Double Loop DC Speed Control System Description According to dynamic and static performance indicators of the speed system, this paper uses engineering design to set parameters of controllers based on principle of three close loop speed system. The approach using electrical principle and toolbox of simulink and power system in the Matlab completes the model and simulation of system. The model of current rate loop and mutual inductance in DC motors are introduced emphatically. Simulation result obtained is close to actual situation which shows the correction of the model Three closed loop DC main circuit is composed of double closed loop DC speed control system improvement. When the double closed loop DC speed control system, in the current rising phase, the current rises sharply, the rate of change is very big, will have serious consequences in the DC motor, such as generating additional electromotive force and mechanical transmission mechanism of high produced strong impact. In order to solve this problem, a current changes in the current ring rate ring, three-ring system composed of speed, current, the current rate of change. Speed regulator ASR to set the output limiting, to limit the maximum starting current. According to the needs of system, when the given voltage, ASR output saturation, the motor to the maximum allowed current starting, at the same time as the rate of change of current ADR ring role, so that the current rising slope has certain limit, when overshoot reaches a given speed speed, ASR desaturation, motor armature current decreases slowly. In this way, the three regulator role, enables the system to quickly achieve stability.With the current rate of change in the three-loop control system, the given signal output of ASR is ACR, and its limit to limit the maximum current; the output of the ACR is not directly control trigger circuit, but as the rate of change of current given input regulator of ADR, ADR negative feedback signal obtained from the current detection by differential link LD, ACR output limit limit current the biggest change rate. Finally, by the third output regulator of ADR limit determines the minimum control pulse trigger angleⅠ.system analysis and synthesis1.1．Analysis1.1.1 In the speed and current dual closed-loop speed control system, in order to change the motor speed, what parameters should be regulating? Change speed regulator Kn magnification work? Power electronic converter to change the magnification factor Ks work? Change the speed of the feedback coefficient of work? To change the motor's stall current system should adjust the parameters of what?A: To change the motor speed, change speed regulator Kn magnification and power electronic converters will not work magnification factor Ks, stable when n = Un = Un *, so the only change in the value of a given coefficient of Un * and feedback before. To change the motor's stall current, only need to change the same value given Uim * and feedback coefficient, because the stability, Uim * = Idm, can be drawn from the type1.1.2 Speed, the current double closed-loop speed control system when the steady-state operation, the two regulator input voltage and output voltage deviation is the number?A: The speed and current dual closed-loop speed control system when the steady-state operation, the two regulators are the input bias voltage is zero, by the formula n = Un = Un *, n = n; Uim * = Idm, Idm = Idl.1.1.3 In the speed and current dual closed-loop speed control system, the two regulators are PI regulator. When the system is running with rated load, the speed feedback line suddenly disconnected, the system re-enter the steady-state, the current regulator is the input bias voltage to zero? Why?A: When the system is running with rated load, the speed feedback line suddenly disconnected, then Un = 0, = Un *- Un = Un *, so that Ui to reach Uim, 0, rate of increase in n, when the system after re-entering the steady-state , that is, Id = Idl, then, = Uim *- Idl 0, are no longer changes, changes in rotational speed n is no longer, but at this time than the rotational speed n at the time of the feedback line speed to break big.1.1.4 Why is the speed with integral control system is not static poor? A: Speed regulator integral system, to achieve non-static error is due to the characteristics of integral control regulator, that is, the accumulation of points and the role of memory.1.1.5 Double-loop speed control system (PI), load changes, Idl> Idm, asked bicyclol speed control system ASR and ACR how-conditioning, the result?A: When the load changes, Idl> Idm, speed decreased rapidly, the current Id soon to Idm, and of limited amplitude, rapid rate of ASR saturation, ACR has been limiting conditions, to form a blocking phenomenon, long-running will damage the system.1.2. SystemSpeed regulator and current regulator in the Double Loop DC Motor Control System can be summarized as