Research And Realization Of SFO Continuous Vector Control Stragety For Induction Motor

It is well known that rotor parameters of induction motor are subjected to variability and hard to be measured, which will deteriorate performance of control systems based on the mathematical model depending upon rotor parameters, such as rotor flux oriented (RFO) vector control system, indirect self-regulation (ISR). To avoid effect of rotor parameters and improve system robustness, direct torque control (DTC) employs stator flux contorl scheme. However, DTC adopts bang-bang control in torque and flux controllers, which can not ensure high performance in low speed range.In this dissertation, an improved stator flux oriented (SFO) control strategy is proposed. Based on coordinate transformation and stator flux orientation, mathematical model of induction motor is derived. In this new system, control algorithm is independent of rotor resistance and all inductance parameters. In one words, new SFO system can not only obtain high steady/dynamic state performance, but also improve system robustness. The main contents and conclusions are as follows:1. Research different mathematical models of induction motor, which are described by various state variables, and analyze their difference in system robustness.2. Introduce and analyze operating principle of bang-bang control. Result of theoretical analysis and simulation indicate that bang-bang controller will result in torque ripple.3. Through analyzing relationship between voltage and flux in induction motor, a stator flux oriented voltage vector control scheme is proposed. This control scheme employs continuous torque and current control, and control algorithm is independent of rotor resistance and all inductance parameters. Therefore, new control scheme can obtain high dynamic performance and system robustness. In the end, we also indicate some disadvantages of this scheme.4. Propose SFO slip frequency vector control scheme. Configuring slip frequency through closed loop control, this control scheme overcomes main disadvantages of the scheme above, and improves dynamic performance remarkably.5. Research and realize M/T speed measurement based on TMS320 microprocessor, and its advantages are as followings: high reliable, applicable to large speed range, and insensitive to interference.6. Through analyzing advantages and disadvantages of existing U-I observation model, propose a novel and applicable control scheme of stator flux.7. Analyze performance characteristics of power device, such as effect of dead time, voltage drop, on/off delay time, and give applicable measures.8. Introduce switch-linear hybrid technique and its application in AC driving system.