CN1111745C - Real time monitering and displaying system for current of brushless magnet excited generator rotor - Google Patents

Abstract

The present invention discloses a real time monitoring and displaying system for a current of a brushless excitation generator rotor, which relates to electric quantity measurement, electromagnetism computation and computer techniques. In order to solve the problem of the longtime unable measurement of a current of a brushless excitation generator rotor, the present invention is composed of an intelligent measuring and controlling terminal, a communication port converter and a computer. A computing module for a current of a rotor, and a computing module for a current of a negative sequence current of a stator are compiled in the computer for monitoring and displaying the current of a rotor in real time and visually displaying the per unit of the negative sequence current; thereby, the goal of safe and economic operation of a machine set is achieved.

Description

A kind of monitoring brushless excitation generator rotor current I in real time that uses a computer fMethod

Technical field

The present invention relates to monitor brushless excitation generator rotor current I _fMethod, specifically, relate to electrical measurement, electromagnetism and calculate and computer technology.

Background technology

The brushless excitation of generator is a kind of novel excitation mode that extensively adopts during the last ten years, has compact conformation, advantage such as easy to maintenance, thereby obtains application more and more widely.But can not insert table meter in Generator's Rotor Circuit,, bring to safety, the economical operation of unit to have a strong impact on so its rotor current can't be measured.In order to overcome the above problems, the field personnel normally checks the P-Q curve of generator at present, finds out its meritorious limit value of exerting oneself, and reaches the purpose of monitoring.Desire to know the size of rotor current in addition, must at first measure the size of active power, reactive power and calculate power factor, check the V-characteristic that manufacturing plant provides according to power factor and the stator current measured again, and then find out the numerical value of rotor current.Obviously, look into that the figure process wastes time and energy and don't accurately.

Summary of the invention

The objective of the invention is to thoroughly change the present situation that the brushless excitation generator rotor current can't be monitored demonstration for a long time in real time, a kind of monitoring brushless excitation generator rotor current I in real time that uses a computer is provided _fMethod, guarantee the unit safety economical operation.

The object of the present invention is achieved like this, promptly the monitoring display system that is connected with the generator unit stator secondary circuit is made up of intelligent monitoring terminal, communication port converter, computing machine, connect with twisted-pair feeder successively, establishment has rotor current computing module and stator negative-sequence current computing module in its computing machine, thereby indirect calculation and show rotor current, and intuitively show the per unit value of negative-sequence current.

The present invention has the following advantages and good effect:

(1) monitors in real time and show rotor current, guarantee the unit safety economical operation, satisfied the needs of power department, filled up the blank of domestic and international this technical field.

(2) not investing in addition under the situation of hardware, utilize same system, only need establishment negative-sequence current computing module, just can intuitively show the negative-sequence current per unit value, make the system performance price than high.

(3) analyze by many-sided test display result, the shown rotor current of this device with check the V-characteristic income value relatively, its deviation is less than 1%, negative-sequence current value that shows and special-purpose negative-sequence current table test value are relatively, its deviation illustrates that less than 1% the present invention can satisfy requirement of engineering fully.

(4) fitting operation is simple, is convenient to promote.

Description of drawings

Fig. 1-monitoring display system composition diagram;

Fig. 2-software flow pattern;

Fig. 3-display.

Wherein: 1-generator, 2-intelligent monitoring terminal, 3-communication port converter, 4-computing machine, 5-generator amature, 6-generator unit stator, 7-current transformer (CT), 8-voltage transformer (VT) (PT), 9-short circuit terminal, 10-initialization, 11-call interface display module, 12-initialization serial communication interface, be timed in 13-1 second not, 14-bottom communication module, 15-conversion, 16-call the rotor current computing module, 17-call the negative-sequence current computing module, 18-call display module, 19-display.

Embodiment

Be described further below in conjunction with accompanying drawing.