follows:1.2.1. The role of speed regulatorSpeed regulator is a speed control system of the dominant regulator, which allows speed n will soon change with a given voltage Un * changes in steady-state speed error can be reduced, if the PI regulator can achieve the non-static error.1) The effect of load changes in the role of anti-disturbance.2) The output amplitude of the decision limit the maximum allowable motor current.1.2.2 The role of current regulator1) As a regulator of the inner ring, outer ring at the speed of the adjustment process, it makes the current closely followed the given voltage Ui * (that is, the outer ring modulator output) changes.2) Fluctuations in voltage from the role of disturbance rejection in time.3) The speed of the dynamic process of ensuring that the maximum allowable motor current, thereby speeding up the dynamic process.4) When the motor overload or stall when the armature current limit of the maximum, automatic protection from the role of acceleration. Once the fault disappears, the system automatically return to normal. Yesterday, the role of the reliable operation is very important.2.Ⅱdouble-loop speed control system common faults analysis 2.1.Introduction of a system2.1.1. Double-loop speed control system components in Figure 1.1 Current loop: from the current regulator LT, trigger CF (input transformation for the CSR), silicon-controlled rectifier bridge, motor armature and current loop transform LB component. the speed of outer ring: the speed regulator from ST, current loop, such as link inertia, motor and load momentof inertia and the speed of transformation components SB. in the double-loop speed control system, the speed of the decision loop of the running characteristics of the whole system and stability, and play a leading role, and to change the current ring plays the role of the internal structure of the system is dependent, but since it is as a whole to participate in the closed-loop speed to the speed of a direct impact on the work of the closed-loop, it must first good debugging current loop, and then testing the speed of outer ring, so that the whole system has good dynamic performance.2.1.2. Double-loop speed control system of the typical working condition1) Start (or the speed):ST in the start-up process has been saturated, so that the speed of this loop in the equivalent open-loop state. System only in the constant current loop under the regulation to ensure the motor at a constant current of the maximum allowable under the start-up.Figure 1 double-loop speed control system structure2) slow down (or stop):ST at this time to reach the output amplitude of the reverse limit. Main circuit current by the bridge is reduced to zero after the inverter. LT and CSR output will soon reach the maximum reverse. CF pulse output to reach βmin, current loop for open-loop. motor torque under deceleration until the motor speed close to the given new value, current loop and speed loop one after another into the closed-loop work, motor in the new value of a given run .3) Grid voltage fluctuation: This motor because of the larger moment of inertia, which caused the first change in armature current, ST output also did not change the effect of current loop, LT rapidly changing the output so that angle α be adjusted quickly, so the impact on the speed .4）Small changes in load: in the operation, load changes, will cause the motor speeddeviation from the given value. speed up the recovery process and the aforementioned speed (or deceleration) is similar to the process.2. 2 Common Fault Analysis and Processing2.2.1 The normal supply voltage, thyristor rectifier output waveform arrhythmia caused by this phenomenon is due to trigger sawtooth slope caused inconsistency. Sawtooth slope adjust potentiometer, the output waveform uniformity could be achieved. in the adjustment process to strike a balance between Qi, this point should be paid attention to the actual debugging.2.2.2 DC Motor Analysis of mechanical properties of soft thyristor DC motor system, when the current intermittent mechanical properties when the first no-load speed is characterized by high ideals, and the second is characterized by mechanical properties of soft . The so-called mechanical features soft, that is, small changes in load will cause great changes in speed. oscilloscope to observe when using the bridge rectifier output waveform, one may find that missing relative. at this time need to check whether the trigger has pulse output, fast whether the fuse melting, whether the breakdown or thyristor circuit, synchronous transformer is damaged, whether the lack of power. to identify the problems, can be resolved.2.2.3The speed of the speed of instability caused by many factors of instability:1) Electric guns are not firmly fixed or with the host of different axis .2) The parameters of the speed regulator inappropriate. Respond to the dynamic parameters to