A Photovoltaic Array Detection System Based On SCM

In the world’s background of energy shortages, solar energy as a large potential,clean, pollution-free and green energy, it obtain more and more national attention. Inrecent years, the world has established a number of photovoltaic power stations, Chinahas also established various sizes of wind or photovoltaic power stations.In the medium or large grid-connected PV array systems, there are a lot of PVstrings and cables. We used PV combiner box to merge a plurality of output lines to bea main current. For real-time monitoring the working conditions of PV arrays, eachbranch has a DC current detection unit. Because of Compact size and Simple circuit, theDC hall sensor has been the mainstream design of the PV current detection. But hallsensor has some problem in application such as high cost, susceptible toelectromagnetic interference and the effect of magnetic stranded.In order to solve the above problems, this thesis proposes a solution that usingsampling resistor, isolation optocoupler and high performance operational amplifiers toreplace the hall sensor. According to building a test circuit board and Programming, wecan solve problems while maintaining accuracy of measurement. In the other side, thisthesis discussed and solved the problem of data transmission when in a complexelectromagnetic environment. The main contents include:1. Elaborate sampling resistor’s advantage over hall sensor, and to propose a PVcurrent detection scheme both have low cost and accuracy. This thesis chose manganinas the sampling resistor to solve problems of hall sensor. In order to take into accountthe different grounding modes, also for safety isolating high and low voltage electricalsignal and accident prevention, the thesis used isolation optocoupler. By using highperformance operational amplifiers, we changed differential output signal into a singleended output signal, and economized ADC resources.2. Discussed the current detection circuit output in an external electromagneticinterference environment, then propose an algorithm to eliminate the pulse interference.The idea of the algorithm is: multiple sampling, bubble sort and choose median.3. In order to complete the whole system detects board, designed a voltagedetecting circuit. 4. For communication with the host computer, designed address and baud rateselection switches. Used RS485protocol and modbus protocol.