Development and Implementation of Some Controllers for Performance Enhancement and Effective Utilization of Induction Motor Drive

The technological development in the field of power electronics and DSP technology is rapidly changing the aspect of drive technology. Implementations of advanced control strategies like field oriented control, linearization control, etc. to AC drives with variable voltage, and variable frequency source is possible because of the advent of high modulating frequency PWM inverters. The modeling complexity in the drive system and the subsequent requirement for modern control algorithms are being easily taken care by high computational power, low-cost DSP controllers. The present work is directed to study, design, development, and implementation of various controllers and their comparative evaluations to identify the proper controller for high-performance induction motor (IM) drives. The dynamic modeling for decoupling control of IM is developed by making the flux and torque decoupled. The simulation is carried out in the stationary reference frame with linearized control based on state-space linearization technique. Further, comprehensive and systematic design procedures are derived to tune the PI controllers for both electrical and mechanical subsystems. However, the PI-controller performance is not satisfactory under various disturbances and system uncertainties. Also, precise mathematical model, gain values, and continuous tuning are required for the controller design to obtain high performance. Thus, to overcome these drawbacks, an adapted control strategy based on Adaptive Neuro-Fuzzy Inference System (ANFIS) based controller is developed and implemented in real-time to validate different control strategies. The superiority of the proposed controller is analyzed and is contrasted with the conventional PI controller-based linearized IM drive. The simplified neuro-fuzzy control (NFC) integrates the concept of fuzzy logic and neural network structure like conventional NFC, but it has the advantages of simplicity and improved computational efficiency over conventional NFC as the single input introduced here is an error instead of two inputs error and change in error as in conventional NFC. This structure makes the proposed NFC robust and simple as compared to conventional NFC and thus, can be easily applied to real-time industrial applications. The proposed system incorporated with different control methods is also validated with extensive experimental results using DSP2812. The effectiveness of the proposed method using feedback linearization of IM drive is investigated in simulation as well as in experiment with different working modes. It is evident from the comparative results that the system performance is not deteriorated using proposed simplified NFC as compared to the conventional NFC, rather it shows superior performance over PI-controller-based drive. A hybrid fuel cell (FC) supply system to deliver the power demanded by the feedback linearization (FBL) based IM drive is designed and implemented. The modified simple hybrid neuro-fuzzy sliding-mode control (NFSMC) incorporated with the intuitive FBL substantially reduces torque chattering and improves speed response, giving optimal drive performance under system uncertainties and disturbances. This novel technique also has the benefit of reduced computational burden over conventional NFSMC and thus, suitable for real-time industrial applications. The parameters of the modified NFC is tuned by an adaptive mechanism based on sliding-mode control (SMC). A FC stack with a dc/dc boost converter is considered here as a separate external source during interruption of main supply for maintaining the supply to the motor drive control through the inverter, thereby reducing the burden and average rating of the inverter. A rechargeable battery used as an energy storage supplements the FC during different operating conditions of the drive system. The effectiveness of the proposed method using FC-based linearized IM drive is investigated in simulation, and the efficacy of the proposed controller is validated in real-time. It is evident from the results that the system provides optimal dynamic performance in terms of ripples, overshoot, and settling time responses and is robust in terms of parameters variation and external load

Development and analysis of a self-tuned neuro-fuzzy controller for induction motor drives

