The common-mode current is an important indicator with transformerless photovoltaic inverters.However,up to now,there is not an accurate method to predict common-mode current in the inverter design process,resulting f...The common-mode current is an important indicator with transformerless photovoltaic inverters.However,up to now,there is not an accurate method to predict common-mode current in the inverter design process,resulting from inappropriate device selection or exceeded the expected common-mode current.In order to solve this problem,this paper proposes an accurate common-mode current prediction method based on graph theory for transformerless photovoltaic inverters.In this paper,the mathematic model of the common-mode current is derived using graph theory analysis method in the full-bridge topology,and it is used to predict common-mode current.The validity and correctness of the proposed prediction method are validated by simulation and experiment.The oscillation frequency and amplitude can be predicted by the proposed common-mode prediction method,whereas the traditional common-mode analysis method cannot.This paper provides a novel way to predict and analyze common-mode current in the transformerless photovoltaic inverters.展开更多
The paper presents a five-level common ground type(5L-CGT),transformer-less inverter topology with double voltage boosting.The proposed inverter uses eight switches and two capacitors,charged at input voltage level.Th...The paper presents a five-level common ground type(5L-CGT),transformer-less inverter topology with double voltage boosting.The proposed inverter uses eight switches and two capacitors,charged at input voltage level.The inverter in its basic form acts as a string inverter for low-power PV applications.However,it can be extended to work as a scalable multi-level inverter with higher power handling capability to act as a centralized inverter.The working of the inverter with the sizing of the components is presented with mathematical analysis.The efficiency of the proposed PV inverter is found using thermal losses associated with switches using PLECS software.A prototype of 1 kW has been designed,and experimentation has been carried out.Various loads with a lagging power factor up to 0.6 have been tested with the inverter to establish the usability of the proposed inverter in a worst-case emulated homeuse scenario.The total harmonic distortion(THD)at the output has been recorded using a power quality analyzer with voltage and current THD values of 4.5%and 2.5%,respectively,which lies within the limits of IEEE 519 standards.The highest power conversion efficiency of the inverter has been recorded to be 96.20%.展开更多
A semi-two-stage common-ground-type transformerless dual-buck-based grid-connected inverter is proposed in this paper.The common-ground-type topology can eliminate common mode(CM)leakage current by connecting the nega...A semi-two-stage common-ground-type transformerless dual-buck-based grid-connected inverter is proposed in this paper.The common-ground-type topology can eliminate common mode(CM)leakage current by connecting the negative terminal of the photovoltaic(PV)directly to the neutral point of the grid,which bypasses the PV array’s stray capacitance.The dual-buck-based topology guarantees increased robustness since the dc-link cannot be short-circuited by a shoot-through event.The semi-two-stage topology features multi-level characteristic,which has a lower forward-voltage drop and smaller dv/dt.Compared with the conventional two-stage inverter,the proposed topology achieves higher efficiency and higher reliability.Experimental results of a 1.5kW prototype show that the proposed inverter is able to achieve high efficiency and low leakage currents.展开更多
基金This work was supported by the National Natural Science Foundation of China under Grant 51577010the Fundamental Research Funds for the Central Universities under Grant 2017JBM054the Natural Science Foundation of Guangdong Province under Grant 1714060000016.
文摘The common-mode current is an important indicator with transformerless photovoltaic inverters.However,up to now,there is not an accurate method to predict common-mode current in the inverter design process,resulting from inappropriate device selection or exceeded the expected common-mode current.In order to solve this problem,this paper proposes an accurate common-mode current prediction method based on graph theory for transformerless photovoltaic inverters.In this paper,the mathematic model of the common-mode current is derived using graph theory analysis method in the full-bridge topology,and it is used to predict common-mode current.The validity and correctness of the proposed prediction method are validated by simulation and experiment.The oscillation frequency and amplitude can be predicted by the proposed common-mode prediction method,whereas the traditional common-mode analysis method cannot.This paper provides a novel way to predict and analyze common-mode current in the transformerless photovoltaic inverters.
文摘The paper presents a five-level common ground type(5L-CGT),transformer-less inverter topology with double voltage boosting.The proposed inverter uses eight switches and two capacitors,charged at input voltage level.The inverter in its basic form acts as a string inverter for low-power PV applications.However,it can be extended to work as a scalable multi-level inverter with higher power handling capability to act as a centralized inverter.The working of the inverter with the sizing of the components is presented with mathematical analysis.The efficiency of the proposed PV inverter is found using thermal losses associated with switches using PLECS software.A prototype of 1 kW has been designed,and experimentation has been carried out.Various loads with a lagging power factor up to 0.6 have been tested with the inverter to establish the usability of the proposed inverter in a worst-case emulated homeuse scenario.The total harmonic distortion(THD)at the output has been recorded using a power quality analyzer with voltage and current THD values of 4.5%and 2.5%,respectively,which lies within the limits of IEEE 519 standards.The highest power conversion efficiency of the inverter has been recorded to be 96.20%.
基金This work was supported in part by the National Natural Science Foundation of China under Grant 51677054in part by the 13th Six Talent Peaks Project in Jiangsu Province under Grant XNY-008.
文摘A semi-two-stage common-ground-type transformerless dual-buck-based grid-connected inverter is proposed in this paper.The common-ground-type topology can eliminate common mode(CM)leakage current by connecting the negative terminal of the photovoltaic(PV)directly to the neutral point of the grid,which bypasses the PV array’s stray capacitance.The dual-buck-based topology guarantees increased robustness since the dc-link cannot be short-circuited by a shoot-through event.The semi-two-stage topology features multi-level characteristic,which has a lower forward-voltage drop and smaller dv/dt.Compared with the conventional two-stage inverter,the proposed topology achieves higher efficiency and higher reliability.Experimental results of a 1.5kW prototype show that the proposed inverter is able to achieve high efficiency and low leakage currents.
