Development Of Digital Phase Shifter Based On DeviceNet

The comprehensive Phase shifter is widely used in phase measurement and thecalibration of phase meter, it applies in the research of the measurement ofAC power,AC electric energy and the measurement circuit.This paper has studied the relative problems of the miniaturize,intelligentize, networking of traditional phase shifter.This project takes advantage of the method of Looking up-table to realizephase shifting and uses SPWM to achieve sinusoidal output. At first, the urbanpower is rectified and filtered to smoothly DC power, then it takes use of theinversion circuit to realize sinusoidal output. On the bases of the initial phaseof urban power as standard phase, it can be able to realize the phase shiftingvalue of every angle with the resolution of 1°. Through adjusting of themodulation depth of SPWM to regulate the output voltage from 0 to 200V.This subject uses ARM7TDMI-S base 32 bit micro-controller LPC2129 as maincontroller.SPWM modulation method adopt unipolar SPWM, its advantage is it can reducesthe THD of the output, at the same time it can use smaller output filter componentetc. This paper focus on studying the realization of unipolar SPWM under theuses of the special MOSFET driver IR2130.Because use IR2130 can greatly simplifythe design of driving circuit, but the input pulse width of IR2130 can not beless than 1.5us, or the output waveform will be distorted obviously, while inthe zero-acrossing. In order to minimize the distortion of the zero-across ofoutput, this paper adopt the method of using overlaps a DC PWM signal onhigh-frequency arm and uses equal DC PWM signal replace low-frequency arm signalto improve the traditional unipolar SPWM.This subject has expand both the interface of CAN and RS485.Through theadoption of DeviceNet as a CAN Application Level protocol the Group 2 Only severhas been realized and it uses Poll to communication, implements Identity, Router,DeviceNet, connection etc. object class. This paper has introduced the dealingprogress of the DeviceNet concretely, include: power on, deal with fragmentmessage, explicit message and implicit message. All parts of the circuitprinciple chart and some parts of the flowchart of the digital phase shifterhas itemized in this paper.Through systematically experiment and test, a prototype had produced and ithas achieved the expected effect.