Induction motors (IM) have been widely utilized in industry for variable speed drives due to some of their advantages, such as rugged construction, low cost and reliable service with easy maintenance, as compared to conventional dc motors. For variable speed drive applications, the controller plays an important role so that the motor can follow the reference trajectories without any significant deviation. Furthermore, a controller which can provide fast speed response and handle uncertainties and disturbances, is absolutely necessary for high performance drive systems. Traditionally, fixed gain proportional-integral (PI) and some adaptive controllers have been utilized in industry for a long time. However, there are some disadvantages of these controllers to handle uncertainties which are inherent to a nonlinear IM. As a result, recently researchers paid their attention to apply intelligent algorithms to control the IM for high performance variable speed drive applications. Intelligent algorithms such as fuzzy logic (FL), neural network (NN), neuro-fuzzy (NF), etc, have inherent advantages as compared to the conventional controllers. In this thesis, a novel neuro-fuzzy controller (NFC) has been developed for speed control o f EM. For the complete drive, the indirect field orientation control is utilized in order to decouple the torque and flux controls. Thus, the induction motor can be controlled like a dc motor and hence the high performance can be achieved without lacking the advantage o f ac over dc motors. The proposed neuro-fuzzy controller incorporates Sugeno model based fuzzy logic laws with a five-layer artificial neural network (ANN) scheme. The controller is designed for low computational burden, which will be suitable for real-time implementation. Furthermore, for the proposed NFC an improved self-tuning method is developed based on the IM theory and its high performance requirements. The main task o f the tuning method is to adjust the parameters o f the fuzzy logic controller (FLC) in order to minimize the square of the error between actual and reference output. In this thesis, a model reference adaptive flux (MRAF) observer is also developed to estimate the d-axis rotor flux linkage in both constant flux and flux weakening regions based on motor voltage, current and reference trajectories for flux linkage. Thus, it provides safe operation to control the motor at high speeds, especially, above the rated speed. The d-axis reference flux linkage of the indirect field oriented control is provided by flux weakening method. Furthermore, a proportional-integral (PI) based flux controller is used to provide the compensation for the reference flux model by comparing the flux reference and the observed flux from Gopinath model flux observer. A complete simulation model for indirect field oriented control of IM incorporating the proposed MRAF observer based NFC is developed in Matlab/Simulink. In order to prove the superiority of the proposed controller, the performance of the proposed controller is compared with a conventional PI as well as fuzzy logic controller (FLC) based IM drives. The performance of the proposed IM drive is investigated extensively at different operating conditions in simulation. The performance of the proposed MRAF observer based NFC controller is found robust and a potential candidate for high performance industrial drive applications

Fuzzy logic based online adaptation of current and speed controllers for improved performance of IPMSM drive

Precise torque and speed control of electric motors is a key issue in industries for variable speed drives (VSD). Over the years the induction motors have been widely utilized in industries for VSD applications. However, induction motor has some significant drawbacks like low efficiency, lagging power factor, asynchronous speed, low torque density etc. Nowadays the interior permanent magnet synchronous motor (IPMSM) is becoming popular for high performance variable speed drive (HPVSD) due to its high torque-current ratio, large power-weight ratio, high efficiency, high power factor, low noise and robustness as compared to conventional induction and other ac motors. Smooth torque response, fast and precise speed response, quick recovery of torque and speed from any disturbance and parameter insensitivity, robustness in variable speed domain and maintenance free operations are the main concerns for HPVSD. This work proposes a closed loop vector control of an IPMSM drive incorporating two separate fuzzy logic controllers (FLCs). Among them one FLC is designed. to minimize the developed torque ripple by varying online the hysteresis band of the PWM current controller. Another Sugeno type FLC is used to tune the gains of a proportional-integral (PI) controller where the PI controller actually serves as the primary speed controller. Thus, the limitations of traditional PI controllers will be avoided and the performance of the drive system can be improved. A flux controller is also incorporated in such a way that both torque and flux of the motor can be controlled while maintaining current and voltage constraints. The flux controller is designed based on maximum-torque- per-ampere (MTPA) operation below the rated speed and flux weakening operation above the rated speed. Thus, the proposed drive extends the operating speed limits for the motor and enables the effective use of the reluctance torque. In order to verify the performance of the proposed IPMSM drive, first a simulation model is developed using Matlab/Simulink. Then the complete IPMSM drive has been implemented in real-time using digital signal processor (DSP) controller board DS1104 for a laboratory 5 HP motor. The effectiveness of the proposed drive is verified both in simulation and experiment at different operating conditions. In this regard, a performance comparison of the proposed FLC based tuned PI and adapted hysteresis controllers based drive with the conventional PI and fixed bandwidth hysteresis controllers based drive is provided. These comparison results demonstrate the better dynamic response in torque and speed for the proposed IPMSM drive over a wide speed range

Self tuned NFC and adaptive hysteresis based DTC scheme for IM drive

The concept of field oriented control scheme brought the revolutionary change in industrial drives. Due to the high initial and running costs of the DC machines, the trend shifted from DC to AC motor drives to obtain high performance variable speed drives. The major achievement with field oriented control was the decoupled and independent control of stator and rotor quantities like DC machines. It is agreed that the control scheme for ac machines is complicated as compared to DC machines. The inherited problem with the ac machine control is the nonlinear relation between process variables e.g. speed and manipulated variables e.g. current, torque etc. Moreover, magnetic saturation of its rotor core causes developed torque relation of nonlinear nature

Development and implementation of various speed controllers for wide speed range operation of IPMSM drive / by Md Muminul Islam Chy.

