Control Of Synchronous Machines Research Articles

Flux Linkage-Based Direct Model Predictive Current Control for Synchronous Machines

This article presents a flux linkage-based direct model predictive current control approach that achieves favorable performance both during steady-state and transient operation. The former is achieved by computing the optimal time instants at which a new switch position is applied to the converter. To this end, the future current behavior is not computed based on the machine inductances or inductance look-up tables; instead, flux linkage maps are utilized to predict the trajectory of the magnetic flux linkage, and subsequently of the current. This is advantageous for electric drives with noticeable magnetic nonlinearity in terms of saturation and/or cross-coupling effects. Hence, by using flux linkage maps in the prediction process, the evolution of the stator current can be calculated more accurately, enabling the controller to make better switching decisions. Moreover, the discussed predictive controller exhibits excellent dynamic performance owing to its direct control nature, i.e., the control and modulation tasks are performed in one computational stage rendering a dedicated modulation stage redundant. Three different drive systems based on permanent magnet synchronous motors are examined to demonstrate the effectiveness of the presented control approach.

An Improved Finite-Control-Set Model Predictive Flux Control for Asymmetrical Six-Phase PMSMs With a Novel Duty-Cycle Regulation Strategy

This work presents an improved finite-control-set model predictive flux control (FCS-MPFC) for asymmetrical six-phase permanent magnet synchronous machine (ASPMSM) with a novel duty-cycle regulation strategy. Firstly, virtual vector concept is adopted to suppress harmonic currents without additional cost function and the corresponding weighting factor. Then, 12 virtual vectors with higher voltage utilization are developed. Meanwhile, for the sake of strengthening steady-state performance, a novel duty-cycle regulation strategy incorporating the well-known Lagrange multiplier method is proposed. In this strategy, the reconfigurable set of voltage vectors (SVV), which consists of an active and a null virtual vector, can be determined without second modification, hence highly mitigating additional computation burden. Furthermore, in order to realize the purpose of unified switching frequency, the SVVs are implemented in terms of regular rather than irregular PWM signal pattern. Finally, experimental results prove the effectiveness of the proposed method.

Analysis of Current Error Space Phasor for a Space Vector-Modulated Indirect Matrix Converter

AC motor drives fed from current-controlled power electronic converters are popular on account of their superior steady-state and transient performance. Hysteresis control is a popular current control technique, which needs modifications to compensate for its demerits. Appraisal of current error as a space phasor for implementing the hysteresis controller is one such modification. Current error space phasor (CESP)-based hysteresis controller for voltage source inverters-fed motor drives are capable of achieving superior dynamic performance. With the modified hysteresis current controller, the drive operates at a constant switching frequency and ensures an optimal switching vector selection. This article presents the analysis of CESP for a space vector-modulated indirect matrix converter (IMC). The modified algorithm for space vector modulation of IMC accommodates for the variations in dc-link voltage since CESP is input voltage dependent. The boundary for the hysteresis current controller is calculated from the computed values of CESP. The time-varying nature of the hysteresis boundary ensures a constant switching frequency operation for IMC. Thus, a CESP-based hysteresis controller is proposed for the vector control of the IMC-fed permanent magnet synchronous machine (PMSM) drive. Experimental results are presented for validating the performance of the proposed controller.

Dead-Time Compensation Based on a Modified Multiple Complex Coefficient Filter for Permanent Magnet Synchronous Machine Drives

In field-oriented vector control of permanent magnet synchronous machine (PMSM) drives, the dead time will cause the 5th and 7th current harmonics in the stationary reference frame. They are mapped to the negative and positive 6th harmonic current in the synchronous reference frame (SynRF), resulting in torque ripple and deterioration of control performance. To solve this problem, a new dead-time compensation method is proposed in this article. First, a multiple complex coefficient filter is modified with a low-pass filter being paralleled to extract positive and negative sequence components of 6th harmonic from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axes currents. Then, based on the extracted harmonics, a voltage feedback path with variable gains is designed in SynRF to eliminate the dead-time effect. Finally, the proposed method is implemented in a prototyped PMSM drive to verify its effectiveness. Both the simulations and experiments indicate that the proposed method can significantly weaken the dead-time effect with no additional hardware. Besides, it is also proved robust to the variable machine parameters.

Sensorless Starting Control of Brushless Synchronous Machine (BSM) For Aircraft

In this paper, the sensorless starting control of brushless AC synchronous machine (BSM) for aircraft is studied. Low speed sensorless control technology is the key to accomplish full speed sensorless control. After injected the high frequency voltage with the three-phase AC excitation, the initial rotor position as the response is shown in this paper. On that basis, the sensorless control from starting to low-speed operation is accomplished. The performance of the starting control system is researched using MATLAB simulation software and the feasibility of the proposed scheme is demonstrated by simulation results.

