Introduction
The excitation governing system is synchronous generator very important constituent [2], its primary mission is provides adjustable direct current or the voltage to synchronous generator’s exciting winding, thus cybertron terminal voltage’s constant, satisfies the generator normal electricity generation the need. In recent years, microcomputer field regulator [1] by its hardware architecture simple, clear, the equipment versatility was good, the standardized degree was high, the software nimble, could facilitate realizes many kinds of functions and satisfies each kind of control rule merits and so on request, obtained the widespread application in many electric power industries. But, the single microcomputer excitation system various links reliability is again high, broke down possibly still to exist, to guarantee that excitation system’s reliability service, the microcomputer field regulator should provide the network the reliable correspondence connection, caused the distant place the dispatcher or the factory level staff could facilitate free operate the engine off, the vertical speed pressure-rise, the incorporation, the adjustment power (including active and idle work) and so on operations. Therefore, this article uses a bench work to control machine takes the superior machine, realizes through many RS-485 industrial control main line to many excitation source’s electric current initialization and the data acquisition. The use microcomputer excitation system realizes the local current control, the excitation source condition monitoring as well as data gathering, carries on the long-distance correspondence through the RS-485 communication mouth, thus constituted a complete excitation source control system.
Figure 1 control system structure drawing
According to the actual need, the excitation source control system’s superior machine picks employing labor to control machine, used the RS-485 industry to insert the card, altogether had 6 communication mouths, then the surface many excitation source assigned in these 6 communication mouth, controlled machine the common control by the labor. Lower position machine of monolithic integrated circuit and other digital circuit system composition. This system’s structure drawing as shown in Figure 1.
2 microcomputer excitation system main return route
The microcomputer field regulator changes the silicon-controlled rectifier along with the excitation source operating condition’s change to lead can control the angle, thus achieves the automatic control generator exciting current the goal, guaranteed that the excitation source can output the stable load voltage.
Figure 2 excitation system wiring diagram
Excitation system main return route wiring way as shown in Figure 2 [1][3], the excitation source is from the generator export bus bar, changes supplies after the appropriate value the rectifier unit rectification the supplies generator armature winding after excitation transformer LB the generator voltage. The leveling circuit uses three-phase bridge-type all controls leveling circuit [1], this electric circuit’s operating feature is, may also work in the rectification condition, will exchange turns the cocurrent to take the generator excitation source, may also work in the contravariant condition, will direct current turns the exchange, realizes the contravariant demagnetization, the release exciting winding’s energy, thus achieves protects generator’s goal. The generator machine terminal voltage, the stator current respectively passes through transformer YH, the current transformer to transform the LH transformation is two values passes through A/D to deliver again to the monolithic integrated circuit, after computer operation the output control quantity controls the thyristor the breakover angle, causes the voltage regulation to permit in the scope.
From shunt excitation excitation way generator terminal voltage Ud0 and between the excitation voltage Ud relations are [2]:
And: Xk- exchange return route reactance;
δu - time bridge arm part breakover forward voltage drop;
r- return route resistance.
If δu neglects the phase change reactance and the rectifier cell pressure drop influence, then machine the terminal voltage and excitation voltage’s relations are:
. May know by this type, excitation voltage Ud is proportional with machine terminal voltage Ud0.
3 microcomputer field regulator’s hardware constitution
Figure 3 field regulator schematic diagram
The microcomputer field regulator by the monolithic integrated circuit and the electric power supply monitoring, the D/A control, a/D gathering and so on is composed, its hardware diagram as shown in Figure 3.
AT89C52 I/O port after isolation carries on the monitoring to the excitation source work power source, as well as the exchange presses the module the working voltage to carry on the control.
In system’s D/A control system is the excitation source works when adjusts the electric current the foundation channel, has selected MAXIM Corporation’s MAX536 chip. The D/A control system needs two channels, controls the excitation source voltage datum and the phase modulation voltage datum separately.
The excitation source system’s data monitoring needs two group A/D. And group A/D through in gathering excitation source main system’s in sample resistance working voltage, but causes the main control room the control personnel can know that each excitation source’s active status is whether normal. Other group A/D carries on the monitoring to the regulation tube voltage. A/D chip uses MAXIM Corporation’s MAX197 multi-measuring ranges, 12 bit data gathering system (DAS). A/D system and the D/A system constitute the closed-loop control system together, achieves adjusts silicon-controlled rectifier’s breakover angle goal.
4 microcomputer field regulator’s software design
The microcomputer field regulator software uses the modulation structural design, each kind of function completes by the corresponding subroutine,
Figure 4 the excitation source loads the process flow chart
The software system is realizes through on lower position machine division of labor coordination. The lower position machine monitor scene’s active status, carries on the data gathering and the primary treatment. The superior machine uses industry PLC to make the long-distance monitoring. The monolithic integrated circuit shoulders in the excitation source is providing the voltage reference, the control regulation tube voltage, operational data gathering, the surveillance excitation source active status as well as controls with the superior labor machine carries on the correspondence, return excitation source functions and so on active status and operational data.
In order to realize the fine adjustment synchronous generator machine the terminal voltage and the control synchronous generator’s reactive power, the field regulator must continuously the comparison machine terminal voltage actual value and the given value, and the real-time change silicon-controlled rectifier’s control angle, guaranteed that the excitation voltage makes the rapid reaction to the operating mode change. Its flow as shown in Figure 4.