Despite many advantageous features of interior permanent magnet synchronous motor (IPMSM), the precise speed control of an IPMSM drive becomes a complex issue due to nonlinear coupling among its winding currents and the rotor speed as well as the nonlinearity present in the electromagnetic developed torque due to magnetic saturation of the rotor core particularly, at high speeds (above rated speed). Fast and accurate response, quick recovery of speed from any disturbances and insensitivity to parameter variations are some of the important characteristics of high performance drive system used in robotics, rolling mills, traction and spindle drives. The conventional controllers such as PI, PID are sensitive to plant parameter variations and load disturbance. For the purpose of obtaining high dynamic performance, recently researchers developed several non-linear as well as intelligent controllers. Most of the reported works on controller design of IPMSM took an assumption of d-axis stator current (i[subscript d]) equal to zero in order to simplify the development of the controller. However, with this assumption it is not possible to control the motor above the rated speed and the reluctance torque of IPMSM can not be utilized efficiently. Furthermore, this assumption leads to an erroneous result for motor at all operating conditions. In this thesis, some controllers are developed for the IPMSM drive system incorporating the flux-weakening technique in order to control the motor above the rated speed. A detailed analysis of the flux control based on various operating regions is also provided in this thesis. In order to get the optimum efficiency, an adaptive backstepping based nonlinear control scheme incorporating flux control for an IPM synchronous motor drive is taken into account at the design stage of the controller. Thus, the proposed adaptive nonlinear backstepping controller is capable of conserving the system robustness and stability against all mechanical parameters variation and external load torque disturbance. To ensure stability the controller is designed based on Lyapunov's stability theory. A novel fuzzy logic controller (FLC) including both torque and flux control is also developed in this work. The proposed FLC overcomes the unknown and nonlinear uncertainties of the drive and controls the motor over a wide speed range. For further improvement of the FLC structure, the membership function of the controller is tuned online. An integral part of this work is directed to develop an adaptive-network based fuzzy interference system (ANFIS) based neuro fuzzy logic controller. In this work, an adaptive tuning algorithm is also developed to adjust the membership function and consequent parameters. In order to verify the effectiveness of the proposed IPMSM drive, at first simulation model is developed using Matlab/Simulink. Then the complete IPMSM drive incorporating various control algorithms have been successfully implemented using digital signal processor (DSP) controller board-DSI104 for a laboratory 5 hp motor. The effectiveness of the proposed drive is verified both in simulation and experiment at different operating conditions. The results show the robustness of the drive and it's potentiality to apply for real-time industrial drive application. This thesis also provides through knowledge about development and various speed real-time applications of controllers for IPMSM drive, which will be useful for researchers and practicing engineers

Rekurzivna izvedba za uočavanje kvarnih stanja i upravljanje otporno na kvarna stanja električnih vozila zasnovanih na indukcijskim motorima

This paper proposes an improved sensorless fault-tolerant control (FTC) for high-performance induction motor drives (IMD) that propels an electric-vehicle (EV). The design strategy is based on the Backstepping control (BC). However an appropriate combination of the BC and extended kalman filter (EKF) is done, this later is designed in order to detect and reconstruct the faults and also to give a sensorless control. Then, additional control laws, based on the estimates of the faults, are designed in order to compensate the faults. The results show the superiority EKF in nonlinear system as it provides better estimates for faults detection. A classical EV traction system is studied, using an IMD. Indeed, the IMD based powertrain is coupled to DC machine-based load torque emulator taking into account the EV mechanics and aerodynamics. Finally, the effectiveness of the proposed strategy for detection of faults, and FTC of the IMD is illustrated through simulation studies.U ovome radu predložena je unaprijeđena bez-senzorska upravljačka strategija otporna na kvarna stanja (FTC) za indukcijski motor visokih performansi koji pokreće električno vozilo (EV). Strategija je temeljena na rekurzivnom upravljanju (BC). Nadalje, izvedena je odgovarajuća kombinacija BC-a i proširenog Kalmanovog filtra (EKF), pri čemu je potonji izveden u svrhu uočavanja i rekonstrukcije kvarova te kako bi omogućio bez-senzorsko upravljanje. Kako bi se kompenzirala kvarna stanja, dizajnirani su dodatni upravljački zakoni zasnovani na estimaciji kvarova. Rezultati prikazuju poboljšanje korištenjem EKF-a za nelinearne sustave budući da on omogućava kvalitetnije uočavanje kvarova. Razmatran je klasični pogon EV-a korištenjem IMD-a. Također, pogonski sklop zasnovan na IMD-u je povezan s emulatorom momenta zasnovanom na DC motoru, uzimajući u obzir mehaničke i aerodinamičke karakteristike EV-a. Na posljetku je simulacijama ilustrirana efikasnost predložene strategije za uočavanje kvarnih stanja i FTC-a IMD-a

