Adaptive backstepping based online loss minimization control of an induction motor drive / by San Woo Nam.

The efficiency of an induction motor (IM) can be improved by the optimum selection of a flux level in the motor. Among the numerous loss minimization algorithms (LMA), a loss-model-based approach offers a fast response and no torque pulsation. However, it requires the accurate loss model and the knowledge of the motor parameters to find the optimum flux level. Therefore, a technical difficulty in deriving the loss-model-based LMA lies in the complexity of the full loss model and the on-line parameter adaptation for the precise motor parameters. In an effort to overcome the drawbacks of on-line loss model controllers (LMC), this thesis presents a new loss-model-based LMA for inverter-fed IM drives aiming at both high efficiency and high dynamic performance. A new LMC is proposed for the loss minimization of vector-controlled IM drives. An IM model in d-q coordinates is referenced to the rotor magnetizing current and then an iron loss resistance is added in parallel to the magnetizing inductance. This transformation leads to no leakage inductance on the rotor side by incorporating it into other parameters. This decomposition feature into d-q components makes the derivation o f the motor loss model and LMC simpler while keeping the effect of leakage inductances. In order to achieve high dynamic performance, an adaptive backstepping based nonlinear controller (ABNC) is designed incorporating iron loss under the parameter uncertainties of rotor resistance and load torque. In proposed IM equations, no additional state variables are added while iron loss is considered. Thus, an ABNC incorporating iron loss can be designed without much m ore complexity compared to the one with neglected iron loss. ABNC achieves desirable motor dynamics at any operating point while the flux level is varied by the LMC in order to reduce the input power. Adaptive backstepping technique provides a tool to design the controller avoiding wasteful cancellations of certain nonlinearities. Another important feature of an adaptive backstepping technique is that it can derive param eter update laws simultaneously with control laws from the error dynamics. With an extra gain introduced in adaptation laws design, we take advantage of this feature by combining the ABNC with LMC, thus an on-line param eter adaptation of LMC can be obtained with no extra effort. The complete closed loop control o f the proposed LMC based IM drive is implemented in real-time using digital signal processor board DS 1104 for a laboratory 1/3 hp motor. The dynamic performance of the proposed controller and parameter adaptation features are examined. The effectiveness of the proposed loss minimization scheme through a wide range of speed regions including the field weakening region is demonstrated through computer simulation and experimental results

Stability Analysis and Robust Controller Design of Indirect Vector Controlled Induction Motor

The thesis considers stability analysis and controller design through different performance measures for indirect vector controlled induction motor (IVCIM).These problems are known to be complex due to nonlinearity, large order and multi-loop scenario. Some new approaches and results on IVCIM are proposed in this work. IVCIM dynamics is well known for having different bifurcation behavior, viz., saddle-node, Hopf, Bogdanov–Takens and Zero–Hopf bifurcations due to rotor resistance variation. These bifurcations affect the control performance and may lead to stalling or permanent damage of motor. A numerical analysis of these bifurcations for proportional integral (PI) controlled IVCIM is made in this thesis using full-order induction motor model (stator dynamics is included). This analysis aids to determine the allowable bifurcation parameter variation range as well as suitable choice of speed-loop gains to avoid these. Some new observations on the bifurcation behavior are made. Simulation and experimental results are presented validating the bifurcation behaviors. For improving dynamic performance in the presence of load torque and rotor resistance variation, a new method for designing PI gains is proposed for IVCIM. The inner-loop current PI controllers are tuned simultaneously along with the speed controller. This method is implemented using a static output feedback scheme in which iterative linear matrix inequality (ILMI) based∞control technique is employed. Such a design makes stator currents and speed response to be robust against rotor resistance and load variations. A comparison between proposed design and a conventional one is shown using simulation and experimental results that validate the superiority of the proposed approach. Owing to multi-loop and nonlinear system behavior, IVCIM dynamics is known to have coupling in between the two inner-loop stator current components (flux and torque). Such coupling affects the dynamic torque output of the motor. Decoupling of the stator currents are important for smoother torque response of IVCIM. Conventionally, additional feedforward decoupler is used to take care of the coupling that requires exact knowledge of the motor parameters and additional circuitry or signal processing. A method is proposed to design the regulating PI gains while minimizing coupling without any requirement of additional decoupler. The variation of the coupling terms for change in load torque is considered as the performance measure. The same ILMI based∞control design approach is used to obtain the controller gains. A comparison between the conventional feedforward decoupling and proposed decoupling scheme is presented through simulation and experimental results that establish the effectiveness of the proposed method riding over its simplicity. Finally, since the PI controller can yield limited performance, a dynamic controller is designed for the IVCIM drive system. In the design process, iron-loss dynamics are incorporated into induction motor model to fetch benefit through better performance. A sequential design method is used for the controller design in which, first, the inner-loop controllers are designed. The designed inner-loop controllers is then used for designing the outer speed-loop controller. The proposed design employs ILMI based∞control design for dynamic output feedback controller that makes stator currents and speed response to be robust against disturbances. A comparison among proposed dynamic controller design, PI controller and compensator design is shown using simulation and experimental results demonstrate enhanced performance of the proposed controller and suitability for industrial purpose

