Multirate Sampling AC Motor Speed Regulation System Based On TMS320F2812

Nowadays, AC speed regulation technology has widely applied in industrial fields. The highly developing economy requests that AC speed regulation system should have higher precision, wider speed-regulating range and faster response, which urges people to study the AC speed regulation technology continuously. Along with the rapid development of semiconductor industry, new power electronic devices and microprocessor make the AC speed regulation system more integrated and intelligent; and the hardware is becoming more compact and simple. The AC speed regulation system based on DSP and IPM has become more and more designers'preferred choice. Therefore, in order to verify the new AC speed regulation technology, AC speed regulation system based on TMS320F2812 and PM50RSA120 has been built up. In this paper, the design of main circuit, control circuit, protection circuit, and detection circuit is introduced in detail, and the anti-interference design is also discussed.Direct Torque Control(DTC) technology of induction motor, which follows the field-oriented control since 1980s, is a new control method for motor drive. Different from the decoupling algorithm of field-oriented control, DTC controls the motor torque directly; therefore, it has high dynamic performance. It only needs simple coordinate transformation. With an uncomplicated structure, it calculates the flux and the torque of AC electromotor using stator parameter, so it's not sensitive to the rotor parameters. Consequently, DTC has a broad application prospect. So, research on the control characteristics and performance improvement has become a hot spot.For the DTC system, the more information can be obtained which can improve the control performance of the system, when using the higher sampling frequency. The A/D conversion time of TMS320F2812 is only scores ns, so it can provide a higher sampling frequency for DTC system. But being limited by the inverter switching frequency, traditional DTC system works under a low sampling frequency, and its performance is restricted seriously. This paper combines the multirate digital control theory with DTC system, deduces a new method to calculate stator flux of the induction motor. The sampling frequency of the motor's output state is augmented meanwhile ensured the switching frequency meets the demand of inverter.In this paper, Matlab/Simulink models of traditional DTC system and DTC system based on multirate digital control theory have been built up to verify the feasibility of the two kinds of methods in theoretically. Then, selecting the 2.2kW motor as the controlled objects, and experimenting on the AC speed regulation system. The design of software and experimental results are introduced in detail. The experimental results show that the hardware design is reasonable; the DTC system has high precision, steady speed, and good dynamic and static performance. The new algorithm based on multirate digital control theory meets the control requirements. It is feasible and has some practical values to some degree.