A Novel DTFC Based Efficiency and Dynamic Performance Improvement of IPMSM Drive

With the advancements in magnetic materials and semiconductor technology, permanent magnet synchronous motor (PMSM) is becoming more and more popular in high power industrial applications due to its high energy density, high power factor, low noise and high efficiency as compared to conventional AC motors. Field oriented vector control (VC) and direct torque and flux control (DTFC) are used for high performance drives. Among these two techniques DTFC is faster and simpler than that of conventional VC scheme as DTFC scheme doesn’t need any coordinate transformation, pulse width modulation and current regulators. The DTFC based motor drives utilizes hysteresis band comparators for both torque and flux controls. Both torque and flux are controlled simultaneously by the selection of appropriate voltage vectors from the inverter. However, DTFC suffers from high torque ripples due to discrete nature of control system and limited voltage vectors from the inverter. Torque ripples can be minimized by increasing the sector numbers of the DTFC scheme which increases the switching frequency of the inverter. Traditionally, researchers chose a constant value of reference air-gap flux to make the control task easy but it is not acceptable for high performance drives as the air-gap flux changes with the operating conditions and system disturbances. Furthermore, if the reference air-gap flux is maintained constant, it is not possible to control the motor over the wide speed range operation. Moreover, conventional six-sector based DTFC scheme suffers from high torque ripples, which is the major drawbacks to achieve high dynamic performance. Therefore, this thesis presents a novel eighteen-sector based DTFC scheme to achieve high dynamic performance with minimum torque ripples. In addition, the loss minimization algorithm (LMA) is incorporated with proposed DTFC scheme in order to improve the efficiency while maintaining high dynamic performance. This thesis further presents modified eighteen-sector based DTFC scheme to overcome the unbalanced voltage effects in any sector of conventional six-sector based system to improve the dynamic performance of the proposed system. This thesis also presents a novel sector determination algorithm to determine the sector number of the stator flux linkage vector which reduces the computational burden to the microprocessor. A five level torque hysteresis comparator based DTFC scheme is also proposed to reduce the torque ripple. Further, a backstepping based nonlinear controller is developed for IPMSM drive that achieves the lowest possible torque ripples in steady state. In this controller development, the control variable is motor electromagnetic developed torque and stator air-gap flux linkages similar to classical DTFC but the errors are forced to zero using backstepping process to get better dynamic performance. The effectiveness of the proposed systems is verified through the development of a simulation model using Matlab/Simulink. Performance of the proposed nonlinear controller is investigated extensively at different operating conditions such as sudden speed and load changes. Then the complete IPMSM drives, incorporating the proposed LMA and eighteen-sector based DTFC scheme and nonlinear controller with torque and flux as virtual control variables are successfully implemented in real-time using digital signal processor (DSP) board-DS1104 board for laboratory 5-hp motor. The effectiveness of the proposed control techniques are verified in both simulation and experiment at different operating conditions. It is found that, the nonlinear controller based IPMSM drive provides the best performance in terms of torque ripple among all the DTFC scheme developed in the thesis. The results show the robustness of the drive and it’s potentiality to apply for real-time industrial drive applications

Online loss minimization based direct torque and flux control of IPMSM drive

With the advent of high energy rare earth magnetic material such as, third generation neodymium-iron-boron (NdFeB), permanent magnet synchronous motor (PMSM) is becoming more and more popular in high power industrial applications (e.g., high-speed railway) due to its advantageous features such as high energy density, stable parameters, high power factor, low noise and high efficiency as compared to the conventional ac motors. Over the years, vector control and direct torque and flux control (DTFC) techniques have been used for high performance motor drives. But, the DTFC is faster than that of conventional vector control as the DTFC scheme doesn't need any coordinate transformation, pulse width modulation (PWM) and current regulators. The DTFC utilizes hysteresis band comparators for both flux and torque controls. Most of the past researches on DTFC based motor drives mainly concentrated on the development of the inverter control algorithm with less torque ripple as it is the major drawback of DTFC. The torque reference value is obtained online based on motor speed error between actual and reference values through a speed controller. Traditionally, researchers chose a constant value of air-gap flux reference based on trial and error method which may not be acceptable for high performance drives as the air-gap flux changes with operating conditions and system disturbance. Efficient high performance drives require fast and accurate speed response to cope with disturbances and algorithm to minimize motor losses. However, if the reference air-gap flux is maintained constant it is not possible to control the motor losses. Therefore, this thesis presents a novel loss minimization based DTFC scheme for interior type PMSM drive so that the drive system can maintain both high efficiency and high dynamic performance. An online model based loss minimization algorithm (LMA) is developed to estimate the air-gap flux so that the motor operates at minimum loss condition while taking the general advantages of DTFC over conventional vector control. The performance the proposed LMA based DTFC for PMSM drive is tested in both simulation and real-time implementation at different operating conditions. The results verify the effectiveness of the proposed flux observer based DTFC scheme for PMSM drive

