| The12thFive Years Plan Period is the critical period for developing the photovoltaicindustry. The target for installing photovoltaic power generation is21GW in this period,the National Energy Board said. The problem which photovoltaic industry encountered washigher input costs and lower power generation efficiency in the photovoltaic industry chaininitially formed in China. Besides, China also suffered the antidumping and countervailinginvestigations initiated by the European Union and the United States. To resolve thedifficulties, the key measurement is expediting technical innovations and enhancingphotovoltaic system reliability.To improve the efficiency and power quality, it is necessary to detect accuratelycurrent, such as direct current, alternating current, pulsating direct current, and leakagecurrent. This paper firstly deduced the high-frequency common mode equivalent model tothe leakage current problem of non-isolated inverter. The generation principle andcalculation method of common mode leakage current were analyzed and discussed in thispaper. Based on the simplest common mode model, this paper proposed two methods toeliminate the leakage current, and simulated the leakage current by Simulink software.Secondly, this paper proposed a low leakage current single-phase two-stage non-isolatedgrid connected photovoltaic inverter, expounded the working principle, designedparameters of Boost circuit and DC-AC circuit in the main topology, and made somesimulations and tests to verify the above theories. Once more, this paper introduced theexisting current detection methods, and highlighted the advantageous property of giantmagneto-resistance (GMR) effect based current sensor by their comparison. The workingprinciple and internal structure were analysed furtherly, providing a theoretical basis for thedesign of new photovoltaic current sensor. Lastly, this paper proposed two kinds of GMReffect based photovoltaic current sensor: GMR effect based current sensor with magneticshielding and bias coil winding, and closed-loop GMR effect based current sensor for DCand AC current. The detailed structure design and working principle were described. Basedtheoretical analysis and simulation results, the two type of prototype were designed andtested for various performance.The tested results show that, the two novel kinds of current sensor has the advantages of high sensitivity and accuracy, low nonlinear error, wide measuring range. Besides, it candetect both DC and AC current with a wide bandwidth. As advance in power electronicproducts development, such as PV inverter and wind inverter, the need of high precisioncurrent sensors in high frequency application keeps increasing. Therefore, the designedcurrent sensors in this paper have wide application prospects. |