Internal Model Loss Minimization Control of Permanent Magnet Synchronous Machine

Electric drives are very useful in propelling the wheels of hybrid electric vehicles (HEVs). They also play a central function in the electric power steering (EPS). This paper describes studies carried out on the efficiency optimization of an interior permanent magnet synchronous machine (IPMSM) for application in the EPS. An analytic loss- minimization algorithm for an IPMSM was derived and the optimization problem took into consideration copper, iron and stray losses. The proposed loss minimization algorithm is simple and cost effective to implement. From the simulations carried out, significant efficiency gains are possible with this model. The internal model control (IMC) method was employed to achieve current and speed control with acceptable sensitivity to machine parameters.

Modelling and vector control of dual three‐phase PMSM with one‐phase open

This study proposes a generic mathematical modelling and decoupling fault-tolerant vector control for dual three-phase permanent magnet synchronous machine (PMSM) with one phase open based on the conventional dual three-phase voltage source inverters, accounting for the mutual coupling between two sets of three-phase windings and the second harmonic inductance. When the dual three-phase PMSM has one phase open, the permanent flux-linkages are asymmetric and there are second harmonic components in the conventional synchronous reference frame (dq-frame). Based on the proposed mathematical modelling, both permanent magnet flux-linkages and currents become DC values in the dq-frame, and therefore, the conventional proportional integral (PI) controller can be used to regulate the dq-axis currents. Then, a decoupling fault-tolerant vector control with/without a dedicated feed-forward compensation is proposed to validate the correctness of the proposed mathematical modelling. Experimental results on a prototype dual three-phase PMSM with one phase open show that the second harmonic dq-axis currents can be well suppressed simply by the conventional PI controller and dedicated feed-forward compensation. It also shows that the decoupling fault-tolerant control based on the proposed modelling and control method has excellent dynamic performance, which is equivalent to the vector space decomposition control for the healthy machine.

A Family of Adaptive Position Estimators for PMSM Using the Gradient Descent Method

This article presents an evaluation of a family of adaptive position estimators (APEs) for anisotropy-based self-sensing control (SSC) of permanent magnet synchronous machine (PMSM). The APEs use the gradient descent method (GDM) to minimize a cost function and thus estimate the rotor position. Three different APEs have been developed in previous work and are revised in this article. Their dynamic performance is experimentally evaluated and compared with each other and with an encoder-based control using the same test bench. Simplified models are derived, which allow an analytic calculation of the individual speed control loop dynamics. The speed control bandwidth using the latest APE reaches almost 50% of when using a 2000 slot incremental encoder. In addition, this version of APE with GDM features parameter tuning based on analytic equations.

Deadbeat Harmonic Current Control of Permanent Magnet Synchronous Machine Drives for Torque Ripple Reduction

This article proposes a torque ripple reduction method based on speed ripples for permanent magnet synchronous machine (PMSM) drives. The torque ripples are first estimated based on speed harmonics at low speed. Based on that, the optimal harmonic current reference is then derived to fully compensate for the estimated torque ripple with minimum stator resistive loss. An extended state observer (ESO)-based deadbeat harmonic current controller (DHCC) is also presented in the rotor reference frame (RRF) to inject the optimal harmonic currents with good performance in steady state and transients. To extract the harmonic currents for harmonic current control and speed harmonics for torque ripple estimation with fast convergence and good accuracy, an adaptive linear neural (ADALINE) network-based filter is implemented in this article. Simulations and experiments are carried out to show the validity and performance of the proposed torque ripple reduction method.

Switching-Table-Based Direct Torque Control of Dual Three-Phase PMSMs With Closed-Loop Current Harmonics Compensation

In this article, the new closed-loop current harmonics compensation strategy is introduced in the switching-table-based direct torque control (ST-DTC) of dual three-phase permanent magnet synchronous machines. The harmonic current distortion is the major problem of ST-DTC of multiphase machines and is typically caused by the lack of control in the auxiliary x-y subspace under the vector space decomposition model. The synthetic vectors to obtain average zero voltage in the x-y subspace can be a solution. However, this cannot compensate for current harmonics; for example, due to dead-time and back-electromotive force distortion, which is also mapped into the x-y subspace. Therefore, in this article, the x-y voltage references are obtained by the closed control loop that controls x-y currents to zero. To modulate the nonzero x-y voltage reference, the new modulation approach employing voltage vector groups in the x-y subspace together with the new switching table is developed and incorporated into ST-DTC. Meanwhile, the analysis of the two available sets of 12 voltage vector groups illustrates a tradeoff between linear range in the x-y subspace and the dc-link voltage utilization rate. Finally, the effectiveness of the proposed ST-DTC strategy is verified through experiments and simulation.

