Application of Optimal Switching Using Adaptive Dynamic Programming in Power Electronics

In this dissertation, optimal switching in switched systems using adaptive dynamic programming (ADP) is presented. Two applications in power electronics, namely single-phase inverter control and permanent magnet synchronous motor (PMSM) control are studied using ADP. In both applications, the objective of the control problem is to design an optimal switching controller, which is also relatively robust to parameter uncertainties and disturbances in the system. An inverter is used to convert the direct current (DC) voltage to an alternating current (AC) voltage. The control scheme of the single-phase inverter uses a single function approximator, called critic, to evaluate the optimal cost and determine the optimal switching. After offline training of the critic, which is a function of system states and elapsed time, the resulting optimal weights are used in online control, to get a smooth output AC voltage in a feedback form. Simulations show the desirable performance of this controller with linear and nonlinear load and its relative robustness to parameter uncertainty and disturbances. Furthermore, the proposed controller is upgraded so that the inverter is suitable for single-phase variable frequency drives. Finally, as one of the few studies in the field of adaptive dynamic programming (ADP), the proposed controllers are implemented on a physical prototype to show the performance in practice. The torque control of PMSMs has become an interesting topic recently. A new approach based on ADP is proposed to control the torque, and consequently the speed of a PMSM when an unknown load torque is applied on it. The proposed controller achieves a fast transient response, low ripples and small steady-state error. The control algorithm uses two neural networks, called critic and actor. The former is utilized to evaluate the cost and the latter is used to generate control signals. The training is done once offline and the calculated optimal weights of actor network are used in online control to achieve fast and accurate torque control of PMSMs. This algorithm is compared with field-oriented control (FOC) and direct torque control based on space vector modulation (DTC-SVM). Simulations and experimental results show that the proposed algorithm provides desirable results under both accurate and uncertain modeled dynamics

Anti-Disturbance Cooperative Fuzzy Tracking Control of Multi-PMSMs Low-Speed Urban Rail Traction Systems

A directed-graph-based cooperative control scheme is proposed, to improve the synchronization performance and reduce its error under disturbance between multiple permanent magnet synchronous traction motors in low-speed urban rail transit. First, each motor is supposed to an agent of multi-agent system, and the information between multiple motors can be transmitted through communication topology network, which ensure the consistency of the response of each agent. Then, considering that the load torque of the motor is disturbed during operation, a finite-time disturbanceobserver is proposed to estimate the unknown load disturbance, thus guarantee the anti-disturbance ability of the system. Besides, the nonlinear parts of the dynamic model are approximated by fuzzy logic systems, and a second-order sliding mode differentiator is designed to avoid the direct derivation of virtual control law and the problem of differential explosion. Finally, the system is proved to be finite-time stable. The feasibility and effectiveness of the proposed control scheme are verified by the hardware-in-the-loop platform

Comparative Study of Sensorless Control Methods of PMSM Drives

Recently, permanent magnet synchronous motors (PMSMs) are increasingly used in high performance variable speed drives of many industrial applications. This is because the PMSM has many features, like high efficiency, compactness, high torque to inertia ratio, rapid dynamic response, simple modeling and control, and maintenance-free operation. In most applications, the presence of such a position sensor presents several disadvantages, such as reduced reliability, susceptibility to noise, additional cost and weight and increased complexity of the drive system. For these reasons, the development of alternative indirect methods for speed and position control becomes an important research topic. Many advantages of sensorless control such as reduced hardware complexity, low cost, reduced size, cable elimination, increased noise immunity, increased reliability and decreased maintenance. The key problem in sensorless vector control of ac drives is the accurate dynamic estimation of the stator flux vector over a wide speed range using only terminal variables (currents and voltages). The difficulty comprises state estimation at very low speeds where the fundamental excitation is low and the observer performance tends to be poor. The reasons are the observer sensitivity to model parameter variations, unmodeled nonlinearities and disturbances, limited accuracy of acquisition signals, drifts, and dc offsets. Poor speed estimation at low speed is attributed to data acquisition errors, voltage distortion due the PWM inverter and stator resistance drop which degrading the performance of sensorless drive. Moreover, the noises of system and measurements are considered other main problems. This paper presents a comprehensive study of the different methods of speed and position estimations for sensorless PMSM drives. A deep insight of the advantages and disadvantages of each method is investigated. Furthermore, the difficulties faced sensorless PMSM drives at low speeds as well as the reasons are highly demonstrated. Keywords: permanent magnet, synchronous motor, sensorless control, speed estimation, position estimation, parameter adaptation

