SUMMARY OF RESEARCH AND DEVELOPMENTS
Work urgencyWORK URGENCY
Now, in the modern automated electric drive is exist the tendencies:
—replacement of a drive of a direct current with an asynchronous drive;
—development of more and more perfect systems of regulation of an alternating current;
—development of digital logic control systems;
The asynchronous short-circuited electromotor (ASKEM) is the most perfect on the electromechanical design that provides high reliability at its operation,
also is the most economic on power consumption. However has an essential lack – has bad regulation properties. Therefore earlier it was use to a drive
of noncontrollable mechanisms or regulated in a small range. Now are developed and new control systems, continue to be developed, allowing most as
much as possible to make ASKEM on its regulation properties to the direct current electromotor.
The greatest successes it was possible to reach thanks to application of a principle of field oriented control. This principle has been offered for a long
time, but has had an opportunity the realisation only with the advent of powerful digital computer facilities.
Realisation of field oriented control contains moments requiring perfection.
The complete electric drive (CED) – the device which is carrying out functions of maintenance of soft start, regulation of speed and the torque, complex
protection of the electric motor, provides combination of the electric motor with a power line. CED it is carried out in the form of functionally finished
device of the compact execution combining in a power part and a control system. CED an alternating current together with ASKEM form mechanotronic
system, which is considered in this work.
Expansion of scope ASKEM, its simplicity and reliability in operation, and also intensive development of digital control systems of the alternating current
made in the form of ready compact devices, grant the right to assert that in the near future, ASKEM will remain the basic type of electromotor for a drive
industrial mechanisms. Thus, the complete electric drive becomes elementary unit of the automation integrated into a control system of higher level (in
an industrial network).
THE PURPOSES AND PROBLEMS
The work purpose is studying modern drive technicians and acquisition of skills at its operation for a drive of various industrial mechanisms, working
out of methodical recommendations about adjustment and parametrization modern CED. In communication by that as main principle on which basis the
majority of control systems modern CED works is field oriented control, and the basic algorithm of management power keys - pulse-width modulation
(PWM) the work purpose also is research and comparison of algorithms of the PWM and ways of their realisation in systems of field oriented control.
According to an object in view, it is necessary to solve following problems:
—Studying of modern complete electric drives, their functionality, main principles of their work;
—To develop mathematical model of experimental installation on the basis of firm Control Technique equipment (Unidrive SP and
Commander SK);
—To make equipment parameterization and equipment adjustment;
—To make methodical recommendations on parameterization CED, to construction of external contours of regulation, visualisation of
signals;
—Revealing in electric drives of industrial mechanisms of problems which can be solved thanks to CED;
—Construction of mathematical model of the universal complete electric drive, suitable for a drive of several groups of industrial
mechanisms;
—Working out of algorithms of autotune CED;
—Research of algorithms of PWM in systems of field oriented control and their comparative analysis;
PLANNED PRACTICAL RESULTS
The core planned practical results are:
1) Mathematical model and results of mathematical modelling of experimental installation on the basis of firm Control Technique electric drives
(Unidrive SP, Commander SK).
2) Methodics of parametrization, constructions of external contours of regulation and visualisation of signals.
3) Mathematical model of universal CED.
4) Algorithms of autotune of CED.
5) Model of control system of CED (with application of field oriented control and pulse-width modulation).
THE REVIEW OF WORKINGS OUT ON A THEME
The theme of MPhil is connected with modern technics, the recognised tool of research is mathematical modelling, therefore and it is necessary to do the
review of workings out, leaning on modern drives technics and the literature on modelling, under the theory of frequency steering and the converting
technics.
Mathematical modelling has passed a long way of the development. Beginning from analogue models and finishing modern applied
packages with ready mathematical models of this or that object. So for electromechanics, now, all over the world, package MatLab which versions are
constantly updated is recognised. At performance given MPhil, version MatLab6.1 is used.
In the literature [1, 2, 4, 6, 10] mathematical description ASKEM in the opened system of regulation is given at frequency steering.
