An Advanced Model Predictive Current Control of Synchronous Reluctance Motors

Synchronous reluctance motors (SynRMs) have, in recent years, attracted much attention due to their high-efficiency output and nature of their construction denoted by the lack of expensive magnetic materials, thus cheapening the overall cost whilst increasing in robustness. These benefits have made the SynRM a strong contender against other established electric motors in the market. Similarly, model predictive current control (MPCC) has recently become a powerful advanced control technology in industrial drives, being, therefore, a suitable choice for SynRM drives granting overall high control performance and efficiency. However, current prediction in MPCC requires a high number of voltage vectors (VVs) synthesizable by the converter, being therefore computationally demanding. Accordingly, the main goal of this work is the development and analysis of a more efficient and advanced MPCC for SynRMs whilst reducing the computational burden and delivering good control performance in contrast with the standard MPCC. Therefore, to achieve the intended levels of efficiency and control performance in SynRM drives, a combination of two control strategies is developed, which combines hysteresis current control (HCC) and MPCC, dubbed in this work HCC-MPCC. Furthermore, the SynRM dynamic model equations comprising the magnetic saturating effects and iron losses are presented through a detailed theoretical and computational analysis of the drive’s control. Conclusively, the developed HCC-MPCC for SynRM drives is analyzed through thorough and rigorous experimental tests alongside the standard MPCC, whose obtained results are detailed comprehensively.Os motores síncronos de relutância (SynRMs) têm, nos últimos anos, atraído muita atenção devido às suas características construtivas, designadamente pela falta de materiais magnéticos caros, depreciando assim o custo em geral; e simultaneamente pelo aumento em robustez. Esses benefícios tornaram o SynRM num forte concorrente face a outros motores elétricos existentes no mercado. Da mesma forma, o modelo preditivo de controlo de corrente (MPCC) tornou-se recentemente numa poderosa estratégia de controlo avançado em acionamentos industriais, sendo, portanto, uma escolha adequada para acionamentos envolvendo SynRMs, garantindo elevado desempenho e eficiência de controlo. No entanto, a previsão da corrente no MPCC requer um grande número de vetores de tensão (VVs) sintetizáveis pelo conversor, sendo, portanto, exigente computacionalmente. Consequentemente, o objetivo principal deste trabalho é o desenvolvimento e análise de um MPCC mais eficiente e avançado para SynRMs, reduzindo a carga computacional e, simultaneamente, demonstrando um bom desempenho de controlo em contraste com o MPCC clássico. Portanto, para atingir os níveis pretendidos de eficiência e desempenho de controlo em acionamentos com SynRMs, uma combinação de duas estratégias de controlo é desenvolvida, combinando o controlo de corrente de histerese (HCC) e MPCC, denominado neste trabalho HCC-MPCC. Além disso, as equações do modelo dinâmico do SynRM, compreendendo os efeitos de saturação magnética e as perdas de ferro, são apresentadas através de uma análise teórica e computacional detalhada do controlo do acionamento. Conclusivamente, o HCC-MPCC desenvolvido para acionamentos com SynRMs é analisado por meio de testes experimentais conjuntamente com o MPCC padrão, sendo os resultados obtidos detalhados de forma abrangente

Finite control set model predictive direct current control strategy with constraints applying to drive three-phase induction motor

In this, work the finite control set (FCS) model predictive direct current control strategy with constraints, is applied to drive three-phase induction motor (IM) using the well-known field-oriented control. As a modern algorithm approach of control, this kind of algorithm decides the suitable switching combination that brings the error between the desired command currents and the predicated currents, as low as possible, according to the process of optimization. The suggested algorithm simulates the constraints of maximum allowable current and the accepted deviation, between the desired command and actual currents. The new constraints produce an improvement in system performance, with the predefined error threshold. This can be applied by avoiding the switching combination that exceeds the limited values. The additional constraints are more suitable for loads that require minimum distortion in harmonic and offer protection from maximum allowable currents. This approach is valuable especially in electrical vehicle (EV) applications since its result offers more reliable system performance with low total harmonics distortion (THD), low motor torque ripple, and better speed tracking

Evolutionary Gaps Stator Current Control of Multi-phase Drives Balancing Harmonic Content

Multiphase machines are increasingly used in research and industry applications due to their inherent advantages. Stator current control is a common strategy for this type of systems. The most important issue it must face is regulation of currents in the torque producing plane and the harmonic plane. For this task, finite control set model predictive control (FCS-MPC) constitutes an interesting alternative to methods using modulation. However, the implementation of FCS-MPC is characterized by a high computational demand, limiting the sampling frequency. This work proposes a predictive algorithm that needs less computation time. As a result, the sampling period can be reduced while producing predictive control. This brings about several benefits resulting from improved current tracking. The proposed method avoids the combinatorial optimization phase of standard FCS-MPC, which is the most time-consuming part. The algorithm is based on physical insights obtained from the application of FCS-MPC to multiphase drives leading to the concept of evolutionary gaps regions. The experimental results for a five-phase motor demonstrate improved performance. Moreover, the method is flexible enough to balance the tradeoff appearing between the torque producing plane and the harmonic plane.Ministerio de Ciencia e Innovación TED2021-129558B-C22 PID2021-125189OBI0