Modeling and control of fuel cell-battery hybrid energy sources

Environmental, political, and availability concerns regarding fossil fuels in recent decades have garnered substantial research and development in the area of alternative energy systems. Among various alternative energy systems, fuel cells and batteries have attracted significant attention both in academia and industry considering their superior performances and numerous advantages. In this dissertation, the modeling and control of these two electrochemical sources as the main constituents of fuel cell-battery hybrid energy sources are studied with ultimate goals of improving their performance, reducing their development and operational costs and consequently, easing their widespread commercialization. More specifically, Paper I provides a comprehensive background and literature review about Li-ion battery and its Battery Management System (BMS). Furthermore, the development of an experimental BMS design testbench is introduced in this paper. Paper II discusses the design of a novel observer for Li-ion battery State of Charge (SOC) estimation, as one of the most important functionalities of BMSs. Paper III addresses the control-oriented modeling and analysis of open-cathode fuel cells in order to provide a comprehensive system-level understanding of their real-time operation and to establish a basis for control design. Finally, in Paper IV a feedback controller, combined with a novel output-injection observer, is designed and implemented for open-cathode fuel cell temperature control. It is shown that temperature control not only ensures the fuel cell temperature reference is properly maintained, but, along with an uncertainty estimator, can also be used to adaptively stabilize the output voltage --Abstract, page iv

Investigations on Direct Torque and Flux Control of Speed Sensorless Induction Motor Drive

The Induction motors (IM) are used worldwide as the workhorse in most of the industrial applications due to their simplicity, high performance, robustness and capability of operating in hazardous as well as extreme environmental conditions. However, the speed control of IM is complex as compared to the DC motor due to the presence of coupling between torque and flux producing components. The speed of the IM can be controlled using scalar control and vector control techniques. The most commonly used technique for speed control of IM is scalar control method. In this method, only the magnitude and frequency of the stator voltage or current is regulated. This method is easy to implement, but suffers from the poor dynamic response. Therefore, the vector control or field oriented control (FOC) is used for IM drives to achieve improved dynamic performance. In this method, the IM is operated like a fully compensated and separately excited DC motor. However, it requires more coordinate transformations, current controllers and modulation schemes. In order to get quick dynamic performance, direct torque and flux controlled (DTFC) IM drive is used. The DTFC is achieved by direct and independent control of flux linkages and electromagnetic torque through the selection of optimal inverter switching which gives fast torque and flux response without the use of current controllers, more coordinate transformations and modulation schemes. Many industries have marked various forms of IM drives using DTFC since 1980. The linear fixed-gain proportional-integral (PI) based speed controller is used in DTFC of an IM drive (IMD) under various operating modes. However, The PI controller (PIC) requires proper and accurate gain values to get high performance. The PIC gain values are tuned for a specific operating point and which may not be able to perform satisfactorily when the load torque and operating point changes. Therefore, the PIC is replaced by Type-1 fuzzy logic controller (T1FLC) to improve the dynamic performance over a wide speed range and also load torque disturbance rejections. The T1FLC is simple, easy to implement and effectively deals with the nonlinear control system without requiring complex mathematical equations using simple logical rules, which are decided by the expert. In order to further improve the controller performance, the T1FLC is replaced by Type-2 fuzzy logic controller (T2FLC). The T2FLC effectively handles the large footprint of uncertainties compared to the T1FLC due to the availability of three-dimensional control with type-reduction technique (i.e. Type-2 fuzzy sets and Type-2 reducer set) in the defuzzification process, whereas the T1FLC consists only a Type-1 fuzzy sets and single membership function. The training data for T1FLC and T2FLC is selected based on the PIC scheme