Sensorless control for limp-home mode of EV applications

PhD ThesisOver the past decade research into electric vehicles’ (EVs) safety, reliability and availability has become a hot topic and has attracted a lot of attention in the literature. Inevitably these key areas require further study and improvement. One of the challenges EVs face is speed/position sensor failure due to vibration and harsh environments. Wires connecting the sensor to the motor controller have a high likelihood of breakage. Loss of signals from the speed/position sensor will bring the EV to halt mode. Speed sensor failure at a busy roundabout or on a high speed motorway can have serious consequences and put the lives of drivers and passengers in great danger. This thesis aims to tackle the aforementioned issues by proposing several novel sensorless schemes based on Model Reference Adaptive Systems (MRAS) suitable for limp-home mode of EV applications. The estimated speed from these schemes is used for the rotor flux position estimation. The estimated rotor flux position is employed for sensorless torque-controlled drive (TCD) based on indirect rotor field oriented control (IRFOC). The capabilities of the proposed schemes have been evaluated and compared to the conventional back-Electromotive Force MRAS (back-EMF MRAS) scheme using simulation environment and a test bench setup. The new schemes have also been tested on electric golf buggies. The results presented for the proposed schemes show that utilising these schemes provide a reliable and smooth sensorless operation during vehicle test-drive starting from standstill and over a wide range of speeds, including the field weakening region. Employing these new schemes for sensorless TCD in limp-home mode of EV applications increases safety, reliability and availability of EVs

