Research On Inverter Of Space Vector Based On DSP

The constant ratio of voltage to frequency control, which also called constant V/F control, is one of the most popular controls in inverter application. With its'simple structure and low cost, constant V/F control is applied to some low dynamic performance applications such as fan, water pump and so forth. At present, there is a big market for this inverter due to its economy and popularity. In this paper, a specimen of the inverter system adopted a TMS320LF2407 DSP chip as its controller by using constant V/F control and space vector PWM technique is designed. Some key problems are analyzed in theory and methods of them are put forward. The main content in this paper is as following.1.After elaborating SPWM and SVPWM technology, their characteristics are compared in order to find which suits the practical application. Finally, SVPWM technology will be adopted.2.The paper expatiates on the reason of dead-time in theory, analyzes the influence of dead-time in SVPWM on output voltage and discusses the relation between the output voltage vector position and the three-phase current direction by using space vector graph. A new method, which divides the three-phase current into six regions and compensates only one phase output voltage in every region, to compensate the dead-time is put forward. Judging the angle of output voltage vector to acquire the direction of three-phase current, this method can avoid an appearance of many zeros when current is detected.3.Three-phase bridge incontrollable full-wave rectifier circuit and the inverter circuit constitute the main circuit of AC-DC-AC voltage source inverter system. In this system, the rectifier part is composed of diodes and the inverter part is made up of IPM. The control part, which takes a TMS320LF2407 chip as the central processor, includes central controlling module, current and voltage sampling module, rotor location collecting module, display module and keyboard module. Each subroutine is written with C language and assembly language in CCS environment. 4.Finally a specimen of the inverter system is designed. After having a performance examination, the result proves that the harmonic distortion of motor current is small, the usage factor of direct-current voltage is higher than the conventional SPWM technology and the power switch losts slightly. This system has the advantages of simple control, little peripheral, high performance and low price, which will meet the demands of the inverter using in fan and water pump.