Research Of New-Style Inverter And Its Data Acquisition System

With the development of power electronic devices, PWM voltage inverter is widely used, suchas AC frequency conversion velocity modulation controlling, UPS, power quality controller,light-duty transmit electricity DC converter. The ideal non-fluctuating DC voltage-source requiredby DC side of PWM voltage inverter is usually acquired through commutating and the heavy DCcapacitance filter. The heavy DC filtering capacitance can take much space,high cost and severelyinfluence power quality. Therefore, it's very important to study how to reduce or even banish theDC side capacitance of the inverter and solve low sub harmonic and relevant problems. This studyhas significant theoretical and practical values.This paper labored operating principle of the three-phase inverter and analyzed the workingsituations of the three-phase inverter under pure resistance load and inductive load on the basis ofdevelopment both here and abroad of the three-phase inverter, and by that excogitated anon-controllable inverter—the new-style inverter, which can banish or retain only a small DCcapacitance. Under the three-phase balanced input system and three-phase unbalanced system, itanalyzed the output voltage harmonics thoroughly, and confirmed way of the harmonicsrestrained—modulating wave reconstructed SPWM technique. The technique can banish theinfluence of harmonics by inverter output voltage, and broke limit of DC side without pulsatingvoltage of the traditional inverter, therefore swingingly reduced or even wiped off DC sidecapacitance of the inverter, so the main circuit and controlling system were simplified.This system centered on DSP-TMS320LF2407A. The new-style inverter's main circuitconsisted of the three-phase non-controllable commutating bridge and three-phase inverting bridge.The data acquisition part designed the pulsating voltage acquisition circuit on DC side usingmagnetic balance type voltage Hall sensor module(CHV—25P) based on Hall effect principle; andthis design can use simulating filter chip MAX291 to realize low pass filter for the output signal ofcircuit on DC side pulsating voltage and acquire DC component of DC pulsating voltage tocalculate modulation wave reconstruction part; and also the system will collect three phase loadcurrent through precision current transformer (CT) TA 14Z—300, and count virtual value for loadcurrent according to root-mean-square value algorithms to achieve overflow protection for thesystem etc.Based on hardware design of data acquisition part we finished designing the software for data acquisition part. Software design is used modular structure, and it is composed of severalapplication subprograms with different functions, relatively independent functional program iscalled as subprogram.Through simulation experiments, it proved that the new-style inverter and its modulating wavereconstructed technique can effectively restrain the low sub harmonic produced by DC sidepulsating voltage in the new-style inverter output voltage, and tested and verified the feasibility ofthe new-style inverter and its modulating wave reconstructed technique.