Understanding String Inverters and MPPT: Common Issues and FAQs
In this article, we will delve into the concept of string inverters and Maximum Power Point Tracking (MPPT) and provide answers to some frequently asked questions.
Table of Contents
- Introduction
- What are String Inverters?
- What is Maximum Power Point Tracking (MPPT)?
- Connecting different MPPTs: What does it mean and when should it be done?
- Which string will the MPPT track in case of voltage differences between two strings under MPPT?
- What is the optimal DC string voltage for an inverter to reach its rated voltage?
- What does the maximum DC operating current on an inverter label mean?
- Inverter current peak clipping issue: What causes it?
- Will shading of two components in a string under the same MPPT affect the normal power generation of another string?
- Can North-facing and South-facing slopes share one inverter?
- FAQs
- Conclusion
What are String Inverters?
String inverters are commonly used in solar photovoltaic (PV) systems to convert the direct current (DC) generated by solar panels into alternating current (AC) electricity that can be fed into the grid. These inverters are named after their ability to convert a string of solar panels connected in series to a single AC output.
What is Maximum Power Point Tracking (MPPT)?
Maximum Power Point Tracking (MPPT) is a technique used in solar PV systems to maximize the amount of power that can be obtained from a solar array. The MPPT algorithm adjusts the voltage of the solar panels to ensure that they operate at their maximum power point, which varies depending on the environmental conditions.
Connecting different MPPTs: What does it mean and when should it be done?
Connecting different MPPTs means connecting strings with different directions, shading, unequal length, and angles to different MPPTs. This should be done when maximizing the advantage of keeping the array at the maximum output state, i.e., when MPPT is used to track the maximum power point.
Which string will the MPPT track in case of voltage differences between two strings under MPPT?
In the case of voltage parallel mismatch, the maximum power tracking point of the MPPT is different, and the low voltage will pull down the high voltage, affecting the overall output power.
What is the optimal DC string voltage for an inverter to reach its rated voltage?
The optimal DC string voltage for an inverter to reach its rated voltage is close to the maximum voltage of the MPPT.
What does the maximum DC operating current on an inverter label mean?
The maximum DC operating current on an inverter label, such as 25/25adv, refers to the maximum input current of each MPPT. If each MPPT has two strings, the maximum input current for each string is 12.5A. If there is only one string, the string current is less than 25A.
Inverter current peak clipping issue: What causes it?
Inverter current peak clipping issue may occur when the selected component current exceeds the maximum input current of the inverter. This may be due to a positive deviation or testing according to STC standards during factory production.
Will shading of two components in a string under the same MPPT affect the normal power generation of another string?
Yes, it will affect the normal power generation of another string because the MPPT algorithm adjusts the voltage to find the maximum power point. In this case, there will be two power peaks, and the MPPT tracking point will be lower than normal, reducing the power generation efficiency.