Memorized approach for implementation of space vector pulse width modulation

Space Vector Pulse Width Modulation, SV-PWM, is an efficient technique for dc to ac voltage conversion through an inverter of power electronics devices. This paper presents a proposed memorized approach for SV-PWM implementation. The work bases on storing six symmetric pattern formats of space vector in a memory structure. Then, sequential fetching of the stored data provides basic optimum firing triggers TRA, TRB and TRC for driving the inverter switching elements. Main contribution of the paper is controlling the inverter output frequency online through adjusting the fetching period. Moreover, the presented approach characterizes by simplicity, cost effective and activity in achieving the space vector technique. Validity of the proposed method was practically examined through a hardware built workbench, which based on the microcontroller ATMEGA 2560. Meanwhile, the optimum firing sequences were exported to a MATLAB algorithm to check the harmonics, which are expected to accompany the inverter output ac power

A review of model predictive control strategies for matrix converters

Matrix converters are a well-known class of direct AC-AC power converter topologies that can be used in applications in which compact volume and low weight are necessary. For good performance, special attention should be paid to the control scheme used for these converters. Model predictive control strategy is a promising, straightforward and flexible choice for controlling various different matrix converter topologies. This work provides a comprehensive study and detailed classification of several predictive control methods and techniques, discussing special capabilities they each add to the operation and control scheme for a range of matrix converter topologies. The paper also considers the issues regarding the implementation of model predictive control strategies for matrix converters. This survey and comparison is intended to be a useful guide for solving the related drawbacks of each topology and to enable the application of this control scheme to matrix converters in practical applications

Predictive Control Applied to Matrix Converters: A Systematic Literature Review

Power electronic devices play an important role in energy conversion. Among the options, matrix converters, in combination with predictive control, represent a good alternative for the power conversion stage. Although several reviews have been undertaken on this topic, they have been conducted in a non-systematic manner, without indicating how the studies considered were chosen. This paper presents results from a systematic literature review on predictive control applied to matrix converters that included 142 primary papers, which were selected after applying a defined protocol with clear inclusion and exclusion criteria. The study provides a detailed classification of predictive control methods and strategies applied to different matrix converter topologies. Research findings require to be understood in combination to develop a common understanding of the topic and ensure that future research effort is based on solid premises. In light of this, this study identifies and characterizes different predictive control techniques and matrix converter topologies through systematic literature review. The results of the review indicate that interest in the area is increasing. A number of open questions in the field are discussed

Speed Sensorless Control of SPMSM Drives for EVs with a Binary Search Algorithm-Based Phase-Locked Loop

© 1967-2012 IEEE. This article presents a new method to extract accurate rotor position for the speed sensorless control of surface-mounted permanent-magnet synchronous motors (SPMSMs), based on the back electromotive force (EMF) information. The concept of finite control set-model predictive control is employed, and its cost function is related to the back EMF. An optimal voltage vector is selected from several given voltage vectors by comparing their fitness values. Moreover, the position space is divided into four sectors, and the fitness of each sector boundary is calculated and compared. The rotor position is first located in the sector surrounded by two boundaries that minimize the cost function. Then the selected sector is split into two parts, and the binary search algorithm is applied to reduce the sector area to improve the accuracy of position estimation. To overcome the drawback of the back EMF-based sensorless scheme, an I-f startup method is employed to accelerate the motor to the desired speed. An experiment has been carried out to compare the performance of the proposed method and the conventional phase-locked loop (PLL) in terms of steady-state and transient conditions

Novel Model Predictive Control of a PM Synchronous Motor Drive; Design of the Innovative Structure, Feasibility and Stability Analysis, Efficient Implementation, Experimental Validation