An Online Estimation Method for Both Stator Inductance and Rotor Flux Linkage of SPMSM Without Dead-Time Influence

It is essential to estimate stator inductance and rotor flux linkage online for fault diagnosis and high-performance control of surface-mounted permanent magnet synchronous machine (SPMSM). Current injection method is a popular way to estimate the two parameters. However, the dead-time influence of voltage-source-inverter (VSI) and the stator inductance variation caused by injected current could not guarantee the converge of the estimation. To solve the above two problems, a method of injecting square-wave angle for online parameter estimation is proposed in this paper. Firstly, the theory of eliminating dead-time influence with and without square-wave angle injection is analysed. Next, the least square algorithm is adopted to estimate stator inductance without injection. Then the rotor flux linkage is estimated with injecting square-wave angle. The saturation effect on estimation is also analyzed and both parameters are estimated without acquiring any nominal values. At last, the appropriate amplitude and frequency of square-wave angle are determined by the parameter error and convergence analysis. The proposed method is evaluated with simulation and extensive experiments under various speed and load conditions. It is noteworthy that not less than two parameters are estimated without the dead-time influence and the injection will not cause inductance variation, which is different from the previous work.

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.

Disturbance Observer Based Predictive Current Control of Six-Phase Permanent Magnet Synchronous Machines for the Mitigation of Steady-State Errors and Current Harmonics

Multiphase machines, associated with state-of-the-art control strategies like finite control set model predictive control (FCS-MPC) are suitable for applications where reliability and disturbance-free operation are key factors. Although FCS-MPC provides good transient performance and straightforward design, the performance of the drive system is affected by model inaccuracies due to parameter mismatch and unmodeled dynamics, such as deadtime effects in the power converters and back-electromotive force harmonics. In this context, this article proposes a novel and robust disturbance observer based predictive current control strategy for six-phase permanent magnet synchronous machine drives that minimizes the steady-state errors due to parameter mismatch errors, while simultaneously reducing the amplitude of the fifth- and seventh-order current harmonics due to unmodeled dynamics, which are non-negligible in six-phase machines. Simulation and experimental results demonstrate the very good performance of the proposed strategy even when considering significant errors in the system parameters and different values of the deadtime in the power converters.

Continuous Control Set Nonlinear Model Predictive Control of Reluctance Synchronous Machines

In this article, we describe the design and implementation of a current controller for a reluctance synchronous machine (RSM) based on continuous control set nonlinear model predictive control (NMPC). A computationally efficient gray box model of the flux linkage map, the Gaussian-linear-arctangent (GLA) model, is proposed and employed in a tracking formulation, which is implemented using the high-performance framework for NMPC <monospace xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">acados</monospace> . The resulting controller is validated in simulation and deployed on a <monospace xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dSPACE real-time</monospace> system connected to a physical RSM. Experimental results are presented where the proposed implementation can reach sampling times in the range typical for electrical drives and can achieve large improvements in terms of control performance with respect to state-of-the-art classical control strategies.

A new hybrid virtual synchronous machine control structure combined with voltage source converters in islanded ac microgrids

The high potentiality of integrating renewable energies into a microgrid system using voltage source converters (VSCs) raises some system stability issues as a result of the absence of inertia in VSCs. The virtual synchronous machine (VSM) control concept was consequently introduced to mimic the properties of traditional synchronous machines (SMs). Several VSM controllers with different structures have been introduced in different studies. However, since all VSM swing equation-based models mimic traditional SMs, these models require the reconstruction of a converter controller with a different control structure. This paper proposes a new yet simple and straightforward way to implement a VSM control concept that offers several advantages, one of which is that the proposed hybrid virtual synchronous machine (HVSM) provides a wide stability region compared to a system based on a conventional droop controller. In fact, the proposed HVSM can be applied via modifying only the first low pass filter (LPF) in the power controller. This paper further presents a comparative comprehensive study of the proposed HVSM with the existing VSC based-droop control and VSC based-VSM control based on the islanded AC microgrid, which was introduced in previous work. The stability of the system has been evaluated on a small signal representation model while the performance of both systems has been validated and investigated in a time-domain simulation environment, namely a PSCAD/EMTDC. The results show promising and significant outcomes that will further extend the field of VSM research.

