The Design Of Reactive Power Compensation Controlling System Based On AVR

Based upon the analysis of the advantages and disadvantages of the various existing system, we designed reactive power compensation control system, it can control the composite switch composed of parallel-connected silicon-controlled and vacuum contactor switches to switch the capacity banks at the PC terminal, which has no capacitor flashy flow and harmonic wave noise. The main function modules includes the data acquisition and process module of the hypostasis computer, composite switch controlling module, communication module, and the centralized display data collection module of the epitasis computer, data calibration, alarm value set, automatically switch controlling, etc.Atmega48 of the AVR single chip series is as the main controlling MCU for the system hardware, which has high speed (most of the instruction execution time is single clock period), rich in memory with built-in EEPROM and ADC, lower price, low power consumption CMOS technology, and support C advance language effectively at the software aspect. In the controller, it uses MOC3061 photo electricity isolator for the input/output of switch capacity, which can effectively restrain the interference of various noise; it adopts method of 96 times continuous AD sampling for each 20ms AC current period, then every sample is to summed and averaged to calculate the current and voltage effective value, which filters the interference of random signal, improves the accuracy of sampling; it uses the method of transforming CAN to RS232 to communicate with the epitasis computer, which can monitor and control remotely.Epitasis and hypostasis computer soft wares are completed for the main part of the software system, A/D conversion program, and composite switch control programs and data communication program using C language for the epitasis computer against single chip. Software for the hypostasis is designed upon the LabWindows/CVI development platform, which provides friendly human-machine dialogue and option interface, can instantly monitor 6 phase voltage (including two ends voltage of three vacuum ac contactor for three phases), and three-phase current, set alarm and switch delay time, visualized switch indicator, over-voltage and over current protection function, achieves intelligent monitoring system. Considering the system may encounter internal and external disturbances, relative anti-interference function is designed both in hardware and software.This instrument has gone through the laboratory and on-site test and application; all the specification can meet the user's requirements.