The base methods of frequency steering are:
1) Scalar frequency - regulation;
2) Field oriented control;
3) Direct control of the torque.
On a data base of principles, in [1] construction systems of regulation of speed is described. The book is focused on modern model
CED on base the frequency converter. Structure CED, and also the tool allowing qualitatively to realise field oriented control by the electric drive and in
general transformation of frequency – pulse-width modulation is well described.
Starting to consider in more details application PWM in modern CED, it is necessary to pass to the literature [2]. More detailed
description ASKEM focused on field oriented control is given, automatic control questions by frequency-regulated asynchronous electric drives with
PWM are considered. In particular, the case in point optimum on speed of vector regulation a current of stator is rather actual. More generalized and it is
short questions of field oriented control and pulse-width modulation are considered in [3].
In the literature [1] - [3] the mathematical description of objects is resulted, but in the given sources does not contain the algorithms,
allowing to spend modelling of objects. Modelling of electromechanical systems of an alternating current, including the questions connected with field
oriented control, pulse-width modulation in system the FC- ASKEM are resulted in [4].
In [5] the important mathematical models of elevating installation, turbomachines, the conveyor are description. Also the basic
approaches to modelling thyristors converters, system the FC- ASKEM are designated. The whole section of the book is devoted modelling nonlinear in
electromechanical systems.
Unfortunately, on modelling in MatLab in application Simulink at present it is not enough applied literature. A source [6] while is the
only thing which is more or less taking up the necessary questions, but unfortunately becoming outdated. At occurrence of new versions of the given
software product, the description of new models Demos in application Help, is frequently executed insufficiently.
Additional, but enough useful literature, it is possible to name sources [7] - [9]. In [7] author gives the description to elements of the
automated electric drive, systems of scalar frequency steering, and the source [9] consecrates new enough question in the alternating current electric
drive – a direct control of the moment.
From foreign authors, special attention the source [11] in which the general questions of modern converting technics are taken well
up deserves.
As to Internet sources [12] on the given theme their use is ineffective. On occasion in the Internet probably to find article consecrating
any concrete question. The information resulted on pages, having end in itself advertising, is insufficient.
The basic lacks of the resulted sources is absence of description CED of an alternating current on the basis of ASKEM as uniform
mechanotronic systems, and the description of its parts is resulted only. That is very important at modelling during designing.
Occurrence of digital control systems has raised reliability of electromechanical system as a whole, and also has allowed to realise difficult algorithms
of management of the electric drive, at its adjustment and steady work.
The structure on base the converter the frequencies (rectifier-filter-inverter-adkz) to which consideration the preference is given in the given
work became classical structure CED of an alternating current recently.
In the world market of converting technics following firms-leaders were allocated: SIMENS, Shneider Electrique, Control Technique, ABB, Lenze
which let out CED an alternating current. Each new generation of converters of frequency contains the increasing number of functions, both operating the
electromotor, and improving technological process. Basically it is functions:
—Maintenance necessary tahograms of acceleration and deceleration ;
—Regulation of speed in the established mode;
—Precision tasks of speed and acceleration;
—Backspacing maintenance;
—Converter autotunes;
—Processing of signals of the feedback got in a control system;
—The organisation of contours of management;
—Protection of the converter from current overloads;
—Realisation of algorithms of power savings;
—Realisation of various principles of management;
—Visualisation of signals;
—Integration of the converter into a control system of higher level (an industrial network);
—Special technological functions;
For the account of application of the specified functions which have been built in in modern CED, firm Shneider Electrique converters have found
application in following electric drives:
—Pump units of modern systems of heating (Altivar 21);
—Systems of ventilation of buildings and constructions (Altivar 21);
—The hoisting-and-transport equipment (Altivar 71);
—Lifts (Altivar 71);
—The packing equipment (Altivar 71);
—Textile machines (Altivar 71);
Firm Control Technique converters:
—An iron and steel industry (Unidrive SP);
—Crane mechanisms (Unidrive SP);
—Lifts (Unidrive SP);
—Pumps and fans (Commander SK);
—Conveyors (Commander SK);
—Mixers (Commander SK);
Apparently from appointment of models developed and widely introduced CED, the firm-manufacturer lets out CED oriented to group or several groups of
mechanisms. The problem of unification CED continues to dare. However unification CED bears also its rise in price with cost increase, both a power part,
and a control system, increase in overall dimensions.