Disturbance/uncertainty estimation and attenuation techniques in PMSM drives–a survey

This paper gives a comprehensive overview on disturbance/uncertainty estimation and attenuation (DUEA) techniques in permanent magnet synchronous motor (PMSM) drives. Various disturbances and uncertainties in PMSM and also other alternating current (AC) motor drives are first reviewed which shows they have different behaviors and appear in different control loops of the system. The existing DUEA and other relevant control methods in handling disturbances and uncertainties widely used in PMSM drives, and their latest developments are then discussed and summarized. It also provides in-depth analysis of the relationship between these advanced control methods in the context of PMSM systems. When dealing with uncertainties,it is shown that DUEA has a different but complementary mechanism to widely used robust control and adaptive control. The similarities and differences in disturbance attenuation of DUEA and other promising methods such as internal model control and output regulation theory have been analyzed in detail. The wide applications of these methods in different AC motor drives (in particular in PMSM drives) are categorized and summarized. Finally the paper ends with the discussion on future directions in this area

PV Array Driven Adjustable Speed Drive for a Lunar Base Heat Pump

A study of various aspects of Adjustable Speed Drives (ASD) is presented. A summary of the relative merits of different ASD systems presently in vogue is discussed. The advantages of using microcomputer based ASDs is now widely understood and accepted. Of the three most popular drive systems, namely the Induction Motor Drive, Switched Reluctance Motor Drive and Brushless DC Motor Drive, any one may be chosen. The choice would depend on the nature of the application and its requirements. The suitability of the above mentioned drive systems for a photovoltaic array driven ASD for an aerospace application are discussed. The discussion is based on the experience of the authors, various researchers and industry. In chapter 2 a PV array power supply scheme has been proposed, this scheme will have an enhanced reliability in addition to the other known advantages of the case where a stand alone PV array is feeding the heat pump. In chapter 3 the results of computer simulation of PV array driven induction motor drive system have been included. A discussion on these preliminary simulation results have also been included in this chapter. Chapter 4 includes a brief discussion on various control techniques for three phase induction motors. A discussion on different power devices and their various performance characteristics is given in Chapter 5

Real-time model-based loss minimisation control for electric vehicle drives

PhD ThesisEnvironmental concern and the opportunity for commercial gain are two factors driving the expansion of the electric vehicle (EV) market. Due to the limitations of current battery technology, the efficiency of the traction drive, which includes the electric motor and power electronic converter, is of prime importance. Whilst electric machines utilising permanent magnets (PMs) are popular due to their high energy density, industry concerns about the security of supply have led to interest in magnet-free solutions. Induction machines (IMs) offer such an option. Control of IMs is a mature but complex field. Many techniques for optimising the efficiency of the drive system have been proposed. The vast majority of these methods involve an analytical study of the system to reveal relationships between the controlled variable and efficiency, allowing the latter to be optimised. This inevitably involves simplifications of the problem to arrive at a practically-implementable control scheme. What has not been investigated is real-time calculation of the system losses in order to optimise the efficiency, and the work presented in this thesis attempts to achieve this. The conventional control scheme is examined and a new structure implemented where a model of the system loss is able to directly influence the switching action of the inverter, thus reducing loss. The need to maintain performance alongside loss minimisation is recognised and a cost function-based solution proposed. The validation of this structure is performed both in simulation and on a practical test platform. A model of the principle losses in the drive system is derived, taking into account the processing power typically available for this application, and implemented in the structure outlined. The effect of the new control scheme on efficiency is investigated and results show gains of up to 3%-points are achievable under certain conditions

