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Advances in Control Systems for Electric Drives, IEE Colloquium on

Date 24 May 1995

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Displaying Results 1 - 12 of 12
  • Combined drive/chargers for electric vehicles: advanced technology to “side-step” the batteries

    Publication Year: 1995 , Page(s): 1/1 - 1/7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The author describes how powerful technologies can be brought to bear to “side-step” the shortcomings of present electric vehicle secondary batteries in some respects. He details how combined drive/charger products are now beginning to become available to the standards the automotive industry expects. These units are offered with battery ratings up to 700V DC, and output currents to 350 A RMS-sufficient for demanding electric vehicle platforms. Multiple units can be combined, if required, for higher ratings View full abstract»

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  • Application of encoderless vector control techniques in a medium performance induction motor drive

    Publication Year: 1995 , Page(s): 2/1 - 2/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    This paper looks at the application of encoderless vector control in medium performance induction motor drives. In recent publications some attention has been given to methods which utilize adaptive flux observers to identify rotor speed. This paper evaluates some of these techniques with particular focus on their application in a single processor drive. The authors discuss three MRAC (model reference adaptive control) speed estimation techniques: rotor flux MRAC, MRAC using counter EMF, and MRAC using reactive power View full abstract»

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  • A new direct torque control strategy

    Publication Year: 1995 , Page(s): 5/1 - 5/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    The paper investigates the performance of three-phase cage rotor induction motor control systems based on direct torque control. Direct torque control is examined and it is found that this scheme is less complex and gives better control characteristics than the vector control methods. A new control strategy based on direct torque control is then considered in detail. It has been found that the performance of direct torque control can be improved further by using a more complex switching table with a mapping algorithm View full abstract»

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  • IEE Colloquium `Advances in Control Systems for Electric Drives' (Digest No. 1995/114)

    Publication Year: 1995
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (40 KB)  

    The following topics were dealt with: electric vehicles; induction motor drives; vector control techniques; AC drives; torque control; flux oriented control; switched reluctance motor based positron servo control; brushless DC motor control; synchronous reluctance drive View full abstract»

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  • Flux oriented control without using rotor time constant and stator resistance

    Publication Year: 1995 , Page(s): 7/1 - 7/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    Flux oriented control systems of induction machines are sensitive to the variation of the machine parameters such as rotor time constant and stator resistance. Speed estimation has been proposed by many papers however they depend on the variation in rotor time constant and stator resistance. A system that has speed estimation and is also independent of rotor time constant and stator resistance is desirable. This paper adapted the methods proposed by G. Yang and T. Chin (1989) and K. Tungpimolrut (1994) and investigates and extends these strategies in rotor flux oriented control. The authors discuss the rotor flux observer and the reactive power model reference adaptive system View full abstract»

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  • Extending the performance limits of vector controlled AC drives

    Publication Year: 1995 , Page(s): 4/1 - 410
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    A range of industrial vector controlled inverter drives is now available for operation at power levels from 5 kW to 1 MW. The entire product range uses insulated gate bipolar transistors (IGBTs) as the power switch in a 3 phase voltage source bridge configuration. The drives provide full four quadrant operation through sinusoidal, line regenerative network bridges which are themselves identical IGBT based voltage source inverters. By adopting a fully controllable network bridge to manage the power flow to and from the DC link, the products achieve extremely low network harmonics and the feature of a fixed DC link voltage, the benefits of which are discussed further in this article. This paper considers two application examples to illustrate the performance levels that can be achieved with correctly specified vector controlled AC drives. The first example discusses the factors influencing high torque production below base speed and considers how motor and inverter characteristics can be tailored to optimise the overall system behaviour. The second example considers operation into the field weakening region. This is of particular interest for machine tool and coiler/un-coiler applications where wide constant horsepower characteristics are required View full abstract»

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  • A unified drive-how and why?

    Publication Year: 1995 , Page(s): 6/1 - 6/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    Some manufacturers offer a range of similar variable speed drives to cover a range of applications and motor types so that their customers do not have to be familiar with several different products. The set-up and control of drives is never the same throughout a range and the user must keep several sets of different spares. A unified drive which incorporates the necessary power and control elements for more than one type of motor would help to address the problem. A majority of AC motor applications from 0.75 kW to 1 MW can be covered by the following: open loop AC motor drive (for induction, reluctance or permanent magnet motors); sensorless vector AC induction motor drive; closed loop vector AC induction motor drive; and closed loop permanent magnet synchronous (servo) motor drive. These are all normally based on a PWM voltage source inverter and controlled by microprocessor based hardware. This has allowed all four to be combined to form the Unidrive in which the type of drive is selected simply by changing a software parameter, and which can operate in each of the four configurations without any additional hardware modules. It is not possible to use exactly the same control algorithm in each case, but as described in this paper there can be a high degree of commonality between drive types. This is an enormous benefit in the design process as it reduces the effort required to produce the drive software. It also benefits the user because the drive parameter set differs little between each drive type View full abstract»