As shown in Figure 1, this monitoring display system is made up of intelligent monitoring terminal 2, communication port converter 3, computing machine 4, connects with twisted-pair feeder successively; Generator 1 interconnects with intelligent monitoring terminal (2) by current transformer (CT) 7 and voltage transformer (VT) (PT) 8.

One intelligent monitoring terminal 2

In order accurately to calculate and demonstrate rotor current and stator negative-sequence current in real time, just must accurately collect active power, reactive power and the power factor of electric current, voltage and the generator of stator in real time, select for use high French DIRISC of the ratio of performance to price or Canadian ACM3300 to survey the inspection terminal for this reason, all had the RS485 interface.

Two communication port converters 3

Behind master-control room (or on screen), again by communication converter, the RS232 interface of last computing machine has guaranteed the reliability of transmission and communication to native system with RS485 interface mode long-distance transmissions data, and the technical indicator of communication port converter design is as follows:

Input RS232 interface (four lines)

Output RS485 interface (two wires)

Speed 19.2K and following

Maximum transmission distance 1200m

Power supply+5V

Power consumption≤1W

Three computing machines 4

1) rotor current computing module

1. electromagnetism calculating formula

The computing method of rotor current have multiple,, have selected the terraced phasor graph method of protecting in principle for use here, and through improving, have got the rotor total current: $I_f=\sqrt{{I^2}_{\mathrm{fa}}+{I^2}_{\mathrm{f\δ}}+2I_{\mathrm{fa}}{I}_{\mathrm{f\δ}}(\mathrm{USin\Φ}+{\mathrm{IX}}_p)/{\left(U\cos \mathrm{\Φ}\right)}^2+{(\mathrm{USin\Φ}+\mathrm{IXp})}^2}$

I _fa＝(I/I _e)I _fk—(X _p/100)I _δ $E_{\mathrm{\δ}}=\sqrt{{\left(U\cos \mathrm{\Φ}\right)}^2+{(\mathrm{USin\Φ}+\mathrm{IXp})}^2}$

Wherein:

I _Fa-corresponding to the part of generator armature reaction mmf rotor current.

I _{F δ}-corresponding to the part of the rotor current of generator built-in potential, it is according to E _δNumerical value check the generator no-load characteristic and try to achieve.

I _f-short-circuit current, the exciting current during for load current value.

I _δ-unloaded air gap exciting current.

I _e-the rated current of generator.

E _δ-generator built-in potential.

X _p-potier reactance.

Φ-power-factor angle.

2. set up generator no-load characteristic optimum mathematics model

According to principle of least square method, obtain:

f(x)＝a+bx+cx+……+nx

3. utilize above-mentioned electromagnetism calculating formula, utilize the service data that records in real time, utilize the mathematical model of setting up, finally set up the rotor current computing module.

2) negative-sequence current computing module

If the stator three-phase current that collects is respectively I _a, I _b, I _c, then have

a＝(I ² _a+I ² _b+I ² _c)/3

b＝(I ⁴ _a+I ⁴ _b+I ⁴ _c)/3 $c=\sqrt{3-2b/a^2}$

(3) interface display module adopts self-control dot matrix Chinese character, does not need the hanzi system support, makes software have dirigibility significantly, and font size can be adjusted arbitrarily simultaneously.

(4) software design

This software designs under DOS, the final * .EXE (execute file) that forms, without any need for environment, byte number is 200KB, there is not specific (special) requirements for internal memory, have very strong practicality, software flow as shown in Figure 2: initialization 10 → call interface display module 11 → initialization serial communication interface was timed to not 13 → bottom communication module 14 → conversion 15 → call rotor current computing module 16 → call negative-sequence current computing module 17 → call display module 18 in 12 → 1 seconds.

The present invention is in software design, and many crucial parts comprise aspects such as communication transmission, reception, timer work and software itself, and very strong fault-tolerant ability is all arranged.

The present invention is simple to operate, by keyboard, as required, calls corresponding module, can obtain real-time monitoring and demonstration.

The invention process is as follows:

(1) implementation principle

(1) to measure and gather the electric parameters of generator in service fast, in real time, exactly: electric current, voltage, active power, reactive power, power factor,

Each electric parameters that (2) will collect in real time is according to above-mentioned program and formula making software.

