Research On Direct Torque Control Based Dynamometer For Dynamic Emulation Of Mechanical Loads

The dynamometer is core equipment of motor performance test station, mechanical drive test station and engine performance test station. Traditional dynamometers, such as hysteretic dynamometers, eddy current dynamometers, mechanic dynamometers and waterpower dynamometers, may consume lots of fuels and electrical energy while working, which causes the energy waste. Also, these dynamometers should be equipped with additional radiators to keep the dynamometers cool. Electrical dynamometer works as a generator when operating, which can convert mechanical energy to electrical energy and feed it back to the AC networks, the others do not have this function. A type of novel electrical dynamometer based on direct torque control (DTC) is presented in this dissertation. A permanent magnet synchronous motor (PMSM) is used and the load torque is estimated so as to eliminate the torque transducer which can reduce the hardware cost. The motor under test receive power from AC network and drive the load machine which feed back the energy to the DC-bus by an inverter. The common DC bus technology which achieves the circular use of power can not only save the energy cost but also improve the testing range.Mostly, dynamometers have been used to perform static load tests. The performance is then evaluated by measuring the torque-speed characteristic, power losses, efficiency, etc. For testing variable speed electric drives, static load tests are not sufficient, because dynamic or non-linear effects in some loads can be dominant. Therefore a dynamometer for testing of drives should be able to perform dynamical tests. The dynamometer presented by this dissertation can not only used for static load test but also make the load torque change with the shaft velocity in order to be used for dynamic load test. Firstly, a variable speed drive system based on DTC is simulated, then a simulation model of dynamometer is established. The simulation consists of two parts: dynamic test and static test. The result shows that the system can track the changing torque reference, so this is a feasible strategy.After the feasible research a experimental platform is established. Use digital signal processor (DSP) TMS320LF2407 as CPU, to control IPM 7MBP50RA120 which drive the PMSM. At last, an experiment is done to check the drive circuit. The result shows that the drive board works well and can output the needed drive signal.