Study On Energy Feedback Technology Of AC Servo

Since the diodes are generally used in AC servo drive, power cannot flowbi-directionally. The energy utilization efficiency is low, because the braking energy of theAC servo motors is converted into heat. Therefore, it is important to improve the energyutilization efficiency of AC servo drive. PWM rectifier has many advantages, includingbi-directional flow of the power, controllable dc bus, sinusoid current, controllable powerfactor and so on. For the reasons above, PWM rectifier, instead of diode, has beenimplemented in the AC servo, and researches on energy feedback system for AC servo havebeen carried out in this paper. It has both important theoretical significance and practicalvalue.Voltage-source PWM rectifier has been designed as the main circuit of the energyfeedback system. Operation modes have been analyzed to demonstrate bi-directional flowof the power. Linear operation area of the energy feedback system has been also analyzedand the mathematical models have been built in both static and rotating coordinate system.Researches on control strategies have been carried out for two kinds of energy feedbacksystems. For the energy feedback systems with grid voltage sensors, synchronizingphase-lock-loop (PLL) has been studied to capture the phase of grid voltage. Currentcontrol has been studied based on fully decoupled method and parameter design principle.For the energy feedback systems without grid voltage sensors, an observer has been studiedto measure the virtual flux. Initial values have been avoided for the numerical integrator,and power control has been used instead of current control. Simulation model of energyfeedback system for AC servo has been also built in Matlab/Simulink usingSimPowerSystems library and the simulation results have been achieved to verify thecontrol strategies.Based on TMS320F28335of Texas Instrument, an experiment platform of AC servo has been designed, including the driving system and the energy feedback system. Key parts ofthe hardware design and software design have been presented in this paper. Throughsimulating the braking operation of the AC servo motor, experiment results have beenachieved to verify that bidirectional flow of the power can be realized in the energyfeedback system for the AC servo.