which can be achieved by changing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> . The smoothness of transition among the maximum torque control, minimum copper loss control, and single three-phase mode control is verified by experimental results on a prototype machine.

Robust Speed and Current Control With Parametric Adaptation for Surface-Mounted PMSM Considering System Perturbations

Permanent magnet synchronous machines (PMSMs), which include a dynamic combination of electronics and mechanics, have been widely deployed in emerging mechatronics systems. However, there exist undesirable perturbations in the electrical and mechanical parameters of the PMSM with different operating conditions, which deteriorate the control performance and pose risks to the connected power conversion systems. To improve the robustness of PMSM control considering multiple system perturbations, a robust control strategy with parametric adaptation is established in this article, where a desired-compensation adaptive robust current controller and a disturbance-observer-based speed controller are proposed. Such controls are capable of achieving robust regulations of stator currents and rotor speed, while accurately estimating machine parameters including stator resistance, stator inductance, and flux linkage of the permanent magnet. When these parameters drift away from their nominal values, the observers/estimators of the proposed algorithms calibrate the prestored data and compensate for the control errors, and thus the control behavior of the PMSM under parameter mismatches will not degrade. A current and speed cascaded control system is configured to integrate the proposed algorithms for robustness considerations of the PMSM. Extensive simulations and experimental results are demonstrated to validate the effectiveness of the proposed robust control strategies.

Robust Predictive Torque Control of Permanent Magnet Synchronous Machine Using Discrete Hybrid Prediction Model

In the prediction stage of finite control set-predictive torque control for permanent magnet synchronous machine (PMSM), the mismatched parameters will inevitably bring about the predictive errors, which will cause the wrong selection of voltage vector in the optimization stage, and even affect the stability of the entire control system. In order to eliminate the prediction errors, a discrete hybrid prediction model-based predictive torque control (DHPM-PTC) of PMSM is proposed to improve robustness. In the stator current prediction model, the traditional open-loop prediction model is abandoned, and the closed-loop model prediction equation is established. In the stator flux prediction model, this article gets rid of the traditional open-loop integral prediction model, and establishes the closed-loop flux prediction model integrating the current model and the voltage model. Secondly, the stability and parameter design principles of the closed-loop current prediction model and the closed-loop flux prediction model are discussed. Finally, the verification of the proposed algorithm is made on a PMSM test platform. The test results indicate that the proposed DHPM-PTC is superior to the traditional predictive torque control (T-PTC) in dynamic, steady and robust performances.

Discrete-Time SMO Sensorless Control of Current Source Converter-Fed PMSM Drives With Low Switching Frequency

In this article, a sensorless control method for medium- and high-speed operation is proposed for a current source converter (CSC)-fed permanent magnet synchronous machine (PMSM) with low switching frequency. The low switching frequency as well as inverter-side capacitor filter can cause great challenges in controller and rotor speed/position observer design, especially under higher speed operation due to the limited updates per fundamental cycle and approaching to the LC resonant point. To improve the system dynamic performance and attenuate the LC resonant, a multi-loop controller with capacitor voltage control was added into conventional field-oriented control. Moreover, an exact discrete-time sliding mode observer based sensorless strategy with adaptive filter is proposed to improve the rotor speed and position estimation accuracy as well as robustness to system uncertainty. The effectiveness of the proposed method is verified on a transformerless CSC-fed PMSM drives with both simulation and experiment.

Modeling and Bumpless Switching Control of Symmetrical Dual Three-Phase PMSM in Two Operating Modes

This paper presents a frequency-domain model of the symmetrical dual three-phase permanent magnet synchronous machine (PMSM) in two working modes. Compared with traditional time-domain model, the presented frequency-domain model has simple expression and can be easily used in control system design and compensation. Furthermore, a frequency-model-based field oriented control (FOC) scheme for this machine is proposed. In this control scheme, parameters of proportional-integral (PI) controllers are analytically designed which can flexibly adjust the steady and dynamic performance of the entire closed-loop system. Moreover, this control strategy allows the drive system to bumpless switch between two operating modes without stopping. Finally, the developed control scheme was verified via simulations and experiments.

Design and Simulation of Direct and Indirect Back EMF Sliding Mode Observer for Sensorless Control of PMSM

Abstract This article compares two sensorless control algorithms for a permanent magnet synchronous machine (PMSM) based on the back-EMF sliding mode observer (SMO). Indirect SMO (I-SMO) treats the back-EMF voltages as a disturbance. Direct SMO (D-SMO) considers back-EMF voltages as state-space variables. The same phase-locked loop (PLL) is used for both observers for extraction of the rotor position and speed values from the observed back-EMF voltages. In a sensorless control, the observed speed is used as feedback for the PI controller, and the observed position is used in the Park transformations. Both observers have been implemented and tested with standard field-oriented control. Simulation results indicate rather comparable speed and position estimation precision for both, but the D-SMO indicates slightly higher precision in steady-state. Even more, a tuning procedure of the D-SMO is more straightforward when compared to the I-SMO. Thus, the D-SMO was further verified experimentally with the OP 5600 rapid prototyping device and with a 350 W PMSM drive. Experimental results of the D-SMO are included at the end of the paper.