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  • A comparison between fuzzy and linear controllers applied to a switched reluctance motor based position servo

    Publication Year: 1995 , Page(s): 8/1 - 8/4
    Cited by:  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    Position control of a switched reluctance motor based on exact input-output linearisation of its torque production characteristics, in an inner control loop, and a simple sliding mode outer control loop using fuzzy logic has been demonstrated. Experimental results confirm the anticipated behaviour of this scheme. The exercise has highlighted some of the advantages of fuzzy systems, notably their flexibility. It has also given some indication of the appropriateness of fuzzy logic in two different situations. It is concluded that learning and representing highly nonlinear functions for which accurate analytic expressions are not available exploits many of the strengths of fuzzy logic. Implementing a simple nonlinear control scheme, for which analytic expressions and established control theory are the starting point exploits fewer. Overall, however, it has been demonstrated that it is appropriate to employ fuzzy systems within larger control system architectures specifically where nonlinear characteristics are required View full abstract»

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  • Improvements in operation of vector controlled induction machines by application of modified machine models

    Publication Year: 1995 , Page(s): 3/1 - 3/8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The theory of induction machine vector control is based on constant parameter induction machine d-q axis model that neglects all the parameter variations, flux saturation and iron core loss. Due to inevitable variation of parameters during operation of the drive, actual performance may significantly deteriorate from ideal. In general, two approaches may be identified as being available to combat the problem of parameter variations. The first approach relies on modern control techniques and attempts to increase the robustness of the drive while still relying on the same basic constant parameter d-q axis model of the machine. The second approach attempts to improve the accuracy of orientation and thus performance of the drive by using modified d-q axis models of induction machines. The modified models account for one or more sources of parameter variations and thus essentially provide an open-loop adaptation for the specific parameter(s) in question. The paper is devoted to this second approach and its purpose is to discuss some of the modified models that enable improved operation of vector controlled induction machines. The emphasis is placed on main flux saturation and iron core loss View full abstract»

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  • Soft-computing in the control of electrical drives

    Publication Year: 1995 , Page(s): 9/1 - 9/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The principal constituents of soft computing are the fuzzy logic (FL), artificial neural networks (NN) and probabilistic reasoning (PR). It is generally regarded that FL primarily deals with imprecision, NN with learning, and PR with uncertainty. They have, however, overlapping boundaries and are known to be complementary rather than competitive to each other in many applications. Here, two control algorithms, one implemented by fuzzy logic and the other by a neural network, are used as the basis to highlight salient features of soft computing. A DC motor servo system with the proposed soft computing based algorithms is discussed. The fuzzy logic control employs the principles of fuzzy logic to calculate an optimal output action based on input conditions, and a knowledge base expressed in linguistic forms, thereby performing a parallel operation to control the output with a high degree of robustness against parameter change. In the neural network control, focus is on how neural networks can overcome deadzone-plus-saturation nonlinearity commonly found in the power driver of a DC servo motor. Simulation results have been performed to establish the validity of these control algorithms View full abstract»

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  • Control of a brushless DC motor using a torque vector method and modulated conduction

    Publication Year: 1995 , Page(s): 10/1 - 10/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    The research work described in this paper was carried out on a brushless DC motor with airgap windings and surface permanent magnets. In a previous research programme, robust speed or position control was achieved using a sliding mode method. However, the scheme suffered from certain disadvantages: the hardware scheme was relatively complex, the period for calculation of speed and acceleration from the position encoder signal was long and closed loop current control using a voltage source inverter was relatively slow. These resulted in limitation of the sampling frequency and also pulsations in speed. The solution applied by the authors uses the direct vector voltage control method. A variable structure controller based on a 3-dimensional sliding surface provides robust results and can be tuned for a fast, well damped response. However, with switching of the system state, the sampling frequency becomes increasingly critical and stress on the drive can be important. Torque vector control has been shown to give good response from a simple control scheme and pulsations may be reduced by modulation of the conduction periods of the power switching devices View full abstract»

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  • Steady state efficiency of a synchronous reluctance drive

    Publication Year: 1995 , Page(s): 11/1 - 11/5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    The performance of a synchronous reluctance drive can be optimised with regard to such parameters as power factor and transient response (or rate of change of torque). Constant current in inductive axis control yields the best transient response and is often termed vector control. A number of control schemes have been proposed and research effort has neglected to consider the effect of these schemes on such parameters as steady state losses and low speed torque ripple. This paper derives empirical models to give an insight into how these parameters are affected by the choice of scheme View full abstract»

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