(3) relate to family curve and related parameter is arranged in calculating, must carry out conscientious search and confirming at the motor model of different models and capacity.

(2) embodiment

(1) adopt French DIRISC type or Canadian ACM3300 type intelligent observe and control instrument, RS/485 and RS/232 interface convertor have the common computer of RS/232 interface, connect with general twisted-pair power cable to get final product, and are applicable to the brushless excitation generator of various capacity.

(2) adopt French DISISC type and Canadian ACM3300 type intelligent observe and control instrument to carry out data acquisition, utilize the control system of unit and the main frame of telemechanical apparatus to carry out making software and computing, show by CRT or RTU, get final product, be applicable to big-and-middle-sized power station with the lead connection.

(3) the Canadian ACM3300 type intelligent observe and control instrument of employing is gathered and is shown, carries out computing with single-chip microcomputer.The rotor current that is applicable to small generator shows, and is easy for installation.

Claims (1)

1, a kind of method of monitoring brushless excitation generator rotor current If in real time that uses a computer,

Comprise the monitoring display system, this system is that intelligent monitoring terminal (2), communication port converter (3), computing machine (4) three parts connect with twisted-pair feeder successively, and generator (1) interconnects with intelligent monitoring terminal (2) by current transformer (CT) (7) and voltage transformer (VT) (PT) (8); It is characterized in that: establishment has rotor current computing module and stator negative-sequence current computing module in the computing machine (4);

1) rotor current computing module

1. electromagnetism calculating formula

Selected the terraced phasor graph method of protecting in principle for use, and, got the rotor total current through improving: $I_f=\sqrt{{I^2}_{\mathrm{fa}}+{I^2}_{\mathrm{f\δ}}+2I_{\mathrm{fa}}{I}_{\mathrm{f\δ}}(\mathrm{USin\Φ}+{\mathrm{IX}}_p)/{\left(U\cos \mathrm{\Φ}\right)}^2+{(\mathrm{USin\Φ}+\mathrm{IXp})}^2}$

I _fa＝(I/I _e)I _fk—(X _p/100)I _δ $E_{\mathrm{\δ}}=\sqrt{{\left(U\cos \mathrm{\Φ}\right)}^2+{(\mathrm{USin\Φ}+\mathrm{IXp})}^2}$

Wherein:

I _Fa-corresponding to the part of generator armature reaction mmf rotor current;

I _{F δ}-corresponding to the part of the rotor current of generator built-in potential, it is according to E _δNumerical value check the generator no-load characteristic and try to achieve;

I _Fk-short-circuit current, the exciting current during for load current value;

I _δ-unloaded air gap exciting current;

I _e-the rated current of generator;

E _δ-generator built-in potential;

X _p-potier reactance;

Φ-power-factor angle;

2. set up generator no-load characteristic optimum mathematics model

According to principle of least square method, obtain:

f(x)＝a+bx+cx+……+nx

3. utilize above-mentioned electromagnetism calculating formula, utilize the service data that records in real time, utilize the mathematical model of setting up, finally set up the rotor current computing module;

2) stator negative-sequence current computing module

If the stator three-phase current that collects is respectively I _a, I _b, I _c, then have

a＝(I ² _a+I ² _b+I ² _c)/3

b＝(I ⁴ _a+I ⁴ _b+I ⁴ _c)/3 $c=\sqrt{3-2b/a^2}$

3) interface display module adopts self-control dot matrix Chinese character, does not need the hanzi system support, makes software have dirigibility significantly, and font size can be adjusted arbitrarily simultaneously;

4) software design

This software designs under DOS, the final * .EXE (execute file) that forms, software flow: initialization (10) → call interface display module (11) → initialization serial communication interface (12) → 1 second is timed to not (13) → bottom communication module (14) → conversion (15) → call rotor current computing module (16) → call negative-sequence current computing module (17) → call display module (18).

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