This text focuses on advanced torque control of permanent magnet synchronous motor drives. A novel modular structure is introduced to simplify the design and implementation of Model Predictive Control (MPC). The layout consists of the control and the control framework. The dynamic control is the novel virtual flux controller, which is used to reach desired reference values, and the state observer, which is used to reduce effects of non-modeled system properties. The control framework consists of static mappings to simplify the control problem. Besides the alpha-beta and d-q transformations, a reference generation procedure is used to generate state references based on optimality criteria. Also, the actuation scheme is part of the control framework and defines the available input set and the resulting control properties. The first method actuates directly switch states, i.e. voltage vectors, which yield an integer set named Finite Control Set (FCS). The other method actuates duty cycles via modulation, which yield the Convex Control Set (CCS). A stability analysis is carried out for both, CCS-MPC and FCS-MPC. MPC is called stable, if it is feasible and convergent, which can be ensured using the main MPC stability theorem. However, stringent computation requirements make it difficult to apply the theorem in practice. Thus, the Lyapunov based MPC approach is applied to the motor drive, which provides stability guarantees independent of the prediction horizon. A stability constraint based on control Lyapunov functions (CLF) ensures convergence to the origin and the resulting optimal control problem is shown to be feasible for all time. In other words, a control input can be found at each sampling instant, which satisfies all constraints and yields a stable closed-loop system. The properties of CCS-MPC are derived using a nonlinear controller and the constrained closed-loop system is shown to be stable in the sense of Lyapunov. The stability properties of FCS-MPC are more complex due to the integer input set. Using set-theoretical methods, it is shown that a sufficiently large control error can be steered towards the origin. In other words, the proposed FCS-MPC is shown to be set stable, i.e. the control error is guaranteed to converge to a well-defined neighborhood of the origin. MPC requires that a Constrained Finite Time Optimal Control (CFTOC) problem is solved at each sampling time. Small sampling periods and limited computation capabilities of embedded hardware require the CFTOC to be sufficiently simple, which is achieved using the virtual flux model in the static reference frame. The problem size is contained using a sufficiently small prediction horizon and efficient algorithms are necessary to provide a result within a sampling period. The CFTOC of the proposed CCS-MPC is a (convex) linear or quadratic programming problem, which can be solved using existing efficient algorithms. To provide a minimal approach, an efficient algorithm is introduced to solve the one-step-ahead prediction CFTOC analytically. FCS-MPC results in a mixed integer programming problem and is therefore more difficult to solve with standard numerical methods. In practice, the CFTOC is solved by enumeration, which is combined with branch-and-bound, i.e. branch-and-cut, techniques to improve the computational efficiency. The control algorithms have been developed on a Software-in-the-Loop (SiL) platform based on Matlab/Simulink and the code is implemented without modification on an experimental test-bench. The evaluation confirms the design and implementation of CCS-MPC and FCS-MPC and shows good results in dynamic and steady-state operation. The two MPC approaches have complimentary properties, which can be used to target different applications. CCS-MPC achieves a constant switching frequency and is a promising alternative to proportional-integral (PI) vector control. The concept can be combined with different modulation schemes, e.g. the Symmetric Space Vector Modulation (SSVM) and the Discontinuous Space Vector Modulation (DSVM) are used in this text. FCS-MPC takes the inverter switching into account and achieves an approximately constant switching ripple but a variable switching frequency. The concept is most profitably applied to systems where a high sampling frequency compared to the switching frequency is desired, e.g. high power or servo drives. Moreover, FCS-MPC lacks Pulse Width Modulation (PWM) harmonics in its current spectrum. Consequently, it is advantageous in terms of acoustic noise since emphasized tones are missing. However, the distinguished PWM harmonics of CCS-MPC are simpler to filter. In summary, it can be said that the work on advanced torque control of permanent magnet synchronous motor drives has produced an innovative strategy. The introduction of a new structure has significantly simplified the model predictive control problem, the concept of stability in particular. Moreover, this structure results in the implementation of simple algorithms, which can be computed efficiently

Model predictive MRAS estimator for sensorless induction motor drives

Ph. D. ThesisThe project presents a novel model predictive reference adaptive system (MRAS) speed observer for sensorless induction motor drives applications. The proposed observer is based on the finite control set-model predictive control principle. The rotor position is calculated using a search-based optimization algorithm which ensures a minimum speed tuning error signal at each sampling period. This eliminates the need for a proportional integral (PI) controller which is conventionally employed in the adaption mechanism of MRAS observers. Extensive simulation and experimental tests have been carried out to evaluate the performance of the proposed observer. Both the simulation and the experimental results show improved performance of the MRAS scheme in both open and closed-loop sensorless modes of operation at low speeds and with different loading conditions including regeneration. The proposed scheme also improves the system robustness against motor parameter variations and increases the maximum bandwidth of the speed loop controller. However, some of the experimental results show oscillations in the estimated rotor speed, especially at light loading conditions. Furthermore, due to the use of the voltage equation in the reference model, the scheme remains sensitive, to a certain extent, to the variations in the machine parameters. Therefore, to reduce rotor speed oscillations at light loading conditions, an adaptive filter is employed in the speed extraction mechanism, where an adaptation mechanism is proposed to adapt the filter time constant depending on the dynamic state of the system. Furthermore, a voltage compensating method is employed in the reference model of the MP-MRAS observer to address the problems associated with sensitivity to motor parameter variation. The performance of the proposed scheme is evaluated both experimentally and by simulation. Results confirm the effectiveness of the proposed scheme for sensorless speed control of IM drives