Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1996-11-05
1998-07-07
Ro, Bentsu
Electricity: motive power systems
Induction motor systems
Primary circuit control
318799, H02P 2100
Patent
active
057774528
DESCRIPTION:
BRIEF SUMMARY
This application is a continuation, under requirement of 35 USC 371, of an international application PCT/FR96/00317, filed Feb. 29, 1996.
BACKGROUND OF THE INVENTION
The present invention relates to apparatuses for controlling asynchronous machines in general, and more particularly it relates to a corrector, to apparatus, and to a method for controlling the electromagnetic torque of an asynchronous machine.
Speed control of an asynchronous machine is generally performed by regulating the rotor or stator flux and by controlling the electromagnetic torque.
The power supply magnitudes fed to the asynchronous machine, i.e. the voltages or currents fed thereto, are delivered by a variable frequency inverter of the voltage source type or of the current source type, which inverter generates power signals that are pulse-width modulated.
Values for flux and for torque are magnitudes that are reconstructed by known electrical means on the basis of measured stator voltage and current.
For a long time, research in the field of apparatuses for controlling asynchronous machines has been directed to increasing the dynamic performance of such control apparatuses.
Nowadays, the performance of such control apparatuses, generally as defined by the response time of the electromagnetic torque, is found to be satisfactory in most industrial and railway applications.
The concept of "robustness" now appears as an additional criterion concerning the performance of apparatuses for controlling asynchronous machines.
The term "robustness" of a control structure is used to mean the potential of said control structure for remaining insensitive to disturbances, e.g. due to errors in models or to variations in parameters.
One of the known technical solutions that is well adapted to solving the problem of robustness in apparatuses for controlling the electromagnetic torque of an asynchronous machine is based firstly on modelling with the singular disturbances of the Park model, and secondly on the initial orientation of the rotating frame of reference concerning stator current.
Because that solution uses linear control relationships, it has the drawback that in the apparatuses for controlling the electromagnetic torque of the asynchronous machine, robustness is favored to the detriment of performance.
Also, when the control relationships used are purely non-linear, then the robustness of such control apparatuses is not assured.
The thesis presented by Xavier ROBOAM to Institut National Polytechnique de Toulouse, entitled "Variateur de vitesse pour machine asynchrone" was published in 1991, relates to developing robust control relationships and to controlling speed without using a mechanical sensor.
The described variable speed controller for an asynchronous machine relies on implanting robust digital control relationships and on reconstituting fundamental magnitudes that are unmeasured, namely: stator flux, speed, and torque.
The drawbacks of the variable speed controller for an asynchronous machine as described in that document are:
linear control of the modulus of the stator flux, with adjustment that is empirical;
linear control of the electromagnetic torque which is applicable essentially at small values for the angular frequency of rotor currents; and
a the dynamic range of the closed loop response of the torque loop is insufficient.
The corrector and the apparatus of the invention for controlling the electromagnetic torque of an asynchronous machine differ from the variable speed controller described in that document, in that:
the stator flux magnitude is replaced by the rotor flux magnitude, thus making it possible to perform non-linear control of the input/output linearization type in order to guarantee maximum dynamic performance;
the robustness of flux regulation is ensured by a corrector of the proportional, integral "without zero" type located upstream from the non-linear control relationship;
the electromagnetic torque is controlled by associating a linear corrector in order to obtain a better performance/robustness compro
REFERENCES:
patent: 3851234 (1974-11-01), Hoffman et al.
patent: 4215305 (1980-07-01), D'Atre et al.
patent: 4677360 (1987-06-01), Garces
patent: 5144216 (1992-09-01), De Doncker
patent: 5296794 (1994-03-01), Lang et al.
X. Roboam et al, "Controle d'une machine asynchroone par estimation robuste de la vitesse", Journal De Physique, vol. 2, No. 3, Paris, France pp. 439-453, Mar. 1992.
Alcatel Alsthom Compagnie Generale d'Electricite
Ro Bentsu
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