On after regulator electricity, carries out the initialization and self-checks, after the initialization had ended, indicated that the field regulator was already ready, then the procedure enters the establishment which urges and urges the condition the distinction, then enters the master routine. First is the data acquisition and the processing part; Mainly by the electrical machinery export alternating voltage sampling submodule, the electrical machinery export alternating current sampling processing submodule and the excitation voltage sampling processing submodule three parts is composed. Then enters the power factor reckoning module and the PID adjustment module; And, selects digital filtering’s method to obtain the power factor cosφ, calculates silicon-controlled rectifier’s breakover angle again through the PID adjustment.
Because the excitation control system is quite complex, needs to survey the quantity are quite many, therefore this systemic voltage and electric current gathering, use cocurrent sampling law and digital PID control adjustment law. The PID adjustment basis for calculation gathering data result and the rated value carry on the comparison, thus carries on the PID adjustment to calculate silicon-controlled rectifier’s triggering angle Alpha; The PID algorithm has used one kind of intelligence the modal control rule, according to the system deviation signal’s size, the direction and the change tendency makes the corresponding decision-making, chooses the suitable control model to carry on the control, has the good adaptiveness and the greatly strengthened robustness. The frequency survey is through transports the input profile puts turns a square-wave, this square-wave pares negative half part through the diode, finally enters monolithic integrated circuit’s high speed input port.
In operational data gathering, to eliminate the random disturbance influence which in a gathering process possibly receives, has used the averaging value method. After like this passes through 6 second gathering process, then deposited time this power source this work in monolithic integrated circuit’s data buffer to be biggest and the smallest effective value, will cause the labor to control machine later to be possible to search. Time work data acquisition flow as shown in Figure 5.
5 antijamming designs
Figure 5 excitation source data acquisition process flow chart
Because system’s monolithic integrated circuit and other digital circuit system with other simulation high voltage, the big electric current’s component places in together an engine case, system’s working conditions are quite bad and complex, its application’s reliability, the security become a very prominent question. For guarantee observation system long-term, stable, reliable movement, presently on the influence observation system reliable, safe operation’s primary factor and the solution explanation is as follows.
5.1 data acquisition error enlarges
The disturbance invasion measuring unit simulated signal’s input channel superimposition above the wanted signal, will cause the data acquisition error to enlarge, because system’s measuring accuracy will be high, the disturbance will appear more serious.
In view of this question, carries on the consideration and the solution from the hardware and the software two aspects.①Hardware aspect: Uses the electric capacity on the integrated circuit and the gathering channel, reduces power source’s disturbance; Next, the signal gathering ties use shielded wire, will cause the gathering signal not to receive the outside in the transmission process the disturbance.②Software aspect: Uses the digital filtering, because system’s disturbance is the random disturbance, and was measured that the parameter variation is slow, may use the digital filtering (is reduces unwanted signal through certain software routine) the method suppresses or the filtration.
5.2 control state malfunction and program run abnormal processing
The control state malfunction and the program run abnormal have mainly used the following methods:①The system uses floats designs;②Uses the software to intercept the technology (instruction redundancy, software trap);③The monolithic integrated circuit uses the power source surveillance and “the watch-dog” the electric circuit;④Carries on the shield to the digital circuit;⑤Load output isolation.
5.3 control circuits (MCU part) and main circuit’s isolation
In the overall system, the monolithic integrated circuit and the outside power switch component will use isolates the drive type, the isolating circuit module the control circuit module, the host exciting circuit module will isolate mutually. Like this carries on the design is mainly avoids leading to the disastrous consequence. Although the isolation actuation may divide into the electromagnetism isolation and the electro-optic isolates two ways, because this article must produce excitation frequency low frequency in 4Hz, high frequency about 100Hz, is bad regarding the electro-optical isolation syntype inhibiting ability, the transmission speed slow shortcoming is unimportant; Simultaneously because the electro-optical isolation has the volume to be small, structure simple and so on merits, moreover may reduce the disturbance, therefore this system selects the electro-optical isolation method. The isolated component uses the TLP521 electro-optic pair, is separately connected with the electro-optical pair connected monolithic integrated circuit’s two pin’s PWM profiles through two 470Ω resistances with two electro-optical pairs, simultaneously controls monolithic integrated circuit’s two pins to output the height level alternately, thus enables in the exciting coil to obtain the pro and con bidirectional voltage. Starts once again, produces in the exciting coil with the monolithic integrated circuit corresponding pin on the same frequency profile, is only the scope is dissimilar. Meanwhile supposed the time delay 0.01ms procedure in the lower position machine specialized middle school to carry on the software time delay, the goal is for the further guaranteed power tube when work will have the overlap breakover to create the damage, increased the reliability.
6 concluding remark
This article introduced in detail controls machine and the monolithic integrated circuit based on the labor has the network control function field regulator system, has realized the dispatcher or the factory level staff can the remote control system operate the engine off, the vertical speed pressure-rise, the incorporation, the adjustment power (including active and idle work) and so on operations.
This article author innovates the spot is: Discussed (PLC) and the lower position machine (at89C52 monolithic integrated circuit) the serial communication realizes the principle of work which and the method based on the superior machine the field regulator adjusts, and has given the superior machine and the lower position machine program structure. Proved after the practice, in excitation source’s scene debugged and in actually the use has achieved the anticipated effect, this system could the long-term stability, the reliable movement.
Reference
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[2] Ding Mou. Power plant excitation adjustment, Beijing: Chinese Electric power Publishing house, 1998.
[3] Gao Shuangyin, Geng Shaoyi. Monolithic integrated circuit field regulator’s application, Heilongjiang water conservation science and technology, 2004,(1):105-106.
[4] Chen Jianwei, Tan Jianping, Gong Zhongliang and so on. Outside miniature axialflow type blood pump magnetism driving circuit design, micro computer information, 2005.21(2):88-89
