Research On Dynamic Mechanical Load Emulation Scheme For Test Of Electric Machine And Its Controller

Electric machine and its controller can be used to emulate real mechanical load,and test the performance of motor under test and its controller.Mechanical load emulation system replaces real loads in laboratory,which greatly reduces test risk,cost and time.Traditional load emulation scheme can emulate the static mechanical load with constant torque to test the steadystate characteristics of electric machine.But it cannot emulate the dynamic and time-varying mechanical load.In fact,it is dynamic mechanical loads that challenge the performance of motors and their controllers,so it is particularly important to emulate dynamic mechanical load for dynamic test of the motor.In order to realize motor dynamic test,specific scheme of dynamic mechanical load emulation are investigated.An induction motors back-to-back test platform for induction motor dynamic test is build,and the related control strategies of the test platform are studied.The main contents are as follows:(1)According to characteristics of motor dynamic test,load motor is coaxial connected with motor under test,and load motor is controlled to emulate torque characteristics of the mechanical loads.(2)Mathematical model of induction motors back-to-back test platform is established.Direct torque control strategy is adopted to control load motor to meet need of fast torque response.Vector control scheme based on grid voltage orientation are utilized in PWM rectifier to realize the bidirectional flow of energy.(3)Control strategy of dynamic mechanical load emulation is proposed.Calculation of the torque of inertial mechanical load involves the derivative of motor velocity,in order to solve the problem of noise interference caused by difference,a speed closed-loop scheme based on inverse dynamics is proposed for inertia mechanical load emulation to solve the problem due to differentiation of speeds.(4)A prototype of induction motors back-to-back connected is manufacture,software and hardware of the prototype are designed.Effectiveness is verified by experiments.