Power-fed Ac Chassis Dynamometer DTC Control System

The chassis dynamometer is a kind of core indoor-frame-test equipment, which can realize the full function vehicle performance test without disassembling it, such as: dynamic performance, exhaust test, automobile detection or diagnosis. With the rapid development of China's automobile industry, China has become the largest auto consumption market and production market. As a result, vehicle performance and quality demands increasingly high, and more attentions have been concentrated on the multi-function and high-performance chassis dynamometer, even on conception of modern chassis dynamometer based driving simulation. In recent years, thanks to high speed and high power electronics technology, such as IGBT, as well as the development and application of power electronics, computer, control theory, the AC automobile chassis dynamometer becomes the main trend of this field. Consequently, building the DTC controlled system of the power-fed AC chassis dynamometer, based on the three phase PWM rectifier and direct torque control (DTC) of AC induction motor, is carried out in the paper.In order to recur the road and resistance of the automobile, we analyze the resistance of the car driving on the road and on the chassis dynamometer respectively, draw a resistance equation separately about the car, make the contrast of the two equations, obtain their difference and put forward the electric simulation model. And then, above the fommer analysis, we try to build the vehicle-performance-test system based on steering simulation, simulate the dynamic responses of vehicle accelerating and braking, and validate the feasiability of chassis dynamometer based on the steering technology. Based on the resistance compensation model, we realize the continuous simulation of the inertia using the method of electric simulation in stead of the traditional mechanical simulation which loads the simulation resistance by assembling limited flywheels. To overcome torque response lag, torque ripple and other issues of the current inertia electric simulation, the main motor control system is realized by the"AC-DC-AC"configuration, which is separated by grid side control system and mechanical control system. In the grid side, we adopt Voltage-Oriented Control (VOC) pulse widths modulate (PWM) commute strategy, as well as the method of space vector PWM (SVPWM), decoupling control strategy to the Voltage Source Rectifier (VSR) to realize the grid-side dismissed-coupling current control and bi-directional energy flow. In the mechanical side, we adopt DTC strategy based on the torque prediction, and select the SVPWM as the modulate strategy of the torque control.Based on the analysis above, combined with the mechanical transform theory of the chassis dynamometer, we build electric-mechanical simulation model to analyze and research the dynamic-static performance. The feasibility of bi-directional energy flow mechanism and PWM converter technology with unit power factor is also discussed. Besides, the torque and speed response on generate electricity state and electro motion state are presented. It can been concluded that no matter what different torque and different speed both not only keep steady and quick dynamic response, but also feed back the generated energy to AC mains with unit power factor.Finally, the whole system selects LabVIEW as the software design tools and development environment, and then, we implement the algorithm design of main control system, develop the vehicle performance test system, finally give the system test interface. In order to load real-time torque resistance, that is, to fellow the expected torque calculated from the method of improved DTC algorithm, NI high-speed sample card and controller, IPM power module, and etc, are chosen for hardware system. On the grounds of the contrast of calculated results and measured results, the system can meet the expected response speed and accuracy.