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
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
This article presents a finite-time robust control(FTRC)of a transformerless STATCOM based on a cascaded multilevel H-bridge converter(CMHC)with star configuration.The FTRC is first proposed for the current loop contr...This article presents a finite-time robust control(FTRC)of a transformerless STATCOM based on a cascaded multilevel H-bridge converter(CMHC)with star configuration.The FTRC is first proposed for the current loop control of a CMHC-based transformerless STATCOM by using the finite time robust control theory.Taking the parameters,perturbations and external disturbances into account and using coordinate transformation method,the nonlinear dynamic model of the CMHC-based transformerless STATCOM is transformed into a standard nonlinear port-controlled dissipative Hamiltonian(PCDH)structure.Based on the PCDH structure,an FTRC is designed for the CMHC-based transformerless STATCOM to improve the transient stability and oscillation damping of power system.Finally,the simulation results demonstrate that the FTRC has better dynamic performance and strong robustness in comparison with the passivity-based control of the CMHC-based transformerless STATCOM.展开更多
共模电流抑制是非隔离型光伏并网逆变器的一个关键技术问题。首先基于考虑所有寄生参数的非隔离型单相并网逆变器高频共模等效模型归纳出两种抑制漏电流的途径,并将其应用到二极管钳位(neutral point clamped,NPC)三电平并网逆变器中得...共模电流抑制是非隔离型光伏并网逆变器的一个关键技术问题。首先基于考虑所有寄生参数的非隔离型单相并网逆变器高频共模等效模型归纳出两种抑制漏电流的途径,并将其应用到二极管钳位(neutral point clamped,NPC)三电平并网逆变器中得出仅通过正弦脉宽调制(sine pulse width modulation,SPWM)策略抑制共模电压不可行和通过电路元件参数匹配抑制共模电压的3种可能方案。针对3种可能的方案分析了它们的成立条件和现实可行性,并通过相应的实验验证结论的可靠性。其中,提出的通过补偿电容来弥补寄生参数差异的措施可以进一步增强NPC三电平并网逆变器漏电流抑制性能,是一种简单、可靠、有效的实用技术。展开更多
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.
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.
基金supported by Guizhou Provincial Science and Technology Foundation(No.QiankeheJzi[2015]2070,Qiankehejichu[2016]1064,Qiankehejichu[2017]1074,Qiankehejichu[2018]1068,Qiankehezhicheng[2018]2164)the Chinese National Natural Science Foundation under Grant No.61563011the Ph.D research fund of Guizhou Normal University under Grant No.11904-0514170High level talent research project of Guizhou Institute of Technology(No.XJGC20150405).
文摘This article presents a finite-time robust control(FTRC)of a transformerless STATCOM based on a cascaded multilevel H-bridge converter(CMHC)with star configuration.The FTRC is first proposed for the current loop control of a CMHC-based transformerless STATCOM by using the finite time robust control theory.Taking the parameters,perturbations and external disturbances into account and using coordinate transformation method,the nonlinear dynamic model of the CMHC-based transformerless STATCOM is transformed into a standard nonlinear port-controlled dissipative Hamiltonian(PCDH)structure.Based on the PCDH structure,an FTRC is designed for the CMHC-based transformerless STATCOM to improve the transient stability and oscillation damping of power system.Finally,the simulation results demonstrate that the FTRC has better dynamic performance and strong robustness in comparison with the passivity-based control of the CMHC-based transformerless STATCOM.