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

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

Adaptive backstepping based nonlinear control of an interior permanent magnet synchronous motor drive

Permanent magnet synchronous machines (PMSM) have shown increasing popularity in recent years for industrial drive applications due to the recent developments in magnetic materials, power converters, and digital signal processors. In particular, Interior Permanent Magnet Synchronous Motor (IPMSM) drives are widely used in high performance drive (HPD) applications. Fast and accurate speed response and quick recovery of speed from any disturbances are essential. The control of a high performance permanent magnet synchronous motor drive for general industrial application has received wide spread interest of researchers. In this work, a novel speed and position control scheme for an IPMSM is developed based on a nonlinear adaptive control scheme. The vector control scheme is used to simplify control of the IPMSM. System model equations are represented in the synchronously rotating reference frame and provide the basis for the controller which is designed using the adaptive backstepping technique. Using Lyapunov’s stability theory, it is also shown that the control variables are asymptotically stable. The complete system model is developed and then simulated using MATLAB/Simulink software. Performance of the proposed controller is investigated extensively at different dynamic operating conditions such as sudden load change, command speed change, command position change and parameter variations. The results show the global stability of the proposed controller and hence found to be suitable for high performance industrial drive applications. The real time implementation of the complete drive system is currently underway

Fuzzy logic based efficiency optimization of IPM synchronous motor drive

Interior permanent magnet synchronous motor (IPMSM) is highly appreciated by researchers in variable speed drive applications due to some of its advantageous features such as small size, high power density, simple maintenance, high output torque, high power factor, low noise and robustness as compared to the conventional IM and other ac motors. Although these motor drives are well known for their relatively high efficiency, improvement margins still exist in their operating efficiency. Particularly, the reduction of power loss for IPMSM still remains a challenge for researchers. Improvement of motor drives efficiency is important not only from the viewpoints of energy loss and hence cost saving, but also from the perspective of environmental pollution. The thesis presents development of a fuzzy logic based efficiency and speed control system of an IPMSM drive. In order to maximize the efficiency in steady state operation while meeting the speed and load torque demands a search based fuzzy efficiency controller is designed to minimize the drive power losses to achieve higher efficiency by reducing the flux. The air gap flux level can be reduced by controlling the d-axis armature current as it is supplied by rotor permanent magnet. In order for the drive to track the reference speed in transient operation another fuzzy logic based controller is designed to increase the flux depending on the speed error and its derivative. The torque component of stator current (q-axis component of stator current) is generated by fuzzy logic based speed controller for different dynamic operation depending on speed error and its derivative. In this work a torque compensation algorithm is also introduced to reduce the torque and speed fluctuations

Feedback Linearization Based Nonlinear Control of SynRM Drives Accounting for Self- and Cross-Saturation

This article proposes a nonlinear controller based on feedback linearization (FL) for synchronous reluctance motor (SynRM) drives which takes into consideration the magnetic saturation. The proposed nonlinear FL control based control technique has been developed starting from the theoretical definition of an original dynamic model of the SynRM taking into consideration both the self- and the cross-saturation effects. Such a control technique permits the dynamics of both the speed and axis flux loops to be maintained constant independently from the load and the saturation of the iron core in both constant flux and variable direct axis flux operating conditions. Finally, sensitivity of the performance of the proposed FL control versus the variation of the main motor parameters has been verified. The proposed technique has been tested experimentally on a suitably developed test setup. The proposed FL control has been further compared with the classic field-oriented control (FOC) in both constant flux and variable flux working conditions