High Reliability and Efficiency Single-Phase Transformerless Inverter for Grid-Connected Photovoltaic Systems
High Reliability and Efficiency Single-Phase Transformerless Inverter for Grid-Connected Photovoltaic Systems
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DOI：
10.1109/tpel.2012.2214237
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发表时间：
2013-05
影响因子：
6.7
通讯作者：
Bin Gu;J. Dominic;J. Lai;Chien-Liang Chen;T. Labella;Baifeng Chen
中科院分区：
文献类型：
--
作者：
Bin Gu;J. Dominic;J. Lai;Chien-Liang Chen;T. Labella;Baifeng Chen
本文提出了一种高可靠性的单相无变压器并网逆变器，利用超结MOSFET实现高效率的光伏应用。建议的转换器采用两个分裂的交流耦合电感器，分别为积极和消极的半电网周期。这消除了传统电压源逆变器遇到的直通问题，从而提高了系统可靠性。在高频脉宽调制开关换向和电网过零时刻都不需要死区时间，从而改善了输出交流电流的质量并提高了变换器效率。所提出的逆变器的分离结构不会导致主功率开关的反向恢复问题，并且因此可以利用超结MOSFET而没有任何可靠性或效率损失。由于在所提出的转换器中使用MOSFET，因此即使在轻负载运行时也可以实现高效率，从而实现转换器系统的高加州能源委员会（CEC）或欧盟效率。它还能够在更高的开关频率下工作，同时保持高效率。更高的工作频率和更高的效率可以降低冷却要求，并通过缩小无源元件来节省系统成本。通过两个额外的交流侧开关在续流阶段传导电流，光伏阵列与电网解耦。这降低了高频共模电压，从而使接地环路漏电流最小化。文中阐述了无变压器逆变器的工作原理、共模特性和设计考虑。对几种现有的以MOSFET为主开关的无变压器逆变器的功率半导体器件的总损耗进行了评估和比较。实验结果与5千瓦的原型电路显示99.0%的CEC效率和99.3%的峰值效率与20 kHz的开关频率。该转换器的高可靠性和高效率使得它对于单相无变压器光伏逆变器应用非常有吸引力。
This paper presents a high-reliability single-phase transformerless grid-connected inverter that utilizes superjunction MOSFETs to achieve high efficiency for photovoltaic applications. The proposed converter utilizes two split ac-coupled inductors that operate separately for positive and negative half grid cycles. This eliminates the shoot-through issue that is encountered by traditional voltage source inverters, leading to enhanced system reliability. Dead time is not required at both the high-frequency pulsewidth modulation switching commutation and the grid zero-crossing instants, improving the quality of the output ac-current and increasing the converter efficiency. The split structure of the proposed inverter does not lead itself to the reverse-recovery issues for the main power switches and as such superjunction MOSFETs can be utilized without any reliability or efficiency penalties. Since MOSFETs are utilized in the proposed converter high efficiency can be achieved even at light load operations achieving a high California energy commission (CEC) or European union efficiency of the converter system. It also has the ability to operate at higher switching frequencies while maintaining high efficiency. The higher operating frequencies with high efficiency enables reduced cooling requirements and results in system cost savings by shrinking passive components. With two additional ac-side switches conducting the currents during the freewheeling phases, the photovoltaic array is decoupled from the grid. This reduces the high-frequency common-mode voltage leading to minimized ground loop leakage current. The operation principle, common-mode characteristic and design considerations of the proposed transformerless inverter are illustrated. The total losses of the power semiconductor devices of several existing transformerless inverters which utilize MOSFETs as main switches are evaluated and compared. The experimental results with a 5 kW prototype circuit show 99.0% CEC efficiency and 99.3% peak efficiency with a 20 kHz switching frequency. The high reliability and efficiency of the proposed converter makes it very attractive for single-phase transformerless photovoltaic inverter applications.