Online multi‐parameter estimation of permanent magnet synchronous machine with step‐pulse injection

Online estimation of the machine parameters is essential to fault diagnosis and high-performance control of permanent magnet synchronous machine (PMSM). The signal injection is an effective way to estimate machine parameters. However, the inductance variation caused by signal injection will result in difficulties for the estimated parameters to converge. At the same time, online parameters estimation brings heavy burden to the operation of control system. To solve these two problems, optimized inductance model is built with the step-pulse injection to improve the accuracy of estimation. Compared with the existing method, the step-by-step parameter estimation method is adopted and orders of feedback matrix are reduced, which improves the computation efficiency. The forgetting factor recursive least square (FFRLS) algorithm is adopted to estimate stator resistance, rotor flux linkage and d-, q-axes inductances without acquiring any nominal parameter. The minimum amplitude and appropriate frequency of step-pulse are determined by the parameter error and convergence analysis. The effectiveness of the proposed method is verified via a 1.5 kW PMSM drive platform.

A new simplified fundamental model‐based sensorless control method for surface‐mounted permanent magnet synchronous machines

For sensorless control of surface-mounted permanent magnet synchronous machines (SPMSMs), the major issue is in zero- and low-speed ranges. Since back-electromotive force (EMF) is proportional to speed, back-EMF based methods fail at zero and low speed. A solution considering the starting process and low speed sensorless control is presented. A simplified fundamental model-based method is proposed. Based on the simplified model, the measured stator currents in the stationary reference frame can be directly utilised for position estimation so that the sensorless control performance at low speed and starting is improved. Moreover, with the knowledge of rotor initial position sector information, a stable and reliable starting performance is achieved with the proposed method. The effectiveness of the proposed method is verified through experimental results.

Self-Adaptive Synergistic Optimization for Parameters Extraction of Synchronous Reluctance Machine Nonlinear Magnetic Model

For mechanism analysis and high-performance control of synchronous reluctance machine (SynRM), accurate and reliable parameter identification of nonlinear magnetic model is always required. However, the accuracy and robustness of traditional heuristic algorithms are restricted by incomplete individual performance evaluation and single population evolution mechanism. In this paper, we propose a self-adaptive synergistic optimization (SSO) algorithm for extracting the parameters of the model. A novel synergistic-performance evaluation is first established to classify candidates automatically. Then, a self-organized mechanism is proposed to select optimal evolution strategies designed for classified candidate solutions. Around the current best candidate, the exploration is guaranteed in priority. Meanwhile, a self-adaptive mechanism is introduced to select other candidates to construct more promising evolutionary direction. Thus, achieving a good balance between exploration and exploitation. The parameter estimation performance of SSO algorithm is evaluated through standard datasets of SynRM magnetic model obtained by the finite element analysis. Comprehensive experiment results demonstrate the competitiveness and effectiveness of the proposed SSO algorithm compared with other algorithms, especially in terms of the accuracy and robustness. According to these superiorities, it can be concluded that the proposed algorithms are promising parameter identification methods for SynRM nonlinear magnetic model.

A Basic Study on Virtual Synchronous Machine Control Applied to Solid State Transformer Composed of MMC and DAB

A Basic Study on Virtual Synchronous Machine Control Applied to Solid State Transformer Composed of MMC and DAB

An improved permanent‐magnet synchronous machine sensorless drive based on the fuzzy‐PI phase‐locked loop and the adjustable boundary‐layer FOSMO

This study proposes a variable boundary-layer full-order sliding-mode observer (FOSMO) with a fuzzy proportional plus integral (PI) phase-locked loop (PLL) for the sensorless control of a permanent-magnet synchronous machine (PMSM). The sigmoid switching function-based FOSMO, which includes feedback speed information, is presented and considered as the conventional method. To address the contradiction between the convergence performance and the chatter-reduction ability of the sliding-mode control, a fuzzy logic controller (FLC) is introduced to adjust the boundary-layer thickness according to the estimation error. Furthermore, a real-time parameter tuning module is integrated into the PI regulator of the conventional PLL to adjust its noise bandwidth. Hence, adverse effects of disturbance and external noise, especially under transient operations, can be eliminated. An overall PMSM sensorless field-oriented control scheme incorporating the proposed method is designed, and the corresponding experimental platform is constructed. Several groups of comparative experiments reveal that system chatters are largely reduced using the proposed method under both of the high- and low-speed running conditions and the dynamic anti-interference performance can also be significantly improved under load and speed disturbances. Therefore, the feasibility and effectiveness of the proposed variable boundary-layer FOSMO + fuzzy-PI PLL method are validated.