RECENT TECHNIQUES ON OBSERVER DESIGN FOR DISTURBANCE ESTIMATION AND REJECTION IN PERMANENT MAGNET SYNCHRONOUS MOTORS

Permanent magnet synchronous machines (PMSMs) (either motor or generator) have attracted attention of research community comparing to other types of AC machines in the recent two decades. PMSMs are preferable than other AC machines in terms of large power-factor, broad speed of operation, compact proportions, and effective operation. Unfortunately, different sources of nonlinearities, model uncertainties, and external perturbations determine severity in a design of accurate speed control scheme for PMSMs. In the era of developing science and technologies, many advanced control solutions are proposed to control PMSMs. Although new solutions show their advantages comparing to traditional methods in terms of performance evaluation, practical realization of those algorithms could require expensive hardware with high computational capabilities. Furthermore, people in industry with less knowledge about the motor control may experience difficulties in using such advanced controllers on their own. Traditional PI/PID control schemes still work as a major control technique in modern industry, and in motor control as well. Numerous positive facts about the PI/PID schemes make such superiority of these control schemes. Firstly, the PI/PID can be implemented easily on most industrial software and hardware components. Secondly, while its scheme has clear mechanism of operation, most industrial processes could be controlled via the PI/PID scheme. These schemes are good in terms of small number of parameters to tune and tuning process itself could be very straightforward. Finally, implementation of the PI/PID controllers would require smaller time comparing to most proposed complex control solutions. It is studied that the traditional PI/PID controllers usually cannot deal with unpredictable disturbances, which in turn leads to degraded performance of an overall control system. Inspired by the advantages and widespread application of PI/PID control structure in industry, we propose a disturbance observer based composite control scheme which uses the PI-like controller for the feedback regulation and disturbance observer for estimation of lumped disturbances presented in a PMSM control system. Under this circumstance, this thesis work proposes three different control solutions for PMSM such as High-order disturbance observer-based composite control (HDOBCC), Disturbance rejection PI (DR-PI) control, and Hierarchical optimal disturbance observer-based control (HODOBC). Furthermore, to deeply understand the similarity and difference between the traditional disturbance observer-based control (DOBC) and active-disturbance rejection control (ADRC) schemes, this thesis also presents results of unification of these two control approaches in the speed control of a PMSM. The HDOBCC as the first method proposed in this thesis is designed to improve reference speed tracking performance of a PMSM under various operational conditions. A structure of the HDOBCC comprises a fuzzy-PI controller in a feedback stabilization part and novel high-order disturbance observer in a feedforward compensation part of the speed control system. The proposed controller is designed based on the research questions such as: firstly, although a fixed gain traditional PI controller is able to present satisfactory performance at some extent, still it does not guarantee such performance when sudden disturbances occur in a system; secondly, many disturbance observers designed for a PMSM in literature consider only a load torque as a disturbance, neglecting model uncertainties and parameter variations in design stage. Therefore, the HDOBCC is proposed such that it utilizes a fuzzy approach to determine parameters of the PI controller to overcome limitations of the fixed gain PI controller. Furthermore, the proposed scheme includes a high-order disturbance observer, which estimates not only the load torque, but also disturbances due to model uncertainties and parameter variations. Moreover, extended simulation and experimental studies are conducted to affirm performance of the HDOBCC under various form of the load torque. In addition to commonly tested step form of a load torque, severe forms of the load torque such as triangular form and sinusoidal form are tested with the proposed controller. Stability analysis of the closed-loop HDOBCC system is further provided. The next proposed method, DR-PI control, is designed by seeking answer for questions such as: firstly, although the traditional DOBC scheme applied for PMSM shows reasonable results in a PMSM control, its design can be limited to known actual parameters of the PMSM. In practice, actual parameters are usually not available, hence it could be hard to design the traditional DOBC in the absence of a plant information; secondly, for tuning a PI controller the traditional Ziegler-Nichols tuning approach still remains as one of the popular tuning approaches, however it does not give a rigorous explanation on selection of parameters during its design. Consequently, to answer these questions, the DR-PI control is designed for the PMSM speed control. The DR-PI control is designed such that it has a simple PI-like structure with intrinsic disturbance rejection mechanism determined by the parameters of a filtering element, desired plant model, and desired closed-loop system. Simulation and experimental validations are provided to validate the performance of the DR-PI. Furthermore, gain tuning mechanism and stability analysis of the closed-loop DR-PI-based speed control are also presented. The HODOBC scheme as a third proposed control scheme targets on the next research questions as: first, parameters of the traditional PI controller are mostly obtained by trial-and-error approach, which in turn may not guarantee satisfactory results; in a cascaded PMSM control, the outer speed loop performance highly depends on the performance of the inner current loop. The well-tuned speed control loop may degrade in performance, if the inner current loop is not tuned properly. To address these questions, we propose the HODOBC scheme, which consists of optimal PIlike controller in the feedback stabilization part and optimal extended-state observer (ESO) in the disturbance compensation part. The proposed HODOBC showed better performance when it is compared with other traditional controllers via experiments. Stability analysis is provided via the root locus approach. The study on unification of the DOBC and ADRC schemes has the following research question: the DOBC and ADRC are both used in estimation of total disturbance, but these two schemes are considered differently in literature. Hence, the study of both scheme is conducted to show the condition at which these two schemes show identical performance. The analysis of the traditional DOBC and ADRC schemes concludes that both scheme are equivalent in terms of performance characteristics if the dynamical delays of disturbance observers in each scheme are same. The results of analysis reveal that both scheme can be utilized to design a robust control system for PMSM, i.e. once the gains of disturbance observers can be calculated under the DOBC framework, further the disturbance rejection mechanism can be achieved via the ADRC framework. The results of PMSM control with the proposed control schemes have been tested on the Lucas-Nuelle DSP-based experimental setup

Dinamički odziv nove adaptivne modificirane povratne Legendrove neuronske mreže upravljanja sinkronim motorom s permanentnim magnetima za električni skuter

Because an electric scooter driven by permanent magnet synchronous motor (PMSM) servo-driven system has the unknown nonlinearity and the time-varying characteristics, its accurate dynamic model is difficult to establish for the design of the linear controller in whole system. In order to conquer this difficulty and raise robustness, a novel adaptive modified recurrent Legendre neural network (NN) control system, which has fast convergence and provide high accuracy, is proposed to control for PMSM servo-driven electric scooter under the external disturbances and parameter variations in this study. The novel adaptive modified recurrent Legendre NN control system consists of a modified recurrent Legendre NN control with adaptation law and a remunerated control with estimation law. In addition, the online parameter tuning methodology of the modified recurrent Legendre NN control and the estimation law of the remunerated control can be derived by using the Lyapunov stability theorem and the gradient descent method. Furthermore, the modified recurrent Legendre NN with variable learning rate is proposed to raise convergence speed. Finally, comparative studies are demonstrated by experimental results in order to show the effectiveness of the proposed control scheme.S obzirom da električni skuter pogonjen servo sustavom sa sinkroni motor s permanentnim magnetima ima nelinearnu dinamiku i vremenski promjenjive parametre, njegov dinamički model nije jednostavno odrediti u svrhu dizajniranja linearnog regulatora. Kako bi se riješio taj problem te povećala robusnost predložen je sustav upravljanja korištenjem adaptivne modificirane povratne Legendrove neuronske mreže za upravljanje skuterom pogonjenim servo sustavom sa sinkronim motorom uz prisustvo vanjskog poremećaja i promjenjivih parametara. Predloženo upravljanje ima brzu konvergenciju i visoku preciznost. Sustav upravljanja sastoji se od modificirane povratne Legendrove neuronske moreže s adaptivnim zakonom upravljanja i estimacijom. Dodatno, \u27on-line\u27 podešavanje parametara takvog sustava može se dobiti korištenjem Ljapunovljevog teorema o stabilnosti sustava i gradijente metode. Modificirana povratne Legendrove neuronska mreža s promjenjivim vremenom učenja predložena je za povećanje brzine konvergencije. Ispravnost predložene sheme upravljanja provjerena je eksperimentalno

