High-performance vector control ac speed regulating

High-performance vector control ac speed regulating system needs the support of modern control

theory,for ac motor,currently the most widely used is the "vector control scheme.Since 1971,Germany's

Siemens F.B laschke vector control principle,put forward the control scheme is popularity.Therefore,in-depth study on it.Vector control of the basic idea is:in ordinary three-phase ac motor on the simulation of the dc motor torque control law,the magnetic field orientation coordinates by the vector transformation,the three-phase ac motor stator current is decomposed into excitation current and 220v ac electric motorstorque current component,and make the two component perpendicular,independent of each other,and then adjust respectively,in order to obtain good dynamic characteristics as dc motor.So the vector control is the key of stator current amplitude and spatial location (the control of frequency and phase).Vector control is the purpose of improving torque control performance,the final implementation is to id,IQ's control.

Due to the quantity of the stator side is communication,the space vector in space to synchronous speed rotation,so isn't very convenient for adjustment,control,and computing.Need a complex coordinate transformation of vector control,and reliance on motor parameter is large,it is difficult to guarantee complete decoupling,make the control effect.3.3 direct torque control of vector control scheme is an effective ac servo motor control scheme.But because of the need of complex vector rotation transformation,and the mechanical constant is lower than the electromagnetic constants of the motor,so can't quickly response to the torque vector control.In view of the vector control of this defect,German scholar Depenbrock in the 1980 s proposed a control scheme with fast torque response characteristics,namely direct torque control (DTC).This control scheme to abandon the idea of decoupling control vector control and current feedback loop,adopt the method of stator flux,using discrete two point control of the stator flux linkage and torque of the motor directly adjusted,has simple structure,fast torque response,etc.The earliest used in induction motor DTC,1997 L Zhong and others,the modification of DTC algorithm for permanent magnet synchronous motor control,there are related to the simulation and experimental research.DTC method to realize double closed loop control of flux and torque.

After getting the flux linkage and torque of the motor values,the permanent magnet synchronous motor DTC.Figure 2 shows the permanent magnet synchronous motor DTC scheme structure diagram.It consists of permanent magnet synchronous motor,inverter,torque estimation,flux estimation and voltage vector switch table link,the ud,uq,id,IQ as static (d,q) voltage and current components in the coordinate

system.Though,the study of DTC has made great progress,but in theory and practice is not enough

mature,such as:low speed performance,load capacity,etc.,and its high real-time requirements,large amount of calculation.3.4 decoupling control of permanent magnet synchronous motor mathematical model after coordinate transformation,id,id still exist between coupling,cannot achieve the independent

regulation of id and IQ.If you want to make the permanent magnet synchronous motor to obtain good dynamic and static performance,it must solve the id,IQ of decoupling problem.If can control id

constant 0,can ac geared motor simplify the equation of state of permanent magnet synchronous motor for:at this point,the id and IQ has no coupling relation,Te = np bits of fiq,independent adjustment IQ can

realize the linearization of the torque.Decoupling control,realize id constant 0 voltage type can be

used decoupling and current mode decoupling.

The former is a completely decoupling control System solutions,can be used to id,generator stator IQ completely decoupled,but implementation is more complicated; The latter is a kind of approximate decoupling control scheme,the control principle is:select appropriate id ring current regulator parameters,make its have considerable gain,and always make the controller of the reference input command id * = O,id available material id * = 0,IQ material IQ * O,thus to obtain the approximate decoupling of permanent magnet synchronous motor.Figure 3 shows based on vector control and id * = O decoupling control of permanent magnet synchronous motor speed control system block diagram.Although current mode decoupling control scheme can't completely decoupled,but is still an effective control method,as long as take the better way to handle it,also can www.facebook.com/guohong.trading get high accuracy of torque control.Therefore,to use the current engineering type more of decoupling control scheme.Current mode decoupling control,however,can only achieve the rotational speed of motor current and static decoupling,if the dynamic coupling will influence the control accuracy of the motor.In addition,current mode decoupling control by making the coupling of a remains the same,will introduce a lagging power factor.