Optimum Design Of Circuit And Communication System For Distributed Monitoring Of PV Station

With the rapid development of photovoltaic industry,it's necessary to build a distributed monitoring system in PV power station to realize the data acquisition and accurate fault location of PV modules.In the traditional PV monitoring system.RS-485 bus and wireless sensor network are usually used for data transmission,but these schemes have obvious shortcomings.In order to deal with these existing problems,based on the traditional communication scheme,according to the characteristics and requirements of large PV plants,this paper optimizes and adjusts part of communication system architecture,and designs a communication technology scheme based on DC single-wire carrier communication between PV modules,which integrates ZigBee wireless ad hoc network and optical fiber Ethernet,so as to make it more adaptable and more flexible in application..In addition,by studying the impedance-frequency characteristics of PV modules in series,the available carrier frequency band has been determined,and a reasonable carrier signal coupling mode is selected.Besides,according to the electromagnetic interference(EMI)model of the inverters and PV array,an X-filter with isolation function is designed to suppress the noise of the carrier transmission channel.Finally,the hardware circuit and software programs of the PV Monitoring Module(PVMM)has been optimized.For instance,the power supply module can work in a wider range of input voltage,the measuring errors have been minimized,the waveform distortion is reduced by choosing a more reasonable carrier modulation mode,A carrier receiving circuit with better performance is designed to reduce the bit error rate.Besides,the structure of software progran is improved to make it run more stably.The distributed monitoring system of PV station designed in this paper has been installed and tested in a grid-connected PV station in Qinghai Province,and has successfully realized continuous and stable operation.In the meantime,each kind of monitoring module has passed the test of China Electric Power Research Institute,and the performance indicators meet the expected requirements.It shows that the monitoring system has reasonable design,perfect function and good application value.