Solar Array Potential Adjustment for PID Prevention
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Solution Overview
Problem
Recent photovoltaic systems with higher voltages are more susceptible to performance reduction due to the potential induced degradation (PID) phenomenon, which occurs when there is a large potential difference between solar cells and the grounded frame, especially under conditions of high temperature and humidity, leading to leakage currents that interfere with electron transfer and reduce solar module performance.
Innovation Solution
A distributed power system that includes a non-isolated DC-DC converter and a potential adjustment section to maintain a higher potential at the negative electrode of the solar array during nighttime, preventing or delaying PID by ensuring the potential at the negative electrode is higher than that of the inverter, thereby reducing the likelihood of performance reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher voltage is used in photovoltaic systems to improve efficiency, then power generation efficiency is improved, but the system becomes more susceptible to PID phenomenon causing performance degradation
Solution Approach 1:
The invention applies preliminary anti-action by introducing a potential adjustment section that proactively equalizes the potential difference between solar cells and grounded frames before PID can occur. The adjustment section includes a switching element connected between the negative electrode of the solar array and ground, which can be activated to prevent potential-induced degradation before it damages the solar modules.
Solution Approach 2:
The invention uses an intermediary approach by introducing a potential adjustment section as a mediator between the high-voltage solar array and ground. This intermediary component (switching element) controls the potential difference, allowing the system to maintain high operating voltages for efficiency while preventing excessive potential differences that would cause PID.
2Loss of energy
If a transformerless inverter is used to achieve higher efficiency, then conversion efficiency is improved, but large potential difference appears between solar cells and grounded frame causing leakage current
Solution Approach 1:
The potential adjustment section provides preliminary anti-action by preventing the formation of large potential differences that would lead to leakage currents. The switching element can be activated to equalize potentials before harmful leakage currents develop, protecting the transformerless inverter system from PID while maintaining its high efficiency benefits.
Solution Approach 2:
The switching element acts as an intermediary between the transformerless inverter system and ground, controlling potential differences to prevent leakage currents. This intermediary component allows the system to operate efficiently without transformer isolation while protecting against the harmful effects of potential-induced degradation.
3Duration of action of stationary object
If the system remains connected to utility grid during nighttime with storage battery charging/discharging, then continuous power supply is maintained, but potential difference causes PID phenomenon
Solution Approach 1:
The potential adjustment section provides continuous protection during nighttime operation when the storage battery is charging or discharging. The switching element can be activated to equalize potentials even when no solar power is being generated, preventing PID during periods when the system remains connected to the utility grid for continuous power supply.
Solution Approach 2:
The switching element serves as an intermediary that continuously manages potential differences during nighttime operations. It mediates between the storage battery system and the solar array, ensuring potential equalization is maintained even when the solar modules are not actively generating power, thus protecting them during extended connection periods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents the reduction in solar module performance caused by PID, allowing for continuous efficient operation even when the system is connected to both the utility grid and a storage battery during both daytime and nighttime.
Implementation Method 1
The cell 13 is a device including a semiconductor layer (power generation layer) that converts light energy into power with the photovoltaic effect
Implementation Method 2
a non-isolated DC-DC converter that has an input terminal and an output terminal and raises, at a predetermined step-up ratio, a DC voltage input from the power supplies via the input terminal and outputs the DC voltage via the output terminal
Implementation Method 3
an inverter that converts the DC voltage output from the DC-DC converter via the output terminal into an alternating current
Data Source
Figure 1
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AI summary
A technique prevents performance reduction of solar arrays caused by potential induced degradation (PID). A distributed power system that is connected to a utility grid during both daytime and nighttime includes a plurality of power supplies including a solar array, a non-isolated DC-DC converter that has an input terminal and an output terminal and raises, at a predetermined step-up ratio, a DC voltage input from the power supplies via the input terminal and outputs the DC voltage via the output terminal, an inverter that converts the DC voltage output from the DC-DC converter via the output terminal into an alternating current, and a potential adjustment section that adjusts a potential at a negative electrode of the solar array to a potential higher than a potential at a negative electrode of the inverter at least during nighttime.