Automatic identification of faulted strings in single inverter photovoltaic systems
Updated: May 10, 2021
One of the challenges in operation and maintenance of single inverter photovoltaic (PV) systems is identification of faulted strings. This is typically relevant to residential and small commercial PV systems, when a single mini-central string inverter is chosen for the system upon sizing and pricing considerations. While in multi-inverter systems, normalized inverter comparison can be utilized to automatically identify string malfunctions in mini-central inverters, this is not possible in single inverter systems. The result is that numerous residential and small commercial PV systems operate for months and even years with faulted strings, which are impossible to detect via conventional monitoring and require costly preventive manual inspections to resolve the issue.
Several technologies can be utlized to provide a solution to this problem. The obvious one is the utlization of micro inverters or single string inverters, where the strings malfunctions issue doesn't exist. However, the mainstream of market inverters in the commercial segment is string inverters and the percentage of single-inverter systems there is quite high. Recently, some inverter manufacturers like Huawei and Billion Watts, have introduced a hardware solution - adding current sensors to each string thus being able to allow string-level monitoring. The disadvantage of this approach is the lack of retrofit ability to existing PV systems. Moreover, additional sensors add-up costs and may require more maintenance.
Soltell Systems allows a different approach to detect string malfunctions in single-inverter PV systems - utilizing Soltell's proprietary Sensorless Weather Measurement technology (SWMT). This approach allows to identify power irregularities with an unprecedented accuracy level of <5%, which is sufficient to automatically identify faulted strings in single inverter PV systems. This is both applicable to residential single inverter systems, where we typically find 2-4 string inverters and to small commercial PV systems, where 4-10 string inverters are utilized. The Soltell platform is suitable for retrofit to various string inverter brands, such as SMA, Fronius and more. The Soltell platform solution doesn't require any hardware modifications and dramatically reduces the need for preventive maintenance inspections.
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