Field weakening and sensorless control solutions for synchronous machines applied to electric vehicles.

184 p.La polución es uno de los mayores problemas en los países industrializados. Por ello, la electrificación del transporte por carretera está en pleno auge, favoreciendo la investigación y el desarrollo industrial. El desarrollo de sistemas de propulsión eficientes, fiables, compactos y económicos juega un papel fundamental para la introducción del vehículo eléctrico en el mercado.Las máquinas síncronas de imanes permanentes son, a día de hoy la tecnología más empleada en vehículos eléctricos e híbridos por sus características. Sin embargo, al depender del uso de tierras raras, se están investigando alternativas a este tipo de máquina, tales como las máquinas de reluctancia síncrona asistidas por imanes. Para este tipo de máquinas síncronas es necesario desarrollar estrategias de control eficientes y robustas. Las desviaciones de parámetros son comunes en estas máquinas debido a la saturación magnética y a otra serie de factores, tales como tolerancias de fabricación, dependencias en función de la temperatura de operación o envejecimiento. Las técnicas de control convencionales, especialmente las estrategias de debilitamiento de campo dependen, en general, del conocimiento previo de dichos parámetros. Si no son lo suficientemente robustos, pueden producir problemas de control en las regiones de debilitamiento de campo y debilitamiento de campo profundo. En este sentido, esta tesis presenta dos nuevas estrategias de control de debilitamiento de campo híbridas basadas en LUTs y reguladores VCT.Por otro lado, otro requisito indispensable para la industria de la automoción es la detección de faltas y la tolerancia a fallos. En este sentido, se presenta una nueva estrategia de control sensorless basada en una estructura PLL/HFI híbrida que permite al vehículo continuar operando de forma pseudo-óptima ante roturas en el sensor de posición y velocidad de la máquina eléctrica. En esta tesis, ambas propuestas se validan experimentalmente en un sistema de propulsión real para vehículo eléctrico que cuenta con una máquina de reluctancia síncrona asistidas por imanes de 51 kW

Advanced Computational-Effective Control and Observation Schemes for Constrained Nonlinear Systems

Constraints are one of the most common challenges that must be faced in control systems design. The sources of constraints in engineering applications are several, ranging from actuator saturations to safety restrictions, from imposed operating conditions to trajectory limitations. Their presence cannot be avoided, and their importance grows even more in high performance or hazardous applications. As a consequence, a common strategy to mitigate their negative effect is to oversize the components. This conservative choice could be largely avoided if the controller was designed taking all limitations into account. Similarly, neglecting the constraints in system estimation often leads to suboptimal solutions, which in turn may negatively affect the control effectiveness. Therefore, with the idea of taking a step further towards reliable and sustainable engineering solutions, based on more conscious use of the plants' dynamics, we decide to address in this thesis two fundamental challenges related to constrained control and observation. In the first part of this work, we consider the control of uncertain nonlinear systems with input and state constraints, for which a general approach remains elusive. In this context, we propose a novel closed-form solution based on Explicit Reference Governors and Barrier Lyapunov Functions. Notably, it is shown that adaptive strategies can be embedded in the constrained controller design, thus handling parametric uncertainties that often hinder the resulting performance of constraint-aware techniques. The second part of the thesis deals with the global observation of dynamical systems subject to topological constraints, such as those evolving on Lie groups or homogeneous spaces. Here, general observability analysis tools are overviewed, and the problem of sensorless control of permanent magnets electrical machines is presented as a case of study. Through simulation and experimental results, we demonstrate that the proposed formalism leads to high control performance and simple implementation in embedded digital controllers