adjust (change the ratio of integral parameters ) .3) Of a speed control system there are(or bad)4) May be caused as a result of interference. should be found to interfere with the reasons for taking anti-jamming measures.2.2.4 A little to the set rated motor speed is higher than that should first check whether it is normal for the external control system, such as outside the normal control system, it may be given points, speed regulator, current regulator, such as caused by link failure. Should be cut off the main circuit power supply, only the control system to the electricity, not a given in the case, testing each of the key points (such as the current regulator, voltage regulator, etc. of thepotential. and then given together with the former to one by one after each of the key points to check the potential changes, you can find out the fault lies.2.2.5 Bridge rectifier output voltage is not high stressed1) the speed regulator and current regulator limiter too small, should be liberalizedin accordance with appropriate amplitude threshold .2) than the speed feedback signal, in that they can reduce the rate of appropriate feedback signals.2.2.6 To the timing system still in the absence of low-speed operation (that is, the phenomenon of emergence of reptiles) This is because the system of "zero drift" caused by. When the input signal is zero, the output voltage by the input amplification stage of the offset potentiometer decisions can be offset by adjusting the potential allows α = 90 °, at this time to zero output voltage rectification system, the electrical will not crawl.2.2.7 With a given system can not runShould first check whether it is normal for the external control system, such as outside the normal control system, it may be given points, speed regulator, currentregulator, such as caused by link failure. Shall be cut off main circuit power supply, only the control system to the electricity, not Add the given circumstances, the key points of each test (such as the current regulator, voltage regulator, etc.) of the potential. and then combined with a given, after the previous one by one to each of the key points to check the potential changes, that is, where to find fault.2.2.8 Lack of control accuracy in the distributor for a given run-time external control often requires precision sufficient parking in order to work properly. If poor precision parking, you can adjust the speed of the appropriate regulator of the PI link, generally by reducing the the ratio of the integral part of efforts to get satisfactory results.2.2.9 Reversible system oscillation1) open-loop system in the state (the main circuit disconnect) the oscillation can be changed at this time given the previous inspection to the key points of the potential changes. If a given unchanged, but the potential is still a point of change, here is the crux of .2) system in the state when the closed-loop oscillation, in which case in order to ensure the safety of the electrical load should be replaced by the general resistance of the load, if there is no suitable resistance box which can be used in place of the two electric sub-series. inspection methods and similar open-loop, focusing on the link to check is: given points, level detection, operation control, such as the speed regulator. oscillations are often caused as a result of operational amplifiers, such as damage to electronic components , system parameters caused by improper, according to the specific circumstances, properly addressed.This paper mainly introduces the structure，working principle and controller tuning method of boiler cascade three—parameter control system．And the characteristic of this control system iS simulated．Simulation results show that the control system can eliminate the interference caused by load(steam volume)changes and water flow，be able to guarantee safe and stable operation of generating units．It can be seen from the simulation results in figure, in the motor start-up phase, the current regulation motor armature current under the action of close to the maximum, the motor starts to rise time optimal criterion. It can be seen from the figure, in the current rising and falling stage, transition time of three closed-loop system than the transition time of double closed loop length, this is because when the current rate of change is too large, because the current regulator ADR, current rise and fall speed slow. In addition to the current rise and decline stage, the rate of change of current loop play a role, others in the same starting process and double closed loop. It not only keeps the advantages of double closed loop, but also overcomes the double closed loop current during start-up rate too much.闭环直流调速系统的说明1 背景在分析三闭环直流调速系统原理基础上，根据系统的动、静态性能指标采用工程设计方法设计调节器参数，并运用Matlab 的Simulink 和Power System 工具箱、面向系统电气原理结构图的仿真方法，实现了转速电流三闭环直流调速系统的建模与仿真；重点介绍了电流变化率环建模、直流电机模块互感等参数的设置，给出了直流可逆调速系统的仿真模型和结果，仿真结果验证了仿真模型及参数设置的正确性。
