Research And Design On Low-voltage Reactive Power Compensation Controller

With the rapid development of modern industry, people have more demand to the quality of power system.The balance of reactive power is one of important guarantee to the quality of power system.Because inductive load equipment in the whole electricity consumption accounts for more than two-thirds.Obviously, nearby providing reactive power for inductive load equipment is important for reducing line loss or capacity of power supply equipment, and improving the power system's power factor or voltage. Fix shunt capacitor in the power network can reduce flow of reactive power,thereby reduce transmission loss.In low-voltage power system, low-voltage reactive power compensation equipment can nearby provide reactive power for inductive load equipment.Low-voltage reactive power compensation controller is control core of shunt capacitor,which can detect voltage and current then figure out power factor,reactive current and reactive power.And it realizes auto-switching capacitor bank and reactive compensation according to definite control law.In this paper: Firstly,the basic theory of reactive power compensation is elaborated and its development and actuality are also given.This paper analyses the shortage of this controller,on the basis of it,design idea of the high accuracy,intelligent,low-voltage reactive power compensation controller is presented.Secondly,the overall system design is given,the system functions and design ideas are analyzed,and the hardware,software and specific circuit of low-voltage reactive power compensation controller are provide.The controller uses a high accuracy,three-phase electric energy,metrology chip ATT7022B,which can measure operation parameters of power network,guarantee system's stability and anti-interference and simplize the software design.By using the ferroelectric memory FM3164,the controller can store 60 days'history data and the reliability is improved.It adopts AVR series ATmega128 as the control core.This chip contains SPI bus joined with metrology chip and I2C bus joined with memory.Switching of capacitors adopts operational method called circular queue to realize auto-tracking reactive power and auto-switching capacitor bank.The controller and PC communicate by GPRS wireless mode,which is used to transmit data.Meanwhile,the controller can link other metering device through RS-232/485, which can realize monitoring function. In addition,this controller has USB interface to be convenience for workers when they will set parameters.Each modules'schematic circuit diagram and software's flow charts are also presented in this paper,and the anti-interference designs are performed in both software and hardware.At the end of this paper,we summarized the whole paper,put forward the method of improvement and the prospect of this research.