Research On New-type Intelligent Synchronous Switch Of Low Voltage Power Compensation

The demand of reactive power in the domestic low power network is increasing and the increment of reactive power will cause many problems such as reduction of power factor,increment of network loss,and so on.But the manufacturing costs of low power equipment for reactive power compensation are too high and easily failed.So this paper presents a new low power intelligent synchronous switch for reactive power compensation(RPC)equipment.The main research contents of this paper are as follows:Firstly,after learning the background and significance of the research on reactive power compensation,the development of reactive power compensation,the development of reactive power compensation device and the current status of the research on the low voltage reactive power compensation are introduced.Then,the basic principle of reactive power compensation,two kinds of different methods of the capacitor to be connected to the grid and the calculation method of the compensation are studied.On the basis of current and voltage detection,various electric parameters is analyzed and calculated,the control strategy of capacitor switching is decided.The theoretical design and Simulation Research on the zero crossing switching module is carried out.And the simulation results show that the zero-cross switching of the capacitor does not produce any surging current,therefore,it will not have any impact on the power grid and the switch contacts.Secondly,a new type intelligent synchronous switch of low voltage power compensation is designed.It is composed of control module,current and voltage detection module,zero-cross switching module,communication module,power module and man-machine interface circuit,uses magnetic latching relay,one part of the zero-cross switching module,as the main loop switch eliminating the TRIAC,the price of which is relatively high and its driving circuit.The driving circuit of the magnetic relay is designed,which makes it have the power protection function and the reliability is relatively high.In addition to the communication module,there is a RS485 communication module and Ethernet interface module.The design of the flyback switching power supply reduces the cost and volume,and improves the efficiency.Thirdly,the main program and subroutine of the software is designed by using C language following the principles of modular.The subroutine program includes the current and voltage sampling program,the detection program of the network frequency,the FFT program,the man-machine interface program,the communication module program,and the zero crossing switching module program and so on.And many anti-interference measures are designed.In the control algorithm,the integrated control strategy is adopted to control the reactive power,the voltage and the harmonic content is the constraint condition.Most of all,it has the function of over-voltage protection,low-voltage protection,lack of phase protection and so on.Finally,the protection experiment and the experiment of zero crossing was conducted on the test device.The test results show that this device can switch capacitor at zero-crossing by cooperating with zero crossing switching module and control module.And this equipment has the advantages of low surging current,no spark at the touch point,no damage to the touch point,low power consumption,long operational lifespan,small volume and low manufacturing cost.It can successfully show all kinds of power value and the working status of each phase capacitor,communicate with other devices in the network.These functions greatly improve the reliability of the system.