Control of Dual Three-Phase Permanent Magnet Synchronous Machine Based on Five-Leg Inverter

This paper proposes a current control of dual three-phase permanent magnet synchronous machine (PMSM) based on five-leg inverter. The five-leg inverter can be utilized to drive dual three-phase PMSM with full torque at slow speed when the conventional dual three-phase voltage source inverter (VSI) has a faulty inverter leg. Usually, the common leg in the five-leg inverter may have severe current stress. By dedicated selection of which two phases as a pair to share the common leg, its current rating is approximately half of current rating of other legs. Meanwhile, the five-leg inverter can fully fulfill the vector space decomposition control for dual three-phase PMSM, which has the same dynamical performance as the conventional dual three-phase VSI. However, due to the asymmetry of five-leg inverter non-linearity, the currents of dual three-phase PMSM are unbalanced. To mitigate this issue, the five-leg inverter non-linearity compensation is also introduced and investigated in this paper, whose effectiveness is verified by comparative experiments on a prototype dual three-phase PMSM.

Predictive direct torque control for permanent-magnet synchronous machines based on duty ratio modulation

In this paper, Two-step model predictive control based on duty ratio modulation of permanent magnet synchronous machine (PMSM) is proposed. There is a large amount of computation in the two-step predictive control. In this paper, a fast vector selection method is proposed to solve the problem of computational complexity. The proposed voltage vector selection method avoids the complete enumeration for testing all feasible voltage vector, and the calculation method of duty are discussed. This control method achieves a constant switching frequency, and the torque fluctuation is smaller, inheriting the advantages of predictive control response speed. To investigate the effectiveness of the proposed method, two-step predictive direct torque control based on duty ratio modulation (TSPTC-DM), comparison of one-step predictive direct torque control based on duty ratio modulation (OSPTC-DM) and finite control set model predictive torque control (FCS-MPTC) is shown.

Improved rotor flux observer for sensorless control of PMSM with adaptive harmonic elimination and phase compensation

In this paper, a sensorless control strategy of a permanent magnet synchronous machine (PMSM) based on an improved rotor flux observer (IFO) is proposed. Due to the unknown integral initial value and the high harmonics caused by current sampling and inverter nonlinearities, the flux linkage estimated by traditional rotor flux observer may be inaccurate. In order to address these issues, a self-adaptive band-pass filter (SABPF) is designed to eliminate the DC component and high-frequency harmonics of the estimated equivalent rotor flux linkage. Furthermore, in order to avoid that the design of PI parameter is influenced by the amplitude of equivalent rotor flux linkage, an improved phase-locked loop (IPLL) is employed to obtain the rotor speed and to normalize the estimated equivalent rotor flux linkage. In addition, angle shift caused by an SABPF is compensated to improve the accuracy of the estimated flux linkage angle. Besides, the parameter robustness of this method is analyzed in detail. Finally, simulation and experimental results demonstrate the effectiveness and parameter robustness of the proposed method.

Non‐linear MPC for winding loss optimised torque control of anisotropic PMSM

For a non-linear anisotropic permanent magnet synchronous machine (PMSM), a prediction model for model predictive control (MPC) considering effects like cross-coupling and saturation is developed in a straight forward procedure. The objective of the designed MPC is either tracking of reference currents or torque tracking. Both approaches use the projected fast gradient method (PFGM) as optimisation algorithm. The latter approach makes look-up-tables for current references obsolete and additionally minimises winding losses. This two approaches are compared in a simulation study with a state of the art PI controller.

Enhanced Robust Deadbeat Predictive Current Control for PMSM Drives

In permanent-magnet synchronous machine (PMSM) applications, traditional deadbeat predictive current control (DPCC) utilizes the PMSM model to evaluate the expected voltage vector and applies it to the inverter through space vector pulse width modulation (SVPWM). Once the expected voltage vector is inaccurate, the torque ripple and speed fluctuation are amplified. There are two main factors that cause the inaccurate voltage vector, namely model parameter mismatch, and current measurement error. To enhance the robustness of DPCC, first, this paper proposes an accurate PMSM voltage model with nonperiodic and periodic disturbance models. Second, this paper proposes a novel current and disturbance observer (NCDO) which is able to predict future stator currents and disturbances caused by model parameter mismatch and current measurement error simultaneously. Finally, the scheme of the proposed DPCC with NCDO is presented to enhance the robustness. This paper presents a comparative study of two types of algorithms, namely traditional DPCC and the proposed DPCC with NCDO. The theoretical verification, simulation results, and experimental results are demonstrated to verify the effectiveness of the proposed DPCC with NCDO.