To achieve useful, fair, and cost-effective design qualification and type approval testing for PV inverters, two procedures were developed and demonstrated to evaluate the bus link capacitors and power transistor—and where applicable, its module—for long-term reliability. We evaluate the inverter under simulated use conditions with heat run tests to find the highest operating temperatures reached by these components. The procedures are demonstrated in this study with a 4-kVA class string inverter. The maximum temperature of the DC bus link capacitors was determined to be 76.4°C when the ambient temperature was at the inverter's maximum rated temperature of 60°C with derating occurring. On the other hand, the power transistor module's maximum temperature using the heat sink temperature as the index, 92.6°C, occurred in an ambient of 40.8°C when derating was not occurring. The conditions found for upper temperatures exhibited by these components are, respectively, proposed for implementation in the dry heat and thermal cycling tests in the IEC 62093 “Power conversion equipment for photovoltaic systems – Design qualification testing” international standard draft so that the levels applied in the tests are in proportion to those experienced in the field. As a result, fairer evaluation of inverter reliability is realized.

中文翻译：

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在光伏逆变器的资格测试中评估直流母线电容器和功率晶体管模块

为了实现对光伏逆变器有用、公平和具有成本效益的设计资格和型式认证测试，开发并演示了两个程序来评估母线电容器和功率晶体管（以及适用的情况下，其模块）的长期可靠性。我们在模拟使用条件下通过热运行测试评估逆变器，以找出这些组件达到的最高工作温度。本研究中使用 4 kVA 级组串逆变器演示了这些程序。当环境温度为逆变器的最高额定温度 60°C 且发生降额时，直流母线电容器的最高温度被确定为 76.4°C。另一方面，以散热片温度为指标的功率晶体管模块的最高温度92.6℃，出现在40℃的环境中。未发生降容时为 8°C。IEC 62093“光伏系统的功率转换设备——设计资格测试”国际标准草案中的干热和热循环测试中分别提出了这些组件表现出的高温条件，以便在干热和热循环测试中实施这些水平。测试与在该领域经验丰富的测试成比例。结果，实现了对逆变器可靠性的更公平的评估。IEC 62093“光伏系统的功率转换设备——设计资格测试”国际标准草案中的干热和热循环测试中建议实施，以便测试中应用的水平与该领域的经验成比例。结果，实现了对逆变器可靠性的更公平的评估。IEC 62093“光伏系统的功率转换设备——设计资格测试”国际标准草案中的干热和热循环测试中建议实施，以便测试中应用的水平与该领域的经验成比例。结果，实现了对逆变器可靠性的更公平的评估。