Thus, modern converting drive the technical, takes huge steps to the development, constantly being improved and by that raising quality of technological
processes. Especially important thus there is a development of new approaches to its working out and designing, with attraction of the most powerful
computing means. For constant perfection, scientific researches and the well-founded decision-making, eliminating arising problems are necessary.
INTRODUCTION TO MPhil
In the given section of the author's abstract the theses added with illustrations, giving representation about
object of research of work are presented.
As noted above, modern most widespread structure CED of an alternating current, is the frequency converter
(fig. 1).
Figure 1- The converter of frequency with PWM
Pulse-width modulation is the tool with which help, formation of operating impulses is made
for maintenance of necessary frequency of feeding pressure on an exit of a link of an alternating current before ASKEM.
There are some algorithms PWM. The first algorithm of PWM has been offered still in the seventies [10]. It
consists in formation of periodical impulses which move on power keys for their opening, with shift on 60 degrees (for the bridge three-phase scheme).
The example of giving of unlocking impulses is presented on fig. 2.
Figure 2 - Example of giving of unlocking impulses at the most simple way PWM
Duration of unlocking impulses pay off on certain parities and allow to provide any target
frequency and any quantity of impulses in target linear pressure of the inverter.
Now other algorithms of PWM are applied: modified, vector, phase. Each of them has the specificity and is
considered in work separately. The possible structure of a control system three-phase AIT with PWM is presented on fig. 3.
Figure 3- Three-phase autonomous inverter with PWM, the feeding asynchronous electromotor
The processes proceeding in system with PWM, are presented on fig. 4.
Figure 4-Processes proceeding in system the inverter-engine at bilateral, sinusoidal PWM
As representation of mathematical model the ASKEM in system of coordinates focused on interlinkage of a rotor (on which basis the system of field oriented control is developed by an asynchronous drive) has been specified above, under condition of indemnification of cross communications, practically coincides with model of direct current motor. The motor block diagramme on which indemnification of internal feedback is shown is presented on fig. 5. By a dotted line the communications which are subject to indemnification are shown
Figure -5 Block diagramme the ASKEM at field oriented control in KS rotating with a speed of a interlinkag vector of a rotor
The full function chart of system of the electric drive of an alternating current on base ASKEM at field oriented control is presented in figure 6.
Figure 6-Function chart of system of field oriented control of ASKEM
OWN RESULTS
During the last period of work over MPhil (since September 2008-May, 2009) the following work has been executed:
1. Questions of electromechanical transformation of energy in CED on a basis of the frequency converter are in details studied.
2. Practical works on adjustment CED of firm Control Technique (Unidrive SP, Commander SK) are spent.
3. Mathematical model CED on a basis of the frequency converter is constructed.
4. Researches on the individual questions, concerning CED:
4.1. working out of algorithms of autotune CED;
4.2. identification of parametres ASKEM;
4.3. indirect definition of interlinkage a rotor in systems of field oriented control;
4.4. definition of speed sans sensors.
5. Article Is written and printed: «Identification of parametres of the asynchronous electromotor at carrying out of experiment of idling».
6. On republican competition of student's scientific works work is protected: «Estimation of rotor interlinkage of the asynchronous short-circuited
electromotor in systems of field oriented control ».
CONCLUTION
The material resulted in the author's abstract shows an urgency of the chosen theme, as on volume of the
made and forthcoming scientific researches, and on its practical importance for modern electromechanical systems.
At a writing of the given author's abstract MPhil is not finished yet. The planned date closed of MPhil: the second decade of
December, 2009. The full text of work can be received at the author (Minaev O.) or the head (Tolochko O.) after the named date.
LITERATURE
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