PV String Voltage Control to Mitigate Potential Induced Degradation
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Solution Overview
Problem
Photovoltaic (PV) module reliability and service lifetime are compromised due to polarization effects, leading to power degradation and potential safety issues, particularly in crystalline silicon wafer-based systems, where reversible polarization affects n-type and p-type cells differently, and voltage-induced degradation is a significant concern.
Innovation Solution
Implementing a power system with dynamic control methods that monitor and regulate voltages, currents, and impedance across interconnected components, including PV generators, wind turbines, and batteries, using DC to DC converters to maintain reference voltages above or below ground potential, thereby alleviating Potential Induced Degradation (PID) and extending the lifespan of PV strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PV modules operate at higher voltages to increase power output, then productivity is improved, but polarization effects cause power degradation and reliability deteriorates
Solution Approach 1:
The system applies periodic polarity reversal to PV strings, alternating between positive and negative voltage polarities. This periodic action prevents permanent polarization effects by regularly resetting the voltage-induced degradation, allowing the system to operate at higher voltages for increased productivity without suffering from cumulative power degradation that would compromise reliability
Solution Approach 2:
The system dynamically changes the voltage polarity parameter over time, switching between positive and negative voltages. This parameter change approach allows the PV modules to operate at high voltage levels for maximum power output while periodically altering the polarity to prevent irreversible polarization damage, thus resolving the contradiction between productivity and reliability
2Reliability
If DC to DC converters are added to regulate voltages and mitigate PID, then reliability is improved, but device complexity increases
Solution Approach 1:
The DC to DC converters are designed to perform multiple functions: voltage regulation, polarity reversal, and PID mitigation. By making the converter multi-functional, the system improves reliability through active voltage management without proportionally increasing complexity, as a single device handles multiple protective and regulatory tasks
Solution Approach 2:
The DC to DC converters automatically monitor and adjust voltage levels and polarity without external intervention. The system self-regulates to prevent PID effects and polarization damage, improving reliability through autonomous protection while minimizing the need for additional control infrastructure that would increase system complexity
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
This approach ensures efficient power delivery, reduces power losses, and extends the service life of PV modules by maintaining non-negative voltages, thus mitigating voltage-induced degradation and enhancing system reliability.
Implementation Method 1
A DC to AC inverter may include a first input terminal and a second input terminal. The first input terminal and the second input terminal may be connectable to the first output terminal and the second output terminal respectively
Implementation Method 2
The system may include a converter adaptable to convert, a source of power on a third input terminal and a fourth input terminal to a DC output voltage on a third output terminal
Implementation Method 3
a photovoltaic panel may connect to the input of the DC to DC converter
Data Source
AI summary
A method may include: applying a first voltage on at least one first terminal of a first direct current (DC) bus electrically connected to a power source, obtaining at least one indication that discharge of a second voltage related to the first voltage should be performed, and discharging the second voltage by electrically connecting at least one second terminal of a second DC bus to a ground in response to the at least one indication. Another method may include: injecting a current at at least one terminal of a direct current (DC) bus that is electrically connected to a power source, simultaneous to injecting the current, measuring an insulation relative to ground, obtaining an electrical parameter related to the power source, and, in response to the electrical parameter, maintaining the current injected at the terminal of the DC bus without ceasing the measuring of the insulation relative to a ground.